Photoelectric converter, photoelectric converter system, and mobile body

Abstract

To suppress crosstalk between adjacent avalanche diodes, and to miniaturize pixel size while suppressing increase of dark current.SOLUTION: Each avalanche diode of a plurality of avalanche diodes at least comprises: an n-type semiconductor region 1 that is formed at a first depth; and a p-type semiconductor region 5 that is formed at a second depth in which a depth from a first surface is deeper than the first depth. The n-type semiconductor region 1 and the p-type semiconductor region 5 form a PN junction. The p-type semiconductor region 5 is a well region, for example. A first separation part 20 is arranged between each n-type semiconductor region in a cross section passing through the n-type semiconductor region 1 of a first avalanche diode and the n-type semiconductor region 1 of a second avalanche diode.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion device, a photoelectric conversion system, and a mobile device. [Background technology]

[0002] A photoelectric converter is known that digitally counts the number of photons arriving at a light-receiving section and outputs the count value as a digital signal from the pixel. Patent Document 1 discloses a photodetector using an avalanche diode that causes avalanche multiplication in the PN junction region of the semiconductor region constituting the photoelectric converter. In the photodetector of Patent Document 1, a high-density P-type semiconductor region is arranged between the N-type semiconductor regions of adjacent avalanche diodes to make electrical contact. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-201005 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In Patent Document 1, reducing the pixel size reduces the distance between the P-type semiconductor region and the N-type semiconductor region constituting the avalanche diode. When a potential is supplied to the avalanche diode in this state, a localized high-electric-field region is formed by the highly concentrated P-type semiconductor region and the N-type semiconductor region that make electrical contact, making it easier for dark current to be generated. [Means for solving the problem]

[0005] One aspect of the photoelectric conversion device of the present invention is The avalanche diode comprises a first avalanche diode including a first semiconductor region of a first conductivity type having the same charge as the signal charge as the majority carriers, and a second avalanche diode including a second semiconductor region of the first conductivity type and arranged adjacent to the first avalanche diode, wherein a first separation portion is disposed between the first semiconductor region and the second semiconductor region, the first separation portion is composed of a third semiconductor region of the first conductivity type, and a seventh semiconductor region of a second conductivity type, which has a different conductivity type from the first conductivity type, is disposed at a position that overlaps with the third semiconductor region in a plan view and is deeper than the third semiconductor region, the third semiconductor region and the seventh semiconductor region form a PN junction, the impurity concentration of the third semiconductor region is lower than the impurity concentration of the seventh semiconductor region, and no semiconductor region of the second conductivity type is disposed between the first semiconductor region and the second semiconductor region. .

[0006] One aspect of the photoelectric conversion device of the present invention is The avalanche diode comprises a first avalanche diode including a first semiconductor region of a first conductivity type having the same charge as the signal charge as the majority carriers, and a second avalanche diode including a second semiconductor region of the first conductivity type and arranged adjacent to the first avalanche diode, wherein a first separation section is disposed between the first and second semiconductor regions, and the first separation section is composed of a fourth semiconductor region of a second conductivity type having a conductivity type different from the first conductivity type, and a third semiconductor region of the first conductivity type arranged on either side of the fourth semiconductor region in a plan view, wherein the fourth semiconductor region satisfies Equation 1, with respect to the impurity concentration Nd of the third semiconductor region, the impurity concentration Na of the fourth semiconductor region, the elementary charge q, the dielectric constant ε of the semiconductor, the potential difference V between the PN junction of the third and fourth semiconductor regions, and the length D of the fourth semiconductor region sandwiched between the third semiconductor regions. .

number

[0007] One side of the photoelectric conversion device of the present invention is, A first avalanche diode comprising: a substrate having a first surface and a second surface facing the first surface; a first semiconductor region of a first conductivity type disposed at a first depth of the substrate and having the same charge as the signal charge as the majority carriers; a fifth semiconductor region of a second conductivity type having a different conductivity type from the first conductivity type, disposed at a second depth between the first depth and the second surface and between the first semiconductor region and the second surface; a second avalanche diode disposed adjacent to the first avalanche diode, comprising: a second semiconductor region of the first conductivity type disposed at the first depth of the substrate; and a sixth semiconductor region of the second conductivity type disposed at the second depth between the second semiconductor region and the second surface; wherein at the first depth, between the first semiconductor region and the second semiconductor region, A separation section is provided, the first separation section contains at least one of an intrinsic semiconductor region, a third semiconductor region of the first conductivity type, and a fourth semiconductor region of the second conductivity type, and at the second depth, a seventh semiconductor region of the second conductivity type is provided between the fifth semiconductor region and the sixth semiconductor region, the potential height for the signal charge in a line passing through the first separation section and the seventh semiconductor region and perpendicular to the first plane decreases from the seventh semiconductor region toward the first separation section, and the difference between the potential height for the signal charge in the first semiconductor region and the potential height for the signal charge in the fifth semiconductor region is greater than the difference between the potential height for the signal charge in the first separation section and the potential height for the signal charge in the seventh semiconductor region. .

Effects of the Invention

[0008] According to the present invention, in a photoelectric conversion device using an avalanche diode, it is possible to reduce the pixel size while suppressing an increase in dark current.

Brief Description of the Drawings

[0009] [Figure 1] Block diagram of the photoelectric conversion device [Figure 2] Block diagram of the pixel [Figure 3] Expanded plan view of a part of the photoelectric conversion device of the first embodiment [Figure 4] Cross-sectional view of the photoelectric conversion device of the first embodiment [Figure 5] Potential diagram of the photoelectric conversion device of the first embodiment [Figure 6] Cross-sectional view and potential diagram of the photoelectric conversion device of the comparative example [Figure 7] Expanded plan view of a part of the photoelectric conversion device of the second embodiment [Figure 8] Cross-sectional view of the photoelectric conversion device of the second embodiment [Figure 9] Expanded plan view of a part of the photoelectric conversion device of the third embodiment [Figure 10] Cross-sectional view of the photoelectric conversion device of the third embodiment [Figure 11] Modified example of the third embodiment [Figure 12] Expanded plan view of a part of the photoelectric conversion device of the fourth embodiment [Figure 13] Cross-sectional view of the photoelectric conversion device of the fourth embodiment [Figure 14] Cross-sectional view of the photoelectric conversion device of the fifth embodiment [Figure 15] Expanded plan view of a part of the photoelectric conversion device of the sixth embodiment [Figure 16] Enlarged plan view of a portion of the photoelectric converter according to the sixth embodiment. [Figure 17] Enlarged plan view of a portion of the photoelectric converter according to the seventh embodiment. [Figure 18] Cross-sectional view of the photoelectric converter of the seventh embodiment. [Figure 19] Cross-sectional view of the photoelectric converter of the eighth embodiment. [Figure 20] Cross-sectional view of the photoelectric converter of the ninth embodiment. [Figure 21] Photoelectric conversion system according to the 10th embodiment [Figure 22] Photoelectric conversion system according to the 11th embodiment [Figure 23] Schematic diagram of the photoelectric conversion system and mobile body according to the 12th embodiment. [Figure 24] Flowchart showing the operation of the photoelectric conversion system of the 12th embodiment. [Figure 25] Photoelectric conversion system according to the 13th embodiment [Figure 26] Photoelectric conversion system according to the 14th embodiment [Figure 27] Block diagram of a photoelectric conversion system according to the 14th embodiment. [Figure 28] Photoelectric conversion system according to the 15th embodiment [Figure 29] Photoelectric conversion system according to the 15th embodiment [Figure 30] Experimental example of a photoelectric conversion system according to the 15th embodiment. [Figure 31] Photoelectric converter according to the 16th embodiment [Figure 32] Spectral transmittance of the filter according to the 17th embodiment [Figure 33] Example of pixel and filter arrangement according to the 17th embodiment [Figure 34] Example of pixel and filter arrangement according to the 17th embodiment [Figure 35] Example of pixel and filter arrangement according to the 17th embodiment [Modes for carrying out the invention]

[0010] The embodiments shown below are intended to embody the technical concept of the present invention and do not limit it. The size and positional relationships of the components shown in each drawing may be exaggerated for clarity of explanation. In the following description, identical components may be given the same number and their explanation may be omitted.

[0011] The following configuration relates to a photoelectric conversion device that includes a SPAD (Single Photon Avalanche Diode) for counting the number of photons incident on an avalanche diode. The photoelectric conversion device includes at least an avalanche diode.

[0012] In the following explanation, the anode of the avalanche diode is set to a fixed potential, and the signal is taken from the cathode side. Therefore, the semiconductor region of the first conductivity type, which has charges of the same conductivity type as the signal charge as the majority carriers, is an N-type semiconductor region, and the semiconductor region of the second conductivity type is a P-type semiconductor region. Note that the present invention also applies when the cathode of the avalanche diode is set to a fixed potential and the signal is taken from the anode side. In this case, the semiconductor region of the first conductivity type, which has charges of the same conductivity type as the signal charge as the majority carriers, is a P-type semiconductor region, and the semiconductor region of the second conductivity type is an N-type semiconductor region. The following explanation describes the case where one node of the avalanche diode is set to a fixed potential, but the potentials of both nodes may fluctuate.

[0013] Figure 1 is a block diagram of the photoelectric converter 1000 of this embodiment. The photoelectric converter 1000 has a pixel area 111, a horizontal scanning circuit section 105, a signal line 104, and a vertical scanning circuit section 103.

[0014] Multiple pixels 110 are arranged in a two-dimensional manner within the pixel region 111. Each pixel 110 consists of a photoelectric conversion unit 101 and a pixel signal processing unit 102. The photoelectric conversion unit 101 converts light into an electrical signal. The pixel signal processing unit 102 outputs the converted electrical signal to the signal line 104.

[0015] The vertical scanning circuit section 103 and the horizontal scanning circuit section 105 supply control pulses to each pixel 110. The vertical scanning circuit section 103 uses logic circuits such as a shift register and an address decoder.

[0016] The signal line 104 supplies the digital signal output from the pixel 110 selected by the vertical scanning circuit unit 103 as a potential signal to the circuit downstream of the pixel 110.

[0017] In Figure 1, the arrangement of pixels 110 in the pixel region 111 may be arranged in a one-dimensional manner. Alternatively, the vertical scanning circuit 103 and the horizontal scanning circuit 105 may be arranged within each block of the pixel region 111, or within each individual pixel column.

[0018] The pixel signal processing unit 102 does not necessarily need to be provided for every pixel 110; for example, one pixel signal processing unit 102 may be shared by multiple pixels 110, and signal processing may be performed sequentially. Furthermore, to increase the aperture ratio of the photoelectric conversion unit 101, at least a portion of the pixel signal processing unit 102 may be provided on a different semiconductor substrate (second substrate) from the photoelectric conversion unit 101. In this case, the photoelectric conversion unit 101 and the pixel signal processing unit 102 are electrically connected via connection wiring provided for each pixel. It is preferable to place the avalanche diode of the photoelectric conversion unit 101 on the first substrate and the other components on the second substrate. The vertical scanning circuit unit 103, the horizontal scanning circuit unit 105, and the signal line 104 may be provided on the second substrate.

