Patent Application
20200295063
The present invention relates to a photoelectric conversion apparatus.
Photoelectric conversion apparatuses are widely used as imaging apparatuses in two-dimensional image-input apparatus such as a digital still camera, a video camcorder, or the like, for example. Due to a demand for improving performance of two-dimensional image-input apparatuses, there is also a demand for improvement of image quality in imaging apparatuses, and study for increasing a signal/noise (S/N) ratio of an output signal has been made. One scheme for increasing the S/N ratio of the imaging apparatus may be a method of reducing a parasitic capacitance of a floating diffusion portion to increase photoelectric conversion efficiency and reducing random noise superimposed on an output signal. Herein, the parasitic capacitance of a floating diffusion portion may be a p-n junction capacitance in a diffusion layer, an interlayer capacitance between the floating diffusion portion and a wiring connected to a floating diffusion portion, a capacitance between the floating diffusion portion and a transfer gate electrode, or the like.
Japanese Patent Application Laid-Open No. 2008-041726 discloses a technology for reducing noise due to hot carriers occurring at p-n junction between a channel region and a drain region of a transfer transistor.
Japanese Patent Application Laid-Open No. 2007-165864 discloses a photoelectric conversion apparatus in which an anti-reflection film is arranged above a light receiving face of a photoelectric conversion element, an element isolation region having an insulating member, and an active region in which a contact is formed. Further, Japanese Patent Application Laid-Open No. 2007-165864 discloses that the anti-reflection film serves as an etching stop film used in etching when the contact is formed.
According to one aspect of the present invention, provided is a photoelectric conversion apparatus including: a substrate having a photoelectric conversion portion and a floating diffusion portion; a gate electrode of a transfer transistor provided on the substrate and configured to transfer charges generated by the photoelectric conversion portion to the floating diffusion portion; a first film formed of an insulating material whose relative dielectric constant is lower than 5.0 and provided so as to cover at least a side face of the gate electrode of the transfer transistor, the side face being on the floating diffusion portion side; a second film provided on the first film; and a contact plug being in contact with the second film and connected to the transfer transistor, wherein in a range which is above the floating diffusion portion and in which a distance from an intersection line of a face including the side face of the gate electrode and a surface of the substrate is less than or equal to a distance corresponding to a height of the gate electrode from the surface, the photoelectric conversion apparatus includes no insulating material whose relative dielectric constant is higher than or equal to 5.0.
According to another aspect of the present invention, provided is a photoelectric conversion apparatus including: a substrate having a photoelectric conversion portion; a gate electrode of a transfer transistor provided on the substrate and configured to transfer charges generated by the photoelectric conversion portion; a first film having a part provided above the photoelectric conversion portion; a second film provided on the first film; and a contact plug being in contact with the second film and connected to the transfer transistor, wherein the part of the first film is located between the second film and the photoelectric conversion portion, wherein the first film has an end portion between the part of the first film and a side face of the gate electrode on the photoelectric conversion side, and wherein a portion of the second film is located between the end portion and the gate electrode.
According to further another aspect of the present invention, provided is a manufacturing method of a photoelectric conversion apparatus, the manufacturing method including steps of: forming a silicon nitride film on a region on a substrate including a photoelectric conversion portion, and a transfer transistor that includes a gate electrode and transfers charges generated by the photoelectric conversion portion, wherein the region includes at least a photoelectric conversion portion; and making the silicon nitride film discontinuous on the photoelectric conversion portion side of a side face of the gate electrode on the photoelectric conversion portion side.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
In the conventional photoelectric conversion apparatus, however, a silicon nitride film that functions as an anti-reflection film is provided over the whole pixel region. Since silicon nitride has a higher relative dielectric constant than silicon oxide widely used for an interlayer insulating film or the like, the parasitic capacitance formed between a transfer gate and a floating diffusion portion via such a silicon nitride film increases, and this causes an increase of random noise.
The present disclosure intends to provide a photoelectric conversion apparatus that can reduce a parasitic capacitance coupled to a floating diffusion portion and reduce noise superimposed on an output signal. A photoelectric conversion apparatus and a manufacturing method thereof according to a first embodiment of the present disclosure will be described with reference to
As illustrated in
In the pixel region 610, a plurality of pixels 612 arranged in a matrix are provided over a plurality of rows and a plurality of columns. Each of the pixels 612 includes a photoelectric conversion portion formed of a photoelectric conversion element such as a photodiode and outputs a pixel signal in accordance with the light amount of an incident light. The number of rows and the number of columns of the pixel array arranged in the pixel region 610 are not particularly limited. Further, in the pixel region 610, an optical black pixel whose photoelectric conversion portion is shielded from light, a dummy pixel that does not output a signal, or the like may be arranged in addition to effective pixels that output pixel signals in accordance with the light amount of an incident light.
On each row of the pixel array of the pixel region 610, a control line 614 is arranged extending in a first direction (the horizontal direction in
On each column of the pixel array of the pixel region 610, an output line 616 is arranged extending in a second direction (the vertical direction in
The vertical scanning circuit 620 is a control circuit unit that supplies, to the pixels 612 via the control lines 614 provided on respective rows of the pixel array, control signals used for driving readout circuits in the pixels 612 when signals are read out from the pixels 612. The vertical scanning circuit 620 can be formed by using a shift register or an address decoder. Signals read out from the pixels 612 on a row basis are input to the readout circuit 630 via the output lines 616 provided on respective columns of the pixel array.
The readout circuit 630 is a circuit unit that implements predetermined signal processing, for example, signal processing such as an amplification process, an analog-to-digital (A/D) conversion process, or the like on a signal read out from the pixels 612 on each column via the output line 616. The readout circuit 630 may include a signal holding unit, a column amplifier, a correlated double sampling (CDS) circuit, an adder circuit, an A/D converter circuit, a column memory, or the like.
The horizontal scanning circuit 40 is a circuit unit that supplies, to the readout circuit 630, control signals used for transferring signals processed by the readout circuit 630 to the output circuit 50 sequentially on a column basis. The horizontal scanning circuit 40 can be formed by using a shift register or an address decoder. The output circuit 50 is a circuit unit that is formed of a buffer amplifier, a differential amplifier, or the like and amplifies and outputs a signal of a column selected by the horizontal scanning circuit 40.
The control circuit 60 is a circuit unit that supplies, to the vertical scanning circuit 620, the readout circuit 630, and the horizontal scanning circuit 40, control signals used for controlling the operations of the above or the timings thereof. Some or all of the control signals supplied to the vertical scanning circuit 620, the readout circuit 630, and the horizontal scanning circuit 40 may be supplied from the outside of the photoelectric conversion apparatus 100.
As illustrated in
The photoelectric conversion portion PD is a photodiode, for example, the anode is connected to a ground node, and the cathode is connected to the source of the transfer transistor M1. The drain of the transfer transistor M1 is connected to the source of the reset transistor M2 and the gate of the amplifier transistor M3. The connection node of the drain of the transfer transistor M1, the source of the reset transistor M2, and the gate of the amplifier transistor M3 is a so-called a floating diffusion portion FD. The floating diffusion portion FD includes a capacitance component (floating diffusion capacitance) and has a function as a charge holding portion.
The drain of the reset transistor M2 and the drain of the amplifier transistor M3 are connected to a power source node to which a voltage Vdd is supplied. The source of the amplifier transistor M3 is connected to the drain of the select transistor M4. The source of the select transistor M4 is connected to the output line 616. The output line 616 is connected to the current source 618.
In the case of the pixel configuration illustrated in
The photoelectric conversion portion PD converts (photoelectrically converts) an incident light into an amount of charges in accordance with a light amount and accumulates the generated charges. When turned on, the transfer transistor M1 transfers charges held in the photoelectric conversion portion PD to the floating diffusion portion FD. The floating diffusion portion FD has a voltage corresponding to the amount of charges transferred from the photoelectric conversion portion PD in accordance with charge-to-voltage conversion caused by the capacitance thereof. The amplifier transistor M3 is configured such that the voltage Vdd is supplied to the drain and a bias current is supplied to the source from the current source 618 via the select transistor M4 and forms an amplifier unit (source follower circuit) whose gate is the input node. Thereby, the amplifier transistor M3 outputs a signal based on the voltage of the floating diffusion portion FD to the output line 616 via the select transistor M4. When turned on, the reset transistor M2 resets the floating diffusion portion FD to a voltage in accordance with the voltage Vdd.
