Photoelectric conversion apparatus and photoelectric conversion system

Abstract

To provide a photoelectric conversion device capable of solving a problem caused in a standby state where a charging means and a power source are separated.SOLUTION: An avalanche photodiode including a first terminal and a second terminal; a charge unit configured to control electrical connection between the first terminal and a first power supply; a second power supply electrically connected to the second terminal; An amplitude conversion unit configured to reduce an amplitude of a voltage output from the first terminal by avalanche multiplication of the avalanche photodiode, and a voltage holding unit connected between the first terminal and the amplitude conversion unit and configured to hold the voltage of the first terminal so that the voltage of the first terminal does not exceed a predetermined value.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion device and a photoelectric conversion system having the same. [Background technology]

[0002] Photoelectric conversion devices are known that have pixels each containing multiple avalanche photodiodes (APDs). Each pixel can detect light at the single-photon level by utilizing the avalanche multiplication that occurs when a photon strikes the APD, generating photocharges.

[0003] Patent Document 1 describes a photodetector that has a charging means provided between the cathode of an APD and a supply wiring for a power supply voltage, and that switches between a charging state and a standby state in which it waits for the incidence of photons. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-123847 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the phenomenon that occurs in a standby state in which the charging means and the power source are disconnected is not sufficiently considered.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photoelectric conversion device that can solve the problems that arise in a standby state in which the charging means is disconnected from the power source. [Means for solving the problem]

[0007] One aspect of the present invention is a photoelectric conversion device comprising: an avalanche photodiode having a first terminal and a second terminal; charging means for controlling the electrical connection between the first terminal and a first power supply; a second power supply electrically connected to the second terminal; amplitude conversion means connected between the first terminal and the charging means for reducing the amplitude of a voltage output from the first terminal by avalanche multiplication of the avalanche photodiode; and voltage holding means connected between the first terminal and the amplitude conversion means for holding the voltage of the first terminal so that the voltage of the first terminal does not exceed a predetermined value. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a photoelectric conversion device that can solve the problems that arise in a standby state in which the charging means is disconnected from the power source. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a configuration of a photoelectric conversion device according to an embodiment. [Figure 2] 3A and 3B are diagrams illustrating the arrangement of sensor substrates in a photoelectric conversion device according to an embodiment. [Figure 3] 3A and 3B are diagrams illustrating a configuration of a circuit board of a photoelectric conversion device according to an embodiment. [Figure 4] FIG. 10 is a block diagram of one pixel of a sensor substrate and a circuit substrate of a comparative example according to an embodiment. [Figure 5] 3A and 3B are schematic diagrams illustrating driving of pixel circuits in a photoelectric conversion device according to an embodiment. [Figure 6] 2 is a configuration example of a pixel circuit of the photoelectric conversion device according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing the relationship between the clock signal, the timing at which photons are incident, the voltage at the cathode terminal, and the current flowing due to the voltage control means in the comparative example and the first embodiment. [Figure 8] FIG. 10 is a diagram showing the relationship between the reverse current and the cathode voltage according to the comparative example and the first embodiment. [Figure 9]FIG. 2 is a configuration diagram of a pixel circuit of the photoelectric conversion device according to the first embodiment. [Figure 10] FIG. 10 is a configuration diagram of a pixel circuit of a photoelectric conversion device according to a second embodiment. [Figure 11] FIG. 10 is a configuration diagram of a pixel circuit of a photoelectric conversion device according to a third embodiment. [Figure 12] FIG. 10 is a diagram illustrating a problem caused by a leakage current according to the third embodiment. [Figure 13] FIG. 10 is a schematic plan view showing the configuration of a charging unit, a waveform shaping unit, and a voltage control unit according to a third embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view taken along the line XX′ in FIG. [Figure 15] FIG. 4 is a schematic plan view showing each wiring layer included in the second wiring structure. [Figure 16] 10 is a configuration example of a pixel circuit of a photoelectric conversion device according to a fourth embodiment. [Figure 17] 10 is a configuration example of a pixel circuit of a photoelectric conversion device according to a fifth embodiment. [Figure 18] FIG. 10 is a diagram showing the relationship between a clock signal, the timing at which photons are incident, the voltage at the cathode terminal, and the voltage at node A according to the fifth embodiment. [Figure 19] FIG. 10 is a schematic plan view showing the configuration of an amplitude conversion means and voltage control means 604 according to a fifth embodiment. [Figure 20] FIG. 20 is a schematic cross-sectional view taken along the line XX' in FIG. [Figure 21] 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a sixth embodiment. [Figure 22] 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a seventh embodiment. [Figure 23] FIG. 10 is a block diagram of one pixel of a sensor substrate, a first circuit substrate, and a second circuit substrate of a photoelectric conversion device according to a second embodiment. [Figure 24] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a third embodiment. [Figure 25] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fourth embodiment. [Figure 26]FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fifth embodiment. [Figure 27] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a sixth embodiment. [Figure 28] FIG. 13 is a functional block diagram of a photoelectric conversion system according to a seventh embodiment. [Figure 29] FIG. 13 is a functional block diagram of a photoelectric conversion system according to an eighth embodiment. [Figure 30] FIG. 13 is a functional block diagram of a photoelectric conversion system according to a ninth embodiment. [Figure 31] FIG. 20 is a functional block diagram of a photoelectric conversion system according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments shown below are intended to embody the technical concept of the present invention and are not intended to limit the present invention. The size and positional relationship of components shown in each drawing may be exaggerated for clarity. In the following description, the same components may be designated by the same reference numerals and their description may be omitted.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, terms indicating specific directions or positions (for example, "upper," "lower," "right," "left," and other terms including these terms) will be used as necessary. The use of these terms is intended to facilitate understanding of the embodiments with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention.

[0012] In this specification, a planar view refers to a view from a direction perpendicular to the light incident surface of the semiconductor layer. A cross-sectional view refers to a surface perpendicular to the light incident surface of the semiconductor layer. When the light incident surface of the semiconductor layer is a rough surface when viewed microscopically, the planar view is defined based on the light incident surface of the semiconductor layer when viewed macroscopically.

[0013] In the following description, the anode of the avalanche photodiode (APD) is set to a fixed potential, and a signal is extracted from the cathode side. Therefore, the first conductivity type semiconductor region having majority carriers of charges of the same polarity as the signal charge is an N-type semiconductor region, and the second conductivity type semiconductor region having majority carriers of charges of a polarity opposite to that of the signal charge is a P-type semiconductor region. The present invention also applies when the cathode of the APD is set to a fixed potential and a signal is extracted from the anode side. In this case, the first conductivity type semiconductor region having majority carriers of charges of the same polarity as the signal charge is a P-type semiconductor region, and the second conductivity type semiconductor region having majority carriers of charges of a polarity opposite to that of the signal charge is an N-type semiconductor region. While the following description focuses on a case where one node of the APD is set to a fixed potential, the potentials of both nodes may fluctuate.

[0014] In this specification, when the term "impurity concentration" is used simply, it means the net impurity concentration minus the amount compensated for by impurities of the opposite conductivity type. In other words, "impurity concentration" refers to the NET doping concentration. A region where the P-type doped impurity concentration is higher than the N-type doped impurity concentration is a P-type semiconductor region. Conversely, a region where the N-type doped impurity concentration is higher than the P-type doped impurity concentration is an N-type semiconductor region.

[0015] In the following embodiments, the connection between elements of a circuit may be described. In this case, even if another element is interposed between the elements of interest, the elements of interest are treated as being connected to each other unless otherwise specified. For example, assume that element A is connected to one node of a capacitive element C having multiple nodes, and element B is connected to the other node. Even in such a case, element A and element B are treated as being connected to each other unless otherwise specified.

[0016] FIG. 1 is a diagram showing the configuration of a stacked-type photoelectric conversion device 100. The photoelectric conversion device 100 is configured by stacking and electrically connecting two substrates: a sensor substrate 11 (first substrate) and a circuit substrate 21 (second substrate). The sensor substrate 11 has a first semiconductor layer having a photoelectric conversion unit 102 (described later) and a first wiring structure. The circuit substrate 21 has a second semiconductor layer having circuits such as a signal processing unit 103 (described later) and a second wiring structure. The photoelectric conversion device 100 is configured by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in this order. The photoelectric conversion device described in each embodiment is a back-illuminated photoelectric conversion device in which light is incident from the second surface of the first semiconductor layer and a circuit substrate is disposed on the first surface of the eleventh semiconductor layer.

[0017] In the following description, the sensor substrate 11 and the circuit substrate 21 are described as diced chips, but are not limited to chips. For example, each substrate may be a wafer. Also, each substrate may be stacked in the wafer state and then diced, or each chip may be stacked and bonded after being chipped from the wafer state.

[0018] The sensor substrate 11 has a pixel region 12 arranged thereon, and the circuit substrate 21 has a circuit region 22 arranged thereon for processing signals detected in the pixel region 12 .

[0019] 2 is a diagram showing an example of the arrangement of the sensor substrate 11. Pixels 101, each having a photoelectric conversion unit 102 including an APD, are arranged in a two-dimensional array in a plan view to form a pixel region 12.

