JP2023077741A - Photoelectric conversion device - Google Patents

Abstract

To provide a photoelectric conversion device having achieved reduction of a dark current noise and enhancement of sensibility.SOLUTION: A photoelectric conversion device includes: a substrate having a first surface and a second surface; an insulation layer arranged on the first surface side; and photoelectric conversion parts that are arranged in the substrate, and generates electric charge in accordance with an incident light coming passing through the insulation layer. The insulation layer includes a structure in which first insulators and second insulators are alternately arranged in a direction parallel to the insulation layer. A plurality of the first insulators and the second insulators are arranged in the direction parallel to the insulation layer in a region where the incident light passed through the insulation layer can be entered into one photoelectric conversion part. A material constituting the second insulator and a material constituting the first insulator are different.SELECTED DRAWING: Figure 3

Description

The present invention relates to a photoelectric conversion device.

Japanese Unexamined Patent Application Publication No. 2002-200000 discloses a structure in which a fine uneven structure is provided at the interface of a semiconductor layer on which a photodiode is formed on the light receiving surface side in order to improve the sensitivity to incident light in a solid-state imaging device.

JP 2020-174158 A

In the semiconductor layer of the photoelectric conversion region having the structure of Patent Document 1, dark current noise may increase due to defect levels at and near the interface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric conversion device that achieves reduction in dark current noise and improvement in sensitivity.

According to one aspect of the present invention, a substrate having a first surface and a second surface, an insulating layer arranged on the side of the first surface, and an insulating layer arranged in the substrate and incident through the insulating layer and a photoelectric conversion unit that generates electric charge according to incident light, and the insulating layer has a structure in which first insulators and second insulators are alternately repeated in a direction parallel to the insulating layer. and the first insulator and the second insulator are arranged in a plurality in a direction parallel to the insulating layer in a region where the incident light passing through the insulating layer can be incident on one photoelectric conversion unit. The photoelectric conversion device is provided, wherein the material forming the second insulator and the material forming the first insulator are different.

ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion apparatus with which the reduction of a dark current noise and the improvement of the sensitivity were implement|achieved is provided.

1 is a schematic diagram showing the overall configuration of a photoelectric conversion device according to a first embodiment; FIG. 2 is a schematic block diagram showing a configuration example of a sensor substrate according to the first embodiment; FIG. 1 is a schematic block diagram showing a configuration example of a circuit board according to a first embodiment; FIG. 3 is a schematic block diagram showing a configuration example for one pixel of a photoelectric conversion unit and a pixel signal processing unit according to the first embodiment; FIG. 4A and 4B are diagrams for explaining the operation of the avalanche photodiode according to the first embodiment; FIG. 1 is a diagram showing the structure of an avalanche photodiode according to a first embodiment; FIG. It is a cross-sectional schematic diagram which expands and shows the trench structure which concerns on 1st Embodiment. 1 is a schematic plan view of an avalanche photodiode according to a first embodiment; FIG. FIG. 10 is a diagram showing the structure of an avalanche photodiode according to a second embodiment; It is a cross-sectional schematic diagram of an avalanche photodiode according to a third embodiment. It is a cross-sectional schematic diagram of an avalanche photodiode according to a fourth embodiment. It is a cross-sectional schematic diagram of the avalanche photodiode based on 5th Embodiment. FIG. 12 is a block diagram of a photodetection system according to a sixth embodiment; FIG. 11 is a block diagram of a photodetection system according to a seventh embodiment; FIG. 21 is a schematic diagram of an endoscopic surgery system according to an eighth embodiment; FIG. 12 is a schematic diagram of a photodetection system according to a ninth embodiment; FIG. 21 is a schematic diagram of a moving body according to a ninth embodiment; FIG. 14 is a flow chart showing the operation of the photodetection system according to the ninth embodiment; FIG. FIG. 20 is a diagram showing a specific example of an electronic device according to the tenth embodiment;

Embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below are for embodying the technical idea of the present invention, and are not intended to limit the present invention. The sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation. The same or corresponding elements are denoted by common reference numerals across multiple drawings, and their description may be omitted or simplified.

In the following description, terms indicating specific directions or positions (eg, "upper", "lower", "right", "left", and other terms containing those terms) are used where appropriate. The use of these terms is for the purpose of facilitating the 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.

[First embodiment]
FIG. 1 is a schematic diagram showing the overall configuration of a photoelectric conversion device 100 according to this embodiment. The photoelectric conversion device 100 can be, for example, a solid-state imaging device, a focus detection device, a distance measuring device, a TOF (Time-Of-Flight) camera, or the like. The photoelectric conversion device 100 has a sensor substrate 11 (first substrate) and a circuit substrate 21 (second substrate) which are laminated to each other. The sensor board 11 and the circuit board 21 are electrically connected to each other. The sensor substrate 11 has a pixel region 12 in which a plurality of pixels 101 are arranged in rows and columns. The circuit board 21 includes a first circuit region 22 in which a plurality of pixel signal processing units 103 arranged in a plurality of rows and a plurality of columns are arranged, and a second circuit region 22 arranged on the periphery of the first circuit region 22 . and a circuit region 23 . The second circuit region 23 can include circuits or the like that control the plurality of pixel signal processing units 103 . The sensor substrate 11 has a light incident surface for receiving incident light and a connection surface facing the light incident surface. The sensor board 11 is connected to the circuit board 21 on the connection surface side. That is, the photoelectric conversion device 100 is a so-called backside illumination type.

In this specification, "planar view" refers to viewing from a direction perpendicular to the surface opposite to the light incident surface. Further, the cross section refers to a surface in a direction perpendicular to the surface of the sensor substrate 11 opposite to the light incident surface. Note that the light incident surface may be a rough surface when viewed microscopically, but in such a case, the plane view is defined with reference to the light incident surface when viewed macroscopically.

In the following description, the sensor substrate 11 and the circuit substrate 21 are diced chips, but the sensor substrate 11 and the circuit substrate 21 are not limited to chips. For example, the sensor substrate 11 and the circuit substrate 21 may be wafers. Further, when the sensor substrate 11 and the circuit substrate 21 are diced chips, the photoelectric conversion device 100 may be manufactured by stacking wafers and then dicing, or may be stacked after dicing. may be manufactured by

FIG. 2 is a schematic block diagram showing an arrangement example of the sensor substrate 11. As shown in FIG. A plurality of pixels 101 arranged in a plurality of rows and a plurality of columns are arranged in the pixel region 12 . Each of the plurality of pixels 101 has a photoelectric conversion section 102 including an avalanche photodiode (hereinafter referred to as APD) as a photoelectric conversion element in the substrate. When the photoelectric conversion device 100 is an imaging device, the plurality of pixels 101 can be elements that generate image signals by photoelectric conversion. However, if the photoelectric conversion device 100 is a distance measuring device using a technology such as TOF, the pixel 101 can be an element for measuring the arrival time and amount of light. That is, the use of the plurality of pixels 101 is not limited to image acquisition.

The conductivity type of the charge used as the signal charge among the charge pairs generated in the APD is called the first conductivity type. The first conductivity type refers to a conductivity type in which majority carriers are charges of the same polarity as the signal charges. A conductivity type opposite to the first conductivity type, that is, a conductivity type in which charges having a polarity different from that of signal charges are majority carriers is referred to as a second conductivity type. In the APD described below, the anode of the APD is at a fixed potential, and a signal is taken out from the cathode of the APD. Therefore, the semiconductor region of the first conductivity type is the N-type semiconductor region, and the semiconductor region of the second conductivity type is the P-type semiconductor region. It should be noted that the cathode of the APD may be at a fixed potential, and the signal may be extracted from the anode of the APD. In this case, the semiconductor region of the first conductivity type is a P-type semiconductor region, and the semiconductor region of the second conductivity type is an N-type semiconductor region. Moreover, although the case where one node of the APD is set to a fixed potential will be described below, the configuration may be such that the potentials of both nodes fluctuate.

In this specification, when the term "impurity concentration" is simply used, it means the net impurity concentration after subtracting the amount compensated by the impurity of the opposite conductivity type. That is, "impurity concentration" refers to NET doping concentration. A region in which the P-type impurity concentration is higher than the N-type impurity concentration is a P-type semiconductor region. On the contrary, a region where the N-type impurity concentration is higher than the P-type impurity concentration is an N-type semiconductor region.

FIG. 3 is a schematic block diagram showing a configuration example of the circuit board 21. As shown in FIG. The circuit board 21 has a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged in a plurality of rows and columns.

