Distance measuring device and driving method of distance measuring sensor

Abstract

In the distance measuring device of the present invention, the control unit performs charge distribution processing, wherein charge transfer signals having different phases from each other are applied to the first transfer gate electrode and the second transfer gate electrode. During a first period, the charge generated in the charge generation region is transferred to the first charge storage region, and during a second period, the charge generated in the charge generation region is transferred to the second charge storage region. The control unit, during the first period, applies a potential to the first overflow gate electrode such that the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region, and during the second period, applies a potential to the second overflow gate electrode such that the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region.

Description

Technical Field

[0001] One aspect of the present disclosure relates to a distance measuring device including a distance measuring sensor and a method for driving the distance measuring sensor. Background Art

[0002] As a distance measuring device that measures the distance to an object using an indirect TOF (Time Of Flight) method, there is known a distance measuring sensor (for example, refer to Patent Document 1) including: a charge generation region, a pair of transfer gate electrodes, and a pair of charge storage regions that store charges transferred from the charge generation region through the pair of transfer gate electrodes. In such a distance measuring device, transfer signals having different phases from each other are applied to the pair of transfer gate electrodes, and charges generated in the charge generation region by the incidence of light are distributed between the pair of charge storage regions. Then, the distance to the object is calculated based on the amounts of charges stored in the pair of charge storage regions.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-133464 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] In the above-described distance measuring device, in order to suppress the saturation of the storage capacity, it is possible to consider providing an additional charge storage region (hereinafter, also referred to as an “overflow region”) and storing the charges that overflow from the charge storage region in the overflow region. However, simply adopting such a structure, when the charges are stored in the charge storage region to the extent that they overflow to the overflow region, a part of the charges remains in the charge generation region. In this case, the accuracy of distance measurement may be reduced due to the charges remaining in the charge storage region.

[0008] An object of one aspect of the present disclosure is to provide a distance measuring device and a method for driving a distance measuring sensor that can improve the accuracy of distance measurement.

[0009] Technical Means for Solving the Problem

[0010] A distance measurement device according to an aspect of the present disclosure includes: a distance measurement sensor; and a control unit that controls the distance measurement sensor. The distance measurement sensor has: a charge generation region that generates charges according to incident light; a first charge storage region; a first overflow region; a second charge storage region; a second overflow region; a first transfer gate electrode disposed on a region between the charge generation region and the first charge storage region; a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region; a second transfer gate electrode disposed on a region between the charge generation region and the second charge storage region; and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region. The control unit performs a charge distribution process, in which charge transfer signals having different phases from each other are applied to the first transfer gate electrode and the second transfer gate electrode. During a first period, a potential is applied to the first transfer gate electrode such that the potential of the region directly below the first transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the first charge storage region. During a second period, a potential is applied to the second transfer gate electrode such that the potential of the region directly below the second transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the second charge storage region. During the first period, a potential is applied to the first overflow gate electrode such that the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region. During the second period, a potential is applied to the second overflow gate electrode such that the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region.

[0011] In this distance measurement device, the distance measurement sensor has: a first overflow region, a second overflow region, a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region, and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region. Thereby, the charges overflowing from the first charge storage region can be stored in the first overflow region, and the charges overflowing from the second charge storage region can be stored in the second overflow region. As a result, saturation of the storage capacity can be suppressed. In addition, during the first period of the charge distribution process, the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region, and during the second period of the charge distribution process, the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region. Thereby, even when the charges are stored in the first charge storage region to the extent of overflowing to the first overflow region and when the charges are stored in the second charge storage region to the extent of overflowing to the second overflow region, it is possible to suppress the charges from remaining in the charge generation region. Therefore, according to this distance measurement device, the accuracy of distance measurement can be improved.

[0012] Alternatively, the charge generation region may include an avalanche multiplication region. In this case, avalanche multiplication can be induced in the charge generation region, and the detection sensitivity of the distance measurement sensor can be improved. On the other hand, when the charge generation region includes an avalanche multiplication region, an extremely large amount of charge is generated. In this distance measurement device, even in such a case, saturation of the storage capacity can be sufficiently suppressed, and the remaining charge in the charge generation region can be sufficiently suppressed.

[0013] Alternatively, the control unit performs: a first reading process of reading the amounts of charge stored in the first charge storage region and the second charge storage region after the charge distribution process; a charge transfer process of, after the first reading process, applying a potential to the first overflow gate electrode in such a way that the potential of the region directly below the first overflow gate electrode is decreased, thereby transferring the charge stored in the first charge storage region to the first overflow region, and applying a potential to the second overflow gate electrode in such a way that the potential of the region directly below the second overflow gate electrode is decreased, thereby transferring the charge stored in the second charge storage region to the second overflow region; and a second reading process of, after the charge transfer process, reading the amounts of charge stored in the first charge storage region and the first overflow region, and reading the amounts of charge stored in the second charge storage region and the second overflow region. In this case, not only the amounts of charge stored in the first and second charge storage regions are read in the first reading process, but also the amounts of charge stored in the first charge storage region and the first overflow region and the amounts of charge stored in the second charge storage region and the second overflow region are read in the second reading process. Therefore, the detection accuracy of the amount of charge can be improved. In addition, the reading of the amounts of charge stored in the first charge storage region and the first overflow region and the reading of the amounts of charge stored in the second charge storage region and the second overflow region may be performed sequentially or simultaneously (as a single process).

[0014] Alternatively, the distance measurement sensor further includes: an excess charge discharge region; and an excess charge transfer gate electrode disposed in a region between the charge generation region and the excess charge discharge region. The control unit performs an excess charge transfer process during a period other than the first period and the second period, in which a potential is applied to the excess charge transfer gate electrode in such a way that the potential of the region directly below the excess charge transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charge generated in the charge generation region to the excess charge discharge region. In this case, the charge generated in the charge generation region during a period other than the first period and the second period can be transferred to the excess charge discharge region, and the remaining charge in the charge generation region can be further suppressed.

[0015] Alternatively, the ranging sensor may further include: a third charge storage region; a third overflow region; a fourth charge storage region; a fourth overflow region; a third transfer gate electrode disposed over a region between the charge generation region and the third charge storage region; a third overflow gate electrode disposed over a region between the third charge storage region and the third overflow region; a fourth transfer gate electrode disposed over a region between the charge generation region and the fourth charge storage region; and a fourth overflow gate electrode disposed over a region between the fourth charge storage region and the fourth overflow region. During the charge distribution process, the control unit applies charge transfer signals having different phases to the first transfer gate electrode, the second transfer gate electrode, the third transfer gate electrode, and the fourth transfer gate electrode. During the third period, the potential of the region directly below the third transfer gate electrode is made lower than the potential of the charge generation region, and the potential is applied to the third transfer gate electrode, so that the charge generated in the charge generation region is transferred to the third charge storage region. During the fourth period, the potential of the region directly below the fourth transfer gate electrode is made lower than the potential of the charge generation region, and the potential is applied to the fourth transfer gate electrode, so that the charge generated in the charge generation region is transferred to the fourth charge storage region. During the third period, the potential of the region directly below the third overflow gate electrode is made lower than the potential of the charge generation region, and the potential is applied to the third overflow gate electrode. During the fourth period, the potential of the region directly below the fourth overflow gate electrode is made lower than the potential of the charge generation region, and the potential is applied to the fourth overflow gate electrode. In this case, charge distribution by the first to fourth transfer gate electrodes can be achieved, and the accuracy of distance measurement can be improved.

