Photoelectric conversion device, photoelectric conversion system, and moving body

Photoelectric conversion device includes first region of first conductivity type arranged in semiconductor layer having first second surfaces, second region of second conductivity type arranged between the second surface and the first region and forming avalanche photodiode, separation region of the second conductivity type arranged between the first and second surfaces to surround the second region, contact region of the second conductivity type contacted to the separation region, first contact plug connected to the first region, and second contact plug connected to the contact region. The second region has shape of rectangle, and the second contact plug is arranged in diagonal direction of the rectangle. Distance between center of the first contact plug and center of the second contact plug is larger than distance between center of the second region and the center of the second contact plug.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a photoelectric conversion device, a photoelectric conversion system, and a moving body.

Description of the Related Art

There is known a light detection device that can detect weak light of a single photon level using avalanche (electron avalanche) multiplication. Japanese Patent Laid-Open No. 2018-201005 discloses a SPAD (Single Photon Avalanche Diode) in which photo charges generated by a single photon cause avalanche multiplication in the p-n junction region of semiconductor regions forming a photoelectric converter.

SUMMARY OF THE INVENTION

The invention provides a technique advantageous in suppressing the increase of the dark count rate (to be referred to as the DCR hereinafter) caused by a high electric field in an avalanche photodiode (to be referred to as an APD hereinafter).

One of aspects of the invention provides a photoelectric conversion device comprising: a first region of a first conductivity type arranged in a semiconductor layer having a first surface and a second surface; a second region of a second conductivity type arranged between the second surface and the first region and forming an avalanche photodiode together with the first region; a separation region of the second conductivity type arranged between the first surface and the second surface to surround the second region in an orthogonal projection with respect to the first surface; a contact region of the second conductivity type arranged to contact the separation region; a first contact plug connected to the first region; and a second contact plug connected to the contact region, wherein the second region has a shape of a rectangle, and the second contact plug is arranged in a diagonal direction of the rectangle, and in the orthogonal projection with respect to the first surface, a distance between a center of the first contact plug and a center of the second contact plug is larger than a distance between a center of the second region and the center of the second contact plug.

DESCRIPTION OF THE EMBODIMENTS

FIG.1exemplifies the arrangement of a photoelectric conversion device100according to an embodiment. Referring toFIG.1, the photoelectric conversion device100can include a pixel array101, a controller115, a horizontal scanning circuit111, a readout circuit112, a plurality of signal lines113, and a vertical scanning circuit110. In the pixel array101, a plurality of pixels104can be arranged to form a plurality of rows and a plurality of columns. Each pixel104can include a photoelectric converter102with an APD (avalanche photodiode) and a signal processor103. The photoelectric converter102converts light into an electrical signal. The signal processor103can be configured to output, to the readout circuit112, a signal obtained by processing the electrical signal output from the photoelectric converter102. The signal processor103can include, for example, a counter and a memory. The memory can store a digital value.

The vertical scanning circuit110can be configured to receive a control signal supplied from the controller115and to supply a control pulse to each pixel104. The vertical scanning circuit110can include, for example, a shift register and an address decoder. The vertical scanning circuit110can be configured to select the plurality of pixels104of the pixel array101on the row basis. The signal processors103of the plurality of pixels104belonging to the row selected by the vertical scanning circuit110output signals to a corresponding one of the plurality of signal lines113.

The horizontal scanning circuit111can be configured to scan the plurality of signal lines113so as to select, among the plurality of signal lines113, the signal line113from which the readout circuit112is to read out the signals. The readout circuit112can supply, to an output circuit114, the signals of the signal line113selected by the horizontal scanning circuit111. The output circuit114can output the signals, supplied from the readout circuit112, to an external device or a device incorporated in the photoelectric conversion device100, for example, a recording unit or a processor.

FIG.1shows an example in which the plurality of pixels104are two-dimensionally arranged but the plurality of pixels104may be one-dimensionally arranged. Furthermore, the pixel array101may be replaced by one pixel104. The function of the signal processor103need not always be individually provided in each of all the pixels104. For example, at least two pixels104may share one signal processor103, and signals output from the photoelectric converters102of the at least two pixels104may sequentially be processed by the shared signal processor103.

