Light receiving element

Abstract

To provide a light receiving element capable of suppressing variation in electrical characteristics even if there is a temperature gradient.SOLUTION: A light receiving element according to the present disclosure includes a pixel region in which a plurality of photodiodes are arranged, a readout circuit region including a plurality of readout circuits provided corresponding to each of the plurality of photodiodes, a first thermometer provided corresponding to a first circuit region of the readout circuit region, a second thermometer provided corresponding to a second circuit region of the readout circuit region, a first control circuit that applies a first voltage corresponding to a temperature of the first circuit region measured by the first thermometer to a photodiode corresponding to a readout circuit in the first circuit region, and a second control circuit that applies a second voltage corresponding to a temperature of the second circuit region measured by the second thermometer to a photodiode corresponding to a readout circuit in the second circuit region.SELECTED DRAWING: Figure 6B

Description

[Technical Field]

[0001] This embodiment relates to a light receiving element. [Background technology]

[0002] In-vehicle dToF (direct Time of Flight) ranging sensors sometimes use SPADs (Single Photon Avalanche Diodes). SPADs are light-receiving elements that operate an avalanche photodiode (APD) in Geiger mode to enable single photon detection. When a single photon is incident on such an APD with a reverse bias voltage higher than the breakdown voltage applied, the carriers undergo avalanche multiplication, generating a large current. The incident photon on the SPAD is detected based on this current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-178249 Summary of the Invention [Problem to be solved by the invention]

[0004] Such SPADs generate heat unevenly due to the photons they detect in the pixel area and the corresponding complementary metal oxide semiconductor (CMOS) circuitry, creating a temperature gradient that causes variations in the SPAD's electrical characteristics, such as its breakdown voltage, and reduces its photon detection efficiency (PDE).

[0005] Therefore, the present disclosure has been made in consideration of the above-mentioned problems, and provides a light-receiving element that can suppress variations in electrical characteristics even when a temperature gradient is present. [Means for solving the problem]

[0006] The light receiving element according to this embodiment comprises a pixel region in which a plurality of photodiodes are arranged, a readout circuit region including a plurality of readout circuits each provided corresponding to the plurality of photodiodes, a first thermometer provided corresponding to a first circuit region in the readout circuit region, a second thermometer provided corresponding to a second circuit region in the readout circuit region, a first control circuit that applies a first voltage corresponding to the temperature of the first circuit region measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit region, and a second control circuit that applies a second voltage corresponding to the temperature of the second circuit region measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit region.

[0007] The readout circuit area has an elongated shape with a long side or a major axis, and includes first and second circuit areas arranged along the long side or the major axis, and the first and second thermometers are arranged along the long side or the major axis corresponding to the first and second circuit areas.

[0008] The light receiving element is provided adjacent to one side of the readout circuit area and further includes a signal processing circuit that processes pixel signals from the readout circuit area, and the first and second thermometers are provided on the opposite side of the readout circuit area from the signal processing circuit.

[0009] The light receiving element further includes a first pad connected to the first control circuit and a second pad connected to the second control circuit, the first thermometer being disposed between the first circuit area and the first pad, and the second thermometer being disposed between the second circuit area and the second pad.

[0010] The light receiving element includes a first bias circuit provided in correspondence with the first circuit area and supplying power to a driver in the readout circuit area, and a second bias circuit provided in correspondence with the second circuit area and supplying power to a driver in the readout circuit area.

[0011] The light receiving element is provided adjacent to one side of the readout circuit area and further includes a signal processing circuit that processes pixel signals from the readout circuit area, and the first and second bias circuits are provided on the opposite side of the readout circuit area from the signal processing circuit.

[0012] The light receiving element further includes a first pad connected to the first control circuit and a second pad connected to the second control circuit, the first bias circuit being disposed between the first circuit area and the first pad, and the second bias circuit being disposed between the second circuit area and the second pad.

[0013] The first bias circuit is disposed proximate to the first thermometer, and the second bias circuit is disposed proximate to the second thermometer.

[0014] The light receiving element includes a first chip including a pixel region, and a second chip including a readout circuit region and bonded to the first chip so that a readout circuit corresponding to the photodiode faces the first chip.

[0015] The pixel region has the same elongated shape as the readout circuit region, and faces the readout circuit region when the first chip and the second chip are joined together.

[0016] When the difference between the temperature of the first circuit area and the temperature of the second circuit area exceeds a first threshold, the first or second control circuit changes the absolute value of the first or second voltage.

[0017] When the temperature of the first circuit area is higher than the temperature of the second circuit area, the first control circuit reduces the absolute value of the first voltage, and when the temperature of the second circuit area is higher than the temperature of the first circuit area, the second control circuit reduces the absolute value of the second voltage.

[0018] The light receiving element is mounted on the automobile.

[0019] The distance measurement system according to the present disclosure includes an illumination device that irradiates an object with illumination light, and a light receiving element that receives reflected light from the object irradiated with the illumination light. The light receiving element includes a pixel region in which a plurality of photodiodes are arranged, a readout circuit region including a plurality of readout circuits each corresponding to the plurality of photodiodes, a first thermometer that is provided in the readout circuit region corresponding to a first circuit region, a second thermometer that is provided in the readout circuit region corresponding to a second circuit region, a first control circuit that applies a first voltage corresponding to the temperature of the first circuit region measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit region, and a second control circuit that applies a second voltage corresponding to the temperature of the second circuit region measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit region.

[0020] The lighting device and the light receiving element are mounted on a vehicle.

[0021] The pixel area and the readout circuit area have an elongated shape with a long side or a major axis, and distance measurement is performed using reflected light obtained by scanning the detection target range in the direction of the short side or the minor axis of the elongated shape.

[0022] The pixel area and the readout circuit area detect the entire detection target range at once and perform distance measurement.

[0023] When the difference between the temperature of the first circuit area and the temperature of the second circuit area exceeds a first threshold, the first or second control circuit changes the absolute value of the first or second voltage.

[0024] When the temperature of the first circuit area is higher than the temperature of the second circuit area, the first control circuit reduces the absolute value of the first voltage, and when the temperature of the second circuit area is higher than the temperature of the first circuit area, the second control circuit reduces the absolute value of the second voltage.

[0025] The light receiving element according to this embodiment comprises a pixel region in which a plurality of photodiodes are arranged, a readout circuit region including a plurality of readout circuits each corresponding to one of the plurality of photodiodes, a signal processing circuit arranged adjacent to a first side of the readout circuit region and processing pixel signals from the readout circuit region, and a first thermometer and a second thermometer arranged on a second side opposite the first side of the readout circuit region, the first thermometer and the second thermometer being arranged between a plurality of pads formed at the end of the chip and the readout circuit region. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a block diagram showing an example of the configuration of an embodiment of a ranging system to which the present technology is applied. [Figure 2] FIG. 2 is a block diagram illustrating an example of the configuration of an imaging unit. [Figure 3] FIG. 2 is a circuit diagram showing an example of the configuration of one pixel circuit arranged in a pixel circuit region. [Figure 4] FIG. 1 is a perspective view showing an example of the configuration of a light receiving element made up of a plurality of stacked semiconductor chips. [Figure 5] FIG. 2 is a schematic cross-sectional view showing a configuration example of a pixel circuit. [Figure 6A] FIG. 2 is a schematic plan view showing an example of the configuration of a first chip. [Figure 6B] FIG. 3 is a schematic plan view showing an example of the configuration of a second chip. [Figure 7] 6 is a graph showing an example of the operation of a SPAD according to the present technology. [Figure 8] 10 is a flowchart showing an example of a feedback control operation of a light receiving element according to the present technology. [Figure 9A] FIG. 1 is a schematic diagram showing an example of the configuration of a distance measuring system operating in a scan mode. [Figure 9B] FIG. 1 is a schematic diagram showing an example of the configuration of a ranging system operating in an array mode. [Figure 10] 1 is a block diagram showing a schematic configuration example of a vehicle control system that is an example of a mobile object control system to which the technology according to the present disclosure can be applied. [Figure 11] FIG. 3 is a diagram showing an example of an installation position of an imaging unit. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment. The drawings are schematic or conceptual, and the proportions of the various parts are not necessarily the same as those in reality. In the specification and drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0028] Figure 1 is a block diagram showing an example of the configuration of an embodiment of a ranging system to which the present technology is applied. The ranging system 11 is a system that captures a distance image using, for example, the ToF method. Here, the distance image is an image that detects the depth distance from the ranging system 11 to a subject for each pixel and is composed of distance pixel signals based on the detected distances.

