Image sensor and manufacturing method thereof

Abstract

The invention discloses an image sensor and a manufacturing method thereof. The image sensor comprises a substrate; the photoelectric sensing areas are arranged on the substrate; the isolation structures are arranged on the substrate and are arranged between the adjacent photoelectric sensing areas; the light filtering element is arranged on the photoelectric sensing area; the grating is arranged on the isolation structure; wherein the photoelectric sensing area comprises a first material layer, the first material layer is doped consistently and comprises a plurality of sub-layers which are arranged in a stacked mode, and at least one side edge of one sub-layer in every two adjacent sub-layers is concave inwards so that one part of the adjacent face of the other sub-layer and the sub-layer can make contact with the isolation structure. The resolution of the image sensor can be effectively improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an image sensor and a method for manufacturing the same. Background Art

[0002] Image sensors are widely used in photography, security systems, smart phones, medical electronics and other fields. They convert light signals into electrical signals by sensing them in the photoelectric sensing area. With the development of society, image sensors are in urgent need of higher resolution in various application fields. Therefore, the resolution of existing image sensors needs to be further improved. Summary of the invention

[0003] In view of the above problems, the present application provides an image sensor and a method for manufacturing the same, aiming to improve the resolution of the image sensor.

[0004] According to a first aspect of the present invention, there is provided an image sensor, comprising:

[0005] substrate;

[0006] A photoelectric sensing region disposed on the substrate and an isolation structure disposed between adjacent photoelectric sensing regions on the substrate;

[0007] A filter element disposed on the photoelectric sensing area and a grid disposed on the isolation structure;

[0008] The photoelectric sensing area includes a first material layer, which is uniformly doped and includes a plurality of stacked sublayers, at least one side of one of two adjacent sublayers is concave so that the other sublayer contacts the isolation structure with a portion of the adjacent surface of the sublayer.

[0009] Optionally, the photoelectric sensing region includes a plurality of material layers stacked in layers, two adjacent material layers have different doping elements, and the first material layer is the uppermost material layer among the plurality of material layers;

[0010] Any side edge of the sublayer is outside the sublayer adjacent to the sublayer surface, or is aligned with the sublayer adjacent to the sublayer surface;

[0011] And, any side edge of the sub-layer is on the inner side of the sub-layer / material layer adjacent to the bottom surface of the sub-layer, or is aligned with the sub-layer / material layer adjacent to the bottom surface of the sub-layer.

[0012] Optionally, the multiple material layers also include a second material layer located below the first material layer, and the two-dimensional size of the second material layer gradually changes in a direction perpendicular to the substrate surface and / or the concentration of the doped element in the second material layer gradually changes in a direction perpendicular to the substrate surface.

[0013] Optionally, the isolation structure comprises a first deep trench isolation structure and a second deep trench isolation structure disposed on the first deep trench isolation structure, and a portion of a surface of the first deep trench isolation structure is covered by a lowermost material layer among the plurality of material layers;

[0014] A projection of the second deep trench isolation structure surface on the first deep trench isolation structure surface falls within an edge of the first deep trench isolation structure surface.

[0015] According to a second aspect of the present invention, there is provided a method for manufacturing an image sensor, comprising:

[0016] providing a substrate;

[0017] forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate;

[0018] forming a filter element on the photoelectric sensing area and forming a grid on the isolation structure;

[0019] The photoelectric sensing area includes a first material layer, which is uniformly doped and includes a plurality of stacked sublayers, at least one side of one of two adjacent sublayers is concave so that the other sublayer contacts the isolation structure with a portion of the adjacent surface of the sublayer.

[0020] Optionally, forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate includes:

[0021] forming a first doping layer on the substrate;

[0022] Etching the first doping layer to form a first groove with a groove wall perpendicular to the substrate surface at a preset position of the isolation structure;

[0023] The first doping layer is partially etched at the wall of the first groove to form the first material layer including a plurality of sub-layers, wherein at least one side of an upper sub-layer of two adjacent sub-layers is concave so that a portion of the surface of the lower sub-layer is exposed.