[0019] Figure 2 is a block diagram of a pixel 110 including an equivalent circuit in this embodiment. In Figure 2, one pixel 110 is composed of a photoelectric conversion unit 101 and a pixel signal processing unit 102.

[0020] The photoelectric conversion unit 101 includes one or more arrayed avalanche diodes 201, a quench element 202, and a waveform shaping unit 203.

[0021] The avalanche diode 201 generates charge pairs corresponding to the incident light through photoelectric conversion. The cathode of the avalanche diode 201 is supplied with a potential based on a potential VH that is higher than the potential VL supplied to the anode. The anode and cathode of the avalanche diode 201 are supplied with a potential that creates a reverse bias, causing the photons incident on the avalanche diode 201 to be avalanche multiplied. By performing photoelectric conversion with this reverse bias potential supplied, the charge generated by the incident light undergoes avalanche multiplication, and an avalanche current is generated.

[0022] When a reverse bias potential is supplied, an avalanche diode operates in Geiger mode when the potential difference between the anode and cathode is greater than the breakdown voltage. An avalanche diode that uses Geiger mode operation to quickly detect weak signals at the single-photon level is called a SPAD (Single Photon Avalanche Diode).

[0023] The quench element 202 is connected to a power supply that provides a high potential VH and to the avalanche diode 201. The quench element 202 is composed of a P-type MOS transistor or a resistive element such as a poly resistor. Alternatively, the quench element 202 may be composed of multiple MOS transistors in series. When the photocurrent is multiplied by avalanche multiplication in the avalanche diode 201, the current obtained from the multiplied charge flows through the connection node between the avalanche diode 201 and the quench element 202. The voltage drop caused by this current lowers the potential of the cathode of the avalanche diode 201, and the avalanche diode 201 stops forming an electron avalanche. As a result, the avalanche multiplication of the avalanche diode 201 stops. Subsequently, the potential VH of the power supply is supplied to the cathode of the avalanche diode 201 via the quench element 202, so the potential supplied to the cathode of the avalanche diode 201 returns to potential VH. In other words, the operating region of the avalanche diode 201 returns to Geiger mode. Thus, the quench element 202 functions as a load circuit (quench circuit) when the charge is multiplied by avalanche multiplication, and has the function of suppressing avalanche multiplication (quench operation). Furthermore, after suppressing avalanche multiplication, the quench element has the function of returning the operating region of the avalanche diode to Geiger mode.

[0024] The waveform shaping unit 203 is connected to the connection node between the node of the avalanche diode 201 and the node of the quench element 202. It shapes the potential change at the cathode of the avalanche diode 201 obtained during photon detection and outputs a rectangular pulse signal. For example, an inverter circuit can be used as the waveform shaping unit 203. An example using one inverter as the waveform shaping unit 203 is shown, but a circuit with multiple inverters connected in series may also be used. Not limited to inverters, other circuits that have a waveform shaping effect may also be used.

[0025] The pixel signal processing unit 102 includes a counter circuit 204 and a selection circuit 205.

[0026] The counter circuit 204 is connected to the waveform shaping unit 203. The pulse signals output from the waveform shaping unit 203 are counted by the counter circuit 204. In the case of an N-bit counter (N: positive integer), the counter circuit 204 can count up to approximately 2 to the power of N pulse signals from single photons. The counted signals are held as detected signals. When a control pulse Res is supplied via a control line, the signals held in the counter circuit 204 are reset.

[0027] The selection circuit 205 is connected to the counter circuit 204 and the signal line 104. The selection circuit 205 is supplied with a control pulse Sel from the vertical scanning circuit section 103 in Figure 1 via a control line, and switches whether or not to output the count value of the counter circuit 204 to the signal line 104. The selection circuit 205 includes, for example, a buffer circuit for outputting a signal.

[0028] Furthermore, a switch such as a transistor may be placed between the quench element 202 and the avalanche diode 201 to switch between a mode in which the avalanche diode 201 can perform avalanche multiplication and a mode in which it cannot. Similarly, the supply of a high potential VH or a low potential VL to the avalanche diode 201 may be electrically switched using a switch such as a transistor. In addition, a switch such as a transistor may be placed between the photoelectric conversion unit 101 and the pixel signal processing unit 102 to control the input of the signal from the photoelectric conversion unit 101 to the counter circuit 204.

[0029] In a pixel region 111 where multiple pixels 110 are arranged in a matrix, the image may be acquired by a rolling shutter operation in which the count of the counter circuit 204 is sequentially reset row by row, and the signals held by the counter circuit 204 are sequentially output row by row.

[0030] Alternatively, the captured image may be acquired by a global electronic shutter operation in which the counts of the counter circuits 204 for all pixel rows are simultaneously reset, and the signals held by the counter circuits 204 are output sequentially row by row. When performing a global electronic shutter operation, it is advisable to provide a means to switch between when to perform the count of the counter circuits 204 and when not to perform it. The means for switching is, for example, the switch mentioned above.

[0031] Figure 2 shows a configuration using the counter circuit 204. Instead of the counter circuit 204, a configuration using a Time to Digital Converter (TDC) and memory to acquire pulse detection timing is also possible.

[0032] At this time, the generation timing of the pulse signal output from the waveform shaping unit 203 is converted into a digital signal by the TDC. The TDC is supplied with a control pulse Ref (reference signal) from the vertical scanning circuit unit 103 in Figure 1 via a drive line to measure the timing of the pulse signal. The TDC uses the control pulse pREF as a reference and acquires the signal as a digital signal when the input timing of the signal output from each pixel via the waveform shaping unit 203 is considered as a relative time.

[0033] <First Embodiment> The configuration of the photoelectric converter according to the first embodiment will be explained using Figures 3 to 5.

[0034] Figure 3 is an enlarged plan view of a portion of the pixel area of ​​the photoelectric converter according to the first embodiment. Figure 4(A) is a schematic cross-sectional view of Figure 3 along A-A', and Figure 4(B) is a schematic cross-sectional view of Figure 3 along B-B'. Figure 5(A) is a potential diagram of Figure 4(A) along X-X' and Y-Y'. Figure 5(B) is a potential diagram of Figure 4(A) along V-V'. Figure 5(C) is a potential diagram of Figure 4(B) along W-W'.

[0035] Figure 3 shows four pixels: two in the first direction and two in the second direction, which is orthogonal to the first direction in a plan view. The first direction can be described as the direction along the pixel row (row direction). In other words, the first direction is the direction from which you view a row of pixels, where there are multiple pixels in the first row. The second direction can be described as the direction along the pixel column (column direction). The direction that intersects the first and second directions is called the third direction. For the sake of explanation, in Figure 3, the avalanche diode in the first row and first column will be called the first avalanche diode, the avalanche diode in the first row and second column will be called the second avalanche diode, and the avalanche diode in the second row and second column will be called the third avalanche diode. In this embodiment, a pixel consists of a counter and a sensitivity region that generates a signal to be read from one of the counters. In this specification, "plan view" refers to viewing from a direction perpendicular to a plane parallel to the light incident surface of the substrate.

[0036] As shown in Figure 4, the avalanche diode is formed inside the substrate 40. The substrate 40 has a first surface 40A and a second surface 40B opposite the first surface 40A. The first surface 40A is the surface on which the contact plugs 6 and 7 are formed. The gate electrode of the transistor may also be located on the side of the first surface 40A. In the following description, it is assumed that light is incident on the substrate 40 from the side of the second surface 40B, but the light may also be incident on the substrate 40 from the side of the first surface 40A. In this specification, "depth" refers to the depth from the first surface 40A to the second surface 40B.

[0037] Each avalanche diode has at least a semiconductor region of a first conductivity type (N-type semiconductor region 1) formed to a first depth, and a semiconductor region of a second conductivity type (P-type semiconductor region 5) formed to a second depth which is deeper from the first surface than the first depth. The N-type semiconductor region 1 and the P-type semiconductor region 5 (seventh semiconductor region) form a PN junction. The P-type semiconductor region 5 is, for example, a well region.

[0038] A contact plug 6 is connected to the N-type semiconductor region 1, which supplies a potential VH via a quench element 202. A contact plug 7 is connected to the P-type semiconductor region 4, which supplies a potential VL. The potential VL is supplied to the P-type semiconductor region 5 via the contact plug 7 and the P-type semiconductor region 4.

[0039] In a cross-section passing through multiple N-type semiconductor regions 1, a first separation portion 20 is provided between each N-type semiconductor region 1. In a cross-section different from the aforementioned one, a second separation portion 30 is provided between each N-type semiconductor region 1. For example, in Figures 3 and 4, in a cross-section passing through the N-type semiconductor region 1 of the first avalanche diode and the N-type semiconductor region 1 of the second avalanche diode, a first separation portion 20 is provided between each N-type semiconductor region. In a cross-section passing through the N-type semiconductor region 1 of the second avalanche diode and the N-type semiconductor region 1 of the third avalanche diode, a first separation portion 20 is provided between each N-type semiconductor region 1. In a cross-section passing through the N-type semiconductor region 1 of the first avalanche diode and the N-type semiconductor region 1 of the third avalanche diode, a second separation portion 30 is provided between each N-type semiconductor region 1. The second separation portion 30 includes at least a P-type semiconductor region 4.

[0040] As shown in Figure 5(A), the difference between the electron potential height of the N-type semiconductor region 3 and the electron potential height of the P-type semiconductor region 5 is smaller than the difference between the electron potential height of the N-type semiconductor region 1 and the electron potential height of the P-type semiconductor region 5. In X-X', the difference between the electron potential height of the N-type semiconductor region 1 and the electron potential height of the P-type semiconductor region 5 is configured to allow avalanche multiplication. Then, in Y-Y', the difference between the electron potential height of the first separation section 20 and the electron potential height of the P-type semiconductor region 5 is configured not to allow avalanche multiplication. The maximum electron potential height in Y-Y' is lower than the maximum electron potential height in X-X'.

[0041] Figures 5(B) and 5(C) show the potential distribution for the signal charge in V-V' and W-W', respectively. In this embodiment, when the potential of the avalanche diode is stable and waiting for a photon (Static), the potential height of the N-type semiconductor region 1 with respect to the signal charge is at its lowest. When a photon or dark charge is detected and avalanche multiplication occurs in the avalanche diode (Quenched), the potential height of the signal charge in the N-type semiconductor region 1 gradually increases. It is preferable that the height of the potential barrier in the first separation section 20 is higher than the potential height of the signal charge in the N-type semiconductor region 1 when avalanche multiplication occurs. This reduces charge crosstalk between adjacent avalanche diodes, making it easier for the separation section to function. Note that if high resolution is not required for the photoelectric conversion device, a potential barrier does not need to be formed in the first separation section 20. In other words, the potential height of the first separation section 20 and the potential height of the N-type semiconductor region 1 in the state where avalanche multiplication occurs may be substantially the same.

[0042] In this embodiment, the potential barrier formed by the first separation unit 20 is lower than the potential barrier formed by the second separation unit 30. Even in this case, it is easier to reduce crosstalk while reducing the pixel size. The reason for this will be explained below by comparing it with the photodetector described in Patent Document 1 and the comparative example shown in Figure 6.

