Optical detection device

Abstract

In the light detection device (1) of the present invention, the circuit board (20) has multiple signal processing units (SPs) for processing detection signals output from corresponding pixels. The light-receiving areas of multiple avalanche photodiodes are arranged in two dimensions in each pixel. In each signal processing unit (SP), the timing measurement unit (42) measures the timing of light incident on the corresponding pixel based on the detection signal. The energy measurement unit (43) measures the energy of the incident light toward the corresponding pixel based on the detection signal. The storage unit (44) stores the measurement results in the timing measurement unit (42) and the energy measurement unit (43). The light detection area (α) with multiple pixels and the signal processing area (β) with multiple signal processing units overlap at least partially.

Description

Technical Field

[0001] This invention relates to a light detection device. Background Technology

[0002] A technique is known that detects an object and measures the distance to it by detecting light reflected from a light source (e.g., Patent Document 1). This technique is, for example, called LiDAR (Light Detection and Ranging). Hereinafter, "object detection" and "distance measurement" will be collectively referred to as "detection work." The apparatus that performs detection work using LiDAR will be called a "measuring device." Patent Document 1 describes a measuring device that uses a scanning unit to scan light emitted from a light source and detects reflected light from an object.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-72097 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] Scanning-type measuring devices have a movable part in the scanning section that operates mechanically to scan light from a light source and sequentially detect reflected light from the area of ​​the object being measured. Therefore, scanning-type measuring devices suffer from the problem of the scanning section being prone to malfunction. Furthermore, in the aforementioned scanning-type measuring devices, if the object moves during the scanning light, it may also lead to problems in achieving accurate detection. To solve these problems, a flash-type measuring device has been considered, which simultaneously projects light from a light source two-dimensionally toward the area of ​​the object being measured and detects reflected light from that area. With a flash-type measuring device, detection over a wide area can be achieved even without light scanning. Since there is no scanning section to scan the light from the light source, malfunctions in the scanning section will not occur, and problems caused by object movement during the scanning light will be eliminated. It is believed that flash-type measuring devices offer improved robustness and shorter detection time in the area of ​​the object being measured compared to scanning-type measuring devices.

[0008] However, various problems exist in performing detection without using a scanning unit. For example, when projecting light simultaneously onto a two-dimensional area without a scanning unit, detecting the reflected light requires arranging multiple pixels of the detection light in a two-dimensional configuration within the optical detection device. Because in flash-based measurement devices, light is projected simultaneously from the light source onto the area of ​​the object being detected, the intensity of reflected light from various parts of that area is weakened compared to detection using a scanning method. Therefore, it is also necessary to improve the sensitivity of each pixel. Since flash-based measurement devices detect light projected simultaneously onto the area of ​​the object being detected, ambient light is easily detected in addition to reflected light from the object. Therefore, it is difficult to distinguish between ambient light and reflected light from the object. To solve these problems in flash-based measurement devices, it is necessary to improve the accuracy and precision of the detection in the optical detection device.

[0009] One aspect of the present invention aims to provide a light detection device with a compact (small) structure, which improves the accuracy and precision of detection when used in a flash-mode measurement device.

[0010] Technical solutions for solving technical problems

[0011] One aspect of the light detection device of the present invention includes a light detection substrate and a circuit board. The light detection substrate has a semiconductor substrate. The semiconductor substrate has a first main surface and a second main surface opposite to each other. The light detection substrate has a light detection region. In the light detection region, a plurality of pixels are provided, arranged in a two-dimensional manner when viewed from a direction orthogonal to the first main surface. The circuit board is connected to the light detection substrate in a direction orthogonal to the first main surface. The circuit board has a signal processing region. In the signal processing region, a plurality of signal processing units are provided for processing detection signals output from corresponding pixels. Each pixel of the light detection substrate has a plurality of avalanche photodiodes, a plurality of quenching resistors, and pad electrodes. Each of the plurality of avalanche photodiodes has a light-receiving region disposed on the semiconductor substrate and operates in Geiger mode. The plurality of quenching resistors are electrically connected in series with the corresponding avalanche photodiodes. The plurality of quenching resistors are electrically connected in parallel to each other to the pad electrodes. When viewed from a direction orthogonal to the first main surface, the light-receiving regions of the plurality of avalanche photodiodes are arranged in a two-dimensional manner in each pixel. Each signal processing unit includes a signal acquisition unit, a timing measurement unit, an energy measurement unit, and a storage unit. The signal acquisition unit acquires a detection signal via the corresponding pad electrode. The timing measurement unit measures the timing of light incident on the corresponding pixel based on the detection signal. The energy measurement unit measures the energy of the incident light directed to the corresponding pixel based on the detection signal. The storage unit stores the measurement results from the timing measurement unit and the energy measurement unit. When viewed from a direction orthogonal to the first principal surface, the light detection area and the signal processing area overlap by at least a portion.

[0012] In one of the above embodiments, the light detection device includes a light detection substrate having a plurality of pixels arranged in a two-dimensional pattern. Each pixel has a plurality of avalanche photodiodes operating in Geiger mode. Each signal processing unit acquires a detection signal through the pad electrodes of each pixel. Therefore, in this light detection device, the sensitivity of each of the two-dimensionally arranged pixels is improved. Therefore, when detecting reflected light from light simultaneously projected from a light source into a two-dimensional area, the accuracy and precision of detection are also improved. In this light detection device, each signal processing unit measures the energy of light in its energy measurement unit based on the detection signal output from each pixel having a plurality of avalanche photodiodes. Therefore, this light detection device can distinguish between reflected light from an object and ambient light based on the energy difference. Therefore, the influence of ambient light can be reduced based on the detection results. A circuit board is connected to the light detection substrate in a direction orthogonal to the first main surface, and the light detection area and the signal processing area at least partially overlap. Therefore, in a direction parallel to the first main surface, miniaturization of the light detection device can be achieved, and the electrical connection path between each pixel and each signal processing unit can be reduced. Each signal processing unit includes a storage unit. Assuming the storage unit is located outside the signal processing unit, a large space is required between adjacent signal processing units to extend the wiring from at least the timing and energy measurement units to the outside. This large space requirement makes it difficult to reduce the size of the photodetector. In this photodetector, since each signal processing unit includes a storage unit, the number of wirings extending from each signal processing unit to the outside is reduced. Therefore, further miniaturization of the photodetector is possible.

[0013] In one of the above embodiments, when viewed from a direction orthogonal to the first main surface, the photodetector substrate is surrounded by the edge of the circuit substrate. In this case, further miniaturization of the photodetector device can be achieved, and the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0014] In one of the above embodiments, the light detection region, when viewed from a direction orthogonal to the first principal surface, may have a first portion overlapping the signal processing region and a second portion not overlapping the signal processing region. Alternatively, the area of ​​the first portion may be larger than the area of ​​the second portion. In this case, further miniaturization of the light detection device can be achieved, and the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0015] In one of the above embodiments, the signal processing region may have a third portion that does not overlap with the light detection region when viewed from a direction orthogonal to the first principal surface. Alternatively, the area of ​​the first portion may be greater than the sum of the areas of the second and third portions. In this case, further miniaturization of the light detection device can be achieved, and the electrical connection paths between each pixel and each signal processing unit can be further reduced.

[0016] In one of the above embodiments, the light detection region may have a unit region for each pixel, and the signal processing region may have a unit region for a signal processing unit corresponding to that pixel, with at least a partial overlap when viewed from a direction orthogonal to the first main surface. In this case, further miniaturization of the light detection device can be achieved, and the electrical connection path between each pixel and each signal processing unit can be further reduced.

[0017] In one of the above methods, when viewed from a direction orthogonal to the first main surface, the center of gravity of the pad electrode is shifted from the center of gravity of the unit area where the signal processing unit connected to the pad electrode is located towards the signal acquisition unit. The center of gravity of the pad electrode is its geometric center. In this case, the electrical connection path between each pixel and each signal processing unit is further reduced. When viewed from a direction orthogonal to the first main surface, the wiring for applying driving voltage to each signal processing unit can be positioned at the center of the signal processing unit. Therefore, wiring is easier to guide.

[0018] In one of the above embodiments, the light detection region may have a unit region for each pixel, and the signal processing region may have a unit region for a signal processing unit corresponding to that pixel. When viewed from a direction orthogonal to the first main surface, these units have portions that are offset along the direction of the first main surface and do not overlap with each other. In this case, the electrical connection path between each pixel and each signal processing unit can be further reduced.

