Rangefinder image sensor

Abstract

In a range-finding image sensor, each pixel has an avalanche multiplication region, a charge distribution region, a pair of first charge transfer regions, a pair of second charge transfer regions, a well region, a photogate electrode, a pair of first transfer gate electrodes, and a pair of second transfer gate electrodes. A first multiplication region of the avalanche multiplication region is formed so as to overlap the charge distribution region and not overlap the well region in the Z direction. A second multiplication region of the avalanche multiplication region is formed so as to overlap the charge distribution region and the well region in the Z direction.

Description

Technical Field

[0001] This invention relates to a ranging image sensor. Background Technology

[0002] As a ranging image sensor that acquires a distance image of an object using an indirect TOF (Time of Flight) method, a known ranging image sensor includes a semiconductor layer with a light-sensing region and a photogate electrode and a transfer gate electrode disposed on the semiconductor layer for each pixel (see, for example, Patent Documents 1 and 2). According to such a ranging image sensor, the charge generated in the light-sensing region can be transferred at high speed through the incident light.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-133464

[0006] Patent Document 2: Japanese Patent Application Publication No. 2013-206903 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] In ranging image sensors as described above, for example, to enable longer measurable distances, it is sometimes necessary to increase light sensitivity.

[0009] The purpose of this invention is to provide a ranging image sensor that can improve light sensitivity while maintaining signal readout accuracy.

[0010] Technical solutions for solving technical problems

[0011] One aspect of the present invention provides a ranging image sensor, comprising: a semiconductor layer having a first surface on a first side and a second surface on the opposite side of the first side, i.e., a second side, for constituting a plurality of pixels arranged along the first surface; and an electrode layer disposed on the first surface for constituting the plurality of pixels, each of the plurality of pixels having: an avalanche multiplication region including a first multiplication region of a first conductivity type formed in the semiconductor layer, and a second multiplication region of a second conductivity type formed in the semiconductor layer on a first side of the first multiplication region; a charge distribution region of a second conductivity type formed in the semiconductor layer on a first side of the second multiplication region and connected to the second multiplication region; and a first charge transfer region of a second conductivity type formed in the semiconductor layer on a first side of the second multiplication region and connected to the charge distribution region; and in the semiconductor layer... A second charge transfer region of a second conductivity type is formed on the first side of the second multiplication region and connected to the charge distribution region; a first conductivity type well region is formed on the first side of the second multiplication region in the semiconductor layer; a photogate electrode is formed on the first side of the charge distribution region in the electrode layer; a first transfer gate electrode is formed on the first side of the charge distribution region in the electrode layer in a manner that the photogate electrode is located on the side of the first charge transfer region; and a second transfer gate electrode is formed on the first side of the charge distribution region in the electrode layer in a manner that the photogate electrode is located on the side of the second charge transfer region. The first multiplication region is formed to overlap with the charge distribution region and not with the well region in the thickness direction of the semiconductor layer, and the second multiplication region is formed to overlap with both the charge distribution region and the well region in the thickness direction of the semiconductor layer.

[0012] In this ranging image sensor, an avalanche multiplication region is formed in the semiconductor layer. This enables high sensitivity in each pixel of a plurality of pixels. Furthermore, on the second side of the well region of the first conductivity type, a second multiplication region of the second conductivity type is formed to overlap with the well region in the thickness direction of the semiconductor layer, and on the second side of the second multiplication region of the second conductivity type, a first multiplication region of the first conductivity type is formed to not overlap with the well region in the thickness direction of the semiconductor layer. Therefore, when a reverse bias voltage is applied to the semiconductor layer, the depletion layer in the portion of the second multiplication region that does not overlap with the first multiplication region in the thickness direction of the semiconductor layer is less likely to extend toward the well region, preventing the depletion layer from reaching the well region. That is, current flow between the avalanche multiplication region and the well region can be prevented due to the depletion layer reaching the well region. Therefore, improved light sensitivity can be achieved while maintaining signal readout accuracy.

[0013] In one aspect of the ranging image sensor of the present invention, each of the plurality of pixels may further have a barrier region of a second conductivity type formed in the semiconductor layer between the second multiplication region and the well region. Thus, even if the depletion layer formed in the second multiplication region extends toward the well region due to the application of a reverse bias to the semiconductor layer, the barrier region can prevent the depletion layer from reaching the well region. That is, it is possible to prevent current from flowing between the avalanche multiplication region and the well region due to the depletion layer reaching the well region.

[0014] In one aspect of the ranging image sensor of the present invention, the barrier region may also include a well region when viewed from the thickness direction of the semiconductor layer. This suppresses current flow between the avalanche multiplication region and the well region due to the depletion layer reaching the well region.

[0015] In one aspect of the ranging image sensor of the present invention, each of the plurality of pixels may further have a second conductivity type receiving region formed in the semiconductor layer on a first side of the barrier region and connected to the barrier region. Thus, because the charge accumulated around the barrier region of the second conductivity type can be introduced into the receiving region of the second conductivity type, the charge accumulated around the barrier region can be suppressed from becoming noise as parasitic charge.

[0016] In one aspect of the ranging image sensor of the present invention, the destination region may be connected to the second charge transfer region. Therefore, when the second charge transfer region is used as a useless charge discharge region, the charge introduced into the destination region can be discharged to the second charge transfer region.

[0017] In one aspect of the ranging image sensor of the present invention, the second multiplication region may include: a first region overlapping the charge distribution region in the thickness direction of the semiconductor layer, and a second region overlapping the well region in the thickness direction of the semiconductor layer, wherein the impurity concentration in the second region is higher than that in the first region. Therefore, even if a depletion layer in the second multiplication region that does not overlap with the first multiplication region in the thickness direction of the semiconductor layer extends towards the well region due to a reverse bias applied to the semiconductor layer, the second region can prevent the depletion layer from reaching the well region. That is, current flow between the avalanche multiplication region and the well region due to the depletion layer reaching the well region can be suppressed.

[0018] In one aspect of the ranging image sensor of the present invention, the second region may include a well region when viewed from the thickness direction of the semiconductor layer. This suppressively prevents current from flowing between the avalanche multiplication region and the well region due to the depletion layer reaching the well region.

[0019] In one aspect of the ranging image sensor of the present invention, each of the plurality of pixels may further have a second conductivity type receiving region formed on a first side of the second region in the semiconductor layer and connected to the second region. Thus, because the charge accumulated around the first region of the second conductivity type is introduced into the receiving region of the second conductivity type, it is possible to suppress the charge accumulated around the first region as parasitic charge from becoming noise.

[0020] In one aspect of the ranging image sensor of the present invention, the destination region may be connected to the second charge transfer region. Therefore, when the second charge transfer region is used as a useless charge discharge region, the charge introduced into the destination region can be discharged to the second charge transfer region.

[0021] In one aspect of the ranging image sensor of the present invention, trenches separating the individual pixels of the plurality of pixels may be formed on the first surface of the semiconductor layer. This reliably suppresses crosstalk between adjacent pixels.

