JP2017037937A - Photoelectric conversion device, ranging device and information processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device having a simple configuration that generates a signal based on electrons and holes.SOLUTION: A photoelectric conversion device includes: a first photodiode for generating electrons; a second photodiode for generating holes; an N-type first semiconductor region for collecting the electrons generated by the first photodiode; a P-type second semiconductor region for collecting the holes generated by the second photodiode; and a signal generator to which the first semiconductor region and the second semiconductor region are commonly connected. A P-type third semiconductor region constituting the anode of the first photodiode and an N-type fourth semiconductor region constituting the cathode of the second photodiode are electrically separated from each other by a PN junction.SELECTED DRAWING: Figure 5

Description

  The present technology relates to a photoelectric conversion device.

  A distance measuring device (distance sensor) using a TOF (Time Of Flight) method is known. In the TOF method, an object whose distance is to be measured is irradiated with light from a light source, and light reflected by the object is received. Then, the distance to the object is calculated based on the relationship between the time from irradiation to light reception and the speed of light. Here, the light that has been irradiated from the light source for distance measurement and reflected from the object is referred to as signal light. However, the received light includes light (environment light) derived from a light source different from the light source for distance measurement, such as natural light and artificial light, in addition to the signal light. In order to increase the distance measurement accuracy, it is effective to separate ambient light and signal light.

  Patent Document 1 discloses that a component corresponding to ambient light is removed in an apparatus that performs distance measurement using a light detection element. In Embodiment 2 of Patent Document 1, a first photosensitive portion having a structure suitable for extracting holes and a second photosensitive portion having a structure suitable for extracting electrons are provided. The holes generated in the first photosensitive part are held in the hole holding part through the gate part, and the electrons generated in the second photosensitive part are held in the electron holding part through the gate part. The holes held in the hole holding unit and the electrons held in the electron holding unit are recombined in the recombination unit, and carriers remaining after the recombination are taken out as target carriers through the output unit.

JP 2005-303268 A

  In the technique of Patent Document 1, in the case of using the photoelectric conversion section for hole photoelectric conversion portion (exposed portion) and electronic (photosensitive unit), studied how the arrangement of the photoelectric conversion unit has not been sufficiently . Therefore, an object of the present invention is to provide a photoelectric conversion device having a simple configuration that generates a signal based on electrons and holes.

  Means for solving the above-described problem is a photoelectric conversion device that collects electrons generated by a first photodiode that generates electrons, a second photodiode that generates holes, and the first photodiode. An N-type first semiconductor region, a P-type second semiconductor region that collects holes generated by the second photodiode, and the first semiconductor region and the second semiconductor region are connected in common A P-type third semiconductor region constituting the anode of the first photodiode and an N-type fourth semiconductor region constituting the cathode of the second photodiode by a PN junction. It is electrically isolated.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion device of a simple structure which produces | generates the signal based on an electron and a hole can be provided.

FIG. 2 is a schematic diagram illustrating a photoelectric conversion device, a distance measuring device, and an information processing system. FIG. 10 is a schematic diagram illustrating a circuit of a photoelectric conversion device. FIG. 6 is a schematic diagram illustrating the operation of a photoelectric conversion device. FIG. 6 is a schematic diagram illustrating the operation of a photoelectric conversion device. FIG. 6 is a schematic diagram illustrating a structure of a photoelectric conversion device. FIG. 6 is a schematic diagram illustrating a structure of a photoelectric conversion device. FIG. 10 is a schematic diagram illustrating a circuit of a photoelectric conversion device. FIG. 6 is a schematic diagram illustrating the operation of a photoelectric conversion device.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that, in the following description and drawings, common reference numerals are given to common configurations over a plurality of drawings. Therefore, a common configuration is described with reference to a plurality of drawings, and a description of a configuration with a common reference numeral is omitted as appropriate.

  An information processing system SYS including the photoelectric conversion device 11 and the photoelectric conversion device 11 will be described with reference to FIG. The information processing system SYS includes a distance measuring device 1, and can further include at least one of an information processing device 2, a control device 3, a driving device 4, an imaging device 5, a display device 6, and a communication device 7. In the information processing system SYS, the photoelectric conversion device 11 is included in the distance measuring apparatus 1. The imaging device 5 includes a photoelectric conversion device different from the photoelectric conversion device 11 of the distance measuring device 1. However, the photoelectric conversion device 11 can also have the functions of the distance measuring device 1 and the imaging device 5. An application example of the information processing system SYS will be described later.

  The distance measuring device 1 includes a light receiving unit 10 and a light emitting unit 20. The light receiving unit 10 includes a photoelectric conversion device 11 and an optical system 12 that controls incident light to the photoelectric conversion device 11. The light emitting unit 20 includes a light emitting device 21 as a light source and an optical system 22 that controls light emitted from the light emitting device 21. The light emitting device 21 is preferably a light emitting diode because it can be repeatedly blinked at high speed. In addition, the emission wavelength of the light emitting device 21 is preferably infrared in order to reduce color mixing with ambient light mainly including visible light. Infrared rays are not easily seen by humans, so there is an advantage that they can be used comfortably. However, this example is not limited to infrared light. The optical systems 12 and 22 include a lens, a diaphragm, a mechanical shutter, a scattering plate, an optical low-pass filter, a wavelength selection filter, and the like. For example, the optical system 12 may include a filter that has a higher transmittance of infrared light than visible light. In the distance measuring device 1 shown in FIG. 1A, the optical systems 12 and 22 are used, but at least one of the optical systems may be omitted. When laser light is used as the light source, the optical system 22 can include a scanning optical system for scanning light emitted from the light emitting unit toward a predetermined region.

Light 81 emitted from the light emitting unit 20 is irradiated onto the object 9, reflected by the object 9, and received by the light receiving unit 10 as signal light 82. There is a difference between the light emission time at the light emitting unit 20 and the light reception time at the light receiving unit 10 based on the distance from the distance measuring apparatus 1 to the object 9 and the speed of light (3 × 10 ⁸ m / s). By detecting a physical quantity corresponding to the magnitude of the difference in time, information based on the distance from the distance measuring device 1 to the object 9 or the distance from the distance measuring device 1 to the object 9 is obtained by, for example, an image. It can be obtained as data. As described above, the distance measuring device 1 is a distance measuring device using a TOF (Time Of Flight) method. The magnitude of the time difference described above can be detected by measuring the phase difference of light that changes periodically or the number of light pulses. If the distance between the light emitting unit 20 and the light receiving unit 10 is large, the distance measurement algorithm becomes complicated. Therefore, the distance between the light emitting unit 20 and the light receiving unit 10 is preferably set shorter than the desired distance measuring accuracy. The interval between the light emitting unit 20 and the light receiving unit 10 is set to 1 m or less, for example.

  Not only the signal light 82 but also ambient light 83 caused by a light source other than the light emitted from the light emitting device 21 as a light source is incident on the light receiving unit 10. The light source of the ambient light 83 is natural light or artificial light. In the distance measurement, the ambient light 83 becomes a noise component. For this reason, when the ratio of the ambient light 83 to the amount of received light is high, the dynamic range of the signal by the signal light 82 is reduced or the S / N is lowered, and distance information can be obtained from the signal light 82 with high accuracy. It becomes difficult. The photoelectric conversion device 11 of the present embodiment can remove at least a part of the component due to the ambient light 83 from the signal generated by the light reception by the photoelectric conversion device 11. Therefore, it is possible to increase the distance measurement accuracy. As will be described in detail later, in the present embodiment, at least a part of the component due to the ambient light 83 is removed by using a signal corresponding to the difference in the amount of signal charges generated by a plurality of photoelectric conversion units. . By using electrons and holes as signal charges, the difference in charge amount can be accurately detected with a simple structure. This makes it possible to increase the distance measurement accuracy.

  An outline of the photoelectric conversion device 11 as an example of the present embodiment will be described with reference to FIG. The photoelectric conversion device 11 includes a cell array 110 on a semiconductor substrate 100. In the cell array 110, a plurality of photoelectric conversion cells 111 are arranged in a matrix over a plurality of rows and a plurality of columns. In addition, the photoelectric conversion device 11 can include the row wiring 120, the column wiring 130, the driving unit 140, the control unit 150, the signal processing unit 160, the scanning unit 170, and the output unit 180 on the semiconductor substrate 100. Each of the plurality of photoelectric conversion cells 111 in the cell array 110 is connected to the drive unit 140 via a row wiring 120 arranged on the semiconductor substrate 100 for each row. The drive unit 140 selectively inputs drive signals such as a transfer signal and a reset signal to each of the plurality of photoelectric conversion cells 111 or simultaneously to the plurality of photoelectric conversion cells 111. Each of the plurality of photoelectric conversion cells 111 in the cell array 110 is connected to the signal processing unit 160 via a column wiring 130 disposed on the semiconductor substrate 100 for each column. The signal processing unit 160 processes a signal output from the photoelectric conversion cell 111 via the column wiring 130. The signal processing unit 160 can include a CDS circuit, an amplifier circuit, and an AD conversion circuit for each column of the cell array 110. The scanning unit 170 outputs a signal corresponding to each column, which is output from the cell array 110 to the signal processing unit 160 via each column wiring 130 and processed by the signal processing unit 160, from the signal processing unit 160 to the output unit 180. Output sequentially. The output unit 180 outputs a signal output from the signal processing unit 160 to the outside of the photoelectric conversion device 11, and includes an amplifier circuit, a protection circuit, and an electrode for connection to a circuit outside the photoelectric conversion device 11. it can. The control unit 150 generates a control signal, and controls the operation timing of the driving unit 140, the signal processing unit 160, the scanning unit 170, and the output unit 180 by using the control signal.

  An on-chip lens array (microlens array) or a wavelength filter can be provided on the light incident surface side of the semiconductor substrate 100. A surface irradiation type photoelectric conversion device can be obtained by setting the same side as the side (surface side) on which the row wiring 120 and the column wiring 130 are provided with respect to the semiconductor substrate 100 as the light incident surface side. A back-illuminated photoelectric conversion device can be obtained by setting the side opposite to the side where the row wiring 120 and the column wiring 130 are provided (back side) to the light incident surface side with respect to the semiconductor substrate 100.

  FIG. 2 shows an operation for eight rows when the cell array 110 has eight rows of photoelectric conversion cells 111. Here, an example of performing progressive scanning from the first line R1 to the eighth line R8 is shown, but interlaced scanning may be performed.

  The driving period Tdr of one photoelectric conversion cell 111 includes a reset period Trs in which a reset operation is performed, an accumulation period Tac in which a charge accumulation operation based on the signal light 82 is performed, and a readout operation in which a signal is read out based on the accumulated charge. Period Tsr. Note that the reading period Tsr can also be referred to as a period in which output from the photoelectric conversion cell to the column wiring is performed. The driving period Tdr can further include a period for performing another desired operation. In the example shown here, a plurality of photoelectric conversion cells 111 belonging to the same row are driven simultaneously within a single drive period Tdr. Signals output from the plurality of photoelectric conversion cells 111 belonging to the same row of the cell array 110 are processed by the signal processing unit 160 and output to the output unit 180 as described with reference to FIG.