As illustrated in
In the configuration example illustrated in
Note that it is not necessarily required to arrange only the pixel region 610 on the substrate 110. For example, any one or more of the vertical scanning circuit 620, the readout circuit 630, the horizontal scanning circuit 40, the output circuit 50, and the control circuit 60 may be arranged on the substrate 110, or some of these components may be arranged on the substrate 110. The former may be an example in which the pixel region 610 and the vertical scanning circuit 620 are arranged on the substrate 110, for example. The latter may be an example in which the pixel region 610 and a part of the readout circuit 630 are arranged on the substrate 110, for example. Further, a circuit other than the blocks illustrated in
A semiconductor region 114 of a second conductivity type (for example, p-type) forming a well is provided in the surface part of the silicon substrate 112 of a first conductivity type (for example, n-type). An element isolation region 116 defining active regions 118 and 120 is provided in the surface part of the semiconductor region 114. The element isolation region 116 is formed of a structure made of a dielectric material formed by a shallow trench isolation (STI) method, a local oxidation of silicon (LOCOS) method, or the like.
For example, the photoelectric conversion portion PD and the transfer transistor M1 out of the components of the pixel 612 are provided in the active region 118. Further, the reset transistor M2, the amplifier transistor M3, and the select transistor M4 out of the components of the pixel 612 are provided in the active region 120. In
The photoelectric conversion portion PD is an embedded photodiode including a semiconductor region 122 of the second conductivity type provided in contact with the surface of the silicon substrate 112 and a semiconductor region 124 of the first conductivity type provided under the semiconductor region 122. The semiconductor region 124 forms p-n junction with the semiconductor region 122. The semiconductor region 124 has a roll as a charge accumulation layer that accumulates signal charges (electrons) generated by the photoelectric conversion portion PD. The semiconductor region 122 has a roll as a surface protection layer that suppresses a surface leak current. The semiconductor region 126 of the first conductivity type forming a part of the floating diffusion portion FD is provided on the surface part of the active region 118 so as to be spaced apart from the semiconductor region 124.
A gate electrode 134 made of a conductive material such as poly-crystal silicon or the like is provided above the silicon substrate 112 between the semiconductor region 124 and the semiconductor region 126 via a gate insulating film 132 made of silicon oxide (SiO), silicon oxy nitride (SiON), or the like. Thereby, the transfer transistor M1 in which the semiconductor region 124 is the source, the semiconductor region 126 is the drain, and the gate electrode 134 is the gate is configured.
A semiconductor region 128 of the first conductivity type and a semiconductor region 130 of the first conductivity type are provided so as to be spaced apart from each other on the surface part of the active region 120.
A gate electrode 136 made of a conductive material such as poly-crystal silicon or the like is provided above the silicon substrate 112 between the semiconductor region 128 and the semiconductor region 130 via the gate insulating film 132 made of SiO, SiON, or the like. Thereby, the amplifier transistor M3 in which the semiconductor region 128 is the source, the semiconductor region 130 is the drain, and the gate electrode 136 is the gate is configured.
An insulating film 138 and an insulating film 140 are provided above the silicon substrate 112 in which the photoelectric conversion portion PD, the transfer transistor M1, the amplifier transistor M3, and the like are provided. The insulating film 138 is formed along the unevenness formed above the surface of the silicon substrate 112 due to the gate electrodes 134 and 136. The film thickness of the insulating film 138 is thinner than a thickness corresponding to the height of the gate electrodes 134 and 136. The insulating film 138 may be formed of a porous insulating material such as nano-clustering silica, a low dielectric constant material such as silicon oxy carbide (SiOC), silicon oxide, or the like. The insulating film 138 may be formed of stacked films of a silicon oxide film and a low dielectric constant film. The insulating film 140 is formed to have a film thickness sufficient to fill the unevenness above the surface of the silicon substrate 112, and the surface is planarized. In other words, the insulating film 140 is at least partially located at a position closer to the silicon substrate 112 than the upper face of the gate electrodes 134 and 136. The insulating film 140 may be formed of silicon oxide. It is desirable that the dielectric constant of the insulating film 138 be smaller than the dielectric constant of the insulating film 140.
Note that, although
Contact plugs 142 electrically connected to the semiconductor regions 126, 128, and 130 are provided through the insulating films 140 and 138 and the gate insulating film 132. The contact plug 142 may be formed of a barrier metal of titanium nitride or the like and tungsten, for example.
An insulating film 144 is provided on the insulating film 140. Wiring layers 146 electrically connected to the transfer transistor M1, the amplifier transistor M3, or the like via the contact plugs 142 are provided in the insulating film 144. The wiring layer 146 may be formed of aluminum or copper, for example.
Note that the photoelectric conversion apparatus of the present embodiment is a backside irradiation photoelectric conversion apparatus. That is, the photoelectric conversion portion PD receives an incident light from a face (the underside in
It is desirable to reduce the parasitic capacitance of the floating diffusion portion FD in terms of reducing random noise to improve the S/N ratio. On the other hand, in a typical front side irradiation imaging apparatus, a SiN film or a SiON film is used as an anti-reflection film arranged above a photoelectric conversion portion, an increase in the capacitance Cf or the interlayer capacitance Cint is unavoidable. That is, compared to the relative dielectric constant of around 3.8 for SiO, the relative dielectric constant of SiN is around 7.0, and the relative dielectric constant of SiON is around 5.0 to 7.0. Thus, when the insulating film 138 is formed of these insulating materials having a relatively high dielectric constant, the capacitance Cf or the interlayer capacitance Cint will increase.
In this regard, in the photoelectric conversion apparatus of the present embodiment, the insulating film 138 is formed of an insulating material having a lower dielectric constant than SiN or SiON, specifically, a lower dielectric constant material such as SiOC or a porous insulating material or SiO. Therefore, the capacitance Cf or the interlayer capacitance Cint can be reduced compared to a case where the insulating film 138 is formed of SiN or SiON, and the S/N ratio can be improved by a reduction of the FD capacitance. In terms of reducing the capacitance Cf, the insulating film 138 covers at least the side face of the gate electrode 134 of the transfer transistor M1 on the floating diffusion portion FD side.
Further, SiON may be used for the gate insulating film 132 for suppressing an increase of a tunnel current or suppressing penetration of an impurity through the gate electrode 134 in a direction of the silicon substrate 112. However, since the dielectric constant of SiON increases as the nitrogen concentration increases, this may cause the gate insulating film 132 to increase the capacitance Cf.
In terms of the above, it is desirable that the relative dielectric constant of an insulating material forming the insulating film (the gate insulating film 132, the insulating films 138 and 140) formed in a range 148 from the surface of the silicon substrate 112 to the upper face of the gate electrode 134 be lower than 5.0. Note that the nitrogen concentration in SiON having a relative dielectric constant of around 5.0 is approximately 10 atm %.
Although the range in which an insulating film is to be formed so as not to contain an insulating material having a relative dielectric constant of 5.0 or higher may change in accordance with the relationship to the stack structure of insulating films or another structure and thus is not necessarily even, the range can be defined based on the geometrical relationship illustrated in
The first range is a range (region A in
The range in which the relative dielectric constant of the insulating material is set to be lower than 5.0 preferably includes at least the first range described above and more preferably includes the second range described above. Further, the range in which the relative dielectric constant of the insulating material is set to be lower than 5.0 more preferably includes the third range described above and more preferably includes the fourth range described above. The photoelectric conversion apparatus may include the insulating material having a relative dielectric constant of 5.0 or higher outside the first range from the surface of the silicon substrate 112, preferably outside the second range, more preferably outside the third range, and more preferably outside the fourth range. For example, the insulating material having a relative dielectric constant of 5.0 or higher may be included outside the fourth range, that is, a position distant by a length that is twice or more the height of the upper face of the gate electrode. The insulating material having a relative dielectric constant of 5.0 or higher may be, for example, silicon nitride or silicon carbide. The member made of the insulating material having a relative dielectric constant of 5.0 or higher may be used as an etching stop member, a member used for suppressing diffusion of a metal, or a passivation member, for example.
