Backside illuminated image sensor and manufacturing method thereof

Abstract

The present invention relates to a backside-illuminated image sensor and a method for manufacturing the same, in which a partition wall is provided or formed in a peripheral region of a semiconductor substrate, and a photosensitive region and a circuit element in the peripheral region are separated by the partition wall. The isolation mode of the isolation wall is physical isolation, leakage current generated by the circuit element can be effectively isolated outside the photosensitive area, and the problem that the edge of the photosensitive area of the backside illuminated image sensor emits light can be solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a back-illuminated image sensor and a method for manufacturing the back-illuminated image sensor. Background Art

[0002] CMOS image sensor technology has become the mainstream sensor type for cameras due to its high sensitivity, wide dynamic range, high resolution, low power consumption, flexible image capture capabilities and excellent system integration capabilities. Among them, the back-illuminated (BSI) CMOS image sensor (hereinafter referred to as back-illuminated image sensor) can obtain more radiation energy per pixel in the same unit time than the front-illuminated (FSI) structure, which significantly improves the image quality.

[0003] In a back-illuminated image sensor, the area used to set photosensitive pixels is called a photosensitive area. The photosensitive pixels are configured to sense incident light projected from the back side of the substrate toward the substrate. In addition to the photosensitive area, the back-illuminated image sensor generally includes a peripheral area located outside the photosensitive area. Digital devices and reference pixels can be set in the peripheral area. The digital devices are used to perform the circuit functions of the back-illuminated image sensor, and the reference pixels are used to establish a light intensity benchmark for the back-illuminated image sensor. The digital devices and reference pixels need to remain optically dark, so a light-blocking layer is usually laid on the back side of the substrate in the area where the digital devices and reference pixels are set to block incident light.

[0004] like Figure 1 As shown, during a dark field test (no incident light is projected to the photosensitive area and the peripheral area), the photosensitive area 10 of the back-illuminated image sensor will have a brightness difference between the edge and the middle area, which is hereinafter referred to as edge luminescence. Figure 1 As shown in the edge luminous area A, the reason is that the photosensitive area 10 is affected by the leakage current generated in the peripheral area. This edge luminous phenomenon has an adverse effect on the performance of the back-illuminated image sensor, resulting in poor image quality when used for taking photos or videos. The current method to solve the edge luminous problem is mainly to reduce the leakage current in the peripheral area by adjusting the process parameters, but this method has high process cost and difficulty, and it is difficult to significantly reduce the risk of leakage current entering the photosensitive area. When the back-illuminated image sensor is working, it may still be affected by the edge luminous problem. Summary of the invention

[0005] In order to effectively solve the edge luminescence problem of a back-illuminated image sensor, the present invention provides a back-illuminated image sensor and a method for manufacturing the back-illuminated image sensor.

[0006] In one aspect, the present invention provides a back-illuminated image sensor, comprising:

[0007] A semiconductor substrate having a front side and a back side opposite to the front side, wherein the semiconductor substrate is provided with a photosensitive region and a peripheral region located outside the photosensitive region, wherein the semiconductor substrate is provided with a plurality of photosensitive pixels in the photosensitive region and a circuit element in the peripheral region;

[0008] a light blocking structure disposed above the back surface of the semiconductor substrate and disposed between the plurality of photosensitive pixels and at least part of the peripheral area along a vertical direction of the back surface of the semiconductor substrate; and

[0009] An isolation wall passes through the semiconductor substrate along the thickness direction of the semiconductor substrate in the peripheral area, and the circuit element and the photosensitive area are respectively located on both sides of the isolation wall.

[0010] Optionally, the back-illuminated image sensor further includes:

[0011] A back dielectric layer fills the opening defined by the light-blocking structure and buries the light-blocking structure, wherein the isolation wall extends from the inside of the semiconductor substrate to the top of the back side of the semiconductor substrate and penetrates the back dielectric layer along the thickness direction of the back dielectric layer.