[0024] Optionally, forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate further comprises performing the following steps before forming the first doping layer on the substrate:

[0025] forming at least one second doping layer on the substrate, wherein the first doping layer and the second doping layer use the same intrinsic semiconductor, the first doping layer is formed on the second doping layer, and the doping elements in the two adjacent doping layers are different;

[0026] Etching the second doped layer to form a second groove at a preset position of the isolation structure and dividing the second doped layer into material layers included in the photoelectric sensing region through the second groove;

[0027] The second groove is filled and a surface planarization process is performed on the material filled in the second groove to form a portion of the isolation structure located in the second doping layer.

[0028] Optionally, the second doped layer is etched into a second groove having a width gradually changing in a direction perpendicular to the substrate surface due to over-etching, and the second doped layer is divided into the second material layer included in the photoelectric sensing area by the second groove.

[0029] Optionally, at least one second doping layer is formed on the substrate, including: depositing at least one doping layer on the substrate and diffusing the doping elements in the formed doping layer downward through an annealing process to form the second doping layer in which the concentration of the doping elements gradually changes in a direction perpendicular to the surface of the substrate.

[0030] Optionally, forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate further comprises: forming an isolation layer and etching the isolation layer before forming at least one second doping layer on the substrate, so as to form a first deep trench isolation structure included in the isolation structure at a preset position of the isolation structure;

[0031] Etching a portion of the first doped layer at the wall of the first groove, comprising: etching a portion of the first doped layer at the wall of the first groove so that a projection of an edge of the formed first material layer on the surface of the first deep trench isolation structure falls within an edge of the surface of the first deep trench isolation structure.

[0032] The unexpected technical effects of this application are:

[0033] The image sensor provided by the present application includes: a substrate; a photoelectric sensing region arranged on the substrate and an isolation structure arranged between adjacent photoelectric sensing regions on the substrate; a filter element arranged on the photoelectric sensing region and a grid arranged on the isolation structure. The photoelectric sensing region includes a first material layer, the first material layer is uniformly doped and includes a plurality of sublayers arranged in a stacked manner, at least one side edge of one of the two adjacent sublayers is concave so that the other sublayer contacts the isolation structure with a portion of the adjacent surface of the sublayer, so that the two adjacent sublayers have different two-dimensional sizes, so that the number of quantum wells in the photoelectric sensing region is increased, and the number of electrons generated under the same illumination conditions is correspondingly increased, that is, the photoelectric reaction efficiency is increased, thereby achieving an improvement in the resolution of the image sensor.

[0034] Furthermore, the photoelectric sensing region includes a plurality of stacked material layers, the doping elements of two adjacent material layers are different, the first material layer is the topmost material layer among the plurality of material layers; any side edge of the sublayer is on the outside of the sublayer adjacent to the surface of the sublayer, or is aligned with the sublayer adjacent to the surface of the sublayer; and any side edge of the sublayer is on the inside of the sublayer / material layer adjacent to the bottom surface of the sublayer, or is aligned with the sublayer / material layer adjacent to the bottom surface of the sublayer. Therefore, the existence of the first material layer will not make other material layers and the sublayers included in the first material layer concave compared to the sublayers adjacent to their respective surfaces, so that the production of multiple material layers is more convenient; in addition, the material layer located below the first material layer does not need to reduce its two-dimensional size due to the existence of the first material layer, so the photoelectric conversion performance of other material layers is not affected.

[0035] Furthermore, the isolation structure includes a first deep trench isolation structure and a second deep trench isolation structure disposed on the first deep trench isolation structure, a portion of the surface of the first deep trench isolation structure is covered by the lowest material layer among the plurality of material layers; the projection of the surface of the second deep trench isolation structure on the surface of the first deep trench isolation structure falls within the edge of the surface of the first deep trench isolation structure. Therefore, the photoelectric sensing region as a whole still has a large space for photoelectric conversion, and the surface of the photoelectric sensing region still has a large area for light sensing, so that the presence of the first material layer will not shrink the photoelectric sensing region to such an extent that the photoelectric conversion performance is adversely affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and other objects, features and advantages of the present application will become more apparent through the following description of the embodiments of the present application with reference to the accompanying drawings, in which:

[0037] Figure 1 A cross-sectional view of a conventional back-illuminated image sensor is shown;

[0038] Figure 2 A cross-sectional view of an exemplary image sensor in an embodiment of the present application is shown;

[0039] Figure 3 A flow chart showing a method for manufacturing an image sensor in an embodiment of the present application;

