JP2019080081A - Solid-state imaging device and imaging apparatus - Google Patents

Abstract

To suppress an increase or decrease in a dark current due to misalignment or dimensional deviation.SOLUTION: A solid-state imaging device includes: a photoelectric conversion unit in which a plurality of pixels are two-dimensionally arrayed on an imaging surface and each of the plurality of pixels accommodates a signal charge according to an incident light amount; a charge detection unit that detects a signal charge; an active region provided with a transfer transistor for transferring the signal charge from the photoelectric conversion unit to the charge detection unit; a separation region formed around the active region; and a guard layer provided in a part of the periphery of the photoelectric conversion unit and formed at a boundary between the active region and the separation region, and in the photoelectric conversion unit, the transfer transistor is connected to a first end, and the guard layer is not formed in a part of the boundary portion around a second end of the photoelectric conversion unit facing the first end.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a solid-state imaging device and an imaging device.

In recent years, video cameras and electronic still cameras have become widespread widely. As these cameras, amplification type solid-state imaging devices such as CCD type and CMOS type are used, and they are manufactured through a general semiconductor process.

The solid-state imaging device has a pixel region in which a plurality of pixels are two-dimensionally arranged, and a peripheral circuit that outputs an optical signal from the pixel to the outside. A charge corresponding to incident light is accumulated in a photoelectric conversion unit (for example, a photodiode) or the like arranged in each pixel, transferred to a charge detection unit by a transfer transistor, and then read out through a peripheral circuit.

Although it is desirable for the solid state imaging device to read out the output according to the incident light, it is known that the phenomenon that the output occurs even if there is no incident light occurs. This phenomenon is generally called dark current. Since the dark current increases in accordance with the accumulation time, it becomes a problem particularly when exposed for a long time in night scene photography, for example.

The main cause of the dark current is the influx of electrons generated from dangling bonds of the crystal present at the interface (boundary) between the semiconductor and the insulator. For example, when an element isolation region which is an insulator is provided around the photoelectric conversion portion, the boundary between the photoelectric conversion portion and the element isolation region becomes a large dark current generation source. As a countermeasure against this dark current component, there is known a technique in which a guard layer of the opposite conductivity type is provided in the vicinity of the boundary between the photoelectric conversion portion and the element isolation region to prevent the depletion layer of the photoelectric conversion portion from reaching the interface Patent Document 1).

The guard layer is provided at the boundary between the photoelectric conversion portion and the element isolation region, and it is not necessary to form the guard layer in the vicinity of the transfer transistor where the element isolation region is not formed in the outer periphery of the photoelectric conversion portion. Therefore, in Patent Document 1, the guard layer is not formed only around the transfer transistor in the outer periphery of the photoelectric conversion unit, and has an asymmetric shape. After that, the transfer direction is Y
It is called an axial direction, and a direction orthogonal to the transfer direction is called an X-axis direction.

JP, 2012-44219, A

In a solid-state imaging device, it is desirable to design it to be robust against alignment and dimensional deviation so that the device characteristics become uniform. For example, it is desired that the design be robust to the alignment and dimensional deviation at the time of injection of the photoelectric conversion unit and the guard layer.

The guard layer is provided across the boundary between the photoelectric conversion unit and the element isolation region, but the suppression capability of dark current according to the width from the boundary to the photoelectric conversion unit side in the entire width of the guard layer (A0). Changes. The width (referred to as A1) on the photoelectric conversion portion side from this boundary changes due to the alignment at the time of injection of the guard layer and the dimensional deviation. For example, when misalignment occurs in the Y-axis direction, the width A1 on the photoelectric conversion unit side increases from the boundary on one side in the Y-axis direction and the dark current decreases, but the width on the photoelectric conversion unit side from the boundary on the opposite side A1 decreases and dark current increases.

As in Patent Document 1, in the case where the guard layer is not formed around the transfer transistor and the guard layer has an asymmetrical shape, if the asymmetrical shape has an alignment or a dimensional deviation in the Y-axis direction, the width A1 With the change, the total amount of dark current flowing into the photoelectric conversion unit increases or decreases. An increase or decrease in the total amount of dark current appears as a variation in element characteristics.

  In a solid-state imaging device according to one aspect of the present invention, a plurality of pixels are two-dimensionally arranged on an imaging surface, and each of the plurality of pixels has a photoelectric conversion unit that stores signal charges according to incident light quantity; An active region provided with a charge detection unit to be detected, a transfer transistor for transferring the signal charge from the photoelectric conversion unit to the charge detection unit, a separation region formed around the active region, and the photoelectric conversion unit And a guard layer formed at a boundary between the active region and the separation region, and the photoelectric conversion unit is connected to the transfer transistor at a first end, The guard layer is characterized in that it is not formed on a part of the periphery of the second end of the photoelectric conversion unit facing the first end in the boundary portion.