[0016] Alternatively, the third overflow region may have a charge storage capacity larger than that of the third charge storage region, and the fourth overflow region may have a charge storage capacity larger than that of the fourth charge storage region. In this case, saturation of the storage capacity can be effectively suppressed.

[0017] Alternatively, the ranging device according to an aspect of the present disclosure may further include a photoelectric gate electrode disposed over the charge generation region. During the first period, the control unit applies potentials to the photoelectric gate electrode and the first transfer gate electrode such that the potential of the region directly below the first transfer gate electrode is lower than the potential of the charge generation region and the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region. During the second period, the control unit applies potentials to the photoelectric gate electrode and the second transfer gate electrode such that the potential of the region directly below the second transfer gate electrode is lower than the potential of the charge generation region and the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region. In this case, the potential can be adjusted with high precision.

[0018] Alternatively, the first overflow region may have a charge storage capacity greater than that of the first charge storage region, and the second overflow region may have a charge storage capacity greater than that of the second charge storage region. In this case, saturation of the storage capacity can be effectively suppressed.

[0019] In a driving method of a distance measuring sensor according to an aspect of the present disclosure, the distance measuring sensor includes: a charge generation region that generates charges according to incident light; a first charge storage region; a first overflow region; a second charge storage region; a second overflow region; a first transfer gate electrode disposed on a region between the charge generation region and the first charge storage region; a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region; a second transfer gate electrode disposed on a region between the charge generation region and the second charge storage region; and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region. The driving method of the distance measuring sensor includes: a charge distribution step in which charge transfer signals having different phases from each other are applied to the first transfer gate electrode and the second transfer gate electrode. During a first period, a potential is applied to the first transfer gate electrode such that the potential of a region directly below the first transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the first charge storage region. During a second period, a potential is applied to the second transfer gate electrode such that the potential of a region directly below the second transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the second charge storage region. During the first period, a potential is applied to the first overflow gate electrode such that the potential of a region directly below the first overflow gate electrode is lower than the potential of the charge generation region. During the second period, a potential is applied to the second overflow gate electrode such that the potential of a region directly below the second overflow gate electrode is lower than the potential of the charge generation region.

[0020] In the driving method of the distance measurement sensor, the distance measurement sensor includes: a first overflow region, a second overflow region, a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region, and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region. Thus, the charge overflowing from the first charge storage region can be stored in the first overflow region, and the charge overflowing from the second charge storage region can be stored in the second overflow region. As a result, saturation of the storage capacity can be suppressed. In addition, during a first period of the charge distribution step, the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region, and during a second period of the charge distribution step, the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region. Thus, even when the charge is stored in the first charge storage region to the extent of overflowing into the first overflow region and when the charge is stored in the second charge storage region to the extent of overflowing into the second overflow region, the charge remaining in the charge generation region can be suppressed. Therefore, according to the driving method of the distance measurement sensor, the accuracy of distance measurement can be improved.

[0021] Advantages of the Invention

[0022] According to one aspect of the present disclosure, a distance measurement device and a driving method of a distance measurement sensor capable of improving the accuracy of distance measurement can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a structural diagram of the distance measurement device according to the embodiment.

[0024] Figure 2 is a top view of a pixel portion of the distance measurement sensor.

[0025] Figure 3 is along Figure 2 the cross-sectional view taken along line III-III shown.

[0026] Figure 4 is a circuit diagram of the distance measurement sensor.

[0027] Figure 5 is a timing chart showing an operation example of the distance measurement sensor.

[0028] Figure 6 (a) to (d) are potential distribution diagrams for explaining an operation example of the distance measurement sensor.

[0029] Figure 7 is a timing chart showing an operation example of an image sensor of a comparative example.

[0030] Figure 8 (a) to (d) are potential distribution diagrams for explaining an operation example of the image sensor of the comparative example.

[0031] Figure 9 Top view of a part of the distance measurement sensor according to the first modification example.

[0032] Figure 10 Timing chart showing an operation example of the distance measurement sensor according to the first modification example.

[0033] Figure 11 Top view of a part of the distance measurement sensor according to the second modification example.

[0034] Figure 12 Timing chart showing an operation example of the distance measurement sensor according to the second modification example.

[0035] Figure 13 Circuit diagram of the distance measurement sensor according to the third modification example. Detailed implementation mode

[0036] Hereinafter, with reference to the accompanying drawings, an embodiment of the present invention will be described in detail. In addition, in the following description, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0037] [Structure of distance measurement device]

[0038] As Figure 1 shown, the distance measurement device 1 includes: a light source 2, a distance measurement sensor (distance measurement image sensor) 10A, a signal processing unit 3, a control unit 4, and a display unit 5. The distance measurement device 1 is a device that uses the indirect TOF method to obtain a distance image (an image including information on the distance d from the object OJ) of the object OJ.

[0039] The light source 2 emits pulsed light L. The light source 2 is composed of, for example, an infrared LED or the like. The pulsed light L is, for example, near-infrared light, and the frequency of the pulsed light L is, for example, 10 kHz or more. The distance measurement sensor 10A detects the pulsed light L that is emitted from the light source 2 and reflected by the object OJ. The distance measurement sensor 10A is configured by monolithically forming a pixel unit 11 and a CMOS readout circuit unit 12 on a semiconductor substrate (e.g., a silicon substrate). The distance measurement sensor 10A is mounted on the signal processing unit 3.

[0040] The signal processing unit 3 controls the pixel unit 11 and the CMOS readout circuit unit 12 of the distance measurement sensor 10A. The signal processing unit 3 performs a predetermined process on the signal output from the distance measurement sensor 10A and generates a detection signal. The control unit 4 controls the light source 2 and the signal processing unit 3. The control unit 4 generates a distance image of the object OJ based on the detection signal output from the signal processing unit 3. The display unit 5 displays the distance image of the object OJ generated by the control unit 4.

[0041] [Structure of distance measurement sensor]

[0042] As Figure 2 and Figure 3 shown, the distance measurement sensor 10A includes a semiconductor layer 20 and an electrode layer 40 in the pixel portion 11. The semiconductor layer 20 has a first surface 20a and a second surface 20b. The first surface 20a is a surface on one side in the thickness direction of the semiconductor layer 20. The second surface 20b is a surface on the other side in the thickness direction of the semiconductor layer 20. The electrode layer 40 is provided on the first surface 20a of the semiconductor layer 20. The semiconductor layer 20 and the electrode layer 40 constitute a plurality of pixels 11a arranged along the first surface 20a. In the distance measurement sensor 10A, the plurality of pixels 11a are two-dimensionally arranged along the first surface 20a. Hereinafter, the thickness direction of the semiconductor layer 20 is referred to as the Z direction, one direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to both the Z direction and the X direction is referred to as the Y direction. In addition, one side in the Z direction is referred to as the first side, and the other side in the Z direction (the opposite side of the first side) is referred to as the second side. Further, in Figure 2 , the configurations of the charge storage regions P1 to P4, overflow regions Q1 to Q4, redundant charge discharge region R, photogate electrode PG, transfer gate electrodes TX1 to TX4, overflow gate electrodes OV1 to OV4, and redundant charge transfer gate electrode RG, which will be described later, are schematically shown, and other elements are appropriately omitted.

