Photoelectric converter

Abstract

To provide a photoelectric conversion device that can reduce the change in a breakdown voltage over time caused by an increase in hot carriers over time.SOLUTION: A photoelectric conversion device having an avalanche photodiode includes an oxide film arranged on a semiconductor layer, and a member arranged on the oxide film. In a plan view, the member is arranged so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region. Since the work function of the member differs from the work functions of the first semiconductor region and the third semiconductor region, a potential gradient for signal charges is formed in the depth direction of the semiconductor layer at least at the boundary.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a photoelectric conversion device, a photoelectric conversion system, and a moving object. Background Art

[0002] Patent Document 1 describes a Single Photon Avalanche Diode (SPAD) including a protective film formed of an oxide film, a nitride film, or a combination thereof on a surface of a silicon substrate. Prior Art Literature Patent Literature

[0003] Patent Document 1 United States Patent Application Publication No. 2020 / 0152807 Specification Summary of the Invention Problem to be Solved by the Invention

[0004] In a SPAD, avalanche multiplication is caused by applying a strong electric field to a PN junction diode provided in a semiconductor layer, thereby detecting photons. However, when the electric field applied to the PN junction diode increases, hot carriers accelerated by the electric field are generated. In the structure described in Patent Document 1, there has been a problem in that trapping of hot carriers near the cathode region changes the potential, causing the breakdown voltage to change over time.

[0005] The present invention has been made in view of the above problem, and an object of the present invention is to reduce a temporal change in breakdown voltage caused by an increase in hot carriers over time. Means for Solving the Problem

[0006] A photoelectric conversion device according to one aspect of the present invention is a photoelectric conversion device having an avalanche photodiode, comprising: a semiconductor layer having a first surface and a second surface; a first semiconductor region of a first conductivity type disposed at a first depth; a second semiconductor region of a second conductivity type disposed at a second depth deeper than the first depth relative to the first surface and constituting the avalanche photodiode with the first semiconductor region; a third semiconductor region of a first conductivity type provided in contact with the edge of the first semiconductor region; an oxide film disposed on the semiconductor layer; and a member provided on the oxide film in cross-sectional view, wherein in plan view, the member is disposed so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region, and the work function of the member and the work functions of the first semiconductor region and the third semiconductor region are different, so that at least at the boundary, a potential gradient for the signal charge is formed in the depth direction of the semiconductor layer.

[0007] A photoelectric conversion device according to another aspect of the present invention is a photoelectric conversion device having an avalanche photodiode, comprising: a semiconductor layer having a first surface and a second surface; a first semiconductor region of a first conductivity type disposed at a first depth; a second semiconductor region of a second conductivity type disposed at a second depth deeper than the first depth relative to the first surface and constituting the avalanche photodiode with the first semiconductor region; a third semiconductor region of a first conductivity type provided in contact with the edge of the first semiconductor region; an oxide film disposed on the semiconductor layer; a protective film disposed on the oxide film and made of a different material from the oxide film; an interlayer film disposed on the protective film; and a member provided between the oxide film and the interlayer film in a cross-sectional view, wherein in a plan view, the member is disposed so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a photoelectric converter that can reduce the change in breakdown voltage over time due to the increase in hot carriers over time. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a photoelectric conversion device according to an embodiment. [Figure 2] This is a schematic diagram of the PD substrate of the photoelectric converter according to the embodiment. [Figure 3] This is a schematic diagram of the circuit board of the photoelectric conversion device according to the embodiment. [Figure 4] This is an example of the configuration of a pixel circuit in a photoelectric conversion device according to an embodiment. [Figure 5] This is a schematic diagram showing the operation of the pixel circuit of the photoelectric converter according to the embodiment. [Figure 6] This is a cross-sectional view of the photoelectric conversion element according to the first embodiment. [Figure 7] This is an explanatory diagram relating to the work function according to the first embodiment. [Figure 8] This is a plan view of the photoelectric conversion element according to the first embodiment. [Figure 9] These are the charge density, potential distribution, and impurity concentration according to the first embodiment. [Figure 10] This is a comparative cross-sectional view of one pixel according to the first embodiment. [Figure 11] This is the potential distribution of the photoelectric conversion element according to the first embodiment. [Figure 12] This is a modified example 1 of the first embodiment. [Figure 13] This is a modified example 2 of the first embodiment. [Figure 14] This is a cross-sectional view of a photoelectric conversion element according to the second embodiment. [Figure 15] This is a modified example of the second embodiment. [Figure 16] This is a modified example of the second embodiment. [Figure 17] These are a cross-sectional view and a plan view of the photoelectric conversion element according to the third embodiment. [Figure 18] This is a modified example of the third embodiment. [Figure 19] This is a functional block diagram of the photoelectric conversion system according to the fourth embodiment. [Figure 20] This is a functional block diagram of the photoelectric conversion system according to the fifth embodiment. [Figure 21] It is a functional block diagram of a photoelectric conversion system according to a sixth embodiment. [Figure 22] It is a functional block diagram of a photoelectric conversion system according to a seventh embodiment. [Figure 23] It is a functional block diagram of a photoelectric conversion system according to an eighth embodiment. MODE FOR CARRYING OUT THE INVENTION

[0010] The embodiments described below are for embodying the technical idea of the present invention, and do not limit the present invention. The sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation. In the following description, the same components are denoted by the same reference numerals, and description thereof may be omitted.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, terms indicating specific directions and positions (for example, "upper", "lower", "right", "left", and other terms including these terms) are used as necessary. The use of these terms is to facilitate understanding of the embodiments with reference to the drawings, and the technical scope of the present invention is not limited by the meanings of these terms.

[0012] In the present specification, "plan view" refers to viewing from a direction perpendicular to the light incident surface of a semiconductor layer. "Cross-sectional view" refers to a plane in a direction perpendicular to the light incident surface of the semiconductor layer. When the light incident surface of the semiconductor layer is microscopically rough, the plan view is defined with reference to the light incident surface of the semiconductor layer when viewed macroscopically.

[0013] In the following description, the anode of the avalanche photodiode (APD) is set to a fixed potential, and the signal is taken from the cathode side. Therefore, the semiconductor region of the first conductivity type, which has majority carriers of the same polarity as the signal charge, is an N-type semiconductor region, and the semiconductor region of the second conductivity type, which has majority carriers of charges with a different polarity than the signal charge, is a P-type semiconductor region. Note that the present invention also applies when the cathode of the APD is set to a fixed potential and the signal is taken from the anode side. In this case, the semiconductor region of the first conductivity type, which has majority carriers of the same polarity as the signal charge, is a P-type semiconductor region, and the semiconductor region of the second conductivity type, which has majority carriers of charges with a different polarity than the signal charge, is an N-type semiconductor region. The following description will focus on the case where one node of the APD is set to a fixed potential, but the potentials of both nodes may fluctuate.

[0014] In this specification, when the term "impurity concentration" is used, it refers to the net impurity concentration after subtracting the amount compensated by reverse-conductivity impurities. In other words, "impurity concentration" refers to the NET doping concentration. The region where the doping concentration of P-type impurities is higher than that of N-type impurities is a P-type semiconductor region. Conversely, the region where the doping concentration of N-type impurities is higher than that of P-type impurities is an N-type semiconductor region.

[0015] The configuration common to each embodiment of the photoelectric conversion device and its driving method according to the present invention will be explained with reference to Figures 1 to 5.

