Photodetector

Abstract

To provide a light detection device which has compact configuration, and which exhibits improved degree of accuracy and precision when used for a flash system measurement device.SOLUTION: A light detection device 1 comprises a circuit board 20 including a plurality of signal processing unit SP processing a detection signal output from a corresponding pixel. Light reception regions of a plurality of avalanche photodiodes are two-dimensionally arranged for each pixel. In each signal processing part SP, a timing measuring unit 42 measures timing at which light enters the corresponding pixel, on the basis of a detection signal. An energy measuring unit 43 measures energy of incident light to the corresponding pixel on the basis of the detection signal. A storage unit 44 stores a result of measurement performed in the timing measuring unit 42 and the energy measuring unit 43. A light detection region α in which a plurality of pixels is provided, and a signal processing region β in which a plurality of signal processing unit is provided, overlap at least partially.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a light detection device. [Background technology]

[0002] There is known a technology for detecting an object and measuring the distance to the object by using a light detection device to detect light projected from a light source and reflected from the object (for example, Patent Document 1). This technology is called, for example, LiDAR (Light Detection and Ranging). Hereinafter, "detecting an object" and "measuring the distance to the object" will be collectively referred to as "detection operation." A device that performs detection operation using LiDAR will be referred to as a "measurement device." Patent Document 1 describes a scanning-type measurement device that uses a scanning unit to scan light emitted from a light source and detects reflected light from the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-72097 Summary of the Invention [Problem to be solved by the invention]

[0004] Scanning-type measurement devices scan light from a light source and sequentially detect reflected light from a detection target area, and therefore have a mechanically movable part in the scanning unit. Therefore, scanning-type measurement devices have a problem in that the scanning unit is prone to malfunction. Scanning-type measurement devices can also have a problem in that accurate detection operations cannot be achieved due to movement of the target area during light scanning. To solve this problem, a flash-type measurement device can be considered, which projects light from a light source simultaneously in two dimensions toward the detection target area and detects reflected light from that area. A flash-type measurement device can achieve detection operations over a wide area without light scanning. The absence of a scanning unit that scans light from a light source eliminates scanning unit malfunctions and eliminates problems caused by movement of the target area during light scanning. Compared to scanning-type measurement devices, flash-type measurement devices are expected to be more robust and to shorten the time required for detection operations in the detection target area.

[0005] However, performing detection without a scanning unit poses various challenges. For example, when simultaneously projecting light onto a two-dimensional area without a scanning unit, detecting the light reflected from the projection requires a two-dimensional array of multiple light-detecting pixels in the photodetector. In detection using a flash-based measurement device, light is simultaneously projected onto the detection target area from a light source, resulting in a weaker intensity of reflected light from each point in the area than in detection using a scanning-based measurement device. Therefore, improved sensitivity at each pixel is also required. In detection using a flash-based measurement device, light projected onto the detection target area simultaneously is detected, making it easy to detect ambient light in addition to reflected light from the target. This makes it difficult to distinguish between ambient light and reflected light from the target. To address these challenges with flash-based measurement devices, improvements in the detection accuracy and precision of photodetector devices are required.

[0006] An object of one aspect of the present invention is to provide a light detection device that has a compact configuration and improved detection accuracy and precision when used in a flash-type measurement device. [Means for solving the problem]

[0007] A photodetector device according to one aspect of the present invention includes a photodetector substrate and a circuit board. The photodetector substrate includes a semiconductor substrate having a first main surface and a second main surface facing each other. The photodetector substrate has a photodetection region in which a plurality of pixels are provided, arranged two-dimensionally, as viewed from a direction perpendicular to the first main surface. The circuit board is connected to the photodetector substrate in a direction perpendicular to the first main surface. The circuit board has a signal processing region in which a plurality of signal processing units are provided for processing detection signals output from corresponding pixels. The photodetector substrate includes, for each pixel, a plurality of avalanche photodiodes, a plurality of quenching resistors, and a pad electrode. Each of the plurality of avalanche photodiodes has a light-receiving region provided on the semiconductor substrate and operates in Geiger mode. The plurality of quenching resistors are electrically connected in series to the corresponding avalanche photodiode. The plurality of quenching resistors are electrically connected in parallel to each other to the pad electrode. The light-receiving regions of the plurality of avalanche photodiodes are arranged two-dimensionally for each pixel, as viewed from a direction perpendicular to the first main surface. Each signal processing unit includes a signal acquisition unit, a timing measurement unit, an energy measurement unit, and a memory unit. The signal acquisition unit acquires a detection signal through a corresponding pad electrode. The timing measurement unit measures the timing at which light is incident on a corresponding pixel based on the detection signal. The energy measurement unit measures the energy of light incident on the corresponding pixel based on the detection signal. The memory unit stores the measurement results of the timing measurement unit and the energy measurement unit. When viewed from a direction perpendicular to the first main surface, the light detection region and the signal processing region at least partially overlap.

[0008] In one aspect, the photodetector device includes a photodetector substrate having a plurality of pixels arranged two-dimensionally. Each pixel includes a plurality of avalanche photodiodes operating in Geiger mode. Each signal processor acquires a detection signal through a pad electrode of each pixel. Therefore, in this photodetector device, the sensitivity of each of the two-dimensionally arranged pixels is improved. Therefore, even when detecting reflected light of light simultaneously projected from a light source into a two-dimensional area, the accuracy and precision of detection are improved. In this photodetector device, each signal processor measures the light energy in the energy measurement unit based on the detection signal output from each pixel including a plurality of avalanche photodiodes. Therefore, this photodetector device can distinguish between reflected light from an object and ambient light based on the difference in energy. Therefore, the influence of ambient light on the detection results can be reduced. The circuit board is connected to the photodetector substrate in a direction perpendicular to the first main surface, and the photodetection region and the signal processing region at least partially overlap. This allows the photodetector to be made more compact in the direction parallel to the first principal surface, while also reducing the electrical connection paths between each pixel and each signal processing unit. Each signal processing unit includes a memory unit. If this memory unit were provided outside the signal processing unit, wiring from at least the timing measurement unit and the energy measurement unit would be drawn out from each signal processing unit to the outside, requiring a large space between adjacent signal processing units. If a large space were required between adjacent signal processing units, it would be difficult to reduce the size of the photodetector. In this photodetector, since each signal processing unit includes a memory unit, the number of wirings drawn out from each signal processing unit to the outside of that signal processing unit is reduced. This allows the photodetector to be made even more compact.

[0009] In the above-described one aspect, the photodetector substrate may be surrounded by an edge of the circuit board when viewed in a direction perpendicular to the first main surface, which makes the photodetector device even more compact and further reduces the electrical connection paths between each pixel and each signal processing unit.

[0010] In one aspect, the photodetection region may have a first portion that overlaps with the signal processing region and a second portion that does not overlap with the signal processing region when viewed in a direction perpendicular to the first main surface. The area of ​​the first portion may be larger than the area of ​​the second portion. In this case, the photodetection device can be made more compact and the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0011] In one aspect, the signal processing region may have a third portion that does not overlap with the photodetection region when viewed in a direction perpendicular to the first main surface. The area of ​​the first portion may be larger than the sum of the areas of the second portion and the third portion. In this case, the photodetection device can be made even more compact, and the electrical connection paths between each pixel and each signal processing portion can be further shortened.

[0012] In one aspect, a unit area in which each pixel is provided in the photodetection region and a unit area in which a signal processing unit corresponding to the pixel is provided in the signal processing region may at least partially overlap when viewed in a direction perpendicular to the first main surface, thereby further reducing the size of the photodetector device and further shortening the electrical connection path between each pixel and each signal processing unit.

[0013] In one of the above aspects, the center of gravity (geometric center) of the pad electrode may be shifted from the center of gravity of the unit area in which the signal processing unit to which the pad electrode is connected is provided toward the signal acquisition unit when viewed from a direction perpendicular to the first main surface. In this case, the electrical connection path between each pixel and each signal processing unit is further shortened. When viewed from a direction perpendicular to the first main surface, wiring for applying a drive voltage to each signal processing unit can be provided at the center of the signal processing unit, making it easy to route the wiring.

[0014] In one aspect, the unit area in which each pixel is provided in the light detection region and the unit area in which a signal processing unit corresponding to that pixel is provided in the signal processing region may be shifted in a direction along the first main surface when viewed from a direction perpendicular to the first main surface, and may have portions that do not overlap with each other. In this case, the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0015] In one aspect, the detection signal may be a current signal. The signal acquisition unit of each signal acquisition unit may include a current-voltage conversion circuit and a signal transmission circuit. The current-voltage conversion circuit may convert the detection signal into a voltage. The signal transmission circuit may input a voltage signal output from the current-voltage conversion circuit to the energy measurement unit. The signal transmission circuit may include a Miller capacitor. The Miller capacitor may be connected in parallel with the current-voltage conversion circuit to the energy measurement unit. The energy measurement unit may measure the energy of light incident on the corresponding pixel based on the waveform of the signal input from the signal transmission circuit. In this case, by including a capacitor in the signal transmission circuit, the capacitor smoothes the waveform. A smoother waveform can improve the accuracy of energy measurement in the energy measurement unit. The waveform of the signal becomes smoother as the capacitance of the capacitor increases. In this photodetector, the signal transmission circuit includes a Miller capacitor. Therefore, the signal transmission circuit can achieve the same effect as when a capacitor with a larger capacitance is used, without increasing the size of the capacitor area. As a result, the accuracy of energy measurement is ensured, and the signal processing sections can be formed compactly in accordance with the two-dimensionally arranged pixels.