FIG.2exemplifies the arrangement of one pixel104. The photoelectric converter102includes an APD201. The APD201photoelectrically converts incident light to generate charge pairs. The anode of the APD201can be supplied with a voltage VL. The cathode of the APD201can be supplied with a voltage VH higher than the voltage VL supplied to the anode. The anode and the cathode are supplied with a reverse bias voltage that causes the APD201to perform an avalanche multiplication operation. If light enters the APD201in the state in which such voltage is supplied, charges generated by the light cause avalanche multiplication, thereby generating an avalanche current. When a reverse bias voltage is supplied, there are a Geiger mode operating in a state in which the potential difference between the anode and the cathode is larger than the breakdown voltage and a linear mode operating in a state in which the potential difference between the anode and the cathode is around or smaller than the breakdown voltage. An APD operated in the Geiger mode is called a SPAD. For example, the voltage VL is −30 V and the voltage VH is 1 V.

A quenching element202can be arranged to connect a power supply line for supplying the voltage VH and the cathode of the APD201. The quenching element202has a function of converting, into a voltage, a change of the avalanche current generated in the APD201. The quenching element202functions as a load circuit (quenching circuit) at the time of signal multiplication by avalanche multiplication, and performs an operation (quenching operation) of suppressing avalanche multiplication by decreasing the voltage supplied to the APD201.

The signal processor103can include, for example, a waveform shaper210, a counter circuit211, and a selection circuit212. The waveform shaper210outputs a pulse signal by shaping the potential change waveform of the cathode of the APD201obtained at the time of detection of a photon. The waveform shaper210can include, for example, an inverter circuit.FIG.2shows an example in which the waveform shaper210is formed by one inverter. However, the waveform shaper210may be formed by series-connecting a plurality of inverters or by another circuit having a waveform shaping effect. The counter circuit211can count the pulse signal output from the waveform shaper210, and hold a thus obtained count value. Furthermore, when the counter circuit211is supplied with a control pulse pRES from the vertical scanning circuit110via a driving line213(not shown inFIG.1), it resets the held signal. When the selection circuit212is supplied with a control pulse pSEL from the vertical scanning circuit110via a driving line214(not shown inFIG.1), it electrically connects the counter circuit211and the signal line113. The selection circuit212may include, for example, a buffer circuit for driving the signal line113. A switch such as a transistor may be arranged between the quenching element202and the photoelectric converter102(APD201) and/or between the photoelectric converter102and the signal processor103. A switch such as a transistor may be arranged in the supply path of the voltage VH or VL to the photoelectric converter102.

In this embodiment, the arrangement using the counter circuit211is described. However, instead of the counter circuit211, a time to digital converter (to be referred to as a TDC hereinafter) and a memory may be used. In this case, the photoelectric conversion device100can function as a photoelectric conversion device that acquires a pulse detection timing. In this case, the occurrence timing of the pulse signal output from the waveform shaper210can be converted into a digital signal by the TDC. The TDC can be supplied with a control pulse pREF (reference signal) from the vertical scanning circuit110via the driving line to measure the timing of the pulse signal. The TDC generates a digital signal indicating the input timing of the signal output from the waveform shaper210with reference to the control pulse pREF.

In the example of the arrangement shown inFIG.2, the anode of the APD201is connected to the supply line of the voltage VL, the quenching element202is connected between the cathode of the APD201and the supply line of the voltage VH, and the cathode is connected to the input terminal of the waveform shaper210. In this case, a signal charge is an electron. Instead of this arrangement, the cathode of the APD201may be connected to the supply line of the voltage VH, the quenching element202may be connected between the anode of the APD201and the supply line of the voltage VL, and the anode may be connected to the input terminal of the waveform shaper210. In this case, a signal charge is a hole.

Detection of a photon using the APD201will be described with reference toFIGS.3A to3C.FIG.3Ashows the APD201, the quenching element202, and the waveform shaper210forming part of the pixel104. The input side of the waveform shaper210is indicated by node A and the output side of the waveform shaper210is indicated by node B.FIG.3Bshows the voltage waveform of node A inFIG.3A.FIG.3Cshows the voltage waveform of node B inFIG.3A.