[0029] The distance measurement system 11 includes an illumination device 21 and an imaging device 22. The illumination device 21 includes an illumination control unit 31 and a light source 32. The illumination control unit 31 controls the pattern in which the light source 32 emits light in accordance with the control of a control unit 42 of the imaging device 22. Specifically, the illumination control unit 31 controls the pattern in which the light source 32 emits light in accordance with an illumination code included in an illumination signal supplied from the control unit 42. For example, the illumination code consists of two values, 1 (High) and 0 (Low), and the illumination control unit 31 turns on the light source 32 when the illumination code value is 1 and turns off the light source 32 when the illumination code value is 0.

[0030] The light source 32 emits light in a predetermined wavelength range under the control of the illumination control unit 31. The light source 32 is, for example, an infrared laser diode. The type of light source 32 and the wavelength range of the irradiated light can be set arbitrarily depending on the application of the distance measurement system 11, etc.

[0031] The imaging device 22 is a device that receives the reflected light that is emitted from the lighting device 21 (illumination light) and reflected by the subjects 12 and 13, etc. The imaging device 22 includes a light receiving element 41, a control unit 42, a display unit 43, and a storage unit 44.

[0032] The light receiving element 41 includes a lens 51, a pixel circuit region 71, and a signal processing circuit 80. The lens 51 focuses incident light onto the light receiving surface of the pixel circuit region 71. The lens 51 may have any configuration, and may be formed, for example, by a group of multiple lenses. The pixel circuit region 71 is configured by arranging multiple pixel circuits two-dimensionally in a matrix. Each pixel includes, for example, one SPAD and a readout circuit provided corresponding to the SPAD. When SPADs are miniaturized, one readout circuit may be shared by multiple SPADs.

[0033] The pixel circuit area 71 receives reflected light from the subjects 12, 13, etc. under the control of the control unit 42, and supplies the resulting pixel signal to the signal processing circuit 80. This pixel signal represents a digital count value that counts the time from when the illumination device 21 emits light to when the pixel circuit area 71 receives the light. A light emission timing signal that indicates the timing at which the light source 32 emits light is also supplied from the control unit 42 to the pixel circuit area 71.

[0034] The signal processing circuit 80 processes pixel signals supplied from the pixel circuit region 71 under the control of the control unit 42. For example, the signal processing circuit 80 detects the distance to the subject for each pixel based on the pixel signals supplied from the pixel circuit region 71 and generates a distance image indicating the distance to the subject for each pixel. Specifically, the signal processing circuit 80 acquires the time (count value) from when the light source 32 emits light to when each pixel in the pixel circuit region 71 receives the light multiple times (e.g., thousands to tens of thousands of times) for each pixel. The signal processing circuit 80 creates a histogram corresponding to the acquired time. Then, by detecting peaks in the histogram, the signal processing circuit 80 determines the time it takes for the light emitted from the light source 32 to be reflected by the subject 12 or 13 and return. Furthermore, the signal processing circuit 80 performs a calculation to determine the distance to the object based on the determined time and the speed of light. The signal processing circuit 80 supplies the generated distance image to the control unit 42.

[0035] The control unit 42 is configured with a control circuit and a processor, such as an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor). The control unit 42 controls the illumination control unit 31 and the light receiving element 41. Specifically, the control unit 42 supplies an irradiation signal to the illumination control unit 31 and a light emission timing signal to the light receiving element 41. The light source 32 emits irradiation light in response to the irradiation signal. The light emission timing signal may be the irradiation signal supplied to the illumination control unit 31. The control unit 42 also supplies the distance image acquired from the light receiving element 41 to the display unit 43 and causes the display unit 43 to display the distance image. The control unit 42 also stores the distance image acquired from the light receiving element 41 in the memory unit 44. The control unit 42 also outputs the distance image acquired from the light receiving element 41 to an external device. The display unit 43 is configured with a panel display device, such as a liquid crystal display device or an organic EL (Electro Luminescence) display device.

[0036] 2 is a block diagram showing an example configuration of the light receiving element 41. The light receiving element 41 includes a pixel circuit region 71, a peripheral circuit 70, a signal processing circuit 80, and a transmission unit 79. The peripheral circuit 70 includes a SPAD control unit 72, a control unit 73, a PLL (Phase Locked Loop) 74, a clock generation unit 75, a reference current source 76, a thermometer 77, and a light emission timing control unit 78.

[0037] As described above, the pixel circuit region 71 includes a plurality of SPADs arranged two-dimensionally in a matrix and a readout circuit provided corresponding to each SPAD. Note that the configuration of the pixel circuit region 71 will be described in more detail later.

[0038] The SPAD control unit 72 controls the operation of the pixel circuit region 71 based on instructions from the control unit 73. The control unit 73 controls each component of the light receiving element 41. The control unit 73 also has a function of communicating with an external device via a terminal COM using, for example, I2C. The PLL 74 operates based on an input clock supplied via a terminal CKIN. The clock generation unit 75 generates one or more clock signals used in the light receiving element 41. The reference current source 76 generates one or more reference currents used in the light receiving element 41. The thermometer 77 detects the temperature of the light receiving element 41. The light emission timing control unit 78 controls the light emission timing based on a light emission trigger signal supplied via a terminal TRGIN. The light emission timing control unit 78 generates a light emission trigger signal, supplies this light emission trigger signal to a signal processing circuit 80, and outputs this light emission trigger signal via a terminal TRGOUT. The signal processing circuit 80 generates a depth image based on the detection results in the pixel circuit region 71. The control signals input via the terminals COM, CKIN, and TRGIN are supplied from the control unit 42 in Fig. 1. The signals output via the terminals DOUT and TRGOUT are output to the control unit 42.

[0039] The signal processing circuit 80 has a TDC (Time to Digital Converter) 81, a histogram generation unit 82, and a processing unit 83. The TDC 81 converts the light reception timing into a digital value based on the detection result in the pixel circuit region 71. The histogram generation unit 82 generates a histogram based on the digital value obtained by the TDC 81. The processing unit 83 performs various processes based on the histogram generated by the histogram generation unit 82. For example, the processing unit 83 performs FIR (Finite Impulse Response) filtering, echo determination, depth value (distance value) calculation, peak detection, and the like.

[0040] The transmitter 79 outputs the depth image generated by the signal processing circuit 80 via a terminal DOUT as, for example, serial data. The interface of the transmitter 79 can be, for example, MIPI (Mobile Industry Processor Interface).

[0041] 3 is a circuit diagram showing an example of the configuration of one pixel circuit 280 arranged in the pixel circuit region 71. The pixel circuit 280 includes a resistive element 281, a SPAD 282, an inverter circuit 283, and a transistor 284. Note that the resistive element 281, the inverter circuit 283, and the transistor 284 other than the SPAD 282 will hereinafter also be referred to as a readout circuit 290.

[0042] The cathode of the SPAD 282 is connected to one end of the resistor element 281 via a junction 285, and is connected to the power supply line of the excess bias voltage VEX via the resistor element 281. The cathode of the SPAD 282 is also connected to the input terminal of the inverter circuit 283 and the drain of the transistor 284. The anode of the SPAD 282 is connected to the power supply line of the bias voltage VSPAD.