[0020] The pixel 101 is typically a pixel for forming an image, but when used for TOF (Time of Flight), it does not necessarily have to form an image. That is, the pixel 101 may be a pixel for measuring the time and amount of light that arrives.

[0021] 3 is a configuration diagram of the circuit board 21. It has a signal processing unit 103 that processes signals output from the photoelectric conversion unit 102 in FIG. 2, a readout circuit 112, a control pulse generation unit 115, a horizontal scanning circuit unit 111, a signal line 113, and a vertical scanning circuit unit 110.

[0022] The photoelectric conversion unit 102 in FIG. 2 and the signal processing unit 103 in FIG. 3 are electrically connected via connection wiring provided for each pixel.

[0023] The vertical scanning circuit unit 110 receives a control pulse supplied from the control pulse generating unit 115 and supplies the control pulse to each pixel. The vertical scanning circuit unit 110 uses logic circuits such as a shift register and an address decoder.

[0024] The signal output from the photoelectric conversion unit 102 of the pixel is processed by the signal processing unit 103. The signal processing unit 103 is provided with a counter, a memory, etc., and the memory holds digital values.

[0025] The horizontal scanning circuit unit 111 inputs a control pulse to the signal processing unit 103 to sequentially select each column in order to read out the signal from the memory of each pixel in which the digital signal is held.

[0026] A signal is output to the signal line 113 from the signal processing unit 103 of the pixel selected by the vertical scanning circuit unit 110 for the selected column.

[0027] The signal output to the signal line 113 is output via an output circuit 114 to a recording unit or a signal processing unit outside the photoelectric conversion device 100 .

[0028] 2, the photoelectric conversion units may be arranged one-dimensionally in the pixel region. The function of the signal processing unit does not necessarily need to be provided for each photoelectric conversion unit. For example, one signal processing unit may be shared by multiple photoelectric conversion units, and signal processing may be performed sequentially.

[0029] 2 and 3, a plurality of signal processing units 103 are arranged in a region overlapping the pixel region 12 in a planar view. A vertical scanning circuit unit 110, a horizontal scanning circuit unit 111, a readout circuit 112, an output circuit 114, and a control pulse generation unit 115 are arranged so as to overlap between an end of the sensor substrate 11 and an end of the pixel region 12 in a planar view. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12. The vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the readout circuit 112, the output circuit 114, and the control pulse generation unit 115 are arranged in a region overlapping the non-pixel region in a planar view.

[0030] Fig. 4 is an example of a block diagram including an equivalent circuit of the pixel of Fig. 2 and Fig. 3. Fig. 4 shows a block diagram of a pixel having a general APD.

[0031] In FIG. 4, the photoelectric conversion unit 102 having the APD 201 is provided on a sensor substrate 11, and the other members are provided on a circuit board 21.

[0032] The APD 201 generates charge pairs in response to incident light through photoelectric conversion. The APD 201 has a first terminal and a second terminal, with the first terminal connected to a first power supply and the second terminal connected to a second power supply. In FIG. 4, the first terminal of the APD 201 is the cathode and the second terminal is the anode. A voltage VL is supplied to the anode of the APD 201 from the second power supply. A voltage VH higher than the voltage VL supplied to the anode from the first power supply is supplied to the cathode of the APD 201. A reverse bias voltage is supplied to the anode and cathode so that the APD 201 performs avalanche multiplication. With this voltage supplied, the charge generated by the incident light undergoes avalanche multiplication, generating an avalanche current.

[0033] When a reverse bias voltage is supplied, there are two modes: a Geiger mode in which the anode and cathode are operated at a potential difference greater than the breakdown voltage, and a linear mode in which the anode and cathode are operated at a potential difference close to or less than the breakdown voltage.

[0034] An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). For example, the voltage VL is −30 V, and the voltage VH is 1 V to 3 V. The APD 201 may be operated in either linear mode or Geiger mode.

[0035] The quench element 202, which serves as charging means, is connected to a power supply that supplies voltage VH and the APD 201. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, suppressing the voltage supplied to the APD 201 and suppressing avalanche multiplication (quench operation). The quench element 202 also functions to return the voltage supplied to the APD 201 to voltage VH by passing a current equivalent to the voltage drop caused by the quench operation (recharge operation). In this way, the charging means has the function of controlling the voltage of the APD 201.

[0036] The signal processing unit 103 has a waveform shaping unit 210, a counter 211, and a selection circuit 212. In this specification, the signal processing unit 103 may have any one of the waveform shaping unit 210, the counter 211, and the selection circuit 212.

[0037] The waveform shaping unit 210 shapes the potential change at the cathode of the APD 201 obtained when photons are detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. While an example using one inverter as the waveform shaping unit 210 is shown in FIG. 4, a circuit in which multiple inverters are connected in series, or another circuit having a waveform shaping effect, may also be used.

[0038] The counter 211 counts the number (number of times) of pulse signals output from the waveform shaping unit 210 and holds the count value. When a control pulse pRES is supplied via the drive line 213, the signal held in the counter 211 is reset.

[0039] A control pulse pSEL is supplied to the selection circuit 212 from the vertical scanning circuit unit 110 in Fig. 3 via a drive line 214 (not shown in Fig. 3) in Fig. 4, and switches between electrical connection and disconnection between the counter 211 and the signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal.

[0040] The electrical connection may be switched by disposing a switch such as a transistor between the quench element 202 and the APD 201 or between the photoelectric conversion unit 102 and the signal processing unit 103. Similarly, the supply of the voltage VH or the voltage VL to the photoelectric conversion unit 102 may be electrically switched using a switch such as a transistor.

[0041] In this embodiment, a configuration using the counter 211 has been described. However, instead of the counter 211, the photoelectric conversion device 100 may be configured to acquire pulse detection timing using a time-to-digital converter (hereinafter referred to as TDC) and a memory. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 is converted into a digital signal by the TDC. To measure the timing of the pulse signal, a control pulse pREF (reference signal) is supplied to the TDC from the vertical scanning circuit unit 110 in FIG. 1 via a drive line. The TDC acquires, as a digital signal, a signal obtained by converting the input timing of the signal output from each pixel via the waveform shaping unit 210 into a relative time based on the control pulse pREF.

[0042] FIG. 5 is a diagram showing a schematic diagram of the relationship between the operation of an APD and an output signal.

[0043] Fig. 5(a) is a diagram illustrating the APD 201, quench element 202, and waveform shaping unit 210 of Fig. 4. Here, the input side of the waveform shaping unit 210 is designated as VC, and the output side is designated as VO. Fig. 5(b) shows the waveform change of VC in Fig. 5(a), and Fig. 5(c) shows the waveform change of VO in Fig. 5(a).

[0044] Between time t0 and time t1, a potential difference of VH-VL is applied to the APD 201 in FIG. 5(a). When a photon is incident on the APD 201 at time t1, avalanche multiplication occurs in the APD 201, an avalanche multiplication current flows through the quench element 202, and the voltage at VC drops. As the voltage drop increases further and the potential difference applied to the APD 201 decreases, avalanche multiplication in the APD 201 stops, as shown at time t2. Thereafter, between time t2 and time t3, a current flows through VC from the voltage VL to compensate for the voltage drop, and at time t3, VC settles to its original potential level. At this time, the portion of the output waveform at VC that exceeds a certain threshold is shaped by the waveform shaping unit 210 and output as a signal at VO.

[0045] The arrangement of the signal lines 113, the readout circuits 112, and the output circuits 114 is not limited to that shown in Fig. 3. For example, the signal lines 113 may be arranged to extend in the row direction, and the readout circuits 112 may be arranged at the ends of the signal lines 113.

[0046] [First embodiment] The photoelectric conversion device according to the first embodiment will be described with reference to FIGS.

[0047] FIG. 6 illustrates a photoelectric conversion unit 102 including an APD 201 having a cathode (first terminal) and an anode (second terminal), and a signal processing unit 703. The cathode of the APD 201 is connected to a first power supply 601 via a quench element 202, which serves as a charging means. A waveform shaping unit 210 is connected to the cathode of the APD 201. The cathode of the APD 201 is also connected to a third power supply 603 via a voltage control means (clipping means, voltage holding means) 604. The voltage control means controls the cathode voltage according to the cathode voltage. For example, when the cathode voltage drops to a predetermined value, the voltage drop of the cathode is reduced. Here, in FIG. 6, the voltage of the first power supply 601 is represented as VH, the voltage of the second power supply 602 is represented as VL, and the voltage of the third power supply 603 is represented as GND. The voltage GND of the third power supply 603 has a voltage value between the voltage VH of the first power supply 601 and the voltage VL of the second power supply 602. Specifically, the voltage VH of the first power supply 601 is, for example, 1.1 V, the voltage VL of the second power supply 602 is, for example, −30 V, and the voltage GND of the third power supply 603 is, for example, 0 V. Furthermore, the voltage GND of the third power supply 603 may be set to the same value as the voltage VH of the first power supply 601. In this case, the voltage of the first power supply 601 is, for example, 1.1 V, the voltage of the second power supply 602 is, for example, −30 V, and the voltage of the third power supply 603 is, for example, 1.1 V.