[0016] Figure 1 shows the configuration of a stacked photoelectric converter 100 according to an embodiment of the present invention. The photoelectric converter 100 is constructed by stacking two substrates, a sensor substrate 11 and a circuit board 21, and electrically connecting them. The sensor substrate 11 has a first semiconductor layer having a photoelectric conversion element 102 (described later) and a first wiring structure. The circuit board 21 has a second semiconductor layer having a circuit such as a signal processing unit 103 (described later) and a second wiring structure. The photoelectric converter 100 is constructed by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in that order. The photoelectric converter described in each embodiment is a back-illuminated type photoelectric converter in which light is incident from the first surface and the circuit board is arranged on the second surface.

[0017] In the following description, the sensor substrate 11 and the circuit board 21 are explained using diced chips, but they are not limited to chips. For example, each substrate may be a wafer. Furthermore, each substrate may be stacked in wafer form and then diced, or it may be made into chips and then stacked and bonded together.

[0018] The sensor board 11 is provided with a pixel region 12, and the circuit board 21 is provided with a circuit region 22 for processing signals detected in the pixel region 12.

[0019] Figure 2 shows 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 a planar view, forming a pixel region 12.

[0020] Pixel 101 is typically a pixel used to form an image, but when used in TOF (Time of Flight), it does not necessarily have to form an image. In other words, pixel 101 may be a pixel used to measure the time and amount of light that arrives.

[0021] Figure 3 is a diagram of the circuit board 21. It includes a signal processing unit 103 for processing the charge photoelectrically converted by the photoelectric conversion element 102 in Figure 2, a column 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.

[0022] The photoelectric conversion element 102 in Figure 2 and the signal processing unit 103 in Figure 3 are electrically connected via connection wiring provided for each pixel.

[0023] The vertical scanning circuit section 110 receives control pulses supplied from the control pulse generation section 115 and supplies control pulses to each pixel. Logic circuits such as a shift register and an address decoder are used in the vertical scanning circuit section 110.

[0024] 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 equipped with a counter and memory, and digital values ​​are stored in the memory.

[0025] The horizontal scanning circuit unit 111 inputs control pulses to the signal processing unit 103 to sequentially select each column in order to read the signal from the memory of each pixel in which the digital signal is held.

[0026] For the selected column, a signal is output from the signal processing unit 103 of the pixel selected by the vertical scanning circuit unit 110 to the signal line 113.

[0027] The signal output to signal line 113 is output via output circuit 114 to an external recording unit or signal processing unit of the photoelectric converter 100.

[0028] In Figure 2, the arrangement of photoelectric conversion elements in the pixel region may be one-dimensional. Furthermore, the effects of the present invention can be obtained even with just one pixel, and the case with one 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, one signal processing unit may be shared by multiple photoelectric conversion elements, and signal processing may be performed sequentially.

[0029] As shown in Figures 2 and 3, multiple signal processing units 103 are arranged in the area that overlaps with the pixel area 12 in a plan view. The vertical scanning circuit unit 110, horizontal scanning circuit unit 111, column circuit 112, output circuit 114, and control pulse generation unit 115 are arranged so as to overlap between the edge of the sensor substrate 11 and the edge of the pixel area 12 in a plan view. In other words, the sensor substrate 11 has a pixel area 12 and a non-pixel area arranged around the pixel area 12, and the vertical scanning circuit unit 110, horizontal scanning circuit unit 111, column circuit 112, output circuit 114, and control pulse generation unit 115 are arranged in the area that overlaps with the non-pixel area in a plan view.

[0030] Figure 4 is an example of a block diagram including the equivalent circuits of Figures 2 and 3.

[0031] In Figure 2, the photoelectric conversion element 102 having the APD201 is provided on the sensor substrate 11, and the other components are provided on the circuit board 21.

[0032] The APD201 generates charge pairs corresponding to incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD201. In addition, a voltage VH (second voltage), which is higher than the voltage VL supplied to the anode, is supplied to the cathode of the APD201. A reverse bias voltage is supplied to the anode and cathode such that the APD201 performs avalanche multiplication. By supplying these voltages, the charge generated by the incident light undergoes avalanche multiplication, and an avalanche current is generated.

[0033] Furthermore, when a reverse bias voltage is supplied, there are two modes: Geiger mode, in which the device operates with a potential difference between the anode and cathode greater than the breakdown voltage, and linear mode, in which the device operates with a potential difference between the anode and cathode near or below the breakdown voltage.

[0034] An APD operating in Geiger mode is called a SPAD. For example, voltage VL (first voltage) is -30V and voltage VH (second voltage) is 1V. The APD201 can be operated in linear mode or Geiger mode.

[0035] The quench element 202 is connected to the power supply that provides voltage VH and to the APD201. When the signal is amplified by avalanche multiplication, the quench element 202 functions as a load circuit (quench circuit), suppressing the voltage supplied to the APD201 and thereby suppressing avalanche multiplication (quench operation). In addition, the quench element 202 also works to restore the voltage supplied to the APD201 to voltage VH by flowing the current that compensates for the voltage drop caused by the quench operation (recharge operation).

[0036] The signal processing unit 103 includes a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. In this specification, the signal processing unit 103 may include any one of the waveform shaping unit 210, the counter circuit 211, or the selection circuit 212.

[0037] The waveform shaping unit 210 shapes the cathode potential change of the APD201 obtained during photon detection and outputs a pulse signal. For example, an inverter circuit can be used as the waveform shaping unit 210. Figure 4 shows an example in which one inverter is used as the waveform shaping unit 210, but a circuit in which multiple inverters are connected in series may be used, or other circuits that have a waveform shaping effect may be used.

[0038] The counter circuit 211 counts the pulse signal output from the waveform shaping unit 210 and holds the count value. When the control pulse pRES is supplied via the drive line 213, the signal held by the counter circuit 211 is reset.

[0039] The selection circuit 212 receives a control pulse pSEL from the vertical scanning circuit section 110 in Figure 3 via the drive line 214 (not shown in Figure 3) in Figure 4, which switches the electrical connection between the counter circuit 211 and the signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal.

[0040] A switch such as a transistor may be placed between the quench element 202 and the APD201, or between the photoelectric conversion element 102 and the signal processing unit 103, to switch the electrical connection. Similarly, the supply of voltage VH or voltage VL to the photoelectric conversion element 102 may be electrically switched using a switch such as a transistor.

[0041] In this embodiment, a configuration using a counter circuit 211 is shown. However, instead of the counter circuit 211, a photoelectric converter 100 may be used that acquires pulse detection timing using a Time to Digital Converter (TDC) and 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. A control pulse pREF (reference signal) is supplied to the TDC from the vertical scanning circuit unit 110 in Figure 3 via a drive line to measure the timing of the pulse signal. The TDC acquires the signal as a digital signal when the input timing of the signal output from each pixel via the waveform shaping unit 210 is relative to the control pulse pREF.

[0042] Figure 5 schematically illustrates the relationship between the operation of the APD and the output signal.

[0043] Figure 5(a) is an excerpt of the APD201, quench element 202, and waveform shaping unit 210 from Figure 4. Here, the input side of the waveform shaping unit 210 is denoted as nodeA and the output side as nodeB. Figure 5(b) shows the waveform change at nodeA in Figure 5(a), and Figure 5(c) shows the waveform change at nodeB in Figure 5(a).

