JP7791251B2 - Photoelectric conversion device and photoelectric conversion system - Google Patents

Description

The present invention relates to a photoelectric conversion device and a photoelectric conversion system including the same.

Photoelectric conversion devices are known that have an arrangement of pixels containing multiple avalanche photodiodes (APDs). By utilizing the avalanche multiplication phenomenon that occurs when a photon strikes an APD, the photocharge generated therein is able to detect light at the single-photon level.

Patent Document 1 describes a photodetector device that has a charging means between the cathode of the APD and the power supply voltage wiring, and switches between a charged state and a standby state in which it waits for incident photons.

Japanese Patent Application Laid-Open No. 2020-123847

Patent Document 1 insufficiently considered the phenomenon that occurs in standby mode when the charging means and power source are disconnected.

The present invention aims to provide a photoelectric conversion device that can solve the problems that arise when the charging means is disconnected from the power source and is in standby mode.

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 including a first MOS transistor connected to the first terminal, the charging means controlling an electrical connection between the first terminal and a first power supply in response to a clock signal input to a gate of the first MOS transistor; a second power supply connected to the second terminal; voltage control means connected to the first terminal, the voltage control means controlling the voltage of the first terminal in accordance with the voltage of the first terminal when the charging means does not electrically connect the first terminal to the first power supply; and a third power supply connected to the voltage control means.

This invention provides a photoelectric conversion device that can solve the problems that arise when the device is in standby mode and the charging means is disconnected from the power source.

1 is a diagram illustrating a configuration of a photoelectric conversion device according to an embodiment. 3A and 3B are diagrams illustrating the arrangement of sensor substrates in a photoelectric conversion device according to an embodiment. 3A and 3B are diagrams illustrating a configuration of a circuit board of a photoelectric conversion device according to an embodiment. 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. 3A and 3B are schematic diagrams illustrating driving of pixel circuits in a photoelectric conversion device according to an embodiment. 2 is a configuration example of a pixel circuit of the photoelectric conversion device according to the first embodiment. 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 according to the comparative example and the first embodiment. FIG. 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. FIG. 2 is a configuration diagram of a pixel circuit of a photoelectric conversion device according to a first embodiment. FIG. 10 is a configuration diagram of a pixel circuit of a photoelectric conversion device according to a second embodiment. FIG. 10 is a configuration diagram of a pixel circuit of a photoelectric conversion device according to a third embodiment. FIG. 10 is a diagram illustrating a problem caused by a leakage current according to the third embodiment. 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. This is a schematic cross-sectional view taken along line X-X' in Figure 13. FIG. 2 is a schematic plan view showing each wiring layer included in a second wiring structure. 10 is a configuration example of a pixel circuit of a photoelectric conversion device according to a fourth embodiment. 10 is a configuration example of a pixel circuit of a photoelectric conversion device according to a fifth embodiment. FIG. 13 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. FIG. 10 is a schematic plan view showing the configuration of an amplitude conversion unit and voltage control unit 604 according to a fifth embodiment. This is a schematic cross-sectional view taken along line X-X' in Figure 19. 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a sixth embodiment. 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a seventh embodiment. 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. FIG. 10 is a functional block diagram of a photoelectric conversion system according to a third embodiment. FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fourth embodiment. FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fifth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a sixth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a seventh embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to an eighth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a ninth embodiment. FIG. 22 is a functional block diagram of a photoelectric conversion system according to a tenth embodiment.

The embodiments shown below are intended to embody the technical concepts of the present invention and are not intended to limit the scope of the present invention. The size and relative positions of components shown in each drawing may be exaggerated for clarity. In the following description, identical components may be designated by the same numbers and their description may be omitted.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "up," "down," "right," "left," and other terms that incorporate 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.

In this specification, a planar view refers to a view from a direction perpendicular to the light incident surface of the semiconductor layer. Furthermore, a cross-sectional view refers to a surface in a direction perpendicular to the light incident surface of the semiconductor layer. Note that if the light incident surface of the semiconductor layer is rough when viewed microscopically, the planar view is defined based on the light incident surface of the semiconductor layer when viewed macroscopically.

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

In this specification, when the term "impurity concentration" is used simply, it refers to 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 added impurity concentration is higher than the N-type added impurity concentration is a P-type semiconductor region. Conversely, a region where the N-type added impurity concentration is higher than the P-type added impurity concentration is an N-type semiconductor region.

Furthermore, in the following embodiments, connections between circuit elements may be described. In such cases, even if another element is interposed between the elements of interest, the elements of interest will be treated as being connected unless otherwise specified. For example, suppose that element A is connected to one node of a capacitive element C with multiple nodes, and element B is connected to the other node. Even in such a case, elements A and B will be treated as being connected unless otherwise specified.

Figure 1 shows the configuration of a stacked photoelectric conversion device 100. The photoelectric conversion device 100 is constructed 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 below), and a first wiring structure. The circuit substrate 21 has a second semiconductor layer having circuits such as a signal processing unit 103 (described below), and a second wiring structure. The photoelectric conversion device 100 is constructed 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.