A vertical scanning circuit 110 , a horizontal scanning circuit 111 , a readout circuit 112 , a pixel output signal line 113 , an output circuit 114 and a control signal generator 115 are arranged on the circuit board 21 . The plurality of photoelectric conversion units 102 shown in FIG. 2 and the plurality of pixel signal processing units 103 shown in FIG. ing.

The control signal generation unit 115 is a control circuit that generates control signals for driving the vertical scanning circuit 110, the horizontal scanning circuit 111, and the readout circuit 112, and supplies the control signals to these units. Thereby, the control signal generation unit 115 controls the driving timing of each unit.

The vertical scanning circuit 110 supplies a control signal to each of the plurality of pixel signal processing units 103 based on the control signal supplied from the control signal generation unit 115 . The vertical scanning circuit 110 supplies a control signal to each pixel signal processing unit 103 for each row through a drive line provided for each row of the first circuit region 22 . As will be described later, each row may have a plurality of drive lines. Logic circuits such as shift registers and address decoders can be used for the vertical scanning circuit 110 . As a result, the vertical scanning circuit 110 selects a row to output a signal from the pixel signal processing unit 103 .

A signal output from the photoelectric conversion unit 102 of the pixel 101 is processed by the pixel signal processing unit 103 . The pixel signal processing unit 103 acquires and holds a digital signal having a plurality of bits by counting the number of pulses output from the APD included in the photoelectric conversion unit 102 .

The horizontal scanning circuit 111 supplies a control signal to the readout circuit 112 based on the control signal supplied from the control signal generator 115 . The pixel signal processing unit 103 is connected to the readout circuit 112 via pixel output signal lines 113 provided for each column of the first circuit region 22 . A pixel output signal line 113 in one column is shared by a plurality of pixel signal processing units 103 in the corresponding column. The pixel output signal line 113 includes a plurality of wirings, and has at least a function of outputting a digital signal from each pixel signal processing unit 103 to the readout circuit 112 and a control signal for selecting a column from which a signal is to be output. It also has a function of supplying to the signal processing unit 103 . The readout circuit 112 outputs a signal to the external storage or signal processing unit of the photoelectric conversion device 100 via the output circuit 114 based on the control signal supplied from the control signal generation unit 115 .

The arrangement of the photoelectric conversion units 102 in the pixel region 12 may be one-dimensional. Further, the function of the pixel signal processing unit 103 does not necessarily have to be provided for each of the pixels 101 . For example, one pixel signal processing unit 103 may be shared by a plurality of pixels 101 . In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing the signals output from each photoelectric conversion unit 102 .

As shown in FIGS. 2 and 3, a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged is arranged in a region overlapping the pixel region 12 in plan view. A vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, an output circuit 114, and a control signal generator 115 are arranged so as to overlap between the edge of the sensor substrate 11 and the edge of the pixel region 12 in plan view. be done. In other words, the sensor substrate 11 has a pixel region 12 and non-pixel regions arranged around the pixel region 12 . A second circuit region 23 in which the vertical scanning circuit 110, the horizontal scanning circuit 111, the readout circuit 112, the output circuit 114, and the control signal generator 115 are arranged in the region overlapping the non-pixel region in plan view on the circuit board 21. are distributed.

Note that the arrangement of the pixel output signal lines 113, the arrangement of the readout circuits 112, and the arrangement of the output circuits 114 are not limited to those shown in FIG. For example, the pixel output signal lines 113 may be arranged extending in the row direction and shared by the plurality of pixel signal processing units 103 in the corresponding row. The readout circuit 112 may be arranged so that the pixel output signal lines 113 of each row are connected.

FIG. 4 is a schematic block diagram showing a configuration example for one pixel of the photoelectric conversion unit 102 and the pixel signal processing unit 103 according to this embodiment. FIG. 4 schematically shows a more specific configuration example including the connection relationship between the photoelectric conversion section 102 arranged on the sensor substrate 11 and the pixel signal processing section 103 arranged on the circuit board 21 . 4, drive lines 213 and 214 are shown as drive lines between the vertical scanning circuit 110 and the pixel signal processing unit 103 in FIG.

The photoelectric conversion unit 102 has an APD 201 . The pixel signal processing section 103 has a quench element 202 , a waveform shaping section 210 , a counter circuit 211 and a selection circuit 212 . Note that the pixel signal processing unit 103 may have at least one of the waveform shaping unit 210 , the counter circuit 211 and the selection circuit 212 .

The APD 201 generates charge pairs according to incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201 . Also, the cathode of the APD 201 is connected to the first terminal of the quench element 202 and the input terminal of the waveform shaping section 210 . A cathode of the APD 201 is supplied with a voltage VH (second voltage) higher than the voltage VL supplied to the anode. As a result, the anode and cathode of the APD 201 are supplied with a reverse bias voltage that causes the APD 201 to perform an avalanche multiplication operation. In the APD 201 to which a reverse bias voltage is supplied, when charges are generated by incident light, the charges cause avalanche multiplication to generate an avalanche current.

Operation modes in the case where a reverse bias voltage is supplied to the APD 201 include a Geiger mode and a linear mode. The Geiger mode is a mode in which the potential difference between the anode and cathode is greater than the breakdown voltage, and the linear mode is a mode in which the potential difference between the anode and cathode is close to or below the breakdown voltage.

An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). At this time, for example, the voltage VL (first voltage) is -30V and the voltage VH (second voltage) is 1V. APD 201 may be operated in linear mode or may be operated in Geiger mode. In the case of SPAD, the potential difference is larger than that of linear mode APD, and the effect of avalanche multiplication is remarkable, so SPAD is preferable.

The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication. The quench element 202 suppresses the voltage supplied to the APD 201 to suppress avalanche multiplication (quench operation). Also, the quench element 202 returns the voltage supplied to the APD 201 to the voltage VH by causing a current corresponding to the voltage drop due to the quench operation (recharge operation). Quenching element 202 can be, for example, a resistive element.

A waveform shaping unit 210 shapes the potential change of the cathode of the APD 201 obtained during photon detection, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping section 210 . Although FIG. 4 shows an example in which one inverter is used as the waveform shaping section 210, the waveform shaping section 210 may use a circuit in which a plurality of inverters are connected in series. may be a circuit of

The counter circuit 211 counts the pulse signals output from the waveform shaping section 210 and holds a digital signal indicating the count value. Also, when a control signal is supplied from the vertical scanning circuit 110 via the drive line 213, the counter circuit 211 resets the signal it holds.

A control signal is supplied to the selection circuit 212 from the vertical scanning circuit 110 shown in FIG. 3 through the drive line 214 shown in FIG. In accordance with this control signal, the selection circuit 212 switches between electrical connection and non-connection between the counter circuit 211 and the pixel output signal line 113 . The selection circuit 212 includes, for example, a buffer circuit or the like for outputting a signal corresponding to the value held in the counter circuit 211 .

In the example of FIG. 4, the selection circuit 212 switches between electrical connection and non-connection between the counter circuit 211 and the pixel output signal line 113, but the signal output to the pixel output signal line 113 is controlled. The method to do is not limited to this. For example, a switch such as a transistor is arranged at a node such as between the quench element 202 and the APD 201 or between the photoelectric conversion unit 102 and the pixel signal processing unit 103, and the pixel output is changed by switching between electrical connection and non-connection. Signal output to the signal line 113 may be controlled. Alternatively, the signal output to the pixel output signal line 113 may be controlled by changing the value of the voltage VH or the voltage VL supplied to the photoelectric conversion unit 102 using a switch such as a transistor.

FIG. 4 shows a configuration example using the counter circuit 211 . However, instead of the counter circuit 211, a time-to-digital converter (hereinafter referred to as TDC) and memory may be used to acquire the timing for detecting the pulse. At this time, the generation timing of the pulse signal output from the waveform shaping section 210 is converted into a digital signal by the TDC. In this case, a control signal (reference signal) can be supplied to the TDC from the vertical scanning circuit 110 of FIG. 3 through the drive line. The TDC obtains as a digital signal a signal indicating the relative time of the pulse input timing with reference to the control signal.

5(a), 5(b) and 5(c) are diagrams for explaining the operation of the APD 201 according to this embodiment. FIG. 5(a) is a diagram showing the APD 201, the quench element 202, and the waveform shaping section 210 extracted from FIG. As shown in FIG. 5A, the connection node of the input terminals of the APD 201, the quench element 202 and the waveform shaping section 210 is nodeA. Also, as shown in FIG. 5A, the output side of the waveform shaping section 210 is nodeB.

