Patent Application
20200295219
The present disclosure relates to an imaging element, a laminated imaging element, and a solid-state imaging device.
In recent years, a laminated imaging element has attracted attention as an imaging element constituting an image sensor and the like. The laminated imaging element has a structure in which a photoelectric conversion layer (light receiving layer) is sandwiched between two electrodes. In addition, the laminated imaging element requires a structure in which signal charges generated in the photoelectric conversion layer on the basis of photoelectric conversion are accumulated and transferred. A conventional structure requires a structure in which signal charges are accumulated in and transferred to a floating drain (FD) electrode, and requires high-speed transfer such that the signal charges are not delayed.
An imaging element (photoelectric conversion element) for solving such a problem is disclosed in, for example, Japanese Patent Application Laid-Open No. 2016-63165. This imaging element includes:
an accumulation electrode formed on a first insulating layer;
a second insulating layer formed on the accumulation electrode;
a semiconductor layer formed so as to cover the accumulation electrode and the second insulating layer;
a collecting electrode formed in contact with the semiconductor layer and apart from the accumulation electrode;
a photoelectric conversion layer formed on the semiconductor layer; and
an upper electrode formed on the photoelectric conversion layer.
An imaging element using an organic semiconductor material for the photoelectric conversion layer can photoelectrically convert a specific color (wavelength band). In addition, because of such a characteristic, in a case where the imaging element is used as an imaging element in a solid-state imaging device, it is possible to obtain a structure having sub-pixels laminated (laminated imaging element), not possible with a conventional solid-state imaging device in which each of sub-pixels includes a combination of an on-chip color filter layer (OCCF) and an imaging element and the sub-pixels are arrayed two-dimensionally (see, for example, Japanese Patent Application Laid-Open No. 2011-138927). Furthermore, there is an advantage that a false color is not generated because demosaic processing is not required. In the following description, an imaging element including a photoelectric conversion unit disposed on or above a semiconductor substrate may be referred to as “first type imaging element” for convenience, a photoelectric conversion unit constituting the first type imaging element may be referred to as “first type photoelectric conversion unit” for convenience, an imaging element disposed in the semiconductor substrate may be referred to as “second type imaging element” for convenience, and a photoelectric conversion unit constituting the second type imaging element may be referred to as “second type photoelectric conversion unit” for convenience.
Charges generated by photoelectric conversion in the second photoelectric conversion unit 341A and the third photoelectric conversion unit 343A are temporarily accumulated in the second photoelectric conversion unit 341A and the third photoelectric conversion unit 343A, then transferred to a second floating diffusion layer (floating diffusion) FD2 and a third floating diffusion layer FD3 by a vertical transistor (a gate portion 345 is illustrated) and a transfer transistor (a gate portion 346 is illustrated), and further output to an external readout circuit (not illustrated), respectively. These transistors and floating diffusion layers FD2 and FD3 are also formed in the semiconductor substrate 370.
Charges generated by photoelectric conversion in the first photoelectric conversion unit 310A are accumulated in the first floating diffusion layer FD1 formed in the semiconductor substrate 370 via a contact hole portion 361 and a wiring layer 362. Furthermore, the first photoelectric conversion unit 310A is also connected to a gate portion 352 of an amplification transistor for converting a charge amount into a voltage via the contact hole portion 361 and the wiring layer 362. In addition, the first floating diffusion layer FD1 constitutes a part of a reset transistor (a gate portion 351 is illustrated). Reference numeral 371 represents an element isolation region, reference numeral 372 represents an oxide film formed on a surface of the semiconductor substrate 370, reference numerals 376 and 381 represent interlayer insulating layers, reference numeral 383 represents an insulating layer, and reference numeral 314 represents an on-chip micro lens.
However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2016-63165 described above, there is a limitation that the accumulation electrode and the second insulating layer formed on the accumulation electrode need to be formed with the same length, and a gap from the collecting electrode and the like are finely defined. This complicates a manufacturing process and may cause a reduction in manufacturing yield. Furthermore, Japanese Patent Application Laid-Open No. 2016-63165 describes some materials constituting the semiconductor layer, but does not describe matters relating to a relationship between the characteristics of a material constituting the semiconductor layer and the characteristics of a material constituting the upper electrode, having a large effect on generation of charges by photoelectric conversion.
Therefore, an object of the present disclosure is to provide an imaging element, a laminated imaging element, and a solid-state imaging device that can generate charges more efficiently by photoelectric conversion.
An imaging element according to the present disclosure for achieving the object described above includes
a photoelectric conversion unit formed by laminating a first electrode, a photoelectric conversion layer, and a second electrode,
between the first electrode and the photoelectric conversion layer, an inorganic oxide semiconductor material layer is formed in contact with the photoelectric conversion layer,
the photoelectric conversion unit further includes an insulating layer and a charge accumulation electrode disposed apart from the first electrode so as to face the inorganic oxide semiconductor material layer via the insulating layer,
a material constituting the inorganic oxide semiconductor material layer has a value of work function of 4.5 eV or less, and
a value obtained by subtracting the value of work function of the material constituting the inorganic oxide semiconductor material layer from a value of work function of a material constituting the second electrode exceeds 0.2 eV.
The laminated imaging element of the present disclosure for achieving the object described above includes at least one of the imaging elements of the present disclosure.
The solid-state imaging device according to a first aspect of the present disclosure for achieving the object described above includes a plurality of the above imaging elements of the present disclosure. Furthermore, a solid-state imaging device according to a second aspect of the present disclosure for achieving the object described above includes a plurality of the above laminated imaging elements of the present disclosure.
In the imaging element of the present disclosure, the imaging element of the present disclosure constituting the laminated imaging element of the present disclosure, and the imaging element of the present disclosure constituting the solid-state imaging devices according to the first and second aspects of the present disclosure (these imaging elements may be collectively referred to as “imaging element and the like of the present disclosure”), the characteristics of a material constituting the inorganic oxide semiconductor material layer and the characteristics of a material constituting the second electrode are defined. Therefore, it is possible to provide an imaging element that can generate charges more efficiently by photoelectric conversion. In addition, the imaging element and the like of the present disclosure have a two-layer structure of the inorganic oxide semiconductor material layer and the photoelectric conversion layer. Therefore, recombination during charge accumulation can be prevented, transfer efficiency of charges accumulated in the photoelectric conversion layer to the first electrode can be increased, and generation of a dark current can be suppressed. Note that effects described here are merely illustrative, and are not restrictive. Furthermore, an additional effect may be present.
Hereinafter, the present disclosure will be described on the basis of Examples with reference to the drawings. However, the present disclosure is not limited to Examples, and various numerical values and materials in Example are illustrative. Note that description will be made in the following order.
1. General description on imaging element of the present disclosure, laminated imaging element of the present disclosure, and solid-state imaging devices according to first and second aspects of the present disclosure
2. Example 1 (imaging element of the present disclosure, laminated imaging element of the present disclosure, and solid-state imaging device according to second aspect of the present disclosure)
3. Example 2 (modification of Example 1)
4. Example 3 (modification of Examples 1 and 2, and solid-state imaging device according first aspect of the present disclosure)
5. Example 4 (modification of Examples 1 to 3, and imaging element including transfer control electrode)
6. Example 5 (modification of Examples 1 to 4, and imaging element including charge discharge electrode)
7. Example 6 (modification of Examples 1 to 5, and imaging element including a plurality of charge accumulation electrode segments)
8. Example 7 (imaging elements of first and sixth configurations)
9. Example 8 (imaging elements of second and sixth configurations of the present disclosure)
10. Example 9 (imaging element of third configuration)
11. Example 10 (imaging element of fourth configuration)
12. Example 11 (imaging element of fifth configuration)
13. Example 12 (imaging element of sixth configuration)
14. Example 13 (solid-state imaging devices of first and second configurations)
15. Example 14 (modification of Example 13)
16. Others
<General Description on Imaging Element of the Present Disclosure, Laminated Imaging Element of the Present Disclosure, and Solid-State Imaging Devices According to First and Second Aspects of the Present Disclosure>
In a conventional imaging element illustrated in
However, the imaging element and the like of the present disclosure include the charge accumulation electrode which is disposed apart from the first electrode so as to face the inorganic oxide semiconductor material layer via an insulating layer. Therefore, when the photoelectric conversion unit is irradiated with light, and the light is photoelectrically converted in the photoelectric conversion unit, charges can be stored in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer in some cases). Therefore, at the time of start of exposure, a charge accumulation portion can be completely depleted and the charge can be erased. As a result, it is possible to suppress occurrence of a phenomenon that a kTC noise increases, a random noise deteriorates, and the quality of an imaged image deteriorates. Note that in the following description, the inorganic oxide semiconductor material layer, or the inorganic oxide semiconductor material layer and the photoelectric conversion layer may be collectively referred to as “inorganic oxide semiconductor material layer and the like”.
In the imaging element and the like of the present disclosure, a value obtained by subtracting a LUMO value of a material constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer is preferably 0 eV or more and less than 0.2 eV, and more preferably 0.1 eV or less. This can achieve smooth transfer of charges (specifically, electrons) generated in the photoelectric conversion layer to the inorganic oxide semiconductor material layer. That is, in this way, by defining the difference between the LUMO value of the material constituting a portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer and the LUMO value of the material constituting the inorganic oxide semiconductor material layer, when carriers (specifically, photoelectrons) generated by photoelectric conversion flow into the inorganic oxide semiconductor material layer from the photoelectric conversion layer, carrier stagnation hardly occurs at an interface between the photoelectric conversion layer and the inorganic oxide semiconductor material layer. Furthermore, carrier transport capability of the photoelectric conversion layer and the inorganic oxide semiconductor material layer as a whole can be improved. As a result, it is possible to provide an imaging element and the like having no adverse effect on photoresponsiveness of the imaging element and the like and having excellent transfer characteristics of charges accumulated in the photoelectric conversion layer.
Here, the “portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer” refers to a portion of the photoelectric conversion layer located in a region corresponding to 10% or less of the thickness of the photoelectric conversion layer based on an interface between the inorganic oxide semiconductor material layer and the photoelectric conversion layer (that is, a region extending from 0% to 10% of the thickness of the photoelectric conversion layer). The LUMO value of the material constituting the portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer is an average value in the portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer, and the work function/LUMO value of the material constituting the inorganic oxide semiconductor material layer is an average value in the inorganic oxide semiconductor material layer.
In the imaging element and the like of the present disclosure including the preferable forms described above, the inorganic oxide semiconductor material layer is desirably constituted by the same material constituting the first electrode (or a material containing the same material as the material constituting the first electrode) from viewpoints of simplification of the configuration and simplification of the manufacturing process.
In the imaging element and the like of the present disclosure including the preferable forms described above, the inorganic oxide semiconductor material layer can contain indium-gallium-zinc composite oxide (IGZO). Furthermore, in the imaging element and the like of the present disclosure including the preferable forms described above, the inorganic oxide semiconductor material layer generally contains a conductive inorganic oxide semiconductor material that is transparent to incident light. Alternatively, in the imaging element and the like of the present disclosure including the above preferable forms described above, the inorganic oxide semiconductor material layer can contain at least two elements selected from the group consisting of indium, tungsten, tin, and zinc. In this case, the inorganic oxide semiconductor material layer does not need to contain a gallium atom. That is, specifically, the inorganic oxide semiconductor material layer can contain indium-tungsten oxide (IWO) which is a material obtained by adding tungsten (W) to indium oxide, indium-tungsten-zinc oxide (IWZO) which is a material obtained by adding tungsten (W) and zinc (Zn) to indium oxide, indium-tin-zinc oxide (ITZO) which is a material obtained by adding tin (Sn) and zinc (Zn) to indium oxide, or zinc-tin oxide (ZTO). More specifically, the inorganic oxide semiconductor material layer contains In—W oxide, In—Sn oxide, In—Zn oxide, W—Sn oxide, W—Zn oxide, Sn—Zn oxide, In—W—Sn oxide, In—W—Zn oxide, In—Sn—Zn oxide, or In—W—Sn—Zn oxide. Alternatively, the inorganic oxide semiconductor material layer contains indium-tin oxide mixed with or doped with silicon oxide (ITO-SiOX-based material), gallium-zinc oxide (GZO) in which gallium is added as a dopant to zinc oxide, and indium-gallium oxide (IGO) in which indium is added as a dopant to gallium oxide. In IWO, when the total mass of indium oxide and tungsten oxide is 100% by mass, the mass ratio of tungsten oxide is preferably 10% by mass to 30% by mass. Moreover, in IWZO, when the total mass of indium oxide, tungsten oxide, and Zn oxide is 100% by mass, the mass ratios of tungsten oxide and Zn oxide are preferably 2% by mass to 15% by mass and 1% by mass to 3% by mass, respectively. Furthermore, in ITZO, when the total mass of indium oxide, Zn oxide, and Sn oxide is 100% by mass, the mass ratios of tungsten oxide and tin oxide are preferably 3% by mass to 10% by mass and 10% by mass to 17% by mass, respectively. However, the present disclosure is not limited thereto. Alternatively, the inorganic oxide semiconductor material layer can also contain a transparent conductive material described later.
Moreover, in the imaging element and the like of the present disclosure including the preferable forms described above, the thickness of the inorganic oxide semiconductor material layer can be 1×10−8 m to 1.5×10−7 m, preferably 2×10−8 m to 1.0×10−7 m, and more preferably 3×10−8 m to 1.0×10−7 m.
Moreover, in the imaging element and the like of the present disclosure including the various preferable forms described above, the mobility of a material constituting the inorganic oxide semiconductor material layer is preferably 10 cm2/V·s or more.
Moreover, in the imaging element and the like of the present disclosure including the preferable forms described above, the inorganic oxide semiconductor material layer can be amorphous (for example, amorphous without a local crystal structure). Whether or not the inorganic oxide semiconductor material layer is amorphous can be determined on the basis of X-ray diffraction analysis.
Moreover, the imaging element and the like of the present disclosure including the preferable forms described above can have a form in which
light is incident from the second electrode,
surface roughness Ra of the inorganic oxide semiconductor material layer at an interface between the photoelectric conversion layer and the inorganic oxide semiconductor material layer is 1.5 nm or less, and a value of root mean square roughness Rq of the inorganic oxide semiconductor material layer is 2.5 nm or less. Values of surface roughness Ra and Rq are determined on the basis of the provisions of HS B0601:2013. Such smoothness of the inorganic oxide semiconductor material layer at the interface between the photoelectric conversion layer and the inorganic oxide semiconductor material layer can suppress surface scattering reflection in the inorganic oxide semiconductor material layer and improve bright current characteristics in photoelectric conversion. A form can be adopted in which surface roughness Ra of the charge accumulation electrode is 1.5 nm or less, and a value of root mean square roughness Rq of the charge accumulation electrode is 2.5 nm or less.
The inorganic oxide semiconductor material layer may have a single layer configuration or a multilayer configuration. Furthermore, a material constituting the inorganic oxide semiconductor material layer located above the charge accumulation electrode may be different from a material constituting the inorganic oxide semiconductor material layer located above the first electrode.
The inorganic oxide semiconductor material layer can be formed, for example, on the basis of a sputtering method. Specifically, a sputtering method using a parallel plate sputtering apparatus or a DC magnetron sputtering apparatus as a sputtering apparatus, using an argon (Ar) gas as a process gas, and using a desired sintered body such as an IGZO sintered body, an InZnO sintered body, or an InWO sintered body as a target can be exemplified.
Note that the energy level of the inorganic oxide semiconductor material layer can be controlled by controlling the amount of oxygen gas introduced (oxygen gas partial pressure) when the inorganic oxide semiconductor material layer is formed on the basis of the sputtering method. Specifically, an oxygen gas partial pressure<=(O2 gas pressure)/(total pressure of Ar gas and O2 gas)>when the composite oxide layer is formed on the basis of the sputtering method is preferably set to 0.005 to 0.02. Moreover, in the imaging element and the like of the present disclosure, the oxygen content in the inorganic oxide semiconductor material layer can be less than that in the stoichiometric composition. Here, the energy level of the inorganic oxide semiconductor material layer can be controlled on the basis of the oxygen content. As the oxygen content is lower than the oxygen content in the stoichiometric composition, that is, as oxygen deficiency increases, the energy level can be deepened.
In the imaging element and the like of the present disclosure, the inorganic oxide semiconductor material layer preferably has light transmittance of 65% or more with respect to light having a wavelength of 400 nm to 660 nm. Furthermore, the charge accumulation electrode also preferably has light transmittance of 65% or more with respect to light having a wavelength of 400 nm to 660 nm. The charge accumulation electrode preferably has a sheet resistance value of 3×10Ω/□ to 1×103Ω/□.
The imaging element and the like of the present disclosure can have a form in which
a semiconductor substrate is further included, and
the photoelectric conversion unit is disposed above the semiconductor substrate. Note that the first electrode, the charge accumulation electrode, and the second electrode are connected to a drive circuit described later.
The second electrode located on a light incident side may be common to a plurality of imaging elements and the like. That is, the second electrode can be a so-called solid electrode. The photoelectric conversion layer may be common to a plurality of imaging elements and the like. That is, one photoelectric conversion layer may be formed in the plurality of imaging elements and the like, or may be disposed for each of the imaging elements and the like. The inorganic oxide semiconductor material layer is preferably disposed for each of the imaging elements and the like, but may be common to a plurality of imaging elements and the like in some cases. That is, for example, by disposing a charge transfer control electrode described later between the imaging elements, one inorganic oxide semiconductor material layer may be formed in the plurality of imaging elements and the like.