[0043] Each pixel 11a has in the semiconductor layer 20: a semiconductor region 21, an avalanche multiplication region 22, a charge distribution region 23, a first charge storage region P1, a second charge storage region P2, a third charge storage region P3, a fourth charge storage region P4, a first overflow region Q1, a second overflow region Q2, a third overflow region Q3, a fourth overflow region Q4, two redundant charge discharge regions R, a well region 31, and a barrier region 32. Each of the regions 21 to 23, P1 to P4, Q1 to Q4, R, 31, and 32 is formed by performing various processes (such as etching, film formation, impurity implantation, etc.) on a semiconductor substrate (such as a silicon substrate).

[0044] The semiconductor region 21 is a p-type (first conductivity type) region provided along the second surface 20b in the semiconductor layer 20. The semiconductor region 21 functions as a light absorption region (photoelectric conversion region). As an example, the semiconductor region 21 is a p-type region having a carrier concentration of 1×10 15 cm -3 or less and a thickness of about 10 μm. In addition, the avalanche multiplication region 22 and the like also function as a light absorption region (photoelectric conversion region).

[0045] The avalanche multiplication region 22 includes a first multiplication region 22a and a second multiplication region 22b. The first multiplication region 22a is a p-type region formed on the first side of the semiconductor region 21 in the semiconductor layer 20. As an example, the first multiplication region 22a is a p-type region having a carrier concentration of 1×10 16 cm -3 or more, and its thickness is on the order of 1 μm. The second multiplication region 22b is an n-type (second conductivity type) region formed on the first side of the first multiplication region 22a in the semiconductor layer 20. As an example, the second multiplication region 22b is an n-type region having a carrier concentration of 1×10 16 cm -3 or more, and its thickness is on the order of 1 μm. The first multiplication region 22a and the second multiplication region 22b form a pn junction. The avalanche multiplication region 22 is a region where avalanche multiplication is initiated. When a reverse bias of a specified value is applied, the electric field strength generated in the avalanche multiplication region 22 is, for example, 3×10 5 ~4×10 5 V / cm.

[0046] The charge distribution region 23 is an n-type region formed on the first side of the second multiplication region 22b in the semiconductor layer 20. As an example, the charge distribution region 23 is an n-type region having a carrier concentration of 5×10 15 ~1×10 16 cm -3 and its thickness is on the order of 1 μm.

[0047] Each charge storage region P1 to P4 is an n-type region formed on the first side of the second multiplication region 22b in the semiconductor layer 20. Each charge storage region P1 to P4 is connected to the charge distribution region 23. As an example, each of the first charge transfer regions P1 to P4 is an n-type region having a carrier concentration of 1×10 18 cm -3 or more, and its thickness is on the order of 0.2 μm.

[0048] Each overflow region Q1 to Q4 is an n-type region formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. The charge storage capacity of the first overflow region Q1 is larger than that of the first charge storage region P1. The charge storage capacity of the second overflow region Q2 is larger than that of the second charge storage region P2. The charge storage capacity of the third overflow region Q3 is larger than that of the third charge storage region P3. The charge storage capacity of the fourth overflow region Q4 is larger than that of the fourth charge storage region P4. For example, the charge storage capacities of the charge storage regions P1 to P4 are equal to each other, and the charge storage capacities of the overflow regions Q1 to Q4 are equal to each other. A PN junction capacitance is used in the charge storage regions P1 to P4. In contrast, an additional capacitance is provided in the overflow regions Q1 to Q4, so that the storage capacity can be increased compared with the charge storage regions P1 to P4. Examples of the additional capacitance include MIM (Metal Insulator Metal) capacitance, MOS capacitance, trench capacitance, and PIP capacitance.

[0049] Each excess charge discharge region R is an n-type region formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. Each excess charge discharge region R is connected to the charge distribution region 23. The excess charge discharge region R has, for example, the same structure as the charge storage regions P1 to P4.

[0050] The potential well region 31 is a p-type region formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. The potential well region 31 surrounds the charge distribution region 23 when viewed from the Z direction. The potential well region 31 constitutes a plurality of read circuits (for example, a source follower amplifier, a reset transistor, etc.). The plurality of read circuits are electrically connected to the charge storage regions P1 to P4 and the overflow regions Q1 to Q4, respectively. As an example, the potential well region 31 is a p-type region having a carrier concentration of 1×10 16 to 5×10 17 cm -3 and has a thickness of about 1 μm.

[0051] The barrier region 32 is an n-type region formed between the second multiplication region 22b and the potential well region 31 in the semiconductor layer 20. The barrier region 32 includes the potential well region 31 when viewed from the Z direction. That is, the potential well region 31 is located within the barrier region 32 when viewed from the Z direction. The barrier region 32 surrounds the charge distribution region 23. The concentration of n-type impurities in the barrier region 32 is higher than the concentration of n-type impurities in the second multiplication region 22b. As an example, the barrier region 32 is an n-type region having a carrier concentration several times that of the carrier concentration in the second multiplication region 22b, and its thickness is on the order of 1 μm. Since the barrier region 32 is formed between the second multiplication region 22b and the potential well region 31, even if a high voltage is applied to the avalanche multiplication region 22 and the depletion layer formed in the avalanche multiplication region 22 extends toward the potential well region 31, it is possible to prevent the depletion layer from reaching the potential well region 31. That is, it is possible to prevent current from flowing between the avalanche multiplication region 22 and the potential well region 31 due to the depletion layer reaching the potential well region 31.

[0052] Here, the positional relationship of each region will be described. The first charge storage region P1 is opposed to the second charge storage region P2 in the X direction with the charge distribution region 23 therebetween. The first overflow region Q1 is disposed on the opposite side of the charge distribution region 23 with respect to the first charge storage region P1. The second overflow region Q2 is disposed on the opposite side of the charge distribution region 23 with respect to the second charge storage region P2.

[0053] The third charge storage region P3 is opposed to the fourth charge storage region P4 in the X direction with the charge distribution region 23 therebetween. The third overflow region Q3 is disposed on the opposite side of the charge distribution region 23 with respect to the third charge storage region P3. The fourth overflow region Q4 is disposed on the opposite side of the charge distribution region 23 with respect to the fourth charge storage region P4. The first charge storage region P1 and the fourth charge storage region P4 are arranged in the Y direction. The second charge storage region P2 and the third charge storage region P3 are arranged in the Y direction. The first overflow region Q1 and the fourth overflow region Q4 are arranged in the Y direction. The second overflow region Q2 and the third overflow region Q3 are arranged in the Y direction. The two redundant charge discharge regions R are opposed to each other in the Y direction with the charge distribution region 23 therebetween.

[0054] Each pixel 11a has, in the electrode layer 40: a photogate electrode PG, a first transfer gate electrode TX1, a second transfer gate electrode TX2, a third transfer gate electrode TX3, a fourth transfer gate electrode TX4, a first overflow gate electrode OV1, a second overflow gate electrode OV2, a third overflow gate electrode OV3, a fourth overflow gate electrode OV4, and two redundant charge transfer gate electrodes RG. Each of the gate electrodes PG, TX1 to TX4, OV1 to OV4, and RG is formed on the first surface 20a of the semiconductor layer 20 with an insulating film 41 therebetween. The insulating film 41 is, for example, a silicon nitride film, a silicon oxide film, or the like.

