Solid-state imaging device and potential setting method

Abstract

To provide a solid-state imaging device and a potential setting method capable of achieving a low power consumption and a high-speed transfer.SOLUTION: A solid-state imaging device 1 includes a plurality of photoelectric conversion units 11 that are arranged along a first direction D1 and generate charges according to incident light, a plurality of transfer electrodes 15 that are arranged along a second direction D2 and provided on the photoelectric conversion units 11 and that transfer the charges to the second direction D2, and a plurality of voltage-dividing resistors 17 which are provided corresponding to the adjacent transfer electrodes 15 and which generate a transfer potential so as to increase from the transfer electrode 15 on the upstream side in the second direction D2 toward the transfer electrode 15 on the downstream side in the second direction D2 and supply the transfer potential to the corresponding transfer electrode 15. Each photoelectric conversion unit 11 includes a first impurity region 131 and a second impurity region 132 having an impurity concentration higher than that of the first impurity region 131. The width of the second impurity region 132 increases from an upstream side toward a downstream side in the second direction D2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid-state imaging device and a potential setting method. [Background technology]

[0002] Patent Document 1 describes a solid-state imaging device. This solid-state imaging device includes a photosensitive region that generates charges corresponding to the intensity of incident light in response to incident light, and an electrode disposed relative to an n-type semiconductor layer that constitutes the photosensitive region. The photosensitive region has a substantially rectangular planar shape formed by two long sides and two short sides. The electrode is made of a light-transmitting material, such as a polysilicon film. The electrode constitutes a resistive gate and is formed extending in a direction from one short side toward the other short side of the planar shape of the n-type semiconductor layer (hereinafter, for convenience of explanation, this direction may be referred to as the "second direction"). By applying a constant potential difference to both ends in the second direction, the electrode forms a potential gradient corresponding to the electrical resistance component of the electrode in the second direction, i.e., a potential gradient that is increased along the second direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-231768 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in a resistive gate type CCD image sensor such as the solid-state imaging device described in Patent Document 1, by using electrodes that constitute the resistive gate, it is possible to form a potential slope in the photosensitive region and achieve high-speed transfer of charges.

[0005] On the other hand, the electrode constituting the resistive gate is formed in a sheet shape using polysilicon. If the electrical resistance of this electrode is low, a large current will flow, resulting in increased power consumption. Therefore, it is desirable to increase the electrical resistance of the electrode. The electrical resistance of the electrode can be controlled, for example, by forming a sheet made of undoped polysilicon and then implanting impurities into the polysilicon sheet. The lower the concentration of the implanted impurities, the higher the electrical resistance can be. On the other hand, if the concentration of the implanted impurities is low, the variation in the amount of implanted impurities in the polysilicon sheet (variation between sheets and at each position within the sheet) increases. In other words, increasing the electrical resistance of the electrode results in a problem of increased variation in the electrical resistance (i.e., characteristic variation).

[0006] Therefore, there is a demand for solving the trade-off between low power consumption and characteristic variations that can occur in resistive gate CCD image sensors.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems of resistive gate CCD image sensors, and as a result have discovered the following. Specifically, the present inventors have investigated a multi-gate CCD image sensor to solve the above-mentioned problems. In a multi-gate CCD image sensor, a photosensitive region is provided with a plurality of electrodes (made of polysilicon) arranged along the second direction, and a plurality of voltage-dividing resistors are provided to divide the output voltage from a power supply so that the potential applied to each electrode increases from the upstream side to the downstream side in the second direction. In this case, by increasing the resistance of the voltage-dividing resistors, it is possible to reduce power consumption without increasing the resistance of each electrode, compared to a single electrode constituting a resistive gate.

[0008] Furthermore, by studying the above-described multi-gate CCD image sensor, the inventors have discovered that the following problem may occur. Specifically, in a multi-gate CCD image sensor, a gap must be provided between adjacent electrodes in the second direction (charge transfer direction) to ensure insulation between the electrodes. Because no voltage is applied across such a gap between the electrodes, a barrier (potential bump) that inhibits charge transfer is formed against the potential generated in the photosensitive region. One way to prevent the formation of potential bumps is to narrow the gap between the electrodes. However, for example, there are limitations to the resolution of photolithography used to form the electrodes, and a gap that is too narrow can also cause short circuits.

[0009] Another way to suppress the formation of potential bumps is to increase the potential difference between adjacent electrodes and increase the corresponding potential difference. However, in this case, the overall potential difference across the multiple electrodes cannot be set to exceed the device's withstand voltage limit, and there is a limit to the potential difference that can be achieved at each stage of the multiple electrodes. Reducing the number of electrode stages would make it possible to achieve a larger potential difference at each stage within the device's withstand voltage limit, but this would increase the distance that a single electrode must transfer charge, thereby increasing the time required for charge transfer. Therefore, in this case, there is a demand for high-speed transfer.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a solid-state imaging device and a potential setting method that enable low power consumption and high-speed transfer. [Means for solving the problem]

[0011] The inventors of the present invention have made the following new discovery through extensive research into the problems associated with the multi-gate CCD image sensor described above. Specifically, by forming a cusp structure in the photosensitive region such that the width of the region with a relatively high impurity concentration increases in the direction of charge transfer, a potential gradient can be formed in the photosensitive region, preventing an increase in the time required for charge transfer even if the distance of charge transfer carried by one electrode increases. The present invention was made through further research based on the above discovery.

[0012] That is, the solid-state imaging device of the present invention is [1] "a solid-state imaging device comprising: a plurality of photoelectric conversion units arranged along a first direction and generating charges in response to incident light; a plurality of transfer electrodes arranged along a second direction intersecting the first direction and provided on the photoelectric conversion units for transferring the charges in the second direction; and a plurality of voltage dividing resistors provided corresponding to adjacent transfer electrodes, dividing the output voltage from a power source to generate a transfer potential that increases from the transfer electrode upstream in the second direction to the transfer electrode downstream in the second direction, and providing the transfer potential to the corresponding transfer electrode, wherein the photoelectric conversion units have a first impurity region and a second impurity region having the same conductivity type as the first impurity region and an impurity concentration higher than the impurity concentration of the first impurity region, and wherein the width of the second impurity region in the first direction increases from the upstream side to the downstream side in the second direction."

[0013] In a solid-state imaging device according to the present invention, a plurality of transfer electrodes arranged along a second direction intersecting the first direction are provided on a plurality of photoelectric conversion units arranged along a first direction. A plurality of voltage-dividing resistors apply a transfer potential to the plurality of transfer electrodes so that the transfer potential increases from the transfer electrode upstream in the second direction to the transfer electrode downstream in the second direction. This generates a potential within the photoelectric conversion units that increases from the upstream side to the downstream side in the second direction, causing charges generated in the photoelectric conversion units to be transferred in the second direction. With this solid-state imaging device having the above-described configuration, by increasing the resistance of the voltage-dividing resistors, it is possible to reduce power consumption without increasing the resistance of each transfer electrode.

