Photoelectric conversion device and method for producing same

Abstract

To provide a photoelectric conversion device that can suppress dark current from around a trench.SOLUTION: A photoelectric conversion device includes a semiconductor substrate including a first main surface and a second main surface, a plurality of photoelectric conversion regions containing impurities with a first conductivity type that are formed in the semiconductor substrate, a trench formed between the photoelectric conversion regions, and an impurity region containing impurities with a second conductivity type, which is opposite to the first conductivity type, formed along a side wall of the trench. The impurity region along the side wall of the trench includes a first region whose impurity concentration is first concentration, and a second region whose impurity concentration is second concentration that is lower than the first concentration. The distance between the first main surface and the first region is smaller than the distance between the first main surface and the second region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion device and a manufacturing method thereof. [Background technology]

[0002] Solid-state imaging devices (photoelectric conversion devices) are widely used as imaging devices in two-dimensional image input devices such as digital still cameras and video camcorders. In order to prevent color mixing between adjacent pixels in a solid-state imaging device in which multiple pixels are arranged, a method has been proposed in which element isolation is formed by trenches with a high aspect ratio between the pixels.

[0003] This element isolation trench is usually formed by RIE (Reactive Ion Etching) or the like. During formation, dangling bonds are generated on the trench surface due to damage caused by RIE, and the resulting charges become dark current. In order to suppress this dark current, Patent Document 1 discloses a solid-state imaging device that includes a P-type impurity diffusion region surrounding the outer periphery of the trench. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-88568 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, there are cases where dark current cannot be sufficiently suppressed by the method of Patent Document 1. In the manufacturing process of a solid-state imaging device (photoelectric conversion device), stress is applied to the semiconductor substrate around the trench due to the insulating film filling process and the heat treatment process after the trench is formed, and as a result, dark current cannot be sufficiently suppressed.

[0006] An object of the present invention is to provide a photoelectric conversion device capable of suppressing dark current from around a trench. [Means for solving the problem]

[0007] The first aspect of the present invention is a semiconductor substrate having a first surface and a second surface; A plurality of photoelectric conversion regions including a first conductivity type impurity and disposed on the semiconductor substrate; a trench disposed between the photoelectric conversion regions; an impurity region including impurities of a second conductivity type opposite to the first conductivity type, the impurity region being disposed along the first surface, the sidewalls of the trench, and a bottom of the trench; a metal compound film disposed on a first surface of the semiconductor substrate and on a sidewall of the trench; having the trench opening is disposed in the first surface; the impurity region along the sidewall of the trench includes a first region having an impurity concentration of a first concentration and a second region having an impurity concentration of a second concentration lower than the first concentration, and a distance between the first surface and the first region is smaller than a distance between the first surface and the second region; It is a photoelectric conversion device.

[0008] A second aspect of the present invention is A method for manufacturing a photoelectric conversion device having a trench between photoelectric conversion regions, comprising the steps of: No. 1st page and 2 sides The semiconductor substrate comprising 1st page a first etching step for forming a trench in the a first introduction step of introducing an impurity of a second conductivity type into a sidewall of the trench after the first etching step; a second etching step for increasing the depth of the trench after the first introducing step; a second introduction step of introducing impurities of a second conductivity type into a sidewall of the trench after the second etching step; Including, The impurity concentration in the first introduction step is greater than the impurity concentration in the second introduction step. A method for manufacturing a photoelectric conversion device. Effect of the Invention

[0009] According to the present invention, it is possible to reduce dark current in a photoelectric conversion device. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a solid-state imaging device according to a first embodiment. [Diagram 2] FIG. 4 is a diagram for explaining a boron concentration profile by plasma doping. [Figure 3-1] 3A to 3C are explanatory diagrams of a manufacturing method of the solid-state imaging device according to the first embodiment. [Figure 3-2] 3A to 3C are explanatory diagrams of a manufacturing method of the solid-state imaging device according to the first embodiment. [Figure 4] FIG. 11 is a configuration diagram of an imaging system according to a second embodiment. [Diagram 5] FIG. 11 is a configuration diagram of an imaging system and a moving object according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The solid-state imaging device (photoelectric conversion device) according to the present invention will be described below. Note that, although the following will be described as an example of application to a back-illuminated solid-state imaging device, the application of the present invention is not limited to this. The present embodiment can have the same effect even when applied to a front-illuminated or back-illuminated solid-state imaging device.