[0055] The photogate electrode PG is disposed on the charge distribution region 23. The photogate electrode PG is formed of a material having conductivity and light transmissivity (e.g., polysilicon). As an example, the photogate electrode PG has a rectangular shape having two sides opposite to each other in the X direction and two sides opposite to each other in the Y direction when viewed from the Z direction. The regions directly under the photogate electrode PG in the semiconductor region 21, the avalanche multiplication region 22, and the charge distribution region 23 function as a charge generation region 24 where charges are generated according to incident light. In other words, the photogate electrode PG is disposed on the charge generation region 24. In the charge generation region 24, the charges generated in the semiconductor region 21 are multiplied in the avalanche multiplication region 22 and distributed in the charge distribution region 23. In a case different from the embodiment, when pulsed light L is incident on the semiconductor layer 20 from the opposite electrode 50 side (back surface incident case), the photogate electrode PG may not have light transmissivity. The region directly under the photogate electrode PG means the region that coincides with the photogate electrode PG when viewed from the Z direction. This also applies to the other gate electrodes TX1 to TX4, OV1 to OV4, and RG.

[0056] The first transfer gate electrode TX1 is disposed on the region between the charge generation region 24 of the charge distribution region 23 and the first charge storage region P1. The second transfer gate electrode TX2 is disposed on the region between the charge generation region 24 of the charge distribution region 23 and the second charge storage region P2. The third transfer gate electrode TX3 is disposed on the region between the charge generation region 24 of the charge distribution region 23 and the third charge storage region P3. The fourth transfer gate electrode TX4 is disposed on the region between the charge generation region 24 of the charge distribution region 23 and the fourth charge storage region P4.

[0057] Each of the transfer gate electrodes TX1 to TX4 is formed of a material having conductivity (e.g., polysilicon). As an example, each of the transfer gate electrodes TX1 to TX4 has a rectangular shape having two sides opposite to each other in the X direction and two sides opposite to each other in the Y direction when viewed from the Z direction.

[0058] The first overflow gate electrode OV1 is disposed on a region between the first charge storage region P1 and the first overflow region Q1 of the potential well region 31. The second overflow gate electrode OV2 is disposed on a region between the second charge storage region P2 and the second overflow region Q2 of the potential well region 31. The third overflow gate electrode OV3 is disposed on a region between the third charge storage region P3 and the third overflow region Q3 of the potential well region 31. The fourth overflow gate electrode OV4 is disposed on a region between the fourth charge storage region P4 and the fourth overflow region Q4 of the potential well region 31.

[0059] Each of the overflow gate electrodes OV1 to OV4 is formed of a conductive material (e.g., polysilicon). As an example, each of the overflow gate electrodes OV1 to OV4 has a rectangular shape having two sides opposite to each other in the X direction and two sides opposite to each other in the Y direction when viewed from the Z direction.

[0060] One of the redundant charge transfer gate electrodes RG is disposed on a region between the charge generation region 24 of the charge distribution region 23 and one of the pair of redundant charge discharge regions R. The other of the redundant charge transfer gate electrodes RG is disposed on a region between the charge generation region 24 of the charge distribution region 23 and the other of the pair of redundant charge discharge regions R. Each of the redundant charge transfer gate electrodes RG is formed of a conductive material (e.g., polysilicon). As an example, each of the redundant charge transfer gate electrodes RG has a rectangular shape having two sides opposite to each other in the X direction and two sides opposite to each other in the Y direction when viewed from the Z direction.

[0061] The distance measuring sensor 10A further includes a counter electrode 50 and a wiring layer 60 in the pixel portion 11. The counter electrode 50 is provided on the second surface 20b of the semiconductor layer 20. The counter electrode 50 includes a plurality of pixels 11a when viewed from the Z direction. The counter electrode 50 faces the electrode layer 40 in the Z direction. The counter electrode 50 is formed of, for example, a metal material. The wiring layer 60 is provided on the first surface 20a of the semiconductor layer 20 so as to cover the electrode layer 40. The wiring layer 60 is electrically connected to each pixel 11a and the CMOS readout circuit section 12 (see Figure 1 ). An optical incident opening 60a is formed in a portion of the wiring layer 60 that faces the photoelectric gate electrode PG of each pixel 11a.

[0062] In Figure 4 , an example of the circuit structure of each pixel 11a is shown. As Figure 4 shown, each pixel 11a has: a plurality (four in this example) of reset transistors RST respectively connected to the overflow regions Q1 to Q4, and a plurality (four in this example) of selection transistors SEL for selecting the pixel 11a.

[0063] [Driving method of distance measuring sensor]

[0064] While referring to Figure 5 and Figure 6 , an operation example of the distance measuring sensor 10A will be described. The following operations are achieved by the control unit 4 controlling the driving of the distance measuring sensor 10A. At each pixel 11a of the distance measuring sensor 10A, a negative voltage (e.g., -50V) based on the potential of the photogate electrode PG is applied to the counter electrode 50 (i.e., a reverse bias is applied to the pn junction formed in the avalanche multiplication region 22), and an electric field intensity of 3×10 5 ~4×10 5 V / cm is generated in the avalanche multiplication region 22. In this state, when the pulsed light L is incident on the semiconductor layer 20 via the light incident opening 60a and the photogate electrode PG, the electrons generated by the absorption of the pulsed light L are multiplied in the avalanche multiplication region 22 and move rapidly toward the charge distribution region 23.

[0065] When generating the distance image of the object OJ (refer to Figure 1 ), first, a reset process (reset step) of applying a reset voltage to each reset transistor RST of each pixel 11a is executed. The reset voltage is a positive voltage based on the potential of the photogate electrode PG. As a result, the charges stored in the charge storage regions P1 to P4 and the overflow regions Q1 to Q4 are discharged to the outside, and a state where no charges are stored in the charge storage regions P1 to P4 and the overflow regions Q1 to Q4 is achieved (time T1, Figure 6 (a)). The discharge of the charges to the outside is performed, for example, via a read circuit composed of the potential well region 31 and the like and the wiring layer 60. Hereinafter, the operation will be described focusing on one selected pixel 11a.

[0066] After the reset process, during the storage period T2, charges are stored in the charge storage regions P1 to P4 and the overflow regions Q1 to Q4( Figure 6 (b)). During the storage period T2, charge transfer signals having different phases from each other are applied to the transfer gate electrodes TX1 to TX4. As a result, a charge distribution process (charge distribution step) of distributing the charges generated in the charge generation region 24 among the charge storage regions P1 to P4 is performed.

[0067] As an example, the charge transfer signal applied to the first transfer gate electrode TX1 is a voltage signal in which a positive voltage and a negative voltage are alternately repeated based on the potential of the photogate electrode PG, and the period, pulse width, and phase are the same as those from the light source 2 (refer to Figure 1) The intensity signal of the emitted pulsed light L is the same voltage signal. The charge transfer signals applied to the second transfer gate electrode TX2, the third transfer gate electrode TX3, and the fourth transfer gate electrode TX4 are the same voltage signals as the pulsed voltage signal applied to the first transfer gate electrode TX1, except that the phases are shifted by 90°, 180°, and 270° respectively.

[0068] During the first period when a positive voltage is applied to the first transfer gate electrode TX1, the electric potential φ in the region directly below the first transfer gate electrode TX1 TX1 is lower than the electric potential φ in the region directly below the photogate electrode PG (charge generation region 24). PG In other words, during the first period, the electric potential φ TX1 is made lower than the electric potential φ PG by applying potentials to the photogate electrode PG and the first transfer gate electrode TX1. As a result, the charges generated in the charge generation region 24 are transferred to the first charge storage region P1. In Figure 6 (b), the electric potential φ when a positive voltage is applied to the first transfer gate electrode TX1 TX1 is represented by a dashed line, and the electric potential φ when a negative voltage is applied to the first transfer gate electrode TX1 TX1 is represented by a solid line. In addition, the charges stored in the first charge storage region P1 and the first overflow region Q1 are represented by shading.