[0022] In one aspect of the ranging image sensor of the present invention, the first doubling region may be divided according to each of a plurality of pixels. This can suppress the generation of crosstalk between adjacent pixels.

[0023] In one aspect of the ranging image sensor of the present invention, a wiring layer electrically connected to each of the plurality of pixels may also be included, disposed on the first surface in a manner covering the electrode layer. This allows for the input and output of electrical signals to each of the plurality of pixels via the wiring layer.

[0024] Invention Effects

[0025] According to the present invention, a ranging image sensor is provided that can improve light sensitivity while maintaining signal readout accuracy. Attached Figure Description

[0026] Figure 1 This is a structural diagram of a light detection device including the ranging image sensor of the first embodiment.

[0027] Figure 2 This is a top view (plan view) of the pixel portion of the ranging image sensor according to the first embodiment.

[0028] Figure 3 It is along Figure 2 The cross-sectional view of line III-III shown.

[0029] Figure 4 It is along Figure 2 The cross-sectional view of line IV-IV is shown.

[0030] Figure 5 This is a cross-sectional view used to explain the manufacturing method of the ranging image sensor according to the first embodiment.

[0031] Figure 6 This is a cross-sectional view used to illustrate the manufacturing method of the ranging image sensor according to the first embodiment.

[0032] Figure 7 This is a top view of a portion of the ranging image sensor according to the second embodiment.

[0033] Figure 8 It is along Figure 7 The cross-sectional view of line VIII-VIII is shown.

[0034] Figure 9 This is a top view of a portion of the ranging image sensor according to the third embodiment.

[0035] Figure 10 It is along Figure 9 The cross-sectional view of the X-X line shown.

[0036] Figure 11 It is along Figure 9 The cross-sectional view of the XI-XI line is shown.

[0037] Figure 12 This is a cross-sectional view of a modified ranging image sensor.

[0038] Figure 13 This is a cross-sectional view of a modified ranging image sensor.

[0039] Figure 14 This is a cross-sectional view of a modified ranging image sensor.

[0040] Figure 15 This is a cross-sectional view of a modified ranging image sensor.

[0041] Figure 16 This is a cross-sectional view of a modified ranging image sensor.

[0042] Figure 17 This is a cross-sectional view of a modified ranging image sensor.

[0043] Figure 18 This is a cross-sectional view of a modified ranging image sensor. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent parts are labeled with the same reference numerals, and repeated descriptions are omitted.

[0045] [First Implementation Method]

[0046] [Structure of the optical detection device]

[0047] like Figure 1 As shown, the light detection device 1 includes a light source 2, a ranging image sensor 10A, a signal processing unit 3, a control unit 4, and a display unit 5. The light detection device 1 is a device that acquires a distance image (containing information about the distance d to the object OJ) of an object OJ using an indirect TOF method.

[0048] Light source 2 emits pulsed light L. Light source 2 is composed of, for example, an infrared LED. The pulsed light L is, for example, near-infrared light. The frequency of the pulsed light L is, for example, 10 kHz or higher. Range-measuring image sensor 10A detects the pulsed light L emitted from light source 2 and reflected by the object OJ. Range-measuring image 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). Range-measuring image sensor 10A is mounted on signal processing unit 3.

[0049] The signal processing unit 3 controls the pixel unit 11 and the CMOS readout circuit unit 12 of the ranging image sensor 10A. The signal processing unit 3 performs prescribed processing on the signal output from the ranging image 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.

[0050] [Structure of a ranging image sensor]

[0051] like Figure 2 , Figure 3 and Figure 4 As shown, the ranging image 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 of the semiconductor layer 20 in the thickness direction. The second surface 20b is a surface on the other side of the semiconductor layer 20 in the thickness direction. The electrode layer 40 is disposed 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 ranging image 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 and X directions 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 side opposite to the first side) is referred to as the second side. Furthermore, in Figure 2 The diagram of wiring layer 60, which will be described later, is omitted in the text.

[0052] Each pixel 11a has a semiconductor region 21, an avalanche multiplication region 22, a charge distribution region 23, a pair of first charge transport regions 24 and 25, a pair of second charge transport regions 26 and 27, multiple charge blocking regions 28, a well region 31, a LOCOS (Local Oxidation of Silicon) region 33, a barrier region 34, and a pair of sink regions 35 in the semiconductor layer 20. Regions 21–28 and 31–35 are formed by performing various processes (e.g., etching, film deposition, impurity implantation, etc.) on the semiconductor substrate (e.g., a silicon substrate).

[0053] Semiconductor region 21 is a p-type (first conductivity type) region, disposed along the second surface 20b in semiconductor layer 20. Semiconductor region 21 functions as a light absorption region (photoelectric conversion region). As an example, semiconductor region 21 has a size of 1 × 10⁻⁶. 15 cm －3 In the p-type region with the following carrier concentration, the thickness of semiconductor region 21 is approximately 10 μm. Furthermore, avalanche multiplication regions 22 and the like also function as light absorption regions (photoelectric conversion regions).

[0054] 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 has a size of 1×10⁻⁶. 16 cm －3 The p-type region with the above carrier concentration has a thickness of approximately 1 μm for the first multiplication region 22a. The second multiplication region 22b is an n-type (second conductivity type) region, formed in the semiconductor layer 20 on the first side of the first multiplication region 22a. As an example, the second multiplication region 22b has a thickness of 1 × 10⁻⁶. 16 cm －3 In the n-type region with the above carrier concentration, the thickness of the second multiplication region 22b is approximately 1 μm. The first multiplication region 22a and the second multiplication region 22b form a pn junction.

[0055] The charge distribution region 23 is an n-type region formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. As an example, the charge distribution region 23 has a size of 5 × 10⁻⁶. 15 ~1×10 16 cm －3 The n-type region with high carrier concentration has a charge distribution region 23 with a thickness of approximately 1 μm.

[0056] Each first charge transfer region 24, 25 is an n-type region, formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. Each first charge transfer region 24, 25 is connected to the charge distribution region 23. A pair of first charge transfer regions 24, 25 sandwiching a portion of the first side of the charge distribution region 23 are opposite each other in the X direction. As an example, each first charge transfer region 24, 25 has a size of 1×10 18 cm －3 In the n-type region with the above-mentioned carrier concentration, the thickness of each of the first charge transport regions 24 and 25 is approximately 0.2 μm. Furthermore, a portion of the second side of the charge distribution region 23 extends between each of the first charge transport regions 24 and 25 and the second multiplication region 22b. In this embodiment, each of the first charge transport regions 24 and 25 functions as a charge accumulation region.