[0012] First Embodiment 1 is a schematic cross-sectional view illustrating a solid-state imaging device according to a first embodiment of the present invention. The semiconductor substrate 100 is a single crystal silicon layer having a thickness of, for example, 1 to 10 μm, preferably 2 to 5 μm. The semiconductor substrate 100 has a first main surface and a second main surface, and the first main surface is a light receiving surface.

[0013] The semiconductor substrate 100 is provided with an element isolation region 101, a photoelectric conversion region 102, an impurity region 103, and a floating diffusion section 104. The element isolation region 101 is formed by STI or a selective oxidation method (LOCOS), etc. The photoelectric conversion region 102 is an impurity region into which a first conductive type (N type) impurity (e.g., phosphorus) is introduced, and converts incident light into photocharges (electrons). The impurity region 103 is a region doped with a second conductive type (P type) impurity to make the photoelectric conversion region 102 have a buried structure. The floating diffusion section 104 is a first conductive type (N type) impurity region. The semiconductor substrate 100 is provided with a pixel transistor including a gate electrode 105. An insulating film 106 made of a silicon nitride film and an interlayer insulating film 107 made of a silicon oxide film are formed so as to cover the gate electrode 105, and the floating diffusion section 104 is connected to a wiring layer 109 through a contact plug 108.

[0014] In this embodiment, the first conductivity type is N type and the second conductivity type is P type, but as long as the first conductivity type and the second conductivity type have opposite polarities, the first conductivity type may be P type and the second conductivity type may be N type. In the latter case, the signal charges are holes.

[0015] The semiconductor substrate 100 has a trench 201 extending from the light receiving surface 200 to the other main surface. are provided. The trench 201 is provided between the photoelectric conversion regions 102 in order to reduce color mixing between adjacent pixels. In this embodiment, the width of the trench 201 is substantially constant from the light receiving surface 200 to the bottom of the trench. Second conductive type (P type) impurity regions 301, 302 are provided on the sidewall of the trench 201 and the light receiving surface 200 of the semiconductor substrate 100 by introducing a second conductive type (P type) impurity by a plasma doping method or a solid phase diffusion method. Boron (B) can be used as the second conductive type (P type) impurity. The second conductive type (P type) impurity region 301 is a region of a predetermined size including a portion where the sidewall of the trench 201 and the light receiving surface 200 intersect, and can also be called a trench corner.

[0016] A metal compound film 400 is provided on the sidewall of the trench 201 and on the light receiving surface of the semiconductor substrate 100. The metal compound film 400 is, for example, a laminated film of aluminum oxide (Al2O3) and tantalum oxide (Ta2O5) having a negative fixed charge. A silicon oxide film 401 and a metal film 402 are provided on the metal compound film 400 as a light shielding film. The silicon oxide film 401 is formed inside the trench 201 and fills the trench, but the silicon oxide film 401 may be in the form of a void (air gap). The metal film 402 is, for example, aluminum or tungsten. A passivation film 403, a planarization film 404, a color filter layer 405, and a microlens 406 are provided on the silicon oxide film 401 and the metal film 402.

[0017] Next, second conductivity type (P type) impurity regions 301, 302 formed on the sidewall of trench 201 and on the surface of light-receiving surface 200 of semiconductor substrate 100 will be described in detail with reference to FIGS. 2A and 2B.

[0018] 2A shows a concentration (impurity concentration) profile of boron introduced into a Si substrate by plasma doping or solid-phase diffusion. The concentration profile of boron introduced into a Si substrate by plasma doping or solid-phase diffusion has a characteristic that the boron concentration decreases monotonically from the Si surface toward the inside of the Si. Therefore, the boron concentration profile from the Si surface toward the inside of the Si of second conductivity type (P-type) impurity regions 301, 302 on the sidewall of trench 201 and light-receiving surface 200 of semiconductor substrate 100 has a profile in which the boron concentration decreases monotonically as shown in FIG. 2A. Furthermore, the peak concentration B of boron introduced into a Si substrate by plasma doping or solid-phase diffusion is, for example, 1.0×10 20 ~1.0×10 23 [atms / cm 3 The peak concentration B of boron by plasma doping or solid-phase diffusion can be in the range of, for example, 1.0×10 21 [atms / cm 3 The peak concentration B of the boron concentration by the plasma doping or solid phase diffusion method may be, for example, 1.0×10 22[atms / cm3] or less.