[0069] In addition, when adjusting the magnitude of the electric potential in the region directly below the adjustment gate electrode, it is also possible to adjust the magnitude of the potential applied to the gate electrode, or instead of or in addition to that, adjust the carrier concentration in the region directly below the gate electrode. When the electric potential φ PG in the region directly below the photogate electrode PG (charge generation region 24) reaches a predetermined level through adjustment of the carrier concentration, it is also possible not to provide the photogate electrode PG. In this case, it is not necessary to apply the above-mentioned negative voltage.

[0070] During the first period, negative voltages are applied to the second to fourth transfer gate electrodes TX2 to TX4, and the electric potential φ in the region directly below the second transfer gate electrode TX2 TX2 , the electric potential φ in the region directly below the third transfer gate electrode TX3 TX3 and the electric potential φ in the region directly below the fourth transfer gate electrode TX4 TX4 are higher than the electric potential φ PG . As a result, a potential barrier is generated between the charge generation region 24 and the second to fourth charge storage regions P2 to P4, and the charges generated in the charge generation region 24 are not transferred to the second to fourth charge storage regions P2 to P4. In other words, during the first period, with each electric potential φ TX2 , φ TX3 and φTX4 Specific potential φ PG Apply potentials to the photogate electrode PG and the second to fourth transfer gate electrodes TX2 to TX4 in a manner that the potential is higher.

[0071] Moreover, during the first period, apply potentials to the photogate electrode PG and the first overflow gate electrode OV1 in a manner that the potential φ in the region directly below the first overflow gate electrode OV1 OV1 is lower than the potential φ in the region directly below the photogate electrode PG (charge generation region 24). PG In other words, during the first period, set the potential applied to the first overflow gate electrode OV1 such that, with the potential of the photogate electrode PG as a reference, the potential φ OV1 is lower than the potential φ. PG As a result, as shown in (b) of Figure 6 even when the charge in the first charge storage region P1 is saturated, the charge overflowing from the first charge storage region P1 can flow into the first overflow region Q1 and be stored in the first overflow region Q1.

[0072] During the second period when a positive voltage is applied to the second transfer gate electrode TX2, the potential φ in the region directly below the second transfer gate electrode TX2 TX2 is lower than the potential φ in the region directly below the photogate electrode PG (charge generation region 24). PG In other words, during the second period, apply potentials to the photogate electrode PG and the second transfer gate electrode TX2 in a manner that the potential φ TX2 is lower than the potential φ. PG As a result, the charge generated in the charge generation region 24 is transferred to the second charge storage region P2. During the second period, apply potentials to the photogate electrode PG and the first, third, and fourth transfer gate electrodes TX1, TX3, TX4 in a manner that each potential φ TX1 、φ TX3 and φ TX4 is higher than the potential φ. PG Moreover, during the second period, apply potentials to the photogate electrode PG and the first, third, and fourth transfer gate electrodes TX1, TX3, TX4 in a manner that the potential is higher.

[0073] Moreover, during the second period, apply potentials to the photogate electrode PG and the second overflow gate electrode OV2 in a manner that the potential φ in the region directly below the second overflow gate electrode OV2 OV2 is lower than the potential φ in the region directly below the photogate electrode PG (charge generation region 24). PG As a result, even when the charge in the second charge storage region P2 is saturated, the charge overflowing from the second charge storage region P2 can flow into the second overflow region Q2 and be stored in the second overflow region Q2.

[0074] During a third period in which a positive voltage is applied to the third transfer gate electrode TX3, the potential φ of the region directly below the third transfer gate electrode TX3 TX3 is lower than the potential φ of the region directly below the photogate electrode PG (charge generation region 24). That is to say, during the third period, the potential φ PG is set to be lower than the potential φ TX3 in such a manner that the potential φ of the photogate electrode PG and the third transfer gate electrode TX3 are applied. As a result, the charges generated in the charge generation region 24 are transferred to the third charge storage region P3. During the third period, the potentials φ PG are each set to be higher than the potential φ TX1 、φ TX2 and φ TX4 in such a manner that the potential φ of the photogate electrode PG and the first, second, and fourth transfer gate electrodes TX1, TX2, TX4 are applied. PG

[0075] Moreover, during the third period, the potential φ of the region directly below the third overflow gate electrode OV3 OV3 is set to be lower than the potential φ of the region directly below the photogate electrode PG (charge generation region 24). PG In this way, even when the charges in the third charge storage region P3 are saturated, the charges overflowing from the third charge storage region P3 can flow into the third overflow region Q3 and be stored in the third overflow region Q3.

[0076] During a fourth period in which a positive voltage is applied to the fourth transfer gate electrode TX4, the potential φ of the region directly below the fourth transfer gate electrode TX4 TX4 is lower than the potential φ of the region directly below the photogate electrode PG (charge generation region 24). That is to say, during the fourth period, the potential φ PG is set to be lower than the potential φ TX4 in such a manner that the potential φ of the photogate electrode PG and the fourth transfer gate electrode TX4 are applied. As a result, the charges generated in the charge generation region 24 are transferred to the fourth charge storage region P4. During the fourth period, the potentials φ PG are each set to be higher than the potential φ TX1 ~φ TX3 in such a manner that the potential φ of the photogate electrode PG and the first to third transfer gate electrodes TX1 to TX3 are applied. PG

[0077] Moreover, during the fourth period, the potential φ of the region directly below the fourth overflow gate electrode OV4 OV4 is set to be lower than the potential φ of the region directly below the photogate electrode PG (charge generation region 24). PG ​​In a low manner, a potential is applied to the photogate electrode PG and the fourth overflow gate electrode OV4. Thereby, even when the charge in the fourth charge storage region P4 is saturated, the charge overflowing from the fourth charge storage region P4 can flow into the fourth overflow region Q4 and be stored in the fourth overflow region Q4.

[0078] After the charge distribution process during the storage period T2, a first reading process (high-sensitivity reading process) (first reading step) (time T3, Figure 6 (c)) for reading the amount of charge stored in each of the charge storage regions P1 to P4 is performed. In this example, after each of the processes of transferring the charge generated in the charge generation region 24 to the first charge storage region P1, the process of transferring the charge generated in the charge generation region 24 to the second charge storage region P2, the process of transferring the charge generated in the charge generation region 24 to the third charge storage region P3, and the process of transferring the charge generated in the charge generation region 24 to the fourth charge storage region P4 are performed multiple times, the first reading process is performed.

[0079] After the first reading process, a charge transfer process (charge transfer step) is performed, in which the potential φ of the region directly below the first overflow gate electrode OV1 is reduced by applying a voltage larger than the voltage applied during the above first period to the first overflow gate electrode OV1 OV1 , so that the charge stored in the first charge storage region P1 is transferred to the first overflow region Q1 ( Figure 6 (d)). In other words, in the charge transfer process, by applying a potential to the first overflow gate electrode OV1 in a manner that reduces the potential φ OV1 , the charge stored in the first charge storage region P1 is transferred to the first overflow region Q1.