[0040] Figure 4a A cross-sectional view of a substrate in an embodiment of the present application is shown;

[0041] Figure 4b A cross-sectional view after an isolation layer is formed on a substrate in an embodiment of the present application is shown;

[0042] Figure 4c A cross-sectional view after a first deep trench isolation structure is formed on a substrate in an embodiment of the present application is shown;

[0043] Figure 4d A cross-sectional view after a doping layer is formed on a substrate in an embodiment of the present application is shown;

[0044] Figure 4e A cross-sectional view after another doping layer is formed on the substrate in an embodiment of the present application is shown;

[0045] Figure 4f A cross-sectional view after two second doping layers are formed on the substrate in the embodiment of the present application is shown;

[0046] Figure 4g A cross-sectional view showing the first doping layer after a first groove is etched in the embodiment of the present application;

[0047] Figure 4h A cross-sectional view after forming the first material layer in an embodiment of the present application is shown;

[0048] Figure 4i A cross-sectional view after forming a second deep trench isolation structure in an embodiment of the present application is shown.

[0049] Description of reference numerals: 111-substrate; 112-deep trench isolation structure; 113-photoelectric sensing area; 114-shallow trench isolation structure; 121-first dielectric layer; 122-second dielectric layer; 123-pad; 124-connection structure; 125-polysilicon structure; 130-mask material layer; 131-first mask layer; 132-second mask layer; 133-third mask layer; 134-fourth mask layer; 140-grid; 211-isolation layer; 212-epitaxial layer; 221-first material layer; 221a-first sublayer; 221b-second sublayer; 22 2-material layer; 223-material layer; 223'-doping layer; 223''-second doping layer; 224-material layer; 224'-doping layer; 224''-second doping layer; 231-first deep trench isolation structure; 232-second deep trench isolation structure; 232a-first sub-isolation structure; 232b-second sub-isolation structure; 232c-third sub-isolation structure; 240-filter element; 241-blue filter element; 242-green filter element; 243-red filter element; 251-high-k dielectric layer; 252-metal layer; 253-protective layer. DETAILED DESCRIPTION

[0050] The present application will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown.

[0051] This application may be presented in a variety of forms, some examples of which are described below.

[0052] Figure 1 The figure shows an existing back-illuminated (BSI) image sensor. Figure 1As shown, the back-illuminated image sensor includes a substrate 111, in which a plurality of photoelectric sensing regions 113 and a deep trench isolation (DTI) structure 112 and a shallow trench isolation (STI) structure 114 are arranged for separating adjacent photoelectric sensing regions 113. The material used by the substrate 111 is, for example, silicon (Si). The substrate 111 is located on the surface of the second dielectric layer 122, and the second dielectric layer 122 is located on the surface of the first dielectric layer 121. A pad 123 is arranged on the bottom surface of the first dielectric layer 121. The pad 123 is connected to a polysilicon structure 125 arranged in the second dielectric layer 122 through a connection structure 124 arranged in the first dielectric layer 121. The material used by the pad 123 is, for example, copper (Cu). A mask material layer 130 is arranged on the surface of the substrate 111, and a grid 140 formed by stacking different materials is arranged on the surface of the mask material layer 130. The mask material layer 130 includes a first mask layer 131, a second mask layer 132, a third mask layer 133 and a fourth mask layer 134, wherein the materials used in the first mask layer 131 and the fourth mask layer 134 may be silicon oxide (SiO2), the material used in the second mask layer 132 may be aluminum oxide (Al2O3), and the material used in the third mask layer 133 may be tantalum oxide (Ta2O5). The thickness of the substrate 111 may be 3um, the thickness of the first mask layer 131 may be 120 angstroms, the thickness of the second mask layer 132 may be 75 angstroms, the thickness of the third mask layer 133 may be 520 angstroms, and the thickness of the fourth mask layer 134 may be 1800 angstroms. The photoelectric sensing region 113 is also called a photodiode (PD for short), which may be as follows Figure 1 The front end of line (FEOL) process shown is formed by implanting ions into the substrate 111 from the bottom surface of the substrate 111 .