[0016] In one aspect, the energy measuring unit may measure the energy of light incident on a corresponding pixel by measuring the time during which the pulse height of a signal input from a corresponding signal acquiring unit is equal to or greater than a threshold. Such an energy measuring unit can be realized by simple digital processing and can be physically compact. This reduces the size of the area of ​​the energy measuring unit. As a result, the multiple signal processing units can be formed compactly to fit the multiple pixels arranged two-dimensionally.

[0017] In one aspect of the invention, the memory unit of each signal processing unit may include multiple memory areas. Each of the multiple memory areas stores measurement results from the timing measurement unit and the energy measurement unit for incident light that is incident on a corresponding pixel at different timings during a predetermined measurement period. Because this photodetector includes multiple memory areas, even if the timing measurement unit and the energy measurement unit output measurement results for ambient light that is incident on a pixel during the predetermined measurement period, the measurement results for reflected light from the target object are also stored. In this photodetector, each signal processing unit includes the multiple memory areas described above. Therefore, the influence of ambient light is reduced, and the number of lead-out wiring from each signal processing unit to the outside of the signal processing unit is reduced. [Effects of the Invention]

[0018] One aspect of the present invention provides a light detection device that has improved detection accuracy and precision in a compact configuration when used in a flash-type metrology device. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic perspective view showing a light detection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view of the light detection device. [Figure 3] FIG. 2 is a schematic plan view of a photodetector substrate. [Figure 4] FIG. 2 is a schematic diagram showing the positional relationship between a light detection region and a signal processing region. [Figure 5]FIG. 2 is a schematic enlarged view of a photodetector substrate. [Figure 6] FIG. 2 is a diagram showing a cross-sectional configuration of a photodetector. [Figure 7] FIG. 2 is a diagram illustrating a configuration of a circuit board. [Figure 8] FIG. 2 is a diagram illustrating a configuration of a signal processing unit. [Figure 9] FIG. 2 is a diagram illustrating a configuration of a front-end circuit. [Figure 10] FIG. 1 illustrates a Miller capacitor. [Figure 11] 10A and 10B are diagrams for explaining the processing operations of an energy comparator and a logic circuit. [Figure 12] 4 is a timing chart showing the operation of the signal processing unit. [Figure 13] FIG. 10 is a diagram showing a cross-sectional configuration of a photodetector according to a modified example of the present embodiment. [Figure 14] FIG. 10 is a diagram for explaining processing in a signal transmission circuit. [Figure 15] FIG. 10 is a diagram showing the positional relationship between pixels and a signal processing unit in a modified example of the present embodiment. [Figure 16] 10 is a diagram showing the positional relationship between a signal acquisition unit and a pad electrode in a modified example of the present embodiment. FIG. [Figure 17] FIG. 10 is a schematic diagram showing the positional relationship between a light detection region and a signal processing region in a modified example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0021] First, the configuration of a photodetector according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic perspective view showing the photodetector according to this embodiment. Figure 2 is an exploded perspective view of the photodetector shown in Figure 1. The photodetector 1 is a semiconductor photodetector.

[0022] 1 and 2, the photodetector device 1 includes a photodetector substrate 10 and a circuit board 20. The photodetector substrate 10 and the circuit board 20 face each other. In this embodiment, a plane parallel to each main surface of the photodetector substrate 10 and the circuit board 20 is an XY-axis plane, and a direction perpendicular to each main surface is a Z-axis direction.

[0023] The photodetector substrate 10 has a semiconductor substrate 50 that has a rectangular shape in a plan view. In this embodiment, the photodetector substrate 10 is a photodetector substrate used in a so-called back-illuminated semiconductor photodetector. The semiconductor substrate 50 is made of Si and is a P-type semiconductor substrate. The semiconductor substrate 50 has principal surfaces 1Na and 1Nb that face each other. The P-type is an example of a first conductivity type. An example of a second conductivity type is N-type. The principal surface 1Na is a light incident surface on the semiconductor substrate 50. When the principal surface 1Na is the first principal surface, the principal surface 1Nb is the second principal surface.

[0024] The circuit board 20 has two opposing principal surfaces 20a and 20b. The circuit board 20 has a rectangular shape in plan view. The light-detecting substrate 10 is connected to the circuit board 20 in the Z-axis direction. The principal surface 20a and the principal surface 1Nb face each other.

[0025] The side surface 20c of the circuit board 20 is located outside the side surface 1Nc of the semiconductor substrate 50 in the XY plane direction. In a plan view, the area of ​​the circuit board 20 is larger than the area of ​​the semiconductor substrate 50. In other words, the side surface 20c of the circuit board 20 is located outside the side surface 1Nc of the semiconductor substrate 50 in the XY plane direction. When viewed from the Z axis direction, the photodetector substrate 10 is surrounded by the edge 20d of the circuit board 20. The side surface 20c of the circuit board 20 and the side surface 1Nc of the semiconductor substrate 50 may be flush with each other.

[0026] The photodetector substrate 10 is mounted on a circuit board 20. The photodetector substrate 10 and the circuit board 20 are connected by bump electrodes BE. The photodetector substrate 10 is disposed at the center of the circuit board 20 when viewed from the Z-axis direction. As shown in FIG. 2, the photodetector substrate 10 has a plurality of pixels U. When viewed from the Z-axis direction, the plurality of pixels U are two-dimensionally arranged in a matrix in a photodetection region α of the photodetector substrate 10. When viewed from the Z-axis direction, the photodetection region α has a rectangular shape. The photodetector device 1 outputs detection signals corresponding to light detected by the plurality of pixels U. The pitch WU between the pixels U is 10 μm to 500 μm in the row and column directions. In this embodiment, the pitch WU is 100 μm. The row direction is the X-axis direction, and the column direction is the Y-axis direction.

[0027] The circuit board 20 constitutes an ASIC (Application Specific Integrated Circuit). As shown in FIG. 2, the circuit board 20 has a plurality of signal processing units SP. Each signal processing unit SP processes a detection signal output from a corresponding pixel U. The plurality of signal processing units SP are two-dimensionally arranged in a signal processing region β of the circuit board 20 when viewed from the Z-axis direction. Each signal processing unit SP is electrically connected to the photodetector substrate 10 through a bump electrode BE. In this embodiment, the signal processing units SP are arranged at the same pitch WU as the corresponding pixels U.

[0028] Next, the configuration of the photodetector substrate 10 will be described with reference to FIGS. 3 to 6. FIG. 3 is a view of the main surface 1Nb of the photodetector substrate 10 as viewed from the Z-axis direction. FIG. 4 is a schematic diagram showing the positional relationship between the photodetection region α and the signal processing region β. FIG. 5 shows the region where the pad electrodes PE1 and the bump electrodes BE are provided corresponding to each pixel U. FIG. 6 shows the cross-sectional configuration of the photodetector device.

[0029] In Fig. 3, the position of the signal processing unit SP when the photodetector 1 is viewed from the Z-axis direction is indicated by a dashed line. That is, Fig. 3 shows the positional relationship between each pixel U, the bump electrode BE, and the signal processing unit SP of the circuit board 20. As shown in Fig. 3, when viewed from the Z-axis direction, the photodetection region α and the signal processing region β at least partially overlap. In this embodiment, when viewed from the Z-axis direction, the photodetection region α and the signal processing region β are shifted from each other in the X-axis direction.

[0030] FIG. 4 shows the positional relationship between the photodetection region α and the signal processing region β as viewed from the Z-axis direction. The photodetection region α includes a portion R1 that overlaps with the signal processing region β as viewed from the Z-axis direction and a portion R2 that does not overlap with the signal processing region β. The signal processing region β includes a portion R1 that overlaps with the photodetection region α as viewed from the Z-axis direction and a portion R3 that does not overlap with the photodetection region α as viewed from the Z-axis direction. In other words, portion R1 is the portion where the photodetection region α and the signal processing region β overlap as viewed from the Z-axis direction. Portion R2 is the portion within the photodetection region α where the photodetection region α and the signal processing region β do not overlap as viewed from the Z-axis direction. Portion R3 is the portion within the signal processing region β where the photodetection region α and the signal processing region β do not overlap as viewed from the Z-axis direction. In FIG. 4, portion R1 is hatched. As viewed from the Z-axis direction, the area of ​​portion R1 is larger than the area of ​​portion R2. When viewed from the Z-axis direction, the area of ​​the portion R1 is greater than the sum of the area of ​​the portion R2 and the area of ​​the portion R3. For example, the portion R1 is the first portion, the portion R2 is the second portion, and the portion R3 is the third portion.

[0031] The light detection region α includes a plurality of unit regions α1, each of which includes a plurality of pixels U. One pixel U is provided in each unit region α1. The signal processing region β includes a plurality of unit regions β1, each of which includes a plurality of signal processing units SP. One signal processing unit SP is provided in each unit region β1. When viewed from the Z-axis direction, the unit region α1 in which each pixel U is provided and the unit region β1 in which the signal processing unit SP corresponding to that pixel U is provided at least partially overlap. When viewed from the Z-axis direction, the unit region α1 in which each pixel U is provided and the unit region β1 in which the signal processing unit SP corresponding to that pixel U are provided are shifted in a direction along the main surface 1Na and have portions that do not overlap with each other. In this embodiment, the unit region β1 in which the corresponding signal processing unit SP is provided is shifted in the X-axis direction with respect to the unit region α1 in which each pixel U is provided.