According to the present invention, it is possible to suppress an increase or decrease in dark current due to alignment or dimensional deviation.

FIG. 1 is a schematic block diagram showing an electronic camera according to a first embodiment of the present invention. It is a schematic circuit diagram showing composition of a solid-state image sensing device. It is a schematic circuit diagram of a pixel provided in a solid-state image sensor. It is an expanded pixel top view of the pixel provided in the solid-state image sensor concerning a 1st embodiment of the present invention. It is an enlarged pixel top view of the pixel provided in the conventional solid-state image sensor. It is an expansion pixel top view of a pixel provided in a solid-state image sensing device concerning a 2nd embodiment of the present invention. It is an expansion pixel top view of a pixel provided in a solid-state image sensing device concerning a 3rd embodiment of the present invention. It is an expansion pixel top view of a pixel provided in a solid-state image sensing device concerning a 4th embodiment of the present invention. It is an expansion pixel top view of the pixel provided in the solid-state image sensing device concerning a 5th embodiment of the present invention. It is an expansion pixel top view of the pixel provided in the solid-state image sensing device concerning a 6th embodiment of the present invention. It is an expansion pixel top view of the pixel provided in the solid-state image sensing device concerning a 7th embodiment of the present invention. It is an expansion pixel top view of a pixel provided in a solid-state image sensing device concerning an 8th embodiment of the present invention. It is an expansion pixel top view of the pixel provided in the solid-state image sensing device concerning a 9th embodiment of the present invention. It is a schematic circuit diagram showing composition of a solid-state image sensing device.

First Embodiment
FIG. 1 is a schematic block diagram showing an electronic camera 1 according to a first embodiment of the present invention.
A photographing lens 2 is attached to the electronic camera 1. The lens control unit 2 a drives the focus and the aperture of the photographing lens 2. A solid-state imaging device 3 is provided in the image space of the photographing lens 2.
The imaging surface of the image sensor 30 which is one of the structures of is arrange | positioned.

The solid-state imaging device 3 is driven by the drive signal output from the imaging control unit 4 and outputs a signal. The signal output from the solid-state imaging device 3 is processed through the signal processing unit 5 and the A / D conversion unit 6 and then temporarily stored in the memory 7.

The memory 7 is connected to the bus 8. A lens control unit 2 a, an imaging control unit 4, a microprocessor 9, a focus calculation unit 10, a recording unit 11, an image compression unit 12 and an image processing unit 13 are connected to the bus 8.
Etc. are also connected. Although not shown in the drawings, the imaging control unit 4 includes a timing generator and the like, and supplies drive signals and the like to each unit of the solid-state imaging device 3. An operation unit 9 a such as a release button is connected to the microprocessor 9. Further, the recording unit 11 described above has a recording medium 11
a is detachably attached.

FIG. 2 is a schematic circuit diagram showing a part of the configuration of the image sensor 30 mounted on the solid-state imaging device 3. The image sensor 30 is formed of a silicon substrate, and is configured as a CMOS type image sensor. The image sensor 30 has a plurality of pixels 20 for outputting an electrical signal corresponding to the amount of incident light, and peripheral circuits for outputting a signal from the pixel 20. The plurality of pixels 20 are two-dimensionally arranged in the pixel area 31 of the image sensor 30.

In FIG. 2, as a peripheral circuit for outputting a signal from the pixel 20, a vertical scanning circuit 21;
Horizontal signal lines 25 connected to the horizontal scanning circuit 22 and the drive signal lines 23 and 24 connected thereto, and the pixels 20 for each pixel column, and receiving the electric signal from each pixel 20, and each vertical signal line 25 The pixel current source 26 for supplying a constant current to the vertical signal line 25, the correlated double sampling circuit (CDS) 27 provided for each vertical signal line 25, and the signal outputted from the correlated double sampling circuit 27 The receiving horizontal signal line 28 and the output amplifier 29 are illustrated.

The vertical scanning circuit 21 and the horizontal scanning circuit 22 output a drive signal based on a command from the imaging control unit 4 of the electronic camera 1. Each pixel 20 receives a drive signal output from the vertical scanning circuit 21 from a predetermined drive signal line 23 and is driven, and outputs a signal corresponding to incident light to the vertical signal line 25. There are a plurality of drive signals output from the vertical scanning circuit 21 and accordingly a plurality of drive signal lines 23.

The signal output from the pixel 20 is subjected to predetermined noise removal in the correlated double sampling circuit 27. Then, a drive signal is output from the horizontal scanning circuit 22 through the drive signal line 24, and the signal is output to the outside through the horizontal signal line 28 and the output amplifier 29.