  The frame period is a period in which the reset operation, the accumulation operation, and the read operation are performed in all the rows of the photoelectric conversion cells 111 constituting the cell array 110. For example, the start point of the first frame period F1 is the time when the reset operation of the first row R1 is started, and the end point of the first frame period F1 is the time when the read operation of the photoelectric conversion cell 111 of the eighth row R8 is finished. It is. The start point of the second frame period F2 is the time when the reset operation for the first row R1 is first started after the read operation for the first row R1 is completed in the first frame period F1. The end point of the second frame period F2 is the time when the read operation of the eighth row R8 is first completed after the read operation of the eighth row R8 is completed in the first frame period F1.

  As shown in FIG. 2, the accumulation operation of a plurality of rows (3 to 4 rows in this example) is performed in parallel, so that the accumulation period can be extended and the output of signals obtained during the accumulation period can be increased. . Even when the accumulation operations for a plurality of rows are performed in parallel, the signals for the plurality of rows can be separated by changing the timing of the read operation for each row.

  In addition, as shown in FIG. 2, the frame rate can be improved or one frame period can be extended by performing a series of operations so that a part of the first frame period F1 and a part of the second frame period F2 overlap. It becomes. That is, in FIG. 2, the reset operation and the accumulation operation of the first row are started at the time when reading of the first to fourth rows is completed in the first frame period F1.

  Not limited to this example, the reset operation, storage operation, and read operation for the next row may be started after all the reset operation, storage operation, and read operation for one row are completed. Further, the reset operation of the first row (first row) may be started after the read operation of the last row (eighth row) is completed.

  Next, an example of the structure of the photoelectric conversion cell 111 will be described. FIG. 3 shows an equivalent circuit of the photoelectric conversion cell 111. In FIG. 3, elements included in the photoelectric conversion cell 111 as a matrix-like repeating unit are surrounded by a chain line. Is done.

  The photoelectric conversion cell 111 includes a photoelectric conversion unit 301 and a photoelectric conversion unit 302. The photoelectric conversion unit 301 generates electrons as signal charges by photoelectric conversion, and the photoelectric conversion unit 302 generates holes as signal charges by photoelectric conversion. That is, the sign of the signal charge is reversed between the photoelectric conversion unit 301 and the photoelectric conversion unit 302. However, the photoelectric conversion unit 301 generates not only electrons but also holes, and the photoelectric conversion unit 302 generates not only holes but also electrons. Each of the photoelectric conversion units 301 and 302 in this example is a PN-type or PIN-type photodiode, and it is preferable to use an embedded type photodiode in order to reduce dark current. Using embedded photodiodes as the photoelectric conversion units 301 and 302 can reduce dark current as compared with the case where a photogate is used for the photoelectric conversion units 301 and 302, and is important in receiving a small amount of signal light. This is advantageous in improving N. The photodiode as the photoelectric conversion unit 301 includes a cathode 201 that is an N-type semiconductor region that uses electrons as a majority carrier, and an anode 211 that is a P-type semiconductor region that uses electrons as a minority carrier. The photodiode as the photoelectric conversion unit 302 includes an anode 202 that is a P-type semiconductor region using holes as a majority carrier, and a cathode 212 that is an N-type semiconductor region using holes as a minority carrier.

  The photoelectric conversion cell 111 includes a capacitor unit 307 capable of holding electrons as signal charges generated by the photoelectric converter 301, and a capacitor unit 310 capable of holding holes as signal charges generated by the photoelectric converter 302. Have.

  The capacity unit 307 includes a reference node 217 and a collection node 207. The collection node 207 collects electrons as signal charges generated by the photoelectric conversion unit 301. The capacitor unit 307 is configured such that a potential difference corresponding to the amount of charge held in the capacitor unit 307 appears between the collection node 207 and the reference node 217. That is, the capacitor unit 307 functions as a charge-voltage conversion unit that converts a charge amount into a voltage. The capacity unit 310 includes a reference node 200 and a collection node 210. The collection node 210 collects holes as signal charges generated by the photoelectric conversion unit 302. The capacitor unit 310 is configured such that a potential difference corresponding to the amount of charge held in the capacitor unit 310 appears between the collection node 210 and the reference node 200. That is, the capacitor 310 functions as a charge-voltage converter that converts the amount of charge into a voltage.

  Each of the capacitor portions 307 and 310 has a PN junction type diode structure. The reference node 217 and the collection node 210 are P-type semiconductor regions, and the reference node 200 and the collection node 207 are N-type semiconductor regions. The collection nodes 207 and 210 that hold signal charges are floating nodes that are electrically floating, and the semiconductor regions that constitute the collection nodes 207 and 210 are floating impurity diffusion regions, that is, floating diffusions. is there. Electrons as signal charges can be collected at the collection node 207 which is an N-type semiconductor region, and the electrons can be held at the collection node 207. Further, holes as signal charges can be collected in the collection node 210 which is a P-type semiconductor region, and the holes can be held in the collection node 210. Although details will be described later, the photoelectric conversion device 11 can operate so that the signal charge is selectively held in one of the collection node 207 and the collection node 210.

  Among the electrons and holes generated by the photoelectric conversion unit 301, the photoelectric conversion cell 111 includes a transfer unit 303 in order to efficiently collect electrons in the collection node 207 of the capacitor unit 307. Similarly, the photoelectric conversion cell 111 includes a transfer unit 306 in order to efficiently collect holes among the electrons and holes generated by the photoelectric conversion unit 301 in the collection node 210 of the capacitor unit 310. Therefore, the collection nodes 207 and 210 can be rephrased as nodes to which signal charges are transferred from the photoelectric conversion units 301 and 302, respectively. Since the collection nodes 207 and 210 can hold the charges transferred from the photoelectric conversion units 301 and 302, the collection node (capacitance unit) can also be referred to as a charge holding unit.

  Each of the transfer unit 303 and the transfer unit 306 has a MIS type gate structure. That is, the transfer unit 303 has a stacked structure of a semiconductor region (channel region), a gate insulating film, and a gate electrode. Therefore, the transfer units 303 and 306 can also be referred to as transfer gates. In the ON state (conductive state), the transfer unit 303 is inverted to form an N-type channel in the semiconductor region, and in the ON state, the transfer unit 306 is inverted to form a P-type channel in the semiconductor region. Thus, the transfer unit 303 and the transfer unit 306 have different conductivity types.

  In this example, the gate electrode of the transfer unit 303 and the gate electrode of the transfer unit 306 are commonly connected to the transfer node 218. In addition, a transfer signal output unit 428 is connected to the transfer node 218, and the transfer signal TX 1 is input from the transfer signal output unit 428 to the transfer node 218. The transfer unit 303 and the transfer unit 306 have different conductivity types and are configured to operate complementarily. That is, the transfer unit 306 is in an OFF state (non-conducting state) while the transfer unit 303 is in the ON state by the transfer signal TX1, and the transfer unit 306 is in the ON state during the period in which the transfer unit 303 is in the OFF state by the transfer signal TX1. Become.

  The transfer unit 303 and the transfer unit 306 may have thresholds set so that both are set to an OFF state by setting the transfer node 218 to a predetermined potential. The predetermined potential may be a potential between a potential at which the transfer unit 303 is turned on and the transfer unit 306 is turned off and a potential at which the transfer unit 303 is turned off and the transfer unit 306 is turned on. Such a predetermined potential is determined in accordance with the potential of the semiconductor region in the MIS type gate structure and the threshold value of the MIS type gate structure. The difference between the potential level High at which the transfer unit 303 is turned on and the potential level Mid at which the transfer unit 303 is turned off is, for example, 1V to 5V. The difference between the potential level Low at which the transfer unit 306 is turned on and the potential level Mid at which the transfer unit 303 is turned off is, for example, 1V to 5V. It is preferable to set the potential level High to a potential (positive potential) higher than the ground potential GND (0 V) and the potential level Low to a potential (negative potential) lower than the ground potential GND. For example, the potential level Mid can be set to the ground potential GND. It is also possible to reduce the circuit scale by setting both the potential level High and the potential level Low to a positive potential, or setting both the potential level High and the potential level Low to a negative potential.

  Note that the transfer unit 303 and the transfer unit 306 may be connected to different transfer nodes, and the ON / OFF states of the transfer unit 303 and the transfer unit 306 may be controlled by independent transfer signals. However, it is preferable that the transfer unit 303 and the transfer unit 306 are connected to a common transfer node 218 so that the same transfer signal TX1 is input to the gate electrodes of the transfer unit 303 and the transfer unit 306. By doing in this way, the precision of the timing control of the ON / OFF state of the transfer part 303 and the transfer part 306 can be improved. In addition, since the transfer units 303 and 306 can be driven by a common drive circuit and wiring, the configuration of the photoelectric conversion device 11 can be simplified.

  In this way, the collection node 207 is connected to the cathode 201 via the transfer unit 303. Similarly, the collection node 210 is connected to the anode 202 via the transfer unit 306.

  Note that the collection node 207 can be connected to the cathode 201 without using an active element such as the transfer unit 303. Similarly, the collection node 210 can be connected to the anode 202 without using an active element such as the transfer unit 306. For example, by setting the potentials of the photoelectric conversion unit 301 and the capacitor unit 307 in an appropriate relationship, electrons generated by the photoelectric conversion unit 301 can be collected in the collection node 207 even if the transfer unit 303 is omitted. Similarly, by setting the potentials of the photoelectric conversion unit 302 and the capacitor unit 310 in an appropriate relationship, holes generated by the photoelectric conversion unit 302 can be collected in the collection node 210 even if the transfer unit 306 is omitted. Can do. Further, the photoelectric conversion unit 302 itself functions as a capacitor unit 307 having a capacity corresponding to the junction capacitance, and the photoelectric conversion unit 302 itself functions as a capacitor unit 310 having a capacity corresponding to the junction capacitance. You may comprise. For example, a high-concentration portion in which an N-type impurity concentration is higher than other portions may be provided in a part of the N-type semiconductor region of the photodiode, and the high-concentration portion may be used as a collection node. Further, as an alternative to switching between transfer and non-transfer of charges from the photoelectric conversion units 301 and 302 by the transfer units 303 and 306, the discharge units connected to the photoelectric conversion units 301 and 302 from the photoelectric conversion units 301 and 302 It is also possible to switch between charge non-discharge and discharge. However, by switching between charge transfer and non-transfer using the transfer units 303 and 306, it is possible to control charges with higher accuracy than when the transfer units 303 and 306 are not used.

  A reference potential supply unit 411 is connected to the anode 211 of the photoelectric conversion unit 301 and the reference node 217 of the capacitor unit 307. The reference potential VF1 is commonly supplied from the reference potential supply unit 411 to the anode 211 of the photoelectric conversion unit 301 and the reference node 217 of the capacitor unit 307. A reference potential supply unit 412 is connected to the cathode 212 of the photoelectric conversion unit 302 and the reference node 200 of the capacitor unit 310. The reference potential VF <b> 2 is commonly supplied from the reference potential supply unit 412 to the cathode 212 of the photoelectric conversion unit 302 and the reference node 200 of the capacitor unit 310.