[0032] 3 and 5, the photodetector substrate 10 has a plurality of avalanche photodiodes 11 operating in Geiger mode, a plurality of quenching resistors 21, and pad electrodes PE1 and PE2. Hereinafter, the "avalanche photodiodes" will be referred to as "APDs."

[0033] The photodetector substrate 10 is provided with a plurality of APDs 11 operating in Geiger mode, a plurality of quenching resistors 21, and at least one pad electrode PE1 for each pixel U. In this embodiment, one pad electrode PE1 is provided for each pixel U. Each signal processing unit SP is connected to only one pad electrode PE1. Each of the plurality of signal processing units SP is connected to only one different pixel U through the corresponding pad electrode PE1. In other words, the plurality of signal processing units SP and the plurality of pixels U are connected in a one-to-one correspondence.

[0034] The multiple APDs 11 are two-dimensionally arrayed on the semiconductor substrate 50. Each APD 11 has a light-receiving region S that receives light incident from the main surface 1Na side. The multiple light-receiving regions S are provided on the main surface 1Nb side of the semiconductor substrate 50. As shown in FIG. 5, in the photodetector substrate 10, each pixel U includes multiple light-receiving regions S. The multiple light-receiving regions S are two-dimensionally arrayed for each pixel U when viewed from the Z-axis direction. The light-receiving region S is a charge-generating region that generates charge in response to incident light. In other words, the light-receiving region S is a photosensitive region. In this embodiment, as shown in FIG. 5, each light-receiving region S has a rectangular shape when viewed from the Z-axis direction.

[0035] As shown in FIG. 6, the photodetector substrate 10 has a plurality of quenching resistors 21 and electrodes 22 for each pixel U. Each quenching resistor 21 is disposed on the principal surface 1Nb side of the semiconductor substrate 50. When viewed from the Z-axis direction, the quenching resistor 21 extends along the outer edge of the light-receiving region S. Each quenching resistor 21 is electrically connected in series with the light-receiving region S of the corresponding APD 11. The quenching resistor 21 forms a passive quenching circuit.

[0036] As shown in FIG. 5 , the electrodes 22 are arranged in a lattice pattern on the main surface 1Nb side so as to pass between the multiple light-receiving regions S included in one pixel U when viewed from the Z-axis direction. The light-receiving regions S are surrounded by the electrodes 22 when viewed from the Z-axis direction. The electrodes 22 are electrically connected to all of the light-receiving regions S included in one pixel U through the multiple quenching resistors 21. The electrodes 22 are electrically connected to the light-receiving regions S corresponding to each quenching resistor 21 through the multiple quenching resistors 21. The electrodes 22 are connected to the pad electrodes PE1 corresponding to the pixel U. In this embodiment, the electrodes 22 are connected to the pad electrode PE1 located at the center of the corresponding pixel U. With the above configuration, all of the quenching resistors 21 included in one pixel U are electrically connected in parallel to one pad electrode PE1 by the electrodes 22. That is, each pad electrode PE1 is electrically connected to the multiple APDs 11 included in the corresponding pixel U through the quenching resistors 21 and the electrodes 22.

[0037] As shown in FIG. 5 , the pad electrodes PE1 are located in a photodetection region α in which the pixels U are two-dimensionally arranged, as viewed from the Z-axis direction. Each pad electrode PE1 is arranged on the main surface 1Nb side so as to overlap with at least one APD 11 of the APDs 11 included in the corresponding pixel U, as viewed from the Z-axis direction. In this embodiment, each pad electrode PE1 has a rectangular shape and is arranged so as to overlap with four APDs 11 located at the center of the pixel U, out of the 16 APDs 11 included in one pixel U. A bump electrode BE is arranged at the center of each pad electrode PE1, as viewed from the Z-axis direction. In this embodiment, each pad electrode PE1 is in contact with an electrode 22 surrounding four light-receiving regions S located at the center of each pixel U, as viewed from the Z-axis direction.

[0038] As a modification of the present embodiment, the pad electrode PE1 may be in contact with all of the APDs 11 included in the pixel U. In this case, each pad electrode PE1 may be disposed on the main surface 1Nb side so as to overlap with all of the APDs 11 included in the pixel U, for example, when viewed from the Z-axis direction.

[0039] 3, the pad electrode PE2 is arranged on the principal surface 1Nb side, spaced apart from the photodetection region α in which the plurality of pixels U are arranged. The pad electrode PE2 is a common electrode for applying a voltage to each APD 11 from the principal surface 1Na side. In this embodiment, the pad electrode PE2 has a rectangular shape and is arranged on each of the four sides of the principal surface 1Nb. Bump electrodes BE are also arranged on the pad electrode PE2.

[0040] As shown in FIG. 6, each APD 11 has a P-type first semiconductor region PA, a P-type second semiconductor region PB, and an N-type third semiconductor region NA. The first semiconductor region PA is located on the main surface 1Nb side of the semiconductor substrate 50. The second semiconductor region PB is located on the main surface 1Na side of the semiconductor substrate 50. The third semiconductor region NA is formed within the first semiconductor region PA. The impurity concentration of the second semiconductor region PB is higher than the impurity concentration of the first semiconductor region PA. The light-receiving region S is formed by the first semiconductor region PA and the third semiconductor region NA. Each APD 11 is located from the main surface 1Na side by the second semiconductor region PB, which is P + layer, the first semiconductor region PA is P - layer, the third semiconductor region N A + It is structured in a layered order.

[0041] A trench 13 is formed in the semiconductor substrate 50 so as to surround the third semiconductor region NA. In this embodiment, the photodetection region α is surrounded by the trench 13 when viewed from the Z-axis direction. The photodetection region α is defined by the inner wall of the trench 13 that surrounds the photodetection region α. ​​When viewed from the Z-axis direction, the outer edge of the photodetection region α coincides with the inner wall of the trench 13 located at the outermost position of the photodetector 1, closer to the pixel U. When viewed from the Z-axis direction, the unit region α1 is surrounded by the trench 13. The unit region α1 is defined by the inner wall of the trench 13 that surrounds the unit region α1. When viewed from the Z-axis direction, the outer edge of the unit region α1 coincides with the inner wall of the trench 13 that surrounds the pixel U within the unit region α1, closer to the pixel U.

[0042] The trench 13 penetrates the first semiconductor region PA in the Z-axis direction and reaches the second semiconductor region PB. A core material 13a is disposed in the trench 13. The core material 13a is made of a high-melting-point metal. The core material 13a is made of, for example, tungsten. The surface of the trench 13 is formed of a P-type semiconductor layer 15 having a higher impurity concentration than the first semiconductor region PA. That is, the core material 13a is covered with the semiconductor layer 15 within the semiconductor substrate 50. As a modification of this embodiment, the trench 13 may extend in the Z-axis direction in the first semiconductor region PA and not reach the second semiconductor region PB.

[0043] An insulating layer L1 is disposed on the first semiconductor region PA, the third semiconductor region NA, and the trench 13. The quenching resistor 21 is covered with the insulating layer L1. The electrode 22 is disposed on the insulating layer L1 and covered with an insulating layer L2. The pad electrode PE1 is disposed on the insulating layer L2. The insulating layer L2 is covered by the pad electrode PE1 and a passivation layer L3. The passivation layer L3 also covers a portion of the pad electrode PE1.

[0044] The above-mentioned quenching resistor 21 is connected to the third semiconductor region NA through an electrode (not shown). The quenching resistor 21 is connected to a corresponding electrode 22 through a connection portion C1. The electrode 22 is connected to a corresponding pad electrode PE1 through a connection portion C2. The pad electrode PE1 is connected to a bump electrode BE at a portion exposed from the passivation layer L3.

[0045] The electrode 22, pad electrodes PE1, PE2, connection portion C1, and connection portion C2 are made of metal. The electrode 22, pad electrodes PE1, PE2, connection portion C1, and connection portion C2 are made of, for example, aluminum (Al). When the semiconductor substrate 50 is made of Si, copper (Cu) is used as the electrode material in addition to aluminum. The electrode 22, pad electrode PE1, connection portion C1, and connection portion C2 may be integrally formed. The electrode 22, pad electrode PE1, connection portion C1, and connection portion C2 are formed by, for example, sputtering.

[0046] When Si is used as the material for the semiconductor substrate 50, a Group 13 element (e.g., B) is used as the P-type impurity, and a Group 15 element (e.g., P or As) is used as the N-type impurity. An element in which the N-type and P-type semiconductor conductor types are interchanged also functions as a photodetector, similar to the photodetector substrate 10. These impurities can be added by, for example, diffusion or ion implantation.

[0047] The insulating layers L1, L2 and the passivation layer L3 are made of, for example, SiO2, SiN, or resin. The insulating layers L1, L2 and the passivation layer L3 are formed by thermal oxidation, sputtering, CVD, or resin coating.

