Photoelectric conversion device, photoelectric conversion system, and mobile body

Abstract

The present application provides a photoelectric conversion device, a photoelectric conversion system, and a mobile body. The photoelectric conversion device includes a plurality of avalanche diodes provided in a layer having a first surface and a second surface opposite to the first surface, wherein each of the plurality of avalanche diodes includes a first region of a first conductivity type at a first depth, a second region of a second conductivity type at a second depth, and a third region of the second conductivity type at a third depth, the second depth is greater than the first depth with respect to the second surface, and the third depth is greater than the second depth with respect to the second surface, wherein the layer includes a plurality of structures provided in the first surface, and wherein an effective period of the plurality of structures is less than hc / E a , h represents Planck's constant [J·s], c represents the speed of light [m / s], and E a represents the band gap of the substrate [J].

Description

Technical Field

[0001] The embodiments relate to photoelectric conversion devices, photoelectric conversion systems, and mobile bodies. Background Technology

[0002] There exists a photoelectric conversion device that includes a patterned structure disposed on the light-receiving surface of a photoelectric conversion element to refract incident light, thereby increasing the optical length of the incident light in the photoelectric conversion element and improving quantum efficiency. Japanese Patent Application Publication No. 2021-002542 discusses a single-photon avalanche diode (SPAD) that includes a patterned structure called a moth-eye structure on the light-incident surface side of its substrate. Summary of the Invention

[0003] According to one aspect of an embodiment, a photoelectric conversion device includes a plurality of avalanche diodes disposed in a layer having a first surface and a second surface opposite to the first surface, wherein each of the plurality of avalanche diodes includes a first region of a first conductivity type located at a first depth, a second region of a second conductivity type located at a second depth, and a third region of the second conductivity type located at a third depth, wherein the second depth is greater than the first depth relative to the second surface, and the third depth is greater than the second depth relative to the second surface, wherein the layer includes a plurality of structures disposed in the first surface, and wherein the effective period of the plurality of structures is less than hc / E. a Where h represents Planck's constant [J·s], c represents the speed of light [m / s], and E a The band gap of the substrate is indicated [J].

[0004] According to another aspect of the embodiment, a photoelectric conversion device includes a plurality of avalanche diodes disposed in a layer having a first surface and a second surface opposite to the first surface, wherein each of the plurality of avalanche diodes includes a first region of a first conductivity type located at a first depth, a second region of a second conductivity type located at a second depth, and a third region of the second conductivity type located at a third depth, wherein the second depth is greater than the first depth relative to the second surface, and the third depth is greater than the second depth relative to the second surface, wherein the layer includes a plurality of structures disposed in the first surface, and wherein the effective period of the plurality of structures is less than 1.1 μm.

[0005] Other features of this disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0006] Figure 1 This is a schematic diagram illustrating a photoelectric conversion device according to an exemplary embodiment.

[0007] Figure 2This is a schematic diagram showing a photodiode (PD) substrate (sensor substrate) of a photoelectric conversion device according to an exemplary embodiment.

[0008] Figure 3 This is a schematic diagram showing a circuit board of a photoelectric conversion device according to an exemplary embodiment.

[0009] Figure 4 An example of the construction of a pixel circuit of a photoelectric conversion device according to an exemplary embodiment is shown.

[0010] Figure 5A , Figure 5B and Figure 5C This is a schematic diagram illustrating the driving of the pixel circuit of a photoelectric conversion device according to an exemplary embodiment.

[0011] Figure 6 This is a cross-sectional view of a photoelectric conversion element according to a first exemplary embodiment.

[0012] Figure 7 It is a potential diagram of a photoelectric conversion element according to a first exemplary embodiment.

[0013] Figure 8 This is a cross-sectional view of the trench structure of the photoelectric conversion element according to the first exemplary embodiment.

[0014] Figure 9A and Figure 9B This is a plan view of a photoelectric conversion element according to a first exemplary embodiment.

[0015] Figure 10 A comparative example of a photoelectric conversion element according to a first exemplary embodiment is shown.

[0016] Figure 11 A cross-section of a photoelectric conversion element according to a first exemplary embodiment is shown.

[0017] Figure 12A and Figure 12B This is a plan view of a photoelectric conversion element according to a second exemplary embodiment.

[0018] Figure 13A and Figure 13B This is a plan view of a photoelectric conversion element according to a variant of the second exemplary embodiment.

[0019] Figure 14 This is a plan view of a photoelectric conversion device according to a third exemplary embodiment.

[0020] Figure 15 This is a plan view of a photoelectric conversion element according to a third exemplary embodiment.

[0021] Figure 16This is a cross-sectional view of a photoelectric conversion element according to a third exemplary embodiment.

[0022] Figure 17 This is a cross-sectional view of a photoelectric conversion element according to a third exemplary embodiment.

[0023] Figure 18 This is a cross-sectional view of a photoelectric conversion element according to a fourth exemplary embodiment.

[0024] Figure 19A and Figure 19B This is a plan view of a photoelectric conversion element according to a fourth exemplary embodiment.

[0025] Figure 20 A comparative example of a photoelectric conversion element according to a fourth exemplary embodiment is shown.

[0026] Figure 21 This is a cross-sectional view of the photoelectric conversion element according to the fifth exemplary embodiment.

[0027] Figure 22A , Figure 22B and Figure 22C This is a cross-sectional view of the trench structure of the photoelectric conversion element according to the sixth exemplary embodiment.

[0028] Figure 23 This is a cross-sectional view of a photoelectric conversion element according to the seventh exemplary embodiment.

[0029] Figure 24A and Figure 24B This is a plan view of a photoelectric conversion element according to the seventh exemplary embodiment.

[0030] Figure 25 This is a functional block diagram of a photoelectric conversion system according to the eighth exemplary embodiment.

[0031] Figure 26A and Figure 26B This is a functional block diagram of a photoelectric conversion system according to the ninth exemplary embodiment.

[0032] Figure 27 This is a functional block diagram of a photoelectric conversion system according to the tenth exemplary embodiment.

[0033] Figure 28 This is a functional block diagram of a photoelectric conversion system according to the eleventh exemplary embodiment.

[0034] Figure 29A and Figure 29B This is a perspective view of a photoelectric conversion system according to the twelfth exemplary embodiment. Detailed Implementation

[0035] The patterns described below are intended to illustrate the technical concept of this disclosure and not to limit it. For clarity of description, the dimensions and / or positional relationships of the components shown in the drawings may be exaggerated. In the following description, similar parts may be indicated by the same reference numerals, and their description may be omitted.

[0036] Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. In the following description, terms describing specific directions or positions (such as “up,” “down,” “right,” and “left,” and other phrases including these terms) are appropriately used. These terms and phrases are used to facilitate understanding of the exemplary embodiments with reference to the accompanying drawings, and the technical scope of the present disclosure is not limited by the meaning of these terms or phrases.

[0037] As used in this paper, a plan view is a view taken in a direction perpendicular to the light incident surface of the semiconductor layer. A cross-section is a plane in a direction perpendicular to the light incident surface of the semiconductor layer. If the light incident surface of the semiconductor layer is rough under a microscope, the plan view is defined with reference to the light incident surface of the semiconductor layer as seen under a microscope.

[0038] In the following description, the anode of the avalanche photodiode (APD) is fixed at a certain potential, and the signal is extracted from the cathode. Therefore, the semiconductor region of the first conductivity type, where the majority carriers are charges of the same polarity as the signal charge, is an N-type semiconductor region. The semiconductor region of the second conductivity type, where the majority carriers are charges of the opposite polarity to the signal charge, is a P-type semiconductor region.

[0039] The exemplary embodiments of this disclosure also hold true if the cathode of the APD is fixed at a certain potential and the signal is extracted from the anode. In this case, the semiconductor region of the first conductivity type, in which the majority charge carriers have the same polarity as the signal charge, refers to a P-type semiconductor region. The semiconductor region of the second conductivity type, in which the majority charge carriers have the opposite polarity to the signal charge, refers to an N-type semiconductor region. Although in the following description, either node of the APD is fixed at a certain potential, the potentials of both nodes can be changed.

[0040] As used herein, the simple phrase "impurity concentration" refers to the net impurity concentration after compensating for impurities of the opposite conductance type. In other words, "impurity concentration" refers to the net doping concentration. Regions where the P-type impurity doping concentration is higher than the N-type impurity doping concentration are P-type semiconductor regions. Conversely, regions where the N-type impurity doping concentration is higher than the P-type impurity doping concentration are N-type semiconductor regions.

[0041] Reference Figures 1 to 5C This document describes common constructions of exemplary embodiments of the photoelectric conversion device and its driving method according to this disclosure.

[0042] Figure 1 This is a diagram illustrating the construction of a stacked photoelectric conversion device 100 according to an exemplary embodiment of the present disclosure.

[0043] The photoelectric conversion device 100 includes two substrates: a sensor substrate 11 and a circuit substrate 21 stacked together and electrically connected to each other. The sensor substrate 11 includes a first semiconductor layer (which includes a photoelectric conversion element 102, described below) and a first wiring structure. The circuit substrate 21 includes a second semiconductor layer (which includes circuitry such as a signal processing unit 103, described below) and a second wiring structure. The photoelectric conversion device 100 is constructed by sequentially stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer. The photoelectric conversion device described in the following exemplary embodiments is a back-illuminated photoelectric conversion device, with light incident on its first surface and the circuit substrate located on its second surface.