  As described above, holes are also generated in the photoelectric conversion unit 301, but the holes are discharged to the anode 211 side. Similarly, electrons are also generated in the photoelectric conversion unit 302, but the electrons are discharged to the cathode 212 side.

  The collection node 207 of the capacity unit 307 and the collection node 210 of the capacity unit 310 are both connected to the detection node 220. A potential corresponding to the amount of electrons transferred from the photoelectric conversion unit 301 to the capacitor unit 307 and the capacitance of the capacitor unit 310 appears at the collection node 207 and the detection node 220. Similarly, a potential corresponding to the amount of holes transferred from the photoelectric conversion unit 302 to the capacitor unit 310 and the capacitance of the capacitor unit 310 appears at the collection node 210 and the detection node 220. As a result, the potential at the detection node 220 is the sum of the potential that can appear at the detection node 220 due to the electrons collected at the collection node 207 and the potential that can appear at the detection node 220 due to the holes collected at the collection node 210. Will appear.

Further, the collection node 207 and the collection node 210 are electrically connected to each other. The electrical connection between the collection node 207 and the collection node 210 is made by a conductor (electric conductor). That is, typically, the collection node 207 and the collection node 210 are directly connected by a conductor. The conductor has a conductivity of 10 ⁴ S / m or more (a resistivity of 10 ⁻⁴ Ω · m or less). Note that the insulator has a conductivity of 10 ⁻⁷ S / m or less (a resistivity of 10 ⁷ Ω · m or more). Further, the semiconductor has a conductivity between 10 ⁻⁷ S / m and 10 ⁴ S / m (a resistivity between 10 ⁻⁴ Ω · m and 10 ⁷ Ω · m). Examples of the conductor include metals, metal compounds, graphite, and polycrystalline silicon. Further, silicon with a high impurity concentration (10 ¹⁹ / cm ³ or more) can also be said to behave like a conductor. Since the collection node 207 and the collection node 210 are connected by a conductor, charge transfer between the collection node 207 and the collection node 210 is smooth. Therefore, the time until the potentials of the collection node 207 and the collection node 210 are stabilized can be shortened.

  The following phenomena are considered to occur transiently. First, a difference occurs between the amount of electrons collected by the collection node 207 and the amount of holes collected by the collection node 210. In accordance with this difference, a potential difference is generated between the collection node 207 and the collection node 210. Electrons move between the collection node 207 and the collection node 210 through the conductor so as to reduce this potential difference. Then, electrons and holes are recombined (pair annihilation) at the collection node 210. Then, a potential corresponding to the amount of charge that is the difference between the amount of electrons collected by the collection node 207 and the amount of holes collected by the collection node 210 appears at the detection node 220.

  In this example, since the collection node 207 and the collection node 210 are directly connected by a conductor, the collection node 207, the collection node 210, and the detection node 220 can be regarded as the same potential. For example, a switch can be provided between the collection node 207 and the detection node 220 and / or between the collection node 210 and the detection node 220. Accordingly, at least two of the collection node 207, the collection node 210, and the detection node 220 can be temporarily driven so as to have different potentials.

  The potential of the detection node 220 is VN, the potential of the collection node 207 is VN1, and the potential of the collection node 210 is VN2. Here, the potentials VN, VN1, and VN2 are variable potentials. As described above, in the present embodiment, the collection node 207 and the collection node 210 are commonly connected to the detection node 220, so that VN≈VN1≈VN2. Here, considering the ease of collecting the electrons of the cathode 201 of the photoelectric conversion unit 301 by the collection node 207, it is preferable that VF1 <VN1. Considering the ease of collecting the holes of the anode 202 of the photoelectric conversion unit 302 by the collection node 210, it is preferable that VN2 <VF2. Since VN1 = VN2 for VF1 <VN1 and VN2 <VF2, VF1 <VF2. As described above, the fact that the reference potential VF2 is higher than the reference potential VF1 (VF1 <VF2) is advantageous in improving the distance measurement accuracy compared with the case where the reference potential VF2 is equal to or lower than the reference potential VF1 (VF1 ≧ VF2). It is. This is because the charge collection efficiency is increased, and high-speed operation and high-accuracy signal acquisition are possible. Practically, the potential difference between the reference potential VF1 and the reference potential VF2 is preferably 0.10V or more. Therefore, in this example, the reference potential supply unit 411 and the reference potential supply unit 412 are provided separately. The potential difference between the reference potential VF1 and the reference potential VF2 is typically 1V or more and 5V or less. The reference potential VF1 can be set lower than the ground potential GND (0V) (VF1 <GND), and the reference potential VF2 can be set higher than the ground potential GND (0V) (GND <VF2). That is, the reference potential VF1 may be a negative potential and the reference potential VF2 may be a positive potential.

  The detection node 220 is connected to the signal generation unit 315. In this example, the signal generation unit 315 is a MOS transistor (amplification transistor) having a gate, a source, and a drain, and the detection node 220 is connected to the gate of the signal generation unit 315 (amplification transistor).

  The drain of the signal generation unit 315 is connected to the power supply unit 432, and the power supply potential VDD is supplied from the power supply unit 432. The source of the signal generation unit 315 is connected to the constant current source 430 via the MOS transistor (selection transistor) 316, and the signal generation unit 315 constitutes a source follower circuit together with the constant current source 430. During the read operation, the selection signal SL is output from the selection signal supply unit 426 connected to the gate of the selection transistor 316 to turn on the selection transistor 316. As a result, the signal generation unit 315 generates a pixel signal corresponding to the potential of the detection node 220, and outputs this pixel signal to the output line 431 that is a part of the column wiring 130 in FIG.

  In this example, an electrical low-pass filter 433 is provided between the detection node 220 and the signal generation unit 315. By providing the electrical low-pass filter 433, the output from the signal generation unit 315 can be stabilized even when the potential of the detection node 220 vibrates, and the ranging accuracy can be improved. The electrical low-pass filter 433 can be configured by a resistor connected in series to the gate of the amplification transistor and a capacitor connected in parallel to the gate, but is not limited thereto. Further, the electrical low-pass filter 433 can be omitted.

  The collection node 207 and the collection node 210 reset potential supply section 413 via the MOS transistor (reset transistor) 313 are commonly connected. The reset potential supply unit 413 outputs a reset potential VS1. The reset transistor 313 is turned on by the reset signal RS1 output from the reset signal output unit 423 to the gate of the reset transistor. As a result, the potential VS11 corresponding to the reset potential VS1 is supplied from the reset potential supply unit 413 to the collection node 207. That is, the potential VN1 of the collection node 207 becomes the potential VS11 (VN1 = VS11). Similarly, the potential VS12 corresponding to the reset potential VS1 is supplied from the reset potential supply unit 413 to the collection node 210. That is, the potential VN1 of the collection node 210 becomes the potential VS11 (VN2 = VS12).

  By supplying the potential VS11 to the collection node 207 of the capacitor 307 during the reset operation, electrons held in the capacitor 307 are discharged to the reset potential supplier 413. By supplying the potential VS12 to the collection node 210 of the capacitor unit 310, holes held in the capacitor unit 310 are discharged to the reset potential supply unit 413.

  The potential difference between the potential VS11 and the potential VS12 is less than 0.10 V, which is advantageous in improving the distance measurement accuracy compared to the potential difference between the potential VS11 and the potential VS12 being 0.10 V or more. With respect to the collection node 207 and the collection node 210 connected in common to the detection node 220, the operation of the accumulation period Tac after the reset period Trs is stabilized by setting the potential difference between the potential VS11 and the potential VS12 to be less than 0.10V. Can do. In order to set the potential difference between the potential VS11 and the potential VS12 to be less than 0.10 V, the collection node 207 and the collection node 210 may be connected by a conductor having high conductivity. Further, in order to make the potential difference between the potential VS11 and the potential VS12 less than 0.10V, the resistance between the collection node 207 and the collection node 210 is such that the difference between the potential VS11 and the potential VS12 is 0.10V or more. If it is not arranged. It should be noted that a slight potential difference of less than 0.10 V due to inevitable resistances or manufacturing errors is acceptable.

  In this example, the potential VS12 is applied to the collection node 210 at the same time as the potential VS11 is applied to the collection node 207. Switches may be provided between the reset signal output unit 423 and the collection node 207 and between the reset signal output unit 423 and the collection node 210, respectively. In that case, the timing at which the potential VS11 is applied to the collection node 207 and the timing at which the potential VS12 is applied to the collection node 210 can be different.

  The potential VS11 is preferably higher than the reference potential VF1 (VF1 <VS11). By doing so, it is possible to increase the electron collection efficiency at the collection node 207 after the reset period Trs. The potential VS12 is preferably lower than the reference potential VF2 (VS12 <VF2). By doing in this way, the collection efficiency of the hole in the collection node 210 after the reset period Trs can be improved. As described above, if VS11 = VS12 = VS1, in order to satisfy both VF1 <VS11 and VS12 <VF2, the reset potential VS1 is set to a potential between the reference potential VF1 and the reference potential VF2 (VF1 <VS1). <VF2) is preferred.

  The potential VS11 can be selected from a range of, for example, -5 to + 5V, preferably -2 to + 2V. The potential VS12 can also be selected from the range of, for example, -5 to + 5V, preferably -2 to + 2V. The difference between the potential VS11 and the potential VS12 is preferably 0. A circuit may be designed so as to satisfy VF1 <VS11 and VS12 <VF2 within the preferable ranges of the reference potentials VF1 and VF2 and within the preferable ranges of the potentials VS11 and VS12.

  In the example of FIG. 3, the transfer unit 304 and the capacitor unit 308 are connected to the photoelectric conversion unit 301 in the same manner as the transfer unit 303 and the capacitor unit 307. That is, the transfer unit 303 and the capacitor unit 307, the transfer unit 304, and the capacitor unit 308 are connected in parallel to the photoelectric conversion unit 301. Similarly, the transfer unit 305 and the capacitor unit 309 are connected to the photoelectric conversion unit 302 in the same manner as the transfer unit 306 and the capacitor unit 310. That is, the transfer unit 306, the capacitor unit 310, the transfer unit 304, the transfer unit 305, and the capacitor unit 309 are connected in parallel to the photoelectric conversion unit 301. Note that the transfer unit 304 and the capacity unit 308 can have the same configuration as the transfer unit 303 and the capacity unit 307, and the transfer unit 305 and the capacity unit 309 have the same configuration as the transfer unit 306 and the capacity unit 310. Can be.