[0014] In particular, in this solid-state imaging device, the photoelectric conversion section has a region (second impurity region) with a relatively high impurity concentration, and the width of the second impurity region in the first direction has a cusp structure in which the width increases from the upstream side to the downstream side in the second direction (charge transfer direction). Therefore, a potential gradient due to the cusp structure can be formed within the photoelectric conversion section, which suppresses the increase in the time required for charge transfer and enables high-speed transfer. Therefore, this solid-state imaging device enables low-power and high-speed transfer.

[0015] The solid-state imaging device according to the present invention may be [2] "the solid-state imaging device according to the above [1], wherein, when viewed from a third direction intersecting the first and second directions, one end of the second impurity region in the second direction is located at the boundary between the transfer electrodes adjacent along the second direction." In this case, the start or end of the potential gradient caused by the cusp structure can be located at the boundary between the transfer electrodes. Furthermore, by locating the start or end of the potential gradient caused by the cusp structure at the boundary between the transfer electrodes, it is possible to easily form a potential having a gradient that slopes in one direction as a whole by utilizing a potential step caused by a potential difference between the transfer electrodes at the boundary.

[0016] The solid-state imaging device according to the present invention may be [3] "the solid-state imaging device according to the above [2], in which, when viewed from the third direction, the other end of the second impurity region in the second direction is located at the boundary portion." In this case, the start and end of the potential gradient caused by the cusp structure can be located at the boundary portion of the transfer electrodes. Furthermore, by locating the start and end of the potential gradient caused by the cusp structure at the boundary portion of the transfer electrodes, it is possible to easily form a potential having a gradient that slopes in one direction as a whole by utilizing a potential step caused by a potential difference between the transfer electrodes at the boundary portion.

[0017] The solid-state imaging device according to the present invention may be the solid-state imaging device according to [4], "wherein, when viewed from the third direction, one end of the second impurity region is located at the boundary between one of the transfer electrodes and another transfer electrode adjacent to the one transfer electrode on the upstream side in the second direction, and the other end of the second impurity region is located at the boundary between the one transfer electrode and yet another transfer electrode adjacent to the one transfer electrode on the downstream side in the second direction." In this case, a cusp structure can be formed within one region corresponding to one transfer electrode in the photoelectric conversion unit. This increases the increase in width per length in the second direction of the second impurity region, enabling further speedup.

[0018] The solid-state imaging device according to the present invention may be [5] "the solid-state imaging device according to any one of [1] to [4] above, wherein the plurality of voltage dividing resistors apply to each of the plurality of transfer electrodes the transfer potential that increases for each of the transfer electrodes from the upstream side to the downstream side in the second direction." In this case, a potential difference can be formed for each of the transfer electrodes. Also, potential reversal at the boundary between the transfer electrodes can be suppressed.

[0019] The solid-state imaging device according to the present invention may be [6] "the solid-state imaging device according to any one of [1] to [5] above, in which the resistance values ​​of the plurality of voltage dividing resistors are the same." In this case, the potential difference between the transfer electrodes can be made constant.

[0020] The solid-state imaging device according to the present invention may be [7] "the solid-state imaging device according to any one of the above [1] to [5], wherein the plurality of voltage dividing resistors include a first voltage dividing resistor and a second voltage dividing resistor having a resistance value different from that of the first voltage dividing resistor." In this case, by appropriately setting the resistance values ​​of the first voltage dividing resistor and the second voltage dividing resistor, it is possible to make the potential gradient in the photoelectric conversion unit more suitable for charge transfer.

[0021] The solid-state imaging device according to the present invention may be [8] "the solid-state imaging device according to any one of the above [1] to [7], including an insulating film formed on the photoelectric conversion section, and the transfer electrode being provided on the photoelectric conversion section via the insulating film." In this way, the transfer electrode can be provided on the photoelectric conversion section via the insulating film.

[0022] The solid-state imaging device according to the present invention may be [9] "the solid-state imaging device according to any one of [1] to [8] above, wherein the amount of change in potential occurring in response to a change in the width from one end of the second impurity region in the second direction to the other end of the second impurity region in the second direction is smaller than a virtual step, which is a potential step that can occur at a boundary between the transfer electrodes adjacent along the second direction in response to the transfer potential, in a hypothetical case where the photoelectric conversion unit does not have the second impurity region." In this case, by leaving a potential step at the boundary between the transfer electrodes, it is possible to improve the transfer speed while suppressing potential reversal.

[0023] The solid-state imaging device according to the present invention may be

[10] "the solid-state imaging device according to any one of the above [1] to [9], wherein each of the plurality of transfer electrodes is provided across all of the photoelectric conversion units." In this way, in the first direction, each transfer electrode may be provided across all of the photoelectric conversion units.

[0024] The solid-state imaging device of the present invention may be

[11] "a solid-state imaging device according to any one of [1] to

[10] above, which is provided with a charge accumulation section that accumulates the charges transferred by the plurality of transfer electrodes for each of the photoelectric conversion sections and outputs the charges accumulated for each of the photoelectric conversion sections collectively."

[0025] The solid-state imaging device of the present invention may be

[12] "the solid-state imaging device according to any one of [1] to

[11] above, comprising a charge output section that sequentially outputs the charges transferred by the plurality of transfer electrodes."

[0026] The solid-state imaging device according to the present invention may be

[13] "the solid-state imaging device according to any one of [1] to

[12] above, wherein the photoelectric conversion unit has a third impurity region having the same conductivity type as the first impurity region and adjacent to the second impurity region along the second direction, and the plurality of transfer electrodes each include a first transfer electrode provided on the second impurity region and a second transfer electrode provided on the third impurity region so as to be adjacent to the first transfer electrode along the second direction." In this case, after forming the second transfer electrode on the third impurity region, the second impurity region adjacent to the third impurity region can be formed by implanting an impurity using the second transfer electrode as a mask. Therefore, when the first transfer electrode is formed adjacent to the second transfer electrode, the first transfer electrode and the second impurity region are aligned.