[0053] With the development of society, various application fields are in urgent need of image sensors with higher resolution. In view of this, an embodiment of the present application improves the existing image sensor. Figure 2 FIG. 1 is a cross-sectional schematic diagram of an exemplary image sensor provided according to an embodiment of the present application, as shown in FIG. Figure 2As shown, the image sensor includes: a substrate 111, a photoelectric sensing region 113 disposed on the substrate 111, an isolation structure 230 disposed between adjacent photoelectric sensing regions 113 on the substrate 111, a filter element 240 disposed on the photoelectric sensing region 113, and a grid 140 disposed on the isolation structure 230. The main improvement of the image sensor in the embodiment of the present application is that: the photoelectric sensing region 113 includes a first material layer 221, the first material layer 221 is uniformly doped and includes a plurality of sub-layers stacked, at least one side edge of one of two adjacent sub-layers is concave so that the other sub-layer contacts the isolation structure 230 with a portion of the adjacent surface of the sub-layer, so that adjacent sub-layers in the first material layer 221 have different two-dimensional sizes, so that the first material layer 221 uniformly doped in the photoelectric sensing region 113 has multiple quantum wells, and the number of electrons generated by the first material layer 221 under the same illumination conditions is increased, that is, the photoelectric reaction efficiency is increased, thereby improving the resolution of the image sensor.

[0054] Figure 2 In the exemplary image sensor shown, the first material layer 221 includes two sublayers, a first sublayer 221a and a second sublayer 221b, which are divided by a dotted line. The left side and the right side of the first sublayer 221a are concave so that the second sublayer 221b is adjacent to a portion of the surface of the first sublayer 221a and contacts the isolation structure 230, so that the two-dimensional size of the first sublayer 221a is smaller than the two-dimensional size of the second sublayer 221b. In other examples, the first sublayer 221a may have only a left side or only a right side concave so that the second sublayer 221b is adjacent to a portion of the surface of the first sublayer 221a and contacts the isolation structure 230. In the embodiment of the present application, the two-dimensional size of the sublayer refers to the size of the sublayer on a two-dimensional plane parallel to the substrate 111, including the length and width of the sublayer. The adjacent sublayers in the first material layer 221 have different two-dimensional sizes, which means that the adjacent sublayers have different lengths and / or widths.

[0055] In an optional embodiment, the photoelectric sensing region 113 includes a plurality of material layers stacked, and the doping elements of two adjacent material layers are different. The first material layer 221 is the topmost material layer among the plurality of material layers. In the first material layer 221: any side edge of a sublayer is aligned with the outer side of the sublayer adjacent to the surface of the sublayer or with the sublayer adjacent to the surface of the sublayer, and any side edge of a sublayer is aligned with the inner side of the sublayer / material layer adjacent to the bottom of the sublayer or with the sublayer / material layer adjacent to the bottom of the sublayer. Therefore, the existence of the first material layer 221 will not make other material layers and the sublayers included in the first material layer 221 concave compared to the sublayers adjacent to their respective surfaces, so that the production of multiple material layers is more convenient; in addition, although there are multiple sublayers whose two-dimensional dimensions are continuously reduced from bottom to top in the first material layer 221, the material layer located below the first material layer 221 does not need to reduce its two-dimensional dimension due to the existence of the first material layer 221, so the photoelectric conversion performance of other material layers is not affected.

[0056] Figure 2 In the exemplary image sensor shown, the photoelectric sensing area 113 includes a first material layer 221 and three material layers 222, 223 and 224 located below the first material layer 221. Among these material layers, only the first sublayer 221a in the first material layer 221 has a side concave compared to the second sublayer 221b on the bottom surface, and the side of the first sublayer 221a and the second sublayer 221b on the same side and the surface of the second sublayer 221b exposed on the side are Figure 2 The outline of the lowercase letter "h" is shown in the cross-sectional schematic diagram, specifically as shown by the white dotted line L in the figure. It should be understood that if the first material layer 221 is not the uppermost material layer among the multiple material layers, when any sub-layer or material layer is required to have no side concave compared to the surface sub-layer or material layer, the material layer above the second sub-layer 221b needs to reduce the two-dimensional size, but Figure 2 In the image sensor shown, the three material layers 222 , 223 , and 224 do not need to be reduced in two dimensions due to the presence of the first material layer 221 .

