Photoelectric conversion device

Abstract

To reduce crosstalk induced by photons due to avalanche light emission reflected at an Si backside of moth-eye structure, as stray light.SOLUTION: A photoelectric conversion apparatus comprises: a plurality of avalanche diodes disposed in a semiconductor layer having a first surface and a second surface facing the first surface; and a light shielding portion having an opening, the light shielding portion covering at least part of the first surface. The plurality of avalanche diodes each includes a first semiconductor region of first conductivity type located at a first depth, and a second semiconductor region of second conductivity type located at a second depth greater than the first depth with respect to the second surface. The semiconductor layer includes a plurality of concavity and convexity structures disposed in the first surface, and in a planar view from a direction perpendicular to the first surface, the first semiconductor region is included in the opening.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] There is a photoelectric conversion device in which a concave-convex structure is provided on the light-receiving surface of the photoelectric conversion element to refract the incident light, thereby lengthening the optical path length of the incident light within the photoelectric conversion element and improving the quantum efficiency. Patent Document 1 describes a single-photon avalanche photodiode (SPAD) that has a concave-convex structure called a moth-eye structure on the light-incident surface side of the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-002542 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the structure described in Patent Document 1 has a problem in that photons generated by avalanche emission are reflected by the rear surface of the Si in the moth-eye structure, and induce crosstalk as stray light.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its object to reduce crosstalk in a photoelectric conversion device using an avalanche photodiode. [Means for solving the problem]

[0006] One aspect of the present invention is a photoelectric conversion device including: a plurality of avalanche diodes arranged in a semiconductor layer having a first surface and a second surface opposite to the first surface; and a reflecting member having an opening and a reflecting portion, the reflecting member covering at least a portion of the first surface, Each of the plurality of avalanche diodes has a first semiconductor region of a first conductivity type arranged at a first depth and a second semiconductor region of a second conductivity type arranged at a second depth deeper than the first depth relative to the second surface, the first conductivity type and the second conductivity type being either N-type or P-type, the first conductivity type and the second conductivity type being different, the semiconductor layer having a plurality of uneven structures provided on the first surface, and an effective period of the plurality of uneven structures being hc / E a (h: Planck's constant [J s], c: speed of light [m / s], E a the second semiconductor region and the reflective portion overlap in a plan view perpendicular to the first surface, the first semiconductor region is included in the opening, and has a third semiconductor region of the second conductivity type disposed at a third depth with respect to the second surface that is deeper than the second depth, and a fourth semiconductor region of the first conductivity type is provided between the second semiconductor region and the third semiconductor region; a sixth semiconductor region of the first conductivity type is provided between the third semiconductor region and the fourth semiconductor region; The photoelectric conversion device is characterized in that the impurity concentration in the fourth semiconductor region is lower than the impurity concentration in the first semiconductor region. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce crosstalk in a photoelectric conversion device using an avalanche photodiode. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a photoelectric conversion device according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of a PD substrate of the photoelectric conversion device according to the embodiment. [Figure 3] FIG. 2 is a schematic diagram of a circuit board of a photoelectric conversion device according to an embodiment. [Figure 4] 2 is a configuration example of a pixel circuit of a photoelectric conversion device according to an embodiment. [Figure 5] FIG. 2 is a schematic diagram illustrating driving of a pixel circuit of a photoelectric conversion device according to an embodiment. [Figure 6] 1 is a cross-sectional view of a photoelectric conversion element according to a first embodiment. [Figure 7] FIG. 2 is a potential diagram of the photoelectric conversion element according to the first embodiment. [Figure 8] 1 is a cross-sectional view of a trench structure of a photoelectric conversion element according to a first embodiment. [Figure 9] FIG. 1 is a plan view of a photoelectric conversion element according to a first embodiment. [Figure 10] 4 is a comparative example of the photoelectric conversion element according to the first embodiment. [Figure 11] 1 is a cross section of a photoelectric conversion element according to a first embodiment. [Figure 12] FIG. 4 is a cross-sectional view of a photoelectric conversion element according to a second embodiment. [Figure 13] FIG. 4 is a plan view of a photoelectric conversion element according to a second embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a photoelectric conversion device according to a modified example of the second embodiment. [Figure 15] FIG. 10 is a plan view of a photoelectric conversion element according to a modified example of the second embodiment. [Figure 16] FIG. 10 is a cross-sectional view of a photoelectric conversion element according to a third embodiment. [Figure 17] FIG. 10 is a plan view of a photoelectric conversion element according to a third embodiment. [Figure 18] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fourth embodiment. [Figure 19] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a fifth embodiment. [Figure 20] FIG. 10 is a functional block diagram of a photoelectric conversion system according to a sixth embodiment. [Figure 21] FIG. 13 is a functional block diagram of a photoelectric conversion system according to a seventh embodiment. [Figure 22] FIG. 13 is a functional block diagram of a photoelectric conversion system according to an eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments shown below are intended to embody the technical concept of the present invention and are not intended to limit the present invention. The size and positional relationship of components shown in each drawing may be exaggerated for clarity. In the following description, the same components may be designated by the same reference numerals and their description may be omitted.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, terms indicating specific directions or positions (for example, "upper," "lower," "right," "left," and other terms including these terms) will be used as necessary. The use of these terms is intended to facilitate understanding of the embodiments with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention.

[0011] In this specification, a planar view refers to a view from a direction perpendicular to the light incident surface of the semiconductor layer. A cross-sectional view refers to a surface perpendicular to the light incident surface of the semiconductor layer. When the light incident surface of the semiconductor layer is a rough surface when viewed microscopically, the planar view is defined based on the light incident surface of the semiconductor layer when viewed macroscopically.

[0012] In the following description, the anode of the avalanche photodiode (APD) is set to a fixed potential, and a signal is extracted from the cathode side. Therefore, the first conductivity type semiconductor region having majority carriers of charges of the same polarity as the signal charge is an N-type semiconductor region, and the second conductivity type semiconductor region having majority carriers of charges of a polarity opposite to that of the signal charge is a P-type semiconductor region. The present invention also applies when the cathode of the APD is set to a fixed potential and a signal is extracted from the anode side. In this case, the first conductivity type semiconductor region having majority carriers of charges of the same polarity as the signal charge is a P-type semiconductor region, and the second conductivity type semiconductor region having majority carriers of charges of a polarity opposite to that of the signal charge is an N-type semiconductor region. While the following description focuses on a case where one node of the APD is set to a fixed potential, the potentials of both nodes may fluctuate.

[0013] In this specification, when the term "impurity concentration" is used simply, it means the net impurity concentration minus the amount compensated for by impurities of the opposite conductivity type. In other words, "impurity concentration" refers to the NET doping concentration. A region where the P-type doped impurity concentration is higher than the N-type doped impurity concentration is a P-type semiconductor region. Conversely, a region where the N-type doped impurity concentration is higher than the P-type doped impurity concentration is an N-type semiconductor region.

[0014] A configuration common to each embodiment of a photoelectric conversion device and a driving method thereof according to the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0015] FIG. 1 is a diagram showing the configuration of a stacked-type photoelectric conversion device 100 according to an embodiment of the present invention. The photoelectric conversion device 100 is configured by stacking and electrically connecting two substrates, a sensor substrate 11 and a circuit substrate 21. The sensor substrate 11 has a first semiconductor layer having a photoelectric conversion element 102 (described later) and a first wiring structure. The circuit substrate 21 has a second semiconductor layer having circuits such as a signal processing unit 103 (described later) and a second wiring structure. The photoelectric conversion device 100 is configured by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in this order. The photoelectric conversion device described in each embodiment is a back-illuminated photoelectric conversion device in which light is incident from a first surface and a circuit substrate is disposed on a second surface.