[0043] In the comparative example shown in Figure 6(A), an N-type semiconductor region 3 is positioned between two N-type semiconductor regions 1. Furthermore, an N-type semiconductor region 3 is positioned with a P-type semiconductor region 8 in between.

[0044] In the photodetector described in Patent Document 1, a P-type semiconductor region with a high impurity concentration is arranged to surround the entire circumference of the N-type semiconductor region constituting the avalanche diode in a plan view. In this case, it is necessary to arrange each semiconductor region at a predetermined distance in order to ensure the breakdown voltage between the N-type semiconductor region and the P-type semiconductor region. Therefore, the N-type semiconductor regions of each avalanche diode cannot be brought closer together, and the pixel pitch cannot be reduced.

[0045] Furthermore, in the photoelectric converter shown in the comparative example, the impurity concentration in the P-type semiconductor region 8 is low, but the P-type semiconductor region remains as a neutral region. Therefore, as shown in Figure 6(B), in Y-Y', the potential for the signal charge increases as it approaches Y. In this structure, electrons generated in the region between the P-type semiconductor region 8 and the P-type semiconductor region 11 are also read out as signal charges. In other words, it becomes impossible to separate the sensitivity region for each N-type semiconductor region 1 in the semiconductor region 13 between the P-type semiconductor region 8 and the P-type semiconductor region 11.

[0046] In this specification, when the term "impurity concentration" is used, it refers to the net impurity concentration compensated for by reverse-conductivity impurities. In other words, "impurity concentration" refers to the NET concentration. The region where the concentration of P-type added impurities is higher than the concentration of N-type added impurities is the P-type semiconductor region. Conversely, the region where the concentration of N-type added impurities is higher than the concentration of P-type added impurities is the N-type semiconductor region.

[0047] In this embodiment, a semiconductor region is arranged as the first separation section 20 between multiple N-type semiconductor regions 1 such that the region between the N-type semiconductor regions 1 is depleted. As the first separation section 20 is depleted, the potential distribution in Y-Y' decreases from the P-type semiconductor region 5 toward the first separation section 20, as shown in Figure 5(A). In other words, the potential distribution in Y-Y' decreases monotonically from the P-type semiconductor region 5 toward the first separation section 20. Therefore, charge flows into the first separation section 20. The charge that flows into the first separation section 20 flows through the N-type semiconductor region 1, but the potential difference between the N-type semiconductor region 1 and the separation section 20 is such that it does not cause avalanche multiplication, so no avalanche current is generated and it is not counted by the counter circuit. Therefore, it is not read out as a signal. In other words, not only the first separation section 20, but also the region between the first separation section 20 and the second surface functions as an insensitive region and can be made to function as a separation section. Therefore, even with a smaller pixel pitch, it becomes possible to read out signals from each pixel while reducing crosstalk.

[0048] In this embodiment, the first separation section 20 is provided with an N-type semiconductor region 3 having a lower impurity concentration than the N-type semiconductor region 1. In other words, instead of surrounding the entire circumference of the N-type semiconductor region 1 with the P-type semiconductor region 4 in a plan view, the P-type semiconductor region 4 is provided in a part of the periphery of the N-type semiconductor region 1, while the P-type semiconductor region 4 is not provided in the other part. That is, the area where the P-type semiconductor region 4, which is necessary to ensure breakdown voltage, is provided is limited to one part, and the other part is configured to have a potential barrier height sufficient to prevent signal charge leakage. This is not the only configuration; as long as the first separation section 20 is depleted, the first separation section 20 may also be provided with a P-type semiconductor region 4 and an N-type semiconductor region 3 sandwiching the P-type semiconductor region 4, as in the embodiment described later. Furthermore, at least a part of the separation section may be provided with an intrinsic semiconductor region (i-type semiconductor region). Moreover, only the P-type semiconductor region 4 may be provided between the N-type semiconductor regions 1.

[0049] The length of the first separation portion 20 in the first direction is shorter than the length of the second separation portion 30 in the third direction. In other words, the distance between N-type semiconductor regions 1 in the first direction is shorter than the distance between N-type semiconductor regions 1 in the third direction. For example, the ratio of the length of the first separation portion 20 to the length of the second separation portion 30 is less than 1 and 1 / 8 or more. For example, in the first direction, the distance between avalanche multiplication portions is preferably 1 μm or more. To ensure withstand voltage, the distance between avalanche multiplication portions in the first direction can be, for example, 0.5 μm or more, and preferably 1 μm or more. On the other hand, in order to reduce the area of ​​the pixel region, the distance between avalanche multiplication portions in the first direction can be, for example, 10 μm or less, and preferably 4 μm or less.

[0050] The impurity concentration in the N-type semiconductor region 3 is preferably lower than the impurity concentration in the P-type semiconductor region 5, which is positioned to overlap the N-type semiconductor region 3 in a plan view. This allows the N-type semiconductor region 3 to be depleted in the vertical direction toward the second surface. For example, the impurity concentration in the N-type semiconductor region 3 is more than twice that of the P-type semiconductor region 5. The impurity concentration in the N-type semiconductor region 3 is, for example, 1E18cm -3 The following applies. It is preferable that the N-type semiconductor region 3 satisfies the following equation (1). In the following equation (1), the impurity concentration of the N-type semiconductor region 3 is denoted as Nd2, the impurity concentration of the P-type semiconductor region 5 as Na2, and the elementary charge as q. Furthermore, the dielectric constant of the semiconductor is denoted as ε, the potential difference between the PN junction of the N-type semiconductor region 3 and the P-type semiconductor region 5 is denoted as potential difference V, and the depth of the N-type semiconductor region 3 is denoted as H. Here, depth refers to the thickness of the N-type semiconductor region 3 in the direction from the first surface to the second surface.

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[0051] The N-type semiconductor region 3 is shared by multiple adjacent avalanche diodes. The second separation region 30 is composed of the N-type semiconductor region 3 and the P-type semiconductor region 4.

[0052] It is preferable to place an N-type semiconductor region 2 with a lower impurity concentration than N-type semiconductor region 1 between N-type semiconductor region 1 and P-type semiconductor region 4. This makes it easier to move the charge near N-type semiconductor region 2 to a position closer to the contact plug 6 of N-type semiconductor region 1. N-type semiconductor region 2 can have the same impurity concentration as N-type semiconductor region 3.

[0053] In Figure 4, the N-type semiconductor region 2 and the P-type semiconductor region 4 are in contact, but the N-type semiconductor region 2 and the P-type semiconductor region 4 may be physically separated. Furthermore, trench isolation may be provided between the N-type semiconductor region 2 and the P-type semiconductor region 4 to improve the breakdown voltage between them. For example, STI (Shallow Trench Isolation) may be provided between the N-type semiconductor region 2 and the P-type semiconductor region 4.

[0054] Although Figure 4 shows a configuration in which a P-type semiconductor region 5 without an impurity concentration gradient is provided, the P-type semiconductor region 5 may also be a region with an impurity concentration gradient. For example, the configuration can be such that the impurity concentration at a deeper depth is higher than the impurity concentration at a certain depth.

[0055] In this case, a first- or second-conductivity impurity region may be located directly beneath the N-type semiconductor region 1 to adjust the electric field of the PN junction.

[0056] In Figure 4, two avalanche diodes aligned in the first or second direction share the semiconductor region 3, but three or more avalanche diodes aligned in the first or second direction may share the N-type semiconductor region 3.

[0057] Furthermore, in Figure 4, in the third direction, P-type semiconductor regions 4 and contact plugs 7 are arranged between each N-type semiconductor region 1, but the P-type semiconductor regions 4 and contact plugs 7 may be arranged sparsely.

[0058] In Figures 3 and 4, in a plan view, the distance between the four contact plugs 6 is greater than or equal to LC, and the distance between the four contact plugs 6 and contact plug 7 is less than or equal to LC. L is the distance between the contact plugs 7 aligned in the first direction, and LC is L / √2. In other words, in Figures 3 and 4, the contact plug 7 is positioned at a distance of less than or equal to LC from all four contact plugs 6. This allows the contact plugs 7 to be shared among the avalanche diodes while maintaining equal spacing between the N-type semiconductor region 1 and the P-type semiconductor region 4 of each avalanche diode. The distance between contact plugs may be, for example, the distance between the contact plugs that are closest to each other. For example, if multiple contact plugs are connected to the P-type semiconductor region 4 and multiple contact plugs 6 are connected to the N-type semiconductor region 1, it is sufficient that the contact plugs 6 and 7 that are closest to each other satisfy the above equation. It is preferable that the shortest distance between the N-type semiconductor region 1 of each avalanche diode and the contact plug 7 closest to the N-type semiconductor region 1 is equal.

[0059] Furthermore, as shown in Figures 3 and 4, in a plan view, contact plug 7, contact plug 6, contact plug 7, contact plug 6, and contact plug 7 are arranged in order in the third direction. In a cross-section in the third direction, contact plug 7, P-type semiconductor region 5, N-type semiconductor region 2, N-type semiconductor region 1, and N-type semiconductor region 2 are arranged in order. Subsequently, contact plug 7, N-type semiconductor region 3, N-type semiconductor region 1, N-type semiconductor region 3, P-type semiconductor region 5, and contact plug 7 are arranged in order. In this embodiment, while the contact plug 7 is shared between the avalanche diodes, each component is arranged symmetrically in the third direction. This makes it possible to reduce variations in signal readout between the avalanche diodes.

[0060] <Second Embodiment> The configuration of the photoelectric converter according to the second embodiment will be described using Figures 7 and 8. The second embodiment differs from the first embodiment in that the first separation unit 20 is composed of an N-type semiconductor region 3 and a P-type semiconductor region 8 with a lower impurity concentration than the P-type semiconductor region 4. Except for the matters described below, the configuration can be substantially the same as that of the first embodiment.

[0061] In this embodiment as well, the height of the potential barrier formed by the second separation section 30 is higher than the height of the potential barrier formed by the first separation section 20. Also in this embodiment as well, the first separation section 20 is configured to be completely depleted.

[0062] The impurity concentration in P-type semiconductor region 8 is lower than that in P-type semiconductor region 4.

[0063] The conditions for a configuration in which the P-type semiconductor region 8 is completely depleted are shown in equation (2) below. Here, the impurity concentration of the N-type semiconductor region 3 is Nd, the impurity concentration of the P-type semiconductor region 8 is Na, and the elementary charge is q. Furthermore, the dielectric constant of the semiconductor is ε, the potential difference between the PN junction of the N-type semiconductor region 3 and the P-type semiconductor region 8 is V, and the length of the P-type semiconductor region 8 sandwiched between the N-type semiconductor regions 3 is D.

number

[0064] In equation (2) above, the dimension of D is [m], the dimension of q is [C], and the dimensions of Nd and Na are [m]. -3 ], the dimension of ε is [F / m], and the dimension of V is [V]. That is, extracting the dimension from equation (2) above, we get the following equation (3).

number

[0065] Also, since Q=CV, [C]=[F][V], so expanding equation (3) above gives the following equation (4).

number

[0066] In Figure 6, the N-type semiconductor region 3 and the P-type semiconductor region 8 are formed at the same depth, but the P-type semiconductor region 8 may be formed at a shallower position than the N-type semiconductor region 3. Also, although the P-type semiconductor region 8 is configured to form a part of the first surface 40A, it may be formed separately from the first surface 40A.

