Light detection device and distance measurement system

Abstract

The present disclosure pertains to a light detection device and a distance measurement system capable of achieving positive bias of a breakdown voltage. A P-type region is provided in a central portion of an SPAD pixel, and is connected to an electrode that outputs a detection signal corresponding to detection of a photon incident on the SPAD pixel. An N+ diffusion layer is provided in a peripheral portion of the SPAD pixel and is connected to an electrode that supplies a first breakdown voltage of the positive bias. A transparent electrode is laminated on the light-incident surface and the side surface of the SPAD pixel via an insulating film, and a second breakdown voltage of the positive bias is supplied. The present technology can be applied to, for example, a distance measurement system that acquires a distance image by a light detection device in which a plurality of SPAD pixels are arranged in an array.

Description

Light detection devices and ranging systems

[0001] The present disclosure relates to a photodetector and a distance measurement system, and more particularly to a photodetector and a distance measurement system that can realize a positive bias of the breakdown voltage.

[0002] In recent years, development of distance measurement systems has progressed, which acquire distance images by arranging multiple SPAD (Single Photon Avalanche Diode) pixels in an array and determining the distance to an object using the ToF (Time of Flight) method. SPAD pixels avalanche amplify the electric charge generated by photoelectric conversion and output it as an electrical signal.

[0003] For example, conventional SPAD pixels can suppress dark current generation by forming a hole accumulation region at the interface by stacking a stable, negative, fixed-charge film (e.g., Al2O3 or Hf2O) on the sidewalls of the trench and on the semiconductor substrate that serves as the light-receiving surface. In this configuration, the anode side around the SPAD pixel is P-type, and the cathode side inside the SPAD pixel is N-type. The breakdown voltage (VBD) required for SPAD operation requires a large negative bias, for example, on the order of -10 V to -30 V. For example, the breakdown voltage corresponds to the breakdown voltage of the PN junction of the SPAD pixel.

[0004] For example, Patent Document 1 discloses a SPAD pixel that generates avalanche amplification stably while suppressing a decrease in resolution.

[0005] Japanese Patent Application Laid-Open No. 2022-055214

[0006] As mentioned above, conventional SPAD pixels require a high negative power supply. However, because semiconductor chips are usually driven by a positive power supply, generating a high negative power supply inside the semiconductor chip is inefficient, and from the perspective of the chipset, a configuration that supplies a negative power supply from an external source would be expensive.

[0007] On the other hand, to operate SPAD pixels with a positive power supply, a configuration in which the P-type and N-type of the SPAD pixel are simply swapped is being considered, but it is difficult to form a high-quality positive fixed charge film, and there are concerns that dark current will increase. Also, in the method of forming an N+ region by solid-phase diffusion using ion implantation as a pinning layer, it is expected that the pixel region will not be used effectively because diffusion into the substrate will be unavoidable, and there are concerns that characteristics will deteriorate, such as a decrease in PDE (Photon Detection Efficiency), which is an index of SPAD pixel efficiency.

[0008] The present disclosure has been made in view of the above circumstances, and makes it possible to realize a positive bias breakdown voltage.

[0009] A photodetector according to one aspect of the present disclosure comprises a P-type region provided in the center of a SPAD pixel and connected to an electrode that outputs a detection signal in response to the detection of photons incident on the SPAD pixel, an N+ diffusion layer provided in the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage, and a transparent electrode that is stacked on the light incident surface and side surfaces of the SPAD pixel via an insulating film and to which a positive bias second breakdown voltage is supplied.

[0010] A ranging system according to one aspect of the present disclosure comprises a photodetector device having a P-type region provided in the center of a SPAD pixel and connected to an electrode that outputs a detection signal in response to the detection of photons incident on the SPAD pixel, an N+ diffusion layer provided in the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage, and a transparent electrode that is stacked on the light incident surface and side surfaces of the SPAD pixel via an insulating film and that supplies a positive bias second breakdown voltage.