[0057] Each second charge transfer region 26, 27 is an n-type region, formed in the semiconductor layer 20 on the first side of the second multiplication region 22b. Each second charge transfer region 26, 27 is connected to the charge distribution region 23. A pair of second charge transfer regions 26, 27 sandwich a portion of the first side of the charge distribution region 23 and are opposite each other in the Y direction. As an example, each second charge transfer region 26, 27 has a size of 1×10⁻⁶. 18 cm －3 In the n-type region with the above-mentioned carrier concentration, the thickness of each of the second charge transport regions 26 and 27 is approximately 0.2 μm. Furthermore, a portion of the second side of the charge distribution region 23 extends between each of the second charge transport regions 26 and 27 and the second multiplication region 22b. In this embodiment, each of the second charge transport regions 26 and 27 functions as a charge discharge region.

[0058] Each charge-blocking region 28 is a p-type region formed in the semiconductor layer 20 between each of the first charge transport regions 24, 25 and the charge distribution region 23 (the portion on the second side of the charge distribution region 23). As an example, each charge-blocking region 28 has a size of 1 × 10⁻⁶. 17 ~1×10 18 cm －3 The p-type region with high carrier concentration has a thickness of approximately 0.2 μm for each charge blocking region 28.

[0059] Well region 31 is a p-type region formed in semiconductor layer 20 on the first side of second multiplication region 22b. When viewed from the Z direction, well region 31 surrounds charge distribution region 23. LOCOS region 33 is formed in semiconductor layer 20 on the first side of well region 31. LOCOS region 33 is connected to well region 31. Well region 31 and LOCOS region 33 together constitute multiple readout circuits (e.g., source follower amplifiers, reset transistors, etc.). Each readout circuit is electrically connected to each first charge transfer region 24, 25. As an example, well region 31 has a size of 1 × 10⁻⁶. 16 ~5×10 17 cm －3 The p-type region has a carrier concentration of approximately 1 μm, and the thickness of the well region 31 is approximately 1 μm. Furthermore, as a structure for electrically separating the pixel section and the readout circuit section, STI (Shallow Trench Isolation) can be used instead of the LOCOS region 33, or only the well region 31 can be used.

[0060] Barrier region 34 is an n-type region formed in semiconductor layer 20 between the second multiplication region 22b and the well region 31. When viewed from the Z direction, barrier region 34 encompasses well region 31. That is, when viewed from the Z direction, well region 31 is located within barrier region 34. Barrier region 34 surrounds charge distribution region 23. The concentration of n-type impurities in barrier region 34 is higher than the concentration of n-type impurities in second multiplication region 22b. As an example, barrier region 34 is an n-type region with a carrier concentration approximately twice that of second multiplication region 22b, and the thickness of barrier region 34 is approximately 1 μm.

[0061] Each destination region 35 is an n-type region formed in the semiconductor layer 20 on the first side of the barrier region 34. The end of the second side of each destination region 35 is connected to the barrier region 34. The end of the first side of each destination region 35 is connected to each of the second charge transport regions 26 and 27. The concentration of n-type impurities in each of the second charge transport regions 26 and 27 is higher than the concentration of n-type impurities in each destination region 35, and the concentration of n-type impurities in each destination region 35 is higher than the concentration of n-type impurities in the barrier region 34 and the concentration of p-type impurities in the well region 31. As an example, each destination region 35 is an n-type region with a carrier concentration higher than that of the well region 31, and the thickness of each destination region 35 depends on the distance between each of the second charge transport regions 26 and 27 and the barrier region 34.

[0062] Each pixel 11a has a photogate electrode 41, a pair of first transfer gate electrodes 42 and 43, and a pair of second transfer gate electrodes 44 and 45 in the electrode layer 40. Each gate electrode 41 to 45 is formed on the first surface 20a of the semiconductor layer 20 through an insulating film 46. The insulating film 46 is, for example, a silicon nitride film or a silicon oxide film.

[0063] A photogate electrode 41 is formed in the electrode layer 40 on the first side of the charge distribution region 23. The photogate electrode 41 is formed of a material that is conductive and transparent (e.g., polycrystalline silicon). As an example, when viewed from the Z direction, the photogate electrode 41 is rectangular with two opposite sides in the X direction and two opposite sides in the Y direction.

[0064] The first transfer gate electrode 42 is formed in the electrode layer 40 on the first side of the charge distribution region 23, relative to the photogate electrode 41 on the side of the first charge transfer region 24. The first transfer gate electrode 43 is formed in the electrode layer 40 on the first side of the charge distribution region 23, relative to the photogate electrode 41 on the side of the first charge transfer region 25. Each of the first transfer gate electrodes 42 and 43 is formed of a conductive and transparent material (e.g., polycrystalline silicon). As an example, when viewed from the Z direction, each of the first transfer gate electrodes 42 and 43 is rectangular with two opposite sides in the X direction and two opposite sides in the Y direction.

[0065] The second transfer gate electrode 44 is formed in the electrode layer 40 on the first side of the charge distribution region 23, relative to the photogate electrode 41 on the side of the second charge transfer region 26. The second transfer gate electrode 45 is formed in the electrode layer 40 on the first side of the charge distribution region 23, relative to the photogate electrode 41 on the side of the second charge transfer region 27. Each of the second transfer gate electrodes 44, 45 is formed of a conductive and transparent material (e.g., polycrystalline silicon). As an example, when viewed from the Z direction, each of the second transfer gate electrodes 44, 45 is rectangular with two opposite sides in the X direction and two opposite sides in the Y direction.

[0066] The ranging image sensor 10A also includes a counter electrode 50 and a wiring layer 60 in the pixel section 11. The counter electrode 50 is disposed on the second surface 20b of the semiconductor layer 20. When viewed from the Z direction, the counter electrode 50 includes a plurality of pixels 11a. The counter electrode 50 is opposite to the electrode layer 40 in the Z direction. The counter electrode 50 is formed, for example, of a metallic material. The wiring layer 60 is disposed on the first surface 20a of the semiconductor layer 20 in a manner that covers the electrode layer 40. The wiring layer 60 is connected to each pixel 11a and the CMOS readout circuit section 12 (see reference). Figure 1 Electrical connection. A light incident opening 60a is formed in the wiring layer 60 at the portion opposite to the photogate electrode 41 of each pixel 11a.

[0067] Trench 29 is formed in semiconductor layer 20 to separate each pixel 11a from each other. Trench 29 is formed on the first surface 20a of semiconductor layer 20. The bottom surface 29a of trench 29 is located on the second side relative to avalanche multiplication region 22. That is, trench 29 completely separates avalanche multiplication region 22. Insulating material 47 such as silicon oxide is disposed in trench 29. Alternatively, instead of insulating material 47, metal material such as tungsten or polysilicon may be disposed in trench 29.