[0016] In the following description, the sensor substrate 11 and the circuit substrate 21 are described as diced chips, but are not limited to chips. For example, each substrate may be a wafer. Furthermore, each substrate may be stacked in the wafer state and then diced, or may be chipped and then stacked and bonded.

[0017] The sensor substrate 11 has a pixel region 12 arranged thereon, and the circuit substrate 21 has a circuit region 22 arranged thereon for processing signals detected in the pixel region 12 .

[0018] 2 is a diagram showing an example of the arrangement of the sensor substrate 11. Pixels 101, each having a photoelectric conversion element 102 including an avalanche photodiode (hereinafter, referred to as APD), are arranged in a two-dimensional array in plan view to form a pixel region 12.

[0019] The pixel 101 is typically a pixel for forming an image, but when used for TOF (Time of Flight), it does not necessarily have to form an image. In other words, the pixel 101 may be a pixel for measuring the time and amount of light that arrives.

[0020] 3 is a configuration diagram of the circuit board 21. It has a signal processing unit 103 that processes the charges photoelectrically converted by the photoelectric conversion element 102 in FIG. 2, a readout circuit 112, a control pulse generation unit 115, a horizontal scanning circuit unit 111, a signal line 113, and a vertical scanning circuit unit 110.

[0021] The photoelectric conversion element 102 in FIG. 2 and the signal processing unit 103 in FIG. 3 are electrically connected via connection wiring provided for each pixel.

[0022] The vertical scanning circuit unit 110 receives a control pulse supplied from the control pulse generating unit 115 and supplies the control pulse to each pixel. The vertical scanning circuit unit 110 uses logic circuits such as a shift register and an address decoder.

[0023] The signal output from the photoelectric conversion element 102 of the pixel is processed by the signal processing unit 103. The signal processing unit 103 is provided with a counter, a memory, etc., and the memory holds digital values.

[0024] The horizontal scanning circuit unit 111 inputs a control pulse to the signal processing unit 103 to sequentially select each column in order to read out the signal from the memory of each pixel in which the digital signal is held.

[0025] A signal is output to the signal line 113 from the signal processing unit 103 of the pixel selected by the vertical scanning circuit unit 110 for the selected column.

[0026] The signal output to the signal line 113 is output via an output circuit 114 to a recording unit or a signal processing unit outside the photoelectric conversion device 100 .

[0027] In Fig. 2, the photoelectric conversion elements in the pixel region may be arranged one-dimensionally. The effects of the present invention can be obtained even with a single pixel, and the case of a single pixel is also included in the present invention. The function of the signal processing unit does not necessarily need to be provided for each photoelectric conversion element; for example, a single signal processing unit may be shared by multiple photoelectric conversion elements, and signal processing may be performed sequentially.

[0028] 2 and 3, a plurality of signal processing units 103 are arranged in a region overlapping the pixel region 12 in a plan view. A vertical scanning circuit unit 110, a horizontal scanning circuit unit 111, column circuits 112, output circuits 114, and a control pulse generating unit 115 are arranged so as to overlap between an edge of the sensor substrate 11 and an edge of the pixel region 12 in a plan view. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12, and the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the column circuits 112, the output circuits 114, and the control pulse generating unit 115 are arranged in a region overlapping the non-pixel region in a plan view.

[0029] FIG. 4 is an example of a block diagram including the equivalent circuits of FIGS.

[0030] In FIG. 2, the photoelectric conversion element 102 having the APD 201 is provided on a sensor substrate 11, and the other members are provided on a circuit board 21.

[0031] The APD 201 generates charge pairs in response to 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 is supplied to the anode and cathode so that the APD 201 performs avalanche multiplication. With this voltage supplied, charges generated by the incident light undergo avalanche multiplication, generating an avalanche current.

[0032] When a reverse bias voltage is supplied, there are two modes: Geiger mode, in which the anode and cathode are operated at a potential difference greater than the breakdown voltage, and linear mode, in which the anode and cathode are operated at a potential difference close to or less than the breakdown voltage.

[0033] An APD operated in Geiger mode is called a SPAD. For example, the voltage VL (first voltage) is −30 V, and the voltage VH (second voltage) is 1 V. The APD 201 may be operated in either linear mode or Geiger mode. A SPAD is preferable because the potential difference is larger than that of a linear mode APD, resulting in a more pronounced effect in terms of withstand voltage.

[0034] The quench element 202 is connected to a power supply that supplies voltage VH and the APD 201. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, suppressing the voltage supplied to the APD 201 and suppressing avalanche multiplication (quench operation). The quench element 202 also functions to return the voltage supplied to the APD 201 to voltage VH by passing a current equivalent to the voltage drop caused by the quench operation (recharge operation).

[0035] The signal processing unit 103 has a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. In this specification, the signal processing unit 103 may have any one of the waveform shaping unit 210, the counter circuit 211, and the selection circuit 212.

[0036] The waveform shaping unit 210 shapes the potential change at the cathode of the APD 201 obtained when photons are detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. While an example using one inverter as the waveform shaping unit 210 is shown in FIG. 4, a circuit in which multiple inverters are connected in series, or another circuit having a waveform shaping effect, may also be used.

[0037] The counter circuit 211 counts the pulse signals output from the waveform shaping unit 210 and holds the count value. When a control pulse pRES is supplied via a drive line 213, the signal held in the counter circuit 211 is reset.

[0038] A control pulse pSEL is supplied to the selection circuit 212 from the vertical scanning circuit unit 110 in Fig. 3 via a drive line 214 (not shown in Fig. 3) in Fig. 4, and switches between 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 outputting a signal.

[0039] The electrical connection may be switched by disposing a switch such as a transistor between the quench element 202 and the APD 201 or between the photoelectric conversion element 102 and the signal processing unit 103. Similarly, the supply of the voltage VH or the voltage VL to the photoelectric conversion element 102 may be electrically switched using a switch such as a transistor.

[0040] In this embodiment, a configuration using the counter circuit 211 has been described. However, instead of the counter circuit 211, the photoelectric conversion device 100 may be configured to acquire pulse detection timing using a time-to-digital converter (hereinafter referred to as TDC) and a memory. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 is converted into a digital signal by the TDC. To measure the timing of the pulse signal, a control pulse pREF (reference signal) is supplied to the TDC from the vertical scanning circuit unit 110 in FIG. 1 via a drive line. The TDC acquires, as a digital signal, a signal obtained by converting the input timing of the signal output from each pixel via the waveform shaping unit 210 into a relative time based on the control pulse pREF.

[0041] FIG. 5 is a diagram showing a schematic diagram of the relationship between the operation of an APD and an output signal.

[0042] Fig. 5(a) is a diagram illustrating the APD 201, quench element 202, and waveform shaping unit 210 of Fig. 4. Here, the input side of the waveform shaping unit 210 is referred to as node A, and the output side is referred to as node B. Fig. 5(b) shows the waveform change at node A in Fig. 5(a), and Fig. 5(c) shows the waveform change at node B in Fig. 5(a).