Moreover, the imaging element and the like of the present disclosure including the various preferable forms described above can have a form in which the first electrode extends in an opening formed in the insulating layer to be connected to the inorganic oxide semiconductor material layer. Alternatively, a form can be adopted in which the inorganic oxide semiconductor material layer extends in an opening formed in the insulating layer to be connected to the first electrode. In this case,
a form can be adopted in which an edge of a top surface of the first electrode is covered with the insulating layer,
the first electrode is exposed on a bottom surface of the opening, and
when a surface of the insulating layer in contact with the top surface of the first electrode is referred to as a first surface, and a surface of the insulating layer in contact with a portion of the inorganic oxide semiconductor material layer facing the charge accumulation electrode is referred to as a second surface, a side surface of the opening has an inclination widening from the first surface toward the second surface. Moreover, a form can be adopted in which the side surface of the opening having an inclination widening from the first surface toward the second surface is located on the charge accumulation electrode side.
Moreover, the imaging element and the like including the charge accumulation electrode of the present disclosure including the various preferable forms and configurations described above can have a configuration in which
a control unit disposed on a semiconductor substrate and having a drive circuit is further included,
the first electrode and the charge accumulation electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode and applies a potential V12 to the charge accumulation electrode, and charges are accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer), and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode and applies a potential V22 to the charge accumulation electrode, and the charges accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer) are read out by the control unit via the first electrode. However, the potential of the first electrode is higher than the potential of the second electrode, and
V12≥V11 and V22<V21 are satisfied
Moreover, the imaging element and the like of the present disclosure including the various preferable forms described above can further include a transfer control electrode (charge transfer electrode) disposed apart from the first electrode and the charge accumulation electrode so as to face the inorganic oxide semiconductor material layer via an insulating layer between the first electrode and the charge accumulation electrode. The image imaging element and the like of the present disclosure having such a form are referred to as “imaging element and the like of the present disclosure including a transfer control electrode” for convenience.
In addition, the imaging element and the like of present disclosure including a transfer control electrode can have a configuration in which
a control unit disposed on a semiconductor substrate and having a drive circuit is further included,
the first electrode, the charge accumulation electrode, and the transfer control electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode, applies a potential V12 to the charge accumulation electrode, and applies a potential V13 to the transfer control electrode, and charges are accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer), and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode, applies a potential V22 to the charge accumulation electrode, and applies a potential V23 to the transfer control electrode, and the charges accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer) are read out by the control unit via the first electrode. However, the potential of the first electrode is higher than the potential of the second electrode, and
V12>V13 and V22≤V23≤V21 are satisfied
Moreover, the imaging element and the like of the present disclosure including the various preferable forms described above can further include a charge discharge electrode connected to the inorganic oxide semiconductor material layer and disposed apart from the first electrode and the charge accumulation electrode. The image imaging element and the like of the present disclosure having such a form are referred to as “imaging element and the like of the present disclosure including a charge discharge electrode” for convenience. In addition, the imaging element and the like of the present disclosure including a charge discharge electrode can have a form in which the charge discharge electrode is disposed so as to surround the first electrode and the charge accumulation electrode (that is, in a frame shape). The charge discharge electrode can be shared by (common to) a plurality of imaging elements and the like. In addition, in this case,
a form can be adopted in which the inorganic oxide semiconductor material layer extends in a second opening formed in the insulating layer to be connected to the charge discharge electrode,
an edge of a top surface of the charge discharge electrode is covered with the insulating layer,
the charge discharge electrode is exposed on a bottom surface of the second opening, and
when a surface of the insulating layer in contact with the top surface of the charge discharge electrode is referred to as a third surface, and a surface of the insulating layer in contact with a portion of the inorganic oxide semiconductor material layer facing the charge accumulation electrode is referred to as a second surface, a side surface of the second opening has an inclination widening from the third surface toward the second surface.
Moreover, the imaging element and the like of the present disclosure including a charge discharge electrode can have a configuration in which
a control unit disposed on a semiconductor substrate and having a drive circuit is further included,
the first electrode, the charge accumulation electrode, and the charge discharge electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode, applies a potential V12 to the charge accumulation electrode, and applies a potential Via to the charge discharge electrode, and charges are accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer), and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode, applies a potential V22 to the charge accumulation electrode, and applies a potential V24 to the charge discharge electrode, and the charges accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer) are read out by the control unit via the first electrode. However, the potential of the first electrode is higher than the potential of the second electrode, and
V14≥V11 and V24<V21 are satisfied
Moreover, in the various preferable forms described above in the imaging element and the like of the present disclosure, the charge accumulation electrode can include a plurality of charge accumulation electrode segments. The imaging element and the like of the present disclosure having such a form are referred to as “imaging element and the like of the present disclosure including a plurality of charge accumulation electrode segments” for convenience. The number of charge accumulation electrode segments only needs to be two or more. In addition, the imaging element and the like of the present disclosure including a plurality of charge accumulation electrode segments can have a form in which,
in a case where different potentials are applied to N charge accumulation electrode segments,
in a case where the potential of the first electrode is higher than that of the second electrode, in a charge transfer period, a potential applied to a charge accumulation electrode segment located closest to the first electrode (first photoelectric conversion unit segment) is higher than a potential applied to a charge accumulation electrode segment located farthest from the first electrode (N-th photoelectric conversion unit segment), and
in a case where the potential of the first electrode is lower than that of the second electrode, in the charge transfer period, the potential applied to the charge accumulation electrode segment located closest to the first electrode (first photoelectric conversion unit segment) is lower than the potential applied to the charge accumulation electrode segment located farthest from the first electrode (N-th photoelectric conversion unit segment).
The imaging element and the like of the present disclosure including the various preferable forms described above can have a configuration in which
on the semiconductor substrate, at least a floating diffusion layer and an amplification transistor constituting a control unit are disposed, and
the first electrode is connected to the floating diffusion layer and a gate portion of the amplification transistor. In addition, in this case, moreover,
a configuration can be adopted in which
on the semiconductor substrate, a reset transistor and a selection transistor constituting the control unit are further disposed,
the floating diffusion layer is connected to one source/drain region of the reset transistor, and
one source/drain region of the amplification transistor is connected to one source/drain region of the selection transistor, and the other source/drain region of the selection transistor is connected to a signal line.
Moreover, the imaging element and the like of the present disclosure including the various preferable forms described above can have a form in which the charge accumulation electrode is larger than the first electrode. When the area of the charge accumulation electrode is represented by S1′, and the area of the first electrode is represented by S1,
4≤S1′/S1
is preferably satisfied although not limited.
Alternatively, examples of a modification of the imaging element and the like of the present disclosure including the various preferable forms described above include imaging elements of the first to sixth configurations described below. That is, in each of the imaging elements of the first to sixth configurations in the imaging element and the like of the present disclosure including the various preferable forms described above,
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
in each of the imaging elements of the first to third configurations, the charge accumulation electrode includes N charge accumulation electrode segments,
in each of the imaging elements of the fourth and fifth configurations, the charge accumulation electrode includes N charge accumulation electrode segments disposed apart from one another,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment, and
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode. Here, the “photoelectric conversion layer segment” refers to a segment formed by laminating the photoelectric conversion layer and the inorganic oxide semiconductor material layer.
In addition, in the imaging element of the first configuration, the thickness of an insulating layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. Furthermore, in the imaging element of the second configuration, the thickness of a photoelectric conversion layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. Note that in a photoelectric conversion layer segment, the thickness of the photoelectric conversion layer segment may be changed by changing the thickness of the photoelectric conversion layer portion and keeping the thickness of the inorganic oxide semiconductor material layer portion constant. Furthermore, the thickness of the photoelectric conversion layer segment may be changed by keeping the thickness of the photoelectric conversion layer portion constant and changing the thickness of the inorganic oxide semiconductor material layer portion. Furthermore, the thickness of the photoelectric conversion layer segment may be changed by changing the thickness of the photoelectric conversion layer portion and changing the thickness of the inorganic oxide semiconductor material layer portion. Moreover, in the imaging element of the third configuration, materials constituting an insulating layer segment are different between adjacent photoelectric conversion unit segments. Furthermore, in the imaging element of the fourth configuration, materials constituting a charge accumulation electrode segment are different between adjacent photoelectric conversion unit segments. Moreover, in the imaging element of the fifth configuration, the area of a charge accumulation electrode segment is gradually reduced from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. The area may be reduced continuously or stepwise.
Alternatively, in the imaging element of the sixth configuration in the imaging element and the like of the present disclosure including the various preferable forms described above, if a lamination direction of the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer is defined as a Z direction, and a direction of separating from the first electrode is defined as an X direction, when a laminated portion where the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode. The change in the cross-sectional area may be a continuous change or a step-like change.
In each of the imaging elements of the first and second configurations, the N photoelectric conversion layer segments are disposed continuously, the N insulating layer segments are also disposed continuously, and the N charge accumulation electrode segments are also disposed continuously. In each of the imaging elements of the third and fifth configurations, the N photoelectric conversion layer segments are disposed continuously. Furthermore, in each of the imaging elements of the fourth and fifth configurations, the N insulating layer segments are disposed continuously. Meanwhile, in the imaging element of the third configuration, the N insulating layer segments are disposed so as to correspond to the respective photoelectric conversion unit segments. Moreover, in each of the imaging elements of the fourth and fifth configurations, and in some cases, in the imaging element of the third configuration, the N charge accumulation electrode segments are disposed so as to correspond to the respective photoelectric conversion unit segments. In addition, in each of the imaging elements of the first to sixth configurations, the same potential is applied to all the charge accumulation electrode segments. Alternatively, in each of the imaging elements of the fourth and fifth configurations, and in some cases, in the imaging element of the third configuration, different potentials may be applied to the N charge accumulation electrode segments.
In the imaging element and the like of the present disclosure including the imaging elements of the first to sixth configurations, the thickness of an insulating layer segment is defined, or the thickness of a photoelectric conversion layer segment is defined, or the materials constituting the insulating layer segments are different, or the materials constituting the charge accumulation electrode segments are different, or the area of the charge accumulation electrode segment is defined, or the cross-sectional area of the laminated portion is defined. Therefore, a kind of charge transfer gradient is formed, and charges generated by photoelectric conversion can be transferred to the first electrode more easily and reliably. In addition, as a result, it is possible to prevent generation of afterimages and transfer residuals.
In each of the imaging elements of the first to fifth configurations, a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, but it is determined on the basis of the X direction whether or not a photoelectric conversion unit segment is located apart from the first electrode. Furthermore, in the imaging element of the sixth configuration, the direction of separating from the first electrode is defined as the X direction, and the “X direction” is defined as follows. That is, a pixel region in which a plurality of imaging elements or laminated imaging elements is arrayed includes pixels regularly arrayed two-dimensionally, that is, in the X and Y directions. In a case where the planar shape of the pixel is rectangular, a direction in which a side closest to the first electrode extends is defined as the Y direction, and a direction orthogonal to the Y direction is defined as the X direction. Alternatively, in a case where the planar shape of the pixel is an arbitrary shape, the overall direction including a line segment or a curve closest to the first electrode is defined as the Y direction, and a direction orthogonal to the Y direction is defined as the X direction.
Hereinafter, regarding the imaging elements of the first to sixth configurations, a case where the potential of the first electrode is higher than that of the second electrode will be described.
In the imaging element of the first configuration, the thickness of an insulating layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. However, the thickness of an insulating layer segment preferably increases gradually, thereby forming a kind of charge transfer gradient. Then, when a state of |V12|≥|V11| is reached in a charge accumulation period, the n-th photoelectric conversion unit segment can accumulate more charges than the (n+1)-th photoelectric conversion unit segment, a stronger electric field is applied to the n-th photoelectric conversion unit segment than to the (n+1)-th photoelectric conversion unit segment, and a flow of charges from the first photoelectric conversion unit segment to the first electrode can be reliably prevented. Furthermore, when a state of |V22|<|V21| is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
In the imaging element of the second configuration, the thickness of a photoelectric conversion layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. However, the thickness of a photoelectric conversion layer segment preferably increases gradually, thereby forming a kind of charge transfer gradient. Then, when a state of |V12|≥|V11| is reached in a charge accumulation period, a stronger electric field is applied to the n-th photoelectric conversion unit segment than to the (n+1)-th photoelectric conversion unit segment, and a flow of charges from the first photoelectric conversion unit segment to the first electrode can be reliably prevented. Furthermore, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
In the imaging element of the third configuration, materials constituting an insulating layer segment are different between adjacent photoelectric conversion unit segments, and this forms a kind of charge transfer gradient. A value of the relative dielectric constant of a material constituting an insulating layer segment preferably decreases gradually from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. Then, by adopting such a configuration, in a charge accumulation period, when a state of V12≥V11 is reached, the n-th photoelectric conversion unit segment can accumulate more charges than the (n+1)-th photoelectric conversion unit segment. Furthermore, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
In the imaging element of the fourth configuration, materials constituting a charge accumulation electrode segment are different between adjacent photoelectric conversion unit segments, and this forms a kind of charge transfer gradient. A value of the work function of a material constituting an insulating layer segment preferably increases gradually from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. In addition, by adopting such a configuration, a potential gradient which is advantageous for signal charge transfer can be formed without depending on whether the voltage is positive or negative.
In the imaging element of the fifth configuration, the area of a charge accumulation electrode segment is gradually reduced from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment, and this forms a kind of charge transfer gradient. Therefore, when a state of V12≥V11 is reached in a charge accumulation period, the n-th photoelectric conversion unit segment can accumulate more charges than the (n+1)-th photoelectric conversion unit segment. Furthermore, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
In the imaging element of the sixth configuration, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode, and this forms a kind of charge transfer gradient. Specifically, by adopting a configuration in which the thickness of the cross section of the laminated portion is constant and the width of the cross section of the laminated portion becomes narrower as the laminated portion goes away from the first electrode, as described in the imaging element of the fifth configuration, when a state of V12≥V11 is reached in a charge accumulation period, a region close to the first electrode can accumulate more charges than a region far from the first electrode. Therefore, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from a region close to the first electrode to the first electrode and a flow of charges from a region far from the first electrode to a region close to the first electrode can be reliably ensured. Meanwhile, by adopting a configuration in which the width of the cross section of the laminated portion is constant, and the thickness of the cross section of the laminated portion, specifically, the thickness of an insulating layer segment gradually increases, as described in the imaging element of the first configuration, when a state of V12≥V11 is reached in a charge accumulation period, a region close to the first electrode can accumulate more charges than a region far from the first electrode, a stronger electric field is applied to the region close to the first electrode than to the region far from the first electrode, and a flow of charges from the region close to the first electrode to the first electrode can be reliably prevented. Then, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from a region close to the first electrode to the first electrode and a flow of charges from a region far from the first electrode to a region close to the first electrode can be reliably ensured. Furthermore, by adopting a configuration in which the thickness of the photoelectric conversion layer segment gradually increases, as described in the imaging element of the second configuration, when a state of V12≥V11 is reached in a charge accumulation period, a stronger electric field is applied to the region close to the first electrode than to the region far from the first electrode, and a flow of charges from the region close to the first electrode to the first electrode can be reliably prevented. Then, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from a region close to the first electrode to the first electrode and a flow of charges from a region far from the first electrode to a region close to the first electrode can be reliably ensured.
A modification of the solid-state imaging devices according to the first and second aspects of the present disclosure can be
a solid-state imaging device including a plurality of the imaging elements of the first to sixth configurations, in which
the plurality of imaging elements constitutes an imaging element block, and
the first electrode is shared by the plurality of imaging elements constituting the imaging element block. A solid-state imaging device having such a configuration is referred to as “solid-state imaging device of first configuration” for convenience. Alternatively, a modification of the solid-state imaging devices according to the first and second aspects of the present disclosure can be,
a solid-state imaging device including a plurality of the imaging elements of the first to sixth configurations or a plurality of laminated imaging elements each including at least one of the imaging elements of the first to sixth configurations,
the plurality of imaging elements or laminated imaging elements constitutes an imaging element block, and
the first electrode is shared by the plurality of imaging elements or laminated imaging elements constituting the imaging element block. A solid-state imaging device having such a configuration is referred to as “solid-state imaging device of second configuration” for convenience. In addition, if the first electrode is shared by the plurality of imaging elements constituting the imaging element block in this way, the configuration and structure in a pixel region in which a plurality of imaging elements is arrayed can be simplified and miniaturized.
In each of the solid-state imaging devices of the first and second configurations, one floating diffusion layer is disposed for a plurality of imaging elements (one imaging element block). Here, the plurality of imaging elements disposed for one floating diffusion layer may be constituted by a plurality of first type imaging elements described later, or may be constituted by at least one first type imaging element and one or more second type imaging elements described later. In addition, by appropriately controlling the timing of a charge transfer period, a plurality of imaging elements can share one floating diffusion layer. The plurality of imaging elements is operated in cooperation to be connected as an imaging element block to a drive circuit described later. That is, the plurality of imaging elements constituting the imaging element block is connected to one drive circuit. However, the charge accumulation electrode is controlled for each of the imaging elements. Furthermore, the plurality of imaging elements can share one contact hole portion. As for an arrangement relationship between the first electrode shared by the plurality of imaging elements and the charge accumulation electrodes of the imaging elements, there is also a case where the first electrode is disposed adjacent to the charge accumulation electrodes of the imaging elements. Alternatively, there is also a case where the first electrode is disposed adjacent to some of the charge accumulation electrodes of the plurality of imaging elements, and is not disposed adjacent to the remaining charge accumulation electrodes of the plurality of imaging elements. In this case, transfer of charges from the rest of the plurality of imaging elements to the first electrode is transfer via some of the plurality of imaging elements. A distance between a charge accumulation electrode constituting an imaging element and a charge accumulation electrode constituting an imaging element (referred to as “distance A” for convenience) is preferably longer than a distance between the first electrode and a charge accumulation electrode in an imaging element adjacent to the first electrode (referred to as “distance B” for convenience) in order to ensure transfer of charges from each of the imaging elements to the first electrode. Furthermore, a value of the distance A is preferably longer as an imaging element is located farther from the first electrode.