[0057] The multiple stacked material layers included in the photoelectric sensing region 113 are formed by doping intrinsic semiconductors with impurities, for example, by doping impurities into silicon (Si) materials. The doped elements in the silicon material may be phosphorus (P), arsenic (As), antimony (Sb), and other suitable elements known to those skilled in the art. Figure 2 In the image sensor shown, the first material layer 221 and the material layer 224 can be silicon materials doped with phosphorus, the material layer 222 can be silicon materials doped with antimony, and the material layer 223 can be silicon materials doped with arsenic. The doping elements of the two adjacent material layers in the photoelectric sensing region 113 are different, so that due to the existence of the heterojunction, independent quantum wells exist in each material layer, thereby achieving a greater photoelectric reaction efficiency.

[0058] Furthermore, the multiple material layers in the photoelectric sensing region 113 may include a second material layer located below the first material layer 221, and the two-dimensional size of the second material layer gradually changes in a direction perpendicular to the surface of the substrate 111 and / or the concentration of the doped element in the second material layer gradually changes in a direction perpendicular to the surface of the substrate 111, so that the photoelectric sensing region 113 increases the number of quantum wells based on the second material layer, thereby achieving a further increase in the photoelectric reaction efficiency. Figure 2 The material layer 223 and the material layer 224 in the image sensor shown are the two second material layers mentioned above. The material layer 223 and the material layer 224 each have not only a two-dimensional size that gradually changes in the direction perpendicular to the surface of the substrate 111, but also a doping concentration that gradually changes in the direction perpendicular to the surface of the substrate 111.

[0059] Furthermore, the isolation structure 230 is as follows Figure 2 The structure shown includes a first deep trench isolation structure 231 and a second deep trench isolation structure 232 disposed on the first deep trench isolation structure 231. A portion of the surface of the first deep trench isolation structure 231 is covered by the lowest material layer among the multiple material layers, and the projection of the surface of the second deep trench isolation structure 232 on the surface of the first deep trench isolation structure 231 falls within the edge of the surface of the first deep trench isolation structure 231. It should be understood that a portion of the surface of the first deep trench isolation structure 231 is covered by the lowest material layer among the multiple material layers, but the adjacent photoelectric sensing region 113 is as shown in FIG. Figure 2 As shown in FIG. 1 , the bottom material layers are still isolated by the first deep trench isolation structure 231; in addition, the second deep trench isolation structure 232 is on the first deep trench isolation structure 231, so that the adjacent photoelectric sensing region 113 is Figure 2 As shown, the first material layers 221 are isolated by the second deep trench isolation structure 232, and the second deep trench isolation structure 232 has multiple cross-sectional areas that increase from bottom to top due to the multiple sub-layers with reduced two-dimensional dimensions from bottom to top in the first material layer 221. The projection of the surface of the second deep trench isolation structure 232 on the surface of the first deep trench isolation structure 231 falls within the edge of the surface of the first deep trench isolation structure 231, that is, the cross-sectional area of ​​the second deep trench isolation structure 232 on each plane parallel to the substrate 111 is smaller than the surface area of ​​the first deep trench isolation structure 231, so that not only the photoelectric sensing region 113 as a whole still has a large space for photoelectric conversion, but also the surface of the photoelectric sensing region 113 still has a large area for photosensitivity, so that the presence of the first material layer 221 will not shrink the photoelectric sensing region 113 to such an extent that the photoelectric conversion performance is adversely affected.

[0060] Corresponding to the image sensor provided in the above embodiment, another embodiment of the present application further provides a method for manufacturing an image sensor. Figure 3The method for manufacturing the image sensor provided by the embodiment of the present application is shown as follows: Figure 3 As shown, the manufacturing method includes:

[0061] Step S110, providing a substrate;

[0062] Step S120, forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate, wherein the photoelectric sensing region includes a first material layer, the first material layer is uniformly doped and includes a plurality of stacked sublayers, at least one side of one of two adjacent sublayers is concave so that the other sublayer contacts a portion of an adjacent surface of the sublayer with the isolation structure;

[0063] Step S130 , forming a filter element on the photoelectric sensing area and forming a grid on the isolation structure.

[0064] Figure 4a to Figure 4h This is a schematic diagram of an execution process of step S120. Figure 4a to Figure 4h Step S120 will be described in detail.

[0065] Step S120 may include: forming an isolation layer on the substrate, and then etching the isolation layer to form a first deep trench isolation structure included in the isolation structure at a preset position of the isolation structure.