[0011] In one aspect of the present disclosure, an electrode that outputs a detection signal in response to the detection of photons incident on the SPAD pixel is connected to a P-type region provided in the center of the SPAD pixel, an electrode that supplies a positive bias first breakdown voltage is connected to an N+ diffusion layer provided in the periphery of the SPAD pixel, and a positive bias second breakdown voltage is supplied to a transparent electrode that is stacked on the light incident surface and side surfaces of the SPAD pixel via an insulating film.

[0012] FIG. 1 is a diagram showing a configuration example of a first embodiment of a photodetector to which the present technology is applied. FIG. 2 is a circuit diagram of a SPAD pixel. FIG. 3 is a circuit diagram of a SPAD pixel having a function of suppressing DCR fluctuations. FIG. 4 is a diagram showing an example of a cross-sectional configuration of a SPAD pixel and a dummy pixel. FIG. 5 is a diagram showing an example of a planar layout of the SPAD pixel and the dummy pixel. FIG. 6 is a diagram showing a configuration example of a second embodiment of a photodetector to which the present technology is applied. FIG. 7 is a diagram showing a configuration example of a third embodiment of a photodetector to which the present technology is applied. FIG. 8 is a diagram showing an example of a cross-sectional configuration of a SPAD pixel, a first dummy pixel, and a second dummy pixel. FIG. 9 is a diagram showing an example of a planar layout of the SPAD pixel, a first dummy pixel, and a second dummy pixel. FIG. 10 is a block diagram showing an example of a configuration of a ranging system to which the present technology is applied.

[0013] Hereinafter, specific embodiments to which the present technology is applied will be described in detail with reference to the drawings.

[0014] <First Configuration Example of Photodetector> A configuration example of a first embodiment of a photodetector 11 to which the present technology is applied will be described with reference to FIGS.

[0015] FIG. 1 is a diagram showing an example of a cross-sectional configuration of a photodetector 11. As shown in FIG.

[0016] As shown in Fig. 1, the photodetector 11 is configured by stacking a sensor substrate 21 and a logic substrate 22, which are electrically and mechanically joined via Cu-Cu joints 23 provided on the bonding surfaces of their respective wiring layers. A plurality of SPAD pixels 31 are arranged in an array on the sensor substrate 21. The logic substrate 22 is provided with a power supply circuit that supplies a potential required to drive the SPAD pixels 31, a distance measurement circuit that measures distances in accordance with detection signals output by the SPAD pixels 31 in response to detecting photons, and other components. Note that Fig. 1 only shows the wiring layers of the logic substrate 22.

[0017] The SPAD pixel 31 is configured with a PN junction of a P-type region 42 and an N-type region 43 provided in a semiconductor layer 41 separated by a groove-shaped trench for each SPAD pixel 31. The SPAD pixel 31 can detect photons incident on the back surface (the surface facing upward in FIG. 1 ), which is the light incident surface of the semiconductor layer 41, one by one.

[0018] In a cross-sectional view of the photodetector 11, the P-type region 42 and the N-type region 43 form a planar PN junction with the P-type region 42 disposed on the front surface side of the semiconductor layer 41 and the N-type region 43 disposed on the back surface side of the semiconductor layer 41, and are disposed near the front surface of the semiconductor layer 41. A convex portion is formed in the center of the P-type region 42 so as to extend to the front surface of the semiconductor layer 41, and the convex portion is a P+ diffusion layer having a higher P-type impurity concentration than the other portions of the P-type region 42.

[0019] The SPAD pixel 31 is provided with a transparent electrode 45 made of, for example, an ITO (Indium-Tin Oxide) film, laminated on the back surface and side surfaces of the semiconductor layer 41, via an insulating film 44 formed on the back surface and side surfaces of the semiconductor layer 41. A positive bias second breakdown voltage VBD2 is supplied to the transparent electrode 45, thereby forming an electron trapping layer 46 on the back surface and side surfaces of the semiconductor layer 41. An N+ diffusion layer 47 is provided on the surface of the semiconductor layer 41 in the peripheral portion of the SPAD pixel 31, so as to be continuous with the electron trapping layer 46.

