Light detection device, method for manufacturing light detection device, and ranging device

Abstract

A light detection device according to an embodiment of the present disclosure comprises: a semiconductor substrate having opposing first and second surfaces; a light-receiving section provided inside the semiconductor substrate to generate, by photoelectric conversion, carriers in accordance with an amount of light received; a multiplying section for avalanche multiplication of the carriers generated in the light-receiving section, the multiplying section being provided inside the semiconductor substrate and farther to the first-surface side than the light-receiving section, and being formed by the stacking of a first conductivity-type region and a second conductivity-type region of a different conductivity type than the first conductivity-type region; a first semiconductor layer provided at least partially on the second-surface side of the semiconductor substrate and having the same conductivity type as the first conductivity-type region; and a light-transmissive first electrode that is stacked on the first semiconductor layer and electrically connected to the first semiconductor layer.

Description

Photodetector, method of manufacturing a photodetector, and distance measuring device

[0001] The present disclosure relates to, for example, a photodetector using an avalanche photodiode, a method for manufacturing a photodetector, and a distance measuring device.

[0002] For example, Patent Document 1 discloses an imaging device in which, in a SPAD (Single Photon Avalanche Diode) pixel, a cathode electrode is provided on the circuit surface (front surface) side of a semiconductor substrate and an anode electrode is provided on the light incident surface (back surface) side of the semiconductor substrate, thereby achieving pixel miniaturization, low noise, and high quantum efficiency, while suppressing interference between pixels and variations between pixels and improving sensitivity at short wavelengths.

[0003] International Publication No. 2018 / 174090

[0004] Incidentally, there is a demand for improved light detection characteristics in light detection devices.

[0005] It is desirable to provide a light detection device, a method for manufacturing a light detection device, and a distance measuring device that can improve light detection characteristics.

[0006] An optical detection device according to one embodiment of the present disclosure includes a semiconductor substrate having opposing first and second surfaces; a light receiving portion provided within the semiconductor substrate for generating carriers by photoelectric conversion in accordance with the amount of received light; a multiplication portion provided within the semiconductor substrate on the first surface side of the light receiving portion and formed by stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region, for avalanche multiplication of carriers generated in the light receiving portion; a first semiconductor layer provided in at least a portion of the second surface side of the semiconductor substrate and having the same conductivity type as the first conductivity type region; and an optically transparent first electrode stacked on the first semiconductor layer and electrically connected to the first semiconductor layer.

[0007] A method for manufacturing a photodetector according to one embodiment of the present disclosure includes forming a light receiving portion inside a semiconductor substrate having opposing first and second surfaces, sequentially stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region on the first surface side of the semiconductor substrate, forming a wiring layer on the first surface of the semiconductor substrate, thinning the semiconductor substrate from the second surface side, and then sequentially stacking a first semiconductor layer having the same conductivity type as the first conductivity type region and a first electrode having optical transparency on at least a portion of the second surface.

[0008] A distance measuring device according to one embodiment of the present disclosure includes an optical system, a photodetector, and a signal processing circuit that calculates the distance to the object to be measured from the output signal of the photodetector, and has the photodetector according to one embodiment of the present disclosure as the photodetector.

[0009] In the photodetector according to an embodiment of the present disclosure, the method for manufacturing the photodetector according to an embodiment, and the distance measuring device according to an embodiment, a first semiconductor layer having the same conductivity type as the first conductivity type region constituting the multiplication section is provided on at least a part of the second surface side of a semiconductor substrate having a light receiving section and a multiplication section provided on the first surface side, and a first electrode electrically connected to this first semiconductor layer is stacked on the first semiconductor layer, thereby suppressing a decrease in sensitivity during miniaturization, for example.

[0010] FIG. 1 is a cross-sectional view schematically illustrating an example of a photodetector according to a first embodiment of the present disclosure. FIG. 2 is a plan view schematically illustrating the front side (A) and the back side (B) of a semiconductor substrate constituting the sensor substrate shown in FIG. 1. FIG. 3 is a block diagram illustrating an example of a schematic configuration of the photodetector shown in FIG. 1. FIG. 4 is an example of an equivalent circuit diagram of a unit pixel of the photodetector shown in FIG. 1. FIG. 5 is a cross-sectional view schematically illustrating an example of power supply to the anode of the photodetector shown in FIG. 1. FIG. 6A is a cross-sectional view for explaining a method of manufacturing the photodetector shown in FIG. 1. FIG. 6B is a cross-sectional view illustrating a step subsequent to FIG. 6A. FIG. 6C is a cross-sectional view illustrating a step subsequent to FIG. 6B. FIG. 6D is a cross-sectional view illustrating a step subsequent to FIG. 6C. FIG. 6E is a cross-sectional view illustrating a step subsequent to FIG. 6D. FIG. 6F is a cross-sectional view illustrating a step subsequent to FIG. 6E. FIG. 6G is a cross-sectional view illustrating a step subsequent to FIG. 6F. FIG. 7 is a plan view schematically illustrating a photodetector according to a first modification of the present disclosure. FIG. 8 is a characteristic diagram illustrating the distribution of p-type impurity concentration in the depth direction of the contact layer shown in FIG. 7. FIG. 9A is a schematic plan view illustrating an example of a layout of electrode layers on the back surface side of a photodetector according to Modification 2 of the present disclosure. FIG. 9B is a schematic plan view illustrating another example of a layout of electrode layers on the back surface side of a photodetector according to Modification 2 of the present disclosure. FIG. 10 is a schematic cross-sectional view of a photodetector according to Modification 3 of the present disclosure. FIG. 11 is a schematic cross-sectional view illustrating an example of a configuration of a photodetector according to Modification 4 of the present disclosure. FIG. 12 is a schematic cross-sectional view illustrating another example of a configuration of a photodetector according to Modification 4 of the present disclosure. FIG. 13 is a schematic cross-sectional view illustrating a configuration of a photodetector according to Modification 5 of the present disclosure. FIG. 14 is a schematic cross-sectional view illustrating a configuration of a photodetector according to Modification 6 of the present disclosure. FIG. 15 is a schematic cross-sectional view illustrating an example of a photodetector according to a second embodiment of the present disclosure. FIG. 16 is a schematic plan view of the back surface side (B) of a semiconductor substrate constituting the sensor substrate shown in FIG. 15. FIG. 17 is a schematic cross-sectional view illustrating another example of a photodetector according to the second embodiment of the present disclosure. Fig. 18 is a functional block diagram showing an example of an electronic device using the photodetector shown in Fig. 1 etc. Fig. 19 is a block diagram showing an example of a schematic configuration of a vehicle control system Fig. 20 is an explanatory diagram showing an example of installation positions of an outside-vehicle information detection unit and an imaging unit.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is one specific example of the present disclosure, and the present disclosure is not limited to the following aspects. Furthermore, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc. of the components shown in the drawings. The order of description is as follows: 1. First embodiment (Example of a photodetector in which connection wiring between a light receiving section and an anode is formed continuously and independently for each pixel along the pixel) 1-1. Configuration of the photodetector 1-2. Method for manufacturing the photodetector 1-3. Actions and effects 2. Modifications 2-1. Modification 1 (Another example of the configuration of the photodetector) 2-2. Modification 2 (Another example of the planar layout of the transparent electrode layer) 2-3. Modification 3 (Another example of the configuration of the photodetector) 2-4. Modification 4 (Another example of the configuration of the photodetector) 2-5. Modification 5 (Another example of the configuration of the photodetector) 2-6. Modification 6 (Another example of the configuration of the photodetector) 3. Second embodiment (an example of a photodetector in which an anode is embedded in a semiconductor substrate along the side of a pixel separating section and electrically connected to a metal film that forms the pixel separating section) 3-1. Configuration of photodetector 3-2. Actions and effects 4. Application examples 5. Application examples