[0019] In one of the above embodiments, the detection signal may be a current signal. Alternatively, each signal acquisition unit may include a current-to-voltage conversion circuit and a signal transmission circuit. Alternatively, the current-to-voltage conversion circuit may convert the detection signal into a voltage. Alternatively, the signal transmission circuit may input the voltage signal output from the current-to-voltage conversion circuit to the energy measurement unit. Alternatively, the signal transmission circuit may include a Miller capacitor. Alternatively, the Miller capacitor may be connected in parallel with the current-to-voltage conversion circuit to the energy measurement unit. Alternatively, the energy measurement unit may measure the energy of the incident light toward the corresponding pixel based on the waveform of the signal input from the signal transmission circuit. In this case, the signal transmission circuit includes a capacitor, thereby smoothing the waveform. When the waveform becomes smoother, the energy measurement accuracy in the energy measurement unit can be improved. The larger the capacitance of the capacitor, the smoother the signal waveform. In this light detection device, the signal transmission circuit includes a Miller capacitor. Therefore, even without increasing the size of the capacitor area, the signal transmission circuit can achieve the same effect as when using a capacitor with a larger capacitance. As a result, energy measurement accuracy can be ensured, and multiple signal processing units are formed in a small size in conjunction with multiple pixels arranged in two dimensions.

[0020] In one of the above methods, the energy measurement unit can measure the energy of incident light onto a corresponding pixel by measuring the time during which the wave height of the signal input from the corresponding signal acquisition unit is above a threshold. Such an energy measurement unit can be implemented through simple digital processing and can also be physically miniaturized. Therefore, the size of the energy measurement unit area can be reduced. As a result, multiple signal processing units can be miniaturized to accommodate multiple pixels arranged in a two-dimensional configuration.

[0021] In one of the above embodiments, the storage unit of each signal processing unit may include multiple storage areas. These multiple storage areas store the measurement results of incident light incident on the corresponding pixel at different times during a predetermined measurement period, obtained by the timing measurement unit and the energy measurement unit. Since this light detection device includes multiple storage areas, even if the timing measurement unit and the energy measurement unit output the measurement results of ambient light incident on the pixel during the predetermined measurement period, the measurement results of reflected light from the object can also be stored. In this light detection device, each signal processing unit includes the aforementioned multiple storage areas. Therefore, the influence of ambient light can be reduced, and the number of wirings leading from each signal processing unit to the outside of the signal processing unit is reduced.

[0022] Invention Effects

[0023] One aspect of the present invention provides a light detection device with a compact (small) structure, which improves the accuracy and precision of detection when used in a flash-mode measurement device. Attached Figure Description

[0024] Figure 1 This is a schematic perspective view showing the light detection device of this embodiment.

[0025] Figure 2 This is an exploded 3D view of the optical detection device.

[0026] Figure 3 This is a schematic top view of the photodetector substrate.

[0027] Figure 4 This is a schematic diagram showing the positional relationship between the light detection area and the signal processing area.

[0028] Figure 5 This is a simplified enlarged view of the photodetector substrate.

[0029] Figure 6 This is a diagram showing the cross-sectional structure of the optical detection device.

[0030] Figure 7 This is a diagram showing the structure of a circuit board.

[0031] Figure 8 This is a diagram showing the structure of the signal processing unit.

[0032] Figure 9 This is a diagram showing the configuration of the preamplifier circuit.

[0033] Figure 10 This is a diagram representing a Miller capacitor.

[0034] Figure 11 This diagram illustrates the operation of the energy comparator and logic circuits.

[0035] Figure 12 It is a timing diagram representing the operation of the signal processing unit.

[0036] Figure 13 This is a cross-sectional view showing the optical detection device of a modified example of this embodiment.

[0037] Figure 14 It is a diagram used to illustrate the processing in a signal transmission circuit.

[0038] Figure 15 This is a diagram showing the positional relationship between the pixels and the signal processing unit in a modified example of this embodiment.

[0039] Figure 16 This is a diagram showing the positional relationship between the signal acquisition unit and the pad electrode in a modified example of this embodiment.

[0040] Figure 17 This is a schematic diagram showing the positional relationship between the light detection region and the signal processing region in a modified example of this embodiment. Detailed Implementation

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the description, the same reference numerals are used for the same elements or elements having the same function, and repeated descriptions are omitted.

[0042] First, refer to Figure 1 and Figure 2 The structure of the optical detection device in this embodiment will be explained. Figure 1 This is a schematic perspective view showing the light detection device of this embodiment. Figure 2 yes Figure 1 The image shows an exploded perspective view of the photodetector. Photodetector 1 is a semiconductor photodetector.

[0043] Optical detection device 1 Figure 1 and Figure 2 As shown, the system includes a photodetector substrate 10 and a circuit substrate 20. The photodetector substrate 10 and the circuit substrate 20 are opposite to each other. In this embodiment, the plane parallel to each main surface of the photodetector substrate 10 and the circuit substrate 20 is the XY-axis plane, and the direction orthogonal to each main surface is the Z-axis direction.

[0044] The photodetector substrate 10 has a semiconductor substrate 50 that is rectangular in shape when viewed from above. In this embodiment, the photodetector substrate 10 is a photodetector substrate for a so-called back-incident type semiconductor photodetector device. The semiconductor substrate 50 contains Si and is a P-type semiconductor substrate. The semiconductor substrate 50 has a principal surface 1Na and a principal surface 1Nb that are opposite each other. P-type is an example of a first conductivity type. N-type is an example of a second conductivity type. The principal surface 1Na is the surface on which light is incident to the semiconductor substrate 50. When the principal surface 1Na is the first principal surface, the principal surface 1Nb is the second principal surface.

[0045] The circuit board 20 has two main surfaces 20a and 20b that are opposite to each other. The circuit board 20 is rectangular in shape when viewed from above. The photodetector substrate 10 is connected to the circuit board 20 in the Z-axis direction. The main surface 20a is opposite to the main surface 20b.

[0046] The side surface 20c of the circuit substrate 20 is located further outward in the XY-axis plane direction than the side surface 1Nc of the semiconductor substrate 50. When viewed from above, the area of ​​the circuit substrate 20 is larger than the area of ​​the semiconductor substrate 50. In other words, the side surface 20c of the circuit substrate 20 is located further outward in the XY-axis plane direction than the side surface 1Nc of the semiconductor substrate 50. When viewed from the Z-axis direction, the photodetector substrate 10 is surrounded by the edge 20d of the circuit substrate 20. The side surface 20c of the circuit substrate 20 and the side surface 1Nc of the semiconductor substrate 50 can also be a single surface.

[0047] A photodetector substrate 10 is mounted on a circuit board 20. The photodetector substrate 10 and the circuit board 20 are connected by a bump electrode BE. When viewed from the Z-axis direction, the photodetector substrate 10 is positioned at the center of the circuit board 20. Figure 2 As shown, the photodetector substrate 10 has multiple pixels U. When viewed from the Z-axis direction, the multiple pixels U are arranged in a matrix-like two-dimensional pattern within the photodetector region α of the photodetector substrate 10. The photodetector region α is rectangular when viewed from the Z-axis direction. The photodetector device 1 outputs a detection signal corresponding to the light detected in the multiple pixels U. The pitch WU between pixels U is 10 μm to 500 μm in both 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.

[0048] The circuit board 20, for example, constitutes an ASIC (Application Specific Integrated Circuit). The circuit board 20, for example... Figure 2As shown, the circuit board 20 has multiple signal processing units SP. Each signal processing unit SP processes the detection signal output from its corresponding pixel U. When viewed from the Z-axis direction, the multiple signal processing units SP are arranged in a two-dimensional arrangement on the signal processing region β of the circuit board 20. Each signal processing unit SP is electrically connected to the photodetector substrate 10 via a bump electrode BE. In this embodiment, each signal processing unit SP and its corresponding pixel U are configured with the same pitch WU.

[0049] Next, refer to Figures 3 to 6 The structure of the photodetector substrate 10 will be described. Figure 3 This is a diagram of the main surface 1Nb of the photodetector substrate 10 viewed from the Z-axis direction. Figure 4 This is a schematic diagram showing the positional relationship between the light detection region α and the signal processing region β. Figure 5 This indicates the area where bump electrodes PE1 and BE are provided corresponding to each pixel U. Figure 6 This shows the cross-sectional structure of the optical detection device.

[0050] Figure 3 In the diagram, the position of the signal processing unit SP when viewing the light detection device 1 from the Z-axis direction is indicated by a dashed line. Figure 3 The diagram shows the positional relationship between each pixel U, the bump electrode BE, and the signal processing unit SP of the circuit board 20. For example... Figure 3 As shown, when viewed from the Z-axis direction, the light detection region α and the signal processing region β at least partially overlap. In this embodiment, when viewed from the Z-axis direction, the light detection region α and the signal processing region β are offset relative to each other in the X-axis direction.