[0020] A trench isolation 48 made of a light-shielding metal (e.g., tungsten) that optically isolates the SPAD pixels 31 is provided inside the trench surrounding the SPAD pixels 31. The upper end of the trench isolation 48 is formed to protrude beyond the insulating film 44, and a planarization layer 49 for planarizing the light receiving surface of the photodetector 11 is laminated to cover the insulating film 44 and the trench isolation 48.

[0021] An interlayer insulating film 52 serving as a wiring layer is provided on the surface (the surface facing downward in FIG. 1 ) of the semiconductor layer 41 via an insulating film 51. An interlayer insulating film 53 serving as a wiring layer of the logic substrate 22 is bonded to the interlayer insulating film 52. A plurality of wirings 54 are provided within the interlayer insulating film 52. Wiring 54a is connected to the P-type region 42 via a contact electrode 55a and to the Cu-Cu junction 23a via a contact electrode 56a. Wiring 54b is connected to the N+ diffusion layer 47 via a contact electrode 55b and to the Cu-Cu junction 23b via a contact electrode 56b. A plurality of wirings 57 are provided within the interlayer insulating film 53. Wiring 57a is connected to the Cu-Cu junction 23a via a contact electrode 58a, and wiring 57b is connected to the Cu-Cu junction 23b via a contact electrode 58b.

[0022] The SPAD pixel 31 configured in this manner can form an avalanche multiplication region in the semiconductor layer 41 by a positive bias first breakdown voltage VBD1 supplied to the N+ diffusion layer 47 and a positive bias second breakdown voltage VBD2 supplied to the transparent electrode 45. The SPAD pixel 31 avalanche-multiplies electrons generated by a single photon incident on the SPAD pixel 31, and a detection signal indicating that the photon has been detected is output from the P-type region 42 provided in the center of the SPAD pixel 31 via the contact electrode 55 a.

[0023] In this way, the SPAD pixel 31 can achieve a positive bias breakdown voltage, eliminating the need for the high negative voltage used in conventional SPAD pixels.

[0024] Furthermore, in the SPAD pixel 31, the positive bias first breakdown voltage VBD1 and the positive bias second breakdown voltage VBD2 can be supplied with independent potentials (i.e., separate power supplies). The positive bias first breakdown voltage VBD1 can be set lower than the positive bias second breakdown voltage VBD2 (VBD2 > VBD1 > 0). This potential difference forms an electron trap layer 46 at the interface, thereby suppressing the generation of dark current.

[0025] FIG. 2 is a diagram showing an example of the circuit configuration of the SPAD pixel 31.

[0026] 2, a photodiode 61 that performs photoelectric conversion by a PN junction of a P-type region 42 and an N-type region 43 has an anode connected to a power supply that supplies a positive bias first breakdown voltage VBD1 and, via a capacitor 62 (insulating film 44), to a power supply that supplies a positive bias second breakdown voltage VBD2, and a cathode that is grounded via an n-type MOSFET 63. A detection signal having a pulse waveform for each photon incident on the photodiode 61 is output via a CMOS inverter 64 that is connected to the cathode of the photodiode 61.

[0027] The SPAD pixel 31 configured in this manner supplies a positive bias first breakdown voltage VBD1 to the anode of the photodiode 61, and also supplies a positive bias second breakdown voltage VBD2 via the capacitor 62, thereby forming an avalanche multiplication region and enabling avalanche multiplication of electrons generated by the incidence of one photon.

[0028] Furthermore, the SPAD pixel 31 can be configured to have a function of suppressing fluctuations in DCR (Dark Count Rate).