FIG. 5(b) is a graph showing the time change of the potential of node A in FIG. 5(a). FIG. 5(c) is a graph showing temporal changes in the potential of node B in FIG. 5(a). During the period from time t0 to time t1, a voltage of VH-VL is applied to the APD 201 in FIG. 5(a). When a photon strikes the APD 201 at time t1, the APD 201 undergoes avalanche multiplication. As a result, an avalanche current flows through the quench element 202, and the potential of nodeA drops. After that, the potential drop amount further increases, and the voltage applied to the APD 201 gradually decreases. Then, at time t2, the avalanche multiplication in APD 201 stops. As a result, the voltage level of nodeA does not drop below a certain value. Thereafter, in the period from time t2 to time t3, a current that compensates for the voltage drop from the node of voltage VH flows through nodeA, and at time t3, nodeA settles to the original potential.

In the above process, the potential of nodeB becomes high level while the potential of nodeA is lower than a certain threshold. In this way, the waveform of the potential drop of nodeA caused by incident photons is shaped by the waveform shaping section 210 and output as a pulse to nodeB.

6A and 6B are diagrams showing the structure of the APD 201 according to this embodiment. FIG. 6A is a schematic cross-sectional view of the APD 201. FIG. FIG. 6B is a schematic plan view showing the structure of the semiconductor layer 300 in the vicinity of the avalanche multiplication region. The structure of the APD 201 will be described with mutual reference to FIGS. 6(a) and 6(b).

A plurality of semiconductor regions forming the APD 201 are arranged on the semiconductor layer 300 of the sensor substrate 11 . FIG. 6 is illustrated so that the direction in which incident light is incident is the upper side. The semiconductor layer 300 has a first surface on which light is incident and a second surface opposite to the first surface. In this specification, the depth direction is the direction from the first surface to the second surface of the semiconductor layer 300 on which the APD 201 is arranged. Hereinafter, the "first surface" may be referred to as the "rear surface", and the "second surface" may be referred to as the "front surface". A direction from a predetermined position of the semiconductor layer 300 toward the surface of the semiconductor layer 300 may be expressed as “deep”. Also, the direction from a predetermined position of the semiconductor layer 300 toward the back surface of the semiconductor layer 300 may be expressed as “shallow”.

As shown in FIG. 6( a ), the APD 201 comprises a semiconductor layer 300 of the sensor substrate 11 , an insulating layer 304 arranged on the first surface side thereof, and an insulating layer 304 arranged on the incident side of the insulating layer 304 . and a microlens 323 . APD 201 may further include a filter layer. Examples of the filter layer include optical filters such as color filters, infrared cut filters, and monochrome filters. The color filters can be, for example, RGB color filters, RGBW color filters, or the like.

The semiconductor layer 300 includes a first semiconductor region 311, a second semiconductor region 312, a third semiconductor region 313, a fourth semiconductor region 314, a fifth semiconductor region 315, a sixth semiconductor region 316, a seventh semiconductor region 317, and a pixel separation portion. 324. The APD 201 includes at least a first conductivity type first semiconductor region 311 and a second conductivity type second semiconductor region 312 . The first semiconductor region 311 and the second semiconductor region 312 form a PN junction. The impurity concentration of the first semiconductor region 311 is higher than that of the second semiconductor region 312 . A predetermined reverse bias voltage is applied to the first semiconductor region 311 and the second semiconductor region 312, thereby forming an avalanche multiplication region.

As shown in FIG. 6A, a third semiconductor region 313 of the first conductivity type can be arranged between the first semiconductor region 311 and the second semiconductor region 312 in the depth direction. The third semiconductor region 313 has a function of alleviating an electric field. The third semiconductor region 313 may be of the second conductivity type as long as the function of alleviating the electric field can be realized. Also, as shown in FIG. 6B, the first semiconductor region 311 may be circular in plan view. Also, the third semiconductor region 313 may be concentric so as to surround the first semiconductor region 311 in plan view.

As shown in FIG. 6A, a fifth semiconductor region 315 of the second conductivity type is arranged at a position shallower than the second semiconductor region 312 . The fifth semiconductor region 315 is arranged so as to be in contact with the fourth semiconductor region 314 of the second conductivity type. As shown in FIG. 6B, the fourth semiconductor region 314 is arranged to surround the first semiconductor region 311, the second semiconductor region 312 and the third semiconductor region 313 in plan view. As shown in FIGS. 6A and 6B, in plan view, the fifth semiconductor region 315 may be arranged over the entire surface of the APD 201, and part of the fifth semiconductor region 315 may be the first semiconductor region. 4 may overlap with the semiconductor region 314 . The fourth semiconductor region 314 may be arranged over the entire depth of the semiconductor layer 300 , or part of the fourth semiconductor region 314 may be at the same depth as the fifth semiconductor region 315 .

Between the APDs 201 adjacent to each other among the plurality of APDs 201 (pixels 101), a pixel separation section 324 having a structure in which an insulator (dielectric) is embedded in the semiconductor layer 300 is arranged. As shown in FIGS. 6A and 6B, the pixel separation section 324 uses a deep trench isolation (DTI) structure in which a deep trench is filled with an insulator such as silicon oxide. can be The deep trenches may be filled with metal other than the insulator. Alternatively, a thin insulator layer may be formed on the sidewalls of the deep trench and the deep trench and insulator layer may be filled with metal. The pixel separation section 324 forms a rectangle (including a square) surrounding one APD 201 in plan view. Thereby, the pixel separation unit 324 separates one APD 201 from other elements. In addition, the pixel separation unit 324 may be arranged so as to surround the entire periphery of the APD 201 in plan view, or may be arranged so as to surround only a part of the periphery such as only the opposite side portion.

A seventh semiconductor region 317 of the first conductivity type is provided between the second semiconductor region 312 and the fifth semiconductor region 315 . The impurity concentration of the seventh semiconductor region 317 is higher than that of the sixth semiconductor region 316 provided around the seventh semiconductor region 317 . With this configuration, for signal charges, the potential of the seventh semiconductor region 317 is lower than the potential of the sixth semiconductor region 316, allowing more charges to be collected in the avalanche multiplication region. The seventh semiconductor region 317 is a semiconductor region that is provided as necessary, and may not be provided. In FIG. 6A, part of the seventh semiconductor region 317 and the second semiconductor region 312 are in contact with each other, but the seventh semiconductor region 317 is provided apart from the second semiconductor region 312. good too.

A pinning layer 321 and an antireflection layer 325 (first antireflection layer) are arranged in this order on the insulating layer 304 on the first surface side of the semiconductor layer 300 . A first insulator 327 and a second insulator 328 are arranged on the incident side of the antireflection layer 325 . An antireflection layer 326 (second antireflection layer) and a planarization layer 322 are arranged in this order on the incident sides of the first insulator 327 and the second insulator 328 . The first insulator 327 and the second insulator 328 form a periodically patterned trench structure such that they are alternately repeated in a direction parallel to the insulating layer 304 . In other words, a plurality of sets of first insulators 327 and second insulators 328 are arranged in a direction parallel to the insulating layer 304 in a region where incident light can be incident on one APD 201 . This trench structure can be formed, for example, by depositing the second insulator 328 so as to fill the trench formed in the first insulator 327 .

The material of each of the first insulator 327 and the second insulator 328 may be an insulating material that transmits light and has a different refractive index. Typically, the refractive index n2 of the second insulator 328 is greater than the refractive index n1 of the first insulator 327 (n2>n1). By arranging the trench structure in which the refractive index changes periodically in the insulating layer 304 in this manner, the incident light passing through the insulating layer 304 is diffracted. Note that the magnitude relationship of the refractive indices may be reversed.

The effect of diffracting incident light by the insulating layer 304 will be described. In order for the light incident on the APD 201 to be sufficiently photoelectrically converted, it is necessary for the light to propagate a sufficient distance (hereinafter referred to as optical path length) in the semiconductor layer 300 . Therefore, in order to improve the efficiency of photoelectric conversion, it is required to secure a sufficient thickness of the semiconductor layer 300 . The optical path length required to improve the efficiency of photoelectric conversion is short for light with a relatively short wavelength such as blue light, and is long for light with a relatively long wavelength such as red light and near-infrared light. Therefore, when the APD 201 is sensitive to red light or near-infrared light, the semiconductor layer 300 is required to be thicker than when the APD 201 is sensitive to blue light.