  In this example, each gate electrode of the MIS type gate structure included in each of the transfer unit 304 and the transfer unit 305 is commonly connected to the transfer node 219. A transfer signal output unit 429 is connected to the transfer node 219. Then, the transfer signal TX <b> 2 is input from the transfer signal output unit 429 to the transfer node 219. The transfer unit 304 and the transfer unit 305 have different conductivity types and are provided in a complementary manner. Therefore, the transfer unit 305 is in the OFF state (non-conduction state) during the period in which the transfer unit 304 is in the ON state (conducting state) by the transfer signal TX2, and the transfer unit is in the period in which the transfer unit 304 is in the OFF state by the transfer signal TX2. 305 is turned on. Note that it is desirable that the transfer unit 304 and the transfer unit 305 have thresholds set so that both are set to an OFF state by setting the transfer node 219 to a predetermined potential. Such a predetermined potential is determined in accordance with the potential of the semiconductor region in the MIS type gate structure and the threshold value of the MIS type gate structure. The difference between the potential level High at which the transfer unit 304 is turned on and the potential level Mid at which the transfer unit 304 is turned off is, for example, 1V to 5V. The difference between the potential level Low at which the transfer unit 305 is turned on and the potential level Mid at which the transfer unit 305 is turned off is, for example, 1V to 5V. It is preferable to set the potential level High to a potential (positive potential) higher than the ground potential GND (0 V) and the potential level Low to a potential (negative potential) lower than the ground potential GND. For example, the potential level Mid can be set to the ground potential GND. It is also possible to reduce the circuit scale by setting both the potential level High and the potential level Low to a positive potential, or setting both the potential level High and the potential level Low to a negative potential. Note that the transfer unit 304 and the transfer unit 305 can be connected to different transfer nodes, and the ON / OFF states of the transfer unit 304 and the transfer unit 305 can be controlled by independent transfer signals. In addition, it is preferable that the transfer unit 303 and the transfer unit 304 connected to the photoelectric conversion unit 301 are operated so that the ON state and the OFF state are opposite to each other, that is, operate in a complementary manner. That is, during the period in which the transfer unit 303 is in the ON state by the transfer signal TX1, the transfer unit 304 is in the OFF state by the transfer signal TX2. Further, during a period in which the transfer unit 303 is in the OFF state by the transfer signal TX1, the transfer unit 304 is in the ON state by the transfer signal TX2. Similarly, it is preferable to operate the transfer unit 305 and the transfer unit 306 connected to the photoelectric conversion unit 302 so that the ON state and the OFF state are opposite to each other, that is, operate in a complementary manner. That is, during a period in which the transfer unit 306 is in the ON state by the transfer signal TX1, the transfer unit 305 is in the OFF state by the transfer signal TX2. Further, during a period in which the transfer unit 306 is in the OFF state by the transfer signal TX1, the transfer unit 305 is in the ON state by the transfer signal TX2. By doing in this way, the transfer of signal charges from one photoelectric conversion unit can be performed alternately between two transfer units connected to the one photoelectric conversion unit.

  The capacitor unit 308 collects the electrons transferred from the photoelectric conversion unit 301 via the transfer unit 304 in the collection node 208. The capacitor unit 309 collects the holes transferred from the photoelectric conversion unit 302 via the transfer unit 305 in the collection node 209. Each of the capacitor portions 308 and 309 has a PN junction type diode structure. The collection node 208 of the capacitor unit 308 is an N-type semiconductor region, and the collection node 209 of the capacitor unit 309 is a P-type semiconductor region. The reference node 228 of the capacitor 308 is a P-type semiconductor region, and the reference node 229 of the capacitor 309 is an N-type semiconductor region. A reference potential supply unit 411 is connected to the reference node 228 to supply a reference potential VF1. A reference potential supply unit 412 is connected to the reference node 229 and supplied with a reference potential VF2.

  The collection node 208 and the collection node 209 are commonly connected to a reset potential supply unit 414 via a MOS transistor (reset transistor) 314. The reset potential supply unit 414 outputs a reset potential VS2. The reset transistor 314 is turned on by the reset signal RS2 output from the reset signal output unit 424. Thereby, the potentials of the collection node 208 and the collection node 209 can be set to a predetermined reset potential.

  In the example of FIG. 3, the charges transferred from the photoelectric conversion unit to the collection nodes 208 and 209 in the capacitor units 308 and 309 are discharged. However, similarly to the signal generation unit 315, a signal generation unit may be connected to the capacitor units 308 and 309 so that signals based on the charges of the capacitor units 308 and 309 are read out. In such a configuration, the signal generated by the signal generator based on the charges of the capacitors 308 and 309 and the signal generated by the signal generator based on the charges of the capacitors 307 and 310 are It can also be synthesized. In this way, it is possible to increase the intensity of the pixel signal.

  The potential used for the circuit mentioned above is illustrated. The ground potential GND is set to 0V. As a first example, VS1, VS2 = 0V, VF1 = −1V, VF2 = + 1V, High = + 2V, Mid = 0V, and Low = −2V. As a second example, VS1, VS2 = + 1V, VF1 = 0V, VF2 = + 2V, High = + 3V, Mid = + 1V, and Low = −1V. The second example is an example in which each potential of the first example is shifted by S (V), and corresponds to the case of S = -1. As a third example, VS1, VS2 = + 0V, VF1 = -2V, VF2 = + 2V, High = + 4V, Mid = + 0V, Low = -4V. The third example is an example in which the potential of the first example is T times, and corresponds to the case of T = 2. The value S described above may be a positive value or a negative value, and the value T described above may be less than 1. The second example may be combined with the second example, and the first example may be shifted S (V) and multiplied by T. The actual value of the potential can be adjusted as appropriate while maintaining the magnitude relationship of the potential, the potential difference, and the magnitude difference of the potential difference obtained from each potential in the three examples described above.

  Next, the operation per driving time Tdr of one photoelectric conversion cell 111 of the distance measuring device 1 will be described with reference to FIG. In the description using FIG. 4, the periods p1 to p10 are periods from time t0 to time t10.

  4A shows the light emission level Le of the light emitting device 21 and the light receiving levels Lr1 and Lr2 of the photoelectric conversion device 11. FIG. In the periods p1, p4, p5, p7, and p9 where the light emission level Le is the light amount Loff, the light emitting device 21 is turned off. During the periods p2, p3, p6, and p8 where the light emission level Le is Lon, the light emitting device 21 is lit. In this way, the light emitting device 21 repeats blinking with the time Tcy from time t1 to t5 as one cycle. Here, for simplification of explanation, it is assumed that the blinking is repeated three times. However, in reality, by repeating blinking, for example, 100 to 10,000 times within the accumulation period Tac for one distance measurement, Sufficient accuracy can be ensured.

When the light speed is c (m / s), the delay time from light emission to light reception based on the distance d (m) from the distance measuring device 1 to the object 9 is 2 × d / c (s). It is only necessary to detect the delay time from light emission to light reception during one cycle Tcy. Since the speed of light is 3 × 10 ⁸ m / s, that is, 0.3 m / ns, one cycle Tcy is set to, for example, 1 ns to 1000 ns, preferably 10 ns to 100 ns. For example, the delay from light emission to light reception corresponding to a distance difference of 0.3 m is 2 ns. Therefore, if one cycle Tcy is 10 ns, a distance difference of 0.3 m can be detected by detecting a physical quantity corresponding to this delay time in 10 ns. From the period Tcy and the number of repetitions of blinking, one distance measurement is completed in a short time of 1 μs to 10 ms at most. Therefore, the cell array 110 can be read about 10 to 1000 rows and about 1 to 1000 frames per second. For example, if the driving period Tdr for one row is 1 μs, 1000 frames can be read out for 1000 frames per second, and if the driving period Tdr for one row is 10 ms, 100 frames are read out for 1 frame per second. Can do.

  Corresponding to the light emission of the light emitting device 21, the light amounts received by the photoelectric conversion device 11 are Lra and Lrb. The waveform indicated by the light reception level Lr1 starts light reception at a time t2 after the time Tda from the light emission start time t1 and a time t4 after the time Tda from the light emission end time t3 according to the distance from the distance measuring device 1 to the object. Indicates that light reception is terminated. The waveform indicated by the light reception level Lr2 starts light reception at a time t2 ′ after the time Tdb from the light emission start time t1 and a time after the time Tdb from the light emission end time t3 according to the distance from the distance measuring device 1 to the object. The light reception is terminated at t4 ′. In this example, since Tda <Tdb, the signal light indicated by the light reception level Lr1 is reflected by an object closer to the distance measuring device 1 than the signal light indicated by the light reception level Lr2. I understand. Further, in this example, since Lrb <Lra, the signal light indicated by the light reception level Lr1 may have a higher reflectance than the signal light indicated by the light reception level Lr2.

  Here, in the period when the photoelectric conversion device 11 receives light corresponding to the light emission of the light emitting device 21, the light amounts Lra and Lrb received by the photoelectric conversion device 11 include not only the signal light 82 shown in FIG. Ambient light 83 is also included. The amount of light received for this ambient light is Lam. Of the received light amounts Lra and Lrb, the light amount obtained by subtracting Lam is signal light having actual distance information.

  FIG. 4B shows temporal changes in the reset signals RS1 and RS2 (dotted lines), the selection signal SL (solid line), the transfer signal TX1 (one-dot chain line), and the transfer signal TX2 (two-dot chain line). Note that the potential level High is a potential higher than the potential level Low, and the potential level Mid is a potential between the potential level High and the potential level Low. The potential level High, the potential level Mid, and the potential level Low can each include a certain range of potentials. For example, the potential level Mid is a certain range of potential including the ground potential (0 V). In FIG. 4B, the potential at the portion where the horizontal axis indicating the time is located is the potential level Mid. In FIG. 4B, for convenience, it is assumed that the transistor operates in the same manner as the potential level High at a transient potential (rising and falling potential) between the potential level Mid and the potential level High. I will explain. Similarly, a transitional potential (rising or falling potential) between the potential level Mid and the potential level High will be described assuming that the same operation as the potential level Low and the potential level High is performed. Note that the potential level at which the transistor is turned on and the potential level at which the transistor is turned off need not be a common potential, and may be different from each other.

  The reset signals RS1 and RS2 are simultaneously at the potential level High, but the period during which the reset signals RS1 and RS2 are at the potential level High may be different. The transfer signal TX1 and the transfer signal TX2 are typically rectangular waves or sine waves having the same period with the polarity reversed. The cycle of the transfer signal TX1 and the transfer signal TX2 is preferably the same as the cycle Tcy of light emission from the light emitting device 21, but the cycle of the transfer signal and the light emission cycle are slightly different unless the accuracy of distance measurement is low. It may be.

  During the period p1 in which the reset signals RS1 and RS2 are higher than the potential level Mid (typically, the potential level High), the reset transistors 313 and 314 are in the ON state. The reset transistors 313 and 314 are in the OFF state at times t1 to t10 during which the reset signals RS1 and RS2 are at the potential level Mid. In FIG. 4A, the reset signal RS1 and the reset signal RS2 are described as being the same, but may be different as necessary in a period not shown.

  In periods p2, p3, p6, and p8 where the transfer signal TX1 is higher than the potential level Mid (typically, the potential level High), the transfer unit 303 is in the ON state and the transfer unit 306 is in the OFF state. During periods p4, p5, p7, and p9 where the transfer signal TX1 is lower than the potential level Mid (typically, the potential level Low), the transfer unit 303 is in the OFF state and the transfer unit 306 is in the ON state. It is preferable that the time from when the reset transistors 313 and 314 change from the ON state to the OFF state until one of the transfer unit 303 and the transfer unit 306 becomes ON is as short as possible.

