Photoelectric conversion device

Abstract

To provide a photoelectric conversion device that can further improve sensitivity.SOLUTION: A photoelectric conversion device includes a substrate, a photoelectric conversion unit arranged in the substrate and generating an electric charge according to incident light, and a pixel separation unit arranged in the substrate and separating the photoelectric conversion unit from other elements, and a side wall of the pixel separation unit has a plurality of unevennesses in a cross-sectional view, and the period of at least a part of the plurality of unevennesses is larger than 1 / 2 of the wavelength of light to which the photoelectric conversion unit is sensitive.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion device. [Background technology]

[0002] Patent Document 1 discloses a solid-state imaging device having an inter-pixel isolation section with a protrusion that protrudes toward a photoelectric conversion section, and also discloses deep trench isolation (DTI) as an example of the inter-pixel isolation section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 139279 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the DTI disclosed in Patent Document 1 may not necessarily be optimal in terms of sensitivity to incident light.

[0005] An object of the present invention is to provide a photoelectric conversion device that can further improve sensitivity. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a liquid crystal display device comprising: a substrate; a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; and a pixel separation unit disposed within the substrate and configured to separate the photoelectric conversion unit from other elements, wherein a sidewall of the pixel separation unit has a plurality of irregularities in a cross-sectional view; The distance between adjacent convex parts is greater than half the wavelength of light to which the photoelectric conversion unit is sensitive. The substrate has irregularities arranged on the incident surface of the photoelectric conversion unit. A photoelectric conversion device characterized by the above features is provided. According to one aspect of the present invention, there is provided a photoelectric conversion device comprising: a substrate; a photoelectric conversion unit arranged within the substrate and generating charges in response to incident light; and a pixel separation unit arranged within the substrate and separating the photoelectric conversion unit from other elements, wherein a sidewall of the pixel separation unit has, in a cross-sectional view, a plurality of irregularities, the plurality of irregularities having a periodic irregular structure, the periodic distance of at least a portion of the irregular structure being greater than 1 / 2 the wavelength of light to which the photoelectric conversion unit is sensitive, and the substrate has irregularities arranged on the incident surface of the photoelectric conversion unit. According to one aspect of the present invention, there is provided a photoelectric conversion device comprising: a substrate; a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; and a pixel separation unit disposed within the substrate and separating the photoelectric conversion unit from other elements, wherein a sidewall of the pixel separation unit has a plurality of protrusions and recesses in a cross-sectional view, the distance between adjacent protrusions among the plurality of protrusions and recesses being greater than 1 / 2 the wavelength of light to which the photoelectric conversion unit is sensitive, and the photoelectric conversion unit includes an avalanche photodiode. According to one aspect of the present invention, there is provided a photoelectric conversion device comprising: a substrate; a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; and a pixel separation unit disposed within the substrate and separating the photoelectric conversion unit from other elements, wherein a sidewall of the pixel separation unit has, in a cross-sectional view, a plurality of irregularities, the plurality of irregularities having a periodic irregular structure, a periodic distance of at least a portion of the irregular structure being greater than 1 / 2 the wavelength of light to which the photoelectric conversion unit is sensitive, and the photoelectric conversion unit includes an avalanche photodiode. [Effects of the Invention]

[0007] According to the present invention, a photoelectric conversion device capable of further improving sensitivity is provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating the overall configuration of a photoelectric conversion device according to a first embodiment. [Figure 2] 2 is a schematic block diagram showing an example of the configuration of a sensor substrate according to the first embodiment. FIG. [Figure 3] 1 is a schematic block diagram showing an example of the configuration of a circuit board according to a first embodiment. [Figure 4] 2 is a schematic block diagram showing an example of the configuration of one pixel of a photoelectric conversion unit and a pixel signal processing unit according to the first embodiment. FIG. [Figure 5] 3A to 3C are diagrams illustrating the operation of the avalanche photodiode according to the first embodiment. [Figure 6] 1A and 1B are diagrams illustrating the structure of an avalanche photodiode according to a first embodiment. [Figure 7] FIG. 2 is a schematic cross-sectional view of a pixel separator according to the first embodiment. [Figure 8] FIG. 10 is a schematic cross-sectional view of a pixel separator according to a modified example of the first embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view of a pixel separator according to a modified example of the first embodiment. [Figure 10] FIG. 4 is a cross-sectional view schematically illustrating an avalanche photodiode according to a modified example of the first embodiment. [Figure 11] FIG. 4 is a cross-sectional view schematically illustrating an avalanche photodiode according to a modified example of the first embodiment. [Figure 12] FIG. 4 is a cross-sectional view schematically illustrating an avalanche photodiode according to a modified example of the first embodiment. [Figure 13] FIG. 4 is a cross-sectional view schematically illustrating an avalanche photodiode according to a modified example of the first embodiment. [Figure 14] 5A and 5B are diagrams illustrating the structure of an avalanche photodiode according to a second embodiment. [Figure 15] FIG. 10 is a schematic plan view of an avalanche photodiode according to a modified example of the second embodiment. [Figure 16] FIG. 10 is a schematic plan view of an avalanche photodiode according to a modified example of the second embodiment. [Figure 17] FIG. 10 is a block diagram of a light detection system according to a third embodiment. [Figure 18] FIG. 10 is a block diagram of a light detection system according to a fourth embodiment. [Figure 19] FIG. 10 is a schematic diagram of an endoscopic surgery system according to a fifth embodiment. [Figure 20] FIG. 10 is a schematic diagram of a light detection system according to a sixth embodiment. [Figure 21] FIG. 10 is a schematic diagram of a moving body according to a sixth embodiment. [Figure 22] 13 is a flowchart showing the operation of the light detection system according to the sixth embodiment. [Figure 23] FIG. 13 is a diagram showing a specific example of an electronic device according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are intended to embody the technical concept of the present invention and are not intended to limit the present invention. The size and positional relationship of components shown in each drawing may be exaggerated for clarity. The same or corresponding elements in multiple drawings are designated by common reference numerals, and their description may be omitted or simplified.

[0010] In the following description, terms indicating specific directions or positions (for example, "up," "down," "right," "left," and other terms including these terms) are used as necessary. The use of these terms is intended to facilitate understanding of the embodiments with reference to the drawings, and the meanings of these terms do not limit the technical scope of the present invention.

[0011] [First embodiment] FIG. 1 is a schematic diagram showing the overall configuration of a photoelectric conversion device 100 according to this embodiment. The photoelectric conversion device 100 may be, for example, a solid-state imaging device, a focus detection device, a distance measurement device, a time-of-flight (TOF) camera, or the like. The photoelectric conversion device 100 includes a sensor substrate 11 (first substrate) and a circuit substrate 21 (second substrate) stacked on top of each other. The sensor substrate 11 and the circuit substrate 21 are electrically connected to each other. The sensor substrate 11 includes a pixel region 12 in which a plurality of pixels 101 are arranged in a plurality of rows and a plurality of columns. The circuit substrate 21 includes a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged in a plurality of rows and a plurality of columns, and a second circuit region 23 arranged on the periphery of the first circuit region 22. The second circuit region 23 may include circuits for controlling the plurality of pixel signal processing units 103. The sensor substrate 11 includes a light incident surface that receives incident light and a connection surface facing the light incident surface. The connection surface of the sensor substrate 11 is connected to the circuit board 21. In other words, the photoelectric conversion device 100 is a so-called backside illuminated type.

[0012] In this specification, "plan view" refers to a view from a direction perpendicular to the surface opposite to the light incident surface. Furthermore, a cross section refers to a surface in a direction perpendicular to the surface opposite to the light incident surface of the sensor substrate 11. Note that the light incident surface may be rough when viewed microscopically, and in such cases, the plan view is defined based on the light incident surface when viewed macroscopically.