[0048] The quench element 202 is configured, for example, with a PMOS transistor, and a clock signal PCLKB is input to the gate of the PMOS transistor. The clock signal PCLKB is input, for example, periodically at a predetermined cycle. In this embodiment, the clock signal PCLK input to the quench element 202 controls the on / off of the quench element 202, thereby switching between the electrical connection and non-connection between the first power supply 601 and the cathode of the APD 201.

[0049] One terminal of the voltage control means 604 is connected to the cathode of the APD 201, and the other terminal is connected to a third power supply. The voltage control means 604 is connected to the cathode of the APD 201 and controls a cathode voltage VC of the APD 201. When the cathode voltage VC reaches a predetermined voltage, a current flows through VC from the third power supply 603. Note that although the voltage control means 604 is connected to the cathode side of the APD 201 in FIG. 6, the voltage control means 604 may be connected to the anode side of the APD 201, as will be described later.

[0050] 7 shows the relationship between the clock signal PCLKB, the timing of photon incidence, the cathode voltage VC, and the current flowing due to the voltage control means. When the clock signal PCLKB goes low at time t1, the PMOS transistor of the quench element 202 turns on, and the cathode voltage VC is charged from V1 to V2. V2 is VH, which is the voltage value of the first power supply 601. At this time, the voltage difference applied between the anode and cathode of the APD 201 is Vbd (breakdown voltage) + Vex (excess voltage). The voltage applied to the APD 201 is in excess of the breakdown voltage by Vex, enabling avalanche multiplication in Geiger mode. When the clock signal PCLKB goes high, the PMOS transistor of the quench element 202 turns off, and the node connected to the cathode terminal of the APD 201 becomes floating.

[0051] When a photon is incident at time t2, avalanche multiplication occurs in the APD 201, and the cathode voltage VC drops from potential V2 to potential V1. Here, V1 is a value smaller than V2 by Vex, and at this time the reverse bias voltage of the APD 201 drops to a voltage below the breakdown voltage. V2 is the voltage VH of the first power supply, which is Vbd+Vex as described above. Therefore, even if avalanche multiplication occurs and the cathode voltage VC drops to potential V1, the voltage difference applied to the APD 201 can be made equal to or greater than the breakdown voltage. When the cathode voltage VC drops below potential V1, the voltage difference applied to the APD 201 becomes a voltage difference less than the breakdown voltage. Subsequently, when photons are incident after time t2, a reverse bias voltage less than the breakdown voltage is applied to the APD 201, so avalanche multiplication due to Geiger mode does not occur. However, a reverse bias voltage is applied to the APD 201 between the first power supply 601 and the second power supply 602, and when light is irradiated, electron-hole pairs are generated, resulting in a reverse current. Therefore, without a voltage control means, the cathode voltage VC continues to decrease to a potential lower than the potential V1, as shown by the dashed line in Figure 7. Then, when the clock signal PCLKB goes low again at time t4, the APD 201 is recharged, and the cathode voltage of the APD 201 returns to V2.

[0052] Figure 8 shows the relationship between the magnitude of the reverse current that occurs after the avalanche multiplication subsides and the cathode voltage VC. As shown in Figure 8, when the reverse current flows, the cathode voltage VC drops. Without a voltage control means, the cathode voltage drops until the clock signal PCLKB goes low, which could exceed the breakdown voltage of the MOS transistor, as shown by the dashed line in Figure 8.

[0053] Therefore, in this embodiment, a voltage control unit 604 is provided as shown in FIG. 6. Even when the voltage control unit 604 is provided, the cathode voltage V C drops due to light irradiation after the avalanche multiplication has subsided. However, as shown in FIG. 7, when the cathode voltage V C drops to a predetermined value at time t3, the voltage control unit 604 causes a current to flow from the third power supply 603 to the cathode of the APD 201. This makes it possible to prevent the cathode voltage V C from dropping below the predetermined value. This makes it possible to prevent the withstand voltage of the MOS transistor from being exceeded, thereby providing a highly stable photoelectric conversion device.

[0054] (First Example) A first example included in the first embodiment described above will be described with reference to FIG. 9 . In this example, the voltage control means 604 is composed of a PMOS transistor 905. The source of the PMOS transistor 905 is connected to the third power supply 603, and the drain of the PMOS transistor 905 is connected to the cathode of the APD 201. The drain of the PMOS transistor 905 is also connected to the gate of the PMOS transistor 905. After the avalanche multiplication subsides, the cathode voltage VC drops due to the photocurrent. When the cathode voltage VC drops to a threshold value at which the PMOS transistor 905 turns on, a current flows from the third power supply 603 to the cathode of the APD 201. This current increases the cathode voltage, thereby preventing the cathode voltage VC from dropping below a predetermined value and preventing it from exceeding the breakdown voltage of the MOS transistor included in the quench element 202. This allows for a highly stable photoelectric conversion device. Furthermore, since the voltage control means can be realized with only one PMOS transistor, the device area can be reduced.

[0055] The PMOS transistor 905 has a higher breakdown voltage than the MOS transistor included in the quench element 202. For example, the gate oxide film of the PMOS transistor 905 is thicker than the gate oxide film of the MOS transistor included in the quench element 202. This increases the breakdown voltage. From the perspective of miniaturization, the breakdown voltage of the MOS transistor included in the quench element 202 needs to be kept below a certain level. On the other hand, the PMOS transistor 905 can be designed relatively freely, so the breakdown voltage can be increased.

[0056] (Second Example) A second example of the first embodiment will be described with reference to FIG. 10 . In this example, the voltage control unit 604 is configured with a diode 1006. The anode of the diode 1006 is connected to the third power supply 603, and the cathode of the diode 1006 is connected to the cathode of the APD 201. The cathode voltage V drops due to the photocurrent after avalanche multiplication subsides. For example, when the cathode voltage V falls below the voltage of the third power supply 603, a forward bias is applied to the diode that was previously reverse biased, and current flows from the third power supply 603 to the cathode of the APD 201 via the diode 1006. This current increases the cathode voltage V, thereby preventing the cathode voltage V from dropping below a predetermined value and preventing it from exceeding the breakdown voltage of the MOS transistor. This allows a highly stable photoelectric conversion device to be provided.

[0057] (Third Example) A third example included in the first embodiment described above will be described with reference to FIG. 11 . In this example, the voltage control means 604 is composed of a diode 1106 and a PMOS transistor 1105. The anode of the diode 1106 is connected to the third power supply 603, and the cathode of the diode 1106 is connected to the source of the PMOS transistor 1105. The drain of the PMOS transistor 1105 is connected to the cathode of the APD 201. The drain of the PMOS transistor 1105 is connected to the gate of the PMOS transistor 1105. After the avalanche multiplication subsides, the photocurrent causes the cathode voltage VC to drop, turning the PMOS transistor 1105 on. As a result, a forward bias is applied to the diode 1106 by the voltage of the third power supply 603 and the cathode voltage of the APD 201, and a current flows from the third power supply 603 to the cathode of the APD 201. This current can increase the cathode voltage VC, thereby limiting the cathode voltage VC from dropping below a predetermined value and preventing it from exceeding the breakdown voltage of the MOS transistor of the quench element 202. This makes it possible to provide a highly stable photoelectric conversion device.

[0058] Furthermore, MOS transistors generally have a larger leakage current than diodes. Therefore, compared to the first embodiment in which only PMOS transistors are provided, using a MOS transistor and a diode together can suppress the leakage current that occurs when current flows from the third power supply 603 to the cathode of the APD 201. The problem that occurs when the leakage current is large will be explained using FIG. 12.

[0059] 12A is a diagram illustrating a case where a photon is detected immediately after recharging. When the clock signal PCLKB goes low at time t1, the PMOS transistor serving as the quench element 202 turns on and is recharged, causing the cathode voltage VC to rise to a voltage value of V2 (e.g., 1.1 V). Next, when a photon is incident at time t2, the cathode voltage VC drops to a voltage value of V1 (e.g., −1.4 V when Vex is 2.5 V). Here, with only a PMOS transistor, a large leakage current flows from the third power supply 603 to the cathode of the APD 201. Then, when the cathode voltage after avalanche multiplication is a negative value (e.g., −1.4 V), the voltage rises in the positive direction, and a reverse bias equal to or greater than the breakdown voltage is applied to the APD 201, resulting in a voltage that allows avalanche multiplication. In this way, under high illumination conditions, there is a possibility that photons will be detected multiple times between time t1 and time t3, when the clock signal PCLKB goes low again, resulting in an increase in power consumption. On the other hand, by using a MOS transistor and a diode together, the leakage current is reduced as shown by the solid line in Figure 12(A), making it easier to reduce the increase in power consumption.