[0051] Figure 4 The diagram illustrates the positional relationship between the light detection region α and the signal processing region β when viewed from the Z-axis. When viewed from the Z-axis, the light detection region α comprises 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. Similarly, when viewed from the Z-axis, the signal processing region β comprises a portion R1 that overlaps with the light detection region α and a portion R3 that does not overlap with the light detection region α. ​​In other words, portion R1 is the portion where the light detection region α and the signal processing region β overlap when viewed from the Z-axis. Portion R2 is the portion within the light detection region α that does not overlap with the signal processing region β when viewed from the Z-axis. Portion R3 is the portion within the signal processing region β that does not overlap with the light detection region α when viewed from the Z-axis. Figure 4 In the diagram, a shaded line is added to part R1. When viewed from the Z-axis, the area of ​​part R1 is larger than the area of ​​part R2. When viewed from the Z-axis, the area of ​​part R1 is larger than the combined area of ​​parts R2 and R3. For example, part R1 is the first part, part R2 is the second part, and part R3 is the third part.

[0052] The light detection region α includes multiple unit regions α1, each equipped with a plurality of pixels U. One pixel U is located in each unit region α1. The signal processing region β includes multiple unit regions β1, each equipped with a plurality of signal processing units SP. One signal processing unit SP is located in each unit region β1. When viewed from the Z-axis direction, the unit region α1 equipped with each pixel U and the unit region β1 equipped with the corresponding signal processing unit SP at least partially overlap. When viewed from the Z-axis direction, the unit region α1 equipped with each pixel U and the unit region β1 equipped with the corresponding signal processing unit SP have portions that are offset from each other in the direction of the salt principal plane 1Na and do not overlap. In this embodiment, the unit region β1 equipped with the corresponding signal processing unit SP is offset in the X-axis direction relative to the unit region α1 equipped with each pixel U.

[0053] like Figure 3 and Figure 5 As shown, 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 photodiode" will be referred to as "APD".

[0054] In the photodetector substrate 10, each pixel U is provided with a plurality of APDs 11 operating in Geiger mode, a plurality of quench resistors 21, and at least one pad electrode PE1. In this embodiment, each pixel U is provided with one pad electrode PE1. Each signal processing unit SP is connected to only one pad electrode PE1. The plurality of signal processing units SP are each connected to a different pixel U through their respective pad electrodes PE1. In other words, the plurality of signal processing units SP are connected to the plurality of pixels U in a one-to-one correspondence.

[0055] Multiple APDs 11 are arranged in a two-dimensional pattern on a 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 disposed on the main surface 1Nb side of the semiconductor substrate 50. For example... Figure 5 As shown, in the photodetector substrate 10, each pixel U includes multiple light-receiving regions S. When viewed from the Z-axis direction, the multiple light-receiving regions S are arranged in a two-dimensional pattern in each pixel U. Each light-receiving region S is a charge-generating region that generates charge based on incident light. Each light-receiving region S is a photosensitive region. In this embodiment, as... Figure 5 As shown, each illuminated area S appears rectangular when viewed from the Z-axis direction.

[0056] like Figure 6As shown, the photodetector substrate 10 has multiple quenching resistors 21 and electrodes 22 in each pixel U. Each quenching resistor 21 is disposed on the main 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 resistors 21 constitute a passive quenching circuit.

[0057] like Figure 5 As shown, electrodes 22 are arranged in a grid pattern on the main surface 1Nb side, passing through the multiple light-receiving areas S contained in a pixel U when viewed from the Z-axis direction. The light-receiving areas S are surrounded by electrodes 22 when viewed from the Z-axis direction. Electrodes 22 are electrically connected to all light-receiving areas S contained in a pixel U through multiple quenching resistors 21. Electrodes 22 are also electrically connected to the light-receiving area S corresponding to each quenching resistor 21 through multiple quenching resistors 21. Electrodes 22 are connected to the pad electrode PE1 corresponding to pixel U. In this embodiment, electrodes 22 are connected to the pad electrode PE1 located at the center of the corresponding pixel U. Based on the above configuration, all quenching resistors 21 contained in a pixel U are electrically connected in parallel to one pad electrode PE1 via electrodes 22. That is, each pad electrode PE1 is electrically connected to the multiple APDs 11 contained in the corresponding pixel U through quenching resistors 21 and electrodes 22.

[0058] Multiple pad electrodes PE1, when viewed from the Z-axis direction, are located in the light detection region α of a two-dimensional array of multiple pixels U. Each pad electrode PE1 is disposed on the main surface 1Nb side such that it overlaps with at least one of the multiple APDs 11 of the corresponding pixel U when viewed from the Z-axis direction. In this embodiment, each pad electrode PE1 is rectangular in shape and is disposed such that it overlaps with four APDs 11 of the 16 APDs 11 of a pixel U located at the center of the pixel U. A bump electrode BE is disposed at the center of each pad electrode PE1 when viewed from the Z-axis direction. In this embodiment, each pad electrode PE1 is in contact with the electrode 22 surrounding the four light-receiving regions S located at the center of each pixel U when viewed from the Z-axis direction.

[0059] As a variation of this embodiment, the pad electrode PE1 may also make contact with all of the plurality of ADP11s of the pixel U. In this case, each pad electrode PE1 may, for example, be arranged on the main surface 1Nb side in such a way that it completely overlaps with all of the plurality of ADP11s of the pixel U when viewed from the Z-axis direction.

[0060] like Figure 3As shown, the pad electrode PE2 is disposed on the main surface 1Nb side at intervals from the photodetector area α, which is configured with multiple pixels U. The pad electrode PE2 is a common electrode for applying voltage to each APD11 from the main surface 1Nb side. In this embodiment, the pad electrode PE2 is rectangular and disposed on the four sides of the main surface 1Nb. A bump electrode BE is also disposed on the pad electrode PE2.

[0061] like Figure 6 As shown, 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 that 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 starts from the main surface 1Na side and begins with the second semiconductor region PB, i.e., P... + The first semiconductor region PA (P-layer) and the third semiconductor region NA (N-layer) are also known as the N-layer. + The layers are arranged sequentially.

[0062] A groove 13 is formed on the semiconductor substrate 50 to surround the third semiconductor region NA. In this embodiment, the light detection region α is surrounded by the groove 13 when viewed from the Z-axis direction. The light detection region α is defined by the inner wall of the groove 13 surrounding the light detection region α. ​​When viewed from the Z-axis direction, the outer edge of the light detection region α coincides with the inner wall of the outermost groove 13 near the pixel U. A unit region α1 is surrounded by the groove 13 when viewed from the Z-axis direction. The unit region α1 is defined by the inner wall of the groove 13 surrounding 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 groove 13 surrounding the pixel U within the unit region α1 near the pixel U.

[0063] The trench 13 extends through 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 contains a high-melting-point metal. For example, the core material 13a contains tungsten. The surface of the trench 13 is formed by a P-type semiconductor layer 15 having an impurity concentration higher than that of the first semiconductor region PA. That is, the core material 13a is covered by the semiconductor layer 15 within the semiconductor substrate 50. As a variation of this embodiment, the trench 13 may extend in the first semiconductor region PA in the Z-axis direction without reaching the second semiconductor region PB.

[0064] An insulating layer L1 is disposed above the first semiconductor region PA, the third semiconductor region NA, and the trench 13. A quenching resistor 21 is covered by the insulating layer L1. An electrode 22 is disposed on the insulating layer L1 and covered by an insulating layer L2. A pad electrode PE1 is disposed on the insulating layer L2. The insulating layer L2 is covered by the pad electrode PE1 and a protective layer L3. The protective layer L3 also covers a portion of the pad electrode PE1.

[0065] The aforementioned quenching resistor 21 is connected to the third semiconductor region NA via an electrode (not shown). The quenching resistor 21 is connected to the corresponding electrode 22 via a connection portion C1. The electrode 22 is connected to the corresponding pad electrode PE1 via a connection portion C2. The pad electrode PE1 is connected to the pad electrode BE at the portion exposed from the protective layer L3.

[0066] Electrode 22, pad electrodes PE1, PE2, and connectors C1 and C2 are made of metal. For example, electrodes 22, pad electrodes PE1, PE2, and connectors C1 and C2 are made of aluminum (Al). When the semiconductor substrate 50 contains Si, copper (Cu), in addition to aluminum, can be used as the electrode material. Electrode 22, pad electrodes PE1, and connectors C1 and C2 can also be formed integrally. Electrode 22, pad electrodes PE1, and connectors C1 and C2 are formed, for example, by sputtering.

[0067] When Si is used as the material for the semiconductor substrate 50, Group III elements are used for P-type impurities, and Group V elements are used for N-type impurities. For example, B is a Group III element used as a P-type impurity. For example, P or As is a Group V element used as an N-type impurity. The semiconductor, with its alternating N-type and P-type conductors, functions as a photodetector, similar to the photodetector substrate 10. These impurities are added using methods such as diffusion or ion implantation.