[0044] In the following description, sensor substrate 11 and circuit substrate 21 are described as diced chips. However, sensor substrate 11 and circuit substrate 21 are not limited to chips. For example, the substrate can be a wafer. Substrates in a wafer state can be stacked before dicing. Diced chips can be stacked and bonded.

[0045] The sensor substrate 11 includes a pixel region 12. The circuit substrate 21 includes a circuit region 22 for processing signals detected in the pixel region 12.

[0046] Figure 2 This is a diagram showing an example layout of the sensor substrate 11. Pixels 101, each including a photoelectric conversion element 102 (which includes an APD), are arranged in a two-dimensional array in the plan view to form pixel regions 12.

[0047] Typically, pixel 101 is the pixel used to form an image. However, in time-of-flight (TOF) applications, pixel 101 does not necessarily need to form an image. More specifically, pixel 101 can be a pixel used to measure the arrival time and amount of light.

[0048] Figure 3 This is a structural diagram of the circuit board 21. The circuit board 21 includes: a structure for processing materials... Figure 2 The photoelectric conversion element 102, the signal processing unit 103 for photoelectric conversion charge, the reading circuit (column circuit) 112, the control pulse generation unit 115, the horizontal scanning circuit unit 111, the signal line 113, and the vertical scanning circuit unit 110.

[0049] Figure 2 The photoelectric conversion element 102 and Figure 3 The signal processing unit 103 is electrically connected via connection wiring set for each pixel.

[0050] Vertical scanning circuit unit 110 receives control pulses supplied from control pulse generation unit 115 and supplies the control pulses to pixel 101. Logic circuits (such as shift registers and address decoders) are used in vertical scanning circuit unit 110.

[0051] The signal output from the photoelectric conversion element 102 of pixel 101 is processed by the signal processing unit 103. Each signal processing unit 103 includes a counter and a memory. The memory stores digital values ​​(digital signals).

[0052] The horizontal scanning circuit unit 111 inputs control pulses to the signal processing unit 103 for sequentially selecting columns in order to read the digital signals stored in the memory of each pixel.

[0053] The signal processing unit 103 outputs a signal (digital signal) to the signal line 113 from the pixel selected in the selected column by the vertical scanning circuit unit 110.

[0054] The signal output to signal line 113 is output to a recording unit or signal processing unit outside the photoelectric conversion device 100 via output circuit 114.

[0055] exist Figure 2 In this embodiment, the photoelectric conversion element 102 can be arranged one-dimensionally in the pixel region 12. The effects of this exemplary embodiment can be achieved even using only one pixel 101, and the use of only one pixel 101 is also included in this disclosure. It is not necessary to provide the signal processing unit 103 functionality one-to-one for all photoelectric conversion elements 102. For example, multiple photoelectric conversion elements 102 can share a single signal processing unit 103 and perform signal processing sequentially.

[0056] like Figure 2 and Figure 3 As shown in the plan view, multiple signal processing units 103 are disposed in the region overlapping with the pixel region 12. In the plan view, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the column circuit 112, the output circuit 114, and the control pulse generation unit 115 are disposed in the region overlapping with the region between the end of the sensor substrate 11 and the end of the pixel region 12. In other words, the sensor substrate 11 includes the pixel region 12 and non-pixel regions surrounding the pixel region 12. In the plan view, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the column circuit 112, the output circuit 114, and the control pulse generation unit 115 are disposed in the region overlapping with the non-pixel regions.

[0057] Figure 4 It includes Figure 2 and Figure 3 An example of a block diagram of the equivalent circuit.

[0058] exist Figure 2 In this design, a photoelectric conversion element 102, including an APD 201, is disposed on a sensor substrate 11. Other components are disposed on a circuit board 21.

[0059] Each APD 201 generates charge pairs corresponding to the incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201. A voltage VH (second voltage), higher than the voltage VL supplied to the anode, is supplied to the cathode of the APD 201. A reverse bias voltage for inducing avalanche multiplication operation of the APD 201 is supplied to the anode and cathode. When this voltage is supplied, the charges generated by the incident light cause avalanche multiplication to generate an avalanche current.

[0060] The APD 201 can be supplied with reverse bias in Geiger mode and linear mode. In Geiger mode, the APD 201 operates when the potential difference between the anode and cathode is greater than the breakdown voltage. In linear mode, the APD 201 operates when the potential difference between the anode and cathode is close to or less than the breakdown voltage.

[0061] An APD operating in Geiger mode is called a single-photon avalanche diode (SPAD). For example, the voltage VL (first voltage) is -30V and the voltage VH (second voltage) is 1V. The APD 201 can operate in either linear or Geiger mode. SPADs are used because they offer a higher potential difference and significantly better breakdown voltage compared to APDs in linear mode.

[0062] Quenching element 202 is connected to APD 201 and the power supply for voltage VH. When the signal is doubled by avalanche multiplication, quenching element 202 acts as a load circuit (quenching circuit) to reduce the voltage supplied to APD 201 and suppress avalanche multiplication (quenching operation). Quenching element 202 also functions to restore the voltage supplied to APD 201 to voltage VH by flowing a current equal to the voltage drop caused by the quenching operation (recharge operation).

[0063] The signal processing unit 103 includes a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. As used herein, the signal processing unit 103 includes at least one of the waveform shaping unit 210, the counter circuit 211, and the selection circuit 212.

[0064] The waveform shaping unit 210 shapes the waveform of the change in the potential of the cathode of the APD 201 when a photon is detected and outputs a pulse signal. An example of the waveform shaping unit 210 is an inverter circuit. Figure 4An example using an inverter as waveform shaping unit 210 is shown; however, a circuit comprising multiple inverters connected in series can be used. Other circuits with waveform shaping effects can also be used.

[0065] The counter circuit 211 counts the pulse signal output from the waveform shaping unit 210 and holds the count value. When a control pulse pRES is supplied via the drive line 213, the signal (count value) held in the counter circuit 211 is reset.

[0066] via Figure 4 drive line 214 (in Figure 3 (Not shown in the image) will control the pulse pSEL from... Figure 3 The vertical scanning circuit unit 110 is supplied to the selection circuit 212. The selection circuit 212 switches the electrical connection and disconnection between the counter circuit 211 and the signal line 113. The selection circuit 212 includes, for example, a buffer circuit for the output signal.

[0067] Switches such as transistors can be positioned between the quenching element 202 and the APD 201, and between the photoelectric conversion element 102 and the signal processing unit 103, to switch the electrical connections. Similarly, switches such as transistors can be used to electrically switch the supply of voltage VH or VL to the photoelectric conversion element 102.

[0068] This exemplary embodiment is described using a configuration employing counter circuit 211. However, the photoelectric conversion device 100 can be configured to obtain pulse detection timing using a time-to-digital converter (TDC) and a memory instead of counter circuit 211. In this case, the generation timing of the pulse signal output from waveform shaping unit 210 is converted into a digital signal by the TDC. To measure the timing of the pulse signal, a control pulse pREF (reference signal) is transmitted from the waveform shaping unit 210 via a drive line. Figure 1 The vertical scanning circuit unit 110 is supplied to the TDC. The TDC obtains a digital signal with reference to the control pulse pREF, which indicates the input timing of the signal output from each pixel 101 via the waveform shaping unit 210 in relative time.

[0069] Figures 5A to 5C This is a diagram that schematically illustrates the relationship between the operation and output signals of the APD 201.

[0070] Figure 5A It is shown Figure 4 An excerpt from the APD 201, quenching element 202, and waveform shaping unit 210. Here, the input node of the waveform shaping unit 210 will be referred to as node A, and the output node will be referred to as node B. Figure 5B It shows Figure 5A The waveform change of node A in the diagram, and Figure 5C It shows Figure 5A The waveform change of node B in the diagram.

[0071] Between times t0 and t1, the VH-VL potential difference is applied to Figure 5A APD 201. At time t1, a photon is incident on APD 201. APD 201 causes avalanche multiplication, and an avalanche multiplication current flows through quenching element 202, causing the voltage at node A to drop. The voltage drop is further increased to reduce the potential difference applied to APD 201, and at time t2, avalanche multiplication of APD 201 stops, and the voltage level at node A does not drop beyond a certain value. Subsequently, between times t2 and t3, a current from voltage VL to compensate for the voltage drop flows through node A. At time t3, node A stabilizes at its original potential level. The portion of the output waveform of node A below a certain threshold is shaped by waveform shaping unit 210 and output as a signal to node B.

[0072] The layout of signal line 113, as well as the layout of column circuit 112 and output circuit 114, are not limited to... Figure 3 The layout in the diagram. For example, signal line 113 can be configured to extend in the row direction, and column circuitry 112 can be located at the end of signal line 113.

[0073] The photoelectric conversion device according to various exemplary embodiments will now be described.

[0074] Reference Figures 6 to 11 A photoelectric conversion device according to a first exemplary embodiment is described.

[0075] Figure 6 This is a cross-sectional view of the photoelectric conversion element 102 in the two pixels 101 of the photoelectric conversion device according to the first exemplary embodiment, taken in a direction perpendicular to the plane of the substrate.

