Light detection device and driving method of a light sensor

Abstract

In the light detecting device of the present application, the control section performs: a first charge transfer process for transferring the charge generated in the charge generation region to the charge storage region by applying a potential to the transfer gate electrode in such a manner that the potential of the region directly below the transfer gate electrode is lower than the potential of the charge generation region; and a first reading process for reading the amount of charge stored in the charge storage region. The control section applies a potential to the overflow gate electrode in such a manner that the potential of the region directly below the overflow gate electrode is lower than the potential of the charge generation region in the first charge transfer process.

Description

TECHNICAL FIELD

[0001] One aspect of the present disclosure relates to a light detection device provided with a light sensor and a driving method of the light sensor. BACKGROUND

[0002] In Patent Literature 1, there is described a light sensor provided with a photodiode that generates electric charges according to incident light, a floating region that stores the electric charges from the photodiode, and a storage capacitor element that stores the electric charges overflowing from the floating region.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2005 / 083790 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the light sensor described in Patent Literature 1, although the electric charges overflowing from the floating region are stored in the storage capacitor element, in a case where the electric charges are stored in the floating region to the extent of overflowing to the storage capacitor element, a part of the electric charges remains in the photodiode. In this case, the detection accuracy of light can be reduced due to the electric charges remaining in the photodiode. In particular, in a case where the light sensor is provided with a gating function that detects light only at a prescribed timing without detecting light across the entirety of a certain period, if the above situation occurs, the electric charges remaining in the photodiode in one period are read as electric charges generated in another period, and thus, the amount of electric charges generated at the prescribed timing can not be detected with high accuracy.

[0008] One aspect of the present disclosure aims to provide a light detection device and a driving method of a light sensor that can improve detection accuracy.

[0009] TECHNICAL MEANS FOR SOLVING THE PROBLEM

[0010] The light detection device of one aspect of the present disclosure includes a light sensor and a control section that controls the light sensor. The light sensor includes a charge generation region that generates charges in accordance with incident light, a charge storage region, an overflow region, a transfer gate electrode that is disposed on a region between the charge generation region and the charge storage region, and an overflow gate electrode that is disposed on a region between the charge storage region and the overflow region. The control section performs a first charge transfer process in which charges generated in the charge generation region are transferred to the charge storage region by applying a potential to the transfer gate electrode in such a manner that a potential of a region directly below the transfer gate electrode is lower than a potential of the charge generation region, and a first read process in which an amount of charges stored in the charge storage region is read after the first charge transfer process. In the first charge transfer process, a potential is applied to the overflow gate electrode in such a manner that a potential of a region directly below the overflow gate electrode is lower than the potential of the charge generation region.

[0011] In the light detection device, the light sensor includes an overflow region and an overflow gate electrode that is disposed on a region between the charge storage region and the overflow region. Thus, charges overflowing from the charge storage region can be stored in the overflow region, and saturation of the storage capacity can be suppressed. Also, during the first charge transfer process in which charges generated in the charge generation region are transferred to the charge storage region, a potential of a region directly below the overflow gate electrode is lower than a potential of the charge generation region. Thus, even in a case where charges stored in the charge storage region overflow to the overflow region, the charges can be suppressed from remaining in the charge generation region. Therefore, according to the light detection device, detection accuracy can be improved.

[0012] The control section can perform the first read process after the first charge transfer process is performed a plurality of times. In this case, an S / N ratio can be improved.

[0013] The charge generation region can include an avalanche multiplication region. In this case, avalanche multiplication can be induced in the charge generation region, and detection sensitivity of the light sensor can be improved. On the other hand, in a case where the charge generation region includes an avalanche multiplication region, an amount of generated charges becomes extremely large. In the light detection device, even in such a case, saturation of the storage capacity can be sufficiently suppressed, and remaining of charges in the charge generation region can be sufficiently suppressed.

[0014] It can also be that the control section performs: a second charge transfer process for transferring the charge stored in the charge storage region to the overflow region by applying a potential to the overflow gate electrode in a manner that the potential of the region directly below the overflow gate electrode is reduced after the first read process; and a second read process for reading the total amount of charge stored in the charge storage region and the overflow region after the second charge transfer process. In this case, not only the amount of charge stored in the charge storage region is read in the first read process, but also the total amount of charge stored in the charge storage region and the overflow region is read in the second read process, and thus the detection accuracy of the amount of charge can be improved.

[0015] It can also be that the light sensor further has: an 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, and the control section performs an excess charge transfer process during a period other than the period during which the first charge transfer process is performed, in which the charge generated in the charge generation region is transferred to the excess charge discharge region by applying a potential to the excess charge transfer gate electrode in a manner that the potential of the region directly below the excess charge transfer gate electrode is lower than the potential of the charge generation region. In this case, the charge generated in the charge generation region can be transferred to the excess charge discharge region during a period other than the period during which the first charge transfer process is performed, and the residual charge in the charge generation region can be further suppressed.

[0016] It can also be that the light detection device of one aspect of the present disclosure further has: a light source that emits detection light, and the control section performs the first charge transfer process during a period in which the reflected light of the detection light of the object enters the charge generation region. In this case, the amount of charge generated in the charge generation region during a period in which the reflected light of the detection light of the object enters the charge generation region can be detected with high accuracy.

[0017] It can also be that the light detection device of one aspect of the present disclosure further has: a photogate electrode disposed on the charge generation region, and the control section applies potentials to the photogate electrode and the overflow gate electrode in the first charge transfer process in a manner that the potential of the region directly below the transfer gate electrode is lower than the potential of the charge generation region and the potential of the region directly below the overflow gate electrode is lower than the potential of the charge generation region. In this case, the height of the potential can be adjusted with high accuracy.

[0018] It can also be that the overflow region has a charge storage capacity larger than the charge storage capacity of the charge storage region. In this case, saturation of the storage capacity can be effectively suppressed.

[0019] The driving method of the light sensor of one aspect of the present disclosure is a driving method of a light sensor that includes a charge generation region that generates electric charges in accordance with incident light, a charge storage region, an overflow region, a transfer gate electrode that is disposed on a region between the charge generation region and the charge storage region, and an overflow gate electrode that is disposed on a region between the charge storage region and the overflow region, the driving method of the light sensor including: a charge transfer step of transferring the electric charges generated in the charge generation region to the charge storage region by applying a potential to the transfer gate electrode in such a manner that the potential of a region directly below the transfer gate electrode is lower than the potential of the charge generation region; and a reading step of reading the amount of electric charges stored in the charge storage region after the charge transfer step, the potential of the overflow gate electrode being applied in such a manner that the potential of a region directly below the overflow gate electrode is lower than the potential of the charge generation region in the charge transfer step.

