Backside illumiated image sensor and method of manufacturing the same

Abstract

The present invention relates to a back-illuminated image sensor (1) and a method for manufacturing, and more specifically, to a back-illuminated image sensor (1) and a method for manufacturing, wherein the path of incident light is extended beyond the thickness of the substrate (101) by forming a scattering film within the substrate (101) to improve light sensitivity, and at the same time, the depth of the scattering film is formed differently for each unit pixel area (P1) to further improve light sensitivity for a specific wavelength of color light selected through a color filter section.

Description

Technology Field

[0001] The present invention relates to a back-illuminated image sensor (1) and a method for manufacturing, and more specifically, to a back-illuminated image sensor (1) and a method for manufacturing, wherein the path of incident light is extended beyond the thickness of the substrate (101) by forming a scattering film within the substrate (101) to improve light sensitivity, and at the same time, the depth of the scattering film is formed differently for each unit pixel area (P1) to further improve light sensitivity for a specific wavelength of color light selected through a color filter section. Background Technology

[0003] An image sensor is a component that generates images in devices such as mobile phone cameras, and can be classified into CCD (Charge Coupled Device) image sensors and CMOS (Complementary Metal Oxide Semiconductor) image sensors depending on the manufacturing process and application method. Among these, CMOS image sensors have become widely established in general semiconductor chip manufacturing processes due to their superior integration competitiveness, cost-effectiveness, and ease of connection with peripheral chips.

[0004] Conventional CMOS image sensors include a wiring section, a color filter section, and a lens section stacked sequentially on the front surface of a silicon wafer. However, in image sensors with such a structure, the amount of incident light received by the light-receiving element may be reduced due to the metal wiring within the wiring section. Accordingly, a so-called Backside Illuminated CMOS Image Sensor (BIS) is being developed, having a structure in which the wiring section is placed on the front surface of a substrate and the color filter section and the lens section are placed on the back surface of the substrate. Such backside illuminated CMOS image sensors are being applied in iris scanners, Time-Of-Flight (Tof) sensors, etc., and the importance of improving light sensitivity in the near-infrared range is emerging. However, there is a problem in that the light sensitivity of existing image sensors in the near-infrared range is insufficient for application in the above fields.

[0006] Accordingly, the inventor of the present invention intends to present a novel back-illuminated image sensor having an improved structure that enables improved light sensitivity in the near-infrared range, and details will be described below. Prior art literature

[0008] Korean Registered Patent No. 10-0660549 'Image sensor and method of manufacturing the same' The problem to be solved

[0009] It was devised to solve the problems of the prior art described above,

[0011] The purpose of the present invention is to provide a back-illuminated image sensor and a method for manufacturing such that light sensitivity in the near-infrared range is improved by forming a scattering film within the substrate and in each individual unit pixel area, thereby extending the path of incident light beyond the thickness of the substrate.

[0012] In addition, the present invention aims to provide a back-illuminated image sensor and a manufacturing method that improves light sensitivity for a specific wavelength of color light selected through a color filter unit by extending the depths of the first to third structures for each unit pixel area incident with red light, blue light, and green light to different positions. means of solving the problem

[0014] The present invention may be implemented by an embodiment having the following configuration to achieve the aforementioned objectives.

[0016] According to one embodiment of the present invention, a back-illuminated image sensor according to the present invention comprises: a substrate having a front surface and a back surface; a light-receiving element on the front side of the substrate; a DTI area within the substrate and on the boundary side of an individual unit pixel area; a scattering film within the substrate and on an individual unit pixel area; a color filter portion on the back surface of the substrate; and a lens portion on the color filter portion; wherein the scattering film has different upper and lower thicknesses for each individual unit pixel area.

[0017] According to another embodiment of the present invention, the scattering film in the back-illuminated image sensor according to the present invention is characterized by extending downward from the back surface of the substrate or from a side adjacent to the back surface to the front surface of the substrate.

[0018] According to another embodiment of the present invention, the scattering film in the back-illuminated image sensor according to the present invention is characterized by being located on the central side of an individual unit pixel area.

[0019] According to another embodiment of the present invention, the scattering film in the back-illuminated image sensor according to the present invention is characterized by having a left-right width size smaller than the separation distance of adjacent DTI regions.