[0012] 1. First Embodiment FIG. 1 is a schematic diagram illustrating an example of a cross-sectional configuration of a photodetector (photodetector 1) according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating the planar configuration of the front side (first surface 11S1 side) and the back side (second surface 11S2 side) of a semiconductor substrate 11 constituting a sensor substrate 10 of the photodetector 1 illustrated in FIG. 1. FIG. 3 is a block diagram illustrating a schematic configuration of the photodetector 1 illustrated in FIG. 1, and FIG. 4 is a diagram illustrating an example of an equivalent circuit of a unit pixel P of the photodetector 1 illustrated in FIG. 1. The photodetector 1 is applicable to, for example, a range image sensor (a range image device 1000 described below, see FIG. 18 ) that measures distances using a time-of-flight (ToF) method, an image sensor, and the like.

[0013] (1-1. Configuration of Photodetection Device) The photodetection device 1 has, for example, a pixel array section 100A in which a plurality of unit pixels P are arranged in an array in the row and column directions. As shown in FIG. 3 , the photodetection device 1 has a bias voltage application section 110 together with the pixel array section 100A. The bias voltage application section 110 applies a bias voltage to each unit pixel P of the pixel array section 100A. In this embodiment, a case will be described in which electrons are read out as signal charges.

[0014] As shown in FIG. 4, the unit pixel P includes a light receiving element 12, a quenching resistance element 120 made of a p-type metal-oxide-semiconductor field-effect transistor (MOSFET), and an inverter 130 made of, for example, a complementary MOSFET.

[0015] The light receiving element 12 converts incident light into an electrical signal by photoelectric conversion and outputs the signal. Additionally, the light receiving element 12 converts incident light (photons) into an electrical signal by photoelectric conversion and outputs a pulse corresponding to the incident photons. The light receiving element 12 is, for example, a SPAD (Single Photon Avalanche Diode) element. The SPAD element has a characteristic that, for example, when a large negative voltage is applied to the cathode, an avalanche multiplication region 12X (depletion layer) is formed, and electrons generated in response to the incidence of one photon undergo avalanche multiplication, resulting in a large current flow. For example, the anode of the light receiving element 12 is connected to the bias voltage application unit 110, and the cathode is connected to the source terminal of the quenching resistance element 120. The anode of the light receiving element 12 is connected to the bias voltage application unit 110, and a device voltage V Ｂ is applied.

[0016] The quenching resistance element 120 is connected in series with the light-receiving element 12, with its source terminal connected to the cathode of the light-receiving element 12 and its drain terminal connected to a power supply (not shown). Ｅ The quenching resistor 120 detects that the voltage due to the electrons avalanche-multiplied in the light-receiving element 12 is a negative voltage V ＢＤWhen the voltage reaches the initial voltage, the photodetector 12 emits the electrons multiplied by the photodetector 12, thereby performing quenching to return the voltage to the initial voltage.

[0017] The inverter 130 has an input terminal connected to the cathode of the light-receiving element 12 and the source terminal of the quenching resistor element 120, and an output terminal connected to a downstream arithmetic processing unit (not shown). The inverter 130 outputs a light-receiving signal based on the carriers (signal charges) multiplied by the light-receiving element 12. More specifically, the inverter 130 shapes the voltage generated by the electrons multiplied by the light-receiving element 12. The inverter 130 then outputs a light-receiving signal (APD OUT) that generates a pulse waveform, such as that shown in FIG. 4 , starting from the arrival time of one font to the arithmetic processing unit. For example, the arithmetic processing unit performs arithmetic processing to determine the distance to the subject based on the timing at which a pulse indicating the arrival time of one font is generated in each light-receiving signal, thereby determining the distance for each unit pixel P. Then, based on these distances, a distance image is generated in which distances to the subject detected by multiple unit pixels P are arranged in a plane.

[0018] The photodetector 1 is a so-called back-illuminated photodetector in which a logic substrate 20 is stacked on the front side of the sensor substrate 10 (for example, the front side (first surface 11S1) of the semiconductor substrate 11 constituting the sensor substrate 10) and light is received from the back side of the sensor substrate 10 (for example, the back side (second surface 11S2) of the semiconductor substrate 11 constituting the sensor substrate 10).

[0019] The photodetector 1 has a light-receiving element 12 for each unit pixel P. The light-receiving element 12 has a light-receiving section 13 and a multiplier section 14. As described above, the photodetector 1 includes a sensor substrate 10 and a logic substrate 20 stacked one on top of the other. The sensor substrate 10 includes, for example, a semiconductor substrate 11 made of a silicon substrate and a multilayer wiring layer 19 provided on the first surface 11S1 side of the semiconductor substrate 11. The light-receiving section 13 and the multiplier section 14 are embedded in the semiconductor substrate 11, for example. The semiconductor substrate 11 is further provided with pixel separators 17 that electrically separate adjacent unit pixels P. The pixel separators 17 are provided between a plurality of unit pixels P adjacent to each other in the row and column directions so as to extend between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11. The pixel separators 17 are arranged in a lattice pattern in a plan view across the entire pixel array section 100A. The semiconductor substrate 11 is further provided with a contact layer 15 (anode) electrically connected to the light receiving section 13 and a contact layer 16 (cathode) electrically connected to the multiplication section 14. In this embodiment, the contact layer 15 is provided over the entire second surface 11S2 of the semiconductor substrate 11, and the contact layer 16 is provided approximately in the center of the unit pixel P on the first surface 11S1 side of the semiconductor substrate 11. An optically transparent electrode layer 18 is further stacked on the contact layer 15.

[0020] In the figures, the symbols "p" and "n" represent p-type semiconductor regions and n-type semiconductor regions, respectively. Furthermore, the "+" or "-" at the end of "p" represents the impurity concentration of the p-type semiconductor region. Similarly, the "+" or "-" at the end of "n" represents the impurity concentration of the n-type semiconductor region. Here, the more "+"s, the higher the impurity concentration, and the more "-"s, the lower the impurity concentration. This also applies to the subsequent figures.

