JP6700687B2 - Photoelectric conversion device, range finder, and information processing system - Google Patents

Description

  The present technology relates to a photoelectric conversion device.

  A distance measuring device (distance sensor) using the 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 emitted from the light source for distance measurement and reflected from the object is referred to as signal light. However, the received light includes light (environmental light) caused by a light source different from the light source for distance measurement, such as natural light and artificial light, in addition to the signal light. It is effective to separate the ambient light and the signal light in order to improve the ranging accuracy.

  Patent Document 1 discloses that components corresponding to ambient light are removed in a device that performs distance measurement using a photodetector. In the second embodiment of Patent Document 1, a first photosensitive portion having a structure suitable for taking out holes and a second photosensitive portion having a structure suitable for taking out electrons are provided. The holes generated in the first photosensitive section are held in the hole holding section via the gate section, and the electrons generated in the second photosensitive section are held in the electron holding section via the gate section. The holes held in the hole holding unit and the electrons held in the electron holding unit are recombined in the recombination unit, and the carrier remaining after the recombination is taken out as the target carrier through the output unit.

JP 2005-303268 A

  The technique of Patent Document 1 does not sufficiently study the movement of electrons and holes when a photoelectric conversion unit (photosensitive unit) for holes and a photoelectric conversion unit (photosensitive unit) for electrons are used. Therefore, electrons and holes cannot be collected efficiently, and the accuracy of signals generated based on the electrons and holes may be low.

  Therefore, an object of the present invention is to provide a photoelectric conversion device that can improve the accuracy of signals generated based on electrons and holes.

  Means for solving the above-mentioned problems is a photoelectric conversion device, in which a first photodiode that produces electrons, a second photodiode that produces holes, and an electron produced by the first photodiode are collected. The N-type first semiconductor region, the P-type second semiconductor region that collects holes generated by the second photodiode, the first semiconductor region, and the second semiconductor region are commonly connected. A signal generation unit, a first potential supply unit that supplies a first potential to the anode of the first photodiode, and a second potential supply unit that supplies a second potential to the cathode of the second photodiode, The second potential is higher than the first potential.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion device which can raise the precision of the signal produced|generated based on an electron and a hole can be provided.

The schematic diagram explaining a photoelectric conversion device, a ranging device, and an information processing system. FIG. 3 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. 3 is a schematic diagram illustrating a structure of a photoelectric conversion device. FIG. 3 is a schematic diagram illustrating a structure of a photoelectric conversion device. FIG. 3 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. In the following description and drawings, common reference numerals are given to common configurations across a plurality of drawings. Therefore, common configurations will be described with reference to a plurality of drawings, and description of configurations with common reference numerals will be appropriately omitted.

  A photoelectric conversion device 11 and an information processing system SYS including the photoelectric conversion device 11 will be described with reference to FIG. The information processing system SYS includes the distance measuring device 1, and may further include at least one of the information processing device 2, the control device 3, the driving device 4, the imaging device 5, the display device 6, and the communication device 7. In the information processing system SYS, the photoelectric conversion device 11 is included in the distance measuring device 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 may 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 the light emitted from the light emitting device 21. As the light emitting device 21, a light emitting diode is preferable because it can repeat blinking at high speed. In addition, the emission wavelength of the light emitting device 21 is preferably infrared light in order to reduce color mixture with ambient light mainly containing visible light. Infrared rays have the advantage that they can be used comfortably because they are less visible to humans. However, this example is not limited to infrared light. The optical systems 12 and 22 include lenses, diaphragms, mechanical shutters, scattering plates, optical low-pass filters, wavelength selection filters, and the like. For example, the optical system 12 may include a filter having a higher transmittance of infrared light than visible light. Although the distance measuring device 1 shown in FIG. 1A uses the optical systems 12 and 22, at least one of the optical systems may be omitted. When a laser beam is used as the light source, the optical system 22 may include a scanning optical system for scanning the light emitted from the light emitting unit toward a predetermined area.

The light 81 emitted from the light emitting unit 20 is applied to the target object 9, is reflected by the target object 9 and is received by the light receiving unit 10 as the signal light 82. A difference occurs based on the distance from the distance measuring device 1 to the object 9 and the speed of light (3×10 ⁸ m/s) between the light emitting time of the light emitting unit 20 and the light receiving time of the light receiving unit 10. By detecting a physical quantity corresponding to the magnitude of this time difference, 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 can be displayed, for example, in an image. It can be obtained as data. As described above, the distance measuring device 1 is a distance measuring device using the TOF (Time Of Flight) method. The magnitude of the above-mentioned time difference 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 measuring algorithm becomes complicated. Therefore, it is preferable to set the distance between the light emitting unit 20 and the light receiving unit 10 shorter than the desired distance measuring accuracy. The distance 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 the 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. This ambient light 83 becomes a noise component when performing distance measurement. Therefore, when the ratio of the ambient light 83 to the amount of received light is high, the dynamic range of the signal due to the signal light 82 becomes small, or the S/N decreases, so that distance information can be obtained accurately from the signal light 82. It gets harder. The photoelectric conversion device 11 of the present embodiment is capable of removing at least a part of the component caused by the ambient light 83 from the signal generated by receiving light by the photoelectric conversion device 11. Therefore, it is possible to improve the distance measurement accuracy. Although described later in detail, in the present embodiment, at least a part of the component caused by the ambient light 83 is removed by using a signal according to the difference in the charge amount of the signal charges generated by the plurality of photoelectric conversion units. .. Then, by using electrons and holes as the signal charges, it is possible to accurately detect the difference in the amount of charges with a simple structure. This makes it possible to improve 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. Further, the photoelectric conversion device 11 may 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 driving unit 140 for each row via a row wiring 120 arranged on the semiconductor substrate 100. The drive unit 140 selectively inputs a drive signal such as a transfer signal or 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 for each column via a column wiring 130 arranged on the semiconductor substrate 100. The signal processing unit 160 processes the signal output from the photoelectric conversion cell 111 via the column wiring 130. The signal processing unit 160 can have a CDS circuit, an amplifier circuit, and an AD conversion circuit for each column of the cell array 110. The scanning unit 170 outputs the signal corresponding to each column, which is output from the cell array 110 to the signal processing unit 160 via each of the column wirings 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 the signal output from the signal processing unit 160 to the outside of the photoelectric conversion device 11, and may have an amplifier circuit, a protection circuit, and electrodes for connection with circuits outside the photoelectric conversion device 11. it can. The control unit 150 generates a control signal and controls the operation timings of the driving unit 140, the signal processing unit 160, the scanning unit 170, and the output unit 180 by 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 is obtained by setting the same side as the side (front side) where 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 is obtained by setting the side (back surface side) opposite to the side where the row wirings 120 and the column wirings 130 are provided to the semiconductor substrate 100 as the light incident surface side.