[0013] In the following description, the sensor substrate 11 and the circuit board 21 are described as being diced chips, but the sensor substrate 11 and the circuit board 21 are not limited to being chips. For example, the sensor substrate 11 and the circuit board 21 may be wafers. Furthermore, if the sensor substrate 11 and the circuit board 21 are diced chips, the photoelectric conversion device 100 may be manufactured by stacking them in a wafer state and then dicing them, or by stacking them after dicing.

[0014] FIG. 2 is a schematic block diagram showing an example of the arrangement of the sensor substrate 11. A plurality of pixels 101 are arranged in a plurality of rows and a plurality of columns in the pixel region 12. Each of the plurality of pixels 101 has a photoelectric conversion unit 102 including an avalanche photodiode (hereinafter referred to as an APD) as a photoelectric conversion element. If the photoelectric conversion device 100 is an imaging device, the plurality of pixels 101 may be elements that generate image signals by photoelectric conversion. However, if the photoelectric conversion device 100 is a distance measuring device using technology such as TOF, the pixels 101 may be elements that measure the time and amount of light that arrives. In other words, the use of the plurality of pixels 101 is not limited to image acquisition.

[0015] The conductivity type of the charge pairs generated in an APD and used as signal charges is referred to as the first conductivity type. The first conductivity type refers to a conductivity type in which charges of the same polarity as the signal charges serve as majority carriers. The conductivity type opposite to the first conductivity type, i.e., a conductivity type in which charges of a different polarity than the signal charges serve as majority carriers, is referred to as the second conductivity type. In the APD described below, the anode of the APD is at a fixed potential, and a signal is output from the cathode of the APD. Therefore, the first conductivity type semiconductor region is an N-type semiconductor region, and the second conductivity type semiconductor region is a P-type semiconductor region. Alternatively, the cathode of the APD may be at a fixed potential, and a signal may be output from the anode of the APD. In this case, the first conductivity type semiconductor region is a P-type semiconductor region, and the second conductivity type semiconductor region is an N-type semiconductor region. While the following description will be given of a case in which one node of the APD is at a fixed potential, the potentials of both nodes may fluctuate.

[0016] In this specification, when the term "impurity concentration" is used simply, it means the net impurity concentration minus the amount compensated for by impurities of the opposite conductivity type. In other words, "impurity concentration" refers to the NET doping concentration. A region where the P-type doped impurity concentration is higher than the N-type doped impurity concentration is a P-type semiconductor region. Conversely, a region where the N-type doped impurity concentration is higher than the P-type doped impurity concentration is an N-type semiconductor region.

[0017] 3 is a schematic block diagram showing an example configuration of the circuit board 21. The circuit board 21 has a first circuit area 22 in which a plurality of pixel signal processing units 103 are arranged in a plurality of rows and a plurality of columns.

[0018] Also arranged on the circuit board 21 are a vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, pixel output signal lines 113, an output circuit 114, and a control signal generation unit 115. The multiple photoelectric conversion units 102 shown in Fig. 2 and the multiple pixel signal processing units 103 shown in Fig. 3 are electrically connected to each other via connection wiring provided for each pixel 101.

[0019] The control signal generation unit 115 is a control circuit that generates control signals for driving the vertical scanning circuit 110, the horizontal scanning circuit 111, and the readout circuit 112, and supplies these signals to each of these units. In this way, the control signal generation unit 115 controls the drive timing of each unit, etc.

[0020] The vertical scanning circuit 110 supplies a control signal to each of the plurality of pixel signal processing units 103 based on the control signal supplied from the control signal generation unit 115. The vertical scanning circuit 110 supplies a control signal to each pixel signal processing unit 103 for each row via a drive line provided for each row in the first circuit area 22. Note that, as will be described later, there may be multiple drive lines for each row. The vertical scanning circuit 110 may include logic circuits such as a shift register and an address decoder. In this way, the vertical scanning circuit 110 selects a row for outputting a signal from the pixel signal processing unit 103.

[0021] The signal output from the photoelectric conversion unit 102 of the pixel 101 is processed by the pixel signal processing unit 103. The pixel signal processing unit 103 counts the number of pulses output from the APD included in the photoelectric conversion unit 102 to acquire and hold a digital signal having multiple bits.

[0022] It is not necessary for one pixel signal processing unit 103 to be provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by multiple pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing the signals output from each photoelectric conversion unit 102.

[0023] The horizontal scanning circuit 111 supplies a control signal to the readout circuit 112 based on a control signal supplied from the control signal generation unit 115. The pixel signal processing units 103 are connected to the readout circuit 112 via pixel output signal lines 113 provided for each column of the first circuit area 22. The pixel output signal line 113 for one column is shared by multiple pixel signal processing units 103 for the corresponding column. The pixel output signal line 113 includes multiple wirings and has at least the function of outputting a digital signal from each pixel signal processing unit 103 to the readout circuit 112 and the function of supplying the pixel signal processing unit 103 with a control signal for selecting a column from which to output a signal. The readout circuit 112 outputs a signal to a storage unit or signal processing unit external to the photoelectric conversion device 100 via the output circuit 114 based on the control signal supplied from the control signal generation unit 115.

[0024] The photoelectric conversion units 102 in the pixel region 12 may be arranged one-dimensionally. Furthermore, it is not necessary for one pixel signal processing unit 103 to be provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by multiple pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing signals output from each photoelectric conversion unit 102.

[0025] 2 and 3, a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged is arranged in a region overlapping the pixel region 12 in a planar view. A vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, an output circuit 114, and a control signal generation unit 115 are arranged so as to overlap between an end of the sensor substrate 11 and an end of the pixel region 12 in a planar view. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12. A second circuit region 23 in which the vertical scanning circuit 110, the horizontal scanning circuit 111, the readout circuit 112, the output circuit 114, and the control signal generation unit 115 are arranged is arranged in a region of the circuit substrate 21 overlapping the non-pixel region in a planar view.

[0026] The arrangement of the pixel output signal lines 113, the arrangement of the readout circuits 112, and the arrangement of the output circuits 114 are not limited to those shown in Fig. 3. For example, the pixel output signal lines 113 may be arranged to extend in the row direction and be shared by multiple pixel signal processing units 103 in the corresponding row. The readout circuits 112 may then be arranged so that the pixel output signal lines 113 in each row are connected.

[0027] Fig. 4 is a schematic block diagram showing an example of the configuration of one pixel of the photoelectric conversion unit 102 and pixel signal processing unit 103 according to this embodiment. Fig. 4 schematically shows a more specific example of the configuration, including the connection relationship between the photoelectric conversion unit 102 arranged on the sensor substrate 11 and the pixel signal processing unit 103 arranged on the circuit board 21. Note that in Fig. 4, the drive lines between the vertical scanning circuit 110 and the pixel signal processing unit 103 in Fig. 3 are shown as drive lines 213 and 214.

[0028] The photoelectric conversion unit 102 has an APD 201. The pixel signal processing unit 103 has a quenching element 202, a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. It is sufficient that the pixel signal processing unit 103 has at least one of the waveform shaping unit 210, the counter circuit 211, and the selection circuit 212.

[0029] The APD 201 generates charge pairs according to incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201. A cathode of the APD 201 is connected to a first terminal of the quench element 202 and an input terminal of the waveform shaping unit 210. A voltage VH (second voltage) higher than the voltage VL supplied to the anode is supplied to the cathode of the APD 201. As a result, a reverse bias voltage is supplied to the anode and cathode of the APD 201 such that the APD 201 performs avalanche multiplication. When charges are generated by incident light in the APD 201 to which the reverse bias voltage is supplied, the charges undergo avalanche multiplication, generating an avalanche current.