In the following, the sensor substrate 11 and the circuit substrate 21 are described as diced chips, but this is not limited to chips. For example, each substrate may be a wafer. Furthermore, each substrate may be stacked in wafer form and then diced, or the substrates may be chipped from the wafer state and then the chips may be stacked and bonded.

A pixel area 12 is arranged on the sensor substrate 11, and a circuit area 22 that processes signals detected in the pixel area 12 is arranged on the circuit substrate 21.

Figure 2 shows 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.

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. In other words, pixel 101 may be a pixel for measuring the time and amount of light that arrives.

Figure 3 is a diagram showing the configuration of the circuit board 21. It includes a signal processing unit 103 that processes the signal output from the photoelectric conversion unit 102 shown in Figure 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.

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

The vertical scanning circuit unit 110 receives control pulses from the control pulse generation unit 115 and supplies control pulses to each pixel. The vertical scanning circuit unit 110 uses logic circuits such as shift registers and address decoders.

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 equipped with a counter, memory, etc., and digital values are stored in the memory.

The horizontal scanning circuit unit 111 inputs control pulses to the signal processing unit 103 to sequentially select each column in order to read out the digital signal from the memory of each pixel.

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.

The signal output to the signal line 113 is output via the output circuit 114 to a recording unit or signal processing unit external to the photoelectric conversion device 100.

In Figure 2, the photoelectric conversion units in the pixel region may be arranged one-dimensionally. The signal processing unit function 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.

As shown in Figures 2 and 3, multiple signal processing units 103 are arranged in an area overlapping the pixel area 12 in a planar view. Then, in a planar view, the vertical scanning circuit unit 110, horizontal scanning circuit unit 111, readout circuit 112, output circuit 114, and control pulse generation unit 115 are arranged so as to overlap between the edge of the sensor substrate 11 and the edge of the pixel area 12. In other words, the sensor substrate 11 has a pixel area 12 and a non-pixel area arranged around the pixel area 12. Then, in a planar view, the vertical scanning circuit unit 110, horizontal scanning circuit unit 111, readout circuit 112, output circuit 114, and control pulse generation unit 115 are arranged in an area overlapping the non-pixel area.

Figure 4 is an example of a block diagram including an equivalent circuit of the pixel in Figures 2 and 3. Figure 4 shows a block diagram of a pixel having a typical APD.

In Figure 4, the photoelectric conversion unit 102 having the APD 201 is provided on the sensor substrate 11, and the other components are provided on the circuit board 21.

The APD 201 generates pairs of charges in response to incident light through photoelectric conversion. The APD 201 has a first terminal and a second terminal, with a first power supply connected to the first terminal and a second power supply connected to the second terminal. In Figure 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 charges generated by the incident light undergo avalanche multiplication, generating an avalanche current.

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

An APD operated in Geiger mode is called a SPAD (single photon avalanche diode). For example, voltage VL is -30 V and voltage VH is 1 V to 3 V. APD 201 may be operated in either linear mode or Geiger mode.

The quench element 202, which serves as charging means, is connected to the APD 201 and a power supply that supplies voltage VH. 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.

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.

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 Figure 4 shows an example in which a single inverter is used as the waveform shaping unit 210, a circuit in which multiple inverters are connected in series or another circuit with a waveform shaping effect may also be used.

Counter 211 counts the number (number of times) of pulse signals output from waveform shaping unit 210 and holds the count value. Furthermore, when control pulse pRES is supplied via drive line 213, the signal held in counter 211 is reset.

The selection circuit 212 receives a control pulse pSEL from the vertical scanning circuit unit 110 in FIG. 3 via the drive line 214 in FIG. 4 (not shown in FIG. 3), 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.

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

In this embodiment, a configuration using a counter 211 is shown. However, instead of the counter 211, the photoelectric conversion device 100 may also acquire pulse detection timing using a time-to-digital converter (TDC) and 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 when the input timing of the signal output from each pixel via the waveform shaping unit 210 is converted into relative time using the control pulse pREF as a reference.

Figure 5 is a diagram showing the relationship between APD operation and output signal.

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

Between time t0 and time t1, a potential difference of VH-VL is applied to APD 201 in Figure 5(a). When a photon is incident on APD 201 at time t1, avalanche multiplication occurs in APD 201, an avalanche multiplication current flows through quench element 202, and the voltage of VC drops. When the voltage drop increases further and the potential difference applied to APD 201 decreases, avalanche multiplication in APD 201 stops, as shown at time t2. Then, between time t2 and time t3, a current flows through VC from 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 of VC that exceeds a certain threshold is shaped by waveform shaping unit 210 and output as a signal at VO.

Note that the arrangement of the signal lines 113, readout circuits 112, and output circuits 114 is not limited to that shown in Figure 3. For example, the signal lines 113 may be arranged to extend in the row direction, with the readout circuits 112 located at the ends of the signal lines 113.

[First embodiment]
The photoelectric conversion device according to the first embodiment will be described with reference to FIGS. 6 to 8. FIG.

Figure 6 shows 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 is 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 (clip 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, it controls to reduce the drop in the cathode voltage. Here, in Figure 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 is 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. The voltage GND of the third power supply 603 may also 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.