A specific example of the thickness of the semiconductor layer 300 when the APD 201 is arranged on a single crystal silicon substrate will be described. For blue light or green light in the visible region, the depth of the photoelectric conversion region (from the first surface to the second semiconductor region 312) in the semiconductor layer 300 shown in FIG. 6A is about 4 μm. If so, 99% or more of the incident light is photoelectrically converted. However, for red light or near-infrared light, it is necessary to make the photoelectric conversion region even thicker in order to photoelectrically convert 99% or more of the incident light. Since the depth of the photoelectric conversion region of the APD 201 is generally about several μm, the efficiency of photoelectric conversion may not be sufficient particularly for light with a relatively long wavelength, such as red light and near-infrared light.

In contrast, in the present embodiment, incident light passing through the insulating layer 304 is diffracted by arranging the trench structure in the insulating layer 304 . As a result, the incident light propagates through the semiconductor layer 300 over a longer distance, thereby facilitating photoelectric conversion. Therefore, according to this embodiment, the sensitivity of the photoelectric conversion device can be improved.

If the semiconductor layer 300 has irregularities such as the trench structure described above, a defect level generated at and near the interface may increase dark current noise. In contrast, in this embodiment, the trench structure is formed in the insulating layer 304 instead of the semiconductor layer 300, so that the dark current noise due to the above factors is reduced. As described above, according to the present embodiment, a photoelectric conversion device that achieves reduction in dark current noise and improvement in sensitivity is provided.

Silicon oxide (SiO ₂ ), silicon nitride (SiN), silicon oxynitride (SiON), tantalum oxide (Ta ₂ O ₅ ), or the like is used as the material of each of the first insulator 327 and the second insulator 328 . It can be used to meet refractive index requirements. Silicon oxide has a refractive index of about 1.5, silicon oxynitride has a refractive index of about 1.8, silicon nitride has a refractive index of about 2, and tantalum oxide has a refractive index of about 2. For example, when the material of the first insulator 327 is silicon oxide, the material of the second insulator 328 is silicon nitride, silicon oxynitride, or tantalum oxide, which has a higher refractive index than silicon oxide. can be used. From the viewpoint of increasing the diffraction effect by increasing the refractive index ratio, it is more preferable to use silicon nitride or tantalum oxide as the material of the second insulator 328 .

FIGS. 7A to 7H are cross-sectional schematic diagrams showing enlarged trench structures according to the present embodiment. FIG. 7A shows an example of a structure in which a second insulator 328 having a rectangular cross section is arranged at a position in contact with the antireflection layer 325 . FIG. 7(b) is an example of a structure in which the second insulator 328 is arranged in the vicinity of the antireflection layer 326. FIG. FIG. 7C shows an example of a structure in which the second insulator 328 is arranged near the center of the first insulator 327 in the thickness direction.

It is desirable that the effective period of repetition of the trench structure formed by the first insulator 327 and the second insulator 328 be smaller than hc/ _Ea . Here, h is Planck's constant [J·s], c is the speed of light [m/s], and _Ea is the bandgap of the substrate [J]. When the sensor substrate 11 is a silicon substrate, hc/ _Ea is approximately 1.1 μm. The wavelength at which photoelectric conversion of incident light mainly occurs in the APD 201 is in a range smaller than hc/ _Ea . Therefore, by setting the effective period of the trench structure as described above, a trench structure capable of effectively diffracting incident light to which the APD 201 is sensitive is realized. Note that the period of the trench structure can be defined as the distance from the center of gravity of one trench to the center of gravity of another adjacent trench in a cross-sectional view. Also, the effective period can be defined as the average of the periods over the entire trench structure.

Also, as shown in FIG. 7(a), the width _W1 of the second insulator 328 may be about half the effective period of repeating the trench structure. That is, the width _W1 of the second insulator 328 is preferably smaller than hc/ _2Ea , which is half the above-mentioned hc/ _Ea . Thereby, the effective period described above can be realized.

FIG. 7(d) is an example where the width W ₂ of the second insulator 328 is greater than half the effective period of the repeating trench structure (ie, W ₂ >W ₁ ). FIG. 7(e) is an example where the width _W3 of the second insulator 328 is less than half of the effective period of repeating the trench structure (that is, _W3 < _W1 ). Thus, the width of the second insulator 328 may be greater than or less than half the effective period.

FIG. 7(f) is an example in which the height of the second insulator 328 is higher than the example in FIG. 7(a). FIG. 7(g) is an example in which the height of the second insulator 328 is lower than the example of FIG. 7(a). Like these, the height of the second insulator 328 in the trench structure can be appropriately set.

FIG. 7(h) is an example in which the second insulator 328 has a triangular cross section. Thus, the shape of the second insulator 328 in the trench structure is not limited to rectangular. The shape of the second insulator 328 in the trench structure may be a reverse tapered shape with a narrow incident side. In this case, the diffraction effect becomes stronger and the sensitivity can be improved. Also, the shape of the second insulator 328 in the trench structure may be hemispherical, arcuate, stepped, or the like. In this case, the steep change in the refractive index in the trench structure is suppressed, thereby reducing unnecessary reflection and improving the sensitivity.

8A and 8B are schematic plan views of the APD 201 according to this embodiment. As shown in FIG. 8A, the second insulators 328 are arranged in a grid pattern in plan view. In FIG. 8(a), the second insulator 328 has a uniform period in plan view. However, the second insulator 328 need not be of uniform periodicity. As shown in FIG. 8(b), the second insulator 328 may have a grid shape with a larger period closer to the outer periphery. In addition, the second insulators 328 may be arranged randomly in a plan view, which makes the angular distribution of diffracted light uniform.

A pixel separator 324 is arranged between the two APDs 201 as shown in FIGS. 8(a) and 8(b). Although some of the light diffracted by the insulating layer 304 may travel toward the adjacent APDs 201 , the pixel separators 324 reduce the amount of such light incident on the adjacent APDs 201 . Therefore, by arranging the pixel separation section 324, crosstalk to adjacent pixels can be reduced.

Although the photoelectric conversion unit 102 includes the APD 201 in this embodiment, the photoelectric conversion unit 102 may include a photodiode other than the APD, and is not limited to using the APD.

[Second embodiment]
A second embodiment of the present invention will be described. In the description of the present embodiment, the description of elements common to the first embodiment may be omitted.

9A and 9B are diagrams showing the structure of the APD 201 according to the second embodiment. FIG. 9A is a schematic cross-sectional view of the APD 201 according to the second embodiment. FIG. 9B is a schematic plan view of the APD 201 according to the second embodiment. The APD 201 of the present embodiment differs from the APD 201 of the first embodiment in that an uneven structure 329 is arranged in the fifth semiconductor region 315 .

The concave-convex structure 329 has a lattice shape in a plan view as shown in FIG. 9B, and is a trench structure having concaves and convexes in a cross-sectional view as shown in FIG. 9A. be. The uneven structure 329 is formed so as to overlap the first semiconductor region 311 and the seventh semiconductor region 317 in plan view, and the center of gravity of the uneven structure 329 is included in the avalanche multiplication region in plan view. In a grid-like trench structure as shown in FIG. 9B, the trench depth at intersections of the trenches is greater than the trench depth at the portion where the trenches extend alone. However, the bottom of the trench where the trenches intersect is positioned closer to the incident side than half the thickness of the semiconductor layer 300 . Here, the trench depth is the depth from the first surface of the semiconductor layer 300 to the bottom of the trench, and can also be referred to as the depth of the concave portion of the concave-convex structure 329 .

The trench structure of the uneven structure 329 contains a material different from that of the fifth semiconductor region 315 . For example, if the material of the fifth semiconductor region 315 is silicon, the main member forming the trench structure may be silicon oxide or silicon nitride, which has a lower refractive index than silicon. However, the trench structure may also contain metal or organic materials. Also, there may be voids inside the trench structure. Because the air gap has a lower refractive index than other materials, the diffraction effect can be improved. The trenches are formed, for example, in the semiconductor layer 300 to a depth of 0.1 μm to 0.6 μm. In order to sufficiently enhance the diffraction of incident light, it is desirable that the depth of the trench is greater than the width of the trench. Here, the width of the trench is the width from the interface between the pinning layer 321 and the third semiconductor region 313 to the interface between the pinning layer 321 and the third semiconductor region 313 on a plane passing through the center of gravity of the trench cross section. The depth is the depth from the light incident surface to the bottom of the trench.

The effect of arranging the concave-convex structure 329 and a suitable example of the trench structure period will be described. When light enters the APD 201, avalanche light emission may occur in the avalanche multiplication region. Avalanche luminescence is a phenomenon in which photons are generated by recombination of a large amount of electrons or holes generated by avalanche multiplication with charges of different polarities. Photons generated by avalanche emission leak into adjacent pixels, which may cause false signals in the adjacent pixels and degrade image quality.