[0067] In Figure 6, the P-type semiconductor region 8 does not have an impurity concentration gradient, but it may have an impurity concentration gradient in at least one of the directions parallel to the first surface 40A and the depth direction.

[0068] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, since the charge generated in the region between the first separation unit 20 and the second surface can be prevented from being read out as a signal, the sensitivity region can be divided for each N-type semiconductor region 1, and the signal can be separated.

[0069] <Third Embodiment> The configuration of the photoelectric converter according to the third embodiment will be described using Figures 9 to 11. The third embodiment differs from the first embodiment in that the first separation section 20 is composed of an N-type semiconductor region 3 and a trench separation section 9. Except for the matters described below, the configuration can be substantially the same as that of the first embodiment.

[0070] Figure 8 is an enlarged plan view of a portion of the pixel area of ​​the photoelectric converter according to the third embodiment. Figures 10 and 11 are schematic cross-sectional views taken along line A-A' in Figure 9.

[0071] The trench isolation section 9 can be constructed using the STI (Semiconductor Trench Isolation) shown in Figure 10, or the DTI (Deep Trench Isolation) shown in Figure 11. For example, one end of the trench isolation section 9 is formed to a position deeper than the N-type semiconductor region 1.

[0072] The trench separation section 9 is embedded with at least one of a dielectric material composed of an oxide, polysilicon arranged via a dielectric film, and a metal.

[0073] A first-conductivity type impurity region may be provided on the side surface of the trench separation portion 9 to inactivate defects that may form at the interface between the trench separation portion 9 and the semiconductor region 3.

[0074] Furthermore, in the case of a back-illuminated sensor, the trench may be formed from the second surface side.

[0075] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, when the trench separation section 9 is composed of DTI, it is possible to reduce color mixing between adjacent pixels due to the influence of light emission from the avalanche diode.

[0076] <Fourth Embodiment> The configuration of the photoelectric converter according to the fourth embodiment will be described using Figures 12 and 13. In the fourth embodiment, the avalanche diode is composed of an N-type semiconductor region 1, an N-type semiconductor region 10, and a P-type semiconductor region 11. The P-type semiconductor region 11 is also provided at a deeper position than the N-type semiconductor regions 2, 3, and the P-type semiconductor region 5. The P-type semiconductor region 4 and the P-type semiconductor region 11 are connected via the P-type semiconductor region 5. Except for these configurations, the configuration is the same as in the first embodiment. Except for the matters described below, the configuration can be substantially the same as in the first embodiment.

[0077] The N-type semiconductor region 10 is a semiconductor region with a lower impurity concentration than the N-type semiconductor region 1. Furthermore, the N-type semiconductor region 10 has a higher impurity concentration than the N-type semiconductor region 3. By forming the N-type semiconductor region 10 between the N-type semiconductor region 1 and the P-type semiconductor region 11, the electric field strength between the N-type semiconductor region 1 and the P-type semiconductor region 11 can be adjusted. Additionally, the inclusion of the N-type semiconductor region 10 makes it easier to detect photocharges generated at deeper depths compared to the first embodiment, thereby improving long-wavelength sensitivity.

[0078] The P-type semiconductor region 11 is arranged continuously in a certain cross-section from below one contact plug 7 to below the other contact plug 7. The presence of the P-type semiconductor region 11 prevents unwanted signal charges that may occur on the second surface 40B of the substrate from being read into the N-type semiconductor region 1. Figure 12 shows a region partitioned by P-type semiconductor regions 4, 5, and 11, with two sets of four avalanche diodes arranged in the partitioned regions.

[0079] The P-type semiconductor region 5 can supply potential to the P-type semiconductor region 11 via the P-type semiconductor region 4. The P-type semiconductor region 5 is a semiconductor region with a lower impurity concentration than the P-type semiconductor region 4.

[0080] The P-type semiconductor region 11 may have a concentration gradient in the depth direction. Also, in Figure 12, a trench separation section may be provided between the P-type semiconductor region 4 and the N-type semiconductor region 2 to ensure breakdown voltage.

[0081] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, it becomes easier to detect photocharges generated in deeper regions compared to the first embodiment, and it is possible to improve long-wavelength sensitivity.

[0082] <Fifth Embodiment> The configuration of the photoelectric converter according to the fifth embodiment will be described using Figure 14. In the fifth embodiment, the second separation unit 20 is composed of an N-type semiconductor region 3 and a P-type semiconductor region 8. The P-type semiconductor region 8 is the same as the P-type semiconductor region 8 in the second embodiment, so its description will be omitted. Furthermore, the configuration other than the second separation unit 20 is as described in the fourth embodiment, so its description will be omitted.

[0083] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, it becomes easier to detect photocharges generated in deeper regions compared to the first embodiment, and it is possible to improve long-wavelength sensitivity.

[0084] <Sixth Embodiment> The configuration of the photoelectric converter according to the sixth embodiment will be described using Figures 15 and 16. Figure 15 is an enlarged plan view of a part of the pixel area of ​​the photoelectric converter according to the sixth embodiment. Figure 16 is a schematic cross-sectional view taken along line A-A' in Figure 15. In the sixth embodiment, a P-type semiconductor region is provided to physically separate the sensitivity region of each pixel. A P-type semiconductor region 12 is provided between the N-type semiconductor region 1 and the P-type semiconductor region 11, and a photoelectric conversion region 13 is provided between the P-type semiconductor region 12 and the P-type semiconductor region 11. A P-type semiconductor region 5 is provided between the first separation unit 20 and the P-type semiconductor region 11. Except for these configurations, the configuration is the same as that of the fourth embodiment. Except for the matters described below, the configuration can be substantially the same as that of the fourth embodiment.

[0085] The P-type semiconductor region 12 forms a PN junction with the N-type semiconductor region 1. Avalanche multiplication can occur near this PN junction. In a cross-sectional view, the P-type semiconductor region 12 is continuously arranged from one P-type semiconductor region 5 to the other P-type semiconductor region 5.

[0086] A photoelectric conversion region 13 is positioned between the P-type semiconductor region 12 and the P-type semiconductor region 11.

[0087] The photoelectric conversion region 13 is composed of an N-type semiconductor region with a lower impurity concentration than the N-type semiconductor region 1, or a P-type semiconductor region with a lower impurity concentration than the P-type semiconductor regions 5 and 11.

[0088] In Figure 15, the P-type semiconductor region 4 and the N-type semiconductor region 2 are separated, but the P-type semiconductor region 4 and the N-type semiconductor region 2 may be in contact.

[0089] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, according to this embodiment, since the photoelectric conversion region is physically separated by the P-type semiconductor region 5, it is easier to reduce charge crosstalk. In addition, since the avalanche multiplication region can be made smaller compared to the first embodiment, dark current can be reduced while maintaining sensitivity.

[0090] <Seventh Embodiment> The configuration of the photoelectric converter according to the seventh embodiment will be described using Figures 17 and 18. Figure 17 is an enlarged plan view of a part of the pixel area of ​​the photoelectric converter according to the seventh embodiment. Figure 18 is a schematic cross-sectional view taken along line A-A' in Figure 17. In the seventh embodiment, the first separation section 20 is composed of an N-type semiconductor region 3 and a P-type semiconductor region 8. In addition, a P-type semiconductor region 14 is arranged between the P-type semiconductor regions 12 in a direction parallel to the first plane, and an N-type semiconductor region 15 is arranged between the photoelectric conversion regions. Except for these configurations, it is the same as the sixth embodiment. Except for the matters described below, it is substantially the same as the sixth embodiment.

[0091] In a plan view, the P-type semiconductor region 14 is surrounded by the P-type semiconductor region 12. The P-type semiconductor region 14 is a P-type semiconductor region with a lower impurity concentration than the P-type semiconductor region 12. A PN junction is formed between the P-type semiconductor region 14 and the N-type semiconductor region 1, and the signal charge is avalanche multiplied near this PN junction. The P-type semiconductor region 14 has a lower potential for electrons compared to the P-type semiconductor region 12. Therefore, the generated signal charge is more easily collected in the P-type semiconductor region 14 and can easily pass through the PN junction interface between the P-type semiconductor region 14 and the N-type semiconductor region 1.

[0092] An N-type semiconductor region 15 is located between the P-type semiconductor region 14 and the P-type semiconductor region 11. The impurity concentration of the N-type semiconductor region 15 is lower than that of semiconductor region 1. If semiconductor region 14 is an N-type semiconductor region, the impurity concentration of the N-type semiconductor region 15 is lower than that of semiconductor region 14.

[0093] In this embodiment, as with the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Also, as with the sixth embodiment, charge crosstalk can be suppressed. Furthermore, it becomes easier to collect charge in the N-type semiconductor region 1.

[0094] <Eighth Embodiment> The photoelectric converter according to the eighth embodiment will be described using Figure 19. In this embodiment, the photoelectric converter consists of two separate substrates: one on which the avalanche diode 201 of pixel 110 in Figure 2 is arranged, and another on which the counter circuit 204 and quench element 202 are arranged. The photoelectric converter is constructed by stacking and joining these substrates.

[0095] In this embodiment, each microlens is arranged to overlap each avalanche diode in a plan view.

[0096] Figure 19 shows light being incident from the second surface, which is the side where the contact plug is not connected. Therefore, the microlens 18 and color filter 19 are positioned on the second surface of the substrate 16. When light is incident from the first surface of the substrate 16, the microlens 18 and color filter 19 are positioned on the first surface.

[0097] In this embodiment, as in the first embodiment, it is possible to reduce the pixel pitch compared to Patent Document 1. Furthermore, by arranging the circuit section on the side of the substrate 17, the area of ​​the substrate 16 can be reduced.

[0098] In Figure 19, the avalanche diode configuration described in the seventh embodiment is adopted, except for the configuration described above. Alternatively, the avalanche diode configuration described in the first to sixth embodiments may be adopted. In this case, as in Figure 19, the contact plug 6 will be connected to the N-type semiconductor region 1 described in each embodiment.

[0099] <Ninth Embodiment> The photoelectric converter of the ninth embodiment will be described using Figure 20. In this embodiment, the photoelectric converter is configured such that light passing through one microlens is incident on multiple avalanche diodes. The other configurations are the same as in the seventh embodiment.

[0100] According to this embodiment, it becomes possible to perform depth detection while reducing the pixel pitch.

[0101] <Tenth Embodiment> An example of a photoelectric conversion system using the photoelectric conversion device of each embodiment will be explained using Figure 21. An example of a photodetection system, an invisible light detection system, and a medical diagnostic system such as PET will be explained using Figure 21. Parts having the same function as in Figures 1 to 20 are denoted by the same reference numerals, and detailed explanations are omitted. Note that the pixels in this embodiment have a TDC and memory instead of the counter circuit in Figure 2. Here, the TDC will be referred to as TDC204 and the memory as memory205.

[0102] Figure 21 is a block diagram illustrating the configuration of the invisible light detection system. The invisible light detection system has a wavelength conversion unit 301, a data processing unit 307, and multiple photoelectric converters 1010.

[0103] The irradiating object 300 emits light in the wavelength range that is invisible. The wavelength conversion unit 301 receives the light in the wavelength range that is invisible emitted from the irradiating object 300 and emits visible light.