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

  The driving period Tdr of one photoelectric conversion cell 111 includes a reset period Trs for performing a reset operation, an accumulation period Tac for accumulating charges based on the signal light 82, and a reading for performing a signal reading operation based on the accumulated charges. And the period Tsr. Note that the reading period Tsr can also be referred to as a period in which output is performed from the photoelectric conversion cell to the column wiring. The driving period Tdr may 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 simultaneously driven within a single drive period Tdr. The 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 storage operation, and the read operation are performed in all the rows of the photoelectric conversion cells 111 included in the cell array 110. For example, the start point of the first frame period F1 is the time point when the reset operation of the first row R1 is started, and the end point of the first frame period F1 is the time point when the read operation of the photoelectric conversion cell 111 of the eighth row R8 is ended. Is. The starting point of the second frame period F2 is the time when the reset operation of the first row R1 first starts after the read operation of the first row R1 ends in the first frame period F1. The end point of the second frame period F2 is the time point 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, by performing the accumulation operation of a plurality of rows (three to four rows in this example) in parallel, the accumulation period can be extended and the output of the signal obtained during the accumulation period can be increased. . Even if the accumulating operation of a plurality of rows is performed in parallel, the signals of a plurality of rows can be separated by making the timing of the read operation of each row different.

  Further, as shown in FIG. 2, it is possible to improve the frame rate or extend one frame period 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. Becomes That is, in FIG. 2, the reset operation and the accumulation operation of the first row are started when the reading of the first to fourth rows is completed in the first frame period F1.

  Not limited to this example, the reset operation, accumulation operation, and read operation of the next row may be started after the reset operation, accumulation operation, and read operation for one row are all completed. Further, the reset operation of the first row (first row) may be started after the read operation of the last row (8th 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-shaped repeating unit are surrounded by chain lines, but some of the elements surrounded by dotted lines are arranged outside the cell array 110 (for example, the driving unit 140). To be 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. In other words, the photoelectric conversion unit 301 and the photoelectric conversion unit 302 have opposite signal charges. However, the photoelectric conversion unit 301 generates not only holes 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 of this example is a PN type or PIN type photodiode, and it is preferable to adopt an embedded type photodiode in order to reduce dark current. The use of 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, which is important in receiving a small amount of signal light. This is advantageous in improving N. The photodiode as the photoelectric conversion unit 301 has a cathode 201, which is an N-type semiconductor region in which electrons are majority carriers, and an anode 211, which is a P-type semiconductor region in which electrons are minority carriers. The photodiode serving as the photoelectric conversion unit 302 has an anode 202 which is a P-type semiconductor region having holes as majority carriers and a cathode 212 which is an N-type semiconductor region having holes as minority carriers.

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

  The capacity unit 307 has a reference node 217 and a collection node 207. Electrons as signal charges generated by the photoelectric conversion unit 301 are collected at the collection node 207. The capacitor portion 307 is configured such that a potential difference according to the amount of charge held in the capacitor portion 307 appears between the collection node 207 and the reference node 217. That is, the capacitor portion 307 functions as a charge-voltage converter that converts the amount of charge into a voltage. The capacitance unit 310 has a reference node 200 and a collection node 210. Holes as signal charges generated by the photoelectric conversion unit 302 are collected at the collection node 210. The capacitance section 310 is configured such that a potential difference according to the amount of charges held in the capacitance section 310 appears between the collection node 210 and the reference node 200. That is, the capacitor unit 310 functions as a charge-voltage converter that converts the amount of charge into a voltage.

  Each of the capacitors 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 holding the signal charges are floating nodes in an electrically floating state, and the semiconductor regions forming the collection nodes 207 and 210 are floating impurity diffusion regions, that is, floating diffusions. is there. Electrons as signal charges can be collected in the collection node 207, which is an N-type semiconductor region, and the electrons can be held in 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 signal charges are selectively retained in one of the collection node 207 and the collection node 210.

  The photoelectric conversion cell 111 includes a transfer unit 303 in order to efficiently collect electrons among the electrons and holes generated in the photoelectric conversion unit 301 in the collection node 207 of the capacitor 307. Similarly, the photoelectric conversion cell 111 includes a transfer unit 306 in order to efficiently collect holes among the electrons and holes generated in 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 the nodes to which the signal charges are transferred from the photoelectric conversion units 301 and 302, respectively. Since the charge transferred from the photoelectric conversion units 301 and 302 can be held in the collection nodes 207 and 210, 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 laminated 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. When the transfer unit 303 is in the ON state (conduction state), an N-type channel is formed in the semiconductor region by inversion, and in the transfer unit 306, the P-type channel is formed in the semiconductor region by inversion in the ON state. As described above, the transfer units 303 and 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. A transfer signal output unit 428 is connected to the transfer node 218, and the transfer signal TX1 is input from the transfer signal output unit 428 to the transfer node 218. The transfer units 303 and 306 have different conductivity types from each other and are configured to operate complementarily. That is, the transfer unit 306 is in the 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 while the transfer unit 303 is in the OFF state by the transfer signal TX1. Become.

  It is preferable that the transfer unit 303 and the transfer unit 306 have threshold values set so that both of them are turned off 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 in the ON state and the transfer unit 306 is at the OFF state and a potential at which the transfer unit 303 is in the OFF state and the transfer unit 306 is in the ON state. Such a predetermined potential is determined according to 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 in the ON state and the potential level Mid at which the transfer unit 303 is in the OFF state is, for example, 1V to 5V. The difference between the potential level Low at which the transfer unit 306 is in the ON state and the potential level Mid at which the transfer unit 303 is in the OFF state is, for example, 1V to 5V. It is preferable that the potential level High is set to a potential (positive potential) higher than the ground potential GND (0V) and the potential level Low is set 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.

  The transfer unit 303 and the transfer unit 306 can be connected to different transfer nodes, and the ON/OFF states of the transfer unit 303 and the transfer unit 306 can be controlled by transfer signals independent of each other. However, it is preferable that the transfer unit 303 and the transfer unit 306 are connected to the 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 so, the accuracy of the timing control of the ON/OFF state of the transfer unit 303 and the transfer unit 306 can be improved. Moreover, since the transfer units 303 and 306 can be driven by a common drive circuit or 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.