[0043] Between time t0 and time t1, a potential difference of VH-VL is applied to the APD 201 in FIG. 5(a). When a photon is incident on the APD 201 at time t1, avalanche multiplication occurs in the APD 201, an avalanche multiplication current flows through the quench element 202, and the voltage at node A drops. As the voltage drop increases and the potential difference applied to the APD 201 decreases, avalanche multiplication in the APD 201 stops, as shown at time t2, and the voltage level at node A drops no more than a certain value. After that, between time t2 and time t3, a current flows through node A from voltage VL to compensate for the voltage drop, and at time t3, node A settles to its original potential level. At this time, the portion of the output waveform at node A that exceeds a certain threshold is shaped by the waveform shaping unit 210 and output as a signal at node B.

[0044] The arrangement of the signal lines 113, the column circuits 112, and the output circuits 114 is not limited to that shown in Fig. 3. For example, the signal lines 113 may be arranged to extend in the row direction, and the column circuits 112 may be arranged at the ends of the signal lines 113.

[0045] The photoelectric conversion devices of the respective embodiments will be described below.

[0046] (First embodiment) The photoelectric conversion device according to the first embodiment will be described with reference to FIGS.

[0047] FIG. 6 is a cross-sectional view of two pixels of the photoelectric conversion element 102 of the photoelectric conversion device according to the first embodiment, taken in a direction perpendicular to the surface direction of the substrate.

[0048] The following describes the structure and function of the photoelectric conversion element 102. The photoelectric conversion element 102 has an N-type first semiconductor region 311, a fourth semiconductor region 314, a sixth semiconductor region 316, and a seventh semiconductor region 317. It also includes a P-type second semiconductor region 312, a third semiconductor region 313, and a fifth semiconductor region 315.

[0049] 6, an N-type first semiconductor region 311 is formed near the surface facing the light incident surface, and an N-type seventh semiconductor region 317 is formed around it. A P-type second semiconductor region 312 is formed at a position overlapping the first semiconductor region and the second semiconductor region in plan view. An N-type fourth semiconductor region 314 is further disposed at a position overlapping the second semiconductor region 312 in plan view, and an N-type sixth semiconductor region 316 is formed around it.

[0050] The first semiconductor region 311 has a higher N-type impurity concentration than 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, and by making the impurity concentration of the second semiconductor region 312 lower than the impurity concentration of the first semiconductor region 311, the entire second semiconductor region 312 becomes a depletion layer region. Furthermore, this depletion layer region extends to a partial region of the first semiconductor region 311, and a strong electric field is induced in the extended depletion layer region. This strong electric field causes avalanche multiplication in the depletion layer region extending to the partial region of the first semiconductor region 311, and a current based on the amplified charge is output as signal charge. Light incident on the photoelectric conversion device 102 is photoelectrically converted, and when avalanche multiplication occurs in this depletion layer region (avalanche multiplication region), the generated first conductivity type charge is collected in the first semiconductor region 311.

[0051] 6, the fourth semiconductor region 314 and the seventh semiconductor region 317 are formed to have approximately the same size, but the size of each semiconductor region is not limited to this. For example, the fourth semiconductor region 314 may be formed to be larger than the seventh semiconductor region 317 so that charges can be collected in the first semiconductor region 311 from a wider range.

[0052] A trench-based uneven structure 325 is formed on the surface of the semiconductor layer on the light incident side. The uneven structure 325 is surrounded by a P-type third semiconductor region 313 and scatters light incident on the photoelectric conversion element 102. Because the incident light travels obliquely within the photoelectric conversion element, an optical path length equal to or greater than the thickness of the semiconductor layer 301 can be ensured, making it possible to photoelectrically convert light with longer wavelengths than in a case where the uneven structure 325 is not provided. Furthermore, the uneven structure 325 prevents reflection of incident light within the substrate, thereby improving the photoelectric conversion efficiency of incident light.

[0053] The fourth semiconductor region 314 and the concave-convex structure 325 are formed so as to overlap in a planar view. The area where the fourth semiconductor region 314 and the concave-convex structure 325 overlap in a planar view is larger than the area of ​​the portion of the fourth semiconductor region 314 that does not overlap with the concave-convex structure 325. Charges generated at a position far from the avalanche multiplication region formed between the first semiconductor region 311 and the fourth semiconductor region 314 take longer to travel to the avalanche multiplication region than charges generated at a position close to the avalanche multiplication region. This may result in worsening timing jitter. By arranging the fourth semiconductor region 314 and the concave-convex structure 325 so as to overlap in a planar view, the electric field deep inside the photodiode can be increased, shortening the collection time for charges generated at a position far from the avalanche multiplication region, thereby reducing timing jitter.

[0054] Furthermore, the third semiconductor region 313 three-dimensionally covers the concave-convex structure, which can suppress the generation of thermally excited charges at the interface of the concave-convex structure, thereby suppressing the DCR (Dark Count Rate) of the photoelectric conversion element.

[0055] Pixels are separated by a pixel separator 324 with a trench structure, and a P-type fifth semiconductor region 315 formed around the pixel separator separates adjacent photoelectric conversion elements by a potential barrier. Because the photoelectric conversion elements are also separated by the potential of the fifth semiconductor region 315, a trench structure such as the pixel separator 324 is not essential for the pixel separator. Furthermore, even when the pixel separator 324 is provided, its depth and position are not limited to the configuration shown in FIG. 6 . The pixel separator 324 may be a deep trench isolation (DTI) that penetrates the semiconductor layer, or a DTI that does not penetrate the semiconductor layer. Metal may be embedded in the DTI to improve light-blocking performance. The pixel separator 324 may be configured to surround the entire periphery of the photoelectric conversion element in a planar view, or may be configured only on the opposite side of the photoelectric conversion element, for example.

[0056] It is also possible to regard the distance from the pixel separation section to the pixel separation section of an adjacent pixel or a pixel provided at the nearest position as the size of one photoelectric conversion element 102. When the size of one photoelectric conversion element 102 is L, the distance d from the light incident surface to the avalanche multiplication region satisfies L√2 / 4 < d < L×√2. When the size and depth of the photoelectric conversion element satisfy this relational expression, the strength of the electric field in the depth direction and the strength of the electric field in the plane direction in the vicinity of the first semiconductor region 311 become approximately the same. Since the variation in the time required for charge collection can be suppressed, the generation of timing jitter can be reduced.

[0057] On the light incident surface side of the semiconductor layer, a pinning film 321, a planarization film 322, and a microlens 323 are further formed. A filter layer (not shown) and the like may be further arranged on the light incident surface side. Various optical filters such as a color filter, an infrared cut filter, and a monochrome filter can be used for the filter layer. For the color filter, an RGB color filter, an RGBW color filter, etc. can be used.

[0058] In addition, in the photoelectric conversion device according to the present embodiment, a reflecting member 326 having an opening 327 is provided on the light incident surface side of the semiconductor layer. The opening 327 is provided so as to enclose the first semiconductor region 311 in a plan view perpendicular to the light incident surface. With such a configuration, by scattering the incident light within the pixel, an optical path length greater than or equal to the thickness of the semiconductor layer is ensured, enabling the conversion of light with a longer wavelength, and at the same time, the avalanche emission light described later can be efficiently escaped from the semiconductor layer.

[0059] FIG. 7 is a potential diagram of the photoelectric conversion element 102 shown in FIG. 6.

[0060] The dotted line 70 in FIG. 7 indicates the potential distribution of the line segment FF' in FIG. 6, and the solid line 71 in FIG. 7 indicates the potential distribution of the line segment EE' in FIG. 6. FIG. 7 shows the potential as seen from the perspective of electrons, which are the main carrier charge in the N-type semiconductor region. If the main carrier charge is holes, the relationship between high and low potentials is reversed. Furthermore, depth A in FIG. 7 corresponds to height A in FIG. 6. Similarly, depth B corresponds to height B, depth C corresponds to height C, and depth D corresponds to height D.