[0068] In each pixel 11a, the second multiplication region 22b is formed to overlap with the charge distribution region 23, a pair of first charge transfer regions 24, 25, a pair of second charge transfer regions 26, 27, and the well region 31 in the Z direction. That is, when viewed from the Z direction, the second multiplication region 22b overlaps with the charge distribution region 23, the pair of first charge transfer regions 24, 25, the pair of second charge transfer regions 26, 27, and the well region 31. Furthermore, in this embodiment, when viewed from the Z direction, the second multiplication region 22b and the pair of second charge transfer regions 26, 27 partially overlap. In this embodiment, in each pixel 11a, the second multiplication region 22b reaches the trench 29. Specifically, when viewed from the Z direction, the second multiplication region 22b completely covers each pixel 11a surrounded by the trench 29. On the other hand, in each pixel 11a, the first multiplication region 22a is formed to overlap with the charge distribution region 23, a pair of first charge transfer regions 24, 25, and a pair of second charge transfer regions 26, 27 in the Z direction, but not with the well region 31. That is, when viewed from the Z direction, the first multiplication region 22a overlaps with the charge distribution region 23, the pair of first charge transfer regions 24, 25, and the pair of second charge transfer regions 26, 27, but not with the well region 31. Furthermore, in this embodiment, when viewed from the Z direction, the first multiplication region 22a partially overlaps with the pair of second charge transfer regions 26, 27. In this embodiment, the first multiplication region 22a does not reach the trench 29. Specifically, the first multiplication region 22a is separated from each pixel 11a on the second side of the second multiplication region 22b. When viewed from the Z direction, a portion of a semiconductor region 21 disposed along the second surface 20b in the semiconductor layer 20 is disposed between the trench 29 and the first multiplication region 22a. That is, on the second side of the well region 31, a second multiplication region 22b and a semiconductor region 21 are formed overlapping in the Z direction.

[0069] Avalanche multiplication region 22 is the region that causes avalanche multiplication. More specifically, in each pixel 11a, the region within avalanche multiplication region 22 where the first multiplication region 22a and the second multiplication region 22b overlap when viewed from the Z direction can generate 3×10⁻⁶ Ω·cm² when a specified reverse bias voltage is applied. 5~4×10 5 An electric field strength of V / cm causes avalanches to multiply.

[0070] An example of the operation of the ranging image sensor 10A configured as described above is described below. In each pixel 11a of the ranging image sensor 10A, a negative voltage (e.g., -50V) is applied to the opposite electrode 50 based on the potential of the photogate electrode 41 (i.e., a reverse bias is applied to the pn junction formed in the avalanche multiplication region 22), generating a 3×10⁻⁶ ohm voltage in the avalanche multiplication region 22. 5 ~4×10 5 The electric field strength is V / cm. In this state, if the pulsed light L is incident on the semiconductor layer 20 through the light incident opening 60a and the photograting electrode 41, the electrons generated by the absorption of the pulsed light L will multiply in the avalanche multiplication region 22 and move at high speed to the charge distribution region 23.

[0071] In generating objects, OJ (refer to) Figure 1 When processing the distance image of the photogate 41, in each pixel 11a, a reset voltage is first applied to a pair of second transfer gate electrodes 44, 45. The reset voltage is a positive voltage based on the potential of the photogate electrode 41. As a result, electrons that have moved to the charge distribution region 23 are discharged from the pair of second charge transfer regions 26, 27.

[0072] Next, a pulsed voltage signal is applied to a pair of first transmission gate electrodes 42, 43. As an example, the pulsed voltage signal applied to the first transmission gate electrode 42 is a voltage signal that alternates between positive and negative voltages, based on the potential of the photogate electrode 41, and has a period, pulse width, and phase that are consistent with those of the light source 2 (refer to...). Figure 1 The pulse voltage signal applied to the first transmission gate electrode 43 is the same voltage signal as the pulse voltage signal applied to the first transmission gate electrode 42, except that the phase is offset by 180°.

[0073] Thus, electrons moving to charge distribution region 23 are alternately and rapidly transferred to a pair of first charge transfer regions 24, 25. Electrons accumulated in each of the first charge transfer regions 24, 25 through this transfer over a predetermined period are transmitted as signals to the CMOS readout circuit section 12 (see reference 12) via the readout circuit and wiring layer 60 formed by the well region 31, etc. Figure 1 ).

[0074] like Figure 1As shown, when the pulsed light L emitted from the light source 2 and reflected by the object OJ is detected by the ranging image sensor 10A, the phase of the intensity signal of the pulsed light L detected by the ranging image sensor 10A is offset (deviation) from the distance d to the object OJ compared to the phase of the intensity signal of the pulsed light L emitted from the light source 2. Therefore, by acquiring the signal based on the electrons accumulated in each of the first charge transfer regions 24, 25 for each pixel 11a, a distance image of the object OJ can be generated.

[0075] [Manufacturing method of ranging image sensor]

[0076] like Figure 5 As shown in (a), a p-type semiconductor substrate 20s is prepared, and a first multiplication region 22a, a second multiplication region 22b, and a charge distribution region 23 are formed on the semiconductor substrate 20s. At this time, the second multiplication region 22b covers multiple pixels 11a (see reference). Figure 5 (b) is formed on the semiconductor substrate 20s in a manner connected to it. The first multiplication region 22a is formed in the semiconductor substrate 20s and, when viewed from the Z direction, is connected to the charge distribution region 23 (see reference). Figure 5 (b)), first charge transfer regions 24, 25 (refer to) Figure 5 (b) and the second charge transfer regions 26 and 27 (refer to) Figure 5 The overlapping part of (b)). Then, as... Figure 5 As shown in (b), a trench 29 is formed on the first surface 20a of the semiconductor layer 20. Next, as... Figure 6 As shown in (a), regions 24-28 and 31-35 are formed on the semiconductor substrate 20s such that each pixel 11a has a pair of first charge transfer regions 24, 25, a pair of second charge transfer regions 26, 27, multiple charge blocking regions 28, a well region 31, a LOCOS region 33, a barrier region 34, and a pair of sink regions 35. Thus, a semiconductor layer 20 with trenches 29 is formed (first process). Semiconductor region 21 is a region present in the semiconductor substrate 20s.

[0077] Next, as Figure 6 As shown in (b), each gate electrode 41 to 45 is formed on the first surface 20a of the semiconductor layer 20 such that each pixel 11a has a photogate electrode 41, a pair of first transfer gate electrodes 42 and 43, and a pair of second transfer gate electrodes 44 and 45. Thus, the electrode layer 40 is formed (second process). Next, as... Figure 3As shown, a wiring layer 60 is formed on the first surface 20a of the semiconductor layer 20 to cover the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a (third process). Next, a counter electrode 50 is formed on the second surface 20b of the semiconductor layer 20. While forming the pixel portion 11 on the semiconductor substrate 20s as described above, a CMOS readout circuit portion 12 is also formed on the semiconductor substrate 20s. By means of the above-described method, a ranging image sensor 10A can be manufactured. The formation of the trench 29 can also be performed after the formation of each region 24-28 and 31-35 on the semiconductor substrate 20s and before the formation of each gate electrode 41-45 on the first surface 20a of the semiconductor layer 20.