[0021] The semiconductor substrate 11 has a first surface 11S1 and a second surface 11S2 facing each other. The semiconductor substrate 11 has a p-well (p) common to a plurality of unit pixels P. The semiconductor substrate 11 is provided with an n-type semiconductor region (n) 111, for example, with an n-type impurity concentration controlled, which constitutes a light receiving section 13, for each unit pixel P. The semiconductor substrate 11 further has a p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y are provided. As a result, a light receiving element 12 is formed for each unit pixel P. A pixel separating section 17 is provided around each unit pixel P to electrically separate adjacent unit pixels P. Between the light receiving element 12 and the pixel separating section 17, for example, a p-type semiconductor region (p ＋ A p-type semiconductor region (p) 112 is provided in contact with the second surface 11S2 of the semiconductor substrate 11 and continues to the second surface 11S2 of the semiconductor substrate 11.

[0022] The light receiving element 12 has a multiplication region (avalanche multiplication region 12X) that avalanche-multiplies carriers using a high electric field region. As described above, the avalanche multiplication region 12X is formed by applying a large negative voltage to the cathode (contact layer 16), and the light receiving element 12 is a SPAD element that can avalanche-multiply electrons generated by the incidence of one photon.

[0023] The light receiving element 12 is composed of a light receiving section 13 and a multiplication section 14 .

[0024] The light receiving section 13 corresponds to a specific example of the "light receiving section" in the first embodiment of the present disclosure, and has a photoelectric conversion function of absorbing light incident from the second surface 11S2 side of the semiconductor substrate 11 and generating carriers according to the amount of light received. As described above, the light receiving section 13 is configured to include the n-type semiconductor region (n) 111 in which the impurity concentration is controlled to be n-type, and the carriers (electrons) generated in the light receiving section 13 are transferred to the multiplication section 14 by a potential gradient.

[0025] The multiplication section 14 corresponds to a specific example of the "multiplication section" in the first embodiment of the present disclosure, and avalanche-multiplies carriers (electrons in this case) generated in the light receiving section 13. The multiplication section 14 is, for example, a p-type semiconductor region (p ＋ ) 14X and an n-type semiconductor region (n) 111 having a higher impurity concentration than the n-type semiconductor region (n) ＋ ) 14Y. ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y is provided on the first surface 11S1 side, and the n-type semiconductor region (n ＋ ) 14Y, p-type semiconductor region (p ＋ ) 14X are laminated in this order. ＋ The area of ​​the n-type semiconductor region (n ＋ ) 14Y in the XY plane direction and is provided over the entire surface of the unit pixel P partitioned by the pixel separating portion 17.

[0026] In the light receiving element 12, a p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ The avalanche multiplication region 12X is formed at the junction with the p-type semiconductor region (p) 14Y. The avalanche multiplication region 12X is formed by the p-type semiconductor region (p ＋ ) 14X and n-type semiconductor region (n ＋ ) 14Y. In the avalanche multiplication region 12X, electrons (e － ) is multiplied.

[0027] The first surface 11S1 of the semiconductor substrate 11 further includes a p-type semiconductor region (p ＋ ) 14X and a p-type semiconductor (p ＋＋ ) contact layer 15 and an n-type semiconductor region (n ＋ ) 14Y and the n-type semiconductor region (n ＋＋ ) and a contact layer 16 made of .

[0028] 2B, the contact layer 15 is provided over the entire surface of the second surface 11S2 of the semiconductor substrate 11 partitioned by the pixel separating section 17. As shown in FIG. 1, the contact layer 15 is provided along the side surface of the pixel separating section 17, and one end of the contact layer 15 is in contact with the p-type semiconductor region (p ＋ The other end of each of these p-type semiconductor regions (p) 112 is electrically connected to the p-type semiconductor region (p) 112 that extends to the second surface 11S2 of the semiconductor substrate 11. ＋ The p-type semiconductor region (p) 14X and the p-type semiconductor region (p) 112 correspond to a specific example of a "first conductivity type region" in the first embodiment of the present disclosure. The contact layer 15 serves as the anode of the light-receiving element 12 and is connected to the bias voltage application unit 110 via, for example, the electrode layer 18. The contact layer 16 serves as the cathode and is connected to the source terminal of the quenching resistor element 120.

[0029] The pixel separator 17 electrically separates adjacent unit pixels P and is provided in a grid pattern in the pixel array section 100A in a plan view, for example, to separate each of the unit pixels P. The pixel separator 17 extends between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11, and for example, penetrates the semiconductor substrate 11. The pixel separator 17 is composed of, for example, a metal film 17A and an insulating film 17B provided around the metal film 17A. The pixel separator 17 may be provided from the first surface 11S1 side of the semiconductor substrate 11, or may be formed from the second surface 11S2 side of the semiconductor substrate 11.

[0030] The metal film 17A can be formed using a conductive material with light-shielding properties. Specifically, the metal film 17A can be formed using a metal material with light-shielding properties, such as tungsten (W), aluminum (Al), copper (Cu), cobalt (Co), nickel (Ni), or titanium (Ti), or a silicon compound thereof. Alternatively, the metal film 17A may be formed using polysilicon (Poly-Si). The metal film 17A may be provided with a widened portion 17X formed on the second surface 11S2 of the semiconductor substrate 11 in order to suppress the incidence of obliquely incident light between adjacent unit pixels P.

[0031] The insulating film 17B is made of, for example, silicon oxide (SiO ｘ ) or the like. Alternatively, the insulating film 17B may be formed using, for example, hafnium oxide (HfO ｘ ), aluminum oxide (AlO ｘ ), zirconium oxide (ZrO ｘ ), tantalum oxide (TaO ｘ ), titanium oxide (TiO ｘ ), lanthanum oxide (LaO ｘ ), praseodymium oxide (PrO ｘ ), cerium oxide (CeO ｘ ), neodymium oxide (NdO ｘ ), promethium oxide (PmO ｘ ), samarium oxide (SmO ｘ ), europium oxide (EuO ｘ ), gadolinium oxide (GdO ｘ ), terbium oxide (TbO ｘ ), dysprosium oxide (DyO ｘ ), holmium oxide (HoO ｘ ), thulium oxide (TmO ｘ ), ytterbium oxide (YbO ｘ ), lutetium oxide (LuO ｘ ), yttrium oxide (YO ｘ ), hafnium nitride (HfN ｘ ), aluminum nitride (AlN ｘ ), hafnium oxynitride (HfO ｘ N ｙ) or aluminum oxynitride (AlO ｘ N ｙ ) or the like. This makes it possible to suppress the generation of dark current at the interface between the semiconductor substrate 11 and the pixel separating portion 17.

[0032] The electrode layer 18 is a power supply path for applying a voltage to the contact layer 15 serving as an anode, and is provided, for example, over the entire surface of the second surface 11S2 of the semiconductor substrate 11. The electrode layer 18 is electrically connected to, for example, a bias voltage application unit 110 provided on the logic substrate 20 via a through electrode 41 that is provided in the peripheral portion 100B outside the pixel array portion 100A and penetrates between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11, as shown in FIG.