[0044] Between time t0 and time t1, a potential difference of VH-VL is applied to APD201 in Figure 5(a). When a photon is incident on APD201 at time t1, avalanche multiplication occurs in APD201, an avalanche multiplication current flows through the quench element 202, and the voltage at nodeA drops. As the voltage drop increases further and the potential difference applied to APD201 decreases, the avalanche multiplication of APD201 stops as at time t2, and the voltage level at nodeA stops dropping below a certain value. Subsequently, between time t2 and time t3, a current flows through nodeA to compensate for the voltage drop from voltage VL, and at time t3, nodeA settles to its original potential level. At this time, any portion of the output waveform at nodeA that exceeds a certain threshold is waveform-shaped by the waveform shaping unit 210 and output as a signal at nodeB.

[0045] Note that the arrangement of the signal line 113, the column circuit 112, and the output circuit 114 is not limited to Figure 3. For example, the signal line 113 may be arranged extending in the row direction, and the column circuit 112 may be located at the end of the signal line 113.

[0046] The following describes the photoelectric conversion device for each embodiment.

[0047] (First Embodiment) A photoelectric conversion device according to the first embodiment will be described using Figures 6 to 13.

[0048] Figure 6 is a cross-sectional view of a photoelectric conversion device having two photoelectric conversion elements 102.

[0049] The structure and function of the photoelectric conversion element 102 will now be described. The photoelectric conversion element 102 has an N-type (first conductivity type) first semiconductor region 311, a third semiconductor region 313, a fifth semiconductor region 315, and a sixth semiconductor region 316. It also includes a P-type (second conductivity type) second semiconductor region 312, a fourth semiconductor region 314, a seventh semiconductor region 317, and a ninth semiconductor region 319.

[0050] In this embodiment, in the cross-sectional view shown in Figure 6, an N-type first semiconductor region 311 is formed near the surface facing the incident light surface, and an N-type third semiconductor region 313 is formed at the edge of the first semiconductor region 311. A P-type second semiconductor region 312 is formed at a position that overlaps with the first and second semiconductor regions in a plan view. A further N-type fifth semiconductor region 315 is arranged at a position that overlaps with the second semiconductor region 312 in a plan view, and an N-type sixth semiconductor region 316 is formed around it.

[0051] The impurity concentration in the first semiconductor region 311 is higher than that in the third semiconductor region 313 and the fifth semiconductor region 315. A PN junction is formed between the P-type second semiconductor region 312 and the N-type first semiconductor region 311, forming an APD. By making the impurity concentration in the second semiconductor region 312 lower than that of the first semiconductor region 311, all regions of the second semiconductor region 312 that overlap with the center of the first semiconductor region in a plan view become a depletion layer region. At this time, the potential difference between the first semiconductor region 311 and the second semiconductor region 312 becomes larger than the potential difference between the second semiconductor region 312 and the fifth semiconductor region 315. This depletion layer region extends to a portion of the first semiconductor region 311, and a strong electric field is induced in the extended depletion layer region. Due to this strong electric field, avalanche multiplication occurs in the depletion layer region that extends to a portion of the first semiconductor region 311, and a current based on the amplified charge is output as a signal charge. When light incident on the photoelectric conversion element 102 is converted into electricity, and avalanche multiplication occurs in this depletion layer region (avalanche multiplication region), the generated charge of the first conductivity type is collected in the first semiconductor region 311.

[0052] In Figure 6, the third semiconductor region 313 and the fifth semiconductor region 315 are formed to be of roughly the same size, but the size of each semiconductor region is not limited to this. For example, the fifth semiconductor region 315 may be formed to be larger than the third semiconductor region 313, thereby collecting charge from a wider area to the first semiconductor region 311.

[0053] Pixels are separated from each other by a trench-structured pixel isolation section 324. Furthermore, a P-type seventh semiconductor region 317 is provided around the pixel isolation section 324, separating adjacent photoelectric conversion elements by a potential gradient. Since photoelectric conversion elements are also separated by the potential of the seventh semiconductor region 317, a trench structure like the pixel isolation section 324 is not essential for the pixel isolation section. Even when a trench-structured pixel isolation section 324 is provided, the depth and position of the trench structure are not limited to the configuration shown in Figure 6. That is, the pixel isolation section 324 may be a DTI (deep trench isolation) penetrating the semiconductor layer, or a DTI that does not penetrate the semiconductor layer. The material filling the trench structure may consist of SiO, a fixed charge film, a metal member, Poly-Si, or a combination of these. Additionally, metal may be embedded in the trench structure to improve light-shielding performance. The pixel separation section 324 may be provided so as to surround the entire circumference of the photoelectric conversion element in a plan view, or it may be provided only on the opposite side of the photoelectric conversion element. Furthermore, if metal or polysilicon is embedded in the trench structure, a voltage may be applied to the metal or polysilicon to induce a charge at the trench interface and suppress the DCR (Dark Current Rate).

[0054] A pinning film 321, a planarization film 322, and a microlens 323 are formed on the light incident surface side of the semiconductor layer 302.

[0055] Furthermore, a trench-based uneven structure (not shown) may be provided on the light incident surface. The uneven structure is surrounded by a P-type fourth semiconductor region 314, scattering the light incident on the photoelectric conversion element 102. Since the incident light travels diagonally through the photoelectric conversion element, an optical path length greater than the thickness of the semiconductor layer 302 can be secured, making it possible to photoelectrically convert longer wavelength light compared to the case without the uneven structure. In addition, the uneven structure prevents reflection of incident light within the substrate, thus improving the photoelectric conversion efficiency of the incident light.

[0056] The fifth semiconductor region 315 and the uneven structure are formed to overlap in a plan view. The area of ​​overlap between the fifth semiconductor region 315 and the uneven structure in a plan view is larger than the area of ​​the fifth semiconductor region 315 that does not overlap with the uneven structure. Charges generated at a position far from the avalanche multiplication region formed between the first semiconductor region 311 and the fifth semiconductor region 315 have a longer travel time to reach the avalanche multiplication region compared to charges generated at a position close to the avalanche multiplication region. Therefore, timing jitter may increase. By positioning the fifth semiconductor region 315 and the uneven structure to overlap in a plan view, the collection time of charges generated at a position far from the avalanche multiplication region can be shortened, thereby reducing timing jitter. The fourth semiconductor region 314 covers the uneven structure three-dimensionally, which suppresses the generation of thermally excited charges at the interface of the uneven structure. As a result, the DCR of the photoelectric conversion element is suppressed.

[0057] Furthermore, a filter layer (not shown) may be placed on the light incident surface. Various optical filters such as color filters, infrared light cut filters, and monochrome filters can be used for the filter layer. RGB color filters, RGBW color filters, etc., can be used for the color filter.

[0058] A wiring structure including a conductor and an insulating film is provided on the surface of the semiconductor layer facing the light incident surface. An interlayer film (interlayer insulating film) 343 is provided between the wiring provided in the wiring layer and the semiconductor layer. Between the interlayer film 343 and the semiconductor layer, an oxide film 341 and a protective film 342 are provided from the side closer to the semiconductor layer. The oxide film 341 and the protective film 342 are films provided across multiple pixels. The oxide film 341 is, for example, silicon oxide (SiO), but silicon oxide (SiON) or the like may also be used. The protective film 342 is a dielectric film and is made of a different material than the oxide film 341. The protective film 342 functions as a film to protect the avalanche photodiode from plasma damage and metal contamination during etching. The protective film 342 is generally made of silicon nitride (SiN), which is a nitride film, but silicon oxynitride film (SiON), silicon carbide film (SiC), silicon carbonitride film (SiCN), etc. may also be used. If both the oxide film 341 and the protective film 342 contain nitrogen, the film with the higher nitrogen content is designated as the protective film.