[0043] The SPAD 282 waits for the incidence of a photon with a reverse bias exceeding the breakdown voltage VBD applied. When a photon is incident on the SPAD 282, electrons generated by photoelectric conversion in the SPAD 282 are amplified by avalanche multiplication. A current flows all at once due to this avalanche breakdown, changing the cathode voltage Vs of the SPAD 282 and inverting the output signal of the inverter circuit 283. In this way, the SPAD 282 can detect the incidence of a single photon. The electron multiplication operation that starts from the arrival time of the photon is called Geiger mode.

[0044] One end of the resistor element 281 is connected to the power supply line of the excess bias voltage VEX. The other end of the resistor element 281 is connected to the cathode of the SPAD 282, the input terminal of the inverter circuit 283, and the drain of the transistor 284. This allows the excess bias voltage VEX to be supplied to the cathode of the SPAD 282 via the resistor element 281. The resistor element 281 reduces the cathode voltage Vs when the SPAD 282 undergoes avalanche breakdown. Note that the resistor element 281 may be a quenching resistor formed of a P-type MOSFET that operates in the saturation region.

[0045] The drain of the transistor 284 is connected to the cathode of the SPAD 282, the input terminal of the inverter circuit 283, and the resistor element 281. The source of the transistor 284 is connected to the ground (GND). A gating control signal GAT is supplied to the gate of the transistor 284 from the control unit 42 in FIG. 1. The transistor 284 is formed of, for example, an N-type MOSFET.

[0046] In Geiger mode, the bias voltage VSPAD is approximately equal to the breakdown voltage VBD of the SPAD 282, and is, for example, a negative bias voltage of −20 V. The excess bias voltage VEX is a voltage that is added to the breakdown voltage VBD to enable the SPAD 282 to detect photons. The excess bias voltage VEX is, for example, a positive bias voltage of +3 V. As a result, during the charge or recharge operation in Geiger mode, a reverse bias voltage corresponding to the sum of the absolute values ​​of VBD and VEX (|VBD|+|VEX|) is applied to the SPAD 282. |VBD|+|VEX| is, for example, 23 V. The bias voltage VSPAD and the excess bias voltage VEX may be supplied from the SPAD control unit 72.

[0047] FIG. 4 is a perspective view showing an example of the configuration of a light receiving element 41 made up of multiple stacked semiconductor chips. As shown in FIG. 4, the light receiving element 41 is made up of two stacked semiconductor chips CH1 and CH2. The first chip CH1 has a pixel region 14. The pixel region 14 is an area in which multiple SPADs 282 are two-dimensionally arranged in a matrix on a semiconductor substrate. The second chip CH2 has a readout circuit region 15. The readout circuit region 15 is an area in which multiple readout circuits 290 are two-dimensionally arranged in a matrix on a semiconductor substrate.

[0048] The readout circuit region 15 is an area of ​​approximately the same size and shape as the pixel region 14, and faces and contacts with each other when the first chip CH1 and the second chip CH2 are stacked. Although the first chip CH1 and the second chip CH2 are spaced apart in FIG. 4, they are stacked on top of each other in the completed product of the light receiving element 41.

[0049] The readout circuits 290 in the readout circuit region 15 correspond to and face the SPADs 282 in the pixel region 14, and are electrically connected via junctions 285. For example, as shown in FIG. 3, in the pixel circuit 280, the readout circuits 290 correspond one-to-one with the SPADs 282, and are electrically connected to the SPADs 282 at the junctions 285. The junctions 285 directly bond wiring exposed on the surfaces of the chips CH1 and CH2, thereby connecting the cathode of the SPAD 282 on the first chip CH1 side to the resistor element 281, inverter circuit 283, and transistor 284 on the second chip CH2 side. In this way, the first chip CH1 and the second chip CH2 are directly bonded to each other by wiring (Cu-Cu bonding) with the readout circuits 290 and SPADs 282 facing each other, and the SPADs 282 and the corresponding readout circuits 290 are electrically connected to each other. The pixel region 14 and the readout circuit region 15 are electrically connected via a joint 285 to form a pixel circuit region 71 .

[0050] Although not shown, the light receiving element 41 may be configured as a single semiconductor chip. In this case, the pixel circuit region 71, the signal processing circuit 80, the transmitting unit 79, and the peripheral circuit 70 are formed in a flat state on the surface of the single semiconductor chip.

[0051] 5 is a schematic cross-sectional view showing an example of the configuration of the pixel circuit 280. The light receiving element 41 according to this embodiment is composed of a first chip CH1 and a second chip CH2 that are stacked. In the first chip CH1, a sensor substrate 341, a sensor wiring layer 342, a logic wiring layer 343, and a logic circuit substrate 344 are stacked.

[0052] The sensor substrate 341 is, for example, a semiconductor substrate using single crystal silicon containing p-type or n-type impurities. The sensor substrate 341 is provided with a SPAD 282 for each pixel circuit 280. In FIG. 5, the front surface of the sensor substrate 341 is a light-receiving surface that receives light L1, and a sensor wiring layer 342 is provided on the back surface side opposite the light-receiving surface. In addition, a second chip CH2 is bonded to the first chip CH1 on the back surface side of the sensor substrate 341.

[0053] The sensor wiring layer 342 and the logic wiring layer 343 are provided with wiring (power supply lines) for supplying bias voltages VSPAD and VEX to be applied to the SPAD 282, or wiring for extracting electrons generated in the SPAD 282 from the sensor substrate 341.

[0054] The SPAD 282 is provided on the sensor substrate 341. The SPAD 282 includes an n-type well 351, a p-type diffusion layer 352, an n-type diffusion layer 353, a hole accumulation layer 354, a pinning layer 355, and a high-concentration p-type diffusion layer 356. The SPAD 282 generates a depletion layer by applying a reverse bias to the pn junction between the p-type diffusion layer 352 and the n-type diffusion layer 353. When photons are incident on this depletion layer, the SPAD 282 undergoes avalanche breakdown. That is, the depletion layer at the pn junction between the p-type diffusion layer 352 and the n-type diffusion layer 353 functions as an avalanche multiplication region 357.

[0055] The n-type diffusion layer 353 is electrically connected to a contact 371 that supplies a bias voltage VSPAD to form an avalanche multiplication region 357. That is, the cathode of the SPAD 282 is electrically connected to the contact 371. The p-type diffusion layer 352 is electrically connected to a heavily doped p-type diffusion layer 356 that supplies a bias voltage VEX and to a contact 372 via a well 351 to form an avalanche multiplication region 357. That is, the anode of the SPAD 282 is electrically connected to the contact 372.

[0056] The hole accumulation layer 354 is a p-type diffusion layer that covers the side and bottom surfaces of the well 351 and accumulates holes. The hole accumulation layer 354 is also electrically connected to the contact 372 (anode of the SPAD 282) to enable bias adjustment. This strengthens the hole concentration in the hole accumulation layer 354 and strengthens the pinning including the pinning layer 355, thereby making it possible to suppress, for example, the generation of dark current.

[0057] The pinning layer 355 is a high-concentration p-type diffusion layer (p+) formed on the surface (the back surface of the sensor substrate 341 or the side surface in contact with the insulating film 362) outside the hole accumulation layer 354, and similar to the hole accumulation layer 354, for example, suppresses the generation of dark current.

[0058] The high-concentration p-type diffusion layer 356 is a high-concentration p-type diffusion layer (p++) formed in the vicinity of the surface of the sensor substrate 341 so as to surround the outer periphery of the well 351, and is used for connection with a contact 372 for electrically connecting the hole accumulation layer 354 to the anode of the SPAD 282.

[0059] The avalanche multiplication region 357 is a depletion layer region generated by a reverse bias voltage applied to the pn junction between the n-type diffusion layer 353 and the p-type diffusion layer 352. The avalanche multiplication region 357 undergoes avalanche breakdown in response to a single photon incident on the SPAD 282, and avalanche multiplication of electrons (e-) is performed.