[0033] The electrode layer 18 can be formed using a light-transmitting conductive material. Specifically, the electrode layer 18 can be formed using, for example, InP doped with tin (Sn). ２ O ３ The crystallinity of the ITO thin film may be high or low (approaching amorphous). In addition to the above, the electrode layer 18 may be formed using tin oxide (SnO ２ The electrode layer 18 can be formed using a zinc oxide (ZnO)-based material, such as ATO with Sb added as a dopant or FTO with fluorine added as a dopant. The electrode layer 18 can also be formed using zinc oxide (ZnO) or a zinc oxide-based material with a dopant added. ZnO-based materials include, for example, aluminum zinc oxide (AZO) with aluminum (Al) added as a dopant, gallium zinc oxide (GZO) with gallium (Ga) added, boron zinc oxide with boron (B) added, and indium zinc oxide (IZO) with indium (In) added. Furthermore, the electrode layer 18 can also be formed using zinc oxide with indium and gallium added as dopants (IGZO, In-GaZnO ４ The electrode layer 18 may be formed using CuI, InSbO ４ , ZnMgO, CuInO２ , MgIN ２ O ４ , CdO, ZnSnO ３ or TiO ２ It may be formed using graphene, spinel oxide, YbFe, etc. ２ O ４ The insulating layer may be formed using an oxide having a structure.

[0034] 5, the pixel separating section 17 can be used as part of the power supply path to apply a voltage to the contact layer 15. For example, although the degree of freedom of wiring within the multilayer wiring layer 19 is reduced compared to when the through electrode 41 is used, the metal film 17A constituting the pixel separating section 17 may be made to penetrate to the wiring layer 191 and electrically connected to, for example, the bias voltage application section 110 provided on the logic substrate 20.

[0035] A multilayer wiring layer 19 is provided on the first surface 11S1 side of the semiconductor substrate 11. In the multilayer wiring layer 19, a wiring layer 191 consisting of one or more wirings is formed in an interlayer insulating layer 192. The wiring layer 191 serves, for example, to supply voltage to the semiconductor substrate 11 and the light-receiving element 12 and to extract carriers generated in the light-receiving element 12. Some of the wirings in the wiring layer 191 are electrically connected to the contact layer 16 through vias V1. Multiple pad electrodes 193 are embedded in the surface of the interlayer insulating layer 192 opposite the semiconductor substrate 11 side (surface 19S1 of the multilayer wiring layer 19). The multiple pad electrodes 193 are electrically connected to some of the wirings in the wiring layer 191 through vias V2. Note that while FIG. 1 shows an example in which one wiring layer 191 is formed in the multilayer wiring layer 19, the total number of wiring layers in the multilayer wiring layer 19 is not limited, and two or more wiring layers may be formed.

[0036] The interlayer insulating layer 192 is made of, for example, silicon oxide (SiO ｘ ), TEOS, silicon nitride (SiN ｘ ) and silicon oxynitride (SiO ｘ N ｙ) or a laminated film made of two or more of these.

[0037] The wiring layer 191 can be formed using, for example, aluminum (Al), copper (Cu), tungsten (W), or the like.

[0038] The vias V1 and V2 can be formed using a metal material having light-shielding properties, such as tungsten (W), aluminum (Al), copper (Cu), cobalt (Co), nickel (Ni), or titanium (Ti), or a silicon compound thereof. Alternatively, the vias V1 and V2 may be formed using polysilicon (Poly-Si).

[0039] The pad electrode 193 is exposed on the bonding surface with the logic substrate 20 (surface 19S1 of the multilayer wiring layer 19), and is used, for example, for connection with the logic substrate 20. The pad electrode 193 can be formed using, for example, copper (Cu).

[0040] The logic substrate 20 has, for example, a semiconductor substrate 21 made of a silicon substrate, and a multilayer wiring layer 22. The logic substrate 20 is configured with, for example, the bias voltage application unit 110 including the cathode voltage generation circuit 51, the anode voltage generation circuit 52, and the modulation voltage generation circuits 53A and 53B described above, a readout circuit that outputs pixel signals based on the charges output from the unit pixels P of the pixel array unit 100A, a vertical drive circuit, a column signal processing circuit, a horizontal drive circuit, an output circuit, and the like.

[0041] The multilayer wiring layer 22 includes, for example, a gate wiring 221 of a transistor constituting a readout circuit, and wiring layers 222, 223, 224, and 225 including one or more wirings, stacked in this order from the semiconductor substrate 21 side with an interlayer insulating layer 226 in between. A plurality of pad electrodes 227 are embedded in the surface of the interlayer insulating layer 226 opposite to the semiconductor substrate 21 side (surface 22S1 of the multilayer wiring layer 22). The plurality of pad electrodes 227 are electrically connected to some of the wirings of the wiring layer 225 through vias V3.

[0042] The interlayer insulating layer 117 is made of, for example, silicon oxide (SiO ｘ ), TEOS, silicon nitride (SiN ｘ ) and silicon oxynitride (SiO ｘ N ｙ ) or a laminated film made of two or more of these.

[0043] The gate wiring 221 and the wiring layers 222, 223, 224, and 225 can be formed using, for example, aluminum (Al), copper (Cu), tungsten (W), or the like, similarly to the wiring layer 191.

[0044] The pad electrode 227 is exposed on the bonding surface (surface 22S1 of the multilayer wiring layer 22) with the sensor substrate 10, and is used, for example, for connection to the sensor substrate 10. Like the pad electrode 193, the pad electrode 227 can be formed using, for example, copper (Cu).

[0045] In the photodetector 1, for example, a CuCu bond is formed between the pad electrode 193 and the pad electrode 227. As a result, the cathode of the light-receiving element 12 is electrically connected to the quenching resistance element 120 provided on the logic substrate 20 side, and the anode of the light-receiving element 12 is electrically connected to the bias voltage application unit 110.

[0046] On the light-receiving surface (second surface 11S2) side of the semiconductor substrate 11, for example, a microlens 33 is provided for each unit pixel P via a protective layer 31 and a color filter 32, for example.

[0047] The microlens 33 is a lens that focuses light incident from above onto the light receiving element 12. For example, the microlens 33 is made of silicon oxide (SiO ｘ ) and the like.

[0048] (1-2. Method for Manufacturing Photodetector) The photodetector 1 shown in Fig. 1 can be manufactured, for example, as follows. Figs. 6A to 6G show an example of a method for manufacturing the photodetector 1 in the order of steps.

[0049] First, as shown in FIG. 6A, in a Front End of Line (FEOL) process, for example, a p-well is formed in a semiconductor substrate 11, and an n-type semiconductor region (n) 111, a p-type semiconductor region (p) 112, and a p-type semiconductor region (p) 113, which will become the light receiving portion 13, are formed in the p-well. ＋ ) 14X, n-type semiconductor region (n ＋ ) 14Y and the n-type semiconductor region (n ＋＋ ) are formed using, for example, ion implantation.

[0050] 6B , in the back end of line (BEOL) process, wiring layers are formed and connections to circuit chips are made. A multilayer wiring layer 19 is formed on the first surface 11S1 of the semiconductor substrate 11. The multilayer wiring layer 19 includes one or more wiring layers 191 and vias V1 and V2 in an interlayer insulating layer 192, and has a plurality of pad electrodes 193 exposed on the surface. Next, a logic substrate 20 is separately formed, with a plurality of pad electrodes 226 exposed on the surface, and the plurality of pad electrodes 193 and the plurality of pad electrodes 226 are bonded to each other.