The spectrum of avalanche emission light spreads to some extent from short wavelengths to long wavelengths, but short wavelength components have a short absorption length in the substrate and are photoelectrically converted at positions close to the light emitting region, so they do not reach adjacent pixels. low probability of generating false signals. On the other hand, long-wavelength components have a long absorption length in the substrate, and have a high probability of generating false signals at positions farther from the light-emitting region, which is a dominant factor in the deterioration of the image quality described above. For this reason, the component with the maximum wavelength in the spectrum of the avalanche emitted light can be approximately regarded as a representative factor of the deterioration of the image quality. The maximum value of the wavelength of avalanche emission is determined by the bandgap of the substrate material, hc/ _Ea (h: Planck's constant [J s], c: speed of light [m/s], _Ea : bandgap of substrate [J] ) shall be required by For example, when the sensor substrate 11 is made of silicon, the maximum wavelength of the avalanche emission light is about 1.1 μm.

When the effective period of the relief structure 329 is larger than the avalanche emission wavelength, the avalanche emission light behaves like a particle with respect to the relief structure 329 . Since the effective refractive index changes steeply with respect to the substrate depth, the avalanche emission light is reflected at the bottom of the uneven structure 329, and the reflected light becomes stray light within the pixel.

On the other hand, when the period of the uneven structure 329 is smaller than the avalanche emission wavelength, the avalanche emission light behaves wave-like. Since the change in the effective refractive index with respect to the depth of the semiconductor layer 300 becomes moderate, the reflection of the avalanche emission light at the bottom of the uneven structure 329 is reduced, and the avalanche emission light incident on the uneven structure 329 travels toward the outside of the substrate. Therefore, stray light within the pixel is suppressed. At this time, by arranging the concave-convex structure 329 in the center of the photoelectric conversion element where the light intensity of the avalanche emission light on the light incident surface of the semiconductor layer 300 is high, the effect of suppressing stray light can be obtained more efficiently. For the above reasons, the period of the concave-convex structure 329 is preferably smaller than hc/ _Ea , so that the effect of suppressing stray light can be obtained more preferably, and crosstalk between pixels can be reduced. In other words, the width of the trench should be less than hc/ _2Ea .

As described above, by forming the uneven structure 329 in the semiconductor layer 300, an effect of reducing crosstalk can be obtained. It may cause noise. On the other hand, in this embodiment, in addition to the uneven structure 329 of the semiconductor layer 300 , the uneven structure is further provided by the first insulator 327 and the second insulator 328 arranged on the insulating layer 304 . The trench structure in this insulating layer 304 can also have the effect of reducing crosstalk by the same mechanism as the uneven structure 329 . Therefore, in this embodiment, the uneven structure 329 of the semiconductor layer 300 and the uneven structure of the first insulator 327 and the second insulator 328 are used together. As a result, a sufficient crosstalk reduction effect can be obtained even if the area of the uneven structure 329 is smaller than when there is no uneven structure by the first insulator 327 and the second insulator 328. Therefore, the area of the uneven structure 329 is reduced. can be reduced to reduce dark current noise.

According to this embodiment, in addition to obtaining the same effects as in the first embodiment, a photoelectric conversion device with reduced crosstalk between pixels is provided.

The antireflection layer 325 is desirably made of a material whose effective refractive index is lower than that of the uneven structure 329 . Here, the effective refractive index is the substantial refractive index of the entire concave-convex structure 329 including the substrate in which the trench is formed and the member filling the trench. For example, when the semiconductor layer 300 is silicon with a refractive index of 4 and the first insulator 327 is silicon oxide with a refractive index of about 1.5, the effective refractive index of the uneven structure 329 is about 2.8 to 3.8. is. In this case, tantalum oxide having a refractive index of about 2 can be used for the antireflection layer 325 . By disposing the antireflection layer 325 between the semiconductor layer 300 and the first insulator 327, the refractive index change from the semiconductor layer 300 to the first insulator 327 can be smoothed. As a result, it is possible to prevent reflection of the avalanche emission light on the back surface of the semiconductor layer and further reduce crosstalk due to the avalanche emission light.

[Third embodiment]
A third embodiment of the present invention will be described. In the description of the present embodiment, the description of elements common to the first embodiment may be omitted.

FIG. 10 is a schematic cross-sectional view of the APD 201 according to this embodiment. The APD 201 of the present embodiment differs from the APD 201 of the first embodiment in that the light shielding portion 330 is arranged inside the first insulator 327 of the insulating layer 304 . A metal film containing materials such as titanium (Ti), titanium nitride (TiN), tungsten (W), aluminum (Al), and tungsten nitride (WN) is used for the light shielding portion 330 . The light shielding portion 330 may be a single layer film of the above materials, or may be a laminated film containing these materials. For example, the light shielding portion 330 may be made of a laminated film of titanium and tungsten, a laminated film of titanium nitride and tungsten, or the like.

In this embodiment, by arranging the light shielding part 330 in the insulating layer between the two APDs 201, part of the light diffracted by the trench structure of the first insulator 327 and the second insulator 328 is shielded. . This reduces the crosstalk caused by the above-described diffracted light entering adjacent pixels. In the light shielding part 330, the upper end (end farthest from the first surface) of the trench structure formed by the first insulator 327 and the second insulator 328 is higher than the lower end (end closest to the first surface) of the light shielding part 330. It is more desirable to arrange As a result, the diffracted light is more likely to be shielded, thereby improving the effect of reducing crosstalk to adjacent pixels.

According to this embodiment, in addition to obtaining the same effects as in the first embodiment, a photoelectric conversion device with reduced crosstalk between pixels is provided.

[Fourth embodiment]
A fourth embodiment of the present invention will be described. In the description of the present embodiment, the description of elements common to the first embodiment may be omitted.

FIG. 11 is a schematic cross-sectional view of the APD 201 according to this embodiment. The APD 201 of the present embodiment differs from the APD 201 of the first embodiment in that a second insulator 331 is arranged in the insulating layer 304 in addition to the first insulator 327 and the second insulator 328 . The first insulator 327 and the second insulator 331 form a periodically patterned trench structure. The trench structure (second layer) formed by the first insulator 327 and the second insulator 331 is arranged on the incident side of the trench structure (first layer) formed by the first insulator 327 and the second insulator 328. there is In other words, the insulating layer 304 has a two-layer trench structure arranged in the depth direction. The material of the second insulator 331 can be selected from the same viewpoint as the material of the second insulator 328 . The material of the second insulator 331 may be the same material as the material of the second insulator 328, or may be a different material.

In the example shown in FIG. 11, the insulating layer 304 has a two-layer trench structure arranged in the depth direction, but the trench structure may have three or more layers.

In the example shown in FIG. 11, the second insulator 328 and the second insulator 331 are arranged at laterally shifted positions when viewed in cross section. That is, they are arranged at positions that do not overlap in plan view. However, the second insulator 328 and the second insulator 331 may be arranged at the same position in the lateral direction when viewed in cross section. That is, they may be arranged at overlapping positions in plan view.

In this embodiment, incident light is diffracted by the trench structure formed by the first insulator 327 and the second insulator 331 . The diffracted light is then diffracted in the trench structure formed by the first insulator 327 and the second insulator 328 . In this way, a diffraction effect greater than that of the configuration of the first embodiment can be obtained by causing multiple diffractions. According to the present embodiment, in addition to obtaining the same effects as in the first embodiment, a photoelectric conversion device capable of further improving the sensitivity is provided.

[Fifth embodiment]
A fifth embodiment of the present invention will be described. In the description of this embodiment, the description of elements common to the first embodiment or the fourth embodiment may be omitted.

FIG. 12 is a schematic cross-sectional view of the APD 201 according to this embodiment. The APD 201 of this embodiment is similar to that of the fourth embodiment in that a two-layer trench structure is formed. However, the APD 201 of this embodiment differs from the APD 201 of the fourth embodiment in that the antireflection layer 326 also functions as the second insulator 331 .

The antireflection layer 326 is deposited so as to fill the trenches formed in the first insulator 327 . Thus, the first insulator 327 and the antireflection layer 326 form a periodically patterned trench structure. The material of the antireflection layer 326 can be selected from the same viewpoint as the material of the second insulator 328 . The material of the antireflection layer 326 may be the same material as the material of the second insulator 328, or may be a different material.