The insulating film 140 may be formed of SiO. It is desirable to form the insulating film 140 by a high density plasma chemical vapor deposition (HDPCVD) method in terms of improving the filling property of a space between the gate electrodes 134 and 136 or the like. Since a SiO film deposited by the HDPCVD method has high permeability of hydrogen and has a large content of hydrogen in the film, such a SiO film is useful for a photoelectric conversion apparatus in terms of noise reduction. The SiO film formed by the HDPCVD method may contain argon in plasma and thus has a higher argon concentration than the insulating film 138 or a SiO film formed by a thermal CVD method or a typical plasma CVD method.
In general, however, plasma damage is likely to occur in deposition by the HDPCVD method, and it is not preferable to deposit the insulating film 140 directly on the gate electrodes 134 and 136 because reliability of the gate insulating film 132 may be reduced. The insulating film 138 arranged between the gate electrodes 134 and 136 and the insulating film 140 also has a roll as a protection film that reduces plasma damage during deposition of the insulating film 140. That is, it is desirable that the entire upper faces and side faces of the gate electrodes 134 and 136 be covered with the insulating film 138 at least when the insulating film 140 is deposited.
While the transfer transistor M1 and the amplifier transistor M3 are described here, plasma damage similarly affects the reset transistor M2 or the select transistor M4, and the insulating film 138 is formed also on the gate electrodes of these transistors.
Next, a manufacturing method of a photoelectric conversion apparatus according to the present embodiment will be described with reference to
First, the element isolation region 116 that defines the active regions 118 and 120 is formed in the primary surface of the silicon substrate 112 of the first conductivity type (n-type) by using an STI method, a LOCOS method, or the like.
Next, the semiconductor region 114 of the second conductivity type (p-type) that is to be a well is formed inside the silicon substrate 112 of the active regions 118 and 120 by using photolithography and ion implantation. Further, the semiconductor region 124 of the first conductivity type that is to be a charge accumulation region of the photoelectric conversion portion PD is formed in a formation region of the photoelectric conversion portion PD (
Next, after the silicon substrate 112 is thermally oxidized to form a silicon oxide film, a nitriding process is performed, and the gate insulating film 132 made of silicon oxy nitride (SiON) is formed on the silicon substrate 112 (
Next, a poly-crystal silicon film is deposited on the gate insulating film 132 by using a CVD method, for example, and this poly-crystal silicon film is then patterned by using photolithography and dry etching to form the gate electrodes 134 and 136 made of poly-crystal silicon. After the gate electrodes 134 and 136 are formed, at least a part of the gate insulating film 132 provided in a region except a region directly under the gate electrodes 134 and 136 may be removed by wet etching or the like.
Next, the semiconductor region 122 of the second conductivity type that is to be a surface protection layer of the photoelectric conversion portion PD and the semiconductor region 126 of the first conductivity type forming the floating diffusion portion FD are formed in the active region 118 by using photolithography and ion implantation. Further, the semiconductor regions 128 and 130 of the first conductivity type that are to be source/drain regions of the amplifier transistor M3 are formed in the active region 120 (
Next, a thermal process at 800 degrees Celsius to 1100 degrees Celsius is performed in a nitrogen atmosphere if necessary, and a recovery process of a crystal defect introduced in the silicon substrate 112 is performed by ion implantation.
Next, the insulating film 138 made of a low dielectric constant material such as silicon oxy carbide (SiOC) or a porous insulating material or silicon oxide is formed by a low pressure CVD method or a plasma CVD method, for example (
Next, the insulating film 140 made of silicon oxide is formed by an HDPCVD method, for example (
Next, contact holes that penetrate the insulating films 140 and 138 and the gate insulating film 132 and reach the silicon substrate 112 are formed by photolithography and dry etching. Next, a bather metal film of a titanium nitride (TiN) or the like and a tungsten (W) film are formed by a CVD method or the like, for example, these conductive films on the insulating film 140 are then removed by a CMP method or the like, and thereby the contact plugs 142 embedded in the contact holes are formed.
Next, the wiring layers 146 provided inside the insulating film 144 are formed by using a known multilayer wiring process on the insulating film 140 in which the contact plugs 142 are provided. The wiring layers 146 are formed with a predetermined total number of layers being stacked via the insulating film 144 and electrically connected to the transfer transistor M1, the amplifier transistor M3, and the like via the contact plugs 142. The insulating film 144 may be formed of stacked films of silicon oxide and silicon oxy carbide, for example. Further, the wiring layer 146 may be formed of aluminum or copper, for example.
As described above, the substrate 110 in which the pixel region 610 is provided on the silicon substrate 112 is formed (
Further, the substrate 150 which is a separate substrate from the substrate 110 and in which the vertical scanning circuit 620, the readout circuit 630, the horizontal scanning circuit 40, the output circuit 50, the control circuit 60, and the like are provided is formed by using a known manufacturing process for a semiconductor apparatus. As an example, as illustrated in
Next, the substrate 110 and the substrate 150 formed in such a way are attached to each other so that the insulating film 144 and the insulating film 160 face each other by using a known substrate attaching technique. Thereby, the substrate 110 and the substrate 150 are physically and electrically joined to each other.
Next, the substrate 110 attached on the substrate 150 is grinded from the silicon substrate 112 side to thin the substrate 110 to a thickness suitable for light incidence to the photoelectric conversion portion PD (
Next, insulating films 170, 172, and 174 are formed on the surface of the substrate 110 on which the thinning process has been performed (
A color filter, a micro-lens, or the like are then formed if necessary, and the photoelectric conversion apparatus according to the present embodiment is completed.
As described above, according to the present embodiment, the parasitic capacitance coupled to a floating diffusion portion can be reduced, and noise superimposed on an output signal can be reduced.
A photoelectric conversion apparatus and a manufacturing method thereof according to a second embodiment of the present disclosure will be described with respect to
First, the structure of the photoelectric conversion apparatus according to the present embodiment will be described with reference to
As described in the first embodiment, there is a concern that the insulating film 138 serves as a hydrogen diffusion suppression film when the insulating film 138 is formed of a low dielectric constant material such as SiOC or a porous insulating material or silicon oxide in terms of reducing a parasitic capacitance of the floating diffusion portion FD. That is, when the insulating film 138 is arranged over a wide region on the silicon substrate 112, supply of hydrogen from the insulating film 140 or a passivation film formed on the upper layer may be prevented by the insulating film 138, and there is a concern that a sufficient effect of reducing the interface state by hydrogen is not obtained.
On the other hand, the insulating film 138 has a roll of suppressing the gate insulating film 132 from being affected and damaged by charges flowing therein via the gate electrodes 134 and 136 at the time of forming the insulating film 140. That is, the insulating film 138 covers at least the gate electrodes 134 and 136.
In terms of the above, in the present embodiment, the insulating film 138 is formed so as to selectively cover the gate electrodes 134 and 136 to suppress the insulating film 138 from preventing supply of hydrogen from the insulating film 140 or the passivation film. With such a configuration of the photoelectric conversion apparatus, it is possible to obtain an effect of reducing the parasitic capacitance of the floating diffusion portion FD and an effect of reducing plasma damage at the time of forming the insulating film 140 as with the first embodiment while suppressing the insulating film 138 from preventing supply of hydrogen.
Note that, although the insulating film 138 is formed so as to selectively cover the gate electrodes 134 and 136 in the present embodiment, an opening may be provided in the insulating film 138 to facilitate supply of hydrogen via this opening. The insulating film 138 covers at least the gate electrodes 134 and 136, and a position where the opening is provided or the area of the opening can be set as appropriate in accordance with the effect of supply of hydrogen.