[0020] According to another embodiment of the present invention, the back-illuminated image sensor according to the present invention further comprises a wiring area on the front surface of the substrate; wherein the wiring area comprises a metal wiring layer having a multilayer wiring structure and a lower insulating layer having a multilayer insulating film composition covering the metal wiring layer.

[0021] According to another embodiment of the present invention, a back-illuminated image sensor according to the present invention comprises: a substrate having a front surface and a back surface; a light receiving element on the front side of the substrate; a DTI area within the substrate and on the boundary side of an individual unit pixel area; a scattering film extending from the back surface of the substrate to the front side in an individual unit pixel area; a color filter portion on the back surface of the substrate; a lens portion on the color filter portion; and a wiring layer on the front surface of the substrate; wherein the scattering film comprises a first structure in a unit pixel area where red light is incident; a second structure in a unit pixel area where green light is incident; and a third structure in a unit pixel area where blue light is incident.

[0022] According to another embodiment of the present invention, the first structure in the back-illuminated image sensor according to the present invention is characterized in that its bottom portion is located at a position adjacent to the front surface of the substrate relative to the bottom portions of the second structure and the third structure, and the second structure is located at a position far from the front surface of the substrate relative to the bottom portion of the third structure.

[0023] According to another embodiment of the present invention, the first structure, the second structure, and the third structure in the back-illuminated image sensor according to the present invention are formed by etching the back surface of the substrate through a separate etching process.

[0024] According to another embodiment of the present invention, the DTI region in the back-illuminated image sensor according to the present invention is characterized by having a vertical width size that is larger than that of the scattering film.

[0025] According to another embodiment of the present invention, the scattering film in the back-illuminated image sensor according to the present invention is characterized by comprising one or more films selected from a silicon oxide film, a metal film, and a polysilicon film.

[0026] According to one embodiment of the present invention, a method for manufacturing a back-illuminated image sensor according to the present invention comprises the steps of: forming a DTI region within a substrate and on the boundary side of an individual unit pixel region; forming a scattering film for each individual unit pixel region within the substrate; forming a color filter portion on the substrate; and forming a lens portion on the color filter portion; wherein the scattering film has a left-right width smaller than the distance between adjacent DTI regions.

[0027] According to another embodiment of the present invention, the scattering film in the method for manufacturing a back-illuminated image sensor according to the present invention comprises: a first structure in a unit pixel area where red light is incident; a second structure in a unit pixel area where green light is incident; and a third structure in a unit pixel area where blue light is incident; wherein the first structure, the second structure, and the third structure are formed to extend to different depths within the substrate.

[0028] According to another embodiment of the present invention, the scattering film formation step in the method for manufacturing a back-illuminated image sensor according to the present invention comprises: a step of etching the back surface of the substrate to form a scattering film region; and a step of gap-filling one or more of an oxide film, a polysilicon film, and a metal film within the scattering film region to form a first structure, a second structure, and a third structure; wherein the scattering film regions of the first to third structures are formed through a separate etching process.

[0029] According to another embodiment of the present invention, in the method for manufacturing a back-illuminated image sensor according to the present invention, the first structure is formed deeper within the substrate than the second structure and the third structure, and the third structure is formed shallower within the substrate than the second structure.

[0030] According to another embodiment of the present invention, a method for manufacturing a back-illuminated image sensor according to the present invention comprises: a step of forming a DTI region within a substrate and on the boundary side of an individual unit pixel region; a step of forming a first structure, a second structure, and a third structure for each individual unit pixel region within the substrate; a step of forming a color filter portion on the substrate; and a step of forming a lens portion on the color filter portion; wherein the step of forming the first to third structures comprises: a step of forming a first structure region, a second structure region, and a third structure region through three etching processes; and a step of gap-filling the first to third structure regions.

[0031] According to another embodiment of the present invention, the step of forming a DTI region in the method for manufacturing a back-illuminated image sensor according to the present invention is characterized by comprising: a step of etching the back surface of the substrate to form a deep trench; and a step of gap-filling an insulating film within the deep trench.

[0032] According to another embodiment of the present invention, the step of forming a DTI region in the method for manufacturing a back-illuminated image sensor according to the present invention further comprises the step of removing the insulating film deposited on the back surface of the substrate after the insulating film gap fill.