[0051] Next, after the semiconductor substrate 11 is inverted as shown in Fig. 6C, the semiconductor substrate 11 is thinned from the second surface 11S2 side to a predetermined film thickness by, for example, CMP (Chemical Mechanical Polishing) as shown in Fig. 6D. Subsequently, as shown in Fig. 6E, a contact layer 15 containing p-type impurities at a predetermined concentration is grown on the second surface 11S2 of the semiconductor substrate 11 by low-temperature epitaxial growth to obtain ohmic contact with the p-type semiconductor region (p) 112.

[0052] Next, as shown in FIG. 6F, an electrode layer 18 is formed on the contact layer 15 using, for example, a sputtering method. Subsequently, as shown in FIG. 6G, a pixel separation portion 17 is formed penetrating the semiconductor substrate 11 from the second surface 11S2 side. Specifically, an opening penetrating the semiconductor substrate 11 from the second surface 11S2 side is formed by, for example, dry etching, and then an insulating film 17B is formed on the side of the opening using, for example, atomic layer deposition (ALD), and then a metal film 17A is embedded in the opening using, for example, a chemical vapor deposition (CVD) method. Then, the metal film 17A and insulating film 17B formed on the electrode layer 18 are removed using a chemical mechanical polishing (CMP) method. Then, a protective layer 31 and a color filter 32 are formed on the electrode layer 18, and then an on-chip lens 33 is disposed. This completes the photodetector 1 shown in FIG. 1 .

[0053] (1-3. Actions and Effects) In the photodetector 1 of this embodiment, the contact layer 15 and electrode layer 18 that serve as the anode are laminated over the entire back surface (second surface 11S2) that serves as the light incident surface, which is the side opposite to the front surface (first surface 11S1) of the semiconductor substrate 11 on which the multiplication section 14 is provided. This prevents a decrease in sensitivity during miniaturization, for example. This is explained below.

[0054] SPAD is a technology that utilizes a high-electric field region to multiply electrons and enable single-electron detection. To create the high-electric field region, a high voltage of, for example, approximately 20 V is typically applied between the anode and cathode. This creates the problem of leakage current when the horizontal distance between electrodes decreases with miniaturization. This phenomenon, also known as edge breakdown (EBD), can be confirmed by measurement results in a deterioration of the dark count rate (DCR), which is equivalent to dark current. Since this problem is primarily due to the coplanar arrangement of the anode and cathode, measures have been proposed to ensure spatial distance by placing one of the electrodes on the back or side of the substrate. For example, in the imaging device described above, the deterioration of DCR during miniaturization can be suppressed by placing the anode on the back side of the semiconductor substrate.

[0055] Meanwhile, a low-resistance metal-semiconductor contact is required for the anode contact. In the imaging device described above, low resistance is achieved by arranging p+ regions (anode electrode portions) formed by ion implantation, solid-phase diffusion, or the like, at the four corners of the pixel. However, if the anode electrode portions are arranged at the four corners of the pixel, as miniaturization progresses, there is a risk of sensitivity being reduced due to light vignetting by the anode electrode portions. Furthermore, in the expected manufacturing process, the p+ region is formed first and then thinned to expose the p+ region at the end. This poses the problem of high resistance if the p+ region is removed due to variations in the amount of thinning.

[0056] In contrast, in this embodiment, the semiconductor substrate 11 is inverted and thinned through the FEOL and BEOL processes, and then the contact layer 15 and electrode layer 18, which serve as the anode, are formed over the entire back surface (second surface 11S2), which serves as the light incident surface of the semiconductor substrate 11. This makes it possible to suppress a decrease in sensitivity during miniaturization, compared to the case where the contact layers 15 are disposed at the four corners of the unit pixel P as described above. Furthermore, because the contact layer 15 is formed after the semiconductor substrate 11 is thinned, it is possible to suppress high resistance due to variations in thinning. Furthermore, because contact is made over the entire back surface (second surface 11S2) of the semiconductor substrate 11, it is possible to reduce contact resistance.

[0057] As described above, the photodetector 1 of this embodiment can improve the photodetection characteristics regardless of the pixel size.

[0058] Next, a second embodiment of the present disclosure, modifications 1 to 6, and application examples will be described. In the following, the same components as those in the first embodiment will be denoted by the same reference numerals, and their description will be omitted as appropriate.

[0059] 7 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1A) according to a modification (modification 1) of the first embodiment. Fig. 8 shows the concentration distribution in the depth direction (Z-axis direction) of p-type impurities contained in the contact layer 15 in the photodetector 1 of the first embodiment and in the contact layer 45 in the photodetector 1A of this modification.

[0060] In the first embodiment, the contact layer 15 having a substantially uniform p-type impurity concentration in the depth direction was formed by low-temperature epitaxial growth. However, this is not limiting. In the photodetector 1A of this modified example, the contact layer 45 is formed using ion implantation. If the semiconductor substrate 11 is inverted and thinned through the FEOL and BEOL processes and then ion implanted from the second surface 11S2 side of the semiconductor substrate 11, high-temperature activation annealing is difficult to perform. However, the contact layer 45 can be formed by using a local heating technique such as laser annealing. In the contact layer 45 thus formed, a p-type impurity concentration gradient is formed from the second surface 11S2 of the semiconductor substrate 11 toward the first surface 11S1, as shown in FIG. 8 . The p-type impurity concentration gradient can be confirmed, for example, by secondary ion mass spectrometry (SIMS) or the like.

[0061] In this manner, in this modification, ion implantation is used to form the contact layer 45, which serves as the anode, on the entire back surface (second surface 11S2) of the semiconductor substrate 11. Even with this configuration, the same effects as those of the first embodiment can be obtained.

[0062] (2-2. Modification 2) Fig. 9A is a schematic diagram showing an example of a planar layout of an electrode layer (electrode layer 48) in a photodetector according to a modification (modification 2) of the first embodiment. Fig. 9B is a schematic diagram showing another example of a planar layout of an electrode layer (electrode layer 48) in a photodetector according to a modification (modification 2) of the first embodiment.

[0063] In the first embodiment, an example was shown in which the electrode layer 18 is formed over the entire back surface (second surface 11S2) of the semiconductor substrate 11 in the same manner as the contact layer 15 formed over the entire back surface (second surface 11S2). However, the layout of the electrode layer 15 is not limited to this. In this modified example, the electrode layer 48 is formed partially. For example, as shown in FIG. 9A , the electrode layer 48 may be partially provided with openings 48H and formed in a grid pattern for each unit pixel P. Alternatively, as shown in FIG. 9B , the electrode layer 48 may be formed along the side surface of the pixel separator 17, and openings 48H may be provided for each unit pixel P, for example, above the light receiving section 13. Alternatively, the electrode layer 48 may be formed in a stripe pattern for each unit pixel P, for example.

[0064] Even with this configuration, it is possible to obtain the same effects as in the first embodiment. Furthermore, in this modification, the electrode layer 18 is partially provided for each unit pixel P, so that the optical loss due to the electrode layer 18 can be reduced. Therefore, it is possible to further improve the light detection characteristics.