[0048] The circuit board 20 is electrically connected to the pad electrodes PE1 via bump electrodes BE. Specifically, each signal processing unit SP has an electrode arranged corresponding to the pad electrode PE1, and the electrode is electrically connected to the corresponding pad electrode PE1 through the bump electrode BE. Detection signals output from the multiple APDs 11 included in the pixel U are guided to the corresponding signal processing unit SP through the quenching resistor 21, the electrode 22, the pad electrode PE1, and the bump electrode BE.

[0049] The bump electrode BE is formed on the pad electrode PE1 via an under bump metal (UBM) (not shown). The UBM is made of a material that has excellent electrical and physical connection with the bump electrode BE. The UBM is formed by, for example, an electroless plating method. The bump electrode BE is formed by, for example, a solder ball mounting method, a printing method, or electrolytic plating. The bump electrode BE is made of, for example, copper, solder, or indium.

[0050] Next, the configuration of the circuit board according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram showing the configuration of a circuit board 20. As shown in Fig. 7, the circuit board 20 has, in addition to a plurality of signal processing units SP, an interface circuit 31, a memory 32, a PLL (Phase Locked Loop) 33, a row random access decoder 34, a clock driver 35, a column random access decoder 37, and an I / O port 38. The PLL 33 and the clock driver 35 are arranged in an area that does not overlap with the photodetection area α when viewed from the Z-axis direction.

[0051] The interface circuit 31 is compatible with, for example, an SPI (Serial Peripheral Interface) bus. The interface circuit 31 receives digital signals such as SCLK (Serial Clock), CS (Chip Select), MOSI (Master Output / Slave Input), and MISO (Master Input / Slave Output) input from the outside, and stores register setting information included in the signals in the memory 32.

[0052] The PLL 33 generates a clock signal based on an externally input master clock (MCLK) and data stored in the memory 32, and transmits the generated clock signal to the clock driver 35. The PLL 33 includes a programmable frequency divider and sets the frequency division number by referring to the data stored in the memory 32. That is, the frequency division number of the PLL 33 can be set to any value according to the external input to the interface circuit 31. The PLL 33 outputs a control voltage that controls each signal processing unit SP together with the clock signal.

[0053] The clock driver 35 supplies a clock signal to each signal processing unit SP. Each of the multiple signal processing units SP is electrically connected to multiple APDs 11 included in the corresponding pixel U via a bump electrode BE. A detection signal output from the corresponding pixel U is input to each signal processing unit SP. The detection signal from the pixel U is a pulse signal having an analog waveform. Each signal processing unit SP calculates pixel data such as the incidence timing and energy of light incident on the corresponding pixel U based on the input detection signal. The pixel data calculated by each signal processing unit SP is output to an I / O port 38 at a timing according to signals from the row random access decoder 34 and the column random access decoder 37.

[0054] Each signal processing unit SP includes a signal acquisition unit 41, a timing measurement unit 42, an energy measurement unit 43, and a storage unit 44. The signal acquisition unit 41 acquires a detection signal output from a pixel U through a corresponding pad electrode PE1. The signal acquisition unit 41 includes a front-end circuit. The timing measurement unit 42 measures the timing at which light is incident on the corresponding pixel U based on the detection signal. The energy measurement unit 43 measures the energy of light incident on the corresponding pixel U based on the detection signal. In this embodiment, the energy measurement unit 43 converts the energy of light incident on the corresponding pixel U into time and measures it. For example, the energy measurement unit 43 uses a TOT (Time-Over Threshold) circuit to measure the time during which the peak height of the signal input from the corresponding signal acquisition unit 41 is equal to or greater than a threshold value as the energy. The storage unit 44 stores the measurement results of the timing measurement unit 42 and the energy measurement unit 43.

[0055] Next, an example of the configuration of each signal processing unit SP will be described in detail with reference to Figures 8 to 10. Figure 8 shows the configuration of the signal processing unit SP in this embodiment.

[0056] Each signal processing unit SP includes a front-end circuit 51, a timing comparator 52, an energy comparator 53, a logic circuit 54, a timing counter 55, an energy counter 56, a delay line 57, a selector 58, an encoder 59, and memories 60 and 61. The front-end circuit 51 constitutes the signal acquisition unit 41. The timing comparator 52, the logic circuit 54, the timing counter 55, and the delay line 57 constitute the timing measurement unit 42. The energy comparator 53, the logic circuit 54, and the energy counter 56 constitute the energy measurement unit 43. The memories 60 and 61 are each storage areas and constitute the storage unit 44.

[0057] 8, when viewed from the Z-axis direction, the center of gravity of the pad electrode PE1 is located closer to the front-end circuit 51 than the center of gravity of the unit area β1 in which the signal processing unit SP to which the pad electrode PE1 is connected is provided. In other words, when viewed from the Z-axis direction, the center of gravity of the pad electrode PE1 is shifted toward the signal acquiring unit 41 from the center of gravity of the unit area β1 in which the signal processing unit SP to which the pad electrode PE1 is connected is provided. In this embodiment, the pad electrode PE1 overlaps with the timing comparator 52 and the energy comparator 53.

[0058] The front-end circuit 51 is connected to the plurality of APDs 11 included in the corresponding pixel U through bump electrodes BE and pad electrodes PE1. A detection signal is input to the front-end circuit 51 from the corresponding pixel U. The detection signal output from the corresponding pixel is a current signal output from the APD 11 included in the corresponding pixel U in response to incident light. The front-end circuit 51 performs predetermined processing on the detection signal output from the corresponding pixel U. The front-end circuit 51 inputs the processed detection signal to a timing comparator 52 and an energy comparator 53. The detection signal input to the timing comparator 52 and the energy comparator 53 has an analog waveform. As shown in FIG. 9, the front-end circuit 51 includes a current-voltage conversion circuit 70 and a signal transmission circuit 75. FIG. 9 shows the configuration of the front-end circuit 51.

[0059] The current-voltage conversion circuit 70 converts the detection signal input from the corresponding pixel U into a voltage signal. The current-voltage conversion circuit 70 includes current-voltage conversion resistors 71 and 72 and a bias circuit 73. The voltage signal output from the current-voltage conversion resistor 71 is input to the timing comparator 52. The voltage signal output from the current-voltage conversion resistor 72 is input to the energy comparator 53. The signal transmission circuit 75 is disposed between the current-voltage conversion resistor 72 and the energy comparator 53. The signal transmission circuit 75 inputs the voltage signal output from the current-voltage conversion resistor 72 of the current-voltage conversion circuit 70 to the energy comparator 53 of the energy measurement unit 43. The current-voltage conversion resistors 71 and 72 are each connected to a bias circuit 73. As shown in FIG. 9 , an external bias voltage is applied to the front-end circuit 51. The bias voltage is applied to the bias circuit 73.

[0060] The signal transmission circuit 75 includes an inverter 76 and a capacitor 78 functioning as a Miller capacitor 77, and functions as a variable capacitance circuit. FIG. 10 shows a partial configuration of the signal transmission circuit 75. The capacitor 78 is connected in parallel to the inverter 76. A threshold voltage is set for the inverter 76. When the input voltage is equal to or greater than the threshold voltage, the inverter 76 generates a negative gain corresponding to the input voltage. When the input voltage is less than the threshold voltage, the inverter 76 generates a positive gain corresponding to the input voltage. As a result, due to the Miller effect, the signal transmission circuit 75 behaves as if a capacitor having a capacitance larger than the individual capacitance of the capacitor 78 were connected in parallel with the current-to-voltage conversion resistor 72 to the energy comparator 53. In other words, the capacitor 78 in the signal transmission circuit 75 functions as a Miller capacitor 77 having an apparent capacitance due to the Miller effect. This apparent capacitance, i.e., the Miller capacitance, increases as the input voltage to the signal transmission circuit 75 increases.

[0061] The capacitor 78 is connected to the energy comparator 53 in parallel with the current-voltage conversion resistor 72. Therefore, the signal transfer circuit 75 includes a Miller capacitor 77 connected to the energy measurement unit 43 in parallel with the current-voltage conversion circuit 70. The larger the capacitance of the capacitor connected in parallel with the current-voltage conversion resistor 72, the smoother the waveform of the detection signal input to the energy comparator 53. Therefore, due to the Miller effect according to the input voltage to the signal transfer circuit 75, the detection signal input to the energy comparator 53 has a smoother waveform than when only the capacitor 78 is connected in parallel with the current-voltage conversion resistor 72 to the energy comparator 53. The energy measurement unit 43 measures the energy of the incident light at the corresponding pixel U based on the waveform of the detection signal input to the energy comparator 53.

[0062] The timing comparator 52 and the energy comparator 53 each select a signal to be output depending on the wave height of the detection signal output from the front-end circuit 51. The detection signals output from the timing comparator 52 and the energy comparator 53 are input to the logic circuit 54. The signals output from the timing comparator 52 and the energy comparator 53 have digital waveforms. The timing comparator 52 and the energy comparator 53 each output a High signal or a Low signal only when the intensity of the detection signal output from the front-end circuit 51 exceeds a predetermined threshold. In this embodiment, the timing comparator 52 and the energy comparator 53 output a High signal when the intensity of the input signal exceeds the threshold, and output a Low signal when the intensity of the input signal does not exceed the threshold. In other words, the timing comparator 52 and the energy comparator 53 output a detection signal having a digital waveform corresponding to the waveform of the detection signal from the corresponding pixel U.