[0078] [Functions and Effects]

[0079] In the ranging image sensor 10A, an avalanche multiplication region 22 is formed in the semiconductor layer 20. This enables high sensitivity in each pixel 11a. Furthermore, on the second side of the p-type well region 31, an n-type second multiplication region 22b is formed to overlap with the well region 31 in the thickness direction of the semiconductor layer 20, and on the second side of the n-type second multiplication region 22b, a p-type first multiplication region 22a is formed to not overlap with the well region 31 in the thickness direction of the semiconductor layer 20. Therefore, when a reverse bias voltage is applied to the semiconductor layer 20, the depletion layer in the second multiplication region 22b that does not overlap with the first multiplication region 22a in the thickness direction of the semiconductor layer 20 is less likely to extend towards the well region 31, thus suppressing the depletion layer from reaching the well region 31. That is, current flow between the avalanche multiplication region 22 and the well region 31 due to the depletion layer reaching the well region 31 can be prevented. Therefore, according to the ranging image sensor 10A, improved light sensitivity can be achieved while maintaining signal readout accuracy.

[0080] The effect of the ranging image sensor 10A will be further described. On the second side of the p-type well region 31, a second multiplication region 22b, which is n-type in the Z direction, overlaps with the p-type semiconductor region 21, wherein the concentration of p-type impurities in the p-type semiconductor region 21 is lower than the concentration of p-type impurities in the well region 31. When a negative voltage is applied to the opposite electrode 50 with reference to the potential of the photogate electrode 41, a depletion layer is formed between the n-type second multiplication region 22b and the p-type semiconductor region 21. However, this depletion layer tends to extend towards the semiconductor region 21 with a lower concentration of p-type impurities, but does not tend to extend towards the well region 31 on the opposite side of the semiconductor region 21. Therefore, according to the ranging image sensor 10A, it is possible to suppress the flow of current between the avalanche multiplication region 22b and the well region 31 due to the depletion layer reaching the well region 31.

[0081] In the ranging image sensor 10A, the bottom surface 29a of the trench 29 is located on the second side compared to the avalanche multiplication region 22. This allows for the suppression of crosstalk between adjacent pixels 11a.

[0082] In the ranging image sensor 10A, an n-type barrier region 34 is formed between the second multiplication region 22b and the well region 31 constituting the readout circuit. Therefore, by applying a reverse bias to the semiconductor layer 20, even if the depletion layer formed in the second multiplication region extends towards the well region 31, the barrier region 34 can prevent the depletion layer from reaching the well region 31. That is, current flow between the avalanche multiplication region 22b and the well region 31 due to the depletion layer reaching the well region 31 can be suppressed.

[0083] In the ranging image sensor 10A, when viewed from the Z direction, the barrier region 34 includes the well region 31. This suppresses current flow between the avalanche multiplication region 22 and the well region 31 caused by the depletion layer reaching the well region 31.

[0084] In the ranging image sensor 10A, an n-type host region 35 connected to the barrier region 34 is formed on the first side of the barrier region 34. Therefore, because electrons accumulated around the n-type barrier region 34 are introduced into the n-type host region 35, it is possible to suppress the electrons accumulated around the barrier region 34 from becoming parasitic electrons and contributing to noise. Furthermore, by adjusting the impurity concentration in the regions between the first charge transfer region 24 and each host region 35, and in the regions between the first charge transfer region 25 and each host region 35, a potential state that makes it easier to introduce parasitic electrons into the host region 35 compared to introducing parasitic electrons into each of the first charge transfer regions 24, 25 can be formed.

[0085] In the ranging image sensor 10A, the destination region 35 is connected to each of the second charge transfer regions 26 and 27. As a result, parasitic electrons introduced into the destination region 35 can be discharged to each of the second charge transfer regions 26 and 27, which function as useless charge discharge regions.

[0086] In the ranging image sensor 10A, a wiring layer 60 is provided on the first surface 20a of the semiconductor layer 20 to cover the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a. Thus, electrical signals can be input and output to each pixel 11a via the wiring layer 60.

[0087] In the manufacturing method of the ranging image sensor 10A, after the formation of each gate electrode 41-45, a wiring layer 60 is formed on the first surface 20a of the semiconductor layer 20 in a manner that covers the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a. Thus, in the manufactured ranging image sensor 10A, electrical signals can be input and output to each pixel 11a via the wiring layer 60.

[0088] [Second Implementation]

[0089] like Figure 7 and Figure 8 As shown, the ranging image sensor 10B differs from the ranging image sensor 10A in that it has points with second charge transfer regions 26a, 26b, 27a, 27b arranged on both sides of the charge distribution region 23 in the X direction, and points with multiple second transfer gate electrodes 44a, 44b, 45a, 45b arranged on both sides of the photoelectric grating electrode 41 in the X direction.

[0090] In each pixel 11a of the ranging image sensor 10B, a pair of second charge transfer regions 26a and 26b are disposed on one side of the charge distribution region 23 in the X direction and on both sides of the first charge transfer region 24 in the Y direction. A pair of second charge transfer regions 27a and 27b are disposed on the other side of the charge distribution region 23 in the X direction and on both sides of the first charge transfer region 25 in the Y direction. When viewed from the Z direction, a second transfer gate electrode 44a is disposed between the photogate electrode 41 and the second charge transfer region 26a. When viewed from the Z direction, a second transfer gate electrode 44b is disposed between the photogate electrode 41 and the second charge transfer region 26b. When viewed from the Z direction, a second transfer gate electrode 45a is disposed between the photogate electrode 41 and the second charge transfer region 27a. When viewed from the Z direction, a second transfer gate electrode 45b is disposed between the photogate electrode 41 and the second charge transfer region 27b.

[0091] In each pixel 11a of the ranging image sensor 10B, a well region 31 is formed to surround a charge distribution region 23 in the X direction when viewed from the Z direction between each pixel 11a. The well region 31 is formed along a portion of the trench 29 extending in both the X and Y directions.

[0092] In each pixel 11a of the ranging image sensor 10B, when viewed from the Z direction, the second multiplication region 22b completely covers the pixel 11a surrounded by the trench 29. In each pixel 11a of the ranging image sensor 10B, when viewed from the Z direction, the first multiplication region 22a covers the portion of the pixel 11a surrounded by the trench 29 excluding the portion on the second side of the well region 31.

[0093] In the ranging image sensor 10B, similarly to the ranging image sensor 10A described above, an avalanche multiplication region 22 is formed in the semiconductor layer 20. This enables high sensitivity in each pixel 11a. Furthermore, on the second side of the p-type well region 31 constituting the readout circuit, an n-type second multiplication region 22b is formed to overlap with the well region 31 in the thickness direction of the semiconductor layer 20, and on the second side of the n-type second multiplication region 22b, a p-type first multiplication region 22a is formed to not overlap with the well region 31 in the thickness direction of the semiconductor layer 20. Therefore, the depletion layer formed in the second multiplication region 22b by applying a reverse bias to the semiconductor layer 20, in the portion that does not overlap with the first multiplication region 22a in the thickness direction of the semiconductor layer 20, is less likely to extend into the well region 31, preventing the depletion layer from reaching the well region 31. In other words, it prevents current from flowing between the avalanche multiplication region 22 and the well region 31 due to the depletion layer reaching the well region 31. Therefore, according to the ranging image sensor 10B, it is possible to improve light sensitivity while maintaining signal readout accuracy.