[0065] (2-3. Modification 3) FIG. 10 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1B) according to a modification (modification 3) of the first embodiment.

[0066] In the first embodiment described above, an example was shown in which the pixel separator 17 was made up of a metal film 17A and an insulating film 17B provided around the metal film 17A, but the present invention is not limited to this. In the photodetector 1B of this modified example, the pixel separator 47 may be formed only of a metal film. In the first embodiment described above, the insulating film 17B ensured pinning of the semiconductor substrate 11 on the side surface of the pixel separator 17, but even when the metal film is in direct contact with the semiconductor substrate 11, as in this modified example, the pinning effect of the metal film can be expected.

[0067] Even with this configuration, the same effects as those of the first embodiment can be obtained.

[0068] (2-4. Modification 4) Fig. 11 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1C) according to a modification (modification 4) of the first embodiment. Fig. 12 is a schematic diagram showing another example of a cross-sectional configuration of a photodetector (photodetector 1C) according to a modification (modification 4) of the first embodiment.

[0069] In the first embodiment, an example was shown in which the pixel separating section 17 penetrates the contact layer 15 and the electrode layer 18, but the present invention is not limited to this. In the photodetector device 1C of this modified example, the pixel separating section 17 penetrates only the semiconductor substrate 11. As shown in Fig. 11, the contact layer 15 may be formed on the pixel separating section 17, or as shown in Fig. 12, the contact layer 15 may be formed only on the semiconductor substrate 11 with the electrode layer 18 embedded therein.

[0070] Note that, when the pixel isolation portion 17 penetrates only the semiconductor substrate 11 as in this modified example, the pixel isolation portion 17 can be formed from the first surface 11S1 side of the semiconductor substrate 11. When the pixel isolation portion 17 is formed from the first surface 11S1 side of the semiconductor substrate 11, a higher temperature of heat can be applied to the semiconductor substrate 11 compared to when the multilayer wiring layer 19 is formed on the first surface 11S1 side of the semiconductor substrate 11 and then the pixel isolation portion 17 is formed from the second surface 11S2 side of the semiconductor substrate 11 as in the above embodiment. Therefore, side surface pinning of the pixel isolation portion 17 can be applied by PLAD (Plasma Lateral Aligned Doping) or solid phase diffusion.

[0071] Even with this configuration, the same effects as those of the first embodiment can be obtained.

[0072] (2-5. Modification 5) FIG. 13 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1D) according to a modification (modification 5) of the first embodiment.

[0073] In the first embodiment, an example in which the electrode layer 18 is directly stacked on the contact layer 15 is shown, but the present invention is not limited to this. In the photodetector 1D of this modified example, a thin insulating film 49 is formed between the contact layer 15 and the electrode layer 18 to form a metal-insulator-semiconductor (MIS) structure. The insulating film 49 is made of, for example, silicon oxide (SiO ｘ ) or the like.

[0074] In this way, in this modification, an MIS structure is formed by providing the insulating film 49 between the contact layer 15 and the electrode layer 18. This makes it possible to suppress the Fermi level pinning phenomenon and realize a lower resistance contact in addition to the effects of the first embodiment.

[0075] (2-6. Modification 6) FIG. 14 is a schematic diagram showing an example of a cross-sectional configuration of a photodetector (photodetector 1E) according to a modification (modification 6) of the first embodiment.

[0076] 14, a refractive index gradient (RIG) structure X consisting of a plurality of concave-convex structures may be formed on the second surface 11S2 of the semiconductor substrate 11, which serves as the light incident surface. The RIG structure X generally diffracts incident light to extend the optical path length within the semiconductor substrate 11, thereby improving the sensitivity to long wavelength light.

[0077] In the photodetector 1E of this modification, the RIG structure X is formed on the second surface 11S2 of the semiconductor substrate 11, which is the light incident surface, thereby further improving the photodetection characteristics. Furthermore, in the photodetector 1E of this modification, the contact area between the contact layer 15 and the electrode layer 18 is increased, thereby further reducing the contact resistance.

[0078] 3. Second embodiment Fig. 15 is a schematic diagram illustrating an example of a cross-sectional configuration of a photodetector (photodetector 2) according to a second embodiment of the present disclosure. Fig. 16 is a schematic diagram illustrating a planar configuration of the back surface side (second surface 11S2 side) of the semiconductor substrate 11 constituting the sensor substrate 10 of the photodetector 2 shown in Fig. 15. The photodetector 2 is applicable to, for example, a range image sensor (a range image device 1000 described below, see Fig. 18 ) that measures distances using the ToF method, an image sensor, etc.

[0079] (3-1. Configuration of the Photodetector) As in the first embodiment, the photodetector 2 has a light-receiving element 12 for each unit pixel P. The light-receiving element 12 has a light-receiving section 13 and a multiplier section 14. As in the first embodiment, the photodetector 2 has a sensor substrate 10 and a logic substrate 20 stacked one on top of the other. The sensor substrate 10 has, for example, a semiconductor substrate 11 made of a silicon substrate and a multilayer wiring layer 19 provided on the first surface 11S1 side of the semiconductor substrate 11. The light-receiving section 13 and the multiplier section 14 are, for example, embedded in the semiconductor substrate 11. The semiconductor substrate 11 is further provided with pixel separators 17 that electrically separate adjacent unit pixels P. The pixel separators 17 are provided between a plurality of unit pixels P adjacent to each other in the row and column directions so as to extend between the first surface 11S1 and the second surface 11S2 of the semiconductor substrate 11. The pixel separators 17 are provided in a lattice pattern in the pixel array section 100A as a whole in a plan view. The semiconductor substrate 11 is further provided with a contact layer 55 (anode) electrically connected to the light receiving section 13 and a contact layer 16 (cathode) electrically connected to the multiplication section 14. In this embodiment, the contact layer 55 is embedded in the second surface 11S2 of the semiconductor substrate 11 along the side surface of the widened portion 17X of the pixel separating section 17 embedded in the second surface 11S2 of the semiconductor substrate 11.

[0080] 17, the contact layer 55 is provided along the side surface of the widened portion 17X embedded in the second surface 11S2 of the semiconductor substrate 11 of the pixel separating portion 17. The contact layer 55 is formed in a p-type semiconductor region (p ＋＋ ) and the p-type semiconductor region (p ＋) 14X. The contact layer 55 serves as the anode of the light-receiving element 12 and is connected to the bias voltage application unit 110 via the pixel separation unit 17, for example. The contact layer 55 can be formed using ion implantation. Alternatively, the contact layer 55 may be formed by selectively growing crystals after partially etching the second surface 11S2 of the semiconductor substrate 11. Alternatively, the contact layer 55 may be formed by implanting a high concentration of p-type impurities into the side surface of the opening that forms the pixel separation unit 17 using solid-phase diffusion or plasma doping in the FEOL process.

[0081] (3-2. Actions and Effects) In the photodetector 2 of this embodiment, the contact layer 55 serving as the anode is embedded in the second surface 11S2 of the semiconductor substrate 11 along the side surface of the widened portion 17X of the pixel separating portion 17 embedded in the second surface 11S2 of the semiconductor substrate 11. This eliminates the need for the material in contact with the contact layer 15 to be optically transparent. This improves the degree of freedom in material selection.