[0027] In contrast, the potential setting method according to the present invention is

[14] "a potential setting method for setting a transfer potential of a solid-state imaging device, comprising a setting step for setting the transfer potential, wherein the solid-state imaging device comprises: a plurality of photoelectric conversion units arranged along a first direction and generating charges in response to incident light; a plurality of transfer electrodes arranged along a second direction intersecting the first direction and provided on the photoelectric conversion units for transferring the charges in the second direction; and a plurality of voltage dividing resistors provided corresponding to adjacent transfer electrodes, the plurality of voltage dividing resistors dividing an output voltage from a power source to generate a transfer potential that increases from the transfer electrode on the upstream side in the second direction toward the transfer electrode on the downstream side in the second direction, and providing the transfer potential to the corresponding transfer electrode; and the photoelectric conversion units each having a first impurity region and a first impurity region. and a second impurity region having the same conductivity type as the impurity region and having an impurity concentration higher than the impurity concentration of the first impurity region, wherein the width of the second impurity region in the first direction increases as it extends in the second direction, and in the setting process, the transfer potential is set so that the magnitude of an actual step generated at the boundary, which is the sum of a virtual step, which is a potential step that may occur at the boundary between the transfer electrodes adjacent to each other along the second direction, and an amount of change in potential that occurs in accordance with a change in the width from one end of the second impurity region in the second direction to the other end of the second impurity region in the second direction, is larger than an error from a design value, in a hypothetical case where the photoelectric conversion unit does not have the second impurity region.

[0028] In this potential setting method, in a hypothetical case where the photoelectric conversion unit does not have the second impurity region, the transfer potential is set so that the magnitude of the actual step occurring at the boundary, which is the sum of the virtual step, which is a step in potential that can occur at the boundary of the transfer electrode depending on the transfer potential, and the amount of change in potential that occurs depending on the change in width from one end to the other end of the second impurity region in the second direction, is larger than the error from the design value. As a result, it is possible to prevent the error from causing a step that is opposite to the overall potential gradient at the boundary of the transfer electrode, which would hinder charge transfer. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide a solid-state imaging device and a potential setting method that enable low power consumption and high-speed transfer. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic plan view showing a solid-state imaging device according to this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a cross section taken along line II-II in FIG. [Figure 3] FIG. 3 is a schematic plan view showing an enlarged view of a portion of the plurality of photoelectric conversion units shown in FIG. [Figure 4] FIG. 4 is a diagram showing the relationship between the cross-sectional structure of the gradient region shown in FIG. 3 and the potential. [Figure 5] FIG. 5 is a schematic cross-sectional view showing the relationship between the transfer electrode and the second impurity region shown in FIG. [Figure 6] FIG. 6 is a diagram showing the transfer potential applied to the transfer electrode and the potential generated in the photoelectric conversion portion. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a solid-state imaging device according to a first modification. [Figure 8] 9 is a diagram showing a transfer potential and a potential in the solid-state imaging device shown in FIG. 8. FIG. [Figure 9] FIG. 9 is a schematic plan view showing a solid-state imaging device according to a second modification. [Figure 10] FIG. 10 is a diagram showing the transfer potential and the potential in the solid-state imaging device shown in FIG. [Figure 11] FIG. 11 is a schematic plan view showing a photoelectric conversion unit and transfer electrodes according to a modified example. [Figure 12] FIG. 12 is a diagram showing the transfer potential and potential when the photoelectric conversion unit and transfer electrode shown in FIG. 11 are provided. DETAILED DESCRIPTION OF THE INVENTION

[0031] A solid-state imaging device and a potential setting method according to an embodiment will be described below with reference to the drawings. In the description of each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant description may be omitted. Each drawing may also show a Cartesian coordinate system including a first axis defining a first direction D1, a second axis defining a second direction D2, and a third axis defining a third direction D3.

[0032] Fig. 1 is a schematic plan view showing a solid-state imaging device according to this embodiment. Fig. 2 is a schematic cross-sectional view showing a cross section taken along line II-II in Fig. 1. As shown in Figs. 1 and 2, the solid-state imaging device 1 includes a plurality of photoelectric conversion sections 11, a plurality of transfer electrodes 15, a plurality of voltage dividing resistors 17, a vertical transfer gate section 21 (charge accumulation section), and a horizontal shift register 31 (charge output section).

[0033] The photoelectric conversion units 11 are arranged along a first direction D1. Each of the photoelectric conversion units 11 extends along a second direction D2 that intersects with the first direction D1, and generates electric charges in response to incident light.

[0034] The multiple transfer electrodes 15 are arranged along the second direction D2 and provided on the photoelectric conversion units 11. Each transfer electrode 15 is intended to transfer charges generated in the photoelectric conversion units 11 in the second direction D2. Here, an insulating film 57 is formed on the photoelectric conversion units 11, and the transfer electrodes 15 are provided on the photoelectric conversion units 11 via the insulating film 57. Each transfer electrode 15 extends along the first direction D1 and is provided across all of the photoelectric conversion units 11 in the first direction D1.

[0035] The plurality of voltage-dividing resistors 17 are electrically interposed between the transfer electrodes 15 adjacent to each other in the second direction D2. The voltage-dividing resistors 17 have the same resistance value. The voltage-dividing resistors 17 are connected in series to a DC power supply 19, and one end 17a of each group of voltage-dividing resistors 17 is maintained at a relatively low potential (for example, a constant negative potential), and the other end 17b is maintained at a relatively high potential (for example, a constant positive potential). As a result, a transfer potential (transfer potential Vg in FIG. 6) that increases in a step-like manner from the upstream side to the downstream side in the second direction D2 is applied to each of the plurality of transfer electrodes 15.

[0036] That is, the voltage dividing resistors 17 are provided corresponding to adjacent transfer electrodes 15, and by dividing the output voltage from the DC power supply 19, generate a transfer potential that increases from the transfer electrode 15 on the upstream side in the second direction D2 toward the transfer electrode 15 on the downstream side in the second direction D2, and provide the transfer potential to the corresponding transfer electrode 15. Here, the voltage dividing resistors 17 provide each of the multiple transfer electrodes 15 with a transfer potential that increases for each transfer electrode 15 from the upstream side toward the downstream side in the second direction D2.

[0037] The vertical transfer gate unit 21 includes storage units 23 that store, for each of the photoelectric conversion units 11 arranged along the first direction D1, the charges generated in the photoelectric conversion units 11 and transferred by the transfer electrodes 15. Each of the storage units 23 stores the charges transferred from the corresponding photoelectric conversion unit 11 and outputs the charges stored for each photoelectric conversion unit 11 collectively.

[0038] The horizontal shift register 31 receives the charges accumulated in and output from each of the accumulation sections 23 of the vertical transfer gate section 21 (i.e., transferred by the transfer electrodes 15), transfers them along the first direction D1, and sequentially outputs them to the amplifier section 41. The charges output from the horizontal shift register 31 are converted into voltages by the amplifier section 41 and output to the outside of the solid-state imaging device 1 for each photoelectric conversion section 11.

[0039] 2, the photoelectric conversion section 11, the transfer electrodes 15, the vertical transfer gate section 21, the horizontal shift register 31, the voltage dividing resistors 17, and other circuits are formed on a semiconductor substrate 51. The semiconductor substrate 51 is made up of a P-type Si substrate 53, an N-type semiconductor layer 55 and a P-type Si layer 56 formed on the surface side of the P-type Si substrate 53. + and a gate semiconductor layer (not shown).