The quench element 202 is composed of, for example, a PMOS transistor, and a clock signal PCLKB is input to the gate of the PMOS transistor. The clock signal PCLKB is input periodically, for example, 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, switching between the electrical connection and non-connection between the first power supply 601 and the cathode of the APD 201.

One terminal of the voltage control means 604 is connected to the cathode of APD201, and the other terminal is connected to a third power supply. The voltage control means 604 is connected to the cathode of APD201 and controls the cathode voltage VC of APD201. When the cathode voltage VC reaches a predetermined voltage, current flows through VC from the third power supply 603. Note that in Figure 6, the voltage control means 604 is connected to the cathode side of APD201, but as will be described later, the voltage control means 604 may also be connected to the anode side of APD201.

Figure 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, 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). At this time, the voltage applied to the APD 201 is in excess of the breakdown voltage by Vex, enabling avalanche multiplication in Geiger mode. Then, 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.

When a photon is incident at time t2, avalanche multiplication occurs in APD201, and 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 APD201 drops to a voltage below the breakdown voltage. V2 is the first power supply voltage VH, which, as described above, is Vbd + Vex. Therefore, even if avalanche multiplication occurs and cathode voltage VC drops to potential V1, the voltage difference applied to APD201 can be made equal to or greater than the breakdown voltage. When cathode voltage VC drops below potential V1, the voltage difference applied to APD201 becomes a voltage difference less than the breakdown voltage.

Next, when a photon is incident after time t2, a reverse bias voltage less than the breakdown voltage is applied to APD201, so avalanche multiplication due to Geiger mode does not occur. However, a reverse bias voltage is applied to APD201 between first power supply 601 and second power supply 602, and when light is irradiated, electron-hole pairs are generated, generating a reverse current. Therefore, without a voltage control means, the cathode voltage VC continues to decrease to a potential lower than potential V1, as shown by the dashed line in Figure 7. Then, when the clock signal PCLKB goes low again at time t4, APD201 is recharged, and the cathode voltage of APD201 returns to V2.

Figure 8 shows the relationship between the magnitude of the reverse current that occurs after avalanche multiplication subsides and the cathode voltage VC. As shown in Figure 8, when a reverse current flows, the cathode voltage VC decreases. Without a voltage control means, the cathode voltage decreases 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.

In this embodiment, therefore, a voltage control means 604 is provided, as shown in FIG. 6. Even when the voltage control means 604 is provided, the cathode voltage VC drops due to light irradiation after the avalanche multiplication has subsided. However, as shown in FIG. 7, when the cathode voltage VC drops to a predetermined value at time t3, the voltage control means 604 causes 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 VC from dropping below the predetermined value. This makes it possible to prevent the withstand voltage of the MOS transistor from being exceeded, making it possible to provide a highly stable photoelectric conversion device.

(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 the threshold 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.

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

(Second Example)
A second example included in the first embodiment described above 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 VC drops due to the photocurrent after the avalanche multiplication subsides. For example, when the cathode voltage VC 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 VC, thereby preventing the cathode voltage VC 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.

(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. The cathode voltage VC drops due to the photocurrent after the avalanche multiplication subsides, and the PMOS transistor 1105 turns 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 toward 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.

In addition, MOS transistors generally have a larger leakage current than diodes. Therefore, compared to the first embodiment, which uses only PMOS transistors, 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 issues that arise when the leakage current is large will be explained using Figure 12.

Figure 12(A) illustrates the 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 recharges, 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, the leakage current is large, causing current to flow from the third power supply 603 to the cathode of the APD 201. If the cathode voltage after avalanche multiplication is negative (e.g., -1.4 V), the voltage rises in the positive direction, and a reverse bias greater than the breakdown voltage is applied to the APD 201, resulting in a voltage that allows avalanche multiplication. As such, under high illuminance 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. However, 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.

Figure 12(B) illustrates the case where photons are detected after a certain time has passed since recharging. When the clock signal PCLKB goes low at time t1, the PMOS 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, current flows from the third power supply 603 to the cathode of APD 201 due to the large leakage current in a PMOS transistor alone. As a result, if the cathode voltage after charging is positive (e.g., 1.1 V), the cathode voltage will decrease toward the negative side. As a result, the voltage Vex of the Vbd + Vex applied to APD 201 decreases, lowering the avalanche multiplication factor and resulting in a problem of reduced sensitivity of 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 Figure 12 (B), making it easier to suppress the voltage drop in the cathode voltage VC.

Figure 13 is a schematic plan view showing the configuration of the quench element 202, which is the charging means, and the voltage control means 604 according to the third embodiment, and Figure 14 is a schematic cross-sectional view taken along line X-X' in Figure 13. Below, the charging means and voltage control means 604 of this embodiment will be explained using Figures 13 and 14, but the arrangement of the components is not limited to this.

Figure 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. The PMOS transistor 2101 of the waveform shaping unit 210 is also arranged in the well region 1107. As shown in Figure 14, the well region 1107 is arranged in a P-type well region 1108.

The NMOS transistor 2102 of the waveform shaping unit 210 is arranged in the well region 1108. The waveform shaping unit 210 is composed of a PMOS transistor 2101 and an NMOS transistor 2102. In plan view, the well region 1108 is sandwiched between P-type well regions 1107.