[0068] The insulating layers L1, L2 and the protective layer L3 may contain, for example, SiO2, SiN or resin. The insulating layers L1, L2 and the protective layer L3 may be formed by thermal oxidation, sputtering, CVD or resin coating.

[0069] The circuit board 20 is electrically connected to the pad electrode PE1 via a bump electrode BE. Each signal processing unit SP has an electrode arranged corresponding to the pad electrode PE1, which is electrically connected to the corresponding pad electrode PE1 via the bump electrode BE. The detection signal output from the plurality of APDs 11 included in the pixel U is 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.

[0070] The bump electrode BE is formed on the pad electrode PE1 via an under-bump metal (UBM) not shown. The UBM contains a material that provides excellent electrical and physical bonding to the bump electrode BE. The UBM is formed, for example, by an electroless plating process. The bump electrode BE is formed, for example, by a solder ball mounting method, a printing method, or an electrolytic plating process. The bump electrode BE contains, for example, copper, solder, or indium.

[0071] Next, refer to Figure 7 The structure of the circuit board in this embodiment will be described. Figure 7 This is a diagram showing the structure of the circuit board 20. The circuit board 20 is as follows... Figure 7 As shown, in addition to multiple signal processing units SP, it also includes interface circuitry 31, memory 32, PLL (Phase Locked Loop) 33, row random access decoder 34, clock driver 35, column random access decoder 37, and I / O port 38. When viewed from the Z-axis direction, PLL 33 and clock driver 35 are positioned in an area that does not overlap with the light detection area α.

[0072] The interface circuit 31 corresponds, for example, to 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) from external inputs, and stores the register setting information contained in the signals in the memory 32.

[0073] The PLL33 generates a clock signal based on the externally input Master Clock (MCLK) and data stored in memory 32, and sends the generated clock signal to clock driver 35. The PLL33 includes a programmable divider, which sets the division factor with reference to the data stored in memory 32. The division factor of the PLL33 can be set to any value according to the input from the external interface circuit 31. The PLL33 outputs the control voltages of the various signal processing units (SPs) along with the clock signal.

[0074] Clock driver 35 supplies clock signals to each signal processing unit SP. Each of the multiple signal processing units SP is electrically connected to multiple APDs 11 contained in the corresponding pixel U via bump electrodes BE. A detection signal output from the corresponding pixel U is input to each signal processing unit SP. The detection signal from pixel U is a pulse signal with an analog waveform. Based on the input detection signal, each signal processing unit SP calculates pixel data such as the incident timing and energy of the incident light to the corresponding pixel U. The pixel data calculated by each signal processing unit SP is output to I / O port 38 according to the timing corresponding to the signals from row random access decoder 34 and column random access decoder 37.

[0075] 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 the detection signal output from the pixel U via the corresponding pad electrode PE1. The signal acquisition unit 41 includes a pre-amplifier circuit. The timing measurement unit 42 measures the timing of light incident on the corresponding pixel U based on the detection signal. The energy measurement unit 43 measures the energy of the incident light to the corresponding pixel U based on the detection signal. In this embodiment, the energy measurement unit 43 converts the energy of the incident light to the corresponding pixel U into time for measurement. For example, the energy measurement unit 43 uses a TOT (Time-Over Threshold) circuit to measure the time during which the wave height of the signal input from the corresponding signal acquisition unit 41 is above the threshold, as the energy. The storage unit 44 stores the measurement results of the timing measurement unit 42 and the energy measurement unit 43.

[0076] Next, refer to Figures 8 to 10 A detailed explanation of an example of the configuration of each signal processing unit (SP) will be provided. Figure 8 The configuration of the signal processing unit SP in this embodiment is shown.

[0077] Each signal processing unit SP includes a preamplifier 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 preamplifier circuit 51 constitutes the signal acquisition unit 41. The timing comparator 52, logic circuit 54, timing counter 55, and delay line 57 constitute the timing measurement unit 42. The energy comparator 53, logic circuit 54, and energy counter 56 constitute the energy measurement unit 43. Memories 60 and 61 are storage areas, constituting the storage unit 44.

[0078] In this embodiment, such as Figure 8As shown, when viewed from the Z-axis direction, the center of gravity of the pad electrode PE1 is located closer to the preamplifier 51 than the center of gravity of the unit area β1 of the signal processing unit SP connected to the pad electrode PE1. In other words, when viewed from the Z-axis direction, the center of gravity of the pad electrode PE1 is shifted from the center of gravity of the unit area β1 of the signal processing unit SP connected to the pad electrode PE1 towards the signal acquisition unit 41. In this embodiment, when viewed from the Z-axis direction, the pad electrode PE1 overlaps with the timing comparator 52 and the energy comparator 53.

[0079] The preamplifier circuit 51 is connected to multiple APDs 11 contained in the corresponding pixel U via bump electrodes BE and pad electrodes PE1. A detection signal is input to the preamplifier circuit 51 from the corresponding pixel U. The detection signal output from the corresponding pixel U is a current signal output from the APDs 11 contained in the corresponding pixel U based on the incident light. The preamplifier circuit 51 performs prescribed processing on the detection signal output from the corresponding pixel U. The preamplifier circuit 51 inputs the processed detection signal to the timing comparator 52 and the energy comparator 53. The detection signal input to the timing comparator 52 and the energy comparator 53 has an analog waveform. The preamplifier circuit 51 is as follows... Figure 9 As shown, it includes a current-to-voltage conversion circuit 70 and a signal transmission circuit 75. Figure 9 The configuration of the preamplifier circuit 51 is shown.

[0080] The current-to-voltage conversion circuit 70 converts the detection signal input from the corresponding pixel U into a voltage signal. The current-to-voltage conversion circuit 70 includes current-to-voltage conversion resistors 71 and 72 and a bias circuit 73. The voltage signal output from the current-to-voltage conversion resistor 71 is input to the timing comparator 52. The voltage signal output from the current-to-voltage conversion resistor 72 is input to the energy comparator 53. A signal transmission circuit 75 is disposed between the current-to-voltage conversion resistor 72 and the energy comparator 53. The signal transmission circuit 75 inputs the voltage signal output from the current-to-voltage conversion resistor 72 of the current-to-voltage conversion circuit 70 to the energy comparator 53 of the energy measurement unit 43. The current-to-voltage conversion resistors 71 and 72 are respectively connected to the bias circuit 73. Figure 9 As shown, a bias voltage is applied to the preamplifier circuit 51 from the outside. This bias voltage is applied to the bias circuit 73.

[0081] The signal transmission circuit 75 includes an inverter 76 and a capacitor 78 that functions as a Miller capacitor 77 and also functions as a variable capacitor circuit. Figure 10The configuration of a portion of the signal transmission circuit 75 is shown. A capacitor 78 is connected in parallel to an inverter 76. A threshold voltage is set for the inverter 76. When the input voltage is above the threshold voltage, the inverter 76 generates a negative gain corresponding to the input voltage. When the input voltage is below the threshold voltage, the inverter 76 generates a positive gain corresponding to the input voltage. As a result, the signal transmission circuit 75 utilizes the Miller effect and can operate by connecting a capacitor with a capacitance larger than that of individual capacitors 78 in parallel with a current-to-voltage conversion resistor 72 to an energy comparator 53. In other words, the capacitor 78 in the signal transmission circuit 75 functions as a Miller capacitor 77 with apparent capacitance utilizing the Miller effect. This apparent capacitance, or Miller capacitance, increases with the increase of the input voltage to the signal transmission circuit 75.

[0082] Capacitor 78 is connected in parallel with current-to-voltage conversion resistor 72 to energy comparator 53. Therefore, signal transmission circuit 75 includes a Miller capacitor 77 connected in parallel with current-to-voltage conversion circuit 70 to energy measurement unit 43. The larger the capacitance of the capacitor connected in parallel with current-to-voltage conversion resistor 72, the smoother the waveform of the detection signal input to energy comparator 53. Therefore, the detection signal input to energy comparator 53 has a smoother waveform than when only capacitor 78 and current-to-voltage conversion resistor 72 are connected in parallel to energy comparator 53, utilizing the Miller effect corresponding to the input voltage to signal transmission circuit 75. Energy measurement unit 43 measures the energy of incident light on the corresponding pixel U based on the waveform of the detection signal input to energy comparator 53.

