Distance measuring image sensor and its manufacturing method

Abstract

To provide a distance measuring image sensor capable of improving photosensitivity evenly in a plurality of pixels, and a manufacturing method for the same.SOLUTION: A distance measuring image sensor includes a semiconductor layer 20 and an electrode layer 40. The semiconductor layer and the electrode layer compose a plurality of pixels. Each of the plurality of pixels has in the semiconductor layer; an avalanche multiplication area 22; a charge distribution region 23; first charge transfer regions 24, 25; and a second charge transfer region. Each of the plurality of pixels has in the electrode layer first transfer gate electrodes 42, 43 and a second transfer gate electrode. The avalanche multiplication region overlaps at least a central part of the charge distribution region when seen from a thickness direction of the semiconductor layer.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a ranging image sensor and a manufacturing method thereof. [Background technology]

[0002] As a distance measurement image sensor that uses an indirect TOF (Time of Flight) method to obtain a distance image of an object, there is known one that includes a semiconductor layer in which a photosensitive region is provided, and a photogate electrode and a transfer gate electrode provided for each pixel on the semiconductor layer (see, for example, Patent Documents 1 and 2). With such a distance measurement image sensor, electric charges generated in the photosensitive region by the incidence of light can be transferred at high speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-133464 A [Patent Document 2] JP 2013-206903 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned distance measuring image sensor, there are cases where an improvement in light receiving sensitivity is required, for example, in order to increase the distance that can be measured.

[0005] An object of the present disclosure is to provide a distance measuring image sensor capable of improving the light receiving sensitivity uniformly across a plurality of pixels, and a method for manufacturing the same. [Means for solving the problem]

[0006] A distance measuring image sensor according to one aspect of the present disclosure includes a semiconductor layer having a first surface on a first side and a second surface on a second side opposite to the first side, and constituting a plurality of pixels arranged along the first surface, and an electrode layer provided on the first surface and constituting the plurality of pixels, each of the plurality of pixels including 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 on a first side of the first multiplication region in the semiconductor layer, a charge distribution region of the second conductivity type formed on the first side of the second multiplication region in the semiconductor layer and connected to the second multiplication region, and a first multiplication region of the second conductivity type formed on the first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region. the avalanche multiplication region includes a charge transfer region, a second charge transfer region of a second conductivity type formed on a first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region, a photogate electrode formed on the first side of the charge distribution region in the electrode layer, a first transfer gate electrode formed on the first side of the charge distribution region in the electrode layer so as to be located on the first charge transfer region side with respect to the photogate electrode, and a second transfer gate electrode formed on the first side of the charge distribution region in the electrode layer so as to be located on the second charge transfer region side with respect to the photogate electrode, and the avalanche multiplication region is connected across a plurality of pixels or reaches a trench formed in the semiconductor layer so as to separate each of the plurality of pixels from one another.

[0007] In this ranging image sensor, the avalanche multiplication region formed in the semiconductor layer is connected across multiple pixels, or reaches a trench formed in the semiconductor layer so as to separate each of the multiple pixels from each other. This allows each of the multiple pixels to have high sensitivity while suppressing variations in light sensitivity between multiple pixels and variations in light sensitivity depending on the location within one pixel. Therefore, this ranging image sensor can improve the light sensitivity uniformly in the multiple pixels.

[0008] In the distance measuring image sensor according to one aspect of the present disclosure, the trench may be formed in the first surface, and the bottom surface of the trench may be located on the second side of the avalanche multiplication region, thereby making it possible to suppress the occurrence of crosstalk between adjacent pixels.

[0009] In the distance measuring image sensor according to one aspect of the present disclosure, the trench may be formed in the first surface, and the bottom surface of the trench may be located within the avalanche multiplication region, thereby shortening the time required to form the trench and sufficiently suppressing the occurrence of crosstalk between adjacent pixels.

[0010] In the distance measuring image sensor according to one aspect of the present disclosure, each of the pixels may further include a well region of a first conductivity type formed on a first side of the second multiplication region in the semiconductor layer and constituting a readout circuit electrically connected to at least one of the first charge transfer region and the second charge transfer region, and a barrier region of a second conductivity type formed between the second multiplication region and the well region in the semiconductor layer. As a result, even if a depletion layer formed in the avalanche multiplication region spreads toward the well region of the first conductivity type due to a high voltage being applied to the avalanche multiplication region, the barrier region of the second conductivity type prevents the depletion layer from reaching the well region of the first conductivity type. In other words, it is possible to prevent a current from flowing between the avalanche multiplication region and the well region due to the depletion layer reaching the well region.

[0011] In the distance measuring image sensor according to one aspect of the present disclosure, the barrier region may include a well region when viewed in a thickness direction of the semiconductor layer, thereby making it possible to suppress a current flow between the avalanche multiplication region and the well region due to a depletion layer reaching the well region.

[0012] In the ranging image sensor according to one aspect of the present disclosure, each of the pixels may further include a sink region of a second conductivity type formed on a first side of the barrier region in the semiconductor layer and connected to the barrier region, whereby charges collected around the barrier region of the second conductivity type are drawn into the sink region of the second conductivity type, making it possible to suppress the charges collected around the barrier region from becoming noise as parasitic charges.

[0013] In the distance measuring image sensor according to one aspect of the present disclosure, the sink region may be connected to the second charge transfer region, so that when the second charge transfer region is used as an unwanted charge discharging region, the charge drawn into the sink region can be discharged to the second charge transfer region.

[0014] The distance measuring image sensor according to one aspect of the present disclosure may further include a wiring layer provided on the first surface so as to cover the electrode layer and electrically connected to each of the plurality of pixels, thereby enabling input and output of electrical signals to each of the plurality of pixels to be performed via the wiring layer.

[0015] A manufacturing method of a ranging image sensor according to one aspect of the present disclosure is a manufacturing method of the ranging image sensor, comprising a first step of forming a semiconductor layer by forming an avalanche multiplication region, a charge distribution region, a first charge transfer region, and a second charge transfer region in a semiconductor substrate, and a second step of forming an electrode layer after the first step by forming a photogate electrode, a first transfer gate electrode, and a second transfer gate electrode on a first surface of the semiconductor layer, in which the avalanche multiplication region is formed in the semiconductor substrate so as to be connected across multiple pixels in the first step.

[0016] In this method for manufacturing a distance measurement image sensor, an avalanche multiplication region is formed in a semiconductor substrate so as to be connected across multiple pixels. As a result, in the manufactured distance measurement image sensor, high sensitivity is achieved in each of the multiple pixels while suppressing variations in light sensitivity between multiple pixels and variations in light sensitivity depending on the location within a pixel. Therefore, according to this method for manufacturing a distance measurement image sensor, a distance measurement image sensor can be obtained in which the light sensitivity is improved uniformly across the multiple pixels.

