Image sensor and method for forming image sensor pixel structure

Abstract

This invention provides an image sensor and a method for forming an image sensor pixel structure, applicable to the field of semiconductor technology. The method involves surface implantation of first-conductivity ions at locations corresponding to the conductive plug formation area in a semiconductor substrate before forming the conductive plug. This implanted ions adsorb metal ions, reducing diffusion and contamination of metal ions within the pixel structure, thereby reducing white pixels. Furthermore, this invention provides three optimized photomasks for implanting the first-conductivity ions into specific areas of the image sensor pixel structure, maximizing the adsorption capacity of the implanted first-conductivity ions on metal ions diffused into the image sensor pixel structure during the first-conductivity ion implantation process on the semiconductor substrate.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an image sensor and a method for forming the pixel structure of the image sensor. Background Technology

[0002] CMOS image sensors have developed rapidly over the past decade and are now widely used in mobile phones, computers, digital cameras, and other fields. Typically, an active pixel unit in a CMOS image sensor contains a photodiode (PD) and several transistors located in an epitaxial layer. Taking a 4T structure CMOS image sensor as an example, the four transistors specifically include a transfer transistor (Tx), a source follower (SF), a reset transistor (RST), and a row select transistor (RS). The basic working principle of a CMOS image sensor is as follows: Before illumination, the reset and transfer transistors are turned on, releasing the existing electrons in the photodiode region; during illumination, all transistors are turned off, generating charge in the space charge region of the photodiode; during readout, the transfer transistor is turned on, transferring the charge stored in the PD region to the floating diffusion node (FD). After the transfer, the transfer transistor is turned off, awaiting the next illumination. The charge signal at the floating diffusion node is then used to adjust the source follower, converting the charge into voltage, and outputting current to the analog-to-digital converter circuit through the row select transistor.

[0003] White pixels are a crucial indicator for evaluating the performance of CMOS image sensors, significantly impacting image quality. Therefore, improving manufacturing processes to reduce white pixel generation is a key direction for CIS process improvement. White pixels (WP) refer to the number of pixels with a DN value greater than 64 output by a CIS device under no-light conditions.

[0004] Currently, a major factor contributing to white pixels in CMOS image sensors is metal contamination introduced during the manufacturing process. These metal ions introduced during manufacturing generate a large number of white pixels, significantly affecting image quality. Summary of the Invention

[0005] The purpose of this invention is to provide a method for forming the pixel structure of an image sensor, so as to improve the problem of white pixels in the image sensor caused by the diffusion of metal ions in the photodiode region and the floating diffusion region when forming the metal plug of the image sensor.

[0006] In a first aspect, to solve the above-mentioned technical problems, the present invention provides a method for forming a pixel structure of an image sensor, comprising at least the following steps:

[0007] A semiconductor substrate is provided, wherein a patterned gate structure is formed on the surface of the semiconductor substrate, and a photodiode region and a floating diffusion region are formed in the semiconductor substrate located on both sides of the patterned gate structure, respectively.

[0008] Using a preset ion implantation mask, at least a portion of the surface region of the photodiode region and the floating diffusion region is implanted with ions of the first conductivity type. The preset ion implantation mask defines the position of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for the first conductivity type ion implantation.

[0009] A metal layer is deposited on the surface of the photodiode region and the floating diffusion region, which have been implanted with ions of the first conductivity type, to form corresponding conductive plugs on the surface of the photodiode region and the floating diffusion region.

[0010] Furthermore, the first conductivity type ion can be a P-type ion.

[0011] Furthermore, the first type of conductive ion may include carbon ions.

[0012] Furthermore, the step of performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region and the floating diffusion region using a preset ion implantation mask may include:

[0013] A first photomask is formed, which shields the patterned gate structure and simultaneously exposes the entire surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region.

[0014] Using the first photomask as a mask, ion implantation of the first conductivity type is performed on the semiconductor substrate to form a first implantation layer on the entire surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region.

[0015] Furthermore, the step of performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region and the floating diffusion region using a preset ion implantation mask may include:

[0016] A second photomask is formed, which shields all areas on the semiconductor substrate surface corresponding to the patterned gate structure, the photodiode region, and the floating diffusion region except for the areas used to form the conductive plug, while simultaneously exposing the areas on the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region used to form the conductive plug.

[0017] Using the second photomask as a mask, a first conductivity type ion implantation is performed on the region on the semiconductor substrate surface corresponding to the exposed photodiode region and the floating diffusion region that is used to form the conductive plug, so as to form a second implantation layer on the surface region on the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region that is used to form the conductive plug.

[0018] The further step of performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region and the floating diffusion region using a preset ion implantation mask may include:

[0019] A third photomask is formed, which shields the patterned gate structure and the portion of the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region that is used to form the conductive plug, while simultaneously exposing the portion of the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region that is used to form the conductive plug and the adjacent side region.

[0020] Using the third photomask as a mask, first conductivity type ion implantation is performed on the region on the semiconductor substrate surface corresponding to the exposed photodiode region and the floating diffusion region where the conductive plug is formed, as well as the region on one side thereto, to form a third implantation layer on the surface region on the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region where the conductive plug is formed, as well as the surface region on one side thereto.

[0021] Furthermore, the material of the deposited metal layer may include tungsten.

[0022] Furthermore, before performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region and the floating diffusion region using a preset ion implantation mask, the formation method provided by the present invention may further include: forming sidewall structures on both sides of the patterned gate structure.