During a period from time t0 to time t1, a potential difference of VH−VL is applied to the APD201shown inFIG.3A. When a photon enters at time t1, an avalanche multiplication current flows through the quenching element202, thereby dropping the voltage of node A. If the voltage drop amount becomes larger and the potential difference applied to the APD201becomes smaller, the avalanche multiplication of the APD201stops, and the voltage level of node A does not drop to a value less than a given value. After that, a current that compensates for the voltage drop flows through node A, and node A is set to the original potential level at time t3. The voltage waveform of node A is shaped by the waveform shaper210. More specifically, the waveform shaper210outputs a signal which is set to an active level in a portion where the voltage of node A exceeds a threshold.

FIG.4shows a plan view or a planar view of the pixel array101according to the first embodiment.

FIGS.5and6each show an enlarged view of a portion inFIG.4.FIG.7shows a sectional view taken along a line X-X′ inFIG.4. The photoelectric conversion device100includes a semiconductor layer301having a first surface S1 and a second surface S2.FIGS.4and5may be understood as an orthogonal projection with respect to the first surface S1 or the second surface S2. In the following description, the first conductivity type and the second conductivity type are different from each other. If the first conductivity type is an n type, the second conductivity type is a p type. If the first conductivity type is a p type, the second conductivity type is an n type. Note that referring toFIGS.4,5,6, and7, the signal processor103is not illustrated for the sake of descriptive simplicity. The same applies to the remaining drawings to be referred to hereinafter. A region of the first conductivity type and a region of the second conductivity type are both semiconductor regions, in other words, impurity semiconductor regions. In the following description, the impurity concentration of the region of the first conductivity type indicates a net impurity concentration obtained by subtracting the impurity concentration of the second conductivity type from the impurity concentration of the first conductivity type when the region includes an impurity of the second conductivity type in addition to an impurity of the first conductivity type. Similarly, the impurity concentration of the region of the second conductivity type indicates a net impurity concentration obtained by subtracting the impurity concentration of the first conductivity type from the impurity concentration of the second conductivity type when the region includes an impurity of the first conductivity type in addition to an impurity of the second conductivity type.

The pixel104can include a first region311of the first conductivity type, a second region312of the second conductivity type, a separation region314of the second conductivity type, and a contact region316of the second conductivity type. The first region311is arranged between the first surface S1 and the second surface S2 of the semiconductor layer301. The second region312can be arranged between the second surface S2 of the semiconductor layer301and the first region311. The second region312can be arranged apart from the first region311. Note that the first region311and the second region312may contact each other. The second region312can form the APD201together with the first region311. The first region311can be the cathode of the APD201and the second region312can be the anode of the APD201. Alternatively, the first region311can be the anode of the APD201and the second region312can be the cathode of the APD201.

In the plan view or the planar view (the orthogonal projection with respect to the first surface S1), the separation region314can be arranged between the first surface S1 and the second surface S2 to surround the second region312. Furthermore, the separation region314can be arranged between the first surface S1 and the second surface S2 to surround the first region311. The boundary of the separation region314may or may not include the first surface S1. The boundary of the separation region314may or may not include the second surface S2. The contact region316can be arranged to contact the separation region314.

The impurity concentration of the second conductivity type of the contact region316may be higher than that of the second conductivity type of the separation region314. The contact region316may be arranged so that its side surface is surrounded by the separation region314or contacts the separation region314. The contact region316may be arranged to cover the entire region of the end face of the separation region314on the side of the first surface S1. The contact region316preferably has at least a portion that contacts the separation region314. This can supply a potential to the separation region314from the second contact plug322(to be described later) via the contact region316. Furthermore, if the separation region314and the second region312contact each other, it is possible to supply a potential to the second region312via the separation region314.