[0017] In the manufacturing method of the distance measuring image sensor according to one aspect of the present disclosure, in the first step, after forming at least an avalanche multiplication region in the semiconductor substrate, a trench may be formed in the first surface, whereby a configuration in which the avalanche multiplication region reaches the trench can be easily and reliably obtained.

[0018] The method for manufacturing a ranging image sensor according to one aspect of the present disclosure may further include a fifth step of forming a wiring layer on the first surface so as to cover the electrode layer and electrically connecting the wiring layer to each of the plurality of pixels after the second step, whereby in the manufactured ranging image sensor, input and output of electrical signals to each of the plurality of pixels can be performed via the wiring layer. Effect of the Invention

[0019] According to the present disclosure, it is possible to provide a distance measuring image sensor capable of improving the light receiving sensitivity uniformly across a plurality of pixels, and a method for manufacturing the same. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a configuration diagram of a photodetection device including a distance measuring image sensor according to the first embodiment. [Diagram 2] FIG. 2 is a plan view of a pixel portion of the distance measuring image sensor of the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. [Figure 4]FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view for explaining a method for manufacturing the distance measuring image sensor of the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view for explaining a manufacturing method of the distance measuring image sensor of the first embodiment. [Figure 7] FIG. 7 is a plan view of a portion of the distance measuring image sensor of the second embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII shown in FIG. [Figure 9] FIG. 9 is a plan view of a portion of the distance measuring image sensor of the third embodiment. [Figure 10] FIG. 10 is a cross-sectional view taken along line XX shown in FIG. [Figure 11] FIG. 11 is a plan view of a portion of the distance measuring image sensor of the fourth embodiment. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII shown in FIG. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII shown in FIG. [Figure 14] FIG. 14 is a plan view of a portion of the distance measuring image sensor of the fifth embodiment. [Figure 15] FIG. 15 is a cross-sectional view taken along line XV-XV shown in FIG. [Figure 16] FIG. 16 is a cross-sectional view of a distance measuring image sensor according to a modified example. [Figure 17] FIG. 17 is a cross-sectional view of a modified distance measuring image sensor. [Figure 18] FIG. 18 is a cross-sectional view of a distance measuring image sensor according to a modified example. [Figure 19] FIG. 19 is a cross-sectional view of a distance measuring image sensor according to a modified example. [Figure 20] FIG. 20 is a cross-sectional view of a distance measuring image sensor according to a modified example. [Figure 21] FIG. 21 is a cross-sectional view of a distance measuring image sensor according to a modified example. [Figure 22] FIG. 22 is a cross-sectional view of a distance measuring image sensor according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [First embodiment] [Configuration of the photodetector]

[0022] 1, the photodetection device 1 includes a light source 2, a distance measurement image sensor 10A, a signal processing unit 3, a control unit 4, and a display unit 5. The photodetection device 1 is a device that obtains a distance image of an object OJ (an image including information on a distance d to the object OJ) using an indirect TOF method.

[0023] The light source 2 emits pulsed light L. The light source 2 is, for example, an infrared LED. The pulsed light L is, for example, near-infrared light, and the frequency of the pulsed light L is, for example, 10 kHz or more. The distance measurement image sensor 10A detects the pulsed light L emitted from the light source 2 and reflected by an object OJ. The distance measurement image sensor 10A is configured by monolithically forming a pixel unit 11 and a CMOS readout circuit unit 12 on a semiconductor substrate (for example, a silicon substrate). The distance measurement image sensor 10A is mounted on a signal processing unit 3.

[0024] The signal processing unit 3 controls the pixel unit 11 and CMOS readout circuit unit 12 of the distance measurement image sensor 10A. The signal processing unit 3 performs predetermined processing on the signal output from the distance measurement 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. [Configuration of distance measurement image sensor]

[0025] As shown in FIG. 2, FIG. 3, and FIG. 4, the distance measurement image sensor 10A includes a semiconductor layer 20 and an electrode layer 40 in the pixel section 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 configure a plurality of pixels 11a arranged along the first surface 20a. In the distance measurement image sensor 10A, the plurality of pixels 11a are two-dimensionally arranged along the first surface 20a. Hereinafter, the thickness direction of the semiconductor layer 20 is referred to as the Z direction, 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. Moreover, one side in the Z direction is referred to as a first side, and the other side in the Z direction (the side opposite to the first side) is referred to as a second side. Note that a wiring layer 60, which will be described later, is not shown in FIG.

[0026] Each pixel 11a has, in a semiconductor layer 20, a semiconductor region 21, an avalanche multiplication region 22, a charge distribution region 23, a pair of first charge transfer regions 24, 25, a pair of second charge transfer regions 26, 27, a plurality of 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. Each of the regions 21 to 28, 31 to 35 is formed by carrying out various processes (e.g., etching, film formation, impurity injection, etc.) on a semiconductor substrate (e.g., a silicon substrate).

[0027] The semiconductor region 21 is a p-type (first conductivity type) region and is provided along the second surface 20b of the semiconductor layer 20. The semiconductor region 21 functions as a light absorption region (photoelectric conversion region). As an example, the semiconductor region 21 has a size of 1×10 15 cm -3 The semiconductor region 21 is a p-type region having the following carrier concentration, and the thickness of the semiconductor region 21 is about 10 μm. Note that the avalanche multiplication region 22 and the like also function as a light absorption region (photoelectric conversion region).

[0028] 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, and is 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 dopant concentration of 1×10 16 cm -3 The first multiplication region 22a is a p-type region having a carrier concentration of 1×10 or more, and the thickness of the first multiplication region 22a is about 1 μm. The second multiplication region 22b is an n-type (second conductivity type) region, and is formed on the first side of the first multiplication region 22a in the semiconductor layer 20. As an example, the second multiplication region 22b has a carrier concentration of 1×10 16 cm -3 The second multiplication region 22b is an n-type region having a carrier concentration of 1 μm or more, and the thickness of the second multiplication region 22b is about 1 μm. The first multiplication region 22a and the second multiplication region 22b form a pn junction.

[0029] The charge distributing region 23 is an n-type region and is formed on the first side of the second multiplication region 22b in the semiconductor layer 20. As an example, the charge distributing region 23 has a capacitance of 5×10 15 ~1×10 16 cm -3 The charge distributing region 23 is an n-type region having a carrier concentration of about 1 μm.