Next, the manufacturing method of the photoelectric conversion apparatus according to the present embodiment will be described with reference to
Next, the insulating film 138 is patterned so as to selectively cover the gate electrodes 134 and 136 by using photolithography and dry etching. Alternatively, an opening is formed in the insulating film 138 so as not to expose the gate electrodes 134 and 136 (
Next, in the same manner as the manufacturing method of the photoelectric conversion apparatus according to the first embodiment, the insulating film 140, the contact plugs 142, the insulating film 144, the wiring layers 146, and the like are formed, and the substrate 110 is formed (
Then, in the same manner as the manufacturing method of the photoelectric conversion apparatus according to the first embodiment, the substrate 110 and the substrate 150 are joined to each other, and the photoelectric conversion apparatus of the present embodiment is then completed after a predetermined backend process.
As described above, according to the present embodiment, the parasitic capacitance coupled to the floating diffusion portion can be reduced, and noise superimposed on an output signal can be reduced.
An imaging system according to a third embodiment of the present disclosure will be described with reference to
The photoelectric conversion apparatus 100 described in the above first and second embodiments is applicable to various imaging systems. An example of the applicable imaging system may be a digital still camera, a digital camcorder, a surveillance camera, a copy machine, a fax machine, a mobile phone, an on-vehicle camera, an observation satellite, or the like. Further, a camera module having an optical system such as a lens and an imaging apparatus is also included in the imaging system.
An imaging system 200 illustrated in
Further, the imaging system 200 has a signal processing unit 208 that performs a process of an output signal output from the imaging apparatus 201. The signal processing unit 208 performs AD conversion to convert an analog signal output from the imaging apparatus 201 into a digital signal. Further, the signal processing unit 208 performs operations to perform various correction or compression if necessary and output image data in addition to the above. The AD conversion unit that is a part of the signal processing unit 208 may be formed on a semiconductor substrate on which the imaging apparatus 201 is provided or may be formed on a semiconductor substrate other than a substrate on which the imaging apparatus 201 is provided. Further, the imaging apparatus 201 and the signal processing portion 208 may be formed on the same semiconductor substrate.
Furthermore, the imaging system 200 has a memory unit 710 used for temporarily storing image data and an external interface unit (external OF unit) 212 used for communicating with external computer or the like. Furthermore, the imaging system 200 has a storage medium 214 such as semiconductor memory used for performing storage or readout of imaging data and a storage medium control interface unit (storage medium control I/F unit) 216 used for performing storage or readout on the storage medium 214. Note that the storage medium 214 may be built in the imaging system 200 or may be removable.
Furthermore, the imaging system 200 has a general control/operation unit 218 that controls various operations and controls the entire digital still camera and a timing generation unit 220 that outputs various timing signals to the imaging apparatus 201 and the signal processing unit 208. Here, the timing signal or the like may be externally input, and the imaging system 200 has at least the imaging apparatus 201 and the signal processing unit 208 that processes an output signal output from the imaging apparatus 201.
The imaging apparatus 201 outputs an imaging signal to the signal processing unit 208. The signal processing unit 208 implements predetermined signal processing on an imaging signal output from the imaging apparatus 201 and outputs image data. The signal processing unit 208 uses an imaging signal to generate an image.
As described above, according to the present embodiment, the imaging system to which the photoelectric conversion apparatus 100 according to the first or second embodiment is applied can be realized.
An imaging system and a moving body according to a fourth embodiment of the present disclosure will be described with reference to
The imaging system 300 is connected to the vehicle information acquisition apparatus 320 and can acquire vehicle information such as a vehicle speed, a yaw rate, a steering angle, or the like. Further, the imaging system 300 is connected to a control ECU 330, which is a control apparatus that outputs a control signal for causing a vehicle to generate braking force based on a determination result by the collision determination portion 318. Further, the imaging system 300 is also connected to an alert apparatus 340 that issues an alert to the driver based on a determination result by the collision determination portion 318. For example, when the collision probability is high as the determination result of the collision determination portion 318, the control ECU 330 performs vehicle control to avoid a collision or reduce damage by applying a brake, pushing back an accelerator, suppressing engine power, or the like. The alert apparatus 340 alerts a user by sounding an alert such as a sound, displaying alert information on a display of a car navigation system or the like, providing vibration to a seat belt or a steering wheel, or the like.
In the present embodiment, an area around a vehicle, for example, a front area or a rear area is captured by using the imaging system 300.
Further, although the example of control for avoiding a collision to another vehicle has been described above in the present embodiment, the embodiment is applicable to automatic driving control for following another vehicle, automatic driving control for not going out of a traffic lane, or the like. Furthermore, the imaging system is not limited to a vehicle such as an automobile and can be applied to a moving body (moving equipment) such as a ship, an airplane, or an industrial robot, for example. In addition, the imaging system can be widely applied to an equipment which utilizes object recognition, such as an intelligent transportation system (ITS), without being limited to moving bodies. The scope of the equipment as used herein includes an electronic equipment, an imaging equipment, a display equipment, a medical equipment, a transportation equipment (moving body), or the like.
The present invention is not limited to the embodiments described above, and various modifications are possible. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment or an example in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment is also one of the embodiments of the present invention.
Further, although a stack type photoelectric conversion apparatus in which the pixel region and the peripheral circuit region are arranged in different substrates has been illustrated in the above first embodiment, the application example of the present invention is not limited to the stack type photoelectric conversion apparatus. For example, the same advantageous effect as described in the above embodiment can be realized also when the present invention is applied to a photoelectric conversion apparatus in which the pixel region and the peripheral circuit region are formed on the same substrate. The photoelectric conversion apparatus may be of a front side irradiation type or a backside irradiation type.
When a front side irradiation photoelectric conversion apparatus is configured, it is preferable to arrange an anti-reflection film made of SiN or the like above the photoelectric conversion portion PD. In such a configuration, the anti-reflection film is arranged only above the photoelectric conversion portion PD side so as not to increase the capacitance Cf between the gate electrode 134 and the impurity region 226 due to the anti-reflection film.
This anti-reflection film can also be used as the protection film that reduces plasma damage at the deposition of the insulating film 140. That is, such a configuration that covers the entire upper face and side face of the gate electrode 134 with the insulating film 138 and the anti-reflection film is possible. In such a case, the insulating film 138 covers at least the side face of the gate electrode 134 on the floating diffusion portion FD side.
Further, although the case where signal charges output by the photoelectric conversion portion PD are electrons has been described as an example in the above embodiments, signal charges output by the photoelectric conversion portion PD may be holes. In such a case, the first conductivity type described above is p-type, and the second conductivity type described above is n-type.
Further, the imaging systems illustrated in the above third and fourth embodiments are examples of imaging systems to which the photoelectric conversion apparatus of the present invention may be applied, and the imaging system to which the photoelectric conversion apparatus of the present invention can be applied is not limited to the configurations illustrated in
Note that all the embodiments described above are mere embodied examples in implementing the present invention, and the technical scope of the present invention should not be construed in a limiting sense by these embodiments. That is, the present invention can be implemented in various forms without departing from the technical concept or the primary feature thereof.
A photoelectric conversion apparatus and a manufacturing method thereof according to a fifth embodiment of the present disclosure will be described with reference to
In a photoelectric conversion apparatus including a photoelectric conversion element, there is a demand for reducing characteristic deterioration. In the conventional photoelectric conversion apparatus, however, when a photoelectric conversion element is irradiated with a significantly intense light, dark output of the pixel thereof changes before and after the light irradiation, and this may result in characteristic deterioration.
The present embodiment intends to provide a photoelectric conversion apparatus and a manufacturing method thereof that can reduce characteristic deterioration due to light irradiation.
According to the present embodiment, characteristic deterioration due to light irradiation can be reduced.
First, the structure of the photoelectric conversion apparatus according to the present embodiment will be described with reference to
As illustrated in
Note that the arrangement of the plurality of pixels P is not limited to a matrix. For example, the arrangement of the plurality of pixels P may be one dimensional. Further, the number of pixels P included in the pixel region 1001 may be one without being limited to two or more.