[0066] Specifically, a substrate may be provided first, and then ion implantation may be performed into the substrate to form Figure 4a The isolation layer 211 shown in the figure has ions implanted therein such as indium (In) ions. The formed isolation layer 211 divides the substrate into the substrate 111 and the epitaxial layer 212, and then the epitaxial layer 212 is removed, so that Figure 4b As shown in FIG. 1 , an isolation layer 211 is formed on the substrate 111. The epitaxial layer 212 can be removed by chemical mechanical polishing (CMP), so that the surface of the isolation layer 211 is flattened while the epitaxial layer 212 is removed. A shallow trench isolation structure 114 is pre-formed in the substrate 111. The isolation layer 211 is etched as follows: Figure 4c As shown, a first deep trench isolation structure 231 corresponding to the shallow trench isolation structure 114 is formed, and dry etching can be used to form the first deep trench isolation structure 231. The shallow trench isolation structure 114, the first deep trench isolation structure 231 and the second deep trench isolation structure 232 formed later are combined to achieve better isolation between adjacent photoelectric sensing regions 113, thereby reducing the crosstalk effect of the image sensor.

[0067] Step S120 may also include: forming at least one second doping layer on the substrate with different doping elements in adjacent doping layers, etching the second doping layer to form a second groove at a preset position of the isolation structure and dividing the second doping layer into material layers included in the photoelectric sensing area through the second groove, filling the second groove and performing surface planarization treatment on the material filled in the second groove to form a portion of the isolation structure located in the second doping layer.

[0068] Furthermore, forming at least one second doping layer on the substrate may include: depositing at least one doping layer on the substrate and diffusing the doping elements in the formed doping layer downward through an annealing process to form a second doping layer in which the concentration of the doping elements gradually changes in a direction perpendicular to the surface of the substrate, so that etching the second doping layer can form a second material layer in which the concentration of the doping elements included in the photoelectric sensing region 113 gradually changes in a direction perpendicular to the surface of the substrate 111.

[0069] Figure 4d As shown, a doping layer 224' is deposited on the substrate 111. Figure 4e It is shown that another doping layer 223 ′ is deposited on the doping layer 224 ′, and the doping layer 223 ′ and the doping layer 224 ′ have different doping elements. Figure 4f It is shown that the doping elements in the doping layer 223' and the doping layer 224' are diffused downward by an annealing process to form a second doping layer 223'' and a second doping layer 224'', wherein the annealing process can be performed using a 10mJ laser to control the execution time of the annealing process, so that the doping elements in the doping layer 224' diffuse downward so that the lower part of the area where the doping layer 224' is located forms the second doping layer 224'' and the upper part no longer contains the doping elements in the doping layer 224', and the second doping layer 224' has a doping concentration that decreases from top to bottom; at the same time, the doping elements in the doping layer 223' diffuse downward so that the upper part of the area where the doping layer 224' is located forms the second doping layer 223'' and the area where the doping layer 223' is located no longer contains the doping elements, and the second doping layer 223' has a doping concentration that decreases from top to bottom, and the area where the doping layer 223' is located is oxidized during the annealing process.

[0070] Figure 4g As shown, after removing the oxide formed in the area where the doping layer 223' is located, a first sub-isolation structure 232a is formed in the second groove obtained by etching the second doping layer 223'' and the second doping layer 224''. The first sub-isolation structure 232a is the part of the second deep trench isolation structure 232 located in the second doping layer 223'' and the second doping layer 224''. Figure 4gAs shown, the width of the first sub-isolation structure 232a changes gradually in a direction perpendicular to the surface of the substrate 111. This is because the second doping layer 223" and the second doping layer 224" are etched into second grooves that are narrow at the bottom and wide at the top due to over-etching during the etching process. Figure 4g The first sub-isolation structure 232 a which is narrow in the middle and the bottom and wide in the top also makes the material layers 223 and 224 of the formed second material layers have not only a gradual doping concentration but also a gradual two-dimensional size in a direction perpendicular to the surface of the substrate 111 .

[0071] Step S120 may also include: forming a first doped layer on the substrate; etching the first doped layer to form a first groove with a groove wall perpendicular to the substrate surface at a preset position of the isolation structure; etching a portion of the first doped layer at the groove wall of the first groove to form a first material layer including multiple sub-layers and at least one side edge of the upper sub-layer of two adjacent sub-layers is concave so that a portion of the surface of the lower sub-layer is exposed.