[0029] 3 is configured such that a detection signal output from a CMOS inverter 64 is input to a DCR detection unit 65, and a voltage adjustment unit 66 adjusts a positive-bias second breakdown voltage VBD2 in accordance with the output of the DCR detection unit 65. The DCR detection unit 65 detects a DCR in accordance with a count value of photons detected in the absence of incident light, and outputs the DCR to the voltage adjustment unit 66. For example, if photons are detected even in the absence of incident light due to operational degradation of the SPAD pixel 31, the DCR detected by the DCR detection unit 65 will increase. Therefore, when the voltage adjustment unit 66 increases the positive-bias second breakdown voltage VBD2 in accordance with the increase in DCR, the increase in DCR can be suppressed in accordance with the increase ΔV (= VBD2 - VBD1).

[0030] The wiring configuration for supplying a second breakdown voltage VBD2 of a positive bias to the transparent electrode 45 will be described with reference to the cross-sectional view of the photodetector 11 shown in FIG.

[0031] 4, the photodetector 11 is configured to include SPAD pixels 31, which are main pixels that detect photons, as well as dummy pixels 32 that do not detect photons. For example, the dummy pixels 32 are arranged in a peripheral region that surrounds the periphery of the main pixel region in which the SPAD pixels 31 are arranged in an array.

[0032] As described above, in the SPAD pixel 31, the wiring 57b that supplies the positive bias first breakdown voltage VBD1 is electrically connected to the anode of the SPAD pixel 31 via the contact electrode 58b, the Cu-Cu junction 23b, the contact electrode 56b, the wiring 54b, and the contact electrode 55b.

[0033] On the other hand, in the dummy pixel 32, a wiring 57c that supplies a positive bias second breakdown voltage VBD2 is provided on the opposite side (left side in FIG. 4) from the SPAD pixel 31. The wiring 57c is electrically connected to the transparent electrode 45 via a contact electrode 58c, a Cu-Cu junction 23c, a contact electrode 56c, a wiring 54c, and a contact electrode 55c.

[0034] In this way, the photodetector 11 can supply the second breakdown voltage VBD2 of a positive bias to the transparent electrode 45 by using a wiring configuration that utilizes the dummy pixels 32 .

[0035] FIG. 5 is a diagram showing an example of a planar layout of the SPAD pixels 31 and the dummy pixels 32. As shown in FIG.

[0036] FIG. 5 shows four SPAD pixels 31 arranged in the main pixel region and two dummy pixels 32 arranged in the dummy pixel region.

[0037] As shown in FIG. 5, when the photodetector 11 is viewed from above, trench isolation portions 48 are provided so as to surround the peripheries of the individual SPAD pixels 31 and dummy pixels 32 .

[0038] The wiring 54b used to supply the positive bias first breakdown voltage VBD1 is arranged in the main pixel region (including the boundary between the main pixel region and the dummy pixel region) so as to surround the periphery of each SPAD pixel 31, similar to the trench isolation portion 48. On the other hand, the wiring 54c used to supply the positive bias second breakdown voltage VBD2 is separated from the wiring 54b outside the dummy pixel region (on the left side of FIG. 5 ) and arranged linearly along the dummy pixels 32.

[0039] In addition, when the photodetector 11 is viewed from above, the contact electrode 55b is disposed at a position overlapping the wiring 54b, and the contact electrode 55c is disposed at a position overlapping the wiring 54c. As a result, the photodetector 11 is configured such that a first positive bias breakdown voltage VBD1 is supplied to the anode of the SPAD pixel 31 from the wiring 54b via the contact electrode 55b, and a second positive bias breakdown voltage VBD2 is supplied to the transparent electrode 45 from the wiring 54c via the contact electrode 55c.

[0040] <Second Configuration Example of Photodetector> A configuration example of a second embodiment of a photodetector 11 to which the present technology is applied will be described with reference to Fig. 6. Note that in the photodetector 11A shown in Fig. 6, components common to the photodetector 11 in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0041] FIG. 6 is a diagram showing an example of a cross-sectional configuration of the photodetector 11A.

[0042] 6, the photodetector 11A is configured by stacking a sensor substrate 21A and a logic substrate 22, and similarly to the photodetector 11 of Fig. 1, the sensor substrate 21A is provided with a trench isolation portion 48 that separates the SPAD pixels 31A from each other. The sensor substrate 21A has a different configuration from the photodetector 11 of Fig. 1 in that a transparent electrode 45A is stacked on the back surface of the semiconductor layer 41 via an insulating film 44 and is provided so as to be electrically connected to the upper end of the trench isolation portion 48.