[0061] 7, the potential height of the solid line 71 at depth A is A1, the potential height of the dotted line 70 is A2, the potential height of the solid line 71 at depth B is B1, and the potential height of the dotted line 70 is B2. Also, the potential height of the solid line 71 at depth C is C1, the potential height of the dotted line 70 is C2, and the potential height of the solid line 71 at depth D is D1, and the potential height of the dotted line 70 is D2.

[0062] 6 and 7, the potential height of the first semiconductor region 311 corresponds to A1, and the potential height near the center of the second semiconductor region 312 corresponds to B1. In addition, the potential height of the seventh semiconductor region 317 corresponds to A2, and the potential height of the outer edge of the second semiconductor region 312 corresponds to B2.

[0063] 7, the potential gradually decreases from depth D to depth C. Then, the potential gradually increases from depth C to depth B, and the potential reaches level B2 at depth B. Furthermore, the potential decreases from depth B to depth A, and reaches level A2 at depth A.

[0064] On the other hand, with respect to the solid line 71, the potential gradually decreases from depth D to depth C and from depth C to depth B, reaching level B1 at depth B. Then, the potential sharply decreases from depth B to depth A, reaching level A1 at depth A. At depth D, the potentials of the dotted line 70 and the solid line 71 are approximately the same height, and in the regions indicated by line segments EE' and FF', there is a potential gradient that gradually decreases toward the second surface of the semiconductor layer 301. Therefore, charges generated in the photodetector move toward the second surface due to the gentle potential gradient.

[0065] In the avalanche diode of this embodiment, the P-type second semiconductor region 312 has a lower impurity concentration than the N-type first semiconductor region 311, and potentials are supplied to the first semiconductor region 311 and the second semiconductor region 312 such that they are reverse biased to each other. As a result, a depletion layer region is formed on the second semiconductor region 312 side. With this structure, the second semiconductor region 312 acts as a potential barrier for charges photoelectrically converted in the fourth semiconductor region 314, making it easier for the charges to be collected in the first semiconductor region 311.

[0066] 6, the second semiconductor region 312 is formed over the entire surface of the photoelectric conversion element. However, for example, the second semiconductor region 312 may not be provided in the portion overlapping the first semiconductor region 311 in a plan view, and a slit through which the fourth semiconductor region 314 extends may be formed. In this case, due to a potential difference between the second semiconductor region 312 and the slit portion, the potential decreases from the line segment FF' to the line segment EE' at depth C in FIG. 6. As a result, in the process of transferring charges photoelectrically converted in the fourth semiconductor region 314, the charges tend to move toward the first semiconductor region 311. On the other hand, when the second semiconductor region 312 is formed over the entire surface as in FIG. 6, the applied voltage required to generate a strong electric field necessary for avalanche multiplication can be lowered compared to when a slit is formed, and noise due to the formation of a localized strong electric field region can be suppressed.

[0067] The charges that have moved to the vicinity of the second semiconductor region 312 are accelerated by the steep potential gradient from depth B to depth A of the solid line 71 in FIG. 7, that is, by the strong electric field, and are avalanche multiplied.

[0068] In contrast, between the seventh semiconductor region 317 and the P-type second semiconductor region 312 in Fig. 6, that is, from depth B to depth A of the dotted line 70 in Fig. 7, the potential distribution is such that avalanche multiplication does not occur. Therefore, the charge generated in the fourth semiconductor region 314 can be counted as signal charge without increasing the area of ​​the strong electric field region (avalanche multiplication region) relative to the size of the photodiode. Note that although the seventh semiconductor region 317 has been described so far as having an N-type conductivity, it may also be a P-type semiconductor region as long as its concentration satisfies the above-mentioned potential relationship.

[0069] Furthermore, the charges photoelectrically converted in the second semiconductor region 312 flow into the fourth semiconductor region 314 due to the potential gradient from depth B to depth C of the dotted line 70 in FIG. 7. For the reasons described above, the fourth semiconductor region 314 has a structure in which the charges easily move to the second semiconductor region 312. Therefore, the charges photoelectrically converted in the second semiconductor region 312 move to the first semiconductor region 311 and are detected as signal charges by avalanche multiplication. Therefore, the fourth semiconductor region 314 is sensitive to the charges photoelectrically converted in the second semiconductor region 312.

[0070] 3. In addition, dotted line 70 in FIG. 7 indicates the cross-sectional potential of line segment FF' in FIG. 3. In the dotted line 70, the intersection of height A and line segment FF' in FIG. 6 is designated A2, the intersection of height B and line segment FF' is designated B2, the intersection of height C and line segment FF' is designated C2, and the intersection of height D and line segment FF' is designated D2. Electrons photoelectrically converted in the fourth semiconductor region 314 in FIG. 6 move along the potential D2 to C2 in FIG. 7. However, the electrons cannot overcome the potential barrier between C2 and B2. Therefore, the electrons move to the center of the fourth semiconductor region 314 in FIG. 6, indicated by line segment EE'. The electrons move along the potential gradient from C1 to B1 in FIG. 7, are avalanche-multiplied by the steep potential gradient from B1 to A1, and are detected as signal charges after passing through the first semiconductor region 311.

[0071] 6 moves along the potential gradient from potential B2 to C2 in FIG. 7. Then, as described above, it moves to the center of the fourth semiconductor region 314 indicated by the line segment EE' in FIG. 6. Then, it is avalanche-multiplied by the steep potential gradient from B1 to A1. The avalanche-multiplied charge passes through the first semiconductor region 311 and is detected as signal charge.

[0072] FIG. 8 is an enlarged cross-sectional view of two of the trenches forming the concave-convex structure 325 of the photovoltaic device according to the first embodiment.

[0073] The trench structure is composed of a material different from that of the third semiconductor region 313. For example, if the third semiconductor region 313 is silicon, the main components constituting the trench structure are a silicon oxide film or a silicon nitride film, but metals or organic materials may also be included. The trench is formed, for example, to a depth of 0.1 to 0.6 μm from the surface of the semiconductor layer. To sufficiently enhance the diffraction of incident light, it is desirable that the trench depth be greater than the trench width. Here, the trench width refers to the width from the interface between the pinning film 321 and the third semiconductor region 313 to the interface between the pinning film 321 and the third semiconductor region 313 on a plane passing through the center of gravity of the trench cross section, and the trench depth refers to the depth from the light incident surface to the bottom of the trench.

[0074] 8 indicates one period of concave-convex structure 325 formed by multiple trenches. The distance from the center of gravity of one trench in the concave-convex structure to the center of gravity of another trench adjacent to that trench in the cross-sectional view is defined as the period of concave-convex structure 325, and the average of the periods of the concaves and convexes of the entire concave-convex structure 325 is defined as the effective period.

[0075] The trench formation process will be described. First, a groove is formed in the third semiconductor region 313 of the semiconductor layer by etching. Then, a pinning 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 inside of the trench covered with the pinning film 321 is filled with a filling material 332. The trench forming the concave-convex structure 325 can be filled using the same process as the trench forming the pixel separating portion. In this case, the sidewall portion of the trench forming the concave-convex structure 325 and the sidewall portion of the trench forming the pixel separating portion have the same impurity concentration.