The pixel104can include a first contact plug321electrically connected to the first region311. The pixel104can also include a second contact plug322electrically connected to the contact region316. The pixel104may further include a ring-shaped region313of the first conductivity type. The impurity concentration of the first conductivity type of the ring-shaped region313may be lower than that of the first conductivity type of the first region311. The ring-shaped region313can function to relax local concentration of an electric field in a region between the first region311and the separation region314and/or the contact region316. The ring-shaped region313can be arranged to cover the side surface of the first region311. The ring-shaped region313can be arranged not to cover the central portion of a surface facing the second region312among the surfaces of the first region311and to cover all or part of the peripheral portion outside the central portion. The second region312can be arranged apart from the ring-shaped region313. The separation region314can be arranged apart from the ring-shaped region313. Referring toFIGS.4to6, the ring-shaped region313is a circle but may be a rectangle or polygon.

The pixel104may include a third region300. The third region300can be a region of the first conductivity type arranged between the first region311of the first conductivity type and the second region312of the second conductivity type and between the ring-shaped region313of the first conductivity type and the second region312of the second conductivity type. In this case, the impurity concentration of the first conductivity type of the third region300is lower than that of the first conductivity type of the ring-shaped region313. Alternatively, the third region300can be a region of the second conductivity type arranged between the first region311of the first conductivity type and the second region312of the second conductivity type and between the ring-shaped region313of the first conductivity type and the second region312of the second conductivity type. In this case, the impurity concentration of the second conductivity type of the third region300is lower than those of the second conductivity type of the second region312and the separation region314.

The pixel104may further include a fourth region315of the second conductivity type. The fourth region315can be arranged between the second region312and the second surface S2. The boundary of the fourth region315may or may not include the second surface S2. A region of the second conductivity type having an impurity concentration lower than the impurity concentrations of the second conductivity type of the second region312and the fourth region315can be arranged between the second region312of the second conductivity type and the fourth region315of the second conductivity type. Alternatively, a region of the first conductivity type can be arranged between the second region312of the second conductivity type and the fourth region315of the second conductivity type. Charges generated in the region between the second region312and the fourth region315are collected to a strong electric field region formed by the first region311and the second region312. Then, the generated charges cause avalanche multiplication in the strong electric field region. The fourth region315and the separation region314preferably contact each other. This surrounds the region between the second region312and the fourth region315by the second region312, the separation region314, and the fourth region315, thereby making it easy to collect the generated charges to the strong electric field region.

The second contact plug322and the contact region316of the second conductivity type can be shared by at least two pixels104, for example, four pixels104. For example, the second contact plug322can be surrounded by the four pixels104and shared by the four pixels. From another viewpoint, the number of second contact plugs322is smaller than that of first contact plugs321. The four pixels104sharing the second contact plug322can be arranged to have symmetry (point symmetry) with respect to the second contact plug322. From another viewpoint, four adjacent pixels104which can arbitrarily be extracted can be arranged to have symmetry (point symmetry) with respect to the center of the four pixels. From another viewpoint, the second region312has a shape of a rectangle, and the second contact plug322assigned to the second region312can be arranged in one of the four diagonal directions of the second region312.

Alternatively, the third region300has a shape of a rectangle, and the second contact plug322assigned to the third region300can be arranged in one of the four diagonal directions of the third region300.

The first contact plug321electrically connected to the first region311forming the cathode can be supplied with the voltage VH via the quenching element202. The second contact plug322electrically connected, via the separation region314, to the second region312forming the anode can be supplied with the voltage VL lower than the voltage VH supplied to the cathode. The anode and the cathode can be supplied with a reverse bias voltage that causes the APD201to perform an avalanche multiplication operation. With this reverse bias voltage, in an avalanche multiplication region302between the first region311and the second region312, charges generated by photoelectric conversion of incident light cause avalanche multiplication and an avalanche current thus flows.

If the distance between the first region311of the first conductivity type and the contact region316of the second conductivity type decreases along with reduction of the size of the pixel104, a local high electric field region can be formed between the first region311and the contact region316. The distance between the first region311of the first conductivity type and the contact region316of the second conductivity type should be made as large as possible.

As shown inFIG.5, in the plan view or the planar view (the orthogonal projection with respect to the first surface S1), D2>D1 is preferably satisfied. D1 represents a distance between a center C1 of the second region312(third region300) and the center of the second contact plug322. D2 represents a distance between the center of the first contact plug321and the center of the second contact plug322.