The electrical signal output to the vertical signal line 25 is subjected to well-known correlated double sampling in the CDS circuit 27 arranged for each vertical signal line 25 to remove noise. CDS circuit 27
Is operated by a drive signal input from the horizontal scanning circuit 22 via the drive signal line 24.

The electrical signal after noise removal and being a component of a true image signal is sequentially performed on the vertical signal line 25.
The signal is output to the horizontal signal line 28 and output to the outside of the image sensor 30 via the output amplifier 29. Although not shown in FIG. 2, in practice, a reset unit that resets the horizontal signal line 28 is connected to the horizontal signal line 28, and the horizontal signal line 28 is output each time a signal is output from the output amplifier 29 to the outside. Is reset.

FIG. 3 is an equivalent circuit diagram of the pixel 20. As shown in FIG. As shown in FIG. 3, the pixel 20 includes a photodiode PD, a floating diffusion FD, a transfer transistor Ta, an amplification transistor Tb of a source follower, a reset transistor Tc, and a selection transistor T.
and d.

The transfer transistor Ta, the amplification transistor Tb, the reset transistor Tc, and the selection transistor Td are N-channel MOS transistors. Each transistor is turned on when its gate goes high (high) and turned off when its gate goes low (low). VDD is a power supply.

The photodiode PD generates and accumulates a charge according to the amount of incident light. When the transfer transistor Ta is turned on, the charge accumulated in the photodiode PD is transferred to the floating diffusion FD.

The floating diffusion FD converts the charge transferred through the transfer transistor Ta into a voltage. The voltage is applied to the gate of the amplification transistor Tb. The amplification transistor Tb generates and outputs an electric signal according to the voltage.

The transfer transistor Ta is turned on / off by a drive signal φTG input to its gate. The drive signal φTG is output from the vertical scanning circuit 21 and applied to the gate of the transfer transistor Ta via the drive signal line 23.

The selection transistor Td electrically connects the pixel to the vertical signal line by being turned on. Then, the selection transistor Td outputs the electric signal generated by the amplification transistor Tb to the vertical signal line. The select transistor Td is turned on / off by a drive signal φS input to its gate. The drive signal φS is output from the vertical scanning circuit 21 and applied to the gate of the selection transistor Td via the drive signal line 23.

The reset transistor Tc is turned on to discharge the charge transferred to the floating diffusion FD and the gate of the amplification transistor Tb, and is brought to a reset state. The reset transistor Tc is turned on / off by a drive signal φFDR input to its gate. Drive signal φFDR is output from vertical scanning circuit 21 and drive signal line 2
3 is applied to the gate of the reset transistor Tc.

The gates of the transfer transistors Ta arranged in the pixel 20 are commonly connected in the row direction. The gates of the reset transistor Tc and the select transistor Td are also commonly connected in the row direction. Then, the pixels 20 in the row direction are simultaneously driven. Therefore, the pixels 20 arranged in the row direction simultaneously output electrical signals to the corresponding vertical signal lines 25.

FIG. 4A is an enlarged plan view of the pixel 20. FIG. Image sensor 3 is shown in FIG.
Two pixels 20 arranged side by side on the 0 imaging plane are shown side by side. Fig. 4 (b)
4 is a cross-sectional view taken along line Y0-Y0 of FIG.

The pixel 20 has an active area 41 surrounded by a thick line in FIG. 4 (a). Inside the active region 41, an N-type photodiode PD, an N-type floating diffusion FD, and a transfer transistor Ta for transferring charges from the photodiode PD to the floating diffusion FD in the Y-axis direction are provided.

As shown in FIG. 4B, in the image sensor 30, an epitaxial layer is formed on a semiconductor substrate, and a P-type well is formed on the epitaxial layer. The photodiode PD is formed by implanting an N-type impurity into the P-type well. A P-type surface layer 42 is formed on the N-type photodiode PD. The P-type impurity concentration of the surface layer 42 is higher than that of the P-type well. The surface layer 42 prevents dark current from flowing into the photodiode PD from the dangling bonds of the crystal present on the semiconductor surface.

As shown in FIGS. 4A and 4B, a separation region 43 of oxide film is formed around the active region 41, and the plurality of pixels 20 are electrically separated. In FIG. 4A, the boundary between the separation region 43 and the active region 41 is represented by a thick line. The oxide separation region 43 is an insulator, and the boundary between the separation region 43 and the active region 41 may cause the inflow of dark current to the photodiode PD.

In order to suppress the flow of dark current from the boundary between isolation region 43 and active region 41 to photodiode PD, a portion of the boundary between isolation region 43 and active region 41 in the vicinity of photodiode PD is selected. A P-type guard layer 44 is implanted except for the above.