[0076] The filling member 332 may have voids 331 therein. Because the refractive index of the voids 331 is lower than the refractive index of the filling member 332, an optical path difference occurs between light that passes through the voids and light that passes through other parts. Compared to when no voids are provided in the filling member, the refractive index difference across the entire uneven structure 325 is larger, and the phase difference generated in the light that passes through the uneven structure 325 is also larger, which makes it easier to strengthen the diffraction of incident light. In other words, by providing voids in the filling member, the intensity of incident light is increased at a specific phase, resulting in the effect of improving sensitivity.

[0077] 9A and 9B are plan views of two pixels of the photoelectric conversion device according to the first embodiment, in which Fig. 9A is a plan view seen from the surface opposite to the light incident surface, and Fig. 9B is a plan view seen from the light incident surface side.

[0078] 9(a), the first semiconductor region 311, the fourth semiconductor region 314, and the seventh semiconductor region 317 are circular and arranged concentrically. This structure has the effect of suppressing local electric field concentration at the edge of the strong electric field region between the first semiconductor region 311 and the second semiconductor region 312, thereby reducing the DCR. The shape of each semiconductor region is not limited to a circle, and may be, for example, a polygon with the center of gravity aligned.

[0079] In FIG. 9(b), the concave-convex structure 325 is formed in a lattice shape in a planar view. The concave-convex structure 325 is formed so as to overlap the first semiconductor region 311 and the fourth semiconductor region 314, and the center of gravity of the concave-convex structure 325 is contained within the avalanche multiplication region in a planar view. In the lattice-shaped trench structure shown in FIG. 9(b), the trench depth at the trench intersection is deeper than the trench depth at the trench portion where the trench extends alone. However, the bottom of the trench at the trench intersection is located closer to the light incident surface than half the thickness of the semiconductor layer. Here, the trench depth is the depth from the second surface to the bottom, and can also be referred to as the depth of the recess of the concave-convex structure 325.

[0080] 10 is a comparative example of the photoelectric conversion device 102 according to the first embodiment. The photoelectric conversion device 102 is shown in a simplified form in FIG. 10. The photoelectric conversion device 102 is a photoelectric conversion device having an avalanche multiplication region 501, a wiring layer 502, and a concave-convex structure 325.

[0081] When light is incident on such a photoelectric conversion element, avalanche emission may occur in the avalanche multiplication region 501. Avalanche emission is a phenomenon in which a large number of electrons or holes generated by avalanche multiplication recombine with charges of opposite polarity to generate photons. Photons generated by avalanche emission leak into adjacent pixels, causing false signals and degrading image quality.

[0082] In the photoelectric conversion element shown in FIG. 10, the effective period of the uneven structure 325 formed on the light incident surface side of the semiconductor layer is longer than the avalanche emission wavelength. Here, the spectrum of the avalanche emission light has a certain extent of spread from short wavelengths to long wavelengths, but the short-wavelength components have a short absorption length in the substrate and are photoelectrically converted at a position close to the light-emitting region, so there is a low probability that they will reach adjacent pixels and generate false signals. On the other hand, the long-wavelength components have a long absorption length in the substrate and are more likely to generate false signals at positions farther from the light-emitting region, which is the dominant cause of the image quality degradation. Therefore, the component with the maximum wavelength in the spectrum of the avalanche emission light can be approximately considered to be the representative cause of the image quality degradation. The maximum wavelength of the avalanche emission is determined by the band gap of the substrate material, and is expressed as hc / E a (h: Planck's constant [J s], c: speed of light [m / s], E a For example, if the sensor substrate is silicon, the maximum wavelength of the avalanche emission light is about 1.1 μm.

[0083] When the effective period of the concave-convex structure is larger than the wavelength of the avalanche emission, the avalanche emission light behaves like particles in relation to the concave-convex structure. Because the effective refractive index changes sharply with depth in the semiconductor layer, the avalanche emission light is reflected by the bottom of the concave-convex structure, and the reflected light becomes stray light within the pixel.

[0084] 11 shows an example of a photoelectric conversion device according to the first embodiment. In FIG. 11, the photoelectric conversion device 102 is shown in a simplified form, similar to FIG.

[0085] In the photoelectric conversion element 102 shown in FIG. 11, the period of the concave-convex structure formed on the light incident surface side of the semiconductor layer is shorter than the wavelength of avalanche emission. When the sensor substrate is made of silicon, the concave-convex structure is formed with a period of 1.1 μm to 0.2 μm. When avalanche emission occurs in such a photoelectric conversion element, the avalanche emission light behaves like a wave. Because the change in effective refractive index with respect to the substrate depth is gradual, the reflection of the avalanche emission light at the bottom of the concave-convex structure is reduced, and the avalanche emission light incident on the concave-convex structure travels toward the outside of the substrate, thereby suppressing stray light within the pixel. In this case, by arranging the concave-convex structure in the center of the photoelectric conversion element where the light intensity of the avalanche emission light is high on the light incident surface of the semiconductor layer, the effect of suppressing stray light can be achieved more efficiently.

[0086] 11 has a smaller avalanche multiplication region 501 than the photoelectric conversion element shown in Fig. 10. As explained in Fig. 7, the structure is such that the charge generated by photoelectric conversion can be counted as signal charge without increasing the area of ​​the avalanche multiplication region relative to the size of the photodiode. If the area of ​​the avalanche multiplication region is small, the range in which avalanche emission light can be generated also becomes smaller, making it easier for the generated avalanche emission light to escape through the opening that overlaps the avalanche multiplication region in a plan view.

[0087] 11 is tapered and does not have a uniform width. In such a concave-convex structure, the effect of the present invention can be obtained as long as the average width in the cross-sectional structure (the width at half the trench depth in FIG. 11) satisfies the condition that the period is smaller than the avalanche emission wavelength. In other words, the trench width is hc / 2E a (h: Planck's constant [J s], c: speed of light [m / s], E aFor example, if the sensor substrate is made of silicon, the trench width is 0.55 μm or less. It can also be said that the effective period is smaller than the wavelength at which the optical absorption length of the semiconductor substrate is equal to the distance from the light incident surface to the interface between the first semiconductor region and the second semiconductor region.

[0088] The wiring layer 502 includes an aluminum wiring or the like, and functions as a reflecting member that reflects light transmitted through the semiconductor layer 301 into the inside of the pixel.

[0089] In this way, by providing a reflective member having an opening that contains the charge collection portion in a planar view, the incident light is scattered, the optical path length is ensured, and the avalanche emission light is efficiently released outside the semiconductor layer, thereby reducing crosstalk.

[0090] (Second embodiment) A photoelectric conversion device according to the second embodiment will be described with reference to FIGS.

[0091] The description of the parts common to the first embodiment will be omitted, and the description will be focused mainly on the parts different from the first embodiment. In this embodiment, a waveguide structure is provided on the light incident surface side of the photoelectric conversion device.

[0092] FIG. 12 is a cross-sectional view of two pixels of the photoelectric conversion device according to the second embodiment, and FIG. 13 is a plan view of the two pixels.

[0093] A stopper film 331 is formed on a reflecting member 326 formed on the light incident surface side of the semiconductor layer 301, and a waveguide 328 is provided in a region overlapping an opening 327 in a planarizing layer 322 formed on the stopper film 331.

[0094] The planarization film 322 is made of, for example, SiO, and the waveguide 328 is made of, for example, SiN or SiON, a material with a higher refractive index than the planarization film 322. The waveguide 328 is formed by filling a groove made in the planarization film 322 by etching with a waveguide material. A stopper film 331 formed on the reflecting member 326 prevents etching damage to the semiconductor layer 301.