As illustrated in
The photoelectric conversion portion PD is a photodiode, for example, the anode is connected to a ground node, and the cathode is connected to the source of the transfer transistor M1. The drain of the transfer transistor M1 is connected to the source of the reset transistor M2 and the gate of the amplifier transistor M3. The connection node of the drain of the transfer transistor M1, the source of the reset transistor M2, and the gate of the amplifier transistor M3 is a so-called a floating diffusion portion FD. The floating diffusion portion FD includes a capacitance component (floating diffusion capacitance Cfd) formed of a parasitic capacitance such as a wiring capacitance, a junction capacitance, or the like and has a function as a charge holding portion. The drain of the reset transistor M2 and the drain of the amplifier transistor M3 are connected to a power source node to which a voltage VDD is supplied. The source of the amplifier transistor M3 is connected to the drain of the select transistor M4. The source of the select transistor M4 is connected to an output line L. The output line L is connected to the current source IS.
The photoelectric conversion portion PD converts (photoelectrically converts) an incident light into an amount of charges in accordance with a light amount and accumulates the generated charges. When turned on, the transfer transistor M1 transfers charges held in the photoelectric conversion portion PD to the floating diffusion portion FD. The floating diffusion portion FD has a voltage corresponding to the amount of charges transferred from the photoelectric conversion portion PD in accordance with charge-to-voltage conversion caused by the capacitance thereof. The amplifier transistor M3 is configured such that the voltage VDD is supplied to the drain and a bias current is supplied to the source from the current source IS via the select transistor M4 and forms an amplifier portion (source follower circuit) whose gate is the input node. Thereby, the amplifier transistor M3 outputs a signal based on the voltage of the floating diffusion portion FD to the output line L via the select transistor M4. When turned on, the reset transistor M2 resets the floating diffusion portion FD to a voltage in accordance with the voltage VDD.
In
The substrate 10 is a semiconductor substrate such as a silicon substrate, for example. An element isolation region 14 electrically isolating the regions of the substrate 10 from each other and defining an active region 12 is provided in the substrate 10. The element isolation region 14 is an insulating isolation region formed of a silicon oxide film, for example, by local oxidation of silicon (LOCOS), shallow trench isolation (STI), or the like, for example.
In the active region 12, a photodiode forming the photoelectric conversion portion PD, the transfer transistor M1, and the floating diffusion portion FD as a charge holding portion that holds charges transferred from the photoelectric conversion portion PD are arranged. The photoelectric conversion portion PD and the floating diffusion portion FD arranged in the active region 12 are isolated from each other by the element isolation region 14 between adjacent pixels P to prevent color mixture. However, the isolation between adjacent pixels P is not limited to the above. The isolation between the pixels P may be isolation by using a diffusion layer in which an impurity region is provided between the pixels P, or both isolation by using the element isolation region 14 and isolation by using the diffusion layer may be used. When the isolation by using the diffusion layer is used, an impurity region of a conductivity type that is opposite to the conductivity type of the impurity region 16 can be provided between the pixels P.
The photoelectric conversion portion PD is an embedded photodiode including the impurity region 16 of the first conductivity type provided on the surface of the active region 12 of the substrate 10 and an impurity region 18 of the second conductivity type provided in contact with the underside of the impurity region 16. The second conductivity type is a conductivity type opposite to the first conductivity type. For example, the first conductivity type is P-type, and the second conductivity type is N-type. The impurity region 16 is provided to form the photoelectric conversion portion PD in the embedded photodiode structure and has a roll of suppressing influence of a dark current occurring by influence of the interface state of the surface part of the substrate 10. The impurity region 18 is a charge accumulation layer used for accumulating signal charges by the photoelectric conversion portion PD. Note that a configuration without the impurity region 16 may be possible. Note that the substrate 10 is of the first conductivity type, or a well of the first conductivity type (not illustrated) is provided inside the active region 12.
The floating diffusion portion FD is formed of an impurity region 20 of the second conductivity type provided on the surface part of the active region 12 of the substrate 10 so as to be spaced apart from the impurity region 18.
The transfer transistor M1 includes a gate electrode 24 provided via a gate insulating film 22 on the substrate 10 between the impurity region 18 and the impurity region 20. The gate insulating film 22 is formed of an insulating film such as a silicon oxide film, for example. The gate electrode 24 is formed of a polysilicon or the like, for example.
In the photodiode forming the photoelectric conversion portion PD, photoelectric conversion is performed by a depletion layer created by p-n junction. When a light enters the photoelectric conversion portion PD, carriers that are to be signal charges are generated. The generated carriers can be transferred to the impurity region 20 forming the floating diffusion portion FD through the transfer transistor M1. The transfer transistor M1 can be switched between an on-state and an off-state by application of a voltage to a contact plug 32 described later connected to the gate electrode 24 via a wiring (not illustrated). Thereby, an accumulation period or the like of charges in the photoelectric conversion portion PD is adjusted.
Further, the impurity region 20 forming the floating diffusion portion FD is of the same conductivity type as the impurity region 18 of the photoelectric conversion portion PD and has a roll as the drain when the impurity region 18 of the photoelectric conversion portion PD is regarded as the source. Carriers transferred to the impurity region 20 are transferred to a wiring (not illustrated) or a transistor (not illustrated) via a contact plug 34 described later connected to the impurity region 20. Thereby, a signal in accordance with the number of carriers accumulated in the impurity region 20 can be read out to the peripheral circuit region 1002. Note that the impurity region 20 forming the floating diffusion portion FD may be shared by a plurality of pixels P.
A silicon oxide film 26 that is an insulating film is provided on the substrate 10 in which the impurity regions 16, 18, and 20 are provided, on the gate electrode 24, and on the side face of the gate electrode 24. Note that another insulating film may be provided instead of the silicon oxide film 26.
A silicon nitride film 28 that may function as an anti-reflection film and an etching stop film as described later is provided on the silicon oxide film 26. For example, the silicon nitride film 28 is provided over the photoelectric conversion portion PD, the transfer transistor M1, and the floating diffusion portion FD provided in the substrate 10. Note that the silicon nitride film 28 is provided on a region including at least photoelectric conversion portion PD of the substrate 10.
An interlayer insulating film 30 is provided on the silicon nitride film 28. The interlayer insulating film 30 is formed of a silicon oxide film or the like, for example. The contact plug 32 connected to the gate electrode 24 and the contact plug 34 connected to the impurity region 20 forming the floating diffusion portion FD are provided inside the silicon oxide film 26, the silicon nitride film 28, and the interlayer insulating film 30 that are stacked in this order. Each of the contact plugs 32 and 34 is formed of a conductive member made of a metal including titanium, tungsten, aluminum, copper, or the like or an alloy containing these metals, for example.
The side of the contact plug 32 connected to the gate electrode 24 is in contact with the silicon nitride film 28 provided on the gate electrode 24. Further, the side of the contact plug 34 connected to the impurity region 20 forming the floating diffusion portion FD is in contact with the silicon nitride film 28 formed above the floating diffusion portion FD.
Note that the silicon nitride film 28 forms a film provided near the surface of the substrate 10. Specifically, it is preferable that the silicon nitride film 28 be provided such that the distance d in the film thickness direction from the surface of the substrate 10, which is an interface with the silicon oxide film 26 of the substrate 10, to the silicon nitride film 28 is smaller than the film thickness t of the silicon nitride film 28. That is, it is preferable that the film thickness t of the silicon nitride film 28 be larger than the distance d. For example, the distance d is 5 to 25 nm corresponding to the film thickness of the silicon oxide film 26. For example, the film thickness t is 25 to 100 nm. Further, it is preferable that the height of the upper face of the silicon nitride film 28 be lower than the height of the gate electrode 24. The height of the gate electrode 24 from the surface of the substrate 10 to the upper face of the gate electrode 24 is 100 to 300 nm, for example.
The silicon nitride film 28 can function as an anti-reflection film that prevents reflection at the light receiving surface of the photoelectric conversion portion PD. That is, the silicon nitride film 28 is a film to reduce reflection of a light entering the photoelectric conversion portion PD occurring at the surface of the substrate 10. The silicon nitride film 28 that functions as an anti-reflection film has a refractive index between the refractive index of the interlayer insulating film 30 and the refractive index of the substrate 10.