[0063] In addition to the detection signals from the timing comparator 52 and the energy comparator 53, the logic circuit 54 receives a clock signal and a control signal supplied from the clock driver 35. The control signal is supplied from outside the ASIC constituted by the circuit board 20. The control signal includes a reset signal and a stop signal. The clock signal, reset signal, and stop signal are H / L signals. The logic circuit 54 controls the supply of a clock signal to the timing counter 55 in response to the control signal and the detection signal from the timing comparator 52. The logic circuit 54 controls the supply of a clock signal to the energy counter 56 in response to the control signal and the detection signal from the energy comparator 53.

[0064] The logic circuit 54 uses a reset signal to instruct the timing counter 55 and the energy counter 56 to reset their counts, and uses a stop signal to instruct the timing counter 55 and the energy counter 56 to end the measurement period.

[0065] The logic circuit 54 synchronizes the control signal with the clock signal. The logic circuit 54 supplies the control signal, the detection signal converted into a digital waveform, and the clock signal to the timing counter 55, the energy counter 56, the delay line 57, and the selector 58. The logic circuit 54 generates a signal that causes the selector 58 to select a memory for storing the count results of the energy counter 56 and the encoder 59, and supplies the signal to the selector 58.

[0066] Based on the detection signal input from the logic circuit 54, the timing counter 55 counts the number of clock signals corresponding to the time from the start of the measurement period to the time when light is incident on the corresponding pixel U. Based on the detection signal input from the logic circuit 54, the energy counter 56 counts the number of clock signals corresponding to the energy of light incident on the corresponding pixel U. The timing counter 55 and the energy counter 56 store the count results in memory 60 or memory 61.

[0067] The delay line 57 includes a plurality of delay elements. The delay line 57 generates a time interval shorter than the period of the clock signal by the operation of the plurality of delay elements. The delay line 57 is controlled by a control voltage supplied from the PLL 33. The encoder 59 counts the number of stages of the delay line 57 that have operated in response to the signal from the delay line 57 and converts the count into a binary signal. For example, the encoder 59 counts the number of delay elements that have operated from the rising edge of the detection signal converted into a digital waveform by the logic circuit 54 to the rising edge of the next clock signal. The encoder 59 stores the count result in memory 60 or memory 61.

[0068] The selector 58 selects a memory for storing the count results of the timing counter 55, the energy counter 56, and the encoder 59. In this embodiment, the selector 58 selects the memory for storing the count results from the memory 60 and the memory 61 based on a signal input from the logic circuit 54.

[0069] The memory 60 and memory 61 of each signal processing unit SP respectively store the measurement results of the timing measurement unit 42 and the energy measurement unit 43 for light incident on the corresponding pixel U at different timings during a predetermined measurement period. In this embodiment, the memory 60 and the memory 61 are storage areas of a storage medium configured as physically separate units. The memory 60 and the memory 61 may also be different storage areas in the same physical storage medium. The data stored in the memory 60 and the memory 61 are output to the I / O port 38 as data of the corresponding pixel U.

[0070] Next, the operation of the photodetector 1 according to this embodiment will be described. On the photodetector substrate 10, each APD 11 operates in Geiger mode. In Geiger mode, a reverse voltage (reverse bias voltage) greater than the breakdown voltage of the APD 11 is applied between the anode and cathode of each APD 11. In this embodiment, the anode is the first semiconductor region PA, and the cathode is the third semiconductor region NA. The first semiconductor region PA is electrically connected to an electrode (not shown) disposed on the main surface 1Na side of the semiconductor substrate 50 through the second semiconductor region PB. This electrode is electrically connected to the pad electrode PE2. The third semiconductor region NA is electrically connected to an electrode (not shown). For example, a negative potential is applied to the first semiconductor region PA through the pad electrode PE2, and a positive potential is applied to the third semiconductor region NA. The polarities of these potentials are relative.

[0071] When light (photons) is incident on the APD 11 included in the pixel U, photoelectric conversion occurs within the semiconductor substrate, generating photoelectrons. Avalanche multiplication occurs in a region near the PN junction interface of the first semiconductor region PA, and the amplified electrons flow to the circuit board 20 through the second semiconductor region PB and the aforementioned electrodes arranged on the principal surface 1Na side of the semiconductor substrate 50. The electrons flow from the circuit board 20 to the third semiconductor region NA through the bump electrode BE, pad electrode PE1, electrode 22, and quenching resistor 21. That is, a current signal is detected on the circuit board 20 through the quenching resistor 21, electrode 22, pad electrode PE1, and bump electrode BE. In other words, when light is incident on any of the light-receiving regions S of the photodetector substrate 10, the generated photoelectrons are multiplied, and a signal based on the multiplied photoelectrons is extracted from the bump electrode BE and input to the corresponding signal processor SP. Each signal processor SP receives a signal from the APD 11 included in the corresponding pixel U. Each signal processing unit SP processes signals from the plurality of APDs 11 included in the corresponding pixel U and outputs the processed signals as pixel data.

[0072] Next, the operation of each signal processing unit SP in this embodiment will be described in detail with reference to Fig. 11 and Fig. 12. Fig. 11 is a diagram for explaining the processing operation of the energy comparator 53 and the logic circuit 54. Fig. 12 is a timing chart showing the operation of the signal processing unit.

[0073] The timing measurement unit 42 and the energy measurement unit 43 process the detection signals output from the corresponding signal acquisition units 41 using the timing comparator 52, the energy comparator 53, and the logic circuit 54. Specifically, the timing measurement unit 42 selects the detection signals output from the front-end circuit 51 using the timing comparator 52 and outputs the selected detection signals as a digital waveform. The energy measurement unit 43 selects the detection signals output from the front-end circuit 51 using the energy comparator 53 and outputs the selected detection signals as a digital waveform. The detection signals output from the logic circuit 54 are H / L signals.

[0074] Referring to Fig. 11, a process of converting the detection signal output from the front-end circuit 51 from an analog waveform to a digital waveform using the energy comparator 53 and the logic circuit 54 will be described. In Fig. 11, the analog signals P1, P2, P3, and P4 input to the energy comparator 53 are shown overlapping for the sake of explanation. The analog signals P1, P2, P3, and P4 are voltage signals, and the wave heights indicate the voltage intensity. The analog signals P1, P2, P3, and P4 have different wave heights from one another. Fig. 11 also shows the threshold V set in the energy comparator 53. TH are shown corresponding to the intensities of the analog signals P1, P2, P3, and P4. Fig. 11 shows digital signals D1, D2, and D3 output from the energy comparator 53. The digital signals D1, D2, and D3 are H / L signals and correspond to the analog signals P2, P3, and P4, respectively.

[0075] In the example shown in FIG. 11, the energy comparator 53 detects the threshold VTH The analog signal P1 has a waveform whose maximum intensity exceeds the threshold V. TH Therefore, when the analog signal P1 is input to the energy comparator 53, the energy comparator 53 outputs a constant signal. In this embodiment, in this case, the energy comparator 53 outputs a Low signal.

[0076] The analog signals P2, P3, and P4 have a maximum intensity exceeding the threshold V TH Therefore, when the analog signals P2, P3, and P4 are input to the energy comparator 53, the energy comparator 53 outputs the threshold V TH 11, the digital signals D1, D2, and D3 output from the energy comparator 53 are generated when the corresponding analog signals P2, P3, and P4 exceed the threshold V. TH The digital signals D1, D2, and D3 output from the energy comparator 53 are switched from Low to High when the corresponding analog signals P2, P3, and P4 exceed the threshold V TH The digital signals D1, D2, and D3 are supplied to an energy counter 56 via a logic circuit 54.

[0077] The timing measurement unit 42 detects the rising or falling edge of the detection signal output from the logic circuit 54, and measures the timing at which light is incident on the corresponding pixel U using a timing counter 55. The energy measurement unit 43 detects the rising and falling edge of the detection signal output from the logic circuit 54, and measures the time between the rising and falling edge as the energy of light incident on the corresponding pixel U using an energy counter 56.

[0078] 12 shows, from top to bottom, the reset signal, stop signal, clock signal, and detection signal output from the logic circuit 54, as well as the count of the timing counter 55 and the count of the energy counter 56. The reset signal corresponds to the start of the measurement period MP, and the stop signal corresponds to the end of the measurement period MP. In other words, the measurement period MP of light incident on pixel U is determined by the reset signal and the stop signal. The reset signal indicates, for example, the timing at which light is projected from a light source in the measurement device. The stop signal indicates a timing that is predetermined depending on the range within which the object detection operation is performed.

[0079] The timing counter 55 and the energy counter 56 reset their counts using a reset signal from the logic circuit 54 as a trigger. When the timing counter 55 detects the falling edge of the reset signal, it starts counting in synchronization with the clock signal. When the energy counter 56 detects the falling edge of the reset signal, it goes into standby mode.

[0080] The timing counter 55 outputs the count result, triggered by a detection signal based on the output signal from the timing comparator 52. The timing counter 55 inputs the count result from when the falling edge of the reset signal is detected to when the rising edge of the detection signal is detected, into memories 60 and 61.