[0019] 2B shows a boron concentration profile A-A' along the depth direction of the sidewall of trench 201. D1 is the depth from light-receiving surface 200 to the bottom of second conductivity type (P-type) impurity region 301, and D2 is the depth from light-receiving surface 200 to the bottom of trench 201.

[0020] As shown in FIG. 2B, the boron concentration profile of the impurity region along the sidewall of the trench 201 has a predetermined concentration at a depth D1, and has a concentration higher than the predetermined concentration up to the depth D1, and a concentration lower than the predetermined concentration in a portion deeper than the depth D1. The predetermined concentration is the boron concentration at the depth D1. The impurity region along the sidewall of the trench 201 includes a first region (301) having a boron concentration C1 between the light-receiving surface 200 and the depth D1, and includes a second region (302) having a boron concentration C2 between the depth D1 and the depth D2. The boron concentration C1 is a value higher than the predetermined concentration, and the boron concentration C2 is a value lower than the predetermined concentration. The boron concentration profile may be monotonically decreased (in a broad sense) from the light-receiving surface 200 in the depth direction of the trench, in addition to that shown in FIG. 2B. However, the boron concentration profile may be partially increased in the depth direction, and the boron concentration C1 in the first region may be increased in the depth direction of the second region. The concentrations in the other regions may be arbitrary so long as they are higher than the boron concentration C2 in the region 302. Note that second conductivity type (P type) impurity region 302 is also formed on light-receiving surface 200, and the boron concentration along light-receiving surface 200 decreases with the distance from the opening of trench 201.

[0021] The depth region A-D1 near the opening of the trench 201 has a shape in which stress is concentrated compared to the trench sidewall, and stress is applied during the insulating film filling process and heat treatment process after the trench is formed, causing defects. Therefore, in order to suppress the dark current, it is desirable to make the boron concentration C1 of the second conductive type impurity region 301 on the trench sidewall in the depth region A-D1 greater than the boron concentration C2 of the second conductive type impurity region 302 on the trench sidewall depth region D1-D2 and the light receiving surface 200. Also, it is desirable to make the boron concentration C2 of the second conductive type impurity region 302 on the trench sidewall depth region D1-D2 smaller than the boron concentration C1 of the second conductive type impurity region 301 so as not to reduce the volume of the first conductive type photoelectric conversion region 102. From the above, it is desirable that the boron concentrations of C1 and C2 have a relationship of C1>C2. It is desirable that the concentration of C1 is more than twice as large as the boron concentration of C2, and more desirably more than 10 times as large. Moreover, it is desirable that depth D1 (predetermined depth) from light receiving surface 200 to the bottom surface of second conductivity type impurity region 301 is shallower than the depth from light receiving surface 200 to the upper surface of first conductivity type photoelectric conversion region 102.

[0022] The second conductive type impurity regions 301 and 302 are formed by plasma doping or solid phase diffusion, so that the boron concentration is 1.0×10 20 ~1.0×10 23 [atms / cm 3 The boron concentration C3 in the depth region D2-A' deeper than the trench bottom D2 is generally in the range of 1.0×10 16 ~1.0×10 20 [atms / cm 3 Although boron may be implanted into the entire depth region of A-A' on the side wall of the trench 201 by ion implantation, as described above, the boron concentration by ion implantation is set to 1.0×10 16 ~1.0×10 20 [atms / cm 3 The peak concentration C1, C2 of boron in the second conductive type impurity region 301 or 302 is in the range of 1.0×10 20 ~1.0×10 23 [atms / cm3 In order to achieve this, it is necessary to control the concentration of boron introduced by plasma doping or solid phase diffusion.

[0023] In this manner, according to this embodiment, it is possible to suppress the dark current around the trench by forming a boron concentration profile on the trench sidewall as shown in FIG. 2B.

[0024] A method for manufacturing the solid-state imaging device according to the present embodiment will be described with reference to FIGS. 3A to 3K.