From another viewpoint, as shown inFIG.6, in the plan view or the planar view (the orthogonal projection with respect to the first surface S1), L1>0.5L2 is preferably satisfied. L1 represents a distance between the center of the second contact plug322and the center of a first contact plug (to be referred to as “recent first contact plug” hereinafter)321aclosest to the second contact plug322among the plurality of first contact plugs321. L2 represents a distance between a first region (to be referred to as “recent first region” hereinafter)311aconnected to the recent first contact plug321aamong the plurality of first regions311and a first region (to be referred to as “adjacent first region” hereinafter)311bclosest to the recent first region311aamong the plurality of first regions311on a straight line (straight line SL) passing through the center of the second contact plug322and the center of the recent first contact plug321a.

From another viewpoint, as shown inFIG.6, in the plan view or the planar view (the orthogonal projection with respect to the first surface S1), L3>L4 is preferably satisfied. In this example, L3 and L4 are located on a straight line passing through the contact region316, a first portion P1 of the separation region314contacting the contact region316, the first region311, and a second portion P2 of the separation region314. The first region311is located between the contact region316and the second portion P2 of the separation region314. L3 represents a distance between the contact region316and the first region311. L4 represents a distance between the second portion of the separation region314and the first region311. The second portion P2 is the separation region314where the contact region316is not arranged.

With this arrangement, the electric field between the first region311of the first conductivity type and the contact region316of the second conductivity type is hardly influenced by reduction of the size of the pixel104. That is, the increase of the DCR caused by reduction of the size of the pixel104can be suppressed.

FIG.8shows a plan view or a planar view of a pixel array101according to the second embodiment.

In the second embodiment, similar to the arrangement exemplified in the first embodiment, a plurality of pixels104arranged in a semiconductor layer301form the rectangular pixel array101. Each pixel104includes a photoelectric converter102with an APD201. The plurality of pixels104are arranged in the semiconductor layer301. A second contact plug322is arranged at each of positions in the diagonal directions of the pixel array101, and the total number of second contact plugs322is four. The second embodiment is advantageous in reducing dark electrons from a contact region316to which the second contact plug322is electrically connected, and this is effective for reducing the DCR. In the second embodiment as well, the arrangement described with reference toFIGS.5and6can be adopted, thereby making it possible to suppress the increase of the DCR.

FIG.9shows a plan view or a planar view of a pixel array101according to the third embodiment.

An arrangement of the third embodiment is a modification of the second embodiment and matters not mentioned in the third embodiment can comply with the first and/or second embodiment. In the third embodiment, the arrangement described with reference toFIGS.5and6is adopted for pixels104at the four corners of the pixel array101. With respect to other pixels104, a first contact plug321can be arranged at the center of a second region312and/or a fourth region315but may be arranged at a position deviated from the center.

From another viewpoint, the pixels104other than the pixels104at the four corners may be arranged at equal intervals. In this arrangement, it is possible to reduce variations in time until photoelectrically converted charges are detected as signals in the plurality of pixels104.

FIG.10shows a plan view or a planar view of a pixel array101according to the fourth embodiment. An arrangement of the fourth embodiment is a modification of the first embodiment and matters not mentioned in the fourth embodiment can comply with the first embodiment. In the fourth embodiment, similar to the arrangement exemplified in the first embodiment, a plurality of pixels104arranged in a semiconductor layer301form the rectangular pixel array101. Each pixel104includes a photoelectric converter102with an APD201. A photoelectric conversion device100according to the fourth embodiment includes a plurality of second contact plugs322, and the plurality of second contact plugs322can be arranged so that two second contact plugs322sandwich at least two pixels104. In one example, the plurality of second contact plugs322can be arranged so that two second contact plugs322sandwich at least two pixels104arrayed in a row direction (a direction orthogonal to a signal line113). In another example, the plurality of second contact plugs322can be arranged so that the second contact plugs322sandwich at least two pixels104. In one example, the plurality of second contact plugs322can be arranged so that two second contact plugs322sandwich at least two pixels104arrayed in a column direction (a direction parallel to the signal line113). In the fourth embodiment, the arrangement described with reference toFIGS.5and6can be adopted, thereby suppressing the increase of the DCR.

