1. Field of the Invention
The present invention relates to a solid-state image pickup device, a method for manufacturing the same, and an electronic apparatus.
2. Description of the Related Art
Electronic apparatuses, such as digital video cameras and camera-equipped cellular phones, include solid-state image pickup devices.
The solid-state image pickup device has an image-pick up region including a plurality of pixels on a semiconductor substrate. Each pixel has a photoelectric conversion portion. The photoelectric conversion portion, which may be a photodiode, generates a signal charge by receiving light coming through an external optical system and converting the light to electricity.
A CMOS (complementary metal oxide semiconductor) image sensor can be used as the solid-state image pickup device.
The CMOS image sensor includes pixels, each including the photoelectric conversion portion and a set of transistors. The set of transistors acts as pixel transistors that read the signal charge generated from the photoelectric conversion portion and output the signal charge to a signal line as an electric signal. For example, pixel transistors including four transistors: a transfer transistor, a reset transistor, an amplification transistor and a selection transistor are provided on the surface of the semiconductor substrate. The transistors of the pixel transistor sets are electrically connected to conductor lines disposed on the surface of the semiconductor substrate.
The CMOS image sensor is generally of front emission type in which the photoelectric conversion portion receives light entering through the front side of the semiconductor substrate having conductor lines and pixel transistors. In the surface emission type, unfortunately, conductor lines are disposed in a plurality of layers in the path through which light enters the photoelectric conversion portion. Therefore the conductor lines in the plurality of layers may reduce the light use efficiency to reduce the sensitivity. Accordingly, a rear emission type is proposed which receives light entering through the rear side of the semiconductor substrate opposite the front side having conductor lines and pixel transistors (for example, Japanese Unexamined Patent Application Publication No. 2003-31785).
It is advantageous that the CMOS image sensor is more miniaturized and achieves high definition. In order to reduce the pixel size for miniaturization of the CMOS image sensor, a pixel structure is proposed in which a plurality of photoelectric conversion portions share the pixel transistors. For example, a technique is proposed in which a single pixel transistor set is provided for two or four photoelectric conversion portions (for example, Japanese Unexamined Patent Application Publication Nos. 2004-172950, 2006-157953 and 2006-54276).
In such a technique, a pixel isolation member is formed in the substrate to separate pixels from each other. For example, a shallow-trench oxide isolation (STI) structure is provided as the pixel isolation member in the semiconductor substrate. Alternatively, an impurity diffusion region, such as a p-well, is provided as the pixel isolation member in the semiconductor substrate (for example, Japanese Unexamined Patent Application Publication No. 2006-93319 and 2007-53250).
In the rear emission CMOS image sensor, the thickness of the semiconductor substrate is reduced from several hundred micrometers to, for example, 10 μm so that light can enter the photoelectric conversion portion. If variation in thickness occurs through the step of reducing the thickness, the intensity of incident light varies. In order to prevent the variation in thickness, silicon-on-insulator (SOI) substrate can be used in manufacture of rear emission CMOS image sensors.
First, an SOI substrate 101J is prepared, as shown in
Turning then to
In this instance, each element or member is formed by implanting impurity ions into the silicon layer. Then, after forming pixel transistors (not shown) including the transfer transistor on the silicon layer AS, a multilayer wiring layer HS is formed in the silicon layer AS by embedding conductor lines HT in an insulating interlayer SZ.
Subsequently, a support substrate SK is bonded onto the multilayer wiring layer HS, as shown in
Turning to
For example, the silicon substrate KB can be removed by applying a technique for reducing thickness, such as chemical mechanical polishing (CMP), with the SOI substrate 101J inverted. For CMP, the silicon oxide layer BOX of the SOI substrate 101J acts as a CMP stopper with which the end point of CMP can be detected.
Then, the silicon oxide layer BOX is removed to expose the rear surface of the silicon layer AS by wet etching. Part of the silicon layer AS is removed from the rear side until the p-type impurity diffusion region PW is exposed. Then, the surface of the silicon layer AS is provided with a passivation layer (not shown), a color filter (not shown) and an on-chip lens (not shown). Thus, a rear emission CMOS image sensor is completed.
When the SOI substrate 101J is used as described above, the silicon oxide layer BOX acts as a stopper in the step of reducing the thickness, thus preventing the variation in thickness.