[0095] By providing the waveguide 328 on the light incident surface side, the light collection efficiency to the opening 327 is increased, improving the PDE. In addition, by configuring the upper surface of the tapered waveguide 328 to include the opening 327 of the reflecting member 326, the light collection efficiency to the opening 327 can be further increased.

[0096] (Modification of the second embodiment) FIG. 14 shows a pixel plan view of two pixels of a photoelectric conversion device according to a modified example of the second embodiment, and FIG. 15 shows a pixel plan view of the two pixels.

[0097] 13, the stopper film 331 is formed parallel to the upper surface of the reflecting member 326. In the photoelectric conversion device shown in Fig. 14, the stopper film 331 is formed along the outer shape of the reflecting member 326, and the lower surface of the waveguide 328 extends to a position closer to the light incident surface of the semiconductor layer 301 than the upper surface of the reflecting member 326. With this configuration, it is possible to further improve the efficiency of light collection by the waveguide 328 onto the opening 327.

[0098] (Third embodiment) A photoelectric conversion device according to the third embodiment will be described with reference to FIGS.

[0099] The explanation of the parts common to the first and second embodiments will be omitted, and the explanation will be focused mainly on the parts that differ from the first embodiment.

[0100] 16 is a cross-sectional view perpendicular to the surface direction of the substrate of the photoelectric conversion element 102 of the photoelectric conversion device according to the seventh embodiment. In the photoelectric conversion device according to this embodiment, the N-type first semiconductor region 311 occupies a larger proportion of the light receiving surface of the pixel than in the photoelectric conversion device according to the first embodiment, and the seventh semiconductor region 317 is disposed between the first semiconductor region 311 and the second semiconductor region 312.

[0101] The uneven structure 325 has a quadrangular pyramidal shape, with its cross section forming a triangle with the light incident surface as the base.

[0102] 17A and 17B are pixel plan views of two pixels of a photoelectric conversion device according to the seventh embodiment. Fig. 17A is a plan view seen from the surface opposite to the light incident surface, and Fig. 17B is a plan view seen from the light incident surface side.

[0103] In a plan view from the light incident surface side, the third semiconductor region 313 is disposed between the first semiconductor region 311 and the second semiconductor region 312. Incident light is avalanche multiplied between the first semiconductor region 311 and the second semiconductor region 312. Therefore, when the pixel aperture is designed so that the first semiconductor region 311 and the second semiconductor region 312 are exposed, the aperture ratio of the photoelectric conversion device according to this embodiment is smaller than the aperture ratios of the photoelectric conversion devices according to the first to fifth embodiments. The smaller aperture ratio makes it possible to reduce the volume of the photoelectric conversion region where a signal can be detected, thereby reducing crosstalk.

[0104] Also in this embodiment, the first semiconductor region 311 is enclosed within the opening 327 in plan view, and therefore, the effect of improving PDE (photon detection efficiency) due to the improvement in light collection efficiency can be obtained.

[0105] (Fourth embodiment) The photoelectric conversion system according to this embodiment will be described with reference to Fig. 18. Fig. 18 is a block diagram showing a schematic configuration of the photoelectric conversion system according to this embodiment.

[0106] The photoelectric conversion devices described in the first to sixth embodiments can be applied to various photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Also included in the photoelectric conversion system is a camera module equipped with an optical system such as a lens and an imaging device. Fig. 18 illustrates a block diagram of a digital still camera as an example of such systems.

[0107] 18 includes an image pickup device 1004, which is an example of a photoelectric conversion device, and a lens 1002 that forms an optical image of a subject on the image pickup device 1004. The system further includes an aperture 1003 that adjusts the amount of light passing through the lens 1002, and a barrier 1001 that protects the lens 1002. The lens 1002 and aperture 1003 form an optical system that focuses light on the image pickup device 1004. The image pickup device 1004 is a photoelectric conversion device according to any of the above embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

[0108] The photoelectric conversion system also includes a signal processing unit 1007, which is an image generation unit that generates an image by processing an output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compressions as necessary to output image data. The signal processing unit 1007 may be formed on the same semiconductor substrate on which the imaging device 1004 is provided, or may be formed on a semiconductor substrate separate from the imaging device 1004.

[0109] The photoelectric conversion system further includes a memory unit 1010 for temporarily storing image data, and an external interface unit (external I / F unit) 1013 for communicating with an external computer or the like. The photoelectric conversion system further includes a recording medium 1012 such as a semiconductor memory for recording or reading out imaging data, and a recording medium control interface unit (recording medium control I / F unit) 1011 for recording or reading out data from the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system or may be detachable.

[0110] The photoelectric conversion system further includes an overall control and calculation unit 1009 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the image capture device 1004 and the signal processing unit 1007. Here, timing signals and the like may be input from outside, and the photoelectric conversion system only needs to include at least the image capture device 1004 and the signal processing unit 1007 that processes the output signal output from the image capture device 1004.

[0111] The imaging device 1004 outputs an imaging signal to a signal processing unit 1007. The signal processing unit 1007 performs predetermined signal processing on the imaging signal output from the imaging device 1004 and outputs image data. The signal processing unit 1007 generates an image using the imaging signal.

[0112] As described above, according to this embodiment, it is possible to realize a photoelectric conversion system to which the photoelectric conversion device (imaging device) according to any one of the above embodiments is applied.

[0113] (Fifth embodiment) The photoelectric conversion system and the moving object of this embodiment will be described with reference to Fig. 19. Fig. 19 is a diagram showing the configuration of the photoelectric conversion system and the moving object of this embodiment.

[0114] FIG. 19(a) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 1300 includes an image capture device 1310. The image capture device 1310 is the photoelectric conversion device described in any of the above embodiments. The photoelectric conversion system 1300 includes an image processing unit 1312 that performs image processing on multiple pieces of image data acquired by the image capture device 1310, and a parallax acquisition unit 1314 that calculates parallax (phase difference between parallax images) from the multiple pieces of 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 an object based on the calculated parallax, and a collision determination unit 1318 that determines whether or not there is a possibility of a collision based on the calculated distance. Here, the parallax acquisition unit 1314 and the distance acquisition unit 1316 are examples of distance information acquisition means that acquire distance information to the object. That is, the distance information is information related to the parallax, the defocus amount, the distance to the object, etc. The collision determination unit 1318 may determine the possibility of a collision using any of these distance information. The distance information acquisition means may be realized by dedicated hardware, a software module, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a combination thereof.

[0115] The photoelectric conversion system 1300 is connected to a 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 a control ECU 1330, which is a control unit that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 1318. The photoelectric conversion system 1300 is also connected to an alarm device 1340 that issues an alarm to the driver based on the determination result of the collision determination unit 1318. For example, if the determination result of the collision determination unit 1318 indicates a high possibility of a collision, the control ECU 1330 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 1340 warns the user by sounding an alarm, displaying alarm information on a screen of a car navigation system, etc., or vibrating the seat belt or steering wheel.

[0116] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are imaged by the photoelectric conversion system 1300. Fig. 19(b) shows the photoelectric conversion system when imaging the area in front of the vehicle (imaging range 1350). A vehicle information acquisition device 1320 sends instructions to the photoelectric conversion system 1300 or the imaging device 1310. This configuration can further improve the accuracy of distance measurement.

[0117] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, and control of automatic driving to prevent deviation from a lane. Furthermore, the photoelectric conversion system is not limited to vehicles such as the subject vehicle, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the present invention can be applied not only to moving bodies but also to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0118] (Sixth embodiment) The photoelectric conversion system of this embodiment will be described with reference to Fig. 20. Fig. 20 is a block diagram showing an example of the configuration of a range image sensor which is the photoelectric conversion system of this embodiment.