[0040] N-type semiconductor layer 55 and P + The P-type semiconductor layers 55 are alternately arranged in the first direction D1 with the second direction D2 as the longitudinal direction. A pn ​​junction is formed between the P-type Si substrate 53 and the N-type semiconductor layer 55, and the N-type semiconductor layer 55 serves as a photoelectric conversion unit 11 that generates charges in response to incident light. + The photoelectric conversion layer functions as an isolation region that separates the photoelectric conversion sections 11 .

[0041] The transfer electrodes 15 are provided on the surface of the semiconductor substrate 51 via an insulating film 57. The transfer electrodes 15 are made of a light-transmitting material. For example, the transfer electrodes 15 are made of a polysilicon film (a polysilicon sheet). The insulating film 57 is made of a light-transmitting material. For example, the insulating film 57 is made of a silicon oxide film.

[0042] A gate electrode 59 and a horizontal transfer electrode 61 are provided on the surface of the semiconductor substrate 51 via an insulating film 57. The gate electrode 59 is provided adjacent to the transfer electrode 15 located most downstream in the second direction D2, with the first direction D1 being the longitudinal direction. A clock signal having a voltage level of H level or L level is input to the gate electrode 59 via a terminal 59a.

[0043] The semiconductor substrate 51 has an N-type semiconductor layer 55 under the gate electrode 59 located near the transfer electrode 15. -The vertical transfer gate portion 21 includes a barrier region 63 formed to be an N-type semiconductor. The barrier region 63 is provided with its longitudinal direction aligned with the first direction D1. Therefore, the barrier region 63 and an N-type semiconductor region 55a are present below the gate electrode 59, and the gate electrode 59, barrier region 63, and region 55a form the vertical transfer gate portion 21.

[0044] The horizontal transfer electrodes 61 are aligned along the first direction D1 adjacent to the gate electrodes 59. The horizontal transfer electrodes 61, the N-type semiconductor layer 55 below the horizontal transfer electrodes 61, and the like constitute a horizontal shift register 31.

[0045] Here, Fig. 3 is a schematic plan view showing an enlarged portion of the plurality of photoelectric conversion units shown in Fig. 1. As shown in Figs. 1 and 3, each photoelectric conversion unit 11 has a gradient region 13. In this embodiment, each photoelectric conversion unit 11 has a plurality of gradient regions 13 arranged along the second direction D2. Therefore, in this embodiment, the gradient regions 13 are arranged two-dimensionally along the first direction D1 and the second direction D2.

[0046] The gradient region 13 includes a first impurity region 131 and a second impurity region 132. Here, the gradient region 13 includes a pair of first impurity regions 131 and a single second impurity region 132, and the second impurity region 132 is located between the pair of first impurity regions 131 when viewed from a third direction D3 that intersects with the first direction D1 and the second direction D2. The first impurity region 131 has a predetermined impurity concentration. The second impurity region 132 has the same conductivity type as the first impurity region 131 and has a higher impurity concentration than the impurity concentration of the first impurity region 131. In this embodiment, the first impurity region 131 is N-type, and the second impurity region 132 is N-type. + It is a type.

[0047] In this embodiment, the gradient region 13 is formed in a rectangular shape that is relatively longer in the second direction D2 than in the first direction D1, as viewed from the third direction D3. The second impurity region 132 extends from one end of the gradient region 13 to the other end in the second direction D2. Therefore, the second impurity regions 132 of adjacent gradient regions 13 along the second direction D2 are continuous with each other. As viewed from the third direction D3, the width W of the second impurity region 132 along the first direction D1 gradually increases from the upstream side to the downstream side in the second direction D2.

[0048] Therefore, the second impurity region 132 is relatively narrow at one end 132p on the upstream side in the second direction D2 and relatively wide at the other end 132r on the downstream side in the second direction D2 in the first direction D1. In this way, the gradient region 13 has a cusp structure in which the width W of the second impurity region 132, which has a relatively high impurity concentration, increases from the upstream side to the downstream side in the second direction D2.

[0049] FIG. 4 is a diagram showing the relationship between the cross-sectional structure of the gradient region shown in FIG. 3 and the potential. (a) of FIG. 4 shows a cross section (cross section intersecting with the second direction D2) of the gradient region 13 at a position where the width W of the second impurity region 132 is relatively narrow, and (b) of FIG. 4 shows a cross section (cross section intersecting with the second direction D2) of the gradient region 13 at a position where the width W of the second impurity region 132 is relatively wide. As shown in FIG. 4, the potential Vc (electric potential) generated in the photoelectric conversion unit 11 due to the cusp structure of the gradient region 13 becomes deeper (higher) as the width W of the second impurity region 132 becomes wider. Therefore, in the photoelectric conversion unit 11, a potential Vc is generated in each gradient region 13, with a gradient that increases from the upstream side to the downstream side in the second direction D2.

[0050] 5 is a schematic cross-sectional view showing the relationship between the transfer electrodes and the second impurity regions shown in FIG. 3. As shown in FIG. 5, the transfer electrode 15 includes a plurality of first transfer electrodes 151 and a plurality of second transfer electrodes 152. In the example of FIG. 3, each of the multiple transfer electrodes 15 is a first transfer electrode 151 or a second transfer electrode 152. The first transfer electrodes 151 and the second transfer electrodes 152 are alternately arranged along the second direction D2. The first transfer electrode 151 includes a base portion 151k provided on the second impurity region 132 and an extension portion 151p that extends from the base portion 151k onto the adjacent second transfer electrode 152 and overlaps with the second transfer electrode 152 along the third direction D3.

[0051] The second transfer electrode 152 is configured from a single layer arranged on the same plane as the base portion 151k of the first transfer electrode 151. As described above, in the solid-state imaging device 1, the transfer electrode 15 has a two-layer structure of the first transfer electrode 151 and the second transfer electrode 152. In this embodiment, the first transfer electrode 151 and the second transfer electrode 152 are provided on separate second impurity regions 132. A boundary portion G, which is a gap filled with an insulating film 57, is formed between the first transfer electrode 151 (base portion 151k) and the second transfer electrode 152.

[0052] In this embodiment, when viewed from the third direction D3, one end 132p of the second impurity region 132 is located at a boundary G between one transfer electrode 15 (first transfer electrode 151) and another transfer electrode 15 (second transfer electrode 152) adjacent to the one transfer electrode 15 on the upstream side in the second direction D2. Also, when viewed from the third direction D3, the other end 132r of the second impurity region 132 is located at a boundary G between one transfer electrode 15 (first transfer electrode 151) and yet another transfer electrode 15 (another second transfer electrode 152) adjacent to the one transfer electrode on the downstream side in the second direction D2. As a result, in this embodiment, one transfer electrode 15 corresponds to one second impurity region 132.