[0012] Optionally, the back-illuminated image sensor further includes:

[0013] an interlayer dielectric layer, disposed above the front surface of the semiconductor substrate, wherein the interlayer dielectric layer is provided with a conductive plug electrically connected to the photosensitive pixel and the circuit element; and

[0014] A metal interconnection layer is arranged on a surface of the interlayer dielectric layer away from the semiconductor substrate and is electrically connected to the conductive plug, wherein the isolation wall extends from the inside of the semiconductor substrate to above the front surface of the semiconductor substrate and penetrates at least a portion of the thickness of the interlayer dielectric layer along the thickness direction of the interlayer dielectric layer, but does not penetrate the metal interconnection layer.

[0015] Optionally, a shallow trench isolation structure surrounding the photosensitive area is embedded on the front surface of the semiconductor substrate, the shallow trench isolation structure surrounds the isolation wall, and the circuit element is located on a side of the shallow trench isolation structure away from the isolation wall.

[0016] Optionally, a minimum distance between the isolation wall and the shallow trench isolation structure is 0.4 μm to 1.2 μm.

[0017] Optionally, the isolation wall extends a set distance along a boundary of the photosensitive area within the peripheral area.

[0018] Optionally, the isolation wall is only arranged along a portion of the boundary of the photosensitive area; or, the isolation wall is arranged around the entire boundary of the photosensitive area to form a closed ring.

[0019] Optionally, the isolation wall has a wall thickness of 0.5 μm to 1.5 μm and a height of 2 μm to 4 μm.

[0020] In one aspect, the present invention provides a method for manufacturing a back-illuminated image sensor, comprising the following steps:

[0021] A semiconductor substrate is provided, wherein the semiconductor substrate has a front side and a back side opposite to the front side, the semiconductor substrate has a photosensitive region and a peripheral region located outside the photosensitive region, the semiconductor substrate has a plurality of photosensitive pixels formed in the photosensitive region, a circuit element formed in the peripheral region, a light-blocking structure formed on one side of the back side of the semiconductor substrate, and the light-blocking structure is arranged between the plurality of photosensitive pixels and at least part of the peripheral region along a vertical direction of the back side of the semiconductor substrate; and

[0022] An isolation wall is embedded in the semiconductor substrate. The isolation wall passes through the semiconductor substrate along the thickness direction of the semiconductor substrate. The circuit element and the photosensitive area are respectively located on both sides of the isolation wall.

[0023] Optionally, before embedding the isolation wall, the semiconductor substrate further includes an interlayer dielectric layer and a metal interconnect layer sequentially formed on the front side of the semiconductor substrate, and a back side dielectric layer formed on the back side of the semiconductor substrate; the method for embedding the isolation wall in the semiconductor substrate includes:

[0024] Etching the back dielectric layer, the semiconductor substrate and the interlayer dielectric layer from the back side of the semiconductor substrate to form a groove, wherein the groove penetrates the back dielectric layer, the semiconductor substrate and at least a portion of the interlayer dielectric layer; and

[0025] An isolation medium is filled in the groove to form the isolation wall.

[0026] In the back-illuminated image sensor and the manufacturing method of the back-illuminated image sensor provided by the present invention, an isolation wall is set or formed in the peripheral area of ​​the semiconductor substrate, and the isolation wall is used to separate the photosensitive area from the circuit elements in the peripheral area. The isolation method of the isolation wall is physical isolation, which can effectively isolate the leakage current generated by the circuit elements outside the photosensitive area, which helps to solve the problem of edge luminescence of the photosensitive area of ​​the back-illuminated image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the luminescence phenomenon at the edge of the photosensitive area under dark field testing.

[0028] Figure 2 FIG. 4 is a schematic plan view of a back-illuminated image sensor according to an embodiment of the present invention.

[0029] Figure 3 FIG. 4 is a cross-sectional schematic diagram of a back-illuminated image sensor according to an embodiment of the present invention.

[0030] Figure 4 FIG. 4 is a flow chart of a method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention.