[0025] FIG. 3A is a diagram showing a structure after the substrate bonding described here has been performed. First, an element isolation region 101 is formed in a semiconductor substrate 100 by an STI method or a LOCOS method, and a first conductive type (N-type) photoelectric conversion region 102 is formed by photolithography and ion implantation. Next, a silicon oxide film formed by a thermal oxidation method and a polycrystalline silicon film formed by a CVD method are deposited, and then the polycrystalline silicon is patterned by photolithography and dry etching to form a gate electrode 105. Next, a second conductive type (P-type) impurity region 103 for making the photoelectric conversion region into a buried structure and an impurity region 104 of the first conductive type (N-type) impurity region of the floating diffusion part are formed. Next, an insulating film 106 made of a silicon nitride film is formed by a CVD method so as to cover the gate electrode 105, and an interlayer insulating film 107, a contact hole 108 filled with a tungsten film, and a wiring layer 109 made of aluminum or copper are formed by a known manufacturing method. Next, the semiconductor substrate is thinned to a thickness suitable for the optical characteristics of the solid-state imaging device using known substrate bonding and substrate thinning techniques. At this time, the thickness of the semiconductor substrate 100 is preferably 2 μm to 4 μm.

[0026] Fig. 3B shows an insulating film forming step. As shown in Fig. 3B, insulating film 110 is formed by plasma CVD on light-receiving surface 200 of semiconductor substrate 100. Insulating film 110 is, for example, a silicon oxide film or a silicon nitride film.

[0027] Fig. 3C shows the first etching step. As shown in Fig. 3C, resist 111 is applied onto insulating film 110, and trenches 201 are formed in light-receiving surface (first main surface) 200 of semiconductor substrate 100 using photolithography and dry etching, and after the trenches are formed, the resist is removed. At this time, it is desirable that the depth of trench 201 is shallower than distance E1 from light-receiving surface (first main surface) 200 to photoelectric conversion region 102.

[0028] 3D shows the first impurity introduction step. As shown in FIG. 3D, boron is introduced into the Si inside the sidewall and bottom surface of the trench 201 by plasma doping or solid phase diffusion to form a second conductivity type (P type) impurity region 301. The boron concentration introduced at this time is 1.0×10 20 ~1.0×10 23 [atms / cm 3 The boron concentration introduced is 1.0×10 21 [atms / cm 3 ] or more, and may be 1.0 × 10 22 [atms / cm 3 After the introduction of boron, it is preferable to activate the introduced boron by heat treatment or laser annealing.

[0029] 3E shows the second etching step. As shown in FIG. 3E, dry etching is performed using the insulating film 110 as a hard mask to deepen the depth of the trench 201. The depth of the trench 201 is preferably deep enough to separate the mixed colors between adjacent pixels. In this embodiment, the depth of the trench 201 is preferably 1 μm to 3 μm.

[0030] 3F shows the insulating film removing step. As shown in FIG. 3F, the insulating film 110 is removed by wet etching or dry etching. In order to reduce damage caused when etching the insulating film 110, it is preferable to remove it by wet etching.

[0031] 3G shows a second impurity introduction step. As shown in FIG. 3G, boron is introduced into the Si on the sidewall and bottom surface of trench 201 by plasma doping or solid phase diffusion to form second conductivity type (P type) impurity region 302. The boron concentration (second concentration) introduced at this time is 1.0×10 20 ~1.0×10 23 [atms / cm 3 2B, the boron concentration must be lower than the boron concentration (first concentration) in the first impurity introduction step. The boron concentration introduced to form second conductivity type (P type) impurity region 302 is lower than the boron concentration introduced to form second conductivity type (P type) impurity region 301. After the boron introduction, it is desirable to activate the introduced boron by heat treatment or laser annealing.

[0032] 3H shows a metal compound film formation process. As shown in FIG. 3H, a metal compound film 400 is formed by the ALD method and the CVD method. The metal compound film is, for example, a laminated film of aluminum oxide (Al2O3) and tantalum oxide (Ta2O5) having a negative fixed charge.

[0033] 3I shows a silicon oxide film forming step. As shown in FIG 3I, a silicon oxide film 401 is formed by the ALD method or the CVD method.

[0034] As shown in FIG. 3J, a metal film 402 is formed by sputtering, and then a passivation film 403 is formed by CVD.

[0035] As shown in FIG. 3K, a planarizing film 404, a color filter layer 405, and a microlens 406 are formed.

[0036] Through the above steps, the above-mentioned solid-state imaging device (photoelectric conversion device) can be manufactured.

[0037] <Embodiment 2> An imaging system according to a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a block diagram showing a schematic configuration of the imaging system according to this embodiment.