In this embodiment, incident light is diffracted in the trench structure formed by the first insulator 327 and the antireflection layer 326 . The diffracted light is then diffracted in the trench structure formed by the first insulator 327 and the second insulator 328 . In this way, a diffraction effect greater than that of the configuration of the first embodiment can be obtained by causing multiple diffractions. According to the present embodiment, in addition to obtaining the same effects as in the first embodiment, a photoelectric conversion device capable of further improving the sensitivity is provided.

[Sixth embodiment]
A photodetection system according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a block diagram of a photodetection system according to this embodiment. The photodetection system of this embodiment is an imaging system that acquires an image based on incident light.

The photoelectric conversion devices in the above-described embodiments are applicable to various imaging systems. Examples of imaging systems include digital still cameras, digital camcorders, camera heads, copiers, facsimiles, mobile phones, on-vehicle cameras, observation satellites, surveillance cameras, and the like. FIG. 13 shows a block diagram of a digital still camera as an example of an imaging system.

The imaging system 7 shown in FIG. 13 includes a barrier 706, a lens 702, an aperture 704, an imaging device 70, a signal processing unit 708, a timing generation unit 720, an overall control/calculation unit 718, a memory unit 710, and a recording medium control I/F unit. 716 , a recording medium 714 and an external I/F section 712 . A barrier 706 protects the lens, and a lens 702 forms an optical image of the subject on the imaging device 70 . A diaphragm 704 varies the amount of light passing through the lens 702 . The imaging device 70 is configured like the photoelectric conversion device of the above-described embodiment, and converts an optical image formed by the lens 702 into image data. A signal processing unit 708 performs processing such as various corrections and data compression on the imaging data output from the imaging device 70 .

The timing generator 720 outputs various timing signals to the imaging device 70 and the signal processor 708 . A general control/calculation unit 718 controls the entire digital still camera, and a memory unit 710 temporarily stores image data. A recording medium control I/F unit 716 is an interface for recording or reading image data on a recording medium 714. The recording medium 714 is a removable recording medium such as a semiconductor memory for recording or reading image data. is. An external I/F unit 712 is an interface for communicating with an external computer or the like. The timing signal and the like may be input from the outside of the imaging system 7 , and the imaging system 7 only needs to have at least the imaging device 70 and the signal processing section 708 that processes the image signal output from the imaging device 70 .

In this embodiment, the imaging device 70 and the signal processing unit 708 may be arranged on the same semiconductor substrate. Also, the imaging device 70 and the signal processing unit 708 may be arranged on different semiconductor substrates.

Also, each pixel of the imaging device 70 may include a first photoelectric conversion unit and a second photoelectric conversion unit. A signal processing unit 708 processes pixel signals based on charges generated in the first photoelectric conversion unit and pixel signals based on charges generated in the second photoelectric conversion unit, and acquires distance information from the imaging device 70 to the subject. can.

[Seventh embodiment]
FIG. 14 is a block diagram of a photodetection system according to this embodiment. More specifically, FIG. 14 is a block diagram of a distance image sensor using the photoelectric conversion device described in the above embodiments.

As shown in FIG. 14, the distance image sensor 401 includes an optical system 402, a photoelectric conversion device 403, an image processing circuit 404, a monitor 405 and a memory 406. The distance image sensor 401 receives light (modulated light, pulsed light) emitted from the light source device 411 toward the subject and reflected from the surface of the subject. The distance image sensor 401 can acquire a distance image corresponding to the distance to the subject based on the time from light emission to light reception.

The optical system 402 includes one or more lenses, guides image light (incident light) from a subject to the photoelectric conversion device 403 , and forms an image on the light receiving surface (sensor unit) of the photoelectric conversion device 403 .

As the photoelectric conversion device 403, the photoelectric conversion device of each embodiment described above can be applied. The photoelectric conversion device 403 supplies the image processing circuit 404 with a distance signal indicating the distance obtained from the received light signal.

The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 403 . A distance image (image data) obtained by image processing can be displayed on the monitor 405 and stored (recorded) in the memory 406 .

The distance image sensor 401 configured in this way can obtain an accurate distance image by applying the photoelectric conversion device described above.

[Eighth Embodiment]
The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be applied to an endoscopic surgery system, which is an example of a light detection system.

FIG. 15 is a schematic diagram of an endoscopic surgery system according to this embodiment. FIG. 15 shows an operator (doctor) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgery system 1103 . As illustrated, the endoscopic surgery system 1103 includes an endoscope 1100, a surgical instrument 1110, an arm 1121, and a cart 1134 loaded with various devices for endoscopic surgery.

An endoscope 1100 includes a lens barrel 1101 whose distal end is inserted into a body cavity of a patient 1132 and a camera head 1102 connected to the proximal end of the lens barrel 1101 . Although FIG. 15 shows an endoscope 1100 configured as a so-called rigid scope having a rigid barrel 1101, the endoscope 1100 may be configured as a so-called flexible scope having a flexible barrel.

The tip of the lens barrel 1101 is provided with an opening into which an objective lens is fitted. A light source device 1203 is connected to the endoscope 1100 . The light generated by the light source device 1203 is guided to the tip of the barrel 1101 by a light guide extending inside the barrel 1101, and radiates toward the observation target inside the body cavity of the patient 1132 through the objective lens. be done. Note that the endoscope 1100 may be a straight scope, a perspective scope, or a side scope.

An optical system and a photoelectric conversion device are provided inside the camera head 1102, and reflected light (observation light) from an observation target is collected by the optical system on the photoelectric conversion device. The photoelectric conversion device photoelectrically converts the observation light to generate an electrical signal corresponding to the observation light, that is, an image signal corresponding to the observation image. As the photoelectric conversion device, the photoelectric conversion device described in each of the above-described embodiments can be used. The image signal is transmitted to a camera control unit (CCU: Camera Control Unit) 1135 as RAW data.

The CCU 1135 is composed of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and controls the operations of the endoscope 1100 and the display device 1136 in an integrated manner. Further, the CCU 1135 receives an image signal from the camera head 1102 and performs various image processing such as development processing (demosaicing) for displaying an image based on the image signal.

The display device 1136 displays an image based on an image signal subjected to image processing by the CCU 1135 under the control of the CCU 1135 .

The light source device 1203 includes a light source such as an LED (Light Emitting Diode), and supplies the endoscope 1100 with irradiation light for imaging a surgical site or the like.

Input device 1137 is an input interface for endoscopic surgery system 1103 . The user can input various information and instructions to the endoscopic surgery system 1103 via the input device 1137 .

The treatment instrument control device 1138 controls driving of the energy treatment instrument 1112 for tissue cauterization, incision, blood vessel sealing, or the like.

The light source device 1203 can supply illumination light to the endoscope 1100 when imaging the surgical site, and may be, for example, a white light source such as an LED, a laser light source, or a combination thereof. When a white light source is configured by combining RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high accuracy. Therefore, the light source device 1203 can adjust the white balance of the captured image. In this case, laser light from each of the RGB laser light sources may be applied to the observation target in a time division manner, and driving of the image sensor of the camera head 1102 may be controlled in synchronization with the irradiation timing. Thereby, it is also possible to capture images corresponding to each of RGB in a time-division manner. According to such a method, a color image can be obtained without providing a color filter in the imaging device.

Further, driving of the light source device 1203 may be controlled such that the intensity of light output from the light source device 1203 is changed at predetermined intervals. By controlling the drive of the imaging device of the camera head 1102 in synchronization with the timing of changing the light intensity to acquire images in a time division manner and synthesizing the images, a high dynamic range without so-called underexposure and overexposure can be achieved. image can be generated.

Furthermore, the light source device 1203 may be configured to be able 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 tissues can be used. Specifically, a predetermined tissue such as a blood vessel on the surface of the mucous membrane is imaged with high contrast by irradiating light with a narrower band than the irradiation light (that is, white light) used during normal observation. Alternatively, in special light observation, fluorescence observation may be performed in which an image is obtained from fluorescence generated by irradiation with excitation light. In fluorescence observation, body tissue is irradiated with excitation light and fluorescence from the body tissue is observed, or a reagent such as indocyanine green (ICG) is locally injected into the body tissue and the fluorescence wavelength of the reagent is observed in the body tissue. It is possible to obtain a fluorescent image by irradiating excitation light corresponding to . The light source device 1203 can be configured to supply narrowband light and/or excitation light corresponding to such special light observation.

[Ninth Embodiment]
A photodetection system and a moving object according to this embodiment will be described with reference to FIGS. In this embodiment, an example of an in-vehicle camera is shown as a light detection system.