Moreover, the imaging element and the like of the present disclosure including the various preferable forms described above can have a form in which light is incident from the second electrode side, and a light shielding layer is formed on the light incident side of the second electrode. Alternatively, a form can be adopted in which light is incident from the second electrode side, and light is not incident on the first electrode (in some cases, the first electrode and the transfer control electrode). In addition, in this case, a configuration can be adopted in which a light shielding layer is formed above the first electrode (in some cases, the first electrode and the transfer control electrode) on the light incident side of the second electrode. Alternatively, a configuration can be adopted in which an on-chip micro lens is disposed above the charge accumulation electrode and the second electrode, and light incident on the on-chip micro lens is collected by the charge accumulation electrode. Here, the light shielding layer may be disposed above the light incident side surface of the second electrode, or may be disposed on the light incident side surface of the second electrode. In some cases, a light shielding layer may be formed in the second electrode. Examples of a material constituting the light shielding layer include chromium (Cr), copper (Cu), aluminum (Al), tungsten (W), and a resin that does not transmit light (for example, polyimide resin).
Specific examples of the imaging element and the like of the present disclosure include: an imaging element including a photoelectric conversion layer or a photoelectric conversion unit that absorbs blue light (light of 425 nm to 495 nm) (referred to as “first type blue light photoelectric conversion layer” or “first type blue light photoelectric conversion unit” for convenience) and sensitive to blue light (referred to as “first type blue light imaging element” for convenience); an imaging element including a photoelectric conversion layer or a photoelectric conversion unit that absorbs green light (light of 495 nm to 570 nm) (referred to as “first type green light photoelectric conversion layer” or “first type green light photoelectric conversion unit” for convenience) and sensitive to green light (referred to as “first type green light imaging element” for convenience); and an imaging element including a photoelectric conversion layer or a photoelectric conversion unit that absorbs red light (light of 620 nm to 750 nm) (referred to as “first type red light photoelectric conversion layer” or “first type red light photoelectric conversion unit” for convenience) and sensitive to red light (referred to as “first type red light imaging element” for convenience). Furthermore, a conventional imaging element not including a charge accumulation electrode and sensitive to blue light is referred to as “second type blue light imaging element” for convenience, a conventional imaging element not including a charge accumulation electrode and sensitive to green light is referred to as “second type green light imaging element” for convenience, a conventional imaging element not including a charge accumulation electrode and sensitive to red light is referred to as “second type red light imaging element” for convenience, a photoelectric conversion layer or a photoelectric conversion unit constituting the second type blue light imaging element is referred to as “second type blue light photoelectric conversion layer” or “second type blue light photoelectric conversion unit” for convenience, a photoelectric conversion layer or a photoelectric conversion unit constituting the second type green light imaging element is referred to as “second type green light photoelectric conversion layer” or “second type green light photoelectric conversion unit” for convenience, and a photoelectric conversion layer or a photoelectric conversion unit constituting the second type red light imaging element is referred to as “second type red light photoelectric conversion layer” or “second type red light photoelectric conversion unit” for convenience.
Specific examples of the laminated imaging element including a charge accumulation electrode include:
[A] a configuration and a structure in which the first type blue light photoelectric conversion unit, the first type green light photoelectric conversion unit, and the first type red light photoelectric conversion unit are laminated in the vertical direction, and
the control units of the first type blue light imaging element, the first type green light imaging element, and the first type red light imaging element are disposed on a semiconductor substrate;
[B] a configuration and a structure in which the first type blue light photoelectric conversion unit and the first type green light photoelectric conversion unit are laminated in the vertical direction,
the second type red light photoelectric conversion unit is disposed below the two first type photoelectric conversion units, and
the control units of the first type blue light imaging element, the first type green light imaging element, and the second type red light imaging element are disposed on a semiconductor substrate;
[C] a configuration and a structure in which the second type blue light photoelectric conversion unit and the second type red light photoelectric conversion unit are disposed below the first type green light photoelectric conversion unit, and
the control units of the first type green light imaging element, the second type blue light imaging element, and the second type red light imaging element are disposed on a semiconductor substrate; and
[D] a configuration and a structure in which the second type green light photoelectric conversion unit and the second type red light photoelectric conversion unit are disposed below the first type blue light photoelectric conversion unit, and
the control units of the first type blue light imaging element, the second type green light imaging element, and the second type red light imaging element are disposed on a semiconductor substrate. The photoelectric conversion units of these imaging elements are preferably disposed in the vertical direction in order of the blue light photoelectric conversion unit, the green light photoelectric conversion unit, and the red light photoelectric conversion unit from the light incident direction, or in order of the green light photoelectric conversion unit, the blue light photoelectric conversion unit, and the red light photoelectric conversion unit from the light incident direction. This is because light having a shorter wavelength is more efficiently absorbed on an incident surface side. Since red has the longest wavelength among the three colors, the red light photoelectric conversion unit is preferably located in the lowermost layer as viewed from the light incident surface. A laminated structure of these imaging elements constitutes one pixel. Furthermore, a first type near-infrared photoelectric conversion unit (or an infrared photoelectric conversion unit) may be included. Here, preferably, the photoelectric conversion layer of the first type infrared photoelectric conversion unit includes, for example, an organic material, and is disposed as the lowermost layer of the laminated structure of the first type imaging elements above the second type imaging element. Alternatively, a second type near-infrared photoelectric conversion unit (or an infrared photoelectric conversion unit) may be disposed below the first type photoelectric conversion unit.
In the first type imaging element, for example, the first electrode is formed on an interlayer insulating layer disposed on a semiconductor substrate. An imaging element formed on a semiconductor substrate can be a backside irradiation type or a frontside irradiation type.
In a case where the photoelectric conversion layer includes an organic material, the photoelectric conversion layer can have any one of the following four forms.
(1) The photoelectric conversion layer is constituted by a p-type organic semiconductor.
(2) The photoelectric conversion layer is constituted by an n-type organic semiconductor.
(3) The photoelectric conversion layer is constituted by a laminated structure of p-type organic semiconductor layer/n-type organic semiconductor layer. The photoelectric conversion layer is constituted by a laminated structure of p-type organic semiconductor layer/mixed layer (bulk heterostructure) of p-type organic semiconductor and n-type organic semiconductor/n-type organic semiconductor layer. The photoelectric conversion layer is constituted by a laminated structure of a mixed layer (bulk heterostructure) of a p-type organic semiconductor layer/p-type organic semiconductor and an n-type organic semiconductor. The photoelectric conversion layer is constituted by a laminated structure of a mixed layer (bulk heterostructure) of an n-type organic semiconductor layer/p-type organic semiconductor and an n-type organic semiconductor.
(4) The photoelectric conversion layer is constituted by a mixture (bulk heterostructure) of a p-type organic semiconductor and an n-type organic semiconductor.
However, the laminating order can be arbitrarily exchanged.
Examples of the p-type organic semiconductor include a naphthalene derivative, an anthracene derivative, a phenanthrene derivative, a pyrene derivative, a perylene derivative, a tetracene derivative, a pentacene derivative, a quinacridone derivative, a thiophene derivative, a thienothiophene derivative, a benzothiophene derivative, a benzothienobenzothiophene derivative, a triallylamine derivative, a carbazole derivative, a perylene derivative, a picene derivative, a chrysene derivative, a fluoranthene derivative, a phthalocyanine derivative, a subphthalocyanine derivative, a subporphyrazine derivative, a metal complex having a heterocyclic compound as a ligand, a polythiophene derivative, a polybenzothiadiazole derivative, and a polyfluorene derivative. Examples of the n-type organic semiconductor include a fullerene and a fullerene derivative <for example, C60, a fullerene such as C70 or C74 (higher fullerene), an endohedral fullerene, or the like, or a fullerene derivative (for example, a fullerene fluoride, a PCBM fullerene compound, a fullerene multimer, or the like)>, an organic semiconductor with larger (deeper) HOMO and LUMO than a p-type organic semiconductor, and a transparent inorganic metal oxide. Specific examples of the n-type organic semiconductor include a heterocyclic compound containing a nitrogen atom, an oxygen atom, or a sulfur atom. Examples thereof include an organic molecule and an organic metal complex containing a pyridine derivative, a pyrazine derivative, a pyrimidine derivative, a triazine derivative, a quinoline derivative, a quinoxaline derivative, an isoquinoline derivative, an acridine derivative, a phenazine derivative, a phenanthroline derivative, a tetrazole derivative, a pyrazole derivative, an imidazole derivative, a thiazole derivative, an oxazole derivative, an imidazole derivative, a benzimidazole derivative, a benzotriazole derivative, a benzoxazole derivative, a benzoxazole derivative, a carbazole derivative, a benzofuran derivative, a dibenzofuran derivative, a subporphyrazine derivative, a polyphenylenevinylene derivative, a polybenzothiadiazole derivative, a polyfluorene derivative, and the like in a part of a molecular skeleton thereof, and a subphthalocyanine derivative. Examples of a group and the like contained in the fullerene derivative include a halogen atom; a linear, branched, or cyclic alkyl group or phenyl group; a group having a linear or condensed aromatic compound; a group having a halide; a partial fluoroalkyl group; a perfluoroalkyl group; a silylalkyl group; a silylalkoxy group; an arylsilyl group; an arylsulfanyl group; an alkylsulfanyl group; an arylsulfonyl group; an alkylsulfonyl group; an arylsulfide group; an alkylsulfide group; an amino group; an alkylamino group; an arylamino group; a hydroxy group; an alkoxy group; an acylamino group; an acyloxy group; a carbonyl group; a carboxy group; a carboxamide group; a carboalkoxy group; an acyl group; a sulfonyl group; a cyano group; a nitro group; a group having a chalcogenide; a phosphine group; a phosphone group, and derivatives thereof. The thickness of the photoelectric conversion layer including an organic material (also referred as “organic photoelectric conversion layer”) is not limited, but is for example, 1×10−8 m to 5×10−7 m, preferably 2.5×10−8 m to 3×10−7 m, more preferably 2.5×10−8 m to 2×10−7 m, and still more preferably 1×10−7 m to 1.8×10−7 m. Note that the organic semiconductor is often classified into a p-type and an n-type. The p-type means that holes are easily transported, and the n-type means that electrons are easily transported without being limited to interpretation that the organic semiconductor has holes or electrons as many thermally-excited carriers like an inorganic semiconductor.
Alternatively, examples of a material constituting the organic photoelectric conversion layer that photoelectrically converts green light include a rhodamine-based dye, a melacyanine-based dye, a quinacridone derivative, a subphthalocyanine dye (subphthalocyanine derivative), and the like. Examples of a material constituting the organic photoelectric conversion layer that photoelectrically converts blue light include a coumarinic acid dye, tris-8-hydryxyquinolialuminium (Alq3), a melacyanine-based dye, and the like. Examples of a material constituting the organic photoelectric conversion layer that photoelectrically converts red light include a phthalocyanine-based dye and a subphthalocyanine-based dye (subphthalocyanine derivative).
Alternatively, examples of the inorganic material constituting the photoelectric conversion layer include crystalline silicon, amorphous silicon, microcrystalline silicon, crystalline selenium, amorphous selenium, a chalcopyrite compound such as CIGS(CuInGaSe), CIS(CuInSe2), CuInS2, CuAlS2, CuAlSe2, CuGaS2, CuGaSe2, AgAlS2, AgAlSe2, AgInS2, or AgInSe2, a group III-V compound such as GaAs, InP, AlGaAs, InGaP, AlGaInP, or InGaAsP, and a compound semiconductor such as CdSe, CdS, In2Se3, In2S3, Bi2Se3, Bi2S3, ZnSe, ZnS, PbSe, or PbS. In addition, quantum dots including these materials can also be used for the photoelectric conversion layer.
A single-plate color solid-state imaging device can be constituted by each of the solid-state imaging devices according to the first and second aspects of the present disclosure and the solid-state imaging devices of the first and second configurations.
In the solid-state imaging device including a laminated imaging element according to the second aspect of the present disclosure, unlike a solid-state imaging device including Bayer-array imaging elements (that is, spectroscopy of blue, green, and red light is not performed using a color filter layer), one pixel is constituted by laminating imaging elements sensitive to light having a plurality of wavelengths in a light incident direction within the same pixel, and therefore it is possible to improve sensitivity and a pixel density per unit volume. Furthermore, an organic material has a high absorption coefficient. Therefore, the film thickness of the organic photoelectric conversion layer can be thinner than that of a conventional Si-based photoelectric conversion layer, and restriction on leakage of light from an adjacent pixel and an incident angle of light is alleviated. Moreover, in the conventional Si-based imaging element, a false color is generated because interpolation processing is performed among pixels of three colors to generate a color signal. However, the solid-state imaging device including a laminated imaging element according to the second aspect of the present disclosure can suppress generation of a false color. The organic photoelectric conversion layer itself also acts as a color filter layer. Therefore, color separation can be performed even without disposing the color filter layer.
Meanwhile, in the solid-state imaging device according to the first aspect of the present disclosure, use of a color filter layer can alleviate demands on the spectral characteristics of blue, green, and red light, and a mass production property is high. Examples of an array of imaging elements in the solid-state imaging device according to the first aspect of the present disclosure include a Bayer array, an interline array, a G stripe RB checkered array, a G stripe RB complete checkered array, a checkered complementary color array, a stripe array, a diagonal stripe array, a primary color chrominance array, a field chrominance sequential array, a frame chrominance sequential array, a MOS-type array, an improved MOS-type array, a frame interleaved array, and a field interleaved array. Here, one imaging element constitutes one pixel (or sub-pixel).
Examples of the color filter layer (wavelength selection means) include a filter layer that transmits not only red, green, and blue light but also light having a specific wavelength, such as cyan, magenta, or yellow light in some cases. The color filter layer can be constituted not only by an organic material-based color filter layer using an organic compound such as a pigment or a dye but also by a thin film containing an inorganic material such as a photonic crystal, a wavelength selection element that applies a plasmon (color filter layer having a conductor lattice structure with a lattice-like hole structure in a conductive thin film, for example, see Japanese Patent Application Laid-Open No. 2008-177191), or amorphous silicon.
A pixel region in which a plurality of imaging elements and the like of the present disclosure is arrayed includes a plurality of pixels regularly arrayed two-dimensionally. The pixel region usually includes an effective pixel region that actually receives light, amplifies signal charges generated by photoelectric conversion, and reads out the signal charges to a drive circuit, and a black reference pixel region that outputs optical black serving as a black level reference (also referred to as an optical black pixel region (OPB)). The black reference pixel region is usually disposed on an outer periphery of an effective pixel region.
The imaging element and the like of the present disclosure including the various preferable forms described above are irradiated with light, photoelectric conversion occurs in the photoelectric conversion layer, and holes and electrons are carrier-separated. In addition, an electrode from which holes are extracted is referred to as a positive electrode, and an electrode from which electrons are extracted is referred to as a negative electrode. The first electrode constitutes the negative electrode, and the second electrode constitutes the positive electrode.
The first electrode, the charge accumulation electrode, the transfer control electrode, the charge discharge electrode, and the second electrode can each contain a transparent conductive material. The first electrode, the charge accumulation electrode, the transfer control electrode, and the charge discharge electrode may be collectively referred to as “first electrode and the like”. Alternatively, in a case where the imaging elements and the like of the present disclosure are disposed in a plane like a Bayer array, for example, the second electrode can contain a transparent conductive material, and the first electrode and the like can contain a metal material. In this case, specifically, the second electrode located on the light incident side can contain a transparent conductive material, and the first electrode and the like can contain, for example, Al—Nd (alloy of aluminum and neodymium) or ASC (alloy of aluminum, samarium, and copper). An electrode containing a transparent conductive material may be referred to as “transparent electrode”. Here, the band gap energy of the transparent conductive material is 2.5 eV or more, and preferably 3.1 eV or more. Examples of the transparent conductive material constituting the transparent electrode include a conductive metal oxide. Specific examples thereof include indium oxide, indium-tin oxide (ITO, including Sn-doped In2O3, crystalline ITO, and amorphous ITO), Indium-zinc oxide (IZO) obtained by adding indium as a dopant to zinc oxide, indium-gallium oxide (IGO) obtained by adding indium as a dopant to gallium oxide, indium-gallium-zinc oxide (IGZO, In—GaZnO4) obtained by adding indium and gallium as a dopant to zinc oxide, indium-tin-zinc oxide (ITZO) obtained by adding indium and tin as a dopant to zinc oxide, IFO (F-doped In2O3), tin oxide (SnO2), ATO (Sb-doped SnO2), FTO (F-doped SnO2), zinc oxide (including ZnO doped with another element), aluminum-zinc oxide (AZO) to which aluminum is added to zinc oxide as a dopant, gallium-zinc oxide (GZO) to which gallium is added to zinc oxide as a dopant, titanium oxide (TiO2), niobium-titanium oxide (TNO) to which niobium is added to titanium oxide as a dopant, antimony oxide, a spinel type oxide, and an oxide having a YbFe2O4 structure. Alternatively, examples of the transparent electrode include a transparent electrode containing gallium oxide, titanium oxide, niobium oxide, nickel oxide, and the like as a base layer. The thickness of the transparent electrode may be 2×10−8 m to 2×10−7 m, and preferably 3×10−8 m to 1×10−7 m. In a case where the first electrode needs to be transparent, the charge discharge electrode also preferably contains a transparent conductive material from a viewpoint of simplifying a manufacturing process.