In the boundary between the isolation region 43 and the active region 41, the guard layer 44 is not injected in the boundary near the photodiode PD, for example, in the vicinity of the transfer transistor Ta. In the vicinity of the transfer transistor Ta, a guard layer 4 is provided to prevent charge transfer failure.
4 is not injected.

Further, the guard layer 44 is not injected also into a part of the boundary between the isolation region 43 and the active region 41 in the vicinity of the second end 52 opposed to the first end 51 of the photodiode PD connected to the transfer transistor Ta. . The boundary portion where the guard layer 44 is not injected near the second end 52 is provided at a position opposite to the connection portion where the photodiode PD is connected to the transfer transistor Ta at the first end 51.

The ability of the guard layer 44 to suppress the dark current becomes higher as the width A1 of the guard layer 44 injected from the boundary between the separation region 43 and the active region 41 toward the active region 41 becomes larger. When the alignment is shifted in the Y-axis direction (transfer direction) when the guard layer 44 is injected:
Although the entire width A0 of the guard layer 44 does not change, the width A1 of the guard layer 44 injected from the boundary toward the active region 41 changes.

In the cross section Y1-Y1 shown in FIG. 4A, the guard layer 44 is a boundary between the separation region 43 and the active region 41 on the side of the first end 51 and the second end 52 of the photodiode PD. Provided on both sides of the When the alignment is shifted by ΔA in the Y-axis direction when implanting the guard layer 44, the width A1 of one of the guard layer 44 of the boundary on the first end 51 side and the boundary on the second end 52 side of the photodiode PD. Becomes smaller by .DELTA.A, and the width A1 of the other guard layer 44 becomes larger by .DELTA.A. In other words, when the guard layer 44 is injected, the alignment is Y
When it shifts in the axial direction, the dark current flowing from one of the boundary on the first end 51 and the boundary on the second end 52 of the photodiode PD increases, and the dark current flowing from the other decreases. That is, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 in the cross section Y1-Y1 corresponds to the injection of the guard layer 44. It does not change due to misalignment in the Y-axis direction.

In the cross section Y2-Y2 shown in FIG. 4A, the guard layer 44 is not at the boundary on the first end 51 side of the photodiode PD in the boundary between the isolation region 43 and the active region 41, and the second
It is provided at the boundary on the end 52 side. The dark current flowing from the boundary on the first end 51 side of the photodiode PD changes due to misalignment in the Y-axis direction when injecting the guard layer 44 because there is no guard layer 44 at the boundary on the first end 51 side. do not do. Second of photodiode PD
The dark current flowing from the boundary on the end 52 side changes due to misalignment in the Y-axis direction when the guard layer 44 is injected. That is, the photodiode PD in the cross section Y2-Y2
The sum of the dark current flowing from the boundary at the first end 51 of the first and the dark current flowing from the boundary at the second end 52 changes due to misalignment in the Y-axis direction when injecting the guard layer 44 .

In the cross section Y0-Y0, an active region 41 near the first end 51 of the photodiode PD.
There is no boundary between and the separation area 43. That is, in the cross section Y0-Y0, the dark current does not flow into the photodiode PD from the first end 51 side of the photodiode PD. And
Of the boundary between isolation region 43 and active region 41, second end 52 of photodiode PD
No guard layer 44 is provided at the side boundary. That is, in the cross section Y0-Y0,
The dark current flowing from the second end 52 side of the photodiode PD does not change due to misalignment in the Y-axis direction. Therefore, the total of the dark current flowing into the photodiode PD at the cross section Y0-Y0 does not change due to the misalignment in the Y-axis direction when the guard layer 44 is injected.

Conventionally, as shown in the enlarged pixel plan view shown in FIG. 5A, the guard layer 44 is formed in the vicinity of the second end 52.
Had been injected. That is, there is no place where the guard layer 44 is not provided at the boundary on the second end 52 side of the photodiode PD as in the cross section Y3-Y3 in FIG. 5A.

The cross section Y4-Y4 shown in FIG. 5A is the same as the cross section Y1-Y1 shown in FIG. 4A. The cross section Y5-Y5 is identical to the cross section Y2-Y2 shown in FIG. 4 (a). That is, when alignment is shifted in the Y-axis direction when injecting the guard layer 44, the sum of the dark current flowing from the boundary at the first end 51 and the dark current flowing from the boundary at the second end 52 is
It does not change with respect to the cross section Y4-Y4, but changes with respect to the cross section Y5-Y5.

The cross section Y3-Y3 of the conventional solid-state imaging device is different from the cross section Y0-Y0 of the image sensor 30 shown in FIG. 4A, and is the same as the cross section Y2-Y2. That is, the cross section Y3-Y
In 3, when the alignment is shifted in the Y-axis direction when injecting the guard layer 44, the dark current flows from the boundary on the first end 51 side of the photodiode PD and the boundary flows from the boundary on the second end 52 side The sum with the dark current changes due to misalignment in the Y-axis direction when the guard layer 44 is injected.