[0030] The APD 201 can operate in either Geiger mode or linear mode when a reverse bias voltage is supplied to it. The Geiger mode is a mode in which the APD operates with a potential difference between the anode and cathode greater than the breakdown voltage, while the linear mode is a mode in which the APD operates with a potential difference between the anode and cathode close to or less than the breakdown voltage.

[0031] An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). In this case, for example, the voltage VL (first voltage) is −30 V and the voltage VH (second voltage) is 1 V. The APD 201 may be operated in either linear mode or Geiger mode. A SPAD is preferable because the potential difference is larger than that of a linear mode APD, making the avalanche multiplication effect more pronounced.

[0032] The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication. The quench element 202 suppresses the voltage supplied to the APD 201 to suppress avalanche multiplication (quench operation). The quench element 202 also returns the voltage supplied to the APD 201 to voltage VH by passing a current corresponding to the voltage drop caused by the quench operation (recharge operation). The quench element 202 may be, for example, a resistive element.

[0033] The waveform shaping unit 210 is a circuit that shapes the potential change of the cathode of the APD 201 obtained when a photon is detected and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. While Fig. 4 shows an example in which one inverter is used as the waveform shaping unit 210, the waveform shaping unit 210 may be a circuit in which multiple inverters are connected in series, or may be any other circuit that has a waveform shaping effect.

[0034] The counter circuit 211 counts the number of pulses output from the waveform shaping unit 210 and holds a digital signal indicating the count value. When a control signal is supplied from the vertical scanning circuit 110 via a drive line 213, the counter circuit 211 resets the signal it holds.

[0035] A control signal is supplied to the selection circuit 212 from the vertical scanning circuit 110 shown in Fig. 3 via a drive line 214 shown in Fig. 4. In response to this control signal, the selection circuit 212 switches between electrical connection and disconnection between the counter circuit 211 and the pixel output signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal corresponding to the value held in the counter circuit 211.

[0036] 4, the selection circuit 212 switches between electrical connection and disconnection between the counter circuit 211 and the pixel output signal line 113, but the method for controlling the signal output to the pixel output signal line 113 is not limited to this. For example, a switch such as a transistor may be disposed at a node between the quench element 202 and the APD 201, or between the photoelectric conversion unit 102 and the pixel signal processing unit 103, and the like, to switch between electrical connection and disconnection, thereby controlling the signal output to the pixel output signal line 113. Alternatively, the signal output to the pixel output signal line 113 may be controlled by changing the value of the voltage VH or voltage VL supplied to the photoelectric conversion unit 102 using a switch such as a transistor.

[0037] 4 shows an example configuration using a counter circuit 211. However, instead of the counter circuit 211, a time-to-digital converter (hereinafter referred to as TDC) and a memory may be used to acquire the timing for detecting a pulse. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 is converted into a digital signal by the TDC. In this case, a control signal (reference signal) may be supplied to the TDC from the vertical scanning circuit 110 in FIG. 3 via a drive line. The TDC acquires, as a digital signal, a signal indicating the relative time of the input timing of the pulse with reference to the control signal.

[0038] 5(a), 5(b), and 5(c) are diagrams illustrating the operation of the APD 201 according to this embodiment. FIG. 5(a) is a diagram illustrating the APD 201, the quench element 202, and the waveform shaping unit 210 extracted from FIG. 4. As shown in FIG. 5(a), the connection node between the APD 201, the quench element 202, and the input terminals of the waveform shaping unit 210 is referred to as node A. Also, as shown in FIG. 5(a), the output side of the waveform shaping unit 210 is referred to as node B.

[0039] FIG. 5(b) is a graph showing the time change in the potential of node A in FIG. 5(a). FIG. 5(c) is a graph showing the time change in the potential of node B in FIG. 5(a). From time t0 to time t1, a voltage of VH-VL is applied to the APD 201 in FIG. 5(a). When a photon is incident on the APD 201 at time t1, avalanche multiplication occurs in the APD 201. This causes an avalanche current to flow through the quench element 202, and the potential of node A drops. Thereafter, the amount of potential drop increases further, and the voltage applied to the APD 201 gradually decreases. Then, at time t2, avalanche multiplication in the APD 201 stops. As a result, the voltage level of node A does not drop below a certain value. Then, from time t2 to time t3, a current flows to node A from the node at voltage VH to compensate for the voltage drop, and at time t3, node A settles to its original potential.

[0040] In the above process, the potential of node B becomes high during the period when the potential of node A is lower than a certain threshold. In this way, the waveform of the drop in the potential of node A caused by the incidence of a photon is shaped by waveform shaping section 210 and output as a pulse to node B.

[0041] 6(a), 6(b), and 6(c) are diagrams showing the structure of an APD 201 according to this embodiment. FIG. 6(a) is a schematic cross-sectional view of the APD 201. FIG. 6(b) is a schematic plan view showing the structure in the vicinity of the light incident surface of the semiconductor layer 300. FIG. 6(c) is a schematic plan view showing the structure in the vicinity of the avalanche multiplication region of the semiconductor layer 300. The structure of the APD 201 will be described with mutual reference to FIGS. 6(a), 6(b), and 6(c).

[0042] The multiple semiconductor regions that make up the APD 201 are disposed in the semiconductor layer 300 of the sensor substrate 11. The semiconductor layer 300 has a first surface onto which light is incident and a second surface opposite the first surface. In this specification, the depth direction is the direction from the first surface of the semiconductor layer 300 on which the APD 201 is disposed toward the second surface. Hereinafter, the "first surface" may be referred to as the "rear surface," and the "second surface" may be referred to as the "front surface." The direction from a predetermined position on the semiconductor layer 300 toward the front surface of the semiconductor layer 300 may be referred to as "deep." The direction from a predetermined position on the semiconductor layer 300 toward the back surface of the semiconductor layer 300 may be referred to as "shallow."

[0043] The semiconductor layer 300 has a first semiconductor region 311, a second semiconductor region 312, a third semiconductor region 313, a fourth semiconductor region 314, a fifth semiconductor region 315, a sixth semiconductor region 316, a seventh semiconductor region 317, and a pixel separation section 324. The APD 201 includes at least a first semiconductor region 311 of a first conductivity type and a second semiconductor region 312 of a second conductivity type. The first semiconductor region 311 and the second semiconductor region 312 form a PN junction. The impurity concentration of the first semiconductor region 311 is higher than the impurity concentration of the second semiconductor region 312. A predetermined reverse bias voltage is applied to the first semiconductor region 311 and the second semiconductor region 312, thereby forming an avalanche multiplication region.

[0044] 6(a), a third semiconductor region 313 of the first conductivity type may be disposed between the first semiconductor region 311 and the second semiconductor region 312 in the depth direction. Also, as shown in FIG. 6(c), the first semiconductor region 311 may be circular in a plan view. Also, the third semiconductor region 313 may be concentrically shaped so as to surround the first semiconductor region 311 in a plan view.

[0045] As shown in FIG. 6( a), a fifth semiconductor region 315 of the second conductivity type is disposed at a position shallower than the second semiconductor region 312. The fifth semiconductor region 315 is disposed so as to contact the fourth semiconductor region 314 of the second conductivity type. As shown in FIGS. 6( b) and 6(c), in a plan view, the fourth semiconductor region 314 is disposed so as to surround the first semiconductor region 311, the second semiconductor region 312, and the third semiconductor region 313. As shown in FIGS. 6( a), 6(b), and 6(c), in a plan view, the fifth semiconductor region 315 may be disposed over the entire surface of the APD 201, or a portion of the fifth semiconductor region 315 may overlap the fourth semiconductor region 314. The fourth semiconductor region 314 may be disposed throughout the entire depth of the semiconductor layer 300, or a portion of the fourth semiconductor region 314 may be at the same depth as the fifth semiconductor region 315.