[0059] In this embodiment, silicon nitride refers to a compound of nitrogen (N) and silicon (Si), wherein the elements other than the light elements that make up the top two in the composition ratio of the constituent elements of the compound are nitrogen (N) and silicon (Si). Silicon nitride can contain light elements such as hydrogen (H) and helium (He), and their amount (atomic %) may be more or less than that of nitrogen (N) and silicon (Si). Silicon nitride can contain elements other than nitrogen (N), silicon (Si), and light elements at lower concentrations than those of nitrogen (N) and silicon (Si). Typical elements that can be contained in silicon nitride are boron (B), carbon (C), oxygen (O), fluorine (F), phosphorus (P), chlorine (Cl), and argon (Ar). When the third most abundant element among the constituent elements of silicon nitride is oxygen, this silicon nitride can be called silicon oxidative nitride or oxygen-containing silicon nitride.

[0060] Similarly, silicon oxide is a compound of oxygen (O) and silicon (Si), where the elements other than the two lightest elements in the composition ratio of the compound are oxygen (O) and silicon (Si). Typical elements that can be contained in silicon oxide include hydrogen (H), helium (He), boron (B), carbon (C), nitrogen (N), fluorine (F), phosphorus (P), chlorine (Cl), and argon (Ar). When nitrogen is the third most abundant element among the constituent elements of silicon oxide, this silicon oxide can be called silicon nitride or nitrogen-containing silicon oxide. The elements contained in the components of photoelectric converters can be analyzed using energy dispersive X-ray spectrometry (EDX). Furthermore, the hydrogen content can be analyzed using methods such as Elastic Recoil Detection Analysis (ERDA).

[0061] The cathode wiring 331A is electrically connected to the first semiconductor region 311 and supplies potential to the first semiconductor region 311. The anode wiring 331B supplies potential to the seventh semiconductor region 317 via the ninth semiconductor region 319. The wiring portions constituting the cathode wiring 331A and the anode wiring 331B are made of conductors containing metals such as Cu or Al. Here, the anode wiring 331B is referred to as the first wiring portion, and the cathode wiring 331A is referred to as the second wiring portion. Depending on the context, the wiring located in the first layer of the wiring layer may also be called the cathode wiring 331A or the anode wiring 331B. In this case, the contact portion that directly contacts the semiconductor layer may be explained separately from the cathode wiring 331A and the anode wiring 331B. On the other hand, the entire wiring portion that supplies voltage to the semiconductor region may be described as the cathode wiring 331A and the anode wiring 331B. In this case, the contact portion will be included in the cathode wiring 331A and the anode wiring 331B.

[0062] Component 332 is electrically connected to the cathode wiring 331A and is supplied with the same potential as the cathode wiring 331A. In cross-sectional view, component 332 is located between the cathode wiring 331A provided in the first wiring layer (M1) and the semiconductor layer 302. In Figure 6, only the first wiring layer, the contact portion connecting the first wiring layer and the semiconductor layer, and the contact portion connecting the first wiring layer and component 332 are shown of the wiring structure. However, in addition to the first wiring layer, a second wiring layer, a third wiring layer, and multiple other wiring layers may be provided as appropriate. An interlayer film 343 is provided between the first wiring layer and the second wiring layer, and another interlayer film 343 (not shown) is provided between the second wiring layer and the third wiring layer. The interlayer film provided between the semiconductor layer and the first wiring layer is sometimes called the first interlayer film, and the interlayer film provided between the first wiring layer and the second wiring layer is sometimes called the second interlayer film, etc.

[0063] Component 332 is, for example, a component having a work function greater than the work functions of the first semiconductor region 311 and the third semiconductor region 313 of the first conductivity type when the first conductivity type is N-type. For example, let's assume component 332 is P-type polysilicon. Figures 7(a) and 7(b) show the difference in work functions when N-type silicon and P-type polysilicon are in close proximity. The work function of N-type silicon generally takes a value between 4.6 eV, which is the Fermi energy of intrinsic silicon, and 4.05 eV, which is the energy at the bottom of the conduction band. On the other hand, the work function of P-type polysilicon takes a value around 5.05 eV, although this depends on the amount of doping. Therefore, a difference in work functions occurs between N-type silicon and P-type polysilicon, and as shown in Figure 7(b), a potential gradient is formed in the depth direction for electrons, which are signal charges.

[0064] On the other hand, if the first conductivity type is P-type, the work function of member 332 should be smaller than the work functions of the first semiconductor region 311 of the first conductivity type and the third semiconductor region 313 of the first conductivity type. In this case, a potential gradient will be formed in the depth direction for holes, which are signal charges. For member 332, for example, N-type polysilicon can be used.

[0065] In other words, the work functions of the first semiconductor region 311 and the third semiconductor region 313 are different from the work function of member 332, so that a potential gradient for the signal charge is formed in the depth direction of the semiconductor layer, at least at the boundary.

[0066] Figure 8(a) is a pixel plan view of one pixel between A and A' in Figure 6. Figure 8(b) is a plan view of the area between B and B' where member 332 is located. In Figure 8(b), member 332 overlaps with the boundary 351 of the first semiconductor region 311 and the third semiconductor region 313 in plan view. This suppresses the trapping of hot carriers at the interface near the boundary 351. Also, in plan view, the extension of member 332 is contained within one pixel, and member 332 is not provided across two or more pixels.

[0067] Figure 9 shows the charge density (a), potential (b), and impurity concentration (c) in the X-X' region of Figure 6. Figure 9(d) is an enlarged view of the area near the first semiconductor region 311 in the X-X' region. As shown in Figure 9(d), the boundary region 351 has a low potential and low charge density for electrons, which are signal charges. As an example of impurity concentration, the impurity concentration of X is 1 × 10⁻⁶. 19 cm -3 In this case, the impurity concentration at the boundary 351 is 1 × 10⁻⁶. 18 cm -3The hot carriers generated by the strong electric field around the first semiconductor region 311 are thought to be trapped, for example, at the interface between the oxide film 341 and the protective film 342, but many are trapped between QS, where the potential is low. When hot carriers are trapped between QR, the charge density in the first semiconductor region 311 between XY is high and it is a neutral region, so no electric field lines are generated. On the other hand, when hot carriers are trapped between RS, the charge density between Y and the boundary 351 is lower than the charge density between XY and it is a depletion region, making it a place that is easily affected by charge trapping. Among these, the boundary 351 has the lowest charge density between Y and the boundary 351, so it is necessary to suppress the trapping of hot carriers generated at the interface of the boundary 351. Between the boundary 351 and X', the potential increases as you approach X', so it becomes more difficult for hot carriers to be trapped between SP.

[0068] Figure 10(a) is a cross-sectional view of one pixel in Figure 6 when member 332 is not placed. Figure 10(b) is a cross-sectional view of one pixel when member 332 is placed. It is assumed that hot carriers generated by the strong electric field around the first semiconductor region 311 are trapped, for example, at the interface between the oxide film 341 and the protective film 342. In this case, if hot carriers are trapped between RP, it may affect the potential distribution in the avalanche region in the semiconductor layer 302, potentially changing the breakdown voltage.

[0069] Figure 11 shows the potential distribution between Z-Z' in Figure 10(a) and between V-V' in Figure 10(b). In Figure 10(b), a potential gradient of ΔX is generated between Z and Z compared to Figure 10(a). Due to this potential gradient, hot carriers are less likely to be trapped at the interface between the oxide film 341 and the protective film 342 near the boundary 351. Therefore, the possibility of changes in the breakdown voltage is reduced.