[0060] Furthermore, an inter-pixel isolation portion 363 having a double structure made of a metal film 361 and an insulating film 362 is provided between adjacent SPADs 282. Adjacent SPADs 282 are insulated and separated by the inter-pixel isolation portion 363. The inter-pixel isolation portion 363 is formed to penetrate the sensor substrate 341 from the rear surface to the front surface. That is, the inter-pixel isolation portion 363 has a full trench isolation structure.

[0061] The metal film 361 is formed of a metal (for example, tungsten) that reflects light. The insulating film 362 is formed of an insulating film such as a silicon oxide film. For example, the inter-pixel isolation portion 363 is formed by embedding the metal film 361 in the sensor substrate 341 so that the surface of the metal film 361 is covered with the insulating film 362. The inter-pixel isolation portion 363 electrically and optically isolates adjacent SPADs 282.

[0062] The sensor wiring layer 342 is provided with contacts 371 to 373, metal wirings 374 to 376, contacts 377 to 379, and metal pads 380 to 382.

[0063] The contact 371 connects the n-type diffusion layer 353 and a metal wiring 374. The contact 372 connects the high-concentration p-type diffusion layer 356 and a metal wiring 375. The contact 373 connects the metal film 361 and a metal wiring 376.

[0064] The metal wiring 374 is formed, for example, wider than the avalanche multiplication region 357 so as to cover at least the avalanche multiplication region 357. As a result, the metal wiring 374 reflects light that has passed through the SPAD 282 back to the SPAD 282. This leads to an improvement in photon detection efficiency (PDE).

[0065] The metal wiring 375 is provided, for example, to surround the outer periphery of the metal wiring 374, and overlaps the high-concentration p-type diffusion layer 356 in a plan view seen from the incident direction of the light L1 (Z direction). The metal wiring 376 is provided, for example, at the four corners of the SPAD 282 and connected to the metal film 361.

[0066] The contact 377 connects the metal wiring 374 and the metal pad 380. The contact 378 connects the metal wiring 375 and the metal pad 381. The contact 379 connects the metal wiring 376 and the metal pad 382.

[0067] The metal pads 380-382 are bonded to metal pads 401-403 provided on the logic wiring layer 343. The metal pads 380-382 and the metal pads 401-403 are formed of a metal such as copper, and are electrically connected to each other by being electrically and mechanically bonded (Cu-Cu bonding). The metal pads 380-382 and the metal pads 401-403 bonded in this manner function as the bonding portion 285 in FIG. 3.

[0068] The logic wiring layer 343 is provided with electrode pads 391 to 393, an insulating layer 394, contacts 395 to 400, and metal pads 401 to 403.

[0069] The electrode pads 391 to 393 are each used for connection to the logic circuit board 344. The insulating layer 394 insulates the electrode pads 391 to 393 from one another.

[0070] Contacts 395 and 396 connect between electrode pad 391 and metal pad 401. Contacts 397 and 398 connect between electrode pad 392 and metal pad 402. Contacts 399 and 400 connect between electrode pad 393 and metal pad 403.

[0071] Metal pad 401 is bonded to metal pad 380 , metal pad 402 is bonded to metal pad 381 , and metal pad 303 is bonded to metal pad 382 .

[0072] With this wiring structure, the electrode pad 391 is connected to the n-type diffusion layer 353 via the contacts 395 and 396, the metal pads 401 and 380, the contact 377, the metal wiring 374, and the contact 371. Therefore, in the SPAD 282, when the bias voltage VSPAD is applied to the electrode pad 391 from the logic circuit 410 of the logic circuit board 344, it is applied to the n-type diffusion layer 353 via the metal pads 401 and 380, etc.

[0073] Furthermore, the electrode pad 392 is connected to the high-concentration p-type diffusion layer 356 via contacts 397 and 398, metal pads 402 and 381, contact 378, metal wiring 375, and contact 372. Therefore, in the SPAD 282, when a bias voltage VEX is applied to the electrode pad 392 from the logic circuit 410 of the logic circuit board 344, it is applied to the high-concentration p-type diffusion layer 356 via the metal pads 402 and 381, etc. In this way, the logic circuit 410 of the logic circuit board 344 can apply the bias voltages VSPAD and VEX to the anode (p-type diffusion layer 352) and cathode (n-type diffusion layer 353) of the SPAD 282, respectively.

[0074] Furthermore, the electrode pad 393 is connected to the metal film 361 via contacts 399 and 400, metal pads 403 and 382, ​​contact 379, metal wiring 376, and contact 373. Therefore, in the SPAD 282, the bias voltage supplied to the electrode pad 393 from the logic circuit board 344 is applied to the metal film 361.

[0075] The logic circuit board 344 is provided with a logic circuit 410. The logic circuit board 344 is, for example, a semiconductor substrate using silicon single crystal containing p-type or n-type impurities. The logic circuit board 344 is provided on the back surface side of the sensor board 341. The logic circuit 410 includes a bias voltage application circuit that applies bias voltages VSPAD and VEX to the SPAD 282, or a readout circuit 290.

[0076] In a plan view seen from the Z direction, the metal wiring 374 is formed wider than the avalanche multiplication region 357 so as to cover it. At the same time, the metal film 361 is formed to penetrate the sensor substrate 341. That is, the SPAD 282 is formed to have a reflective structure in which the metal wiring 374 and the metal film 361 surround the entire SPAD 282 except for the light incident surface. Reflecting the light L1 by the metal wiring 374 and the metal film 361 can suppress optical crosstalk and improve photon detection efficiency (PDE). Furthermore, the metal wiring 374 prevents the light L1 from entering the logic circuit 410, thereby suppressing noise contained in pixel signals of the logic circuit 410 and malfunction of the logic circuit 410.

[0077] An on-chip lens OCL is provided on the front surface (incident light) side of the sensor substrate 341. The on-chip lens OCL is provided to collect the incident light L1 onto the avalanche multiplication region 357. The on-chip lens OCL is formed using, for example, a transparent resin material.

[0078] 6A is a schematic plan view showing an example of the configuration of the first chip CH1. The first chip CH1 has a pixel region 14 provided on a semiconductor substrate. The pixel region 14 is configured by arranging a plurality of photodiodes (282 in FIG. 3) two-dimensionally in a matrix.

[0079] 6B is a schematic plan view showing an example of the configuration of the second chip CH2. The second chip CH2 includes, on a semiconductor substrate, a readout circuit area 15, a row driver 291, a column driver 292, a signal processing circuit (DSP) 80, a PLL 74, a transmitter 79, a PoR (Power on Reset) circuit 296, multiple thermometers Temp1 and Temp2, multiple bias circuits Bias1 and Bias2, and multiple bias control circuits LDO (Low Drop Out)1 and LDO2.

[0080] The readout circuit region 15 is configured by arranging a plurality of readout circuits (290 in FIG. 3) in a two-dimensional matrix. The readout circuits 290 are provided corresponding to the SPADs 282 in the pixel region 14, respectively.

[0081] The row driver 291 and the column driver 292 select any pixel circuit 280 from the pixel circuit region 71, and output a pixel signal from the readout circuit 290 of the selected pixel circuit 280 to the signal processing circuit 80. The row driver 291 and the column driver 292 are composed of logic circuits, and are controlled by control signals from the SPAD control unit 72 in FIG. 2.

[0082] The signal processing circuit 80 is configured to process pixel signals from the readout circuit 290, and is configured by, for example, a control circuit or processor such as an FPGA or DSP. The function of the signal processing circuit 80 is as described with reference to FIG.

[0083] The transmitter 79 outputs the image signal processed by the signal processing circuit 80 to the outside of the light receiving element 41 in accordance with the timing of the PLL 74. As described above, for example, MIPI is used for the transmitter 79. The PoR circuit 296 is a circuit that activates the light receiving element 41 in accordance with the timing of the PLL 74.

[0084] In the present disclosure, a plurality of thermometers Temp1 and Temp2 are provided near the readout circuit area 15. The thermometer Temp1 as a first thermometer is provided corresponding to the circuit area 15_1 as the first circuit area in the readout circuit area 15. The thermometer Temp2 as a second thermometer is provided corresponding to the circuit area 15_2 as the second circuit area in the readout circuit area 15.