[0020] In the driving method of the light sensor, the light sensor includes an overflow region and an overflow gate electrode disposed on a region between the charge storage region and the overflow region. Thus, it is possible to store electric charges overflowing from the charge storage region in the overflow region, and it is possible to suppress saturation of the storage capacity. Also, during the charge transfer step of transferring the electric charges generated in the charge generation region to the charge storage region, the potential of a region directly below the overflow gate electrode is lower than the potential of the charge generation region. Thus, even in a case where the electric charges are stored in the charge storage region to the extent of overflowing to the overflow region, it is possible to suppress the electric charges from remaining in the charge generation region. Therefore, according to the driving method of the light sensor, it is possible to improve the detection accuracy.

[0021] Effects of Invention

[0022] According to one aspect of the present disclosure, it is possible to provide a light detection device and a driving method of a light sensor that can improve detection accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a configuration diagram of a distance measuring device of a first embodiment.

[0024] Figure 2 is a plan view of a pixel portion of a distance measuring sensor.

[0025] Figure 3 is a cross-sectional view along Figure 2 line III-III shown in FIG. 8.

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

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

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

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

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

[0031] Figure 9 is a plan view of a part of the distance measuring sensor of the first modification example.

[0032] Figure 10 is a timing chart showing an example of the operation of the distance measuring sensor of the first modification example.

[0033] Figure 11 is a plan view of a part of the distance measuring sensor of the second modification example.

[0034] Figure 12 is a timing chart showing an example of the operation of the distance measuring sensor of the second modification example.

[0035] Figure 13 is a circuit diagram of the distance measuring sensor of the third modification example.

[0036] Figure 14 is a configuration diagram of the light detecting device of the second embodiment.

[0037] Figure 15 is a plan view of a part of the image sensor of the second embodiment.

[0038] Figure 16 is a timing chart showing an example of the operation of the image sensor of the second embodiment.

[0039] Figure 17 is a diagram for illustrating the gating function of the light detecting device of the second embodiment.

[0040] Figure 18 is a timing chart showing an example of the operation of the image sensor of the modification example of the second embodiment. DETAILED DESCRIPTION

[0041] Hereinafter, one embodiment of the present disclosure will be explained in detail with reference to the drawings. Also, in the following explanation, the same reference signs are used for the same or equivalent elements, and repeated explanation is omitted.

[0042] [First Embodiment]

[0043] [Structure of Distance Measuring Device]

[0044] As Figure 1As shown, a distance measuring device (light detection device) 1 includes a light source 2, a distance measuring sensor (distance measuring image sensor, light sensor) 10A, a signal processing unit 3, a control unit 4, and a display unit 5. The distance measuring device 1 is a device that uses an indirect TOF method to obtain a distance image of an object OJ (an image containing information about the distance d to the object OJ).

[0045] Light source 2 emits pulsed light (detection light) L. Light source 2 is comprised of, for example, an infrared LED. Pulsed light L is, for example, near-infrared light, and the frequency of pulsed light L is, for example, 10 kHz or higher. Distance sensor 10A detects pulsed light L emitted from light source 2 and reflected by object OJ. Distance sensor 10A is constructed by monolithically forming a pixel unit 11 and a CMOS readout circuit unit 12 on a semiconductor substrate (e.g., a silicon substrate). Distance sensor 10A is mounted on signal processing unit 3.

[0046] The signal processing unit 3 controls the pixel unit 11 and CMOS readout circuit unit 12 of the distance measuring sensor 10A. The signal processing unit 3 performs predetermined processing on the signal output from the distance measuring sensor 10A to generate 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.

[0047] [Structure of the distance measuring sensor]

[0048] like Figure 2 and Figure 3 As shown, the distance measuring 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 measuring sensor 10A, the plurality of pixels 11a are arranged two-dimensionally along the first surface 20a. Hereinafter, the thickness direction of the semiconductor layer 20 is referred to as the Z direction, a direction perpendicular to the Z direction is referred to as the X direction, and a 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 to the first side) is referred to as the second side. In addition, in Figure 2In the figure, the configuration of the charge storage regions P1 to P4, the overflow regions Q1 to Q4, the excess charge discharge region R, the photogate electrode PG, the transfer gate electrodes TX1 to TX4, the overflow gate electrodes OV1 to OV4, and the excess charge transfer gate electrode RG, which will be described later, are schematically shown, and other elements are appropriately omitted.

[0049] 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 excess 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 various processes (e.g., etching, film formation, impurity implantation, and the like) performed on a semiconductor substrate (e.g., a silicon substrate).

[0050] The semiconductor region 21 is a region of p-type (first conductive type) and is provided in the semiconductor layer 20 along the second surface 20b. The semiconductor region 21 functions as a light absorption region (photoelectric conversion region). As an example, the semiconductor region 21 is a region having a carrier concentration of 1 x 1018cm-3and a thickness of 10 μm or less. 15 cm -3 The p-type region having the above carrier concentration has a thickness of 10 μm or less. Also, the avalanche multiplication region 22 and the like function as a light absorption region (photoelectric conversion region).

[0051] The avalanche multiplication region 22 includes a first multiplication region 22a and a second multiplication region 22b. The first multiplication region 22a is a region of p-type and is formed in the semiconductor layer 20 on a first side of the semiconductor region 21. As an example, the first multiplication region 22a is a region having a carrier concentration of 1 x 1018cm-3and a thickness of 1 μm or less. 16 cm -3 The p-type region having the above carrier concentration has a thickness of 1 μm or less. The second multiplication region 22b is a region of n-type (second conductive type) and is formed in the semiconductor layer 20 on a first side of the first multiplication region 22a. As an example, the second multiplication region 22b is a region having a carrier concentration of 1 x 1018cm-3and a thickness of 1 μm or less. 16 cm -3 The n-type region having the above carrier concentration has a thickness of 1 μm or less. The first multiplication region 22a and the second multiplication region 22b form a pn junction. The avalanche multiplication region 22 is a region in which avalanche multiplication is induced. In a case where a reverse bias of a prescribed value is applied, the electric field strength generated in the avalanche multiplication region 22 is, for example, 3 x 108to 4 x 108V / cm. 5 ~4 x 1085 V / cm.

[0052] The charge sharing 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 sharing region 23 has a 5×10 15 ~1×10 16 cm -3 The n-type region has a carrier concentration of about 1 μm in thickness.

[0053] Each charge storage region P1-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-P4 is connected to the charge distribution region 23. As an example, each first charge storage region P1-P4 has a 1×10 18 cm -3 The thickness of the n-type region having the above carrier concentration is approximately 0.2 μm.