FIG. 5B is a cross-sectional view taken along line Y3-Y3 of FIG. It differs from FIG. 4B in that a P-type guard layer 44 is injected between the isolation region 43 and the photodiode PD.

Image sensor 30 according to the first embodiment of the present invention shown in FIGS. 4 (a) and 4 (b).
According to this, the following effects can be obtained as compared with the conventional solid-state imaging device shown in FIGS. 5 (a) and 5 (b).
In the image sensor 30 according to the first embodiment of the present invention, the guard layer 44 is not injected in a part in the vicinity of the second end 52, as in the cross section Y3-Y3 in FIG. 5A. By the misalignment in the Y-axis direction when the guard layer 44 is injected, it is possible to reduce the location where the total dark current changes and the variation of the total dark current due to the misalignment.

Second Embodiment
FIG. 6A is an enlarged plan view of the pixel 20 of the image sensor 30 according to the second embodiment of the present invention. In FIG. 6A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 6B is a cross-sectional view taken along line Y6-Y6 of FIG.

As compared with the first embodiment, the pixel 20 of the image sensor 30 according to the second embodiment has an enlarged area in which the guard layer 44 provided near the second end 52 is not injected. It is different. Specifically, the length B of the region where the guard layer 44 provided near the second end 52 is not injected
1 is a length B0 of the region where the guard layer 44 provided in the vicinity of the transfer transistor Ta is not injected
Make it the same as

By expanding the region where the guard layer 44 provided near the second end 52 is not injected,
As in the cross section Y2-Y2 of FIG. 4, the portion where the guard layer 44 is provided only in the vicinity of the second end 52 is eliminated. That is, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 is misalignment in the Y-axis direction when the guard layer 44 is injected. There is no place to change.

The cross section Y7-Y7 shown in FIG. 6A is identical to the cross section Y1-Y1 shown in FIG. That is, dark current flowing from the boundary on the first end 51 side of the photodiode PD;
The sum with the dark current flowing from the boundary at the second end 52 does not change due to the misalignment in the Y-axis direction when the guard layer 44 is injected.

In the cross section Y8-Y8 shown in FIG. 6A, the guard layer 44 is a boundary between the first end 51 side and the second end 52 side of the photodiode PD in the boundary between the separation region 43 and the active region 41. Not provided for both. Therefore, the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 are also deviated by the misalignment in the Y-axis direction when injecting the guard layer 44. It does not change. Therefore, in the cross section Y8-Y8, the dark current flowing from the boundary on the first end 51 side of the photodiode PD, and the second end 52
The sum with the dark current flowing from the side boundary does not change due to the misalignment in the Y-axis direction when the guard layer 44 is injected.

The cross section Y6-Y6 shown in FIG. 6A is identical to the cross section Y0-Y0 shown in FIG. That is, the dark current does not flow from the first end 51 side of the photodiode PD, and the second
The dark current flowing from the end 52 does not change due to misalignment in the Y-axis direction. Therefore, the total of the dark current flowing into the photodiode PD at the cross section Y6-Y6 does not change due to the misalignment in the Y-axis direction when the guard layer 44 is injected.

Note that the magnitude of the dark current itself flowing into the photodiode PD from the boundary on the second end 52 side of the photodiode PD is larger than the region where the guard layer 44 is not injected, so that the image sensor 30 in the first embodiment To increase. At the design stage of the image sensor 30, in the vicinity of the second end 52 in consideration of both the total amount of dark current and the change in the total amount of dark current due to misalignment in the Y-axis direction when injecting the guard layer 44. It is preferable to define the length B1 of the region where the provided guard layer 44 is not injected.

Image sensor 30 according to the second embodiment of the present invention shown in FIGS. 6 (a) and 6 (b).
According to this, the following effects can be obtained as compared to the first embodiment shown in FIGS. 4 (a) and 4 (b).
In the image sensor 30 according to the second embodiment of the present invention, the region where the guard layer 44 provided near the second end 52 is not injected is enlarged as compared with the first embodiment, as shown in FIG.
As in the cross section Y2-Y2 of a), the position where the total of the dark current changes due to the misalignment in the Y-axis direction when injecting the guard layer 44 is reduced, and the change of the total dark current due to the misalignment is further reduced be able to.

Third Embodiment
FIG. 7A is an enlarged plan view of a pixel 20 of an image sensor 30 according to a third embodiment of the present invention. In FIG. 7A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG.7 (b) is Y9-Y9 sectional drawing of FIG. 7 (a).