However, the SOI substrate 101J is expensive, and the use of the SOI substrate 101J undesirably increases the manufacturing cost. On the other hand, it may be difficult to prevent the thickness of the substrate from varying in the step of reducing the thickness when a substrate other than the SOI substrate is used.
In addition, if impurity ions are implanted into the silicon layer AS to form the pixel isolation member PSJ as described above, the pixel isolation region PSJ is formed to a large depth at a high density for further miniaturizing the pixels. In this instance, a resist pattern used as a mask for ion implantation is formed in a thick fine shape. Accordingly, the resist pattern may fall down due to stress. Efficient manufacture of rear surface emission CMOS image sensors may be difficult in some cases.
As described above, in manufacture of some types of solid-state image pickup device, it may be difficult to reduce the cost and to enhance the productivity. For this reason, it may be difficult to enhance the quality of taken images.
Accordingly, it is desirable to provide a solid-state image pickup device and an electronic apparatus that can be efficiently manufactured at low cost and can take high-quality images, and a method for efficiently manufacturing the solid-state image pickup device at low cost.
According to an embodiment of the present invention, a method is provided for manufacturing a solid-state image pickup device. The method includes the steps of forming a pixel isolation member in a semiconductor substrate in which a plurality of pixels each including a photoelectric conversion element are arranged, and reducing the thickness of the semiconductor substrate by chemical mechanical polishing of the semiconductor substrate. The step of forming a pixel isolation member includes the sub steps of forming a first pixel isolation member by implanting impurity ions in a region of the semiconductor substrate so that the pixels are disposed between portions of the region when viewed from a surface of the semiconductor substrate, and forming a second isolation member by forming a trench in a region of the semiconductor substrate different from the first pixel isolation member so that the pixels are disposed between portions of the region, and then filling the trench with an electroconductive material harder to polish by chemical mechanical polishing than the semiconductor substrate. The step of reducing the thickness is performed by chemical mechanical polishing of a rear surface of the semiconductor substrate using the second pixel isolation member as a stopper.
According to another embodiment of the present invention, a solid-state image pickup device is provided which includes a pixel isolation member in a semiconductor substrate including a plurality of pixels, each including a photoelectric conversion element. The pixel isolation member includes a first pixel isolation member formed by implanting impurity ions in a region of the semiconductor substrate so that the pixels are disposed between portions of the region when viewed from a surface of the semiconductor substrate, and a second pixel isolation member formed by filling a trench with an electroconductive material. The trench is formed in a region different from the first pixel isolation member so that the pixels are disposed between portions of the region when viewed from the surface of the semiconductor substrate.
According to another embodiment of the present invention, an electronic apparatus is provided which includes a pixel isolation member in a semiconductor substrate including a plurality of pixels, each including a photoelectric conversion element. The pixel isolation member includes a first pixel isolation member formed by implanting impurity ions in a region of the semiconductor substrate so that the pixels are disposed between portions of the region when viewed from a surface of the semiconductor substrate, and a second pixel isolation member formed by filling a trench with an electroconductive material. The trench is formed in a region different from the first pixel isolation member so that the pixels are disposed between portions of the region when viewed from the surface of the semiconductor substrate.
In embodiments of the invention, a pixel isolation member is formed in a semiconductor substrate including a plurality of pixels, each including a photoelectric conversion element. The thickness of the semiconductor substrate is reduced by chemical mechanical polishing (CMP). For forming the first pixel isolation member, impurity ions are implanted into a region of the semiconductor substrate so that pixels are disposed between the portions of the region when viewed from a surface of the substrate. Also, the second pixel isolation member is formed in a different region from the first isolation member so that the pixels are disposed between portions of the region when viewed from the surface of the semiconductor substrate. For forming the second pixel isolation member, a trench is formed in a region of the semiconductor substrate in which the second pixel isolation member is to be formed, and then the trench is filled with an electroconductive material harder to polish by CMP than the semiconductor substrate. For reducing the thickness of the semiconductor substrate, CMP is performed on the rear surface of the semiconductor substrate using the second pixel isolation member as a CMP stopper.