[0082] For example, it is possible to achieve lower resistance by using a metal material for the pixel separating portion 17 that makes contact with the contact layer 15. Furthermore, since a large current flows through the anode wiring, it is possible to select a material that is advantageous from the viewpoints of IR drop and electromigration (EM).

[0083] 17 , an insulating film (e.g., insulating film 17B) may be provided between the widened portion 17X and the contact layer 55, similarly to the above-described modification 5. This makes it possible to suppress the Fermi level pinning phenomenon, similarly to the above-described modification 5, and to achieve a lower-resistance contact.

[0084] 18 shows an example of the schematic configuration of a distance image device 1000 as an electronic device equipped with a photodetector (e.g., photodetector 1) according to the first and second embodiments and modifications 1 to 6. This distance image device 1000 corresponds to a specific example of a "distance measuring device" of the present disclosure.

[0085] The range image device 1000 includes, for example, a light source device 1100 , an optical system 1200 , a light detection device 1 , an image processing circuit 1300 , a monitor 1400 , and a memory 1500 .

[0086] The distance image device 1000 receives light (modulated light or pulsed light) projected from the light source device 1100 toward the object to be illuminated 2000 and reflected from the surface of the object to be illuminated 2000, thereby obtaining a distance image corresponding to the distance to the object to be illuminated 2000.

[0087] The optical system 1200 is configured with one or more lenses, and guides image light (incident light) from the irradiation object 2000 to the light detection device 1, forming an image on the light receiving surface (sensor section) of the light detection device 1.

[0088] The image processing circuit 1300 performs image processing to construct a distance image based on the distance signal supplied from the light detection device 1, and the distance image (image data) obtained by this image processing is supplied to the monitor 1400 for display, or supplied to the memory 1500 for storage (recording).

[0089] In the range imaging device 1000 configured in this manner, by applying the above-described photodetector (e.g., photodetector 1), it is possible to calculate the distance to the illuminated object 2000 based solely on the light-receiving signals from the highly stable unit pixels P, and generate a highly accurate range image. In other words, the range imaging device 1000 can acquire a more accurate range image.

[0090] 5. Application Examples (Application Examples to Mobile Bodies) The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, a robot, construction machinery, or agricultural machinery (tractor).

[0091] FIG. 19 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0092] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 19, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0093] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0094] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0095] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0096] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0097] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0098] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0099] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0100] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0101] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying the passengers of the vehicle or the outside of the vehicle of information. In the example of Fig. 19, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0102] FIG. 20 is a diagram showing an example of the installation position of the imaging unit 12031.

[0103] In FIG. 20, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0104] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0105] 20 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0106] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0107] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0108] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0109] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0110] The first and second embodiments, Modifications 1 to 6, and application examples have been described above. However, the present disclosure is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the contact layer 16 provided on the first surface 11S1 side of the semiconductor substrate 11 is the cathode, and the contact layer 15 provided on the second surface 11S2 side of the semiconductor substrate 11 is the anode. However, this is not limiting. For example, the contact layer 16 provided on the first surface 11S1 side of the semiconductor substrate 11 may be the anode, and the contact layer 15 provided on the second surface 11S2 side of the semiconductor substrate 11 may be the cathode. In this case, the impurities contained therein and the conductivity types of the semiconductor regions formed within the semiconductor substrate 11 will be opposite polarities.

[0111] Furthermore, the photodetector of the present disclosure does not need to include all of the components described in the above embodiments, etc. Conversely, other layers may be included. For example, if the photodetector 1 detects light other than visible light (e.g., near-infrared light (IR)), the color filter 32 may be omitted.

[0112] Furthermore, in the photodetector of the present disclosure, the potentials of the anode and cathode are not limited as long as avalanche multiplication occurs when a reverse bias is applied between them.

[0113] In addition, in the above embodiments, examples have been shown in which silicon is used as the semiconductor substrate 11, but the semiconductor substrate 11 may also be, for example, germanium (Ge) or a compound semiconductor of silicon (Si) and germanium (Ge) (for example, silicon germanium (SiGe)).

[0114] Furthermore, the shape of the unit pixel P is not limited to a rectangular shape. For example, the unit pixel P may be octagonal, and a plurality of unit pixels P constituting the pixel array section 100A may be arranged in a honeycomb pattern.

[0115] Furthermore, the techniques described in the first and second embodiments and modifications 1 to 6 can be combined with each other to the extent possible.

[0116] The effects described in the above embodiments are merely examples, and other effects may be achieved, or may further include other effects.