Each pixel 20 of the image sensor 30 according to the third embodiment includes each active area 4.
1 is different in that it extends from a part on the second end 52 side of the photodiode PD to the floating diffusion FD of the pixel 20 adjacent to each pixel 20. In other words, as is apparent from FIG. 7A, in the image sensor 30 according to the third embodiment, the active regions 41 of the pixels 20 arranged in the Y-axis direction are integrated. Thereafter, a pixel 20 adjacent to each pixel 20 from a part on the second end 52 side of the photodiode PD of each pixel 20
The partial region 61 of the active region 41 extending to the end is referred to as a non-separation region 61.

In FIG. 7A, the non-separation region 61 is a part of a P-type well. The non-separation region 61 extends from the position on the second end 52 facing the connecting portion between the photodiode PD and the transfer transistor Ta provided at the first end 51 toward the adjacent pixel.

The non-separation region 61 physically connects the active regions 41 between the pixels 20 adjacent to each other in the Y-axis direction, but electrically separates the two pixels 20 from each other. In addition, non-separation area 6
The ability of 1 to electrically isolate between two pixels 20 is inferior to insulators such as isolation region 43 and the like.

The boundary between the second end 52 of the photodiode PD and the non-separation region 61 is the active region 41
The guard layer 44 is not provided because it is not a boundary between the first and second separation regions 43.

The section Y10-Y10 shown in FIG. 7A is identical to the section Y1-Y1 shown in FIG. 4A. That is, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 is Y at the time of injecting the guard layer 44.
It does not change due to misalignment in the axial direction.

The cross section Y11-Y11 is the same as the cross section Y2-Y2 shown in FIG. 4 (a). That is, in the cross section Y11-Y11, when the alignment is shifted in the Y-axis direction when implanting the guard layer 44, the dark current flowing from the boundary at the first end 51 and the dark current flowing from the boundary at the second end 52 The sum with the current changes.

The cross section Y9-Y9 is different from the cross section Y0-Y0 of the image sensor 30 shown in FIG. 4A, and the active region 41 is formed at both the first end 51 and the second end 52 of the photodiode PD.
There is no boundary between and the separation area 43. That is, in the cross section Y9-Y9, the dark current does not flow into the photodiode PD.

In the cross section Y12-Y12, the dark current does not flow into the photodiode PD from the boundary on the first end 51 side of the photodiode PD, and the dark current flowing from the second end 52 side of the photodiode PD is aligned in the Y axis direction It changes with the gap of Therefore, the cross section Y12-
The total dark current flowing into the photodiode PD at Y12 changes due to misalignment in the Y-axis direction when the guard layer 44 is injected.

Image sensor 30 according to the third embodiment of the present invention shown in FIGS. 7 (a) and 7 (b).
According to this, the following effects can be obtained as compared to the first embodiment shown in FIGS. 4 (a) and 4 (b).
The image sensor 30 according to the third embodiment has a non-separation region 61 extending toward the adjacent pixel from a position on the second end 52 facing the connection connected to the transfer transistor Ta. Since the image sensor 30 according to the third embodiment has the non-separation region 61, the total amount of dark current flowing from the second end 52 side of the photodiode PD into the photodiode PD is higher than that in the first embodiment. It can be reduced.
Further, the image sensor 30 according to the third embodiment prevents injection of the guard layer 44 in the area where the non-separation area 61 is provided in the vicinity of the second end 52, as shown in FIG. As in the cross section Y3-Y3, a shift in alignment in the Y-axis direction at the time of implanting the guard layer 44 can reduce the location where the total dark current changes, and reduce the change in the total dark current due to the shift.

Fourth Embodiment
FIG. 8A is an enlarged plan view of a pixel 20 of the image sensor 30 according to the fourth embodiment of the present invention. In FIG. 8A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 8 (b) shows Y13-Y13 of FIG. 8 (a).
FIG.

The pixel 20 of the image sensor 30 according to the fourth embodiment enlarges the length C1 of the non-separation region 61 as compared to the third embodiment. Specifically, the length C1 of the non-separation region 61 is made equal to the gate width W of the transfer transistor Ta.

By expanding the length C1 of the non-separation region 61 to the gate width W of the transfer transistor Ta, the guard layer 44 is provided only in the vicinity of the second end 52 as in the section Y11-Y11 of FIG. Eliminate the place. That is, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 is misalignment in the Y-axis direction when the guard layer 44 is injected. I am eliminating the part that changes due to

The cross section Y14-Y14 shown in FIG. 8 (a) is the same as the cross section Y1-Y1 shown in FIG. 4 (a). The cross section Y15-Y15 is the same as the cross section Y2-Y2 shown in FIG. That is, when alignment is shifted in the Y-axis direction when injecting the guard layer 44, the sum of the dark current flowing from the boundary at the first end 51 and the dark current flowing from the boundary at the second end 52 is It does not change with respect to the cross section Y14-Y14, but changes with respect to the cross section Y15-Y15.