[0072] Figure 4g It is also shown that two other doping layers are deposited on the material layer 223 and the two deposited doping layers are etched to form a groove with a wall perpendicular to the surface of the substrate 111 at a preset position of the isolation structure 230. The two doping layers can be deposited thinner and the flow rate of the etching gas can be controlled so that the two doping layers are etched to form a groove with a wall perpendicular to the surface of the substrate 111. The doping elements of the adjacent doping layers in the above-mentioned two other doping layers and the second doping layer 223'' and the second doping layer 224'' formed previously are different, and the upper one of the two other doping layers deposited is the first doping layer, so Figure 4g The groove wall formed is perpendicular to the surface of the substrate 111 to divide the material layer included in the photoelectric sensing area 113. Figure 4h As shown, the upper doping layer of the other two doping layers is etched at the first groove wall to form the first material layer 221 included in the photoelectric sensing region 113, and the etching process is to make the projection of the edge of the formed first material layer 221 on the surface of the first deep trench isolation structure 231 fall within the edge of the surface of the first deep trench isolation structure 231. Since the first material layer 221 includes a first sub-layer 221a and a second sub-layer 221b, it is specifically to make the projection of the respective edges of the first sub-layer 221a and the second sub-layer 221b on the surface of the first deep trench isolation structure 231 fall within the edge of the surface of the first deep trench isolation structure 231.

[0073] Figure 4iAs shown, the grooves between the material layers 222 are filled to form the second sub-isolation structure 232b, and the grooves between the first material layers 221 are filled and the surface of the material filled in the grooves is flattened to form the third sub-isolation structure 232c. The first sub-isolation structure 232a, the second sub-isolation structure 232b and the third sub-isolation structure 232c constitute the second deep trench isolation structure 232. The material used for the second deep trench isolation structure 232 can be silicon dioxide. In the embodiment of the present application, the first deep trench isolation structure 231 and the second deep trench isolation structure 232 are both backside deep trench isolation (BDTI) structures.

[0074] The second doping layer 223'', the second doping layer 224'' and the other two doping layers deposited later use the same intrinsic semiconductor, so it can be seen from Figure 4f The surface of the second doping layer 223'' is shown to be etched downward until a portion of the second doping layer 224'' is etched away to form a second groove. In addition, the other two doping layers can be etched downward from the surface of the first doping layer until the first sub-isolation structure 232a is exposed. The first sub-isolation structure 232a serves as an etching stop. It should be understood that it is not necessary to etch downward from the surface of the first doping layer to the surface of the first deep trench isolation structure 231, which is conducive to ensuring that the first groove described above is formed with the groove wall perpendicular to the surface of the substrate 111.

[0075] for Figure 4i As shown in the structure, a structure such as Figure 2 The grid 140 shown in FIG. 1 is formed by a multi-layer structure, thereby reducing the generation of dark current and improving the product yield. Figure 2 As shown, the high-k dielectric layer 251, the metal layer 252 and the protective layer 253 are included, so that it belongs to a composite metal grid (CMG), which can effectively reduce the generation of dark current. The material used for the high-k dielectric layer 251 is, for example, tantalum oxide (Ta2O5), the material used for the metal layer 252 is, for example, aluminum (Al), and the material used for the protective layer 253 is, for example, titanium nitride (TiN). Further, after the grid 140 is formed, Figure 2 As shown, a filter element 240 is formed between the grids 140 and located on the surface of the photoelectric sensing area 113. The filter element 240 includes a blue filter element 241, a green filter element 242 and a red filter element 243. It should be noted that the filter element includes a color filter and a micro lens located on the surface of the color filter. Since the surface of the micro lens is convex, Figure 2The blue filter element 241 , the green filter element 242 , and the red filter element 243 are all in a convex shape.

[0076] The embodiments of the present application are described above, and these embodiments do not describe all the details in detail, nor do they limit the application to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can make good use of the present application and the modifications based on the present application. The present application is only limited by the claims and their full scope and equivalents.