  The collection node 207 may be connected to the cathode 201 without an active element such as the transfer unit 303. Similarly, the collection node 210 can be connected to the anode 202 without an active element such as the transfer unit 306. For example, by setting the potentials of the photoelectric conversion unit 301 and the capacitance unit 307 in an appropriate relationship, the electrons generated in 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 capacitance unit 310 in an appropriate relationship, the holes generated in the photoelectric conversion unit 302 can be collected in the collection node 210 even if the transfer unit 306 is omitted. You can Furthermore, the photoelectric conversion unit 302 itself also functions as the capacitance unit 307 having a capacitance corresponding to the junction capacitance thereof, and the photoelectric conversion unit 302 itself also functions as the capacitance unit 310 having a capacitance corresponding to the junction capacitance thereof. You may comprise. For example, a high-concentration portion having an N-type impurity concentration higher than that of 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 a substitute for switching between transfer and non-transfer of the 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 are used. It is also possible to switch between non-discharge and discharge of electric charges. However, by switching the transfer and non-transfer of the charges by using the transfer units 303 and 306, it is possible to control the charges more accurately than in the case where 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 VF2 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 capacitance 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, although electrons are also generated in the photoelectric conversion unit 302, 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 capacitance unit 310 and the capacitance of the capacitance unit 310 appears at the collection node 210 and the detection node 220. As a result, the detection node 220 has a potential obtained by adding 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 of 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 (resistivity of 10 ⁻⁴ Ω·m or less). The insulator has a conductivity of 10 ⁻⁷ S/m or less (resistivity of 10 ⁷ Ω·m or more). The semiconductor also has a conductivity between 10 ⁻⁷ S/m and 10 ⁴ S/m (resistivity between 10 ⁻⁴ Ω·m and 10 ⁷ Ω·m). Examples of the conductor include metals, metal compounds, graphite and polycrystalline silicon. Further, it can be said that silicon with a high impurity concentration (10 ¹⁹ /cm ³ or more) also behaves like a conductor. Since the collection node 207 and the collection node 210 are connected by a conductor, the 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 settle can be shortened.

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

  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. In addition, 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 at the collecting node 207, it is preferable that VF1<VN1. Further, considering the ease of collecting the holes of the anode 202 of the photoelectric conversion unit 302 at the collection node 210, it is preferable that VN2<VF2. For VF1<VN1 and VN2<VF2, since VN1=VN2, VF1<VF2. As described above, the fact that the reference potential VF2 is higher than the reference potential VF1 (VF1<VF2) is more advantageous than the fact that the reference potential VF2 is equal to or less than the reference potential VF1 (VF1≧VF2) in improving the distance measurement accuracy. Is. By doing so, the charge collection efficiency is increased, and high-speed operation and highly accurate signal acquisition are possible. Practically, the potential difference between the reference potential VF1 and the reference potential VF2 is preferably 0.10 V or more. Therefore, in this example, the reference potential supply section 411 and the reference potential supply section 412 are separately provided. The potential difference between the reference potential VF1 and the reference potential VF2 is typically 1 V or more and 5 V or less. The reference potential VF1 may be lower than the ground potential GND (0V) (VF1<GND), and the reference potential VF2 may be 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 a 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 supply unit 426 connected to the gate of the selection transistor 316 outputs the selection signal SL to turn on the selection transistor 316. As a result, the signal generation unit 315 generates a pixel signal according to the potential of the detection node 220, and outputs this pixel signal to the output line 431 which is a part of the column wiring 130 in FIG. 1B.

  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 electric low-pass filter 433, even if the potential of the detection node 220 oscillates, the output from the signal generation unit 315 is stabilized and the distance measurement accuracy can be improved. The electrical low-pass filter 433 can be composed of a resistor connected in series to the gate of the amplification transistor and a capacitor connected in parallel to the gate, but the invention is not limited to this. Also, the electrical low-pass filter 433 can be omitted.

  A reset potential supply unit 413 is commonly connected to the collection node 207 and the collection node 210 via a MOS transistor (reset transistor) 313. The reset potential supply unit 413 outputs the 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 reset potential supply unit 413 supplies the potential VS12 corresponding to the reset potential VS1 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, the electrons held in the capacitor 307 are discharged to the reset potential supply unit 413. By supplying the potential VS12 to the collection node 210 of the capacitor 310, the holes held in the capacitor 310 are discharged to the reset potential supplier 413.

  The potential difference between the potential VS11 and the potential VS12 is less than 0.10 V, which is advantageous in improving the ranging accuracy, as compared with the potential difference between the potential VS11 and the potential VS12 being 0.10 V or more. Regarding the collection node 207 and the collection node 210 commonly connected to the detection node 220, the potential difference between the potential VS11 and the potential VS12 is set to less than 0.10 V to stabilize the operation in the accumulation period Tac after the reset period Trs. You can In order to make the potential difference between the potential VS11 and the potential VS12 less than 0.10 V, the collecting node 207 and the collecting node 210 may be connected with a conductor having high conductivity. Further, in order to reduce the potential difference between the potential VS11 and the potential VS12 to less than 0.10 V, a resistor such that the difference between the potential VS11 and the potential VS12 becomes 0.10 V or more between the collection node 207 and the collection node 210. It does not have to be placed. Note that a slight potential difference of less than 0.10 V can be tolerated due to inevitable resistance, manufacturing error, and the like.

  In this example, the potential VS11 is applied to the collecting node 207, and at the same time, the potential VS12 is applied to the collecting node 210. A switch 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. In that case, the timing of applying the potential VS11 to the collecting node 207 and the timing of applying the potential VS12 to the collecting node 210 can be different.

  The potential VS11 is preferably higher than the reference potential VF1 (VF1<VS11). By doing so, the collection efficiency of electrons at the collection node 207 after the reset period Trs can be improved. Further, the potential VS12 is preferably lower than the reference potential VF2 (VS12<VF2). By doing so, the collection efficiency of holes in the collection node 210 after the reset period Trs can be improved. If VS11=VS12=VS1 as described above, in order to satisfy VF1<VS11 and VS12<VF2, the reset potential VS1 should be a potential between the reference potential VF1 and the reference potential VF2 (VF1<VS1. <VF2) is preferred.

  The potential VS11 can be selected from the 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. The circuit may be designed so as to satisfy VF1<VS11 and VS12<VF2 within the preferable range of the reference potentials VF1 and VF2 and within the preferable range of the potentials VS11 and VS12.