[0046] A pixel separator 324 having a structure in which an insulator (dielectric) is embedded in the semiconductor layer 300 is disposed between adjacent APDs 201 (pixels 101). As shown in FIGS. 6(a), 6(b), and 6(c), the pixel separator 324 may have a deep trench isolation (DTI) structure in which an insulator such as silicon oxide is embedded in a deep trench. The deep trench may be filled with a metal other than an insulator. Alternatively, a thin insulator layer may be formed on the sidewall of the deep trench, and the deep trench and the insulator layer may be filled with a metal. In a plan view, the pixel separator 324 has a rectangular shape (including a square) surrounding one APD 201. This allows the pixel separator 324 to isolate one APD 201 from other elements.

[0047] A seventh semiconductor region 317 of the first conductivity type is provided between the second semiconductor region 312 and the fifth semiconductor region 315. The impurity concentration of the seventh semiconductor region 317 is higher than the impurity concentration of the sixth semiconductor region 316 provided around the seventh semiconductor region 317. With this configuration, the potential of the seventh semiconductor region 317 is lower than the potential of the sixth semiconductor region 316 for signal charges, allowing more charges to be collected in the avalanche multiplication region. The seventh semiconductor region 317 is a semiconductor region provided as needed and does not necessarily have to be provided. Also, although part of the seventh semiconductor region 317 is in contact with the second semiconductor region 312 in FIG. 6(a), the seventh semiconductor region 317 may be provided spaced apart from the second semiconductor region 312.

[0048] A pinning film 321, a planarizing layer 322, and a microlens 323 are arranged on the incident surface side of the semiconductor layer 300. An anti-reflection film that prevents reflection of incident light may be further arranged on the incident surface side of the semiconductor layer 300. A color filter may also be provided between the microlens 323 and the semiconductor layer 300.

[0049] 7 is a schematic cross-sectional view of a pixel separator according to this embodiment, which shows the pixel separator 324 and the fourth semiconductor region 314 and fifth semiconductor region 315 in the vicinity thereof extracted from FIG.

[0050] 7, in a cross-sectional view, the pixel separating portion 324 is disposed inside the fourth semiconductor region 314 and the fifth semiconductor region 315 from the back surface side toward the depth direction of the sensor substrate 11. As shown in Fig. 7, the sidewall of the pixel separating portion 324 has a plurality of projections and recesses disposed in the depth direction of the sensor substrate 11. These projections and recesses can be formed by appropriately setting process conditions when forming the pixel separating portion 324 using, for example, a Bosch process or the like.

[0051] Here, the relationship between the period of the unevenness arranged on the sidewall of the pixel separator 324 and the sensitivity of the APD 201 will be described. In order for light incident on the APD 201 to be sufficiently photoelectrically converted, the light needs to propagate a sufficient distance (hereinafter referred to as the optical path length) within the semiconductor layer 300. Therefore, in order to improve the efficiency of photoelectric conversion, it is necessary to ensure that the semiconductor layer 300 is sufficiently thick. The optical path length required to improve the efficiency of photoelectric conversion is short for light with a relatively short wavelength, such as blue light, and long for light with a relatively long wavelength, such as red light or near-infrared light. Therefore, when the APD 201 is sensitive to red light or near-infrared light, the semiconductor layer 300 needs to be thicker than when the APD 201 is sensitive to blue light.

[0052] A specific example of the thickness of the semiconductor layer 300 when the APD 201 is disposed on a single-crystal silicon substrate will be described. For blue or green light in the visible range, if the depth L1 of the photoelectric conversion region shown in FIG. 6(a) is approximately 4 μm, 99% or more of the incident light is photoelectrically converted. However, for red or near-infrared light, the photoelectric conversion region must be made thicker to photoelectrically convert 99% or more of the incident light. Generally, the depth of the photoelectric conversion region of the APD 201 is approximately several μm, and therefore the photoelectric conversion efficiency may be insufficient, particularly for light with relatively long wavelengths such as red or near-infrared light.

[0053] In this embodiment, the sidewalls of the pixel separator 324 are uneven, and the unevenness causes incident light to be diffused by the sidewalls. The diffused light propagates mainly within the photoelectric conversion region. Therefore, this diffuse reflection increases the optical path length of light propagating within the semiconductor layer 300, which can improve the efficiency of photoelectric conversion.

[0054] The interaction between incident light and asperities can be explained by ray approximation in geometric optics, but by wave optics. Under conditions where ray approximation is applicable, the point of incidence of light is treated as the reflecting surface, and reflection occurs so that the angle of incidence and the angle of reflection with respect to the normal to the reflecting surface are equal. The angle of reflection varies depending on the point of incidence within the asperities, resulting in diffuse reflection of the incident light. In contrast, under conditions where ray approximation is not applicable and wave properties must be considered, the incident light is less affected by the asperities due to diffraction. Therefore, diffuse reflection is unlikely to occur under these conditions. Whether ray approximation is applicable depends on the relationship between the wavelength of the incident light and the period H of the asperities. When the period H of the asperities is greater than half the wavelength of the incident light, diffraction is unlikely to occur, and ray approximation is applicable, resulting in sufficient diffuse reflection. Therefore, when the period H of the asperities is greater than half the wavelength of the incident light, the incident light is diffusely reflected by the asperities, thereby achieving the desired effect of lengthening the optical path length within the semiconductor layer 300. This can improve the efficiency of photoelectric conversion.

[0055] As described above, according to this embodiment, in the pixel separation section 324 formed by DTI, the period H of the unevenness of the sidewall is greater than 1 / 2 the wavelength of the incident light, thereby providing a photoelectric conversion device that can further improve sensitivity.

[0056] For example, if the APD 201 is sensitive to red light (approximately 650 nm), the period H of the unevenness on the sidewall of the pixel separating section 324 is preferably greater than 325 nm, which is half of 650 nm. This provides a photoelectric conversion device that can further improve sensitivity to red light. If the period H is greater than 325 nm, the condition for diffuse reflection is also met for green and blue light, which have wavelengths shorter than red light. Therefore, under these conditions, a photoelectric conversion device that can further improve sensitivity to almost the entire visible light range is provided. Furthermore, since the depth L1 of the photoelectric conversion region within the substrate is approximately 4 μm as described above, the period H of the unevenness on the sidewall of the pixel separating section 324 is preferably less than 4 μm. If the period H is less than 4 μm, at least one pair of concave and convex portions exists within the photoelectric conversion region, which is favorable for generating diffuse reflection. Therefore, the period H is preferably greater than 325 nm and less than 4 μm.

[0057] 6(a) and 6(b), it is more preferable that a concave-convex structure 325 be arranged on the light incident surface side of the semiconductor layer 300, i.e., on the fifth semiconductor region 315. The concave-convex structure 325 has a lattice shape in a plan view and a trench shape in a cross-sectional view. The provision of the concave-convex structure 325 causes light to be diffracted at the light incident surface of the APD 201, increasing the likelihood that light will be incident on the sidewall, further lengthening the optical path length. Therefore, although not essential, it is more preferable to use the concave-convex structure 325 in combination with the concave-convex structure on the sidewall of the pixel separator 324.

[0058] Modifications of this embodiment will be described below. Figures 8(a), 8(b), 8(c), and 8(d) are schematic cross-sectional views of pixel separators according to modifications of this embodiment. Each of Figures 8(a), 8(b), 8(c), and 8(d) shows an example in which the unevenness of the sidewalls of the pixel separator is arranged in part of the depth direction.