The present invention can provide a solid-state image pickup device and an electronic apparatus that can be efficiently manufactured at low cost and can take high-quality images, and methods for efficiently manufacturing the solid-state image pickup device and the electronic apparatus.
FIGS. 20CA and 20B are sectional views of the process for manufacturing the rear emission CMOS image sensor.
The present invention will be further described using exemplary embodiments with reference to the drawings.
The description will be made in the following order:
1. First embodiment
2. Second embodiment
3. Modifications
As shown in
The solid-state image pickup device 1 receives light (subject image) H coming through the optical system 42 at an image pickup face Ps and converts the light into electricity to generate a signal charge. In the present embodiment, the solid-state image pickup device 1 is operated according to control signals output from the controller 43. More specifically, the solid-state image pickup device 1 reads out the signal charge and output it as raw data.
The optical system 42 includes optical members, such as an image-forming lens and an iris, which are arranged so that the light H of the subject image is focused on the image pickup face Ps of the solid-state image pickup device 1.
The controller 43 outputs signals to the solid-state image pickup device 1 and the signal processing circuit 44 to control and operate the solid-state image pickup device 1 and the signal processing circuit 44.
The signal processing circuit 44 is configured to process raw data output from the solid-state image pickup device 1 to form the digital image of a subject image.
The entire structure of the solid-state image pickup device 1 will now be described.
The solid-state image pickup device 1 of the present embodiment is a CMOS image sensor, and includes a substrate 101, as shown in
The image-pickup region PA is rectangular, as shown in
In the image pickup region PA, the pixels P receive incident light to generate a signal charge. Pixel transistors read and output the generated signal charge. Details of the structure of the pixel P will be described later.
The outer region SA lies around the image pickup region PA, as shown in
More specifically, a vertical drive circuit 13, a column circuit 14, a horizontal drive circuit 15, an external output circuit 17, a timing generator (TG) 18, and a shutter drive circuit 19 are disposed as the peripheral circuits, as shown in
The vertical drive circuit 13 is disposed in the outer region SA along a side of the image pickup region PA, and is configured to select pixels P by the row in the image pickup region PA and drive the selected pixels.
The column circuit 14 is disposed in the outer region SA along a lower side (shown in
The horizontal drive circuit 15 is electrically connected to the column circuit 14, as shown in
The external output circuit 17 is electrically connected to the column circuit 14, as shown in
The timing generator 18 is electrically connected to the vertical drive circuit 13, the column circuit 14, the horizontal drive circuit 15, the external output circuit 17 and the shutter drive circuit 19, as shown in
The shutter drive circuit 19 is configured to select pixels P by the row to adjust the exposure time of the selected pixels P.
The solid-state image pickup device 1 will be further described in detail.
As shown in
The solid-state image pickup device 1 of the present embodiment, which is of so-called rear emission type, is configured so that the photodiode 21 receives light H entering the substrate 101 from the lower surface (rear side) of the substrate opposite to the upper surface (front side) of the multilayer wiring layer HS. More specifically, the substrate 101 has been thinned to a thickness of, for example, 2 to 10 μm, so that the photodiode 21 can receive light from the rear side.
Elements of the solid-state image pickup device will now be described one by one in detail.
In the solid-state image pickup device 1, a plurality of photodiodes 21 are provided according to the respective pixels P, as shown in
As shown in
The photodiodes 21 are configured so that each of the photodiodes 21 reads out the signal charge stored in the pixel transistors PTr, as shown in
In the present embodiment, each photodiode 21 is provided with a transfer transistor 22, which is one of the pixel transistors PTr, as shown in
The plurality of photodiodes 21 share a single floating diffusion portion FD, as shown in
The set of those photodiodes 21 is provided with common pixel transistors PTr including an amplification transistor 23, a selection transistor 24 and a reset transistor 25. In the present embodiment, the set of the four photodiodes 21 (21_1, 21_2, 21_3 and 21_4) is provided with an amplification transistor 23, a selection transistor 24 and a reset transistor 25.
In the solid-state image pickup device 1, the pixel transistors PTr, which are not shown in
The transfer transistor 22 of the pixel transistors PTr is configured so as to read out the signal charge generated in the photodiode 21 to the floating diffusion portion FD, as shown in
More specifically, the transfer transistor 22 transmits the signal charge stored in the photodiode 21 to the floating diffusion portion FD as an output signal when a transmission signal has been applied to the gate of the transistor 22 through a transfer line 26.