[0094] Furthermore, in the ranging image sensor 10B, the first multiplication region 22a is also configured such that it is separated according to each pixel 11a. This suppresses crosstalk between adjacent pixels 11a. Particularly in the X-direction portion of the boundary between adjacent pixels 11a, when viewed from the Z-direction, the first multiplication region 22a overlaps with the second multiplication region 22b. By forming a groove 29 in this portion, crosstalk can be suppressed.

[0095] [Third Implementation Method]

[0096] like Figure 9 , Figure 10 and Figure 11 As shown, the ranging image sensor 10C differs from the ranging image sensor 10A in the following aspects: the first charge transfer region 24 is disposed at the center of the charge distribution region 23; the plurality of second charge transfer regions 26 are disposed along the outer edge of the charge distribution region 23; the photogate electrode 41 and the first transfer gate electrode 42 are formed in a ring shape; the plurality of second transfer gate electrodes 44 are disposed in a manner surrounding the photogate electrode 41; and the semiconductor layer 20 does not have a trench 29 and the avalanche multiplication region 22 is connected to the plurality of pixels 11a.

[0097] In each pixel 11a of the ranging image sensor 10C, when viewed from the Z direction, a first charge transfer region 24 is disposed at the center of the charge distribution region 23. When viewed from the Z direction, a plurality of second charge transfer regions 26 are disposed along the outer edge of the charge distribution region 23. Each second charge transfer region 26 is shared by two adjacent pixels 11a. When viewed from the Z direction, a photogate electrode 41, for example, is in the shape of a rectangular ring and is disposed outside the first charge transfer region 24 and inside the plurality of second charge transfer regions 26. When viewed from the Z direction, a first charge transfer gate electrode 42, for example, is in the shape of a rectangular ring and is disposed outside the first charge transfer region 24 and inside the photogate electrode 41. When viewed from the Z direction, each second charge transfer gate electrode 44 is disposed between the photogate electrode 41 and each second charge transfer region 26.

[0098] In each pixel 11a of the ranging image sensor 10C, when viewed from the Z direction, the well region 31 and the barrier region 34 are disposed at the intersection of a plurality of virtual lines arranged in a lattice pattern to separate the plurality of pixels 11a. Therefore, no trench 29 is formed in the semiconductor layer 20. In this embodiment, the second multiplication region 22b is connected to the plurality of pixels 11a. On the other hand, the first multiplication region 22a is connected to the plurality of pixels 11a except for the portion on the second side of the well region 31.

[0099] In the ranging image sensor 10C, an avalanche multiplication region 22 is also formed in the semiconductor layer 20. This enables high sensitivity in each pixel 11a. Furthermore, on the second side of the p-type well region 31 constituting the readout circuit, an n-type second multiplication region 22b is formed to overlap with the well region 31 in the thickness direction of the semiconductor layer 20, and on the second side of the n-type second multiplication region 22b, a p-type first multiplication region 22a is formed to not overlap with the well region 31 in the thickness direction of the semiconductor layer 20. Therefore, the depletion layer formed in the second multiplication region 22b by applying a reverse bias to the semiconductor layer 20, in the portion that does not overlap with the first multiplication region 22a in the thickness direction of the semiconductor layer 20, is less likely to extend into the well region 31, preventing the depletion layer from reaching the well region 31. That is, current flow between the avalanche multiplication region 22 and the well region 31 due to the depletion layer reaching the well region 31 can be prevented. Therefore, according to the ranging image sensor 10C, improved light sensitivity can be achieved while maintaining signal readout accuracy.

[0100] Furthermore, in the ranging image sensor 10C, the destination region 35 (reference) Figure 3The potential barrier region 34 is not formed in the semiconductor layer 20. The reason is that, in the ranging image sensor 10C, compared with the ranging image sensor 10A described above, the potential barrier region 34 is separated from the first charge transfer region 24. As a result, electrons gathered around the potential barrier region 34 have difficulty entering the first charge transfer region 24.

[0101] [Variation Example]

[0102] The present invention is not limited to the first to third embodiments described above. In the ranging image sensor 10A, the first multiplication region 22a is formed such that it does not overlap with the well region 31 in the Z direction. When viewed from the Z direction, it can also cover the portion of the pixel 11a surrounded by the trench 29, excluding the portion on the second side of the well region 31. Alternatively, in the ranging image sensor 10C, the first multiplication region 22a can also be formed separately for each pixel 11a.

[0103] In the ranging image sensors 10A, 10B, and 10C, the first multiplication region 22a is formed such that it overlaps with a portion of the charge distribution region 23 in the Z direction, and the second multiplication region 22b is formed such that it overlaps with a portion of the charge distribution region 23 and a portion of the well region 31 in the Z direction. That is, in the ranging image sensors 10A, 10B, and 10C, when viewed from the Z direction, it is not necessary for the first multiplication region 22a to overlap with each of the regions 24, 25, 26, and 27, nor is it necessary for the second multiplication region 22b to overlap with each of the regions 24, 25, 26, and 27. Furthermore, in the ranging image sensors 10A, 10B, and 10C, if the structure does not allow current to flow between the avalanche multiplication region 22 and the well region 31 due to the depletion layer formed in the first multiplication region 22a reaching the well region 31 (or if there is current flow between the avalanche multiplication region 22 and the well region 31, it is not a problem in practice), then the first multiplication region 22a can also be formed to partially overlap with the well region 31 in the Z direction.

[0104] The ranging image sensors 10A, 10B, and 10C may also have electrodes different from the opposing electrode 50. As an example, the ranging image sensors 10A, 10B, and 10C may also have through electrodes formed by a TSV (Through-Silicon Via) structure on the semiconductor substrate. Alternatively, the ranging image sensors 10A, 10B, and 10C may also have electrodes formed on a surface portion of a first side of the semiconductor substrate.

[0105] In the ranging image sensors 10A, 10B, and 10C, the well region 31 may not be used to form multiple readout circuits. In this case, the well region 31 may also function as a separate region (separated region), and multiple readout circuits may be formed in a semiconductor substrate in a different well region than the well region 31, and electrically connected to each of the first charge transfer regions 24 and 25 via the wiring layer 60.