[0059] 8(a) has a sidewall of the pixel separating section 324A that has an uneven surface near the light incident surface. In this modification, the reflectance of long-wavelength light that is obliquely incident on the sidewall of the pixel separating section 324A is improved, which can improve the sensitivity of the APD 201.

[0060] The sidewall of the pixel separator 324B shown in FIG. 8(b) has an uneven surface near the avalanche multiplication region. In this modification, the reflectivity of photons generated by avalanche multiplication is improved, which can reduce crosstalk to adjacent pixels. As such, it is desirable that the uneven surface of the sidewall be provided at least to a depth where avalanche multiplication occurs in the APD 201, thereby achieving the effect of reducing crosstalk to adjacent pixels.

[0061] As another variation, the unevenness may be arranged near the center of the depth direction of the side wall, as in pixel separation section 324C shown in Figure 8(c), or unevenness may be arranged at multiple positions on the side wall, as in pixel separation section 324D shown in Figure 8(d).

[0062] In addition, in pixel separation sections 324A to 324D shown in Figures 8(a) to 8(d), the side walls of the parts without unevenness may be flat, or may have fine unevenness to the extent that the effect of diffuse reflection is not produced.

[0063] 9(a) and 9(b) are cross-sectional schematic diagrams of pixel separators according to modifications of this embodiment. The side walls of the pixel separators in each of Fig. 9(a) and Fig. 9(b) have a combination of relatively large and relatively small irregularities.

[0064] 9(a), relatively large and relatively small irregularities are alternately arranged in the depth direction on the sidewall of the pixel separating section 324E. In this case, if the distance L2 between the convex portions of the relatively large irregularities is greater than half the wavelength of the incident light, the effect of lengthening the optical path length within the semiconductor layer 300 can be sufficiently obtained.

[0065] 9(b), the unevenness is arranged so that the deeper the position, the smaller the unevenness becomes. In this way, the size of the unevenness may vary along the depth direction of the side wall.

[0066] 10 to 13, a cross section of one APD 201 is illustrated, and the planarization layer 322 and the microlenses 323 are omitted. FIG. 10 is a schematic cross-sectional view of an APD 201 according to a modification of this embodiment. FIG. 10 shows a pixel isolation portion 324 disposed on the left side of the APD 201 and a pixel isolation portion 324G disposed on the right side of the APD 201. The pixel isolation portion 324 and the pixel isolation portion 324G have different shapes. More specifically, the width W1 of the pixel isolation portion 324 and the width W2 of the pixel isolation portion 324G are different from each other. Furthermore, the period H1 of the concave-convex pattern of the pixel isolation portion 324 and the period H2 of the concave-convex pattern of the pixel isolation portion 324 are different from each other. In this manner, a combination of multiple types of pixel isolation portions having different shapes, such as the width and period of the concave-convex pattern, may be used.

[0067] Fig. 11 is a schematic cross-sectional view of an APD 201 according to a modified example of this embodiment. The pixel separator 324H shown in Fig. 11 is arranged to penetrate the sensor substrate 11. This makes it possible to sufficiently obtain the effect of lengthening the optical path length at any position in the depth direction within the semiconductor layer 300.

[0068] FIG. 12 is a cross-sectional schematic diagram of an APD 201 according to a modified example of this embodiment. A light-shielding layer 326 is embedded in the pixel separator 324I shown in FIG. 12. The light-shielding layer 326 may be made of a material that has a lower transmittance for light to which the APD 201 is sensitive than the material of the sensor substrate 11 constituting the semiconductor layer 300. This allows light incident at an angle that does not cause total reflection on the sidewall of the pixel separator 324I to be reflected or absorbed by the light-shielding layer 326, thereby further reducing light leakage to adjacent pixels. Note that, because the light transmittance of metal materials is sufficiently low, it is more preferable that the light-shielding layer 326 be made of metal. Alternatively, the light-shielding layer 326 may be made of polysilicon, which provides the same effects as when the light-shielding layer 326 is made of metal.

[0069] Fig. 13 is a cross-sectional schematic diagram of an APD 201 according to a modified example of this embodiment. As shown in Fig. 13, a light-shielding layer 327 such as a metal layer is arranged on the incident surface side of the pixel separating section 324. This can reduce noise caused by light incident on the pixel separating section 324. The arrangement of the light-shielding layer 327 is not limited to that shown in Fig. 13. For example, the light-shielding layer 327 may be arranged on the surface opposite the incident surface, or may be arranged on both the incident surface side and the surface opposite the incident surface.

[0070] [Second embodiment] A second embodiment of the present invention will be described below. In the description of this embodiment, the description of elements common to the first embodiment may be omitted.

[0071] FIG. 14 is a diagram showing the structure of an APD 201 according to this embodiment. In addition to a schematic plan view similar to FIG. 6(b) and a schematic cross-sectional view similar to FIG. 7, FIG. 14 also shows a schematic enlarged plan view of the pixel separator 324J and a plan view of the pixel separator 324J in a cross-sectional view perpendicular to the sidewall. As shown in the enlarged schematic plan view of the pixel separator 324J in FIG. 14, the sidewall of the pixel separator 324J has irregularities not only in the cross-sectional view but also in the plan view from the light incident surface side. That is, as shown in the plan view of the sidewall, when viewed perpendicular to the sidewall, the sidewall has irregularities arranged two-dimensionally. The irregularities have a structure in which convex portions are repeatedly arranged in the depth direction and the lateral direction. This allows for more diffuse reflection of light than when the sidewall has irregularities only in the depth direction, thereby further improving sensitivity.

[0072] A modified example of this embodiment will be described below. FIGS. 15(a) and 15(b) are schematic plan views of an APD 201 according to this modified example. The sidewall of the pixel separator 324K shown in FIG. 15(a) has a right-triangular convex portion in a plan view from the light incident surface side. The sidewall of the pixel separator 324L shown in FIG. 15(b) has a trapezoidal convex portion in a plan view from the light incident surface side. That is, the shape of the concaves and convexes in a plan view from the light incident surface side is not limited to the curved shape shown in FIG. 14 , but may be a polygonal shape, such as a triangle or a rectangle, including straight lines, as shown in FIGS. 15(a) and 15(b). These shapes are merely examples, and a designer can appropriately design the shape of the concaves and convexes of the pixel separator, taking into consideration the trade-off between the throughput during formation of the pixel separator, manufacturing costs due to photomask costs, and the effect of improving sensitivity.

[0073] 16(a) and 16(b) are schematic plan views of an APD 201 according to a modification of this embodiment. The sidewall of the pixel separator 324M shown in FIG. 16(a) has irregularities only partially near the center in a plan view from the light incident surface side. The sidewall of the pixel separator 324N shown in FIG. 16(b) has irregularities only partially near both ends in a plan view from the light incident surface side. That is, the irregularities in a plan view from the light incident surface side are not limited to being arranged over the entire surface as in FIG. 14 , but may be arranged only partially as in FIGS. 16(a) and 16(b). For example, in a configuration in which irregularities are arranged near the center of one side of the rectangle (square) formed by the pixel separator 324M as in FIG. 16(a), photons generated by avalanche multiplication are effectively reflected, thereby reducing photon leakage to adjacent pixels.

[0074] [Third embodiment] A light detection system according to a third embodiment of the present invention will be described with reference to Fig. 17. Fig. 17 is a block diagram of the light detection system according to this embodiment. The light detection system according to this embodiment is an imaging system that acquires an image based on incident light.

[0075] The photoelectric conversion device in the above-described embodiment can be applied to various imaging systems. Examples of imaging systems include digital still cameras, digital camcorders, camera heads, copiers, fax machines, mobile phones, vehicle-mounted cameras, observation satellites, and surveillance cameras. Fig. 17 shows a block diagram of a digital still camera as an example of an imaging system.