The 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. It is also 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.

As shown in FIG. 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 PMOS transistor 1105 and PMOS transistor 2101. The element isolation region 1118 may include, for example, an STI or DTI that includes an insulating material. The element isolation region 1118 may also be a semiconductor isolation, or may include a semiconductor isolation and an insulating material.

Figure 15 is a schematic plan view showing a portion of the wiring layer included in the second wiring structure. Figure 15(a) shows the first wiring layer close to the second semiconductor layer, Figure 15(b) shows the second wiring layer between the first wiring layer and the first wiring structure, and Figure 15(c) shows the 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.

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

Wiring pattern 1113 of the first wiring layer is connected to wiring pattern 1113 of the second wiring layer. As shown in Figure 15(b), it is preferable to arrange wiring pattern 1113 diagonally in a plan view and to keep it as far away as possible from wiring patterns 1114 and 1115. This reduces the coupling capacitance between wiring pattern 1113, which serves as the cathode wiring, and wiring patterns 1114 and 1115, which serve as 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.

The wiring pattern 1113 of the second wiring layer is connected to the wiring pattern 1113 of the third wiring layer shown in Figure 15(c). Furthermore, the wiring pattern 1115 of the second wiring layer is connected to the wiring pattern 1115 of the third wiring layer shown in Figure 15(c).

(Fourth Example)
A fourth example included in the first embodiment 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. The voltage of the first power supply and the voltage of the third power supply are the same.

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

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

In addition, amplifying the current using the bipolar transistor 1120 makes it easier to suppress a drop in the cathode potential VC. The bipolar transistor 1120 may be a parasitic bipolar.

(Fifth Example)
A fifth example included in the first embodiment described above will be described with reference to FIG. 17 . In this example, the voltage control means 604 is configured with multiple diodes. For example, the voltage control means 604 can be configured with three diodes. Furthermore, an amplitude conversion means 610 is connected between the quench element 202 and the cathode of the APD 201. The amplitude conversion means 610 can be configured with, for example, a PMOS transistor. The amplitude conversion means 610 controls the voltage of the node NodeA using the gate voltage of the amplitude conversion means 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 means 610. For example, a 2.5 V transistor is used. On the other hand, because the quench element 202 and the waveform shaping unit 210 do not require such a high voltage resistance, 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.

The cathode of the APD 201 is connected to the cathode of the diode. The three diodes are connected in series. This embodiment also limits the cathode voltage VC from dropping below a predetermined value, 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. Furthermore, by connecting three diodes as in this embodiment, it is easier to control the voltage of the cathode voltage VC compared to when it is controlled by a single diode.

Using Figure 18, we will explain the operation when the amplitude conversion means 610 is provided. Figure 18 is a diagram showing the clock signal, the timing at which photons are incident, the cathode voltage VC, and the 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 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 node NodeA. This allows the quench element 202 and waveform shaping section 210 to use low-voltage transistors, thereby reducing the layout area.

Figure 19 shows a schematic plan view illustrating the configuration of the amplitude conversion means and voltage control means 604 according to the fifth embodiment, and Figure 20 shows a schematic cross-sectional view taken along line X-X' in Figure 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, which constitutes the amplitude conversion means 610, is arranged in the N-type well region 1107. Furthermore, the PMOS transistor 2103 is arranged between two diodes 1106 and one diode 1106.

Of the three diodes 1106, the central diode 1106 is the diode connected to VC (the cathode terminal of APD201) in Figure 17, and is therefore preferably placed adjacent to PMOS transistor 2103. This reduces the cathode wiring capacitance and reduces power consumption. Furthermore, the diode 1106 placed on the opposite side of 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 surrounding transistors.

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

As shown in Figure 21, the voltage control means 604 of this embodiment includes four diodes. The 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 placed for each APD 201, and the subsequent diodes are shared by multiple APDs 201.

Note that in Figure 21, two APDs 201 share part of the voltage control means 604, but the voltage control means 604 may be shared by three or more APDs 201.

(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 serves as charging means. The cathode (second terminal) of the APD 201 is connected to a second power supply 1302. An NMOS transistor 1304, which serves as 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. 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.

After the avalanche multiplication subsides, the anode voltage VA rises due to the photocurrent. When the anode voltage VA reaches the threshold value at which the NMOS transistor 1304 turns on, current flows from the anode of the APD 201 to the third power supply 1303. This current lowers 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, because the voltage control means can be realized with just one NMOS transistor, the area can also be reduced.

In addition, in the first through sixth embodiments, the anode and cathode terminals may be interchanged, as in the seventh embodiment.

(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. However, 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 from the charging means, the cathode potential may exceed the breakdown voltage of the MOS transistor. Even in such a case, the breakdown voltage of the MOS transistor can be easily ensured by using the voltage control means 604 under high illuminance.

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 this 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.

In FIG. 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 board, 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 board, which is a third substrate. The first, second, and third substrates are then stacked.

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-shaped digital signal, so high-voltage MOS transistors are not necessary. Conversely, using low-voltage MOS transistors in the signal processing circuitry downstream of the waveform shaping unit 210 allows for lower voltages and reduced power consumption. Furthermore, using low-voltage MOS transistors allows for transistor miniaturization and space savings. For example, the gate oxide thickness 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.