  In the example of FIG. 3, the transfer unit 304 and the capacitance unit 308 are connected to the photoelectric conversion unit 301 similarly to the transfer unit 303 and the capacitance unit 307. That is, the transfer unit 303 and the capacitor unit 307 and 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 similarly to the transfer unit 306 and the capacitor unit 310. That is, the transfer unit 306 and 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. 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 provided 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 TX2 is input from the transfer signal output unit 429 to the transfer node 219. The transfer units 304 and 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) while the transfer unit 304 is in the ON state (conduction state) by the transfer signal TX2, and the transfer unit is in the OFF state during the transfer signal TX2. 305 is turned on. It is desirable that the transfer unit 304 and the transfer unit 305 have threshold values set so that both of them are turned off by setting the transfer node 219 to a predetermined potential. Such a predetermined potential is determined according to 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 in the ON state and the potential level Mid at which the transfer unit 304 is in the OFF state is, for example, 1V to 5V. The difference between the potential level Low at which the transfer unit 305 is in the ON state and the potential level Mid at which the transfer unit 305 is in the OFF state is, for example, 1V to 5V. It is preferable that the potential level High is set to a potential (positive potential) higher than the ground potential GND (0V) and the potential level Low is set 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. 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. Further, it is preferable that the transfer unit 303 and the transfer unit 304 connected to the photoelectric conversion unit 301 be operated so that the ON state and the OFF state are opposite to each other, that is, they are complementarily operated. That is, the transfer unit 304 is in the OFF state by the transfer signal TX2 while the transfer unit 303 is in the ON state by the transfer signal TX1. The transfer unit 304 is turned on by the transfer signal TX2 while the transfer unit 303 is turned off by the transfer signal TX1. Similarly, it is preferable that the transfer unit 305 and the transfer unit 306 connected to the photoelectric conversion unit 302 be operated so that the ON state and the OFF state are opposite to each other, that is, they are complementarily operated. That is, while 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. The transfer unit 305 is turned on by the transfer signal TX2 while the transfer unit 306 is turned off by the transfer signal TX1. By doing so, the signal charge from one photoelectric conversion unit can be transferred alternately between the 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 capacitors 308 and 309 has a PN junction type diode structure. The collecting node 208 of the capacitor 308 is an N-type semiconductor region, and the collecting node 209 of the capacitor 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. The reference potential supply unit 411 is connected to the reference node 228 to supply the reference potential VF1. The reference potential supply unit 412 is connected to the reference node 229 to supply the reference potential VF2.

  The collection potential 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 the 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 units to the collection nodes 208 and 209 in the capacitance units 308 and 309 are discharged. However, similarly to the signal generation unit 315, a signal generation unit may be connected to the capacitance units 308 and 309 so that a signal based on the charge of the capacitance units 308 and 309 is read. Then, in the case of such a configuration, the signal generated by the signal generation unit based on the charges of the capacitor units 308 and 309 and the signal generated by the signal generation unit based on the charges of the capacitor units 307 and 310 are used. It can also be synthesized. By doing so, it is possible to increase the intensity of the pixel signal.

  The potentials used in the circuits described above are illustrated. The ground potential GND is 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, 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 multiplied by T, 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. By combining the second example and the second example, the first example may be S(V) shifted and then multiplied by T. It is possible to appropriately adjust the actual value of the potential while maintaining the magnitude relationship of the potentials, the potential difference, and the magnitude difference of the potentials grasped from the respective potentials in the above-described three examples.

  Next, the operation of one photoelectric conversion cell 111 of the distance measuring apparatus 1 per drive time Tdr will be described with reference to FIG. Note that in the description using FIG. 4, the period p1 to the period p10 is a period from time t0 to time t10.

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

When the speed of light 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 suffices if the delay time from light emission to light reception can be detected 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 set to 10 ns, the distance difference of 0.3 m can be detected by detecting the physical quantity corresponding to this delay time within 10 ns. From the cycle Tcy and the number of times 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 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 rows can be read for 1000 frames per second, and if the driving period Tdr for one row is 10 ms, 100 rows for 1 frame can be read per second. You can

  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 time t2 after time Tda from the light emission start time t1 according to the distance from the distance measuring device 1 to the object, and at time t4 after time Tda from the light emission end time t3. Indicates that the light reception is finished. The waveform indicated by the light reception level Lr2 starts light reception at time t2′ after time Tdb from the light emission start time t1 according to the distance from the distance measuring device 1 to the object, and after time Tdb from the light emission end time t3. It indicates that the light reception is terminated at t4'. In this example, since Tda<Tdb, the signal light indicated by the light reception level Lr1 may be reflected by the object located 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, it can be seen that 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, 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 becomes the signal light having the actual distance information.

  FIG. 4B shows changes over time of the reset signals RS1 and RS2 (dotted line), the selection signal SL (solid line), the transfer signal TX1 (dashed line), and the transfer signal TX2 (dashed line). 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 potential. For example, the potential level Mid is a potential in a certain range including the ground potential (0V). In FIG. 4B, the potential of the portion where the horizontal axis indicating the time is located is the potential level Mid. Note that, in FIG. 4B, for convenience, it is considered that the transistor operates in the same manner as the potential level High at a transitional potential (rising potential or falling potential) between the potential level Mid and the potential level High. Explain. Similarly, a transitional potential (rising potential, falling potential) between the potential level Mid and the potential level High is assumed to operate in the same manner as the potential level Low and the potential level High. Note that the potential level in which the transistor is turned on and the potential level in which it is turned off do not have to be the same potential for each transistor, and may be different potentials.

  The reset signals RS1 and RS2 are at the potential level High at the same time, but the periods 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 of the same period with positive and negative inverted. It is preferable that the cycles of the transfer signals TX1 and TX2 match the cycle Tcy of light emission of 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 lowered. May be.

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

  In the periods p2, p3, p6, and p8 in which the transfer signal TX1 has a potential 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 the periods p4, p5, p7, and p9 in which the transfer signal TX1 has a potential lower than the potential level Mid (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 to when one of the transfer unit 303 and the transfer unit 306 is turned ON is as short as possible.

  The potential of the transfer signal TX2 is lower than the potential level Mid (typically, during the periods p2, p3, p6, and p8 in which the potential level is Low, the transfer unit 305 is in the ON state and the transfer unit 304 is in the OFF state. Transfer signal TX2 The transfer unit 305 is in the OFF state and the transfer unit 304 is in the ON state during periods p4, p5, p7, and p9 in which is higher than the potential level Mid (typically, the potential level High). It is preferable that the time from the change from the ON state to the OFF state to the ON state of one of the transfer units 304 and 305 is as short as possible.

  During the period (or time) when the transfer signal TX1 is at the potential level Mid, the transfer units 303 and 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 set. Also, the transfer unit 304 is in the 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 changes in the potential of the detection node 220. The potential change S1 shows a change in potential due to the light receiving level Lr1, and the potential change S2 shows a change in potential according to the light receiving level Lr2.