[0083] Timing comparator 52 and energy comparator 53 select the signal to be output based on the waveform height of the detection signal output from the preamplifier circuit 51. The detection signals output from timing comparator 52 and energy comparator 53 are input to logic circuit 54. The signals output from timing comparator 52 and energy comparator 53 have digital waveforms. Timing comparator 52 and energy comparator 53 output a high signal or a low signal only if the strength of the detection signal output from the preamplifier circuit 51 exceeds a predetermined threshold. In this embodiment, timing comparator 52 and energy comparator 53 output a high signal if the strength of the input signal exceeds the threshold, and output a low signal if the strength of the input signal does not exceed the threshold. That is, timing comparator 52 and energy comparator 53 output detection signals with digital waveforms corresponding to the waveform of the detection signal from the corresponding pixel U.

[0084] In addition to the detection signals from timing comparator 52 and energy comparator 53, logic circuit 54 also receives clock signals and control signals supplied from clock driver 35. The control signals are supplied externally from the ASIC constructed from circuit board 20. The control signals include a reset signal and a stop signal. The clock signal, reset signal, and stop signal are H / L signals. Logic circuit 54 controls the supply of clock signals to timing counter 55 based on the aforementioned control signals and the detection signal from timing comparator 52. Logic circuit 54 also controls the supply of clock signals to energy counter 56 based on the aforementioned control signals and the detection signal from energy comparator 53.

[0085] Logic circuit 54 instructs timing counter 55 and energy counter 56 to reset the count based on the reset signal. Logic circuit 54 also instructs timing counter 55 and energy counter 56 to end the measurement time based on the stop signal.

[0086] Logic circuit 54 synchronizes the control signal with the clock signal. Logic circuit 54 supplies control signals, converts them into digital waveform detection signals and clock signals to timing counter 55, energy counter 56, delay line 57, and selector 58. Logic circuit 54 generates a signal that causes selector 58 to select the memory storing the counting results of energy counter 56 and encoder 59, and supplies it to selector 58.

[0087] 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. Energy counter 56 counts the number of clock signals corresponding to the energy of the light incident on the corresponding pixel U, based on the detection signal input from the clock circuit 54. Timing counter 55 and energy counter 56 store the counting results in memory 60 or memory 61.

[0088] Delay line 57 includes multiple delay elements. Delay line 57 utilizes the operation of these multiple delay elements to generate a time interval shorter than the period of the clock signal. Delay line 57 is controlled by a control voltage supplied from PLL 33. Encoder 59 counts the order of operation of the delay elements in delay line 57 based on signals from delay line 57 and converts this count into a binary signal. For example, encoder 59 counts the number of delay elements that operate from the rise of the detection signal converted into a digital waveform in logic circuit 54 until the next rise of the clock signal. Encoder 59 stores the counting result in memory 60 or memory 61.

[0089] Selector 58 selects a memory to store the counting results of timing counter 55, energy counter 56, and encoder 59. In this embodiment, selector 58 selects a memory from memory 60 and memory 61 to store the counting results based on a signal input from logic circuit 54.

[0090] Each signal processing unit SP's memory 60 and memory 61 stores the measurement results of light incident on the corresponding pixel U at different times during a predetermined measurement period by the timing measurement unit 42 and the energy measurement unit 43. In this embodiment, memory 60 and memory 61 are storage areas of a physically separate storage medium. Memory 60 and memory 61 may also be different storage areas within the same physical storage medium. The data stored in memory 60 and memory 61 is output to I / O port 38 as data for the corresponding pixel U.

[0091] Next, the operation of the photodetector 1 of this embodiment will be described. In the photodetector substrate 10, each APD 11 operates in Geiger mode. In Geiger mode, a reverse voltage greater than the breakdown voltage of the APD 11 is applied between the anode and cathode of each APD 11. This reverse voltage is also called the reverse bias voltage. 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 via a second semiconductor region PB. This electrode is electrically connected to a 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 via the pad electrode PE2, and a positive potential is applied to the third semiconductor region NA. The polarities of these potentials are opposite.

[0092] When light (photons) is incident on the APD11 contained in pixel U, photoelectric conversion occurs inside the semiconductor substrate to generate photoelectrons. Avalanche multiplication occurs in the region near the PN junction interface of the first semiconductor region PA. The amplified electron group flows to the circuit board 20 through the second semiconductor region PB and the aforementioned electrodes disposed on the main surface 1Na side of the semiconductor substrate 50. The electron group flows from the circuit board 20 into the third semiconductor region NA through the bump electrode BE, pad electrode PE1, electrode 22, and quench resistor 21. A current signal is detected on the circuit board 20 through the quench resistor 21, electrode 22, pad electrode PE1, and bump electrode BE. In other words, when light is incident on any light-receiving region S of the photodetector substrate 10, the generated photoelectrons are multiplied, and the signal of the multiplied photoelectrons is extracted from the bump electrode BE and input to the corresponding signal processing unit SP. The signal from each APD11 contained in the corresponding pixel U is input to each signal processing unit SP. In each signal processing unit SP, signals from multiple APD11 contained in the corresponding pixel U are processed and output as pixel data.

[0093] Next, refer to Figure 11 and Figure 12 The operation of each signal processing unit SP in this embodiment will be explained in detail. Figure 11 This diagram illustrates the processing operation of the energy comparator 53 and the logic circuit 54. Figure 12 It is a timing diagram representing the operation of the signal processing unit.

[0094] The timing measurement unit 42 and the energy measurement unit 43 use a timing comparator 52, an energy comparator 53, and a logic circuit 54 to process the detection signals output from the corresponding signal acquisition unit 41. Specifically, the timing measurement unit 42 uses the timing comparator 52 to select the detection signal output from the preamplifier circuit 51 and outputs the selected detection signal as a digital waveform. The energy measurement unit 43 uses the energy comparator 53 to select the detection signal output from the preamplifier circuit 51 and outputs the selected detection signal as a digital waveform. The detection signal output from the logic circuit 54 is an H / L signal.

[0095] Reference Figure 11 The process of converting the detection signal output from the preamplifier circuit 51 from an analog waveform to a digital waveform using an energy comparator 53 and logic circuit 54 will be explained. Figure 11 For illustrative purposes, analog signals P1, P2, P3, and P4 input to the energy comparator 53 are shown superimposed. Analog signals P1, P2, P3, and P4 are voltage signals, with wave height representing voltage intensity. Analog signals P1, P2, P3, and P4 have different wave heights than each other. Figure 11In this context, the threshold VTH set in the energy comparator 53 is represented in correspondence with the intensity of the analog signals P1, P2, P3, and P4. Figure 11 The diagram shows the digital signals D1, D2, and D3 output from the energy comparator 53. These digital signals D1, D2, and D3 are H / L signals, corresponding to the analog signals P2, P3, and P4, respectively.

[0096] Figure 11 In the example shown, the energy comparator 53 converts the analog signal from the detection signal received from the preamplifier circuit 51, which contains a component exceeding the threshold VTH, into a digital signal and outputs it. The maximum strength of the analog signal P1 is below the threshold VTH. Therefore, when the analog signal P1 is input to the energy comparator 53, the energy comparator 53 outputs a certain signal. In this embodiment, the energy comparator 53 outputs a low signal in this case.

[0097] The maximum intensity of analog signals P2, P3, and P4 exceeds the threshold VTH. Therefore, when analog signals P2, P3, and P4 are input to energy comparator 53, energy comparator 53 outputs an H / L signal corresponding to the waveform of the component exceeding the threshold VTH. Figure 11 As shown, the digital signals D1, D2, and D3 output from the energy comparator 53 switch from low to high when the corresponding analog signals P2, P3, and P4 exceed the threshold VTH. Conversely, the digital signals D1, D2, and D3 output from the energy comparator 53 switch from high to low when the corresponding analog signals P2, P3, and P4 are respectively below the threshold VTH. The digital signals D1, D2, and D3 are supplied to the energy counter 56 via logic circuit 54.

[0098] The timing measurement unit 42 detects the rise or fall of the detection signal output from the logic circuit 54, and uses the timing counter 55 to measure the timing when light is incident on the corresponding pixel U. The energy measurement unit 43 detects the rise and fall of the detection signal output from the logic circuit 54, and uses the energy counter 56 to measure the time between the rise and fall, which is taken as the energy of the light incident on the corresponding pixel U.

[0099] exist Figure 12 In the diagram, from top to bottom, are shown the reset signal, stop signal, clock signal, and detection signal output from logic circuit 54, as well as the counts of timing counter 55 and 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. The measurement period MP of the incident light to pixel U is determined using the reset and stop signals. The reset signal, for example, indicates the timing of light projection from the light source in the measuring device. The stop signal indicates a timing predetermined based on the scope of the object detection operation.

[0100] Timing counter 55 and energy counter 56 are reset by using the reset signal from logic circuit 54 as a trigger. When timing counter 55 detects a drop in the reset signal, it starts counting synchronously with the clock signal. When energy counter 56 detects a drop in the reset signal, it enters standby mode.