[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.

The photoelectric conversion devices described in the first and second embodiments above 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 photoelectric conversion systems. Figure 24 shows a block diagram of a digital still camera as an example of such a system.

The photoelectric conversion system illustrated in FIG. 24 includes an image capture 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 capture device 1004. It also 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 capture device 1004. The image capture 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.

The photoelectric conversion system also has a signal processing unit 1007, which is an image generation unit that generates an image by processing the output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compression as necessary and outputs 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.

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 also includes a recording medium 1012 such as a semiconductor memory for recording or reading image data, and a recording medium control interface unit (recording medium control I/F unit) 1011 for recording or reading data from the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system or may be removable.

The photoelectric conversion system further includes an overall control/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 signal processing unit 1007. Here, timing signals and the like may be input from an external source, 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 from the image capture device 1004.

The imaging device 1004 outputs an imaging signal to the 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.

In this way, according to this embodiment, it is possible to realize a photoelectric conversion system that applies the photoelectric conversion device (imaging device) of any of the above embodiments.

[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.

Figure 25(a) shows an example of a photoelectric conversion system for an in-vehicle camera. The photoelectric conversion system 2300 includes an image capture device 2310. The image capture 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 capture device 2310, and a parallax acquisition unit 2314 that calculates parallax (phase difference of 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, defocus amount, distance to the object, etc. The collision determination unit 2318 may use any of this distance information to determine the possibility of a collision. The distance information acquisition means may be implemented by specially designed hardware, or by a software module. It may also be implemented by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination of these.

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 braking force to 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 alert 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 collision, the control ECU 2330 applies the brakes, releases the accelerator, suppresses engine output, or performs other vehicle control to avoid the collision and mitigate damage. The alarm device 2340 warns the user by sounding an alarm, displaying alarm information on a screen such as a car navigation system, or vibrating the seat belt or steering wheel.

In this embodiment, the photoelectric conversion system 2300 captures images of the area around the vehicle, for example, the front or rear. Figure 25(b) shows a photoelectric conversion system for capturing images of the area in front of the vehicle (imaging range 2350). The 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.

The above describes an example of control to prevent collisions with other vehicles, but the system can also be applied to control automatic driving by following other vehicles, or automatic driving to prevent vehicles from leaving their lanes. Furthermore, the photoelectric conversion system is not limited to vehicles such as the vehicle itself, but can also be applied to moving objects (mobile devices) such as ships, aircraft, or industrial robots. In addition, the system can be applied not only to moving objects, but also to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS).

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.

As shown in Figure 26, the distance image sensor 401 is composed of an optical system 402, a photoelectric conversion device 403, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 401 is able to obtain a distance image corresponding to the distance to the subject by receiving light (modulated light or pulsed light) that is projected toward the subject from a light source device 411 and reflected from the surface of the subject.

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

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

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 the monitor 405 for display, or supplied to the memory 406 for storage (recording).

In the range image sensor 401 configured in this manner, by applying the photoelectric conversion device described above, it is possible to obtain, for example, more accurate range images as pixel characteristics improve.

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 the schematic configuration of an endoscopic surgery system, which is the photoelectric conversion system of this embodiment.

Figure 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, the endoscopic surgery system 1003 is composed of an endoscope 1100, surgical tools 1110, and a cart 1134 on which various devices for endoscopic surgery are mounted.

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

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 1101 by a light guide extending inside the lens barrel 1101, and is then irradiated via the objective lens towards an object to be observed 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.

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

The CCU 1135 is composed of a CPU (Central Processing Unit), GPU (Graphics Processing Unit), etc., and provides overall control over the operation of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives image signals from the camera head 1102 and performs various image processing on the image signals, such as development processing (demosaic processing), to display an image based on the image signals.

The display device 1136, under the control of the CCU 1135, displays an image based on the image signal that has been image processed by the CCU 1135.

The light source device 1203 is composed of a light source such as an LED (Light Emitting Diode), and supplies illumination light to the endoscope 1100 when photographing the surgical site, etc.

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

The treatment tool control device 1138 controls the operation of the energy treatment tool 1112 for cauterizing tissue, incising, sealing blood vessels, etc.

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, such as 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 time-share images corresponding to each RGB by irradiating the object of observation with laser light from each RGB laser light source and controlling the drive of the image sensor in the camera head 1102 in synchronization with the irradiation timing. This method makes it possible to obtain color images without providing a color filter to the image sensor.

The light source device 1203 may also be controlled to change the intensity of the light it outputs at predetermined time intervals. The image sensor of the camera head 1102 is controlled to acquire images in a time-division manner in synchronization with the timing of the change in light intensity, and these images are then combined to generate a high dynamic range image free of so-called blocked-up shadows and blown-out highlights.

The light source device 1203 may also be configured to provide light in a predetermined wavelength band compatible with special light observation. Special light observation, for example, utilizes the wavelength dependence of light absorption in body tissue. Specifically, by irradiating light with a narrower band than the light irradiated during normal observation (i.e., white light), specific tissue, such as blood vessels on the surface of the mucosa, can be photographed with high contrast. Alternatively, special light observation may involve fluorescence observation, in which images are obtained using fluorescence generated by irradiating excitation light. Fluorescence observation can involve irradiating excitation light onto body tissue and observing the fluorescence from the tissue, or locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the 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 provide narrow band light and/or excitation light compatible with such special light observation.