[0070] Incidentally, in order to avoid hot carrier trapping, it is conceivable to extend the anode wiring and provide the anode wiring in the region that overlaps with the first semiconductor region 311 and the third semiconductor region 313 in a plan view. However, if the distance between the anode wiring and the cathode wiring is too close, there is a concern about voltage withstand capability. According to the configuration of this embodiment, by arranging member 332, hot carrier trapping is suppressed, so the distance between the cathode wiring 331A and the anode wiring 331B can be kept sufficient, and concerns regarding voltage withstand capability are reduced.

[0071] (modified version) Next, Figure 12 shows the first modified example. As shown in Figure 12, the cathode wiring 331A may be extended to the anode wiring 331B side. In this configuration, the incident light from the microlens 323 is reflected by the cathode wiring, thereby improving sensitivity while suppressing changes in the breakdown voltage over time.

[0072] Next, Figure 13 shows a second modified example. Figure 13(a) is a cross-sectional view, and Figure 13(b) is a plan view. As shown in Figure 13, member 332 may be formed to overlap with the entire area of ​​the third semiconductor region 313. This suppresses carrier trapping that occurs at the interface of the entire area of ​​the third semiconductor region 313. This further suppresses the change in breakdown voltage over time.

[0073] The above describes an example in which member 332 and cathode wiring 331A are electrically connected. However, even without electrically connecting member 332 and cathode wiring 331, the above potential gradient may occur depending on the work function conditions of member 332 and the semiconductor region. Therefore, a configuration in which a predetermined voltage is not applied to member 332 is also possible.

[0074] Furthermore, although the above describes an example in which member 332 is placed between the protective film 342 and the interlayer film 343, member 332 may also be placed between the oxide film 341 and the protective film 342. In this case, the contact that electrically connects the cathode wiring 331A and member 332 will penetrate the protective film 342. Note that, as described above, it is not necessary to apply a predetermined voltage to member 332, so contact wiring is not necessarily required.

[0075] (Second Embodiment) A photoelectric conversion device according to the second embodiment will be described with reference to Figure 14. Parts that are common to the description with the first embodiment will be omitted, and mainly the parts that differ from the first embodiment will be described.

[0076] In this embodiment, in a cross-sectional view, member 332 is formed between the oxide film 341 and the protective film 342. Also in a cross-sectional view, the protective film 342 is formed between the two members 332. Furthermore, in a plan view, the boundary between the first semiconductor region 311 and the third semiconductor region 313 is covered by member 332. Unlike the first embodiment, member 332 is insulated and isolated from the cathode wiring 331A, and no potential is supplied to it.

[0077] Component 332 is made of a material that allows the interface state density between component 332 and the oxide film 341 to be smaller than the interface state density between the oxide film 341 and the protective film 342. Here, interface state density is synonymous with interface defect density. Interface state density (interface defect density) is the density of defects caused by inconsistencies occurring at the heterointerface of each component.

[0078] Hot carriers are trapped at the interface between the oxide film 341 and the protective film 342. This can affect the potential distribution in the avalanche region of the semiconductor layer 302, potentially causing a change in the breakdown voltage. Therefore, by placing a component 332 that satisfies the condition that the interface state density between the oxide film 341 and the component 332 is smaller than the interface state density between the oxide film 341 and the protective film 342, the trapping of hot carriers can be reduced. In this way, by forming a component 332 between the oxide film 341 and the protective film 342, the change in breakdown voltage over time can be reduced.

[0079] Furthermore, similar to the first embodiment, the distance between the cathode wiring 331A and the anode wiring 331B can be sufficiently maintained, thus reducing concerns about voltage withstand capability.

[0080] In this embodiment, as shown in Figure 15, the cathode wiring 331A may be configured to extend toward the anode wiring 331B. Alternatively, as shown in Figure 16, the member 332 may be formed to overlap with the entire area of ​​the third semiconductor region 313.

[0081] (Third embodiment) The photoelectric conversion device according to this embodiment will be described using Figure 17. Parts that are common to the description with the first and second embodiments will be omitted, and parts that differ from the first embodiment will be described. In this embodiment, as shown in Figure 17(b), in a plan view, the member 332 overlaps with the entire first semiconductor region 311.

[0082] Incidentally, in the configuration shown in Figure 6, a contact portion is provided to electrically connect the cathode wiring 331A and the first semiconductor region 311, which are located in the first wiring layer. Therefore, it is necessary to secure space between this contact portion and the component 332. Consequently, in a plan view, the area occupied by the component 332 may limit the process, potentially making pixel miniaturization difficult.

[0083] On the other hand, according to the configuration shown in Figure 17, a contact plug 331C is provided that penetrates the oxide film 341 and the protective film 342, and the member 332 and the first semiconductor region 311 are electrically connected via the contact plug 331C. In addition, the cathode wiring 331A and the member 332 are electrically connected via the contact plug. With this configuration, there is no need to secure space between the contact plug connecting the cathode wiring 331A and the first semiconductor region 311 and the member 332, thus enabling pixel miniaturization.

[0084] The contact plug 331C may be made of the same material as the contact plug that electrically connects the cathode wiring 331A and the component 332. Alternatively, the contact plug 331C may be made of a different material than the component 332.

[0085] On the other hand, as shown in the configuration in Figure 18, the contact plug 331C may be made of the same material as the member 332.

[0086] According to the configuration of this embodiment, pixel miniaturization is possible compared to the configuration of the first embodiment. Furthermore, similar to the configuration of the first embodiment, the change in breakdown voltage over time can be reduced. In addition, concerns about withstand voltage can also be reduced.

[0087] (Fourth embodiment) The photoelectric conversion system according to this embodiment will be described with reference to Figure 19. Figure 19 is a block diagram showing the schematic configuration of the photoelectric conversion system according to this embodiment.

[0088] The photoelectric conversion devices described in the first to third embodiments above are applicable to various photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, photocopiers, fax machines, mobile phones, in-vehicle cameras, and observation satellites. Camera modules, which include optical systems such as lenses and imaging devices, are also included in photoelectric conversion systems.

[0089] Figure 19 illustrates a block diagram of a digital still camera as an example of these. The photoelectric conversion system illustrated in Figure 19 includes an imaging device 1004, which is an example of a photoelectric conversion device, and a lens 1002 that forms an optical image of the subject on the imaging device 1004. Furthermore, it has an aperture 1003 for varying the amount of light passing through the lens 1002, and a barrier 1001 for protecting the lens 1002. The lens 1002 and aperture 1003 constitute an optical system that focuses light onto the imaging device 1004.

[0090] The imaging device 1004 is a photoelectric conversion device according to any of the above embodiments, which converts the optical image formed by the lens 1002 into an electrical signal. The photoelectric conversion system also includes a signal processing unit 1007, which is an image generation unit that generates an image by processing the output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compressions as needed and outputs image data. The signal processing unit 1007 may be formed on the semiconductor substrate on which the imaging device 1004 is provided, or it may be formed on a semiconductor substrate separate from the imaging device 1004.

[0091] 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. Furthermore, the photoelectric conversion system includes a recording medium 1012 such as a semiconductor memory for recording or reading imaging data, and a recording medium control interface unit (recording medium control I / F unit) 1011 for recording or reading data from the recording medium 1012.

[0092] The recording medium 1012 may be built into the photoelectric conversion system or it may be detachable. Furthermore, the photoelectric conversion system includes an overall control / calculation unit 1009 that controls various calculations and the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the imaging device 1004 and the signal processing unit 1007.