FIG. 16 is a schematic diagram of a photodetection system according to the present embodiment, showing an example of a vehicle system and a photodetection system mounted on the vehicle system. The photodetection system 1301 includes a photoelectric conversion device 1302 , an image preprocessing unit 1315 , an integrated circuit 1303 and an optical system 1314 . An optical system 1314 forms an optical image of a subject on the photoelectric conversion device 1302 . The photoelectric conversion device 1302 converts the optical image of the subject formed by the optical system 1314 into an electrical signal. The photoelectric conversion device 1302 is the photoelectric conversion device according to any one of the embodiments described above. An image preprocessing unit 1315 performs predetermined signal processing on the signal output from the photoelectric conversion device 1302 . The functions of the image preprocessing unit 1315 may be incorporated within the photoelectric conversion device 1302 . The photodetection system 1301 is provided with at least two sets of an optical system 1314, a photoelectric conversion device 1302, and an image preprocessing unit 1315, and the output from each set of image preprocessing units 1315 is input to an integrated circuit 1303. .

The integrated circuit 1303 is an integrated circuit for use in imaging systems, and includes an image processing unit 1304 including a storage medium 1305 , an optical distance measurement unit 1306 , a parallax calculation unit 1307 , an object recognition unit 1308 and an abnormality detection unit 1309 . An image processing unit 1304 performs image processing such as development processing and defect correction on the output signal of the image preprocessing unit 1315 . A storage medium 1305 temporarily stores captured images and stores defect positions of captured pixels. An optical distance measurement unit 1306 performs focusing or distance measurement on a subject. A parallax calculation unit 1307 calculates ranging information from a plurality of image data acquired by a plurality of photoelectric conversion devices 1302 . The object recognition unit 1308 recognizes subjects such as cars, roads, signs, and people. When the abnormality detection unit 1309 detects an abnormality in the photoelectric conversion device 1302, the abnormality detection unit 1309 notifies the main control unit 1313 of the abnormality.

The integrated circuit 1303 may be realized by specially designed hardware, software modules, or a combination thereof. Moreover, it may be implemented by FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like, or by a combination thereof.

The main control unit 1313 integrates and controls the operations of the light detection system 1301, the vehicle sensor 1310, the control unit 1320, and the like. The light detection system 1301, the vehicle sensor 1310, and the control unit 1320 may individually have communication interfaces without the main control unit 1313, and each may transmit and receive control signals via a communication network according to, for example, the CAN standard.

The integrated circuit 1303 has a function of receiving a control signal from the main control unit 1313 or transmitting a control signal or setting value to the photoelectric conversion device 1302 by its own control unit.

The light detection system 1301 is connected to a vehicle sensor 1310, and is capable of detecting vehicle running conditions such as vehicle speed, yaw rate, and steering angle, the environment outside the vehicle, and the conditions of other vehicles and obstacles. Vehicle sensor 1310 also serves as a distance information acquisition unit that acquires distance information to an object. The light detection system 1301 is also connected to a driving support control unit 1311 that performs various driving support functions such as automatic steering, automatic cruise, and anti-collision functions. In particular, regarding the collision determination function, based on the detection results of the light detection system 1301 and the vehicle sensor 1310, it is possible to estimate a collision with another vehicle/obstacle and determine whether or not there is a collision. As a result, avoidance control when a collision is presumed and safety device activation at the time of collision are performed.

The light detection system 1301 is also connected to an alarm device 1312 that issues an alarm to the driver based on the judgment result of the collision judgment unit. For example, when the collision possibility is high as a result of the judgment by the collision judging section, the main control section 1313 performs vehicle control such as applying the brakes, releasing the accelerator, and suppressing the engine output to avoid the collision or reduce the damage. come true. The alarm device 1312 issues an alarm such as sound, displays alarm information on a display unit screen such as a car navigation system and a meter panel, and applies vibration to a seat belt and a steering wheel to warn the user. .

The light detection system 1301 in this embodiment can photograph the surroundings of the vehicle, for example, the front or rear. 17(a), 17(b), and 17(c) are schematic diagrams of a moving body according to the present embodiment, showing a configuration for capturing an image in front of the vehicle with a light detection system 1301. FIG.

Two photoelectric conversion devices 1302 are arranged in front of the vehicle 1300 . Specifically, it is preferable that the center line of the vehicle 1300 with respect to the forward/retreat orientation or the outer shape (for example, the width of the vehicle) is regarded as the axis of symmetry, and the two photoelectric conversion devices 1302 are arranged line-symmetrically with respect to the axis of symmetry. This makes it possible to effectively acquire distance information between the vehicle 1300 and the subject and determine the possibility of collision. Moreover, photoelectric conversion device 1302 is preferably arranged at a position that does not obstruct the driver's field of view when the driver visually recognizes the situation outside vehicle 1300 from the driver's seat. It is preferable that the warning device 1312 be arranged at a position that is easily visible to the driver.

Next, failure detection operation of the photoelectric conversion device 1302 in the photodetection system 1301 will be described with reference to FIG. FIG. 18 is a flow chart showing the operation of the photodetection system in this embodiment. The failure detection operation of photoelectric conversion device 1302 can be performed according to steps S1410 to S1480 shown in FIG.

In step S1410, startup settings of the photoelectric conversion device 1302 are performed. That is, the setting information for the operation of the photoelectric conversion device 1302 is transmitted from the outside of the photodetection system 1301 (for example, the main control unit 1313) or the inside of the photodetection system 1301, and the photoelectric conversion device 1302 performs the imaging operation and the failure detection operation. to start.

Next, in step S1420, the photoelectric conversion device 1302 acquires pixel signals from effective pixels. Also, in step S1430, the photoelectric conversion device 1302 acquires an output value from a failure detection pixel provided for failure detection. This failure detection pixel has a photoelectric conversion element like an effective pixel. A predetermined voltage is written in the photoelectric conversion element. The failure detection pixel outputs a signal corresponding to the voltage written to the photoelectric conversion element. Note that steps S1420 and S1430 may be executed in the reverse order.

Next, in step S1440, the photodetection system 1301 determines whether the expected output value of the failure-detected pixel and the actual output value from the failure-detected pixel match. As a result of the pertinence determination in step S1440, if the expected output value and the actual output value match, the photodetection system 1301 proceeds to the process of step S1450 and determines that the imaging operation is performed normally. Then, the process proceeds to step S1460. In step S1460, the photodetection system 1301 transmits the pixel signals of the scan line to the storage medium 1305 for temporary storage. After that, the photodetection system 1301 returns to the process of step S1420 and continues the failure detection operation. On the other hand, if the result of pertinence determination in step S1440 is that the expected output value and the actual output value do not match, the photodetection system 1301 proceeds to processing in step S1470. In step S<b>1470 , the photodetection system 1301 determines that there is an abnormality in the imaging operation, and issues an alarm to the main controller 1313 or the alarm device 1312 . The alarm device 1312 causes the display unit to display that an abnormality has been detected. After that, in step S1480, the photodetection system 1301 stops the photoelectric conversion device 1302 and ends the operation of the photodetection system 1301. FIG.

In the present embodiment, an example in which the flowchart is looped for each line was exemplified, but the flowchart may be looped for each of a plurality of lines, or the failure detection operation may be performed for each frame. The issuance of the warning in step S1470 may be notified to the outside of the vehicle via a wireless network.

In addition, in the present embodiment, the control that does not collide with another vehicle has been described, but it is also applicable to control that automatically drives following another vehicle, control that automatically drives so as not to stray from the lane, and the like. . Furthermore, the light detection system 1301 can be applied not only to a vehicle such as the own vehicle, but also to a moving body (moving device) such as a ship, an aircraft, or an industrial robot. In addition, the present invention can be applied not only to mobile objects but also to devices that widely use object recognition, such as intelligent transportation systems (ITS).

The photoelectric conversion device of the present invention may further have a configuration capable of acquiring various information such as distance information.

[Tenth embodiment]
FIG. 19(a) is a diagram showing a specific example of the electronic device according to the present embodiment, showing spectacles 1600 (smart glasses). The spectacles 1600 are provided with the photoelectric conversion device 1602 described in each of the above-described embodiments. That is, the glasses 1600 are an example of a photodetection system to which the photoelectric conversion device 1602 described in each of the above embodiments can be applied. A display device including a light-emitting device such as an OLED or an LED may be provided on the rear surface side of the lens 1601 . One or more photoelectric conversion devices 1602 may be provided. Also, a plurality of types of photoelectric conversion devices may be combined. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in FIG.