[0030] Each of the first charge transfer regions 24, 25 is an n-type region, and is formed on the first side of the second multiplication region 22b in the semiconductor layer 20. Each of the first charge transfer regions 24, 25 is connected to the charge distribution region 23. The pair of first charge transfer regions 24, 25 face each other in the X direction, sandwiching a portion of the charge distribution region 23 on the first side therebetween. As an example, each of the first charge transfer regions 24, 25 has a capacitance of 1×10 18 cm -3 The first charge transfer regions 24, 25 are n-type regions having a carrier concentration of 0.2 μm or more, and the thickness of each of the first charge transfer regions 24, 25 is about 0.2 μm. The second side portion of the charge distribution region 23 is inserted between each of the first charge transfer regions 24, 25 and the second multiplication region 22b. In this embodiment, each of the first charge transfer regions 24, 25 functions as a charge accumulation region.

[0031] Each of the second charge transfer regions 26, 27 is an n-type region, and is formed on the first side of the second multiplication region 22b in the semiconductor layer 20. Each of the second charge transfer regions 26, 27 is connected to the charge distribution region 23. The pair of second charge transfer regions 26, 27 face each other in the Y direction, sandwiching a portion of the charge distribution region 23 on the first side therebetween. As an example, each of the second charge transfer regions 26, 27 has a capacitance of 1×10 18 cm -3 The second charge transfer regions 26, 27 are n-type regions having a carrier concentration of 0.2 μm or more, and the thickness of each of the second charge transfer regions 26, 27 is about 0.2 μm. The second side portion of the charge distribution region 23 is inserted between each of the second charge transfer regions 26, 27 and the second multiplication region 22b. In this embodiment, each of the second charge transfer regions 26, 27 functions as a charge discharge region.

[0032] Each charge blocking region 28 is a p-type region and is formed between each of the first charge transfer regions 24, 25 and the charge distributing region 23 (the second side portion of the charge distributing region 23) in the semiconductor layer 20. As an example, each charge blocking region 28 has a capacitance of 1×10 17 ~1×10 18 cm -3 The charge blocking regions 28 are p-type regions having a carrier concentration of about 0.2 μm.

[0033] The well region 31 is a p-type region, and is formed on a first side of the second multiplication region 22b in the semiconductor layer 20. The well region 31 surrounds the charge distribution region 23 when viewed from the Z direction. The LOCOS region 33 is formed on the first side of the well region 31 in the semiconductor layer 20. The LOCOS region 33 is connected to the well region 31. The well region 31 and the LOCOS region 33 configure a plurality of readout circuits (e.g., source follower amplifiers, reset transistors, etc.). Each readout circuit is electrically connected to each of the first charge transfer regions 24, 25. As an example, the well region 31 has a capacitance of 1×10 16 ~5×10 17 cm -3The well region 31 is a p-type region having a carrier concentration of about 1 μm, and the thickness of the well region 31 is about 1 μm. As a structure for electrically isolating the pixel section and the readout circuit section, STI (Shallow Trench Isolation) may be used instead of the LOCOS region 33, or simply the well region 31 may be used.

[0034] The barrier region 34 is an n-type region and is formed between the second multiplication region 22b and the well region 31 in the semiconductor layer 20. The barrier region 34 includes the well region 31 when viewed from the Z direction. That is, the well region 31 is located within the barrier region 34 when viewed from the Z direction. The barrier region 34 surrounds the charge distribution region 23. The concentration of n-type impurities in the barrier region 34 is higher than the concentration of n-type impurities in the second multiplication region 22b. As an example, the barrier region 34 is an n-type region having a carrier concentration ranging from the carrier concentration of the second multiplication region 22b to about twice the carrier concentration of the second multiplication region 22b, and the thickness of the barrier region 34 is about 1 μm.

[0035] Each sink region 35 is an n-type region and is formed on the first side of the barrier region 34 in the semiconductor layer 20. The second end of each sink region 35 is connected to the barrier region 34. The first end of each sink region 35 is connected to each second charge transfer region 26, 27. The concentration of n-type impurities in each second charge transfer region 26, 27 is higher than the concentration of n-type impurities in each sink region 35, and the concentration of n-type impurities in each sink 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 sink region 35 is an n-type region having a carrier concentration equal to or higher than the carrier concentration of the well region 31, and the thickness of each sink region 35 depends on the distance between each second charge transfer region 26, 27 and the barrier region 34.

[0036] Each pixel 11a has a photogate electrode 41, a pair of first transfer gate electrodes 42, 43, and a pair of second transfer gate electrodes 44, 45 in the electrode layer 40. Each of the gate electrodes 41 to 45 is formed on the first surface 20a of the semiconductor layer 20 via an insulating film 46. The insulating film 46 is, for example, a silicon nitride film, a silicon oxide film, or the like.

[0037] The photogate electrode 41 is formed on the first side of the charge distribution region 23 in the electrode layer 40. The photogate electrode 41 is formed of a material (e.g., polysilicon) having electrical conductivity and optical transparency. As an example, the photogate electrode 41 has a rectangular shape having two sides facing each other in the X direction and two sides facing each other in the Y direction when viewed from the Z direction.

[0038] The first transfer gate electrode 42 is formed on the electrode layer 40 on the first side of the charge distribution region 23 so as to be located on the first charge transfer region 24 side with respect to the photogate electrode 41. The first transfer gate electrode 43 is formed on the electrode layer 40 on the first side of the charge distribution region 23 so as to be located on the first charge transfer region 25 side with respect to the photogate electrode 41. Each of the first transfer gate electrodes 42, 43 is formed of a material (e.g., polysilicon) having electrical conductivity and optical transparency. As an example, each of the first transfer gate electrodes 42, 43 has a rectangular shape having two sides facing each other in the X direction and two sides facing each other in the Y direction when viewed from the Z direction.

[0039] The second transfer gate electrode 44 is formed on the electrode layer 40 on the first side of the charge distribution region 23 so as to be located on the second charge transfer region 26 side with respect to the photogate electrode 41. The second transfer gate electrode 45 is formed on the electrode layer 40 on the first side of the charge distribution region 23 so as to be located on the second charge transfer region 27 side with respect to the photogate electrode 41. Each of the second transfer gate electrodes 44, 45 is formed of a material having electrical conductivity and optical transparency (e.g., polysilicon). As an example, each of the second transfer gate electrodes 44, 45 has a rectangular shape having two sides facing each other in the X direction and two sides facing each other in the Y direction when viewed from the Z direction.