  In the periods p2, p3, p6, and p8 when the transfer signal TX2 is lower than the potential level Mid (typically, the periods p2, p3, p6, and p8, the transfer unit 305 is in the ON state and the transfer unit 304 is in the OFF state. In the periods p4, p5, p7, and p9 during which p is higher than the potential level Mid (typically, the potential level High), the transfer unit 305 is in the OFF state and the transfer unit 304 is in the ON state. It is better that the time from when the ON state is changed to the OFF state until one of the transfer unit 304 and the transfer unit 305 becomes ON is as short as possible.

  During the period (or time) when the transfer signal TX1 is at the potential level Mid, the transfer unit 303 and the transfer unit 306 are in the OFF state, and during the period (or time) when the transfer signal TX2 is at the potential level Mid. The transfer unit 304 is in an OFF state. Such a potential level Mid is determined according to the characteristics of the transfer units 303, 304, 305, and 306 as described above.

  FIG. 4C shows a change in the potential of the detection node 220. The potential change S1 indicates a change in potential due to the light reception level Lr1, and the potential change S2 indicates a change in potential due to the light reception level Lr2.

  In the period p1, the collection nodes 207 and 210 and the detection node 220 are set to potentials (potentials VS11 and VS12) corresponding to the reset potential VS1 by the reset potential supply unit 413.

  In the period p <b> 2, electrons generated by the photoelectric conversion unit 301 according to the light amount Lam of the ambient light 83 are transferred to the capacitor unit 307. When electrons are generated by the photoelectric conversion unit 301, the potential of the cathode 201 becomes higher than the potential of the anode 211. If the potential of the anode 211 is, for example, VF1 = -2V, the potential of the cathode 201 is about -1V. Due to the reset potential VS1, the potential of the collection node 207 is higher than the potential of the anode 211 (VF1 <VS1). For this reason, if the transfer unit 303 is in the ON state, the generated electrons quickly move to the collection node 207 having a higher potential than the potential of the cathode 201. As the electrons are transferred, the potential of the detection node 220 connected to the collection node 207 decreases.

  In the period p <b> 3, electrons generated by the photoelectric conversion unit 301 according to the light amount Lra including the signal light 82 that is stronger than the light amount Lam of the ambient light 83 are transferred to the capacitor unit 307. As the electrons are transferred, the potential of the detection node 220 connected to the collection node 207 decreases with a larger gradient than the period p2. This is because the amount of light received per unit time increases by the amount of the signal light 82.

  In the period p <b> 4, holes generated by the photoelectric conversion unit 302 according to the light amount Lra including the signal light 82, which is stronger than the light amount Lam of the ambient light 83, are transferred to the capacitor unit 310. As the holes are transferred, the potential of the detection node 220 connected to the collection node 210 increases.

  Here, in the periods p2 and p3, the transfer unit 305 is in the ON state. Therefore, holes generated by the photoelectric conversion unit 302 in the periods p2 and p3 are transferred to the capacitor unit 309 during the periods p2 and p3. Therefore, after the transfer unit 306 is switched to the ON state at time t3, for example, the holes transferred to the capacitor unit 310 in the period p4 are longer than the holes generated in the photoelectric conversion unit 302 in the periods p2 and p3. More holes are generated at p4. Ideally, holes generated by the photoelectric conversion unit 302 in the periods p2 and p3 are not transferred to the capacitor unit 310 in the period p4.

  In the period p <b> 5, holes generated by the photoelectric conversion unit 302 according to the light amount Lam of the ambient light 83 are transferred to the capacitor unit 310. As the holes are transferred, the potential of the detection node 220 connected to the collection node 210 increases.

  The same is repeated for periods p6, p7, p8, and p9. Here, in the periods p4 and p5, the transfer unit 304 is in the ON state. Therefore, electrons generated by the photoelectric conversion unit 301 in the periods p4 and p5 are transferred to the capacitor unit 308 during the periods p4 and p5. Therefore, after the transfer unit 303 is switched to the ON state at time t5, for example, electrons transferred to the capacitor unit 307 in the period p6 are in the period p6, compared to electrons generated in the photoelectric conversion unit 301 in the periods p4 and p5. More electrons are generated. Ideally, electrons generated by the photoelectric conversion unit 301 in the periods p4 and p5 are not transferred to the capacitor unit 307 in the period p6.

  By repeating such a cycle Tcy many times, it is possible to obtain a signal suitable for distance measurement in which the components of the ambient light 83 are removed and the components of the signal light 82 are integrated.

  The light reception level Lr1 is such that the delay time Tda is less than ¼ of the cycle Tcy (Tda <Tcy / 4). Therefore, the potential of the detection node 220 is effectively controlled by the electrons transferred in the period p3, and the potential of the detection node 220 is lower than the reset potential VS1 (the absolute value is increased). When the delay time Tdb is ¼ of the cycle Tcy (Tdb = Tcy / 4) as in the light reception level Lr2, the amounts of electrons and holes transferred to the collection nodes 207 and 210 within one cycle Tcy are equal. Therefore, the potential of the detection node 220 is equal to the reset potential VS1. When the delay time Tda> T / cy4, the potential of the detection node 220 is effectively controlled by the holes transferred in the period p4, and the potential of the detection node 220 becomes higher than the reset potential VS1 (the absolute value is large). Become).

  Here, the lighting period and the extinguishing period of the light emitting device 21 in one cycle Tcy are made equal, but the lighting period and the extinguishing period may be different. In the case where the lighting period and the extinguishing period are different, the signal output from the signal generation unit 315 may be corrected based on the difference between the lighting period and the extinguishing period. Here, the ON and OFF periods of the transfer gate in one cycle Tcy are made equal, but even if the ON period and the OFF period are different, the output from the signal generator 315 is based on the difference between the ON period and the OFF period. The corrected signal may be corrected.

  The potential appearing at the detection node 220 will be quantitatively described. Of the amount of electrons as signal charge, the component due to ambient light 83 is (−N), the component due to signal light 82 is (−S), and the amount of holes as signal charge is ambient light. The component due to 83 is (+ N), and the component due to the signal light 82 is (+ S). A coefficient proportional to the length of the period p2 is a, a coefficient proportional to the length of the period p3 is b, a coefficient proportional to the length of the period p4 is c, and a coefficient proportional to the length of the period p5 is d.

  First, the charge amounts of the collection nodes 207 and 210 are calculated on the assumption that recombination of electrons and holes at the detection node 220 does not occur. The increment of the charge amount of the collection node 207 in the period p2 is a × (−N), and the charge amount of the collection node 207 at the time t2 is a × (−N). On the other hand, the increment of the charge amount of the collection node 210 in the period p2 is 0, and the charge amount of the collection node 210 at the time t2 is 0. The increment of the charge amount of the collection node 207 in the period p3 is b × (−N−S), and the charge amount of the collection node 207 at the time t3 is a × (−N) + b × (−N−S). On the other hand, the increase in the charge amount of the collection node 210 in the period p3 is 0, and the charge amount of the collection node 210 at time t3 is 0. The increment of the charge amount of the collection node 207 in the period p4 is 0, and the charge amount of the collection node 207 at the time t4 is a × (−N) + b × (−N−S). The increment of the charge amount of the collection node 210 in the period p4 is c × (+ N + S), while the charge amount of the collection node 210 at the time t4 is c × (+ N + S). The increment of the charge amount of the collection node 207 in the period p5 is 0, and the charge amount of the collection node 210 at time t5 is a × (−N) + b × (−N−S). On the other hand, the increment of the charge amount of the collection node 210 in the period p5 is d × (+ N), and the charge amount of the collection node 210 at the time t5 is c × (+ N + S) + d × (+ N).

  The actual charge amount of the detection node 220 at time t5 corresponds to a value obtained by subtracting electrons and holes. That is, a × (−N) + b × (−N−S) + c × (+ N + S) + d × (+ N) = (a + b) × (−N) + (c + d) × (+ N) + b × (−S) + c X (+ S) = ((c + d)-(a + b)) * N + (c-b) * S. Here, if the ambient light 83 is constant during the period from time t1 to time t5 and the time during which the transfer unit 303 and the transfer unit 306 are complementarily turned on is the same, (c + d) -(A + b) = 0. Therefore, the potential appearing at the detection node 220 at time t5 is such that at least a part of the component of the ambient light 83 is removed and (c−b) × S indicating only the component of the signal light 82 is obtained as a signal. I understand.

  FIG. 5 shows an example of the layout of the photoelectric conversion cell 111. FIG. 5A is a schematic plan view of the photoelectric conversion cell 111. 5B is a schematic cross-sectional view taken along line AA ′ in FIG. 5A, FIG. 5C is a schematic cross-sectional view taken along line BB ′ in FIG. 5A, and FIG. FIG. 6 is a schematic cross-sectional view taken along line CC ′ of FIG.

  The semiconductor substrate 100 is provided with a P-type semiconductor region 511 as a P-type well and an N-type semiconductor region 512 as an N-type well. For example, the N-type semiconductor region 512 is an N-type epitaxial layer, and the semiconductor region 511 is a P-type impurity diffusion region formed by ion-implanting P-type impurities into the N-type epitaxial layer. Note that a plurality of portions constituting the single semiconductor regions 511 and 512 have the same conductivity type and are continuous with each other. Here, the plurality of portions are portions having positions different from each other in at least one of the X, Y, and Z directions. The impurity concentrations of a plurality of portions constituting the single semiconductor regions 511 and 512 may be different from each other. For example, the P-type semiconductor region 511 may have an impurity concentration that is inclined in the depth direction (Z direction) of the semiconductor substrate 100.

  In the photoelectric conversion cell 111, a photoelectric conversion unit 301 and a photoelectric conversion unit 302 are provided side by side along the main surface 1000 of the semiconductor substrate 100. A direction in which the photoelectric conversion unit 301 and the photoelectric conversion unit 302 are arranged is an X direction, a direction parallel to the surface 1000 and perpendicular to the X direction is a Y direction, and a direction perpendicular to the surface 1000 is a Z direction.

  As a structure different from the structure illustrated in FIG. 5, the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be arranged along the Z direction. That is, one of the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be arranged at a deeper position on the semiconductor substrate 100 than the other. For example, the cathode (N-type semiconductor region) of the photoelectric conversion unit 301 and the anode (P-type semiconductor region) of the photoelectric conversion unit 302 are arranged in the Z direction from the surface 1000. Between them, the anode (P-type semiconductor region) of the photoelectric conversion unit 301 and the cathode (N-type semiconductor region) of the photoelectric conversion unit 302 are arranged so as to be separated by PN junction. By extending a P-type semiconductor region as a charge transfer path continuous to the anode of the photoelectric conversion section 302 toward the surface 1000, a signal of the photoelectric conversion section 302 disposed at a deep position through the charge transfer path Charges can be collected. However, if this is done, the amount of photoelectrically converted light differs between the photoelectric conversion unit disposed at a shallow position and the photoelectric conversion unit disposed at a deep position, and a large difference also occurs in the amount of signal charge generated. This is because light is attenuated by absorption of light in the semiconductor substrate 100. Therefore, in order to reduce the difference in the amount of received light between the photoelectric conversion unit 301 and the photoelectric conversion unit 302, it is preferable that the photoelectric conversion unit 301 and the photoelectric conversion unit 302 are arranged along the main surface 1000 of the semiconductor substrate 100.