[0119] 20, the range image sensor 401 is configured to include an optical system 407, a photoelectric conversion device 408, an image processing circuit 404, a monitor 405, and a memory 406. The range image sensor 401 can obtain a range image according to the distance to the subject by receiving light (modulated light or pulsed light) that is projected toward the subject from a light source device 409 and reflected from the surface of the subject.

[0120] The optical system 407 is configured to have one or more lenses, and guides image light (incident light) from a subject to the photoelectric conversion device 408, forming an image on the light receiving surface (sensor section) of the photoelectric conversion device 408.

[0121] The photoelectric conversion device 408 is the photoelectric conversion device of each of the above-described embodiments, and a distance signal indicating a distance determined from a light reception signal output from the photoelectric conversion device 408 is supplied to the image processing circuit 404.

[0122] 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 by this image processing is then supplied to a monitor 405 for display, or supplied to a memory 406 for storage (recording).

[0123] In the range image sensor 401 configured in this way, by applying the above-described photoelectric conversion device, it is possible to obtain, for example, a more accurate range image as the pixel characteristics improve.

[0124] (Seventh embodiment) The photoelectric conversion system of this embodiment will be described with reference to Fig. 21. Fig. 21 is a diagram showing an example of a schematic configuration of an endoscopic surgery system, which is the photoelectric conversion system of this embodiment.

[0125] 21 shows an operator (doctor) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgery system 1150. As shown in the figure, the endoscopic surgery system 1150 is composed of an endoscope 1100, a surgical tool 1110, and a cart 1134 on which various devices for endoscopic surgery are mounted.

[0126] The endoscope 1100 is composed of a lens barrel 1101, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 1132, and a camera head 1102 connected to the base end of the lens barrel 1101. In the example shown, the endoscope 1100 is configured as a so-called rigid lens barrel having a rigid lens barrel 1101, but the endoscope 1100 may also be configured as a so-called flexible lens barrel having a flexible lens barrel.

[0127] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 1101. A light source device 1203 is connected to the endoscope 1100, and light generated by the light source device 1203 is guided to the tip of the lens barrel by a light guide extending inside the lens barrel 1101, and is irradiated via the objective lens towards an observation target inside the body cavity of the patient 1132. The endoscope 1100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0128] An optical system and a photoelectric conversion device are provided inside the camera head 1102, and light reflected from an observation object (observation light) is focused onto the photoelectric conversion device by the optical system. The observation light is photoelectrically converted by the photoelectric conversion device to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observation image. The photoelectric conversion device may be any of the photoelectric conversion devices described in the above-described embodiments. The image signal is sent to a camera control unit (CCU) 1135 as RAW data.

[0129] The CCU 1135 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and performs overall control of the operations of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives an image signal from the camera head 1102, and performs various types of image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

[0130] Under the control of the CCU 1135 , the display device 1136 displays an image based on the image signal that has been subjected to image processing by the CCU 1135 .

[0131] The light source device 1203 is configured from a light source such as an LED (Light Emitting Diode), and supplies the endoscope 1100 with irradiation light when photographing an operation site or the like.

[0132] The input device 1137 is an input interface for the endoscopic surgery system 1150. A user can input various information and instructions to the endoscopic surgery system 1150 via the input device 1137.

[0133] The treatment tool control device 1138 controls the driving of the energy treatment tool 1112 for cauterizing tissue, incising, sealing blood vessels, or the like.

[0134] The light source device 1203, which supplies illumination light to the endoscope 1100 when photographing the surgical site, can be configured from a white light source configured from, for example, an LED, a laser light source, or a combination of these. When the white light source is configured from a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, making it possible to adjust the white balance of the captured image in the light source device 1203. In this case, it is also possible to capture images corresponding to each RGB color in a time-division manner by irradiating the object of observation with laser light from each RGB laser light source in a time-division manner and controlling the drive of the image sensor of the camera head 1102 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter to the image sensor.

[0135] Furthermore, the light source device 1203 may be controlled to change the intensity of light it outputs at predetermined time intervals. By controlling the driving of the image sensor of the camera head 1102 in synchronization with the timing of the change in the light intensity to acquire images in a time-division manner and combining the images, it is possible to generate an image with a high dynamic range that is free of so-called blocked-up shadows and blown-out highlights.

[0136] The light source device 1203 may also be configured to supply light in a predetermined wavelength band corresponding to special light observation. Special light observation utilizes, for example, the wavelength dependency of light absorption in body tissue. Specifically, specific tissue, such as blood vessels on the surface of the mucous membrane, can be photographed with high contrast by irradiating light with a narrower band than the light (i.e., white light) used in normal observation. Alternatively, special light observation may involve fluorescence observation, in which an image is obtained using fluorescence generated by irradiating excitation light. Fluorescence observation can involve irradiating excitation light onto body tissue and observing the fluorescence from the body tissue, or locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the body tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 1203 may be configured to supply narrow band light and / or excitation light corresponding to such special light observation.

[0137] (Eighth embodiment) The photoelectric conversion system of this embodiment will be described with reference to FIGS. 22(a) and (b). FIG. 22(a) illustrates glasses 1600 (smart glasses) which are the photoelectric conversion system of this embodiment. The glasses 1600 have a photoelectric conversion device 1602. The photoelectric conversion device 1602 is the photoelectric conversion device described in each of the above embodiments. A display device including a light-emitting device such as an OLED or LED may be provided on the back side of the lens 1601. There may be one or more photoelectric conversion devices 1602. A combination of multiple types of photoelectric conversion devices may also be used. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in FIG. 22(a).

[0138] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device. The control device 1603 also controls the operations of the photoelectric conversion device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light onto the photoelectric conversion device 1602.

[0139] FIG. 22(b) illustrates glasses 1610 (smart glasses) according to one application example. The glasses 1610 include a control device 1612, which includes a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. A lens 1611 includes an optical system for projecting light emitted from the photoelectric conversion device and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source for supplying power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device may include a gaze detection unit for detecting the gaze of the wearer. Infrared light may be used for gaze detection. The infrared light emitter emits infrared light toward the eyeball of a user gazing at a displayed image. An imaging unit with a light-receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. A reduction unit for reducing light from the infrared light emitter to the display unit in a planar view reduces degradation of image quality.

[0140] The gaze of the user relative to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be used for gaze detection using an image of the eyeball. One example is a gaze detection method based on the Purkinje image formed by reflection of irradiated light on the cornea.

[0141] More specifically, gaze detection processing is performed based on the pupil-corneal reflex method, which calculates a gaze vector representing the direction (rotation angle) of the eyeball based on the pupil image and Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0142] The display device of this embodiment may have a photoelectric conversion device having a light receiving element, and may control the image displayed on the display device based on information about the user's line of sight from the photoelectric conversion device.

[0143] Specifically, the display device determines a first field of view area where the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be determined by an external control device and received. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0144] The display area may include a first display area and a second display area different from the first display area, and a high-priority area may be determined from the first display area and the second display area based on line-of-sight information. The first and second field-of-view areas may be determined by a control device of the display device, or may be determined by an external control device and received. The resolution of the high-priority area may be controlled to be higher than the resolution of areas other than the high-priority area. In other words, the resolution of an area with a relatively low priority may be lowered.