[0040] The distance measuring image sensor 10A further includes a counter electrode 50 and a wiring layer 60 in the pixel section 11. The counter electrode 50 is provided on the second surface 20b of the semiconductor layer 20. The counter electrode 50 includes a plurality of pixels 11a when viewed from the Z direction. The counter electrode 50 faces the electrode layer 40 in the Z direction. The counter electrode 50 is formed of, for example, a metal material. The wiring layer 60 is provided on the first surface 20a of the semiconductor layer 20 so as to cover the electrode layer 40. The wiring layer 60 is electrically connected to each pixel 11a and the CMOS readout circuit section 12 (see FIG. 1). A light incident opening 60a is formed in a portion of the wiring layer 60 facing the photogate electrode 41 of each pixel 11a.

[0041] A trench 29 is formed in the semiconductor layer 20 so as to separate the pixels 11a from each other. The trench 29 is formed in the first surface 20a of the semiconductor layer 20. A bottom surface 29a of the trench 29 is located on the second side with respect to the avalanche multiplication region 22. In other words, the trench 29 completely separates the avalanche multiplication region 22. An insulating material 47 such as silicon oxide is disposed in the trench 29. Note that instead of the insulating material 47, a metal material such as tungsten, polysilicon, or the like may be disposed in the trench 29.

[0042] In each pixel 11a, the avalanche multiplication region 22 reaches the trench 29. The avalanche multiplication region 22 is a region that causes avalanche multiplication. That is, in each pixel 11a, when a predetermined reverse bias is applied, a voltage of 3×10 5 ~4×10 5 An avalanche multiplication region 22 capable of generating an electric field strength of 100 V / cm extends over the entire area surrounded by trench 29 .

[0043] An example of the operation of the distance measurement image sensor 10A configured as above is as follows. In each pixel 11a of the distance measurement image sensor 10A, a negative voltage (e.g., −50 V) is applied to the counter electrode 50 with respect to 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), and 3×10 5 ~4×10 5 In this state, when pulsed light L is incident on the semiconductor layer 20 through the light incident opening 60a and the photogate electrode 41, electrons generated by absorption of the pulsed light L are multiplied in the avalanche multiplication region 22 and move at high speed to the charge distribution region 23.

[0044] When generating a distance image of the object OJ (see FIG. 1), in each pixel 11a, first, a reset voltage is applied to the pair of second transfer gate electrodes 44, 45. The reset voltage is a positive voltage with respect to the potential of the photogate electrode 41. As a result, the electrons that have moved to the charge distribution region 23 are discharged from the pair of second charge transfer regions 26, 27.

[0045] Subsequently, a pulse voltage signal is applied to the pair of first transfer gate electrodes 42 and 43. As an example, the pulse voltage signal applied to the first transfer gate electrode 42 is a voltage signal in which positive and negative voltages are alternately repeated with respect to the potential of the photogate electrode 41, and is a voltage signal having the same period, pulse width, and phase as the intensity signal of the pulsed light L emitted from the light source 2 (see FIG. 1). On the other hand, the pulse voltage signal applied to the first transfer gate electrode 43 is a voltage signal identical to the pulse voltage signal applied to the first transfer gate electrode 42, except that the phase is shifted by 180°.

[0046] As a result, the electrons that have moved to the charge distribution region 23 are transferred alternately at high speed to the pair of first charge transfer regions 24, 25. The electrons that have accumulated in each of the first charge transfer regions 24, 25 by the transfer for a predetermined period of time are transferred as a signal to the CMOS readout circuit unit 12 (see FIG. 1) via the readout circuit formed by the well region 31 etc. and the wiring layer 60.

[0047] 1, when a pulsed light L is emitted from the light source 2 and the pulsed light L reflected by the object OJ is detected by the distance measurement image sensor 10A, the phase of the intensity signal of the pulsed light L detected by the distance measurement image sensor 10A shifts in accordance with the distance d to the object OJ from the phase of the intensity signal of the pulsed light L emitted from the light source 2. Therefore, a distance image of the object OJ can be generated by acquiring a signal based on the electrons accumulated in each of the first charge transfer regions 24, 25 for each pixel 11a. [Manufacturing method of distance measurement image sensor]

[0048] As shown in (a) of FIG. 5, a p-type semiconductor substrate 20s is prepared, and an avalanche multiplication region 22 and a charge distribution region 23 are formed in the semiconductor substrate 20s. At this time, the avalanche multiplication region 22 is formed in the semiconductor substrate 20s so as to be connected across a plurality of pixels 11a (see (b) of FIG. 5). Then, as shown in (b) of FIG. 5, a trench 29 is formed in the first surface 20a of the semiconductor layer 20. Then, as shown in (a) of FIG. 6, each of the regions 24-28, 31-35 is formed in the semiconductor substrate 20s so that each pixel 11a has a pair of first charge transfer regions 24, 25, a pair of second charge transfer regions 26, 27, a plurality of charge blocking regions 28, a well region 31, a LOCOS region 33, a barrier region 34, and a pair of sink regions 35. As a result, the semiconductor layer 20 in which the trench 29 is formed is formed (first step). The semiconductor region 21 is a region that was included in the semiconductor substrate 20s.

[0049] Next, as shown in FIG. 6(b), the gate electrodes 41 to 45 are formed on the first surface 20a of the semiconductor layer 20 so 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. This forms the electrode layer 40 (second step). Next, as shown in FIG. 3, the wiring layer 60 is formed on the first surface 20a of the semiconductor layer 20 so as to cover the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a (third step). Next, the counter electrode 50 is formed on the second surface 20b of the semiconductor layer 20. In parallel with the formation of the pixel section 11 on the semiconductor substrate 20s, the CMOS readout circuit section 12 is formed on the semiconductor substrate 20s. Through the above steps, the distance measurement image sensor 10A is manufactured. The trench 29 may be formed after the regions 24 to 28 and 31 to 35 are formed in the semiconductor substrate 20s and before the gate electrodes 41 to 45 are formed on the first surface 20a of the semiconductor layer 20. [Action and Effects]

[0050] In the distance measurement image sensor 10A, the avalanche multiplication region 22 formed in the semiconductor layer 20 reaches a trench 29 formed in the semiconductor layer 20 so as to separate each pixel 11a from another. This realizes high sensitivity in each pixel 11a while suppressing variations in light sensitivity among the pixels 11a and variations in light sensitivity depending on the location within one pixel 11a. Therefore, according to the distance measurement image sensor 10A, it is possible to uniformly improve the light sensitivity in the multiple pixels 11a.

[0051] In the distance measurement image sensor 10A, the bottom surface 29a of the trench 29 is located on the second side with respect to the avalanche multiplication region 22. This makes it possible to suppress the occurrence of crosstalk between adjacent pixels 11a.