[0076] The structure and function of the photoelectric conversion element 102 will be described. Each photoelectric conversion element 102 includes an N-type first semiconductor region 311, a fourth semiconductor region 314, a sixth semiconductor region 316, and a seventh semiconductor region 317. The photoelectric conversion element 102 also includes a P-type second semiconductor region 312, a third semiconductor region 313, and a fifth semiconductor region 315.

[0077] In this exemplary embodiment, in Figure 6In the cross-section shown, the N-type first semiconductor region 311 is located near the surface opposite to the light incident surface. The N-type seventh semiconductor region 317 is located around the first semiconductor region 311. In the plan view, the P-type second semiconductor region 312 is positioned to overlap with the first semiconductor region 311 and the seventh semiconductor region 317. In the plan view, the N-type fourth semiconductor region 314 is further positioned to overlap with the second semiconductor region 312. The N-type sixth semiconductor region 316 is located around the fourth semiconductor region 314.

[0078] The N-type impurity concentration in the first semiconductor region 311 is higher than that in the fourth semiconductor region 314 and the seventh semiconductor region 317. A PN junction is formed between the P-type second semiconductor region 312 and the N-type first semiconductor region 311. The impurity concentration in the second semiconductor region 312 is lower than that in the first semiconductor region 311, thus the entire second semiconductor region 312 constitutes a depletion layer region. The depletion layer region extends further into a portion of the first semiconductor region 311, inducing a high electric field in the extended depletion layer region. The high electric field causes avalanche multiplication in the depletion layer region extending into a portion of the first semiconductor region 311, and a current based on the amplified charge is output as a signal charge. Light incident on the photoelectric conversion element 102 is photoelectrically converted to induce avalanche multiplication in the depletion layer region (avalanche multiplication region), and the generated charge of the first conductivity type is collected in the first semiconductor region 311.

[0079] exist Figure 6 In this design, the fourth semiconductor region 314 and the seventh semiconductor region 317 are substantially the same size. However, the size of the semiconductor regions is not limited to this. For example, the fourth semiconductor region 314 can be formed to be larger than the seventh semiconductor region 317 to collect charge from a wider area to the first semiconductor region 311.

[0080] A patterned structure 325, made of trenches, is formed in the surface of the semiconductor layer 301 on the light incident side. The patterned structure 325 is surrounded by a P-type third semiconductor region 313 and scatters light incident on the photoelectric conversion element 102. Since the incident light passes through the photoelectric conversion element 102 at an angle, an optical path length greater than or equal to the thickness of the semiconductor layer 301 can be provided. Compared with the case without the patterned structure 325, this enables photoelectric conversion of longer wavelengths of light. Since the patterned structure 325 prevents the incident light from reflecting inside the substrate, this also provides the effect of improving the photoelectric conversion efficiency of the incident light.

[0081] In the plan view, the fourth semiconductor region 314 and the patterned structure 325 are positioned in an overlapping manner. The area of ​​the overlapping portion of the fourth semiconductor region 314 and the patterned structure 325 is larger than the area of ​​the portion of the fourth semiconductor region 314 that does not overlap with the patterned structure 325. Compared to charges appearing near the avalanche multiplication region, charges appearing far from the avalanche multiplication region formed between the first semiconductor region 311 and the fourth semiconductor region 314 require a much longer travel time to reach the avalanche multiplication region. This can degrade timing jitter. Positioning the fourth semiconductor region 314 and the patterned structure 325 in an overlapping manner in the plan view increases the electric field deep within the photodiode and reduces the collection time of charges appearing far from the avalanche multiplication region. Therefore, timing jitter can be reduced.

[0082] The third semiconductor region 313 three-dimensionally covers the patterned structure 325, thereby reducing the occurrence of thermally excited charges at the interface of the patterned structure 325. This can reduce the dark count rate (DCR) of the photoelectric conversion element 102.

[0083] Pixel 101 is isolated by a trenched pixel isolation portion 324. A P-type fifth semiconductor region 315 surrounding the pixel isolation portion 324 isolates adjacent photoelectric conversion elements 102 from each other using a potential barrier. Since the photoelectric conversion elements 102 are also isolated by the potential of the fifth semiconductor region 315, a trenched pixel isolation portion 324 is not necessarily required. If a pixel isolation portion 324 is provided, its depth or position is not limited. Figure 6 The pixel isolation portion 324 can be a deep trench isolation (DTI) that penetrates through the semiconductor layer 301 or a DTI that does not penetrate the semiconductor layer 301. Metal can be embedded in the DTI to improve light shielding performance. In a plan view, the pixel isolation portion 324 can be configured to completely surround the photoelectric conversion element 102. The pixel isolation portion 324 can be located between opposite sides of the photoelectric conversion element 102.

[0084] The distance from a pixel isolation portion 324 to the pixel isolation portion 324 of an adjacent pixel 101 or the pixel isolation portion 324 of the nearest pixel 101 can be considered as the size of a photoelectric conversion element 102. With the size of a photoelectric conversion element 102 as L, the distance d from the light incident surface to the avalanche multiplication region satisfies L√2 / 4 < d < L×√2. If the size and depth of the photoelectric conversion element 102 satisfy this formula, the electric field strength in the depth direction near the first semiconductor region 311 is substantially the same as the electric field strength in the planar direction. This reduces the variation in the time required to collect charge and thus reduces the occurrence of timing jitter.

[0085] A needle-punched film 321, a planarization film 322, and a microlens 323 are further formed on the light incident surface side of the semiconductor layer 301. A filter layer (not shown) may also be provided on the light incident surface side. Various optical filters (such as color filters, infrared cut-off filters, and monochromatic filters) can be used in the filter layer. Examples of color filters may include red-green-blue (RGB) filters and red-green-blue-white (RGBW) filters.

[0086] Figure 7 yes Figure 6 The potential diagram of the photoelectric conversion element 102 shown in the figure.

[0087] Figure 7 The dashed line 70 in the middle indicates along Figure 6 The potential distribution of line segment FF'. Figure 7 The solid line 71 in the middle indicates along Figure 6 The potential distribution of line segment EE'. Figure 7 The diagram shows the potential for electrons, which represent the majority carrier charge in an N-type semiconductor region. If the majority carrier charge were holes, the relationship between higher and lower potentials would be reversed. Figure 7 Depth A in the middle corresponds to Figure 6 Height A. Similarly, depths B, C, and D correspond to heights B, C, and D, respectively.

[0088] exist Figure 7 In the diagram, the potential level of the solid line 71 at depth A will be represented by A1, the potential level of the dashed line 70 at depth A will be represented by A2, the potential level of the solid line 71 at depth B will be represented by B1, and the potential level of the dashed line 70 at depth B will be represented by B2. Similarly, the potential level of the solid line 71 at depth C will be represented by C1, the potential level of the dashed line 70 at depth C will be represented by C2, the potential level of the solid line 71 at depth D will be represented by D1, and the potential level of the dashed line 70 at depth D will be represented by D2.

[0089] from Figure 6 and Figure 7 It can be seen that the potential level of the first semiconductor region 311 corresponds to A1. The potential level near the center of the second semiconductor region 312 corresponds to B1. The potential level of the seventh semiconductor region 317 corresponds to A2. The potential level at the outer edge of the second semiconductor region 312 corresponds to B2.

[0090] Depend on Figure 7 The dashed line 70 indicates that the potential gradually decreases from depth D to depth C. Then the potential gradually increases from depth C to depth B, reaching potential level B2 at depth B. The potential decreases from depth B to depth A, reaching potential level A2 at depth A.

[0091] Simultaneously, the potential indicated by solid line 71 gradually decreases from depth D to depth C and from depth C to depth B, reaching potential level B1 at depth B. Then, the potential drops sharply from depth B to depth A, reaching potential level A1 at depth A. At depth D, the potentials of dashed line 70 and solid line 71 are essentially at the same potential. In the region indicated by line segments EE' and FF', the potential gradient decreases gently towards the second surface of semiconductor layer 301. Therefore, the charge appearing in photoelectric conversion element 102 moves downwards towards the second surface with a gentle potential gradient.

[0092] In the APD 201 according to this exemplary embodiment, the impurity concentration of the P-type second semiconductor region 312 is lower than the impurity concentration of the N-type first semiconductor region 311. Furthermore, reverse bias potentials are supplied to the first semiconductor region 311 and the second semiconductor region 312, respectively. This forms a depletion layer region in the second semiconductor region 312. Utilizing this structure, the second semiconductor region 312 serves as a barrier against the charge converted by photoelectric conversion in the fourth semiconductor layer 314, thereby facilitating the collection of charge into the first semiconductor region 311.

[0093] exist Figure 6 In the photoelectric conversion element 102, a second semiconductor region 312 is disposed throughout the entire photoelectric conversion element 102. However, the photoelectric conversion element 102 can be configured such that, in the plan view, the second semiconductor region 312 is not disposed in the portion overlapping with the first semiconductor region 311, but a slit extending from the fourth semiconductor region 314 is disposed in that portion. In this case, the potential difference between the second semiconductor region 312 and the slit portion leads to... Figure 6 The potential at depth C decreases from line segment FF' to line segment EE'. This facilitates the movement of charge towards the first semiconductor region 311 during the charge movement for photoelectric conversion in the fourth semiconductor region 314. On the other hand, if as Figure 6 By providing a second semiconductor region 312 throughout the photoelectric conversion element 102, the voltage applied to obtain a high electric field with avalanche multiplication can be reduced compared to the case of forming a slit, thereby reducing noise caused by the formation of a local high electric field region.