[0060] FIG. 12(B) illustrates a case where a photon is detected after a certain time has passed since recharging. When the clock signal PCLKB goes low at time t1, the PMOS transistor serving as the quench element 202 turns on and is recharged, causing the cathode voltage VC to rise to a voltage value of V2 (e.g., 1.1 V). Next, after charging is completed at time t2, a current flows from the third power supply 603 to the cathode of the APD 201 due to a large leakage current when only the PMOS transistor is used. As a result, if the cathode voltage after charging is a positive value (e.g., 1.1 V), the cathode voltage drops toward the negative side. As a result, the voltage corresponding to Vex in the Vbd+Vex voltage applied to the APD 201 decreases, reducing the avalanche multiplication factor and resulting in a problem of reduced sensitivity of the APD 201. On the other hand, by using a MOS transistor and a diode together, the leakage current is reduced as shown by the solid line in FIG. 12(B), making it easier to suppress the voltage drop of the cathode voltage VC.

[0061] Fig. 13 is a schematic plan view showing the configuration of quench element 202, which is charging means, and voltage control means 604 according to the third embodiment, and Fig. 14 is a schematic cross-sectional view taken along line X-X' in Fig. 13. The charging means and voltage control means 604 of this embodiment will be described below using Figs. 13 and 14, but the arrangement of the components is not limited to this.

[0062] FIG. 13 shows the quench elements 202 and voltage control means 604 of four pixels. The quench elements 202 of the four pixels are arranged near adjacent pixels. For example, the quench elements 202 and parts of the voltage control means 604 of the four pixels share one well region 1107. The well region 1107 is an N-type well region. In this embodiment, the PMOS transistor of the quench element 202 and the PMOS transistor 1105 of the voltage control means 604 are arranged in the N-type well region 1107. Furthermore, the PMOS transistor 2101 of the waveform shaping unit 210 is arranged in the well region 1107. As shown in FIG. 14, the well region 1107 is arranged in a P-type well region 1108.

[0063] An NMOS transistor 2102 of the waveform shaping unit 210 is disposed in the well region 1108. The waveform shaping unit 210 is composed of a PMOS transistor 2101 and an NMOS transistor 2102. The well region 1108 is sandwiched between P-type well regions 1107 in plan view.

[0064] A diode 1106 of the voltage control means 604 is disposed in the P-type well region 1107. In this embodiment, the diode 1106 includes an N-type active region 1109 and a P-type active region 1122. Here, in this embodiment, a well contact region is disposed between the NMOS transistor 2102 and the diode 1106. Specifically, an N-type well contact region 1111 and a P-type well contact region 1119 are disposed around the diode 1106. This prevents a parasitic bipolar from operating between the NMOS transistor 2102 and the diode 1106. In addition, it is possible to configure a bipolar transistor with the N-type well contact region 1111 as the collector, the P-type active region 1122 as the base, and the N-type active region 1109 as the emitter. Furthermore, the presence of the N-type well contact region 1111 makes it less likely to affect the operation of surrounding transistors.

[0065] 14, the gate of each MOS transistor includes a gate electrode 1121 and a gate oxide film 1104. An element isolation region 1118 is disposed between the PMOS transistor 1105 and the PMOS transistor 2101. The element isolation region 1118 may include, for example, an STI or DTI that includes an insulating member. The element isolation region 1118 may also be a semiconductor isolation, or may include a semiconductor isolation and an insulating member.

[0066] Fig. 15 is a schematic plan view showing a portion of a wiring layer included in the second wiring structure. Fig. 15(a) shows a first wiring layer close to the second semiconductor layer, Fig. 15(b) shows a second wiring layer between the first wiring layer and the first wiring structure, and Fig. 15(c) shows a third wiring layer between the second wiring layer and the first wiring structure. Note that another wiring layer may be disposed between the first wiring layer and the second semiconductor layer.

[0067] In the first wiring layer, wiring patterns 1113, 1114, 1115, and 1116 are arranged so as to correspond to the quench element 202, the voltage control means 604, and the waveform shaping unit 210 in a plan view. The wiring pattern 1113 is a cathode wiring and is connected to the cathode of the APD 201. The wiring pattern 1114 supplies power and can also be a wiring that supplies a potential to the anode of the APD 201. The wiring pattern 1114 is also connected to the MOS transistor of the quench element 202. The wiring pattern 1115 is a wiring that supplies a GND potential and is connected to the anode of the diode 1106. The wiring pattern 1116 is a signal wiring through which a signal output from the counter passes.

[0068] The wiring pattern 1113 of the first wiring layer and the wiring pattern 1113 of the second wiring layer are connected. As shown in FIG. 15(b), it is preferable to arrange the wiring pattern 1113 obliquely in a plan view and to keep it as far away as possible from the wiring patterns 1114 and 1115. This reduces the coupling capacitance between the wiring pattern 1113, which serves as the cathode wiring, and the wiring patterns 1114 and 1115, which serve as the power supply wiring. The amount of charge when the cathode potential VC is recharged is determined by the cathode capacitance, including the capacitance of the cathode wiring, and the excess bias. Reducing the amount of charge when the cathode potential is recharged reduces power consumption.

[0069] The wiring pattern 1113 of the second wiring layer is connected to the wiring pattern 1113 of the third wiring layer shown in Fig. 15(c). Moreover, the wiring pattern 1115 of the second wiring layer is connected to the wiring pattern 1115 of the third wiring layer shown in Fig. 15(c).

[0070] (Fourth Example) A fourth example included in the first embodiment described above will be described with reference to Fig. 16. In this example, the voltage control means 604 is composed of a bipolar transistor 1120 and a PMOS transistor 1105. In addition, the voltage of the first power supply and the voltage of the third power supply are the same.

[0071] The collector of the bipolar transistor 1120 is connected to the third power supply. The emitter of the bipolar transistor 1120 is connected to the source of the PMOS transistor 1105. The GND voltage is supplied to the base of the bipolar transistor 1120. The voltage supplied to the base of the bipolar transistor 1120 is, for example, 1.1 V.

[0072] The drain of the PMOS transistor 1105 is connected to the cathode of the APD 201. The drain of the PMOS transistor 1105 is also connected to the gate of the PMOS transistor 1105. After the avalanche multiplication subsides, the photocurrent causes the cathode voltage Vc to drop, turning the PMOS transistor 1105 on. As a result, a forward bias is applied to the diode 1106 by the voltage of the third power supply 603 and the cathode voltage of the APD 201, causing a current to flow from the third power supply 603 to the cathode of the APD 201. This current increases the cathode voltage Vc, preventing the cathode voltage Vc from dropping below a predetermined value and preventing it from exceeding the breakdown voltage of the MOS transistor of the quench element 202. This makes it possible to provide a highly stable photoelectric conversion device.

[0073] Furthermore, the decrease in the cathode potential VC can be more easily suppressed by amplifying the current with the bipolar transistor 1120. The bipolar transistor 1120 may be a parasitic bipolar transistor.

[0074] (Fifth Example) A fifth example included in the first embodiment will be described with reference to FIG. 17 . In this example, the voltage control unit 604 is configured with multiple diodes. For example, the voltage control unit 604 can be configured with three diodes. Furthermore, an amplitude conversion unit 610 is connected between the quench element 202 and the cathode of the APD 201. The amplitude conversion unit 610 can be configured with, for example, a PMOS transistor. The amplitude conversion unit 610 controls the voltage of the node NodeA using the gate voltage of the amplitude conversion unit 610. Because the amplitude of the cathode voltage VC (e.g., 2.1 V) is applied between the source and drain of the MOS transistor, it is preferable to use a high-voltage transistor for the amplitude conversion unit 610. For example, a 2.5 V transistor is used. On the other hand, the quench element 202 and the waveform shaping unit 210 do not require such a high voltage resistance, so it is preferable to use a low-voltage transistor. For example, the quench element 202 and the waveform shaping unit 210 use a 1.3 V transistor.

[0075] The cathode of the APD 201 and the cathode of the diode are connected. The three diodes are connected in series. This embodiment also limits the cathode voltage VC from dropping below a predetermined value, and prevents the voltage from exceeding the breakdown voltage of the MOS transistor of the quench element 202. This makes it possible to provide a highly stable photoelectric conversion device. Furthermore, by connecting three diodes as in this embodiment, it becomes easier to control the voltage of the cathode voltage VC compared to when it is controlled by a single diode.

[0076] An operation image when the amplitude conversion means 610 is provided will be described using Figure 18. Figure 18 is a diagram showing a clock signal, the timing at which a photon is incident, a cathode voltage VC, and a node NodeA between the quench element 202 and the amplitude conversion means 610. When a photon is incident and the cathode voltage VC drops, the voltage at the node NodeA also drops. At this time, the amplitude conversion means 610 can convert the amplitude Vex of the cathode voltage VC to the amplitude (VH) of the node NodeA. This allows the quench element 202 and the waveform shaping section 210 to use low-voltage transistors, thereby reducing the layout area.

[0077] Fig. 19 shows a schematic plan view illustrating the configuration of amplitude conversion means and voltage control means 604 according to the fifth embodiment, and Fig. 20 shows a schematic cross-sectional view taken along line X-X' in Fig. 19. In this embodiment, an N-type well region 1107 and a P-type well region 1108 are arranged in a P-type substrate region 1117. A PMOS transistor 2103 constituting amplitude conversion means 610 is arranged in N-type well region 1107. Furthermore, PMOS transistor 2103 is arranged between two diodes 1106 and one diode 1106.