Furthermore, the silicon nitride film 28 may function as an anti-reflection film and also may function as an etching stop film when contact holes in which the contact plugs 32 and 34 are embedded are opened in the interlayer insulating film 30. That is, the silicon nitride film 28 is a film that is less likely to be etched than the interlayer insulating film 30 in the etching to form contact holes in which the contact plugs 32 and 34 are embedded.
The silicon nitride film 28 is a film deposited by a thermal chemical vapor deposition (CVD) method using hexachlorodisilane (HCD) Si2Cl6 as a source gas as described later, for example. The silicon nitride film 28 deposited by using HCD as a source gas contains a certain amount of chlorine. Specifically, the chlorine concentration of the silicon nitride film 28 deposited by using HCD as a source gas is 0.5 to 5 atom %, for example.
The silicon nitride film 28 has an end portion on the photoelectric conversion portion PD side of the side face of the gate electrode 24 on the photoelectric conversion portion PD side. Thereby, a path of carries via the silicon nitride film 28 from a portion on the photoelectric conversion portion PD of the silicon nitride film 28 to the gate electrode 24 is made discontinuous. The end portion of the silicon nitride film 28 defines the opening 36. The end portion of the silicon nitride film 28 includes a part or the whole of the end face of the silicon nitride film 28 continuous to at least the upper face of the silicon nitride film 28. In this example, in the silicon nitride film 28, the opening 36 forming a discontinuous portion of the silicon nitride film 28 is provided in the region between a part above the photoelectric conversion portion PD and the gate electrode 24. The opening 36 is provided in the region of the silicon nitride film 28 on the photoelectric conversion portion PD side of the side face of the gate electrode 24 on the photoelectric conversion portion PD side. Thus, the end portion of the gate electrode 24 side of the silicon nitride film 28 located above the photoelectric conversion portion PD is located on the photoelectric conversion portion PD side of the gate electrode 24. A portion of the silicon nitride film 28 covering the photoelectric conversion portion PD is cut by the opening 36 on the photoelectric conversion portion PD side of the side face of the gate electrode 24 on the photoelectric conversion portion PD side and is discontinuous from a portion of the silicon nitride film 28 covering the gate electrode 24.
The opening 36 that makes the silicon nitride film 28 discontinuous may reach the silicon oxide film 26 that is a base layer of the silicon nitride film 28 or may be a hole or a recess where the silicon nitride film 28 partially remains at a predetermined film thickness in the bottom that is the end on the silicon oxide film 26 side. When the opening 36 reaches the silicon oxide film 26, the end face of the silicon nitride film 28 continues to the under face of the silicon nitride film 28. Note that the silicon nitride film 28 can have a discontinuous path of carriers to the gate electrode 24 by any means without being limited to the opening 36. For example, with the end portion of the silicon nitride film 28 on the gate electrode 24 side being located on the photoelectric conversion portion PD side of the gate electrode 24, the silicon nitride film 28 can have a discontinuous path of carriers to the gate electrode 24. In such a case, the silicon nitride film 28 is not required to cover the gate electrode 24. When the silicon nitride film 28 does not cover the gate electrode 24, the silicon nitride film 28 covering one photoelectric conversion portion PD may be discontinuous with the silicon nitride film 28 covering another photoelectric conversion portion PD.
The opening 36 has a thin rectangular plane shape extending in the gate width direction of the gate electrode 24 of the transfer transistor M1, for example, when viewed from a direction perpendicular to the substrate 10. Note that the plane shape of the opening 36 is not particularly limited, and various shapes may be employed.
The opening 36 may be provided so as to overlap a part or the whole of the impurity region 16 of the photoelectric conversion portion PD when viewed from a direction perpendicular to the substrate 10, for example. Further, the opening 36 may be provided so as not to overlap the impurity region 16 of the photoelectric conversion portion PD between the gate electrode 24 and the impurity region 16 of the photoelectric conversion portion PD, for example.
Note that, when the silicon nitride film 28 has a function of an anti-reflection film, reflection of light in the opening 36 increases, and this may result in a reduction of sensitivity. Thus, it is desirable that the opening 36 be provided so that a part overlapping the photoelectric conversion portion PD is further reduced or a part overlapping the photoelectric conversion portion PD is eliminated.
The interlayer insulating film 30 is filled in the opening 36. Note that a part or the whole of the opening 36 may be a void, or another insulating substance may be filled in the opening 36, for example, without being limited to the interlayer insulating film 30 being filled in the opening 36.
As illustrated in
Each of the openings 36 provided in the silicon nitride film 28 is arranged on a column of the photoelectric conversion portions PD side of the region R1 in which the transfer transistors M1 and the like are provided, that is, on the photoelectric conversion portion PD side of the side face of the gate electrode of the transistor M1 on the photoelectric conversion portion PD side. The opening 36 is continuously formed in a belt shape along the plurality of photoelectric conversion portions PD on a column of the photoelectric conversion portions PD. Note that a plurality of openings 36 separated from each other may be arranged with respect to a plurality of photoelectric conversion portions PD on a column of the photoelectric conversion portions PD.
In the photoelectric conversion apparatus 100 according to the present embodiment, in the silicon nitride film 28 formed above the photoelectric conversion portion PD and the gate electrode 24, the opening 36 is provided on the photoelectric conversion portion PD side of the side face of the gate electrode 24. Thereby, the silicon nitride film 28 is made discontinuous by the opening 36 on the photoelectric conversion portion PD side of the side face of the gate electrode 24. With the silicon nitride film 28 being discontinuous in such a way, an increase in dark output of the pixel P occurring after the photoelectric conversion portion PD is irradiated with light is reduced, and characteristic deterioration due to light irradiation to the photoelectric conversion portion PD is therefore reduced in the photoelectric conversion apparatus 100 according to the present embodiment. This feature will be further described below with reference to
As illustrated in
When a photoelectric conversion apparatus is irradiated with a light, in particular when irradiated with an intense light, this may generate carriers optically excited by a defect or the like present in the silicon nitride film 28 above the photoelectric conversion portion PD that the light enters. The carriers generated in such a way are attracted to a part near the gate electrode 24 when a voltage is applied to the gate electrode 24 that is a transfer gate, and an electric field is applied to the substrate interface. Charges may be trapped therein, or a dark current may occur, which may contribute to variation of output from the photoelectric conversion portion PD. In particular, in a case of the silicon nitride film 28 deposited by a thermal CVD method using HCD as a source gas, carriers which may contribute to output variation are likely to occur. As described above, when the silicon nitride film 28 is a film provided near the surface of the substrate 10, output from the photoelectric conversion portion PD may significantly vary. The opening 36 can block a transfer path of such carriers toward the gate electrode 24 and reduce a retention region of the carriers. Thus, it is considered that, in the photoelectric conversion apparatus 100 according to the present embodiment, the increase of dark output occurring after light irradiation was reduced and characteristic deterioration was therefore reduced.
Herein, the opening 36 may be provided with a shorter length than the length L1 of the photoelectric conversion portion PD in the gate width direction of the gate electrode 24 of the transfer transistor M1, may be provided with the same length as the length L1, or may be provided with a longer length than the length L1. However, the opening 36 longer than the length L1 enhances the effect of blocking the transfer path of carriers. It is therefore preferable that the opening 36 be provided with a length that is longer than the length L1 of the photoelectric conversion portion PD in the gate width direction of the gate electrode 24.
Further, as described above, a part or the whole of the opening 36 may be a void, or a part of the whole of the opening 36 may be filled with an insulating substance. When the insulating substance filled in the opening 36 is a substance having a higher insulating property than the silicon nitride film 28, that is, a substance having a higher resistance than the silicon nitride film 28, transfer of carriers can be more reduced. It is therefore preferable that the insulating substance filled in the opening 36 be a substance having a higher resistance than the silicon nitride film 28.
Further, it is preferable that the opening 36 be opened with a width by which a sufficient insulating effect is obtained in the gate length direction of the gate electrode 24 of the transfer transistor M1, for example, a width of 50 nm or larger.