[0031] Description of reference numerals:

[0032] 10-photosensitive area; 20-peripheral area; 100-semiconductor substrate; 100a-front side; 100b-back side; 101-shallow trench isolation structure; 200-isolation wall; 110-light blocking structure; 120-back side dielectric layer; 130-interlayer dielectric layer; 140-conductive plug; 150-metal interconnect layer. DETAILED DESCRIPTION

[0033] The back-illuminated image sensor and the method for manufacturing the same of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be understood that the drawings in the specification are all in a very simplified form and are all in non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be noted that the order of the steps in the method presented herein is not necessarily the only order for performing these steps, some of the steps described may be omitted and / or some other steps not described herein may be added to the method. It should be understood that spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the figure. For example, if the structure in the figure is inverted or positioned in other different ways (such as rotation), the exemplary term "on..." may also include "under..." and other orientation relationships. For the sake of clarity, in all the drawings used to assist in explaining the embodiments of the present invention, the same components are marked with the same reference numerals in principle, and repeated descriptions thereof are omitted.

[0034] The following first refers to Figure 2 and Figure 3 The back-illuminated image sensor according to the embodiment of the present invention is described. Figure 2 and Figure 3The back-illuminated image sensor of the embodiment of the present invention includes a semiconductor substrate 100, wherein the semiconductor substrate 100 has a front side 100a and a back side 100b opposite to the front side 100a, wherein the semiconductor substrate 100 is provided with a photosensitive region 10 and a peripheral region 20 located outside the photosensitive region 10, wherein the semiconductor substrate 100 is provided with a plurality of photosensitive pixels (not shown) in the photosensitive region 10, and circuit elements and reference pixels (not shown) are provided in the peripheral region 20; and, the back-illuminated image sensor of the embodiment of the present invention further includes an isolation wall 200, wherein the isolation wall 200 passes through the semiconductor substrate 100 in the peripheral region 20 along the thickness direction of the semiconductor substrate 100, wherein the circuit elements and the reference pixels are located on the same side of the isolation wall 200, and the photosensitive region 10 is located on the other side of the isolation wall 200.

[0035] The semiconductor substrate 100 may include semiconductor materials such as silicon, germanium, silicon germanium, silicon carbide, gallium oxide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide or indium antimonide. The semiconductor substrate 100 may be provided with an active region and an isolation region for isolating the active region. Certain doping ions may be implanted according to design requirements to change electrical parameters. The semiconductor substrate 100 may include components formed according to design requirements. Figure 2 and Figure 3 As shown, in the embodiment of the present invention, the semiconductor substrate 100 is used as a device substrate of a back-illuminated image sensor, and the production of pixels (including photosensitive pixels and reference pixels) and circuit elements has been completed. Specifically, the two opposite surfaces of the semiconductor substrate 100 are respectively referred to as the front side 100a and the back side 100b, wherein the front side 100a is a side surface for producing pixels and circuit elements, and the back side 100b is a side surface for receiving incident light and sensing. The photosensitive area arranged on the semiconductor substrate 100 is an area for setting photosensitive pixels, i.e., image sensor pixels. In the photosensitive area 10, the photosensitive pixels are arranged in an array, for example, and the photosensitive pixels are configured to sense the incident light projected from the back side 100b of the semiconductor substrate 100 into the semiconductor substrate 100. The photosensitive pixels include, for example, a photodiode arranged in the semiconductor substrate 100 and a transistor arranged on the front side 100a of the semiconductor substrate 100. The area outside the photosensitive area 10, that is, the peripheral area 20, is located outside the photosensitive area 10. The peripheral circuit of the back-illuminated image sensor can be set in the peripheral area 20. In addition, in the embodiment of the present invention, circuit elements and reference pixels are set in the semiconductor substrate 100 and the front side 100a of the peripheral area 20. The circuit elements are used to realize the circuit function of the back-illuminated image sensor, and the reference pixels are used to establish a light intensity benchmark for the back-illuminated image sensor. The circuit elements and the reference pixels are not used to sense the incident light projected onto the back side 100b of the semiconductor substrate 100, that is, optical darkness needs to be maintained.