[0054] Each overflow region Q1-Q4 is an n-type region formed on the first side of the second multiplication region 22b in the semiconductor layer 20. The charge storage capacity of the first overflow region Q1 is greater than that of the first charge storage region P1. The charge storage capacity of the second overflow region Q2 is greater than that of the second charge storage region P2. The charge storage capacity of the third overflow region Q3 is greater than that of the third charge storage region P3. The charge storage capacity of the fourth overflow region Q4 is greater than that of the fourth charge storage region P4. For example, the charge storage capacities of the charge storage regions P1-P4 are equal, and the charge storage capacities of the overflow regions Q1-Q4 are equal. While charge storage regions P1-P4 use PN junction capacitors, additional capacitors are provided in the overflow regions Q1-Q4, thereby increasing the storage capacity compared to charge storage regions P1-P4. Examples of the additional capacitors include MIM (Metal Insulator Metal) capacitors, MOS capacitors, trench capacitors, and PIP capacitors.

[0055] Each excess charge discharge region R is an n-type region formed on the first side of the second multiplication region 22b in the semiconductor layer 20. Each excess charge discharge region R is connected to the charge sharing region 23. For example, the excess charge discharge region R has the same structure as the charge storage regions P1 to P4.

[0056] The potential well region 31 is a region of p-type formed on a first side of the second multiplication region 22b on which the semiconductor layer 20 is formed. The potential well region 31 surrounds the charge distribution region 23 when viewed in the Z direction. The potential well region 31 constitutes a plurality of read circuits (e.g., a source follower amplifier, a reset transistor, and the like). 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 region of p-type having a carrier concentration of 1 x 10 16 ~ 5 x 10 17 cm -3 , and a thickness of 1 μm or less.

[0057] The potential barrier region 32 is a region of n-type formed between the second multiplication region 22b and the potential well region 31 on which the semiconductor layer 20 is formed. The potential barrier region 32 includes the potential well region 31 when viewed in the Z direction. That is, the potential well region 31 is located within the potential barrier region 32 when viewed in the Z direction. The potential barrier region 32 surrounds the charge distribution region 23. The concentration of n-type impurities of the potential barrier region 32 is higher than the concentration of n-type impurities of the second multiplication region 22b. As an example, the potential barrier region 32 is a region of n-type having a carrier concentration of from the carrier concentration of the second multiplication region 22b to several times the carrier concentration of the second multiplication region 22b, and a thickness of 1 μm or less. Since the potential barrier region 32 is formed between the second multiplication region 22b and the potential well region 31, even if a depletion layer formed in the avalanche multiplication region 22 by application of a high voltage to the avalanche multiplication region 22 spreads toward the potential well region 31, the depletion layer can be prevented from reaching the potential well region 31. That is, a current flow between the avalanche multiplication region 22 and the potential well region 31 due to the depletion layer reaching the potential well region 31 can be prevented.

[0058] Here, the positional relationship of the regions will be described. The first charge storage region P1 opposes the second charge storage region P2 in the X direction with the charge distribution region 23 interposed 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.

[0059] The third charge storage region P3 opposes the fourth charge storage region P4 in the X direction through the charge distribution region 23. 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 PI 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 Ql 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 excess charge drain regions R oppose each other in the Y direction through the charge distribution region 23.

[0060] The pixel 11a has, on 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 excess charge transfer gate electrodes RG. The gate electrodes PG, TX1 to TX4, OV1 to OV4, and RG are formed on the first surface 20a of the semiconductor layer 20 through the insulating film 41. The insulating film 41 is, for example, a silicon nitride film, a silicon oxide film, or the like.

[0061] 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, such as polysilicon. As an example, the photogate electrode PG has, in a case where viewed from the Z direction, a rectangular shape having two edges opposing in the X direction and two edges opposing in the Y direction. The region directly below the photogate electrode PG in the semiconductor region 21, the avalanche multiplication region 22, and the charge distribution region 23 functions as a charge generation region 24 that generates charges in accordance with 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 where the pulsed light L is incident on the semiconductor layer 20 from the opposite electrode 50 side (a back surface incidence case), the photogate electrode PG can not have light transmissivity, unlike the embodiment. The region directly below the photogate electrode PG refers to a region that coincides with the photogate electrode PG in a case where viewed from the Z direction. This is the same for the other gate electrodes TX1 to TX4, OV1 to OV4, and RG.

[0062] The first transfer gate electrode TX1 is disposed on a region between the charge generation region 24 and the first charge storage region P1 of the charge distribution region 23. The second transfer gate electrode TX2 is disposed on a region between the charge generation region 24 and the second charge storage region P2 of the charge distribution region 23. The third transfer gate electrode TX3 is disposed on a region between the charge generation region 24 and the third charge storage region P3 of the charge distribution region 23. The fourth transfer gate electrode TX4 is disposed on a region between the charge generation region 24 and the fourth charge storage region P4 of the charge distribution region 23.

[0063] Each of the transfer gate electrodes TX1 to TX4 is formed of a material having conductivity, such as polysilicon. As an example, each of the transfer gate electrodes TX1 to TX4 has a rectangular shape having two edges opposite in the X direction and two edges opposite in the Y direction when viewed in the Z direction.

[0064] 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.

[0065] Each of the overflow gate electrodes OV1 to OV4 is formed of a material having conductivity, such as polysilicon. As an example, each of the overflow gate electrodes OV1 to OV4 has a rectangular shape having two edges opposite in the X direction and two edges opposite in the Y direction when viewed in the Z direction.

[0066] One of the excess charge transfer gate electrodes RG is disposed on a region between the charge generation region 24 and one of the pair of excess charge discharge regions R of the charge distribution region 23. The other of the excess charge transfer gate electrodes RG is disposed on a region between the charge generation region 24 and the other of the pair of excess charge discharge regions R of the charge distribution region 23. Each of the excess charge transfer gate electrodes RG is formed of a material having conductivity, such as polysilicon. As an example, each of the excess charge transfer gate electrodes RG has a rectangular shape having two edges opposite in the X direction and two edges opposite in the Y direction when viewed in the Z direction.

[0067] The distance measuring sensor 10A further includes a relative electrode 50 and a wiring layer 60 in the pixel portion 11. The relative electrode 50 is provided on the second surface 20b of the semiconductor layer 20. The relative electrode 50 includes a plurality of pixels 11a when viewed from the Z direction. The relative electrode 50 is opposite to the electrode layer 40 in the Z direction. The relative 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 connected to each pixel 11a and the CMOS reading circuit portion 12 (see Figure 1 A light incident opening 60a is formed in a portion of the wiring layer 60 that faces the photogate electrode PG of each pixel 11a.

[0068] exist Figure 4 , an example of the circuit structure of each pixel 11a is shown. Figure 4 As shown, each pixel 11 a includes a plurality of (four in this example) reset transistors RST connected to the overflow regions Q1 to Q4 , respectively, and a plurality of (four in this example) selection transistors SEL for selecting the pixel 11 a .

[0069] [Distance measuring sensor driving method]

[0070] While referring to Figure 5 and Figure 6 , while explaining an example of the operation of the distance measuring sensor 10A. The following operation is realized by the control unit 4 controlling the driving of the distance measuring sensor 10A. In 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 a 3×10 5 ~4×10 5 In this state, when pulse light L enters the semiconductor layer 20 through the light incident opening 60 a and the photogate electrode PG, electrons generated by absorption of the pulse light L are multiplied in the avalanche multiplication region 22 and move to the charge sharing region 23 at high speed.