  In FIG. 5, a thick line is a local wiring arranged in the photoelectric conversion cell 111. In addition, a circle indicates the position of a contact portion for connecting the local wiring or global wiring (not shown) such as the row wiring 120 and the column wiring 130 described in FIG. . In a typical contact portion, the contact plug and the semiconductor substrate 100 are joined. Here, the local wiring is a wiring for electrically connecting the components in the photoelectric conversion cell 111 to each other. On the other hand, the global wiring is wiring for connecting the photoelectric conversion cells 111 or between the photoelectric conversion cells 111 and a circuit outside the cell array 110. The row wiring 120 and the column wiring 130 described in FIG. 1B are typical global wirings. The wiring is a member made of a conductor for electrical connection. Note that in a contact portion for connecting to a semiconductor region, it is preferable that a part of the semiconductor region connected to a conductor such as a contact plug is an impurity region having a higher concentration than other regions. It is preferable to ensure electrical connection.

  As shown in FIG. 5B, in the Y direction, on the line AA ′, an N-type semiconductor region 507, a transfer gate electrode 503, an N-type semiconductor region 501, a transfer gate electrode 504, and an N-type semiconductor. Regions 508 are arranged in this order.

  As shown in FIG. 5C, in the Y direction, on the line BB ′, a P-type semiconductor region 510, a transfer gate electrode 505, a P-type semiconductor region 502, a transfer gate electrode 506, and a P-type semiconductor. Regions 509 are arranged in this order.

  As shown in FIG. In the X direction, the gate electrode 513 of the reset transistor 313, the gate electrode 514 of the reset transistor 314, the gate electrode 515 of the amplification transistor, and the gate electrode 516 of the selection transistor 316 are arranged in this order. The gate electrode 515 of the amplification transistor that constitutes the signal generation unit 315 is an input node of the signal generation unit 315 and is connected to the detection node 220 directly or through an electrical low-pass filter 433.

  The N-type semiconductor region 507 forms a collection node 207 as part of the capacitor unit 307. That is, the N-type semiconductor region 507 is the first floating diffusion. The semiconductor region 511 forms a PN junction with the semiconductor region 507, and the semiconductor region 511 forms a reference node 217 of the capacitor 307.

  The P-type semiconductor region 510 forms a collection node 210 as a part of the capacitor unit 310. That is, the P-type semiconductor region 507 is the second floating diffusion. The semiconductor region 512 forms a PN junction with the semiconductor region 510, and the semiconductor region 512 constitutes the reference node 200 of the capacitor portion 310.

  The N-type semiconductor region 501 constitutes a cathode 201 of the photodiode as a part of the photoelectric conversion unit 301. The semiconductor region 501 forms a PN junction with the semiconductor region 511, and the semiconductor region 511 constitutes an anode 211 of the photodiode. The impurity concentration of the N-type semiconductor region 501 is preferably low enough to be depleted by the built-in potential. With this configuration, electrons generated as signal charges among the electron-hole pairs generated in the photoelectric conversion unit 301 are difficult to accumulate in the photoelectric conversion unit 301. By doing so, the transfer efficiency of electrons from the photoelectric conversion unit 301 to the semiconductor region 507 is increased. Further, electrons generated by light can always be completely transferred to the semiconductor region 507, and noise caused by low transfer efficiency can be reduced. Note that holes that are not used as signal charges in the photoelectric conversion unit 301 are discharged through the P-type semiconductor region 511. A surface region which is a P-type semiconductor region is provided between the N-type semiconductor region 501 and the surface 1000 of the semiconductor substrate 100, and the N-type semiconductor region 501 is arranged away from the surface 1000. Thus, the photoelectric conversion unit 301 is an embedded photodiode. In FIG. 5, a P-type semiconductor region as a surface region is integrally described as a P-type semiconductor region 511.

  The P-type semiconductor region 502 forms the anode 202 of the photodiode as a part of the photoelectric conversion unit 302. The semiconductor region 502 forms a PN junction with the semiconductor region 512, and the semiconductor region 512 constitutes the cathode 212 of the photodiode. The impurity concentration of the P-type semiconductor region 502 is preferably low enough to be depleted by the built-in potential. With this configuration, the holes generated as signal charges among the electron-hole pairs generated in the photoelectric conversion unit 302 are difficult to accumulate in the photoelectric conversion unit 302. By doing so, the transfer efficiency of holes from the photoelectric conversion unit 302 to the semiconductor region 510 is increased. In addition, electrons generated by light can always be completely transferred to the semiconductor region 510, and noise resulting from low transfer efficiency can be reduced. Note that holes that are not used as signal charges in the photoelectric conversion unit 302 are discharged through the P-type semiconductor region 511. A surface region which is an N-type semiconductor region is provided between the P-type semiconductor region 502 and the surface 1000 of the semiconductor substrate 100, and the P-type semiconductor region 502 is disposed away from the surface 1000. Thus, the photoelectric conversion unit 302 is an embedded photodiode. In FIG. 5, an N-type semiconductor region as a surface region is integrally described as an N-type semiconductor region 512.

  The N-type semiconductor region 508 forms a PN junction with the semiconductor region 511, and the semiconductor region 508 forms a collection node 208 as a part of the capacitor portion 308. The P-type semiconductor region 509 forms a PN junction with the semiconductor region 512, and the semiconductor region 509 forms a collection node 209 as part of the capacitor portion 309. The N-type semiconductor region 501 and the P-type semiconductor region 502 are provided along the surface 1000 of the semiconductor substrate 100 in the X direction. The N-type semiconductor region 501 and the P-type semiconductor region 502 may be in contact with each other, but are preferably separated.

  In this example, the N-type semiconductor region 511 and the P-type semiconductor region 512 form a PN junction between the N-type semiconductor region 501 and the P-type semiconductor region 502. As a result, the semiconductor region 501 and the semiconductor region 502 are electrically separated (PN junction separation). A reference potential VF <b> 1 is supplied to the semiconductor region 511 from the contact plug 611 constituting the reference potential supply unit 411. Then, the reference potential VF <b> 2 is supplied from the contact plug 612 constituting the reference potential supply unit 412 to the semiconductor region 512. When the reference potential VF1 is lower than the reference potential VF2, a reverse bias voltage is applied between the semiconductor region 511 and the semiconductor region 512. Therefore, the semiconductor region 511 and the semiconductor region 512 are electrically separated by a depletion layer generated between the semiconductor region 511 and the semiconductor region 512. By doing so, electrons generated in the N-type semiconductor region 501 and holes generated in the P-type semiconductor region 502 can be electrically separated. Therefore, charges can be collected at a corresponding collection node at an appropriate timing, and signal charges necessary for distance measurement can be selectively recombined. In addition, by performing separation between the photoelectric conversion unit 301 and the photoelectric conversion unit 302 by PN junction separation, the interval between the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be reduced (for example, less than 1 μm). Therefore, the difference in the amount of light received by the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be reduced. Further, the PN junction isolation can suppress the generation of dark current compared to the insulator isolation, so that the S / N can be improved.

  In the cell array 110, the structure [a] in FIG. 5 is arranged in a matrix. The P-type semiconductor region 512 is continuously arranged between the plurality of photoelectric conversion cells 111 as a common well. On the other hand, the N-type semiconductor region 511 is discontinuously arranged between the plurality of photoelectric conversion cells 111 as an isolated well. That is, the N-type semiconductor region 511 of a certain photoelectric conversion cell 111 is separated from the N-type semiconductor region 511 of at least one adjacent photoelectric conversion cell 111 by separation means such as PN junction separation from the P-type semiconductor region 512. And can be electrically separated. Contrary to the above-described example, the P-type semiconductor region 512 can be an isolated well and the N-type semiconductor region 511 can be a common well. In this manner, by using one of the P-type semiconductor region 512 and the N-type semiconductor region 511 as a common well, the configuration of the photoelectric conversion cell 111 can be simplified.

  The transfer gate electrode 503 having at least a portion disposed between the N-type semiconductor region 501 and the N-type semiconductor region 507 in the plan view constitutes the transfer unit 303. Note that in this example, the transfer gate electrode 503 is located on part of the semiconductor region 501 and part of the semiconductor region 507. The transfer gate electrode 504 having at least a portion disposed between the N-type semiconductor region 501 and the N-type semiconductor region 508 in plan view constitutes the transfer unit 304. In this example, the transfer gate electrode 504 is also located on part of the semiconductor region 502 and part of the semiconductor region 508.

  On the other hand, the transfer gate electrode 505 having at least a portion disposed between the P-type semiconductor region 502 and the P-type semiconductor region 510 in plan view constitutes the transfer unit 305. In this example, the transfer gate electrode 505 is located on part of the semiconductor region 502 and part of the semiconductor region 510. The transfer gate electrode 506 having at least a portion disposed between the P-type semiconductor region 502 and the P-type semiconductor region 509 in the plan view constitutes the transfer unit 306. In this example, the transfer gate electrode 506 is also located on part of the semiconductor region 502 and part of the semiconductor region 509.

  An insulating film 500 is provided between the transfer gate electrodes 503, 504, 505 and 506 and the semiconductor substrate 100. The insulating film 500 functions as a gate insulating film.

  A local wiring 618 is commonly connected to the transfer gate electrode 503 and the transfer gate electrode 505 via contact plugs 603 and 605 so that the same transfer signal TX1 is supplied. Here, the transfer gate electrode 503 and the transfer gate electrode 505 are provided as separate gate electrodes. Since the gate electrode charges and discharges every time it is driven, a current corresponding to the MOS capacitance flows every time switching is performed. When driving at high speed, the smaller the gate electrode of the transistor is, the smaller the MOS capacitance is. Therefore, by providing the transfer gate electrode 503 and the transfer gate electrode 505 separately, the gate electrode can be made as small as possible.

  On the other hand, it can also be provided as an integral gate electrode having a portion constituting the transfer portion 303 and a portion constituting the transfer portion 305. By doing so, it is possible to increase the accuracy of complementary control of the transfer units 303 and 305 by reducing the wiring and reducing the wiring capacity and resistance. Further, by reducing the wiring, the aperture ratio can be increased and the sensitivity can be improved. The same applies to the transfer gate electrode 503 and the transfer gate electrode 505.

  A reset transistor having a gate electrode 513 is connected to the semiconductor region 507 and the semiconductor region 510 through contact plugs 607 and 610, a local wiring 620 and a contact plug 613. In this example, the local wiring 620 constitutes the detection node 220. The gate electrode 513 is connected to a reset signal output unit 423 outside the cell array via a contact plug, local wiring, and global wiring. The contact plug 613 is connected to the semiconductor region 523 which is one source / drain region of the reset transistor. The other source / drain region of the reset transistor is connected to a reset potential supply unit 413 outside the cell array via a global wiring. Similarly, a reset transistor having a gate electrode 514 is connected to the semiconductor region 508 and the semiconductor region 509 through a local wiring and a contact plug.

  An amplification transistor having a gate electrode 513 is connected to the semiconductor region 507 and the semiconductor region 510 through a local wiring 620 and a contact plug 615. The contact plug 615 is connected to the gate electrode 515 of the amplification transistor. The drain of the amplification transistor is connected to the power supply unit 432 through a contact plug and a global wiring. The source of the amplification transistor is connected to the drain of the selection transistor 316 having the gate electrode 516. The source of the selection transistor 316 is connected to the global wiring (column wiring 130) through a contact plug.