Alternatively, in a case where transparency is not required, as a conductive material constituting a negative electrode functioning as an electrode for extracting electrons, the negative electrode is preferably constituted by a conductive material having a low work function (for example, φ=3.5 eV to 4.5 eV). Specific examples thereof include an alkali metal (for example, Li, Na, K, or the like), a fluoride thereof, an oxide thereof, an alkaline earth metal (for example, Mg, Ca, or the like), a fluoride thereof, an oxide thereof, aluminum (Al), zinc (Zn), tin (Sn), thallium (Tl), a sodium-potassium alloy, an aluminum-lithium alloy, a magnesium-silver alloy, a rare earth metal such as indium or ytterbium, and an alloy thereof. Alternatively, examples of a material constituting the negative electrode include a metal such as platinum (Pt), gold (Au), palladium (Pd), chromium (Cr), nickel (Ni), aluminum (Al), silver (Ag), tantalum (Ta), tungsten (W), copper (Cu), titanium (Ti), indium (In), tin (Sn), iron (Fe), cobalt (Co), or molybdenum (Mo), an alloy containing these metal elements, a conductive particle containing these metals, a conductive particle of an alloy containing these metals, a polysilicon containing impurities, a carbon material, an oxide semiconductor material, and a conductive material such as a carbon nanotube or graphene. A laminated structure of layers containing these elements can be also used. Furthermore, examples of the material constituting the negative electrode include an organic material (conductive polymer) such as poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid [PEDOT/PSS]. Furthermore, these conductive materials may be mixed with a binder (polymer) to form a paste or an ink, and the paste or the ink may be cured to be used as an electrode.
As a method for forming a film of the first electrode and the like or the second electrode (negative electrode or positive electrode), a dry method or a wet method can be used. Examples of the dry method include a physical vapor deposition method (PVD method) and a chemical vapor deposition method (CVD method). Examples of a film formation using the principle of the PVD method include a vacuum vapor deposition method using resistance heating or high frequency heating, an electron beam (EB) vapor deposition method, various sputtering methods (magnetron sputtering method, RF-DC coupled bias sputtering method, ECR sputtering method, opposing target sputtering method, or high frequency sputtering method), an ion plating method, a laser ablation method, a molecular beam epitaxy method, and a laser transfer method. Furthermore, examples of the CVD method include a plasma CVD method, a thermal CVD method, an organic metal (MO) CVD method, and an optical CVD method. Meanwhile, examples of the wet method include an electrolytic plating method, an electroless plating method, a spin coating method, an ink jet method, a spray coating method, a stamping method, a micro contact printing method, a flexographic printing method, an offset printing method, a gravure printing method, and a dipping method. Examples of a patterning method include chemical etching such as shadow masking, laser transfer, or photolithography and physical etching using an ultraviolet ray, a laser, and the like. Examples of a technique for planarizing the first electrode and the like or the second electrode include a laser planarization method, a reflow method, and a chemical mechanical polishing (CMP) method.
Examples of a material constituting the insulating layer include not only an inorganic insulating material exemplified by a metal oxide high dielectric insulating material such as a silicon oxide material; silicon nitride (SiNy); or aluminum oxide (Al2O3), but also include an organic insulating material (organic polymer) exemplified by a straight chain hydrocarbon having a functional group capable of bonding to a control electrode at one end, such as polymethyl methacrylate (PMMA); polyvinyl phenol (PVP); polyvinyl alcohol (PVA); polyimide; polycarbonate (PC); polyethylene terephthalate (PET); polystyrene; a silanol derivative (silane coupling agent) such as N-2 (aminoethyl) 3-aminopropyltrimethoxysilane (AEAPTMS), 3-mercaptopropyltrimethoxysilane (MPTMS), or octadecyl trichlorosilane (OTS); a novolac type phenol resin; a fluorine-based resin; octadecanethiol, or dodecyl isocyanate. A combination thereof can be also used. Examples of the silicon oxide material include silicon oxide (SiOX), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), spin on glass (SOG), low dielectric constant insulating material (for example, polyaryl ether, cyclo perfluorocarbon polymer and benzocyclobutene, a cyclic fluorocarbon resin, polytetrafluoroethylene, fluorinated aryl ether, fluorinated polyimide, amorphous carbon, and organic SOG). The insulating layer can have a single-layer configuration or a configuration in which a plurality of layers (for example, two layers) is laminated. In the latter case, by forming an insulating layer/lower layer at least on the charge accumulation electrode and in a region between the charge accumulation electrode and the first electrode, and planarizing the insulating layer/lower layer, the insulating layer/lower layer only needs to be left at least in the region between the charge accumulation electrode and the first electrode, and an insulating layer/upper layer only needs to be formed on the remaining insulating layer/lower layer and the charge accumulation electrode. As a result, planarization of the insulating layer can be achieved reliably. Materials constituting the various interlayer insulating layers and insulating material films only need to be appropriately selected from these materials.
The configuration and structure of the floating diffusion layer, amplification transistor, reset transistor, and selection transistor constituting the control unit can be similar to the configuration and structure of the conventional floating diffusion layer, amplification transistor, reset transistor, and selection transistor. The drive circuit can also have a well-known configuration and structure.
The first electrode is connected to the floating diffusion layer and a gate portion of the amplification transistor, and a contact hole portion only needs to be formed in order to connect the first electrode to the floating diffusion layer and the gate portion of the amplification transistor. Examples of a material constituting the contact hole portion include polysilicon doped with impurities, a high melting point metal such as tungsten, Ti, Pt, Pd, Cu, TiW, TiN, TiNW, WSi2, or MoSi2, a metal silicide, and a laminated structure of layers containing these materials (for example, Ti/TiN/W).
A first carrier blocking layer may be disposed between the inorganic oxide semiconductor material layer and the first electrode, and a second carrier blocking layer may be disposed between the organic photoelectric conversion layer and the second electrode. Furthermore, a first charge injection layer may be disposed between the first carrier blocking layer and the first electrode, and a second charge injection layer may be disposed between the second carrier blocking layer and the second electrode. Examples of a material constituting an electron injection layer include an alkali metal such as lithium (Li), sodium (Na), or potassium (K), a fluoride thereof, an oxide thereof, an alkaline earth metal such as magnesium (Mg) or calcium (Ca), a fluoride thereof, and an oxide thereof.
Examples of a method for forming films of various organic layers include a dry film formation method and a wet film formation method. Examples of the dry film formation method include a vacuum vapor deposition method using resistance heating, high frequency heating, or electron beam heating, a flash vapor deposition method, a plasma vapor deposition method, an EB vapor deposition method, various sputtering methods (a bipolar sputtering method, a direct current sputtering method, a direct current magnetron sputtering method, a high frequency sputtering method, a magnetron sputtering method, an RF-DC coupled bias sputtering method, an ECR sputtering method, a counter target sputtering method, a high frequency sputtering method, and an ion beam sputtering method), a direct current (DC) method, an RF method, a multi-negative electrode method, an activation reaction method, an electric field vapor deposition method, various ion plating methods such as a high frequency ion plating method and a reactive ion plating method, a laser ablation method, a molecular beam epitaxy method, a laser transfer method, and a molecular beam epitaxy method (MBE method). Furthermore, examples of the CVD method include a plasma CVD method, a thermal CVD method, an MOCVD method, and an optical CVD method. Meanwhile, specific examples of the wet method include a spin coating method; an immersion method; a casting method; a micro-contact printing method; a drop casting method; various printing methods such as a screen printing method, an inkjet printing method, an offset printing method, a gravure printing method, and a flexographic printing method; a stamping method; a spraying method; and various coating methods such as an air doctor coater method, a blade coater method, a rod coater method, a knife coater method, a squeeze coater method, a reverse roll coater method, a transfer roll coater method, a gravure coater method, a kiss coater method, a cast coater method, a spray coater method, a slit orifice coater method, and a calendar coater method. In the coating method, examples of a solvent include an organic solvent having a no polarity or low polarity, such as toluene, chloroform, hexane, or ethanol. Examples of a patterning method include chemical etching such as shadow masking, laser transfer, or photolithography and physical etching using an ultraviolet ray, a laser, and the like. Examples of a technique for planarizing various organic layers include a laser planarization method and a reflow method.
Two or more of the imaging elements of the first to sixth configurations described above can be appropriately combined as desired.
As described above, the imaging element or the solid-state imaging device may include an on-chip micro lens or a light shielding layer, if necessary, and includes a drive circuit or wiring for driving the imaging element. If necessary, a shutter for controlling incidence of light on the imaging element may be disposed, or an optical cut filter may be disposed according to a purpose of the solid-state imaging device.
Furthermore, each of the solid-state imaging devices of the first and second configurations can have a form in which one on-chip micro lens is disposed above one of the imaging elements and the like of the present disclosure, or can have a form in which an imaging element block is constituted by two of the imaging elements and the like of the present disclosure, and one on-chip micro lens is disposed above the imaging element block.
For example, in a case where the solid-state imaging device is laminated with a readout integrated circuit (ROIC), by superposing a drive substrate on which a readout integrated circuit and a connection portion containing copper (Cu) are formed, and an imaging element and the like in which a connection portion is formed such that the connection portions come into contact with each other, and bonding the connection portions to each other, lamination can be performed, and the connection portions can be bonded to each other using solder bumps and the like.
Furthermore, the driving method for driving the solid-state imaging devices according to the first and second aspects of the present disclosure can be a solid-state imaging device driving method for repeating,
discharging charges in the first electrode out of the system while charges are accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer) all at once in all the imaging elements, and then
transferring the charges accumulated in the inorganic oxide semiconductor material layer (or the inorganic oxide semiconductor material layer and the photoelectric conversion layer) to the first electrode all at once in all the imaging elements, and sequentially reading out the charges transferred to the first electrode in each of the imaging elements after completion of the transfer.
In such a method for driving a solid-state imaging device, each of the imaging elements has a structure in which light incident from the second electrode side is not incident on the first electrode, and the charges in the first electrode are discharged out of the system while the charges are accumulated in the inorganic oxide semiconductor material layer and the like all at once in all the imaging elements. Therefore, the first electrode can be reliably reset simultaneously in all the imaging elements. Then, thereafter, the charges accumulated in the inorganic oxide semiconductor material layer and the like are transferred to the first electrode all at once in all the imaging elements, and after completion of the transfer, the charges transferred to the first electrode are sequentially read out in each of the imaging elements. Therefore, a so-called global shutter function can be easily implemented.
Examples of the imaging element of the present disclosure include a CCD element, a CMOS image sensor, a contact imaging sensor (CIS), and a charge modulation device (CMD) type signal amplification image sensor. For example, a digital still camera, a video camera, a camcorder, a surveillance camera, a vehicle-mounted camera, a smartphone camera, a game user interface camera, and a biometric authentication camera can be constituted by the solid-state imaging devices according to the first and second aspects of the present disclosure and the solid-state imaging devices of the first and second configurations.
Example 1 relates to the imaging element of the present disclosure, the laminated imaging element of the present disclosure, and the solid-state imaging device according to the second aspect of the present disclosure.
The imaging element of Example 1 includes a photoelectric conversion unit formed by laminating a first electrode 21, a photoelectric conversion layer 23A, and a second electrode 22. Between the first electrode 21 and the photoelectric conversion layer 23A, an inorganic oxide semiconductor material layer 23B is formed in contact with the photoelectric conversion layer 23A. The photoelectric conversion unit further includes an insulating layer 82 and a charge accumulation electrode 24 disposed apart from the first electrode 21 so as to face the inorganic oxide semiconductor material layer 23B via the insulating layer 82. Note that light is incident from the second electrode side. In addition, a material constituting the inorganic oxide semiconductor material layer 23B has a value of work function of 4.5 eV or less, and a value obtained by subtracting the value of work function of the material constituting the inorganic oxide semiconductor material layer 23B from a value of work function of a material constituting the second electrode 21 exceeds 0.2 eV. Furthermore, the inorganic oxide semiconductor material layer 23B is constituted by the same material as that constituting the first electrode 21.
The laminated imaging element of Example 1 includes at least one imaging element of Example 1. Furthermore, the solid-state imaging device of Example 1 includes a plurality of the laminated imaging elements of Example 1. In addition, for example, a digital still camera, a video camera, a camcorder, a surveillance camera, a vehicle-mounted camera, a smartphone camera, a game user interface camera, a biometric authentication camera, and the like are constituted by the solid-state imaging device of Example 1.
Hereinafter, first, various characteristics of the imaging element of Example 1 will be described. Subsequently, the imaging element and the solid-state imaging device of Example 1 will be described in detail.
When the film thickness of the inorganic oxide semiconductor material layer 23B is 50 nm, and the inorganic oxide semiconductor material layer 23B is constituted by IWO having a thickness of 50 nm, results of a relationship between an oxygen gas partial pressure and an energy level determined from inverse photoelectron spectroscopy are illustrated in Table 1 below. In the imaging element of Example 1, by controlling the amount of oxygen gas introduced (oxygen gas partial pressure) when the inorganic oxide semiconductor material layer 23B is formed on the basis of a sputtering method, the energy level of the inorganic oxide semiconductor material layer 23B can be controlled. The oxygen gas partial pressure is preferably 0.005 (0.5%) to 0.02 (2%). Note that in the inorganic oxide semiconductor material layer 23B, the oxygen content is lower than that in the stoichiometric composition.
The second electrode 22 was constituted by indium-tin oxide (ITO) having a value of work function of 4.8 eV. Furthermore, a LUMO value of a material constituting a portion of the photoelectric conversion layer 23A located near the inorganic oxide semiconductor material layer 23B was 4.5 eV. Then, using the value of work function of the inorganic oxide semiconductor material layer 23B as a parameter, the number of electrons generated by photoelectric conversion when light was incident from the second electrode 22 was determined by device simulation on the basis of the imaging element having the structure illustrated in
Also in a case where the inorganic oxide semiconductor material layer 23B was constituted by, for example, IGZO, IWZO, ITZO, ZTO, an ITO-SiOX-based material, GZO, IGO, and the like, by using the second electrode 22 and the photoelectric conversion layer 23A constituted by appropriate materials, similar result to the case where the inorganic oxide semiconductor material layer 23B was constituted by IWO could be obtained.
Furthermore, in the imaging element of Example 1, a value obtained by subtracting a LUMO value of a material constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer 23A located near the inorganic oxide semiconductor material layer 23B is 0 eV or more and less than 0.2 eV, and desirably 0.1 eV or less. Moreover, the mobility of the material constituting the inorganic oxide semiconductor material layer 23B is 10 cm2/V·s or more. Furthermore, LUMO values of IGZO, IWZO, ITZO, ZTO, an ITO-SiOX-based material, GZO, IGO, and the like are 4.3 eV to 4.5 eV. A value obtained by subtracting a LUMO value of each of these materials constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer 23A located near the inorganic oxide semiconductor material layer 23B is 0 eV or more and less than 0.2 eV, and desirably 0.1 eV or less. Moreover, the mobility of the material constituting the inorganic oxide semiconductor material layer 23B is 10 cm2/V·s or more.
From results of X-ray diffraction analysis, it has been found that the inorganic oxide semiconductor material layer 23B is amorphous (for example, amorphous without a local crystal structure). Moreover, surface roughness Ra of the inorganic oxide semiconductor material layer 23B at an interface between the photoelectric conversion layer 23A and the inorganic oxide semiconductor material layer 23B is 1.5 nm or less, and a value of root mean square roughness Rq of the inorganic oxide semiconductor material layer is 2.5 nm or less. Specifically,
Ra=0.8 nm and
Rq=2.1 nm
were obtained. Furthermore, surface roughness Ra of the charge accumulation electrode 24 is 1.5 nm or less, and a value of root mean square roughness Rq of the charge accumulation electrode 24 is 2.5 nm or less. Specifically,
Ra=0.7 nm and
Rq=2.3 nm
were obtained. Moreover, the light transmittance of the inorganic oxide semiconductor material layer 23B with respect to light having a wavelength of 400 nm to 660 nm is 65% or more (specifically, 80%), and the light transmittance of the charge accumulation electrode 24 with respect to light having a wavelength of 400 nm to 660 nm is also 65% or more (specifically, 75%). The charge accumulation electrode 24 has a sheet resistance value of 3×10Ω/□ to 1×103Ω/□ (specifically, 84Ω/□).
In the imaging element of Example 1, the characteristics of a material constituting the inorganic oxide semiconductor material layer and a material constituting the second electrode are defined. Therefore, it is possible to provide an imaging element that can generate charges more efficiently by photoelectric conversion. That is, a material constituting the inorganic oxide semiconductor material layer has a value of work function of 4.5 eV or less, and a value obtained by subtracting the value of work function of the material constituting the inorganic oxide semiconductor material layer from a value of work function of a material constituting the second electrode exceeds 0.2 eV. Therefore, when light is incident on the photoelectric conversion layer with a reverse bias voltage applied to the second electrode and the charge accumulation electrode to generate charges, a large internal electric field can be generated in the photoelectric conversion layer on the basis of the difference in value of work function. Therefore, charges can be generated more efficiently in the photoelectric conversion layer. In addition, the imaging element and the like of Example 1 have a two-layer structure of the inorganic oxide semiconductor material layer and the photoelectric conversion layer. Therefore, recombination during charge accumulation can be prevented, transfer efficiency of charges accumulated in the photoelectric conversion layer to the first electrode can be increased, and generation of a dark current can be suppressed.
Hereinafter, the imaging element and the solid-state imaging device of Example 1 will be described in detail.