[0071] In the generated object OJ (refer to Figure 1 ) is generated, a reset process (reset step) is first performed to apply a reset voltage to each reset transistor RST of each pixel 11a. 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 areas P1 to P4 and the overflow areas Q1 to Q4 are discharged to the outside, and the charge storage areas P1 to P4 and the overflow areas Q1 to Q4 are not charged (time T1, Figure 6(a)) The discharge of electric charges to the outside is performed, for example, via a reading circuit constituted by the well region 31 and the like, and the wiring layer 60. The operation will be described below focusing on one selected pixel 11a.

[0072] 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 are applied to the transfer gate electrodes TX1 to TX4. This causes a charge sharing process (charge sharing step) to distribute the charge generated in the charge generation region 24 among the charge storage regions P1 to P4.

[0073] For example, the charge transfer signal applied to the first transfer gate electrode TX1 is a voltage signal that alternates between positive and negative voltages with the potential of the photogate electrode PG as a reference, and has a period, pulse width, and phase that are the same as those of the charge transfer signal from the light source 2 (see Figure 1 ) are the same voltage signals as the intensity signals of the pulsed light L emitted by the second transfer gate electrode TX2, the third transfer gate electrode TX3, and the fourth transfer gate electrode TX4. 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 their phases are shifted by 90°, 180°, and 270°, respectively.

[0074] During the first period in which a positive voltage is applied to the first transfer gate electrode TX1, the potential φ of the region immediately below the first transfer gate electrode TX1 is TX1 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG In other words, during the first period, the potential φ TX1 Specific potential φ PG In a low-voltage mode, a potential is applied 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 (first charge transfer process, first charge transfer step). Figure 6 In (b), the potential φ when a positive voltage is applied to the first transfer gate electrode TX1 TX1 The dotted line indicates the potential φ when a negative voltage is applied to the first transfer gate electrode TX1. TX1 In addition, the charges stored in the first charge storage region P1 and the first overflow region Q1 are indicated by hatching.

[0075] Furthermore, when adjusting the potential of the region directly below the gate electrode, the potential applied to the gate electrode may be adjusted, or the carrier concentration of the region directly below the gate electrode may be adjusted instead of or in addition to the potential. PG When the carrier concentration is adjusted to a predetermined height, the photogate electrode PG may not be provided. In this case, the negative voltage may not be applied.

[0076] During the first period, a negative voltage is applied to the second to fourth transfer gate electrodes TX2 to TX4, and the potential φ of the region directly below the second transfer gate electrode TX2 is TX2 , the potential φ of the region directly below the third transfer gate electrode TX3 TX3 and the potential φ of the region immediately below the fourth transfer gate electrode TX4 TX4 Specific 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 charge generated in the charge generation region 24 is not transferred to the second to fourth charge storage regions P2 to P4. In other words, during the first period, the potential φ TX2 、φ TX3 and φ TX4 Specific potential φ PG In the high mode, a potential is applied to the photo gate electrode PG and the second to fourth transfer gate electrodes TX2 to TX4.

[0077] Furthermore, during the first period, the potential φ of the region directly below the first overflow gate electrode OV1 is OV1 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG In other words, the potential applied to the first overflow gate electrode OV1 during the first period is set so that the potential φ is equal to the potential of the photogate electrode PG. OV1 Specific potential φ PG Low. Therefore, Figure 6 As shown in (b), even when the first charge storage region P1 is saturated with charges, charges 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.

[0078] During the second period in which the positive voltage is applied to the second transfer gate electrode TX2, the potential φ of the region immediately below the second transfer gate electrode TX2 is TX2 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG In other words, during the second period, the potential φTX2 the potential φ PG In the second period, the potential is applied to the photoelectric gate electrode PG and the second transfer gate electrode TX2 in such a manner that the potential φ TX1 , φ TX3 , and φ TX4 is higher than the potential φ PG In the second period, the potential is applied to the photoelectric gate electrode PG and the second transfer gate electrode TX2 in such a manner that the potential φ

[0079] In the second period, the potential is applied to the photoelectric gate electrode PG and the second transfer gate electrode TX2 in such a manner that the potential φ OV2 is lower than the potential φ PG In the second period, the potential is applied to the photoelectric gate electrode PG and the second transfer gate electrode TX2 in such a manner that the potential φ

[0080] In the third period in which a positive voltage is applied to the third transfer gate electrode TX3, the potential φ TX3 is lower than the potential φ PG In the third period, the potential is applied to the photoelectric gate electrode PG and the third transfer gate electrode TX3 in such a manner that the potential φ TX3 is lower than the potential φ PG In the third period, the potential is applied to the photoelectric gate electrode PG and the third transfer gate electrode TX3 in such a manner that the potential φ TX1 , φ TX2 , and φ TX4 is higher than the potential φ PG In the third period, the potential is applied to the photoelectric gate electrode PG and the third transfer gate electrode TX3 in such a manner that the potential φ

[0081] In the third period, the potential is applied to the photoelectric gate electrode PG and the third transfer gate electrode TX3 in such a manner that the potential φ OV3 is lower than the potential φ PGThe potential is applied to the photoelectric gate electrode PG and the third overflow gate electrode OV3 in such a manner that the potential of the region directly below the third overflow gate electrode OV3 is lower than the potential of the region directly below the photoelectric gate electrode PG. Thus, even in the case where the charge of the third charge storage region P3 is saturated, the charge 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.

[0082] In the 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 is higher than the potential φ of the region directly below the photoelectric gate electrode PG. TX4 PG In other words, in the fourth period, the potential φ of the region directly below the photoelectric gate electrode PG is lower than the potential φ of the region directly below the fourth transfer gate electrode TX4. TX4 PG The potential is applied to the photoelectric gate electrode PG and the fourth transfer gate electrode TX4 in such a manner that the potential of the region directly below the fourth transfer gate electrode TX4 is lower than the potential of the region directly below the photoelectric gate electrode PG. Thus, the charge generated in the charge generation region 24 is transferred to the fourth charge storage region P4 (first charge transfer processing, first charge transfer step). In the fourth period, the potentials φ TX1 TX3 PG The potential is applied to the photoelectric gate electrode PG and the first to third transfer gate electrodes TX1 to TX3 in such a manner that the potential of the region directly below each of the first to third transfer gate electrodes TX1 to TX3 is higher than the potential of the region directly below the photoelectric gate electrode PG.

[0083] In the fourth period, the potential φ of the region directly below the fourth overflow gate electrode OV4 is lower than the potential φ of the region directly below the photoelectric gate electrode PG. OV4 PG The potential is applied to the photoelectric gate electrode PG and the fourth overflow gate electrode OV4 in such a manner that the potential of the region directly below the fourth overflow gate electrode OV4 is lower than the potential of the region directly below the photoelectric gate electrode PG. Thus, even in the case where the charge of 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.