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

  In the period p2, the 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 in 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. The reset potential VS1 causes the potential of the collection node 207 to be higher than the potential of the anode 211 (VF1<VS1). Therefore, when the transfer unit 303 is in the ON state, the generated electrons quickly move to the collection node 207 whose potential is higher than that 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 p3, the electrons generated by the photoelectric conversion unit 301 according to the light amount Lra containing the signal light 82, which is stronger than the light amount Lam of the ambient light 83, are transferred to the capacitor unit 307. With the transfer of electrons, the potential of the detection node 220 connected to the collection node 207 decreases with a larger gradient than that in 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 p4, the holes generated in 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 rises.

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

  In the period p5, the holes generated in the photoelectric conversion unit 302 according to the light amount Lam of the ambient light 83 are transferred to the capacitor unit 310. With the transfer of holes, the potential of the detection node 220 connected to the collection node 210 rises.

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

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

  The light reception level Lr1 has a delay time Tda of 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 becomes lower than the reset potential VS1 (absolute value becomes larger). When the delay time Tdb is ¼ of the cycle Tcy (Tdb=Tcy/4) like 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 becomes equal to the reset potential VS1. If the delay time Tda>T/cy4, the potential of the detection node 220 is effectively dominated by the holes transferred during the period p4, and the potential of the detection node 220 becomes higher than the reset potential VS1 (the absolute value is large. Become).

  Although the lighting period and the extinguishing period of the light emitting device 21 in one cycle Tcy are equalized here, the lighting period and the extinguishing period may be different. When the lighting period and the extinguishing period are different from each other, the signal output from the signal generation unit 315 may be corrected based on the difference between the lighting period and the extinguishing period. Further, although the ON and OFF periods of the transfer gate in one cycle Tcy are equalized here, even if the ON period and the OFF period are different, the output from the signal generation unit 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 the signal charge, the component due to the ambient light 83 is (−N), the component due to the signal light 82 is (−S), and the amount of the hole as the signal charge is the ambient light. The component caused by 83 is (+N), and the component caused by the signal light 82 is (+S). The coefficient proportional to the length of the period p2 is a, the coefficient proportional to the length of the period p3 is b, the coefficient proportional to the length of the period p4 is c, and the coefficient proportional to the length of the period p5 is d.

  First, assuming that recombination of electrons and holes at the detection node 220 does not occur, the charge amounts of the collection nodes 207 and 210 are calculated. 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 collecting node 210 in the period p2 is 0, and the charge amount of the collecting 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 increment of the charge amount of the collection node 210 in the period p3 is 0, and the charge amount of the collection node 210 at the 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*(-NS). The increment of the charge amount of the collecting node 210 in the period p4 is c×(+N+S), while the charge amount of the collecting node 210 at the time t4 is c×(+N+S). The increment of the charge amount of the collecting node 207 in the period p5 is 0, and the charge amount of the collecting node 210 at the 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 the time t5 corresponds to a value obtained by subtracting electrons and holes. That is, a*(-N)+b*(-NS)+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, in the period from time t1 to t5, if the ambient light 83 is constant and the transfer unit 303 and the transfer unit 306 are in the complementary ON state at the same time, (c+d) -(A+b)=0. Therefore, at the time t5, at least a part of the component of the ambient light 83 is removed from the potential appearing at the detection node 220, and (c−b)×S indicating only the component of the signal light 82 can be 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 sectional view taken along the line AA′ in FIG. 5A, FIG. 5C is a schematic sectional view taken along the line BB′ in FIG. 5A, and FIG. It is a cross-sectional schematic diagram in line CC' of FIG. 5 [a].

  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. It should be noted that a plurality of portions forming the single semiconductor regions 511 and 512 have the same conductivity type and are continuous with each other. The plurality of portions here are portions having different positions in at least one of the X, Y, and Z directions. The impurity concentrations of a plurality of portions forming 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. The direction in which the photoelectric conversion units 301 and 302 are arranged is the X direction, the direction parallel to the surface 1000 and perpendicular to the X direction is the Y direction, and the direction perpendicular to the surface 1000 is the Z direction.

  As a structure different from the structure shown in FIG. 5, the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be arranged in the Z direction. That is, one of the photoelectric conversion portion 301 and the photoelectric conversion portion 302 can be arranged at a position deeper in 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. Then, between these, the anode of the photoelectric conversion unit 301 (P-type semiconductor region) and the cathode of the photoelectric conversion unit 302 (N-type semiconductor region) 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, the signal of the photoelectric conversion section 302 arranged at a deep position via the charge transfer path. The charge can be collected. However, in this case, the amount of light that is photoelectrically converted differs between the photoelectric conversion unit arranged in the shallow position and the photoelectric conversion unit arranged in the deep position, and a large difference occurs in the generated signal charge amount. This is because the light is attenuated due to the absorption of the light in the semiconductor substrate 100. Therefore, in order to reduce the difference in the amount of light received between the photoelectric conversion unit 301 and the photoelectric conversion unit 302, it is preferable to arrange the photoelectric conversion unit 301 and the photoelectric conversion unit 302 along the main surface 1000 of the semiconductor substrate 100.

  In FIG. 5, thick lines are local wirings arranged in the photoelectric conversion cell 111. In addition, a circle mark indicates the position of a contact portion for connecting the local wiring or the global wiring (not shown) such as the row wiring 120 and the column wiring 130 described in FIG. 1B to the semiconductor substrate 100. . In a typical contact portion, the contact plug and the semiconductor substrate 100 are joined together. Here, the local wiring is a wiring for electrically connecting the constituent elements in the photoelectric conversion cell 111. On the other hand, the global wiring is a wiring for connecting between 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. In the contact portion for connecting to the semiconductor region, a region of the semiconductor region, which is connected to a conductor such as a contact plug, is a high-concentration impurity region as compared with other regions, so that good electrical connection can be achieved. Is preferably ensured.

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

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

  As shown in FIG. 5A, 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 in the X direction. There is. The gate electrode 515 of the amplification transistor forming 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 the electrical low pass filter 433.

  The N-type semiconductor region 507 constitutes the collection node 207 as a 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 the reference node 217 of the capacitor portion 307.

  The P-type semiconductor region 510 constitutes the collection node 210 as a part of the capacitor 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 310.