Seventh Embodiment
The photoelectric conversion system of this embodiment will be described with reference to FIGS. 28( a) and 28(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).

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 operation 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.

Figure 28(b) illustrates glasses 1610 (smart glasses) according to one application example. The glasses 1610 have a control device 1612, which is equipped with a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. The lens 1611 is formed with an optical system for projecting light emitted from the photoelectric conversion device in the control device 1612 and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source that supplies 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 also have a gaze detection unit that detects 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. By providing a reduction means for reducing light from the infrared light emitter to the display unit in a planar view, degradation of image quality is reduced.

The user's line of sight with respect to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be used to detect the line of sight using an image of the eyeball. As an example, a line of sight detection method based on the Purkinje image formed by the reflection of irradiated light on the cornea can be used.

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

The display device of this embodiment may have a photoelectric conversion device with a light-receiving element, and may control the image displayed on the display device based on user line-of-sight information from the photoelectric conversion device.

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 received from an external control device. 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.

The display area may also have a first display area and a second display area different from the first display area, and an area with a high priority 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 areas with a relatively low priority may be lowered.

In addition, AI may be used to determine the first field of view area and high-priority areas. 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 the 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 stored in the display device, the photoelectric conversion device, or an external device. If stored in an external device, it is transmitted to the display device via communication.

When display control is based on visual recognition detection, it is preferably applied to smart glasses that also have a photoelectric conversion device that captures images of the outside world. The smart glasses can display captured external information in real time.

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.

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

As shown in FIG. 29(a), a display 1510 for displaying images is disposed in the center of the surface of electronic device 1500. Also, along the upper edge of the surface of electronic device 1500, front cameras 1521 and 1522 that use photoelectric conversion devices, an IR light source 1530 that emits infrared light, and a visible light source 1540 that emits visible light are disposed.

Also, as shown in FIG. 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 surface of the electronic device 1500.

By applying the photoelectric conversion device described above, the electronic device 1500 configured in this manner can capture higher-quality images, for example. The photoelectric conversion device can also be applied to other electronic devices, such as infrared sensors, distance measurement 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.

Ninth Embodiment
30 is a block diagram of an X-ray CT apparatus according to this embodiment. This embodiment is applicable to both the first and second embodiments. The X-ray CT apparatus 30 according to 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.

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

The wedge 311 is a filter that adjusts the amount of X-rays irradiated from the X-ray generator 310. The wedge 311 attenuates the amount of X-rays so that the X-rays irradiated from the X-ray generator 310 to the subject have a predetermined distribution. The collimator 312 is composed 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 generator 310 are shaped into a cone beam via the collimator 312 and irradiated onto the subject on the tabletop 330.

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

The rotating frame 340 is annular and rotatable. Inside the rotating frame 340, the X-ray generation unit 310 (wedge 311, collimator 312) and the X-ray detection unit 320 are arranged facing each other. The X-ray generation unit 310 and the X-ray detection unit 320 can rotate together with the rotating frame 340.

The high-voltage generator 350 includes a boost circuit and outputs a high voltage to the X-ray generator 310. The DAS 351 includes an amplifier circuit and an A/D converter circuit, and outputs the signal from the X-ray detector 320 to the signal processor 352 as digital data.

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 other components, and controls the overall operation of the X-ray CT device 30.

Tenth Embodiment
This embodiment is applicable to both the first and second embodiments. FIG. 31A is a schematic diagram illustrating an apparatus 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 apparatus 9191 including the semiconductor device 930 will be described in detail. The semiconductor device 930 may include a semiconductor device 910. In addition to the semiconductor device 910, the semiconductor device 930 may also include a package 920 that houses 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.

The equipment 9191 may 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, shutter, or 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.

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 that constitutes an AFE (analog front end) or DFE (digital front end). The display device 970 is an EL display device or liquid crystal display device that displays the information (image) obtained by the semiconductor device 930. The memory device 980 is a magnetic device or semiconductor device that stores the information (image) obtained by the semiconductor device 930. The memory device 980 is a volatile memory such as SRAM or DRAM, or a non-volatile memory such as a flash memory or hard disk drive.

The mechanical device 990 has a moving part or propulsion part such as a motor or 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 via a communication device (not shown) provided in the device 9191. For this reason, 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.

The device 9191 is also suitable for electronic devices such as information terminals with a photographing function (e.g., smartphones and wearable devices) and cameras (e.g., 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.

The device 9191 may also be transportation equipment such as a vehicle, ship, or flying object (drone, aircraft, etc.). The mechanical device 990 in the transportation equipment may 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 to operate 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 sensor, an analytical device such as an electron microscope, office equipment such as a copier, or industrial equipment such as a robot.

The above-described embodiments make it possible to obtain good pixel characteristics. This increases the value of the semiconductor device. In this context, increasing value refers to at least one of the following: adding functions, improving performance, improving characteristics, improving reliability, improving manufacturing yield, reducing environmental impact, reducing costs, making the device smaller, and reducing weight.