[0084] After the charge distribution processing in the storage period T2, the first read processing (high-sensitivity read processing) of reading the amount of charge stored in each of the charge storage regions P1 to P4 is performed (first read step) (time T3, Figure 6 (c)). The first read processing is performed after each of the processing in which the charge generated in the charge generation region 24 is transferred to the first charge storage region P1, the processing in which the charge generated in the charge generation region 24 is transferred to the second charge storage region P2, the processing in which the charge generated in the charge generation region 24 is transferred to the third charge storage region P3, and the processing in which the charge generated in the charge generation region 24 is transferred to the fourth charge storage region P4 is performed a plurality of times.

[0085] ​​​​​After the first reading process, a charge transfer process (charge transfer step) is performed (second charge transfer process, second charge transfer step) in which a potential φ of a region directly below the first overflow gate electrode OV1 is lowered by applying a voltage greater than the voltage applied in the first period to the first overflow gate electrode OV1. OV1 , thereby transferring the charges stored in the first charge storage region P1 to the first overflow region Q1 ( Figure 6 (d)). In other words, in the charge transfer process, by OV1 A potential is applied to the first overflow gate electrode OV1 in a decreasing manner, so that the charges stored in the first charge storage region P1 are transferred to the first overflow region Q1.

[0086] Likewise, in the charge transfer process, the potential φ of the region immediately below the second overflow gate electrode OV2 is set to OV2 The potential of the second overflow gate electrode OV2 is applied in a decreasing manner, so that the charge stored in the second charge storage region P2 is transferred to the second overflow region Q2. OV3 The potential of the third overflow gate electrode OV3 is applied in a decreasing manner, so that the charge stored in the third charge storage region P3 is transferred to the third overflow region Q3. OV4 A potential is applied to the fourth overflow gate electrode OV4 in a decreasing manner, so that the charges stored in the fourth charge storage region P4 are transferred to the fourth overflow region Q4.

[0087] 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. After the second read process, the above reset process is performed again (time T1, Figure 6 (a)), the above series of processing is repeatedly performed.

[0088] 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 φ. RGThe potential φ of the region (charge generation region 24) directly below the photoelectric grid electrode PG PG is low. In other words, the potential φ of the photoelectric grid electrode PG and the excess charge transfer grid electrode RG is applied in a manner lower than the potential φ of the charge generation region 24. RG The potential φ of the region (charge generation region 24) directly below the photoelectric grid electrode PG PG is low. In other words, the potential φ of the photoelectric grid electrode PG and the excess charge transfer grid electrode RG is applied in a manner lower than the potential φ of the charge generation region 24.

[0089] As shown in FIG. 1, when the pulsed light L is emitted from the light source 2, the phase of the intensity signal of the pulsed light L detected by the distance measuring sensor 10A shifts from the phase of the intensity signal of the pulsed light L emitted from the light source 2 depending on the distance d to the object OJ when the pulsed light L reflected at the object OJ is detected by the distance measuring sensor 10A. Therefore, by taking a signal based on the amount of charge stored in the charge storage regions P1 to P4 and the overflow regions Q1 to Q4 (i.e., the amount of charge read in the first read processing and the second read processing) for each pixel 11a, it is possible to generate a distance image of the object OJ. Figure 1 [Effects of the First Embodiment]

[0090] [Effects of the First Embodiment]

[0091] In the distance measuring device 1, the distance measuring sensor 10A has: a first overflow region Q1 having a charge storage capacity larger than the charge storage capacity of the first charge storage region P1; a second overflow region Q2 having a charge storage capacity larger than the charge storage capacity of the second charge storage region P2; a first overflow grid electrode OV1 disposed on a region between the first charge storage region P1 and the first overflow region Q1; and a second overflow grid electrode OV2 disposed on a region between the second charge storage region P2 and the second overflow region Q2. Thereby, it is possible to store the charge overflowing from the first charge storage region P1 in the first overflow region Q1, and it is possible to store the charge overflowing from the second charge storage region P2 in the second overflow region Q2. As a result, it is possible to suppress saturation of the storage capacity. In addition, in the first period of the charge distribution processing, the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the charge generation region 24, and in the second period of the charge distribution processing, the potential φ of the region directly below the second overflow grid electrode OV2 is lower than the potential φ of the charge generation region 24. OV1 the potential φ of the charge generation region 24, and in the second period of the charge distribution processing, the potential φ of the region directly below the second overflow grid electrode OV2 is lower than the potential φ of the charge generation region 24. PG the potential φ of the charge generation region 24, and in the second period of the charge distribution processing, the potential φ of the region directly below the second overflow grid electrode OV2 is lower than the potential φ of the charge generation region 24. OV2 the potential φ of the charge generation region 24, and in the second period of the charge distribution processing, the potential φ of the region directly below the second overflow grid electrode OV2 is lower than the potential φ of the charge generation region 24. PGThus, even when charge is accumulated in the first charge storage region P1 to the extent that it overflows into the first overflow region Q1, and even when charge is accumulated in the second charge storage region P2 to the extent that it overflows into the second overflow region Q2, it is possible to suppress charge from remaining in the charge generation region 24. Therefore, the distance measuring device 1 can improve the accuracy of distance measurement. Furthermore, it can achieve higher sensitivity and a wider dynamic range.

[0092] Regarding this, see Figure 7 and Figure 8 In the image sensor of the comparative example, the potential φ of the region directly below the gate electrode TX is transferred over the entire storage period T2. TX than the potential φ of the region directly below the photogate electrode PG PG high( Figure 8 (b)). In addition, the potential φ of the region directly below the gate electrode 0V overflows over the entire storage period T2. OV than the potential φ of the region directly below the photogate electrode PG PG After the storage period T2, the potential φ of the region directly below the transfer gate electrode TX is TX than the potential φ of the region directly below the photogate electrode PG (charge generation region) PG The charge stored in the charge generation region is transferred to the charge storage region P. Then, the charge amount stored in the charge storage region P is read (time T3, Figure 8 (c)).

[0093] In the image sensor of the comparative example, the potential φ overflows from the region immediately below the gate electrode 0V during the storage period T2. OV than the potential φ of the region directly below the photogate electrode PG PG High, therefore, Figure 8 As shown in (c), when charge is accumulated in the charge storage region P to the extent that it overflows into the overflow region Q, some of the charge remains in the region (charge generation region) directly below the photogate electrode PG. In this case, the charge remaining in the charge storage region may cause a decrease in the accuracy of distance measurement.