[0033] According to another embodiment of the present invention, a method for manufacturing a back-illuminated image sensor according to the present invention further comprises the step of forming a light-receiving element on the front side of the substrate; and the first to third structures are spaced apart from each other by different distances from the light-extinguishing element. Effects of the invention

[0035] The present invention has the following effects based on the configuration described above.

[0037] The present invention has the effect of improving light sensitivity in the near-infrared range by forming a scattering film within the substrate and in each individual unit pixel area, thereby extending the path of incident light beyond the thickness of the substrate.

[0038] In addition, the present invention has the effect of improving light sensitivity for a specific wavelength of color light selected through a color filter unit by extending the depths of the first to third structures for each unit pixel area incident with red light, blue light, and green light to different positions.

[0040] Meanwhile, it should be added that even if an effect is not explicitly mentioned here, the effects described in the following specification and the provisional effects expected by the technical features of the present invention are treated as described in the specification of the present invention. Brief explanation of the drawing

[0042] FIG. 1 is a plan view of a back-illuminated image sensor according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of a back-illuminated image sensor according to FIG. 1; FIGS. 3 to 12 are cross-sectional views illustrating a method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention. Specific details for implementing the invention

[0043] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be interpreted as being limited to the embodiments below, but should be interpreted based on the matters described in the claims. Furthermore, these embodiments are provided merely for reference to more completely explain the present invention to those with average knowledge in the art.

[0044] As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Additionally, as used herein, “comprise” and / or “comprising” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0045] In the following description, it should be noted that when one component (or layer) is described as being placed on another component (or layer), the component may be placed directly on the other component, or other component(s) or layer(s) may be located between the components. Furthermore, when one component is described as being placed directly on or above another component, no other component(s) are located between the components. Additionally, being located on the 'top', 'upper', 'lower', 'upper side', 'lower side', or 'one side' or 'side' of a component refers to a relative positional relationship.

[0046] Meanwhile, if an embodiment can be implemented differently, the functions or operations specified within a particular block may occur differently from the order described in the flowchart. For example, the functions or operations of two consecutive blocks may be performed substantially simultaneously or in reverse order.

[0047] The back-illuminated image sensor (1) according to the present invention includes a pixel area (P). The pixel area (P) is an area that absorbs light incident from the outside toward the back side of the substrate (101), and may include a plurality of unit pixel areas (P1).

[0048] In addition, the back-illuminated image sensor (1) according to the present invention may be, for example, a CMOS image sensor.

[0050] FIG. 1 is a plan view of a back-illuminated image sensor according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of a back-illuminated image sensor according to FIG. 1.

[0052] Hereinafter, a back-illuminated image sensor (1) according to one embodiment of the present invention will be described in detail with reference to the attached drawings.

[0054] Referring to FIGS. 1 and 2, the present invention relates to a back-illuminated image sensor (1), and more specifically, to a back-illuminated image sensor (1) that improves light sensitivity by extending the path of incident light beyond the thickness of the substrate (101) by forming a scattering film within the substrate (101), and at the same time, improves light sensitivity for a specific wavelength of color light selected through a color filter unit by forming the depth of the scattering film differently for each unit pixel area (P1).

[0055] The above-described back-illuminated image sensor (1) may include a substrate (101). The substrate (101) may be made of, for example, an epitaxial substrate or a bulk substrate. The substrate (101) has a front surface (1011) and a back surface (1013). Additionally, one or more light-receiving elements (110) and one or more transistors (not shown) electrically connected to the light-receiving elements (110) may be located in the pixel area (P) of the substrate (101). The light-receiving elements (110) may be formed on the front side of the substrate (101) or on a side adjacent to the front surface.

[0056] Additionally, the light receiving element (110) is configured to generate charge in response to incident light and may be composed of any known or known configuration, such as a photodiode, photogate, or phototransistor, and there are no separate limitations thereon.

[0057] Additionally, a wiring area (120) may be formed on the front surface of the substrate (101). This wiring area (120) may include a metal wiring layer (121) and an insulating layer (123).