[0081] 12, the timing measurement unit 42 and the energy measurement unit 43 measure light incident on the corresponding pixel U at different timings during the measurement period MP. As a result, a falling edge of the reset signal occurs during the measurement period MP. The timing counter 55 inputs the count from when the falling edge of the reset signal is detected to when the first rising edge of the detection signal is detected into the memory 60 as the first timing measurement result T1. The timing counter 55 inputs the count from when the falling edge of the reset signal is detected to when the second rising edge of the detection signal is detected into the memory 61 as the second timing measurement result T2.

[0082] The energy counter 56 starts and stops counting using a detection signal based on the output signal from the energy comparator 53 as a trigger. The energy counter 56 inputs the count result from when the rising edge of the detection signal is detected to when the falling edge of the detection signal is detected into memories 60 and 61.

[0083] 12, the energy counter 56 inputs the count from when the rising edge of the first detection signal is detected to when the falling edge of the first detection signal is detected as the first energy measurement result E1 into the memory 60. The energy counter 56 inputs the count from when the rising edge of the second detection signal is detected to when the falling edge of the second detection signal is detected as the second energy measurement result E2 into the memory 61.

[0084] The count result of the timing counter 55 is synchronized with the period of the clock signal. Therefore, the timing counter 55 cannot measure time using a period shorter than that of the clock signal. In other words, the count result of the timing counter 55 contains an error equal to or smaller than the period of the clock signal. In this embodiment, the count result of the encoder 59 is used to correct the count result of the timing counter 55, thereby deriving more accurate data.

[0085] In this embodiment, the photodetector 1 is a so-called back-illuminated semiconductor photodetector. However, as a modification of this embodiment, the photodetector 1 may be a so-called front-illuminated semiconductor photodetector. Referring to FIG. 13, the configuration of the photodetector substrate when the photodetector 1 is a front-illuminated semiconductor photodetector will be described. FIG. 13 shows a cross-sectional configuration of the photodetector 1 according to a modification of this embodiment. The photodetector 1 in this modification differs from the photodetector 1 in the above embodiment in that it includes a photodetector substrate 10A instead of the photodetector substrate 10. The following mainly describes the differences from the above embodiment. The photodetector substrate 10A in this modification is a photodetector substrate used in a so-called front-illuminated semiconductor photodetector. That is, the photodetector 1 according to this modification is a front-illuminated semiconductor photodetector.

[0086] In the photodetector substrate 10A, a plurality of light-receiving regions S are provided on the principal surface 1Na side of the semiconductor substrate 50. Each APD 11 has a P-type first semiconductor region PC, an N-type second semiconductor region NC, and a P-type third semiconductor region PD. The first semiconductor region PC is located on the principal surface 1Na side of the semiconductor substrate 50. The second semiconductor region NC is located on the principal surface 1Nb side of the semiconductor substrate 50. The third semiconductor region PD is formed within the first semiconductor region PC. The impurity concentration of the third semiconductor region PD is higher than the impurity concentration of the first semiconductor region PC. The third semiconductor region PD is a light-receiving region S. Each APD 11 is provided on the principal surface 1Na side of the semiconductor substrate 50, and has a P-type third semiconductor region PD. + layer, the P layer being the first semiconductor region PC, and the N layer being the second semiconductor region NC. + It is structured in a layered order.

[0087] A trench 13 is formed in the semiconductor substrate 50 of the photo-detector substrate 10A so as to surround the third semiconductor region PD. As shown in Fig. 13 , the trench 13 penetrates the first semiconductor region PC in the Z-axis direction and reaches the second semiconductor region NC.

[0088] The photodetector substrate 10A has a through electrode TE for each pixel U, in addition to multiple APDs 11 and multiple quenching resistors 21. The through electrodes TE penetrate the semiconductor substrate 50 in the thickness direction (Z-axis direction). In the photodetector substrate 10A, the electrodes 22 are provided in a lattice pattern on the main surface 1Na side so as to pass between the multiple light-receiving regions S included in one pixel U when viewed from the Z-axis direction. Each quenching resistor 21 is arranged on the main surface 1Na side of the semiconductor substrate 50.

[0089] The electrode 23 extends from the electrode 22 and is electrically connected to the corresponding through-electrode TE. All of the quenching resistors 21 included in one pixel U are electrically connected in parallel to one through-electrode TE by the electrode 22 and the electrode 23.

[0090] The plurality of through electrodes TE are located in a photodetection region α, in which a plurality of pixels U are two-dimensionally arranged, as viewed from the Z-axis direction. Each through electrode TE is arranged in a region surrounded by four adjacent pixels U, excluding the through electrodes TE located at the edge of the photodetector substrate 10. Each through electrode TE is electrically connected to one of the four adjacent pixels U. The through electrodes TE and the pixels U are alternately arranged in a direction intersecting the X-axis and Y-axis. Each through electrode TE is electrically connected to the plurality of APDs 11 included in the corresponding pixel U via a quenching resistor 21, an electrode 22, and an electrode 23.

[0091] The through electrode TE is disposed in a through hole TH that penetrates in the Z-axis direction. An insulating layer L11, a through electrode TE, and an insulating layer L12 are disposed in the through hole TH. The insulating layer L11 is formed on the inner surface of the through hole TH. The insulating layer L11 is located between the through electrode TE and the through hole TH. The insulating layer L12 is disposed in a space formed inside the through electrode TE. In this embodiment, the through electrode TE has a cylindrical shape. The members disposed in the through hole TH are composed of the insulating layer L11, the through electrode TE, and the insulating layer L12, in this order from the inner surface side of the through hole TH.

[0092] The photo-detector substrate 10A has a pad electrode PE3, an electrode 24, and a pad electrode PE4 for each pixel U. The pad electrodes PE3, PE4, and the electrode 24 are arranged corresponding to the through-electrodes TE. The pad electrode PE3 is located on the main surface 1Na side, and the electrode 24 and the pad electrode PE4 are located on the main surface 1Nb side. The pad electrode PE3 is electrically connected to the electrode 23 through a connection portion C3. The pad electrode PE3 electrically connects the electrode 23 and the through-electrode TE.

[0093] An insulating layer L13 is disposed on the first semiconductor region PC, the second semiconductor region NC, the third semiconductor region PD, and the trench 13. The quenching resistor 21 and the pad electrode PE3 are covered with the insulating layer L13. The electrodes 22 and 23 are disposed on the insulating layer L13 and are covered with an insulating layer L14.

[0094] The electrode 24 and the pad electrode PE4 are arranged on the main surface 1Nb via an insulating layer L15. The electrode 24 has an end connected to the through electrode TE and an end connected to the pad electrode PE4. The electrode 24 connects the through electrode TE and the pad electrode PE4. The electrode 24 is covered with an insulating layer L16. The pad electrode PE4 is connected to the bump electrode BE. The pad electrode PE4 is covered with the insulating layer L16 except for the portion connected to the bump electrode BE.

[0095] When viewed from the Z-axis direction, the pad electrodes PE3 and PE4 of the photodetector substrate 10A are located in a photodetection region α in which a plurality of pixels U are two-dimensionally arranged. When viewed from the Z-axis direction, each pad electrode PE4 is arranged on the main surface 1Nb side so as to overlap with at least one APD 11 of the plurality of APDs 11 included in the corresponding pixel U.

[0096] The electrodes 22, 23, 24, pad electrodes PE3, PE4, connection portion C3, and through-electrode TE are made of metal. The electrodes 22, 23, 24, pad electrodes PE3, PE4, connection portion C3, and through-electrode TE are made of, for example, aluminum (Al). When the semiconductor substrate 50 is made of Si, copper (Cu) is used as the electrode material in addition to aluminum. The electrodes 22, 23, 24, pad electrodes PE3, PE4, connection portion C3, and through-electrode TE may be integrally formed. The electrodes 22, 23, 24, pad electrodes PE3, PE4, connection portion C3, and through-electrode TE are formed by, for example, sputtering.

[0097] The insulating layers L11, L12, L13, L14, L15, and L16 are made of, for example, SiO2, SiN, or resin. The insulating layers L11, L12, L13, L14, L15, and L16 are formed by thermal oxidation, sputtering, CVD, or resin coating.

[0098] The photo-detector substrate 10A is mounted on the circuit board 20, similar to the photo-detector substrate 10. The photo-detector substrate 10A is connected to the circuit board 20 in the Z-axis direction. The photo-detector substrate 10A and the circuit board 20 are connected by bump electrodes BE. Therefore, in this modification, the circuit board 20 is electrically connected to the pad electrodes PE4 by the bump electrodes BE. Detection signals output from the multiple APDs 11 included in the pixels U of the photo-detector substrate 10A are guided to the corresponding signal processing units SP via the quenching resistors 21, the electrodes 22, the pad electrodes PE4, and the bump electrodes BE.

[0099] In this modification, the photodetection region α and the signal processing region β also at least partially overlap when viewed in the Z-axis direction. The photodetection region α includes a plurality of unit regions α1, each of which includes a plurality of pixels U. The signal processing region β includes a plurality of unit regions β1, each of which includes a plurality of signal processing units SP. When viewed in the Z-axis direction, the unit region α1 in which each pixel U is provided and the unit region β1 in which the signal processing unit SP corresponding to that pixel U is provided overlap at least partially. When viewed in the Z-axis direction, the unit region α1 in which each pixel U is provided and the unit region β1 in which the signal processing unit SP corresponding to that pixel U are provided are shifted in a direction along the main surface 1Na and have portions that do not overlap with each other. When viewed in the Z-axis direction, the center of gravity of the pad electrode PE4 is shifted toward the signal acquisition unit 41 from the center of gravity of the unit region β1 in which the signal processing unit SP to which the pad electrode PE1 is connected is provided.