[0094] In contrast, as described above, in the distance measuring device 1, during the charge sharing process, the potential φ of the region immediately below the first overflow gate electrode OV1 is OV1 and the potential φ just below the second overflow gate electrode OV2 OV2 The potential φ of the charge generation region 24 PGLow. Thus, even in a case where the electric charges are stored in the first charge storage region P1 or the second charge storage region P2 to the extent of overflowing to the first overflow region Q1 or the second overflow region Q2, the electric charges can be suppressed from remaining in the charge generation region 24.

[0095] The control section 4 executes, after a plurality of times of execution of the first charge transfer process of transferring the electric charges generated in the charge generation region 24 to the first charge storage region P1, the first read process of reading the amount of electric charges stored in the charge storage region P1. Thus, the S / N ratio can be improved.

[0096] The charge generation region 24 includes the avalanche multiplication region 22. In this case, the avalanche multiplication can be induced in the charge generation region 24, and the detection sensitivity of the distance measuring sensor 10A can be improved. On the other hand, in a case where the charge generation region 24 includes the avalanche multiplication region 22, the amount of generated electric charges 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 of the electric charges in the charge generation region 24 can be sufficiently suppressed.

[0097] The control section 4 executes the first read process, the second charge transfer process, and the second read process, in which, in the first read process, the amount of electric charges stored in the first charge storage region P1 and the second charge storage region P2 is read, in the second charge transfer process, the electric charges stored in the first charge storage region P1 are transferred to the first overflow region Q1 and the electric charges stored in the second charge storage region P2 are transferred to the second overflow region Q2, and in the second read process, the total amount of electric charges stored in the first charge storage region P1 and the first overflow region Q1 is read, and the total amount of electric charges stored in the second charge storage region P2 and the second overflow region Q2 is read. Thus, not only the amount of electric charges stored in the first and second charge storage regions P2 is read in the first read process, but also the total amount of electric charges stored in the first charge storage region P1 and the first overflow region Q1 and the total amount of electric charges stored in the second charge storage region P2 and the second overflow region Q2 are read in the second read process, and thus, the detection accuracy of the amount of electric charges can be improved.

[0098] The control section 4 executes, in a period other than the first period and the second period (i.e., a period other than the period in which the first charge transfer process is executed), the excess charge transfer process of transferring the electric charges generated in the charge generation region 24 to the excess charge discharge region R by the excess charge transfer gate electrode RG. Thus, the electric charges generated in the charge generation region 24 in the period other than the first and second periods can be transferred to the excess charge discharge region R, and the remaining of the electric charges in the charge generation region 24 can be further suppressed. The excess charge transfer process is particularly effective in an environment where ambient light is much.

[0099] The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. TX1 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. OV1 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. TX2 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. OV2 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. TX3 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. OV3 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. TX4 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. OV4 The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period. PG The control section 4 applies potentials to the photoelectric grid electrode PG and the first transfer grid electrode TX1 in a manner that the potential φ of the region directly below the first transfer grid electrode TX1 is higher than the potential φ of the region directly below the photoelectric grid electrode PG and the potential φ of the region directly below the first overflow grid electrode OV1 is lower than the potential φ of the region directly below the photoelectric grid electrode PG during the first period.

[0100] The distance measuring sensor 10A has not only 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 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. Also, the control section 4, in the charge distribution processing, distributes the charge generated in the charge generation region 24 among the charge storage regions P1 to P4 by applying the charge transfer signals having different phases from each other to the transfer gate electrodes TX1 to TX4. Thus, the charge distribution by the first to fourth transfer gate electrodes TX1 to TX4 can be achieved, and the precision of distance measurement can be improved.

[0101] [Modified example of the first embodiment]

[0102] In the distance measuring sensor 10B of the first modified example shown in Figure 9 In the distance measuring sensor 10B of the first modified example shown in Figure 10 In the distance measuring sensor 10B of the first modified example shown in

[0103] In the distance measuring sensor 10C of the second modified example shown in Figure 11 In the distance measuring sensor 10C of the second modified example shown in

[0104] In the distance measuring sensor 10C of the second modified example shown in Figure 12is driven as shown. In this driving method, during the storage period T2, the first period in which a positive voltage is applied to the first transfer gate electrode TX1, the second period in which a positive voltage is applied to the second transfer gate electrode TX2, and the period in which the excess charge transfer processing of transferring the charge generated in the charge generation region 24 to the excess charge discharge region R are sequentially repeated. By such a driving method, it is also possible to generate a distance image of the object OJ. By the third modification example as well, as with the above embodiment, it is possible to suppress saturation of the storage capacity and the residual of the charge in the charge generation region 24, and improve the precision of distance measurement.

[0105] As shown in a third modification example as shown in Figure 13 , the reset transistor RST can also be disposed at a position different from the embodiment. In Figure 13 , only the circuit structure of a part of the pixel 11a is shown. By the third modification example as well, as with the above embodiment, it is possible to suppress saturation of the storage capacity and the residual of the charge in the charge generation region 24, and improve the precision of distance measurement.

[0106] [Second Embodiment]

[0107] As shown in Figure 14 , the light detection device 100 is provided with the light source 2, the image sensor 10D, the control section 4, and the optical system 6. The light detection device 100 is configured as a range gate camera, which is provided with a gate function (shutter function) of detecting light coming at a prescribed time (prescribed period). The optical system 6 guides the pulsed light L emitted from the light source 2 and reflected at the object OJ to the pixel section 11 of the image sensor 10D.

[0108] As shown in Figure 15 , the image sensor 10D differs from the above distance measuring sensor 10A in that the second to fourth charge storage regions P2 to P4, the second to fourth overflow regions Q2 to Q4, the second to fourth transfer gate electrodes TX2 to TX4, and the second to fourth overflow gate electrodes OV2 to OV4 are not provided. In the image sensor 10D, the first charge storage region P1 and the excess charge discharge region R are disposed on one side in the X direction with respect to the charge generation region 24 (photogate electrode PG). The first charge storage region P1 and the excess charge discharge region R are arranged in the Y direction. The first transfer gate electrode TX1 and the excess charge transfer gate electrode RG are arranged in the Y direction.

[0109] The light detection device 100, for example, is like Figure 16The drive method is shown in FIG. In this driving method, during the storage period T2, a first charge transfer process (first charge transfer step) is repeatedly performed to transfer the charge generated in the charge generation region 24 to the first charge storage region P1, instead of the charge sharing process. For example, the charge transfer signal applied to the first transfer gate electrode TX1 is a voltage signal that alternates between positive and negative voltages with the potential of the photogate electrode PG as a reference. The voltage signal has a period and pulse width identical to the intensity signal of the pulsed light L emitted from the light source 2, except for a phase shift of a predetermined amount.

[0110] During the period in which a positive voltage is applied to the first transfer gate electrode TX1, the potential φ of the region immediately below the first transfer gate electrode TX1 is TX1 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG In other words, during this period, the potential φ TX1 Specific potential φ PG In a low state, a potential is applied to the photo gate electrode PG and the first transfer gate electrode TX1 , thereby transferring the charges generated in the charge generation region 24 to the first charge accumulation region P1 .