[0076] The imaging system 7 shown in Fig. 17 includes a barrier 706, a lens 702, an aperture 704, an imaging device 70, a signal processing unit 708, a timing generating unit 720, an overall control and calculation unit 718, a memory unit 710, a recording medium control I / F unit 716, a recording medium 714, and an external I / F unit 712. The barrier 706 protects the lens, and the lens 702 forms an optical image of a subject on the imaging device 70. The aperture 704 varies the amount of light that passes through the lens 702. The imaging device 70 is configured like the photoelectric conversion device of the above-mentioned embodiment, and converts the optical image formed by the lens 702 into image data. The signal processing unit 708 performs various processes such as correction and data compression on the imaging data output from the imaging device 70.

[0077] The timing generating unit 720 outputs various timing signals to the imaging device 70 and the signal processing unit 708. The overall control / calculation unit 718 controls the entire digital still camera, and the memory unit 710 temporarily stores image data. The recording medium control I / F unit 716 is an interface for recording or reading image data to or from the recording medium 714, and the recording medium 714 is a removable recording medium such as a semiconductor memory for recording or reading image data. The external I / F unit 712 is an interface for communicating with an external computer or the like. Timing signals and the like may be input from outside the imaging system 7, and the imaging system 7 only needs to have at least the imaging device 70 and the signal processing unit 708 for processing image signals output from the imaging device 70.

[0078] In this embodiment, the imaging device 70 and the signal processing unit 708 may be arranged on the same semiconductor substrate, or the imaging device 70 and the signal processing unit 708 may be arranged on different semiconductor substrates.

[0079] Furthermore, each pixel of the image capture device 70 may include a first photoelectric conversion unit and a second photoelectric conversion unit. The signal processing unit 708 processes a pixel signal based on the charge generated in the first photoelectric conversion unit and a pixel signal based on the charge generated in the second photoelectric conversion unit, and can acquire information about the distance from the image capture device 70 to the subject.

[0080] [Fourth embodiment] Fig. 18 is a block diagram of a light detection system according to this embodiment, more specifically, a range image sensor using the photoelectric conversion device described in the above embodiment.

[0081] 18, the range image sensor 401 includes an optical system 402, a photoelectric conversion device 403, an image processing circuit 404, a monitor 405, and a memory 406. The range image sensor 401 receives light (modulated light, pulsed light) emitted from a light source device 411 toward a subject and reflected by the surface of the subject. The range image sensor 401 can acquire a range image according to the distance to the subject, based on the time between light emission and light reception.

[0082] The optical system 402 includes one or more lenses, guides image light (incident light) from a subject to the photoelectric conversion device 403 , and forms an image on the light receiving surface (sensor section) of the photoelectric conversion device 403 .

[0083] The photoelectric conversion devices of the above-described embodiments can be applied as the photoelectric conversion device 403. The photoelectric conversion device 403 supplies the image processing circuit 404 with a distance signal indicating the distance determined from the light reception signal.

[0084] The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 403. The distance image (image data) obtained by the image processing can be displayed on a monitor 405 and stored (recorded) in a memory 406.

[0085] The range image sensor 401 configured in this manner can acquire an accurate range image by applying the above-described photoelectric conversion device.

[0086] [Fifth embodiment] The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be applied to an endoscopic surgery system, which is an example of an optical detection system.

[0087] Figure 19 is a schematic diagram of an endoscopic surgery system according to this embodiment. Figure 19 shows an operator (doctor) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgery system 1103. As shown in the figure, the endoscopic surgery system 1103 includes an endoscope 1100, a surgical tool 1110, an arm 1121, and a cart 1134 on which various devices for endoscopic surgery are mounted.

[0088] The endoscope 1100 includes a lens barrel 1101, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 1132, and a camera head 1102 connected to the base end of the lens barrel 1101. Although Fig. 19 shows the endoscope 1100 configured as a so-called rigid scope having a rigid lens barrel 1101, the endoscope 1100 may also be configured as a so-called flexible scope having a flexible lens barrel.

[0089] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 1101. A light source device 1203 is connected to the endoscope 1100. Light generated by the light source device 1203 is guided to the tip of the lens barrel 1101 by a light guide extending inside the lens barrel 1101, and is irradiated via the objective lens towards an observation target inside the body cavity of the patient 1132. Note that the endoscope 1100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0090] An optical system and a photoelectric conversion device are provided inside the camera head 1102, and light reflected from an observation object (observation light) is focused onto the photoelectric conversion device by the optical system. The observation light is photoelectrically converted by the photoelectric conversion device to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observation image. The photoelectric conversion device may be any of the photoelectric conversion devices described in the above-described embodiments. The image signal is transmitted to a camera control unit (CCU) 1135 as RAW data.

[0091] The CCU 1135 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and comprehensively controls the operations of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives an image signal from the camera head 1102 and performs various image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

[0092] Under the control of the CCU 1135 , the display device 1136 displays an image based on the image signal that has been subjected to image processing by the CCU 1135 .

[0093] The light source device 1203 includes a light source such as an LED (Light Emitting Diode), and supplies the endoscope 1100 with irradiation light when photographing an operation site or the like.

[0094] The input device 1137 is an input interface for the endoscopic surgery system 1103. A user can input various information and instructions to the endoscopic surgery system 1103 via the input device 1137.

[0095] The treatment tool control device 1138 controls the driving of the energy treatment tool 1112 for cauterizing tissue, incising, sealing blood vessels, or the like.

[0096] The light source device 1203 can supply illumination light to the endoscope 1100 when photographing the surgical site, and can be, for example, a white light source such as an LED, a laser light source, or a combination of these. When the white light source is configured by combining RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision. This makes it possible to adjust the white balance of the captured image in the light source device 1203. In this case, laser light from each of the RGB laser light sources can be irradiated onto the observation object in a time-division manner, and the drive of the image sensor of the camera head 1102 can be controlled in synchronization with the irradiation timing. This makes it possible to capture images corresponding to each RGB in a time-division manner. According to this method, a color image can be obtained without providing a color filter to the image sensor.

[0097] Furthermore, the driving of the light source device 1203 may be controlled so that the intensity of light output from the light source device 1203 is changed at predetermined time intervals. By controlling the driving of the image sensor of the camera head 1102 in synchronization with the timing of the change in the light intensity to acquire images in a time-division manner and combining the images, it is possible to generate an image with a high dynamic range that is free from so-called blocked-up shadows and blown-out highlights.

[0098] Furthermore, the light source device 1203 may be configured to supply light in a predetermined wavelength band corresponding to special light observation. Special light observation can utilize, for example, the wavelength dependence of light absorption in body tissue. Specifically, by irradiating light with a narrower band than the light (i.e., white light) used in normal observation, a specific tissue, such as blood vessels on the surface of the mucosa, can be photographed with high contrast. Alternatively, special light observation may involve fluorescence observation, in which an image is obtained using fluorescence generated by irradiating excitation light. Fluorescence observation can involve irradiating excitation light onto a body tissue and observing the fluorescence from the body tissue, or locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the body tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 1203 can be configured to supply narrow band light and / or excitation light corresponding to such special light observation.

[0099] [Sixth embodiment] The light detection system and moving body of this embodiment will be described with reference to Figures 20, 21(a), 21(b), 21(c), and 22. In this embodiment, an example of an in-vehicle camera will be shown as the light detection system.