In the present embodiment, the transfer transistors 22 are provided corresponding to the respective photodiodes 21, as shown in
The transfer transistors 22, which are now shown in
The amplification transistor 23 of the pixel transistors PTr amplifies electrical signals output from the transfer transistors 22 and outputs the amplified signals, as shown in
More specifically, the gate of the amplification transistor 23 is connected to the floating diffusion portion FD. One of the terminals of the amplification transistor 23 is connected to the selection transistor 24, and the other is connected to a vertical signal line 27. When the selection transistor 24 has been selected so as to come into an on-state, the amplification transistor 23 receives a constant current from a constant current source (not shown) to act as a source follower. Thus, the amplification transistor 23 amplifies the signal output from the floating diffusion portion FD when the selection transistor 24 has received a selection signal.
In the present embodiment, the amplification transistor 23 is provided for each set composed of four photodiodes 21 (21_1, 21_2, 21_3 and 21_4), as shown in
The selection transistor 24 of the pixel transistors PTr outputs the electrical signal from the amplification transistor 23 to the vertical signal line 27, as shown in
More specifically, the gate of the selection transistor 24 is connected to an address line 28 through which the selection signal is transmitted, as shown in
In the present embodiment, a single selection transistor 24 is provided for the set of four photodiodes 21 (21_1, 21_2, 21_3 and 21_4), as shown in
The reset transistor 25 of the pixel transistors PTr is configured so as to reset the gate potential of the amplification transistor 23, as shown in
More specifically, the gate of the reset transistor 25 is connected to a reset line 29 through which a reset signal is transmitted, as shown in
In the present embodiment, the reset transistor 25 is provided for the set of four photodiodes 21 (21_1, 21_2, 21_3 and 21_4), as shown in
In the solid-state image pickup device 1, the pixel isolation members PS are disposed between the lines of the pixels P running in the horizontal direction x and between the lines of the pixels P running in the vertical direction y so as to separate the pixels P from each other, as shown in
The pixel isolation members PS extend in the depth direction from the surface of the substrate 101 so as to separate the respective photodiodes 21 of the pixels P from each other, as shown in
In the present embodiment, the pixel isolation members PS include a first pixel isolation member PS1 and a second pixel isolation member PS2, as shown in
The first pixel isolation member PS1 is formed in a grid manner so as to partition first pixel array regions P1, each in which pixels P are arranged two by two in the horizontal direction x and the vertical direction y when viewed from the image pickup face (xy face), as shown in
More specifically, the first pixel isolation member PS1 includes horizontal portions extending in the horizontal direction x in such a manner that two pixels P lie between the horizontal portions arranged in the vertical direction y. The first pixel isolation member PS1 also includes vertical portions extending in the vertical direction y in such a manner that two pixels P in the horizontal direction x lie between the vertical portions. Hence, the first pixel isolation member PS1 includes the horizontal portions extending in the horizontal direction x and the vertical portions extending in the vertical direction y, and the horizontal portions and the vertical portions are arranged at a pitch of 2 pixels in the respective directions.
In the present embodiment, the first pixel isolation member PS1 is a p well, and is formed from the surface of the substrate 101 in the depth direction by implanting p-type impurity ions into the silicon semiconductor substrate 101, as shown in
As shown in
The second pixel isolation member PS2 is formed so as to partition second pixel array regions P2, each in which pixels P are arranged two by two in the horizontal direction x and the vertical direction y when viewed from the image pickup face (xy face), as shown in
More specifically, the second pixel isolation member PS2 includes horizontal portions extending in the horizontal direction x in such a manner that two pixels P lies between the horizontal portions arranged in the vertical direction y. The second pixel isolation member PS2 also includes vertical portions extending in the vertical direction y in such a manner that two pixels P lie between the vertical portions arranged in the horizontal direction x. Hence, the second pixel isolation member PS2 includes the horizontal portions extending in the horizontal direction x and the vertical portions extending in the vertical direction y, and the horizontal portions and the vertical portions are arranged at a pitch of 2 pixels in the respective directions.