[0043] That is, in the photodetector 11 of FIG. 1, the transparent electrode 45 is provided via the insulating film 44 even in the trench that forms the side surface of the semiconductor layer 41, whereas in the photodetector 11A, the transparent electrode 45A is not provided in the trench.

[0044] In the photodetector 11A, the transparent electrode 45A is electrically connected to the upper end of the trench isolation 48, so that the positive bias second breakdown voltage VBD2 can also be supplied to the trench isolation 48 via the transparent electrode 45A. Therefore, in the photodetector 11A, the positive bias second breakdown voltage VBD2 supplied to the transparent electrode 45A can form an electron trap layer 46 on the back surface of the semiconductor layer 41, and at the same time, the positive bias second breakdown voltage VBD2 supplied to the trench isolation 48 via the transparent electrode 45A can form an electron trap layer 46 on the side surface of the semiconductor layer 41. In addition, in the photodetector 11A, the positive bias second breakdown voltage VBD2 can be supplied to the transparent electrode 45A using the dummy pixel 32, as described above with reference to FIGS. 2 and 3 .

[0045] The photodetector 11A configured in this manner can achieve a positive bias for the breakdown voltage, similar to the photodetector 11 in FIG.

[0046] <Third Configuration Example of Photodetector> A configuration example of a third embodiment of a photodetector 11 to which the present technology is applied will be described with reference to Figures 7 to 9. Note that in the photodetector 11B shown in Figures 7 to 9, components common to the photodetector 11 in Figure 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0047] FIG. 7 is a diagram showing an example of the cross-sectional configuration of the photodetector 11B.

[0048] 7, the photodetector 11B is configured by stacking a sensor substrate 21B and a logic substrate 22, and similarly to the photodetector 11 of Fig. 1, the sensor substrate 21B is provided with a trench isolation portion 48 that separates the SPAD pixels 31B from each other. The sensor substrate 21B is configured differently from the photodetector 11 of Fig. 1 in that an insulating film 50 is provided between the transparent electrode 45B and the insulating film 44, and the transparent electrode 45B and the upper end of the trench isolation portion 48 are also insulated by the insulating film 50.

[0049] Therefore, in the photodetector 11B, by supplying a positive bias third breakdown voltage VBD3 to the transparent electrode 45B, an electron trapping layer 46 can be provided on the back surface of the semiconductor layer 41. Furthermore, in the photodetector 11B, by supplying a positive bias fourth breakdown voltage VBD4 to the trench isolation portion 48 in addition to the positive bias third breakdown voltage VBD3, an electron trapping layer 46 can be provided on the side surface of the semiconductor layer 41.

[0050] That is, the photodetector 11B is configured so that the third breakdown voltage VBD3 supplied to the transparent electrode 45B and the fourth breakdown voltage VBD4 supplied to the trench isolation portion 48 can be set to different potentials. For example, since a trench formed by digging into the semiconductor layer 41 generates more dark current than the back surface of the semiconductor layer 41, the photodetector 11B is configured to supply a positive bias fourth breakdown voltage VBD4, which has a higher potential than the positive bias third breakdown voltage VBD3, to the trench isolation portion 48. This allows the photodetector 11B to further suppress the generation of dark current.

[0051] Referring to the cross-sectional view of the photodetector 11B shown in FIG. 8, a wiring configuration for supplying a positive bias third breakdown voltage VBD3 to the transparent electrode 45B and a positive bias fourth breakdown voltage VBD4 to the trench isolation portion 48 will be described.

[0052] 8 , the photodetector 11B is configured to include, in addition to SPAD pixels 31B, which are main pixels that detect photons, first dummy pixels 33 and second dummy pixels 34 that do not detect photons. For example, the first dummy pixels 33 and the second dummy pixels 34 are arranged in a peripheral region that surrounds the outer periphery of the main pixel region in which the SPAD pixels 31B are arranged in an array, and the second dummy pixels 34 are arranged outside the first dummy pixels 33.