[0093] Here, timing signals and the like may be input from an external source, and the photoelectric conversion system only needs to have at least an imaging device 1004 and a signal processing unit 1007 that processes the output signals output from the imaging device 1004.

[0094] The imaging device 1004 outputs an imaging signal to the 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. Thus, according to this embodiment, a photoelectric conversion system can be realized by applying a photoelectric conversion device (imaging device) of any of the above embodiments.

[0095] (Fifth embodiment) The photoelectric conversion system and mobile unit of this embodiment will be described with reference to Figure 20. Figure 20 is a diagram showing the configuration of the photoelectric conversion system and mobile unit of this embodiment.

[0096] Figure 20(a) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 1300 includes an imaging device 1310. The imaging device 1310 is a photoelectric conversion device as described in any of the embodiments described above.

[0097] The photoelectric conversion system 1300 has an image processing unit 1312 that performs image processing on multiple image data acquired by the imaging device 1310. The photoelectric conversion system 1300 also has a parallax acquisition unit 1314 that calculates parallax (phase difference of parallax images) from multiple image data acquired by the photoelectric conversion system 1300. The photoelectric conversion system 1300 also has 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 collision based on the calculated distance.

[0098] Here, the parallax acquisition unit 1314 and the distance acquisition unit 1316 are examples of distance information acquisition means for acquiring distance information to an object. That is, distance information refers to information such as parallax, defocus amount, and distance to the object. The collision determination unit 1318 may use any of this distance information to determine the possibility of a collision. The distance information acquisition means may be implemented by specially designed hardware or by a software module. It may also be implemented by an FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), or a combination thereof. Furthermore, the distance acquisition unit may use a ToF type distance sensor, which will be described in the following embodiment.

[0099] 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 control ECU 1330, which is a control unit that outputs a control signal to generate braking force on the vehicle based on the judgment result of the collision judgment unit 1318. The photoelectric conversion system 1300 is also connected to the warning device 1340, which issues a warning to the driver based on the judgment result of the collision judgment unit 1318. For example, if the collision judgment result of the collision judgment unit 1318 indicates a high probability of collision, the control ECU 1330 performs vehicle control to avoid a collision or mitigate damage by applying the brakes, releasing the accelerator, or suppressing engine output. The warning device 1340 warns the user by sounding an alarm, displaying warning information on a screen such as a car navigation system, or vibrating the seat belt or steering wheel.

[0100] In this embodiment, the photoelectric conversion system 1300 images the area around the vehicle, for example, in front of or behind it. Figure 20(b) shows the photoelectric conversion system when imaging 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 can further improve the accuracy of distance measurement.

[0101] The above example illustrates control to prevent collisions with other vehicles, but it can also be applied to control systems that automatically follow other vehicles or automatically drive to prevent vehicles from straying from their lanes. Furthermore, the photoelectric conversion system can be applied not only to vehicles such as automobiles, but also to mobile objects (mobile devices) such as ships, aircraft, or industrial robots. In addition, it can be applied not only to mobile objects but also to a wide range of devices that utilize object recognition, such as intelligent transportation systems (ITS).

[0102] (Sixth Embodiment) The photoelectric conversion system of this embodiment will be described with reference to Figure 21. Figure 21 is a block diagram showing an example configuration of a distance image sensor, which is the photoelectric conversion system of this embodiment.

[0103] As shown in Figure 21, the distance image sensor 401 is configured to include an optical system 407, a photoelectric converter 408, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 401 receives light (modulated light or pulsed light) that is projected from a light source device 409 toward the subject and reflected from the surface of the subject, and based on the time from projection to reception, it can acquire a distance image corresponding to the distance to the subject.

[0104] The optical system 407 is composed of one or more lenses and guides the image light (incident light) from the subject to the photoelectric converter 408, where it forms an image on the light-receiving surface (sensor part) of the photoelectric converter 408.

[0105] The photoelectric converter 408 is one of the photoelectric converters from each of the embodiments described above, and a distance signal indicating the distance, which is determined from the light received signal output from the photoelectric converter 408, is supplied to the image processing circuit 404.

[0106] The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric converter 408. The distance image (image data) obtained through this image processing is then supplied to the monitor 405 for display or supplied to the memory 406 for storage (recording).

[0107] In the distance image sensor 401 configured in this way, by applying the photoelectric conversion device described above, it is possible to acquire, for example, a more accurate distance image as the characteristics of the pixels improve. Furthermore, this photoelectric conversion system may output the result of calculations using distance information, but may not output the image information used in the calculations. Alternatively, a predetermined exposure time may be set from the emission of light, and distance information may be acquired using the light reception information for that predetermined exposure time. In this case, distance information can be acquired without using the time from emission to reception of light.

[0108] (Seventh Embodiment) The photoelectric conversion system of this embodiment will be described with reference to Figure 22. Figure 22 is a diagram showing an example of a schematic configuration of an endoscopic surgical system, which is the photoelectric conversion system of this embodiment.

[0109] Figure 22 illustrates a surgeon (physician) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgical system 1150. As shown in the figure, the endoscopic surgical system 1150 consists of an endoscope 1100, surgical instruments 1110, and a cart 1134 equipped with various devices for endoscopic surgery.

[0110] The endoscope 1100 consists of a barrel 1101, the tip of which is inserted into the body cavity of the patient 1132 for a predetermined length, and a camera head 1102 connected to the base end of the barrel 1101. In the illustrated example, the endoscope 1100 is shown as a so-called rigid endoscope having a rigid barrel 1101, but the endoscope 1100 may also be configured as a so-called flexible endoscope having a flexible barrel.

[0111] An opening into which an objective lens is fitted is provided at the tip of the endoscope tube 1101. A light source device 1203 is connected to the endoscope 1100, and the light generated by the light source device 1203 is guided to the tip of the endoscope tube by a light guide extending inside the endoscope tube 1101, and is irradiated through the objective lens towards the object to be observed inside the body cavity of the patient 1132. The endoscope 1100 may be a straight-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0112] The camera head 1102 contains an optical system and a photoelectric converter. Reflected light from the object being observed (observation light) is focused by the optical system into the photoelectric converter. The photoelectric converter converts the observation light into electrical signals, generating an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. The photoelectric converter can be any of the photoelectric converters described in the embodiments described above. The image signal is transmitted as RAW data to the camera control unit (CCU) 1135.

[0113] The CCU1135 consists of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and other components, and comprehensively controls the operation of the endoscope 1100 and the display device 1136. Furthermore, the CCU1135 receives an image signal from the camera head 1102 and performs various image processing operations on that image signal, such as development processing (demosaic processing), to display the image based on that image signal.

[0114] The display device 1136 displays an image based on an image signal that has been processed by the CCU 1135, under control from the CCU 1135.

[0115] The light source device 1203 consists of a light source such as an LED (Light Emitting Diode) and supplies illumination light to the endoscope 1100 when photographing the surgical area, etc.

[0116] The input device 1137 is an input interface for the endoscopic surgical system 1150. The user can input various types of information and instructions to the endoscopic surgical system 1150 via the input device 1137.

[0117] The treatment instrument control device 1138 controls the driving of the energy treatment instrument 1112 for purposes such as tissue cauterization, incision, or blood vessel sealing.

[0118] The light source device 1203, which supplies illumination light to the endoscope 1100 when photographing the surgical area, can be composed of, for example, an LED, a laser light source, or a combination thereof. When the white light source is composed of a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, so the white balance of the captured image can be adjusted in the light source device 1203. In this case, it is also possible to capture images corresponding to each of the RGB colors in time-division by irradiating the observation target with laser light from each of the RGB laser light sources in time-division 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 on the image sensor.