[0104] The avalanche diode 201, upon receiving visible light irradiated from the wavelength conversion unit 301, performs photoelectric conversion. Then, via the control unit 202, waveform shaping unit 203, and TDC 204, the photoelectric conversion device 1010 stores a digital signal based on the charge converted by photoelectric conversion in the memory 205. Multiple photoelectric conversion devices 1010 may be formed as a single device or by arranging multiple devices.

[0105] Multiple digital signals held in the memory 205 of the multiple photoelectric converters 1010 are processed by the data processing unit 1207. Here, the signal processing means involves combining multiple images obtained from the multiple digital signals.

[0106] Next, as a specific example of an invisible light detection system, we will explain the configuration of medical diagnostic systems such as PET.

[0107] The subject, which is the irradiated object 300, emits radiation pairs from within its body. The wavelength conversion unit 301 constitutes a scintillator, and when radiation pairs emitted from the subject enter the scintillator, it irradiates it with visible light.

[0108] The avalanche diode 201, upon receiving visible light irradiated from the scintillator, undergoes photoelectric conversion. The photoelectric conversion device 1010, via the control unit 202, waveform shaping unit 203, and TDC 204, stores a digital signal based on the photoelectrically converted charge in the memory 205. In other words, the photoelectric conversion device 1010 is positioned to detect the arrival time of radiation pairs emitted from the subject, detects visible light irradiated from the scintillator, and stores the digital signal in the memory 205.

[0109] The digital signals held in the memory 205 of the multiple photoelectric converters 1010 are processed by the data processing unit 307. Here, as a signal processing means, image reconstruction and other synthesis processes are performed using multiple images obtained from the multiple digital signals to form an image of the subject's body.

[0110] <Embodiment 11> Figure 22 is a block diagram showing the configuration of the photoelectric conversion system 1200 according to this embodiment. The photoelectric conversion system 1200 of this embodiment includes a photoelectric conversion device 1215. Here, the photoelectric conversion device 1215 can be any of the photoelectric conversion devices described in the above embodiments. The photoelectric conversion system 1200 can be used, for example, as an imaging system. Specific examples of imaging systems include digital still cameras, digital camcorders, and surveillance cameras. Figure 21 shows an example of a digital still camera as the photoelectric conversion system 1200.

[0111] The photoelectric conversion system 1200 shown in Figure 22 includes a photoelectric conversion device 1215, a lens 1213 that forms an optical image of the subject onto the photoelectric conversion device 1215, an aperture 1214 for varying the amount of light passing through the lens 1213, and a barrier 1212 for protecting the lens 1213. The lens 1213 and aperture 1214 form an optical system that focuses light onto the photoelectric conversion device 1215.

[0112] The photoelectric conversion system 1200 has a signal processing unit 1216 that processes the output signal output from the photoelectric conversion device 1215. The signal processing unit 1216 performs signal processing operations that perform various corrections and compressions on the input signal as needed before outputting it. The photoelectric conversion system 1200 further has a buffer memory unit 1206 for temporarily storing image data, and an external interface unit (external I / F unit) 1209 for communicating with an external computer or the like. Furthermore, the photoelectric conversion system 1200 has a recording medium 1211 such as a semiconductor memory for recording or reading imaging data, and a recording medium control interface unit (recording medium control I / F unit) 1210 for recording or reading from the recording medium 1211. The recording medium 1211 may be built into the photoelectric conversion system 1200 or it may be detachable. In addition, communication from the recording medium control I / F unit 1210 to the recording medium 1211 and communication from the external I / F unit 1209 may be performed wirelessly.

[0113] Furthermore, the photoelectric conversion system 1200 includes an overall control and calculation unit 1208 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1217 that outputs various timing signals to the photoelectric conversion device 1215 and the signal processing unit 1216. Here, the timing signals and the like may be input from an external source, and the photoelectric conversion system 1200 only needs to include at least the photoelectric conversion device 1215 and the signal processing unit 1216 that processes the output signals output from the photoelectric conversion device 1215. As described in the fourth embodiment, the timing generation unit 1217 may be mounted on the photoelectric conversion device. The overall control and calculation unit 1208 and the timing generation unit 1217 may be configured to perform some or all of the control functions of the photoelectric conversion device 1215.

[0114] The photoelectric converter 1215 outputs an image signal to the signal processing unit 1216. The signal processing unit 1216 performs predetermined signal processing on the image signal output from the photoelectric converter 1215 and outputs image data. The signal processing unit 1216 also generates an image using the image signal. The signal processing unit 1216 may also perform distance measurement calculations on the signal output from the photoelectric converter 1215. The signal processing unit 1216 and the timing generation unit 1217 may be mounted on the photoelectric converter. In other words, the signal processing unit 1216 and the timing generation unit 1217 may be provided on the substrate on which the pixels are arranged, or they may be provided on a separate substrate. By configuring an imaging system using the photoelectric converters of each embodiment described above, an imaging system capable of acquiring higher quality images can be realized.

[0115] <Twelfth Embodiment> The photoelectric conversion system and mobile unit of this embodiment will be described with reference to Figures 23 and 24. Figure 23 is a schematic diagram showing an example configuration of the photoelectric conversion system and mobile unit according to this embodiment. Figure 24 is a flowchart showing the operation of the photoelectric conversion system according to this embodiment. In this embodiment, an example of an in-vehicle camera is shown as the photoelectric conversion system.

[0116] Figure 23 shows an example of a vehicle system and a photoelectric conversion system mounted thereon for imaging. The photoelectric conversion system 1301 includes a photoelectric converter 1302, an image preprocessing unit 1315, an integrated circuit 1303, and an optical system 1314. The optical system 1314 forms an optical image of the subject on the photoelectric converter 1302. The photoelectric converter 1302 converts the optical image of the subject formed by the optical system 1314 into an electrical signal. The photoelectric converter 1302 is one of the photoelectric converters in each of the embodiments described above. The image preprocessing unit 1315 performs predetermined signal processing on the signal output from the photoelectric converter 1302. The functions of the image preprocessing unit 1315 may be incorporated into the photoelectric converter 1302. The photoelectric conversion system 1301 is provided with at least two sets of optical systems 1314, photoelectric conversion devices 1302, and image preprocessing units 1315, and the output from each set of image preprocessing units 1315 is input to the integrated circuit 1303.

[0117] The integrated circuit 1303 is an integrated circuit for imaging system applications and includes an image processing unit 1304 with memory 1305, an optical distance measuring unit 1306, a distance measurement calculation unit 1307, an object recognition unit 1308, and an anomaly detection unit 1309. The image processing unit 1304 performs image processing such as development and defect correction on the output signal of the image preprocessing unit 1315. The memory 1305 stores the primary storage of the captured image and the location of defects in the captured pixels. The optical distance measuring unit 1306 focuses on the subject and measures the distance. The distance measurement calculation unit 1307 calculates distance measurement information from multiple image data acquired by multiple photoelectric converters 1302. The object recognition unit 1308 recognizes subjects such as cars, roads, signs, and people. When the anomaly detection unit 1309 detects an anomaly in the photoelectric converter 1302, it alerts the main control unit 1313 to the anomaly.

[0118] The integrated circuit 1303 may be implemented by specially designed hardware, by a software module, or by a combination of these. It may also be implemented by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination of these.

[0119] The main control unit 1313 coordinates and controls the operation of the photoelectric conversion system 1301, vehicle sensor 1310, control unit 1320, etc. Alternatively, there may be no main control unit 1313, and the photoelectric conversion system 1301, vehicle sensor 1310, and control unit 1320 may each have their own communication interfaces and send and receive control signals via a communication network (e.g., CAN standard).

[0120] The integrated circuit 1303 has the function of receiving control signals from the main control unit 1313 or transmitting control signals and set values ​​to the photoelectric converter 1302 via its own control unit.

[0121] The photoelectric conversion system 1301 is connected to the vehicle sensor 1310 and can detect the vehicle's driving conditions, such as vehicle speed, yaw rate, and steering angle, as well as the external environment and the state of other vehicles and obstacles. The vehicle sensor 1310 also serves as a distance information acquisition means for acquiring distance information to objects. Furthermore, the photoelectric conversion system 1301 is connected to the driver assistance control unit 1311, which performs various driver assistance functions such as automatic steering, automatic cruising, and collision avoidance. In particular, regarding the collision judgment function, it determines whether a collision with another vehicle or obstacle has occurred and estimates a collision based on the detection results of the photoelectric conversion system 1301 and the vehicle sensor 1310. This enables avoidance control when a collision is estimated and activation of safety devices in the event of a collision.

[0122] Furthermore, the photoelectric conversion system 1301 is also connected to a warning device 1312 that issues a warning to the driver based on the judgment result of the collision judgment unit. For example, if the collision judgment unit determines that there is a high probability of collision, the main control unit 1313 performs vehicle control to avoid a collision or mitigate damage by applying the brakes, releasing the accelerator, or suppressing engine output. The warning device 1312 warns the user by sounding an alarm, displaying warning information on a display screen such as the car navigation system or instrument panel, or vibrating the seat belt or steering wheel.

[0123] In this embodiment, the photoelectric conversion system 1301 captures images of the area around the vehicle, for example, the front or rear. Figure 23(b) shows an example of the arrangement of the photoelectric conversion system 1301 when it captures images of the area in front of the vehicle.

[0124] The two photoelectric converters 1302 are positioned in front of the vehicle 1300. Specifically, it is preferable for the two photoelectric converters 1302 to be positioned symmetrically with respect to the axis of symmetry, considering the center line of the vehicle 1300's direction of movement or external shape (e.g., vehicle width), when acquiring distance information between the vehicle 1300 and the object being photographed and determining the possibility of collision. Furthermore, it is preferable that the photoelectric converters 1302 are positioned so as not to obstruct the driver's field of view when the driver is visually observing the situation outside the vehicle 1300 from the driver's seat. The warning device 1312 is preferably positioned so as to be easily visible to the driver.

[0125] Next, the fault detection operation of the photoelectric converter 1302 in the photoelectric conversion system 1301 will be explained using Figure 24. The fault detection operation of the photoelectric converter 1302 is performed according to steps S1410 to S1480 shown in Figure 24.

[0126] Step S1410 is a step in which the photoelectric converter 1302 is configured for startup. Specifically, settings for the operation of the photoelectric converter 1302 are transmitted from outside the photoelectric conversion system 1301 (e.g., the main control unit 1313) or from inside the photoelectric conversion system 1301, and the imaging operation and fault detection operation of the photoelectric converter 1302 are started.

[0127] Next, in step S1420, a pixel signal is acquired from the active pixels. Also, in step S1430, an output value is acquired from a fault detection pixel provided for fault detection. This fault detection pixel, like the active pixels, is equipped with a photoelectric conversion unit. A predetermined voltage is written to this photoelectric conversion unit. The fault detection pixel outputs a signal corresponding to the voltage written to this photoelectric conversion unit. Note that steps S1420 and S1430 may be reversed.