[0101] Timing counter 55 takes a detection signal based on the output signal from timing comparator 52 as a trigger and outputs a counting result. Timing counter 55 inputs the counting result from the detection of the reset signal falling to the detection of the detection signal rising into memory 60, 61.

[0102] For example, in Figure 12 In the example shown, the timing measurement unit 42 and the energy measurement unit 43 measure the light incident on the corresponding pixel U at different times during the measurement period MP. Therefore, a drop in the reset signal occurs during the measurement period MP. The timing counter 55 inputs the count from the detection of the reset signal drop to the detection of the first rise in the detection signal as the first timing measurement result T1 into the memory 60. The timing counter 55 inputs the count from the detection of the reset signal drop to the detection of the second rise in the detection signal as the second timing measurement result T2 into the memory 61.

[0103] The energy counter 56 uses the detection signal based on the output signal from the energy encoder 53 as a trigger to start and end the counting. The energy counter 56 inputs the counting result from the rise of the detection signal to the fall of the detection signal into the memory 60, 61.

[0104] For example, in Figure 12 In the example shown, the energy counter 56 inputs the count from the detection of the first rise in the detection signal to the detection of the first fall in the first detection signal as the first energy measurement result E1 into the memory 60. The energy counter 56 inputs the count from the detection of the second rise in the second detection signal to the detection of the second fall in the second energy measurement result E2 into the memory 61.

[0105] The timing counter 55's counting result is synchronized with the clock signal's period. Therefore, the timing counter 55 cannot measure time with a period shorter than the clock signal. The timing counter 55's counting result includes an error less than the clock signal's period. In this embodiment, the timing counter 55's counting result is corrected using the encoder 59's counting result, thereby deriving more accurate data.

[0106] In this embodiment, the light detection device 1 is described as a so-called back-attribution semiconductor light detection device. However, as a variation of this embodiment, the light detection device 1 may also be a so-called front-attribution semiconductor light detection device. (Refer to...) Figure 13 The structure of the photodetector substrate is described when the photodetector 1 is a front-incident semiconductor photodetector. Figure 13 A cross-sectional structure of the photodetector 1 of this embodiment is shown. In this modified example, the photodetector 1 differs from the photodetector 1 in that it has a photodetector substrate 10A instead of the photodetector substrate 10. Hereinafter, the differences from the above embodiment will be mainly explained. The photodetector substrate 10A in this modified example is a photodetector substrate used in so-called front-incident semiconductor photodetectors. That is, the photodetector 1 of this modified example is a front-incident semiconductor photodetector.

[0107] In the photodetector substrate 10A, multiple light-receiving regions S are disposed on the main 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 main surface 1Na side of the semiconductor substrate 50. The second semiconductor region NC is located on the main 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 that of the first semiconductor region PC. The third semiconductor region PD is the light-receiving region S. Each APD 11, starting from the main surface 1Na side, is sequentially P, which serves as the third semiconductor region PD. + Layer, P layer as the first semiconductor region PC, N layer as the second semiconductor region NC + It is composed of layers.

[0108] A groove 13 is formed on the semiconductor substrate 50 of the photodetector substrate 10A in a manner that surrounds the third semiconductor region PD. For example... Figure 13 As shown, the groove 13 penetrates the first semiconductor region PC in the Z-axis direction and reaches the second semiconductor region NC.

[0109] In addition to multiple APDs 11 and multiple quenching resistors 21, each pixel U of the photodetector substrate 10A also has a through electrode TE. The through electrode TE penetrates the semiconductor substrate 50 in the thickness direction. The thickness direction corresponds to, for example, the Z-axis direction. In the photodetector substrate 10A, the electrodes 22 are arranged in a grid pattern, passing through the multiple light-receiving regions S included in one pixel U when viewed from the Z-axis direction on the main surface 1Na side. Each quenching resistor 21 is disposed on the main surface 1Na side of the semiconductor substrate 50.

[0110] Electrode 23 extends from electrode 22 and is electrically connected to the corresponding through electrode TE. All quenching resistors 21 contained in a pixel U are electrically connected in parallel to each other via electrode TE using electrodes 22 and 23.

[0111] When viewed from the Z-axis, the multiple through electrodes TE are located in the photodetector region α, which has multiple pixels U arranged in a two-dimensional array. Each through electrode TE, except for the one located at one end of the photodetector substrate 10, is disposed in a region surrounded by four adjacent pixels U. Each through electrode TE is electrically connected to one of the four adjacent pixels U. The through electrodes TE and pixels U are arranged alternately in directions intersecting the X and Y axes. Each through electrode TE is electrically connected to multiple APDs 11, quenching resistors 21, electrodes 22, and electrodes 23 contained in the corresponding pixel U.

[0112] A through electrode TE is disposed within a through hole TH extending in the Z-axis direction. An insulating layer L11, the through electrode TE, and an insulating layer L12 are disposed within the through hole TH. The insulating layer L11 is formed on the inner circumferential 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 the space formed inside the through electrode TE. In this embodiment, the through electrode TE is cylindrical. The components disposed within the through hole TH are, from the inner circumferential surface side of the through hole TH, sequentially consisting of the insulating layer L11, the through electrode TE, and the insulating layer L12.

[0113] The photodetector substrate 10A has a pad electrode PE3, an electrode 24, and a pad electrode PE4 in each pixel U. The pad electrodes PE3, PE4, and 24 are configured corresponding to the through electrode TE. The pad electrode PE3 is located on the main surface 1Na side, and the electrodes 24 and PE4 are located on the main surface 1Nb side. The pad electrode PE3 is electrically connected to the electrode 23 via a connecting portion C3. The pad electrode PE3 electrically connects the electrode 23 to the through electrode TE.

[0114] 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 by the insulating layer L13. Electrodes 22 and 23 are disposed on the insulating layer L13 and are covered by the insulating layer L14.

[0115] Electrode 24 and pad electrode PE4 are disposed on the main surface 1Nb via insulating layer L15. Electrode 24 has an end connected to the through electrode TE and an end connected to the pad electrode PE4. Electrode 24 connects the through electrode TE and the pad electrode PE4. Electrode 24 is covered by insulating layer L16. Pad electrode PE4 is connected to bump electrode BE. Except for the portion of pad electrode PE4 connected to bump electrode BE, it is covered by insulating layer L16.

[0116] When viewed from the Z-axis direction, the multiple pad electrodes PE3 and PE4 of the photodetector substrate 10A are located in the photodetector region α, which has multiple pixels U arranged in a two-dimensional pattern. When viewed from the Z-axis direction, each pad electrode PE4 is arranged on the main surface 1Nb side in a manner that overlaps with at least one of the multiple APD11 of the corresponding pixel U.

[0117] Electrodes 22, 23, 24, pad electrodes PE3, PE4, connector C3, and through electrode TE comprise metal. Electrodes 22, 23, 24, pad electrodes PE3, PE4, connector C3, and through electrode TE, for example, comprise aluminum (Al). When the semiconductor substrate 50 comprises Si, copper (Cu) can be used as the electrode material, in addition to aluminum. Electrodes 22, 23, 24, pad electrodes PE3, PE4, connector C3, and through electrode TE can also be formed integrally. Electrodes 22, 23, 24, pad electrodes PE3, PE4, connector C3, and through electrode TE, for example, are formed by sputtering.

[0118] Insulating layers L11, L12, L13, L14, L15, and L16 may contain, for example, SiO2, SiN, or resin. The insulating layers L11, L12, L13, L14, L15, and L16 may be formed by thermal oxidation, sputtering, CVD, or resin coating.

[0119] The photodetector substrate 10A is mounted on the circuit board 20, just like the photodetector substrate 10. The photodetector substrate 10A is connected to the circuit board 20 in the Z-axis direction. The photodetector substrate 10A and the circuit board 20 are connected by a bump electrode BE. Therefore, in this modified example, the circuit board 20 is electrically connected to the pad electrode PE4 via the bump electrode BE. The detection signals output from the plurality of APDs 11 included in the pixel U of the photodetector substrate 10A are guided to the corresponding signal processing unit SP through the quenching resistor 21, electrode 22, pad electrode PE4, and bump electrode BE.

[0120] In this modified example, when viewed from the Z-axis direction, the light detection region α and the signal processing region β at least partially overlap. The light detection region α includes multiple unit regions α1 each having a plurality of pixels U. The signal processing region β includes multiple unit regions β1 each having a plurality of signal processing units SP. When viewed from the Z-axis direction, the unit region α1 having each pixel U and the unit region β1 having the corresponding signal processing unit SP overlap at least partially. When viewed from the Z-axis direction, the unit region α1 having each pixel U and the unit region β1 having the corresponding signal processing unit SP have portions that are offset from each other in the direction along the main surface 1Na and do not overlap. When viewed from the Z-axis direction, the center of gravity of the pad electrode PE4 is offset from the center of gravity of the unit region β1 having the signal processing unit SP connected to the pad electrode PE4 towards the signal acquisition unit 41.