The imaging element of Example 1 further includes a semiconductor substrate (more specifically, a silicon semiconductor layer) 70, and the photoelectric conversion unit is disposed above the semiconductor substrate 70. Furthermore, the imaging element and the like of Example 1 further include a control unit disposed on the semiconductor substrate 70 and having a drive circuit to which the first electrode 21 and the second electrode 22 are connected. Here, a light incident surface in the semiconductor substrate 70 is defined as an upper side, and the opposite side of the semiconductor substrate 70 is defined as a lower side. A wiring layer 62 including a plurality of wiring lines is disposed below the semiconductor substrate 70.
The semiconductor substrate 70 includes at least a floating diffusion layer FD1 and an amplification transistor TR1amp constituting a control unit, and the first electrode 21 is connected to the floating diffusion layer FD1 and a gate portion of the amplification transistor TR1amp. The semiconductor substrate 70 further includes a reset transistor TR1rst and a selection transistor TR1sel constituting the control unit. The floating diffusion layer FD1 is connected to one source/drain region of the reset transistor TR1rst. One source/drain region of the amplification transistor TR1amp is connected to one source/drain region of the selection transistor TR1sel. The other source/drain region of the selection transistor TR1sel is connected to a signal line VSL1. These amplification transistor TR1amp, reset transistor TR1rst, and selection transistor TR1sel constitute a drive circuit.
Specifically, the imaging element of Example 1 is a backside irradiation type imaging element, and have a structure formed by laminating three imaging elements of a first type green light imaging element of Example 1, including a first type green light photoelectric conversion layer that absorbs green light and sensitive to green light (hereinafter referred to as “first imaging element”), a second type conventional blue light imaging element including a second type blue light photoelectric conversion layer that absorbs blue light and sensitive to blue light (hereinafter referred to as “second imaging element”), and a second type conventional red light imaging element including a second type red light photoelectric conversion layer that absorbs red light and sensitive to red light (hereinafter referred to as “third imaging element”). Here, the red light imaging element (third imaging element) and the blue light imaging element (second imaging element) are disposed in the semiconductor substrate 70, and the second imaging element is located closer to the light incident side than the third imaging element. Furthermore, the green light imaging element (first imaging element) is disposed above the blue light imaging element (second imaging element). One pixel is constituted by the laminated structure of the first imaging element, the second imaging element, and the third imaging element. No color filter layer is disposed.
In the first imaging element, the first electrode 21 and the charge accumulation electrode 24 are formed on an interlayer insulating layer 81 so as to be separated from each other. The interlayer insulating layer 81 and the charge accumulation electrode 24 are covered with the insulating layer 82. The inorganic oxide semiconductor material layer 23B and the photoelectric conversion layer 23A are formed on the insulating layer 82, and the second electrode 22 is formed on the photoelectric conversion layer 23A. An insulating layer 83 is formed on the entire surface including the second electrode 22, and an on-chip micro lens 14 is disposed on the insulating layer 83. No color filter layer is disposed. The first electrode 21, the inorganic oxide semiconductor material layer 23B, and the charge accumulation electrode 24 are each constituted by a transparent electrode containing, for example, IGZO (work function: about 4.4 eV). Furthermore, the second electrode 22 is constituted by a transparent electrode containing, for example, ITO (work function: about 4.8 eV). Alternatively, the first electrode 21 and the inorganic oxide semiconductor material layer 23B are each constituted by, for example, IGZO, IWZO, IWO, ZTO, ITZO, an ITO-SiOX-based material, GZO, IGO, or the like. The photoelectric conversion layer 23A is constituted by a layer containing a known organic photoelectric conversion material sensitive to at least green light (for example, an organic material such as a rhodamine-based dye, a meracyanine-based dye, or quinacridone). The interlayer insulating layer 81 and the insulating layers 82 and 83 each contain a known insulating material (for example, SiO2 or SiN). The inorganic oxide semiconductor material layer 23B and the first electrode 21 are connected to each other by a connection portion 67 disposed in the insulating layer 82. In the connection portion 67, the inorganic oxide semiconductor material layer 23B extends. That is, the inorganic oxide semiconductor material layer 23B extends in an opening 85 formed in the insulating layer 82 to be connected to the first electrode 21.
The charge accumulation electrode 24 is connected to a drive circuit. Specifically, the charge accumulation electrode 24 is connected to a vertical drive circuit 112 constituting the drive circuit via a connection hole 66, a pad portion 64, and wiring VOA formed in the interlayer insulating layer 81.
The charge accumulation electrode 24 is larger than the first electrode 21. When the area of the charge accumulation electrode 24 is represented by S1′, and the area of the first electrode 21 is represented by S1,
4≤S1′/S1 is preferably satisfied although not limited.
In Example 1, for example,
S1′/S1 was set to 8 although not limited. Note that in Examples 7 to 10 described later, the sizes of three photoelectric conversion unit segments 10′1, 10′2, and 10′3) are the same, and the planar shapes thereof are also the same.
An element isolation region 71 is formed on a first surface (front surface) 70A side of the semiconductor substrate 70. Furthermore, an oxide film 72 is formed on the first surface 70A of the semiconductor substrate 70. Moreover, on the first surface side of the semiconductor substrate 70, the reset transistor TR1rst, the amplification transistor TR1amp, and the selection transistor TR1sel constituting the control unit of the first imaging element are disposed, and the first floating diffusion layer FD1 is further disposed.
The reset transistor TR1rst includes a gate portion 51, a channel formation region 51A, and source/drain regions 51B and 51C. The gate portion 51 of the reset transistor TR1rst is connected to a reset line RST1. One source/drain region 51C of the reset transistor TR1rst also serves as the first floating diffusion layer FD1, and the other source/drain region 51B is connected to a power source VDD.
The first electrode 21 is connected to one source/drain region 51C (first floating diffusion layer FD1) of the reset transistor TR1rst via a connection hole 65 and a pad portion 63 formed in the interlayer insulating layer 81, a contact hole portion 61 formed in the semiconductor substrate 70 and the interlayer insulating layer 76, and the wiring layer 62 formed in the interlayer insulating layer 76.
The amplification transistor TR1amp includes a gate portion 52, a channel formation region 52A, and source/drain regions 52B and 52C. The gate portion 52 is connected to the first electrode 21 and one source/drain region 51C (first floating diffusion layer FD1) of the reset transistor TR1rst via the wiring layer 62. Furthermore, one source/drain region 52B is connected to the power source VDD.
The selection transistor TR1sel includes a gate portion 53, a channel formation region 53A, and source/drain regions 53B and 53C. The gate portion 53 is connected to a selection line SELL Furthermore, one source/drain region 53B shares a region with the other source/drain region 52C constituting the amplification transistor TR1amp, and the other source/drain region 53C is connected to a signal line (data output line) VSL1 (117).
The second imaging element includes an n-type semiconductor region 41 disposed on the semiconductor substrate 70 as a photoelectric conversion layer. A gate portion 45 of a transfer transistor TR2trs constituted by a vertical transistor extends to the n-type semiconductor region 41 to be connected to a transfer gate line TG2. Furthermore, the second floating diffusion layer FD2 is disposed in a region 45C of the semiconductor substrate 70 near the gate portion 45 of the transfer transistor TR2trs. Charges accumulated in the n-type semiconductor region 41 are read out to the second floating diffusion layer FD2 via a transfer channel formed along the gate portion 45.
In the second imaging element, on the first surface side of the semiconductor substrate 70, the reset transistor TR2rst, the amplification transistor TR2amp, and the selection transistor TR2sel constituting the control unit of the second imaging element are further disposed.
The reset transistor TR2rst includes a gate portion, a channel formation region, and a source/drain region. The gate portion of the reset transistor TR2rst is connected to a reset line RST2. One source/drain region of the reset transistor TR2rst is connected to the power source VDD, and the other source/drain region also serves as the second floating diffusion layer FD2.
The amplification transistor TR2amp includes a gate portion, a channel formation region, and a source/drain region. The gate portion is connected to the other source/drain region (second floating diffusion layer FD2) of the reset transistor TR2rst. Furthermore, one source/drain region is connected to the power source VDD.
The selection transistor TR2sel includes a gate portion, a channel formation region, and a source/drain region. The gate portion is connected to a selection line SEL2. Furthermore, one source/drain region shares a region with the other source/drain region constituting the amplification transistor TR2amp, and the other source/drain region is connected to a signal line (data output line) VSL2.
The third imaging element includes an n-type semiconductor region 43 disposed on the semiconductor substrate 70 as a photoelectric conversion layer. A gate portion 46 of the transfer transistor TR3trs is connected to a transfer gate line TG3. Furthermore, the third floating diffusion layer FD3 is disposed in a region 46C of the semiconductor substrate 70 near the gate portion 46 of the transfer transistor TR3trs. Charges accumulated in the n-type semiconductor region 43 are read out to the third floating diffusion layer FD3 via a transfer channel 46A formed along the gate portion 46.
In the third imaging element, on the first surface side of the semiconductor substrate 70, the reset transistor TR3rst, the amplification transistor TR3amp, and the selection transistor TR3sel constituting the control unit of the third imaging element are further disposed.
The reset transistor TR3rst includes a gate portion, a channel formation region, and a source/drain region. The gate portion of the reset transistor TR3rst is connected to a reset line RST3. One source/drain region of the reset transistor TR3rst is connected to the power source VDD, and the other source/drain region also serves as the third floating diffusion layer FD3.
The amplification transistor TR3amp includes a gate portion, a channel formation region, and a source/drain region. The gate portion is connected to the other source/drain region (third floating diffusion layer FD3) of the reset transistor TR3rst. Furthermore, one source/drain region is connected to the power source VDD.
The selection transistor TR3sel includes a gate portion, a channel formation region, and a source/drain region. The gate portion is connected to the selection line SEL3. Furthermore, one source/drain region shares a region with the other source/drain region constituting the amplification transistor TR3amp, and the other source/drain region is connected to a signal line (data output line) VSL3.
The reset lines RST1, RST2, and RST3, the selection lines SEL1, SEL2, and SEL3, and the transfer gate lines TG2 and TG3 are connected to the vertical drive circuit 112 constituting a drive circuit, and the signal lines (data output lines) VSL1, VSL2, and VSL3 are connected to a column signal processing circuit 113 constituting a drive circuit.
A p+ layer 44 is disposed between the n-type semiconductor region 43 and the front surface 70A of the semiconductor substrate 70 to suppress generation of a dark current. A p+ layer 42 is formed between the n-type semiconductor region 41 and the n-type semiconductor region 43, and moreover, a part of a side surface of the n-type semiconductor region 43 is surrounded by the p+ layer 42. A p+ layer 73 is formed on a back surface 70B side of the semiconductor substrate 70. An HfO2 film 74 and an insulating material film 75 are formed from the p+ layer 73 to a portion where the contact hole portion 61 is to be formed inside the semiconductor substrate 70. In the interlayer insulating layer 76, wiring is formed in a plurality of layers, but not illustrated.
The HfO2 film 74 has negative fixed charges. By forming such a film, generation of a dark current can be suppressed. Instead of the HfO2 film, an aluminum oxide (Al2O3) film, a zirconium oxide (ZrO2) film, a tantalum oxide (Ta2O5) film, a titanium oxide (TiO2) film, a lanthanum oxide (La2O3) film, a praseodymium oxide (Pr2O3) film, a cerium oxide (CeO2) film, a neodymium oxide (Nd2O3) film, a promethium oxide (Pm2O3) film, a samarium oxide (Sm2O3) film, an europium oxide (Eu2O3) film, a gadolinium oxide ((Gd2O3) film, a terbium oxide (Tb2O3) film, a dysprosium oxide (Dy2O3) film, a holmium oxide (Ho2O3) film, a thulium oxide (Tm2O3) film, a ytterbium oxide (Yb2O3) film, a lutetium oxide (Lu2O3) film, a yttrium oxide (Y2O3) film, a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film can be used. Examples of a method for forming these films include a CVD method, a PVD method, and an ALD method.
Hereinafter, with reference to
Reference numerals used in
PA: Potential at point PA of the inorganic oxide semiconductor material layer 23B facing a region located between the charge accumulation electrode 24 or the transfer control electrode (charge transfer electrode) 25 and the first electrode 21
PB: Potential at point PB in a region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 24
PC1: Potential at point PC1 in a region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode segment 24A
PC2: Potential at point PC2 in a region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode segment 24B
PC3: Potential at point PC3 in a region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode segment 24C
PD: Potential at point PD in a region of the inorganic oxide semiconductor material layer 23B facing the transfer control electrode (charge transfer electrode) 25
FD: Potential in the first floating diffusion layer FD1
VOA: Potential in the charge accumulation electrode 24
VOA-A: Potential in the charge accumulation electrode segment 24A
VOA-B: Potential in the charge accumulation electrode segment 24B
VOA-C: Potential in the charge accumulation electrode segment 24C
VOT: Potential in the transfer control electrode (charge transfer electrode) 25
RST: Potential in the gate portion 51 of the reset transistor TR1rst
VDD: Potential of power source
VSL1: Signal line (data output line) VSL1
TR1rst: Reset transistor TR1rst
TR1amp: Amplification transistor TR1amp
TR1sel: Selection transistor TR1sel
In a charge accumulation period, the potential V11 is applied to the first electrode 21 and the potential V12 is applied to the charge accumulation electrode 24 from a drive circuit. Photoelectric conversion occurs in the photoelectric conversion layer 23A by light incident on the photoelectric conversion layer 23A. Holes generated by the photoelectric conversion are sent from the second electrode 22 to a drive circuit via the wiring VOU. Meanwhile, the potential of the first electrode 21 is set to be higher than the potential of the second electrode 22, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. Therefore, V12≥V11 is satisfied, preferably V12>V11 is satisfied. As a result, electrons generated by the photoelectric conversion are attracted to the charge accumulation electrode 24, and stop in a region of the inorganic oxide semiconductor material layer 23B or the inorganic oxide semiconductor material layer 23B and the photoelectric conversion layer 23A (hereinafter collectively referred to as “inorganic oxide semiconductor material layer 23B and the like”) facing the charge accumulation electrode 24. That is, charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like. Since V12>V11 is satisfied, electrons generated inside the photoelectric conversion layer 23A are not transferred toward the first electrode 21. As the time for the photoelectric conversion elapses, the potential in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 becomes a more negative value.
In a later stage of the charge accumulation period, a reset operation is performed. As a result, the potential of the first floating diffusion layer FD1 is reset, and the potential of the first floating diffusion layer FD1 becomes the potential VDD of the power source.
After the reset operation is completed, charges are read out. That is, in a charge transfer period, the potential V21 is applied to the first electrode 21 and the potential V22 is applied to the charge accumulation electrode 24 from a drive circuit. Here, V22<V21 is satisfied. As a result, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
In this way, a series of operations including charge accumulation, reset operation, and charge transfer are completed.
The operations of the amplification transistor TR1amp and the selection transistor TR1sel after electrons are read out to the first floating diffusion layer FD1 are the same as the conventional operations of these transistors. Furthermore, a series of operations including charge accumulation, reset operation, and charge transfer of the second imaging element and the third imaging element are similar to a conventional series of operations including charge accumulation, reset operation, and charge transfer. Furthermore, a reset noise of the first floating diffusion layer FD1 can be removed by a correlated double sampling (CDS) process as in prior art.
As described above, in Example 1, since the charge accumulation electrode is included which is disposed apart from the first electrode so as to face the photoelectric conversion layer via the insulating layer, when the photoelectric conversion layer is irradiated with light, and the light is photoelectrically converted in the photoelectric conversion layer, the inorganic oxide semiconductor material layer and the like, the insulating layer, and the charge accumulation electrode form a kind of capacitor, and charges can be stored in the inorganic oxide semiconductor material layer and the like. Therefore, at the time of start of exposure, a charge accumulation portion can be completely depleted and the charge can be erased. As a result, it is possible to suppress occurrence of a phenomenon that a kTC noise increases, a random noise deteriorates, and the quality of an imaged image deteriorates. Furthermore, since all the pixels can be reset all at once, a so-called global shutter function can be achieved.
The drive control circuit 116 generates a clock signal or a control signal as a reference of operations of the vertical drive circuit 112, the column signal processing circuit 113, and the horizontal drive circuit 114 on the basis of a vertical synchronizing signal, a horizontal synchronizing signal, and a master clock. Then, the generated clock signal or control signal is input to the vertical drive circuit 112, the column signal processing circuit 113, and the horizontal drive circuit 114.
For example, the vertical drive circuit 112 is constituted by a shift register, and sequentially selects and scans the laminated imaging elements 101 in the imaging region 111 in a row unit in the vertical direction. Then, a pixel signal (image signal) based on a current (signal) generated according to the amount of light received by each of the laminated imaging elements 101 is sent to the column signal processing circuit 113 via a signal line (data output line) 117, VSL.
For example, the column signal processing circuit 113 is disposed for each column of the laminated imaging elements 101. Image signals output from the laminated imaging elements 101 in one row are subjected to signal processing such as noise removal or signal amplification with a signal from a black reference pixel (not illustrated, but formed around an effective pixel region) for each of the imaging elements. In an output stage of the column signal processing circuit 113, a horizontal selection switch (not illustrated) is connected and disposed between the column signal processing circuit 113 and a horizontal signal line 118.
For example, the horizontal drive circuit 114 is constituted by a shift register. By sequentially outputting a horizontal scanning pulse, the horizontal drive circuit 114 sequentially selects each of the column signal processing circuits 113, and outputs a signal from each of the column signal processing circuits 113 to the horizontal signal line 118.
The output circuit 115 performs signal processing to a signal sequentially supplied from each of the column signal processing circuits 113 via the horizontal signal line 118, and outputs the signal.