[0053] 6(a), the plurality of voltage-dividing resistors 17 apply a transfer potential Vg, which increases stepwise for each transfer electrode 15 from the upstream side to the downstream side in the second direction D2, to each of the plurality of transfer electrodes 15. At the same time, as described above, in the photoelectric conversion unit 11, a potential Vc having a gradient due to the cusp structure of the gradient region 13 (i.e., a potential Vc generated in response to a change in the width W from one end 132p to the other end 132r in the second direction D2 of the second impurity region 132) is formed in each gradient region 13.

[0054] 6(b), in a state in which a transfer potential Vg is applied to each of the transfer electrodes 15, a potential Vp is generated in the photoelectric conversion unit 11, which increases stepwise for each transfer electrode 15 from the upstream side to the downstream side in the second direction D2, and which has a gradient that increases from the upstream side to the downstream side in the second direction D2 in the gradient regions 13 corresponding to each transfer electrode 15. The charge generated in the photoelectric conversion unit 11 is transferred in the second direction D2 in accordance with this potential Vp.

[0055] In addition, in a pair of second impurity regions 132 adjacent to each other along the second direction D2, one end 132p having a relatively narrow width W of one second impurity region 132 and the other end 132r having a relatively wide width W of the other second impurity region 132 are in contact with each other. In other words, the width W of the second impurity regions 132 adjacent to each other along the second direction D2 varies discontinuously. The region where the width W varies discontinuously is located at the boundary G of the transfer electrode 15.

[0056] That is, when viewed from the third direction, the photoelectric conversion unit 11 has a plurality of second impurity regions 132 arranged along the second direction D2, and thus has an actual step Rs at the boundary G between adjacent second impurity regions 132 along the second direction D2, which is a step in the potential Vp depending on a change in the width W of the second impurity regions 132. The actual step Rs may be smaller than a virtual step Is, which is a step in the potential (potential Vt corresponding to the transfer potential Vg in FIG. 6(a)) that can occur at the boundary G depending on the transfer potential Vg in a hypothetical case in which the photoelectric conversion unit 11 does not have the second impurity regions 132. Furthermore, a change ΔVc (see FIG. 4) in the potential Vc that occurs depending on a change in the width W of the second impurity region 132 from one end 132p to the other end 132r in the second direction D2 is smaller than the virtual step Is.

[0057] According to the findings of the present inventors, one idea for suppressing potential bumps, which are one of the problems in multi-gate CCD image sensors, is to form two layers of transfer electrodes so that adjacent transfer electrodes in the charge transfer direction overlap each other at their ends in the charge transfer direction. In this case, no gaps are generated between adjacent transfer electrodes as viewed from the direction in which the transfer electrodes overlap, and therefore the formation of potential bumps can be suppressed.

[0058] To form two layers of transfer electrodes, the first layer of transfer electrodes is formed uniformly on the photoelectric conversion unit, and then the first layer of transfer electrodes is removed by etching in the formation region of the second layer of transfer electrodes, which can cause variations in the thickness of the insulating film interposed between the photoelectric conversion unit and the transfer electrodes. Such variations in the thickness of the insulating film can cause a step in the potential within the photoelectric conversion unit corresponding to each adjacent transfer electrode that is opposite to the overall potential gradient, which may hinder charge transfer.

[0059] As described above, the transfer electrodes 15 in the solid-state imaging device 1 according to this embodiment also have a two-layer structure. When forming such transfer electrodes 15, first, the second transfer electrodes 152 are uniformly formed on the photoelectric conversion units 11, and then the second transfer electrodes 152 are removed by etching in the regions where the base portions 151k of the first transfer electrodes 151 are to be formed. Thereafter, the first transfer electrodes 151 are formed on the photoelectric conversion units 11 in the regions from which the second transfer electrodes 152 have been removed, thereby forming the transfer electrodes 15.

[0060] Therefore, when etching the second transfer electrodes 152, a portion of the insulating film 57 is removed in the region where the first transfer electrodes 151 are to be formed, which may result in the insulating film 57 becoming relatively thin. Therefore, even in the solid-state imaging device 1, variations in the thickness of the insulating film 57 may occur, which may result in a step in the potential within the photoelectric conversion units 11 corresponding to each of the adjacent transfer electrodes 15 that is opposite to the gradient of the overall potential Vp, thereby hindering charge transfer. In other words, in the solid-state imaging device 1, an error in the thickness of the insulating film 57 during manufacturing may result in an error in the designed value of the potential Vp. In response to this, the solid-state imaging device 1 can reduce the effect of such an error by setting the transfer potential as follows:

[0061] That is, the potential setting method according to this embodiment includes a setting step of setting a transfer potential Vg to be applied to the transfer electrode 15. In the setting step, the transfer potential is set so that the magnitude of an actual step Rs (i.e., actual step Rs of the potential Vp at the boundary G) generated at the boundary G, which is the sum of a virtual step Is, which is a step in the potential Vt that can occur at the boundary G between the transfer electrodes 15 adjacent to each other along the second direction D2, and a change ΔVc in the potential Vc that occurs in accordance with a change in the width W of the second impurity region 132 from one end 132p to the other end 132r in the second direction D2, according to the transfer potential Vg, is larger than an error from a design value of the potential Vp.

[0062] As a result, this potential setting method prevents the error from causing a step opposite to the gradient of the overall potential Vp at the boundary G of the transfer electrode 15, thereby preventing charge transfer from being hindered.

[0063] As described above, in the solid-state imaging device 1 according to this embodiment, a plurality of transfer electrodes 15 arranged along a second direction D2 intersecting the first direction D1 are provided on a plurality of photoelectric conversion units 11 arranged along a first direction D1. A transfer potential is applied to the plurality of transfer electrodes 15 by a plurality of voltage-dividing resistors 17 so that the transfer potential increases from the transfer electrode 15 located upstream in the second direction D2 to the transfer electrode 15 located downstream in the second direction D2. This generates a potential (potential Vp) within the photoelectric conversion units 11 that increases from the upstream side to the downstream side in the second direction D2, and charges generated in the photoelectric conversion units 11 are transferred in the second direction D2. With the above-described configuration, the solid-state imaging device 1 can achieve low power consumption by increasing the resistance of the voltage-dividing resistors 17 without increasing the resistance of the transfer electrodes 15.

[0064] In particular, in the solid-state imaging device 1, the photoelectric conversion unit 11 has a region (second impurity region 132) with a relatively high impurity concentration, and the second impurity region 132 has a cusp structure in which the width W in the first direction D1 of the second impurity region 132 increases from the upstream side to the downstream side in the second direction D2 (charge transfer direction). Therefore, a gradient of the potential Vc due to the cusp structure can be formed within the photoelectric conversion unit 11, which makes it possible to suppress an increase in the time required for charge transfer and achieve high-speed transfer. Therefore, the solid-state imaging device 1 enables low-power and high-speed transfer.