Therefore, using the semiconductor device 930 according to this embodiment in equipment 9191 can also improve the value of the equipment. For example, by installing the semiconductor device 930 in transportation equipment, excellent performance can be obtained when photographing the exterior of the transportation equipment and measuring the external environment. Therefore, when manufacturing and selling transportation equipment, deciding to install the semiconductor device according to this embodiment in the transportation equipment is advantageous in improving the performance of the transportation equipment itself. In particular, the semiconductor device 930 is suitable for transportation equipment that uses information obtained by the semiconductor device to perform driving assistance and/or automatic driving of the transportation equipment.

The photoelectric conversion system and mobile object of this embodiment will also be described using Figure 31(b).

Figure 31(b) shows an example of a photoelectric conversion system for an in-vehicle camera. The photoelectric conversion system 8 has a photoelectric conversion device 80. The photoelectric conversion device 80 is a photoelectric conversion device (imaging device) described in any of the above embodiments. The photoelectric conversion system 8 has an image processing unit 801 that performs image processing on multiple 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 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 the 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. Here, 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. In other words, the distance information includes information about the parallax, the defocus amount, the distance to the object, etc. 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 by ToF (Time of Flight). The distance information acquisition means may be implemented by dedicated hardware or a software module. It may also be realized using an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination of these.

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 braking force to 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 alert 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 collision, the control ECU 820 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, or suppressing engine output. The alarm device 830 warns the user by sounding an alarm, displaying alarm information on a screen such as a car navigation system, or vibrating the seat belt or steering wheel.

In this embodiment, the photoelectric conversion system 8 captures images of the area around the vehicle, for example, the front or rear. Figure 31(c) shows a photoelectric conversion system for capturing images of the area in front of the vehicle (imaging range 850). The 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.

The above describes an example of control to prevent collisions with other vehicles, but the system can also be applied to automatic driving control to follow other vehicles and automatic driving control to prevent vehicles from drifting out of their lanes. Furthermore, the photoelectric conversion system 8 can be applied not only to vehicles such as automobiles, but also to moving bodies (mobile devices) such as ships, aircraft, and industrial robots. These moving bodies include one or both of a driving force generation unit that generates driving force primarily used to move the moving body, and a rotating body primarily used to move the moving body. The driving force generation unit 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 system can be applied to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS).

While various devices have been described in the above embodiments, a mechanical device may also be included. The mechanical device in the camera can drive optical system components for zooming, focusing, and shutter operation. Alternatively, the mechanical device in the camera can move the photoelectric conversion device for vibration isolation.

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

[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.

Furthermore, in the above embodiment, an example was described in which MOS transistors were used as transistors, but transistors other than MOS transistors may also be used. For example, bipolar transistors may be used instead of MOS transistors.

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.

The above-described embodiments are merely examples of specific ways of implementing the present invention, and should not be construed as limiting the technical scope of the present invention. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

In this specification, expressions such as "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 applies equally to combinations of three or more elements.

The embodiments described above can be modified as appropriate without departing from the technical concept. The disclosure of this specification includes not only what is described herein, 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 herein. In other words, if this specification states, for example, that "A is greater than B," then even if the statement "A is not greater than B" is omitted, it can be said that this specification discloses that "A is not greater than B." This is because when it states that "A is greater than B," it is assumed that the case where "A is not greater than B" is taken into consideration.

The disclosure of this embodiment includes the following configurations and methods.

(Configuration 1)
an avalanche photodiode having a first terminal and a second terminal;
a first power supply connected to the first terminal;
a second power supply connected to the second terminal;
charging means for controlling the voltage of the first terminal;
a voltage control means connected to the first terminal and configured to control the voltage of the first terminal in accordance with the voltage of the first terminal;
a third power supply connected to the voltage control means.

(Configuration 2)
2. The photoelectric conversion device according to configuration 1, 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.

(Configuration 3)
2. The photoelectric conversion device according to configuration 1, wherein the voltage of the third power supply is the same as the voltage of the first power supply.

(Configuration 4)
the voltage control means includes a MOS transistor;
one terminal of the MOS transistor is connected to the first terminal;
2. The photoelectric conversion device according to claim 1, wherein the other terminal of the MOS transistor is connected to the third power supply.

(Configuration 5)
5. The photoelectric conversion device according to claim 1, wherein the gate of the MOS transistor is connected to the first terminal.

(Configuration 6)
The photoelectric conversion device according to any one of the first to fifth configurations, wherein the MOS transistor is a P-type MOS transistor.

(Configuration 7)
The photoelectric conversion device according to any one of the first to fifth configurations, wherein the MOS transistor is an N-type MOS transistor.

(Configuration 8)
the voltage control means includes a diode;
one terminal of the diode is connected to the first terminal;
2. The photoelectric conversion device according to claim 1, wherein the other terminal of the diode is connected to the third power supply.

(Configuration 9)
the one terminal of the diode is a cathode,
9. The photoelectric conversion device according to any one of the first to eighth configurations, wherein the other terminal of the diode is an anode.