[0100] As described above, the photodetector 1 includes a photodetector substrate 10, 10A having a plurality of pixels U arranged two-dimensionally. Each pixel U has a plurality of APDs 11 operating in Geiger mode. Each signal processor SP acquires a detection signal through the pad electrodes PE1, PE4 of each pixel U. This improves the sensitivity of each of the two-dimensionally arranged pixels U in the photodetector 1. With this configuration, the waveform of the photodetection signal from each pixel U is steep, reducing the so-called time walk effect. Therefore, even when detecting reflected light from light simultaneously projected from a light source into a two-dimensional area, the accuracy and precision of detection are improved.

[0101] In this photodetector 1, each signal processor SP measures the light energy in the energy measuring unit 43 based on the detection signals output from each pixel U having multiple APDs 11. This allows the photodetector 1 to distinguish between reflected light from an object and ambient light based on the difference in energy. This reduces the influence of ambient light on the detection results, further improving the accuracy of detection.

[0102] The circuit board 20 is connected to the photodetector substrates 10, 10A in the Z-axis direction, and the photodetection region α, in which the plurality of pixels U are provided, and the signal processing region β, in which the plurality of signal processing units SP are provided, at least partially overlap with each other. This makes it possible to make the photodetector 1 more compact in the direction parallel to the main surface 1Na, and also reduces the electrical connection paths between each pixel U and each signal processing unit SP.

[0103] Each signal processing unit SP includes a memory unit 44. If this memory unit 44 were provided outside the signal processing unit SP, wiring from at least the timing measurement unit 42 and the energy measurement unit 43 would be drawn out from each signal processing unit SP to the outside, requiring a large space between adjacent signal processing units SP. If a large space is required between adjacent signal processing units SP, it would be difficult to reduce the size of the photodetector 1. In this photodetector 1, since each signal processing unit SP includes a memory unit 44, the number of wirings drawn out from each signal processing unit SP to the outside of that signal processing unit SP is reduced. This allows the photodetector 1 to be made even more compact.

[0104] When viewed from the Z-axis direction, the photodetector substrate 10 is surrounded by the edge of the circuit board 20. In this case, the photodetector device can be made even more compact, and the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0105] When viewed from the Z-axis direction, the photodetection region α has a portion R1 that overlaps with the signal processing region β and a portion R2 that does not overlap with the signal processing region β. The area of ​​portion R1 is larger than the area of ​​portion R2. In this case, the photodetection device can be made even more compact, and the electrical connection paths between each pixel and each signal processing unit can be further shortened.

[0106] The signal processing region β has a portion R3 that does not overlap with the photodetection region α when viewed from the Z-axis direction. The area of ​​portion R1 is larger than the sum of the areas of portions R2 and R3. In this case, the photodetection device can be made even more compact, and the electrical connection paths between each pixel and each signal processing unit can be further shortened.

[0107] When viewed from the Z-axis direction, the unit area α1 in which each of the multiple pixels U is provided in the photodetection region α and the unit area β1 in which the signal processing section SP corresponding to that pixel U is provided in the signal processing region β at least partially overlap with each other. In this case, the photodetection device 1 can be made even more compact, and the electrical connection path between each pixel U and each signal processing section SP can be further shortened.

[0108] When viewed from the Z-axis direction, the centers of gravity of the pad electrodes PE1, PE4 are shifted toward the signal acquisition unit 41 from the center of gravity of the unit area β1 in which the signal processing unit SP to which the pad electrodes PE1, PE4 are connected is provided. In this case, the electrical connection path between each pixel U and each signal processing unit SP is further shortened. When viewed from the Z-axis direction, wiring for applying a drive voltage to each signal processing unit SP can be provided in the center of the signal processing unit SP, making it easy to route the wiring.

[0109] The unit area α1 in which each pixel U is provided in the photodetection region α and the unit area β1 in which the signal processing unit SP corresponding to that pixel is provided in the signal processing region β are offset in the direction along the main surface 1Na when viewed from the Z-axis direction. The unit area α1 in which each pixel U is provided and the unit area β1 in which the signal processing unit SP corresponding to that pixel is provided have portions that do not overlap with each other. In this case, the electrical connection path between each pixel U and each signal processing unit SP can be further shortened.

[0110] The detection signal output from the corresponding pixel U is a current signal. Each signal acquisition unit 41 includes a current-voltage conversion circuit 70 and a signal transmission circuit 75. The current-voltage conversion circuit 70 converts the detection signal into a voltage. The signal transmission circuit 75 inputs the voltage signal output from the current-voltage conversion circuit 70 to the energy measurement unit 43. The signal transmission circuit 75 includes a Miller capacitor 77. The Miller capacitor 77 is connected to the energy measurement unit 43 in parallel with the current-voltage conversion circuit 70. The energy measurement unit 43 measures the energy of light incident on the corresponding pixel U based on the waveform of the signal input from the signal transmission circuit 75. Since a capacitor is connected to the energy measurement unit 43 in parallel with the current-voltage conversion circuit 70, the waveform becomes smooth. A smoother waveform can improve the accuracy of energy measurement by the energy measurement unit 43.

[0111] 14 is a diagram comparing the signal input to the timing comparator 52 and the signal input to the energy comparator 53. Each of the multiple signals S1 represents a signal input to the timing comparator 52 when light having different intensities is incident on the pixel U. Each of the multiple signals S2 represents a signal input to the energy comparator 53 when light having different intensities is incident on the pixel U. While no signal transmission circuit including a capacitor is provided upstream of the timing comparator 52, a signal transmission circuit 75 including a capacitor 78 is provided upstream of the energy comparator 53.

[0112] If a capacitor is provided in the energy measurement unit 43 in parallel with the current-voltage conversion circuit 70, the waveform of the signal input to the energy comparator 53 becomes gentler due to the discharge of the capacitor. If the waveform of the signal input to the energy comparator 53 becomes gentler, the difference in the time measured by the energy counter 56 corresponding to the difference in the energy of the light incident on the pixel U also becomes larger. This improves the accuracy of energy measurement in the energy measurement unit 43. The larger the capacitance of the capacitor connected in parallel with the current-voltage conversion circuit 70 to the energy measurement unit 43, the gentler the waveform of the signal becomes.

[0113] In this photodetector 1, the signal transmission circuit 75 includes a Miller capacitor 77 configured by a capacitor 78. In this case, without increasing the size of the capacitor area, it is possible to obtain the same effect as when a capacitor with a larger capacitance is used, depending on the voltage input to the signal transmission circuit 75. Therefore, the multiple signal processing units SP can be formed compactly to match the multiple pixels U arranged two-dimensionally, while ensuring the accuracy of energy measurement.

[0114] The energy measuring unit 43 measures whether the wave height of the signal input from the corresponding signal acquiring unit 41 is equal to or exceeds a threshold value V TH By measuring the time during which the above occurs, the energy of the light incident on the corresponding pixel U is measured. Such an energy measurement unit 43 can be realized by simple digital processing and can be configured to be physically compact. This reduces the size of the area of ​​the energy measurement unit 43. As a result, the multiple signal processing units SP can be formed compactly to match the multiple pixels U that are two-dimensionally arranged.

[0115] The storage unit 44 of each signal processing unit SP includes multiple memories 60 and 61. Each of the multiple memories 60 and 61 stores measurement results from the timing measurement unit 42 and the energy measurement unit 43 for incident light beams incident on the corresponding pixel U at different timings during a predetermined measurement period. Because the photodetector 1 includes the memories 60 and 61, even if the timing measurement unit 42 and the energy measurement unit 43 output measurement results for ambient light beams incident on the pixel U during the predetermined measurement period, the measurement results for reflected light from the target are also stored. For example, even if a signal due to ambient light is output from the logic circuit 54 as shown in FIG. 12, multiple energy measurement results E1 and E2 during the measurement period MP are stored. Therefore, even if the energy measurement result E1 is a measurement result based on a signal due to ambient light, the measurement result for reflected light from the target can be stored as the energy measurement result E2. In the photodetector 1, each signal processing unit SP includes the multiple memories 60 and 61 described above. Therefore, the influence of ambient light is reduced, and the number of lead wires extending from each signal processing unit SP to the outside of the signal processing unit SP is reduced.

[0116] The above describes embodiments and modifications of the present invention, but the present invention is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible without departing from the spirit of the present invention.

[0117] For example, in the above-described embodiment, as shown in FIG. 8, the pad electrode PE1 overlaps with the timing comparator 52 and the energy comparator 53 when viewed from the Z-axis direction. As shown in FIG. 3, the unit area α1 in which each pixel U is provided is offset in the X-axis direction from the unit area β1 in which the corresponding signal processing unit SP is provided. However, as a modification of this embodiment, as shown in FIG. 15, the pad electrode PE1 may overlap with the front-end circuit 51 when viewed from the Z-axis direction. In this modification, as shown in FIG. 16, the photodetection region α and the signal processing region β are offset from each other in the X-axis and Y-axis directions when viewed from the Z-axis direction. FIG. 15 is a diagram showing the positional relationship between the pixel and the signal processing unit in this modification. FIG. 16 is a diagram showing the positional relationship between the signal acquisition unit and the pad electrode in this modification.