As described above, in the photoelectric conversion apparatus 100 according to the present embodiment, the opening 36 is provided in a region that is in the silicon nitride film 28 above the photoelectric conversion portion PD and is on the photoelectric conversion portion PD side of the side face of the gate electrode 24 on the photoelectric conversion portion PD. Thus, according to the photoelectric conversion apparatus 100 of the present embodiment, characteristic deterioration due to light irradiation can be reduced.
The photoelectric conversion apparatus 100 according to the present embodiment can be accommodated in a package, for example, to build an imaging system such as a camera or an information terminal embedding the package. The imaging system will be described in seventh and eighth embodiments.
Next, a manufacturing method of the photoelectric conversion apparatus 100 according to the present embodiment will be described with reference to
First, a trench is formed in the substrate 10 that is a semiconductor substrate such as a silicon substrate. Next, the element isolation region 14 is formed by filling an insulating member such as a silicon oxide in the trench (
Next, the impurity region 18 and the impurity region 202 in which impurities are introduced are formed in the substrate 10 (
Next, the gate insulating film 22 is formed on the surface of the substrate 10 of the pixel region 1001, and a gate insulating film 222 is formed on the surface of the substrate 10 of the peripheral circuit region 1002 by using a thermal oxidation method, a CVD method, or the like, for example.
Next, after a conductive film such as a poly-crystal silicon film or the like is deposited by using a CVD method, for example, this conductive film and the gate insulating films 22 and 222 are patterned to form the gate electrodes 24 and 224 (
Next, the impurity region 16, the impurity region 20, and an impurity region 226 in which impurities are introduced are formed inside the substrate 10 (
Next, the silicon oxide film 26, the silicon nitride film 28, and the silicon oxide film 38 are sequentially deposited on the substrate 10 (
Next, a sidewall 228 of the peripheral transistor or the like is formed (
Next, an impurity region 230 in which an impurity is introduced is formed in the substrate 10 (
Next, a silicide 210 is formed in an active region on the substrate 10 including the upper face of the gate electrode 224 and the upper face of the impurity region 226 (
Next, the opening 36 is patterned and formed in the silicon nitride film 28 and the silicon oxide film 38 (
Next, after a silicon nitride film 234 is formed on the whole surface, the silicon nitride film 234 in the pixel region 1001 is removed by patterning the silicon nitride film 234. The silicon nitride film 234 can be deposited by an LPCVD method or the like. Next, the interlayer insulating film 30 is formed on the whole surface (
Next, the contact plugs 32 and 34 are formed inside the interlayer insulating film 30, the silicon nitride film 28, and the silicon oxide film 26 in the pixel region 1001. In addition, the contact plugs 236, 238, and 240 are formed inside the interlayer insulating film 30 and the silicon nitride film 234 in the peripheral circuit region 1002 (
Next, a wiring layer, a light guide, an inner lens, a color filter, a micro-lens, and the like (which are not illustrated) are formed, and thereby the photoelectric conversion apparatus 100 according to the present embodiment can be completed.
As described above, according to the present embodiment, since the opening 36 is provided in a region that is in the silicon nitride film 28 above the photoelectric conversion portion PD and is on the photoelectric conversion portion PD side of the side face of the gate electrode 24 on the photoelectric conversion portion PD side, characteristic deterioration due to light irradiation can be reduced.
A photoelectric conversion apparatus and a manufacturing method thereof according to a sixth embodiment of the present disclosure will be described with reference to
Although the case where the opening 36 having a rectangular plane shape when viewed from the direction perpendicular to the substrate 10 is provided in the silicon nitride film 28 has been described in the fifth embodiment, the plane shape of the opening 36 is not limited to a rectangle. In the present embodiment, a case where, instead of the opening 36 having a rectangular plane shape, an opening 336 having a frame-like plane shape surrounding the photoelectric conversion portion PD is provided in the silicon nitride film 28 will be described.
In the photoelectric conversion apparatus according to the present embodiment, the opening 336 is provided in a region that is in the silicon nitride film 28 and is on the photoelectric conversion portion PD side of the side face of the gate electrode 24 so as to surround the photoelectric conversion portion PD. The opening 336 has a frame-like plane shape surrounding the photoelectric conversion portion PD when viewed from a direction perpendicular to the substrate 10. The opening 336 forms a discontinuous part in the silicon nitride film 28 in the same manner as the opening 36 according to the fifth embodiment. The silicon nitride film 28 is cut by the opening 336 to be discontinuous.
For example, the opening 336 may be provided so as to overlap a part of the photoelectric conversion portion PD when viewed from a direction perpendicular to the substrate 10 or may be provided outside the photoelectric conversion portion PD so as not to overlap the photoelectric conversion portion PD.
In the present embodiment, as described above, the opening 336 is provided in the silicon nitride film 28 so as to surround the photoelectric conversion portion PD. With such the opening 336, even when carriers occur in the silicon nitride film 28 on the photoelectric conversion portion PD when the photoelectric conversion apparatus is irradiated with light, there is no transfer path through which the carries travel to the gate electrode 24. Therefore, according to the present embodiment, an increase in dark output after light irradiation can be further reduced, and thus characteristic deterioration can be further reduced.
In the frame-like opening 336, at least a portion on the gate electrode 24 side of the transfer transistor M1 can be provided with a length in the gate width direction and a width in the gate length direction that are the same as those of the opening 36 according to the fifth embodiment.
Further, in the same manner as the opening 36 according to the fifth embodiment, a part or the whole of the opening 336 may be a void, or an insulating substance may be filled in a part or the whole of the opening 336. Note that the photoelectric conversion apparatus according to the present embodiment can be manufactured in the same manner as in the fifth embodiment.
As described above, according to the present embodiment, since the opening 336 is provided in the silicon nitride film 28 so as to surround the photoelectric conversion portion PD, characteristic deterioration due to light irradiation can be further reduced.
An imaging system according to a seventh embodiment of the present disclosure will be described with reference to
The photoelectric conversion apparatus 100 described in the above fifth and sixth embodiments is applicable to various imaging systems. An example of the applicable imaging system may be a digital still camera, a digital camcorder, a surveillance camera, an image reading equipment such as a copy machine or a fax machine, a mobile phone, an on-vehicle camera, an observation satellite, or the like. Further, a camera module having an optical system such as a lens and an imaging apparatus is also included in the imaging system.
An imaging system 400 illustrated in
Further, the imaging system 400 has a signal processing unit 408 that performs a process of an output signal output from the imaging apparatus 401. The signal processing unit 408 performs AD conversion to convert an analog signal output from the imaging apparatus 401 into a digital signal. Further, the signal processing unit 408 performs operations to perform various correction or compression if necessary and output image data in addition to the above. The AD conversion portion that is a part of the signal processing unit 408 may be formed on a semiconductor substrate on which the imaging apparatus 401 is provided or may be formed on a semiconductor substrate other than a substrate on which the imaging apparatus 401 is provided. Further, the imaging apparatus 401 and the signal processing unit 408 may be formed on the same semiconductor substrate.
Furthermore, the imaging system 400 has a memory unit 410 used for temporarily storing image data and an external interface unit (external OF unit) 412 used for communicating with external computer or the like. Furthermore, the imaging system 400 has a storage medium 414 such as semiconductor memory used for performing storage or readout of imaging data and a storage medium control interface unit (storage medium control I/F unit) 416 used for performing storage or readout on the storage medium 414. Note that the storage medium 414 may be built in the imaging system 400 or may be removable.
Furthermore, the imaging system 400 has a general control/operation unit 418 that controls various operations and controls the entire digital still camera and a timing generation unit 420 that outputs various timing signals to the imaging apparatus 401 and the signal processing unit 408. Here, the timing signal or the like may be externally input, and the imaging system 400 has at least the imaging apparatus 401 and the signal processing unit 408 that processes an output signal output from the imaging apparatus 401.
The imaging apparatus 401 outputs an imaging signal to the signal processing unit 408. The signal processing unit 408 implements predetermined signal processing on an imaging signal output from the imaging apparatus 401 and outputs image data. The signal processing unit 408 uses an imaging signal to generate an image.
As described above, according to the present embodiment, the imaging system to which the photoelectric conversion apparatus 100 according to each of the fifth and sixth embodiments is applied can be realized.