As
The imaging element of Example 1 can be manufactured, for example, by the following method. That is, first, an SOI substrate is prepared. Then, a first silicon layer is formed on a surface of the SOI substrate on the basis of an epitaxial growth method, and the p+ layer 73 and the n-type semiconductor region 41 are formed on the first silicon layer. Subsequently, a second silicon layer is formed on the first silicon layer on the basis of an epitaxial growth method, and the element isolation region 71, the oxide film 72, p+ layer 42, the n-type semiconductor region 43, and the p+ layer 44 are formed on the second silicon layer. Furthermore, various transistors and the like constituting the control unit of the imaging element are formed on the second silicon layer. The wiring layer 62, the interlayer insulating layer 76, and various wiring lines are further formed thereon, and then the interlayer insulating layer 76 is bonded to a support substrate (not illustrated). Thereafter, the SOI substrate is removed to expose the first silicon layer. The surface of the second silicon layer corresponds to the front surface 70A of the semiconductor substrate 70, and the surface of the first silicon layer corresponds to the back surface 70B of the semiconductor substrate 70. Furthermore, the first silicon layer and the second silicon layer are collectively expressed as the semiconductor substrate 70. Subsequently, an opening for forming the contact hole portion 61 is formed on the back surface 70B side of the semiconductor substrate 70. The HfO2 film 74, the insulating material film 75, and the contact hole portion 61 are formed. The pad portions 63 and 64, the interlayer insulating layer 81, the connection holes 65 and 66, the first electrode 21, the charge accumulation electrode 24, and the insulating layer 82 are further formed. Next, the connection portion 67 is opened, and the inorganic oxide semiconductor material layer 23B, the photoelectric conversion layer 23A, the second electrode 22, the insulating layer 83, and the on-chip micro lens 14 are formed. As a result, the imaging element of Example 1 can be obtained.
Furthermore, although not illustrated, the insulating layer 82 can have a two-layer configuration of an insulating layer/lower layer and an insulating layer/upper layer. That is, it is only required to form the insulating layer/lower layer at least on the charge accumulation electrode 24 and in a region between the charge accumulation electrode 24 and the first electrode 21 (more specifically, to form the insulating layer/lower layer on the interlayer insulating layer 81 including the charge accumulation electrode 24), to planarize the insulating layer/lower layer, and then to form an insulating layer/upper layer on the insulating layer/lower layer and the charge accumulation electrode 24. As a result, the insulating layer 82 can be reliably planarized. Then, it is only required to open the connection portion 67 in the insulating layer 82 thus obtained.
Example 2 is a modification of Example 1. An imaging element of Example 2, illustrated in the schematic partial cross-sectional view of
On the front surface 70A side of the semiconductor substrate 70, various transistors constituting a control unit are disposed as in Example 1. These transistors can have substantially similar configurations and structures to the transistors described in Example 1. Furthermore, the semiconductor substrate 70 includes the second imaging element and the third imaging element, and these imaging elements can have substantially similar configurations and structures to the second imaging element and the third imaging element described in Example 1.
The interlayer insulating layer 81 is formed above the front surface 70A of the semiconductor substrate 70. Above the interlayer insulating layer 81, the photoelectric conversion unit (first electrode 21, inorganic oxide semiconductor material layer 23B, photoelectric conversion layer 23A, second electrode 22, charge accumulation electrode 24, and the like) including the charge accumulation electrode and constituting the imaging element of Example 1 is disposed.
In this way, the configuration and structure of the imaging element of Example 2 can be similar to the configuration and structure of the imaging element of Example 1 except for being the frontside irradiation type. Therefore, detailed description thereof is omitted.
Example 3 is a modification of Examples 1 and 2.
An imaging element of Example 3, illustrated in the schematic partial cross-sectional view of
A modification of the imaging element of Example 3, illustrated in the schematic partial cross-sectional view of
Instead of disposing one first type photoelectric conversion unit including the charge accumulation electrode of Example 1, a form can be adopted in which two first type photoelectric conversion units are laminated (that is, a form in which two photoelectric conversion units each including the charge accumulation electrode are laminated, and a control unit for the two photoelectric conversion units is disposed on a semiconductor substrate), or a form can be adopted in which three first type photoelectric conversion units are laminated (that is, a form in which three photoelectric conversion units each including the charge accumulation electrode are laminated, and a control unit for the three photoelectric conversion units is disposed on a semiconductor substrate). Examples of the laminated structure of the first type imaging element and the second type imaging element are illustrated in the following table.
Example 4 is a modification of Examples 1 to 3, and relates to an imaging element and the like of the present disclosure including a transfer control electrode (charge transfer electrode).
The imaging element of Example 4 further includes the transfer control electrode (charge transfer electrode) 25 disposed apart from the first electrode 21 and the charge accumulation electrode 24 so as to face the inorganic oxide semiconductor material layer 23B via the insulating layer 82 between the first electrode 21 and the charge accumulation electrode 24. The transfer control electrode 25 is connected to a pixel drive circuit constituting a drive circuit via a connection hole 68B, a pad portion 68A, and wiring VOT formed in the interlayer insulating layer 81. Note that various imaging element components located below the interlayer insulating layer 81 are collectively denoted by reference numeral 13 for convenience in order to simplify the drawing.
Hereinafter, with reference to
In a charge accumulation period, the potential V11 is applied to the first electrode 21, the potential V12 is applied to the charge accumulation electrode 24, and the potential V13 is applied to the transfer control electrode 25 from a drive circuit. Photoelectric conversion occurs in the photoelectric conversion layer 23A by light incident on the photoelectric conversion layer 23A. Holes generated by the photoelectric conversion are sent from the second electrode 22 to a drive circuit via the wiring VOU. Meanwhile, the potential of the first electrode 21 is set to be higher than the potential of the second electrode 22, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. Therefore, V12>V13 (for example, V12>V11>V13 or V11>V12>V13) is satisfied. As a result, electrons generated by the photoelectric conversion are attracted to the charge accumulation electrode 24 and stop in a region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24. That is, charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like. Since V12>V13 is satisfied, transfer of electrons generated inside the photoelectric conversion layer 23A toward the first electrode 21 can be prevented reliably. As the time for the photoelectric conversion elapses, the potential in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 becomes a more negative value.
In a later stage of the charge accumulation period, a reset operation is performed. As a result, the potential of the first floating diffusion layer FD1 is reset, and the potential of the first floating diffusion layer FD1 becomes the potential VDD of the power source.
After the reset operation is completed, charges are read out. That is, in a charge transfer period, the potential V21 is applied to the first electrode 21, the potential V22 is applied to the charge accumulation electrode 24, and the potential V23 is applied to the transfer control electrode 25 from a drive circuit. Here, V22≤V23≤V21 (preferably V22<V23<V21) is satisfied. In a case where the potential Via is applied to the transfer control electrode 25, it is only required to satisfy V22≤V13≤V21 (preferably V22<V13<V21). As a result, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are reliably read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
In this way, a series of operations including charge accumulation, reset operation, and charge transfer are completed.
The operations of the amplification transistor TR1amp and the selection transistor TR1sel after electrons are read out to the first floating diffusion layer FD1 are the same as the conventional operations of these transistors. Furthermore, for example, a series of operations including charge accumulation, reset operation, and charge transfer of the second imaging element and the third imaging element are similar to a conventional series of operations including charge accumulation, reset operation, and charge transfer.
As
Example 5 is a modification of Examples 1 to 4, and relates to an imaging element and the like of the present disclosure including a charge discharge electrode.
The imaging element of Example 5 further include a charge discharge electrode 26 connected to the inorganic oxide semiconductor material layer 23B via the connection portion 69 and disposed apart from the first electrode 21 and the charge accumulation electrode 24. Here, the charge discharge electrode 26 is disposed so as to surround the first electrode 21 and the charge accumulation electrode 24 (that is, in a frame shape). The charge discharge electrode 26 is connected to a pixel drive circuit constituting a drive circuit. In the connection portion 69, the inorganic oxide semiconductor material layer 23B extends. That is, the inorganic oxide semiconductor material layer 23B extends in a second opening 86 formed in the insulating layer 82 to be connected to the charge discharge electrode 26. The charge discharge electrode 26 is shared by (common to) a plurality of imaging elements.
In Example 5, in a charge accumulation period, the potential V11 is applied to the first electrode 21, the potential V12 is applied to the charge accumulation electrode 24, and the potential V14 is applied to the charge discharge electrode 26 from a drive circuit, and charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like. Photoelectric conversion occurs in the photoelectric conversion layer 23A by light incident on the photoelectric conversion layer 23A. Holes generated by the photoelectric conversion are sent from the second electrode 22 to a drive circuit via the wiring VOU. Meanwhile, the potential of the first electrode 21 is set to be higher than the potential of the second electrode 22, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. Therefore, V14>V11 (for example, V12>V14>V11) is satisfied. As a result, electrons generated by the photoelectric conversion are attracted to the charge accumulation electrode 24 and stop in a region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24. Transfer of the electrons toward the first electrode 21 can be prevented reliably. However, electrons that are not sufficiently attracted to the charge accumulation electrode 24 or cannot be accumulated in the inorganic oxide semiconductor material layer 23B and the like (so-called overflowed electrons) are sent to a drive circuit via the charge discharge electrode 26.
In a later stage of the charge accumulation period, a reset operation is performed. As a result, the potential of the first floating diffusion layer FD1 is reset, and the potential of the first floating diffusion layer FD1 becomes the potential VDD of the power source.
After the reset operation is completed, charges are read out. That is, in a charge transfer period, the potential V21 is applied to the first electrode 21, the potential V22 is applied to the charge accumulation electrode 24, and the potential V24 is applied to the charge discharge electrode 26 from a drive circuit. Here, V24<V21 (for example, V24<V22<V21) is satisfied. As a result, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are reliably read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
In this way, a series of operations including charge accumulation, reset operation, and charge transfer are completed.
The operations of the amplification transistor TR1amp and the selection transistor TR1sel after electrons are read out to the first floating diffusion layer FD1 are the same as the conventional operations of these transistors. Furthermore, for example, a series of operations including charge accumulation, reset operation, and charge transfer of the second imaging element and the third imaging element are similar to a conventional series of operations including charge accumulation, reset operation, and charge transfer.
In Example 5, so-called overflowed electrons are sent to a drive circuit via the charge discharge electrode 26. Therefore, leakage to a charge accumulation portion of an adjacent pixel can be suppressed, and occurrence of blooming can be suppressed. In addition, this can improve imaging performance of the imaging element.
Example 6 is a modification of Examples 1 to 5, and relates to an imaging element and the like of the present disclosure including a plurality of charge accumulation electrode segments.
In Example 6, the charge accumulation electrode 24 includes a plurality of charge accumulation electrode segments 24A, 24B, and 24C. The number of charge accumulation electrode segments only needs to be two or more, and is set to “three” in Example 6. In addition, in the imaging element of Example 6, the potential of the first electrode 21 is higher than the potential of the second electrode 22. Therefore, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. In addition, in a charge transfer period, the potential applied to the charge accumulation electrode segment 24A located closest to the first electrode 21 is higher than the potential applied to the charge accumulation electrode segment 24C located farthest from the first electrode 21. In this way, by applying a potential gradient to the charge accumulation electrode 24, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are more reliably read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
In the example illustrated in
As
Example 7 is a modification of Examples 1 to 6, and relates to the imaging elements of the first and sixth configurations.
Here, in the imaging element of Example 7 or the imaging elements of Examples 8 to 12 described later,
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments (specifically, three photoelectric conversion unit segments 10′1, 10′2, and 10′3),
the inorganic oxide semiconductor material layer 23B and the photoelectric conversion layer 23A include N photoelectric conversion layer segments (specifically, three photoelectric conversion layer segments 23′1, 23′2, and 23′3),
the insulating layer 82 includes N insulating layer segments (specifically, three insulating layer segments 82′1, 82′2, and 82′3),
in Examples 7 to 9, the charge accumulation electrode 24 includes N charge accumulation electrode segments (specifically, three charge accumulation electrode segments 24′1, 24′2, and 24′3 in each of the Examples),
in Examples 10 and 11, in some cases, in Example 9, the charge accumulation electrode 24 includes N charge accumulation electrode segments (specifically, three charge accumulation electrode segments 24′1, 24′2, and 24′3) disposed apart from one another,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment 10′n includes the n-th charge accumulation electrode segment 24′n, the n-th insulating layer segment 82′n, and the n-th photoelectric conversion layer segment 23′n, and a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode 21. Here, the photoelectric conversion layer segments 23′1, 23′2, and 23′3 indicate segments formed by laminating the inorganic oxide semiconductor material layer and the photoelectric conversion layer, and are expressed by one layer in the drawings for simplifying the drawings. This also applies to the following.
Note that in a photoelectric conversion layer segment, the thickness of the photoelectric conversion layer segment may be changed by changing the thickness of the photoelectric conversion layer portion and keeping the thickness of the inorganic oxide semiconductor material layer portion constant. Furthermore, the thickness of the photoelectric conversion layer segment may be changed by keeping the thickness of the photoelectric conversion layer portion constant and changing the thickness of the inorganic oxide semiconductor material layer portion. Furthermore, the thickness of the photoelectric conversion layer segment may be changed by changing the thickness of the photoelectric conversion layer portion and changing the thickness of the inorganic oxide semiconductor material layer portion.
Alternatively, the imaging element of Example 7 or the imaging elements of Examples 8 and 11 described later include,
a photoelectric conversion unit formed by laminating the first electrode 21, the inorganic oxide semiconductor material layer 23B, the photoelectric conversion layer 23A, and the second electrode 22.
The photoelectric conversion unit further includes the charge accumulation electrode 24 disposed apart from the first electrode 21 so as to face the inorganic oxide semiconductor material layer 23B via the insulating layer 82.
If a lamination direction of the charge accumulation electrode 24, the insulating layer 82, the inorganic oxide semiconductor material layer 23B, and the photoelectric conversion layer 23A is defined as a Z direction, and a direction of separating from the first electrode 21 is defined as an X direction, when a laminated portion where the charge accumulation electrode 24, the insulating layer 82, the inorganic oxide semiconductor material layer 23B, and the photoelectric conversion layer 23A are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode.
Moreover, in the imaging element of Example 7, the thickness of an insulating layer segment gradually changes from the first photoelectric conversion unit segment 10′1 to the N-th photoelectric conversion unit segment 10′N. Specifically, the thickness of an insulating layer segment gradually increases. Alternatively, in the imaging element of Example 7, the width of the cross section of the laminated portion is constant, and the thickness of the cross section of the laminated portion, specifically, the thickness of an insulating layer segment gradually increases depending on a distance from the first electrode 21. Note that the thickness of an insulating layer segment increases stepwise. The thickness of the insulating layer segment 82′n in the n-th photoelectric conversion unit segment 10′n is constant. When the thickness of the insulating layer segment 82′n in the n-th photoelectric conversion unit segment 10′n is “1”, examples of the thickness of the insulating layer segment 829′(n+1) in the (n+1)-th photoelectric conversion unit segment 10′(n+1) include 2 to 10, but are not limited to such values. In Example 7, by gradually reducing the thicknesses of the charge accumulation electrode segments 24′1, 24′2, and 24′3, the thicknesses of the insulating layer segments 82′1, 82′2, and 82′3 are gradually increased. The thicknesses of the photoelectric conversion layer segments 23′1, 23′2, and 23′3 are constant.
Hereinafter, the operation of the imaging element of Example 7 will be described.
In a charge accumulation period, the potential V11 is applied to the first electrode 21 and the potential V12 is applied to the charge accumulation electrode 24 from a drive circuit. Photoelectric conversion occurs in the photoelectric conversion layer 23A by light incident on the photoelectric conversion layer 23A. Holes generated by the photoelectric conversion are sent from the second electrode 22 to a drive circuit via the wiring VOU. Meanwhile, the potential of the first electrode 21 is set to be higher than the potential of the second electrode 22, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. Therefore, V12≥V11 is satisfied, preferably V12>V11 is satisfied. As a result, electrons generated by the photoelectric conversion are attracted to the charge accumulation electrode 24 and stop in a region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24. That is, charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like. Since V12>V11 is satisfied, electrons generated inside the photoelectric conversion layer 23A are not transferred toward the first electrode 21. As the time for the photoelectric conversion elapses, the potential in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 becomes a more negative value.
In the imaging element of Example 7, the configuration is adopted in which the thickness of an insulating layer segment gradually increases. Therefore, when a state of |V12|≥|V11| is reached in a charge accumulation period, the n-th photoelectric conversion unit segment 10′n can accumulate more charges than the (n+1)-th photoelectric conversion unit segment 10′(n+1), a stronger electric field is applied to the n-th photoelectric conversion unit segment 10′n than to the (n+1)-th photoelectric conversion unit segment 10′(n+1), and a flow of charges from the first photoelectric conversion unit segment 10′1 to the first electrode 21 can be reliably prevented.
In a later stage of the charge accumulation period, a reset operation is performed. As a result, the potential of the first floating diffusion layer FD1 is reset, and the potential of the first floating diffusion layer FD1 becomes the potential VDD of the power source.
After the reset operation is completed, charges are read out. That is, in a charge transfer period, the potential V21 is applied to the first electrode 21 and the potential V22 is applied to the charge accumulation electrode 24 from a drive circuit. Here, V21>V22 is satisfied. As a result, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
More specifically, when a state of V21>V22 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment 10′1 to the first electrode 21, and a flow of charges from the (n+1)-th photoelectric conversion unit segment 10′(n+1) to the n-th photoelectric conversion unit segment 10′n can be reliably ensured.
In this way, a series of operations including charge accumulation, reset operation, and charge transfer are completed.