[0121] As explained above, the light detection device 1 includes light detection substrates 10 and 10A having a plurality of pixels U arranged in a two-dimensional pattern. Each pixel U has a plurality of APDs 11 operating in Geiger mode. Each signal processing unit SP acquires detection signals through the pad electrodes PE1 and PE4 of each pixel U. Therefore, in this light detection device 1, the sensitivity of each of the two-dimensionally arranged pixels U is improved. In this configuration, since the waveform of the light detection signal from each pixel U is steep, the influence of the so-called time walk effect is also reduced. Therefore, when detecting reflected light from light simultaneously projected from a light source onto a two-dimensional area, the accuracy and precision of detection are also improved.

[0122] In this light detection device 1, the energy measurement unit 43 of each signal processing unit SP measures the light energy based on the detection signal output from each pixel U, which has multiple APDs 11. Therefore, the light detection device 1 can distinguish between reflected light from an object and ambient light based on the energy difference. Thus, the influence of ambient light can be reduced from the detection results, and the detection accuracy can be further improved.

[0123] The circuit board 20 is connected to the light detection boards 10 and 10A in the Z-axis direction. The light detection region α, which has multiple pixels U, overlaps at least partially with the signal processing region β, which has multiple signal processing units SP. Therefore, in the direction parallel to the main surface 1Na, the light detection device 1 can be miniaturized (compacted), and the electrical connection path between each pixel U and each signal processing unit SP can be reduced.

[0124] Each signal processing unit SP includes a storage unit 44. Assuming the storage unit 44 is located outside the signal processing unit SP, a large space is required between adjacent signal processing units SP in order to extend the wiring from the timing measurement unit 42 and the energy measurement unit 43 to the outside. With such a large space required between adjacent signal processing units SP, it is difficult to reduce the size of the photodetector 1. In this photodetector 1, since each signal processing unit SP includes a storage unit 44, the number of wirings extending from each signal processing unit SP to the outside is reduced. Therefore, further miniaturization of the photodetector 1 is possible.

[0125] When viewed from the Z-axis direction, the light detection substrate 10 is surrounded by the edge of the circuit substrate 20. In this case, it is possible to further miniaturize the light detection device and further reduce the electrical connection path between each pixel and each signal processing unit.

[0126] When viewed from the Z-axis, the light detection 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, it is possible to further miniaturize the light detection device and further reduce the electrical connection path between each pixel and each signal processing unit.

[0127] When viewed from the Z-axis, the signal processing region β has a portion R3 that does not overlap with the light detection region α. ​​The area of ​​portion R1 is larger than the combined area of ​​portion R2 and portion R3. In this case, further miniaturization of the light detection device can be achieved, and the electrical connection path between each pixel and each signal processing unit can be further reduced.

[0128] The light detection region α has a unit region α1 for each of the plurality of pixels U, and the signal processing region β has a unit region β1 for the signal processing unit SP corresponding to the pixel U. When viewed from the Z-axis direction, they at least partially overlap. In this case, the light detection device 1 can be further miniaturized, and the electrical connection path between each pixel U and each signal processing unit SP can be further reduced.

[0129] When viewed from the Z-axis, the center of gravity of the pad electrodes PE1 and PE4 is shifted from the center of gravity of the unit region β1 of the signal processing unit SP, which is connected to the pad electrodes PE1 and PE4, towards the signal acquisition unit 41. In this case, the electrical connection path between each pixel U and each signal processing unit SP is further reduced. When viewed from the Z-axis, the wiring used to apply the driving voltage to each signal processing unit SP can be placed in the center of the signal processing unit SP, thus facilitating wiring guidance.

[0130] The light detection region α contains a unit region α1 for each pixel U, and the signal processing region β contains a unit region β1 for the signal processing unit SP corresponding to that pixel. When viewed from the Z-axis direction, they are offset along the direction of the main surface 1Na. The unit region α1 for each pixel U and the unit region β1 for the signal processing unit SP corresponding to that pixel have non-overlapping portions. In this case, the electrical connection path between each pixel U and each signal processing unit SP can be further reduced.

[0131] The detection signal output from the corresponding pixel U is a current signal. Each signal acquisition unit 41 includes a current-to-voltage conversion circuit 70 and a signal transmission circuit 75. The current-to-voltage conversion circuit 70 converts the detection signal into a voltage. The signal transmission circuit 75 inputs the voltage signal output from the current-to-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 in parallel with the current-to-voltage conversion circuit 70 to the energy measurement unit 43. The energy measurement unit 43 measures the energy of the incident light directed to the corresponding pixel U based on the waveform of the signal input from the signal transmission circuit 75. Thus, since the capacitor is connected in parallel with the current-to-voltage conversion circuit 70 to the energy measurement unit 43, the waveform becomes smoother. When the waveform becomes smoother, the energy measurement accuracy in the energy measurement unit 43 can be improved.

[0132] Figure 14 This diagram compares the signals input to the timing comparator 52 with the signals input to the energy comparator 53. Multiple signals S1 each represent the signals input to the timing comparator 52 when light of different intensities is incident on the pixel U. Multiple signals S2 each represent the signals input to the energy comparator 53 when light of different intensities is incident on the pixel U. No signal transmission circuit including a capacitor is provided before the timing comparator 52; in contrast, a signal transmission circuit 75 including a capacitor 78 is provided before the energy comparator 53.

[0133] When the capacitor is connected in parallel with the current-to-voltage conversion circuit 70 in the energy measurement unit 43, the waveform of the signal input to the energy comparator 53 becomes smoother due to the discharge of the capacitor. When the waveform of the signal input to the energy comparator 53 becomes smoother, the time difference measured in the energy counter 56, corresponding to the energy difference of the incident light to the pixel U, also increases. Therefore, the energy measurement accuracy in the energy measurement unit 43 is improved. The larger the capacitance of the capacitor connected in parallel with the current-to-voltage conversion circuit 70 in the energy measurement unit 43, the smoother the waveform of the signal.

[0134] In this light detection device 1, the signal transmission circuit 75 includes a Miller capacitor 77 composed of a capacitor 78. In this case, even without increasing the size of the capacitor region, the same effect as when using a larger capacitor can be obtained based on the voltage input to the signal transmission circuit 75. Therefore, energy measurement accuracy can be ensured, and multiple signal processing units SP can be formed in a compact manner in conjunction with multiple pixels U arranged in a two-dimensional pattern.

[0135] The energy measurement unit 43 measures the energy of incident light onto the corresponding pixel U by measuring the time during which the wavelength of the signal input from the corresponding signal acquisition unit 41 is above a threshold VTH. This energy measurement unit 43 can be implemented using simple digital processing and can also be physically miniaturized. Therefore, the size of the area of ​​the energy measurement unit 43 can be reduced. As a result, multiple signal processing units SP can be miniaturized to accommodate multiple pixels U arranged in a two-dimensional configuration.

[0136] Each signal processing unit SP's storage unit 44 includes multiple memories 60 and 61. The multiple memories 60 and 61 respectively store the measurement results of incident light incident on the corresponding pixel U at different times during a predetermined measurement period by the timing measurement unit 42 and the energy measurement unit 43. Since the light detection device 1 includes memories 60 and 61, even if the timing measurement unit 42 and the energy measurement unit 43 output the measurement results of ambient light incident on the pixel U during the aforementioned predetermined measurement period, the measurement results of reflected light from the object are also stored. For example, as... Figure 12 In the example shown, even when the ambient light signal is output from the logic circuit 54, multiple energy measurement results E1 and E2 from the measurement period MP are stored. Therefore, even if the energy measurement result E1 is a measurement result based on the ambient light signal, the measurement result of reflected light from the object can be stored as the energy measurement result E2. In the light detection device 1, each signal processing unit SP includes the aforementioned multiple memories 60 and 61. Therefore, the influence of ambient light is reduced, and the number of wirings leading from each signal processing unit SP to the outside of the signal processing unit SP is reduced.

[0137] While the embodiments and variations of the present invention have been described above, the present invention is not limited to the embodiments and variations described above, and various modifications can be made without departing from its spirit.