[0119] Furthermore, the light source device 1203 may be controlled to change the intensity of the light it outputs at predetermined time intervals. By controlling the drive of the image sensor of the camera head 1102 in synchronization with the timing of the change in light intensity, images can be acquired in time-division order, and these images can be combined to generate high dynamic range images without so-called black crushing and white clipping.

[0120] Furthermore, the light source device 1203 may be configured to supply light in a predetermined wavelength band corresponding to special light observation. In special light observation, for example, the wavelength dependence of light absorption in body tissue is utilized. Specifically, by irradiating with narrowband light compared to the irradiation light used during normal observation (i.e., white light), predetermined tissues such as blood vessels on the surface of mucosa can be imaged with high contrast. Alternatively, in special light observation, fluorescence observation may be performed to obtain an image from fluorescence generated by irradiation with excitation light. In fluorescence observation, excitation light can be irradiated onto body tissue and fluorescence from the body tissue can be observed, or a reagent such as indocyanine green (ICG) can be injected into body tissue and excitation light corresponding to the fluorescence wavelength of the reagent can be irradiated onto the body tissue to obtain a fluorescence image. The light source device 1203 may be configured to supply narrowband light and / or excitation light corresponding to such special light observation.

[0121] (Eighth embodiment) The photoelectric conversion system of this embodiment will be described using Figures 23(a) and (b). Figure 23(a) illustrates the eyeglasses 1600 (smart glasses), which are the photoelectric conversion system of this embodiment. The eyeglasses 1600 have a photoelectric conversion device 1602. The photoelectric conversion device 1602 is the photoelectric conversion device described in each of the embodiments described above. In addition, 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. In addition, multiple types of photoelectric conversion devices may be used in combination. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in Figure 23(a).

[0122] The eyeglasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric converter 1602 and the display device. The control device 1603 also controls the operation of the photoelectric converter 1602 and the display device. The lens 1601 has an optical system formed therein for focusing light onto the photoelectric converter 1602.

[0123] Figure 23(b) illustrates a pair of glasses 1610 (smart glasses) relating to one application example. The glasses 1610 have a control device 1612, which is equipped with a photoelectric converter equivalent to a photoelectric converter 1602 and a display device. The lens 1611 has an optical system formed therein for projecting light emitted from the photoelectric converter in the control device 1612 and from the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power supply that provides power to the photoelectric converter and the display device, and also controls the operation of the photoelectric converter and the display device. The control device may have a gaze detection unit that detects the wearer's gaze. Gaze detection may use infrared light. The infrared light emitter emits infrared light towards the user's eyeball that is fixated on the displayed image. An imaging unit having a light-receiving element detects the reflected light from the eyeball of the emitted infrared light, thereby obtaining an image of the eyeball. By having a reduction means that reduces the light from the infrared light emitter to the display unit in planar view, the deterioration of image quality is reduced.

[0124] The user's gaze towards the displayed image is detected from an image of the eyeball obtained by imaging with infrared light. Any known method can be applied to gaze detection using an image of the eyeball. For example, a gaze detection method based on the Purkinje image obtained by the reflection of the irradiated light from the cornea can be used.

[0125] More specifically, gaze detection processing is performed based on the pupil-corneal reflection method. Using the pupil-corneal reflection method, a gaze vector representing the orientation (rotation angle) of the eyeball is calculated based on the pupil image and Purkinje image contained in the captured image of the eyeball, thereby detecting the user's gaze.

[0126] The display device of this embodiment includes a photoelectric converter having a light-receiving element, and may control the display image of the display device based on the user's gaze information from the photoelectric converter.

[0127] Specifically, the display device determines a first field of view that the user is fixated on, and a second field of view other than the first field of view, based on gaze information. The first and second field of view may be determined by the control device of the display device, or they may be determined by an external control device and received. Within the display area of ​​the display device, the display resolution of the first field of view may be controlled to be higher than that of the second field of view. In other words, the resolution of the second field of view may be lower than that of the first field of view.

[0128] Furthermore, the display area may have a first display area and a second display area different from the first display area, and a higher priority area may be determined from the first and second display areas based on line-of-sight information. The first and second field-of-sight areas may be determined by the control device of the display device, or they may be determined by an external control device and received. The resolution of the higher priority area may be controlled to be higher than the resolution of the areas other than the higher priority area. In other words, the resolution of areas with relatively lower priority may be set lower.

[0129] AI may be used to determine the first field of view area and the areas with higher priority. The AI ​​may be a model configured to estimate the angle of gaze and the distance to the target object at the end of the line of sight from the image of the eye, using the image of the eye and the direction the eye was actually looking in that image as training data. The AI ​​program may be installed in the display device, the photoelectric converter, or an external device. If installed in an external device, it will be transmitted to the display device via communication.

[0130] When display control is based on visual detection, this method is preferably applicable to smart glasses that further include a photoelectric converter for capturing images of the surrounding environment. The smart glasses can display the captured external information in real time.

[0131] The present invention is not limited to the embodiments described above and can be modified in various ways. For example, examples in which a part of the configuration of one embodiment is added to another embodiment, or in which a part of the configuration of another embodiment is replaced, are also included as embodiments of the present invention.

[0132] Furthermore, the photoelectric conversion systems shown in the fourth and fifth embodiments above are merely examples of photoelectric conversion systems to which the photoelectric conversion device can be applied, and the 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 19 and 20. 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.

[0133] It should be noted that the above embodiments are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted as being limited by them. In other words, the present invention can be implemented in various forms without departing from its technical concept or its main features.

[0134] Furthermore, the disclosure of this embodiment includes the following configurations and methods.

[0135] (Composition 1) A photoelectric conversion device having an avalanche photodiode, A semiconductor layer having a first surface and a second surface, A first semiconductor region of the first conductivity type located at the first depth, Displaced at a second depth deeper than the first depth relative to the first surface, the first semiconductor region and the second semiconductor region of the second conductivity type constituting the avalanche photodiode, A third semiconductor region of a first conductivity type is provided adjacent to the edge of the first semiconductor region, An oxide film disposed on the semiconductor layer, In cross-sectional view, it has a member provided on the oxide film, In a plan view, the member is arranged so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region. A photoelectric conversion device characterized in that the work function of the member is different from the work functions of the first semiconductor region and the third semiconductor region, so that a potential gradient for the signal charge is formed in the depth direction of the semiconductor layer at least at the boundary.

[0136] (Configuration 2) The photoelectric conversion device according to configuration 1, characterized in that the aforementioned member is a polysilicon of the second conductivity type.

[0137] (Composition 3) The first conductivity type is N-type, The photoelectric conversion device according to configuration 1 or 2, characterized in that the work function of the member is greater than the work functions of the first semiconductor region and the third semiconductor region.

[0138] (Composition 4) The photoelectric conversion device according to configuration 3, characterized in that the aforementioned member is P-type polysilicon.

[0139] (Composition 5) The first conductivity type is P-type, The photoelectric conversion device according to configuration 1 or 2, characterized in that the work function of the member is smaller than the work functions of the first semiconductor region and the third semiconductor region.

[0140] (Composition 6) The photoelectric conversion device according to configuration 5, characterized in that the aforementioned member is N-type polysilicon.