[0118] FIG. 17 shows the positional relationship between the photodetection region α and the signal processing region β as viewed from the Z-axis direction in the modified example shown in FIGS. 15 and 16. In this modified example, the photodetection region α also includes a portion R1 that overlaps with the signal processing region β as viewed from the Z-axis direction and a portion R2 that does not overlap with the signal processing region β. The signal processing region β also includes a portion R1 that overlaps with the photodetection region α as viewed from the Z-axis direction and a portion R3 that does not overlap with the photodetection region α. ​​In FIG. 17, the portion R1 is hatched. As viewed from the Z-axis direction, the area of ​​the portion R1 is larger than the area of ​​the portion R2. As viewed from the Z-axis direction, the area of ​​the portion R1 is larger than the sum of the areas of the portions R2 and R3.

[0119] As shown in Fig. 16, the unit area β1 in which the corresponding signal processing unit SP is provided is shifted in the X-axis and Y-axis directions with respect to the unit area α1 in which each pixel U is provided. Fig. 15 shows the positional relationship between the pixel U and the signal processing unit SP in a photodetector 1 according to a modification of this embodiment. Fig. 16 is a diagram showing the positional relationship between the signal acquisition unit 41 and the pad electrode PE1 in a photodetector 1 according to a modification of this embodiment.

[0120] In the above-described embodiment and modified examples, the photo-detector substrates 10, 10A and the circuit board 20 are connected by bump electrodes BE, but the configuration of the photo-detector device 1 is not limited to this. The pad electrodes PE1, PE4 of the photo-detector substrates 10, 10A and the signal processing unit SP of the circuit board 20 may be electrically connected without the bump electrodes BE.

[0121] In the above-described embodiment, the energy measurement unit 43 measures the energy of light incident on the corresponding pixel U by using a TOT circuit to measure the time during which the pulse height of the signal input from the corresponding signal acquisition unit 41 is equal to or greater than a threshold. However, as a modification of this embodiment, the energy measurement unit 43 may measure the energy using an ADC (Analog-Digital Converter). In this case, the energy measurement unit 43 can detect the pulse height of the signal input from the corresponding signal acquisition unit 41 with higher accuracy, thereby measuring the energy of light incident on the corresponding pixel U with higher accuracy. As a modification of this embodiment, the energy measurement unit 43 may measure the energy using multiple comparators, each with a different threshold. In these modifications, the energy measurement unit 43 requires a larger space than when a TOT circuit is used.

[0122] In the above-described embodiment and modified examples, each signal processing unit SP is connected to only one pad electrode PE1. Each of the multiple signal processing units SP is connected to only one different pixel U through the corresponding pad electrode PE1. The photodetector 1 does not include a switch for switching the electrical connection between each pixel U and the signal processing unit SP corresponding to that pixel U. In other words, the signal output from each pixel U is input to only one fixed signal processing unit SP through the corresponding bump electrode BE. However, the photodetector 1 may include a switch for switching the signal processing unit SP electrically connected to each pixel U.

[0123] The pad electrodes PE1 and PE2 include not only electrodes having a shape in which their width is greater than their thickness, but also electrodes having a thickness greater than their width. For example, the minimum thickness of the pad electrodes PE1 and PE2 may be greater than the maximum width of the pad electrodes PE1 and PE2. In this specification, the thickness of the pad electrodes PE1 and PE2 refers to the length in the Z-axis direction. The width of the pad electrodes PE1 and PE2 refers to the length in a direction perpendicular to the Z-axis direction.

[0124] In the above-described embodiment and modified examples, the photodetection region α is defined by the inner wall of the groove 13 that surrounds the photodetection region α. ​​However, the photodetection region α does not have to be surrounded by the groove 13. In this case, the outer edge of the photodetection region α coincides with the outer edges of the outermost third semiconductor regions NA and PD when viewed from the Z-axis direction.

[0125] In the above-described embodiment and modified examples, the unit region α1 is defined by the inner wall of the groove 13 that surrounds the unit region α1. However, the unit region α1 does not have to be surrounded by the groove 13. In this case, when viewed from the Z-axis direction, the outer edge of the unit region α1 coincides with the outer edges of the third semiconductor regions NA and PD that are located outermost of the pixel U within the unit region α1. [Explanation of symbols]

[0126] 1...photodetector device, 10, 10A...photodetector substrate, 11...avalanche photodiode, 20...circuit board, 20d...edge, 21...quenching resistor, 41...signal acquisition section, 42...timing measurement section, 43...energy measurement section, 44...storage section, 50...semiconductor substrate, 60, 61...memory, 70...current-voltage conversion circuit, 75...signal transmission circuit, 77...mirror capacitor, 1Na, 1Nb...main surface, MP...measurement period, PE1, PE4...pad electrode, R1, R2, R3...portion, S...light receiving region, SP...signal processing section, U...pixel, V TH ...threshold value, α...photodetection area, α1, β1...unit area, β...signal processing area.

Claims

1. a photodetector substrate including a semiconductor substrate having a first main surface and a second main surface facing each other, and a photodetection region including a plurality of pixels that are two-dimensionally arranged when viewed from a direction perpendicular to the first main surface; a circuit board connected to the photodetector substrate in a direction perpendicular to the first main surface, the circuit board having a signal processing area in which a plurality of signal processing units are provided to process detection signals output from the corresponding pixels; The photodetector substrate includes, for each pixel, a plurality of avalanche photodiodes each having a light receiving region provided on the semiconductor substrate and operating in Geiger mode; a plurality of quenching resistors electrically connected in series with the corresponding avalanche photodiodes; a pad electrode to which the plurality of quenching resistors are electrically connected in parallel; the light receiving regions of the plurality of avalanche photodiodes are two-dimensionally arranged for each pixel when viewed from a direction perpendicular to the first main surface, Each of the signal processing units comprises: a signal acquisition unit that acquires the detection signal through the corresponding pad electrode; a timing measurement unit that measures the timing at which light is incident on the corresponding pixel based on the detection signal; an energy measurement unit that measures the energy of light incident on the corresponding pixel based on the detection signal; a storage unit that stores measurement results of the timing measurement unit and the energy measurement unit, The photodetector device, wherein the photodetection region and the signal processing region at least partially overlap when viewed from a direction perpendicular to the first main surface.

2. The photodetector device according to claim 1 , wherein the photodetector substrate is surrounded by an edge of the circuit board when viewed in a direction perpendicular to the first main surface.

3. the photodetection region has a first portion overlapping with the signal processing region and a second portion not overlapping with the signal processing region when viewed in a direction perpendicular to the first main surface, The light detection device according to claim 1 or 2, wherein the area of ​​the first portion is larger than the area of ​​the second portion.

4. the signal processing region has a third portion that does not overlap with the light detection region when viewed in a direction perpendicular to the first main surface, The photodetector device according to claim 3 , wherein the area of ​​the first portion is greater than the sum of the area of ​​the second portion and the area of ​​the third portion.

5. The light detection region includes a plurality of first unit regions each having the plurality of pixels, the signal processing area includes a plurality of second unit areas in which the plurality of signal processing units are respectively provided, the plurality of first unit areas are areas obtained by dividing the photodetection area into a matrix of pixels when viewed in a direction perpendicular to the first main surface, the plurality of second unit areas are areas obtained by dividing the signal processing area into a matrix for each of the signal processing units when viewed in a direction orthogonal to the first main surface, The photodetector device according to any one of claims 1 to 4, wherein each of the first unit regions in which the pixels are provided and the second unit region in which the signal processing unit corresponding to the pixel provided in the first unit region are provided are at least partially overlapped when viewed from a direction perpendicular to the first main surface.

6. 6. A photodetector device as described in any one of claims 5 to 5, wherein, when viewed from a direction perpendicular to the first main surface, the center of gravity of the pad electrode is shifted toward the signal acquisition section from the center of gravity of the second unit area in which the signal processing section to which the pad electrode is connected is provided.

7. An optical detection device as described in Claim 5, wherein each first unit area in which the pixels are provided and the second unit area in which the signal processing unit corresponding to the pixel provided in the first unit area is provided are shifted in a direction along the first main surface when viewed from a direction perpendicular to the first main surface, and have portions that do not overlap with each other.

8. the detection signal is a current signal, the signal acquisition unit of each of the signal processing units includes a current-voltage conversion circuit that converts the detection signal into a voltage, and a signal transmission circuit that inputs the voltage signal output from the current-voltage conversion circuit to the energy measurement unit; the signal transmission circuit includes a Miller capacitor connected in parallel with the current-voltage conversion circuit to the energy measurement unit; 8. The photodetector according to claim 1, wherein the energy measurement unit measures the energy of light incident on the corresponding pixel based on the waveform of the signal input from the signal transmission circuit.

9. The photodetector according to any one of claims 1 to 8, wherein the energy measurement unit measures the energy of incident light on the corresponding pixel by measuring the time during which the pulse height of the signal input from the corresponding signal acquisition unit is equal to or greater than a threshold value.

10. The photodetector device according to any one of claims 1 to 9, wherein the memory unit of each of the signal processing units includes a plurality of memory areas that respectively store measurement results of the timing measurement unit and the energy measurement unit for light incident on the corresponding pixel at different timings during a predetermined measurement period.

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