[0065] Furthermore, in the potential setting method according to this embodiment, the transfer potential is set so that the magnitude of the actual step Rs occurring at the boundary G, which is the sum of the virtual step Is and the change ΔVc in the potential Vc, is larger than the error from the design value of the potential Vp. This prevents the error from causing a step R that is opposite to the gradient of the overall potential Vp at the boundary G of the transfer electrode 15, which would otherwise be caused by the error, and thus inhibits charge transfer from being hindered.

[0066] Furthermore, in the solid-state imaging device 1 according to this embodiment, when viewed from the third direction D3, one end 132p of the second impurity region 132 is located at a boundary G between one transfer electrode 15 and another transfer electrode 15 adjacent to the one transfer electrode 15 on the upstream side in the second direction D2. When viewed from the third direction D3, the other end 132r of the second impurity region 132 is located at a boundary G between one transfer electrode 15 and yet another transfer electrode 15 adjacent to the one transfer electrode 15 on the downstream side in the second direction D2. This allows a cusp structure to be formed within one region corresponding to one transfer electrode 15 in the photoelectric conversion unit 11. This increases the increase in width W per length in the second direction D2 of the second impurity region 132, enabling further speed increase.

[0067] Furthermore, in the solid-state imaging device 1 according to this embodiment, the multiple voltage dividing resistors 17 apply to each of the multiple transfer electrodes a transfer potential that increases for each transfer electrode 15 from the upstream side to the downstream side in the second direction D2. This makes it possible to form a potential difference for each transfer electrode 15. Furthermore, it is possible to prevent the potential Vp from reversing at the boundary G between the transfer electrodes 15.

[0068] Furthermore, in the solid-state imaging device 1 according to this embodiment, the resistance values ​​of the plurality of voltage dividing resistors 17 are the same, which makes it possible to keep the potential difference between the transfer electrodes 15 constant.

[0069] The solid-state imaging device 1 according to this embodiment also includes an insulating film 57 formed on the photoelectric conversion unit 11. The transfer electrodes 15 are provided on the photoelectric conversion unit 11 via the insulating film 57. In this manner, the transfer electrodes 15 can be provided on the photoelectric conversion unit 11 via the insulating film 57.

[0070] Furthermore, in the solid-state imaging device 1 according to the present embodiment, when viewed from the third direction D3, the photoelectric conversion unit 11 has a plurality of second impurity regions 132 arranged along the second direction D2, and thus has an actual step Rs at the boundary G between adjacent second impurity regions 132 along the second direction D2, which is a step in potential Vp corresponding to a change in width W of the second impurity regions 132. The actual step Rs may be smaller than a virtual step Is, which is a step in potential Vt that can occur at the boundary G in response to the transfer potential Vg in a hypothetical case in which the photoelectric conversion unit 11 does not have the second impurity regions 132. In this case, the cusp structure of the photoelectric conversion unit 11 can further reduce the step in potential Vp occurring in the region of the transfer electrode 15 corresponding to the boundary G.

[0071] Furthermore, in the solid-state imaging device 1 according to this embodiment, a change ΔVc in the potential Vc occurring in response to a change in the width W from one end 132p of the second impurity region 132 in the second direction D2 to the other end 132r of the second impurity region 132 in the second direction D2 is smaller than a virtual step Is, which is a step in the potential Vt that can occur at the boundary G between adjacent transfer electrodes 15 along the second direction D2 in response to the transfer potential Vg, in a hypothetical case in which the photoelectric conversion unit 11 does not have the second impurity region 132. Therefore, by leaving a step in the potential Vp at the boundary G between the transfer electrodes 15, it is possible to improve the transfer speed while suppressing potential reversal.

[0072] Furthermore, in the solid-state imaging device 1 according to this embodiment, each of the multiple transfer electrodes 15 is provided across all of the photoelectric conversion units 11. In this manner, the transfer electrodes 15 may be provided across all of the photoelectric conversion units 11 in the first direction D1.

[0073] The above embodiment has described one aspect of the solid-state imaging device and potential setting method according to the present invention. Therefore, the solid-state imaging device and potential setting method according to the present invention are not limited to the above embodiment and can be modified as desired. Next, modifications will be described.

[0074] Fig. 7 is a schematic cross-sectional view showing a solid-state imaging device according to Modification 1. The solid-state imaging device 1A shown in Fig. 7 differs from the solid-state imaging device 1 according to the above embodiment in that it includes a configuration for distributing charge transfer between one side and the other side in the second direction D2.

[0075] Specifically, in the solid-state imaging device 1A, when viewed from the third direction D3, a terminal 17c maintained at a relatively low potential (e.g., a constant negative potential) is connected to a pair of adjacent transfer electrodes 15 across a (virtual) boundary line L at a desired position (e.g., the center) of the photoelectric conversion unit 11 in the second direction D2, and one end 17a and the other end 17b of a group of voltage-dividing resistors 17 are each maintained at a relatively high potential (e.g., a constant positive potential).

[0076] As a result, as shown in Figure 8, a transfer potential Vg is applied to the multiple transfer electrodes 15 on one side of the boundary line L, which increases with a step-like slope from the upstream side to the downstream side in the second direction D2, and on the other side of the boundary line L, a transfer potential Vg is applied that increases with a step-like slope from the upstream side to the downstream side in the opposite direction to the second direction D2.

[0077] Furthermore, in the photoelectric conversion section 11, in the gradient region 13 located on one side of the boundary line L in the second direction D2, the second impurity region 132 is formed so that the width W increases as it moves from the upstream side to the downstream side in the second direction D2, and in the gradient region 13 located on the other side of the boundary line L in the second direction D2, the second impurity region 132 is formed so that the width W increases as it moves from the upstream side to the downstream side in the opposite direction of the second direction D2.

[0078] As a result, as shown in Figure 8, within the photoelectric conversion unit 11, on one side of the boundary line L, a potential Vp is generated that gradually increases for each transfer electrode 15 as it moves from the upstream side to the downstream side in the second direction D2, and has a gradient that increases within the gradient regions 13 corresponding to each transfer electrode 15 as it moves from the upstream side to the downstream side in the second direction D2, and on the other side of the boundary line L, a potential Vp is generated that gradually increases for each transfer electrode 15 as it moves from the upstream side to the downstream side in the opposite direction of the second direction D2, and has a gradient that increases within the gradient regions 13 corresponding to each transfer electrode 15 as it moves from the upstream side to the downstream side in the opposite direction of the second direction D2.