[0141] (Composition 7) A first wiring section electrically connected to the first semiconductor region, The second semiconductor region has a second wiring section electrically connected to it, The photoelectric conversion device according to any one of configurations 1 to 6, characterized in that the first wiring section is electrically connected to the member.

[0142] (Composition 8) The photoelectric conversion device according to configuration 1, characterized in that, in a plan view, the member overlaps with the entirety of the first semiconductor region.

[0143] (Composition 9) A photoelectric conversion device according to any one of configurations 1 to 8, characterized in that, in a plan view, the member overlaps with the entirety of the third semiconductor region.

[0144] (Composition 10) A protective film provided on the oxide film, It has an interlayer film provided on the protective film, The photoelectric conversion device according to any one of configurations 1 to 9, characterized in that the member is provided between the protective film and the interlayer film.

[0145] (Composition 11) A photoelectric conversion device having an avalanche photodiode, A semiconductor layer having a first surface and a second surface, A first semiconductor region of the first conductivity type located at the first depth, Displaced at a second depth deeper than the first depth relative to the first surface, the first semiconductor region and the second semiconductor region of the second conductivity type constituting the avalanche photodiode, A third semiconductor region of a first conductivity type is provided adjacent to the edge of the first semiconductor region, An oxide film disposed on the semiconductor layer, A protective film is disposed on the oxide film and is made of a different material from the oxide film, An interlayer film placed on the aforementioned protective film, In cross-sectional view, the oxide film and a member provided substantially between the film are present, A photoelectric conversion device characterized in that, in a plan view, the member is arranged to overlap with at least the boundary between the first semiconductor region and the third semiconductor region.

[0146] (Composition 12) The photoelectric conversion device according to configuration 11, characterized in that the interface state density between the oxide film and the member is configured to be smaller than the interface state density between the oxide film and the protective film.

[0147] (Composition 13) The photoelectric conversion device according to configuration 11 or 12, characterized in that, in a plan view, the extension of the member is located within one pixel.

[0148] (Composition 14) A first wiring section electrically connected to the first semiconductor region, The second semiconductor region has a second wiring section electrically connected to it, The photoelectric conversion device according to any one of configurations 11 to 13, characterized in that the first wiring section is electrically connected to the member.

[0149] (Composition 15) A photoelectric conversion device according to any one of configurations 11 to 14, characterized in that, in a plan view, the member overlaps with the entirety of the first semiconductor region.

[0150] (Composition 16) A photoelectric conversion device according to any one of configurations 10 to 15, characterized in that, in a plan view, the member overlaps with the entirety of the third semiconductor region.

[0151] (Composition 17) A photoelectric conversion device as described in any of configurations 1 to 16, A photoelectric conversion system characterized by having a signal processing unit that generates an image using the signal output by the aforementioned photoelectric conversion device.

[0152] (Composition 18) A mobile body comprising a photoelectric conversion device described in any of configurations 1 to 16, A mobile body characterized by having a control unit that controls the movement of the mobile body using a signal output by the photoelectric converter. [Explanation of Symbols]

[0153] 100 Photoelectric converter 102 Avalanche Photodiode 311 First Semiconductor Region (First Conductivity Type) 312 Second Semiconductor Region (Second Conductivity Type) 313 Third Semiconductor Region (First Conductivity Type) 314. Fourth semiconductor region (second conductivity type) 315. Fifth Semiconductor Region (First Conductivity Type) 316. Semiconductor Region 6 (First Conductivity Type) 317. Semiconductor Region VII (Second Conductivity Type) 331A 1st wiring section 331B 2nd wiring section 332 components 341 Oxide film 342 Protective film

Claims

1. A photoelectric conversion device having an avalanche photodiode, A semiconductor layer having a first surface and a second surface, A first semiconductor region of a first conductivity type located at a first depth, Displaced at a second depth deeper than the first depth relative to the first surface, the first semiconductor region and the second semiconductor region of the second conductivity type constituting the avalanche photodiode, A third semiconductor region of a first conductivity type is provided in contact with the edge of the first semiconductor region, An oxide film disposed on the semiconductor layer, In cross-sectional view, it has a member provided on the oxide film, In a plan view, the member is arranged so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region. The photoelectric conversion device is characterized in that, by having a different work function for the member and a different work function for the first semiconductor region and the third semiconductor region, a potential gradient for the signal charge is formed in the depth direction of the semiconductor layer at least at the boundary.

2. The photoelectric conversion device according to claim 1, characterized in that the aforementioned member is a second-conductivity type polysilicon.

3. The first conductivity type is N-type, The photoelectric conversion device according to claim 1, characterized in that the work function of the member is greater than the work functions of the first semiconductor region and the third semiconductor region.

4. The photoelectric conversion device according to claim 3, characterized in that the aforementioned member is P-type polysilicon.

5. The first conductivity type is P-type, The photoelectric conversion device according to claim 1, characterized in that the work function of the member is smaller than the work functions of the first semiconductor region and the third semiconductor region.

6. The photoelectric conversion device according to claim 5, characterized in that the aforementioned member is N-type polysilicon.

7. A first wiring section electrically connected to the first semiconductor region, The second semiconductor region is electrically connected to a second wiring section, The photoelectric conversion device according to claim 1, characterized in that the first wiring section is electrically connected to the member.

8. The photoelectric conversion device according to claim 1, characterized in that, in a plan view, the member overlaps with the entirety of the first semiconductor region.

9. The photoelectric conversion device according to claim 1, characterized in that, in a plan view, the member overlaps with the entirety of the third semiconductor region.

10. A protective film provided on the oxide film, It has an interlayer film provided on the protective film, The photoelectric conversion device according to claim 1, characterized in that the member is provided between the protective film and the interlayer film.

11. A photoelectric conversion device having an avalanche photodiode, A semiconductor layer having a first surface and a second surface, A first semiconductor region of a first conductivity type located at a first depth, Displaced at a second depth deeper than the first depth relative to the first surface, the first semiconductor region and the second semiconductor region of the second conductivity type constituting the avalanche photodiode, A third semiconductor region of a first conductivity type is provided in contact with the edge of the first semiconductor region, An oxide film disposed on the semiconductor layer, A protective film is disposed on the oxide film and is made of a different material from the oxide film, An interlayer film placed on the aforementioned protective film, In cross-sectional view, the member provided between the oxide film and the protective film is, A photoelectric conversion device characterized in that, in a plan view, the member is arranged so as to overlap at least the boundary between the first semiconductor region and the third semiconductor region.

12. The photoelectric conversion device according to claim 11, characterized in that the interface state density between the oxide film and the member is configured to be smaller than the interface state density between the oxide film and the protective film.

13. The photoelectric conversion device according to claim 11, characterized in that, in a plan view, the extension of the member is located within one pixel.

14. A first wiring section electrically connected to the first semiconductor region, The second semiconductor region is electrically connected to a second wiring section, The photoelectric conversion device according to claim 11, characterized in that the first wiring section is electrically connected to the member.

15. The photoelectric conversion device according to claim 11, characterized in that, in a plan view, the member overlaps with the entirety of the first semiconductor region.

16. The photoelectric conversion device according to claim 11, characterized in that, in a plan view, the member overlaps with the entirety of the third semiconductor region.

17. A photoelectric conversion device according to any one of claims 1 to 16, A photoelectric conversion system characterized by having a signal processing unit that generates an image using the signal output by the aforementioned photoelectric conversion device.

18. A mobile body comprising a photoelectric converter according to any one of claims 1 to 16, A mobile body characterized by having a control unit that controls the movement of the mobile body using a signal output by the photoelectric converter.

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