[0100] FIG. 20 is a schematic diagram of a photodetection system according to this embodiment, illustrating an example of a vehicle system and a photodetection system mounted on the vehicle system. The photodetection system 1301 includes a photoelectric conversion device 1302, an image preprocessing unit 1315, an integrated circuit 1303, and an optical system 1314. The optical system 1314 forms an optical image of a subject on the photoelectric conversion device 1302. The photoelectric conversion device 1302 converts the optical image of the subject formed by the optical system 1314 into an electrical signal. The photoelectric conversion device 1302 is any one of the photoelectric conversion devices according to the above-described embodiments. The image preprocessing unit 1315 performs predetermined signal processing on the signal output from the photoelectric conversion device 1302. The function of the image preprocessing unit 1315 may be incorporated into the photoelectric conversion device 1302. The light detection system 1301 is provided with at least two sets of an optical system 1314 , a photoelectric conversion device 1302 and an image pre-processing unit 1315 , and the output from each set of image pre-processing units 1315 is input to the integrated circuit 1303 .

[0101] The integrated circuit 1303 is an integrated circuit for use in an imaging system, and includes an image processing unit 1304 including a storage medium 1305, an optical distance measurement unit 1306, a parallax calculation unit 1307, an object recognition unit 1308, and an abnormality detection unit 1309. The image processing unit 1304 performs image processing such as development and defect correction on the output signal of the image pre-processing unit 1315. The storage medium 1305 temporarily stores the captured image and stores the defect positions of the captured pixels. The optical distance measurement unit 1306 focuses or measures the distance to the subject. The parallax calculation unit 1307 calculates distance measurement information from multiple image data acquired by multiple photoelectric conversion devices 1302. The object recognition unit 1308 recognizes subjects such as cars, roads, signs, and people. If the abnormality detection unit 1309 detects an abnormality in the photoelectric conversion device 1302, it notifies the main control unit 1313 of the abnormality.

[0102] The integrated circuit 1303 may be realized by dedicated hardware, a software module, or a combination thereof. It may also be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like, or a combination thereof.

[0103] The main control unit 1313 supervises and controls the operations of the light detection system 1301, the vehicle sensor 1310, the control unit 1320, etc. Instead of having the main control unit 1313, the light detection system 1301, the vehicle sensor 1310, and the control unit 1320 may each have a communication interface and send and receive control signals via a communication network according to, for example, the CAN standard.

[0104] The integrated circuit 1303 has a function of receiving a control signal from the main control unit 1313 or transmitting a control signal or a set value to the photoelectric conversion device 1302 by its own control unit.

[0105] The optical detection system 1301 is connected to a vehicle sensor 1310 and can detect the vehicle's driving conditions, such as vehicle speed, yaw rate, and steering angle, as well as the conditions of the environment outside the vehicle and other vehicles and obstacles. The vehicle sensor 1310 also serves as a distance information acquisition unit that acquires distance information to an object. The optical detection system 1301 is also connected to a driving assistance control unit 1311 that performs various driving assistance functions, such as automatic steering, automatic cruising, and collision prevention functions. In particular, the collision determination function determines whether or not a collision with another vehicle or obstacle has occurred based on the detection results of the optical detection system 1301 and the vehicle sensor 1310. This allows for avoidance control when a collision is predicted, and activation of safety devices in the event of a collision.

[0106] The light detection system 1301 is also connected to an alarm device 1312 that issues an alarm to the driver based on the determination result of the collision determination unit. For example, if the collision determination unit determines that there is a high possibility of a collision, the main control unit 1313 performs vehicle control such as applying the brakes, releasing the accelerator, and suppressing engine output, thereby avoiding the collision or mitigating damage. The alarm device 1312 issues an alarm to the user by issuing an alarm such as a sound, displaying alarm information on the display screen of a car navigation system or an instrument panel, applying vibration to the seat belt or steering wheel, etc.

[0107] The light detection system 1301 in this embodiment can capture images of the surroundings of the vehicle, for example, the front or rear. Figures 21(a), 21(b), and 21(c) are schematic diagrams of a moving object in this embodiment, showing a configuration in which the light detection system 1301 captures an image of the area in front of the vehicle.

[0108] The two photoelectric conversion devices 1302 are disposed in front of the vehicle 1300. Specifically, it is preferable that the center line of the vehicle 1300 relative to its forward / backward direction or its outer shape (for example, its width) be regarded as an axis of symmetry, and that the two photoelectric conversion devices 1302 be disposed symmetrically about the axis of symmetry. This makes it possible to effectively obtain distance information between the vehicle 1300 and an object to be photographed and to determine the possibility of a collision. It is also preferable that the photoelectric conversion devices 1302 be disposed in a position that does not obstruct the driver's field of vision when the driver visually checks the situation outside the vehicle 1300 from the driver's seat. It is preferable that the warning device 1312 be disposed in a position that is easily within the driver's field of vision.

[0109] Next, a fault detection operation of the photoelectric conversion device 1302 in the photodetection system 1301 will be described with reference to Fig. 22. Fig. 22 is a flowchart showing the operation of the photodetection system in this embodiment. The fault detection operation of the photoelectric conversion device 1302 can be performed in accordance with steps S1410 to S1480 shown in Fig. 22.

[0110] In step S1410, startup settings are made for the photoelectric conversion device 1302. That is, setting information for the operation of the photoelectric conversion device 1302 is transmitted from outside the photodetection system 1301 (for example, from the main control unit 1313) or from inside the photodetection system 1301, and the photoelectric conversion device 1302 starts imaging operations and fault detection operations.

[0111] Next, in step S1420, the photoelectric conversion device 1302 acquires pixel signals from the valid pixels. Furthermore, in step S1430, the photoelectric conversion device 1302 acquires output values ​​from failure detection pixels provided for failure detection. These failure detection pixels include photoelectric conversion elements, just like the valid pixels. A predetermined voltage is written to these photoelectric conversion elements. The failure detection pixels output signals corresponding to the voltage written to these photoelectric conversion elements. Note that steps S1420 and S1430 may be executed in reverse order.

[0112] Next, in step S1440, the photodetection system 1301 determines whether the expected output value of the fault detection pixel matches the actual output value from the fault detection pixel. If the result of the determination in step S1440 indicates that the expected output value and the actual output value match, the photodetection system 1301 proceeds to processing in step S1450, determines that the imaging operation is being performed normally, and proceeds to processing in step S1460. In step S1460, the photodetection system 1301 transmits the pixel signals of the scanning row to the storage medium 1305 for temporary storage. Thereafter, the photodetection system 1301 returns to processing in step S1420 and continues the fault detection operation. On the other hand, if the result of the determination in step S1440 indicates that the expected output value and the actual output value do not match, the photodetection system 1301 proceeds to processing in step S1470. In step S1470, the light detection system 1301 determines that there is an abnormality in the imaging operation, and issues an alarm to the main control unit 1313 or the alarm device 1312. The alarm device 1312 displays on the display unit that an abnormality has been detected. Thereafter, in step S1480, the light detection system 1301 stops the photoelectric conversion device 1302, and ends the operation of the light detection system 1301.

[0113] In this embodiment, the flowchart is looped for each line, but the flowchart may be looped for each set of lines, or the fault detection operation may be performed for each frame. The issuance of the alarm in step S1470 may be notified to the outside of the vehicle via a wireless network.

[0114] Furthermore, although the present embodiment has been described as a control for preventing collisions with other vehicles, the present invention is also applicable to control for automatic driving by following other vehicles, control for automatic driving so as not to deviate from a lane, and the like. Furthermore, the light detection system 1301 is not limited to vehicles such as the subject vehicle, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the present invention is not limited to moving bodies, but can be applied to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0115] The photoelectric conversion device of the present invention may further be configured to be capable of acquiring various types of information such as distance information.