[0058] The metal wiring layer (121) is preferably formed of, for example, a single metal or an alloy film mixed with two or more metals, and is preferably made of, for example, an aluminum (Al) film.

[0059] The lower insulating layer (123) is configured to be formed of an insulating material, such as a silicon oxide film, for example, and is preferably formed by repeatedly stacking the metal wiring layer (121) with each other to form the metal wiring layer (121), thereby forming a multilayer wiring of the metal wiring layer (121). One layer of the multilayer wiring layer (121) can be connected to another layer of the metal wiring layer (121) through a contact plug. The contact plug can be formed within the corresponding lower insulating layer (123) through a damascene process, and can be formed of one or more selected from a conductive material, such as a polycrystalline silicon film doped with impurity ions, a metal, or an alloy film mixed with at least two types of metals, in order to electrically connect the metal wiring layers (121) stacked vertically.

[0060] The lower insulating layer (123) may be formed from an oxide film selected from BPSG, PSG, BSG, USG, TEOS, or HDP film, or from a laminated film in which two or more layers thereof are stacked. Additionally, the lower insulating layer (123) may be flattened through a CMP process after deposition.

[0061] Additionally, a DTI region (130) may be formed as an isolation film to prevent cross-talk between adjacent unit pixel regions (P1) within the substrate (101) and at the boundary side of the individual unit pixel region (P1). The DTI region (130) is formed to extend from the back side of the substrate (101) toward the front side, and it is preferable that it extends to the side adjacent to the front side.

[0062] These DTI regions (130) can be formed by gap-filling an oxide film selected from BPSG, PSG, BSG, USG, TEOS, or HDP films, just like the lower insulating layer (123), but are not limited thereto. Additionally, the DTI regions (130) can be formed by a single gap-fill process or two or more gap-fill processes using an insulating material, but are not limited thereto. The DTI regions (130) can allow incident light scattered by the scattering film (140), which will be described later, to be reflected back into the unit pixel region (P1) and incident on the light receiving element (110).

[0063] The scattering film (140) is configured to be formed within the substrate (101) for each unit pixel area (P1), and is configured to scatter incident light that has passed through the color filter section (150) within the substrate (101). The scattering film (140) may be composed of, for example, a silicon oxide film, an alloy film of a single metal or a mixture of two or more metals, or a polysilicon film, and there are no separate limitations. As an example, the scattering film (140) may include the same material as the gap fill material of the DTI area (130). In addition, the scattering film (140) for each unit pixel area (P1) is formed to extend downward from the back surface of the substrate (101) or from a side adjacent to the back surface to the front surface, extending to a different depth for each unit pixel area (P1). That is, it is characterized by forming different optical path distances by making the formation depth different for each channel of individual color light.

[0064] For example, the first structure (141) in the unit pixel area (P1a) where the longest wavelength red light is incident within the substrate (101) may be formed relatively deeper than the second structure (143) in the unit pixel area (P1b) where the green light is incident. Additionally, it is preferable that the third structure (145) in the unit pixel area (P1c) where the shortest wavelength blue light is incident has the shallowest depth. Unlike the example described above, the second structure (143) or the third structure (145) may be formed deepest, or the first structure (141) or the second structure (143) may be formed shallowest, and there are no limitations thereto. Additionally, it is preferable that the scattering film (140) be formed on the central side of each unit pixel area (P1). In addition, it is preferable that the scattering film (140) be formed with a width in the left and right directions smaller than the horizontal separation distance between adjacent DTI regions (130) so that scattering and reflection of incident light are possible.

[0065] A color filter section (150) may be formed on the back surface of the substrate (101). In the color filter section (150), light incident through the lens section (160) to be described later is selected only for the necessary colored light (e.g., red light, green light, blue light) by the corresponding color filter (Red, Green, Blue) of the color filter section (150), and the selected colored light is incident on the light receiving element (110) of the corresponding unit pixel area (P1).

[0066] Additionally, a lens portion (160) is formed on the color filter portion (150), and the lens portion (160) is configured to have a plurality of micro lenses formed on the color filter portion (150) so that light incident from the back side of the substrate (101) is focused to a light receiving element (110) within a corresponding unit pixel area (P1).

[0068] FIGS. 3 to 12 are cross-sectional views illustrating a method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention.