  The N-type semiconductor region 501 constitutes the 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 the 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. This makes it difficult for the photoelectric conversion unit 301 to accumulate electrons generated as signal charges in the electron-hole pairs generated in the photoelectric conversion unit 301. By doing so, the efficiency of electron transfer from the photoelectric conversion unit 301 to the semiconductor region 507 is improved. 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 not used as signal charges in the photoelectric conversion portion 301 are discharged through the P-type semiconductor region 511. A surface region that 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 apart from the surface 1000. As a result, the photoelectric conversion unit 301 becomes an embedded photodiode. Note that in FIG. 5, the P-type semiconductor region as the surface region is integrally shown as the P-type semiconductor region 511.

  The P-type semiconductor region 502 constitutes 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. This makes it difficult for the photoelectric conversion unit 302 to accumulate holes generated as signal charges in the electron-hole pairs generated in the photoelectric conversion unit 302. By doing so, the efficiency of transfer of holes from the photoelectric conversion unit 302 to the semiconductor region 510 is improved. In addition, the electrons generated by light can always be completely transferred to the semiconductor region 510, and noise due to low transfer efficiency can be reduced. Note that holes that are not used as signal charges in the photoelectric conversion portion 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 arranged apart from the surface 1000. As a result, the photoelectric conversion unit 302 becomes an embedded photodiode. In FIG. 5, the N-type semiconductor region as the surface region is integrally shown as the 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 constitutes the collecting 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 constitutes the collecting node 209 as a part of the capacitor portion 309. The N-type semiconductor region 501 and the P-type semiconductor region 502 are provided side by side in the X direction along the surface 1000. 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).

  The reference potential VF1 is supplied to the semiconductor region 511 from the contact plug 611 forming the reference potential supply unit 411. Then, the reference potential VF2 is supplied to the semiconductor region 512 from the contact plug 612 forming the reference potential supply unit 412. Since the reference potential VF1 is lower than the reference potential VF2, the 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 the depletion layer generated between the semiconductor region 511 and the semiconductor region 512. By doing so, the electrons generated in the N-type semiconductor region 501 and the holes generated in the P-type semiconductor region 502 can be electrically separated. Therefore, it is possible to collect charges at the corresponding collection node at an appropriate timing and selectively recombine the signal charges necessary for distance measurement. By separating the photoelectric conversion unit 301 and the photoelectric conversion unit 302 by the PN junction separation, the distance between the photoelectric conversion unit 301 and the photoelectric conversion unit 302 can be reduced (for example, less than 1 μm). The difference in the amount of light received by the conversion unit 301 and the photoelectric conversion unit 302 can be reduced. Further, the PN junction isolation can suppress the generation of dark current as compared with the insulator isolation.

  In the cell array 110, the structure shown in FIG. 5A is arranged in a matrix. The P-type semiconductor region 512 is continuously arranged among 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 P-type semiconductor region 512 by a separating means such as a PN junction separation, and the N-type semiconductor region 511 of at least one adjacent photoelectric conversion cell 111 is separated. Can be electrically separated from. Note that, conversely to the example described above, the P-type semiconductor region 512 may be an isolated well and the N-type semiconductor region 511 may be a common well. Thus, 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, which has at least a portion disposed between the N-type semiconductor region 501 and the N-type semiconductor region 507 in plan view, constitutes the transfer unit 303. In this example, the transfer gate electrode 503 is located on a part of the semiconductor region 501 and a part of the semiconductor region 507. The transfer gate electrode 504, which has 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 a part of the semiconductor region 502 and a part of the semiconductor region 508.

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

  An insulating film 500 is provided between the transfer gate electrodes 503, 504, 505, 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 electric charge each time it is driven, a current corresponding to the MOS capacitance flows each time it is switched. When driving at high speed, the smaller the gate electrode of the transistor is, the smaller the MOS capacitance is, so that the current is small and the power is saved. 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 may be provided as an integrated gate electrode having a portion forming the transfer portion 303 and a portion forming the transfer portion 305. By doing so, it is possible to increase the precision of complementary control of the transfer units 303 and 305 by reducing wiring and reducing wiring capacitance and resistance. In addition, the aperture ratio can be increased and the sensitivity can be improved by reducing the wiring. 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 regions 507 and 510 via 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 the reset signal output section 423 outside the cell array via a contact plug, a local wiring and a 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 the reset potential supply unit 413 outside the cell array via the global wiring. Similarly, a reset transistor having a gate electrode 514 is connected to the semiconductor regions 508 and 509 via 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 via 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 via the contact plug and the 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) via a contact plug.

  A contact plug 611 is connected to the semiconductor region 511. The contact plug 611 is connected to the reference potential supply unit 411 outside the cell array 110 via the global wiring. A contact plug 612 is connected to the semiconductor region 512. The contact plug 612 is connected to the reference potential supply unit 412 outside the cell array 110 via the global wiring. In this manner, by supplying the reference potential to the semiconductor regions 511 and 512 through the wiring, variation in the reference potential in each photoelectric conversion cell 111 in the cell array 110 can be reduced. It is also possible to supply the reference potential without disposing the contact plug 611 or the contact plug 612 in the photoelectric conversion cell 111. In that case, the impurity diffusion layer extending from the inside of the cell array 110 to the outside of the cell array 110 may be provided on the semiconductor substrate 100, and the 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 through the conductor such as the global wiring, the local wiring, and the contact plug arranged on the semiconductor substrate 100. 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 via a conductor. In this example, conductors that connect the semiconductor region 507 and the semiconductor region 510 to each other are shown as the local wiring 620 and the contact plugs 607 and 610. A conductor connecting the semiconductor region 507 and the semiconductor region 510 is made of a material having higher electric conductivity than the semiconductor substrate 100, such as a metal material, a metal compound material, or polycrystalline silicon. Metallic materials and metallic 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. Since the semiconductor region 507 and the semiconductor region 510 are thus connected via the conductor, the semiconductor region 507 and the semiconductor region 510 can be connected without the PN junction. Typically, the semiconductor region 507 and the semiconductor region 510 can be connected to each other through an ohmic junction. By connecting the semiconductor region 507 and the semiconductor region 510 via a conductor, 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 the electrons and holes are recombined can be shortened. As a result, it is possible to stabilize the output of the detection node 220 and realize highly accurate distance measurement.