[0038] The solid-state imaging device (photoelectric conversion device) described in the first embodiment is applicable to various imaging systems. Applicable imaging systems are not particularly limited, and include, for example, various devices such as digital still cameras, digital camcorders, security cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, observation satellites, and medical cameras. These devices include electronic devices, office equipment, industrial equipment, medical equipment, analytical equipment, and transportation equipment. Camera modules equipped with an optical system such as a lens and a solid-state imaging device (photoelectric conversion device) are also included in imaging systems. The figure illustrates a block diagram of a digital still camera as an example of these.

[0039] 4, the imaging system 2000 includes the imaging device 10, an imaging optical system 2002, a CPU 2010, a lens control unit 2012, an imaging device control unit 2014, an image processing unit 2016, and an aperture shutter control unit 2018. The imaging system 2000 also includes a display unit 2020, an operation switch 2022, and a recording medium 2024.

[0040] The imaging optical system 2002 is an optical system for forming an optical image of a subject, and includes a lens group, an aperture 2004, etc. The aperture 2004 has a function of adjusting the amount of light during shooting by adjusting its opening diameter, and also functions as a shutter for adjusting the exposure time when shooting a still image. The lens group and aperture 2004 are held so that they can move forward and backward along the optical axis, and their linked operation realizes a variable magnification function (zoom function) and a focus adjustment function. The imaging optical system 2002 may be integrated into the imaging system, or may be an imaging lens that can be attached to the imaging system.

[0041] The imaging device 10 is disposed in the image space of the imaging optical system 2002 so that its imaging surface is located therein. The imaging device 10 is the solid-state imaging device (photoelectric conversion device) described in the first embodiment, and is configured to include a CMOS sensor (pixel section) and its peripheral circuit (peripheral circuit region). The imaging device 10 has pixels, each having a plurality of photoelectric conversion sections, arranged two-dimensionally, and a color filter is arranged for each of these pixels, thereby forming a two-dimensional single-plate color sensor. The imaging device 10 photoelectrically converts the subject image formed by the imaging optical system 2002, and outputs the converted image signal and focus detection signal.

[0042] The lens control unit 2012 controls the forward and backward movement of the lens group of the imaging optical system 2002 to perform variable magnification and focus adjustment, and is composed of circuits and a processing device configured to realize this function. The aperture shutter control unit 2018 changes the aperture diameter of the aperture 2004 (variable aperture value) to adjust the amount of light for photographing, and is composed of circuits and a processing device configured to realize this function.

[0043] The CPU 2010 is a control device within the camera that handles various controls of the camera body, and includes an arithmetic unit, ROM, RAM, an A / D converter, a D / A converter, a communication interface circuit, etc. The CPU 2010 controls the operation of each unit within the camera in accordance with a computer program stored in the ROM or the like, and executes a series of photographing operations such as AF, including detection of the focus state of the imaging optical system 2002 (focus detection), imaging, image processing, recording, etc. The CPU 2010 also functions as a signal processing unit.

[0044] The imaging device control unit 2014 controls the operation of the imaging device 10 and also transmits the image data to the imaging device 10. The A / D conversion function is performed on the signal output from the A / D converter 2013 and transmitted to the CPU 2010, and the A / D conversion function is configured by a circuit and a control device configured to realize the function. The imaging device 10 may have the A / D conversion function. The image processing unit 2016 is a processing device that performs image processing such as gamma conversion and color interpolation on the A / D converted signal to generate an image signal, and the image processing unit 2016 is configured by a circuit and a control device configured to realize the function. The display unit 2020 is a display device such as a liquid crystal display (LCD), and displays information on the shooting mode of the camera, a preview image before shooting, a confirmation image after shooting, a focus state at the time of focus detection, and the like. The operation switch 2022 is configured by a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The recording medium 2024 is for recording the shot image, and may be built in the imaging system, or may be a removable one such as a memory card.

[0045] In this manner, by configuring the imaging system 2000 to which the solid-state imaging device according to the first embodiment is applied, a high-performance imaging system can be realized.

[0046] <Embodiment 3> An imaging system and a moving object according to a third embodiment of the present invention will be described with reference to Figures 5A and 5B. Figures 5A and 5B are diagrams showing the configurations of the imaging system and the moving object according to this embodiment.

