Photodetection device

Abstract

Provided is a photodetection device capable of improving performance. A photodetection device includes a semiconductor substrate having a first surface on which light is incident and a second surface located on an opposite side of the first surface, and plural sensor pixels provided on the semiconductor substrate. The plural sensor pixels include a first pixel. The first pixel includes a first uneven part provided on the first surface, and a first photoelectric conversion unit capable of photoelectrically converting light incident from the first surface to generate charge. The first uneven part extends in a first direction in plan view from the normal direction of the first surface. When a cross section obtained by cutting the first uneven part along a plane orthogonal to the first direction is a first cross section, the first cross section has an asymmetric structure in which left and right side surfaces are not symmetrical.

Description

PHOTODETECTION DEVICECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Japanese Priority Patent Application JP 2023-120374 filed on July 25, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a photodetection device.

[0003] In an imaging device such as a back-illuminated complementary metal oxide semiconductor (CMOS) image sensor, an uneven structure (e.g., moth-eye structure) is provided on an incident surface of a semiconductor substrate in some cases (see Patent Literature 1). Due to the uneven structure, for example, an optical path length can be extended by inclination of incident light, and a photoelectric conversion efficiency Qe (quantum efficiency) can be improved in some cases.

[0004] Furthermore, there is known an imaging device having a structure in which a photodiode and a memory are laminated in a light incident direction, and a light shielding film is disposed between the photodiode and the memory (see Patent Literature 2, for example).

[0005] WO 2017 / 126329WO 2021 / 117648

[0006] When incident light passes through the photodiode and enters an unintended region (e.g., memory), photoelectric conversion may occur in the unintended region, and an unintended charge signal may be generated. Due to this unintentional charge signal, the performance of the imaging device may be degraded.

[0007] The present disclosure has been made in view of such circumstances, and it is desirable to provide a photodetection device capable of curbing deterioration in performance.

[0008] A photodetection device according to one aspect of the present disclosure includes a semiconductor substrate having a first surface on which light is incident and a second surface located on an opposite side of the first surface, and a plurality of sensor pixels provided on the semiconductor substrate. The plurality of sensor pixels includes a first pixel. The first pixel includes a first uneven part provided on the first surface, and a first photoelectric conversion unit capable of photoelectrically converting light incident from the first surface to generate charge. The first uneven part extends in a first direction in plan view from a normal direction of the first surface. When a cross section obtained by cutting the first uneven part along a plane orthogonal to the first direction is a first cross section, the first cross section has an asymmetric structure in which left and right side surfaces are not symmetrical. In further aspects a light detection device is provided. The light detection device includes features that increase an optical path length over which light travels through the light detection device, improving a photoelectric conversion efficiency of the device. The device includes a semiconductor substrate in which a plurality pixels that each include at least one photoelectric conversion region are formed. A first or light incident surface of the semiconductor substrate includes a plurality of side surfaces in an area of a first photoelectric conversion region that are inclined relative to a first plane. In addition, in a plane perpendicular to the first plane, a first side surface of the plurality of side surfaces has an angle relative to the first plane that is different than an angle of a second side surface of the plurality of side surfaces relative to the first plane.

[0009] With this configuration, it is possible to refract light (incident light) incident on the first uneven part and advance the light obliquely with respect to the first surface. As a result, the optical path length in the first photoelectric conversion unit can be extended, so that the photoelectric conversion efficiency Qe can be improved. In addition, since the uneven part has an asymmetric structure, it is easy to direct the traveling direction of the incident light in the semiconductor substrate in a specific direction, and it is possible to curb entry of the incident light into an unintended region. As a result, generation of an unintentional charge signal can be curbed, so that parasitic light sensitivity (PLS) can be reduced. This makes it possible to curb deterioration in performance of the photodetection device.

[0010] Fig. 1 is a block diagram illustrating a configuration example of functions of an imaging device according to an embodiment of the present disclosure.Fig. 2 is an equivalent circuit diagram illustrating a configuration example of a readout circuit.Fig. 3 illustrates a planar layout of pixel regions of two pixels in an X direction and four pixels in a Y direction.Fig. 4 is a diagram illustrating a cross-sectional configuration example 1 of the imaging device according to the embodiment of the present disclosure.Fig. 5 is a diagram illustrating a cross-sectional configuration example 2 of the imaging device according to the embodiment of the present disclosure.Fig. 6 is a cross-sectional view illustrating a method of forming an uneven part suitable for the imaging device according to the embodiment of the present disclosure in order of steps.Fig. 7A is a plan view schematically illustrating the anisotropy of alkali wet etching of a Si (111) substrate.Fig. 7B is a plan view schematically illustrating the anisotropy of alkali wet etching of the Si (111) substrate.Fig. 8 is a diagram illustrating examples of the cross-sectional shape of a protrusion of an uneven part.Fig. 9 is a diagram illustrating a layout example (1) of a trench and an uneven part formed in a Si (111) substrate.Fig. 10 is a diagram illustrating a layout example (2) of a trench and an uneven part formed in a Si (111) substrate.Fig. 11 is a diagram illustrating a layout example (3) of a trench and an uneven part formed in a Si (111) substrate.Fig. 12 is a plan view (1) illustrating variations of a layout example (minimum unit) of a trench and an uneven part formed in a Si (111) substrate.Fig. 13 is a plan view (2) illustrating variations of a layout example (minimum unit) of a trench and an uneven part formed in a Si (111) substrate.Fig. 14 is a plan view (3) illustrating a variation of a layout example (minimum unit) of a trench and an uneven part formed on a Si (111) substrate.Fig. 15 is a plan view illustrating configuration examples of a color filter according to the embodiment of the present disclosure.Fig. 16 is a plan view illustrating examples of mixed arrangement of uneven parts according to the embodiment of the present disclosure.Fig. 17 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 18 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 19 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 20 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 21 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 22 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 23 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.Fig. 24 is a cross-sectional view illustrating a configuration of an imaging device according to a modification of the embodiment of the present disclosure.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings referred to in the following description, the same or similar parts are denoted by the same or similar reference signs. Note, however, that the drawings are schematic, and the relationship between the thickness and the plane dimension, the ratio of the thickness between layers, and the like are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Furthermore, it goes without saying that dimensional relationships and ratios are partly different between the drawings.

[0012] The definition of directions such as up and down in the following description is merely a definition for convenience of description, and does not limit the technical idea of the present disclosure. For example, it goes without saying that if a target is observed while being rotated by 90°, the upward and downward directions are converted into rightward and leftward directions, and if the target is observed while being rotated by 180°, the upward and downward directions are inverted.

[0013] In the following description, a thickness direction of a semiconductor substrate 11 refers to a direction from one of a front surface 11A and a back surface 11B of the semiconductor substrate toward the other. In addition, a plan view means viewing from the normal direction of the back surface 11B of the semiconductor substrate 11.

[0014] <Embodiment> Hereinafter, an embodiment of the present disclosure will be described in detail. An imaging device will be described as one example of a “photodetection device ” of the present disclosure. The imaging device is, for example, a global shutter type back-illuminated image sensor such as a complementary metal oxide semiconductor (CMOS) image sensor. The imaging device receives light from a subject for each pixel, photoelectrically converts the light, and generates a pixel signal that is an electric signal.

[0015] The global shutter method is a method of simultaneously starting and ending exposure of all pixels. Here, all pixels refer to all pixels that form an effective image, and dummy pixels and the like that do not contribute to image formation are excluded. Furthermore, if image distortion and the exposure time difference are sufficiently small so as not to cause a problem, the exposure does not necessarily have to be simultaneous. For example, the global shutter method also includes a case where the operation of performing simultaneous exposure in units of a plurality of rows (e.g., several tens of rows) is repeated while being shifted in units of a plurality of rows in the row direction. In addition, the global shutter method also includes a case where simultaneous exposure is performed only for some pixel regions.

[0016] A back-illuminated image sensor is an image sensor in which a photoelectric conversion unit such as a photodiode that receives light from a subject and converts the light into an electric signal is arranged for each pixel between a light receiving surface on which light from the subject is incident and a wiring layer provided with wiring of a transistor or the like that drives each pixel. Note that the present disclosure is applicable to an image sensor of an imaging system other than the CMOS image sensor in some cases.

[0017] (Overall configuration example of imaging device) Fig. 1 is a block diagram illustrating an overall configuration example of an imaging device 101 according to an embodiment of the present disclosure. Since the imaging device 101 of Fig. 1 is formed on the semiconductor substrate 11, the imaging device is accurately a solid-state imaging device, but is simply referred to as an imaging device 101 below. The imaging device 101 of Fig. 1 includes a pixel array unit 111 in which a plurality of sensor pixels 121 that performs photoelectric conversion is arranged in a matrix, that is, in a two-dimensional plane. The sensor pixel 121 is one example of a “pixel” of the present disclosure. The pixel signal photoelectrically converted by the pixel array unit 111 is read out via a readout circuit.

[0018] The imaging device 101 includes, for example, the pixel array unit 111, a vertical drive unit 112, a ramp wave module 113, a column signal processing unit 114, a clock module 115, a data storage unit 116, a horizontal drive unit 117, a system control unit 118, and a signal processing unit 119.

[0019] The imaging device 101 includes a single or a plurality of semiconductor substrates 11. For example, the imaging device 101 can be configured by electrically connecting another semiconductor substrate 11 on which the vertical drive unit 112, the ramp wave module 113, the column signal processing unit 114, the clock module 115, the data storage unit 116, the horizontal drive unit 117, the system control unit 118, the signal processing unit 119, and the like are formed by Cu-Cu bonding or the like to the semiconductor substrate 11 on which the pixel array unit 111 is formed.

[0020] The pixel array unit 111 includes a plurality of the sensor pixels 121 including a photoelectric conversion element that generates and accumulates charge corresponding to the amount of light incident from the subject. As illustrated in Fig. 1, the sensor pixels 121 are arranged in the horizontal direction (row direction) and the vertical direction (column direction). In the pixel array unit 111, a pixel drive line 122 is wired along the row direction for each pixel row including the sensor pixels 121 arrayed in a line in the row direction, and a vertical signal line 123 is wired along the column direction for each pixel column including the sensor pixels 121 arrayed in a line in the column direction.