  FIG. 6 illustrates a structure for obtaining an electrical connection between the semiconductor region 507 and the semiconductor region 510. FIGS. 6A to 6D correspond to the cross section including the transfer gate electrodes 503 and 505 and the semiconductor regions 507 and 510 in FIG. 5A. FIG. 6A shows a structure for obtaining electrical connection between the semiconductor region 507 and the semiconductor region 510 in FIG. 6B to 6D show a mode different from the mode shown in FIG. 6A for obtaining the electrical connection between the semiconductor region 507 and the semiconductor region 510. Note that in FIGS. 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 contacts the contact plug 603 on the transfer gate electrode 503, the contact plug 605 on the transfer gate electrode 505, and 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 arranged on the interlayer insulating film 526. Note that 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 containing copper as a main component 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. The other local wirings are also 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 connecting 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. The contact plugs 607 and 610 have a conductive portion containing tungsten as a main component and a barrier metal portion having a titanium layer and/or a titanium nitride layer, which is arranged between the conductive portion and the interlayer insulating film 526. Local wiring 620 is 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, which is located between the conductive portion and 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, which is 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 via the contact plug 623 which is a conductor that contacts both the semiconductor region 507 and the semiconductor region 510. The contact plug 623 has a conductive portion containing tungsten as a main component and a barrier metal portion including a titanium layer and/or a titanium nitride layer, which is arranged between the conductive portion and the interlayer insulating film 526. An insulating film 527 is provided between the contact plug 623 and the semiconductor substrate 100 separately from the insulating film 500 and the interlayer insulating film 526. The insulating film 527 insulates the contact plug 623 and the N-type semiconductor region 511, and insulates the contact plug 623 and the P-type semiconductor region 512. This can prevent 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 via the local wiring 624, which is a conductor that contacts 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 between the local wiring 624 and the semiconductor substrate 100 separately from the insulating film 500 and the interlayer insulating film 526. 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. This can prevent conduction between the N-type semiconductor region 511 and the P-type semiconductor region 512.

  In the configuration of FIG. 6D, the semiconductor region 507 and the semiconductor region 510 are connected via the 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 to insulate the local wiring 625 from the N-type semiconductor region 511 and between the local wiring 625 and the P-type semiconductor region 512. There is.

  Each of the local wirings and the global wirings 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 modified example of the equivalent circuit of the photoelectric conversion cell 111 described with reference to FIG. 3 will be described with reference to FIG. 7.

  The collection node 207 of the capacitor unit 307 is connected to the detection node 220 via the switch transistor 318. By turning on the switch transistor 318 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 capacitance section 310 is connected to the detection node 220 via the switch transistor 319. By turning on the switch transistor 319 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. Thus, in this example, it is possible to switch ON/OFF of the electrical connection between the collection node 207 and the collection node 210. 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.

  The reset potential supply unit 413 is connected to the collection node 207 of the capacitor unit 307 via the reset transistor 313. The reset signal RS1 output from the reset signal output unit 423 turns on the reset transistor 313. As a result, the reset potential VS1 is supplied from the reset potential supply unit 413 to the collection node 207 of the capacitor unit 307. The reset potential supply unit 417 is connected to the collection node 210 of the capacitance unit 310 via the 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 capacitance 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 preferably 0 V, but there may be a slight potential difference of less than 0.10 V due to unavoidable resistance, manufacturing error, and the like. It is preferable that the reset potential VS3 and the reset potential VS3 be a potential between the reference potential VF1 and the reference potential VF2. For example, the reset potential VS1 can be set higher than the reference potential VF1 (VF1<VS1). The reset potential VS3 can be 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 VS1 to the capacitor portion 307, the 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, the 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 charges (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 is set. It can be read selectively. By realizing such an operation mode, it is possible to obtain the photoelectric conversion device 11 capable of performing both imaging and distance measurement.

  Further, in this example, it is also possible to omit the capacitors 308 and 309 and employ a configuration in which unnecessary charges can be promptly discharged by turning ON/OFF the transfer units 304 and 305. By doing so, it is possible to increase the aperture ratio due to the wiring and the area of the photoelectric conversion portion, and improve the sensitivity.

  FIG. 8 shows an example of the operation of the circuit shown in FIG. Between the accumulation period Tac and the read period Tsr shown in FIGS. 3 and 4, there are a read period Tnr for reading the ambient light 83 and a removal period Tcl for removing a component of the ambient light 83. During the accumulation period Tac after the reset period Trs, 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 kept off. As a result, the signal of the detection node 220 at which the potential corresponding to the potential of the collection node 207 appears is read. After the read-out period Tnr, there is a removal period Tcl for removing at least part of the components of the ambient light 83. In the removal period Tcl, the selection transistor 316 is turned off and the switch transistors 318 and 319 in FIG. 7 are turned on. As a result, the components of the ambient light 83 are canceled by the electrons and the holes due to the recombination of the electrons and the holes. Then, the potential from which the component of the ambient light 83 has been removed appears at the detection node 220. In the read period Tsr, the selection transistor 316 is turned on to read the signal from which the component of the ambient light 83 has been removed. By reading out the ambient light 83 in this manner, 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.

  A 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 to the information processing device 2 a signal including the distance information to the object 9 which is a subject. The information processing device 2 processes the signal and generates a drive signal for driving mechanical parts such as a lens, a diaphragm, and a shutter so that the condition suitable for photographing the target 9 is obtained. Then, this drive signal is output to the drive device 4 such as a motor for driving the lens, diaphragm, shutter, and the like. The drive device 4 drives the above-mentioned mechanical component based on the drive signal. When the control device 3 sends a signal for instructing the information processing device 2 to perform imaging, the information processing device 2 instructs the imaging device 5 to perform imaging, and the imaging device 5 performs imaging of the target object 9. The information processing device 2 displays the image obtained from the imaging device 5 on the display device 6. The information processing device 2 can add distance information to the obtained image and display it on the display device 6. In addition, the communication device 7 communicates with the storage device or the network and stores the image in the storage device or the storage on the network.

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

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

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

  As described above, the photoelectric conversion device 11 according to the present embodiment includes the first photodiode (photoelectric conversion unit 301) that generates electrons, the second photodiode (photoelectric conversion unit 301) that generates holes, and Equipped with. Furthermore, the N-type first semiconductor region 507 that collects the electrons generated by the first photodiode (photoelectric conversion unit 301) and the P that collects the holes generated by the second photodiode (photoelectric conversion unit 302). Second semiconductor region 510 of the mold. Further, the signal generation unit 315 is commonly connected to the first semiconductor region 507 and the second semiconductor region 510. Further, a reference potential supply unit 411 that supplies the reference potential VF1 to the anode 211 of the first photodiode (photoelectric conversion unit 301) and a reference potential VF2 that supplies the reference potential VF2 to the cathode 212 of the second photodiode (photoelectric conversion unit 302). And a potential supply unit 412. The reference potential VF2 is higher than the reference potential VF1. Such a photoelectric conversion device can accurately obtain signals based on electrons and holes.