[0094] Charge moving to the vicinity of the second semiconductor region 312 passes through Figure 7 The steep potential gradient (i.e., through a high electric field) of the solid line 71 from depth B to depth A is accelerated for avalanche multiplication.

[0095] In comparison, Figure 6 The potential distribution between the N-type seventh semiconductor region 317 and the P-type second semiconductor region 312 (i.e. Figure 7The dashed line 70 from depth B to depth A does not cause avalanche multiplication. Therefore, the charge appearing in the fourth semiconductor region 314 can be considered as signal charge, without needing to increase the area of ​​the high electric field region (avalanche multiplication region) relative to the size of APD 201. Although the conductivity type of the seventh semiconductor region 317 has been described as N-type so far, the seventh semiconductor region 317 can be a P-type semiconductor region, as long as its impurity concentration satisfies the aforementioned potential relationship.

[0096] because Figure 7 The potential gradient 70 from depth B to depth C, indicated by the dashed line, causes the photoelectric converted charge in the second semiconductor region 312 to flow into the fourth semiconductor region 314. Due to the aforementioned reasons, the charge in the fourth semiconductor region 314 readily moves to the second semiconductor region 312. Therefore, the photoelectric converted charge in the second semiconductor region 312 moves to the first semiconductor region 311 and is detected as a signal charge through avalanche multiplication. Thus, the photoelectric conversion element 102 is sensitive to the photoelectric converted charge in the second semiconductor region 312.

[0097] Figure 7 The dashed line 70 indicates along Figure 6 The sectional potential of line segment FF'. On the dashed line 70, A2 corresponds to... Figure 6 In the diagram, B2 corresponds to the point where height A intersects with line segment FF', C2 corresponds to the point where height C intersects with line segment FF', and D2 corresponds to the point where height D intersects with line segment FF'. Figure 6 In the fourth semiconductor region 314, the electrons undergo photoelectric conversion along... Figure 7 The potential gradient shifts from D2 to C2, but because the second semiconductor region 312 acts as a potential barrier for electrons, it is difficult for electrons to move from C2 to B2. Therefore, electrons move from the fourth semiconductor region 314 due to the potential gradient shift. Figure 6 The line segment EE' in the diagram indicates the vicinity of the center. Moving electrons follow... Figure 7 The potential gradient from C1 to B1 moves, avalanches and multiplies along the steep potential gradient from B1 to A1, and passes through the first semiconductor region 311, and is then detected as a signal charge.

[0098] exist Figure 6 The charge that appears near the boundary between the third semiconductor region 313 and the sixth semiconductor region 316 along Figure 7 The potential gradient shifts from D2 to C2. As described above, the charge then moves to the point where... Figure 6The line segment EE' indicates the vicinity of the center of the fourth semiconductor region 314. The charge then avalanche multiplies along the steep potential gradient from B1 to A1. The avalanche multiplied charge passes through the first semiconductor region 311 and is then detected as signal charge.

[0099] Figure 8 This is an enlarged cross-sectional view of two grooves in the patterned structure 325 constituting the photoelectric conversion device 100 according to the first exemplary embodiment.

[0100] The trench structure is formed of a material different from that of the third semiconductor region 313. For example, if the third semiconductor region 313 is formed of silicon, the main components constituting the trench structure are formed of a silicon oxide film or a silicon nitride film. Metallic or organic materials may be included. For example, the trench is formed at a depth of 0.1 μm to 0.6 μm from the surface of the semiconductor layer 301. To sufficiently enhance the diffraction of incident light, in one embodiment, the trench depth is greater than the trench width. As used herein, the trench width refers to the width on the plane passing through the centroid of the cross-section of the trench, from the interface between the needle-punched film 321 and the third semiconductor region 313 to the other interface between the needle-punched film 321 and the third semiconductor region 313. The trench depth refers to the depth from the light incident surface to the bottom of the trench.

[0101] exist Figure 8 The period p indicated by the arrow represents one period of the patterned structure 325, which includes multiple grooves. The period of the patterned structure 325 is the distance from the centroid of a groove in the patterned structure 325 to the centroid of another groove adjacent to that groove in the cross-sectional view. The average value of the patterned periods of the entire patterned structure 325 is called the effective period.

[0102] The process for forming the trench will be described. First, a trench is formed in the third semiconductor region 313 of the semiconductor layer 301 by etching. Then, a needle-punched film 321 is formed on the surface of the third semiconductor region 313 and inside the trench by a method such as chemical vapor deposition. The interior of the trench covered by the needle-punched film 321 is filled using a filling member 332. The trench constituting the patterned structure 325 can be formed by the same process as that for forming the trench constituting the pixel isolation portion 324. In this case, the side portions of the trench constituting the patterned structure 325 and the side portions of the trench constituting the pixel isolation portion 324 have the same impurity concentration.

[0103] The filling member 332 may contain voids 331. Since the refractive index of the voids 331 is lower than that of the filling member 332, light passing through the voids 331 has a different optical path than light passing through other parts. Compared to the filling member 332 without voids, this increases the refractive index difference of the entire patterned structure 325 and increases the phase difference of the light transmitted through the patterned structure 325, thereby making it easier to enhance the diffraction of the incident light. In other words, the formation of voids 331 in the filling member 332 provides the effect of enhancing the intensity of incident light with a specific phase and improving sensitivity.

[0104] Figure 9A and Figure 9B This is a plan view of two pixels of the photoelectric conversion device 100 according to the first exemplary embodiment. Figure 9A It is a plan view from the opposite side of the light incident surface. Figure 9B This is a planar view from the side of the light incident surface.

[0105] exist Figure 9A In this configuration, the first semiconductor region 311, the fourth semiconductor region 314, and the seventh semiconductor region 317 have circular shapes and are arranged concentrically. This structure provides the following effects: it reduces the local electric field concentration at the ends of the high electric field region between the first semiconductor region 311 and the second semiconductor region 312, and lowers the DCR (Distribution Rate of Change). The shapes of the semiconductor regions 311, 314, and 317 are not limited to circular shapes, and can, for example, have polygonal shapes with the same centroid.

[0106] exist Figure 9B In the plan view, the patterned structure 325 is formed in a grid shape. The patterned structure 325 is positioned to overlap with the first semiconductor region 311 and the fourth semiconductor region 314. The center of gravity of the patterned structure 325 in the plan view is located within the avalanche multiplication region. Figure 9B In the mesh-like trench structure shown, the trench depth at the intersection of the trenches is greater than the trench depth of the individual extensions of the trenches. The bottom of the trench at the intersection is closer to the light incident surface than the position corresponding to half the thickness of the semiconductor layer 301. As used herein, trench depth refers to the depth from the first surface to the bottom, and can be described as the depth of the grooves in the patterned structure 325.

[0107] Figure 10 A comparative example of a photoelectric conversion device 100 according to a first exemplary embodiment is shown. Figure 10 The photoelectric conversion device 100 is shown in a simplified form. The photoelectric conversion device 100 includes an avalanche multiplication region 501, a wiring layer 502, and a patterned structure 325.

[0108] If light is incident on this photoelectric conversion device 100, avalanche luminescence may occur in the avalanche multiplication region 501. Avalanche luminescence is the phenomenon in which a large number of electrons or holes generated by avalanche multiplication recombine with charges of opposite polarity to generate photons. Leakage of photons generated by avalanche luminescence into adjacent pixels can cause spurious signals and degrade image quality.

[0109] exist Figure 10 The patterned structure 325 disposed on the light-emitting side of the semiconductor layer of the photoelectric conversion device 100 shown has an effective period longer than the wavelength of avalanche emission light. Avalanche emission light has a spectrum that ranges to some extent from short to long wavelengths. Components with shorter wavelengths have shorter absorption lengths in the substrate and are photoelectrically converted closer to the light-emitting area. Therefore, such components are less likely to reach adjacent pixels and cause spurious signals. In contrast, components with longer wavelengths have longer absorption lengths in the substrate and are more likely to cause spurious signals at locations farther from the light-emitting area. Therefore, such components are a major factor contributing to the aforementioned image quality degradation. Thus, the component with the longest wavelength in the spectrum of avalanche emission light can be approximated as a typical factor contributing to image quality degradation. The maximum wavelength of avalanche emission light depends on the band gap of the substrate material and is determined by hc / E. a (h: Planck's constant [J·s], c: speed of light [m / s], and E) a The band gap of the substrate is determined [J]. For example, if the sensor substrate is made of silicon, the maximum wavelength of the avalanche emission light is approximately 1.1 μm.

[0110] If the effective period of the patterned structure 325 is longer than the wavelength of the avalanche-emitted light, the avalanche-emitted light behaves as particles relative to the patterned structure 325. Because the effective refractive index changes drastically with substrate depth, the avalanche-emitted light is reflected from the bottom of the patterned structure 325. The reflected light becomes stray light within the pixel.

[0111] Figure 11 An example of a photoelectric conversion device 100 according to a first exemplary embodiment is shown. Figure 10 Same, Figure 11 The photoelectric conversion device 100 is shown in a simplified form.