In the imaging element of Example 7, the thickness of an insulating layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. Alternatively, when a laminated portion where the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode. Therefore, a kind of charge transfer gradient is formed, and charges generated by photoelectric conversion can be transferred more easily and reliably.
Since the imaging element of Example 7 can be manufactured by a substantially similar method to the imaging element of Example 1, detailed description thereof is omitted.
Note that in the imaging element of Example 7, in formation of the first electrode 21, the charge accumulation electrode 24, and the insulating layer 82, first, a conductive material layer for forming the charge accumulation electrode 24′3 is formed on the interlayer insulating layer 81. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segments 10′1, 10′2, and 10′3 and the first electrode 21 are to be formed. Thus, a part of the first electrode 21 and the charge accumulation electrode 24′3 can be obtained. Next, an insulating layer for forming the insulating layer segment 82′3 is formed on the entire surface. The insulating layer is patterned and planarized to obtain the insulating layer segment 82′3. Next, a conductive material layer for forming the charge accumulation electrode 24′2 is formed on the entire surface. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segments 10′1 and 10′2 and the first electrode 21 are to be formed. Thus, a part of the first electrode 21 and the charge accumulation electrode 24′2 can be obtained. Next, an insulating layer for forming the insulating layer segment 82′2 is formed on the entire surface. The insulating layer is patterned and planarized to obtain the insulating layer segment 82′2. Next, a conductive material layer for forming the charge accumulation electrode 24′1 is formed on the entire surface. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segment 10′1 and the first electrode 21 are to be formed. Thus, the first electrode 21 and the charge accumulation electrode 24′1 can be obtained. Next, an insulating layer is formed on the entire surface. The insulating layer is planarized to obtain the insulating layer segment 82′1 (insulating layer 82). Then, the inorganic oxide semiconductor material layer 23B and the photoelectric conversion layer 23A are formed on the insulating layer 82. In this way, the photoelectric conversion unit segments 10′1, 10′2, and 10′3 can be obtained.
As
The imaging element of Example 8 relates to the imaging elements of the second and sixth configurations of the present disclosure. As
In the imaging element of Example 8, the thickness of a photoelectric conversion layer segment gradually increases. Therefore, when a state of |V12|≥|V11| is reached in a charge accumulation period, a stronger electric field is applied to the n-th photoelectric conversion unit segment 10′n than to the (n+1)-th photoelectric conversion unit segment 10′(n+1), and a flow of charges from the first photoelectric conversion unit segment 10′1 to the first electrode 21 can be reliably prevented. Then, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment 10′1 to the first electrode 21, and a flow of charges from the (n+1)-th photoelectric conversion unit segment 10′(n+1) to the n-th photoelectric conversion unit segment 10′n can be reliably ensured.
In this way, in the imaging element of Example 8, the thickness of a photoelectric conversion layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment. Alternatively, when a laminated portion where the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode. Therefore, a kind of charge transfer gradient is formed, and charges generated by photoelectric conversion can be transferred more easily and reliably.
In the imaging element of Example 8, in formation of the first electrode 21, the charge accumulation electrode 24, the insulating layer 82, the inorganic oxide semiconductor material layer 23B, and the photoelectric conversion layer 23A, first, a conductive material layer for forming the charge accumulation electrode 24′3 is formed on the interlayer insulating layer 81. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segments 10′1, 10′2, and 10′3 and the first electrode 21 are to be formed. Thus, a part of the first electrode 21 and the charge accumulation electrode 24′3 can be obtained. Subsequently, a conductive material layer for forming the charge accumulation electrode 24′2 is formed on the entire surface. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segments 10′1 and 10′2 and the first electrode 21 are to be formed. Thus, a part of the first electrode 21 and the charge accumulation electrode 24′2 can be obtained. Subsequently, a conductive material layer for forming the charge accumulation electrode 24′1 is formed on the entire surface. The conductive material layer is patterned to leave the conductive material layer in a region where the photoelectric conversion unit segment 10′1 and the first electrode 21 are to be formed. Thus, the first electrode 21 and the charge accumulation electrode 24′1 can be obtained. Next, the insulating layer 82 is conformally formed on the entire surface. Then, the inorganic oxide semiconductor material layer 23B and the photoelectric conversion layer 23A are formed on the insulating layer 82, and the photoelectric conversion layer 23A is planarized. In this way, the photoelectric conversion unit segments 10′1, 10′2, and 10′3 can be obtained.
Example 9 relates to the imaging element of the third configuration.
Then, by adopting such a configuration, a kind of charge transfer gradient is formed. In a charge accumulation period, when a state of V12≥V11 is reached, the n-th photoelectric conversion unit segment can accumulate more charges than the (n+1)-th photoelectric conversion unit segment. Then, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
Example 10 relates to the imaging element of the fourth configuration.
The imaging element of Example 11 relates to the imaging element of the fifth configuration.
In Example 11, the charge accumulation electrode 24 includes a plurality of charge accumulation electrode segments 24′1, 24′2, and 24′3. The number of charge accumulation electrode segments only needs to be two or more, and is set to “three” in Example 11. In addition, in the imaging element of Example 11, the potential of the first electrode 21 is higher than the potential of the second electrode 22. Therefore, that is, for example, a positive potential is applied to the first electrode 21, and a negative potential is applied to the second electrode 22. Therefore, in a charge transfer period, the potential applied to the charge accumulation electrode segment 24′1 located closest to the first electrode 21 is higher than the potential applied to the charge accumulation electrode segment 24′3 located farthest from the first electrode 21. In this way, by applying a potential gradient to the charge accumulation electrode 24, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 24 are more reliably read out to the first electrode 21 and further to the first floating diffusion layer FD1. That is, the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like are read out to the control unit.
Then, in a charge transfer period, by satisfying the potential of the charge accumulation electrode segment 24′3<the potential of the charge accumulation electrode segment 24′2<the potential of the charge accumulation electrode segment 24′1, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like can be read out to the first floating diffusion layer FD1 all at once. Alternatively, in a charge transfer period, by gradually changing the potential of the charge accumulation electrode segment 24′3, the potential of the charge accumulation electrode segment 24′2, and the potential of the charge accumulation electrode segment 24′1 (that is, by changing the potential of the charge accumulation electrode segment 24′3, the potential of the charge accumulation electrode segment 24′2, and the potential of the charge accumulation electrode segment 24′1 in a step shape or a slope shape), electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode segment 24′3 are transferred to the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode segment 24′2. Subsequently, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode segment 24′2 are transferred to the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode segment 24′1. Subsequently, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode segment 24′1 can be reliably read out to the first floating diffusion layer FD1.
As
Also in the imaging element of Example 11, by adopting such a configuration, a kind of charge transfer gradient is formed. That is, the area of a charge accumulation electrode segment is gradually reduced from the first photoelectric conversion unit segment 10′1 to the N-th photoelectric conversion unit segment 10′N. Therefore, when a state of V12≥V11 is reached in a charge accumulation period, the n-th photoelectric conversion unit segment can accumulate more charges than the (n+1)-th photoelectric conversion unit segment. Then, when a state of V22<V21 is reached in a charge transfer period, a flow of charges from the first photoelectric conversion unit segment to the first electrode, and a flow of charges from the (n+1)-th photoelectric conversion unit segment to the n-th photoelectric conversion unit segment can be reliably ensured.
Example 12 relates to the imaging element of the sixth configuration.
Specifically, in the imaging element of Example 12, the thickness of the cross section of the laminated portion is constant, and the width of the cross section of the laminated portion becomes narrower as the laminated portion goes away from the first electrode 21. Note that the width may be continuously narrowed (see
In this way, in the imaging element of Example 12, when a laminated portion where the charge accumulation electrode 24 (24″1, 24″2, and 24″3), the insulating layer 82, and the photoelectric conversion layer 23A are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode. Therefore, a kind of charge transfer gradient is formed, and charges generated by photoelectric conversion can be transferred more easily and reliably.
Example 13 relates to solid-state imaging devices of first and second configurations.
The solid-state imaging device of Example 13 includes
a photoelectric conversion unit formed by laminating the first electrode 21, the inorganic oxide semiconductor material layer 23B, the photoelectric conversion layer 23A, and the second electrode 22.
The solid-state imaging device of Example 13 includes a plurality of imaging elements in each of which the photoelectric conversion unit further includes the charge accumulation electrode 24 disposed apart from the first electrode 21 so as to face the inorganic oxide semiconductor material layer 23B via the insulating layer 82.
The plurality of imaging elements constitutes an imaging element block.
The first electrode 21 is shared by the plurality of imaging elements constituting the imaging element block.
Alternatively, the solid-state imaging device of Example 13 includes a plurality of the imaging elements described in Examples 1 to 12.
In Example 13, one floating diffusion layer is disposed for the plurality of imaging elements. In addition, by appropriately controlling the timing of a charge transfer period, a plurality of imaging elements can share one floating diffusion layer. In addition, in this case, the plurality of imaging elements can share one contact hole portion.
Note that the solid-state imaging device of Example 13 has substantially a similar configuration and structure to the solid-state imaging devices described in Examples 1 to 12 except that the first electrode 21 is shared by the plurality of imaging elements constituting an imaging element block.
The arrangement state of the first electrode 21 and the charge accumulation electrode 24 in the solid-state imaging device of Example 13 is schematically illustrated in
The charge transfer control electrode 27 may be formed, on the first electrode side, at the same level as the first electrode 21 or the charge accumulation electrode 24 or at a different level (specifically, at a level lower than the first electrode 21 or the charge accumulation electrode 24). In the former case, since a distance between the charge transfer control electrode 27 and the photoelectric conversion layer can be shortened, the potential can be easily controlled. Meanwhile, the latter case is advantageous for miniaturization because a distance between the charge transfer control electrode 27 and the charge accumulation electrode 24 can be shortened.
Hereinafter, an operation of an imaging element block constituted by the first electrode 212 and the two charge accumulation electrodes 2421 and 2422 will be described.
In a charge accumulation period, a potential Va is applied to the first electrode 212 and a potential VA is applied to the charge accumulation electrodes 2421 and 2422 from a drive circuit. Photoelectric conversion occurs in the photoelectric conversion layer 23A by light incident on the photoelectric conversion layer 23A. Holes generated by the photoelectric conversion are sent from the second electrode 22 to a drive circuit via the wiring VOU. Meanwhile, the potential of the first electrode 212 is set to be higher than the potential of the second electrode 22, that is, for example, a positive potential is applied to the first electrode 212, and a negative potential is applied to the second electrode 22. Therefore, VA≥Va is satisfied, preferably VA>Va is satisfied. As a result, electrons generated by the photoelectric conversion are attracted to the charge accumulation electrodes 2421 and 2422 and stop in a region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrodes 2421 and 2422. That is, charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like. Since VA≥Va is satisfied, electrons generated inside the photoelectric conversion layer 23A are not transferred toward the first electrode 212. As the time for the photoelectric conversion elapses, the potential in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrodes 2421 and 2422 becomes a more negative value.
In a later stage of the charge accumulation period, a reset operation is performed. As a result, the potential of the first floating diffusion layer is reset, and the potential of the first floating diffusion layer becomes the potential VDD of the power source.
After the reset operation is completed, charges are read out. That is, in a charge transfer period, a potential Vb is applied to the first electrode 212, a potential V21-B is applied to the charge accumulation electrode 2421, and a potential V22-B is applied to the charge accumulation electrode 2422 from a drive circuit. Here, V21-B<Vb<V22-B is satisfied. As a result, electrons that have stopped in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 2421 are read out to the first electrode 212 and further to the first floating diffusion layer. That is, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B and the like facing the charge accumulation electrode 2421 are read out to the control unit. When readout is completed, V22-B<V21-B<Vb is satisfied. Note that in examples illustrated in
Through the following steps A to H, signals from two imaging elements corresponding to the charge accumulation electrode 2421 and the charge accumulation electrode 2422 are read out.
Input of an auto zero signal to a comparator
Reset operation of one shared floating diffusion layer
P-phase readout and transfer of charges to the first electrode 212 in an imaging element corresponding to the charge accumulation electrode 2421
D-phase readout and transfer of charge to the first electrode 212 in an imaging element corresponding to the charge accumulation electrode 2421
Reset operation of one shared floating diffusion layer
Input of an auto zero signal to a comparator
P-phase readout and transfer of charges to the first electrode 212 in an imaging element corresponding to the charge accumulation electrode 2422
D-phase readout and transfer of charges to the first electrode 212 in an imaging element corresponding to the charge accumulation electrode 2422
On the basis of a correlated double sampling (CDS) process, a difference between the P-phase readout in [step-C] and the D-phase readout in [step-D] is a signal from an imaging element corresponding to the charge accumulation electrode 2421, and a difference between the P-phase readout in [step-G] and the D-phase readout in [step-H] is a signal from an imaging element corresponding to the charge accumulation electrode 2422.
Note that the operation of [Step-E] may be omitted (see
In the modifications illustrated in
In the eighth and ninth modifications illustrated in
Specifically, first, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2411 are read out from the first electrode 21. Next, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2412 are read out from the first electrode 21 via the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2411. Next, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2413 are read out from the first electrode 21 via the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2412 and the charge accumulation electrode 2411.
Thereafter, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2411. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2412. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2413. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2414.
The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2431 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2432 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2433 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2434 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424.
The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2441 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2431. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2442 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2432. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2443 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2433. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2444 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2434.
Then, by executing [step-10] again, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423, and the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424 can be read out via the first electrode 21.
Thereafter, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2411. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2412. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2413. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2414.
The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2431 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2432 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2433 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2434 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424.
Then, by executing [step-10] again, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2431, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2432, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2433, and the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2434 can be read out via the first electrode 21.
Thereafter, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2421 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2411. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2422 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2412. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2423 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2413. The charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2424 are transferred to the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2414.
Then, by executing [step-10] again, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2441, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2442, the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2443, and the charges accumulated in the region of the inorganic oxide semiconductor material layer 23B facing the charge accumulation electrode 2444 can be read out via the first electrode 21.
In the solid-state imaging device of Example 13, since the first electrode is shared by the plurality of imaging elements constituting the imaging element block, the configuration and structure in a pixel region in which a plurality of imaging elements is arrayed can be simplified and miniaturized. Note that the plurality of imaging elements disposed for one floating diffusion layer may be constituted by a plurality of first type imaging elements, or may be constituted by at least one first type imaging element and one or more second type imaging elements.
Example 14 is a modification of Example 13. In the solid-state imaging device of Example 14 illustrated in
For example, photoelectric conversion layers corresponding to the charge accumulation electrodes 2411, 2421, 2431, and 2441 constituting an imaging element block are highly sensitive to incident light from the upper right in the drawings. Furthermore, photoelectric conversion layers corresponding to the charge accumulation electrodes 2412, 2422, 2432, and 2442 constituting an imaging element block are highly sensitive to incident light from the upper left in the drawing. Therefore, for example, by combining an imaging element including the charge accumulation electrode 2411 with an imaging element including the charge accumulation electrode 2412, an image plane phase difference signal can be acquired. Furthermore, if a signal from an imaging element including the charge accumulation electrode 2411 is added to a signal from an imaging element including the charge accumulation electrode 2412, one imaging element can be constituted by a combination with these imaging elements. In the example illustrated in
Hitherto, the present disclosure has been described on the basis of preferable Examples. However, the present disclosure is not limited to these Examples. The structures and configurations, the manufacturing conditions, the manufacturing methods, and the used materials of the imaging element, the laminated imaging element, and the solid-state imaging device described in Examples are illustrative and can be modified appropriately. The imaging elements of Examples can be combined appropriately. For example, the imaging element of Example 7, the imaging element of Example 8, the imaging element of Example 9, the imaging element of Example 10, and the imaging element of Example 11 can be arbitrarily combined. The imaging element of Example 7, the imaging element of Example 8, the imaging element of Example 9, the imaging element of Example 10, and the imaging element of Example 12 can be arbitrarily combined.
In some cases, the floating diffusion layers FD1, FD2, FD3, 51C, 45C, and 46C can be shared.
For example, as
Alternatively, for example, as
These openings 85B and 85C can be formed by reflowing an etching mask containing a resist material to be formed when an opening is formed in the insulating layer on the basis of an etching method to incline the opening side surface of the etching mask, and etching the insulating layer 82 using the etching mask.
Alternatively, regarding the charge discharge electrode 26 described in Example 5, as illustrated in
Furthermore, for example, as
Note that in the example illustrated in
Alternatively, a structure can be adopted in which light is incident from the second electrode side and light is not incident on the first electrode 21. Specifically, as illustrated in
By adopting these configurations and structures, or alternatively by disposing the light shielding layer 15 such that light is incident only on a portion of the photoelectric conversion layer 23A located above the charge accumulation electrode 24, or alternatively by designing the on-chip micro lens 14, a portion of the photoelectric conversion layer 23A located above the first electrode 21 (or above the first electrode 21 and the transfer control electrode 25) does not contribute to photoelectric conversion. Therefore, all the pixels can be reset more reliably all at once, and a global shutter function can be achieved more easily. That is, a method for driving a solid-state imaging device including the plurality of imaging elements having these configurations and structures repeats,
discharging charges in the first electrode 21 out of the system while charges are accumulated in the inorganic oxide semiconductor material layer 23B and the like all at once in all the imaging elements, and then
transferring the charges accumulated in the inorganic oxide semiconductor material layer 23B and the like to the first electrode 21 all at once in all the imaging elements, and sequentially reading out the charges transferred to the first electrode 21 in each of the imaging elements after completion of the transfer.