Claims

1. An image sensor, comprising: substrate; A photoelectric sensing region disposed on the substrate and an isolation structure disposed between adjacent photoelectric sensing regions on the substrate; A filter element disposed on the photoelectric sensing area and a grid disposed on the isolation structure; The photoelectric sensing area includes a first material layer, which is uniformly doped and includes a plurality of stacked sublayers, at least one side of one of two adjacent sublayers is concave so that the other sublayer contacts the isolation structure with a portion of the adjacent surface of the sublayer.

2. The image sensor according to claim 1, wherein: The photoelectric sensing region includes a plurality of stacked material layers, two adjacent material layers have different doping elements, and the first material layer is the uppermost material layer among the plurality of material layers; Any side edge of the sublayer is outside the sublayer adjacent to the sublayer surface, or is aligned with the sublayer adjacent to the sublayer surface; And, any side edge of the sub-layer is on the inner side of the sub-layer / material layer adjacent to the bottom surface of the sub-layer, or is aligned with the sub-layer / material layer adjacent to the bottom surface of the sub-layer.

3. The image sensor according to claim 2, wherein: The multiple material layers also include a second material layer located below the first material layer, wherein the two-dimensional size of the second material layer gradually changes in a direction perpendicular to the substrate surface and / or the concentration of the doped element in the second material layer gradually changes in a direction perpendicular to the substrate surface.

4. The image sensor according to claim 2, wherein: The isolation structure comprises a first deep trench isolation structure and a second deep trench isolation structure disposed on the first deep trench isolation structure, wherein a portion of a surface of the first deep trench isolation structure is covered by a lowermost material layer among the plurality of material layers; A projection of the second deep trench isolation structure surface on the first deep trench isolation structure surface falls within an edge of the first deep trench isolation structure surface.

5. A method for manufacturing an image sensor, comprising: providing a substrate; forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate; forming a filter element on the photoelectric sensing area and forming a grid on the isolation structure; The photoelectric sensing area includes a first material layer, which is uniformly doped and includes a plurality of stacked sublayers, at least one side of one of two adjacent sublayers is concave so that the other sublayer contacts the isolation structure with a portion of the adjacent surface of the sublayer.

6. The method for manufacturing an image sensor according to claim 5, wherein: Forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate, comprising: forming a first doping layer on the substrate; Etching the first doping layer to form a first groove with a groove wall perpendicular to the substrate surface at a preset position of the isolation structure; The first doping layer is partially etched at the wall of the first groove to form the first material layer including a plurality of sub-layers, wherein at least one side of an upper sub-layer of two adjacent sub-layers is concave so that a portion of the surface of the lower sub-layer is exposed.

7. The method for manufacturing an image sensor according to claim 6, wherein: The method further comprises forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate, and performing the following steps before forming the first doping layer on the substrate: forming at least one second doping layer on the substrate, wherein the first doping layer and the second doping layer use the same intrinsic semiconductor, the first doping layer is formed on the second doping layer, and the doping elements in the two adjacent doping layers are different; Etching the second doped layer to form a second groove at a preset position of the isolation structure and dividing the second doped layer into material layers included in the photoelectric sensing region through the second groove; The second groove is filled and a surface planarization process is performed on the material filled in the second groove to form a portion of the isolation structure located in the second doping layer.

8. The method for manufacturing an image sensor according to claim 7, wherein: The second doped layer is etched into the second groove whose width gradually changes in a direction perpendicular to the substrate surface due to over-etching, and the second doped layer is divided into the second material layer included in the photoelectric sensing area by the second groove.

9. The method for manufacturing an image sensor according to claim 8, wherein: At least one second doping layer is formed on the substrate, comprising: depositing at least one doping layer on the substrate and diffusing the doping elements in the formed doping layer downward through an annealing process to form the second doping layer with a concentration of the doping elements gradually changing in a direction perpendicular to the surface of the substrate.

10. The method for manufacturing an image sensor according to claim 7, wherein: Forming a photoelectric sensing region on the substrate and forming an isolation structure between adjacent photoelectric sensing regions on the substrate, further comprising: forming an isolation layer and etching the isolation layer before forming at least one second doping layer on the substrate to form a first deep trench isolation structure included in the isolation structure at a preset position of the isolation structure; Etching a portion of the first doped layer at the wall of the first groove, comprising: etching a portion of the first doped layer at the wall of the first groove so that a projection of an edge of the formed first material layer on the surface of the first deep trench isolation structure falls within an edge of the surface of the first deep trench isolation structure.

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