[0112] exist Figure 11The patterned structure 325 disposed on the light incident surface side of the semiconductor layer 301 of the photoelectric conversion device 100 shown has a period shorter than the wavelength of avalanche emission light. If the sensor substrate 11 is formed of silicon, the patterned structure 325 is formed with a period of 1.1 μm to 0.2 μm. If avalanche emission occurs in this photoelectric conversion device 100, the avalanche emission light behaves as a wave. Since the effective refractive index changes gradually with the depth of the semiconductor layer 301, the avalanche emission light is less reflected by the bottom of the patterned structure 325. The avalanche emission light incident on the patterned structure 325 travels to the outside of the sensor substrate 11, thereby reducing stray light within the pixel 101. By placing the patterned structure 325 at the center of the photoelectric conversion element 102 (where the light intensity of avalanche emission light is high at the light incident surface of the semiconductor layer 301), the effect of reducing stray light can be obtained more effectively.

[0113] constitute Figure 11 The grooves of the patterned structure 325 shown are tapered and do not have a constant width. If the average width of the cross-section (in...) Figure 11 If the width at half the trench depth satisfies the condition that the period is shorter than the wavelength of the avalanche emission light, then this patterned structure 325 can provide the effect of this exemplary embodiment. In other words, the trench width satisfies hc / 2E. a (h: Planck's constant [J·s], c: speed of light [m / s], and E) a : The band gap of the substrate [J]). For example, if the sensor substrate 11 is formed of silicon, the trench width is less than or equal to 0.55 μm. It can be said that the effective period is shorter than a wavelength at which the light absorption length of the semiconductor substrate is the same as the distance from the light incident surface to the interface between the first semiconductor region 311 and the second semiconductor region 312.

[0114] Wiring layer 502 includes A1 wiring and serves as a reflective member to reflect light passing through semiconductor layer 301 back to pixel 101.

[0115] In this way, crosstalk can be reduced by making the period of the patterned structure 325 disposed on the light incident side of the semiconductor layer 301 shorter than the wavelength of the avalanche emission light.

[0116] Reference Figure 12A and Figure 12B A photoelectric conversion device according to a second exemplary embodiment is described.

[0117] Descriptions of portions common to the first exemplary embodiment will be omitted, and the differences from the first exemplary embodiment will be primarily described. In this exemplary embodiment, when viewed in a plan view, the patterned structure is formed to include T-shaped overlapping points.

[0118] Figure 12A and Figure 12B This is a plan view of two pixels of the photoelectric conversion device according to the second exemplary embodiment.

[0119] Plan view from the light incident surface ( Figure 12B In the patterned structure 325, the grooves are arranged such that multiple rectangles are arranged side-by-side through repeated T-shaped constructions. The patterned structure 325 can be described as... Figure 9B The grid-shaped trench structure shown is formed by shifting each row by half a pitch.

[0120] This construction reduces the amount of overlapping and over-etched trenches during the etching process used for trench formation, compared to the patterned structure 325 which forms a grid of intersecting vertical and horizontal lines. This reduces the likelihood of etching damaging the semiconductor layer (such as lattice defects) and causing dark current degradation (DCR).

[0121] Variations of the second exemplary embodiment

[0122] Figure 13A and Figure 13B A plan view of two pixels of a photoelectric conversion device according to a variant of a second exemplary embodiment is shown.

[0123] Plan view from the light incident surface ( Figure 13B In the patterned structure 325, the grooves are arranged such that multiple rectangles with different areas are arranged side by side by repeating the T-shaped construction.

[0124] Even with this configuration, compared to the patterned structure 325 which forms a grid of intersecting vertical and horizontal lines, the amount of trench overlap and over-etched portions is reduced. This reduces the likelihood of etching damaging the semiconductor layer (such as lattice defects) and causing dark current degradation of the DCR.

[0125] Reference Figures 14 to 17 A photoelectric conversion device according to a third exemplary embodiment is described.

[0126] Descriptions of parts common to the first and second exemplary embodiments will be omitted, and the differences from the first exemplary embodiment will be described primarily.

[0127] Figure 14This is a plan view of four pixels of the photoelectric conversion device according to the third exemplary embodiment, viewed from the surface opposite to the light incident surface. The difference from the photoelectric conversion device 100 according to the first and second exemplary embodiments is that an N-type eighth semiconductor region 318 is disposed around the seventh semiconductor region 317. The N-type impurity concentration of the eighth semiconductor region 318 disposed on the surface opposite to the light incident surface is lower than the N-type impurity concentration of the first semiconductor region 311.

[0128] Figure 15 This is a plan view of four pixels of the photoelectric conversion device according to the third exemplary embodiment, from the light incident surface side.

[0129] In the planar view from the light incident surface side, the patterned structure 325 includes a non-periodic structure of randomly arranged grooves. Even in this case, the patterned structure 325 is configured to have an effective period shorter than the wavelength of the avalanche emission light.

[0130] The random distribution of grooves in the patterned structure 325 can make the angle distribution of the diffracted light diffracted by the incident light by the patterned structure 325 uniform, thereby improving sensitivity and performance. The patterned structure 325 is not limited to this layout; for example, multiple independent island-like structures can be formed in the plane.

[0131] Figure 16 The edge of the pixel of the photoelectric conversion device according to the third exemplary embodiment Figure 15 The cross-sectional view taken in the direction A-A'. Figure 17 The edge of the pixel of the photoelectric conversion device according to the third exemplary embodiment Figure 15 The cross-sectional view taken in the direction B-B'.

[0132] In a cross-section along direction A-A' (the opposite side direction of the pixel), the pixel according to this exemplary embodiment does not include a fifth semiconductor region 315 extending downward to the surface opposite the light incident surface. The fifth semiconductor region 315 and the eighth semiconductor region 318 are separate from each other. In contrast, in a cross-section along direction B-B' (the diagonal direction of the pixel), the fifth semiconductor region 315 extends from the light incident surface side to the surface opposite the light incident surface.

[0133] Instead of placing the fifth semiconductor region 315, the eighth semiconductor region 318 is positioned at the pixel corner, which alleviates the electric field in the planar direction. This facilitates the collection of dark charges appearing at the pixel corner to the first semiconductor region 311 via the lateral electric field, and the discharge of dark charges without passing through the high electric field region that induces avalanche multiplication. This reduces DCR degradation. The absence of the fifth semiconductor region 315 at the pixel corner also prevents the concentration of the lateral electric field between the fifth semiconductor region 315 and the first semiconductor region 311, thereby facilitating pixel miniaturization.

[0134] Reference Figures 18 to 20 A photoelectric conversion device according to a fourth exemplary embodiment is described.

[0135] Descriptions of parts common to the first to third exemplary embodiments will be omitted, and the differences from the first exemplary embodiment will be described primarily.

[0136] Figure 18 This is a cross-sectional view of two pixels of the photoelectric conversion device 100 according to the fourth exemplary embodiment. Figure 19A and Figure 19B This is a plan view of two pixels of the photoelectric conversion device 100 according to the fourth exemplary embodiment. Figure 19A It is a planar view from the surface opposite to the incident surface of the light. Figure 19B This is a planar view from the side of the light incident surface.

[0137] like Figure 18 , Figure 19A and Figure 19B As shown, the photoelectric conversion device 100 according to this exemplary embodiment includes an antireflective film 326 between a semiconductor layer 301 and an interlayer film (planarization film) 322. The differences from the first to third exemplary embodiments include: light-shielding portions 327 are disposed between pixels, and a patterned structure 325 is formed within each pixel with a non-uniform density distribution.

[0138] Reference Figure 20 Describing the effects of the fourth exemplary embodiment, Figure 20 This is a comparison diagram showing two pixels of the photoelectric conversion device 100 according to the fourth exemplary embodiment. Figure 20 The photoelectric conversion device 100 is shown in a simplified form. The photoelectric conversion device 100 is a photoelectric conversion device including an avalanche multiplication region 501, a wiring layer 502, a patterned structure 325, an anti-reflection film 326, and a light shielding portion 327.

[0139] The antireflective coating 326 has a lower refractive index than the effective refractive index of the patterned structure 325. As used herein, the effective refractive index refers to the substantial refractive index of the entire patterned structure 325 when the trench substrate and the trench-filling components are combined. For example, if the semiconductor layer 301 is formed of Si with a refractive index of 4 and the interlayer film 322 is formed of SiO with a refractive index of 1.5, the effective refractive index of the patterned structure 325 is 2.8 to 3.8. The antireflective coating 326 is formed, for example, of Ta2O5 with a refractive index of approximately 2. Distributing the antireflective coating 326 between the semiconductor layer 301 and the interlayer film 322 smooths the refractive index change from the semiconductor layer 301 to the interlayer film 322. This prevents avalanche emission light from being reflected from the back side of the semiconductor layer 301 and reduces crosstalk caused by avalanche emission light.

[0140] Placing the light-shielding portion 327 between pixels can reduce crosstalk because avalanche emission light occurring in each pixel leaves that pixel and does not enter adjacent pixels.

[0141] like Figure 19B As shown, the patterned structure 325 according to this exemplary embodiment is formed with a non-uniform density distribution within each pixel. Specifically, in each pixel, the trench density is reduced in the peripheral region where the intensity distribution of avalanche emission light is lower. This reduces the area occupancy of the trenches over the entire pixel. Since the trench portion can be a source of dark current due to damage to the semiconductor layer 301 caused by etching, crosstalk can be reduced, and the DCR can be reduced by decreasing the area occupancy of the trenches.