The second pixel isolation member PS2 is formed so as to partition second pixel array regions P2 that are shifted by the width of the pixel P (at a pitch of one pixel) in the horizontal direction x and the vertical direction y with respect to the first pixel array regions P1 when viewed from the image pickup face (xy face).
Thus, the horizontal portions of the first pixel isolation member PS1 are each disposed between the horizontal portions of the second pixel isolation member PS2 arranged in the vertical direction y. Also, the vertical portions of the first pixel isolation member PS1 are each disposed between the vertical portions of the second pixel isolation member PS2 arranged in the horizontal direction x.
The second pixel isolation member PS2 passes through the thickness of the substrate 101, as shown in
Unlike the first pixel isolation member PS1, the second pixel isolation member PS2 is made of an electroconductive material. Hence, the second pixel isolation member PS2 acts as a through-electrode.
More specifically, the second pixel isolation member PS2 includes a first metal layer KD1 and a second metal layer KD2.
The first metal layer KD1 of the second pixel isolation member PS2 is formed so as to surround each second pixel array region P2, as shown in
The second metal layer KD2 of the second pixel isolation member PS2 is formed between portions of the first metal layer KD1 around the second pixel array regions P2, as shown in
The first metal layer KD1 acts a so-called barrier metal layer, and prevents the second metal layer KD2 made of, for example, copper from diffusing into the substrate 101.
In the solid-state image pickup device 1, the multilayer wiring layer HS is formed on the surface of the substrate 101, as shown in
In addition, the substrate 101 has optical members, such as on-chip lenses (not shown) and color filters (not shown), corresponding to the respective pixels P. Since the solid-state image pickup device 1 of the present embodiment is of rear emission type, those optical members are provided at the rear side of the substrate 101. The solid-state image pickup device 1 is configured so that the photodiode 21 receives light coming through optical members, such as the on-chip lens and the color filter.
A method for manufacturing the solid-state image pickup device 1 will now be described.
(B-1) Formation of p-Type Impurity Diffusion Region PW
First, a p-type impurity diffusion region PW is formed in the substrate 101, as shown in
In this step, the silicon semiconductor substrate 101 is subjected to ion implantation of a p-type impurity to form a p-type impurity diffusion region PW in the substrate 101, as shown in
For example, the p-type impurity diffusion region PW can be formed by ion implantation performed under the following conditions.
p-type impurity: B (boron)
Impurity concentration: 1×1012 to 5×1012 atoms/cm2
Implantation energy: 1000 to 3000 eV
Turning to
In this step, the first pixel isolation member PS1 is formed from the surface of the substrate 101 in the thickness direction by implanting p-type impurity ions, as shown in
More specifically, a resist pattern PR1 having an opening is formed on the surface of the substrate 101 so that the region of the surface of the substrate 101 in which the first pixel isolation member PS1 is to be formed is exposed in the opening, as shown in
For forming the resist pattern PR1, photolithography can be applied. More specifically, a pattern image is formed in a photoresist layer (not shown) formed on the substrate 101 by exposure, and is then developed to form the resist pattern PR1.
For example, the resist pattern PR1 is formed in the following dimensions so that the pixels P can have a width of 1.2 μm:
Thickness: 4.5 μm
Pattern width: 0.86 μm
Opening width: 0.34 μm
Subsequently, the substrate 101 is subjected to ion implantation of a p-type impurity using the resist pattern PR1 as a mask.
For example, the ion implantation is performed to form the first pixel isolation member PS1 under the following conditions:
p-type impurity: B (boron)
Impurity concentration: 1×1012 to 5×1012 atoms/cm2
Implantation energy: 50 to 300 eV
Thus, the first pixel isolation member PS1 is formed between the surface of the substrate 101 and the p-type impurity diffusion region PW.
Then, the resist pattern PR1 is removed.
Turning to
The trench TR is formed by removing the portion of the substrate 101 in which the second pixel isolation member PS2 is to be formed, as shown in
More specifically, a resist pattern PR2 having an opening is formed on the surface of the substrate 101 so that the region of the surface of the substrate 101 in which the second pixel isolation member PS2 is to be formed is exposed in the opening, as shown in
For example, the resist pattern PR2 is formed in the following dimensions:
Thickness: 4.5 μm
Pattern width: 0.86 μm
Opening width: 0.34 μm
Subsequently, the substrate 101 is etched using the resist pattern PR2 as a mask, and thus the trench TR is formed.