An imaging system and a moving body according to an eighth embodiment of the present disclosure will be described with reference to
The imaging system 500 is connected to the vehicle information acquisition apparatus 520 and can acquire vehicle information such as a vehicle speed, a yaw rate, a steering angle, or the like. Further, the imaging system 500 is connected to a control ECU 530, which is a control apparatus that outputs a control signal for causing a vehicle to generate braking force based on a determination result by the collision determination unit 518. Further, the imaging system 500 is also connected to an alert apparatus 540 that issues an alert to the driver based on a determination result by the collision determination unit 518. For example, when the collision probability is high as the determination result of the collision determination unit 518, the control ECU 530 performs vehicle control to avoid a collision or reduce damage by applying a brake, pushing back an accelerator, suppressing engine power, or the like. The alert apparatus 540 alerts a user by sounding an alert such as a sound, displaying alert information on a display of a car navigation system or the like, providing vibration to a seat belt or a steering wheel, or the like.
In the present embodiment, an area around a vehicle, for example, a front area or a rear area is captured by using the imaging system 500.
Although the example of control for avoiding a collision to another vehicle has been described above, the embodiment is applicable to automatic driving control for following another vehicle, automatic driving control for not going out of a traffic lane, or the like. Furthermore, the imaging system is not limited to a vehicle such as an automobile and can be applied to a moving body (moving equipment) such as a ship, an airplane, or an industrial robot, for example. In addition, the imaging system can be widely applied to an equipment which utilizes object recognition, such as an intelligent transportation system (ITS), without being limited to moving bodies.
The present invention is not limited to the embodiments described above, and various modifications are possible. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment or an example in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment is also one of the embodiments of the present invention.
For example, although the case where the silicon nitride film 28 is provided over the photoelectric conversion portion PD, the transfer transistor M1, and the floating diffusion portion FD has been described as an example in the above embodiments, the present invention is not limited thereto. For example, the silicon nitride film 28 may not be provided on a part or the whole of the floating diffusion portion FD while being provided on the photoelectric conversion portion PD and the transfer transistor M1. In such a case, the contact plug 34 connected to the impurity region 20 forming the floating diffusion portion FD can be formed so as not to contact with the silicon nitride film 28.
Further, the first to fourth embodiments and the fifth to eighth embodiments may be combined. For example, both the first embodiment and the fifth embodiment may be applied to the photoelectric conversion portion PD, the floating diffusion portion FD (charge holding portion), and the transfer transistor having the gate electrode 134/24. Specifically, the configuration in which no insulating material whose relative dielectric constant is higher than or equal to 5.0 is included near the floating diffusion portion FD may be employed as with the first embodiment, and the silicon nitride film 28 on the photoelectric conversion portion PD may have the end portion (the opening 36) on the gate electrode 134/24 side as with the fifth embodiment. In such a case, the silicon nitride film is removed from the part above the floating diffusion portion FD so that the silicon nitride film deposited to form the silicon nitride film 28 does not remain above the floating diffusion potion FD. Alternatively, the insulating film 138 present above the photoelectric conversion portion PD and the floating diffusion portion FD as with the first embodiment may have the end portion or the opening 36 between a portion above the photoelectric conversion portion PD and the gate electrode 134/24 as with the fifth embodiment.
The process illustrated in
It is also possible to form the contact hole in which the contact plug 34 is to be arranged and the contact hole in which the contact plug 32 is to be arranged at respective timings in the interlayer insulating film 30. For example, the contact hole in which the contact plug 32 is to be arranged may be formed in the interlayer insulating film 30 after the contact hole in which the contact plug 34 is to be arranged is formed in the interlayer insulating film 30. In such a case, before the contact hole in which the contact plug 32 is to be arranged is formed, an impurity of the same conductivity type as the impurity region 20 may be ion-implanted into the impurity region 20 via the contact hole in which the contact plug 34 is to be arranged. Thereby, the resistance between the floating diffusion portion FD and the contact plug 34 can be reduced. At this time, since the contact hole in which the contact plug 32 is to be arranged is not formed on the gate electrode 24, substantially no impurity is ion-implanted into the gate electrode 24. By filling a conductive material in the contact hole in which the contact plug 32 is to be arranged and the contact hole in which the contact plug 34 is to be arranged, it is possible to form the contact plug 32 and the contact plug 34 at the same time. The contact hole in which the contact plug 34 is to be arranged may be formed in the interlayer insulating film 30 after the contact hole in which the contact plug 32 is to be arranged is formed in the interlayer insulating film 30.
The contact plug 142 connected to the semiconductor region 126 (the floating diffusion portion FD) described in the first to fourth embodiments can be formed in the same manner as the contact plug 34. Although description of the contact plug connected to the gate electrode 134 has been omitted in the first to fourth embodiments, the contact plug connected to the gate electrode 134 can be formed in the same manner as the contact plug 32. That is, the contact hole in which the contact plug 142 connected to the floating diffusion portion FD is to be arranged and the contact hole in which the contact plug connected to the gate electrode 134 is to be arranged can be formed at the same time or separately in the insulating film 140 that is an interlayer insulating film. Further, it is possible to ion-implant an impurity into the semiconductor region 126 via the contact hole in which the contact plug 142 connected to the floating diffusion portion FD is to be arranged so that no impurity is implanted into the gate electrode 134.
The contact hole in which the contact plug 142 is to be arranged and the contact hole in which the contact plug connected to the gate electrode 134 is to be arranged differ in the depth of the contact hole by the thickness of the gate electrode 134. Thus, if both the contact holes are formed in the insulating film 140 at the same time, this may cause excessive etching under the contact hole on the gate electrode 134 or insufficient etching under the contact hole in which the contact plug 142 is to be arranged. Accordingly, it is preferable to separately form the contact hole in which the contact plug 142 is to be arranged and the contact hole in which the contact plug connected to the gate electrode 134 is to be arranged. In particular, when both the insulating film 140 and the insulating film 138 are made of an insulating material whose primary component is silicon oxide, it is difficult to have etching selection of the insulating film 140 and the insulating film 138, and a sufficient etching stop function is not expected for the insulating film 138. The insulating material whose primary component is silicon oxide as used herein may include not only silicon oxide but also a porous insulating material such as nano-clustering silica, a low dielectric constant material such as silicon oxy carbide (SiOC), or the like. Therefore, when both the insulating film 140 and the insulating film 138 are made of an insulating material whose primary component is silicon oxide, it is preferable to separately form the contact hole in which the contact plug 142 is to be arranged and the contact hole in which the contact plug connected to the gate electrode 134 is to be arranged.
Further, the conductivity type of the impurity region illustrated in the above embodiment can be changed, and all the conductivity types may be opposite, for example. Further, the circuit configuration within the pixel illustrated in
Further, each of the photoelectric conversion apparatuses illustrated in the above embodiments can be used as an apparatus intended for acquiring an image, that is, an imaging apparatus. Further, an application example of the photoelectric conversion apparatuses illustrated in the above embodiments is not necessarily limited to an imaging apparatus and, in the application to the apparatus intended for ranging as described in the above eighth embodiment, for example, it is not necessarily required to output an image. In such a case, it can be said that the above apparatus is a photoelectric conversion apparatus that converts optical information into a predetermined electrical signal. An imaging apparatus is one of the photoelectric conversion apparatuses.
Further, the imaging systems illustrated in the above third, fourth, seventh and eighth embodiments are examples of imaging systems to which the photoelectric conversion apparatus of the present invention may be applied, and the imaging system to which the photoelectric conversion apparatus of the present invention can be applied is not limited to the configurations illustrated in
Note that all the embodiments described above are mere embodied examples in implementing the present invention, and the technical scope of the present invention should not be construed in a limiting sense by these embodiments. That is, the present invention can be implemented in various forms without departing from the technical concept or the primary feature thereof.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2019-047077, filed Mar. 14, 2019, and Japanese Patent Application No. 2019-068300, filed Mar. 29, 2019, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-047077 | Mar 2019 | JP | national |
| 2019-068300 | Mar 2019 | JP | national |