[0142] Reference Figure 21 A photoelectric conversion device according to a fifth exemplary embodiment is described.

[0143] Descriptions of parts common to the first to fourth exemplary embodiments will be omitted, and the differences from the first exemplary embodiment will be described primarily.

[0144] Figure 21 This is a cross-sectional view of a pixel of the photoelectric conversion device according to the fifth exemplary embodiment.

[0145] In the photoelectric conversion device according to the fifth exemplary embodiment, the patterned structure 325 includes trenches of varying depths. Figure 21 In the pixels shown, for example, grooves are formed near the center of pixels with high avalanche emission intensity at a depth of 0.1 μm to 0.6 μm. Grooves are formed relatively shallower near the periphery of pixels with lower avalanche emission intensity.

[0146] Forming a patterned structure 325 comprising trenches of varying depths can effectively reduce avalanche emission reflections near the pixel center where avalanche emission is strongly concentrated, and also reduce crosstalk. Because the overall volume of the patterned structure 325 can be reduced, dark current generation is minimized, thus preventing DCR degradation.

[0147] Reference Figures 22A to 22C A photoelectric conversion device according to a sixth exemplary embodiment is described.

[0148] Descriptions of parts common to the first to fifth exemplary embodiments will be omitted, and the differences from the first exemplary embodiment will be described primarily.

[0149] The cross-sectional shape of the grooves constituting the patterned structure 325 is not limited to... Figure 8 The cross-sectional shape is shown in the figure. For example, as shown in the figure. Figure 22A As shown, the groove can have an inverted conical shape that is narrow on the side of the light incident surface and wide near the surface opposite to the light incident surface. Forming the groove constituting the patterned structure 325 with this shape can enhance the diffraction effect and improve sensitivity.

[0150] The grooves constituting the patterned structure 325 can have, for example, Figure 22B The hemispherical shape shown reduces abrupt changes in refractive index, providing an anti-reflective effect to improve sensitivity. Although Figure 22B A hemisphere with a semi-circular cross-section of 180° is shown, but a similar effect can be achieved by any shape with an arcuate cross-section.

[0151] Such as Figure 22C The stepped grooves shown can also reduce abrupt changes in refractive index to provide anti-reflective effects and improve sensitivity. Although Figure 22C A stepped groove with two planes parallel to the light incident surface is shown, but the number of planes (the number of steps) is not limited to this.

[0152] Reference Figure 23 , Figure 24A and Figure 24B A photoelectric conversion device according to a seventh exemplary embodiment is described.

[0153] Descriptions of parts common to the first to sixth exemplary embodiments will be omitted, and the differences from the first exemplary embodiment will be described primarily.

[0154] Figure 23This is a cross-sectional view of the photoelectric conversion element 102 of the photoelectric conversion apparatus according to the seventh exemplary embodiment, taken in a direction perpendicular to the plane direction of the semiconductor layer. In the photoelectric conversion apparatus according to this exemplary embodiment, compared with the photoelectric conversion apparatus 100 according to the first exemplary embodiment, the N-type first semiconductor region 311 occupies a large proportion of the light receiving surface of the pixel. The seventh semiconductor region 317 is disposed between the first semiconductor region 311 and the second semiconductor region 312.

[0155] The patterned structure 325 includes a rectangular pyramid-shaped groove with a triangular cross-section at the bottom and a light incident surface.

[0156] Figure 24A and Figure 24B This is a plan view of two pixels of the photoelectric conversion device according to the seventh exemplary embodiment. Figure 24A It is a planar view from the surface opposite to the incident surface of the light. Figure 24B This is a planar view from the side of the light incident surface.

[0157] In the plan view from the light incident surface side, the seventh semiconductor region 317 is located between the first semiconductor region 311 and the second semiconductor region 312. Incident light undergoes avalanche multiplication between the first semiconductor region 311 and the second semiconductor region 312. If the pixel aperture is designed to expose both the first semiconductor region 311 and the second semiconductor region 312, the aperture ratio of the photoelectric conversion device according to this exemplary embodiment is lower than the aperture ratio of the photoelectric conversion devices according to the first to fifth exemplary embodiments. A lower aperture ratio can reduce the volume of the photoelectric conversion region capable of signal detection, and thus can reduce crosstalk.

[0158] Reference Figure 25 A photoelectric conversion system according to an eighth exemplary embodiment is described. Figure 25 This is a block diagram illustrating a schematic construction of a photoelectric conversion system according to this exemplary embodiment.

[0159] The photoelectric conversion device described in the first to seventh exemplary embodiments above can be applied to various photoelectric conversion systems. Examples of suitable photoelectric conversion systems include digital still cameras, digital video cameras, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Camera modules that include optical systems (such as lenses) and imaging devices are also included in photoelectric conversion systems. As an example, Figure 25 A block diagram of a digital still camera is shown.

[0160] Figure 25The photoelectric conversion system shown includes an imaging device 1004, an example of a photoelectric conversion device, and a lens 1002 for forming an optical image of a subject on the imaging device 1004. The photoelectric conversion system also includes an aperture 1003 for changing the amount of light passing through the lens 1002, and a barrier 1001 for protecting the lens 1002. The lens 1002 and the aperture 1003 constitute an optical system for collecting light into the imaging device 1004. The imaging device 1004 is a photoelectric conversion device according to any of the foregoing exemplary embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

[0161] The photoelectric conversion system also includes a signal processing unit 1007, which is an image generation unit for generating an image by processing the output signal (electrical signal) output from the imaging device 1004. The signal processing unit 1007 performs various appropriate corrections and compressions, and outputs image data. The signal processing unit 1007 can be formed on a semiconductor substrate on which the imaging device 1004 is disposed, or on a semiconductor substrate different from the semiconductor substrate on which the imaging device 1004 is disposed.

[0162] The photoelectric conversion system also includes a memory unit 1010 for temporarily storing image data and an external interface (I / F) unit 1013 for communicating with an external computer. The photoelectric conversion system also includes a recording medium 1012 (such as a semiconductor memory) for recording and reading imaging data, and a recording medium control I / F unit 1011 for recording and reading on the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system or detachably attached to it.

[0163] The photoelectric conversion system also includes: a general control and computing unit 1009 for controlling various calculations and the entire digital still camera, and a timing generation unit 1008 for outputting various timing signals to the imaging device 1004 and the signal processing unit 1007. These timing signals can be input from outside the system. The photoelectric conversion system includes at least the imaging device 1004 and the signal processing unit 1007 for processing the output signals from the imaging device 1004.

[0164] Imaging device 1004 outputs an imaging signal to signal processing unit 1007. Signal processing unit 1007 applies predetermined signal processing to the imaging signal output from imaging device 1004 and outputs image data. Signal processing unit 1007 uses the imaging signal to generate an image.

[0165] As described above, according to this exemplary embodiment, a photoelectric conversion system applying a photoelectric conversion device (imaging device) according to any of the foregoing exemplary embodiments can be implemented.

[0166] Reference Figure 26A and Figure 26B A photoelectric conversion system and a moving body according to a ninth exemplary embodiment are described. Figure 26A and Figure 26B This is a diagram illustrating the construction of the photoelectric conversion system and the moving body according to this exemplary embodiment.

[0167] Figure 26A An example of a photoelectric conversion system related to an in-vehicle camera is shown. The photoelectric conversion system 1300 includes an imaging device 1310. The imaging device 1310 is the photoelectric conversion device described in any of the foregoing exemplary embodiments. The photoelectric conversion system 1300 includes: an image processing unit 1312 that performs image processing on multiple image data acquired by the imaging device 1310; and a disparity acquisition unit 1314 that calculates disparity (phase difference between disparity images) based on the multiple image data acquired by the photoelectric conversion system 1300. The photoelectric conversion system 1300 also includes: a distance acquisition unit 1316 that calculates the distance to a target object based on the calculated disparity; and a collision determination unit 1318 that determines the probability of a collision based on the calculated distance. Here, the disparity acquisition unit 1314 and the distance acquisition unit 1316 are examples of distance information acquisition units that obtain distance information about a target object. In other words, distance information refers to information about disparity, defocus, distance to the target object, etc. The collision determination unit 1318 can determine the probability of a collision based on any one of the distance information. The distance information acquisition unit can be implemented by specially designed hardware or software modules.

[0168] Alternatively, the distance information acquisition unit can be implemented using a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). A combination of these can also be used to implement the distance information acquisition unit.

[0169] The photoelectric conversion system 1300 is connected to the vehicle information acquisition device 1320 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 1300 is also connected to the electronic control unit (ECU) 1330, which is a control unit that outputs a control signal to apply braking force to the vehicle based on the determination result made by the collision determination unit 1318. The photoelectric conversion system 1300 is also connected to an alarm device 1340, which issues an alarm to the driver based on the determination result made by the collision determination unit 1318. For example, if the determination result made by the collision determination unit 1318 indicates a high probability of collision, the ECU 1330 performs vehicle control to avoid a collision or reduce damage by applying the brakes, releasing the accelerator pedal, and / or reducing engine output. The alarm device 1340 warns the user by emitting an alarm sound, displaying alarm information on the screen of the vehicle navigation system, and / or vibrating the seatbelt or steering wheel.