For example, the etching is performed to form the trench TR under the following conditions:
Etching gas and gas flow rate: C5F8/Ar/O2=15/500/10 sccm
Then, the resist pattern PR2 is removed.
Turning to
In this step, the second isolation member PS2 is formed in the trench TR in the substrate 101. The first pixel isolation member PS2 is formed in a grid manner so as to partition the second pixel array regions P2, each in which pixels are arranged two by two in the horizontal direction x and the vertical direction y, as shown in
In this step, the trench TR is filled with an electroconductive material harder to polish than the substrate 101 in the subsequent step (
More specifically, for forming the second pixel isolation member PS2, a first metal layer KD1 and a second metal layer KD2 are formed in that order in the trench TR in the substrate 101, as shown in
Also, the first metal layer KD1 is formed over the inner surface of the trench so as to surround each second pixel array region P2, as shown in
For example, the first metal layer KD1 is formed under the following conditions:
Material: tantalum (Ta)
Method: sputtering
Thickness: 15 to 30 nm
For example, the second metal layer KD2 is formed under the following conditions:
Material: copper (Cu)
Method: electroplating
Thickness: 3 to 5 μm
Turning to
In this step, the floating diffusion portions FD are formed in the upper surface of the first pixel isolation member PS1, as shown in
For example, the ion implantation for forming the floating diffusion portions FD may be performed under the following conditions:
Impurity: phosphorus (P)
Impurity concentration: 1×1013 to 1×1016 atoms/cm2
Implantation energy: 10 to 100 eV
In addition, photodiodes 21 are formed between the pixel isolation members PS, as shown in
More specifically, each photodiode 21 is formed in the substrate 101 by forming an n-type charge storage region (not shown) and a shallow p-type impurity diffusion region (not shown) above the p-type impurity diffusion region PW.
In the present embodiment, the photodiodes 21 are formed in such a manner that four photodiodes 21_1, 21_2, 21_3 and 21_4 are disposed around one floating diffusion portion FD.
For example, the photodiodes 21 are formed by performing ion implantation under the following conditions:
Impurity: arsenic (As)
Impurity concentration: 1×1012 to 5×1012 atoms/cm2
Implantation energy: 100 to 400 eV
Turning to
After the pixel transistors PTr (not shown in
More specifically, the pixel transistors PTr are formed at the surface of the substrate 101 by forming active regions in the substrate 101 and forming gates of polysilicon. The conductor lines HT of the multilayer wiring layer HS is formed of a metal material, such as aluminum. The insulating interlayer SZ of the multilayer wiring layer HS is formed of, for example, silicon oxide.
Then, the support substrate SK is formed on the surface of the multilayer wiring layer HS. For example, a silicon substrate is bonded to the multilayer wiring layer HS as the support substrate SK.
Turning to
In this step, the substrate 101 is inverted so that the surface having the multilayer wiring layer HS and the support substrate SK faces down. Hence, the rear side of the substrate 101 faces up.
Turning to
The thickness of the substrate 101 is reduced by partially removing the rear side (upper surface in
For example, the above CMP may be performed with silica (SiO2) slurry.
Then, the substrate 101 is provided with a passivation layer (not shown), a color filter (not shown) and an on-chip lens (not shown) on the rear side. Thus, a rear emission CMOS image sensor is completed.
In the present embodiment, the pixel isolation members PS are formed in the substrate 101 that includes pixels P each including a photodiode 21, as shown in
For forming the first pixel isolation member PS1, impurity ions are implanted into a region in the substrate 101 so that the pixels are disposed between portions of the region when viewed from the surface of the substrate 101, as shown in
In addition, the second pixel isolation member PS2 is formed in a different region from the first pixel isolation member PS1 so that the pixels are disposed between portions of the region when viewed from the surface of the substrate 101, as shown in
The second pixel isolation member PS2 is used as a CMP stopper when the rear side of the substrate 101 is subjected to CMP for reducing the thickness of the substrate 101.