[0078] Of the three diodes 1106, the central diode 1106 is connected to VC (the cathode terminal of the APD 201) in FIG. 17, and is therefore preferably disposed adjacent to the PMOS transistor 2103. This reduces the cathode wiring capacitance and power consumption. Furthermore, the diode 1106 disposed on the opposite side of the PMOS transistor 2103 from the central diode 1106 is preferably a diode connected to a third power supply. The layout area can be reduced because the P-type substrate region can be shared with peripheral transistors.

[0079] (Sixth Example) A sixth example included in the first embodiment described above will be described with reference to Fig. 21. In this example, a part of the voltage control means 604 is shared by multiple APDs 201. This makes it possible to reduce the layout area.

[0080] 21, the voltage control means 604 of this embodiment includes four diodes. Two diodes of the voltage control means 604 connected to the cathode voltage VC of each APD 201 must correctly detect the signal from the APD 201. Therefore, the diode closest to the cathode voltage VC is provided for each APD 201, and the subsequent diodes are shared by multiple APDs 201.

[0081] Although two APDs 201 share a part of the voltage control means 604 in FIG. 21, three or more APDs 201 may share the voltage control means 604.

[0082] (Seventh Example) The seventh embodiment is a modification of the first to sixth embodiments, and will be described with reference to FIG. 22. In this embodiment, the anode (first terminal) of the APD 201 is connected to a first power supply 1301 via a quench element 202, which is a charging means. The cathode (second terminal) of the APD 201 is connected to a second power supply 1302. An NMOS transistor 1304, which is a voltage control means 604, is connected to the anode of the APD 201. Specifically, the source of the NMOS transistor 1304 is connected to the anode of the APD 201, and the drain of the NMOS transistor 1304 is connected to a third power supply 1303. Here, in FIG. 13, the first power supply 1301 is represented as GND, the second power supply 1302 is represented as VH, and the third power supply 1303 is represented as VL. The voltage of the third power supply 1303 is a voltage value between the voltage of the first power supply 1301 and the voltage of the second power supply 1302. Specifically, the voltage of the first power supply 1301 is, for example, 0 V, the voltage of the second power supply 1302 is, for example, 30 V, and the voltage of the third power supply 1303 is, for example, 1.1 V. The voltage of the third power supply 1303 may also be the same value as the voltage of the first power supply 1301. Specifically, the voltage of the first power supply 1301 is, for example, 0 V, the voltage of the second power supply 1302 is, for example, 30 V, and the voltage of the third power supply 1303 is, for example, 0 V.

[0083] After the avalanche multiplication subsides, the photocurrent increases the anode voltage VA. When the anode voltage VA reaches the threshold value at which the NMOS transistor 1304 turns on, a current flows from the anode of the APD 201 to the third power supply 1303. This current reduces the anode voltage, preventing the anode voltage VA from rising above a predetermined value and preventing it from exceeding the breakdown voltage of the MOS transistor, thereby providing a highly stable photoelectric conversion device. Furthermore, since the voltage control means can be realized with just one NMOS transistor, the device area can be reduced.

[0084] In the first to sixth embodiments, the anode terminal and the cathode terminal may be interchanged as in the seventh embodiment.

[0085] (Eighth Example) The eighth embodiment is a modification of the first to seventh embodiments. In each of the above-described embodiments, a MOS transistor is used as the charging means, and a clock signal is used to switch the electrical connection between the cathode of the APD 201 and the first power supply. This is not a limitation, and the charging means may be a resistor. Alternatively, a MOS transistor to which no clock signal is input may be used as the charging means. Specifically, passive charging may be used. For example, if the APD current at high illuminance is greater than the recharge current by the charging means, the cathode potential may exceed the withstand voltage of the MOS transistor. Even in such a case, the withstand voltage of the MOS transistor can be easily ensured at high illuminance by using the voltage control means 604.

[0086] [Second embodiment] In the above embodiment, a two-layer stacked photoelectric conversion device has been described with reference to Fig. 1 to Fig. 22. Specifically, this is an example in which the photoelectric conversion unit 102 is arranged on the sensor substrate 11, which is a first substrate, and the signal processing unit 103 is arranged on the circuit substrate 21, which is a second substrate, and the first substrate and the second substrate are stacked. However, in the present embodiment, with reference to Fig. 23, a photoelectric conversion device in which a third substrate is also stacked in addition to the first substrate and the second substrate will be described.

[0087] 23, the photoelectric conversion unit 102 is arranged on a sensor substrate, which is a first substrate. Furthermore, a first signal processing unit including a quench element 202, a voltage control means 604, and a waveform shaping unit 210 is arranged on a first circuit substrate, which is a second substrate. Furthermore, a second signal processing unit including a counter circuit and a selection circuit is arranged on a second circuit substrate, which is a third substrate. The first substrate, second substrate, and third substrate are stacked.

[0088] The APD 201 experiences large voltage changes at the cathode or anode due to avalanche multiplication. Therefore, the MOS transistors constituting the quench element 202 of the charging means, the elements (e.g., MOS transistors) constituting the voltage control means 604, and the elements (e.g., MOS transistors) constituting the waveform shaping unit 210 must be high-voltage MOS transistors. On the other hand, the output from the waveform shaping unit 210 is a pulse-wave digital signal, so high-voltage MOS transistors are not required. Conversely, by using low-voltage MOS transistors in the signal processing circuit downstream of the waveform shaping unit 210, lower voltages can be achieved, thereby reducing power consumption. Furthermore, using low-voltage MOS transistors allows for transistor miniaturization, thereby saving space. For example, the gate oxide film of a high-voltage MOS transistor is thicker than that of a low-voltage MOS transistor. Furthermore, the channel length of a high-voltage MOS transistor is longer than that of a low-voltage MOS transistor. The configurations of the first and second substrates can be the same as those described in the first embodiment.

[0089] [Third embodiment] The photoelectric conversion system according to this embodiment will be described with reference to Fig. 24. Fig. 24 is a block diagram showing a schematic configuration of the photoelectric conversion system according to this embodiment.

[0090] The photoelectric conversion devices described in the first and second embodiments can be applied to various photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Camera modules equipped with an optical system such as a lens and an imaging device are also included in the photoelectric conversion system. Figure 24 illustrates a block diagram of a digital still camera as an example of such systems.

[0091] 24 includes an image pickup device 1004, which is an example of a photoelectric conversion device, and a lens 1002 that forms an optical image of a subject on the image pickup device 1004. The system further includes an aperture 1003 that adjusts the amount of light passing through the lens 1002, and a barrier 1001 that protects the lens 1002. The lens 1002 and aperture 1003 form an optical system that focuses light on the image pickup device 1004. The image pickup device 1004 is a photoelectric conversion device according to any of the above embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

[0092] The photoelectric conversion system also includes a signal processing unit 1007, which is an image generation unit that generates an image by processing an output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compressions as necessary to output image data. The signal processing unit 1007 may be formed on the same semiconductor substrate on which the imaging device 1004 is provided, or may be formed on a semiconductor substrate separate from the imaging device 1004.

[0093] The photoelectric conversion system further includes a memory unit 1010 for temporarily storing image data, and an external interface unit (external I / F unit) 1013 for communicating with an external computer or the like. The photoelectric conversion system further includes a recording medium 1012 such as a semiconductor memory for recording or reading out imaging data, and a recording medium control interface unit (recording medium control I / F unit) 1011 for recording or reading out data from the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system or may be detachable.

[0094] The photoelectric conversion system further includes an overall control and calculation unit 1009 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the image capture device 1004 and the signal processing unit 1007. Here, timing signals and the like may be input from outside, and the photoelectric conversion system only needs to include at least the image capture device 1004 and the signal processing unit 1007 that processes the output signal output from the image capture device 1004.

[0095] The imaging device 1004 outputs an imaging signal to a signal processing unit 1007. The signal processing unit 1007 performs predetermined signal processing on the imaging signal output from the imaging device 1004 and outputs image data. The signal processing unit 1007 generates an image using the imaging signal.

[0096] As described above, according to this embodiment, it is possible to realize a photoelectric conversion system to which the photoelectric conversion device (imaging device) according to any one of the above embodiments is applied.

[0097] [Fourth embodiment] The photoelectric conversion system and the moving object of this embodiment will be described with reference to Fig. 25. Fig. 25 is a diagram showing the configuration of the photoelectric conversion system and the moving object of this embodiment.

[0098] FIG. 25(a) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 2300 includes an image capturing device 2310. The image capturing device 2310 is the photoelectric conversion device described in any of the above embodiments. The photoelectric conversion system 2300 includes an image processing unit 2312 that performs image processing on multiple pieces of image data acquired by the image capturing device 2310, and a parallax acquisition unit 2314 that calculates parallax (phase difference between parallax images) from the multiple pieces of image data acquired by the photoelectric conversion system 2300. The photoelectric conversion system 2300 also includes a distance measurement unit 2316 that calculates the distance to an object based on the calculated parallax, and a collision determination unit 2318 that determines whether or not there is a possibility of a collision based on the calculated distance. Here, the parallax acquisition unit 2314 and the distance measurement unit 2316 are examples of distance information acquisition means that acquire distance information to the object. In other words, the distance information is information related to the parallax, the amount of defocus, the distance to the object, etc. The collision determination unit 2318 may determine the possibility of a collision using any of these distance information. The distance information acquisition means may be realized by dedicated hardware, a software module, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a combination thereof.