[0021] The vertical drive unit 112 includes a shift register, an address decoder, and the like. The vertical drive unit 112 supplies a signal or the like to the plurality of sensor pixels 121 via the plurality of pixel drive lines 122, thereby driving all of the plurality of sensor pixels 121 in the pixel array unit 111 at the same time or in units of pixel rows.

[0022] The ramp wave module 113 generates a ramp wave signal used for analog / digital (A / D) conversion of a pixel signal, and supplies the ramp wave signal to the column signal processing unit 114. The column signal processing unit 114 includes, for example, a shift register, an address decoder, and the like, and performs noise removal processing, correlated double sampling processing, A / D conversion processing, and the like to generate a pixel signal. The column signal processing unit 114 supplies the generated pixel signal to the signal processing unit 119.

[0023] The clock module 115 supplies a clock signal for operation to each unit of the imaging device 101.

[0024] The horizontal drive unit 117 sequentially selects unit circuits corresponding to the pixel columns of the column signal processing unit 114. The selective scanning is performed by the horizontal drive unit 117 so that the pixel signals subjected to signal processing for each unit circuit in the column signal processing unit 114 are sequentially output to the signal processing unit 119.

[0025] The system control unit 118 includes a timing generator and the like that generate various timing signals. The system control unit 118 performs drive control of the vertical drive unit 112, the ramp wave module 113, the column signal processing unit 114, the clock module 115, and the horizontal drive unit 117 on the basis of the timing signal generated by the timing generator.

[0026] The signal processing unit 119 performs signal processing such as arithmetic processing on the pixel signal supplied from the column signal processing unit 114 while temporarily storing data in the data storage unit 116 as necessary, and outputs an image signal including each pixel signal.

[0027] (Configuration example of readout circuit and pixel region) Fig. 2 is an equivalent circuit diagram illustrating a configuration example of a readout circuit 120. Fig. 3 is a planar layout diagram illustrating a configuration example of some pixel regions in the pixel array unit 111. Fig. 3 illustrates a planar layout of pixel regions of two pixels in the X direction and four pixels in the Y direction.

[0028] As illustrated in Figs. 2 and 3, the readout circuit 120 includes four transfer transistors TRZ, TRY, TRX, and TRG, a discharge transistor OFG, a reset transistor RST, an amplification transistor AMP, and a selection transistor SEL. These transistors are N-type MOS transistors. In the layout example illustrated in Fig. 3, the reset transistor RST, the amplification transistor AMP, and the selection transistor SEL are bonded after being formed on a semiconductor substrate different from the semiconductor substrate 11 on which the pixel array unit 111 is arranged. Therefore, the reset transistor RST, the amplification transistor AMP, and the selection transistor SEL are not illustrated in the planar layout of Fig. 3.

[0029] Hereinafter, an example in which a photodiode PD is used as a photoelectric conversion unit 51 will be mainly described. The transfer transistor TRZ is connected to the photodiode PD in the sensor pixel 121, and transfers the charge (pixel signal) photoelectrically converted by the photodiode PD to the transfer transistor TRY. The transfer transistor TRZ is assumed to be a vertical transistor and has a vertical gate electrode.

[0030] The transfer transistor TRY transfers the charge transferred from the transfer transistor TRZ to the transfer transistor TRX. The transfer transistors TRY and TRX may be replaced with one transfer transistor. A charge holding unit (MEM) 54 is connected to the transfer transistors TRY and TRX. The potential of the charge holding unit (MEM) 54 is controlled by a control signal applied to each gate electrode of the transfer transistors TRY and TRX.

[0031] For example, when the transfer transistors TRY and TRX are turned on, the potential of the charge holding unit (MEM) 54 becomes deep, and when the transfer transistors TRY and TRX are turned off, the potential of the charge holding unit (MEM) 54 becomes shallow. Then, for example, when the transfer transistors TRZ, TRY, and TRX are turned on, the charge accumulated in the photodiode PD is transferred to the charge holding unit (MEM) 54 via the transfer transistors TRZ, TRY, and TRX. The drain of the transfer transistor TRX is electrically connected to the source of the transfer transistor TRG, and the gates of the transfer transistors TRY and TRX are connected to the pixel drive line.

[0032] The charge holding unit (MEM) 54 is a region that temporarily holds the charge accumulated in the photodiode PD in order to achieve the global shutter function. The charge holding unit (MEM) 54 holds the charge transferred from the photodiode PD.

[0033] The transfer transistor TRG is connected between the transfer transistor TRX and a floating diffusion FD, and transfers the charge held in the charge holding unit (MEM) 54 to the floating diffusion FD according to a control signal applied to the gate electrode. For example, when the transfer transistor TRX is turned off and the transfer transistor TRG is turned on, the charge held in the charge holding unit (MEM) 54 is transferred to the floating diffusion FD. The drain of the transfer transistor TRG is electrically connected to the floating diffusion FD, and the gate of the transfer transistor TRG is connected to the pixel drive line.

[0034] The floating diffusion FD is a floating diffusion region that temporarily holds the charge output from the photodiode PD via the transfer transistor TRG. For example, the reset transistor RST is connected to the floating diffusion FD, and a vertical signal line VSL is also connected to the floating diffusion FD via the amplification transistor AMP and the selection transistor SEL.

[0035] The discharge transistor OFG initializes (resets) the photodiode PD according to a control signal applied to the gate electrode. The drain of the discharge transistor OFG is connected to a power supply line VDD, and the source is connected between the transfer transistor TRZ and the transfer transistor TRY.

[0036] For example, when the transfer transistor TRZ and the discharge transistor OFG are turned on, the potential of the photodiode PD is reset to the potential level of the power supply line VDD. That is, the photodiode PD is initialized. Furthermore, the discharge transistor OFG forms, for example, an overflow path between the transfer transistor TRZ and the power supply line VDD, and discharges the charge overflowing from the photodiode PD to the power supply line VDD.

[0037] The reset transistor RST initializes (resets) each region from the charge holding unit (MEM) 54 to the floating diffusion FD according to a control signal applied to the gate electrode. The reset transistor RST has the drain connected to the power supply line VDD and the source connected to the floating diffusion FD. For example, when the transfer transistor TRG and the reset transistor RST are turned on, the potentials of the charge holding unit (MEM) 54 and the floating diffusion FD are reset to the potential level of the power supply line VDD. That is, by turning on the reset transistor RST, the charge holding unit (MEM) 54 and the floating diffusion FD are initialized.

[0038] The amplification transistor AMP has the gate electrode connected to the floating diffusion FD and the drain connected to the power supply line VDD, and serves as an input unit of a source follower circuit that reads out the charge obtained by photoelectric conversion in the photodiode PD. That is, the amplification transistor AMP has the source connected to the vertical signal line VSL via the selection transistor SEL, thereby forming a source follower circuit with a constant current source connected to one end of the vertical signal line VSL.

[0039] The selection transistor SEL is connected between the source of the amplification transistor AMP and the vertical signal line VSL, and a control signal is supplied to the gate electrode of the selection transistor SEL as a selection signal. When the control signal is turned on, the selection transistor SEL is brought into conduction, and the sensor pixel 121 coupled to the selection transistor SEL is brought into a selected state. When the sensor pixel 121 is brought into the selected state, the pixel signal output from the amplification transistor AMP is read out by the column signal processing circuit 22 via the vertical signal line VSL.

[0040] As illustrated in Fig. 3, the transfer transistors TRG, TRX, TRY, and TRZ in the readout circuit 120 of one sensor pixel 121 and the discharge transistor OFG are arranged in order in the Y direction. The transistors in two sensor pixels 121 adjacent in the Y direction are arranged symmetrically with respect to the boundary of the pixels in the Y direction. A case where the arrangements of the transistors in the readout circuit 120 for two sensor pixels 121 adjacent in the X direction are reversed and a case where the arrangements are the same are alternately repeated.

[0041] The charge holding unit (MEM) 54 is disposed at a position facing the transfer transistors TRG, TRX, and TRY (in lower position in Fig. 4 described later). Furthermore, in Fig. 4 described later, the photodiode PD in one sensor pixel 121 is arranged so as to straddle a part below the transfer transistors TRG, TRX, and TRY of the sensor pixel 121 and a part below the discharge transistor OFG and the transfer transistors TRZ and TRY of the sensor pixel 121 adjacent in the X direction.

[0042] Note that the planar layout of each transistor in the readout circuit 120 is not limited to the mode illustrated in Fig. 3. When the arrangement of the transistors in the readout circuit 120 is changed, the arrangement places of the photodiodes PD and the charge holding units (MEM) 54 arranged below the transistors are also changed.

[0043] (Cross-sectional configuration example of imaging device) (1) Configuration example 1 Fig. 4 is a diagram illustrating a cross-sectional configuration example 1 of the imaging device 101 according to the embodiment of the present disclosure. Fig. 4 illustrates a cross section of the planar layout diagram illustrated in Fig. 3 taken along line A-A. Symbols “P” and “N” in Fig. 4 represent a P type semiconductor region and an N type semiconductor region, respectively. Furthermore, + or - added to P or N represents a semiconductor region having a relatively high or low impurity concentration as compared with a semiconductor region in which + or - is not added. Note, however, that even if semiconductor regions are denoted with the same symbol “P” (or the same symbol “N”), it does not mean that the semiconductor regions have exactly the same impurity concentrations. The same applies to the following drawings.

[0044] As illustrated in Fig. 4, the imaging device 101 includes the semiconductor substrate 11, the photoelectric conversion unit 51 (one example of “first photoelectric conversion unit” of present disclosure), the charge holding unit (MEM) 54, a charge transfer unit 50, a vertical gate electrode 52V which is a vertical electrode of the transfer transistor TRZ, a first light shielding unit 12, and a second light shielding unit 13.

[0045] The semiconductor substrate 11 is, for example, a single crystal silicon substrate having a crystal orientation of a plane index (111). The front surface 11A and the back surface 11B of the semiconductor substrate 11 are both (111) planes. Hereinafter, the semiconductor substrate 11 is sometimes referred to as a Si (111) substrate. One of the reasons for using the Si (111) substrate is to include a step of performing alkali wet etching in a direction along the crystal plane as described later. Here, the plane index (111) is intended to include crystal orientations in which arbitrary directions in three-dimensional directions are reversed, such as (-111), (1-11), and (11-1).