[0047] FIG. 5A shows an example of an imaging system 2100 related to an in-vehicle camera. The imaging system 2100 includes an imaging device 2110. The imaging device 2110 is any one of the solid-state imaging devices (photoelectric conversion devices) described in the above-mentioned embodiment 1. The imaging system 2100 includes an image processing unit 2112 and a parallax acquisition unit 2114. The image processing unit 2112 is a processing device that performs image processing on a plurality of image data acquired by the imaging device 2110. The parallax acquisition unit 2114 is a processing device that calculates parallax (phase difference of parallax images) from a plurality of image data acquired by the imaging device 2110. The imaging system 2100 also includes a distance acquisition unit 2116, which is a processing device that calculates a distance to an object based on the calculated parallax, and a collision determination unit 2118, which is a processing device that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax acquisition unit 2114 and the distance acquisition unit 2116 are examples of information acquisition means that acquire information such as distance information to an object. That is, the distance information is information related to the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 2118 may determine the possibility of a collision using any of these pieces of distance information. The above-mentioned processing device may be realized by dedicated hardware, or may be realized by general-purpose hardware that performs calculations based on software modules. In addition, the processing device may be realized by a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like, or may be realized by a combination of these.

[0048] The imaging system 2100 is connected to a vehicle information acquisition device 2120, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The imaging system 2100 is also connected to a control ECU 2130, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 2118. That is, the control ECU 2130 is an example of a moving body control means that controls a moving body based on distance information. The imaging system 2100 is also connected to an alarm device 2140 that issues an alarm to the driver based on the judgment result of the collision judgment unit 2118. For example, when the judgment result of the collision judgment unit 2118 indicates that there is a high possibility of a collision, the control ECU 2130 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 2140 warns the user by sounding an alarm, displaying alarm information on a screen of a car navigation system, etc., or vibrating a seat belt or steering wheel.

[0049] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are captured by the imaging system 2100. Fig. 5B shows the imaging system 2100 when capturing an image of the area in front of the vehicle (imaging range 2150). The vehicle information acquisition device 2120 sends an instruction to operate the imaging system 2100 to perform imaging. By using the solid-state imaging device of the above-mentioned embodiment 1 as the imaging device 2110, the imaging system 2100 of this embodiment can further improve the accuracy of distance measurement.

[0050] In the above description, an example of control to avoid collision with other vehicles has been described, but the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to avoid going out of a lane, and the like. Furthermore, the imaging system is not limited to vehicles such as automobiles, but can be applied to moving bodies (transportation equipment) such as ships, aircraft, and industrial robots. The moving devices in moving bodies (transportation equipment) are various driving sources such as engines, motors, wheels, and propellers. In addition, the present invention can be applied not only to moving bodies, but also to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS). [Explanation of symbols]

[0051] 100 semiconductor substrate, 102 photoelectric conversion region 301 302 Second conductivity type (P type) impurity region 200 light receiving surface, 201 trench

Claims

1. a semiconductor substrate having a first surface and a second surface; a plurality of photoelectric conversion regions including a first conductivity type impurity and disposed on the semiconductor substrate; a trench disposed between the photoelectric conversion regions; an impurity region including impurities of a second conductivity type opposite to the first conductivity type, the impurity region being disposed along the first surface, the sidewalls of the trench, and a bottom of the trench; a metal compound film disposed on a first surface of the semiconductor substrate and on a sidewall of the trench; having an opening of the trench is disposed on the first surface, the impurity region along a sidewall of the trench includes a first region having an impurity concentration of a first concentration and a second region having an impurity concentration of a second concentration lower than the first concentration, and a distance between the first surface and the first region is smaller than a distance between the first surface and the second region; Photoelectric conversion device.

2. In a direction along the first surface, a distance between the metal compound film and the first region is greater than a distance between the metal compound film and the second region disposed along a sidewall of the trench. The photoelectric conversion device according to claim 1 .

3. the impurity region along the first surface includes the first region disposed at a first distance from an opening of the trench, and a third region disposed at a second distance from the opening of the trench and having an impurity concentration of a third concentration lower than the first concentration, the second distance being greater than the first distance; The photoelectric conversion device according to claim 1 .

4. a distance between the metal compound film and the first region is greater than a distance between the metal compound film and the third region in a direction along a sidewall of the trench; The photoelectric conversion device according to claim 3 .