[0138] For example, in the above embodiments, such as Figure 8 As shown, when viewed from the Z-axis, the pad electrode PE1 overlaps with the timing comparator 52 and the energy comparator 53. Figure 3 As shown, relative to the unit region α1 where each pixel U is located, the unit region β1 where the corresponding signal processing unit SP is located is offset in the X-axis direction. However, as a variation of this embodiment, such as Figure 15 As shown, the pad electrode PE1 can also overlap with the preamplifier circuit 51 when viewed from the Z-axis direction. In this modified example, as... Figure 16 As shown, when viewed from the Z-axis direction, the light detection region α and the signal processing region β are offset relative to each other in the XY-axis direction. Figure 15 This is a diagram showing the positional relationship between the pixels and the signal processing unit in this modified example. Figure 16This is a diagram showing the positional relationship between the signal acquisition unit and the pad electrode in this modified example.

[0139] Figure 17 It shows Figure 15 and Figure 16 In the illustrated variation, the positional relationship between the light detection region α and the signal processing region β when viewed from the Z-axis direction is shown. In this variation, the light detection region α also includes a portion R1 that overlaps with the signal processing region β when 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 light detection region α when viewed from the Z-axis direction and a portion R3 that does not overlap with the light detection region α. Figure 17 In the diagram, part R1 is marked with a shaded line. When viewed from the Z-axis, the area of ​​part R1 is larger than the area of ​​part R2. When viewed from the Z-axis, the area of ​​part R1 is larger than the combined area of ​​parts R2 and R3.

[0140] like Figure 16 As shown, relative to the unit region α1 with each pixel U, the unit region β1 with the corresponding signal processing unit SP is offset in the X and Y axis directions. Figure 15 This indicates the positional relationship between pixel U and signal processing unit SP in the light detection device 1 of this embodiment's modified example. Figure 16 This is a diagram showing the positional relationship between the signal acquisition unit 41 and the pad electrode PE1 in the photodetector 1 of the modified embodiment of this invention.

[0141] In the above-described embodiments and variations, the photodetector substrates 10 and 10A are connected to the circuit board 20 via bump electrodes BE, but the structure of the photodetector device 1 is not limited to this. The pad electrodes PE1 and PE4 of the photodetector substrates 10 and 10A may also be electrically connected to the signal processing unit SP of the circuit board 20 without passing through the bump electrodes BE.

[0142] In the above embodiment, the energy measurement unit 43 uses a TOT circuit to measure the time during which the wave height of the signal input from the corresponding signal acquisition unit 41 is above a threshold in order to measure the energy of the incident light to the corresponding pixel U. However, as a variation of this embodiment, the energy measurement unit 43 can also use an ADC (Analog-Digital Converter) to measure the energy. In this case, since the energy measurement unit 43 can detect the wave height of the signal input from the corresponding signal acquisition unit 41 with higher accuracy, it can measure the energy of the incident light to the corresponding pixel U with higher accuracy. As a variation of this embodiment, the energy measurement unit 43 can also use multiple comparators with different thresholds to measure the energy. In these variations, the energy measurement unit 43 requires more space compared to the case where a TOT circuit is used.

[0143] In the above-described embodiments and variations, each signal processing unit SP is connected to only one pad electrode PE1. Multiple signal processing units SP are each connected to a different pixel U via their respective pad electrodes PE1. The photodetector 1 does not include a switch for switching the electrical connection between each pixel U and the corresponding signal processing unit SP. In other words, the signal output from each pixel U is input to only one fixed signal processing unit SP via its corresponding bump electrode BE. However, a switch for switching the signal processing unit SP electrically connected to each pixel U may also be included.

[0144] The pad electrodes PE1 and PE2 include electrodes with shapes where the width is greater than the thickness, and electrodes where the thickness is greater than the 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 is referred to as the length in the Z-axis direction. The width of the pad electrodes PE1 and PE2 is referred to as the length in a direction orthogonal to the Z-axis direction.

[0145] In the above-described embodiments and variations, the light detection region α is defined by the inner wall of the groove 13 surrounding the light detection region α. ​​However, the light detection region α may not be surrounded by the groove 13. In this case, when viewed from the Z-axis direction, the outer edge of the light detection region α coincides with the outer edge of the outermost third semiconductor regions NA and PD.

[0146] In the above-described embodiments and variations, the unit region α1 is defined by the inner wall of the groove 13 surrounding the unit region α1. However, the unit region α1 may not 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 edge of the outermost third semiconductor region NA, PD of the pixel U located within the unit region α1.

[0147] Explanation of reference numerals in the attached figures

[0148] 1…Photodetector, 10, 10A…Photodetector substrate, 11…Avalanche photodiode, 20…Circuit board, 20d…Edge, 21…Quenching resistor, 41…Signal acquisition unit, 42…Timing measurement unit, 43…Energy measurement unit, 44…Storage unit, 50…Semiconductor substrate, 60, 61…Memory, 70…Current-to-voltage conversion circuit, 75…Signal transmission circuit, 77…Miller capacitor, 1Na, 1Nb…Main surface, MP…Measurement period, PE1, PE4…Pad electrodes, R1, R2, R3…Parts, S…Light-receiving area, SP…Signal processing unit, U…Pixel, VTH…Threshold, α…Photodetector area, α1, β1…Unit area, β…Signal processing area.

Claims

1. A light detection device, comprising: A light detection substrate has a semiconductor substrate comprising a first main surface and a second main surface that are opposite to each other, and has a light detection area having a plurality of pixels arranged in two dimensions when viewed from a direction orthogonal to the first main surface; as well as A circuit board is connected to the photodetector board in a direction orthogonal to the first main surface, and has a signal processing area provided with multiple signal processing units for processing detection signals output from the corresponding pixel. The photodetector substrate includes, in each pixel: Multiple avalanche photodiodes, each having a light-receiving area disposed on the semiconductor substrate and operating in Geiger mode; Multiple quenching resistors are electrically connected in series with the corresponding avalanche photodiodes; and The pad electrode, wherein the plurality of quenching resistors are electrically connected in parallel to each other. When viewed from a direction orthogonal to the first main surface, the light-receiving areas of the plurality of avalanche photodiodes are arranged in two dimensions in each pixel. Each of the aforementioned signal processing units comprises, for each of the aforementioned pixels: The signal acquisition unit acquires the detection signal through the corresponding pad electrode; A timing measurement unit measures the timing of light incident on the corresponding pixel based on the detection signal; An energy measurement unit, based on the detection signal, measures the energy of incident light directed towards the corresponding pixel; and A storage unit that stores the measurement results from the timing measurement unit and the energy measurement unit; When viewed from a direction orthogonal to the first main surface, the light detection area and the signal processing area overlap by at least a portion.

2. The optical detection device according to claim 1, wherein, When viewed from a direction orthogonal to the first main surface, the light detection substrate is surrounded by the edge of the circuit substrate.

3. The optical detection device according to claim 1 or 2, wherein, When viewed from a direction orthogonal to the first principal surface, the light detection region has a first portion that overlaps with the signal processing region and a second portion that does not overlap with the signal processing region. The area of ​​the first part is larger than the area of ​​the second part.

4. The optical detection device according to claim 3, wherein, When viewed from a direction orthogonal to the first main surface, the signal processing region has a third portion that does not overlap with the light detection region; The area of ​​the first part is greater than the sum of the areas of the second part and the third part.

5. The light detection device according to any one of claims 1 to 4, wherein, The light detection region has a unit region for each pixel, and the signal processing region has a unit region for the signal processing unit corresponding to the pixel, which overlaps at least partially when viewed from a direction orthogonal to the first main surface.

6. The light detection device according to any one of claims 1 to 5, wherein, When viewed from a direction orthogonal to the first main surface, the center of gravity of the pad electrode shifts from the center of gravity of the unit area of ​​the signal processing unit connected to the pad electrode toward the signal acquisition unit.

7. The optical detection device according to claim 5, wherein, The light detection region is provided with a unit region for each pixel, and the signal processing region is provided with a unit region for the signal processing unit corresponding to the pixel. When viewed from a direction orthogonal to the first main surface, the units have portions that are offset in the direction along the first main surface and do not overlap with each other.

8. The light detection device according to any one of claims 1 to 7, wherein, The detection signal is a current signal. The signal acquisition unit of each signal processing unit includes: a current-to-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-to-voltage conversion circuit to the energy measurement unit. The signal transmission circuit includes a Miller capacitor connected in parallel with the current-to-voltage conversion circuit to the energy measurement unit. The energy measurement unit measures the energy of the incident light directed to the corresponding pixel based on the waveform of the signal input from the signal transmission circuit.

9. The light detection device according to any one of claims 1 to 8, wherein, The energy measurement unit measures the energy of incident light toward the corresponding pixel by measuring the time during which the wave height of the signal input from the corresponding signal acquisition unit is above a threshold.

10. The light detection device according to any one of claims 1 to 9, wherein, The storage unit of each signal processing unit includes multiple storage areas, which respectively store the measurement results of light incident on the corresponding pixel at different times during a predetermined measurement period by the timing measurement unit and the energy measurement unit.

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