[0046] In addition, the imaging device 101 includes inter-pixel separation units or regions 20 and 30, an etching stopper 17, a transparent insulating film 56, a color filter CF, and a light receiving lens LNS. In the present specification, of the semiconductor substrate 11, one main surface on the side where the light receiving lens LNS is disposed is referred to as the back surface 11B or a light receiving surface, and one main surface on the side where the readout circuit 120 is disposed is referred to as a front surface 11A.

[0047] The photoelectric conversion unit 51 in the semiconductor substrate 11 includes, for example, an N- type semiconductor region 51A, an N type semiconductor region 51B, and a P type semiconductor region 51C in order of closeness to the back surface 11B. The light incident on the back surface 11B is photoelectrically converted in the N- type semiconductor region 51A to generate charge, and then the charge is accumulated in the N type semiconductor region 51B. Note that the boundary between the N- type semiconductor region 51A and the N type semiconductor region 51B is not necessarily clear, and for example, the N type impurity concentration may be gradually increased from the N- type semiconductor region 51A toward the N type semiconductor region 51B. Furthermore, a P + type semiconductor region having a higher P type impurity concentration than the P type semiconductor region 51C may be provided between the N type semiconductor region and the P type semiconductor region 51C. As described above, the layer configuration of the photoelectric conversion unit 51 formed in the semiconductor substrate 11 is not necessarily limited to that illustrated in Fig. 4.

[0048] The first light shielding unit 12 is a member that functions to prevent light from entering the charge holding unit (MEM) 54, and is provided so as to surround the charge holding unit (MEM) 54. Specifically, the first light shielding unit 12 has a two-layer structure of an inner layer part 12A and an outer layer part 12B surrounding the inner layer part 12A. The inner layer part 12A includes, for example, a material containing at least one of a single metal having a light shielding property, a metal alloy, a metal nitride, and a metal silicide.

[0049] Examples of a constituent material of the inner layer part 12A include Al (aluminum), Cu (copper), Co (cobalt), W (tungsten), Ti (titanium), Ta (tantalum), Ni (nickel), Mo (molybdenum), Cr (chromium), Ir (iridium), platinum iridium, TiN (titanium nitride), a tungsten silicon compound, and the like. Among them, Al (aluminum) is the most optically preferable constituent material. Note that the inner layer part 12A may include graphite or an organic material. The outer layer part 12B includes an insulating material such as silicon oxide (SiO2), for example. The outer layer part 12B ensures electrical insulation between the inner layer part 12A and the semiconductor substrate 11.

[0050] The second light shielding unit 13 is disposed closer to the back surface 11B of the semiconductor substrate 11 than the first light shielding unit 12. The second light shielding unit 13 has a vertical light shielding part 13V extending in the thickness direction of the semiconductor substrate 11 (i.e., depth direction from back surface 12B; Z-axis direction) and a horizontal light shielding part 13H extending in the horizontal direction of the semiconductor substrate 11. The vertical light shielding part 13V also serves as the inter-pixel separation unit 30.

[0051] As illustrated in Fig. 4, the cross-sectional shape of the second light shielding unit 13 is a T-shape formed by the vertical light shielding part 13V and the horizontal light shielding part 13H. The horizontal light shielding part 13H is connected to an end of the vertical light shielding part 13V on the front surface 11A side. The horizontal light shielding part 13H is disposed in a position overlapping the vertical gate electrode 52V in the thickness direction (Z-axis direction). As a result, light incident from the back surface 11B side of the semiconductor substrate 11 is shielded by the horizontal light shielding part 13H, and is prevented from directly entering the vertical gate electrode 52V. The second light shielding unit 13 includes a material having excellent light reflection characteristics (e.g., Al) or a material having excellent light absorption characteristics (e.g., W).

[0052] The inter-pixel separation units 20 and 30 are provided along the boundary between the pixels. The inter-pixel separation unit 30 corresponds to the vertical light shielding part 13V of the second light shielding unit 13 described above. The inter-pixel separation units 20 and 30 are wall-shaped members extending in the depth (Z-axis) direction along the boundary position between the sensor pixels 121 adjacent to each other and surrounding the photoelectric conversion units 51. The inter-pixel separation units 20 and 30 can electrically separate the adjacent sensor pixels 121 from each other.

[0053] The inter-pixel separation unit 20 includes an insulating material such as silicon oxide (SiO2). Alternatively, similarly to the vertical light shielding part 13V, the inter-pixel separation unit 20 includes a material having excellent light reflection characteristics (e.g., Al) or a material having excellent light absorption characteristics (e.g., W). As a result, the inter-pixel separation unit 20 can curb entry of light from one adjacent sensor pixel 121 into the other sensor pixel 121, and color mixture can be curbed.

[0054] Note that while the inter-pixel separation unit 20 includes only the vertical light shielding part in Fig. 4, the inter-pixel separation unit 20 may include a vertical light shielding part and a horizontal light shielding part. As the cross-sectional shape of the inter-pixel separation unit 20, various cross-sectional shapes such as a T-shape and a cross-shape are conceivable.

[0055] Both of the inter-pixel separation units 20 and 30 (vertical light shielding part 13V) can prevent light incident on each sensor pixel 121 from the back surface 11B side of the semiconductor substrate 11 from leaking out to the adjacent sensor pixel 121, and can reduce inter-pixel crosstalk.

[0056] The gate electrodes of the transfer transistors TRZ, TRY, TRX, and TRG and the discharge transistor OFG in the readout circuit 120 are all provided on the front surface 11A side of the semiconductor substrate 11 via an insulating layer 18. Furthermore, the charge holding unit (MEM) 54, which is an N type semiconductor region, is provided in the P type semiconductor region 51C in the semiconductor substrate 11. More specifically, the charge holding unit (MEM) 54 is disposed between the front surface 11A of the semiconductor substrate 11 and a horizontal light shielding part 12H of the first light shielding unit 12. As illustrated in Fig. 4, the first light shielding unit 12 surrounds the charge holding unit (MEM) 54 so that light from the back surface 11B side is not incident on the charge holding unit (MEM) 54.

[0057] The transfer transistor TRZ includes a horizontal gate electrode 52H disposed in the horizontal plane direction of the semiconductor substrate 11 and the vertical gate electrode 52V extending in the thickness direction (Z-axis direction) of the semiconductor substrate 11. The deepest position of the vertical gate electrode 52V is, for example, in an N- type semiconductor region 52A. While each sensor pixel 121 has two vertical gate electrodes 52V in the example of Fig. 4, the number of vertical gate electrodes 52V is not limited, and may be one or more. The transfer transistor TRZ transfers the charge photoelectrically converted by the photoelectric conversion unit 51 to the transfer transistor TRY via the vertical gate electrode 52V.

[0058] As illustrated in Fig. 4, a planarization film 55 is provided between the back surface 11B and the color filter CF. The planarization film 55 is provided along the back surface 11B of the semiconductor substrate 11. The planarization film 55 closely connects the back surface 11B and the color filter CF. The planarization film 55 includes, for example, an organic material such as resin or an insulating film such as silicon oxide (SiO2). The refractive index of the planarization film 55 is lower than the refractive index of the semiconductor substrate 11. Here, a > b holds when the refractive index of the semiconductor substrate 11 is a and the refractive index of the planarization film 55 is b.

[0059] As illustrated in Fig. 4, the transparent insulating film 56 may be interposed between the back surface 11B and the planarization film 55. The transparent insulating film 56 is provided along an uneven part 60. The transparent insulating film 56 includes, for example, silicon oxide (SiO2), silicon nitride (SiN), silicon oxynitride (SiON), hafnium oxide (HfO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), titanium oxide (TiO2), lanthanum oxide (La2O3), praseodymium oxide (Pr2O3), cerium oxide (CeO2), neodymium oxide (Nd2O3), promethium oxide (Pm2O3), samarium oxide (Sm2O3), europium oxide (Eu2O3), gadolinium oxide (Gd2O3), terbium oxide (Tb2O3), dysprosium oxide (Dy2O3), holmium oxide (Ho2O3), thulium oxide (Tm2O3), ytterbium oxide (Yb2O3), lutetium oxide (Lu2O3), yttrium oxide (Y2O3), resin, and the like. Furthermore, the transparent insulating film 56 may be formed by laminating one or more of these materials.

[0060] The color filter CF is disposed on the surface of the planarization film 55, and the light receiving lens LNS is disposed on the surface of the color filter CF. The color filter CF and the light receiving lens LNS are provided for each pixel.

[0061] (Uneven part of back surface) As illustrated in Fig. 4, the semiconductor substrate 11 has the uneven part 60 (one example of “first uneven part” of present disclosure) provided on the back surface 11B. In the example illustrated in Fig. 4, each of the plurality of sensor pixels 121 includes a plurality of uneven parts 60. The uneven part 60 can alleviate a rapid change in refractive index at the interface, which is one of causes of light reflection, and can reduce the influence of reflected light. That is, since the refractive index gradually changes along the incident direction of light, reflection of light can be reduced.

[0062] The uneven part 60 extends in a first direction (e.g., Y-axis direction in Fig. 4) in plan view from the back surface 11B. The plurality of sensor pixels 121 has the same depth d60 of the uneven part 60. The depth of the uneven part 60 is indicated by the distance from the vertex of the protrusion of the uneven part 60 to the bottom surface of the recess in the thickness direction (Z-axis direction) of the semiconductor substrate 11.

[0063] Assuming that a cross section obtained by cutting the uneven part 60 along a plane (XZ plane) orthogonal to the first direction (Y-axis direction) is a first cross section, the first cross section has an asymmetric structure in which left (or first) and right (or second) side surfaces are not symmetrical. For example, the uneven part 60 includes a protrusion 61 and a recess 62. In addition, side surfaces 63 and 64 (one example of “left and right side surfaces” of the present disclosure) are provided between the protrusion 61 and the recess 62. In a cross-sectional view obtained by cutting the uneven part 60 along the XZ plane, the left and right side surfaces 63 and 64 are inclined with respect to the thickness direction (Z-axis direction) of the semiconductor substrate 11. Furthermore, in a cross-sectional view obtained by cutting the uneven part 60 along the XZ plane, the left and right side surfaces 63 and 64 are not symmetrical. An inclination angle with respect to the thickness direction (Z-axis direction) of the semiconductor substrate 11 is different between the side surface 63 and the side surface 64.

[0064] For example, each of the sensor pixels 121 has a plurality of uneven parts 60. The plurality of uneven parts 60 is arranged in a second direction (X-axis direction) intersecting the first direction in plan view.