The section Y13-Y13 shown in FIG. 8A is identical to the section Y9-Y9 shown in FIG. 7A. That is, in the cross section Y13-Y13, the dark current does not flow into the photodiode PD.

The cross section Y16-Y16 shown in FIG. 8A is the cross section Y12-Y1 shown in FIG. 7A.
7A, it is identical to the cross section Y9-Y9 shown in FIG. 7A. That is, the cross section Y13
Also at -Y13, dark current does not flow into the photodiode PD.

Image sensor 30 according to the fourth embodiment of the present invention shown in FIGS. 8 (a) and 8 (b).
According to the third embodiment shown in FIGS. 7A and 7B, the following effects can be obtained.
The image sensor 30 according to the fourth embodiment expands the length C1 of the non-separation region 61 as compared with the third embodiment, thereby forming a guard layer as in the cross section Y12-Y12 of FIG. 7A. 4
It is possible to reduce the change in the dark current flowing into the photodiode PD due to the misalignment in the Y-axis direction at the time of injecting 4 and to further reduce the change in the total dark current due to the misalignment.

Fifth Embodiment
FIG. 9A is an enlarged plan view of a pixel 20 of an image sensor 30 according to a fifth embodiment of the present invention. In FIG. 9A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 9 (b) is Y17-Y17 of FIG. 9 (a).
FIG.

The fifth embodiment is a combination of the second embodiment and the fourth embodiment. That is, the fifth embodiment is different from the fourth embodiment in the length B1 of the region where the guard layer 44 provided in the vicinity of the second end 52 of the photodiode PD is not injected.
The length B0 of the region in which the guard layer 44 provided in the vicinity of a is not injected is the same.

The cross section Y18-Y18 shown in FIG. 9A is the same as the cross section Y1-Y1 shown in FIG. 4A. That is, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 is Y at the time of injecting the guard layer 44.
It does not change due to misalignment in the axial direction.

In the cross section Y19-Y19 shown in FIG. 9A, the guard layer 44 is a boundary between the first end 51 side and the second end 52 side of the photodiode PD in the boundary between the separation region 43 and the active region 41. Not provided for both. Therefore, the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 are also deviated by the misalignment in the Y-axis direction when injecting the guard layer 44. It does not change. Therefore, the cross section Y19-
In Y19, the sum of the dark current flowing from the boundary on the first end 51 side of the photodiode PD and the dark current flowing from the boundary on the second end 52 side is the Y-axis direction when injecting the guard layer 44 It does not change due to misalignment.

The cross section Y17-Y17 and the cross section Y20-Y20 shown in FIG. 9A are the same as the cross section Y13-Y13 shown in FIG. 8A. That is, the cross section Y17-Y17 and the cross section Y
In 20-Y20, dark current does not flow into the photodiode PD.

Image sensor 30 according to the fifth embodiment of the present invention shown in FIGS. 9 (a) and 9 (b).
According to this, the following effects can be obtained as compared with the fourth embodiment shown in FIGS. 8 (a) and 8 (b).
In the image sensor 30 according to the second embodiment of the present invention, the region where the guard layer 44 provided near the second end 52 is not injected is enlarged as compared with the fourth embodiment, as shown in FIG.
As in the cross section Y15-Y15 of a), the position where the total of the dark current changes due to the misalignment in the Y-axis direction when the guard layer 44 is injected is reduced, and the change of the total dark current due to the misalignment is reduced It can be further reduced than the embodiment.

Sixth Embodiment
FIG. 10A is an enlarged plan view of a pixel 20 of an image sensor 30 according to a sixth embodiment of the present invention. In FIG. 10A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 10 (b) is Y21 of FIG. 10 (a).
It is -Y21 sectional drawing.

The pixel 20 of the image sensor 30 according to the sixth embodiment injects a P-type impurity into the non-separation region 61 to form a P-type injection layer 62. The P-type injection layer 62 has a higher concentration of impurities than the P-type well, and has a high performance of electrically separating the two pixels 20 than the P-type well.

Image sensor 3 according to the sixth embodiment of the present invention shown in FIGS. 10 (a) and 10 (b).
According to 0, the following effects can be obtained as compared with the third to fifth embodiments.
In order to miniaturize the image sensor 30 or to increase the pixel density, it is conceivable to shorten the distance between the photodiode PD and the floating diffusion FD which face each other across the non-separation region 61. If the distance between the photodiode PD and the floating diffusion FD both of which have the N conductivity type is shortened, the probability of an unexpected leak current flowing between the photodiode PD and the floating diffusion FD increases.
By providing the P-type injection layer 62 having a higher impurity concentration than the P-type well in the non-separation region 61, the occurrence probability of the leak current between the photodiode PD and the floating diffusion FD facing each other across the non-separation region 61 is reduced. can do.