[0053] As described above, in the SPAD pixel 31B, the wiring 57b that supplies the positive bias first breakdown voltage VBD1 is electrically connected to the anode of the SPAD pixel 31B via the contact electrode 58b, the Cu-Cu junction 23b, the contact electrode 56b, the wiring 54b, and the contact electrode 55b.

[0054] On the other hand, in the first dummy pixel 33, a wiring 57d that supplies a fourth breakdown voltage VBD4 of a positive bias is provided on the opposite side (left side in FIG. 8 ) from the SPAD pixel 31B. The wiring 57d is electrically connected to the trench isolation portion 48 via a contact electrode 58d, a Cu-Cu junction 23d, a contact electrode 56d, a wiring 54d, and a contact electrode 55d.

[0055] In the second dummy pixel 34, a wiring 57e that supplies a positive bias third breakdown voltage VBD3 is provided on the opposite side (left side in FIG. 8 ) from the first dummy pixel 33. The wiring 57e is electrically connected to the transparent electrode 45B via a contact electrode 58e, a Cu-Cu junction 23e, a contact electrode 56e, a wiring 54e, a contact electrode 55e, and a trench isolation 48B. In the photodetector 11B, the insulating film 50 is provided partway through the second dummy pixel 34, and the transparent electrode 45B is electrically connected to the upper end of the trench isolation 48B that is provided outside the second dummy pixel 34.

[0056] In this way, the photodetector 11B can supply a positive bias third breakdown voltage VBD3 to the transparent electrode 45B and a positive bias fourth breakdown voltage VBD4 to the trench isolation portion 48 by using a wiring configuration that utilizes the first dummy pixel 33 and the second dummy pixel 34.

[0057] FIG. 9 is a diagram showing an example of a planar layout of the SPAD pixel 31B, the first dummy pixel 33, and the second dummy pixel 34. As shown in FIG.

[0058] FIG. 9 illustrates four SPAD pixels 31B arranged in the main pixel region, and two first dummy pixels 33 and two second dummy pixels 34 arranged in the dummy pixel region.

[0059] As shown in Figure 9, when viewing the photodetector 11B in a plan view, trench isolation portions 48 are provided to surround the outer peripheries of the individual SPAD pixels 31B and the first dummy pixels 33, and trench isolation portions 48B are provided in a linear fashion along the second dummy pixels 34, separated from the trench isolation portions 48, outside the second dummy pixels 34 (on the left side of Figure 9).

[0060] The wiring 54b used to supply the positive bias first breakdown voltage VBD1 is arranged in the main pixel region (including the boundary between the main pixel region and the dummy pixel region) so as to surround the outer periphery of each SPAD pixel 31B, similar to the trench isolation portion 48. On the other hand, the wiring 54d used to supply the positive bias fourth breakdown voltage VBD4 is separated from the wiring 54b outside the first dummy pixel 33 (left side of FIG. 9 ) and arranged linearly along the first dummy pixel 33. Furthermore, the wiring 54e used to supply the positive bias third breakdown voltage VBD3 is separated from the wiring 54b outside the second dummy pixel 34 (left side of FIG. 9 ) and arranged linearly along the second dummy pixel 34.

[0061] In a plan view of the photodetector 11B, the contact electrode 55b is disposed at a position overlapping the wiring 54b, the contact electrode 55d is disposed at a position overlapping the wiring 54d, and the contact electrode 55e is disposed at a position overlapping the wiring 54e. As a result, the photodetector 11B is configured such that a positive bias first breakdown voltage VBD1 is supplied to the anode of the SPAD pixel 31B from the wiring 54b via the contact electrode 55b, a positive bias fourth breakdown voltage VBD4 is supplied to the trench isolation portion 48 from the wiring 54d via the contact electrode 55d, and a positive bias third breakdown voltage VBD3 is supplied to the transparent electrode 45B from the wiring 54e via the contact electrode 55e.