Glasses 1600 further comprise a controller 1603 . The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device described above. Further, the control device 1603 controls operations of the photoelectric conversion device 1602 and the display device. The lens 1601 is provided with an optical system for condensing light onto the photoelectric conversion device 1602 .

FIG. 19(b) shows glasses 1610 (smart glasses) according to one application. The glasses 1610 have a control device 1612, and the control device 1612 is equipped with a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. A photoelectric conversion device in the control device 1612 and an optical system for projecting light emitted from the display device are arranged on the lens 1611 , and an image is projected onto the lens 1611 . The control device 1612 functions as a power source that supplies power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device 1612 may have a line-of-sight detection unit that detects the line of sight of the wearer. Infrared rays may be used for line-of-sight detection. The infrared light emitting section emits infrared light to the eyeballs of the user who is gazing at the display image. A captured image of the eyeball is obtained by detecting reflected light of the emitted infrared light from the eyeball by an imaging unit having a light receiving element. By having the reduction means for reducing the light from the infrared light emitting section to the display section in a plan view, deterioration in image quality is reduced.

The control device 1612 detects the line of sight of the user with respect to the display image from the captured image of the eye obtained by imaging the infrared light. Any known method can be applied to line-of-sight detection using captured images of eyeballs. As an example, it is possible to use a line-of-sight detection method based on a Purkinje image obtained by reflection of irradiation light on the cornea.

More specifically, line-of-sight detection processing based on the pupillary corneal reflection method is performed. The user's line of sight is detected by calculating a line-of-sight vector representing the orientation (rotational angle) of the eyeball based on the pupil image and the Purkinje image included in the captured image of the eyeball using the pupillary corneal reflection method. be.

The display device of the present embodiment may have a photoelectric conversion device having a light receiving element, and may control a display image of the display device based on the user's line-of-sight information from the photoelectric conversion device.

Specifically, the display device determines a first visual field area that the user gazes at and a second visual field area other than the first visual field area, based on the line-of-sight information. The first viewing area and the second viewing area may be determined by the control device of the display device, or may be determined by an external control device. In the display area of the display device, the display resolution of the first viewing area may be controlled to be higher than the display resolution of the second viewing area. That is, the resolution of the second viewing area may be lower than that of the first viewing area.

Also, the display area may include a first display area and a second display area different from the first display area. A high priority area may be determined from the first display area and the second display area based on the line-of-sight information. The first viewing area and the second viewing area may be determined by the control device of the display device, or may be determined by an external control device. The resolution of the high priority area may be controlled to be higher than the resolution of the areas other than the high priority area. That is, the resolution of areas with relatively low priority can be reduced.

AI (Artificial Intelligence) may be used to determine the first field of view area and the area with high priority. The AI is a model configured to estimate the angle of the line of sight from the eyeball image and the distance to the object ahead of the line of sight, using the image of the eyeball and the direction in which the eyeball of the image was actually viewed as training data. It can be. The AI program may be provided in either the display device or the photoelectric conversion device, or may be provided in an external device. If the external device has an AI program, it can be sent from a server or the like to the display device via communication.

When display control is performed based on visual detection, the present embodiment can be preferably applied to smart glasses that further have a photoelectric conversion device that captures an image of the outside. Smart glasses can display captured external information in real time.

[Modified embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, an example in which a part of the configuration of any one of the embodiments is added to another embodiment, and an example in which a part of the configuration of another embodiment is replaced are also embodiments of the present invention.

The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

It should be noted that the above-described embodiments are merely examples of specific implementations of the present invention, and the technical scope of the present invention should not be construed to be limited by these. That is, the present invention can be embodied in various forms without departing from its technical concept or its main features.

11 sensor substrate 201 avalanche photodiode 300 semiconductor layer 304 insulating layer 327 first insulator 328 second insulator

Claims (25)

a substrate having a first side and a second side;
an insulating layer disposed on the first surface side;
a photoelectric conversion unit arranged in the substrate and generating charges according to incident light incident through the insulating layer;
has
the insulating layer has a structure in which a first insulator and a second insulator are alternately repeated in a direction parallel to the insulating layer;
A plurality of sets of the first insulator and the second insulator are arranged in a direction parallel to the insulating layer in a region where the incident light passing through the insulating layer can be incident on one photoelectric conversion unit. ,
A photoelectric conversion device, wherein a material forming the second insulator is different from a material forming the first insulator. The photoelectric conversion device according to claim 1, wherein the refractive index of the second insulator is higher than that of the first insulator. The effective period of the first insulator and the second insulator is hc/E _a (h: Planck's constant [J s], c: speed of light [m/s], E _a : bandgap of the substrate [J ]), the photoelectric conversion device according to claim 1 or 2. The width of at least one of the first insulator and the second insulator is hc/2E _a (h: Planck's constant [J·s], c: speed of light [m/s], E _a : bandgap of the substrate [J]). The photoelectric conversion device according to claim 1 . The photoelectric conversion device according to any one of claims 1 to 4, wherein the second insulator is embedded in a trench formed in the first insulator. The photoelectric conversion device according to any one of claims 1 to 5, wherein the substrate has an uneven structure arranged on the first surface. The effective period of the uneven structure is smaller than hc/ _Ea (h: Planck's constant [J s], c: speed of light [m/s], _Ea : bandgap of the substrate [J]). The photoelectric conversion device according to claim 6. Having a plurality of photoelectric conversion units,
8. The light shielding part according to any one of claims 1 to 7, characterized in that in a plan view from a direction perpendicular to the substrate, a light shielding part is arranged between two photoelectric conversion parts in the insulating layer. photoelectric conversion device. The end of the light shielding portion closest to the first surface is further than either the end of the first insulator furthest from the first surface or the end of the second insulator furthest from the first surface. , near the first surface. In the insulating layer, a structure in which the first insulator and the second insulator are alternately arranged is arranged over two layers of a first layer and a second layer at different depths in the insulating layer. The photoelectric conversion device according to any one of claims 1 to 9, characterized in that: The material of the first insulator of the first layer is the same as the material of the first insulator of the second layer, and the material of the second insulator of the first layer is the second insulator of the second layer. 11. The photoelectric conversion device according to claim 10, wherein the material is the same as that of the second insulator. The material of the first insulator of the first layer is different from the material of the first insulator of the second layer, or the material of the second insulator of the first layer is the material of the second layer. 11. The photoelectric conversion device according to claim 10, wherein the material is different from that of the second insulator. 13. The photoelectric conversion device according to any one of claims 1 to 12, wherein the second insulators are arranged in a grid pattern in plan view from a direction perpendicular to the substrate. . The photoelectric conversion device according to any one of claims 1 to 13, wherein the second insulators are arranged with a uniform period in plan view from a direction perpendicular to the substrate. 14. The second insulator is arranged so as to have a larger period closer to the outer periphery of the photoelectric conversion part in plan view from a direction perpendicular to the substrate. 1. The photoelectric conversion device according to claim 1. The photoelectric conversion device according to any one of claims 1 to 15, wherein the second insulator contains silicon nitride. The photoelectric conversion device according to any one of claims 1 to 15, wherein the second insulator contains tantalum oxide. Having a plurality of photoelectric conversion units,
The photoelectric conversion device according to any one of Claims 1 to 17, wherein a pixel separation section is provided between the two photoelectric conversion sections. Having a plurality of photoelectric conversion units,
The photoelectric conversion device according to any one of claims 1 to 18, wherein each of the plurality of photoelectric conversion units includes an avalanche photodiode. further comprising a microlens arranged on the first surface side;
The photoelectric conversion device according to any one of claims 1 to 19, wherein the incident light that has entered the microlens passes through the insulating layer and enters the photoelectric conversion section. The photoelectric conversion device according to any one of claims 1 to 20, wherein the insulating layer further comprises a first antireflection layer disposed between the first surface and the first insulator. . The photoelectric conversion according to any one of claims 1 to 20, wherein the insulating layer further comprises a second antireflection layer arranged on the side of the first insulator on which the incident light is incident. Device. 23. The photoelectric device according to claim 22, wherein the insulating layer has a structure in which the first insulator and the second antireflection layer are alternately repeated in a direction parallel to the insulating layer. conversion device. a photoelectric conversion device according to any one of claims 1 to 23;
a signal processing unit that processes a signal output from the photoelectric conversion device;
A light detection system comprising: being mobile,
a photoelectric conversion device according to any one of claims 1 to 23;
a distance information acquisition unit that acquires distance information to an object from a signal output from the photoelectric conversion device;
a control unit that controls the moving object based on the distance information;
A mobile object comprising:

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