[0106] In ranging image sensors 10A, 10B, and 10C, the barrier region 34 may not be formed in the semiconductor layer 20. Alternatively, in ranging image sensors 10A, 10B, and 10C, a portion of the second multiplication region 22b may function as a barrier region. As an example, in... Figure 12 and Figure 13 In the ranging image sensor 10A shown, a barrier region 34 is not formed. Furthermore, in the ranging image sensor 10A, the second multiplication region 22b includes a first region 22c and a second region 22d. The first region 22c is the region in the second multiplication region 22b that overlaps with the charge distribution region 23, a pair of first charge transfer regions 24 and 25, and a pair of second charge transfer regions 26 and 27 in the Z direction. That is, when viewed from the Z direction, the first region 22c in the second multiplication region 22b overlaps with the charge distribution region 23, the pair of first charge transfer regions 24 and 25, and the pair of second charge transfer regions 26 and 27. The second region 22d is the region in the second multiplication region 22b that overlaps with the well region 31 in the Z direction. That is, when viewed from the Z direction, the second region 22d in the second multiplication region 22b overlaps with the well region 31. The impurity concentration in the second region 22d is higher than the impurity concentration in the first region 22c. As an example, the first region 22c has a concentration of 1 × 10⁻⁶. 16 cm －3 The concentration of the above-mentioned n-type impurities, in the second region 22d, is 2 to 3 × 10⁻⁶. 16 cm －3 The concentration of n-type impurities. When viewed from the Z direction, the second region 22d contains the trap region 31. The sink region 35 is connected to the second region 22d.

[0107] Therefore, the same effect as forming a barrier region 34 in the semiconductor layer 20 can be achieved through the second region 22d. Specifically, if the structure prevents current flow between the avalanche multiplication region 22 and the well region 31 due to the depletion layer formed in the first region 22c reaching the well region 31 (or if current flow between the avalanche multiplication region 22 and the well region 31 is practically acceptable), then the first region 22c can also be formed such that it partially overlaps with the well region 31 when viewed from the Z direction. Alternatively, the first region 22c may not be formed to not overlap with regions 24, 25, 26, and 27. The second region 22d can also be formed such that it partially overlaps with the charge distribution region 23, the first charge transfer regions 24 and 25, and the second charge transfer regions 26 and 27 in the Z direction. That is, the second region 22d only needs to be formed such that it partially overlaps with the well region 31 when viewed from the Z direction.

[0108] In the ranging image sensors 10A and 10B, the bottom surface 29a of the trench 29 can also be located within the avalanche multiplication region 22 in the Z direction. In this case, crosstalk between adjacent pixels 11a can also be suppressed.

[0109] In the ranging image sensors 10A and 10B, the bottom surface 29a of the trench 29 may be located on the first side relative to the avalanche multiplication region 22, and the second multiplication region 22b may be distributed across multiple pixels 11a. Alternatively, in the ranging image sensors 10A and 10B, the trench 29 may not be formed in the semiconductor layer 20, and the second multiplication region 22b may be distributed across multiple pixels 11a. Even in these cases, because in the ranging image sensors 10A and 10B, the first multiplication region 22a is separated according to each pixel 11a on the second side of the second multiplication region 22b, current flow between the avalanche multiplication regions 22 of adjacent pixels 11a can be prevented, and the generation of crosstalk between adjacent pixels 11a can be sufficiently suppressed.

[0110] In ranging image sensors 10A and 10B, each destination region 35 may not be connected to each of the second charge transfer regions 26 and 27. In ranging image sensors 10A and 10B, the destination region 35 may not be formed in the semiconductor layer 20. In ranging image sensors 10A and 10B, the charge blocking region 28 may not be formed in the semiconductor layer 20.

[0111] In the ranging image sensor 10C, the destination region 35 connected to the barrier region 34 can also be formed on the semiconductor layer 20. In the ranging image sensor 10C, the destination region 35 connected to both the barrier region 34 and the second charge transfer region 26 can also be formed on the semiconductor layer 20. In the ranging image sensor 10C, a charge blocking region 28 can also be formed on the semiconductor layer 20.

[0112] like Figure 14 , Figure 15 , Figure 16 , Figure 17 and Figure 18 As shown, in the ranging image sensors 10A to 10C, a buried region 36 can also be formed in the semiconductor layer 20 of each pixel 11a. By forming the buried region 36 in the semiconductor layer 20 of each pixel 11a, the generation of dark current in each pixel 11a can be suppressed.

[0113] Figure 14 and Figure 15 The ranging image sensor 10A shown is different from the ranging image sensor 10A described above, mainly because there are points where multiple charge blocking regions 28 are not formed in the semiconductor layer 20 of each pixel 11a, and points where buried regions 36 are formed in the semiconductor layer 20 of each pixel 11a. Figure 14 and Figure 15 The structure of the semiconductor layer 20 of each pixel 11a in the ranging image sensor 10A shown is as follows.

[0114] like Figure 14 and Figure 15 As shown, the charge distribution region 23 is formed to overlap with the photogate electrode 41 when viewed from the Z direction, but not to overlap with the plurality of transfer gate electrodes 42, 43, 44, and 45 when viewed from the Z direction. The buried region 36 is a p-type region formed in the semiconductor layer 20 on the first side of the charge distribution region 23. That is, the charge distribution region 23 is buried in the semiconductor layer 20 through the buried region 36. The well region 31 surrounds the portion of the first side of the charge distribution region 23 and the buried region 36. A portion of the well region 31 is located between the buried region 36 and each charge transfer region 24, 25, 26, and 27. The barrier region 34 surrounds the portion of the second side of the charge distribution region 23. When viewed from the Z direction, the inner edge of the barrier region 34 surrounding the charge distribution region 23 is located further inward than the inner edge of the well region 31 surrounding the charge distribution region 23 and the buried region 36.

[0115] Figure 16 The ranging image sensor 10B shown is different from the ranging image sensor 10B described above, mainly because there are points where multiple charge blocking regions 28 are not formed in the semiconductor layer 20 of each pixel 11a, and points where buried regions 36 are formed in the semiconductor layer 20 of each pixel 11a. Figure 16 The structure of the semiconductor layer 20 of each pixel 11a in the ranging image sensor 10B shown is as follows.

[0116] like Figure 16As shown, the charge distribution region 23 is formed to overlap with the photogate electrode 41 when viewed from the Z direction, and to overlap with multiple transfer gate electrodes 42, 43, 44a, 44b, 45a, 45b (see reference) when viewed from the Z direction. Figure 7 The buried region 36 is a p-type region formed in the semiconductor layer 20 on the first side of the charge distribution region 23. That is, the charge distribution region 23 is buried in the semiconductor layer 20 through the buried region 36. The well region 31 surrounds a portion of the first side of the charge distribution region 23 and the buried region 36. A portion of the well region 31 is located between the buried region 36 and each charge transport region 24, 25, 26a, 26b, 27a, 27b (see reference). Figure 7 Between ), the barrier region 34 surrounds the second side portion of the charge distribution region 23. When viewed from the Z direction, the inner edge of the barrier region 34 surrounding the charge distribution region 23 is located inside the inner edge of the well region 31 surrounding the charge distribution region 23 and the buried region 36.

[0117] Figure 17 and Figure 18 The ranging image sensor 10C shown differs from the ranging image sensor 10C described above mainly in the following aspects: points where a buried region 36 is formed in the semiconductor layer 20 of each pixel 11a; points where a well region 31 (hereinafter referred to as "inner well region 31") is formed in the semiconductor layer 20 of each pixel 11a in a manner that includes (surrounds) the first charge transfer region 24; points where a well region 31 (hereinafter referred to as "outer well region 31") is formed in the semiconductor layer 20 of each pixel 11a in a manner that includes (surrounds) multiple second charge transfer regions 26; and points where a barrier region 34 is formed on the second side of each of the inner well region 31 and the outer well region 31. Figure 17 and Figure 18 The structure of the semiconductor layer 20 of each pixel 11a in the ranging image sensor 10C shown is as follows.