[0170] In this exemplary embodiment, the photoelectric conversion system 1300 captures images of the area around the vehicle (e.g., in front of or behind the vehicle). Figure 26B A photoelectric conversion system is shown that captures an image of the area in front of the vehicle (imaging range 1350). The vehicle information acquisition device 1320 sends instructions to the photoelectric conversion system 1300 or the imaging device 1310. This configuration further improves the accuracy of distance measurement.

[0171] While the aforementioned photoelectric conversion system is described as being used for control to avoid collisions with other vehicles, it can also be applied to: autonomous driving control for following other vehicles or autonomous driving control for maintaining lane position. Furthermore, photoelectric conversion systems are not limited to vehicles such as automobiles, but can also be applied to mobile bodies (mobile devices) such as ships, aircraft, and industrial robots. Photoelectric conversion systems are also not limited to mobile bodies and can be widely applied to equipment using object recognition (such as Intelligent Transportation Systems (ITS)).

[0172] Reference Figure 27 A photoelectric conversion system according to a tenth exemplary embodiment is described. Figure 27 This is a block diagram illustrating an example construction of a distance image sensor as a photoelectric conversion system according to this exemplary embodiment.

[0173] like Figure 27 As shown, the distance image sensor 401 includes an optical system 407, a photoelectric conversion device 408, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 401 can obtain a distance image based on the distance to the subject by receiving light (modulated light or pulsed light) projected from the light source device 411 onto the subject and reflected from the surface of the subject.

[0174] The optical system 407 includes one or more lenses. The optical system 407 guides image light (incident light) from the subject to the photoelectric conversion device 408, and forms an image on the light receiving surface (sensor unit) of the photoelectric conversion device 408.

[0175] Any of the photoelectric conversion devices according to the foregoing exemplary embodiments is used as photoelectric conversion device 408. A distance signal indicating the distance is supplied to image processing circuit 404, the distance being determined based on a light receiving signal output from photoelectric conversion device 408.

[0176] The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 408. The distance image (image data) obtained through image processing is supplied to the monitor 405 and displayed on the monitor 405, or supplied to the memory 406 and stored (recorded) in the memory 406.

[0177] The distance image sensor 401 constructed in this way can obtain, for example, a more accurate distance image by applying the aforementioned photoelectric conversion device and improving pixel characteristics.

[0178] Reference Figure 28 A photoelectric conversion system according to an eleventh exemplary embodiment is described. Figure 28 This is a diagram illustrating an example of a schematic construction of an endoscopic surgical system as a photoelectric conversion system according to this exemplary embodiment.

[0179] Figure 28 The illustration shows an operator (doctor) 1131 performing surgery on a patient 1132 on a bed 1133 using an endoscopic surgery system 1150. As shown, the endoscopic surgery system 1150 includes an endoscope 1100, surgical instruments 1110, and a trolley 1134 equipped with various devices for endoscopic surgery.

[0180] Endoscope 1100 includes a tube 1101 and a camera 1102 attached to the base of the tube 1101. The tube 1101 is inserted into the body cavity of a patient 1132 at a predetermined length from its tip. Although the endoscope 1100 shown is configured as a rigid endoscope including a rigid tube 1101, the endoscope 1100 may be configured as a flexible endoscope including a flexible tube.

[0181] The endoscope tube 1101 has an opening at its top for mounting an objective lens. A light source device 1203 is connected to the endoscope 1100. Light generated by the light source device 1203 is guided to the top of the endoscope tube 1101 via a light guide extending through the tube 1101, and emitted via the objective lens towards the object being observed within the body cavity of the patient 1132. The endoscope 1100 can be a forward-viewing endoscope, a forward-oblique-viewing endoscope, or a lateral-viewing endoscope.

[0182] An optical system and a photoelectric conversion device are provided in the camera 1102. Reflected light from the object being observed (observation light) is collected by the optical system and fed into the photoelectric conversion device. The photoelectric conversion device performs photoelectric conversion on the observation light to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. Any of the photoelectric conversion devices described in the above exemplary embodiments can be used as a photoelectric conversion device. The image signal is sent as raw data to the camera control unit (CCU) 1135.

[0183] The CCU 1135 includes a central processing unit (CPU) and a graphics processing unit (GPU), and centrally controls the operation of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives image signals from the camera 1102 and applies various types of image processing (such as image rendering (de-mosaicing)) to the image signals for displaying images based on them.

[0184] The display device 1136, under the control of the CCU 1135, displays an image based on the image signal processed by the CCU 1135.

[0185] The light source device 1203 includes a light source such as a light-emitting diode (LED) and supplies illumination light to the endoscope 1100 when taking images of the surgical site.

[0186] Input device 1137 is the input interface of endoscopic surgery system 1150. Users can input various types of information and commands into endoscopic surgery system 1150 via input device 1137.

[0187] The treatment tool control device 1138 controls the drive of the energy treatment tool 1112 used for cauterizing or cutting tissue or sealing blood vessels.

[0188] The light source device 1203 that supplies illumination light to the endoscope 1100 when capturing images of the surgical site includes, for example, LEDs, laser light sources, or white light sources combining these. A white light source including a combination of R, G, and B laser light sources allows for precise control of the output intensity and timing of each color (wavelength). Therefore, the light source device 1203 can adjust the white balance of the captured image. In this case, by using laser beams from each of the R, G, and B laser light sources to illuminate the object of observation in a time-division manner and controlling the drive of the image sensor in the camera 1102 in sync with the illumination timing, images corresponding to each of the R, G, and B colors can be captured in a time-division manner. According to this method, color images can be obtained without a color filter on the image sensor.

[0189] Furthermore, the drive of the light source device 1203 can be controlled to change the intensity of the output light at predetermined time intervals. By controlling the drive of the image sensor in the camera 1102 in time-division multiplexing in sync with the timing of the light intensity changes, and by combining these images, high dynamic range images without underexposure or overexposure can be generated.

[0190] The light source device 1203 can be configured to supply light of a predetermined wavelength band for special light observation. For example, special light observation utilizes the wavelength dependence of light absorption by body tissues. Specifically, images of predetermined tissues (such as blood vessels in the mucosal surface) are captured with high contrast by emitting light in a narrower band than the illumination light (i.e., white light) used during normal observation.

[0191] Alternatively, fluorescence observation can be performed to obtain images using fluorescence induced by excitation light, as a special light observation. Fluorescence observation involves irradiating body tissue with excitation light and observing the fluorescence emanating from the body tissue. Fluorescence images can be obtained by locally injecting a reagent (such as indocyanine green (ICG)) into the body tissue and irradiating the tissue with excitation light corresponding to the fluorescence wavelength of the reagent. The light source device 1203 can be configured such that narrowband light and / or excitation light can be supplied for this special light observation.

[0192] Reference Figure 29A and Figure 29B A photoelectric conversion device according to a twelfth exemplary embodiment is described. Figure 29A Eyeglasses 1600 (smart glasses) are shown as a photoelectric conversion system according to this exemplary embodiment. Eyeglasses 1600 includes a photoelectric conversion device 1602. The photoelectric conversion device 1602 is any of the photoelectric conversion devices described in the foregoing exemplary embodiments. A display device including light-emitting devices such as organic light-emitting diodes (OLEDs) and LEDs can be disposed on the back of the lens 1601. Eyeglasses 1600 may include one or more photoelectric conversion devices 1602. Various types of photoelectric conversion devices can be used in combination. The mounting location of the photoelectric conversion device 1602 is not limited to... Figure 29A The installation location is shown in the figure.

[0193] The eyeglasses 1600 also include a control device 1603. The control device 1603 serves as a power source to supply power to the aforementioned photoelectric conversion device 1602 and display device. The control device 1603 also controls the operation of the photoelectric conversion device 1602 and the display device. The lens 1601 includes an optical system for collecting light into the photoelectric conversion device 1602.

[0194] Figure 29BEyeglasses 1610 (smart glasses) according to an application example are shown. Eyeglasses 1610 includes a control device 1612. The control device 1612 includes a display device and a photoelectric conversion device equivalent to photoelectric conversion device 1602. Lens 1611 includes the optical system of the photoelectric conversion device in the control device 1612 and an optical system for projecting light emitted from the display device, and an image is projected onto lens 1611. The control device 1612 serves as a power source for supplying power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device 1612 may include a gaze detection unit for detecting the gaze of the wearer (user). The gaze can be detected by using infrared light. An infrared emitting unit emits infrared light toward the eyeball of the user gazing at the projected image (displayed image). An imaging unit including a light receiving element detects the reflection of the emitted infrared light from the eyeball to obtain an image of the eyeball. A reduction unit is included for reducing the infrared light traveling from the infrared emitting unit to lens 1611 to reduce image quality degradation.

[0195] The user's gaze at the displayed image is detected from an image of the eye obtained through infrared imaging. Any conventional technique can be applied to detect gaze from the image of the eye. For example, a gaze detection method based on Purkinje images obtained from the reflection of illumination light at the cornea can be used.

[0196] More specifically, gaze detection processing based on the pupil-corneal reflection method is performed. Using the pupil-corneal reflection method, the user's gaze is detected by calculating a gaze vector representing the direction (rotation angle) of the eyeball based on the pupil image and Purkinje image included in the captured image of the eyeball.