[0111] On the other hand, during the period in which a negative voltage is applied to the first transfer gate electrode TX1, the potential φ of the region immediately below the first transfer gate electrode TX1 is TX1 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG In other words, during this period, the potential φ TX1 Specific potential φ PG A potential is applied to the photo gate electrode PG and the first transfer gate electrode TX1 in a high manner. This creates a potential barrier between the charge generation region 24 and the first charge accumulation region P1, and the charges generated in the charge generation region 24 are not transferred to the first charge accumulation region P1.

[0112] Furthermore, during the storage period T2, the potential φ of the region directly below the first overflow gate electrode OV1 is OV1 than the potential φ of the region directly below the photogate electrode PG (charge generation region 24) PG A potential is applied to the photo gate electrode PG and the first overflow gate electrode OV1 in a low manner. Thus, even when the first charge storage region P1 is saturated with charge, 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.

[0113] Further, during a period other than the period during which the first charge transfer processing is performed, a surplus charge transfer processing (surplus charge transfer step) of transferring the charge generated in the charge generation region 24 to the surplus charge discharge region R is performed. In the surplus charge transfer processing, the potential φ RG of the region directly below the photogate electrode PG (charge generation region 24) is made lower than the potential φ PG of the region directly below the surplus charge transfer gate electrode RG in such a manner that the potential is applied to the photogate electrode PG and the surplus charge transfer gate electrode RG. Thereby, the charge generated in the charge generation region 24 is transferred to the surplus charge discharge region R.

[0114] After the charge transfer processing is performed a plurality of times during the storage period T2, a first read processing (high sensitivity read processing) of reading the amount of the charge stored in the first charge storage region P1 is performed (first read step) (time T3). After the first read processing, a second charge transfer processing (second charge transfer step) is performed in which the potential φ OV1 of the region directly below the first overflow gate electrode OV1 is lowered by applying a voltage larger than the voltage applied during the storage period T2 to the first overflow gate electrode OV1, so that the charge stored in the first charge storage region P1 is transferred to the first overflow region Q1. In other words, in the second charge transfer processing, the potential φ OV1 of the region directly below the first overflow gate electrode OV1 is made lower than the potential φ OV1 of the region directly below the surplus charge transfer gate electrode RG in such a manner that the potential is applied to the first overflow gate electrode OV1, so that the charge stored in the first charge storage region P1 is transferred to the first overflow region Q1. After the second charge transfer processing, a second read processing (low sensitivity read processing) of reading the total amount of the charge stored in the first charge storage region P1 and the first overflow region Q1 is performed (second read step) (time T4).

[0115] Reference Figure 17 will be described. As shown in the example of (1) shown in FIG. 10, in a case where the pulsed light L reflected in the vicinity of the object OJ1 at a distance d1 from the image sensor 10D is detected, the voltage signal whose phase is shifted by an amount corresponding to the distance d1 is applied to the first transfer gate electrode TX1. Thereby, during a period in which the pulsed light L reflected in the vicinity of the object OJ1 (i.e., in a range of a prescribed distance from the image sensor 10D) is incident on the charge generation region 24, the first charge transfer processing of transferring the charge generated in the charge generation region 24 to the first charge storage region P1 can be performed. As a result, only the pulsed light L reflected in the vicinity of the object OJ1 can be detected. Similarly, as shown in the example of (2) shown in FIG. 11, in a case where the pulsed light L reflected in the vicinity of the object OJ2 at a distance d2 from the image sensor 10D is detected, the voltage signal whose phase is shifted by an amount corresponding to the distance d2 is applied to the first transfer gate electrode TX1. Thereby, during a period in which the pulsed light L reflected in the vicinity of the object OJ2 (i.e., in a range of a prescribed distance from the image sensor 10D) is incident on the charge generation region 24, the first charge transfer processing of transferring the charge generated in the charge generation region 24 to the first charge storage region P1 can be performed. As a result, only the pulsed light L reflected in the vicinity of the object OJ2 can be detected. Figure 17As shown in the examples of (2) to (4), in a case where the pulse light L reflected in a range of a prescribed distance from the image sensor 10D is detected, a voltage signal of an amount of phase shift corresponding to the distance is applied to the first transfer gate electrode TX1. In this way, according to the light detection device 100, a gating function of detecting only light coming at a prescribed timing can be implemented. The gating function can be applied to, for example, measurement of fluorescence lifetime.

[0116] [Effects and advantages of the second embodiment]

[0117] In the light detection device 100, the image sensor 10D has a first overflow region Q1 having a charge storage capacity larger than a charge storage capacity of the first charge storage region P1, and a first overflow gate electrode OV1 disposed on a region between the first charge storage region P1 and the first overflow region Q1. Thereby, the charge overflowing from the first charge storage region P1 can be stored in the first overflow region Q1, and saturation of the storage capacity can be suppressed. Also, during execution of the first charge transfer processing of transferring the charge generated in the charge generation region 24 to the first charge storage region P1, the potential φ OV1 of the region directly below the first overflow gate electrode OV1 is lower than the potential φ PG of the charge generation region 24. Thereby, even in a case where the charge is stored in the first charge storage region P1 to the extent of overflowing to the first overflow region Q1, the charge can be suppressed from remaining in the charge generation region 24. Therefore, according to the light detection device 100, the detection accuracy can be improved.

[0118] The control section 4 executes the first read processing after the first charge transfer processing is executed a plurality of times. Thereby, the S / N ratio can be improved.

[0119] The charge generation region 24 includes an avalanche multiplication region 22. Thereby, avalanche multiplication can be induced in the charge generation region 24, and the detection sensitivity of the image sensor 10D can be improved. On the other hand, in a case where the charge generation region 24 includes the avalanche multiplication region 22, the amount of generated charge becomes extremely large, but in the light detection device 100, even in such a case, saturation of the storage capacity can be sufficiently suppressed, and the charge remaining in the charge generation region 24 can be sufficiently suppressed.

[0120] The control section 4 executes: a second charge transfer processing of transferring the charge stored in the first charge storage region P1 to the first overflow region Q1, and a second read processing of reading the total amount of charge stored in the first charge storage region P1 and the first overflow region Q1. Thereby, not only the amount of charge stored in the first charge storage region P1 is read in the first read processing, but also the total amount of charge stored in the first charge storage region P1 and the first overflow region Q1 is read in the second read processing, and therefore, the detection accuracy of the amount of charge can be improved.

[0121] The control unit 4 performs an excess charge transfer process to transfer the charge generated in the charge generation region 24 to the excess charge discharge region R via the excess charge transfer gate electrode RG during periods other than the period during which the first charge transfer process is performed. This allows the charge generated in the charge generation region 24 during periods other than the period during which the first charge transfer process is performed to be transferred to the excess charge discharge region R, further suppressing the residual charge in the charge generation region 24. The excess charge transfer process is particularly effective in environments with high ambient light levels.