[0070] Hereinafter, a method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0072] First, referring to FIG. 3, a light receiving element (110) is formed on the front side (1011) of a substrate (101) having a front side (1011) and a back side (1013), and the light receiving element (110) may be, for example, a photodiode (PD). Then, a wiring area (120) may be formed on the front side of the substrate (101), and a detailed description thereof will be omitted.

[0073] Then, a DTI region (130) is formed on the substrate (101). The DTI region (130) may be formed at a predetermined depth on the boundary side between adjacent unit pixel regions (P1). An exemplary process for forming the DTI region (130) is described. First, referring to FIG. 4, a photoresist film (PR) is patterned on the back surface (1013) of the substrate (101) so that the side corresponding to the side where the DTI region (130) is to be formed is open. Then, the open side is etched to form a deep trench (131).

[0074] Afterward, referring to FIG. 5, the insulating film (133) within the deep trench (131) is gap-filled. During this gap-filling process, since the insulating film (133) is deposited on the back surface (1013) of the substrate (101), a process to remove it is performed, and referring to FIG. 6, for example, a CMP process can be performed. As described above, the process of forming the DTI region (130) can be performed in a single gap-filling process or through two or more gap-filling processes. Accordingly, the DTI region (130) can be formed as an isolation film on the boundary side of the unit pixel region (P1).

[0075] After that, a scattering film (140) is formed. This is explained in detail. Referring to FIGS. 7 to 9, a photoresist film (PR) is patterned on the back surface (1013) of the substrate (101), and then the open side is etched to form a scattering film formation region (147). It is preferable that the scattering film formation region (147) be formed on the central side of each unit pixel region (P1). After that, referring to FIG. 10, an insulating film or a polysilicon film, etc., is gap-filled within the scattering film formation region (147) to form a scattering film (140).

[0076] As described above, the first to third structures (141, 143, 145) may be formed with different depths. Therefore, it is preferable to perform a trench formation process separately for forming individual structures (141, 143, 145).

[0077] For example, to form a first structure (141), a photoresist film (not shown) is patterned on the back surface (1013) of the substrate (101), and then a first structure region (147a) is formed (see FIG. 7), and then a second structure region (147b) is formed (see FIG. 8) and then a third structure region (147c) is formed (see FIG. 9). Then, each structure region (147a, 147b, 147c) is gap-filled to form the first to third structures (141, 143, 145) (see FIG. 10). Although it was explained above that the first structure (141) is formed first, this is optional, and the order of forming each structure area (147a, 147b, 147c) may vary depending on the process and is not subject to any separate restrictions.

[0078] After that, referring to FIG. 11, a color filter portion (150) can be formed on the back surface (1013) of the substrate (101), and referring to FIG. 12, a lens portion (160) can be formed on the color filter portion (150). Additionally, a flattening layer (not shown) may be additionally formed after the color filter portion (150) is formed and before the lens portion (160) is formed, or a separate process for removing surface residue may be performed after the lens portion (160) is formed.

[0080] The above detailed description is illustrative of the present invention. Furthermore, the foregoing describes preferred embodiments of the present invention, and the present invention may be used in various other combinations, modifications, and environments. That is, modifications or alterations are possible within the scope of the concept of the invention disclosed herein, the scope equivalent to the written disclosure, and / or the scope of the art or knowledge. The foregoing embodiments describe the best state for implementing the technical concept of the present invention, and various modifications required for specific fields of application and uses of the present invention are also possible. Accordingly, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Explanation of the symbols

[0082] 1 : Back-illuminated image sensor 101 : Substrate 1011: Front of the board 1013: Back of the board 110 : Photodetector 120 : Wiring area 121: Metal wiring layer 123: Lower insulation layer 130: DTI Area 131 : Deep trench 133 : Insulating film 140 : Spawning membrane 141 : 1st structure 143 : 2nd structure 145 : 3rd structure 147 : Scattering film formation area 147a : 1st structure area 147b : 2nd structure area 147c : Third structure area 150 : Color filter section 160 : Lens part P: Pixel area P1, P1a, P1b, P1c: Unit pixel area PR: Photoresist film