[0036] like Figure 2 and Figure 3 As shown, the back-illuminated image sensor of the embodiment of the present invention is provided with an isolation wall 200 in the peripheral region 20 of the semiconductor substrate 100. The isolation wall 200 passes through the semiconductor substrate 100 along the thickness direction of the semiconductor substrate 100, and the circuit element and the reference pixel are located on the same side of the isolation wall 200, and the photosensitive region 10 is located on the other side of the isolation wall 200. The material of the isolation wall 200 includes insulating materials such as silicon oxide, silicon nitride or silicon oxynitride, and the average wall thickness of the isolation wall 200 is, for example, 0.5 μm to 1.5 μm. With the isolation wall 200, the leakage current generated by the circuit element and the reference pixel during operation is difficult to cross the isolation wall 200 and enter the photosensitive region 10, thereby avoiding the problem of edge light emission in the photosensitive region 10.

[0037] In some embodiments, the back-illuminated image sensor of the present invention further includes a light-blocking structure 110 and a back dielectric layer 120 disposed on the back side 100b of the semiconductor substrate 100. Specifically, the light-blocking structure 110 is disposed above the back side 100b of the semiconductor substrate 100 (here, "above the back side 100b" refers to the side of the back side 100b away from the front side 100a), and is disposed between a plurality of photosensitive pixels in the photosensitive region 10 and above the circuit elements and reference pixels in the non-photosensitive region 20 along the vertical direction of the back side 100b of the semiconductor substrate 100. The light-blocking structure 110 may include non-metallic materials such as silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or may also include metal materials (such as tungsten or aluminum). In the photosensitive region 10, there is a certain gap between adjacent photosensitive pixels, and the light-blocking structure 110 disposed in the photosensitive region 10 is vertically aligned with the corresponding gap between adjacent photosensitive pixels, so that the incident light targeting one photosensitive pixel can be reduced from diffusing into adjacent photosensitive pixels, that is, the purpose is to reduce crosstalk. The light blocking structure 110 provided on the circuit element and the reference pixel is formed in the peripheral region 20 and vertically aligned with the circuit element and the reference pixel above the back side 100b of the semiconductor substrate 100 to fully block the incident light from reaching the circuit element and the reference pixel. The light blocking structure 110 provided on the back side 100b of the semiconductor substrate 100 defines a plurality of openings, and the back dielectric layer 120 fills the openings defined by the light blocking structure 110 and buries the light blocking structure 110. The back dielectric layer 120 includes, for example, a dielectric material with good transparency such as silicon oxide. In an optional solution, the isolation wall 200 extends from the inside of the semiconductor substrate 100 to above the back side 100b of the semiconductor substrate 100 (here, "above the back side 100b" refers to the side of the back side 100b away from the front side 100a), and penetrates the back dielectric layer 120 along the thickness direction of the back dielectric layer 120 to further improve the isolation effect between the photosensitive region 10 and the circuit element and the reference pixel, and avoid edge luminescence problems in the photosensitive region 10.