In one example, the fourth embodiment can be implemented so that two second contact plugs322sandwich two pixels104. In this arrangement, the number of second contact plugs322is larger than that in the arrangement exemplified in the first embodiment in which four pixels104share one second contact plug322. This is advantageous in suppressing the voltage drop amount at the time of the operation of the APD.

FIG.11shows a plan view or a planar view of a pixel array101according to the fifth embodiment. An arrangement of the fifth embodiment is a modification of the first embodiment and matters not mentioned in the fifth embodiment can comply with the first embodiment. In the fifth embodiment, similar to the arrangement exemplified in the first embodiment, a plurality of pixels104arranged in a semiconductor layer301form the rectangular pixel array101. Each pixel104includes a photoelectric converter102with an APD201.

In the fifth embodiment, in a group of four pixels104surrounded by four second contact plugs322arranged at the vertices of a virtual rectangle, four ring-shaped regions313are coupled and arranged. This arrangement is advantageous since the condition described with reference toFIG.6is satisfied even if the size of the pixel104is reduced.

FIG.12shows a plan view or a planar view of a pixel array101according to the sixth embodiment. An arrangement of the sixth embodiment is a modification or application of each of the first to fifth embodiments and matters not mentioned in the sixth embodiment can comply with the first embodiment. In the sixth embodiment, similar to the arrangement exemplified in the first embodiment, a plurality of pixels104arranged in a semiconductor layer301form the rectangular pixel array101. Each pixel104includes a photoelectric converter102with an APD201. A photoelectric conversion device100according to the sixth embodiment includes a microlens331in each pixel104. The microlens331can be provided on, for example, the side of a first surface S1 but may be provided on the side of a second surface S2. If the microlens331is provided on the side of the first surface S1, the first surface S1 is located between the microlens331and the second surface S2.

If the microlens331is provided on the side of the second surface S2, the second surface S2 is located between the microlens331and the first surface S1.

In an orthogonal projection with respect to the first surface S1, the microlens331can be arranged so that the center of the microlens331matches the center of a second region312. Alternatively, in the orthogonal projection with respect to the first surface S1, the microlens331can be arranged so that the center of the microlens331matches the center of a third region300.

In one example, the first contact plug321can be arranged so that the center of the first contact plug321deviates from the center of the second region312, and the microlens331can be arranged so that the center of the microlens331matches the center of the second region312. In one example, the first contact plug321can be arranged so that the center of the first contact plug321deviates from the center of the third region300, and the microlens331can be arranged so that the center of the microlens331matches the center of the third region300. This arrangement is advantageous since the APD201efficiently receives light or photons when the microlens331is provided on the side of the first surface S1.

FIG.13shows a plan view or a planar view of a pixel array101according to the seventh embodiment. An arrangement of the seventh embodiment is a modification or application of each of the first to sixth embodiments and matters not mentioned in the seventh embodiment can comply with the first embodiment. In the seventh embodiment, similar to the arrangement exemplified in the first embodiment, a plurality of pixels104arranged in a semiconductor layer301form the rectangular pixel array101. The seventh embodiment provides an example of a photoelectric conversion device100formed as a back-side illumination type. A contact region316is arranged on the side of a second surface S2, and a second contact plug322is also arranged on the side of the second surface S2. For example, a voltage line332for supplying a voltage VL is electrically connected to the second contact plug322. In this arrangement, an electric field between a first region311of the first conductivity type and the contact region316of the second conductivity type is irrelevant to reduction of the size of the pixel104. Therefore, it is possible to suppress the increase of the DCR caused by reduction of the size of the pixel104.

The contact region316can be arranged to contact a separation region314. Furthermore, the contact region316can be arranged to contact a fourth region315. In one example, the side surface of the contact region316contacts the fourth region315and is surrounded by the fourth region315. In another example, the side surface of the contact region316contacts the separation region314and is surrounded by the separation region314.