[0145] Note that AI may be used to determine the first field of view area and areas with high priority. The AI ​​may be a model configured to estimate the angle of gaze and the distance to an object in the line of sight from an image of the eyeball, using as training data an image of the eyeball and the direction in which the eyeball in the image was actually looking. The AI ​​program may be included in the display device, the photoelectric conversion device, or an external device. If included in an external device, it is transmitted to the display device via communication.

[0146] When display control is performed based on visual recognition detection, the present invention is preferably applied to smart glasses that further include a photoelectric conversion device for capturing images of the outside world. The smart glasses can display captured external information in real time.

[0147] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0148] For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is replaced with another embodiment, is also included in the embodiments of the present invention.

[0149] Furthermore, the photoelectric conversion systems shown in the fourth and fifth embodiments are examples of photoelectric conversion systems to which a photoelectric conversion device can be applied, and photoelectric conversion systems to which the photoelectric conversion device of the present invention can be applied are not limited to the configurations shown in Figures 18 and 19. The same applies to the ToF system shown in the sixth embodiment, the endoscope shown in the seventh embodiment, and the smart glasses shown in the eighth embodiment.

[0150] It should be noted that the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0151] 100 Photoelectric conversion device 101 pixels 311 first semiconductor region 312 Second semiconductor region 325 Uneven structure 326 Reflective material 327 Opening

Claims

1. A photoelectric conversion device comprising: a plurality of avalanche diodes disposed in a semiconductor layer having a first surface and a second surface opposite to the first surface; and a reflecting member having an opening and a reflecting portion, the reflecting member covering at least a portion of the first surface, each of the plurality of avalanche diodes includes a first semiconductor region of a first conductivity type disposed at a first depth, and a second semiconductor region of a second conductivity type disposed at a second depth that is deeper than the first depth relative to the second surface; The first conductivity type and the second conductivity type are either N-type or P-type, and the first conductivity type and the second conductivity type are different, the semiconductor layer has a plurality of uneven structures provided on the first surface, The effective period of the plurality of concave-convex structures is hc / E ａ (h: Planck's constant [J s], c: speed of light [m / s], E ａ : smaller than the band gap of silicon [J], the second semiconductor region and the reflective portion overlap each other in a plan view perpendicular to the first surface, and the first semiconductor region is included in the opening; a third semiconductor region of the second conductivity type disposed at a third depth that is deeper than the second depth relative to the second surface; a fourth semiconductor region of the first conductivity type is provided between the second semiconductor region and the third semiconductor region; a sixth semiconductor region of the first conductivity type is provided between the third semiconductor region and the fourth semiconductor region; A photoelectric conversion device, characterized in that the impurity concentration in the fourth semiconductor region is lower than the impurity concentration in the first semiconductor region.

2. the plurality of concave-convex structures are formed by trench structures, The width of the trench structure at half the depth of the trench structure is hc / 2E ａ (h: Planck's constant [J s], c: speed of light [m / s], E ａ 2. The photoelectric conversion device according to claim 1, wherein the band gap [J] of the photoelectric conversion element is smaller than the band gap [J] of silicon.

3. A photoelectric conversion device comprising: a plurality of avalanche diodes disposed in a semiconductor layer having a first surface and a second surface opposite to the first surface; and a reflecting member having an opening and a reflecting portion, the reflecting member covering at least a portion of the first surface, each of the plurality of avalanche diodes includes a first semiconductor region of a first conductivity type disposed at a first depth, and a second semiconductor region of a second conductivity type disposed at a second depth that is deeper than the first depth relative to the second surface; The first conductivity type and the second conductivity type are either N-type or P-type, and the first conductivity type and the second conductivity type are different, the semiconductor layer has a plurality of uneven structures provided on the first surface, the substrate having the semiconductor layer is made of silicon, and the effective period of the plurality of uneven structures is smaller than 1.1 μm; the second semiconductor region and the reflective portion overlap each other in a plan view perpendicular to the first surface, and the first semiconductor region is included in the opening; a third semiconductor region of the second conductivity type disposed at a third depth that is deeper than the second depth relative to the second surface; a fourth semiconductor region of the first conductivity type is provided between the second semiconductor region and the third semiconductor region; a sixth semiconductor region of the first conductivity type is provided between the third semiconductor region and the fourth semiconductor region; a first semiconductor region having a first conductivity type impurity concentration lower than a first semiconductor region having a first conductivity type impurity concentration higher than a first semiconductor region having a first conductivity type impurity concentration higher than a first semiconductor region having a first conductivity type impurity concentration higher than a first semiconductor region;

4. the plurality of concave-convex structures are formed by trench structures, 2. The photoelectric conversion device according to claim 1, wherein the width of the trench structure at half the depth of the trench structure is smaller than 0.55 [mu]m.

5. 2 . The photoelectric conversion device according to claim 1 , wherein an area of ​​the fourth semiconductor region in a plan view perpendicular to the first surface is larger than an area of ​​the opening.

6. a fifth semiconductor region of the first conductivity type is provided, the fifth semiconductor region being disposed at the first depth and surrounding the first semiconductor region in a plan view from the first surface; 6. The photoelectric conversion device according to claim 1, wherein the impurity concentration in the fifth semiconductor region is lower than the impurity concentration in the first semiconductor region.

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

8. the plurality of avalanche diodes include a first avalanche diode and a second avalanche diode adjacent to the first avalanche diode; 8. The photoelectric conversion device according to claim 1, further comprising a pixel separating section between the first avalanche diode and the second avalanche diode.

9. the plurality of avalanche diodes include a third avalanche diode adjacent to the second avalanche diode; a first pixel separating portion between the first avalanche diode and the second avalanche diode; a second pixel separating portion between the second avalanche diode and the third avalanche diode; 9. The photoelectric conversion device according to claim 8, wherein the second semiconductor region in the second avalanche diode extends from the first pixel isolation portion to the second pixel isolation portion in a cross section perpendicular to the first surface.

10. 10. The photoelectric conversion device according to claim 1, wherein each of the plurality of avalanche diodes has a microlens provided on the first surface side.

11. an insulating film provided between the first surface and the microlens; 11. The photoelectric conversion device according to claim 10, further comprising: a waveguide provided in the insulating film and having a refractive index higher than that of the insulating film.

12. a SiO film provided between the first surface and the microlens; 11. The photoelectric conversion device according to claim 10, further comprising: a waveguide made of SiN or SiON provided in the SiO film.

13. the waveguide has two surfaces, a lower surface close to the first surface and an upper surface opposite to the lower surface and far from the first surface; 12. The photoelectric conversion device according to claim 11, wherein the upper surface includes the opening in a plan view from a direction perpendicular to the light incident surface.

14. the reflecting member has a third surface close to the first surface and a fourth surface facing the lower surface and far from the first surface; 14. The photoelectric conversion device according to claim 13, wherein the lower surface of the waveguide is located between the third surface and the fourth surface of the reflecting member.

15. 15. The photoelectric conversion device according to claim 1, wherein an area of ​​the range where the concave-convex structure is formed is larger than an area of ​​the opening.

16. 16. The photoelectric conversion device according to claim 1, wherein the plurality of concave-convex structures and the reflecting member overlap in a plan view from a direction perpendicular to the first surface.

17. The photoelectric conversion device according to any one of claims 1 to 16, a signal processing unit that generates an image using a signal output from the photoelectric conversion device.

18. A moving object comprising the photoelectric conversion device according to any one of claims 1 to 16, a control unit that controls the movement of the moving body using a signal output from the photoelectric conversion device; A moving object characterized by:

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