  The photoelectric conversion device is not limited to the example described above, and can be applied to various information processing systems SYS. Further, 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. Not limited to the above driving, driving may be performed for purposes other than distance measurement. For example, it is possible to perform edge detection for detecting the contour of an object such as a human face, focus detection by a phase difference detection method, or distance measurement using a signal corresponding to the difference in signal charges of a plurality of photoelectric conversion units. This is because it is possible to detect the difference in the amount of light received by the plurality of photoelectric conversion units, depending on the magnitude of the signal output from the signal generation unit according to the difference in signal charge. Generally, a complicated structure such as a differential circuit is required to obtain a difference between electric signals after converting the signal charges into an electric signal by a signal generation unit such as a source follower circuit. However, the photoelectric conversion device of the present embodiment can easily obtain the difference in signal charge between a plurality of photoelectric conversion units by recombination of electrons and holes. Then, 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, a signal corresponding to the difference between the signal charges of the plurality of photoelectric conversion units can be obtained. Note that by providing a switch transistor between the collection node and the detection node as in the form shown in FIG. 7, each of the plurality of photoelectric conversion units corresponds to an original signal charge that is not a signal corresponding to the difference. It is also possible to read the signal separately from the signal according to the difference. Thereby, the imaging operation can be performed.

301 photoelectric conversion unit 302 photoelectric conversion unit 507 semiconductor region 510 semiconductor region 315 signal generation unit 411 reference potential supply unit 412 reference potential supply unit

Claims (25)

A first photodiode that produces 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 commonly connected;
A first potential supply unit that supplies a first potential to the anode of the first photodiode;
A second potential supply unit that supplies a second potential to the cathode of the second photodiode,
The second potential is higher than the first potential,
The photoelectric conversion device, wherein the difference between the first potential and the second potential is 0.10 V or more. A first photodiode that produces 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 commonly connected;
A first potential supply unit that supplies a first potential to the anode of the first photodiode;
A second potential supply unit that supplies a second potential to the cathode of the second photodiode,
The second potential is higher than the first potential,
The photoelectric conversion device, wherein the first potential is lower than the ground potential and the second potential is higher than the ground potential. A potential supply unit that supplies a third potential to the first semiconductor region and a fourth potential to the second semiconductor region,
The photoelectric conversion device according to claim 1, wherein the third potential and the fourth potential are potentials between the first potential and the second potential.   The photoelectric conversion device according to claim 3, wherein the difference between the third potential and the fourth potential is less than 0.10 V, and the difference between the first potential and the second potential is 1 V or more and 5 V or less. A P-type third semiconductor region forming a PN junction with the first semiconductor region,
An N-type fourth semiconductor region forming a PN junction with the second semiconductor region,
The first potential supply section is connected to the third semiconductor region,
The photoelectric conversion device according to claim 1, wherein the second potential supply unit is connected to the fourth semiconductor region.   The first semiconductor region and the second semiconductor region are connected to the signal generation unit so that the difference between the potential of the first semiconductor region and the potential of the second semiconductor region is set to less than 0.10V. The photoelectric conversion device according to any one of claims 1 to 5.   The photoelectric conversion device according to any one of claims 1 to 6, wherein the first semiconductor region and the second semiconductor region are connected via a conductor.   A first transfer unit that transfers the electrons generated by the first photodiode to the first semiconductor region; and a second transfer unit that transfers the holes generated by the second photodiode to the second semiconductor region. The photoelectric conversion device according to any one of claims 1 to 7, further comprising:   The photoelectric conversion device according to claim 8, wherein the first transfer unit and the second transfer unit are connected to a common node. By supplying a certain potential to the node, the first transfer unit is turned on and the second transfer unit is turned off, and a potential different from the certain potential is supplied to the node. The photoelectric conversion device according to claim 9 , wherein the first transfer unit is in an OFF state and the second transfer unit is in an ON state.   The photoelectric conversion device according to claim 10, wherein the certain potential is higher than a ground potential and the another potential is lower than the ground potential.   A third transfer unit that transfers electrons generated by the first photodiode to an N-type fifth semiconductor region different from the first semiconductor region, and holes generated by the second photodiode by the third transfer unit. The photoelectric conversion device according to claim 8, further comprising: a fourth transfer unit that transfers the second semiconductor region to a P-type sixth semiconductor region different from the second semiconductor region.   The cathode of the first photodiode is located between the first semiconductor region and the fifth semiconductor region, and the anode of the second photodiode is located between the second semiconductor region and the sixth semiconductor region. The photoelectric conversion device according to claim 12, wherein the fifth semiconductor region and the sixth semiconductor region are connected to each other via a conductor.   Second signal generation in which the fifth semiconductor region and the sixth semiconductor region are commonly connected, with the signal generation unit in which the first semiconductor region and the second semiconductor region are commonly connected as a first signal generation unit 14. The photoelectric conversion device according to claim 12, further comprising a unit, and combining the signal generated by the first signal generation unit and the signal generated by the second signal generation unit.   The P-type seventh semiconductor region forming the anode of the first photodiode and the N-type eighth semiconductor region forming the cathode of the second photodiode form a PN junction, and the first semiconductor region is formed. The photoelectric conversion device according to claim 1, wherein a reverse bias voltage is applied between the second semiconductor region and the eighth semiconductor region.   16. The signal generation unit according to claim 1, wherein the signal generation unit includes a transistor forming 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 items.   The photoelectric conversion device according to claim 1, wherein the first semiconductor region is connected to the signal generating unit via an electrical low pass filter.   18. 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. The semiconductor substrate on which the first photodiode and the second photodiode are arranged has a surface,
The cathode of the first photodiode and the anode of the second photodiode are aligned in the first direction along the surface,
The cathode and the first semiconductor region of the first photodiode are aligned in a second direction along the surface,
The anode of the second photodiode and the second semiconductor region are aligned in a third direction along the surface,
The photoelectric conversion device according to any one of claims 1 to 18, wherein the second direction and the third direction are perpendicular to the first direction. The photoelectric conversion device according to any one of claims 1 to 19, wherein cells including the first photodiode , the first semiconductor region, the second photodiode, and the second semiconductor region are arranged in a matrix. .   A distance measuring device comprising a light emitting device and the photoelectric conversion device according to claim 1, wherein the photoelectric conversion device receives light emitted from the light emitting device.   The distance measuring apparatus according to claim 21, wherein the light emitting device repeats blinking.   An information processing system comprising: a distance measuring device including the photoelectric conversion device according to claim 1; and an information processing device that processes information obtained from the distance measuring device.   The information processing system according to claim 23, wherein the information processing device displays information processed by the information processing device on a display device.   The information processing system according to claim 23, wherein the information processing device drives a drive device based on information processed by the information processing device.

Images