[0197] The display device according to this exemplary embodiment may include a photoelectric conversion device having a light receiving element, and control the display image of the display device based on user gaze information from the photoelectric conversion device.

[0198] Specifically, the display device determines a first field of view and a second field of view outside the first field of view based on gaze information. The first and second field of view can be determined by the control unit of the display device. The first and second field of view can be received from an external control device. The display resolution of the first field of view within the display area of ​​the display device can be controlled to be higher than the display resolution of the second field of view. In other words, the resolution of the second field of view can be lower than the resolution of the first field of view.

[0199] The display area may include a first display area and a second display area different from the first display area, and a display area with higher priority between the first and second display areas can be determined based on gaze information. The first and second display areas can be determined by the control unit of the display device. The first and second display areas determined by an external control device can be received. The resolution of the area with higher priority can be controlled to be higher than the resolution of areas other than the area with higher priority. In other words, the resolution of areas with relatively lower priority can be reduced.

[0200] Artificial intelligence (AI) can be used to determine the primary field of view or regions with higher priority. The AI ​​can be a model trained in such a way that it estimates the angle of the gaze and the distance to objects in front of the gaze based on eye images and the actual direction the eye points in the image, using the eye images as teaching data. The AI ​​program can be included in a display device, a photoelectric conversion device, or an external device. If the AI ​​program is included in an external device, the estimation results are communicated to the display device.

[0201] If the display device is controlled based on visual recognition detection, this exemplary embodiment can be suitably applied to smart glasses that also include a photoelectric conversion device for capturing external images. The smart glasses can display the captured external information in real time.

[0202] Exemplary embodiments of the variant

[0203] This disclosure is not limited to the foregoing exemplary embodiments, and various modifications are possible.

[0204] For example, a portion of the construction of one exemplary embodiment may be added to or replaced by a portion of the construction of another exemplary embodiment. Such variations are also included in the exemplary embodiments of this disclosure.

[0205] The photoelectric conversion systems described in the aforementioned seventh and eighth exemplary embodiments are examples of photoelectric conversion systems to which photoelectric conversion devices can be applied. Photoelectric conversion systems to which photoelectric conversion devices according to exemplary embodiments of this disclosure can be applied are not limited to... Figures 25 to 26B The construction shown is identical to that described in the tenth exemplary embodiment, the endoscope described in the eleventh exemplary embodiment, and the smart glasses described in the twelfth exemplary embodiment.

[0206] All the foregoing exemplary embodiments are merely examples of embodiments implemented in accordance with this disclosure, and the interpretation of the technical scope of this disclosure should not be limited thereto. In other words, this disclosure can be implemented in various forms without departing from the technical concept or essential characteristics of this disclosure.

[0207] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The appended claims should be interpreted in the broadest possible sense to encompass all such variations and equivalent structures and functions.

Claims

1. A photoelectric conversion device comprising a plurality of avalanche diodes disposed in a layer having a first surface and a second surface opposite to the first surface. in, Each of the plurality of avalanche diodes includes a first region of a first conductivity type located at a first depth, a second region of a second conductivity type located at a second depth, and a third region of the second conductivity type located at a third depth. The second depth is greater than the first depth relative to the second surface, and the third depth is greater than the second depth relative to the second surface. The layer includes multiple structures disposed in the first surface, and The effective period of the plurality of structures is less than hc / E. a h represents Planck's constant [J∙s], c represents the speed of light [m / s], and E a The band gap of the substrate is indicated [J].

2. The photoelectric conversion device according to claim 1, in, The plurality of structures include trench structures, and Wherein, the width of the trench structure is less than hc / 2E a .

3. The photoelectric conversion device according to claim 1, in, The fourth region of the first conductivity type is located between the second region and the third region, and The impurity concentration of the first conductivity type in the fourth region is lower than that in the first region.

4. The photoelectric conversion device according to claim 3, wherein, In a plan view perpendicular to the first surface, the area where the plurality of structures overlap with the fourth region is greater than the area where the plurality of structures do not overlap with the fourth region.

5. The photoelectric conversion device according to claim 1, in, The fifth region is located at the first depth, and in the plan view from the first surface, the fifth region surrounds the first region, and The impurity concentration in the fifth region is lower than that in the first region.

6. The photoelectric conversion device according to claim 5, wherein, The potential difference between the first region and the second region is greater than the potential difference between the second region and the fifth region.

7. The photoelectric conversion device according to claim 1, wherein, In a plan view perpendicular to the first surface, the multiplication region between the first region and the second region is covered by the plurality of structures.

8. The photoelectric conversion device according to claim 7, wherein, In the plan view in the direction perpendicular to the first surface, the center of gravity of the plurality of structures is located within the multiplication region.

9. The photoelectric conversion device according to claim 7, in, The plurality of avalanche diodes includes a first avalanche diode and a second avalanche diode adjacent to the first avalanche diode, and The pixel isolation portion is disposed between the first avalanche diode and the second avalanche diode.

10. The photoelectric conversion device according to claim 9, in, The plurality of avalanche diodes includes a third avalanche diode adjacent to the second avalanche diode. The first pixel isolation portion is disposed between the first avalanche diode and the second avalanche diode. The second pixel isolation portion is disposed between the second avalanche diode and the third avalanche diode, and In a cross-section perpendicular to the first surface, the second region of the second avalanche diode extends from the first pixel isolation portion to the second pixel isolation portion.

11. The photoelectric conversion device according to claim 10, wherein, In each of the plurality of avalanche diodes, the distance from the first surface to the multiplication region satisfies L√2 / 4 < d < L × √2, where L is the distance from the pixel isolation portion to the nearest pixel isolation portion.

12. The photoelectric conversion device according to claim 7, further comprising an anti-reflective film stacked on the first surface side of the plurality of structures. in, The refractive index of the antireflective film is lower than the effective refractive index of the region sandwiched between the second surface and the first surface of the plurality of structures, and in the plan view in the direction perpendicular to the first surface, the region overlaps with the multiplication region.

13. The photoelectric conversion device according to claim 1, wherein, In a plan view perpendicular to the first surface, the plurality of structures include a T-shaped groove structure.

14. The photoelectric conversion device according to claim 1, wherein, In a plan view perpendicular to the first surface, the plurality of structures include non-periodicly arranged groove structures.

15. The photoelectric conversion device according to claim 1, wherein, The plurality of structures have a non-uniform density distribution within the first surface.

16. The photoelectric conversion device according to claim 15, wherein, The density of the plurality of structures at the center of the avalanche diode is higher than the density of the plurality of structures at the periphery of the avalanche diode.

17. The photoelectric conversion device according to claim 1, wherein, The plurality of structures includes a first structure and a second structure, and the depth from the first surface to the bottom of the first structure is different from the depth from the first surface to the bottom of the second structure.

18. The photoelectric conversion device according to claim 17, wherein, The depth of the first structure from the first surface to the bottom is greater than the depth of the second structure from the first surface to the bottom. The first structure is disposed in the central portion of each of the avalanche diodes, and the second structure is disposed in the peripheral portion of each of the avalanche diodes.

19. The photoelectric conversion device according to claim 17, wherein, The depth of the plurality of structures from the first surface to the bottom at the intersection of the groove portion extending in the first direction and the groove portion extending in the second direction is greater than the depth from the first surface to the bottom of the groove portion extending in the second direction, which is not at the bottom at the intersection with the groove portion extending in the first direction.

20. The photoelectric conversion device according to claim 19, wherein, Compared to half the distance between the first and second faces, the bottom at the intersection is closer to the first face.

21. The photoelectric conversion device according to claim 1, wherein, In a plan view perpendicular to the first surface, the plurality of structures comprise multiple independent regions.

22. The photoelectric conversion device according to claim 1, wherein, The plurality of structures include gaps.

23. The photoelectric conversion device according to claim 1, wherein, The plurality of structures include needle-punched membranes.

24. The photoelectric conversion device according to claim 1, wherein, The effective period of the plurality of structures is less than a wavelength at which the absolute length of the layer is equal to the distance from the first surface to the midpoint between the first region and the second region.

25. A photoelectric conversion device comprising a plurality of avalanche diodes disposed in a layer having a first surface and a second surface opposite to the first surface. in, Each of the plurality of avalanche diodes includes a first region of a first conductivity type located at a first depth, a second region of a second conductivity type located at a second depth, and a third region of the second conductivity type located at a third depth. The second depth is greater than the first depth relative to the second surface, and the third depth is greater than the second depth relative to the second surface. The layer includes multiple structures disposed in the first surface, and The effective period of the plurality of structures is less than 1.1 μm.

26. The photoelectric conversion device according to claim 25, in, The plurality of structures include trench structures, and The width of the groove structure is less than 0.55 μm.

27. The photoelectric conversion device according to claim 25, in, The fourth region of the first conductivity type is located between the second region and the third region, and The impurity concentration of the first conductivity type in the fourth region is lower than that in the first region.

28. The photoelectric conversion device according to claim 25, wherein, The plurality of structures include gaps.

29. A photoelectric conversion system, comprising: The photoelectric conversion device according to any one of claims 1 to 28; as well as A signal processing unit is configured to generate an image using a signal output from the photoelectric conversion device.

30. A mobile body comprising: The photoelectric conversion device according to any one of claims 1 to 28; as well as A control unit is configured to control the movement of the moving body using signals output from the photoelectric conversion device.

Images