[0128] Next, in step S1440, a determination is made between the expected output value of the fault-detection pixel and the actual output value from the fault-detection pixel. If the determination in step S1440 shows that the expected output value and the actual output value match, the process proceeds to step S1450, where it is determined that the imaging operation is functioning normally, and the process moves to step S1460. In step S1460, the pixel signals of the scanned row are transmitted to the memory 1305 for temporary storage. After that, the process returns to step S1420, and the fault detection operation continues. On the other hand, if the determination in step S1440 shows that the expected output value and the actual output value do not match, the process proceeds to step S1470. In step S1470, it is determined that there is an abnormality in the imaging operation, and an alarm is issued to the main control unit 1313 or the alarm device 1312. The alarm device 1312 displays that an abnormality has been detected on its display unit. Subsequently, in step S1480, the photoelectric converter 1302 is stopped, and the operation of the photoelectric converter system 1301 is terminated.

[0129] In this embodiment, an example is shown where the flowchart is looped every row, but the flowchart may be looped every multiple rows, or the fault detection operation may be performed every frame. The alarm in step S1470 may be notified to an external party via a wireless network.

[0130] Furthermore, although this embodiment describes control to avoid collisions with other vehicles, it can also be applied to control that automatically follows other vehicles or control that automatically drives without deviating from the lane. In addition, the photoelectric conversion system 1301 can be applied not only to vehicles such as the vehicle itself, but also to mobile objects (mobile devices) such as ships, aircraft, or industrial robots. Moreover, it can be applied not only to mobile objects, but also to a wide range of devices that utilize object recognition, such as intelligent transportation systems (ITS).

[0131] The photoelectric conversion device of the present invention may further be configured to acquire various types of information, such as distance information.

[0132] <13th Embodiment> Figure 25 is a block diagram showing an example configuration of a distance image sensor, which is an electronic device utilizing the photoelectric conversion device described in the above embodiment.

[0133] As shown in Figure 25, the distance image sensor 401 is configured to include an optical system 402, a photoelectric converter 403, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 401 receives light (modulated light or pulsed light) that is projected from the light source device 411 toward the subject and reflected from the surface of the subject, thereby acquiring a distance image corresponding to the distance to the subject.

[0134] The optical system 402 is composed of one or more lenses and guides the image light (incident light) from the subject to the photoelectric converter 403, where it forms an image on the light-receiving surface (sensor part) of the photoelectric converter 403.

[0135] The photoelectric converter 403 is one of the photoelectric converters from each of the embodiments described above, and a distance signal indicating the distance obtained from the received light signal output from the photoelectric converter 403 is supplied to the image processing circuit 404.

[0136] The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric converter 403. The distance image (image data) obtained through this image processing is then supplied to the monitor 405 for display or supplied to the memory 406 for storage (recording).

[0137] With the distance image sensor 401 configured in this way, by applying the photoelectric conversion device described above, the characteristics of the pixels are improved, and for example, more accurate distance images can be acquired.

[0138] <Embodiment 14> The technology disclosed herein (the Technology) can be applied to a variety of products. For example, the Technology disclosed herein may be applied to an endoscopic surgical system.

[0139] Figure 26 is a diagram showing an example of a schematic configuration of an endoscopic surgical system to which the technology described herein (the technology) may be applied.

[0140] Figure 26 illustrates a surgeon (physician) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgical system 1000. As shown in the figure, the endoscopic surgical system 1000 consists of an endoscope 1100, surgical instruments 1110, and a cart 1140 equipped with various devices for endoscopic surgery.

[0141] The endoscope 1100 consists of a barrel 1101, the tip of which is inserted into the body cavity of the patient 1132 for a predetermined length, and a camera head 1102 connected to the base end of the barrel 1101. In the illustrated example, the endoscope 1100 is shown as a so-called rigid endoscope having a rigid barrel 1101, but the endoscope 1100 may also be configured as a so-called flexible endoscope having a flexible barrel.

[0142] An opening into which an objective lens is fitted is provided at the tip of the endoscope tube 1101. A light source device 1203 is connected to the endoscope 1100, and the light generated by the light source device 1203 is guided to the tip of the endoscope tube by a light guide extending inside the endoscope tube 1101, and is irradiated through the objective lens towards the object to be observed inside the body cavity of the patient 1132. The endoscope 1100 may be a straight-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0143] The camera head 1102 contains an optical system and a photoelectric converter. Reflected light from the object being observed (observation light) is focused by the optical system into the photoelectric converter. The photoelectric converter converts the observation light into electrical signals, generating an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. The photoelectric converter can be any of the photoelectric converters described in the embodiments described above. The image signal is transmitted as RAW data to the camera control unit (CCU) 1201.

[0144] The CCU1201 consists of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and other components, and comprehensively controls the operation of the endoscope 1100 and the display device 1202. Furthermore, the CCU1201 receives image signals from the camera head 1102 and performs various image processing operations on these image signals, such as development processing (demosaic processing), to display the image based on those signal.

[0145] The display device 1202 displays an image based on an image signal that has been processed by the CCU 1201, under control from the CCU 1201.

[0146] The light source device 1203 consists of a light source such as an LED (Light Emitting Diode) and supplies illumination light to the endoscope 1100 when photographing the surgical area, etc.

[0147] The input device 1204 is an input interface for the endoscopic surgical system 1000. The user can input various types of information and instructions to the endoscopic surgical system 1000 via the input device 1204.

[0148] The treatment instrument control device 1205 controls the driving of the energy treatment instrument 1112 for purposes such as tissue cauterization, incision, or blood vessel sealing.

[0149] The light source device 1203, which supplies illumination light to the endoscope 1100 when photographing the surgical area, can be composed of, for example, an LED, a laser light source, or a combination thereof. When the white light source is composed of a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, so the white balance of the captured image can be adjusted in the light source device 1203. In this case, it is also possible to capture images corresponding to each of the RGB colors in time-division by irradiating the observation target with laser light from each of the RGB laser light sources in time-division and controlling the drive of the image sensor of the camera head 1102 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter on the image sensor.

[0150] Furthermore, the light source device 1203 may be controlled to change the intensity of the light it outputs at predetermined time intervals. By controlling the drive of the image sensor of the camera head 1102 in synchronization with the timing of the change in light intensity, images can be acquired in time-division order, and these images can be combined to generate high dynamic range images without so-called black crushing and white clipping.

[0151] Furthermore, the light source device 1203 may be configured to supply light in a predetermined wavelength band corresponding to special light observation. In special light observation, for example, the wavelength dependence of light absorption in body tissue is utilized. Specifically, by irradiating with narrowband light compared to the irradiation light used during normal observation (i.e., white light), predetermined tissues such as blood vessels on the surface of mucosa can be imaged with high contrast. Alternatively, in special light observation, fluorescence observation may be performed to obtain an image from fluorescence generated by irradiation with excitation light. In fluorescence observation, excitation light can be irradiated onto body tissue and fluorescence from the body tissue can be observed, or a reagent such as indocyanine green (ICG) can be injected into body tissue and excitation light corresponding to the fluorescence wavelength of the reagent can be irradiated onto the body tissue to obtain a fluorescence image. The light source device 1203 may be configured to supply narrowband light and / or excitation light corresponding to such special light observation.

[0152] Figure 27 is a block diagram showing an example of the functional configuration of the camera head 1102 and CCU 1201 shown in Figure 26.

[0153] The camera head 1102 includes a lens unit 1401, a photoelectric converter 1402, a drive unit 1403, a communication unit 1404, and a camera head control unit 1405. The CCU 1201 includes a communication unit 1411, an image processing unit 1412, and a control unit 1413. The camera head 1102 and the CCU 1201 are connected to each other via a transmission cable 1400 so that they can communicate with one another.

[0154] The lens unit 1401 is an optical system provided at the connection point with the lens barrel 1101. Observation light taken in from the tip of the lens barrel 1101 is guided to the camera head 1102 and then incident on the lens unit 1401. The lens unit 1401 is composed of a combination of multiple lenses, including a zoom lens and a focus lens.

[0155] As the photoelectric converter 1402, the photoelectric converters of each embodiment described above can be used. The photoelectric converter 1402 may consist of one photoelectric converter or multiple photoelectric converters. When the photoelectric converter 1402 consists of multiple photoelectric converters, for example, each photoelectric converter may generate an image signal corresponding to RGB, and these may be combined to obtain a color image. Alternatively, the photoelectric converter 1402 may be configured to have a pair of photoelectric converters for acquiring image signals for the right eye and left eye, respectively, corresponding to 3D (dimensional) display. By performing 3D display, the surgeon 1131 can more accurately grasp the depth of the biological tissue in the surgical area. When the photoelectric converter 1402 consists of multiple photoelectric converters, multiple lens units 1401 may also be provided corresponding to each photoelectric converter.

[0156] The drive unit 1403 is composed of actuators and, under control from the camera head control unit 1405, moves the zoom lens and focus lens of the lens unit 1401 along the optical axis by a predetermined distance. This allows the magnification and focus of the image captured by the photoelectric converter 1402 to be adjusted as appropriate.

[0157] The communication unit 1404 consists of communication devices for sending and receiving various types of information with the CCU 1201. The communication unit 1404 transmits the image signal obtained from the photoelectric converter 1402 as RAW data to the CCU 1201 via the transmission cable 1400.

[0158] Furthermore, the communication unit 1404 receives control signals from the CCU 1201 to control the drive of the camera head 1102 and supplies them to the camera head control unit 1405. These control signals include information regarding imaging conditions, such as information to specify the frame rate of the captured image, information to specify the exposure value at the time of imaging, and / or information to specify the magnification and focus of the captured image.

[0159] The above imaging conditions, such as frame rate, exposure value, magnification, and focus, may be specified by the user as appropriate, or they may be automatically set by the control unit 1413 of the CCU1201 based on the acquired image signal. In the latter case, the endoscope 1100 will be equipped with so-called AE (Auto Exposure), AF (Auto Focus), and AWB (Auto White Balance) functions.

[0160] The camera head control unit 1405 controls the drive of the camera head 1102 based on the control signal received from the CCU 1201 via the communication unit 1404.

[0161] The communication unit 1411 consists of a communication device for sending and receiving various types of information with the camera head 1102. The communication unit 1411 receives image signals transmitted from the camera head 1102 via the transmission cable 1400.

[0162] Furthermore, the communication unit 1411 transmits control signals to the camera head 1102 to control the driving of the camera head 1102. Image signals and control signals can be transmitted by telecommunications, optical communications, etc.

[0163] The image processing unit 1412 performs various image processing operations on the image signal, which is RAW data transmitted from the camera head 1102.

[0164] The control unit 1413 performs various controls related to imaging the surgical area, etc., by the endoscope 1100, and the display of the images obtained from imaging the surgical area, etc. For example, the control unit 1413 generates a control signal to control the driving of the camera head 1102.

[0165] Furthermore, the control unit 1413 displays the captured image showing the surgical area on the display device 1202 based on the image signal processed by the image processing unit 1412. At this time, the control unit 1413 may recognize various objects in the captured image using various image recognition technologies. For example, the control unit 1413 can recognize surgical instruments such as forceps, specific biological sites, bleeding, mist when using the energy treatment device 1112, etc., by detecting the shape and color of the edges of objects included in the captured image. When the control unit 1413 displays the captured image on the display device 1202, it may use the recognition results to superimpose various surgical support information onto the image of the surgical area. By superimposing the surgical support information and presenting it to the surgeon 1131, the burden on the surgeon 1131 can be reduced, and the surgeon 1131 can proceed with the surgery reliably.