5. The impurity region is disposed so as to entirely surround the sidewall and the bottom of the trench. The photoelectric conversion device according to claim 1 .

6. The second conductivity type impurity concentration of the semiconductor substrate is lower than the second concentration. The photoelectric conversion device according to claim 1 .

7. a profile of an impurity concentration of the impurity region along a sidewall of the trench has a concentration higher than a predetermined concentration from the first surface to a predetermined depth, and has a concentration lower than the predetermined concentration in a portion deeper than the predetermined depth; The photoelectric conversion device according to claim 1 .

8. an impurity concentration of the impurity region along a sidewall of the trench monotonically decreases from the first surface in a depth direction of the trench; The photoelectric conversion device according to claim 1 .

9. The first concentration is equal to or greater than twice the second concentration. The photoelectric conversion device according to claim 1 .

10. The impurity concentration of the impurity region along the sidewall of the trench is 1.0×10 ２０ ~1.0 x 10 ２３ [atms / cm ３ ] in the range The photoelectric conversion device according to claim 1 .

11. a portion of the semiconductor substrate is disposed between the first surface and the photoelectric conversion region, an impurity concentration of the first conductivity type of the portion of the semiconductor substrate is lower than an impurity concentration of the first conductivity type of the photoelectric conversion region, and a depth from the first surface to the first region is shallower than a depth from the first surface to the photoelectric conversion region; The photoelectric conversion device according to claim 1 .

12. an impurity concentration of the impurity region along the first surface decreases with distance from the opening of the trench; The photoelectric conversion device according to claim 1 .

13. The impurity of the impurity region is boron. The photoelectric conversion device according to claim 1 .

14. The metal compound film is a laminated film of aluminum oxide and tantalum oxide. The photoelectric conversion device according to claim 1 .

15. The second area is located between the first surface and a third surface which is a virtual surface located equidistant from the first surface and the second surface. The photoelectric conversion device according to claim 1 .

16. The photoelectric conversion device according to any one of claims 1 to 15, a signal processing unit that processes a signal output from the photoelectric conversion device; An apparatus comprising:

17. The photoelectric conversion device according to any one of claims 1 to 15, A mobile device; a processing device that acquires information from a signal output from the photoelectric conversion device; a control device that controls the moving device based on the information; An apparatus comprising:

18. A method for manufacturing a photoelectric conversion device having a trench between photoelectric conversion regions, comprising the steps of: a first etching step of forming a trench in a first surface of a semiconductor substrate having a first surface and a second surface; a first introduction step of introducing an impurity of a second conductivity type into a sidewall of the trench after the first etching step; a second etching step for increasing the depth of the trench after the first introducing step; a second introduction step of introducing impurities of a second conductivity type into a sidewall of the trench after the second etching step; Including, The impurity concentration in the first introduction step is higher than the impurity concentration in the second introduction step. A method for manufacturing a photoelectric conversion device.

19. The impurity concentration in the first introduction step is at least twice as high as the impurity concentration in the second introduction step. A method for producing a photoelectric conversion device according to claim 18.

20. The impurity concentration in the first introduction step and the impurity concentration in the second introduction step are 1.0×10 ２０ ~1.0 x 10 ２３ [atms / cm ３ ] in the range A method for producing a photoelectric conversion device according to claim 18 or 19.

21. In the first introduction step and the second introduction step, the impurity is introduced by plasma doping or a solid phase diffusion method. A method for producing the photoelectric conversion device according to any one of claims 18 to 20.

22. The method includes a step of performing a heat treatment after at least one of the first introduction step and the second introduction step. A method for producing the photoelectric conversion device according to any one of claims 18 to 21.

23. The heat treatment is performed by laser annealing. A method for producing the photoelectric conversion device according to claim 22.

24. The method further includes, before the first etching step, forming an insulating film on the first surface of the semiconductor substrate; In the second etching step, etching is performed to deepen the depth of the trench using the insulating film obtained after the first etching step as a hard mask. A method for producing the photoelectric conversion device according to any one of claims 18 to 23.

25. The method further includes a step of removing the insulating film by wet etching after the second etching step. A method for producing the photoelectric conversion device according to claim 24.

26. a depth of the trench formed in the first etching step is shallower than a depth from the first surface to the photoelectric conversion region; A method for producing the photoelectric conversion device according to any one of claims 18 to 25.

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