[0085] The pixel region 14 and the readout circuit region 15 have an elongated shape with a long side or major axis in a plan view from the incident direction of light L1 (Z direction), and are, for example, approximately rectangular as shown in FIGS. 6A and 6B. The pixel region 14 has an elongated shape similar to the readout circuit region 15, and faces the readout circuit region 15 when the first chip CH1 and the second chip CH2 are bonded together. This allows each SPAD 282 in the pixel region 14 to correspond to each readout circuit 290 in the readout circuit region 15 and to be electrically connected to the corresponding readout circuit 290 via the bonding portion 285. Note that the pixel region 14 and the readout circuit region 15 may also have an approximately elliptical shape with a major axis or other elongated shapes.

[0086] For such an elongated readout circuit region 15, thermometers Temp1 and Temp2 are arranged in parallel along the long side or major axis, corresponding to circuit regions 15_1 and 15_2, respectively. Thermometer Temp1 corresponds to and is arranged adjacent to circuit region 15_1, so that thermometer Temp1 can measure the temperature of circuit region 15_1. Thermometer Temp2 corresponds to and is arranged adjacent to circuit region 15_2, so that thermometer Temp2 can measure the temperature of circuit region 15_2. This makes it possible to know the temperature distribution of the readout circuit region 15. The temperature distribution of the readout circuit region 15 is used for feedback control of bias voltages VSPAD and BEX. Details of the feedback control of bias voltages VSPAD and BEX will be described later.

[0087] The signal processing circuit 80 is also provided adjacent to one side of the readout circuit region 15. However, the thermometers Temp1 and Temp2 are provided on the opposite side of the signal processing circuit 80, sandwiching the readout circuit region 15 between them. That is, the signal processing circuit 80 is provided on one side of the readout circuit region 15, and the thermometers Temp1 and Temp2 are provided on the other side of the readout circuit region 15. This allows the thermometers Temp1 and Temp2 to be located near the bias control circuits LDO1 and LDO2 included in the input / output circuits, facilitating wiring connections between the thermometer Temp1 and the bias control circuit LDO1 and between the thermometer Temp2 and the bias control circuit LDO2. Furthermore, there is no need to provide the thermometers Temp1 and Temp2 between the readout circuit region 15 and the signal processing circuit 80, which also simplifies wiring connections between the readout circuit region 15 and the signal processing circuit 80.

[0088] The bias control circuit LDO1, which serves as a first control circuit, is a regulator circuit provided in the input / output circuit near the thermometer Temp1. The bias control circuit LDO1 is connected to a power supply input pad PAD1, and receives bias voltages VSPAD and VEX from the outside through the pad PAD1. The bias control circuit LDO1 controls the bias voltages VSPAD and VEX and supplies them to the SPAD282 corresponding to the circuit area 15_1.

[0089] Moreover, the bias control circuit LDO1 applies bias voltages VSPAD, BEX according to the temperature of the circuit area 15_1 measured by the thermometer Temp1 to the SPAD 282 corresponding to the readout circuit 290 in the circuit area 15_1. This allows the bias control circuit LDO1 to feedback-control the bias voltages VSPAD, VEX applied to the SPAD 282 corresponding to the circuit area 15_1 according to the temperature of the circuit area 15_1. Because the thermometer Temp1 is close to the bias control circuit LDO1, delays in the feedback control can be suppressed.

[0090] The bias control circuit LDO2 serving as the second control circuit is a regulator circuit provided in the input / output circuit near the thermometer Temp2. ​​The bias control circuit LDO2 is connected to the power supply input pad PAD2 and receives bias voltages VSPAD and VEX from the outside through the pad PAD2. The bias control circuit LDO2 controls the bias voltages VSPAD and VEX and supplies them to the SPAD282 corresponding to the circuit area 15_2.

[0091] Moreover, the bias control circuit LDO2 applies bias voltages VSPAD, BEX according to the temperature of the circuit area 15_2 measured by the thermometer Temp2 to the SPAD 282 corresponding to the readout circuit 290 in the circuit area 15_2. This allows the bias control circuit LDO1 to feedback control the bias voltages VSPAD, BEX to be applied to the SPAD 282 corresponding to the circuit area 15_2 according to the temperature of the circuit area 15_2. Because the thermometer Temp2 is close to the bias control circuit LDO2, delays in the feedback control can be suppressed.

[0092] The bias control circuits LDO1 and LDO2 are synchronized but can apply different bias voltages VSPAD and VEX to the circuit areas 15_1 and 15_2, respectively.

[0093] Here, the power supply input pads PAD1 and PAD2 are, for example, some of a plurality of pads provided at the chip edge of the second chip CH2. The plurality of pads are provided on the four sides of the chip, respectively, and are used for inputting and outputting signals to and from the outside, and for inputting and outputting signals for chip inspection. The power supply input pads PAD1 and PAD2 may be included in a group of a plurality of pads provided on one side of the chip.

[0094] The thermometers Temp1 and Temp2 are located near the bias control circuits LDO1 and LDO2. The thermometer Temp1 is disposed between the readout circuit area 15 and the pad PAD1, and the thermometer Temp2 is disposed between the readout circuit area 15 and the pad PAD2. This allows the thermometers Temp1 and Temp2 to quickly feed back the temperatures of the circuit areas 15_1 and 15_2 to the bias control circuits LDO1 and LDO2.

[0095] Furthermore, this technology provides multiple bias circuits Bias1 and Bias2. The bias circuit Bias1, which serves as a first bias circuit, supplies power to the row driver 291, the column driver 292, the thermometers Temp1 and Temp2, and the like, of the readout circuit region 15. The bias circuit Bias2, which serves as a second bias circuit, also supplies power to the row driver 291, the column driver 292, the thermometers Temp1 and Temp2, and the like, of the readout circuit region 15. By providing multiple bias circuits Bias1 and Bias2 within a single second chip CH2, even if one of the bias circuits Bias1 and Bias2 fails, the other can supply power to the second chip CH2. In other words, the multiple bias circuits Bias1 and Bias2 ensure redundancy in the power supply to the second chip CH2, making it robust against power supply failures.

[0096] The bias circuits Bias1 and Bias2 are also provided on the opposite side of the readout circuit region 15 from the signal processing circuit 80. For example, the bias circuit Bias1 is provided between the circuit region 15_1 and the pad PAD1 and is arranged near the thermometer Temp1. The bias circuit Bias2 is provided between the circuit region 15_2 and the pad PAD2 and is arranged near the thermometer Temp2.

[0097] Next, the operation of the light receiving element 41 will be described.

[0098] 7 is a graph showing an example of the operation of a SPAD 282 according to the present technology. Fig. 7 shows the operation of one SPAD 282. The vertical axis of the graph represents the current I flowing through one SPAD 282, and the horizontal axis represents the voltage V applied to that SPAD 282.

[0099] In Geiger mode, the voltage V applied to the SPAD 282 is a reverse bias voltage corresponding to the sum of the bias voltage VSPAD on the anode side and the bias voltage VEX on the cathode side of the SPAD 282 in Fig. 3. For example, when the bias voltage VSPAD is equal to the breakdown voltage VBD of the SPAD 282, a reverse bias voltage corresponding to the sum of the absolute value of VBD and the absolute value of VEX (|VBD| + |VEX|) is applied to the SPAD 282 as the voltage V. In other words, a reverse bias voltage that exceeds the breakdown voltage VBD by the excess bias voltage VEX is applied to the SPAD 282 and charged.

[0100] The SPAD 282 is charged to a reverse bias voltage of (|VBD|+|VEX|) in the dark state. At this time, since it is a dark state with no incident photons, avalanche breakdown does not occur in the SPAD 282, and the SPAD 282 is maintained in the first state St1. At this time, almost no current I flows through the SPAD 282.