[0065] As illustrated in Fig. 4, an incident light L having passed through the back surface 11B is scattered by the uneven part 60. For example, the incident light L perpendicularly incident on the back surface 11B passes through the uneven part 60, is refracted, and obliquely travels in the N- type semiconductor region 51A. In this manner, the traveling direction of the incident light L changes obliquely. As a result, the optical path length can be extended.

[0066] Furthermore, in the example illustrated in Fig. 4, the incident light L having passed through the uneven part 60 is reflected by the vertical light shielding part 13V and the horizontal light shielding part 13H of the second light shielding unit 13 and the first light shielding unit 12. As the number of reflecting parts of the incident light L increases, the optical path length can be extended even more. By the first light shielding unit 12 and the second light shielding unit 13, the incident light L can be confined in the N- type semiconductor region 51A to easily generate diffuse reflection, and the optical path length can be extended. As a result, the incident light L is easily converted into charge in the N- type semiconductor region 51A, so that the photoelectric conversion efficiency Qe can be improved.

[0067] Furthermore, since the uneven part 60 has an asymmetric structure as described above, it is easy to refract (bend) the incident light L incident on the back surface 11B toward a specific direction (e.g., direction of horizontal light shielding part 13H). As a result, the optical path length of the incident light L can be extended, and the incident light L can be prevented from directly entering the charge holding unit (MEM) 54 or the floating diffusion FD. Since unintentional generation of charge signal can be curbed in the charge holding unit (MEM) 54 and the floating diffusion FD, parasitic light sensitivity (PLS) can be reduced. The effect of reducing PLS becomes more remarkable in the sensor pixel 121 that detects light of a red (R) component having a long wavelength and not easily attenuated.

[0068] (2) Configuration example 2 Fig. 5 is a diagram illustrating a cross-sectional configuration example 2 of the imaging device 101 according to the embodiment of the present disclosure. Fig. 5 is illustrated upside down from Fig. 4. In the cross-sectional configuration example 2 illustrated in Fig. 5, a vertical light shielding part 12V of the first light shielding unit 12 also serves as the inter-pixel separation unit 20. As illustrated in Fig. 5, the vertical light shielding part 12V is embedded, for example, in a trench provided from the back surface 11B toward the front surface 11A of the semiconductor substrate 11 via an insulating film (e.g., transparent insulating film 56 illustrated in Fig. 4). The vertical light shielding part 12V extends in the depth (Z-axis) direction along the boundary position between the adjacent sensor pixels 121.

[0069] The cross-sectional shape of the first light shielding unit 12 is a T-shape formed by the vertical light shielding part 12V and the horizontal light shielding part 12H. The horizontal light shielding part 12H is connected to an end of the vertical light shielding part 12V on the front surface 11A side. The horizontal light shielding part 12H extends from one side of the vertical light shielding part 12V (i.e., inter-pixel separation unit 20) toward a central part of the sensor pixel 121, and is disposed between the back surface 11B, which is a light receiving surface, and the charge holding unit (MEM) 54. The horizontal light shielding part 12H is disposed in a position overlapping the charge holding unit (MEM) 54 in the thickness direction (Z-axis direction). As a result, light incident from the back surface 11B side of the semiconductor substrate 11 is shielded by the horizontal light shielding part 12H, and is prevented from directly entering the charge holding unit (MEM) 54. The first light shielding unit 12 includes, for example, a material having excellent light reflection characteristics (e.g., Al) or a material having excellent light absorption characteristics (e.g., W).

[0070] The horizontal light shielding part 13H of the second light shielding unit 13 also extends from the vertical light shielding part 13V (i.e., inter-pixel separation unit 30) toward a central part of the sensor pixel 121, and is disposed between the back surface 11B, which is the light receiving surface, and the vertical gate electrode 52V of the transfer transistor TRZ. The horizontal light shielding part 13H is disposed in a position overlapping the vertical gate electrode 52V in the thickness direction (Z-axis direction). As a result, light incident from the back surface 11B side of the semiconductor substrate 11 is shielded by the horizontal light shielding part 13H, and is prevented from directly entering the vertical gate electrode 52V. The second light shielding unit 13 includes, for example, a material having excellent light reflection characteristics (e.g., Al) or a material having excellent light absorption characteristics (e.g., W).

[0071] As illustrated in Fig. 5, the horizontal light shielding part 12H of the second light shielding unit 13 is located closer to the back surface 11B than the horizontal light shielding part 13H of the first light shielding unit 12. An end 12He on the pixel central part side of the horizontal light shielding part 12H and the end 13He on the pixel central part side of the horizontal light shielding part 13H are arranged at positions overlapping each other in the thickness direction (Z-axis direction) of the semiconductor substrate 11.

[0072] Note that Fig. 5 illustrates a case where the vertical light shielding part 12V has a deep trench isolation (DTI) mode that does not penetrate the semiconductor substrate 11, but this is merely one example. The vertical light shielding part 12V may penetrate between the back surface 11B and the front surface 11A of the semiconductor substrate 11.

[0073] Similarly to the case of the cross-sectional configuration example 1, the cross-sectional configuration example 2, too, can improve the photoelectric conversion efficiency Qe and reduce PLS.

[0074] Furthermore, in the cross-sectional configuration example 2 illustrated in Fig. 5, the cross-sectional shapes of the uneven parts 60 are different between the adjacent sensor pixels 121. For example, the plurality of sensor pixels 121 includes a sensor pixel 121 (R) (one example of “first pixel” of present disclosure) that detects light of a red (R) component, a sensor pixel 121 (G) (one example of “second pixel” of present disclosure) that detects light of a green (G) component, and a sensor pixel 121 (G) (not illustrated) that detects light of a blue (B) component. The sensor pixel 121 (R) that detects red light has a red color filter CF (R) on the back surface 11B side, the sensor pixel 121 (G) that detects green light has a green color filter CF (G) on the back surface 11B side, and the sensor pixel 121 (B) that detects blue light has a blue color filter CF (B) (not illustrated) on the back surface 11B side. Hereinafter, the sensor pixel that detects red light is also referred to as a “red sensor pixel”. The sensor pixel that detects green light is also referred to as a “green sensor pixel”. The sensor pixel that detects blue light is also referred to as a “blue sensor pixel”.

[0075] The red sensor pixel 121 (R) includes an uneven part 60 (R) (one example of “first uneven part” of present disclosure) provided on the back surface 11B of the semiconductor substrate 11. The green sensor pixel 121 (G) includes an uneven part 60 (G) (one example of “second uneven part” of present disclosure) provided on the back surface 11B of the semiconductor substrate 11. Each of the uneven parts 60 (R) and 60 (G) extends in the first direction (Y-axis direction) in plan view from the back surface 11B side.

[0076] As illustrated in Fig. 5, a cross section (one example of “first cross section” of present disclosure) obtained by cutting the uneven part 60 (R) of the red sensor pixel 121 (R) along an XZ plane orthogonal to the Y-axis direction has an asymmetric structure in which left and right side surfaces are not symmetrical, similarly to the uneven part 60 illustrated in Fig. 4. In the uneven part 60 (R), the inclination of the side surface with respect to the thickness direction (Z-axis direction) of the semiconductor substrate 11 is larger in the side surface 63 (one example of “first side surface” of present disclosure) than in the side surface 64 (“second side surface” of present disclosure). In plan view from the Z-axis direction, the side surface 63 is larger in area than the side surface 64. The horizontal light shielding part 13H of the second light shielding unit 13 is located on the optical path of the light incident on the side surface 63 and refracted.

[0077] A cross section (one example of “second cross section” of present disclosure) obtained by cutting the uneven part 60 (G) of the green sensor pixel 121 (B) along the XZ plane also has an asymmetric structure in which the left and right side surfaces are not symmetrical, similarly to the uneven part 60 illustrated in Fig. 4.

[0078] In the cross-sectional configuration example 2 illustrated in Fig. 5, a cross-sectional shape obtained by cutting the uneven part 60 (R) of the red sensor pixel 121 (R) along the XZ plane and a cross-sectional shape obtained by cutting the uneven part 60 (G) of the green sensor pixel 121 (B) along the XZ plane are different from each other. That is, the uneven parts 60 are also asymmetrical in the adjacent sensor pixels 121.

[0079] For example, the green sensor pixel 121 (B) has a plurality of uneven parts 60 (G). The plurality of uneven parts 60 (G) is arranged in the second direction (X-axis direction). The uneven parts 60 (G) are arranged more densely in the X-axis direction than the uneven parts 60 (R). More specifically, the side surfaces 63 and 64 of the uneven part 60 (R) and the side surfaces 63 and 64 of the uneven part 60 (G) are both inclined with respect to the thickness direction (Z-axis direction) of the semiconductor substrate 11. The side surface 63 of the uneven part 60 (G) has a larger inclination angle with respect to the Z-axis direction than the side surface 63 of the uneven part 60 (R). Similarly, the side surface 64 of the uneven part 60 (G) has a larger inclination angle with respect to the Z-axis direction than the side surface 64 of the uneven part 60 (R). As a result, the incident light L can be scattered further in the green sensor pixel (G) than in the red sensor pixel 121 (R).

[0080] As compared with red light, green light with a short wavelength is easily attenuated, and is less likely to reach the charge holding unit (MEM) 54 located at a deep position from the back surface 11B (light receiving surface). Therefore, in the green sensor pixel 121 (G), the uneven parts 60 (G) are arranged densely to prioritize scattering of the incident light L over guiding the incident light L to the horizontal light shielding part 13H. In the green sensor pixel 121 (G), the incident light L is guided to the horizontal light shielding part 13H while being scattered to further extend the optical path length. As a result, in the green sensor pixel 121 (G), the photoelectric conversion efficiency Qe can be improved further while the PLS is kept low.

[0081] Note that although not illustrated in Fig. 5, the blue sensor pixel 121 (B) may also have an uneven part 60 (B) (not illustrated) provided on the back surface 11B of the semiconductor substrate 11. For example, the uneven part 60 (B) extends in the first direction (Y-axis direction) in plan view from the back surface 11B side. Similarly to the uneven part 60 illustrated in Fig. 4, the uneven part 60 (B) has an asymmetric structure in which the left and right side surfaces are not symmetrical.