  A contact plug 611 is connected to the semiconductor region 511. The contact plug 611 is connected to a reference potential supply unit 411 outside the cell array 110 via a global wiring. A contact plug 612 is connected to the semiconductor region 512. The contact plug 612 is connected to a reference potential supply unit 412 outside the cell array 110 via a global wiring. In this manner, by supplying the reference potential to the semiconductor region 511 and the semiconductor region 512 through the wiring, variation in the reference potential in each of the photoelectric conversion cells 111 in the cell array 110 can be reduced. Note that the reference potential can be supplied without the contact plug 611 and the contact plug 612 being provided in the photoelectric conversion cell 111. In that case, an impurity diffusion layer extending from the cell array 110 to the outside of the cell array 110 may be provided in the semiconductor substrate 100, and a reference potential may be supplied to the impurity diffusion layer outside the cell array 110 via a wiring or a contact plug. However, as described above, if the N-type semiconductor region 511 is an isolated well, it is difficult to extend the N-type semiconductor region 511 outside the cell array 110. Therefore, at least for the isolated well, it is preferable to supply the reference potential via a conductor arranged on the semiconductor substrate 100 such as a global wiring, a local wiring, or a contact plug. The same applies when the P-type semiconductor region 512 becomes an isolated well.

  The semiconductor region 507 and the semiconductor region 510 are connected to each other through a conductor. In this example, a conductor that connects the semiconductor region 507 and the semiconductor region 510 to each other is shown as a local wiring 620 and contact plugs 607 and 610. A conductor that connects the semiconductor region 507 and the semiconductor region 510 is formed using a material having higher electrical conductivity than the semiconductor substrate 100, such as a metal material, a metal compound material, or polycrystalline silicon. Metal materials and metal compound materials are materials used for wiring and contact plugs, and polycrystalline silicon is a material used for gate electrodes. The metal compound material may be a semiconductor-metal compound material such as silicide. The semiconductor region 507 and the semiconductor region 510 are connected by using these materials alone or in combination. Thus, since the semiconductor region 507 and the semiconductor region 510 are connected via the conductor, the semiconductor region 507 and the semiconductor region 510 can be connected without passing through the PN junction. Typically, the semiconductor region 507 and the semiconductor region 510 can be connected to each other through an ohmic junction. The semiconductor region 507 and the semiconductor region 510 are connected via a conductor, whereby the semiconductor region 507 and the semiconductor region 510 do not form a PN junction with each other. Therefore, the relaxation time of the potential difference between the semiconductor region 507 and the semiconductor region 510 when recombining electrons and holes can be shortened. As a result, the output of the detection node 220 can be stabilized, and highly accurate distance measurement can be realized.

  FIG. 6 illustrates a structure for obtaining electrical connection between the semiconductor region 507 and the semiconductor region 510. 6A to 6D correspond to a cross section including the transfer gate electrodes 503 and 505 and the semiconductor regions 507 and 510 in FIG. FIG. 6A shows a structure for obtaining electrical connection between the semiconductor region 507 and the semiconductor region 510 in FIG. FIGS. 6B to 6D show a form different from the form of FIG. 6A for obtaining an electrical connection between the semiconductor region 507 and the semiconductor region 510. 6A to 6D, the transfer gate electrode 503 and the transfer gate electrode 505 are electrically connected by a local wiring 618. The local wiring 618 is in contact with the contact plug 603 over the transfer gate electrode 503, the contact plug 605 over the transfer gate electrode 505, the contact plug 603, and the contact plug 605. The contact plug 603 and the contact plug 605 penetrate the interlayer insulating film 526, and the local wiring 618 is disposed on the interlayer insulating film 526. As the local wiring 618, for example, an aluminum wiring having a conductive portion containing aluminum as a main component and a barrier metal portion including a titanium layer and / or a titanium nitride layer can be used. Alternatively, the local wiring 618 can be a copper wiring having a conductive portion mainly composed of copper and a barrier metal portion including a tantalum layer and / or a tantalum nitride layer. The copper wiring has a single damascene structure or a dual damascene structure. Other local wirings are similarly aluminum wirings or copper wirings.

  In the form of FIG. 6A, the semiconductor region 507 and the semiconductor region 510 are connected by the contact plug 607, the contact plug 610, and the local wiring 620 that connects the contact plug 607 and the contact plug 610. The contact plug 607 is connected to the semiconductor region 507 through the interlayer insulating film 526, and the contact plug 610 is connected to the semiconductor region 510 through the interlayer insulating film 526. Contact plugs 607 and 610 each have a conductive portion mainly composed of tungsten, and a barrier metal portion having a titanium layer and / or a titanium nitride layer disposed between the conductive portion and interlayer insulating film 526. The local wiring 620 is an aluminum wiring having a conductive portion mainly composed of aluminum and a barrier metal portion including a titanium layer and / or a titanium nitride layer located between the conductive portion and the interlayer insulating film 526. Alternatively, the local wiring 620 is a copper wiring having a conductive portion containing copper as a main component and a barrier metal portion including a tantalum layer and / or a tantalum nitride layer located between the conductive portion and the interlayer insulating film 526. is there.

  In the form of FIG. 6B, the semiconductor region 507 and the semiconductor region 510 are connected through a contact plug 623 that is a conductor that contacts both the semiconductor region 507 and the semiconductor region 510. Contact plug 623 includes a conductive portion mainly composed of tungsten, and a barrier metal portion including a titanium layer and / or a titanium nitride layer disposed between the conductive portion and interlayer insulating film 526. An insulating film 527 is provided separately from the insulating film 500 and the interlayer insulating film 526 between the contact plug 623 and the semiconductor substrate 100. The insulating film 527 insulates the contact plug 623 from the N-type semiconductor region 511 and insulates the contact plug 623 from the P-type semiconductor region 512. Thereby, it is possible to suppress conduction between the N-type semiconductor region 511 and the P-type semiconductor region 512.

  In the form of FIG. 6C, the semiconductor region 507 and the semiconductor region 510 are connected through a local wiring 624 that is a conductor in contact with both the semiconductor region 507 and the semiconductor region 510. The local wiring 624 can be formed by patterning a tungsten film or a silicide film. The local wiring 624 is located between the interlayer insulating film 526 and the semiconductor substrate 100. After forming the transfer gate electrode 503 and the transfer gate electrode 505, the local wiring 624 may be formed, and then the interlayer insulating film 526 and the contact plugs 603 and 605 may be formed. An insulating film 528 is provided separately from the insulating film 500 and the interlayer insulating film 526 between the local wiring 624 and the semiconductor substrate 100. The insulating film 528 insulates the local wiring 624 from the N-type semiconductor region 511 and insulates the local wiring 624 from the P-type semiconductor region 512. Thereby, it is possible to suppress conduction between the N-type semiconductor region 511 and the P-type semiconductor region 512.

  In the form of FIG. 6D, the semiconductor region 507 and the semiconductor region 510 are connected through a local wiring 625 which is a conductor that contacts both the semiconductor region 507 and the semiconductor region 510. The local wiring 625 can be formed by patterning a polysilicon film, and can be formed simultaneously with the transfer gate electrode 503 and the transfer gate electrode 505. The local wiring 625 is located between the interlayer insulating film 526 and the semiconductor substrate 100. An insulating film 500 is provided between the local wiring 625 and the semiconductor substrate 100 in order to insulate the local wiring 625 from the N-type semiconductor region 511 and insulate the local wiring 625 from the P-type semiconductor region 512. Yes.

  Each local wiring and global wiring described above can be configured by connecting a plurality of wiring layers stacked in a direction perpendicular to the surface 1000 of the semiconductor substrate 100 to each other via via plugs.

  Next, a modification of the equivalent circuit of the photoelectric conversion cell 111 described with reference to FIG. 3 will be described with reference to FIG.

  The collection node 207 of the capacitor unit 307 is connected to the detection node 220 via the switch transistor 318. When the switch transistor 318 is turned on by the switch signal SW1 output from the switch signal output unit 438, a potential corresponding to the potential of the collection node 207 appears at the detection node 220. The collection node 210 of the capacitor unit 310 is connected to the detection node 220 via the switch transistor 319. When the switch transistor 319 is turned on by the switch signal SW2 output from the switch signal output unit 439, a potential corresponding to the potential of the collection node 207 appears at the detection node 220. As described above, in this example, the electrical connection between the collection node 207 and the collection node 210 can be switched ON and OFF. In other words, the collection node 207 and the collection node 210 are electrically connected via the switch transistors 318 and 319. Note that one of the switch transistor 318 and the switch transistor 319 can be omitted.

  A reset potential supply unit 413 is connected to the collection node 207 of the capacitor unit 307 via a reset transistor 313. The reset transistor 313 is turned on by the reset signal RS1 output from the reset signal output unit 423. As a result, the reset potential VS <b> 1 is supplied from the reset potential supply unit 413 to the collection node 207 of the capacitor unit 307. A reset potential supply unit 417 is connected to the collection node 210 of the capacitor unit 310 via a reset transistor 317. The reset transistor 317 is turned on by the reset signal RS3 output from the reset signal output unit 427. As a result, the reset potential VS3 is supplied from the reset potential supply unit 417 to the collection node 210 of the capacitor unit 310.

  The potential difference between the reset potential VS1 and the reset potential VS3 is preferably less than 0.10V. The potential difference between the reset potential VS1 and the reset potential VS3 is desirably 0 V, but there may be a slight potential difference of less than 0.10 V due to inevitable resistance, manufacturing errors, and the like. The reset potential VS3 and the reset potential VS3 are preferably set to a potential between the reference potential VF1 and the reference potential VF2. For example, the reset potential VS1 can be higher than the reference potential VF1 (VF1 <VS1). Further, the reset potential VS3 can be made lower than the reference potential VF2 (VS3 <VF2). The reset potential VS1 is, for example, −1 to + 1V, preferably −0.5 to + 0.5V. The reset potential VS3 is also, for example, −1 to + 1V, preferably −0.5 to + 0.5V.

  By supplying the reset potential VS <b> 1 to the capacitor portion 307, electrons held in the capacitor portion 307 are discharged to the reset potential supply portion 413. By supplying the reset potential VS3 to the capacitor portion 310, holes held in the capacitor portion 310 are discharged to the reset potential supply portion 417. According to this example, one of the signal based on the charge (electrons) photoelectrically converted by the photoelectric conversion unit 301 from the detection node 220 and the signal based on the charges (holes) photoelectrically converted by the photoelectric conversion unit 302 are obtained. It can be read selectively. By realizing such an operation mode, it is possible to obtain the photoelectric conversion device 11 that can perform both imaging and ranging.

  In this example, the capacity units 308 and 309 can be omitted, and unnecessary charges can be quickly discharged by turning the transfer units 304 and 305 on and off. By doing in this way, it becomes possible to raise the aperture ratio by wiring and the area of a photoelectric conversion part, and to improve a sensitivity.