[0166] The transmission cable 1400 connecting the camera head 1102 and the CCU 1201 is an electrical signal cable compatible with electrical signal communication, an optical fiber compatible with optical communication, or a composite cable thereof.

[0167] In the illustrated example, communication was performed via a wired connection using a transmission cable 1400, but communication between the camera head 1102 and the CCU 1201 may be performed wirelessly.

[0168] The above describes an example of an endoscopic surgical system to which the technology described herein may be applied. The technology described herein can be applied to the endoscope 1100, the camera head 1102 (photoelectric converter 1402), etc., among the configurations described above. By applying the technology described herein to the endoscope 1100, the camera head 1102 (photoelectric converter 1402), etc., it becomes possible to reduce the effects of afterpulses generated by avalanche amplification.

[0169] While an endoscopic surgical system has been described here as an example, the technology described herein may also be applied to other systems, such as microsurgical systems.

[0170] <Embodiment 15> The photoelectric conversion system according to the 15th embodiment will be described using Figures 28 and 29.

[0171] Figure 28(a) shows the operation of time-gating ToF (Time of Flight). Laser pulses are shone multiple times onto the object to be measured for distance. The light reflected by the object is detected by a detector (the photoelectric converter described above) with a delay of Δt. Typical time-gate measurements involve scanning by gradually shifting the gate window (the period of photodetection by the photoelectric converter) to acquire information for consecutive frames. At each gate window position, photon counting is accumulated N times. While finer gate scanning improves accuracy over time, it has the disadvantage of increasing the measurement time.

[0172] Figure 28(b) shows a histogram of the measurement results. The histogram includes the background photon count value and the dark current component value when the reflected laser pulse is outside the gate window. In the histogram, when the peak intensity of the reflected light is greater than the count value of the background component, the profile of the reflected light count value becomes a rectangular distribution. This rectangular distribution has a width corresponding to the length of the gate window. The delay time Δt can be determined from the rising or falling edge of the count value profile. The distance L from the object to the detector is calculated as L = cΔt / 2, where c is the speed of light.

[0173] Figure 28(c) shows a time-gate type SPAD pixel. A transistor acting as a quench element 202 is connected to the avalanche diode 201. The quench element 202 is an element for suppressing electron avalanches (avalanche breakdown). When the global gate switch 280 is turned from off to on, the output signal from the avalanche diode 201 is selectively output to the memory 281. The gate control pulse is on the order of a few nanoseconds and is controlled in synchronization with the irradiation of the laser pulse. The memory 281, provided for each pixel, is located in the counter circuit 204 in Figure 2, and the signals stored in the memory 281 are read out via the output unit 282. Note that a constant voltage may be applied to the gate voltage VQ of the quench element 202. In addition, a pulse signal may be applied to VQ to forcibly recharge the avalanche diode 201 before turning on the global gate switch 280.

[0174] Figure 29 shows the gate window profile, reflected light distribution, and detected intensity. The detected intensity h(t) is the convolution of two functions. That is, the convolution of the gate window profile f(t) and the reflected light distribution g(t) results in the detected intensity h(t). In Figure 29, the upper figure shows one reflection peak, and the lower figure shows two reflection peaks. In actual measurement environments, the detected intensity profile takes on a complex shape. For example, when laser light is shone on an object through a translucent material (semi-reflector). In this case, both the light reflected by the translucent material such as glass or transparent plastic, and the light that passes through the translucent material, hits the object, and is reflected by the object are detected. The lower figure in Figure 29 shows such a measurement example. Since the detected intensity h(t) is measurement data and the gate window profile f(t) is known, the reflected light distribution g(t) can be obtained by deconvolution. If the reflected light distribution g(t) can be obtained, distance information to translucent objects and other objects can be acquired, and it is also possible to isolate only the distance information to the object.

[0175] This embodiment is a type of distance image sensor described in the 13th embodiment, and the detection and calculation of distance information described above are performed by the photoelectric converter 403. Based on the acquired distance signal, the image processing circuit 404 forms a distance image. The formed distance image is supplied to the monitor 405 for display or supplied to the memory 406 for storage.

[0176] (Example of experiment) Figure 30 shows an experimental example of the 15th embodiment.

[0177] Figure 30(a) shows the experimental setup. A 510 nm laser 320 emits pulsed laser light at 40 MHz. The pulsed laser light, diffused by the light-diffusing member 330, is directed onto the object 350. The SPAD camera 310 and the laser 320 are synchronized by the pulse generator 325. A transparent plate 340 made of plastic is placed between the SPAD camera 310 and the object 350.

[0178] Figures 30(b) and 30(c) show the relationship between the gate window position (gate position) and the detected count value at a pixel corresponding to a specific location on object 350. Figure 30(b) is the profile without the transparent plate 340, and Figure 30(c) is the profile with the transparent plate 340. The profile in Figure 30(c) has two rising stages (position 40, position 100). This profile with two rising stages corresponds to double reflection from the transparent plate 340 and object 350. The reflected light distribution is obtained from the measurement profile in Figure 30, and distance information is obtained from the reflected light distribution. For each pixel arranged in two dimensions, distance information and light intensity distribution information are obtained, and by displaying the light intensity distribution information in monochrome and the distance information in color, three-dimensional imaging becomes possible.

[0179] Also, if distance information is obtained, 3D imaging with a specified distance range is also possible. For example, it is possible to separate signals with a short distance from the SPAD camera and signals with a long distance from the SPAD camera to form separate 3D imaging images.

[0180] For example, when the transparent plate is the window glass of a vehicle and it is desired to observe only the object behind the window glass, if distance images of both the window glass and the object are formed using a commonly used indirect ToF method or the like, errors may occur in distance measurement due to the influence of reflection by the window glass. In this case, as described in the 12th embodiment, when controlling a moving body (e.g., an automobile) by distance measurement, it may result in unintended control and pose a problem in terms of safety. According to this embodiment, since objects with different distances from the camera can be separately 3D imaged, such concerns can be reduced.

[0181] <16th Embodiment> The photoelectric conversion device according to the 16th embodiment will be described using FIG. 31.

[0182] FIG. 31(a) is a circuit diagram of a pixel. Specifically, it shows the circuit included in the photoelectric conversion unit 101 of FIG. 2. The avalanche current generated in the avalanche diode is converted into a voltage through the quenching transistor M Q The voltage pulse is transferred to the pull-down transistor M G through the gating transistor M PD controlled by VG. As a result, the feedback transistor M FB is turned off. Thereby, the source of the quenching transistor M Q becomes non-connected, disabling the quenching function in the SPAD. The drain voltage of the pull-down transistor M PD is maintained near the ground voltage (grounding voltage) for a sufficiently long time until the signals of the entire chip are read out. It is charged to the potential of VDDH - VTH - VDSAT for the next light detection. After that, the feedback transistor M FBThe transistor MSW, controlled by VSW, is a pull-down transistor M PD Drain and transistor M RS It is connected to the source and transistor M RS The source is pre-charged VDD-VTH via the control signal VRES. Transistor M is controlled by VSEL. SEL When it turns ON, transistor M PDO This is used for a dropdown menu that covers the entire column. For example, rows are selected row by row.

[0183] Here, the transistor M is shown by the dotted line. RS , transistor M PDO , transistor M SEL This circuit is shared by multiple pixels (multiple avalanche diodes). Specifically, it is shared by four pixels in a 2x2 arrangement (four avalanche diodes). Because multiple pixels share the same circuit, more avalanche diodes can be placed in the same area. In the above embodiment, as shown in Figure 5, the potential barrier formed by the first separation unit 20 is made lower than the potential barrier formed by the second separation unit 30, thereby reducing crosstalk and reducing the pixel size. In addition, by using the pixel circuit of this embodiment, the pixel size can be further reduced when arrayed, thus providing a SPAD array sensor with more pixels.

[0184] The feedback loop in the pixels of this embodiment can prevent subsequent avalanche occurrences in the frame. The feedback loop can suppress current from the cathode voltage node VOP. This is advantageous in large-area arrays, as it can affect power dissipation when the count exceeds 100,000.

[0185] Figure 31(b) shows the driving method. When VQR and VG transition from H level to L level, exposure begins, and when VQR and VG transition from L level to H level, exposure for one subframe is performed. At this time, the exposure period of the subframe is roughly defined as the period from the timing when VQR transitions from H level to L level to the timing when VG transitions from H level to L level. By repeating the subframe period multiple times, a sufficient photon count value can be obtained even for weak optical signals. In the readout period, first VRES is set to H level and M RS Reset the source terminal. Next, set VSW to the H level, M RS The output signal is written to the source terminal. If a photon is detected during the exposure period, it will be at an L level; otherwise, it will be at an H level. Furthermore, the pixel signal is output to the vertical signal line with VSEL set to an H level. After the readout is complete, a reset is performed by simultaneously setting VRES, VSW, VQR, and VG to an H level.

[0186] <Embodiment 17> The filters of the photoelectric conversion device, which is the 17th embodiment, will be described using Figures 32 and 33 to 35. Figure 32 is a graph showing the spectral transmittance of each filter, and Figures 33 to 35 are specific examples of filter arrangements in the photoelectric conversion device of this embodiment.

[0187] The photoelectric converter may be equipped with filters that transmit light of specific wavelengths to the avalanche photodiodes arranged on the substrate. Examples of filters include color filters (sometimes denoted as CF), infrared light filters, and infrared light cut filters. These filters may be used individually or in combination.

[0188] A CF (Camera Filter) is a filter that transmits visible light, such as red, green, and blue. Hereafter, red, green, and blue will be denoted as R, G, and B. A pixel with an R CF will be called an R pixel, a pixel with a G CF will be called a G pixel, and a pixel with a B CF will be called a B pixel. When R, G, and B pixels are referred to together, they may be called RGB pixels. Hereafter, infrared light will be referred to as IR. A pixel with a filter that transmits IR will be called an IR pixel.

[0189] Figure 32 shows the spectral transmittance of the filters. Figure 32 is a graph with wavelength (in nm) on the horizontal axis and spectral transmittance (in %) on the vertical axis. First, the wavelength range of visible light is generally from 400 nm to less than 700 nm, and the wavelength range of infrared light is from 750 nm to 1 mm. Here, the spectral transmittance of the IR filter is 50% or more in the wavelength range of at least 700 nm and less than 50% in the wavelength range below 700 nm. In other words, an IR filter is a filter that mainly transmits infrared light, and cuts out visible light. As shown by the solid IR line in Figure 19, the spectral transmittance of the IR filter shows a value of 90% or more around 740 nm, but does not exceed 50% below 700 nm. On the other hand, the spectral transmittance of the visible light filter is 50% or more in the wavelength range below 700 nm. In other words, a visible light filter is a filter that mainly transmits visible light. A visible light filter only needs to transmit light in the visible light wavelength range below the wavelength of infrared light; for example, it transmits light with wavelengths less than 700 nm. As shown by the solid lines R, G, and B in Figure 32, the spectral transmittance of each visible light filter exceeds 50% at specific wavelengths below 700 nm. For example, the peak spectral transmittance of the R filter is approximately 650 nm, the peak spectral transmittance of the G filter is approximately 550 nm, and the peak spectral transmittance of the B filter is approximately 450 nm. Although a visible light filter may transmit some light in the infrared wavelength range, it may be designed not to transmit light in the infrared wavelength range, for example, light above 700 nm, in order to eliminate the influence of infrared light. In other words, a visible light filter may also function as a so-called IR cut filter. Furthermore, a visible light filter may include, for example, an infrared cut filter that cuts light above 700 nm. Figure 32 illustrates the range through which an IR cut filter transmits light. The material of each filter may be organic or inorganic. Note that "opaque" or "not transmit light" is not limited to materials that do not transmit 100% of light. For example, it can refer to materials that do not transmit 50% or more of light.