[0099] The photoelectric conversion system 2300 is connected to a vehicle information acquisition device 2320 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 2300 is also connected to a control ECU 2330, which is a control unit that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 2318. The photoelectric conversion system 2300 is also connected to an alarm device 2340 that issues an alarm to the driver based on the determination result of the collision determination unit 2318. For example, if the determination result of the collision determination unit 2318 indicates a high possibility of a collision, the control ECU 2330 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 2340 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel.

[0100] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are imaged by the photoelectric conversion system 2300. Fig. 25(b) shows the photoelectric conversion system when imaging the area in front of the vehicle (imaging range 2350). A vehicle information acquisition device 2320 sends instructions to the photoelectric conversion system 2300 or the imaging device 2310. This configuration can further improve the accuracy of distance measurement.

[0101] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, and control of automatic driving to prevent deviation from a lane. Furthermore, the photoelectric conversion system is not limited to vehicles such as the subject vehicle, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the present invention can be applied not only to moving bodies but also to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0102] [Fifth embodiment] The photoelectric conversion system of this embodiment will be described with reference to Fig. 26. Fig. 26 is a block diagram showing an example of the configuration of a range image sensor which is the photoelectric conversion system of this embodiment.

[0103] 26, the range image sensor 401 is configured to include an optical system 402, a photoelectric conversion device 403, an image processing circuit 404, a monitor 405, and a memory 406. The range image sensor 401 can obtain a range image according to the distance to the subject by receiving light (modulated light or pulsed light) that is projected from a light source device 411 toward the subject and reflected from the surface of the subject.

[0104] The optical system 402 is configured to have one or more lenses, and guides image light (incident light) from a subject to the photoelectric conversion device 403 , forming an image on the light receiving surface (sensor section) of the photoelectric conversion device 403 .

[0105] The photoelectric conversion device 403 is one of the photoelectric conversion devices according to the above-described embodiments, and a distance signal indicating a distance determined from a light reception signal output from the photoelectric conversion device 403 is supplied to the image processing circuit 404 .

[0106] The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 403. The distance image (image data) obtained by this image processing is then supplied to a monitor 405 for display, or supplied to a memory 406 for storage (recording).

[0107] In the range image sensor 401 configured in this way, by applying the above-described photoelectric conversion device, it is possible to obtain, for example, a more accurate range image as the pixel characteristics improve.

[0108] [Sixth embodiment] The photoelectric conversion system of this embodiment will be described with reference to Fig. 27. Fig. 27 is a diagram showing an example of a schematic configuration of an endoscopic surgery system, which is the photoelectric conversion system of this embodiment.

[0109] 27 shows an operator (doctor) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgery system 1003. As shown in the figure, the endoscopic surgery system 1003 is composed of an endoscope 1100, a surgical tool 1110, and a cart 1134 on which various devices for endoscopic surgery are mounted.

[0110] The endoscope 1100 is composed of a lens barrel 1101, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 1132, and a camera head 1102 connected to the base end of the lens barrel 1101. In the example shown, the endoscope 1100 is configured as a so-called rigid lens barrel having a rigid lens barrel 1101, but the endoscope 1100 may also be configured as a so-called flexible lens barrel having a flexible lens barrel.

[0111] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 1101. A light source device 1203 is connected to the endoscope 1100, and light generated by the light source device 1203 is guided to the tip of the lens barrel by a light guide extending inside the lens barrel 1101, and is irradiated via the objective lens towards an observation target inside the body cavity of the patient 1132. The endoscope 1100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0112] An optical system and a photoelectric conversion device are provided inside the camera head 1102, and light reflected from an observation object (observation light) is focused onto the photoelectric conversion device by the optical system. The observation light is photoelectrically converted by the photoelectric conversion device to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observation image. The photoelectric conversion device may be any of the photoelectric conversion devices described in the above-described embodiments. The image signal is transmitted to a camera control unit (CCU) 1135 as RAW data.

[0113] The CCU 1135 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and performs overall control of the operations of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives an image signal from the camera head 1102, and performs various types of image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

[0114] Under the control of the CCU 1135 , the display device 1136 displays an image based on the image signal that has been subjected to image processing by the CCU 1135 .

[0115] The light source device 1203 is configured from a light source such as an LED (Light Emitting Diode), and supplies the endoscope 1100 with irradiation light when photographing an operation site or the like.

[0116] The input device 1137 is an input interface for the endoscopic surgery system 1003. A user can input various information and instructions to the endoscopic surgery system 1003 via the input device 1137.

[0117] The treatment tool control device 1138 controls the driving of the energy treatment tool 1112 for cauterizing tissue, incising, sealing blood vessels, or the like.

[0118] The light source device 1203, which supplies illumination light to the endoscope 1100 when photographing the surgical site, can be configured from a white light source configured from, for example, an LED, a laser light source, or a combination of these. When the white light source is configured from a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, making it possible to adjust the white balance of the captured image in the light source device 1203. In this case, it is also possible to capture images corresponding to each RGB color in a time-division manner by irradiating the object of observation with laser light from each RGB laser light source in a time-division manner and controlling the drive of the image sensor of the camera head 1102 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter to the image sensor.

[0119] Furthermore, the light source device 1203 may be controlled to change the intensity of light it outputs at predetermined time intervals. By controlling the driving of the image sensor of the camera head 1102 in synchronization with the timing of the change in the light intensity to acquire images in a time-division manner and combining the images, it is possible to generate an image with a high dynamic range that is free of so-called blocked-up shadows and blown-out highlights.

[0120] The light source device 1203 may also be configured to supply light in a predetermined wavelength band corresponding to special light observation. Special light observation utilizes, for example, the wavelength dependency of light absorption in body tissue. Specifically, specific tissue, such as blood vessels on the surface of the mucous membrane, can be photographed with high contrast by irradiating light with a narrower band than the light (i.e., white light) used in normal observation. Alternatively, special light observation may involve fluorescence observation, in which an image is obtained using fluorescence generated by irradiating excitation light. Fluorescence observation can involve irradiating excitation light onto body tissue and observing the fluorescence from the body tissue, or locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the body tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 1203 may be configured to supply narrow band light and / or excitation light corresponding to such special light observation.

[0121] [Seventh embodiment] The photoelectric conversion system of this embodiment will be described with reference to FIGS. 28(a) and (b). FIG. 28(a) illustrates glasses 1600 (smart glasses) which are the photoelectric conversion system of this embodiment. The glasses 1600 have a photoelectric conversion device 1602. The photoelectric conversion device 1602 is the photoelectric conversion device described in each of the above embodiments. A display device including a light-emitting device such as an OLED or LED may be provided on the back side of the lens 1601. There may be one or more photoelectric conversion devices 1602. A combination of multiple types of photoelectric conversion devices may also be used. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in FIG. 28(a).

[0122] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device. The control device 1603 also controls the operations of the photoelectric conversion device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light onto the photoelectric conversion device 1602.

[0123] FIG. 28(b) illustrates glasses 1610 (smart glasses) according to one application example. The glasses 1610 include a control device 1612, which includes a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. A lens 1611 includes an optical system for projecting light emitted from the photoelectric conversion device and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source for supplying power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device may include a gaze detection unit for detecting the gaze of the wearer. Infrared light may be used for gaze detection. The infrared light emitter emits infrared light toward the eyeball of a user gazing at a displayed image. An imaging unit with a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. A reduction unit for reducing light from the infrared light emitter to the display unit in a planar view reduces degradation of image quality.

[0124] The gaze of the user relative to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be used for gaze detection using an image of the eyeball. One example is a gaze detection method based on the Purkinje image formed by reflection of irradiated light on the cornea.

[0125] More specifically, gaze detection processing is performed based on the pupil-corneal reflex method, which calculates a gaze vector representing the direction (rotation angle) of the eyeball based on the pupil image and Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0126] The display device of this embodiment may have a photoelectric conversion device having a light receiving element, and may control the image displayed on the display device based on information about the user's line of sight from the photoelectric conversion device.

[0127] Specifically, the display device determines a first field of view area where the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be determined by an external control device and received. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0128] The display area may include a first display area and a second display area different from the first display area, and a high-priority area may be determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be determined by an external control device and received. The resolution of the high-priority area may be controlled to be higher than the resolution of areas other than the high-priority area. In other words, the resolution of an area with a relatively low priority may be lowered.

[0129] Note that AI may be used to determine the first field of view area and areas with high priority. The AI ​​may be a model configured to estimate the angle of gaze and the distance to an object in the line of sight from an image of the eyeball, using as training data an image of the eyeball and the direction in which the eyeball in the image was actually looking. The AI ​​program may be included in the display device, the photoelectric conversion device, or an external device. If included in an external device, it is transmitted to the display device via communication.

[0130] When display control is performed based on visual recognition detection, the present invention is preferably applied to smart glasses that further include a photoelectric conversion device for capturing images of the outside world. The smart glasses can display captured external information in real time.