[0079] Therefore, in the solid-state imaging device 1A, charges generated on one side of the boundary line L are transferred in the second direction D2, and charges generated on the other side of the boundary line L are transferred in the opposite direction to the second direction D2. For this reason, the solid-state imaging device 1A includes a pair of vertical transfer gate units 21 and a pair of horizontal shift registers 31 provided at one end and the other end of the photoelectric conversion unit 11 in the second direction D2. Furthermore, each of the pair of horizontal shift registers 31 is provided with an amplifier unit 41.

[0080] In the above-described solid-state imaging device 1A, the charge transfer distance can be shortened, thereby enabling further speedup. Note that the solid-state imaging device 1A may be configured such that outputs from a pair of horizontal shift registers 31 are joined together and output to a single amplifier section 41.

[0081] Fig. 9 is a schematic plan view showing a solid-state imaging device according to Modification 2. The solid-state imaging device 1B shown in Fig. 9 differs from the solid-state imaging device 1 according to the above embodiment in that the voltage-dividing resistors 17 include a plurality of first voltage-dividing resistors 171 and a plurality of second voltage-dividing resistors 172 having resistance values ​​different from the resistance values ​​of the first voltage-dividing resistors 171.

[0082] As described above, when the transfer electrode 15 has a two-layer structure, the insulating film 57 immediately below the first transfer electrode 151, which is formed later, tends to be thin due to manufacturing reasons, and therefore, even when a constant potential difference (transfer potential Vga in FIG. 10) is applied to the first transfer electrode 151 and the second transfer electrode 152, the potential (potential Vpa in FIG. 10) generated in the photoelectric conversion unit 11 at that time tends to be deeper (higher) in the region immediately below the first transfer electrode 151 than in the region immediately below the second transfer electrode 152. This may cause a step R in the potential Vpa that is opposite to the gradient of the overall potential.

[0083] In order to suppress such an error (step R) in the potential Vpa inside the photoelectric conversion unit 11, the resistance value of the first voltage dividing resistor 171 and the resistance value of the second voltage dividing resistor 172 are adjusted to be different values, thereby making it possible to apply different potential differences in advance to the first transfer electrode 151 and the second transfer electrode 152 (transfer potential Vg in FIG. 10). This makes it possible to prevent a step R that is opposite to the gradient of the overall potential from occurring in the potential (potential Vp in FIG. 10) that occurs inside the photoelectric conversion unit 11 at that time.

[0084] In this way, in the solid-state imaging device 1B, the multiple voltage-dividing resistors 17 include a first voltage-dividing resistor 171 and a second voltage-dividing resistor 172 having a resistance value different from that of the first voltage-dividing resistor 171. By appropriately setting the resistance values ​​of the first voltage-dividing resistor 171 and the second voltage-dividing resistor 172, it is possible to make the gradient of the potential Vp in the photoelectric conversion unit 11 more suitable for charge transfer.

[0085] 10 indicates the potential generated in the photoelectric conversion unit 11 when a transfer potential Vga is applied to the transfer electrodes 15 and each of the gradient regions 13 of the photoelectric conversion unit 11 does not have a cusp structure. Also, the potential Vr in Fig. 10 indicates the potential generated in the photoelectric conversion unit 11 when a transfer potential Vg is applied to the transfer electrodes 15 and each of the gradient regions 13 of the photoelectric conversion unit 11 does not have a cusp structure.

[0086] In the solid-state imaging devices 1 to 1B described above, the photoelectric conversion unit 11 may have a plurality of third impurity regions 133 as shown in FIG. 11. The third impurity regions 133 have the same conductivity type as the first impurity regions 131. For example, the third impurity regions 133 have a higher impurity concentration than the impurity concentration of the first impurity regions 131, and are N + It is a type.

[0087] In the illustrated example, the third impurity region 133 is disposed adjacent to the gradient region 13 (i.e., the second impurity region 132) along the second direction D2. Specifically, the gradient region 13 and the third impurity region 133 are alternately arranged along the second direction D2. The length of the third impurity region 133 in the second direction D2 is shorter than the length of the second impurity region 132 in the second direction D2. The third impurity region 133 does not have a cusp structure and has a uniform impurity concentration along the first direction D1 and the second direction D2.

[0088] Furthermore, a first transfer electrode 151 is provided on the gradient region 13 (i.e., the second impurity region 132), and a second transfer electrode 152 is provided on the third impurity region 133. The relationship between the length of the second transfer electrode 152 and the length of the first transfer electrode 151 in the second direction D2 corresponds to the relationship between the length of the third impurity region 133 and the length of the second impurity region 132 in the second direction D2. That is, the length of the second transfer electrode 152 in the second direction D2 is shorter than the length of the first transfer electrode 151 in the second direction D2.

[0089] 11 and 12, a transfer potential Vg is applied so that a first transfer electrode 151 provided on one second impurity region 132 and a second transfer electrode 152 provided on a third impurity region 133 adjacent to the one second impurity region 132 on the downstream side in the second direction D2 are at the same potential. That is, in the example of FIGS. 11 and 12, each of the multiple transfer electrodes 15 includes a first transfer electrode 151 and a second transfer electrode 152. As a result, the potential Vp generated in the photoelectric conversion unit 11 has a gradient that increases from the upstream side to the downstream side in the second direction D2 in the second impurity region 132, and is constant along the second direction D2 in the third impurity region 133.

[0090] When forming such a structure, after forming the second transfer electrode 152 on the third impurity region 133, impurities are implanted using the second transfer electrode 152 as a mask, thereby forming the second impurity region 132 adjacent to the third impurity region 133. Therefore, when the first transfer electrode 151 is formed adjacent to the second transfer electrode 152, the first transfer electrode 151 and the second impurity region 132 are aligned (self-alignment is achieved).

[0091] The third impurity region 133 may have an impurity concentration lower than that of the second impurity region 132 (for example, an impurity concentration approximately equal to that of the first impurity region 131) (i.e., may be N-type). A transfer potential Vg may be applied so that the first transfer electrode 151 provided on one second impurity region 132 and the second transfer electrode 152 provided on the adjacent third impurity region 133 upstream of the one second impurity region 132 in the second direction D2 have the same potential.

[0092] Here, in the solid-state imaging devices 1 to 1B, the number of the transfer electrodes 15 arranged in the second direction D2 is the same as the number of the second impurity regions 132 (i.e., the gradient regions 13) arranged in the second direction D2, and one end 132p and the other end 132r of the second impurity regions 132 are each located at the boundary portion G of the transfer electrodes 15. However, the relationship between the transfer electrodes 15 and the second impurity regions 132 is not limited to this.

[0093] For example, when viewed from the third direction D3, one end 132p (or the other end 132r) of the second impurity region 132 in the second direction D2 may be located at the boundary G between adjacent transfer electrodes 15 along the second direction D2, and the other end 132r (or the one end 132p) of the second impurity region 132 in the second direction D2 may not be located at the boundary G between adjacent transfer electrodes 15 along the second direction D2.