[0118] like Figure 17 and Figure 18 As shown, a portion of the first side of the charge distribution region 23 is formed such that it overlaps with the photogate electrode 41 when viewed from the Z direction, but does not overlap with the plurality of transfer gate electrodes 42, 44 when viewed from the Z direction. The buried region 36 is a p-type region formed in the semiconductor layer 20 on the first side of the charge distribution region 23. That is, the charge distribution region 23 is buried in the semiconductor layer 20 through the buried region 36. When viewed from the Z direction, the buried region 36, like the photogate electrode 41, is, for example, rectangular and annular. When viewed from the Z direction, the buried region 36 surrounds the inner well region 31. When viewed from the Z direction, the outer well region 31 surrounds the buried region 36.

[0119] In the ranging image sensors 10A to 10C, light can be incident on the semiconductor layer 20 from either the first side or the second side. For example, when light is incident on the semiconductor layer 20 from the second side, the counter electrode 50 can be formed of a material with conductivity and light transmittance (e.g., polycrystalline silicon). The electrodes connected to the semiconductor region 21 and the electrodes connected to the first multiplication region 22a side (electrodes on the first conductivity side) are not limited to the counter electrode 50, but can also be through electrodes that reach the semiconductor region 21 from the first surface 20a of the semiconductor layer 20, or electrodes formed on the surface of the semiconductor region 21 that reach the first surface 20a of the semiconductor layer 20. In any of the ranging image sensors 10A to 10C, at least one first charge transfer region, at least one second charge transfer region, at least one first transfer gate electrode, and at least one second transfer gate electrode can be provided for each pixel 11a. The manner in which voltage is applied to the first transfer gate electrode and the second transfer gate electrode, and the manner in which charge is extracted from the first charge transfer region and the manner in which charge is discharged, are not limited to the manner described above. In any of the ranging image sensors 10A to 10C, the p-type and n-type conductivity types can also be reversed as described above. In any of the ranging image 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.

[0120] Explanation of reference numerals in the attached figures

[0121] 10A, 10B, 10C ranging image sensors;

[0122] 11a pixels;

[0123] 20 Semiconductor layers;

[0124] 20a First surface;

[0125] 20b Second surface;

[0126] 20s semiconductor substrate;

[0127] 22 Avalanche multiplication zones;

[0128] 22a First doubling region;

[0129] 22b Second doubling region;

[0130] 22c First Region;

[0131] 22d Second Region;

[0132] 23. Charge distribution region;

[0133] 24, 25 First charge transfer region;

[0134] 26, 26a, 26b, 27, 27a, 27b Second charge transfer region;

[0135] 29. Grooves;

[0136] 29a Bottom surface;

[0137] 31. Trap region;

[0138] 34 Barrier Area;

[0139] 35 Accommodation Area;

[0140] 40 electrode layers;

[0141] 41. Photograting electrode;

[0142] 42, 43 First transfer gate electrode;

[0143] 44, 44a, 44b, 45, 45a, 45b Second transfer gate electrodes;

[0144] 60 wiring layers.

Claims

1. A ranging image sensor, characterized in that: include: A semiconductor layer having a first surface on a first side and a second surface on a second side opposite to the first side, for constituting a plurality of pixels arranged along the first surface; and An electrode layer disposed on the first surface for constituting the plurality of pixels. Each pixel in the plurality of pixels has: The avalanche multiplication region includes a first multiplication region of a first conductivity type formed in the semiconductor layer, and a second multiplication region of a second conductivity type formed in the semiconductor layer on the side of the first multiplication region adjacent to the first side; A charge distribution region of a second conductivity type, formed in the semiconductor layer on the side of the second multiplication region near the first side and connected to the second multiplication region; A first charge transport region of a second conductivity type, formed in the semiconductor layer on the side of the second multiplication region near the first side and connected to the charge distribution region; A second charge transport region of a second conductivity type is formed in the semiconductor layer on the side of the second multiplication region near the first side and is connected to the charge distribution region; A first conductivity type well region is formed in the semiconductor layer on the side of the second multiplication region closest to the first side; A photogate electrode is formed in the electrode layer on the side of the charge distribution region closest to the first side; A first transfer gate electrode is formed in the electrode layer on the side of the charge distribution region closer to the first side, in a manner that is different from the photogate electrode being located on the side of the first charge transfer region; and In contrast to the photogate electrode being located on the side of the second charge transfer region, a second transfer gate electrode is formed in the electrode layer on the side of the charge distribution region closer to the first side. The first multiplication region is formed such that it overlaps with the charge distribution region in the thickness direction of the semiconductor layer but does not overlap with the well region. The second multiplication region is formed to overlap with the charge distribution region and the well region in the thickness direction of the semiconductor layer.

2. The ranging image sensor according to claim 1, characterized in that: Each of the plurality of pixels further comprises: a barrier region of a second conductivity type formed in the semiconductor layer between the second multiplication region and the well region.

3. The ranging image sensor according to claim 2, characterized in that: When viewed in the thickness direction of the semiconductor layer, the barrier region includes the well region.

4. The ranging image sensor according to claim 2 or 3, characterized in that: Each of the plurality of pixels further comprises: a second conductivity type sink region formed in the semiconductor layer on the side of the barrier region near the first side, which is connected to the barrier region.

5. The ranging image sensor according to claim 4, characterized in that: The destination region is connected to the second charge transfer region.

6. The ranging image sensor according to claim 1, characterized in that: The second multiplication region includes: a first region overlapping the charge distribution region in the thickness direction of the semiconductor layer, and a second region overlapping the well region in the thickness direction of the semiconductor layer. The concentration of impurities in the second region is higher than that in the first region.

7. The ranging image sensor according to claim 6, characterized in that: When viewed in the thickness direction of the semiconductor layer, the second region includes the well region.

8. The ranging image sensor according to claim 6 or 7, characterized in that: Each of the plurality of pixels further comprises: a second conductivity type sink region formed in the semiconductor layer on the side of the second region close to the first side and connected to the second region.

9. The ranging image sensor according to claim 8, characterized in that: The destination region is connected to the second charge transfer region.

10. The ranging image sensor according to any one of claims 1 to 9, characterized in that: The first surface of the semiconductor layer has grooves that separate the individual pixels among the plurality of pixels.

11. The ranging image sensor according to any one of claims 1 to 10, characterized in that: The first multiplication region is divided according to each of the plurality of pixels.

12. The ranging image sensor according to any one of claims 1 to 11, characterized in that, Also includes: A wiring layer disposed on the first surface in a manner that covers the electrode layer and is electrically connected to each of the plurality of pixels.

Images