[0082] In this case, the uneven parts 60 (B) are preferably arranged more densely in the X-axis direction than the uneven parts 60 (G). As a result, in the blue sensor pixel (G), the incident light L can be scattered even more, and the photoelectric conversion efficiency Qe can be improved further while the PLS is kept low.

[0083] (Method of forming uneven part) Next, a method of forming the uneven part 60 will be described. Fig. 6 is a cross-sectional view illustrating the method of forming the uneven part 60 suitable for the imaging device 101 according to the embodiment of the present disclosure in order of steps. In step ST1 of Fig. 6, the semiconductor substrate 11 on which the photoelectric conversion unit 51 (not illustrated, see Fig. 5) and the like are formed is prepared. Next, a hard mask (not illustrated) is formed on the back surface 11B (upper surface in Fig. 6) of the semiconductor substrate 11. The hard mask includes an insulating material such as a silicon nitride film (SiN film) or a silicon oxide film (SiO2film), for example.

[0084] Next, as illustrated in step ST2 of Fig. 6, the back surface 11B of the semiconductor substrate 11 is partially dug down shallowly by dry etching using the hard mask to form a trench T. For example, the trench T is formed to be long in the <110> direction.

[0085] Next, as illustrated in step ST3 of Fig. 6, the Si (111) surface forming the back surface 11B of the semiconductor substrate 11 is partially removed by wet etching (hereinafter also referred to as alkali wet etching) using an alkali aqueous solution. As the alkali aqueous solution, KOH, NaOH, CsOH, or the like can be used in the case of an inorganic solution, and EDP (ethylenediamine pyrocatechol aqueous solution), N2H4(hydrazine), NH4OH (ammonium hydroxide), TMAH (tetramethylammonium hydroxide), or the like can be used in the case of an organic solution.

[0086] Here, crystal anisotropic etching using the property in which the etching rate varies depending on the plane orientation of Si (111) is performed. Specifically, for in a Si (111) substrate, the etching rate in the <110> direction, i.e., with one or two Si back bonds, is sufficiently high compared to the etching rate in the <111> direction, i.e., with three Si back bonds. In alkali wet etching, the etching rate of the surface index (111) is lower than the etching rates of the surface index (110) and the surface index (112).

[0087] Figs. 7A and 7B are plan views schematically illustrating the anisotropy of alkali wet etching of the Si (111) substrate. The plan view of Fig. 7A illustrates a trench T that is long in the <112> direction, and the plan view of Fig. 7B illustrates a trench that is long in the <110> direction. For example, as in the plan view of Fig. 7A, the trench T elongated in the <112> direction is formed on the (111) plane of the Si (111) substrate by dry etching. Then, when the trench T is subjected to alkali wet etching, etching proceeds from the side surface of the trench T as indicated by an arrow in Fig. 7A, and for example, a recess 62 having a rhombic shape in plan view is formed.

[0088] In addition, as illustrated in the plan view of Fig. 7B, the trench T elongated in the <110> direction is formed on the (111) plane of the Si (111) substrate by dry etching. When the trench T is subjected to alkali wet etching, etching proceeds from the side surface of the trench T as indicated by an arrow in Fig. 7B, and for example, a recess 62 having an elongated rectangular shape in plan view is formed.

[0089] In step ST3 of Fig. 6, due to the anisotropy of alkali wet etching on Si, the trench T is etched at a higher etching rate in the <110> direction relative to the <111> direction. As a result, the trench T is widened, and the left and right side surfaces are formed obliquely with respect to the back surface 11B. In addition, in this alkali wet etching, since a corner Tc of the open end of the trench T is etched from both the upper and lower directions as indicated by the arrows in step ST3, the corner Tc is removed earlier than other parts. As a result, as illustrated in step ST4 of Fig. 6, the uneven part 60 having an asymmetric structure in which the left and right side surfaces 63 and 64 are not symmetric is formed on the back surface 11B of the semiconductor substrate 11. For example, the side surface 63 is a (112) plane, and the side surface 64 is a (111) plane.

[0090] (Example of shape of protrusion) While step ST4 of Fig. 6 illustrates a case where the cross-sectional shape of the protrusion 61 is a triangle, the cross-sectional shape of the protrusion 61 is not limited to a triangle. The cross-sectional shape of the protrusion 61 may be any shape on the premise that it has an asymmetric structure where the left and right side surfaces 63 and 64 are not symmetric.

[0091] Fig. 8 is a diagram illustrating examples of the cross-sectional shape of the protrusion 61. As illustrated in Fig. 8, the cross-sectional shape of the protrusion 61 may be a triangle, a quadrilateral (quadrangle), a polygon, or a nonlinear shape. A nonlinear shape 1 in Fig. 8 exemplifies a case where the side surface 63 is linear and the side surface 64 is nonlinear (curved). A nonlinear shape 2 in Fig. 8 exemplifies a case where both of the side surfaces 63 and 64 are nonlinear (curved). Each of the protrusions 61 illustrated in Fig. 8 has an asymmetric structure in which the left and right side surfaces 63 and 64 are not symmetrical. The cross-sectional shape of the protrusion 61 can be controlled by, for example, the width of the trench T or the alkali wet etching processing time.

[0092] (Layout example of trench and uneven part) Fig. 9 is a diagram illustrating a layout example (1) of the trench T and the uneven part 60 formed in the Si (111) substrate. The left side of Fig. 9 illustrates a shape in plan view (hereinafter referred to as planar shape) and a shape in cross-sectional view (hereinafter referred to as cross-sectional shape) of the trench T formed by dry etching. A cross section of the plan view on the upper left side of Fig. 9 taken along line A9-A9' corresponds to the cross-sectional view on the lower left side of Fig. 9. The right side of Fig. 9 illustrates a planar shape and a cross-sectional shape of the uneven part 60 formed by performing alkali wet etching on the trench T illustrated on the left side. A cross section of the plan view on the upper right side of Fig. 9 taken along line B9-B9' corresponds to the cross-sectional view on the lower right side of Fig. 9.

[0093] As illustrated in Fig. 9, when the trench T long in the <110> direction is formed by dry etching and then alkali wet etching is performed, the uneven part 60 having an asymmetric structure long in the <110> direction is formed. For example, the plurality of uneven parts 60 can be formed in a line and space shape by forming the plurality of trenches T next to one another in the <112> direction.

[0094] Fig. 10 is a diagram illustrating a layout example (2) of the trench T and the uneven part 60 formed in the Si (111) substrate. The left side of Fig. 10 illustrates a planar shape and a cross-sectional shape of the trench T formed by dry etching. A cross section of the plan view on the upper left side of Fig. 10 taken along line A10-A10' corresponds to the cross-sectional view on the lower left side of Fig. 10. The right side of Fig. 10 illustrates a planar shape and a cross-sectional shape of the uneven part 60 formed by performing alkali wet etching on the trench T illustrated on the left side. A cross section of the plan view on the upper right side of Fig. 10 taken along line B10-B10' corresponds to the cross-sectional view on the lower right side of Fig. 10.

[0095] As illustrated in Fig. 10, when the trench T elongated in the <112> direction is formed by dry etching and then alkali wet etching is performed, the uneven part 60 having an asymmetric structure having a rhombic planar shape is formed. For example, the rhombic uneven parts 60 can be arranged next to one another by forming the rhombic trenches T in a staggered manner in the <110> direction.

[0096] Fig. 11 is a diagram illustrating a layout example (3) of the trench T and the uneven part 60 formed in the Si (111) substrate. The left side of Fig. 11 illustrates a planar shape and a cross-sectional shape of the trench T formed by dry etching. A cross section of the plan view on the upper left side of Fig. 11 taken along line A11-A11' corresponds to the cross-sectional view on the lower left side of Fig. 11. The right side of Fig. 11 illustrates a planar shape and a cross-sectional shape of the uneven part 60 formed by performing alkali wet etching on the trench T illustrated on the left side. A cross section of the plan view on the upper right side of Fig. 11 taken along line B11-B11' corresponds to the cross-sectional view on the lower right side of Fig. 11.

[0097] As illustrated in Fig. 11, a cross-shaped trench T having a shape in which a trench elongated in the <110> direction and a trench elongated in the <112> direction intersect each other in plan view is formed by dry etching. Thereafter, when alkali wet etching is performed, etching proceeds from the side surface of the trench T, and the uneven part 60 having an asymmetric structure having a hexagonal planar shape is formed. For example, the hexagonal uneven parts 60 can be arranged next to one another by forming the cross-shaped trenches T in a staggered manner in the <110> direction.

[0098] As illustrated in Figs. 9 to 11, the plurality of uneven parts 60 extends in at least one direction in plan view from the back surface side of the semiconductor substrate 11, and is arranged side by side in the other direction orthogonal to the one direction. Next, more variations of the layout of the uneven part 60 in plan view will be described.

[0099] Figs. 12 to 14 are plan views (1 to 3) illustrating variations of a layout example (minimum unit) of the trench T and the uneven part 60 formed in the Si (111) substrate. The uneven part 60 illustrated in Figs. 12 and 13 is a minimum unit of layout, and is, for example, one of the plurality of uneven parts 60 arranged in a line-and-space manner. Note that while the trench T formed by dry etching is illustrated in each layout illustrated in Figs. 12 and 13, in the actual uneven part 60, the trench T may be integrated with a recess formed by alkali wet etching and may be indistinguishable in appearance.

[0100] In addition, in Figs. 12 and 13 and Fig. 14 described later, branch numbers -1 to -9 are attached to reference numerals 60 in order to identify each layout of the uneven part 60. The branch number is omitted in a case where identification is not necessary.

[0101] As illustrated in Figs. 12 and 13, in the embodiment of the present disclosure, the uneven part 60 arranged in a line-and-space shape may be formed using a trench T in which a trench elongated in the <110> direction and a trench elongated in the <112> direction are combined. The trench T is formed by dry etching. Alkali wet etching after formation of the trench T etches Si from the side surface of the trench T to form the recess 62 and the side surfaces 63 and 64.

[0102] In each of the uneven parts 60-1 to 60-4 illustrated in Fig. 12, the side surfaces 63 and 64 are formed in a linear shape in plan view by alkali wet etching. Each of the uneven parts 60-5 to 60-8 illustrated in Fig. 13 illustrates a case where the side surfaces 63 and 64 are formed in a polygonal line shape or a curved line shape in plan view by alkali wet etching.