[0038] In some embodiments, the back-illuminated image sensor of the present invention further includes an interlayer dielectric layer 130 and a metal interconnect layer 150 disposed on the front side 100a of the semiconductor substrate 100. The interlayer dielectric layer 130 is disposed above the front side 100a of the semiconductor substrate 100 (here, "above the front side 100a" refers to the side of the front side 100a away from the back side 100b), and a conductive plug 140 electrically connected to the above-mentioned photosensitive pixels, circuit elements and reference pixels is disposed in the interlayer dielectric layer 130. The interlayer dielectric layer 130 may include at least one of insulating materials such as silicon oxide, silicon nitride and silicon oxynitride, and the conductive plug 140 disposed in the interlayer dielectric layer 130 is electrically connected to the photosensitive pixels, circuit elements and reference pixels disposed on the front side 100a of the semiconductor substrate 100, so that the control terminals of the photosensitive pixels, circuit elements and reference pixels can be led out from the front side 100a of the semiconductor substrate 100, which is convenient for rewiring processing. The metal interconnection layer 150 is disposed on a side surface of the interlayer dielectric layer 130 away from the semiconductor substrate 100 and is electrically connected to the conductive plug 140. The metal interconnection layer 150 has been patterned by one or more photolithography processes known in the art, and dielectric material is filled between the metal lines. In an optional solution, the isolation wall 200 extends from the semiconductor substrate 100 to above the front surface 100a of the semiconductor substrate 100 (here, "above the front surface 100a" refers to the side of the front surface 100a away from the back surface 100b), and penetrates at least a portion of the thickness of the interlayer dielectric layer 130 along the thickness direction of the interlayer dielectric layer 130, for example, completely penetrates the interlayer dielectric layer 130, and contacts the metal interconnection layer 150 (in order to avoid affecting the line pattern of the metal interconnection layer 150, the isolation wall 200 does not penetrate the metal interconnection layer 150), or only penetrates a portion of the thickness of the interlayer dielectric layer 130. The purpose of extending the isolation wall 200 into the interlayer dielectric layer 130 is to further improve the isolation effect between the photosensitive region 10 and the above-mentioned circuit elements and reference pixels, and to avoid edge light emission in the photosensitive region 10. Figure 3 In the illustrated case, the isolation wall 200 continuously penetrates the back dielectric layer 120 , the semiconductor substrate 100 , and the interlayer dielectric layer 130 . The total height of the isolation wall 200 is, for example, 2 μm to 4 μm.

[0039] Reference Figure 2 and Figure 3In some embodiments, a shallow trench isolation structure 101 (STI) surrounding the photosensitive region 10 is embedded in the front surface 100a of the semiconductor substrate 100. The shallow trench isolation structure 101 and the isolation wall 200 are both physically isolated. However, since the shallow trench isolation structure 101 is only embedded in a semiconductor substrate 100 with a partial thickness, it is difficult to completely block the influence of the leakage current generated at the circuit element and the reference pixel on the photosensitive region 10 by setting the shallow trench isolation structure 101 alone. In some embodiments, the isolation wall 200 is set on the inner side of the shallow trench isolation structure 101, that is, surrounding the isolation wall 200. In this way, in the area where the isolation wall 200 is set, the shallow trench isolation structure 101 and the isolation wall 200 form two barriers to the leakage current of the circuit element and the reference pixel, which can improve the isolation effect between the photosensitive region 10 and the peripheral region 20, and avoid the edge light emission problem of the photosensitive region 10. The minimum distance between the isolation wall 200 and the shallow trench isolation structure 101 (eg Figure 2 The d in the figure indicates that the thickness of the nanostructured carbon nanotubes is, for example, between 0.4 μm and 1.2 μm.

[0040] The setting range of the isolation wall 200 can be set according to the positions of the above-mentioned electronic components and reference pixels in the peripheral area 20. In addition, in order to ensure effective isolation between the photosensitive area 10 and the circuit components and reference pixels in the peripheral area 20 while saving the substrate area as much as possible, the isolation wall 200 can extend a set distance in the peripheral area 20 along the boundary of the photosensitive area 10. For example, in some embodiments, the plane where the wall surface of the isolation wall 200 is located is parallel to the boundary of the photosensitive area 10. In addition, according to the need for isolation, the isolation wall 200 can be set only along part of the boundary of the photosensitive area 10 (such as Figure 2 Alternatively, the partition wall 200 may be disposed around the entire boundary of the photosensitive region 10 (ie, the cross section of the partition wall 200 may be in the shape of a closed ring).