Since the second pixel isolation member PS2 acts as a CMP stopper in the present embodiment, the thickness of the substrate 101 can be reduced by CMP without variation in thickness of the substrate 101 even if the substrate is not made of expensive SOI.
In the present embodiment, in addition, portions of the first pixel isolation member PS1 extending in the horizontal direction x and portions of the second pixel isolation member PS2 extending in the horizontal direction x are alternately arranged in the vertical direction y. Similarly, portions of the first pixel isolation member PS1 extending in the vertical direction y and portions of the second pixel isolation member PS2 extending in the vertical direction y are alternately arranged in the horizontal direction x.
In the present embodiment, the pixel isolation member PS thus includes plural types of members, and the first and second pixel isolation members PS1 and PS2 are formed through a wide resist pattern. Consequently, the resist pattern can be prevented from, for example, falling down due to stress. Accordingly, a high efficiency in manufacture can be achieved.
In addition, the surface potential of the electroconductive second pixel isolation member PS2 can be controlled to prevent dark current by applying, for example, a negative bias voltage. Furthermore, dark current can be prevented by grounding the second pixel isolation portion PS2.
The solid-state image pickup device of the present invention can be efficiently manufactured at low cost, and can take high-quality images.
In the present embodiment, the pixel isolation member PSb is different from that of the first embodiment, as shown in
As shown in
As shown in
Also, the p-type impurity diffusion layer PS2b extends in the thickness direction from the surface of the substrate 101, as shown in
A method for manufacturing the solid-state image pickup device of the present embodiment will now be described.
(B-1) Formation of p-Type Impurity Diffusion Layer PS2b
For manufacturing the solid-state image pickup device in the present embodiment, first, a p-type impurity diffusion region PW is formed in the substrate 101 as in the first embodiment (see
Subsequently, the p-type impurity diffusion layer PS2b is formed in the substrate 101, as shown in
More specifically, the p-type impurity diffusion layer PS2b is formed from the surface of the substrate 101 in the thickness direction by implanting p-type impurity ions into the substrate 101, as shown in
More specifically, a resist pattern PR1b having an opening is formed on the surface of the substrate 101 so that the region of the substrate 101 in which the p-type impurity diffusion layer PS2b is to be formed is exposed in the opening, as shown in
Then, p-type impurity ions are implanted into the substrate 101 using the resist pattern PR1b as a mask. Thus the p-type impurity diffusion layer PS2b is formed from the surface of the substrate 101 to the p-type impurity diffusion region PW. For example, the p-type impurity diffusion layer PS2b is formed by ion implantation under the same conditions as the ion implantation for forming the first pixel isolation member PS1.
Then, the resist pattern PR1b is removed.
Turning to
The trench TR is formed by removing the portion of the substrate 101 in which the second pixel isolation member PS2 is to be formed, as shown in
More specifically, a resist pattern PR2b having an opening is formed on the surface of the substrate 101 so that the region of the substrate 101 in which the second pixel isolation member PS2 is to be formed is exposed in the opening, as shown in
For example, the formation of the resist pattern PR2b and the etching of the substrate 101 may be performed under the same conditions as in the formation of the second pixel isolation member PS2 in the first embodiment. Then, the resist pattern PR2b is removed.
Turning to
In this step, the second isolation member PS2 is formed in the trench TR in the substrate 101, as shown in
More specifically, for forming the second pixel isolation member PS2, a first metal layer KD1 and a second metal layer KD2 are formed in that order in the trench TR in the substrate 101, as shown in
For example, after forming the first metal layer KD1, the second metal layer KD2 is formed so as to fill the trench TR whose surface is covered with the first metal layer KD1 under the same conditions as in the first embodiment. Subsequently, the surface of the substrate 101 is planarized by CMP to complete the second pixel isolation member PS2.
Subsequently, other members are formed as shown in
In this step, the floating diffusion portions FD are formed in the upper surface of the first pixel isolation member PS1, as shown in
Then, after forming pixel transistors PTr in the surface of the substrate 101, a multilayer wiring layer HS is formed as shown in
These members are formed in the same manner as in the first embodiment.
Then, the substrate 101 is inverted and the thickness of the substrate 101 is reduced in the same manner as in the first embodiment.