[0131] [Eighth embodiment] The above-described photoelectric conversion device and photoelectric conversion system may be applied to electronic devices such as so-called smartphones and tablets.

[0132] 29(a) and 29(b) are diagrams showing an example of an electronic device 1500 equipped with a photoelectric conversion device. Fig. 29(a) shows the front side of the electronic device 1500, and Fig. 29(b) shows the back side of the electronic device 1500.

[0133] 29(a), a display 1510 for displaying an image is disposed in the center of the surface of the electronic device 1500. Then, along the upper side of the surface of the electronic device 1500, front cameras 1521 and 1522 using photoelectric conversion devices, an IR light source 1530 that emits infrared light, and a visible light source 1540 that emits visible light are disposed.

[0134] Also, as shown in Figure 29(b), rear cameras 1551 and 1552 using photoelectric conversion devices, an IR light source 1560 that emits infrared light, and a visible light source 1570 that emits visible light are arranged along the upper edge of the back of the electronic device 1500.

[0135] By applying the photoelectric conversion device described above to the electronic device 1500 configured as described above, it is possible to capture higher quality images, for example. The photoelectric conversion device can also be applied to other electronic devices such as infrared sensors, distance measuring sensors using active infrared light sources, security cameras, and personal or biometric authentication cameras. This can improve the accuracy and performance of these electronic devices.

[0136] [Ninth embodiment] 30 is a block diagram of an X-ray CT apparatus in this embodiment. This embodiment is applicable to both the first and second embodiments. The X-ray CT apparatus 30 in this embodiment includes an X-ray generation unit 310, a wedge 311, a collimator 312, an X-ray detection unit 320, a top plate 330, a rotating frame 340, and a high-voltage generation device 350. The X-ray CT apparatus 30 also includes a data acquisition system (DAS) 351, a signal processing unit 352, a display unit 353, and a control unit 354.

[0137] The X-ray generating unit 310 is composed of, for example, a vacuum tube that generates X-rays. A high voltage and a filament current are supplied to the vacuum tube of the X-ray generating unit 310 from a high voltage generator 350. X-rays are generated by irradiating the anode (target) with thermoelectrons from the cathode (filament).

[0138] The wedge 311 is a filter that adjusts the amount of X-rays irradiated from the X-ray generation unit 310. The wedge 311 attenuates the amount of X-rays so that the X-rays irradiated from the X-ray generation unit 310 to the subject have a predetermined distribution. The collimator 312 is made of a lead plate or the like that narrows the irradiation range of the X-rays that have passed through the wedge 311. The X-rays generated by the X-ray generation unit 310 are shaped into a cone beam via the collimator 312 and are irradiated onto the subject on the tabletop 330.

[0139] The X-ray detection unit 320 is configured using the semiconductor device in the above-described embodiments 1 and 2. The X-ray detection unit 320 detects X-rays that have passed through the subject from the X-ray generation unit 310, and outputs a signal corresponding to the X-ray dose to the DAS 351.

[0140] The rotating frame 340 has an annular shape and is configured to be rotatable. An X-ray generation unit 310 (wedge 311, collimator 312) and an X-ray detection unit 320 are arranged facing each other inside the rotating frame 340. The X-ray generation unit 310 and the X-ray detection unit 320 can rotate together with the rotating frame 340.

[0141] The high voltage generator 350 includes a booster circuit and outputs a high voltage to the X-ray generation unit 310. The DAS 351 includes an amplifier circuit and an A / D conversion circuit and outputs a signal from the X-ray detection unit 320 to the signal processing unit 352 as digital data.

[0142] The signal processing unit 352 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and is capable of performing image processing on digital data. The display unit 353 includes a flat display device and is capable of displaying X-ray images. The control unit 354 includes a CPU, ROM, RAM, and the like, and controls the overall operation of the X-ray CT device 30.

[0143] [Tenth embodiment] This embodiment is applicable to both the first and second embodiments. FIG. 31(a) is a schematic diagram illustrating a device 9191 including a semiconductor device 930 according to this embodiment. The photoelectric conversion device (imaging device) of each of the above-described embodiments can be used as the semiconductor device 930. The device 9191 including the semiconductor device 930 will be described in detail. The semiconductor device 930 may include a semiconductor device 910. The semiconductor device 930 may also include a package 920 that houses the semiconductor device 910, in addition to the semiconductor device 910. The package 920 may include a base to which the semiconductor device 910 is fixed, and a lid such as glass that faces the semiconductor device 910. The package 920 may further include bonding members such as bonding wires or bumps that connect terminals provided on the base to terminals provided on the semiconductor device 910.

[0144] The equipment 9191 can include at least one of an optical device 940, a control device 950, a processing device 960, a display device 970, a storage device 980, and a mechanical device 990. The optical device 940 corresponds to the semiconductor device 930. The optical device 940 is, for example, a lens, a shutter, or a mirror, and includes an optical system that guides light to the semiconductor device 930. The control device 950 controls the semiconductor device 930. The control device 950 is, for example, a semiconductor device such as an ASIC.

[0145] The processing device 960 processes the signal output from the semiconductor device 930. The processing device 960 is a semiconductor device such as a CPU or ASIC for configuring an AFE (analog front end) or a DFE (digital front end). The display device 970 is an EL display device or a liquid crystal display device that displays information (images) obtained by the semiconductor device 930. The storage device 980 is a magnetic device or a semiconductor device that stores information (images) obtained by the semiconductor device 930. The storage device 980 is a volatile memory such as an SRAM or a DRAM, or a non-volatile memory such as a flash memory or a hard disk drive.

[0146] The mechanical device 990 has a moving part or a propulsion part such as a motor or an engine. In the device 9191, the signal output from the semiconductor device 930 is displayed on the display device 970, or transmitted to the outside by a communication device (not shown) provided in the device 9191. For this purpose, the device 9191 preferably further includes a memory device 980 and a processing device 960 in addition to the memory circuit and arithmetic circuit provided in the semiconductor device 930. The mechanical device 990 may be controlled based on the signal output from the semiconductor device 930.

[0147] The device 9191 is also suitable for electronic devices such as information terminals with a photographing function (for example, smartphones and wearable devices) and cameras (for example, interchangeable lens cameras, compact cameras, video cameras, and surveillance cameras). The mechanical device 990 in the camera can drive components of the optical device 940 for zooming, focusing, and shutter operation. Alternatively, the mechanical device 990 in the camera can move the semiconductor device 930 for vibration isolation operations.

[0148] Furthermore, the device 9191 may be transportation equipment such as a vehicle, a ship, or an aircraft (drone, aircraft, etc.). The mechanical device 990 in transportation equipment can be used as a moving device. The device 9191 as transportation equipment is suitable for transporting the semiconductor device 930 or for assisting and / or automating driving (piloting) using a photographing function. The processing device 960 for assisting and / or automating driving (piloting) can perform processing for operating the mechanical device 990 as a moving device based on information obtained by the semiconductor device 930. Alternatively, the device 9191 may be a medical device such as an endoscope, a measuring device such as a distance measuring sensor, an analytical device such as an electron microscope, an office machine such as a copier, or an industrial device such as a robot.

[0149] According to the above-described embodiment, it is possible to obtain good pixel characteristics. Therefore, the value of the semiconductor device can be increased. In this case, increasing the value corresponds to at least one of adding functions, improving performance, improving characteristics, improving reliability, improving manufacturing yield, reducing environmental impact, reducing costs, reducing size, and reducing weight.

[0150] Therefore, if the semiconductor device 930 according to this embodiment is used in the equipment 9191, the value of the equipment can also be improved. For example, by installing the semiconductor device 930 in a transport equipment, excellent performance can be obtained when photographing the exterior of the transport equipment or measuring the external environment. Therefore, when manufacturing and selling transport equipment, deciding to install the semiconductor device according to this embodiment in the transport equipment is advantageous in terms of improving the performance of the transport equipment itself. In particular, the semiconductor device 930 is suitable for transport equipment that performs driving assistance and / or automatic driving of the transport equipment using information obtained by the semiconductor device.

[0151] The photoelectric conversion system and the moving object of this embodiment will be described with reference to FIG. 31(b).

[0152] FIG. 31(b) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 8 includes a photoelectric conversion device 80. The photoelectric conversion device 80 is the photoelectric conversion device (imaging device) described in any of the above embodiments. The photoelectric conversion system 8 includes an image processing unit 801 that performs image processing on multiple pieces of image data acquired by the photoelectric conversion device 80, and a parallax acquisition unit 802 that calculates parallax (phase difference of parallax images) from the multiple pieces of image data acquired by the photoelectric conversion system 8. Here, the photoelectric conversion system 8 may include an optical system (not shown) that guides light to the photoelectric conversion device 80, such as a lens, shutter, or mirror. Furthermore, multiple photoelectric conversion units that are approximately conjugate with the pupil of the optical system may be arranged in pixels of the photoelectric conversion device 80. For example, multiple photoelectric conversion units that are approximately conjugate with the pupil are arranged corresponding to one microlens. The photoelectric conversion units receive light beams that have passed through different positions of the pupil of the optical system, and the photoelectric conversion device 80 outputs image data corresponding to the light beams that have passed through the different positions. The parallax acquisition unit 802 may then calculate parallax using the output image data. The photoelectric conversion system 8 also includes a distance acquisition unit 803 that calculates the distance to an object based on the calculated parallax, and a collision determination unit 804 that determines whether or not there is a possibility of a collision based on the calculated distance. The parallax acquisition unit 802 and the distance acquisition unit 803 are examples of distance information acquisition means that acquire information about the distance to the object. The distance information includes information about the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 804 may use any of this distance information to determine the possibility of a collision. The distance information may be acquired using ToF (Time of Flight). The distance information acquisition means may be implemented by dedicated hardware or a software module. Furthermore, it may be realized by a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like, or may be realized by a combination of these.