[0052] In the distance measuring image sensor 10A, an n-type barrier region 34 is formed between the n-type second multiplication region 22b and the p-type well region 31 constituting the readout circuit. As a result, even if a depletion layer formed in the avalanche multiplication region 22 spreads toward the p-type well region 31 due to application of a high voltage to the avalanche multiplication region 22, the n-type barrier region 34 prevents the depletion layer from reaching the p-type well region 31. In other words, it is possible to prevent a current from flowing between the avalanche multiplication region 22 and the well region 31 due to the depletion layer reaching the well region 31.

[0053] In the distance measurement image sensor 10A, the barrier region 34 includes the well region 31 when viewed from the Z direction. This makes it possible to suppress a current flow between the avalanche multiplication region 22 and the well region 31 caused by the depletion layer reaching the well region 31.

[0054] In the distance measuring image sensor 10A, an n-type sink region 35 connected to the barrier region 34 is formed on the first side of the barrier region 34. This allows electrons gathered around the n-type barrier region 34 to be drawn into the n-type sink region 35, making it possible to prevent the electrons gathered around the barrier region 34 from becoming noise as parasitic electrons. By adjusting the impurity concentration in the region between the first charge transfer region 24 and each sink region 35 and the region between the first charge transfer region 25 and each sink region 35, it is possible to form a potential state in which parasitic electrons are more easily drawn into the sink region 35 than into each of the first charge transfer regions 24, 25.

[0055] In the distance measuring image sensor 10A, the sink region 35 is connected to each of the second charge transfer regions 26 and 27. This allows parasitic electrons attracted to the sink region 35 to be discharged to each of the second charge transfer regions 26 and 27, which function as unnecessary charge discharge regions.

[0056] In the distance measurement image sensor 10A, a wiring layer 60 is provided on the first surface 20a of the semiconductor layer 20 so as to cover the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a. This allows input and output of electrical signals to and from each pixel 11a to be performed via the wiring layer 60.

[0057] In the manufacturing method of the distance measurement image sensor 10A, an avalanche multiplication region 22 is formed in the semiconductor substrate 20s so as to be connected across the multiple pixels 11a. As a result, in the manufactured distance measurement image sensor 10A, high sensitivity is realized in each pixel 11a while the variation in light receiving sensitivity among the multiple pixels 11a and the variation in light receiving sensitivity depending on the location within one pixel 11a are suppressed. Therefore, according to the manufacturing method of the distance measurement image sensor 10A, it is possible to obtain a distance measurement image sensor 10A in which the light receiving sensitivity is uniformly improved in the multiple pixels 11a.

[0058] In the manufacturing method of the distance measuring image sensor 10A, after the formation of the avalanche multiplication region 22, a trench 29 is formed in the first surface 20a of the semiconductor layer 20. This makes it possible to easily and reliably obtain a configuration in which the avalanche multiplication region 22 reaches the trench 29.

[0059] In the manufacturing method of the distance measurement image sensor 10A, after forming each of the gate electrodes 41-45, a wiring layer 60 is formed on the first surface 20a of the semiconductor layer 20 so as to cover the electrode layer 40, and the wiring layer 60 is electrically connected to each pixel 11a. As a result, in the manufactured distance measurement image sensor 10A, input and output of electrical signals to and from each pixel 11a can be performed via the wiring layer 60. [Second embodiment]

[0060] As shown in Figures 7 and 8, the distance measurement image sensor 10B differs from the distance measurement image sensor 10A described above mainly in that second charge transfer regions 26a, 26b, 27a, and 27b are arranged on both sides of the charge distribution region 23 in the X direction, and that multiple second transfer gate electrodes 44a, 44b, 45a, and 45b are arranged on both sides of the photogate electrode 41 in the X direction.

[0061] In each pixel 11a of the distance measuring image sensor 10B, a pair of second charge transfer regions 26a, 26b are arranged 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, 27b are arranged 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. The second transfer gate electrode 44a is arranged between the photogate electrode 41 and the second charge transfer region 26a when viewed from the Z direction. The second transfer gate electrode 44b is arranged between the photogate electrode 41 and the second charge transfer region 26b when viewed from the Z direction. The second transfer gate electrode 45a is arranged between the photogate electrode 41 and the second charge transfer region 27a when viewed from the Z direction. The second transfer gate electrode 45b is arranged between the photogate electrode 41 and the second charge transfer region 27b when viewed from the Z direction.

[0062] In the distance measurement image sensor 10B, similarly to the distance measurement image sensor 10A described above, the avalanche multiplication region 22 formed in the semiconductor layer 20 reaches a trench 29 formed in the semiconductor layer 20 so as to separate each pixel 11a from another. This realizes high sensitivity in each pixel 11a while suppressing variations in light receiving sensitivity among the pixels 11a and variations in light receiving sensitivity depending on the location within one pixel 11a. Therefore, according to the distance measurement image sensor 10B, it is possible to uniformly improve the light receiving sensitivity in the multiple pixels 11a. [Third embodiment]

[0063] As shown in Figures 9 and 10, the distance measurement image sensor 10C differs from the distance measurement image sensor 10A described above mainly in that the first charge transfer region 24 is located in the center of the charge distribution region 23, the second charge transfer region 26 is formed in a ring shape, and each of the electrodes 41, 42, 44 is formed in a ring shape.

[0064] In each pixel 11a of the distance measuring image sensor 10C, the first charge transfer region 24 is disposed in the center of the charge distribution region 23 when viewed from the Z direction. The second charge transfer region 26 has, for example, a rectangular ring shape when viewed from the Z direction, and is disposed along the outer edge of the charge distribution region 23. The photogate electrode 41 has, for example, a rectangular ring shape when viewed from the Z direction, and is disposed outside the first charge transfer region 24 and inside the second charge transfer region 26. The first transfer gate electrode 42 has, for example, a rectangular ring shape when viewed from the Z direction, and is disposed outside the first charge transfer region 24 and inside the photogate electrode 41. The second transfer gate electrode 44 has, for example, a rectangular ring shape when viewed from the Z direction, and is disposed outside the photogate electrode 41 and inside the second charge transfer region 26.

[0065] In the distance measurement image sensor 10C, similarly to the distance measurement image sensor 10A described above, the avalanche multiplication region 22 formed in the semiconductor layer 20 reaches a trench 29 formed in the semiconductor layer 20 so as to separate each pixel 11a from another. This realizes high sensitivity in each pixel 11a while suppressing variations in light receiving sensitivity among the pixels 11a and variations in light receiving sensitivity depending on the location within one pixel 11a. Therefore, according to the distance measurement image sensor 10C, it is possible to uniformly improve the light receiving sensitivity in the multiple pixels 11a.