[0103] The planar shapes of the side surfaces 63 and 64 can be controlled by the alkali wet etching processing time. For example, the uneven part 60-5 illustrated in Fig. 13 can be formed by shortening the processing time of the alkali wet etching as compared with the uneven part 60-1 illustrated in Fig. 12. In addition, the uneven part 60-6 illustrated in Fig. 13 can be formed by shortening the processing time of the alkali wet etching as compared with the uneven part 60-4 illustrated in Fig. 12. The uneven part 60-8 illustrated in Fig. 13 can be formed by shortening the processing time of the alkali wet etching as compared with the uneven part 60-7 illustrated in Fig. 13.

[0104] In the embodiment of the present disclosure, for example, a trench T in a direction intersecting the <110> direction and the <112> direction may be formed on the (111) plane of the Si (111) substrate. In the uneven part 60-9 illustrated in Fig. 14, two trenches T extending in a direction intersecting both the <110> direction and the <112> direction are formed on the (111) plane of the Si (111) substrate so as to intersect each other, and then alkali wet etching is performed. Such a method can also be adopted to form the uneven part 60-9 having an asymmetric structure. While the planar shape of the uneven part 60-9 illustrated in Fig. 14 is a hexagon, for example, the planar shape of the uneven part 60-9 may be formed in a shape other than the hexagon by adjusting the processing time of the alkali wet etching.

[0105] (Color filter) Fig. 15 is a plan view illustrating configuration examples of the color filter CF according to the embodiment of the present disclosure. As in the plan view illustrated on the left side of Fig. 15, the color filter CF has three colors of red (R), green (G), and blue (B), for example, and has a configuration in which these colors are arranged in a Bayer array. Alternatively, as illustrated in the plan view illustrated in the center of Fig. 15, the color filter CF may have a pixel array called Quad Bayer coding in which four adjacent 2 × 2 sensor pixels 121 are formed by color filters of the same color (Modification 1). Alternatively, as in the plan view illustrated on the right side of Fig. 15, the color filter CF may have a configuration in which three colors of cyan (C), magenta (M), and yellow (Y) are arranged in a Bayer array.

[0106] In the case of any of the color filters CF illustrated in Fig. 15, the uneven part 60 having an asymmetric structure is provided on the back surface 11B of the semiconductor substrate 11 facing the color filter CF. Accordingly, the effects of the above embodiment are obtained.

[0107] (Mixed arrangement of uneven parts) Fig. 16 is a plan view illustrating examples of mixed arrangement of the uneven parts 60 according to the embodiment of the present disclosure. As in the plan view illustrated on the left side of Fig. 16, in the imaging device 101, the uneven part 60 having an asymmetric structure may be arranged only in some of the sensor pixels 121 (e.g., red sensor pixel 121 (R)). Furthermore, as in the plan view illustrated in the center of Fig. 16, the uneven part 60 having an asymmetric structure may be arranged in all the sensor pixels 121 (e.g., red sensor pixel 121 (R), green sensor pixel 121 (G), and blue sensor pixel 121 (B)).

[0108] Alternatively, as in the plan view illustrated on the right side of Fig. 16, the uneven part 60 having an asymmetric structure may be provided in some sensor pixels 121 (e.g., red sensor pixel 121 (R)), and an uneven part 70 having a shape different from that of the uneven part 60 having an asymmetric structure may be provided in another sensor pixel 121 (e.g., green sensor pixel 121 (G) and blue sensor pixel 121 (B)). Examples of the uneven part 70 include an uneven part having a symmetrical structure in which left and right side surfaces are symmetrically disposed, and an uneven part having a hexagonal planar shape as illustrated in the drawing.

[0109] With the configuration illustrated on the left side of Fig. 16, in the red sensor pixel 121 (R), the photoelectric conversion efficiency Qe can be improved and the PLS can be reduced by the presence of the uneven part 60. In the green sensor pixel 121 (G) and the blue sensor pixel 121 (B), the photoelectric conversion efficiency Qe can be improved by the presence of the uneven part 70.

[0110] (Effect of embodiment) As described above, the imaging device 101 according to the embodiment of the present disclosure includes the semiconductor substrate 11 having the back surface 11B on which light is incident and the front surface 11A located on the opposite side of the back surface 11B, and the plurality of sensor pixels 121 provided on the semiconductor substrate 11. The plurality of sensor pixels 121 includes a red sensor pixel 121 (R). The red sensor pixel 121 (R) has an uneven part 60 provided on the back surface 11B, and a photoelectric conversion unit 51 (photodiode PD) capable of photoelectrically converting light incident from the back surface 11B to generate a charge. The uneven part 60 extends in the first direction (e.g., Y-axis direction in Figs. 4 and 5) in plan view from the normal direction of the back surface 11B. When a cross section obtained by cutting the uneven part 60 along a plane (e.g., XZ plane) orthogonal to the first direction is a first cross section, the first cross section has an asymmetric structure in which left and right side surfaces are not symmetrical.

[0111] With this configuration, the imaging device 101 can refract light (incident light) incident on the uneven part 60 and advance the light obliquely with respect to the back surface 11B. As a result, the optical path length in the first photoelectric conversion unit can be extended, so that the photoelectric conversion efficiency Qe can be improved.

[0112] In addition, since the uneven part 60 has an asymmetric structure, it is easy to direct the traveling direction of the incident light in the semiconductor substrate 11 in a specific direction, and it is possible to curb entry of the incident light into an unintended region (e.g., charge holding unit (MEM) 54, floating diffusion FD, or the like). As a result, generation of an unintentional charge signal can be curbed, so that PLS can be reduced.

[0113] Since the imaging device 101 can achieve both improvement in the photoelectric conversion efficiency Qe and reduction in PLS, it is possible to curb deterioration in performance.

[0114] <Modification> (Depth of uneven part) In the above embodiment, it has been described that the depth d60 of the uneven part 60 is the same among the plurality of sensor pixels 121. However, the embodiment of the present disclosure is not limited thereto. The depth d60 of the uneven part 60 may be different among the plurality of sensor pixels 121.

[0115] Fig. 17 is a cross-sectional view illustrating a configuration of an imaging device 101A according to a modification of the embodiment of the present disclosure. In the imaging device 101A illustrated in Fig. 17, a depth d60 (R) of the uneven part 60 (R) provided in the red sensor pixel 121 (R) and a depth d60 (G) of the uneven part 60 (G) provided in the green sensor pixel 121 (G) are different from each other. For example, the depth d60 (R) is deeper than the depth d60 (G) (d60 (R) > d60 (G)).

[0116] When the uneven parts 60 (R) and 60 (G) are formed, the trench T of the uneven part 60 (R) and the trench T of the uneven part 60 (G) are separately formed by dry etching, and depths thereof are made different from each other. Thereafter, the uneven parts 60 (R) and 60 (G) having different depths can be formed by collectively performing the alkali wet etch.

[0117] Even with such a configuration, since each of the uneven parts 60 (R) and 60 (G) has an asymmetric structure in which the left and right side surfaces are not symmetrical, effects similar to those of the above embodiment are obtained.

[0118] (Number of disposed uneven parts) In the embodiment of the present disclosure, each of the plurality of sensor pixels may have one uneven part or a plurality of uneven parts. Furthermore, it is possible to provide the uneven part only in some of the plurality of sensor pixels.

[0119] Figs. 18 to 21 are cross-sectional views illustrating configurations of imaging devices 101B to 101E according to modifications of the embodiment of the present disclosure. The imaging devices 101B and 101C illustrated in Figs. 18 and 19 are examples in which one uneven part 60 is provided in one sensor pixel 121. The imaging device 101D illustrated in Fig. 20 is an example in which, among the plurality of sensor pixels 121, the green sensor pixel 121 (G) is provided with a plurality of uneven parts 60, and the red sensor pixel 121 (R) is not provided with the uneven part 60. The imaging device 101E illustrated in Fig. 21 is an example in which one uneven part 60 is provided in a plurality of sensor pixels 121 (e.g., two adjacent sensor pixels 121 (R) and 121 (G)).

[0120] In any of the imaging devices 101B to 101E, since each of the uneven part 60 and the uneven part 60 (G) has an asymmetric structure in which the left and right side surfaces 63 and 64 are not symmetric, effects similar to those of the above embodiment are obtained.

[0121] (Arrangement of light receiving lens) Figs. 22 and 23 are cross-sectional views illustrating configurations of imaging devices 101F and 101G according to modifications of the embodiment of the present disclosure. In the embodiment of the present disclosure, as in the imaging device 101F illustrated in Fig. 22, one light receiving lens LNS may be arranged in a plurality of sensor pixels 121 (e.g., four adjacent 2 × 2 sensor pixels 121 or two adjacent 2 × 1 sensor pixels 121). Furthermore, as in the imaging device 101G illustrated in Fig. 23, a plurality of light receiving lenses LNS (e.g., four adjacent 2 × 2 light receiving lenses LNS or two adjacent 2 × 1 light receiving lenses LNS) may be arranged in one sensor pixel 121.

[0122] In any of the modes illustrated in Figs. 22 and 23, in the sensor pixel 121 having the uneven part 60 having an asymmetric structure, both improvement of the photoelectric conversion efficiency Qe and reduction of the PLS can be achieved.

[0123] (Arrangement of light shielding part) In the above embodiment, for example, as illustrated in Fig. 5, it has been described that the horizontal light shielding part 12H of the first light shielding unit 12 is arranged symmetrically with respect to the vertical light shielding part 12V. In addition, it has been described that the horizontal light shielding part 13H of the second light shielding unit 13 is arranged symmetrically with respect to the vertical light shielding part 13V. However, the embodiment of the present disclosure is not limited thereto.

[0124] Fig. 24 is a cross-sectional view illustrating a configuration of an imaging device 101H according to a modification of the embodiment of the present disclosure. For example, as illustrated in Fig. 24, the charge holding units (MEM) 54 do not need to be arranged symmetrically in the adjacent sensor pixels 121. In this case, as with the charge holding unit (MEM) 54, the horizontal light shielding parts 12H of the first light shielding units 12 also do not need to be arranged symmetrically. Since the horizontal light shielding part 12H is arranged between the back surface 11B which is a light receiving surface and the charge holding unit (MEM) 54, it is possible to curb entry of light into the charge holding unit (MEM) 54.