[0153] The photoelectric conversion system 8 is connected to a vehicle information acquisition device 810 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 8 is also connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 804. The photoelectric conversion system 8 is also connected to an alarm device 830 that issues an alarm to the driver based on the determination result of the collision determination unit 804. For example, if the determination result of the collision determination unit 804 indicates a high possibility of a collision, the control ECU 820 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel.

[0154] In this embodiment, the photoelectric conversion system 8 captures an image of the surroundings of the vehicle, for example, the front or rear. Fig. 31(c) shows a photoelectric conversion system for capturing an image of the area in front of the vehicle (imaging range 850). A vehicle information acquisition device 810 sends instructions to the photoelectric conversion system 8 or the photoelectric conversion device 80. This configuration can further improve the accuracy of distance measurement.

[0155] While the above describes an example of control to prevent collisions with other vehicles, the present invention can also be applied to other applications, such as autonomous driving control to follow other vehicles and autonomous driving control to prevent vehicles from drifting out of their lanes. Furthermore, the photoelectric conversion system 8 can be applied not only to automobiles and other vehicles, but also to moving bodies (mobile devices) such as ships, aircraft, and industrial robots. The moving body includes one or both of a driving force generator that generates a driving force primarily used to move the moving body and a rotating body primarily used to move the moving body. The driving force generator can be an engine, a motor, or the like. The rotating body can be a tire, a wheel, a ship's screw, an aircraft's propeller, or the like. In addition to moving bodies, the present invention can be applied to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0156] Various devices have been described in the above embodiments, but a mechanical device may also be provided. The mechanical device in the camera can drive optical components for zooming, focusing, and shutter operation. Alternatively, the mechanical device in the camera can move a photoelectric conversion device for vibration reduction.

[0157] The equipment may also be transportation equipment such as a vehicle, a ship, or an aircraft. A mechanical device in the transportation equipment category may be used as a moving device. Equipment serving as transportation equipment is suitable for transporting a photoelectric conversion device or for assisting and / or automating driving (piloting) using a photographing function. A processing device for assisting and / or automating driving (piloting) can perform processing for operating the mechanical device as a moving device based on information obtained by the photoelectric conversion device.

[0158] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which part of the configuration of one embodiment is added to another embodiment, or an example in which part of the configuration of another embodiment is replaced with another embodiment, is also included in the embodiments of the present invention.

[0159] In the above embodiment, an example has been described in which MOS transistors are used as transistors, but transistors other than MOS transistors may also be used. For example, bipolar transistors may be used instead of MOS transistors.

[0160] Furthermore, the photoelectric conversion systems shown in the third and fourth embodiments are examples of photoelectric conversion systems to which a photoelectric conversion device can be applied, and photoelectric conversion systems to which the photoelectric conversion device of the present invention can be applied are not limited to the configurations shown in Figures 24 and 25. The same applies to the ToF system shown in the fifth embodiment, the endoscope shown in the sixth embodiment, the smart glasses shown in the seventh embodiment, the smartphone shown in the eighth embodiment, the CT device shown in the ninth embodiment, and the device shown in the tenth embodiment.

[0161] It should be noted that the above-described embodiments are merely examples of specific embodiments of the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be embodied in various forms without departing from its technical concept or main features.

[0162] As used herein, the expressions "A or B" and "at least one of A and B" include all possible combinations of the listed items unless otherwise explicitly defined. Furthermore, expressions such as "at least one of A and / or B" and "one or more of A and / or B" include all possible combinations of the listed items unless otherwise explicitly defined. In other words, the above expressions are understood to disclose all cases, such as cases containing at least one A, cases containing at least one B, and cases containing both at least one A and at least one B. This also applies to combinations of three or more elements.

[0163] The above-described embodiments can be modified as appropriate without departing from the technical spirit. The disclosure of this specification includes not only what is described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto. The disclosure of this specification also includes the complement of the concepts described in this specification. In other words, if this specification states, for example, that "A is greater than B," it can be said that this specification discloses that "A is not greater than B" even if the statement that "A is not greater than B" is omitted. This is because the statement that "A is greater than B" is based on the premise that the case in which "A is not greater than B" is taken into consideration.

Claims

1. an avalanche photodiode having a first terminal and a second terminal; charging means for controlling the electrical connection between the first terminal and a first power source; a second power source electrically connected to the second terminal; an amplitude conversion means connected between the first terminal and the charging means, for reducing the amplitude of a voltage output from the first terminal by avalanche multiplication of the avalanche photodiode; a voltage holding means connected between the first terminal and the amplitude conversion means, for holding the voltage of the first terminal so that the voltage of the first terminal does not exceed a predetermined value.

2. the voltage holding means is electrically connected to a third power supply; 2. The photoelectric conversion device according to claim 1, wherein the voltage holding means holds the voltage of the first terminal so that the voltage of the first terminal does not exceed a predetermined value when the voltage of the first terminal becomes equal to or lower than the voltage of the third power supply.

3. 3. The photoelectric conversion device according to claim 2, wherein the voltage of the third power supply is a voltage between the voltage of the first power supply and the voltage of the second power supply.

4. 3. The photoelectric conversion device according to claim 2, wherein the voltage of the third power supply is the same as the voltage of the first power supply.

5. the voltage holding means includes a MOS transistor; one terminal of the MOS transistor is connected to the first terminal; 3. The photoelectric conversion device according to claim 2, wherein the other terminal of the MOS transistor is connected to the third power supply.

6. 6. The photoelectric conversion device according to claim 5, wherein the gate of the MOS transistor is connected to the first terminal.

7. 7. The photoelectric conversion device according to claim 6, wherein the MOS transistor is a P-type MOS transistor.

8. 7. The photoelectric conversion device according to claim 6, wherein the MOS transistor is an N-type MOS transistor.

9. the voltage holding means includes a diode; one terminal of the diode is connected to the first terminal; 3. The photoelectric conversion device according to claim 2, wherein the other terminal of the diode is connected to the third power supply.

10. the one terminal of the diode is a cathode, 10. The photoelectric conversion device according to claim 9, wherein the other terminal of the diode is an anode.

11. the voltage holding means further includes a MOS transistor; one terminal of the MOS transistor is connected to the first terminal; 10. The photoelectric conversion device according to claim 9, wherein the other terminal of the MOS transistor is connected to the third power supply via the diode.

12. 12. The photoelectric conversion device according to claim 11, wherein the gate of the MOS transistor is connected to the first terminal.

13. 13. The photoelectric conversion device according to claim 12, wherein the MOS transistor is a P-type MOS transistor.

14. 13. The photoelectric conversion device according to claim 12, wherein the MOS transistor is an N-type MOS transistor.

15. 2. The photoelectric conversion device according to claim 1, wherein the first terminal is a cathode of the avalanche photodiode.

16. 2. The photoelectric conversion device according to claim 1, wherein the first terminal is an anode of the avalanche photodiode.

17. a waveform shaping unit connected to the first terminal, 2. The photoelectric conversion device according to claim 1, wherein the waveform shaping section is connected to the voltage holding means.

18. a first substrate on which the avalanche photodiode is disposed; a second substrate on which a first signal processing unit having the charging means, the voltage holding means, and the waveform shaping unit is disposed; 18. The photoelectric conversion device according to claim 17, further comprising: a third substrate on which a second signal processing section for processing a signal output from the waveform shaping section is disposed.

19. 19. The photoelectric conversion device according to claim 18, wherein the second signal processing section has a counter that counts the signal output from the waveform shaping section.

20. the charging means includes a MOS transistor; 2. The photoelectric conversion device according to claim 1, wherein a clock signal is input to the gate of the MOS transistor of the charging means.

21. the charging means electrically connects the first terminal and the first power supply to transition the avalanche photodiode to a standby state in which avalanche multiplication is possible; 2. The photoelectric conversion device according to claim 1, wherein the voltage holding means holds the voltage of the first terminal so that the voltage of the first terminal does not exceed a predetermined value when the avalanche photodiode is in the standby state and the first terminal is not connected to the first power supply.

22. The photoelectric conversion device according to any one of claims 1 to 21, a signal processing unit that generates an image using a signal output from the photoelectric conversion device.

23. A moving object comprising the photoelectric conversion device according to any one of claims 1 to 21, A moving body comprising a control unit that controls the movement of the moving body using a signal output from the photoelectric conversion device.

Images