[0117] The present disclosure may also be configured as follows. According to the present technology configured as follows, for example, it is possible to suppress a decrease in sensitivity during miniaturization. Therefore, it is possible to improve photodetection characteristics regardless of pixel size. (1) A photodetector device comprising: a semiconductor substrate having a first surface and a second surface facing each other; a light receiving portion provided inside the semiconductor substrate and generating carriers by photoelectric conversion according to an amount of received light; a multiplier portion provided inside the semiconductor substrate closer to the first surface than the light receiving portion, the multiplier portion being formed by stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region; a first semiconductor layer provided on at least a portion of the second surface side of the semiconductor substrate and having the same conductivity type as the first conductivity type region; and a first electrode having optical transparency stacked on the first semiconductor layer and electrically connected to the first semiconductor layer. (2) The photodetector according to (1), wherein the first semiconductor layer is provided over the entire second surface of the semiconductor substrate. (3) The photodetector according to (1) or (2), wherein the first semiconductor layer has a substantially uniform impurity concentration from the second surface to the first surface of the semiconductor substrate. (4) The photodetector according to (1) or (2), wherein the first semiconductor layer has an impurity concentration gradient from the second surface to the first surface of the semiconductor substrate. (5) The photodetector according to any one of (2) to (4), wherein the first electrode is stacked over the entire surface of the first semiconductor layer. (6) The photodetector according to any one of (2) to (5), wherein the first electrode is stacked partially on the first semiconductor layer. (7) The photodetector device according to any one of (1) to (6), wherein the semiconductor substrate further includes a pixel array section in which a plurality of pixels, each having the light receiving section and the multiplication section, are arranged in an array in an in-plane direction, and a pixel separation section provided between the plurality of adjacent pixels so as to extend between the first surface and the second surface of the semiconductor substrate, and electrically separating the plurality of adjacent pixels.(8) The photodetector according to (7), wherein the first conductivity type region extends from the first surface side of the semiconductor substrate along the pixel separating portion to the second surface and is electrically connected to the first semiconductor layer. (9) The photodetector according to (7) or (8), wherein the pixel separating portion is formed using a conductive material having light-blocking properties. (10) The photodetector according to any one of (7) to (9), further including a first insulating film between the semiconductor substrate and the pixel separating portion. (11) The photodetector according to any one of (7) to (10), wherein the semiconductor substrate and the pixel separating portion are in contact with each other. (12) The photodetector according to any one of (7) to (11), wherein the pixel separating portion protrudes toward the second surface side of the semiconductor substrate and penetrates the first semiconductor layer. (13) The photodetector according to (12), wherein the pixel separating portion further penetrates the first electrode. (14) The photodetector according to any one of (7) to (13), wherein one end of the pixel separating portion forms a substantially flat surface with the second surface of the semiconductor substrate and is in contact with the first semiconductor layer or the first electrode. (15) The photodetector according to any one of (1) to (14), further comprising a second insulating film between the first semiconductor layer and the first electrode. (16) The photodetector according to any one of (1) to (15), wherein the second surface is a light incident surface. (17) The photodetector according to any one of (1) to (16), further comprising a second electrode electrically connected to the second conductivity type region on the first surface side of the semiconductor substrate. (18) A method for manufacturing a photodetector, comprising: forming a light receiving portion inside a semiconductor substrate having opposing first and second surfaces; sequentially stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region on the first surface side of the semiconductor substrate; forming a wiring layer on the first surface of the semiconductor substrate; thinning the semiconductor substrate from the second surface side, and then sequentially stacking a first semiconductor layer having the same conductivity type as the first conductivity type region and a first electrode having optical transparency on at least a portion of the second surface.(19) A distance measuring device comprising an optical system, a photodetector, and a signal processing circuit that calculates a distance to a measurement object from an output signal of the photodetector, wherein the photodetector comprises: a semiconductor substrate having opposing first and second surfaces; a light receiving portion provided inside the semiconductor substrate that generates carriers by photoelectric conversion according to the amount of received light; a multiplication portion provided inside the semiconductor substrate on the first surface side of the light receiving portion and formed by stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region, that avalanche multiplies the carriers generated in the light receiving portion; a first semiconductor layer provided in at least a part of the second surface side of the semiconductor substrate and having the same conductivity type as the first conductivity type region; and a first electrode that is stacked on the first semiconductor layer and is optically transparent and electrically connected to the first semiconductor layer. (20) A photodetector comprising: a semiconductor substrate having a first surface and a second surface opposite to each other; a light receiving portion provided inside the semiconductor substrate for generating carriers by photoelectric conversion according to an amount of received light; a multiplication portion provided inside the semiconductor substrate closer to the first surface than the light receiving portion, the multiplication portion being formed by stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region, and for avalanche multiplication of the carriers generated in the light receiving portion; a pixel separation portion extending between the first surface and the second surface, separating the semiconductor substrate into pixels, and formed using a metal material; and a first semiconductor layer having the same conductivity type as the first conductivity type region, formed along a side surface of the pixel separation portion on the second surface side of the semiconductor substrate. (21) The photodetector according to (20), further comprising an insulating film between the pixel separation portion and the first semiconductor layer, wherein a metal-insulator-semiconductor structure is formed between the pixel separation portion and the first semiconductor layer.

Claims

1. A photodetector comprising: a semiconductor substrate having opposing first and second surfaces; a light receiving section disposed within the semiconductor substrate for generating carriers by photoelectric conversion in accordance with the amount of received light; a multiplication section disposed within the semiconductor substrate on the first surface side of the light receiving section, the multiplication section being formed by stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region, and for avalanche multiplication of the carriers generated in the light receiving section; a first semiconductor layer disposed on at least a portion of the second surface side of the semiconductor substrate, the first semiconductor layer having the same conductivity type as the first conductivity type region; and a first electrode laminated on the first semiconductor layer and electrically connected to the first semiconductor layer, the first electrode having optical transparency.

2. The photodetector according to claim 1, wherein the first semiconductor layer is provided over the entire second surface of the semiconductor substrate.

3. The photodetector device according to claim 1, wherein said first semiconductor layer has a substantially uniform impurity concentration from said second surface toward said first surface of said semiconductor substrate.

4. The photodetector device according to claim 1, wherein said first semiconductor layer has an impurity concentration gradient from said second surface toward said first surface of said semiconductor substrate.

5. The photodetector device according to claim 2, wherein the first electrode is laminated over the entire surface of the first semiconductor layer.

6. The photodetector device according to claim 2, wherein the first electrode is partially stacked on the first semiconductor layer.

7. The photodetector device according to claim 1, wherein the semiconductor substrate further comprises a pixel array section in which a plurality of pixels, each having the light receiving section and the multiplication section, are arranged in an array in an in-plane direction, and a pixel separation section provided between adjacent pixels so as to extend between the first surface and the second surface of the semiconductor substrate, and electrically separating the adjacent pixels.

8. The photodetector device described in claim 7, wherein the first conductivity type region extends from the first surface side of the semiconductor substrate along the pixel separating portion to the second surface and is electrically connected to the first semiconductor layer.

9. The photodetector according to claim 7, wherein the pixel separating section is formed using a conductive material having light-shielding properties.

10. The photodetector according to claim 7, further comprising a first insulating film between said semiconductor substrate and said pixel separating section.

11. The photodetector according to claim 7, wherein the semiconductor substrate and the pixel separating portion are in contact with each other.

12. The photodetector according to claim 7, wherein said pixel separating portion protrudes toward said second surface side of said semiconductor substrate and penetrates said first semiconductor layer.

13. The photodetector device according to claim 12, wherein the pixel separating portion further penetrates the first electrode.

14. The photodetector according to claim 7, wherein one end of said pixel separating portion forms a substantially flat surface together with said second surface of said semiconductor substrate and is in contact with said first semiconductor layer or said first electrode.

15. The photodetector device according to claim 1, further comprising a second insulating film between said first semiconductor layer and said first electrode.

16. The optical detection device of claim 1, wherein the second surface is a light incidence surface.

17. The photodetector according to claim 1, further comprising a second electrode electrically connected to said second conductivity type region on said first surface side of said semiconductor substrate.

18. A method for manufacturing a photodetector, comprising: forming a light receiving section inside a semiconductor substrate having opposing first and second surfaces; sequentially stacking a first conductivity type region and a second conductivity type region having a conductivity type different from that of the first conductivity type region on the first surface side of the semiconductor substrate; forming a wiring layer on the first surface of the semiconductor substrate; thinning the semiconductor substrate from the second surface side, and then sequentially stacking a first semiconductor layer having the same conductivity type as the first conductivity type region and a first electrode having optical transparency on at least a portion of the second surface.

19. A distance measuring device comprising an optical system, a photodetector, and a signal processing circuit that calculates the distance to an object to be measured from the output signal of the photodetector, wherein the photodetector comprises: a semiconductor substrate having opposing first and second surfaces; a light receiving section provided inside the semiconductor substrate that generates carriers by photoelectric conversion according to the amount of received light; a multiplication section provided inside the semiconductor substrate on the first surface side of the light receiving section and consisting of a first conductivity type region and a second conductivity type region that has a conductivity type different from that of the first conductivity type region stacked together, that avalanche multiplies the carriers generated in the light receiving section; a first semiconductor layer provided on at least a part of the second surface side of the semiconductor substrate and having the same conductivity type as the first conductivity type region; and a first electrode that is stacked on the first semiconductor layer and is optically transparent and electrically connected to the first semiconductor layer.

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