[0041] The following reference Figure 4 The method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention is described. Figure 4 and Figure 3 The embodiment of the present invention also includes a method for manufacturing a back-illuminated image sensor, which can be used to manufacture the back-illuminated image sensor described in the above embodiment. The manufacturing method includes the following first step S1 and second step S2:

[0042] In the first step S1, a semiconductor substrate 100 is provided, wherein the semiconductor substrate 100 has a front side 100a and a back side 100b opposite to the front side 100a, the semiconductor substrate 100 has a photosensitive region 10 and a peripheral region 20 located outside the photosensitive region 10, the semiconductor substrate 100 has a plurality of photosensitive pixels formed in the photosensitive region 10, and circuit elements and reference pixels formed in the peripheral region 20;

[0043] In the second step S2, an isolation wall 200 is embedded in the semiconductor substrate 100, and the isolation wall 200 passes through the semiconductor substrate 100 in the peripheral area 20 along the thickness direction of the semiconductor substrate 100, the circuit element and the reference pixel are located on the same side of the isolation wall 200, and the photosensitive area 10 is located on the other side of the isolation wall 200.

[0044] Combination Figure 2 and Figure 3 In some embodiments, before performing the second step S2, the semiconductor substrate 100 provided in the first step S1 further includes an interlayer dielectric layer 130 and a metal interconnection layer 150 formed in sequence above the front side 100a of the semiconductor substrate 100 (herein, "above the front side 100a" refers to the side of the front side 100a away from the back side 100b), and may also include a light-blocking structure 110 and a back dielectric layer 120 formed above the back side 100b of the semiconductor substrate 100 (herein, "above the back side 100b" refers to the side of the back side 100b away from the front side 100a), and the back dielectric layer 120 fills the opening defined by the light-blocking structure 110 and buries the light-blocking structure 110. In some embodiments, the back dielectric layer formed on the back side of the semiconductor substrate 100 may also directly cover the back side 100b, and a light-blocking structure is provided inside or above the back dielectric layer (herein, above the back dielectric layer refers to the side of the back dielectric layer away from the back side 100b). Regarding the production of the photosensitive pixels, reference pixels and circuit elements, as well as the production of the interlayer dielectric layer 130, the metal interconnection layer 150, the light blocking structure 110 and the back dielectric layer 120, reference may be made to the methods disclosed in the art and will not be repeated here.

[0045] In the second step S2, the method for embedding the isolation wall 200 in the semiconductor substrate 100 includes the following steps: first, etching the back dielectric layer 120, the semiconductor substrate 100 and the interlayer dielectric layer 130 from the back side 100b of the semiconductor substrate 100 to form a groove, the groove penetrating the back dielectric layer 120, the semiconductor substrate 100 and at least a portion of the interlayer dielectric layer 130; then, filling the groove with isolation dielectric to form the isolation wall 200. For example, the isolation dielectric filled in the groove includes silicon oxide, and at the end of the deposition stage of the isolation dielectric, the isolation dielectric fills the groove and is higher than the back dielectric layer 120, and then the isolation dielectric higher than the back dielectric layer 120 is removed by planarization, and the remaining isolation dielectric serves as the isolation wall 200.

[0046] In the back-illuminated image sensor and the method for manufacturing the back-illuminated image sensor provided by the present invention, an isolation wall 200 is set or formed in the peripheral area 20 of the semiconductor substrate 100, and the isolation wall 200 is used to separate the photosensitive area 10 from the circuit elements and reference pixels in the peripheral area 20. The isolation method of the isolation wall 200 is physical isolation, which can isolate the leakage current generated by the circuit elements and the reference pixels outside the photosensitive area 10, effectively solving the problem of light emission at the edge of the photosensitive area of ​​the back-illuminated image sensor.

[0047] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0048] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A back-illuminated image sensor, characterized in that: include: A semiconductor substrate having a front side and a back side opposite to the front side, wherein the semiconductor substrate is provided with a photosensitive region and a peripheral region located outside the photosensitive region, wherein the semiconductor substrate is provided with a plurality of photosensitive pixels in the photosensitive region and a circuit element in the peripheral region; A light blocking structure is disposed above the back surface of the semiconductor substrate and is disposed between the plurality of photosensitive pixels and at least part of the peripheral area along a vertical direction of the back surface of the semiconductor substrate; as well as, An isolation wall passes through the semiconductor substrate along the thickness direction of the semiconductor substrate in the peripheral area, and the circuit element and the photosensitive area are respectively located on both sides of the isolation wall.