[0101] Next, when a photon of the light L1 is incident on the SPAD 282, avalanche breakdown occurs in the avalanche multiplication region 357, and a current I flows suddenly due to avalanche multiplication. This causes the SPAD 282 to enter the second state St2.

[0102] When the voltage (reverse bias voltage) V applied to the SPAD 282 drops to the breakdown voltage VBD due to the flow of the current I, the avalanche multiplication stops. That is, the SPAD 282 enters the third state St3. The operation in which electrons generated by avalanche multiplication are discharged from the SPAD 282 and the voltage V returns to the breakdown voltage is also called the quenching operation.

[0103] After the quenching operation, when the excess bias voltage VEX is applied again to the SPAD 282, the SPAD 282 is recharged and returns to the first state St1, making it possible to detect photons.

[0104] In this way, the SPAD 282 repeatedly executes the first to third states St1, St2, and St3, including a recharge operation, avalanche multiplication operation by photons, a quenching operation, and another recharge operation. As a result, the SPAD 282 passes a large current I every time it detects a photon, thereby lowering the cathode voltage Vs in Fig. 3. As a result, the logic of the output signal 230 of the inverter circuit 283 is inverted every time the SPAD 282 detects a photon.

[0105] 3 can perform subsequent signal processing, such as generating a histogram, by counting inversions of the output signal 230. This allows the signal processing circuit 80 to generate a depth image and output it via MIPI 79.

[0106] FIG. 8 is a flowchart showing an example of a feedback control operation of the light receiving element 41 according to the present technology.

[0107] First, a threshold value for the temperature difference between the circuit areas 15_1 and 15_2 is set (S10). That is, a tolerance for temperature variation between the circuit areas 15_1 and 15_2 is set. The threshold value can be set by an operator via a user interface (not shown). As will be described later, when the temperature difference between the circuit areas 15_1 and 15_2 does not exceed the threshold value, the bias control circuits LDO1 and LDO2 apply the same bias voltages VSPAD and VEX to the read circuit area 15 without changing them. On the other hand, when the temperature difference between the circuit areas 15_1 and 15_2 exceeds the threshold value, the bias control circuits LDO1 and LDO2 adjust the bias voltages VSPAD and VEX applied to the circuit areas 15_1 and 15_2.

[0108] Next, the light receiving element 41 performs a photon detection operation (S20). The photon detection operation is as described with reference to FIG.

[0109] During the photon detection operation, the thermometers Temp1 and Temp2 measure the temperatures of the circuit areas 15_1 and 15_2 and calculate the temperature difference (S30). As a result, the thermometers Temp1 and Temp2 calculate the temperature variation between the circuit areas 15_1 and 15_2. This temperature variation calculation may be performed by a logic circuit (not shown) other than the thermometers Temp1 and Temp2. ​​Furthermore, the temperature information of the circuit areas 15_1 and 15_2 may be output to an external device (e.g., the control unit 42 in FIG. 1) of the light receiving element 41. In this case, for example, the control unit 42 calculates the temperature difference between the circuit areas 15_1 and 15_2 measured by the thermometers Temp1 and Temp2. ​​The calculated temperature difference is input to the light receiving element 41. As will be described later, the bias control circuits LDO1 and LDO2 control the bias voltages VSPAD and VEX in accordance with this temperature difference.

[0110] For example, if the temperature difference does not exceed the threshold set in step S10 (NO in S40), the bias control circuits LDO1 and LDO2 apply the same bias voltages VSPAD and VEX without changing them, and the SPAD 282 continues to detect photons.

[0111] On the other hand, if the temperature difference exceeds the threshold set in step S10 (YES in S40), the bias control circuits LDO1 and LDO2 change the bias voltages VSPAD and VEX. That is, the bias control circuit LDO1 or LDO2 changes the reverse bias voltage (|VBD|+|VEX|) applied to the circuit area 15_1 or 15_2.

[0112] For example, as the temperature rises, the SPAD 282 becomes more susceptible to avalanche breakdown. Therefore, when the temperature of the circuit region 15_1 becomes higher than the temperature of the circuit region 15_2 by a threshold value or more, the breakdown voltage VBD of the SPAD 282 in the pixel region 14 corresponding to the circuit region 15_1 decreases. In this case, the bias control circuit LDO1 changes the bias voltage VSPAD to match the breakdown voltage VBD of the SPAD 282 corresponding to the circuit region 15_1. As a result, the circuit region 15_1 reduces the reverse bias voltage (|VBD|+|VEX|) as the first voltage applied to the corresponding SPAD 282. The circuit region 15_2 does not need to change the reverse bias voltage (|VBD|+|VEX|) applied to the corresponding SPAD 282. As a result, in the pixel region 14 corresponding to the circuit region 15_1, malfunctions of the SPAD 282 and erroneous detection of photons can be suppressed, and the photon detection efficiency (PDE) of the entire light-receiving element 41 can be maintained.

[0113] On the other hand, for example, if the temperature of the circuit area 15_2 becomes higher than the temperature of the circuit area 15_1 by a threshold value or more, the breakdown voltage VBD of the SPAD 282 in the pixel area 14 corresponding to the circuit area 15_2 decreases. In this case, the bias control circuit LDO2 changes the bias voltage VSPAD to match the breakdown voltage VBD of the SPAD 282 corresponding to the circuit area 15_2. As a result, the circuit area 15_2 decreases the reverse bias voltage (|VBD|+|VEX|) as the second voltage applied to the corresponding SPAD 282. The circuit area 15_1 does not need to change the reverse bias voltage (|VBD|+|VEX|) applied to the corresponding SPAD 282. As a result, in the pixel area 14 corresponding to the circuit area 15_2, malfunctions of the SPAD 282 and erroneous detection of photons can be suppressed, and the photon detection efficiency (PDE) of the entire light-receiving element 41 can be maintained.

[0114] For example, if the light receiving element 41 is an automotive dToF, the distance between the light receiving element 41 and the detection target may vary significantly in a specific part of the pixel region 14 (e.g., a road or a building in the lower half) and not vary much in other parts (e.g., the sky in the upper half). In such a case, the temperature of the circuit region 15_1 in the lower half of the readout circuit region 15 may become extremely high compared to the temperature of the circuit region 15_2 in the upper half. In such a case, the bias control circuit LDO1 reduces the bias voltage VSPAD in accordance with the temperature difference between the circuit regions 15_1 and 15_2. This allows the photon detection efficiency (PDE) of the entire light receiving element 41 to be maintained.

[0115] The relationship between the temperature and the breakdown voltage VBD of the SPAD 282 may be measured in advance, or may be known in advance from the structure of the SPAD 282. Therefore, the relational expression between the temperature and the breakdown voltage VBD may be stored in advance in a memory (not shown) in the light receiving element 41 or the control unit 42.

[0116] Steps S20 to S50 are repeatedly executed until photon detection is completed (NO in S60). When photon detection is completed (YES in S60), photon detection by the light receiving element 41 is completed.

[0117] As described above, the photodetector 41 according to the present technology includes a plurality of thermometers Temp1 and Temp2 corresponding to the plurality of circuit regions 15_1 and 15_2 of the readout circuit region 15. The plurality of thermometers Temp1 and Temp2 can provide a temperature distribution in the readout circuit region 15. The bias control circuits LDO1 and LDO2 feedback-control the bias voltages VSPAD and VEX input from the pads PAD1 and PAD2, and apply the bias voltages VSPAD and VEX corresponding to the temperature distribution (temperature variation) in the readout circuit region 15 to the pixel regions 14 corresponding to the circuit regions 15_1 and 15_2. This allows the photodetector 41 to apply different reverse bias voltages (|VBD|+|VEX|) to the circuit regions 15_1 and 15_2, thereby compensating for variations in the breakdown voltage VBD of the SPAD 282 due to temperature variations and improving the photon detection efficiency (PDE). That is, the light receiving element 41 according to the present technology can suppress variations in the electrical characteristics of the pixel region 14 even when there is a temperature gradient in the readout circuit region 15, and can improve the photon detection efficiency (PDE).