[0062] The photodetector 11B configured in this manner can achieve a positive bias for the breakdown voltage, similar to the photodetector 11 of FIG.

[0063] <Configuration Example of Distance Measuring System> FIG. 10 is a block diagram showing a configuration example of a distance measuring system to which the present technology is applied.

[0064] As shown in Figure 10, the distance measurement system 101 is configured to include an illumination device 102 that emits laser light toward an object to be measured, a light receiving device 103 that receives the reflected laser light reflected by the object to be measured, and a control device 104 that controls the illumination device 102 and the light receiving device 103.

[0065] The illumination device 102 has a laser driving unit 111, a laser light source 112, and a diffusing lens 113. The laser driving unit 111 drives the laser light source 112 under the control of the control device 104, causing the laser light source 112 to emit pulsed irradiation laser light, which is then diffused by the diffusing lens 113 and directed toward the object to be measured.

[0066] The light receiving device 103 has a condenser lens 121, an optical sensor 122, and a signal processing unit 123. The condenser lens 121 condenses the pulsed reflected laser light reflected by the object to be measured onto the light receiving surface of the optical sensor 122. The optical sensor 122 receives the pulsed reflected laser light pixel by pixel and outputs an output signal. The output signal is subjected to signal processing in the signal processing unit 123 and then supplied to the control device 104.

[0067] The control device 104 controls the laser driving unit 111 to control the timing at which the pulsed irradiated laser light is emitted, and measures the time until the pulsed reflected laser light is detected by the optical sensor 122, thereby measuring the distance to the object to be measured.

[0068] Furthermore, by applying the photodetector 11 of each of the above-described embodiments to the optical sensor 122, the ranging system 101 can, for example, further suppress the generation of dark current and improve ranging performance.

[0069] <Examples of Combinations of Configurations> The present technology can also be configured as follows. (1) A photodetector comprising: a P-type region provided in the center of a SPAD pixel and connected to an electrode that outputs a detection signal in response to detection of photons incident on the SPAD pixel; an N+ diffusion layer provided in the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage; and a transparent electrode that is stacked on a light incident surface and a side surface of the SPAD pixel via an insulating film and that is supplied with a positive bias second breakdown voltage. (2) The photodetector according to (1) above, wherein the transparent electrode is formed of an ITO (Indium-Tin Oxide) film. (3) The photodetector according to (1) or (2) above, wherein the positive bias first breakdown voltage supplied to the N+ diffusion layer and the positive bias second breakdown voltage supplied to the transparent electrode are independent potentials. (4) The photodetector according to (3) above, wherein the positive bias first breakdown voltage supplied to the N+ diffusion layer is a potential lower than the positive bias second breakdown voltage supplied to the transparent electrode. (5) The photodetector according to any one of (1) to (4), further comprising: a DCR detector that detects, from the detection signal, a DCR (Dark Count Rate) according to a count value of photons detected when no light is incident on the SPAD pixel; and a voltage adjuster that increases a second breakdown voltage of a positive bias supplied to the transparent electrode in accordance with an increase in the DCR. (6) The photodetector according to any one of (1) to (5), further comprising: a trench isolation that is provided in a trench separating the SPAD pixels and is made of a metal having light-blocking properties. (7) The photodetector according to (6), wherein the transparent electrode is not provided on a side surface of the SPAD pixel, but is stacked on the light incident surface of the SPAD pixel via the insulating film. (8) The photodetector according to (7), wherein the transparent electrode is electrically connected to the trench isolation, and a second breakdown voltage of a positive bias is supplied to the trench isolation via the transparent electrode.(9) The photodetector according to (7), wherein the transparent electrode is configured so as not to be electrically connected to the trench isolation, and a positive bias breakdown voltage is supplied to the trench isolation separately from the positive bias second breakdown voltage supplied to the transparent electrode. (10) A ranging system including a photodetector having: a P-type region provided in the center of a SPAD pixel and connected to an electrode that outputs a detection signal in response to detection of a photon incident on the SPAD pixel; an N+ diffusion layer provided in the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage; and transparent electrodes stacked on the light incident surface and side surfaces of the SPAD pixel via insulating films, and that supply a positive bias second breakdown voltage.