The end face of the separation region314on the side of a first surface S1 can be arranged between the first surface S1 and the second surface S2. From another viewpoint, the end face of the separation region314on the side of the first surface S1 can be arranged apart from the first surface S1. In this arrangement, an electric field between the first region311of the first conductivity type and the separation region314of the second conductivity type is hardly influenced by reduction of the size of the pixel104. That is, it is possible to suppress the increase of the DCR caused by reduction of the size of the pixel104.

In another example, the end face of the separation region314on the side of the first surface S1 may match the first surface S1. This arrangement is advantageous in improving the separation characteristic between the pixels104.

An example of a photoelectric conversion system using a photoelectric conversion device of each of the above-described embodiments will be described below.

FIG.14is a block diagram showing the arrangement of a photoelectric conversion system1200according to this embodiment. The photoelectric conversion system1200according to this embodiment includes a photoelectric conversion device1215. Any one of the photoelectric conversion devices described in the above embodiments can be applied as the photoelectric conversion device1215. The photoelectric conversion system1200can be used as, for example, an image capturing system. Practical examples of the image capturing system are a digital still camera, a digital camcorder, and a monitoring camera.FIG.14shows an example of a digital still camera as the photoelectric conversion system1200.

The photoelectric conversion system1200shown inFIG.14includes the photoelectric conversion device1215, a lens1213for forming an optical image of an object on the photoelectric conversion device1215, an aperture1214for changing the amount of light passing through the lens1213, and a barrier1212for protecting the lens1213. The lens1213and aperture1214form an optical system for concentrating light to the photoelectric conversion device1215.

The photoelectric conversion system1200includes a signal processor1216for processing an output signal output from the photoelectric conversion device1215. The signal processor1216performs an operation of signal processing of performing various kinds of correction and compression for an input signal, as needed, thereby outputting the resultant signal. The photoelectric conversion system1200further includes a buffer memory unit1206for temporarily storing image data and an external interface unit (external I/F unit)1209for communicating with an external computer or the like.

Furthermore, the photoelectric conversion system1200includes a recording medium1211such as a semiconductor memory for recording or reading out image capturing data, and a recording medium control interface unit (recording medium control I/F unit)1210for performing a recording or readout operation in or from the recording medium1211. The recording medium1211may be incorporated in the photoelectric conversion system1200or may be detachable.

In addition, communication with the recording medium1211from the recording medium control I/F unit1210or communication from the external I/F unit1209may be performed wirelessly.

Furthermore, the photoelectric conversion system1200includes a general control/arithmetic unit1208that controls various kinds of operations and the entire digital still camera, and a timing generation unit1217that outputs various kinds of timing signals to the photoelectric conversion device1215and the signal processor1216. In this example, the timing signal and the like may be input from the outside, and the photoelectric conversion system1200need only include at least the photoelectric conversion device1215and the signal processor1216that processes an output signal output from the photoelectric conversion device1215. As described in the fourth embodiment, the timing generation unit1217may be incorporated in the photoelectric conversion device. The general control/arithmetic unit1208and the timing generation unit1217may be configured to perform some or all of the control functions of the photoelectric conversion device1215.

The photoelectric conversion device1215outputs an image signal to the signal processor1216. The signal processor1216performs predetermined signal processing for the image signal output from the photoelectric conversion device1215and outputs image data. The signal processor1216also generates an image using the image signal. Furthermore, the signal processor1216may perform distance measurement calculation for the signal output from the photoelectric conversion device1215. Note that the signal processor1216and the timing generation unit1217may be incorporated in the photoelectric conversion device. That is, each of the signal processor1216and the timing generation unit1217may be provided on a substrate on which pixels are arranged or may be provided on another substrate. An image capturing system capable of acquiring a higher-quality image can be implemented by forming an image capturing system using the photoelectric conversion device of each of the above-described embodiments.

The photoelectric conversion system and a moving body according to this embodiment will be described with reference toFIGS.15A,15B and16.FIGS.15A and15Bare schematic views showing an example of the arrangement of the photoelectric conversion system and the moving body according to this embodiment.FIG.16is a flowchart illustrating the operation of the photoelectric conversion system according to this embodiment. This embodiment will describe an example of an in-vehicle camera as the photoelectric conversion system.