[0118] In this embodiment, two thermometers Temp1 and Temp2 are arranged along the long side of one readout circuit area 15. Also, two bias control circuits LDO1 and LDO2 are arranged along the long side of one readout circuit area 15. However, the number and arrangement of the thermometers and bias control circuits are not limited to this. For example, three or more thermometers and three or more bias control circuits may be arranged along the long side of one readout circuit area 15. In this case, the number of thermometers and the number of bias control circuits should be equal. This makes it possible to obtain a more detailed temperature distribution (temperature variation) in the readout circuit area 15, and accordingly, it becomes possible to set the bias voltage more precisely.

[0119] For example, in the above example of an in-vehicle dToF, many thermometers are arranged along the lower half of the circuit area 15_1 where the distance changes drastically. A smaller number of thermometers may be arranged in the upper half of the circuit area 15_2 where the distance changes more slowly. This allows a more detailed temperature distribution (temperature variation) of the circuit area 15_1 to be obtained, and accordingly, it becomes possible to more precisely set the bias voltage to the pixel area 14 corresponding to the circuit area 15_1. This allows the photon detection efficiency (PDE) of the entire light receiving element 41 to be maintained at a higher level.

[0120] (Scan mode) 9A is a schematic diagram showing an example of the configuration of a distance measuring system 500 operating in scan mode. The distance measuring system 500 includes a light receiving element 41, a laser diode 510, a condenser lens 520, a half mirror 530, a polygon mirror 540, a light receiving lens 545, a drive unit 550, and a control unit 560.

[0121] The laser diode 510 generates laser light Le. The condenser lens 520 condenses the laser light Le and irradiates it onto the half mirror 530. The half mirror 530 reflects the laser light Le onto the polygon mirror 540. The polygon mirror 540 irradiates the laser light Le onto a scanning region SR within a scanning area AR, which is a detection target range. The scanning region SR is a portion of the entire scanning area AR, and the entire scanning area AR can be scanned by operating the polygon mirror 540. The polygon mirror 540 is operated by a driver 550.

[0122] Reflected light Lr from the scanning region SR in response to the laser light Le is transmitted from the polygon mirror 540 through the half mirror 530 and then irradiated onto the pixel region 14 of the light receiving element 41 via the light receiving lens 545. This allows the light receiving element 41 to detect the reflected light Lr from the scanning region SR and generate a depth image. The control unit 560 controls the entire distance measurement system 500.

[0123] For example, the pixel region 14 and readout circuit region 15 of the light receiving element 41 have an elongated shape, and distance measurement is performed using reflected light Lr obtained by scanning laser light Le along the short side or short diameter of the elongated shape. In this case, the scanning region SR may be, for example, a vertically elongated region extending from the ground to the sky. In this case, the light receiving element 41 detects the vertically elongated scanning region SR at once. For example, the light receiving element 41 detects reflected light Lr from the scanning region SR extending from the ground to the sky at once. In scan mode, the light receiving element 41 only captures the scanning region SR at a time, but can also capture the entire scanning area AR by scanning the scanning region SR horizontally. In this way, the distance measurement system 500 can obtain a depth image of the object OBJ in scan mode.

[0124] (Array Mode) 9B is a schematic diagram showing an example of the configuration of a distance measuring system 600 operating in array mode. The distance measuring system 600 includes a light receiving element 41, a laser diode 610, an irradiation lens 620, and a light receiving lens 645.

[0125] The laser diode 610 generates a laser beam Le. The illumination lens 620 illuminates the laser beam Le over the entire scanning area AR.

[0126] Reflected light Lr from the detection target range AR in response to the laser light is irradiated onto the pixel region 14 of the light receiving element 41 via the light receiving lens 645. As a result, the light receiving element 41 detects the reflected light Lr from the detection target range AR and generates a depth image.

[0127] In the array mode, the light receiving element 41 can detect and measure the distance to the entire detection target range AR at once. In this way, in the array mode, the distance measuring system 600 can obtain a depth image of the target object OBJ in a short time.

[0128] The light receiving element 41 according to the present technology may be used in either the scanning mode ranging system 500 or the array mode ranging system 600.

[0129] <Application to moving objects> The technology according to the present disclosure (the present technology) 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 moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0130] FIG. 10 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.

[0131] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 10, 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.

[0132] 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, a braking device for generating a braking force of the vehicle, etc.

[0133] 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 may 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.

[0134] 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.

[0135] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according 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.

[0136] 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.

[0137] 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 drivetrain 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 avoiding or mitigating collisions between vehicles, following based on the distance between vehicles, maintaining vehicle speed, warning of vehicle collisions, or warning of vehicle lane departure.

[0138] 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.

[0139] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12030 based on the information about the outside of 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 for the purpose of preventing glare, such as switching from high beams to low beams.

[0140] 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 information to passengers in the vehicle or to the outside of the vehicle. In the example of Fig. 10, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0141] FIG. 11 is a diagram showing an example of the installation position of the imaging unit 12031.

[0142] In FIG. 11, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0143] 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 at the front nose and the imaging unit 12105 provided at 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 at the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided at the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0144] 11 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, a bird's-eye view image of the vehicle 12100 viewed from above can be obtained.

[0145] At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera made up of multiple imaging elements, or may be an imaging element having pixels for phase difference detection.

[0146] For example, 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) based on the distance information obtained from the imaging units 12101 to 12104, 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 (for example, 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 automatic driving, which runs autonomously without relying on driver operation.

[0147] 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 the collision risk, which indicates the degree of 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 drivetrain control unit 12010.

[0148] 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 or not a pedestrian is present in the images captured by the image capturing units 12101 to 12104. The pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104, which are infrared cameras, and then performing pattern matching on a series of feature points that indicate the outline of an object to determine whether or not 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.

[0149] The above describes an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to, for example, the image capture unit 12031 of the above-described configuration.