[0070] It should be noted that the present embodiment is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained.

[0071] REFERENCE SIGNS LIST 11 Photodetector, 21 Sensor substrate, 22 Logic substrate, 23 Cu-Cu junction, 31 SPAD pixel, 32 Dummy pixel, 33 First dummy pixel, 34 Second dummy pixel, 41 Semiconductor layer, 42 P-type region, 43 N-type region, 44 Insulating film, 45 Transparent electrode, 46 Electron trap layer, 47 N+ diffusion layer, 48 Trench isolation portion, 49 Planarization layer, 50 Insulating film, 51 Insulating film, 52 Interlayer insulating film, 53 Interlayer insulating film, 54 Wiring, 55 Contact electrode, 56 Contact electrode, 57 Wiring, 58 Contact electrode, 61 Photodiode, 62 Capacitor, 63 n-type MOSFET, 64 CMOS inverter, 65 DCR detection portion, 66 Voltage adjustment portion, 101 Distance measuring system, 102 illumination device, 103 light receiving device, 104 control device, 111 laser driving unit, 112 laser light source, 113 diffusing lens, 121 condensing lens, 122 optical sensor, 123 signal processing unit

Claims

1. A photodetection device comprising: a P-type region provided in the center of a SPAD (Single Photon Avalanche Diode) pixel and connected to an electrode that outputs a detection signal in response to the detection of a photon incident on the SPAD pixel; an N+ diffusion layer provided on the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage; and a transparent electrode laminated on the light incident surface and side surfaces of the SPAD pixel via an insulating film, and to which a positive bias second breakdown voltage is supplied.

2. The photodetector according to claim 1, wherein the transparent electrode is made of an ITO (Indium-Tin Oxide) film.

3. The photodetector according to claim 1, wherein a first breakdown voltage of a positive bias supplied to the N+ diffusion layer and a second breakdown voltage of a positive bias supplied to the transparent electrode are independent potentials.

4. The photodetector according to claim 3, wherein a first breakdown voltage of a positive bias supplied to the N+ diffusion layer is a potential lower than a second breakdown voltage of a positive bias supplied to the transparent electrode.

5. The photodetection device according to claim 1, further comprising: a DCR detection unit that detects a DCR (Dark Count Rate) based on a count value of photons detected when no light is incident on the SPAD pixel from the detection signal; and a voltage adjustment unit that increases a second breakdown voltage of a positive bias supplied to the transparent electrode in response to an increase in the DCR.

6. The photodetection device according to claim 1, further comprising a trench isolation portion provided within a trench that separates the SPAD pixels from each other and made of a metal having light-shielding properties.

7. The photodetector according to claim 6, wherein the transparent electrode is not provided on a side surface of the SPAD pixel, but is laminated on the light incident surface of the SPAD pixel via the insulating film.

8. The photodetector according to claim 7, wherein the transparent electrode is electrically connected to the trench isolation, and a positive bias second breakdown voltage is supplied to the trench isolation via the transparent electrode.

9. The photodetector device of claim 7, wherein the transparent electrode is configured not to be electrically connected to the trench isolation, and a positive bias breakdown voltage is supplied to the trench isolation in addition to a positive bias second breakdown voltage supplied to the transparent electrode.

10. A ranging system equipped with a photodetection device having: a P-type region provided in the center of a SPAD (Single Photon Avalanche Diode) pixel and connected to an electrode that outputs a detection signal in response to the detection of a photon incident on the SPAD pixel; an N+ diffusion layer provided on the periphery of the SPAD pixel and connected to an electrode that supplies a positive bias first breakdown voltage; and a transparent electrode laminated on the light incident surface and side surfaces of the SPAD pixel via an insulating film and that supplies a positive bias second breakdown voltage.

Images