[0125] Furthermore, in the adjacent sensor pixels 121, the vertical gate electrodes 52V of the transfer transistors TRZ also do not need to be arranged symmetrically. In this case, as with the vertical gate electrode 52V, the horizontal light shielding parts 13H of the second light shielding units 13 also do not need to be arranged symmetrically. Since the horizontal light shielding part 13H is arranged between the back surface 11B which is a light receiving surface and the vertical gate electrode 52V, it is possible to curb entry of light into the vertical gate electrode 52V.

[0126] In the imaging device 101H illustrated in Fig. 24, the shape of the uneven part 60 is set such that the incident light L hits the horizontal light shielding part 13H not only in the red sensor pixel 121 (R) but also in the green sensor pixel 121 (G). For example, in a case where the thickness of the semiconductor substrate 11 is further reduced, and green light is more likely to reach the charge holding unit (MEM) 54, by adopting the structure illustrated in Fig. 24, it is possible to effectively keep green light from reaching the charge holding unit (MEM) 54. The structure illustrated in Fig. 24 is a preferred example corresponding to thinning of the semiconductor substrate 11.

[0127] Furthermore, as illustrated in Fig. 24, the inter-pixel separation unit 20 may be provided on the front surface 11A side of the semiconductor substrate 11, the inter-pixel separation unit 30 may be provided on the back surface 11B side of the semiconductor substrate 11, and the inter-pixel separation units 20 and 30 may be arranged to face each other in the thickness direction (e.g., Z-axis direction) of the semiconductor substrate 11. Even in such a mode, the horizontal light shielding part 12H can be provided integrally with the inter-pixel separation unit 20. The horizontal light shielding part 13H can be provided integrally with the inter-pixel separation unit 30.

[0128] (Type of semiconductor substrate) In the above embodiment, it has been described that a Si (111) substrate is used as the semiconductor substrate 11. However, in the embodiment of the present disclosure, the type of the semiconductor substrate 11 is not limited thereto. For example, as the semiconductor substrate 11, a Si <112> substrate in which the front surface 11A and the back surface 11B are (112) planes may be used, or a Si <110> substrate in which the front surface 11A and the back surface 11B are (110) planes may be used. Even with such a configuration, by providing the uneven part 60 having an asymmetric structure on the light receiving surface of the semiconductor substrate 11, effects similar to those of the above embodiment are obtained.

[0129] <Other embodiment> As described above, the present disclosure is described according to the embodiments and modifications thereof, but it should not be understood that the description and drawings forming a part of this disclosure limit the present disclosure. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

[0130] For example, a material included in the first light shielding unit 12 and a material included in the second light shielding unit 13 may be appropriately selected and used. Specifically, in a case where priority is given to improvement of the photoelectric conversion efficiency Qe, each of the first light shielding unit 12 and the second light shielding unit 13 includes a material having excellent reflection characteristics (e.g., Al). In a case where priority is given to reduction of PLS, each of the first light shielding unit 12 and the second light shielding unit 13 includes a material having excellent light absorption characteristics (e.g., W). In order to achieve both the improvement of the photoelectric conversion efficiency Qe and the reduction of PLS in a well-balanced manner, the first light shielding unit 12 includes a material having excellent light absorption characteristics (e.g., W), and the second light shielding unit 13 includes a material having excellent light reflection characteristics (e.g., Al). As a result, a desired effect can be efficiently obtained.

[0131] Furthermore, in the above-described embodiment, the imaging devices 101 to 101H having a global shutter function have been exemplified as the “photodetection device ” of the present disclosure. However, the “photodetection device” of the present disclosure may also be applied to an imaging device that does not have a global shutter function. In that case, for example, the floating diffusion FD is preferably shielded by the first light shielding unit. Alternatively, the “photodetection device” of the present disclosure may be applied to, for example, a distance measuring device having single photon avalanche diode (SPAD) pixels. In that case, for example, the PN junction of the SPAD is preferably shielded by the first light shielding unit. As described above, the technology of the present disclosure may be applied to an imaging device not having a global shutter function or a distance measuring device having SPAD pixels, and even in that case, it is possible to curb generation of an unintentional charge signal and to curb deterioration in performance.

[0132] As described above, it is needless to say that the present technology includes various embodiments and the like that are not described herein. At least one of various omissions, substitutions, and changes of the components may be made without departing from the gist of the above-described embodiments and modifications. Furthermore, the effect described in the present description is illustrative only; the effect is not limited thereto and there may also be other effects.

[0133] Note that the present disclosure can also have the following configurations. (1) A light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the first and second surfaces extend in directions that are parallel to an X-Y plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, and, wherein, in a cross section taken along a first plane perpendicular to the X-Y plane, an angle of the first side surface relative to the X-Y plane is different than an angle of the second side surface relative to the X-Y plane. (2) The light detection device according to (1), wherein the first side surface and the second side surface are inclined with respect to the X-Y plane. (3) The light detection device according to (1) or (2), wherein, in the area of the first pixel, the first surface of the semiconductor substrate includes a plurality of first side surfaces and a plurality of second side surfaces, and wherein at least one of protrusions or recesses are formed at intersections between the first side surfaces and the second side surfaces. (4) The light detection device according to any of (1) to (3), wherein the second surface of the semiconductor substrate is parallel to the X-Y plane, and wherein each recess is a first distance from the second surface of the semiconductor substrate. (5) The light detection device according to (4), wherein each protrusion is a second distance from the second surface of the semiconductor substrate. (6) The light detection device according to any of (1) to (5), wherein each protrusion in the area of the first pixel is parallel to each recess in the area of the first pixel. (7) The light detection device according to (6), wherein each protrusion of the first pixel and each recess of the first pixel is parallel to a Y axis. (8) The light detection device according to (3), wherein the first side surfaces and the second side surfaces each have one at least one of a polygonal line shape or a curved line shape in a view taken perpendicular to the first surface. (9) The light detection device according to any of (1) to (8), further comprising: a planarization film, wherein the planarization film is disposed on the first surface side of the semiconductor substrate, wherein the planarization film includes a first surface that is parallel to the X-Y plane, and a second surface that complements the first surface of the semiconductor substrate, and wherein an index of refraction of the planarization film is different than an index of refraction of the semiconductor substrate. (10) The light detection device according to any of (1) to (9), further comprising an inter-pixel separation region that is disposed in the semiconductor substrate and separates one pixel and another pixel adjacent to each other among the plurality of sensor pixels, wherein the first pixel further includes a first charge holding region that is disposed on the side opposite the side of the first surface, wherein the first photoelectric conversion region is interposed between the first charge holding region and the first surface, and a first light shielding region disposed between the first surface and the first charge holding region, wherein the first light shielding region extends from the inter-pixel separation region toward a central part of the first pixel. (11) The light detection device according to (10), wherein the first pixel further includes: a first transfer transistor disposed on the second side of the semiconductor substrate with the first photoelectric conversion region interposed between the first surface of the semiconductor substrate and the first transfer transistor, wherein the first transfer transistor transfers charge generated in the first photoelectric conversion region, and a second light shielding region disposed between the first surface and the first transfer transistor and extending from the inter-pixel separation region toward a central part of the first pixel, wherein the second light shielding region is located closer to the first surface than the first light shielding region. (12) The light detection device according to (11), wherein an end of the first light shielding region in a cross-section view on the central part side and an end of the second light shielding region on the central part side are arranged at positions overlapping each other in the cross section taken along the X-Y plane. (13) The light detection device according to (12), wherein the first side surface is more inclined than the second side surface with respect to the X-Y plane, the first side surface has a larger area than the second side surface, and the second light shielding region is located on an optical path of light incident on the first side surface. (14) The light detection device according to any of (1) to (13), further comprising: a second pixel that is adjacent to the first pixel; an inter-pixel separation region that is disposed in the semiconductor substrate and that is between the first pixel and the second pixel, wherein light incident on the first pixel is of a different color than light incident on the second pixel, wherein the first surface of the semiconductor substrate in an area of the second pixel includes a plurality of side surfaces, one or more protrusions, and one or more recesses, wherein, in the area of the second pixel, a third side surface of the plurality of side surfaces is joined to a fourth side surface in the plurality of side surfaces along either one of the protrusions or one of the recesses, wherein, in the cross section taken along the X-Y plane, an angle of the third side surface relative to the X-Y plane is different than an angle of the fourth side surface relative to the X-Y plane. (15) The light detection device according to (14), wherein, in the cross section taken along the X-Y plane, a shape of the first surface in the area of the first pixel is different than a shape of the first surface in the area of the second pixel. (16) The light detection device according to (14), wherein the third side surface is more inclined than the fourth side surface with respect to the X-Y plane. (17) The light detection device according to (14), wherein each protrusion in the area of the second pixel is parallel to each recess in the area of the second pixel. (18) The light detection device according to any of (1) to (17), wherein side surfaces facing a first direction are at a larger angle relative to the X-Y plane than side surfaces facing a second direction. (19) The light detection device according to any of (1) to (18), wherein the first surface of the semiconductor substrate is a (111) plane. (20) The light detection device according to any of (1) to (19), wherein the first side surface is separated from the second side surface by a planar area of the first surface of the semiconductor surface. (21) A light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the second surface is parallel to the first plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, wherein a first side surface is joined to a second side surface at one of a shared protrusion or a shared recess, and wherein an area of the first side surface is different than an area of the second side surface. (22) An electronic apparatus, comprising: an optical system; a light detection device; and a signal processing circuit, wherein the light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the first and second surfaces extend in directions that are parallel to an X-Y plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, and, wherein, in a cross section taken along a first plane perpendicular to the X-Y plane, an angle of the first side surface relative to the X-Y plane is different than an angle of the second side surface relative to the X-Y plane. (23) An electronic apparatus, comprising: an optical system; a light detection device; and a signal processing circuit, wherein the light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the second surface is parallel to the first plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, wherein a first side surface is joined to a second side surface at one of a shared protrusion or a shared recess, and wherein an area of the first side surface is different than an area of the second side surface. (24) A photodetection device including: a semiconductor substrate having a first surface on which light is incident and a second surface located on an opposite side of the first surface; and a plurality of sensor pixels provided on the semiconductor substrate, in which the plurality of sensor pixels includes a first pixel, the first pixel includes a first uneven part provided on the first surface, and a first photoelectric conversion unit capable of photoelectrically converting light incident from the first surface to generate charge, the first uneven part extends in a first direction in plan view from a normal direction of the first surface, and when a cross section obtained by cutting the first uneven part along a plane orthogonal to the first direction is a first cross section, the first cross section has an asymmetric structure in which left and right side surfaces are not symmetric. (25) The photodetection device according to (24), in which left and right side surfaces of the first uneven part are inclined with respect to a thickness direction from the first surface to the second surface of the semiconductor substrate. (26) The photodetection device according to (24) or (25), in which the first pixel includes a plurality of the first uneven parts, and the plurality of first uneven parts is arranged in a second direction intersecting the first direction in the plan view. (27) The photodetection device according to any one of (24) to (26), further including an inter-pixel separation unit that is provided in the semiconductor substrate and separates one pixel and another pixel adjacent to each other among the plurality of sensor pixels, in which the first pixel further includes a first charge holding unit that is provided on an opposite side of the first surface with the first photoelectric conversion unit interposed therebetween and is capable of holding charge transferred from the first photoelectric conversion unit, and a first light shielding unit provided between the first surface and the first charge holding unit and extending from the inter-pixel separation unit toward a central part of the first pixel. (28) The photodetection device according to (27), in which the first pixel further includes a first transfer transistor that is provided on the opposite side of the first surface with the first photoelectric conversion unit interposed therebetween and transfers charge generated in the first photoelectric conversion unit, and a second light shielding unit provided between the first surface and the first transfer transistor and extending from the inter-pixel separation unit toward the central part of the first pixel, and the second light shielding unit is located closer to the first surface than the first light shielding unit. (29) The photodetection device according to (28), in which an end of the first light shielding unit on the central part side and an end of the second light shielding unit on the central part side are arranged at positions overlapping each other in a thickness direction from the first surface to the second surface of the semiconductor substrate. (30) The photodetection device according to (29), in which when one of left and right side surfaces of the first uneven part is a first side surface and another is a second side surface, the first side surface is more inclined than the second side surface with respect to the thickness direction from the first surface to the second surface of the semiconductor substrate, the first side surface has a larger area than the second side surface in the plan view, and the second light shielding unit is located on an optical path of light incident on the first side surface and refracted. (31) The photodetection device according to any one of (24) to (30), further including an inter-pixel separation unit that is provided in the semiconductor substrate and separates one pixel and another pixel adjacent to each other among the plurality of sensor pixels, in which the plurality of sensor pixels further includes a second pixel that is arranged adjacent to the first pixel via the inter-pixel separation unit and in which light of a color different from that of the first pixel is incident on the first surface, the second pixel includes a second uneven part provided on the first surface, and a second photoelectric conversion unit capable of photoelectrically converting light incident from the first surface to generate charge, the second uneven part extends in the first direction in the plan view, and when a cross section obtained by cutting the second uneven part along the plane orthogonal to the first direction is a second cross section, the second cross section has an asymmetric structure in which left and right side surfaces are not symmetric. (32) The photodetection device according to (31), in which the first cross section and the second cross section have different shapes. (33) The photodetection device according to (31) or (32), in which left and right side surfaces of the second uneven part are inclined with respect to a thickness direction from the first surface to the second surface of the semiconductor substrate. (34) The photodetection device according to any one of (31) to (33), in which the second pixel includes a plurality of the second uneven parts, and the plurality of second uneven parts is arranged in a second direction intersecting the first direction in the plan view. (35) The photodetection device according to (34), in which the second uneven parts are arranged more densely in the second direction than the first uneven parts. (36) The photodetection device according to any one of (24) to (35), in which the first surface of the semiconductor substrate is a (111) plane.