[0122] The control unit 4 executes the first charge transfer process while the pulsed light L reflected by the object OJ is incident on the charge generation region 24. This allows for highly accurate detection of the amount of charge generated in the charge generation region 24 while the pulsed light L reflected by the object OJ is incident on the charge generation region 24.

[0123] [Modification of the Second Embodiment]

[0124] As a modified example, in the image sensor 10D, the excess charge discharge region R and the excess charge transfer gate electrode RG may not be provided in each pixel portion 11. Figure 18 The image sensor is driven as shown. In this driving method, the excess charge transfer process, which transfers the charge generated in the charge generation region 24 to the excess charge discharge region R, is not performed. This modification, similar to the second embodiment described above, can also suppress saturation of the storage capacity and residual charge in the charge generation region 24, thereby improving detection accuracy. For example, the image sensor of this modification can be used in situations where ambient light is unlikely to enter the charge generation region 24 during periods other than the period during which the first charge transfer process is performed. An example of such a situation is when light detection is performed in a dark room.

[0125] The present disclosure is not limited to the above-described embodiments and modifications. For example, the materials and shapes of each structure are not limited to those described above, and various materials and shapes can be used. In the distance measuring sensors 10A, 10C, and the image sensor 10D, the charges transferred to the excess charge discharge regions R, R1 to R4 can be stored and read without being discharged to the outside. In other words, the excess charge discharge regions R, R1 to R4 can also function as charge storage regions. In this case, light other than signal light (light that does not contain distance information) can be read and used.

[0126] The avalanche multiplication region 22 can not be formed in the semiconductor layer 20. That is, the charge generation region 24 can not include the avalanche multiplication region 22. At least one of the potential well region 31 and the potential barrier region 32 can not be formed in the semiconductor layer 20. The signal processing section 3 can be omitted, and the control section 4 can be directly connected to the distance measuring sensors 10A to 10C. The second charge transfer processing and the second reading processing can not be performed. The first reading processing can be performed after the first charge transfer processing is performed once.

[0127] In the distance measuring sensors 10A to 10C and the image sensor 10D, light can be made incident on the semiconductor layer 20 from either of the first side and the second side. For example, in a case where light is made incident on the semiconductor layer 20 from the second side, the counter electrode 50 can be formed of a material having conductivity and light transmittance, such as polysilicon. In any one of the distance measuring sensors 10A to 10C and the image sensor 10D, the respective conductive types of p-type and n-type can be reversed from the above-described case. In any one of the distance measuring sensors 10A to 10C and the image sensor 10D, the plurality of pixels 11a can be arranged one-dimensionally along the first surface 20a of the semiconductor layer 20. Any one of the distance measuring sensors 10A to 10C and the image sensor 10D can have only a single pixel 11a. The charge storage capacity of the first overflow region Q1 can 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 be equal to or less than the charge storage capacity of the second charge storage region P2.

[0128] Explanation of Reference Signs

[0129] 1 …… distance measuring device (light detecting device), 100 …… light detecting device, 2 …… light source, 4 …… control section, 10A, 10B, 10C …… distance measuring sensor (image sensor, light sensor), 10D …… image sensor (light sensor), 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 …… excess charge discharge region, 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 …… excess charge transfer gate electrode.

Claims

1. A light detection device, wherein: have: Light sensor; and a control unit that controls the light sensor, The light sensor has: a charge generation region that generates charge in response to incident light; charge storage area; overflow area; a transfer gate electrode disposed on a region between the charge generation region and the charge storage region; and an overflow gate electrode disposed on a region between the charge storage region and the overflow region, The control unit performs: a first charge transfer process of applying a potential to the transfer gate electrode so that the potential of a region immediately below the 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 charge storage region; and a first reading process, after the first charge transfer process, reading the amount of charge stored in the charge storage region; In the first charge transfer process, a potential is applied to the overflow gate electrode so that the potential of the region immediately below the overflow gate electrode is lower than the potential of the charge generation region. In the first charge transfer process, a potential is applied to the overflow gate electrode so that the potential of the region immediately below the overflow gate electrode is higher than the potential of the region immediately below the transfer gate electrode.

2. The light detection device according to claim 1, wherein The control unit executes the first reading process after executing the first charge transfer process a plurality of times.

3. The light detection device according to claim 1 or 2, wherein: The charge generation region includes an avalanche multiplication region.

4. The light detection device according to any one of claims 1 to 3, wherein The control unit performs: a second charge transfer process of transferring the charge stored in the charge storage region to the overflow region by applying a potential to the overflow gate electrode in such a manner that the potential of the region directly below the overflow gate electrode decreases after the first reading process; and The second reading process reads the total amount of charge stored in the charge storage region and the overflow region after the second charge transfer process.

5. The light detection device according to any one of claims 1 to 4, wherein The light sensor also has: Excess charge drain area; and an excess charge transfer gate electrode, which is arranged on a region between the charge generation region and the excess charge discharge region, The control unit performs excess charge transfer processing during a period other than a period during which the first charge transfer processing is performed, wherein a potential is applied to the excess charge transfer gate electrode in such a manner that the potential of the area directly below the excess charge transfer gate electrode is lower than the potential of the charge generation area, thereby transferring the charge generated in the charge generation area to the excess charge discharge area.

6. The light detection device according to any one of claims 1 to 5, wherein It also includes: a light source for emitting detection light, The control unit executes the first charge transfer process while reflected light of the detection light of the object is incident on the charge generation region.

7. The light detection device according to any one of claims 1 to 6, wherein It also includes: a photogate electrode, which is arranged on the charge generation region, The control unit applies a potential to the photogate electrode and the overflow gate electrode in the first charge transfer process in such a manner that the potential of the area directly below the transfer gate electrode is lower than the potential of the charge generation area and the potential of the area directly below the overflow gate electrode is lower than the potential of the charge generation area.

8. The light detection device according to any one of claims 1 to 7, wherein The overflow region has a charge storage capacity greater than a charge storage capacity of the charge storage region.

9. A method for driving a light sensor, wherein: is the driving method of the light sensor, The light sensor comprises: a charge generation region that generates charge in response to incident light; charge storage area; overflow area; a transfer gate electrode disposed on a region between the charge generation region and the charge storage region; and an overflow gate electrode disposed on a region between the charge storage region and the overflow region, The driving method of the light sensor includes: a charge transfer step of applying a potential to the transfer gate electrode so that the potential of a region immediately below the 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 charge storage region; and a reading step of reading the amount of charge stored in the charge storage region after the charge transfer step, In the charge transfer step, a potential is applied to the overflow gate electrode so that the potential of the region immediately below the overflow gate electrode is lower than the potential of the charge generation region. In the charge transfer step, a potential is applied to the overflow gate electrode so that the potential of a region immediately below the overflow gate electrode is higher than the potential of a region immediately below the transfer gate electrode.

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