[0066] In the distance measurement image sensor 10C, the well region 31, the LOCOS region 33, the barrier region 34, and the sink region 35 (see FIG. 3) are not formed in the semiconductor layer 20. Therefore, the distance measurement image sensor 10C can increase the density of the pixels 11a and simplify the structure of the semiconductor layer 20. As an example, a semiconductor substrate on which a readout circuit for each pixel 11a and a CMOS readout circuit unit 12 are formed is joined from a first side to the distance measurement image sensor 10C. [Fourth embodiment]

[0067] As shown in Figures 11, 12 and 13, the distance measurement image sensor 10D differs from the distance measurement image sensor 10A described above mainly in that the first charge transfer region 24 is arranged in the center of the charge distribution region 23, multiple second charge transfer regions 26 are arranged along the outer edge of the charge distribution region 23, the photogate electrode 41 and the first transfer gate electrode 42 are formed in an annular shape, multiple second transfer gate electrodes 44 are arranged to surround the photogate electrode 41, and in that no trench 29 is formed in the semiconductor layer 20 and the avalanche multiplication region 22 is connected across multiple pixels 11a.

[0068] In each pixel 11a of the distance measuring image sensor 10D, the first charge transfer region 24 is disposed in the center of the charge distribution region 23 when viewed from the Z direction. The second charge transfer regions 26 are disposed along the outer edge of the charge distribution region 23 when viewed from the Z direction. Each second charge transfer region 26 is shared by two adjacent pixels 11a. The photogate electrode 41 has, for example, a rectangular annular shape when viewed from the Z direction, and is disposed outside the first charge transfer region 24 and inside the second charge transfer regions 26. The first transfer gate electrode 42 has, for example, a rectangular annular shape when viewed from the Z direction, and is disposed outside the first charge transfer region 24 and inside the photogate electrode 41. Each second transfer gate electrode 44 is disposed between the photogate electrode 41 and each second charge transfer region 26 when viewed from the Z direction.

[0069] In each pixel 11a of the distance measurement image sensor 10D, the well region 31 and the barrier region 34 are disposed on the intersections of a plurality of imaginary lines arranged in a lattice pattern so as to separate the plurality of pixels 11a when viewed from the Z direction. Therefore, no trench 29 is formed in the semiconductor layer 20, and the avalanche multiplication region 22 is connected across the plurality of pixels 11a.

[0070] In the distance measurement image sensor 10D, the avalanche multiplication region 22 formed in the semiconductor layer 20 is connected across multiple pixels 11a. This allows each pixel 11a to have high sensitivity while suppressing variations in light sensitivity among the multiple pixels 11a and variations in light sensitivity depending on the location within one pixel 11a. Therefore, the distance measurement image sensor 10D can improve the light sensitivity uniformly in the multiple pixels 11a.

[0071] In the ranging image sensor 10D, the sink region 35 (see FIG. 3) is not formed in the semiconductor layer 20. This is because, in the ranging image sensor 10D, the barrier region 34 is farther away from the first charge transfer region 24 than in the ranging image sensor 10A described above, and as a result, electrons gathered around the barrier region 34 are less likely to enter the first charge transfer region 24. [Fifth embodiment]

[0072] As shown in Figures 14 and 15, the distance measurement image sensor 10E differs from the distance measurement image sensor 10A described above mainly in that the first charge transfer region 24 is arranged in the center of each pixel 11a, multiple second charge transfer regions 26 are arranged in multiple corners of each pixel 11a, the first transfer gate electrode 42 is formed in a ring shape, the photogate electrode 41 is arranged so as to avoid the center and multiple corners of each pixel 11a, multiple second transfer gate electrodes 44 are arranged in multiple corners of each pixel 11a, and in that no trench 29 is formed in the semiconductor layer 20 and the avalanche multiplication region 22 is connected across multiple pixels 11a.

[0073] In each pixel 11a of the distance measuring image sensor 10E, the first charge transfer region 24 is disposed in the center of each pixel 11a when viewed from the Z direction. The second charge transfer regions 26 are disposed in the corners of each pixel 11a when viewed from the Z direction. The photogate electrode 41 is disposed so as to avoid the center and the corners of each pixel 11a (i.e., so as to avoid the first charge transfer region 24 and the second charge transfer regions 26). The photogate electrode 41 is connected across the pixels 11a. The first transfer gate electrode 42 has, for example, a rectangular ring shape when viewed from the Z direction, and is disposed outside the first charge transfer region 24 and inside the photogate electrode 41. Each second transfer gate electrode 44 is disposed between the photogate electrode 41 and each second charge transfer region 26 when viewed from the Z direction.

[0074] In each pixel 11a of the distance measurement image sensor 10E, the corresponding second charge transfer region 26 and second transfer gate electrode 44 are shared by four adjacent pixels 11a. Therefore, no trench 29 is formed in the semiconductor layer 20, and the avalanche multiplication region 22 is connected across the multiple pixels 11a.

[0075] In the distance measurement image sensor 10E, the avalanche multiplication region 22 formed in the semiconductor layer 20 is connected across multiple pixels 11a. This allows each pixel 11a to have high sensitivity while suppressing variations in light sensitivity among the multiple pixels 11a and variations in light sensitivity depending on the location within one pixel 11a. Therefore, the distance measurement image sensor 10E can improve the light sensitivity uniformly in the multiple pixels 11a.

[0076] In the distance measurement image sensor 10E, the well region 31, the LOCOS region 33, the barrier region 34, and the sink region 35 (see FIG. 3) are not formed in the semiconductor layer 20. Therefore, the distance measurement image sensor 10E can increase the density of the pixels 11a and simplify the structure of the semiconductor layer 20. As an example, a semiconductor substrate on which a readout circuit for each pixel 11a and a CMOS readout circuit unit 12 are formed is joined from a first side to the distance measurement image sensor 10E. [Variations]

[0077] The present disclosure is not limited to the above-described first to fifth embodiments. In the distance measurement image sensors 10A, 10B, and 10C, the bottom surface 29a of the trench 29 may be located within the avalanche multiplication region 22. In this case, it is possible to reduce the time required to form the trench 29 and sufficiently suppress the occurrence of crosstalk between adjacent pixels 11a.