(Configuration 10)
the voltage control means further includes a MOS transistor;
one terminal of the MOS transistor is connected to the first terminal;
9. The photoelectric conversion device according to any one of configurations 1 to 8, wherein the other terminal of the MOS transistor is connected to the third power supply via the diode.

(Configuration 11)
11. The photoelectric conversion device according to any one of configurations 1 to 10, wherein the gate of the MOS transistor is connected to the first terminal.

(Configuration 12)
12. The photoelectric conversion device according to any one of configurations 1 to 11, wherein the MOS transistor is a P-type MOS transistor.

(Configuration 13)
12. The photoelectric conversion device according to any one of configurations 1 to 11, wherein the MOS transistor is an N-type MOS transistor.

(Configuration 14)
2. The photoelectric conversion device according to configuration 1, wherein the first terminal is a cathode of the avalanche photodiode.

(Configuration 15)
2. The photoelectric conversion device according to claim 1, wherein the first terminal is an anode of the avalanche photodiode.

(Configuration 16)
a waveform shaping unit connected to the first terminal,
2. The photoelectric conversion device according to configuration 1, wherein the waveform shaping section is connected to the voltage control means.

(Configuration 17)
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 control means, and the waveform shaping unit is disposed;
and a third substrate on which a second signal processing unit that processes the signal output from the waveform shaping unit is disposed.

(Configuration 18)
18. The photoelectric conversion device according to any one of configurations 1 to 17, wherein the second signal processing section has a counter that counts the signal output from the waveform shaping section.

(Configuration 19)
the charging means includes a MOS transistor;
19. The photoelectric conversion device according to any one of configurations 1 to 18, wherein a clock signal is input to the gate of the MOS transistor of the charging means.

(Configuration 20)
The photoelectric conversion device according to any one of configurations 1 to 19,
a signal processing unit that generates an image using a signal output from the photoelectric conversion device.

(Configuration 21)
A moving object including the photoelectric conversion device according to any one of configurations 1 to 19,
A moving body comprising: a control unit that controls movement of the moving body using a signal output from the photoelectric conversion device.

Claims (21)

an avalanche photodiode having a first terminal and a second terminal;
a charging means including a first MOS transistor connected to the first terminal, the charging means controlling an electrical connection between the first terminal and a first power supply in response to a clock signal input to a gate of the first MOS transistor;
a second power supply connected to the second terminal;
a voltage control means connected to the first terminal, the voltage control means controlling the voltage of the first terminal in accordance with the voltage of the first terminal when the charging means does not electrically connect the first terminal to the first power supply;
a third power supply connected to the voltage control means. The photoelectric conversion device described in claim 1, characterized in that 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. The photoelectric conversion device described in claim 1, characterized in that the voltage of the third power supply is the same as the voltage of the first power supply. the voltage control means has a second MOS transistor;
one terminal of the second MOS transistor is connected to the first terminal;
2. The photoelectric conversion device according to claim 1, wherein the other terminal of the second MOS transistor is connected to the third power supply. 5. The photoelectric conversion device according to claim 4, wherein the gate of the second MOS transistor is connected to the first terminal. 6. The photoelectric conversion device according to claim 5, wherein the second MOS transistor is a P-type MOS transistor. 6. The photoelectric conversion device according to claim 5, wherein the second MOS transistor is an N-type MOS transistor. the voltage control means includes a diode;
one terminal of the diode is connected to the first terminal;
2. The photoelectric conversion device according to claim 1, wherein the other terminal of the diode is connected to the third power supply. the one terminal of the diode is a cathode,
9. The photoelectric conversion device according to claim 8, wherein the other terminal of the diode is an anode. the voltage control means further includes a second MOS transistor;
one terminal of the second MOS transistor is connected to the first terminal;
9. The photoelectric conversion device according to claim 8, wherein the other terminal of the second MOS transistor is connected to the third power supply via the diode. 11. The photoelectric conversion device according to claim 10, wherein the gate of the second MOS transistor is connected to the first terminal. 12. The photoelectric conversion device according to claim 11, wherein the second MOS transistor is a P-type MOS transistor. 12. The photoelectric conversion device according to claim 11, wherein the second MOS transistor is an N-type MOS transistor. The photoelectric conversion device described in claim 1, characterized in that the first terminal is the cathode of the avalanche photodiode. The photoelectric conversion device described in claim 1, characterized in that the first terminal is the anode of the avalanche photodiode. 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 control means. 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 control means, and the waveform shaping unit is disposed;
17. The photoelectric conversion device according to claim 16, further comprising: a third substrate on which a second signal processing section for processing the signal output from the waveform shaping section is disposed. The photoelectric conversion device described in claim 17, characterized in that the second signal processing unit has a counter that counts the signal output from the waveform shaping unit. 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 control means controls the voltage of the first terminal in accordance with the voltage of the first terminal when the avalanche photodiode is in the standby state and the first terminal is not connected to the first power supply. The photoelectric conversion device according to any one of claims 1 to 19,
a signal processing unit that generates an image using a signal output from the photoelectric conversion device. A moving object comprising the photoelectric conversion device according to any one of claims 1 to 19,
A moving body comprising: a control unit that controls movement of the moving body using a signal output from the photoelectric conversion device.