[0080] Similarly, in the charge transfer process, by applying a potential to the second overflow gate electrode OV2 in a manner that reduces the potential φ of the region directly below the second overflow gate electrode OV2 OV2 , the charge stored in the second charge storage region P2 is transferred to the second overflow region Q2. By applying a potential to the third overflow gate electrode OV3 in a manner that reduces the potential φ of the region directly below the third overflow gate electrode OV3 OV3 , the charge stored in the third charge storage region P3 is transferred to the third overflow region Q3. By applying a potential to the fourth overflow gate electrode OV4 in a manner that reduces the potential φ of the region directly below the fourth overflow gate electrode OV4 OV4 , the charge stored in the fourth charge storage region P4 is transferred to the fourth overflow region Q4.

[0081] After the charge transfer process, a second reading process (low-sensitivity reading process) (second reading step) of reading the total amount of charge stored in the first charge storage region P1 and the first overflow region Q1 is performed (time T4, Figure 6 (d)). Similarly, in the second read process, the total amount of charge stored in the second charge storage region P2 and the second overflow region Q2 is read. The total amount of charge stored in the third charge storage region P3 and the third overflow region Q3 is read. The total amount of charge stored in the fourth charge storage region P4 and the fourth overflow region Q4 is read. The above reset process is performed again after the second read process (time T1, Figure 6 (a)), the above series of processing is repeatedly performed.

[0082] In addition, during the periods other than the first to fourth periods, an excess charge transfer process (excess charge transfer step) is performed to transfer the charge generated in the charge generation region 24 to the excess charge discharge region R. In the excess charge transfer process, a positive voltage is applied to the excess charge transfer gate electrode RG, so that the potential φ of the region directly below the excess charge transfer gate electrode RG is increased to RG The potential φ of the region directly below the photogate electrode PG (charge generation region 24) is PG In other words, with the potential φ RG Specific potential φ PG In a low mode, a potential is applied to the photogate electrode PG and the excess charge transfer gate electrode RG. As a result, the charges generated in the charge generation region 24 are transferred to the excess charge discharge region R. The charges transferred to the excess charge discharge region R are discharged to the outside. For example, the excess charge discharge region R is connected to a fixed potential, and the charges transferred to the excess charge discharge region R are discharged to the outside without passing through the reading circuit.

[0083] like Figure 1 As shown, when the pulse light L is emitted from the light source 2 and the pulse light L reflected by the object OJ is detected by the distance measuring sensor 10A, the phase of the intensity signal of the pulse light L detected by the distance measuring sensor 10A is shifted relative to the phase of the intensity signal of the pulse light L emitted from the light source 2 according to the distance d from the object OJ. Therefore, by obtaining a signal based on the amount of charge stored in the charge storage areas P1 to P4 and the overflow areas Q1 to Q4 (that is, the amount of charge read in the first reading process and the second reading process) for each pixel 11a, it is possible to generate a distance image of the object OJ.

[0084] [Function and Effect]

[0085] In the distance measuring device 1, the distance measuring sensor 10A has: a first overflow region Q1 having a charge storage capacity larger than that of the first charge storage region P1; a second overflow region Q2 having a charge storage capacity larger than that of the second charge storage region P2; a first overflow gate electrode OV1 disposed on a region between the first charge storage region P1 and the first overflow region Q1; and a second overflow gate electrode OV2 disposed on a region between the second charge storage region P2 and the second overflow region Q2. Thereby, the charge overflowing from the first charge storage region P1 can be stored in the first overflow region Q1, and the charge overflowing from the second charge storage region P2 can be stored in the second overflow region Q2. As a result, saturation of the storage capacity can be suppressed. Further, during a first period of the charge distribution process, the potential φ of the region directly under the first overflow gate electrode OV1 OV1 is lower than the potential φ of the charge generation region 24 PG and during a second period of the charge distribution process, the potential φ of the region directly under the second overflow gate electrode OV2 OV2 is lower than the potential φ of the charge generation region 24 PG Accordingly, even when the charge is stored in the first charge storage region P1 to such an extent as to overflow into the first overflow region Q1 and when the charge is stored in the second charge storage region P2 to such an extent as to overflow into the second overflow region Q2, the charge remaining in the charge generation region 24 can be suppressed. Therefore, according to the distance measuring device 1, the accuracy of distance measurement can be improved. Further, high sensitivity and a high dynamic range can be achieved.

[0086] Regarding this point, a further description will be given with reference to Figure 7 and Figure 8 the comparative examples shown. In the image sensor of the comparative example, during the entire storage period T2, the potential φ of the region directly under the transfer gate electrode TX TX is higher than the potential φ of the region directly under the photogate electrode PG PG ( Figure 8 (b)). Further, during the entire storage period T2, the potential φ of the region directly under the overflow gate electrode OV OV is higher than the potential φ of the region directly under the photogate electrode PG PG . After the storage period T2, the potential φ of the region directly under the transfer gate electrode TX TX is lower than the potential φ of the region (charge generation region) directly under the photogate electrode PG PG and the charge stored in the charge generation region is transferred to the charge storage region P. Thereafter, the amount of charge stored in the charge storage region P is read (time T3, Figure 8 (c)).

[0087] In the image sensor of the comparative example, since the electric potential φ of the region directly under the T2 overflow gate electrode OV during storage OV is higher than the electric potential φ of the region directly under the photogate electrode PG PG , as shown in Figure 8 (c), when the charge is stored in the charge storage region P to the extent of overflowing into the overflow region Q, a part of the charge remains in the region directly under the photogate electrode PG (charge generation region). In this case, the accuracy of distance measurement may be reduced due to the charge remaining in the charge storage region.

[0088] In contrast, as described above, in the distance measuring device 1, during the charge distribution process, the electric potential φ of the region directly under the first overflow gate electrode OV1 OV1 and the electric potential φ under the second overflow gate electrode OV2 OV2 are lower than the electric potential φ of the charge generation region 24 PG . Thus, even when the charge is stored in the first charge storage region P1 or the second charge storage region P2 to the extent of overflowing into the first overflow region Q1 or the second overflow region Q2, the charge remaining in the charge generation region 24 can be suppressed.

[0089] The charge generation region 24 includes an avalanche multiplication region 22. In this case, avalanche multiplication can be triggered in the charge generation region 24, and the detection sensitivity of the distance measuring sensor 10A can be improved. On the other hand, when the charge generation region 24 includes the avalanche multiplication region 22, the amount of generated charge becomes extremely large. In the distance measuring device 1, even in such a case, the saturation of the storage capacity can be sufficiently suppressed, and the remaining charge in the charge generation region 24 can be sufficiently suppressed.

[0090] The control unit 4 performs a first reading process, a charge transfer process, and a second reading process. In the first reading process, the amounts of charge stored in the first charge storage region P1 and the second charge storage region P2 are read. In the charge transfer process, the charge stored in the first charge storage region P1 is transferred to the first overflow region Q1, and the charge stored in the second charge storage region P2 is transferred to the second overflow region Q2. In the second reading process, the amounts of charge stored in the first charge storage region P1 and the first overflow region Q1 are read, and the amounts of charge stored in the second charge storage region P2 and the second overflow region Q2 are read. Thus, not only the amounts of charge stored in the first and second charge storage regions P2 are read in the first reading process, but also the amounts of charge stored in the first charge storage region P1 and the first overflow region Q1 and the amounts of charge stored in the second charge storage region P2 and the second overflow region Q2 are read in the second reading process. Therefore, the detection accuracy of the amount of charge can be improved.

[0091] During periods other than the first period and the second period, the control unit 4 performs an excess charge transfer process of transferring the charge generated in the charge generation region 24 to the excess charge discharge region R through the excess charge transfer gate electrode RG. Thereby, the charge generated in the charge generation region 24 during periods other than the first and second periods can be transferred to the excess charge discharge region, and the residual charge in the charge generation region 24 can be further suppressed. The excess charge transfer process is particularly effective in an environment with a large amount of ambient light.