Seventh Embodiment
FIG. 11A is an enlarged plan view of a pixel 20 of an image sensor 30 according to a seventh embodiment of the present invention. In FIG. 11A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 11 (b) is Y22 of FIG. 11 (a).
It is -Y22 sectional drawing.

In the pixel 20 of the image sensor 30 according to the seventh embodiment, the surface layer 42 formed on the photodiode PD is extended to the non-separation region 61. The surface layer 42 above the non-separation region 61 is a dangling bond (tangling bond) present on the semiconductor surface of the non-separation region 61.
Thus, it is possible to prevent the inflow of dark current to the photodiode PD, and to reduce the occurrence probability of the leak current between the photodiode PD and the floating diffusion FD which face each other across the non-separation region 61.

Eighth Embodiment
FIG. 12A is an enlarged pixel plan view of the pixel 20 of the image sensor 30 according to the eighth embodiment of the present invention. In FIG. 12A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 12 (b) is Y23 of FIG. 12 (a).
It is -Y23 sectional drawing.

The eighth embodiment is a combination of the fifth embodiment and the sixth embodiment. That is, in the eighth embodiment, the P-type injection layer 62 is provided in the non-separation region 61 of the fifth embodiment. By doing this, the change in the total amount of dark current due to misalignment in the Y-axis direction when implanting guard layer 44 can be reduced as in the fifth embodiment, and non-separation region 61 As in the sixth embodiment, the occurrence probability of the leak current between the photodiode PD and the floating diffusion FD facing each other can be reduced.

(The ninth embodiment)
FIG. 13A is an enlarged plan view of a pixel 20 of an image sensor 30 according to a ninth embodiment of the present invention. In FIG. 13A, two pixels 20 arranged side by side on the imaging surface of the image sensor 30 are shown side by side. FIG. 13 (b) is Y24 in FIG. 13 (a).
It is -Y24 sectional drawing.

In the image sensor 30 according to the ninth embodiment, the shape of the photodiode PD in the fifth embodiment is symmetrical (left-right symmetrical) in the Y-axis direction, and the position of the photodiode PD in the active region 41 Has changed. Specifically, the X-axis dimension D1 from the boundary on the first end 51 of the photodiode PD to the first end 51 and the X-axis dimension D2 from the boundary on the second end 52 to the second end 52 are the same. The photodiode PD is provided at the following position. By doing this, it is possible to reduce the change in the total amount of dark current due to misalignment in the Y-axis direction when injecting the photodiode PD.

  The embodiment described above can be modified as follows.

(Modification 1)
In each of the above embodiments, the pixel 20 of the image sensor 30 is a transfer transistor Ta,
The amplification transistor Tb, the reset transistor Tc, and the selection transistor Td are provided. However, one or more transistors may be shared by a plurality of pixels. An equivalent circuit diagram in the case where the amplification transistor Tb, the reset transistor Tc, and the selection transistor Td are shared by two pixels is shown in FIG.

(Modification 2)
In each of the above embodiments, the pixels 20 of the image sensor 30 each have the floating diffusion FD. However, the floating diffusion FD may be shared by a plurality of pixels. For example, transfer transistors Ta of two pixels may be disposed face to face, and a floating diffusion FD may be disposed between the two transfer transistors Ta, and the floating diffusion FD may be shared between the two pixels. .

The present invention is not limited to the above embodiment as long as the features of the present invention are not impaired.
Other forms considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

1: Electronic camera, 3: Solid-state image pickup device, 20: Pixel, 30: Image sensor, 31: Non-separation area, 41: Active area, 42: Surface layer, 43: Separation area, 44: Guard layer, 51:
First end, 52: second end, 61: non-separation area, 62: P-type injection layer

Claims (1)

A plurality of pixels are two-dimensionally arrayed on the imaging surface,
In each of the plurality of pixels,
Active region provided with a photoelectric conversion unit that accumulates signal charge according to the amount of incident light, a charge detection unit that detects the signal charge, and a transfer transistor that transfers the signal charge from the photoelectric conversion unit to the charge detection unit When,
A separation area formed around the active area;
A guard layer provided on a part of the periphery of the photoelectric conversion unit and formed at the boundary between the active region and the separation region;
The transfer transistor is connected to a first end of the photoelectric conversion unit,
The solid-state imaging device according to claim 1, wherein the guard layer is not formed on a part of the periphery of a second end of the photoelectric conversion unit facing the first end in the boundary portion.

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