[0094] In this case, the number of second impurity regions 132 arranged in the second direction D2 may be less than the number of transfer electrodes 15 arranged in the second direction D2, and one second impurity region 132 may be provided across multiple transfer electrodes 15 when viewed from the third direction D3.

[0095] Furthermore, when viewed from the third direction D3, even if one end 132p (or the other end 132r) of the second impurity region 132 in the second direction D2 is located at the boundary G between adjacent transfer electrodes 15 along the second direction D2, and the other end 132r (or one end 132p) of the second impurity region 132 in the second direction D2 is located at the boundary G between adjacent transfer electrodes 15 along the second direction D2, the number of transfer electrodes 15 arranged in the second direction D2 and the number of second impurity regions 132 arranged in the second direction D2 do not need to be the same, and one second impurity region 132 may be provided across multiple transfer electrodes 15 when viewed from the third direction D3.

[0096] Furthermore, in the solid-state imaging devices 1 to 1B, it is not essential that the transfer electrode 15 has a two-layer structure. Furthermore, the structures of the solid-state imaging device 1 according to the above embodiment and the solid-state imaging devices 1A and 1B according to the modifications can be partially interchanged and adopted. For example, the solid-state imaging device 1B according to the second modification can adopt a configuration for distributing charge transfer to one side and the other side of the second direction D2, as in the solid-state imaging device 1A according to the first modification. [Explanation of symbols]

[0097] 1, 1A, 1B...solid-state imaging device, 11...photoelectric conversion section, 15...transfer electrode, 17...voltage dividing resistor, 21...vertical transfer gate section (charge accumulation section), 31...horizontal shift register (charge output section), 57...insulating film, 131...first impurity region, 132...second impurity region, 132p...one end, 132r...other end, 133...third impurity region, 151...first transfer electrode, 152...second transfer electrode, 171...first voltage dividing resistor, 172...second voltage dividing resistor, G...boundary section.

Claims

1. a plurality of photoelectric conversion units arranged along a first direction and generating charges in response to incident light; a plurality of transfer electrodes arranged along a second direction intersecting the first direction and provided on the photoelectric conversion unit, for transferring the charges in the second direction; a plurality of voltage dividing resistors provided corresponding to the adjacent transfer electrodes, which divide an output voltage from a power supply to generate a transfer potential that increases from the transfer electrode on the upstream side in the second direction toward the transfer electrode on the downstream side in the second direction, and which supply the transfer potential to the corresponding transfer electrode; Equipped with The photoelectric conversion unit is a first impurity region; a second impurity region having the same conductivity type as the first impurity region and having an impurity concentration higher than the impurity concentration of the first impurity region; and a width of the second impurity region in the first direction increasing from the upstream side to the downstream side in the second direction; Solid-state imaging device.

2. When viewed from a third direction intersecting the first direction and the second direction, one end of the second impurity region in the second direction is located at a boundary between the transfer electrodes adjacent to each other along the second direction. The solid-state imaging device according to claim 1 .

3. When viewed from the third direction, the other end of the second impurity region in the second direction is located at the boundary portion. The solid-state imaging device according to claim 2 .

4. When viewed from the third direction, the one end of the second impurity region is located at the boundary between one of the transfer electrodes and another of the transfer electrodes adjacent to the one transfer electrode on the upstream side in the second direction, When viewed from the third direction, the other end of the second impurity region is located at the boundary between the one transfer electrode and another transfer electrode adjacent to the one transfer electrode on the downstream side in the second direction. The solid-state imaging device according to claim 3 .

5. the plurality of voltage dividing resistors apply the transfer potential, which increases for each of the transfer electrodes from the upstream side to the downstream side in the second direction, to each of the plurality of transfer electrodes; The solid-state imaging device according to claim 1 .

6. The resistance values ​​of the plurality of voltage dividing resistors are the same. The solid-state imaging device according to claim 1 .

7. the plurality of voltage dividing resistors include a first voltage dividing resistor and a second voltage dividing resistor having a resistance value different from a resistance value of the first voltage dividing resistor; The solid-state imaging device according to claim 1 .

8. an insulating film formed on the photoelectric conversion portion, the transfer electrode is provided on the photoelectric conversion unit via the insulating film; The solid-state imaging device according to claim 1 .

9. a change in potential occurring in response to a change in the width from one end of the second impurity region in the second direction to the other end of the second impurity region in the second direction is smaller than a virtual step, which is a potential step that may occur at a boundary between the transfer electrodes adjacent to each other along the second direction in response to the transfer potential, in a virtual case in which the photoelectric conversion unit does not have the second impurity region. The solid-state imaging device according to claim 1 .

10. Each of the plurality of transfer electrodes is provided across all of the photoelectric conversion units. The solid-state imaging device according to claim 1 .

11. a charge storage unit that stores the charges transferred by the plurality of transfer electrodes for each of the photoelectric conversion units and outputs the charges stored for each of the photoelectric conversion units collectively; The solid-state imaging device according to claim 1 .

12. a charge output section that sequentially outputs the charges transferred by the plurality of transfer electrodes; The solid-state imaging device according to claim 1 .

13. the photoelectric conversion portion includes a third impurity region having the same conductivity type as the first impurity region and adjacent to the second impurity region along the second direction; each of the plurality of transfer electrodes includes a first transfer electrode provided on the second impurity region and a second transfer electrode provided on the third impurity region so as to be adjacent to the first transfer electrode along a second direction; The solid-state imaging device according to any one of claims 1 to 12.

14. A potential setting method for setting a transfer potential of a solid-state imaging device, comprising: a setting step of setting the transfer potential, the solid-state imaging device, a plurality of photoelectric conversion units arranged along a first direction and generating charges in response to incident light; a plurality of transfer electrodes arranged along a second direction intersecting the first direction and provided on the photoelectric conversion unit, for transferring the charges in the second direction; a plurality of voltage dividing resistors provided corresponding to the adjacent transfer electrodes, which divide an output voltage from a power supply to generate a transfer potential that increases from the transfer electrode on the upstream side in the second direction toward the transfer electrode on the downstream side in the second direction, and which supply the transfer potential to the corresponding transfer electrode; Equipped with The photoelectric conversion unit is a first impurity region; a second impurity region having the same conductivity type as the first impurity region and having an impurity concentration higher than the impurity concentration of the first impurity region; and a width of the second impurity region in the first direction increasing toward the second direction; In the setting step, the transfer potential is set so that the magnitude of an actual step occurring at the boundary, which is a sum of a virtual step, which is a step in potential that can occur at the boundary between the transfer electrodes adjacent to each other along the second direction, and a potential change amount occurring in accordance with a change in the width from one end of the second impurity region in the second direction to the other end of the second impurity region in the second direction, in a hypothetical case in which the photoelectric conversion unit does not have the second impurity region, is larger than an error from a design value. Potential setting method.

Images