[0190] Figure 33(a) shows an example of a configuration with a so-called Bayer arrangement. The CF ratio R:G:B is 1:2:1.

[0191] Figure 33(b) shows an example of the arrangement of CFs in RGBW12. In this arrangement, each CF is arranged in a 4x4 pixel array in the ratio R:G:B:W = 1:2:1:12. W represents a white pixel, which is a pixel without a CF. Each of the color pixels (R, G, and B) has W pixels adjacent to it in the vertical, horizontal, and diagonal directions in a planar view. That is, each of the R, G, and B pixels is surrounded by eight W pixels. W pixels occupy a ratio of 3 / 4 of all pixels. Because each of the RGB color pixels is surrounded by W pixels, the interpolation accuracy of interpolating the W pixel signal to the signals of the R, G, and B pixels is improved.

[0192] Figure 34 shows an example of a configuration where IR pixels are used instead of W pixels in Figure 33(b). Such a filter configuration is also acceptable.

[0193] Alternatively, as shown in Figure 35, each pixel may be arranged in a honeycomb pattern. In Figure 35, IR pixels are used, but W pixels may be used instead of IR pixels.

[0194] Thus, the photoelectric conversion device according to this embodiment can employ various filter arrangements.

[0195] The present invention is not limited to the embodiments described above and can be modified in various ways. For example, an example in which a part of the configuration of one embodiment is added to another embodiment, or in which a part of the configuration of another embodiment is replaced, is also an embodiment of the present invention.

[0196] It should be noted that the above embodiments are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted as being limited by them. In other words, the present invention can be implemented in various forms without departing from its technical concept or its main features.

[0197] For example, although the 17th embodiment shows an example in which a filter is placed, the photoelectric converter of each embodiment may be used as a photoelectric converter that converts monochrome light into photoelectric light without placing a CF, IR cut filter, or visible light cut filter. [Explanation of Symbols]

[0198] 1. N-type semiconductor region 2 N-type semiconductor region 3. N-type semiconductor region 20 1st separation section 30 Second separation section

Claims

1. The avalanche diode comprises: a first avalanche diode including a first semiconductor region of a first conductivity type having the same charge as the signal charge as the majority carriers; a second avalanche diode including a second semiconductor region of the first conductivity type and arranged adjacent to the first avalanche diode; and a third avalanche diode arranged adjacent to the second avalanche diode and including an eighth semiconductor region of the first conductivity type. In a plan view, the first avalanche diode and the second avalanche diode are arranged side by side in a first direction, and the second avalanche diode and the third avalanche diode are arranged side by side in a second direction intersecting the first direction. A first separation portion is provided between the first semiconductor region and the second semiconductor region. The first separation portion is composed of the third semiconductor region of the first conductivity type, In a plan view, a seventh semiconductor region of a second conductivity type, which is a different conductivity type from the first conductivity type, is arranged at a position that overlaps with the third semiconductor region and is deeper than the third semiconductor region. The third semiconductor region and the seventh semiconductor region constitute a PN junction. The impurity concentration in the third semiconductor region is lower than the impurity concentration in the seventh semiconductor region. No semiconductor region of the second conductivity type is located between the first semiconductor region and the second semiconductor region. A photoelectric conversion device characterized in that, in a plan view, a contact plug is provided between the first semiconductor region and the eighth semiconductor region to supply potential to one node of the first avalanche diode.

2. The avalanche diode comprises a first avalanche diode including a first semiconductor region of a first conductivity type having the same charge as the signal charge as the majority carriers, and a second avalanche diode including a second semiconductor region of the first conductivity type and arranged adjacent to the first avalanche diode. A first separation portion is provided between the first semiconductor region and the second semiconductor region. The first separation portion is composed of a fourth semiconductor region of a second conductivity type, which is a different conductivity type from the first conductivity type, and a third semiconductor region of the first conductivity type, which is arranged on either side of the fourth semiconductor region in a plan view. The photoelectric converter is characterized in that the fourth semiconductor region satisfies Equation 1, with respect to the impurity concentration Nd of the third semiconductor region, the impurity concentration Na of the fourth semiconductor region, the elementary charge q, the dielectric constant ε of the semiconductor, the potential difference V between the PN junction of the third semiconductor region and the fourth semiconductor region, and the length D of the fourth semiconductor region sandwiched between the third semiconductor regions. [Math 1]

3. A substrate having a first surface and a second surface facing the first surface, A first avalanche diode comprising: a first semiconductor region having a first conductivity type and having the same charge as the signal charge as the majority carriers, disposed at a first depth of the substrate; and a fifth semiconductor region having a second conductivity type different from the first conductivity type, disposed at a second depth between the first depth and the second surface and between the first semiconductor region and the second surface; The substrate includes a second semiconductor region of the first conductivity type disposed at the first depth, and a sixth semiconductor region of the second conductivity type disposed at the second depth between the second semiconductor region and the second surface, and a second avalanche diode disposed adjacent to the first avalanche diode, The present invention comprises a third avalanche diode, which is arranged adjacent to the second avalanche diode and includes an eighth semiconductor region of the first conductivity type, In a plan view, the first avalanche diode and the second avalanche diode are arranged side by side in a first direction, and the second avalanche diode and the third avalanche diode are arranged side by side in a second direction intersecting the first direction. At the first depth, a first separation portion is provided between the first semiconductor region and the second semiconductor region. The first separation portion is provided with at least one of an intrinsic semiconductor region, a third semiconductor region of the first conductivity type, and a fourth semiconductor region of the second conductivity type. At the second depth, the seventh semiconductor region of the second conductivity type is arranged between the fifth semiconductor region and the sixth semiconductor region. In a line passing through the first separation portion and the seventh semiconductor region and perpendicular to the first plane, the potential height for the signal charge decreases from the seventh semiconductor region toward the first separation portion, and the difference between the potential height for the signal charge in the first semiconductor region and the potential height for the signal charge in the fifth semiconductor region is greater than the difference between the potential height for the signal charge in the first separation portion and the potential height for the signal charge in the seventh semiconductor region. A photoelectric conversion device characterized in that, in a plan view, a contact plug is provided between the first semiconductor region and the eighth semiconductor region to supply potential to one node of the first avalanche diode.

4. The photoelectric conversion apparatus according to claim 3, characterized in that the first separation portion includes the third semiconductor region.

5. The photoelectric conversion device according to claim 1, 2, or 4, characterized in that the third semiconductor region is shared by the first avalanche diode and the second avalanche diode.

6. The photoelectric conversion apparatus according to claim 5, characterized in that the impurity concentration in the third semiconductor region is lower than the impurity concentration in the first semiconductor region.

7. The present invention comprises a third avalanche diode, which is arranged adjacent to the second avalanche diode and includes an eighth semiconductor region of the first conductivity type, In a plan view, the first avalanche diode and the second avalanche diode are arranged side by side in a first direction, and the second avalanche diode and the third avalanche diode are arranged side by side in a second direction intersecting the first direction. The photoelectric conversion device according to claim 2, characterized in that, in a plan view, a contact plug is provided between the first semiconductor region and the eighth semiconductor region to supply potential to one node of the first avalanche diode.

8. A ninth semiconductor region of the second conductivity type is disposed between the first semiconductor region and the eighth semiconductor region, The semiconductor has a fourth semiconductor region of the second conductivity type disposed between the first semiconductor region and the second semiconductor region, The contact plug is connected to the ninth semiconductor region, The photoelectric conversion apparatus according to claim 7, characterized in that the impurity concentration in the ninth semiconductor region is higher than the impurity concentration in the fourth semiconductor region.

9. The contact plug is formed on the first surface side of the substrate. The photoelectric conversion device according to claim 8, characterized in that the light is incident on the substrate from the side of the second surface facing the first surface.

10. The photoelectric conversion apparatus according to claim 8 or 9, characterized in that the first distance between the first semiconductor region and the second semiconductor region is shorter than the second distance between the first semiconductor region and the eighth semiconductor region.

11. The photoelectric conversion device according to claim 10, characterized in that the first distance is 1 / 8 times or more the second distance.

12. The system comprises at least one of a memory, a time-to-digital conversion circuit, and a counter, which are arranged in correspondence with the first avalanche diode and the second avalanche diode and detect the avalanche current generated by avalanche multiplication, In a plan view, the contact plug is not located between the first semiconductor region and the second semiconductor region. The photoelectric converter according to any one of claims 8 to 11, characterized in that the contact plug and the ninth semiconductor region are shared by the first avalanche diode, the second avalanche diode, and the third avalanche diode.

13. The photoelectric conversion device according to claim 12, comprising a second contact plug for supplying potential to the first semiconductor region, a third contact plug for supplying potential to the second semiconductor region, and a fourth contact plug for supplying potential to the eighth semiconductor region, wherein the distance between the second contact plug and the contact plug, the distance between the third contact plug and the contact plug, and the distance between the fourth contact plug and the contact plug are the same.

14. The contact plug is formed on the first surface side of the substrate. The photoelectric conversion device according to claim 1, characterized in that the light is incident on the substrate from the side of the second surface facing the first surface.

15. The substrate has the first semiconductor region and the second semiconductor region arranged on it. A second substrate, different from the aforementioned substrate, is provided with a memory or counter circuit for detecting the avalanche current generated based on the signal from the first avalanche diode. The photoelectric conversion device according to any one of claims 1 to 14, characterized in that the substrate and the second substrate are stacked together.

16. The photoelectric conversion apparatus according to any one of claims 1 to 15, characterized in that a trench separator is provided between the first semiconductor region and the second semiconductor region.

17. The photoelectric conversion apparatus according to claim 16, characterized in that one end of the trench separation is formed to a position deeper than the first semiconductor region.

18. The photoelectric converter according to any one of claims 1 to 17, characterized in that the first avalanche diode operates in Geiger mode.

19. Equipped with a color filter, The photoelectric conversion device according to any one of claims 1 to 18, characterized in that light transmitted through the color filter is incident on the first avalanche diode.

20. A photoelectric conversion device according to any one of claims 1 to 19, A photoelectric conversion system characterized by having a signal processing unit that processes the signal output by the aforementioned photoelectric conversion device.

21. A photoelectric conversion device according to any one of claims 1 to 19, A mobile body having distance information acquisition means for acquiring distance information to an object from distance measurement information based on a signal from the aforementioned photoelectric converter, A mobile body further comprising control means for controlling the mobile body based on the distance information.

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