[0078] In the distance measurement image sensors 10A, 10B, and 10C, the bottom surface 29a of the trench 29 may be located on the first side with respect to the avalanche multiplication region 22, and the avalanche multiplication region 22 may be connected across multiple pixels 11a. Alternatively, in the distance measurement image sensors 10A and 10B, the trench 29 may not be formed in the semiconductor layer 20, and the avalanche multiplication region 22 may be connected across multiple pixels 11a. In either case, the light receiving sensitivity can be improved uniformly in the multiple pixels 11a.

[0079] In the ranging image sensors 10A and 10B, each sink region 35 may not be connected to each second charge transfer region 26, 27. In the ranging image sensors 10A and 10B, the sink region 35 may not be formed in the semiconductor layer 20. In the ranging image sensors 10A and 10B, the well region 31 and the barrier region 34 may not be formed in the semiconductor layer 20. In the ranging image sensors 10A, 10B, and 10C, the charge blocking region 28 may not be formed in the semiconductor layer 20.

[0080] In the ranging image sensor 10D, a sink region 35 connected to the barrier region 34 may be formed in the semiconductor layer 20. In the ranging image sensor 10D, a sink region 35 connected to each of the barrier region 34 and the second charge transfer region 26 may be formed in the semiconductor layer 20. In the ranging image sensor 10D, the well region 31 and the barrier region 34 may not be formed in the semiconductor layer 20. In the ranging image sensors 10D and 10E, a charge blocking region 28 may be formed in the semiconductor layer 20.

[0081] 16 to 22, in the distance measurement image sensors 10A to 10E, a buried region 36 may be formed in the semiconductor layer 20 of each pixel 11a. The buried region 36 formed in the semiconductor layer 20 of each pixel 11a suppresses the generation of dark current in each pixel 11a.

[0082] The distance measurement image sensor 10A shown in Figures 16 and 17 differs from the distance measurement image sensor 10A described above mainly in that the semiconductor layer 20 of each pixel 11a does not have a plurality of charge blocking regions 28 formed therein and in that a buried region 36 is formed in the semiconductor layer 20 of each pixel 11a. The configuration of the semiconductor layer 20 of each pixel 11a in the distance measurement image sensor 10A shown in Figures 16 and 17 is as follows.

[0083] 16 and 17, the charge distribution region 23 is formed so as to overlap the photogate electrode 41 when viewed from the Z direction, and not to overlap the transfer gate electrodes 42, 43, 44, and 45 when viewed from the Z direction. The buried region 36 is a p-type region, and is formed on the first side of the charge distribution region 23 in the semiconductor layer 20. That is, the charge distribution region 23 is buried in the semiconductor layer 20 by the buried region 36. The well region 31 surrounds the first side portion of the charge distribution region 23 and the buried region 36. A part of the well region 31 is located between the buried region 36 and each of the charge transfer regions 24, 25, 26, and 27. 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 surrounding the charge distributing region is located inside the inner edge of the well region 31 surrounding the charge distributing region and the buried region .

[0084] The distance measurement image sensor 10B shown in Fig. 18 differs from the distance measurement image sensor 10B described above mainly in that the semiconductor layer 20 of each pixel 11a does not have a plurality of charge blocking regions 28 formed therein and in that the semiconductor layer 20 of each pixel 11a has a buried region 36 formed therein. The configuration of the semiconductor layer 20 of each pixel 11a in the distance measurement image sensor 10B shown in Fig. 18 is as follows.

[0085] As shown in FIG. 18, the charge distribution region 23 is formed so as to overlap the photogate electrode 41 when viewed from the Z direction, and not to overlap the transfer gate electrodes 42, 43, 44a, 44b, 45a, and 45b (see FIG. 7) when viewed from the Z direction. The buried region 36 is a p-type region and is formed on the first side of the charge distribution region 23 in the semiconductor layer 20. That is, the charge distribution region 23 is buried in the semiconductor layer 20 by the buried region 36. The well region 31 surrounds the first side portion of the charge distribution region 23 and the buried region 36. A part of the well region 31 is located between the buried region 36 and each of the charge transfer regions 24, 25, 26a, 26b, 27a, and 27b (see FIG. 7). 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 surrounding the charge distributing region is located inside the inner edge of the well region 31 surrounding the charge distributing region and the buried region .

[0086] The distance measurement image sensor 10C shown in Fig. 19 differs from the distance measurement image sensor 10C described above mainly in that a buried region 36 is formed in the semiconductor layer 20 of each pixel 11a, a well region 31 (hereinafter referred to as the "inner well region 31") is formed in the semiconductor layer 20 so as to include the first charge transfer region 24 in each pixel 11a, a well region 31 (hereinafter referred to as the "outer well region 31") is formed in the semiconductor layer 20 so as to include the second charge transfer region 26 in each pixel 11a, and a barrier region 34 is formed on the second side of each of the inner well region 31 and the outer well region 31. The configuration of the semiconductor layer 20 of each pixel 11a in the distance measurement image sensor 10C shown in Fig. 19 is as follows.

[0087] As shown in FIG. 19, the first side portion of the charge distribution region 23 is formed so as to overlap the photogate electrode 41 when viewed from the Z direction, and not overlap the multiple transfer gate electrodes 42, 44 when viewed from the Z direction. The buried region 36 is a p-type region and is formed on the first side of the charge distribution region 23 in the semiconductor layer 20. That is, the charge distribution region 23 is buried in the semiconductor layer 20 by the buried region 36. When viewed from the Z direction, the buried region 36 has, for example, a rectangular ring shape, similar to the photogate electrode 41. 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.

[0088] The distance measurement image sensor 10D shown in Figures 20 and 21 differs from the distance measurement image sensor 10D described above mainly in that an embedded region 36 is formed in the semiconductor layer 20 of each pixel 11a, a well region 31 (hereinafter referred to as the "inner well region 31") is formed in the semiconductor layer 20 so as to include the first charge transfer region 24 in each pixel 11a, a well region 31 (hereinafter referred to as the "outer well region 31") is formed in the semiconductor layer 20 so as to include a plurality of second charge transfer regions 26 in each pixel 11a, and a barrier region 34 is formed on the second side of each of the inner well region 31 and the outer well region 31. The configuration of the semiconductor layer 20 of each pixel 11a in the distance measurement image sensor 10D shown in Figures 20 and 21 is as follows.

[0089] As shown in FIG. 20 and FIG. 21, the first side portion of the charge distribution region 23 is formed so as to overlap the photogate electrode 41 when viewed from the Z direction, and not overlap the multiple transfer gate electrodes 42, 44 when viewed from the Z direction. The buried region 36 is a p-type region, and is formed on the first side of the charge distribution region 23 in the semiconductor layer 20. That is, the charge distribution region 23 is buried in the semiconductor layer 20 by the buried region 36. The buried region 36 has, for example, a rectangular ring shape when viewed from the Z direction, similar to the photogate electrode 41. 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 when viewed from the Z direction.