Claims

Claim 1 A back-illuminated image sensor comprising: a substrate having a front surface and a back surface; a light-receiving element on the front side of the substrate; a DTI area on the boundary side of an individual unit pixel area within the substrate; a scattering film on the substrate and on an individual unit pixel area; a color filter portion on the back surface of the substrate; and a lens portion on the color filter portion; wherein the scattering film comprises: a first structure in a unit pixel area where red light is incident; a second structure in a unit pixel area where green light is incident; and a third structure in a unit pixel area where blue light is incident; wherein the bottom portion of the first structure is located at a position deeper from the back surface of the substrate relative to the bottom portion of the second structure, and the bottom portion of the second structure is located at a position deeper from the back surface of the substrate relative to the bottom portion of the third structure. Claim 2 A back-illuminated image sensor according to claim 1, wherein the scattering film extends downward from the back surface of the substrate or from a side adjacent to the back surface to the front surface of the substrate. Claim 3 A back-illuminated image sensor according to claim 1, characterized in that the scattering film is located on the central side of an individual unit pixel area. Claim 4 A back-illuminated image sensor according to claim 1, characterized in that the scattering film has a left-right width smaller than the separation distance of adjacent DTI regions. Claim 5 A back-illuminated image sensor according to claim 1, further comprising a wiring area on the front surface of the substrate; wherein the wiring area comprises a metal wiring layer having a multilayer wiring structure and a lower insulating layer having a multilayer insulating film composition covering the metal wiring layer. Claim 6 delete Claim 7 A back-illuminated image sensor according to claim 1, wherein the bottom portion of the first structure is located at a position adjacent to the front surface of the substrate relative to the bottom portions of the second structure and the third structure, and the bottom portion of the second structure is located at a position far from the front surface of the substrate relative to the bottom portion of the third structure. Claim 8 A back-illuminated image sensor according to claim 1, characterized in that the first structure, the second structure, and the third structure are formed by etching the back surface of the substrate through a separate etching process. Claim 9 A back-illuminated image sensor according to claim 1, characterized in that the DTI area has a vertical width size larger than the scattering film. Claim 10 A back-illuminated image sensor according to claim 1, characterized in that the scattering film comprises one or more films selected from a silicon oxide film, a metal film, and a polysilicon film. Claim 11 A method for manufacturing a back-illuminated image sensor according to claim 1, comprising: a step of forming a DTI region within a substrate and on the boundary side of an individual unit pixel region; a step of forming a scattering film for each individual unit pixel region within the substrate; a step of forming a color filter portion on the substrate; and a step of forming a lens portion on the color filter portion; wherein the scattering film has a left-right width size smaller than the distance between adjacent DTI regions. Claim 12 A method for manufacturing a back-illuminated image sensor according to claim 11, wherein the scattering film comprises a metal film. Claim 13 A method for manufacturing a back-illuminated image sensor according to claim 11, wherein the scattering film forming step comprises: a step of etching the back surface of the substrate to form a scattering film region; and a step of gap-filling one or more of an oxide film, a polysilicon film, and a metal film within the scattering film region to form a first structure, a second structure, and a third structure; wherein the scattering film regions of the first to third structures are formed through a separate etching process. Claim 14 A method for manufacturing a back-illuminated image sensor according to claim 11, wherein the scattering film comprises a polysilicon film. Claim 15 A method for manufacturing a back-illuminated image sensor according to claim 13, wherein the scattering film forming step comprises forming a first structure, a second structure, and a third structure for each individual unit pixel area within the substrate; and the first to third structure forming step comprises forming a first structure area, a second structure area, and a third structure area through three etching processes; and gap-filling the first to third structure areas. Claim 16 A method for manufacturing a back-illuminated image sensor according to claim 11, wherein the step of forming a DTI region comprises: a step of etching the back surface of the substrate to form a deep trench; and a step of gap-filling an insulating film within the deep trench. Claim 17 A method for manufacturing a back-illuminated image sensor according to claim 16, wherein the DTI region forming step further comprises the step of removing the insulating film deposited on the back surface of the substrate after the insulating film gap fill. Claim 18 A method for manufacturing a back-illuminated image sensor according to claim 15, further comprising the step of forming a light-receiving element on the front side of the substrate; wherein the first to third structures are spaced apart from each other by different distances from the light-receiving element.

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