FIGS.15A and15Bshow examples of a vehicle system and a photoelectric conversion system that is incorporated in the vehicle system and performs image capturing. A photoelectric conversion system1301includes a photoelectric conversion device1302, an image preprocessing unit1315, an integrated circuit1303, and an optical system1314. The optical system1314forms an optical image of an object on the photoelectric conversion device1302. The photoelectric conversion device1302converts, into an electrical signal, the optical image of the object formed by the optical system1314. The photoelectric conversion device1302is one of the photoelectric conversion devices according to the above-described embodiments. The image preprocessing unit1315performs predetermined signal processing for the signal output from the photoelectric conversion device1302. The function of the image preprocessing unit1315may be incorporated in the photoelectric conversion device1302. In the photoelectric conversion system1301, at least two sets of the optical systems1314, the photoelectric conversion devices1302, and the image preprocessing units1315are arranged, and an output from the image preprocessing unit1315of each set is input to the integrated circuit1303.

The integrated circuit1303is an image capturing system application specific integrated circuit, and includes an image processing unit1304with a memory1305, an optical distance measurement unit1306, a distance measurement calculation unit1307, an object recognition unit1308, and an abnormality detection unit1309. The image processing unit1304performs image processing such as development processing and defect correction for the output signal from each image preprocessing unit1315. The memory1305temporarily stores a captured image, and stores the position of a defect in the captured image. The optical distance measurement unit1306performs focusing or distance measurement of an object. The distance measurement calculation unit1307calculates distance measurement information from a plurality of image data acquired by the plurality of photoelectric conversion devices1302. The object recognition unit1308recognizes objects such as a vehicle, a road, a road sign, and a person. Upon detecting an abnormality of the photoelectric conversion device1302, the abnormality detection unit1309notifies a main controller1313of the abnormality.

The integrated circuit1303may be implemented by dedicated hardware, a software module, or a combination thereof. Alternatively, the integrated circuit may be implemented by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination thereof.

The main controller1313comprehensively controls the operations of the photoelectric conversion system1301, vehicle sensors1310, a controller1320, and the like. A method in which the photoelectric conversion system1301, the vehicle sensors1310, and the controller1320each individually include a communication interface and transmit/receive control signals via a communication network (for example, CAN standards) may be adopted without providing the main controller1313.

The integrated circuit1303has a function of transmitting a control signal or a setting value to each photoelectric conversion device1302by receiving the control signal from the main controller1313or by its own controller.

The photoelectric conversion system1301is connected to the vehicle sensors1310and can detect the traveling state of the self-vehicle such as the vehicle speed, the yaw rate, and the steering angle, the external environment of the self-vehicle, and the states of other vehicles and obstacles. The vehicle sensors1310also serve as a distance information acquisition unit that acquires distance information to a target object. Furthermore, the photoelectric conversion system1301is connected to a driving support controller1311that performs various driving support operations such as automatic steering, adaptive cruise control, and anti-collision function. More specifically, with respect to a collision determination function, based on the detection results from the photoelectric conversion system1301and the vehicle sensors1310, a collision with another vehicle or an obstacle is estimated or the presence/absence of a collision is determined. This performs control to avoid a collision when the collision is estimated or activates a safety apparatus at the time of a collision.

Furthermore, the photoelectric conversion system1301is also connected to an alarm device1312that generates an alarm to the driver based on the determination result of a collision determination unit. For example, if the determination result of the collision determination unit indicates that the possibility of a collision is high, the main controller1313performs vehicle control to avoid a collision or reduce damage by braking, releasing the accelerator pedal, or suppressing the engine output. The alarm device1312sounds an alarm such as a sound, displays alarm information on the screen of a display unit such as a car navigation system or a meter panel, applies a vibration to the seat belt or a steering wheel, thereby giving an alarm to the user.

According to the present invention, there is provided a technique advantageous in suppressing the increase of the DCR caused by a high electric field in the APD.

This application claims the benefit of Japanese Patent Application No. 2021-008942 filed Jan. 22, 2021, which is hereby incorporated by reference herein in its entirety.