[0134] 11 Semiconductor substrate 11A Front surface 11B Back surface 12 First light shielding unit 12H, 13H Horizontal light shielding part 12V, 13V Vertical light shielding part 13 Second light shielding unit 17 Etching stopper 18 Insulating layer 20, 30 Inter-pixel separation unit 22 Column signal processing circuit 50 Charge transfer unit 51 Photoelectric conversion unit 51A, 52A N- type semiconductor region 51B N type semiconductor region 51C P type semiconductor region 52H Horizontal gate electrode 52V Vertical gate electrode 54 Charge holding unit (MEM) 55 Planarization film 56 Transparent insulating film 60, 60-1, 60-2, 60-3, 60-4, 60-5, 60-6, 60-7, 60-8, 60-9, 60(B), 60(G), 60(R), 70 Uneven part 61 Protrusion 62 Recess 63, 64 Side surface 101, 101A, 101B, 101C, 101D, 101E, 101F, 101G, 101H Imaging device 111 Pixel array unit 112 Vertical drive unit 113 Ramp wave module 114 Column signal processing unit 115 Clock module 116 Data storage unit 117 Horizontal drive unit 118 System control unit 119 Signal processing unit 120 Readout circuit 121 Sensor pixel 121(R) Red sensor pixel 121(G) Green sensor pixel 121(B) Blue sensor pixel 122 Pixel drive line 123 Vertical signal line AMP Amplification transistor CF Color filter FD Floating diffusion L Incident light LNS Light receiving lens OFG Discharge transistor PD Photodiode RST Reset transistor SEL Selection transistor T Trench Tc Corner VDD Power supply line VSL Vertical signal line

Claims

1. A light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the first and second surfaces extend in directions that are parallel to an X-Y plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, and, wherein, in a cross section taken along a first plane perpendicular to the X-Y plane, an angle of the first side surface relative to the X-Y plane is different than an angle of the second side surface relative to the X-Y plane.

2. The light detection device according to claim 1, wherein the first side surface and the second side surface are inclined with respect to the X-Y plane.

3. The light detection device according to claim 1, wherein, in the area of the first pixel, the first surface of the semiconductor substrate includes a plurality of first side surfaces and a plurality of second side surfaces, and wherein at least one of protrusions or recesses are formed at intersections between the first side surfaces and the second side surfaces.

4. The light detection device according to claim 3, wherein the second surface of the semiconductor substrate is parallel to the X-Y plane, and wherein each recess is a first distance from the second surface of the semiconductor substrate.

5. The light detection device according to claim 4, wherein each protrusion is a second distance from the second surface of the semiconductor substrate.

6. The light detection device according to claim 3, wherein each protrusion in the area of the first pixel is parallel to each recess in the area of the first pixel.

7. The light detection device according to claim 6, wherein each protrusion of the first pixel and each recess of the first pixel is parallel to a Y axis.

8. The light detection device according to claim 3, wherein the first side surfaces and the second side surfaces each have one at least one of a polygonal line shape or a curved line shape in a view taken perpendicular to the first surface.

9. The light detection device according to claim 1, further comprising: a planarization film, wherein the planarization film is disposed on the first surface side of the semiconductor substrate, wherein the planarization film includes a first surface that is parallel to the X-Y plane, and a second surface that complements the first surface of the semiconductor substrate, and wherein an index of refraction of the planarization film is different than an index of refraction of the semiconductor substrate.

10. The light detection device according to claim 1, further comprising an inter-pixel separation region that is disposed in the semiconductor substrate and separates one pixel and another pixel adjacent to each other among the plurality of sensor pixels, wherein the first pixel further includes a first charge holding region that is disposed on the side opposite the side of the first surface, wherein the first photoelectric conversion region is interposed between the first charge holding region and the first surface, and a first light shielding region disposed between the first surface and the first charge holding region, wherein the first light shielding region extends from the inter-pixel separation region toward a central part of the first pixel.

11. The light detection device according to claim 10, wherein the first pixel further includes: a first transfer transistor disposed on the second side of the semiconductor substrate with the first photoelectric conversion region interposed between the first surface of the semiconductor substrate and the first transfer transistor, wherein the first transfer transistor transfers charge generated in the first photoelectric conversion region, and a second light shielding region disposed between the first surface and the first transfer transistor and extending from the inter-pixel separation region toward a central part of the first pixel, wherein the second light shielding region is located closer to the first surface than the first light shielding region.

12. The light detection device according to claim 11, wherein an end of the first light shielding region in a cross-section view on the central part side and an end of the second light shielding region on the central part side are arranged at positions overlapping each other in the cross section taken along the X-Y plane.

13. The light detection device according to claim 12, wherein the first side surface is more inclined than the second side surface with respect to the X-Y plane, the first side surface has a larger area than the second side surface, and the second light shielding region is located on an optical path of light incident on the first side surface.

14. The light detection device according to claim 1, further comprising: a second pixel that is adjacent to the first pixel; an inter-pixel separation region that is disposed in the semiconductor substrate and that is between the first pixel and the second pixel, wherein light incident on the first pixel is of a different color than light incident on the second pixel, wherein the first surface of the semiconductor substrate in an area of the second pixel includes a plurality of side surfaces, one or more protrusions, and one or more recesses, wherein, in the area of the second pixel, a third side surface of the plurality of side surfaces is joined to a fourth side surface in the plurality of side surfaces along either one of the protrusions or one of the recesses, wherein, in the cross section taken along the X-Y plane, an angle of the third side surface relative to the X-Y plane is different than an angle of the fourth side surface relative to the X-Y plane.

15. The light detection device according to claim 14, wherein, in the cross section taken along the X-Y plane, a shape of the first surface in the area of the first pixel is different than a shape of the first surface in the area of the second pixel.

16. The light detection device according to claim 14, wherein the third side surface is more inclined than the fourth side surface with respect to the X-Y plane.

17. The light detection device according to claim 14, wherein each protrusion in the area of the second pixel is parallel to each recess in the area of the second pixel.

18. The light detection device according to claim 1, wherein side surfaces facing a first direction are at a larger angle relative to the X-Y plane than side surfaces facing a second direction.

19. The light detection device according to claim 1, wherein the first surface of the semiconductor substrate is a (111) plane.

20. The light detection device according to claim 1, wherein the first side surface is separated from the second side surface by a planar area of the first surface of the semiconductor surface.

21. A light detection device, comprising: a semiconductor substrate having a first surface on which light is incident and a second surface on a side of the semiconductor substrate opposite a side of the first surface, wherein the second surface is parallel to the first plane; and a plurality of sensor pixels disposed in the semiconductor substrate, wherein the plurality of sensor pixels includes a first pixel, wherein the first pixel includes a first photoelectric conversion region, wherein the first surface of the semiconductor substrate in an area of the first pixel includes a plurality of side surfaces, wherein a first side surface is joined to a second side surface at one of a shared protrusion or a shared recess, and wherein an area of the first side surface is different than an area of the second side surface.

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