[0150] The present technology can be configured as follows. (1) a pixel region in which a plurality of photodiodes are arranged; a readout circuit region including a plurality of readout circuits provided corresponding to the plurality of photodiodes, respectively; a first thermometer provided in correspondence with a first circuit area of ​​the readout circuit area; a second thermometer provided in correspondence with a second circuit area of ​​the readout circuit area; a first control circuit that applies a first voltage corresponding to the temperature of the first circuit area measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit area; a second control circuit that applies a second voltage corresponding to the temperature of the second circuit area measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit area. (2) the readout circuit area has an elongated shape with a long side or a major axis, and includes the first and second circuit areas arranged along the long side or the major axis; The light-receiving element according to (1), wherein the first and second thermometers are arranged along the long side or the major axis in correspondence with the first and second circuit regions. (3) a signal processing circuit provided adjacent to one side of the readout circuit area and configured to process pixel signals from the readout circuit area; The light-receiving element according to (1) or (2), wherein the first and second thermometers are provided on the opposite side of the signal processing circuit across the readout circuit region. (4) a first pad connected to the first control circuit; a second pad connected to the second control circuit; the first thermometer is disposed between the first circuit area and the first pad; The light receiving element according to (3), wherein the second thermometer is disposed between the second circuit region and the second pad. (5) a first bias circuit provided in correspondence with the first circuit area and supplying power to a driver in the readout circuit area; The light receiving element according to any one of (1) to (4), further comprising: a second bias circuit provided in correspondence with the second circuit area and supplying power to a driver in the readout circuit area. (6) a signal processing circuit provided adjacent to one side of the readout circuit area and configured to process pixel signals from the readout circuit area; The light-receiving element according to (5), wherein the first and second bias circuits are provided on the opposite side of the readout circuit region from the signal processing circuit. (7) a first pad connected to the first control circuit; a second pad connected to the second control circuit; the first bias circuit is disposed between the first circuit area and the first pad; The light receiving element according to (5) or (6), wherein the second bias circuit is disposed between the second circuit region and the second pad. (8) the first bias circuit is disposed adjacent to the first thermometer; The light receiving element according to any one of (5) to (7), wherein the second bias circuit is disposed in proximity to the second thermometer. (9) a first chip including the pixel region; A photodetector according to any one of (1) to (8), comprising a second chip including the readout circuit region and bonded to the first chip so that the readout circuit corresponding to the photodiode faces the second chip. (10) The light receiving element according to (9), wherein the pixel region has an elongated shape similar to that of the readout circuit region, and faces the readout circuit region when the first chip and the second chip are joined together. (11) A light receiving element described in any one of (1) to (10), wherein when the difference between the temperature of the first circuit area and the temperature of the second circuit area exceeds a first threshold, the first or second control circuit changes the absolute value of the first or second voltage. (12) When the temperature of the first circuit area is higher than the temperature of the second circuit area, the first control circuit reduces the absolute value of the first voltage; The light receiving element according to (11), wherein when the temperature of the second circuit area is higher than the temperature of the first circuit area, the second control circuit reduces the absolute value of the second voltage. (13) The light receiving element according to any one of (1) to (12), wherein the light receiving element is mounted on an automobile. (14) an illumination device that irradiates an object with irradiation light; a light receiving element that receives reflected light from the object onto which the irradiation light is irradiated, The light receiving element is a pixel region in which a plurality of photodiodes are arranged; a readout circuit region including a plurality of readout circuits provided corresponding to the plurality of photodiodes, respectively; a first thermometer provided in correspondence with a first circuit area of ​​the readout circuit area; a second thermometer provided in correspondence with a second circuit area of ​​the readout circuit area; a first control circuit that applies a first voltage corresponding to the temperature of the first circuit area measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit area; A distance measurement system comprising: a second control circuit that applies a second voltage corresponding to the temperature of the second circuit area measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit area. (15) The distance measuring system according to (14), wherein the lighting device and the light receiving element are mounted on a vehicle. (16) The pixel area and the readout circuit area have an elongated shape with a long side or a long diameter, and distance measurement is performed using the reflected light obtained by scanning the detection target range in the direction of the short side or the short diameter of the elongated shape. (17) The distance measurement system according to (14) or (15), wherein the pixel area and the readout circuit area detect the entire detection target range at once and perform distance measurement. (18) A ranging system according to any one of (14) to (17), wherein when the difference between the temperature of the first circuit area and the temperature of the second circuit area exceeds a first threshold, the first or second control circuit changes the absolute value of the first or second voltage. (19) When the temperature of the first circuit area is higher than the temperature of the second circuit area, the first control circuit reduces the absolute value of the first voltage; The distance measurement system according to (18), wherein when the temperature of the second circuit area is higher than the temperature of the first circuit area, the second control circuit reduces the absolute value of the second voltage. (20) a pixel region in which a plurality of photodiodes are arranged; a readout circuit region including a plurality of readout circuits provided corresponding to the plurality of photodiodes, respectively; a signal processing circuit provided adjacent to a first side of the readout circuit area, the signal processing circuit processing pixel signals from the readout circuit area; a first thermometer and a second thermometer provided on a second side of the readout circuit area opposite to the first side; Equipped with The first thermometer and the second thermometer are provided between a plurality of pads formed on an end of a chip and the readout circuit region.

[0151] The present disclosure is not limited to the above-described embodiments, 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. [Explanation of symbols]

[0152] 41 photodetector, CH1 first chip, CH2 second chip, 14 pixel area, 15 readout circuit area, 280 pixel circuit, 290 readout circuit, 70 peripheral circuit, 71 pixel circuit area, 80 signal processing unit, 79 transmitter, 281 resistor element, 282 SPAD, 283 inverter circuit, 284 transistor, 285 junction, 80 signal processing circuit, 74 PLL, 79 transmitter, 296 PoR circuit, Temp1, Temp2 thermometer, Bias1, Bias2 bias circuit, LDO1, LDO2 bias control circuit

Claims

1. a pixel region in which a plurality of photodiodes are arranged; a readout circuit area including a plurality of readout circuits provided corresponding to the plurality of photodiodes; a signal processing circuit provided on a first side of the readout circuit area and configured to process pixel signals from the readout circuit area; a first thermometer and a second thermometer provided on a second side of the readout circuit area opposite to the first side, The light receiving element, wherein the first thermometer and the second thermometer are provided between a plurality of pads formed on an end of the chip and the readout circuit region.

2. 2. The light-receiving element according to claim 1, wherein one readout circuit is provided in common for the plurality of photodiodes.

3. 2. The light receiving element according to claim 1, wherein the plurality of photodiodes and the plurality of readout circuits are provided in one-to-one correspondence.

4. the readout circuit area has an elongated shape with a long side or a major axis, and includes first and second circuit areas arranged along the long side or the major axis; The light-receiving element according to claim 1 , wherein the first and second thermometers are arranged along the long side or the major axis in correspondence with the first and second circuit regions.

5. a first control circuit disposed between the plurality of pads and the readout circuit area, the first control circuit applying a first voltage corresponding to the temperature of the first circuit area measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit area; 2. The light receiving element according to claim 1, further comprising: a second control circuit arranged between the plurality of pads and the readout circuit area, the second control circuit applying a second voltage corresponding to the temperature of the second circuit area measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit area.

6. The light receiving element according to claim 1 , further comprising first and second bias circuits located on opposite sides of the readout circuit area from the signal processing circuit and supplying power to a driver of the readout circuit area.

7. a first chip including the pixel region; 2. The light-receiving element according to claim 1, further comprising: a second chip including the readout circuit region and bonded to the first chip so that the readout circuits corresponding to the photodiodes face each other.

8. 8. The light-receiving element according to claim 7, wherein the pixel region has the same elongated shape as the readout circuit region, and faces the readout circuit region when the first chip and the second chip are joined together.

9. The light receiving element according to claim 1 , wherein the light receiving element is mounted on an automobile.

10. an illumination device that irradiates an object with irradiation light; a light receiving element that receives reflected light from the object onto which the irradiation light is irradiated, The light receiving element is a pixel region in which a plurality of photodiodes are arranged; a readout circuit area including a plurality of readout circuits provided corresponding to the plurality of photodiodes; a signal processing circuit provided on a first side of the readout circuit area and configured to process pixel signals from the readout circuit area; a first thermometer and a second thermometer provided on a second side of the readout circuit area opposite to the first side, the first thermometer and the second thermometer are provided between a plurality of pads formed at an end of the chip and the readout circuit region; Ranging system.

11. 11. The distance measuring system according to claim 10, wherein one readout circuit is provided in common for the plurality of photodiodes.

12. 11. The distance measuring system according to claim 10, wherein the plurality of photodiodes and the plurality of readout circuits are provided in one-to-one correspondence.

13. the readout circuit area has an elongated shape with a long side or a major axis, and includes first and second circuit areas arranged along the long side or the major axis; The distance measuring system according to claim 10 , wherein the first and second thermometers are arranged along the long side or the major axis so as to correspond to the first and second circuit areas.

14. a first control circuit disposed between the plurality of pads and the readout circuit area, the first control circuit applying a first voltage corresponding to the temperature of the first circuit area measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit area; 11. The ranging system of claim 10, further comprising: a second control circuit arranged between the plurality of pads and the readout circuit area, the second control circuit applying a second voltage corresponding to the temperature of the second circuit area measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit area.

15. The ranging system according to claim 10 , further comprising first and second bias circuits located on opposite sides of the readout circuit area from the signal processing circuit and supplying power to a driver in the readout circuit area.

16. a first chip including the pixel region; 11. The distance measuring system according to claim 10, further comprising: a second chip including the readout circuit region and bonded to the first chip so that the readout circuits corresponding to the photodiodes face each other.

17. 17. The distance measuring system according to claim 16, wherein the pixel region has an elongated shape similar to that of the readout circuit region, and faces the readout circuit region when the first chip and the second chip are joined together.

18. The distance measuring system according to claim 10 , wherein the lighting device and the light receiving element are mounted on a vehicle.

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