[0092] During the first period, the control unit 4 sets the potential φ of the region directly below the first transfer gate electrode TX1 TX1 lower than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG and the potential φ of the region directly below the first overflow gate electrode OV1 OV1 lower than the potential φ of the region directly below the photogate electrode PG PG and applies potentials to the photogate electrode PG and the first transfer gate electrode TX1. During the second period, the control unit 4 sets the potential φ of the region directly below the second transfer gate electrode TX2 TX2 lower than the potential φ of the region directly below the photogate electrode PG PG and the potential φ of the region directly below the second overflow gate electrode OV2 OV2 lower than the potential φ of the region directly below the photogate electrode PG PG and applies potentials to the photogate electrode PG and the second transfer gate electrode TX2. During the third period, the control unit 4 sets the potential φ of the region directly below the third transfer gate electrode TX3 TX3 lower than the potential φ of the region directly below the photogate electrode PG PG and the potential φ of the region directly below the third overflow gate electrode OV3 OV3 lower than the potential φ of the region directly below the photogate electrode PG PG and applies potentials to the photogate electrode PG and the third transfer gate electrode TX3. During the fourth period, the control unit 4 sets the potential φ of the region directly below the fourth transfer gate electrode TX4 TX4 lower than the potential φ of the region directly below the photogate electrode PG PG and the potential φ of the region directly below the fourth overflow gate electrode OV4 OV4 lower than the potential φ of the region directly below the photogate electrode PG PG and applies potentials to the photogate electrode PG and the fourth transfer gate electrode TX4. Thereby, the levels of the respective potentials can be adjusted with high precision.

[0093] The ranging sensor 10A not only has the first and second charge storage regions P1, P2, the first and second overflow regions Q1, Q2, the first and second transfer gate electrodes TX1, TX2, and the first and second overflow gate electrodes OV1, OV2, but also has the third and fourth charge storage regions P3, P4, the third and fourth overflow regions Q3, Q4, the third and fourth transfer gate electrodes TX3, TX4, and the third and fourth overflow gate electrodes OV3, OV4. Moreover, the control unit 4, in the charge distribution process, distributes the charge generated in the charge generation region 24 among the charge storage regions P1 to P4 by applying charge transfer signals with different phases to the transfer gate electrodes TX1 to TX4. Thus, charge distribution through the first to fourth transfer gate electrodes TX1 to TX4 can be achieved, and the accuracy of distance measurement can be improved.

[0094] [Modified Example]

[0095] In Figure 9 the ranging sensor 10B of the first modified example shown, the redundant charge discharge region R and the redundant charge transfer gate electrode RG are not provided. The third charge storage region P3 faces the fourth charge storage region P4 in the Y direction across the charge generation region 24 (photo gate electrode PG). The ranging sensor 10B is driven, for example, as Figure 10 shown. In this driving method, the redundant charge transfer process of transferring the charge generated in the charge generation region 24 to the redundant charge discharge region R is not performed. Through the first modified example, similar to the above-described embodiment, saturation of the storage capacity and residue of charge in the charge generation region 24 can also be suppressed, and the accuracy of distance measurement can be improved.

[0096] In Figure 11 the ranging sensor 10C of the second modified example shown, the third and fourth charge storage regions P3, P4, the third and fourth overflow regions Q3, Q4, the third and fourth transfer gate electrodes TX3, TX4, and the third and fourth overflow gate electrodes OV3, OV4 are not provided. The ranging sensor 10C has four redundant charge discharge regions R1, R2, R3, R4 and four redundant charge transfer gate electrodes RG. The redundant charge discharge regions R1, R2 face each other in the X direction across the charge generation region 24 (photo gate electrode PG). The redundant charge discharge regions R3, R4 face each other in the X direction across the charge generation region 24. The redundant charge discharge regions R1, R4 face each other in the Y direction across the first charge storage region P1. The redundant charge discharge regions R2, R3 face each other in the Y direction across the second charge storage region P2.

[0097] The ranging sensor 10C is driven, for example, as Figure 12is driven as shown. In this driving method, during the storage period T2, the following is repeated in sequence: a first period in which a positive voltage is applied to the first transfer gate electrode TX1, a second period in which a positive voltage is applied to the second transfer gate electrode TX2, and a period in which an excess charge transfer process is performed to transfer the charge generated in the charge generation region 24 to the excess charge discharge region R. By such a driving method, a distance image of the object OJ can also be generated. By the second modification example, similarly to the above-described embodiment, saturation of the storage capacity and residual charge in the charge generation region 24 can also be suppressed, and the accuracy of distance measurement can be improved.

[0098] As Figure 13 shown in the third modification example, the reset transistor RST may also be arranged at a position different from that of the embodiment. In Figure 13 it, only the circuit structure of a part of the pixel 11a is shown. By the third modification example, similarly to the above-described embodiment, saturation of the storage capacity and residual charge in the charge generation region 24 can also be suppressed, and the accuracy of distance measurement can be improved.

[0099] The present disclosure is not limited to the above-described embodiment and modification examples. For example, the materials and shapes of the respective structures are not limited to the above materials and shapes, and various materials and shapes can be adopted. In the distance measurement sensors 10A and 10C, the charges transferred to the excess charge discharge regions R, R1 to R4 may not be discharged to the outside but may be stored and read. That is, the excess charge discharge regions R, R1 to R4 may also function as charge storage regions. In this case, light other than the signal light (light that does not include distance information) can be read and utilized.

[0100] The avalanche multiplication region 22 may not be formed in the semiconductor layer 20. That is, the charge generation region 24 may not include the avalanche multiplication region 22. At least one of the potential well region 31 and the potential barrier region 32 may not be formed in the semiconductor layer 20. The signal processing unit 3 may be omitted, and the control unit 4 may be directly connected to the distance measurement sensors 10A to 10C. The second charge transfer process and the second read process may not be performed.

[0101] In the distance measurement sensors 10A to 10C, light can be made to enter the semiconductor layer 20 from either the first side or the second side. For example, when light is made to enter the semiconductor layer 20 from the second side, the counter electrode 50 can also be formed of a material having conductivity and light transmissivity (e.g., polysilicon). In any one of the distance measurement sensors 10A to 10C, the p-type and n-type conductivity types can also be opposite to the above case. In any one of the distance measurement sensors 10A to 10C, the plurality of pixels 11a can also be arranged one-dimensionally along the first surface 20a of the semiconductor layer 20. Any one of the distance measurement sensors 10A to 10C can also have only a single pixel 11a. The charge storage capacity of the first overflow region Q1 can also be equal to or less than the charge storage capacity of the first charge storage region P1. The charge storage capacity of the second overflow region Q2 can also be equal to or less than the charge storage capacity of the second charge storage region P2. The charge storage capacity of the third overflow region Q3 can also be equal to or less than the charge storage capacity of the third charge storage region P3. The charge storage capacity of the fourth overflow region Q4 can also be equal to or less than the charge storage capacity of the fourth charge storage region P4.