In such a method for driving a solid-state imaging device, each of the imaging elements has a structure in which light incident from the second electrode side is not incident on the first electrode, and the charges in the first electrode are discharged out of the system while the charges are accumulated in the inorganic oxide semiconductor material layer and the like all at once in all the imaging elements. Therefore, the first electrode can be reliably reset simultaneously in all the imaging elements. Then, thereafter, the charges accumulated in the inorganic oxide semiconductor material layer and the like are transferred to the first electrode all at once in all the imaging elements, and after completion of the transfer, the charges transferred to the first electrode are sequentially read out in each of the imaging elements. Therefore, a so-called global shutter function can be easily implemented.
Furthermore, as a modification of Example 4, as illustrated in
In Example 7 illustrated in
Furthermore, in Example 8 illustrated in
It goes without saying that the various modifications described above can also be applied to Examples 2 to 14.
In Examples, the case where the present disclosure is applied to a CMOS type solid-state imaging device in which unit pixels that detect signal charges corresponding to the amount of incident light as physical quantities are arranged in a matrix has been described as an example. However, the present disclosure is not limited to application to the CMOS type solid-state imaging device, and can also be applied to a CCD type solid-state imaging device. In the latter case, signal charges are transferred in the vertical direction by a vertical transfer register having a CCD type structure, transferred in the horizontal direction by a horizontal transfer register, and amplified to output a pixel signal (image signal). Furthermore, the present disclosure is not limited to a general column type solid-state imaging device in which pixels are formed in a two-dimensional matrix and a column signal processing circuit is disposed for each pixel column. Moreover, in some cases, the selection transistor can be omitted.
Moreover, the imaging element and the laminated imaging element of the present disclosure are not limited to application to a solid-state imaging device that detects distribution of the amount of incident visible light and images the distribution as an image, but can also be applied to a solid-state imaging device that images distribution of the incident amount of infrared rays, X-rays, particles, and the like as an image. Furthermore, in a broad sense, the present disclosure can be applied to a general solid-state imaging device (physical quantity distribution detection device) such as a fingerprint detection sensor that detects distribution of other physical quantities such as pressure and capacitance, and images the physical quantities as an image.
Moreover, the present disclosure is not limited to a solid-state imaging device that sequentially scans each unit pixel of an imaging region in row units and reads out a pixel signal from each unit pixel. The present disclosure can also be applied to an X-Y address type solid-state imaging device that selects an arbitrary pixel in pixel units and reads out a pixel signal in pixel units from a selected pixel. The solid-state imaging device may be formed as one chip, or may be a modular form having an imaging function in which an imaging region and a drive circuit or an optical system are packaged collectively.
Furthermore, the present disclosure is not limited to application to a solid-state imaging device, but can also be applied to an imaging device. Here, the imaging device refers to a camera system such as a digital still camera or a digital video camera, or an electronic device having an imaging function, such as a mobile phone. There is a case where a module form mounted on an electronic device, that is, a camera module is used as an imaging device.
Note that the present disclosure can have the following configurations.
An imaging element including a photoelectric conversion unit formed by laminating a first electrode, a photoelectric conversion layer, and a second electrode, in which
between the first electrode and the photoelectric conversion layer, an inorganic oxide semiconductor material layer is formed in contact with the photoelectric conversion layer,
the photoelectric conversion unit further includes an insulating layer and a charge accumulation electrode disposed apart from the first electrode so as to face the inorganic oxide semiconductor material layer via the insulating layer,
a material constituting the inorganic oxide semiconductor material layer has a value of work function of 4.5 eV or less, and
a value obtained by subtracting the value of work function of the material constituting the inorganic oxide semiconductor material layer from a value of work function of a material constituting the second electrode exceeds 0.2 eV.
[A02] The imaging element according to [A01], in which a value obtained by subtracting a LUMO value of a material constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer is 0 eV or more.
[A03] The imaging element according to [A02], in which a value obtained by subtracting a LUMO value of a material constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer is less than 0.2 eV.
[A04] The imaging element according to [A03], in which a value obtained by subtracting a LUMO value of a material constituting the inorganic oxide semiconductor material layer from a LUMO value of a material constituting a portion of the photoelectric conversion layer located near the inorganic oxide semiconductor material layer is 0.1 eV or less.
[A05] The imaging element according to any one of [A01] to [A04], in which the inorganic oxide semiconductor material layer is constituted by the same material as that constituting the first electrode.
[A06] The imaging element according to any one of [A01] to [A05], in which the inorganic oxide semiconductor material layer contains indium-gallium-zinc composite oxide.
[A07] The imaging element according to any one of [A01] to [A05], in which the inorganic oxide semiconductor material layer contains at least two elements selected from the group consisting of indium, tungsten, tin, and zinc.
[A08] The imaging element according to [A07], in which the inorganic oxide semiconductor material layer does not contain a gallium atom.
[A09] The imaging element according to [A07], in which the inorganic oxide semiconductor material layer contains indium-tungsten oxide (IWO), indium-tungsten-zinc oxide (IWZO), indium-tin-zinc oxide (ITZO), or zinc-tin oxide (ZTO).
[A10] The imaging element according to [A07], in which the inorganic oxide semiconductor material layer contains indium-tungsten-zinc oxide (IWZO).
[A11] The imaging element according to [A07], in which the inorganic oxide semiconductor material layer contains indium-tungsten oxide (IWO).
[A12] The imaging element according to any one of [A01] to [A11], in which the inorganic oxide semiconductor material layer has a thickness of 3×10−8 m to 1.0×10−7 m.
[A13] The imaging element according to any one of [A01] to [A12], in which a material constituting the inorganic oxide semiconductor material layer has a mobility of 10 cm2/V·s or more.
[A14] The imaging element according to any one of [A01] to [A13], in which the inorganic oxide semiconductor material layer is amorphous.
[A15] The imaging element according to any one of [A01] to [A14], in which
light is incident from the second electrode,
surface roughness Ra of the inorganic oxide semiconductor material layer at an interface between the photoelectric conversion layer and the inorganic oxide semiconductor material layer is 1.5 nm or less, and a value of root mean square roughness Rq of the inorganic oxide semiconductor material layer is 2.5 nm or less.
[A16] The imaging element according to any one of [A01] to [A15], further including a semiconductor substrate, in which
the photoelectric conversion unit is disposed above the semiconductor substrate.
[A17] The imaging element according to any one of [A01] to [A16], in which the first electrode extends in an opening formed in the insulating layer to be connected to the inorganic oxide semiconductor material layer.
[A18] The imaging element according to any one of [A01] to [A16], in which the inorganic oxide semiconductor material layer extends in an opening formed in the insulating layer to be connected to the first electrode.
[A19] The imaging element according to [A18], in which
an edge of a top surface of the first electrode is covered with the insulating layer,
the first electrode is exposed on a bottom surface of the opening, and
when a surface of the insulating layer in contact with the top surface of the first electrode is referred to as a first surface, and a surface of the insulating layer in contact with a portion of the inorganic oxide semiconductor material layer facing the charge accumulation electrode is referred to as a second surface, a side surface of the opening has an inclination widening from the first surface toward the second surface.
[A20] The imaging element according to [A19], in which the side surface of the opening having an inclination widening from the first surface toward the second surface is located on the charge accumulation electrode side.
The imaging element according to any one of [A01] to [A20], further including a control unit disposed on the semiconductor substrate and having a drive circuit, in which
the first electrode and the charge accumulation electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode and applies a potential V12 to the charge accumulation electrode, and charges are accumulated in the inorganic oxide semiconductor material layer, and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode and applies a potential V22 to the charge accumulation electrode, and the charges accumulated in the inorganic oxide semiconductor material layer are read out by the control unit via the first electrode.
However, the potential of the first electrode is higher than the potential of the second electrode, and
V12≥V11 and V22<V21 are satisfied
The imaging element according to any one of [A01] to [A21], further including a transfer control electrode disposed apart from the first electrode and the charge accumulation electrode so as to face the inorganic oxide semiconductor material layer via the insulating layer between the first electrode and the charge accumulation electrode.
The imaging element according to [A22], further including a control unit disposed on a semiconductor substrate and having a drive circuit, in which
the first electrode, the charge accumulation electrode, and the transfer control electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode, applies a potential V12 to the charge accumulation electrode, and applies a potential V13 to the transfer control electrode, and charges are accumulated in the inorganic oxide semiconductor material layer, and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode, applies a potential V22 to the charge accumulation electrode, and applies a potential V23 to the transfer control electrode, and the charges accumulated in the inorganic oxide semiconductor material layer are read out by the control unit via the first electrode.
However, the potential of the first electrode is higher than the potential of the second electrode, and
V12>V13 and V22<V23<V21 are satisfied
The imaging element according to any one of [A01] to [A23], further including a charge discharge electrode connected to the inorganic oxide semiconductor material layer and disposed apart from the first electrode and the charge accumulation electrode.
[A25] The imaging element according to [A24], in which the charge discharge electrode is disposed so as to surround the first electrode and the charge accumulation electrode.
[A26] The imaging element according to [A24] or [A25], in which
the inorganic oxide semiconductor material layer extends in a second opening formed in the insulating layer to be connected to the charge discharge electrode,
an edge of a top surface of the charge discharge electrode is covered with the insulating layer,
the charge discharge electrode is exposed on a bottom surface of the second opening, and
when a surface of the insulating layer in contact with the top surface of the charge discharge electrode is referred to as a third surface, and a surface of the insulating layer in contact with a portion of the inorganic oxide semiconductor material layer facing the charge accumulation electrode is referred to as a second surface, a side surface of the second opening has an inclination widening from the third surface toward the second surface.
The imaging element according to any one of [A24] to [A26], further including a control unit disposed on a semiconductor substrate and having a drive circuit, in which
the first electrode, the charge accumulation electrode, and the charge discharge electrode are connected to the drive circuit,
in a charge accumulation period, the drive circuit applies a potential V11 to the first electrode, applies a potential V12 to the charge accumulation electrode, and applies a potential V14 to the charge discharge electrode, and charges are accumulated in the inorganic oxide semiconductor material layer, and
in a charge transfer period, the drive circuit applies a potential V21 to the first electrode, applies a potential V22 to the charge accumulation electrode, and applies a potential V24 to the charge discharge electrode, and the charges accumulated in the inorganic oxide semiconductor material layer are read out by the control unit via the first electrode.
However, the potential of the first electrode is higher than the potential of the second electrode, and
V14≥V11 and V24<V21 are satisfied
The imaging element according to any one of [A01] to [A27], in which the charge accumulation electrode includes a plurality of charge accumulation electrode segments.
[A29] The imaging element according to [A28], in which
in a case where the potential of the first electrode is higher than that of the second electrode, in a charge transfer period, a potential applied to a charge accumulation electrode segment located closest to the first electrode is higher than a potential applied to a charge accumulation electrode segment located farthest from the first electrode, and
in a case where the potential of the first electrode is lower than that of the second electrode, in the charge transfer period, the potential applied to the charge accumulation electrode segment located closest to the first electrode is lower than the potential applied to the charge accumulation electrode segment located farthest from the first electrode.
[A30] The imaging element according to any one of [A01] to [A29], in which
light is incident from the second electrode,
surface roughness Ra of the inorganic oxide semiconductor material layer at an interface between the photoelectric conversion layer and the inorganic oxide semiconductor material layer is 1.5 nm or less, and a value of root mean square roughness Rq of the inorganic oxide semiconductor material layer is 2.5 nm or less.
[A31] The imaging element according to any one of [A01] to [A30], in which the inorganic oxide semiconductor material layer has a light transmittance of 65% or more with respect to light having a wavelength of 400 nm to 660 nm.
[A32] The imaging element according to any one of [A01] to [A31], in which the charge accumulation electrode has a light transmittance of 65% or more with respect to light having a wavelength of 400 nm to 660 nm.
[A33] The imaging element according to any one of [A01] to [A32], in which the charge accumulation electrode has a sheet resistance value of 3×10Ω/□ to 1×103Ω/□.
[A34] The imaging element according to any one of [A01] to [A33], in which
on the semiconductor substrate, at least a floating diffusion layer and an amplification transistor constituting a control unit are disposed, and
the first electrode is connected to the floating diffusion layer and a gate portion of the amplification transistor.
[A35] The imaging element according to [A34], in which
on the semiconductor substrate, a reset transistor and a selection transistor constituting the control unit are further disposed,
the floating diffusion layer is connected to one source/drain region of the reset transistor, and
one source/drain region of the amplification transistor is connected to one source/drain region of the selection transistor, and the other source/drain region of the selection transistor is connected to a signal line.
[A36] The imaging element according to any one of [A01] to [A35], in which the charge accumulation electrode is larger than the first electrode.
[A37] The imaging element according to any one of [A01] to [A36], in which light is incident from the second electrode side, and a light shielding layer is formed on a light incident side of the second electrode.
[A38] The imaging element according to any one of [A01] to [A36], in which light is incident from the second electrode side, and light is not incident on the first electrode.
[A39] The imaging element according to [A38], in which a light shielding layer is formed on the light incident side of the second electrode and above the first electrode.
[A40] The imaging element according to [A38], in which
an on-chip micro lens is disposed above the charge accumulation electrode and the second electrode, and
light incident on the on-chip micro lens is collected by the charge accumulation electrode.
The imaging element according to any one of [A01] to [A40], in which
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
the charge accumulation electrode includes N charge accumulation electrode segments,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment,
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, and
the thickness of an insulating layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment.
The imaging element according to any one of [A01] to [A40], in which
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
the charge accumulation electrode includes N charge accumulation electrode segments,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment,
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, and
the thickness of a photoelectric conversion layer segment gradually changes from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment.
The imaging element according to any one of [A01] to [A40], in which
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
the charge accumulation electrode includes N charge accumulation electrode segments,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment,
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, and
materials constituting an insulating layer segment are different between adjacent photoelectric conversion unit segments.
The imaging element according to any one of [A01] to [A40], in which
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
the charge accumulation electrode includes N charge accumulation electrode segments disposed apart from one another,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment,
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, and
materials constituting a charge accumulation electrode segment are different between adjacent photoelectric conversion unit segments.
The imaging element according to any one of [A01] to [A40], in which
the photoelectric conversion unit includes N (where N≥2) photoelectric conversion unit segments,
the inorganic oxide semiconductor material layer and the photoelectric conversion layer include N photoelectric conversion layer segments,
the insulating layer includes N insulating layer segments,
the charge accumulation electrode includes N charge accumulation electrode segments disposed apart from one another,
the n-th (where n=1, 2, 3 . . . N) photoelectric conversion unit segment includes the n-th charge accumulation electrode segment, the n-th insulating layer segment, and the n-th photoelectric conversion layer segment,
a photoelectric conversion unit segment with a larger value of n is located farther from the first electrode, and
the area of a charge accumulation electrode segment is gradually reduced from the first photoelectric conversion unit segment to the N-th photoelectric conversion unit segment.
The imaging element according to any one of [A01] to [A40], in which, if a lamination direction of the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer is defined as a Z direction, and a direction of separating from the first electrode is defined as an X direction, when a laminated portion where the charge accumulation electrode, the insulating layer, the inorganic oxide semiconductor material layer, and the photoelectric conversion layer are laminated is cut with a YZ virtual plane, the cross-sectional area of the laminated portion changes depending on a distance from the first electrode.
A laminated imaging element including at least one of the imaging elements according to any one of [A01] to [A46].
A solid-state imaging device including a plurality of the imaging elements according to any one of [A01] to [A46].
A solid-state imaging device including a plurality of the laminated imaging elements according to [B01].
A solid-state imaging device including a photoelectric conversion unit formed by laminating a first electrode, a photoelectric conversion layer, and a second electrode, in which
the photoelectric conversion unit includes a plurality of the imaging elements according to any one of [A01] to [A46],
the plurality of imaging elements constitutes an imaging element block, and
the first electrode is shared by the plurality of imaging elements constituting the imaging element block.
A solid-state imaging device including a plurality of the imaging elements according to any one of [A01] to [A46],
the plurality of imaging elements constitutes an imaging element block, and
the first electrode is shared by the plurality of imaging elements constituting the imaging element block.
[D03] The solid-state imaging device according to [D01] or [D02], in which one on-chip micro lens is disposed above one of the imaging elements.
[D04] The solid-state imaging device according to [D01] or [D02], in which
two of the imaging elements constitute an imaging element block, and
one on-chip micro lens is disposed above the imaging element block.
[D05] The solid-state imaging device according to any one of [D01] to [D04], in which one floating diffusion layer is disposed for the plurality of imaging elements.
[D06] The solid-state imaging device according to any one of [D01] to [D05], in which the first electrode is disposed adjacent to the charge accumulation electrode of each of the imaging elements.
[D07] The solid-state imaging device according to any one of [D01] to [D06], in which the first electrode is disposed adjacent to some of the charge accumulation electrodes of the plurality of imaging elements, and is not disposed adjacent to the remaining charge accumulation electrodes of the plurality of imaging elements.
[D08] The solid-state imaging device according to [D07], in which a distance between a charge accumulation electrode constituting an imaging element and a charge accumulation electrode constituting an imaging element is longer than a distance between a first electrode and a charge accumulation electrode in an imaging element adjacent to the first electrode.
A method for driving a solid-state imaging device including a plurality of imaging elements according to any one of [A01] to [A46], each of the imaging elements having a structure in which light is incident from the second electrode side, and light is not incident on the first electrode, in which
the method repeats
discharging charges in the first electrode out of the system while charges are accumulated in the inorganic oxide semiconductor material layer all at once in all the imaging elements, and then
transferring the charges accumulated in the inorganic oxide semiconductor material layer to the first electrode all at once in all the imaging elements, and sequentially reading out the charges transferred to the first electrode in each of the imaging elements after completion of the transfer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-157155 | Aug 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/022396 | 6/12/2018 | WO | 00 |