2. The back-illuminated image sensor according to claim 1, wherein: Also includes: A back dielectric layer fills the opening defined by the light-blocking structure and buries the light-blocking structure, wherein the isolation wall extends from the inside of the semiconductor substrate to the top of the back side of the semiconductor substrate and penetrates the back dielectric layer along the thickness direction of the back dielectric layer.

3. The back-illuminated image sensor according to claim 1, wherein: Also includes: An interlayer dielectric layer, disposed above the front surface of the semiconductor substrate, wherein the interlayer dielectric layer is provided with a conductive plug electrically connected to the photosensitive pixel and the circuit element; as well as, A metal interconnection layer is arranged on a surface of the interlayer dielectric layer away from the semiconductor substrate and is electrically connected to the conductive plug, wherein the isolation wall extends from the inside of the semiconductor substrate to above the front surface of the semiconductor substrate and penetrates at least a portion of the thickness of the interlayer dielectric layer along the thickness direction of the interlayer dielectric layer, but does not penetrate the metal interconnection layer.

4. The back-illuminated image sensor according to claim 1, wherein: A shallow trench isolation structure surrounding the photosensitive area is embedded on the front surface of the semiconductor substrate, the shallow trench isolation structure surrounds the isolation wall, and the circuit element is located on a side of the shallow trench isolation structure away from the isolation wall.

5. The back-illuminated image sensor according to claim 4, wherein: The minimum distance between the isolation wall and the shallow trench isolation structure is 0.4 μm to 1.2 μm.

6. The back-illuminated image sensor according to claim 1, wherein: The isolation wall extends a set distance in the peripheral area along the boundary of the photosensitive area.

7. The back-illuminated image sensor according to claim 1, wherein: The isolation wall is only arranged along a portion of the boundary of the photosensitive area; or, the isolation wall is arranged around the entire boundary of the photosensitive area, thereby forming a closed ring.

8. The back-illuminated image sensor according to any one of claims 1 to 7, characterized in that: The isolation wall has a wall thickness of 0.5 μm to 1.5 μm and a height of 2 μm to 4 μm.

9. A method for manufacturing a back-illuminated image sensor, characterized in that: include: A semiconductor substrate is provided, wherein the semiconductor substrate has a front surface and a back surface opposite to the front surface, the semiconductor substrate has a photosensitive region and a peripheral region located outside the photosensitive region, the semiconductor substrate has a plurality of photosensitive pixels formed in the photosensitive region, a circuit element formed in the peripheral region, a light-blocking structure formed on one side of the back surface of the semiconductor substrate, and the light-blocking structure is arranged between the plurality of photosensitive pixels and at least part of the peripheral region along a vertical direction of the back surface of the semiconductor substrate; as well as, An isolation wall is embedded in the semiconductor substrate. The isolation wall passes through the semiconductor substrate along the thickness direction of the semiconductor substrate. The circuit element and the photosensitive area are respectively located on both sides of the isolation wall.

10. The manufacturing method according to claim 9, characterized in that: Before embedding the isolation wall, the semiconductor substrate further includes an interlayer dielectric layer and a metal interconnect layer formed in sequence above the front surface of the semiconductor substrate, and a back dielectric layer formed above the back surface of the semiconductor substrate; The method of embedding the isolation wall in the semiconductor substrate comprises: Etching the back dielectric layer, the semiconductor substrate and the interlayer dielectric layer from the back side of the semiconductor substrate to form a groove, wherein the groove penetrates the back dielectric layer, the semiconductor substrate and at least a portion of the interlayer dielectric layer; as well as, An isolation medium is filled in the groove to form the isolation wall.

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