In this step, part of the substrate 101 is removed from the rear side by CMP in the same manner as in the first embodiment. In the present embodiment as well as in the first embodiment, the second pixel isolation member PS2 has a higher hardness and is accordingly harder to remove by CMP than the substrate 101. The second pixel isolation member PS2 extends from the surface of the substrate 101 to the rear side of the p-type impurity diffusion region PW as in the first embodiment. Consequently, the thickness of the substrate 101 is reduced to expose the rear side of the p-type impurity diffusion region PW, using the second pixel isolation member PS2 as a stopper as in the first embodiment.
Then, the substrate 101 is provided with a passivation layer (not shown), a color filter (not shown) and an on-chip lens (not shown) on the rear side. Thus, a rear emission CMOS image sensor is completed.
In the present embodiment, for forming the pixel isolation member PS, the first pixel isolation member PS1 and the second pixel isolation member PS2 are formed, as in the first embodiment. The second pixel isolation member PS2 is used as a CMP stopper when the thickness of the substrate is reduced by CMP. The pixel isolation member PS thus includes a plurality of types, and the first and second pixel isolation members PS1 and PS2 are formed through a wide resist pattern.
The solid-state image pickup device of the present invention can be efficiently manufactured at low cost, and can take high-quality images.
The present invention is not limited to the above-described embodiments, and various modifications may be made.
Although the above embodiments illustrate the case in which the first and second pixel isolation members PS1 and PS2 are formed so as to partition the regions P1 and P2 respectively, each including two-by-two pixels P, the invention is not limited to this form. The pixel isolation members may partition regions each in which at least three pixels P are arranged in one direction. For example, the step of forming part of the pixel isolation member so as to partition regions each in which three pixels are arranged in one direction may be repeated at least three times, thereby forming the pixel isolation members.
Although the above embodiment illustrates the case where the present invention will be applied to cameras, the invention is not limited to this. The present invention may be applied to other electric apparatuses including a solid-state image pickup device, such as a scanner and a copy machine.
Although the above embodiments illustrate structures in which a plurality of photodiodes share pixel transistors, the present invention is not limited to the above form. The present invention may be applied to a case where a set of pixel transistors is provided for each photodiode.
In the above embodiments, four photodiodes share one floating diffusion portion, but the invention is not limited to this form.
The second pixel isolation member PS2 (through-electrode) which is made of an electroconductive material in the above embodiments may be configured so as to be used as a conductor line, such as a reset line.
CMP may be evenly stopped in chips by additionally forming the second pixel isolation member PS2 (through-electrode) in a peripheral circuit portion.
In addition to the above method in which a metal is exposed to stop the polishing, the rear surface of the substrate may be polished by combining SiN and a metal, SiN and polysilicon, and other combinations in addition to the technique in which a metal is exposed to stop the polishing.
The second pixel isolation member PS2 (through-electrode) can be used as an alignment mark for forming a color filter and an on-chip lens that are to be formed on the rear side of the substrate.
The elements or components described in the above embodiments are each a form of the corresponding element of the invention, including the solid-state image pickup device 1, the photodiodes 21 corresponding to photoelectric conversion elements, the camera 40 corresponding to an electronic apparatus, the substrate 101 corresponding to a semiconductor substrate, the floating diffusion portion FD, the pixel P, and the pixel isolation members PS and PSb. Also, the first pixel isolation member PS1 and the second pixel isolation member PS2 are exemplary forms of the first pixel isolation member and the second pixel isolation member of the invention, respectively. The p-type impurity diffusion layer PS2b of the above embodiments corresponds to an impurity diffusion region.
The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2009-231462 filed in the Japan Patent Office on Oct. 5, 2009, the entire content of which is hereby incorporated by reference.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Number | Date | Country | Kind |
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2009-231462 | Oct 2009 | JP | national |
This application is a division of U.S. patent application Ser. No. 12/892,077 filed Sep. 28, 2010, the entirety of which is incorporated herein by reference to the extent permitted by law. The present application claims the benefit of priority to Japanese Patent Application No. JP 2009-231462 filed on Oct. 5, 2009 in the Japan Patent Office, the entirety of which is incorporated by reference herein to the extent permitted by law.
Number | Date | Country | |
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Parent | 12892007 | Sep 2010 | US |
Child | 13785998 | US |