[0116] [Seventh embodiment] FIG. 23(a) is a diagram showing a specific example of an electronic device according to this embodiment, illustrating glasses 1600 (smart glasses). The glasses 1600 are provided with a photoelectric conversion device 1602 according to any of the above-described embodiments. That is, the glasses 1600 are an example of a light detection system to which the photoelectric conversion device 1602 according to any of the above-described embodiments can be applied. A display device including a light-emitting device such as an OLED or LED may be provided on the rear side of the lens 1601. There may be one or more photoelectric conversion devices 1602. Furthermore, multiple types of photoelectric conversion devices may be combined. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in FIG. 23(a).

[0117] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device described above. The control device 1603 also controls the operations of the photoelectric conversion device 1602 and the display device. The lens 1601 is provided with an optical system for focusing light onto the photoelectric conversion device 1602.

[0118] FIG. 23(b) shows glasses 1610 (smart glasses) according to one application example. The glasses 1610 include a control device 1612, which is equipped with a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. A lens 1611 includes the photoelectric conversion device in the control device 1612 and an optical system for projecting light emitted from the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source for supplying power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device 1612 may also include a gaze detection unit for detecting the gaze of the wearer. Infrared light may be used for gaze detection. The infrared light emitter emits infrared light toward the eyeball of a user gazing at a displayed image. An imaging unit having a light receiving element detects the emitted infrared light reflected from the eyeball, thereby obtaining an image of the eyeball. By providing a reduction means for reducing the amount of light from the infrared light emitting section to the display section in a plan view, degradation of image quality is reduced.

[0119] The control device 1612 detects the user's line of sight with respect to the displayed image from the captured image of the eyeball obtained by capturing infrared light. Any known method can be used for gaze detection using the captured image of the eyeball. As an example, a gaze detection method based on the Purkinje image formed by reflection of irradiated light on the cornea can be used.

[0120] More specifically, gaze detection processing is performed based on the pupil-corneal reflex method, which calculates a gaze vector representing the direction (rotation angle) of the eyeball based on the pupil image and Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0121] The display device of this embodiment may have a photoelectric conversion device having a light receiving element, and may control the image displayed on the display device based on information on the user's line of sight from the photoelectric conversion device.

[0122] Specifically, the display device determines a first field of view area where the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device or by an external control device. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0123] The display area may also include a first display area and a second display area different from the first display area. A high-priority area may be determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device or by an external control device. The resolution of the high-priority area may be controlled to be higher than the resolution of areas other than the high-priority area. In other words, the resolution of an area with a relatively low priority may be lowered.

[0124] Note that AI (Artificial Intelligence) may be used in determining the first field of view area and the area with high priority. The AI ​​may be a model configured to estimate the angle of gaze and the distance to an object in the line of sight from the image of the eyeball, using as training data an image of the eyeball and the direction in which the eyeball in the image was actually looking. The AI ​​program may be provided in either the display device or the photoelectric conversion device, or in an external device. If the external device has the AI ​​program, it may be transmitted to the display device from a server or the like via communication.

[0125] When display control is performed based on visual recognition detection, this embodiment can be preferably applied to smart glasses that further include a photoelectric conversion device that captures an image of the outside world. The smart glasses can display captured external information in real time.

[0126] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which part of the configuration of one embodiment is added to another embodiment, or an example in which part of the configuration of another embodiment is replaced with another embodiment, is also an embodiment of the present invention.

[0127] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0128] It should be noted that the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0129] 11 Sensor board 100 Photoelectric conversion device 102 Photoelectric conversion unit 324 pixel separation section

Claims

1. A substrate; a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; a pixel separating section disposed within the substrate and separating the photoelectric conversion section from other elements; and a sidewall of the pixel separating portion has a plurality of projections and recesses in a cross-sectional view; a distance between adjacent convex portions among the plurality of concave and convex portions is greater than half the wavelength of light to which the photoelectric conversion portion is sensitive; The substrate has irregularities arranged on the incident surface of the photoelectric conversion unit. A photoelectric conversion device characterized by:

2. A substrate, a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; a pixel separating section disposed within the substrate and separating the photoelectric conversion section from other elements; and a sidewall of the pixel separating portion has a plurality of projections and recesses in a cross-sectional view; the plurality of projections and recesses have a periodic projection and recess structure, a periodic distance of at least a part of the concave-convex structure is greater than half the wavelength of light to which the photoelectric conversion unit is sensitive; The substrate has irregularities arranged on the incident surface of the photoelectric conversion unit. A photoelectric conversion device characterized by:

3. A substrate, a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; a pixel separating section disposed within the substrate and separating the photoelectric conversion section from other elements; and a sidewall of the pixel separating portion has a plurality of projections and recesses in a cross-sectional view; a distance between adjacent convex portions among the plurality of concave and convex portions is greater than half the wavelength of light to which the photoelectric conversion portion is sensitive; The photoelectric conversion unit includes an avalanche photodiode. A photoelectric conversion device characterized by:

4. A substrate, a photoelectric conversion unit disposed within the substrate and configured to generate charges in response to incident light; a pixel separating section disposed within the substrate and separating the photoelectric conversion section from other elements; and a sidewall of the pixel separating portion has a plurality of projections and recesses in a cross-sectional view; the plurality of projections and recesses have a periodic projection and recess structure, a periodic distance of at least a part of the concave-convex structure is greater than half the wavelength of light to which the photoelectric conversion unit is sensitive; The photoelectric conversion unit includes an avalanche photodiode. A photoelectric conversion device characterized by:

5. The substrate has irregularities arranged on the incident surface of the photoelectric conversion unit.

5. The photoelectric conversion device according to claim 3 or 4.

6. The plurality of irregularities on the side wall are arranged two-dimensionally in a cross-sectional view taken from a direction perpendicular to the side wall.

6. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

7. At least a portion of the plurality of irregularities on the sidewall are arranged at a depth at which avalanche multiplication occurs in the avalanche photodiode.

6. The photoelectric conversion device according to claim 3, wherein the first and second electrodes are electrically connected to each other.

8. The pixel separating portion has a rectangular shape surrounding the photoelectric conversion portion in a plan view of the substrate.

8. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

9. At least a portion of the plurality of irregularities on the side wall are arranged at the center of one side of the rectangle.

9. The photoelectric conversion device according to claim 8.

10. The pixel separating portion is disposed so as to penetrate the substrate.

10. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

11. A material having a lower transmittance than the material of the substrate for light to which the photoelectric conversion unit is sensitive is embedded in at least a part of the pixel separation unit.

11. The photoelectric conversion device according to claim 1.

12. A metal is embedded in at least a part of the pixel separating portion.

12. The photoelectric conversion device according to claim 11.

13. Polysilicon is embedded in at least a part of the pixel separating portion.

12. The photoelectric conversion device according to claim 11.

14. The optical element further includes a light-shielding layer disposed on at least one of the side of the incident surface of the incident light and the side opposite to the incident surface.

14. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

15. The period of at least a portion of the plurality of projections and recesses on the side wall is greater than 325 nm.

15. The photoelectric conversion device according to claim 1.

16. The period of at least a portion of the plurality of projections and recesses on the side wall is smaller than 4 μm.

16. The photoelectric conversion device according to claim 1,

17. A semiconductor region disposed within the substrate and having a conductivity type different from that of the charge, the pixel separating portion is disposed inside the semiconductor region, the semiconductor region includes a plurality of regions along a normal direction of the surface of the substrate, The length of one of the plurality of regions along the normal direction is greater than the distance between adjacent convex portions of the plurality of concave and convex portions of the side wall.

17. The photoelectric conversion device according to claim 1.

18. The photoelectric conversion device according to any one of claims 1 to 17, a signal processing unit that processes a signal output from the photoelectric conversion device; An optical detection system comprising:

19. A mobile object, The photoelectric conversion device according to any one of claims 1 to 17, a distance information acquisition unit that acquires distance information to an object from a signal output from the photoelectric conversion device; a control unit that controls the moving object based on the distance information; A moving object comprising:

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