  FIG. 8 shows an example of the operation of the circuit shown in FIG. Between the accumulation period Tac and the readout period Tsr shown in FIGS. 3 and 4, there are a readout period Tnr for reading the ambient light 83 and a removal period Tcl for removing the components of the ambient light 83. After the reset period Trs, during the accumulation period Tac, the switch transistor 318 is turned on and the switch transistor 319 is turned off. In the read period Tnr, the selection transistor 316 is turned on while the switch transistor 318 is turned on and the switch transistor 319 is turned off. As a result, the signal of the detection node 220 in which the potential corresponding to the potential of the collection node 207 appears is read out. After the readout period Tnr, a removal period Tcl for removing at least a part of the components of the ambient light 83 is provided. In the removal period Tcl, the selection transistor 316 is turned off, and the switch transistor 318 and the switch transistor 319 in FIG. 7 are turned on. Thereby, the component of the ambient light 83 is canceled by the electrons and holes due to recombination of the electrons and holes. The potential from which the component of the ambient light 83 is removed appears at the detection node 220. In the reading period Tsr, the selection transistor 316 is turned on to read a signal from which the component of the ambient light 83 is removed. By reading out the ambient light 83 in this way, not only an image including distance information but also an image based on the ambient light 83 can be obtained.

  An application example of the information processing system SYS will be described with reference to FIG.

  The first application example of the information processing system SYS is an example applied to a camera including an imaging device. First, when a signal for instructing distance measurement is sent from the control device 3 including an input unit such as a focus control unit (for example, a focus button) to the information processing device 2, the information processing device 2 operates the distance measuring device 1. Then, the distance measuring device 1 outputs a signal including distance information to the object 9 that is a subject to the information processing device 2. The information processing apparatus 2 processes the signal and generates a drive signal for driving mechanical parts such as a lens, an aperture, and a shutter so as to satisfy conditions suitable for photographing the object 9. Then, this drive signal is output to a drive device 4 such as a motor for driving a lens, a diaphragm, a shutter and the like. The driving device 4 drives the mechanical parts described above based on the driving signal. When a signal for instructing photographing is transmitted from the control device 3 to the information processing device 2, the information processing device 2 instructs the imaging device 5 to perform imaging, and the imaging device 5 performs imaging of the object 9. The information processing device 2 displays an image obtained from the imaging device 5 on the display device 6. The information processing device 2 can also add distance information to the obtained image and display it on the display device 6. Further, the communication device 7 communicates with a storage device or a network, and stores the image in a storage device or a storage on the network.

  The second application example of the information processing system SYS is an example applied to a video information processing system that provides mixed reality to the user. When the information processing apparatus 2 operates the distance measuring apparatus 1 and the imaging apparatus 5, the imaging apparatus 5 captures an object 9 that is a subject and outputs a real image. On the other hand, the distance measuring device 1 outputs a signal including distance information to the subject that is the object 9. The information processing device 2 processes the signal, and synthesizes a virtual image obtained by computer graphics or the like and a real image obtained by photographing by the imaging device 5 based on the distance information to generate a synthesized image. The information processing device 2 displays the composite image on a display device 6 such as a head mounted display.

  The third application example of the information processing system SYS is an example in which the information processing system SYS is applied to a transportation device having power (for example, an automobile or a train). When a signal for instructing movement or preparation of transportation equipment is sent to the information processing device 2 from the control device 3 including a device (for example, a start button) for generating a signal for starting the engine and an input unit such as a handle or an accelerator. The information processing apparatus 2 operates the distance measuring apparatus 1. Then, the distance measuring device 1 outputs a signal including distance information to the subject that is the object 9. The information processing device 2 processes the signal, and displays a warning on the display device 6 when the distance from the object 9 becomes short, for example. The information processing device 2 can also display information indicating the distance from the object 9 on the display device 6. In addition, the information processing device 2 can drive the driving device 4 such as a brake or an engine based on the distance information to decelerate or accelerate the speed of the transportation device. Further, the information processing device 2 can also adjust the relative distance from the transport equipment traveling ahead by driving the drive device 4 such as a brake or an engine based on the distance information.

  The fourth application example of the information processing system SYS is an example applied to a game system. The user instructs the game machine body to use the gesture mode using the control device 3 including an input unit such as a controller. When the information processing apparatus 2 operates the distance measuring apparatus 1 in response to an instruction from the user, the distance measuring apparatus 1 detects the user's operation (gesture) as distance information. Based on the obtained distance information, the information processing apparatus 2 creates an image in which a virtual character in the game is operated in accordance with the user's action. The information processing device 2 displays this video on the display device 6 connected to the game machine main body (information processing device 2).

  As described above, the photoelectric conversion device 11 according to this embodiment includes the first photodiode (photoelectric conversion unit 301) that generates electrons, the second photodiode (photoelectric conversion unit 301) that generates holes, Is provided. In addition, an N-type first semiconductor region 507 that collects electrons generated by the first photodiode (photoelectric conversion unit 301) and a P that collects holes generated by the second photodiode (photoelectric conversion unit 302). A second semiconductor region 510 of a type. Further, a signal generation unit 315 in which the first semiconductor region 507 and the second semiconductor region 510 are connected in common is provided. Then, a P-type semiconductor region 511 constituting the anode 311 of the first photodiode (photoelectric conversion unit 301), an N-type semiconductor region 512 constituting the cathode 212 of the second photodiode (photoelectric conversion unit 302), Are electrically separated by a PN junction.

  Such a photoelectric conversion device can obtain a signal corresponding to a difference in signal charges of a plurality of photoelectric conversion units with a simple configuration. In addition, a signal corresponding to the difference between signal charges of a plurality of photoelectric conversion units can be obtained with high accuracy.

  The photoelectric conversion device is not limited to the example described above, and can be applied to various information processing systems SYS. In the above-described embodiment, an example of a photoelectric conversion device optimized for performing driving for distance measurement, a distance measuring device including the photoelectric conversion device, and an imaging system has been described. However, the photoelectric conversion device is used for distance measurement. In addition to driving, driving other than distance measurement may be performed. For example, it is possible to perform focus detection or distance measurement by edge detection or phase difference detection method for detecting the contour of an object such as a human face, using a signal corresponding to the difference between signal charges of a plurality of photoelectric conversion units. This is because the difference in the amount of light received by the plurality of photoelectric conversion units can be detected based on the magnitude of the signal output from the signal generation unit in accordance with the difference in signal charge. In general, a complex structure such as a differential circuit is required to obtain a difference between electrical signals after a signal charge is converted into an electrical signal by a signal generator such as a source follower circuit. However, the photoelectric conversion device of the present embodiment can easily obtain the difference between the signal charges of a plurality of photoelectric conversion units by recombination of electrons and holes. Then, a signal corresponding to the difference between the signal charges of the plurality of photoelectric conversion units can be obtained by converting the difference between the signal charges into an electric signal by a signal generation unit having a simple structure, for example, a source follower circuit. In addition, by providing a switch transistor between the collection node and the detection node as in the form shown in FIG. 7, a signal corresponding to the charge amount of the original signal charge is transmitted from each of the plurality of photoelectric conversion units to the signal. It is also possible to read the signal separately from the signal corresponding to the difference in charge amount. Thereby, an imaging operation can be performed.

301 Photoelectric conversion unit 302 Photoelectric conversion unit 507 Semiconductor region 510 Semiconductor region 511 Semiconductor region 512 Semiconductor region 315 Signal generation unit

Claims (20)

A first photodiode for generating electrons;
A second photodiode for generating holes;
An N-type first semiconductor region for collecting electrons generated by the first photodiode;
A P-type second semiconductor region for collecting holes generated by the second photodiode;
A signal generator in which the first semiconductor region and the second semiconductor region are connected in common;
The P-type third semiconductor region constituting the anode of the first photodiode and the N-type fourth semiconductor region constituting the cathode of the second photodiode are electrically separated by a PN junction. A photoelectric conversion device characterized by   2. The photoelectric conversion device according to claim 1, wherein the first photodiode and the second photodiode are arranged in a direction along a surface of a semiconductor substrate on which the first photodiode and the second photodiode are arranged. .   Between the N-type fifth semiconductor region constituting the cathode of the first photodiode and the P-type sixth semiconductor region constituting the anode of the second photodiode, the third semiconductor region and the The photoelectric conversion device according to claim 1, wherein the fourth semiconductor region forms a PN junction.   The photoelectric conversion device according to any one of claims 1 to 3, wherein cells including the first photodiode and the second photodiode are arranged in a matrix.   One of the third semiconductor region and the fourth semiconductor region is continuous between the plurality of cells arranged in the matrix, and the other of the third semiconductor region and the fourth semiconductor region is The photoelectric conversion device according to claim 4, which is discontinuous between the plurality of cells. The third semiconductor region forms a PN junction with the first semiconductor region;
The photoelectric conversion device according to claim 1, wherein the fourth semiconductor region forms a PN junction with the second semiconductor region. A first potential supply unit for supplying a first potential to the third semiconductor region;
A second potential supply unit for supplying a second potential to the fourth semiconductor region,
The photoelectric conversion device according to claim 1, wherein a difference between the first potential and the second potential is 0.10 V or more.   The photoelectric conversion device according to claim 7, wherein the first potential is lower than the second potential.   A first transfer unit for transferring electrons generated by the first photodiode to the first semiconductor region; and a second transfer unit for transferring holes generated by the second photodiode to the second semiconductor region; A photoelectric conversion device according to claim 1, comprising:   A third transfer unit for transferring electrons generated by the first photodiode to an N-type semiconductor region different from the first semiconductor region; and holes generated by the second photodiode by the second semiconductor. The photoelectric conversion device according to claim 9, further comprising: a fourth transfer unit that transfers to a P-type semiconductor region different from the region.   The signal generation unit includes a transistor constituting a source follower circuit, and the first semiconductor region and the second semiconductor region are connected to a gate electrode of the transistor of the signal generation unit. The photoelectric conversion device according to any one of claims.   The photoelectric conversion device according to claim 1, wherein the first semiconductor region is connected to the signal generation unit via an electrical low-pass filter.   The photoelectric conversion device according to claim 1, wherein at least one of the first semiconductor region and the second semiconductor region is connected to the signal generation unit via a transistor.   A first transfer unit for transferring electrons generated by the first photodiode to the first semiconductor region; and a second transfer unit for transferring holes generated by the second photodiode to the second semiconductor region; The photoelectric conversion device according to claim 1, comprising:   A third transfer unit for transferring electrons generated by the first photodiode to an N-type semiconductor region different from the first semiconductor region; and holes generated by the second photodiode by the second semiconductor. The photoelectric conversion device according to claim 14, further comprising: a fourth transfer unit that transfers to a P-type semiconductor region different from the region.   A ranging apparatus comprising a light emitting device and the photoelectric conversion device according to claim 1, wherein the photoelectric conversion device receives light emitted by the light emitting device.   The distance measuring device according to claim 16, wherein the light emitting device repeats blinking.   An information processing system comprising: a distance measuring device including the photoelectric conversion device according to any one of claims 1 to 15; and an information processing device that processes information obtained from the distance measuring device.   The information processing system according to claim 18, wherein the information processing device displays information processed by the information processing device on a display device.   The information processing system according to claim 18, wherein the information processing device drives a drive device based on information processed by the information processing device.

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