[0090] The distance measurement image sensor 10E shown in Fig. 22 differs from the distance measurement image sensor 10E described above mainly in that an embedded region 36 is formed in the semiconductor layer 20 of each pixel 11a, a well region 31 (hereinafter referred to as "inner well region 31") is formed in the semiconductor layer 20 so as to include the first charge transfer region 24 in each pixel 11a, a well region 31 (hereinafter referred to as "outer well region 31") is formed in the semiconductor layer 20 so as to include each of the multiple second charge transfer regions 26 in each pixel 11a, and a barrier region 34 is formed on the second side of each of the inner well region 31 and the outer well region 31. The configuration of the semiconductor layer 20 of each pixel 11a in the distance measurement image sensor 10E shown in Fig. 22 is as follows.

[0091] 22, a first side portion of the charge distribution region 23 is formed so as to overlap the photogate electrode 41 when viewed from the Z direction, but not overlap the multiple transfer gate electrodes 42, 44 when viewed from the Z direction. The buried region 36 is a p-type region, and is formed on the first side of the charge distribution region 23 in the semiconductor layer 20. That is, the charge distribution region 23 is buried in the semiconductor layer 20 by the buried region 36. The buried region 36 surrounds the inner well region 31 when viewed from the Z direction.

[0092] In the distance measuring image sensors 10A to 10E, 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 may be formed of a material having electrical conductivity and optical transparency (e.g., polysilicon). An electrode (electrode on the first conductivity type side) connected to the first multiplication region 22a side, such as an electrode connected to the semiconductor region 21, is not limited to the counter electrode 50, and may be a through electrode from the first surface 20a of the semiconductor layer 20 to the semiconductor region 21, or an electrode formed on the surface of the semiconductor region 21 to the first surface 20a of the semiconductor layer 20. In any of the distance measurement image sensors 10A to 10E, 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 are provided for one pixel 11a, and the method of applying voltage to the first transfer gate electrode and the second transfer gate electrode, and the method of taking out and discharging charges from the first charge transfer region and the second charge transfer region are not limited to those described above. In any of the distance measurement image sensors 10A to 10E, the p-type and n-type conductivity types may be reversed from those described above. In any of the distance measurement image sensors 10A to 10E, the multiple pixels 11a may be arranged one-dimensionally along the first surface 20a of the semiconductor layer 20. [Explanation of symbols]

[0093] 10A, 10B, 10C, 10D, 10E... distance measuring image sensor, 11a... pixel, 20... semiconductor layer, 20a... first surface, 20b... second surface, 20s... semiconductor substrate, 22... avalanche multiplication region, 22a... first multiplication region, 22b... second multiplication region, 23... charge distribution region, 24, 25... first charge transfer region, 26, 26a, 26b, 27, 27a, 27b... second charge transfer region, 29... trench, 29a... bottom surface, 31... well region, 34... barrier region, 35... sink region, 40... electrode layer, 41... photogate electrode, 42, 43... first transfer gate electrode, 44, 44a, 44b, 45, 45a, 45b... second transfer gate electrode, 60... wiring layer.

Claims

1. a semiconductor layer having a first surface on a first side and a second surface on a second side opposite to the first side, the semiconductor layer constituting a plurality of pixels arranged along the first surface; an electrode layer provided on the first surface and constituting the plurality of pixels; Each of the plurality of pixels is 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 on the first side of the first multiplication region in the semiconductor layer; a charge distributing region of a second conductivity type formed on the first side of the second multiplication region in the semiconductor layer and connected to the second multiplication region; a first charge transfer region of a second conductivity type formed on the first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region; a second charge transfer region of a second conductivity type formed on the first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region; a first transfer gate electrode formed on the electrode layer on the first side of the charge distribution region so as to be located on the first charge transfer region side with respect to a predetermined portion of the charge distribution region when viewed in a thickness direction of the semiconductor layer; a second transfer gate electrode formed in the electrode layer on the first side of the charge distribution region so as to be located on the second charge transfer region side with respect to the predetermined portion of the charge distribution region when viewed in a thickness direction of the semiconductor layer, A distance measurement image sensor, wherein the avalanche multiplication region is connected across the plurality of pixels or reaches a trench formed in the semiconductor layer so as to separate each of the plurality of pixels from each other.

2. the trench is formed in the first surface; The distance measuring image sensor according to claim 1 , wherein a bottom surface of the trench is located on the second side with respect to the avalanche multiplication region.

3. the trench is formed in the first surface; The distance measuring image sensor according to claim 1 , wherein a bottom surface of the trench is located within the avalanche multiplication region.

4. Each of the plurality of pixels is a well region of a first conductivity type that constitutes a readout circuit formed on the first side of the second multiplication region in the semiconductor layer and electrically connected to at least one of the first charge transfer region and the second charge transfer region; 4. The distance measuring image sensor according to claim 1, further comprising: a barrier region of a second conductivity type formed between the second multiplication region and the well region in the semiconductor layer.

5. The distance measuring image sensor according to claim 4 , wherein the barrier region includes the well region when viewed in a thickness direction of the semiconductor layer.

6. Each of the plurality of pixels is 6. The distance measuring image sensor according to claim 4, further comprising a sink region of a second conductivity type formed on the first side of the barrier region in the semiconductor layer and connected to the barrier region.

7. 7. The distance measuring image sensor according to claim 6, wherein the sink region is connected to the second charge transfer region.

8. 8. The distance measuring image sensor according to claim 1, further comprising a wiring layer provided on the first surface so as to cover the electrode layer, the wiring layer being electrically connected to each of the plurality of pixels.

9. A method for manufacturing the distance measuring image sensor according to claim 1, comprising the steps of: a first step of forming the semiconductor layer by forming the avalanche multiplication region, the charge distribution region, the first charge transfer region, and the second charge transfer region in a semiconductor substrate; a second step of forming the electrode layer by forming the first transfer gate electrode and the second transfer gate electrode on the first surface of the semiconductor layer after the first step, In the first step, the avalanche multiplication region is formed in the semiconductor substrate so as to be connected across the plurality of pixels.

10. 10. The method of claim 9, wherein in the first step, the trench is formed in the first surface after at least the avalanche multiplication region is formed in the semiconductor substrate.

11. 11. The method for manufacturing a distance measuring image sensor according to claim 10, further comprising a third step of forming a wiring layer on the first surface so as to cover the electrode layer after the second step, and electrically connecting the wiring layer to each of the plurality of pixels.

Images