[0102] Description of Reference Numerals

[0103] 1... distance measurement device, 4... control unit, 10A, 10B, 10C... distance measurement sensors, 22... avalanche multiplication region, 24... charge generation region, P1... first charge storage region, P2... second charge storage region, P3... third charge storage region, P4... fourth charge storage region, Q1... first overflow region, Q2... second overflow region, Q3... third overflow region, Q4... fourth overflow region, R, R1, R2, R3, R4... redundant charge discharge regions, PG... photogate electrode, TX1... first transfer gate electrode, TX2... second transfer gate electrode, TX3... third transfer gate electrode, TX4... fourth transfer gate electrode, OV1... first overflow gate electrode, OV2... second overflow gate electrode, OV3... third overflow gate electrode, OV4... fourth overflow gate electrode, RG... redundant charge transfer gate electrode.

Claims

1. A distance measuring device, wherein, it includes: a distance measuring sensor; and a control unit that controls the distance measuring sensor, the distance measuring sensor has: a charge generation region that generates charges according to incident light; a first charge storage region; a first overflow region; a second charge storage region; a second overflow region; a first transfer gate electrode disposed on a region between the charge generation region and the first charge storage region; a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region; a second transfer gate electrode disposed on a region between the charge generation region and the second charge storage region; and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region, the control unit performs: a charge distribution process, in which charge transfer signals having different phases from each other are applied to the first transfer gate electrode and the second transfer gate electrode. During a first period, a potential is applied to the first transfer gate electrode such that the potential of the region directly below the first transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the first charge storage region. During a second period, a potential is applied to the second transfer gate electrode such that the potential of the region directly below the second transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the second charge storage region, during the first period, a potential is applied to the first overflow gate electrode such that the potential of the region directly below the first overflow gate electrode is lower than the potential of the charge generation region, and during the second period, a potential is applied to the second overflow gate electrode such that the potential of the region directly below the second overflow gate electrode is lower than the potential of the charge generation region, the control unit also performs: a first reading process, after the charge distribution process, reading the amounts of charges stored in the first charge storage region and the second charge storage region; a charge transfer process, after the first reading process, applying a potential to the first overflow gate electrode such that the potential of the region directly below the first overflow gate electrode decreases, thereby transferring the charges stored in the first charge storage region to the first overflow region, and applying a potential to the second overflow gate electrode such that the potential of the region directly below the second overflow gate electrode decreases, thereby transferring the charges stored in the second charge storage region to the second overflow region; and a second reading process, after the charge transfer process, reading the amounts of charges stored in the first charge storage region and the first overflow region, and reading the amounts of charges stored in the second charge storage region and the second overflow region.

2. The distance measuring device according to claim 1, wherein, the charge generation region includes an avalanche multiplication region.

3. The distance measuring device according to claim 1 or 2, wherein, the distance measuring sensor further has: Excess charge discharge region; and An excess charge transfer gate electrode disposed on a region between the charge generation region and the excess charge discharge region, The control unit performs an excess charge transfer process during a period other than the first period and the second period, wherein by making the potential of the region directly below the excess charge transfer gate electrode lower than the potential of the charge generation region, a potential is applied to the excess charge transfer gate electrode, thereby transferring the charge generated in the charge generation region to the excess charge discharge region.

4. The distance measuring device according to any one of claims 1 to 3, wherein, The distance measuring sensor further has: A third charge storage region; A third overflow region; A fourth charge storage region; A fourth overflow region; A third transfer gate electrode disposed on a region between the charge generation region and the third charge storage region; A third overflow gate electrode disposed on a region between the third charge storage region and the third overflow region; A fourth transfer gate electrode disposed on a region between the charge generation region and the fourth charge storage region; and A fourth overflow gate electrode disposed on a region between the fourth charge storage region and the fourth overflow region, The control unit, In the charge distribution process, charge transfer signals having different phases from each other are applied to the first transfer gate electrode, the second transfer gate electrode, the third transfer gate electrode, and the fourth transfer gate electrode. During a third period, by making the potential of the region directly below the third transfer gate electrode lower than the potential of the charge generation region, a potential is applied to the third transfer gate electrode, thereby transferring the charge generated in the charge generation region to the third charge storage region. During a fourth period, by making the potential of the region directly below the fourth transfer gate electrode lower than the potential of the charge generation region, a potential is applied to the fourth transfer gate electrode, thereby transferring the charge generated in the charge generation region to the fourth charge storage region, During the third period, a potential is applied to the third overflow gate electrode such that the potential of the region directly below the third overflow gate electrode is lower than the potential of the charge generation region. During the fourth period, a potential is applied to the fourth overflow gate electrode such that the potential of the region directly below the fourth overflow gate electrode is lower than the potential of the charge generation region.

5. The distance measuring device according to claim 4, wherein, The third overflow region has a charge storage capacity larger than that of the third charge storage region, and the fourth overflow region has a charge storage capacity larger than that of the fourth charge storage region.

6. The distance measuring device according to any one of claims 1 to 5, wherein, It further includes: a photoelectric gate electrode disposed on the charge generation region, The control unit, In a first period, a potential is applied to the photogate electrode and the first transfer gate electrode such that the potential of the region directly under the first transfer gate electrode is lower than the potential of the charge generation region and the potential of the region directly under the first overflow gate electrode is lower than the potential of the charge generation region. In a second period, a potential is applied to the photogate electrode and the second transfer gate electrode such that the potential of the region directly under the second transfer gate electrode is lower than the potential of the charge generation region and the potential of the region directly under the second overflow gate electrode is lower than the potential of the charge generation region.

7. The distance measuring device according to any one of claims 1 to 6, wherein, the first overflow region has a charge storage capacity larger than that of the first charge storage region, and the second overflow region has a charge storage capacity larger than that of the second charge storage region.

8. A driving method for a distance measuring sensor, wherein, it is a driving method for a distance measuring sensor, the distance measuring sensor includes: a charge generation region that generates charges according to incident light; a first charge storage region; a first overflow region; a second charge storage region; a second overflow region; a first transfer gate electrode disposed on a region between the charge generation region and the first charge storage region; a first overflow gate electrode disposed on a region between the first charge storage region and the first overflow region; a second transfer gate electrode disposed on a region between the charge generation region and the second charge storage region; and a second overflow gate electrode disposed on a region between the second charge storage region and the second overflow region, the driving method for the distance measuring sensor includes: a charge distribution step, in which charge transfer signals having different phases from each other are applied to the first transfer gate electrode and the second transfer gate electrode. In the first period, a potential is applied to the first transfer gate electrode such that the potential of the region directly under the first transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the first charge storage region. In the second period, a potential is applied to the second transfer gate electrode such that the potential of the region directly under the second transfer gate electrode is lower than the potential of the charge generation region, thereby transferring the charges generated in the charge generation region to the second charge storage region. In the first period, a potential is applied to the first overflow gate electrode such that the potential of the region directly under the first overflow gate electrode is lower than the potential of the charge generation region. In the second period, a potential is applied to the second overflow gate electrode such that the potential of the region directly under the second overflow gate electrode is lower than the potential of the charge generation region. The driving method for the distance measuring sensor further includes: a first reading process of reading the amounts of charges stored in the first charge storage region and the second charge storage region after the charge distribution process. A charge transfer process, after the first reading process, by applying a potential to the first overflow gate electrode in such a way that the potential of the region directly below the first overflow gate electrode is lowered, thereby transferring the charge stored in the first charge storage region to the first overflow region, and by applying a potential to the second overflow gate electrode in such a way that the potential of the region directly below the second overflow gate electrode is lowered, thereby transferring the charge stored in the second charge storage region to the second overflow region; and A second reading process, after the charge transfer process, reading the amount of charge stored in the first charge storage region and the first overflow region, and reading the amount of charge stored in the second charge storage region and the second overflow region.

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