[0023] Furthermore, after performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region and the floating diffusion region using a preset ion implantation mask, the formation method provided by the present invention may further include: annealing the semiconductor substrate after first conductivity type ion implantation.

[0024] Secondly, based on the same inventive concept as the image sensor pixel structure formation method described above, the present invention also provides an image sensor, wherein the image sensor provided by the present invention may include a plurality of pixel structures, wherein each pixel structure is formed using the image sensor pixel structure formation method described above.

[0025] Compared with the prior art, the technical solution of the present invention has at least one of the following beneficial effects:

[0026] This invention provides a method for forming an image sensor pixel structure. Specifically, before forming the conductive plugs of the image sensor pixel structure, a first type of conductive ions are implanted into the semiconductor substrate at the location corresponding to the region where the conductive plugs are formed. This is done by adsorbing metal ions with the implanted ions, thereby reducing the diffusion and contamination of metal ions in the pixel structure and thus reducing the number of white pixels in the image sensor pixel structure.

[0027] Furthermore, the present invention provides three optimized photomasks for implanting the first conductivity type ions into specific regions of the image sensor pixel structure, so as to maximize the adsorption capacity of the implanted first conductivity type ions on the metal ions diffused into the image sensor pixel structure when implanting the first conductivity type ions into the semiconductor substrate. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a method for forming the pixel structure of an image sensor according to an embodiment of the present invention;

[0029] Figures 2a to 2f This is a schematic diagram of the fabrication process of a method for forming the pixel structure of an image sensor according to an embodiment of the present invention.

[0030] The reference numerals in the attached figures are as follows:

[0031] 100 - Semiconductor substrate; 110 - Patterned gate structure;

[0032] 120a - First injection layer; 120b - Second injection layer;

[0033] 120c - Third injection layer; 130 - Conductive plug;

[0034] PD - Photodiode region; FD - Floating diffusion region. Detailed Implementation

[0035] As described in the background section, white pixels are an important indicator for evaluating the performance of CMOS image sensors and can significantly affect the imaging quality. Therefore, improving the manufacturing process to reduce white pixel generation is a crucial direction for CIS process improvement. White pixels (WP) refer to the number of pixels with a DN value greater than 64 output by a CIS device under no-light conditions.

[0036] Currently, a major factor contributing to white pixels in CMOS image sensors is metal contamination introduced during the manufacturing process. These metal ions introduced during manufacturing generate a large number of white pixels, significantly affecting image quality.

[0037] To address this problem, the researchers of this invention proposed a novel ion implantation method. Specifically, before the formation of the metal conductive plug (CT) in the pixel structure of a CMOS image sensor, carbon compounds are implanted into the surface layer of the corresponding semiconductor substrate to absorb metal ions. This reduces the impact of metal ion contamination on the pixel structure and ultimately improves the white pixel problem in CIS devices.

[0038] Based on this, the present invention provides a method for forming the pixel structure of an image sensor to improve the problem of white pixels in the image sensor caused by the diffusion of metal ions in the photodiode region and the floating diffusion region when forming the metal plug of the image sensor.

[0039] refer to Figure 1 , Figure 1 This is a flowchart illustrating a method for forming a pixel structure in an image sensor according to the present invention. Specifically, it may include the following steps:

[0040] Step S100: A semiconductor substrate is provided, wherein a patterned gate structure is formed on the surface of the semiconductor substrate, and a photodiode region and a floating diffusion region are formed in the semiconductor substrate located on both sides of the patterned gate structure, respectively.

[0041] Step S200: Using a preset ion implantation mask, at least a portion of the surface region of the photodiode region and the floating diffusion region is implanted with ions of the first conductivity type. The preset ion implantation mask defines the position of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for the first conductivity type ion implantation.

[0042] Step S300: Deposit a metal layer on the surface of the photodiode region and the floating diffusion region where the first type of conductivity ions have been implanted, so as to form a corresponding conductive plug on the surface of the photodiode region and the floating diffusion region.

[0043] That is, the present invention provides a method for forming an image sensor pixel structure. Specifically, before forming the conductive plug of the image sensor pixel structure, a first type of conductive ion is implanted into the semiconductor substrate at the position corresponding to the region for forming the conductive plug. The diffusion and contamination of metal ions in the pixel structure are reduced by the adsorption of the implanted ions on metal ions, thereby reducing the number of white pixels in the image sensor pixel structure.

[0044] The image sensor and the method for forming the pixel structure of the image sensor proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention. Many specific details are set forth in the following description to provide a thorough understanding of this invention; however, this invention may also be implemented in other ways different from those described herein, and therefore this invention is not limited to the specific embodiments disclosed below.

[0045] As shown in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. In detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0046] Figures 2a to 2f This is a schematic diagram of the fabrication process of a method for forming the pixel structure of an image sensor according to an embodiment of the present invention.

[0047] In step S100, please refer to the following for details. Figure 2a As shown, a semiconductor substrate 100 is provided, on the surface of which a patterned gate structure 110 is formed, and a photodiode region PD and a floating diffusion region FD are formed in the semiconductor substrate 100 located on both sides of the patterned gate structure 110, respectively. The semiconductor substrate 100 can be any suitable substrate known in the art, such as at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon-on-insulator (SOI), silicon-on-insulator stacked (SSOI), silicon-on-insulator stacked (S-SiGeOI), silicon-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or it can be a double-sided polished wafer (DSP), or a ceramic substrate such as alumina, a quartz, or a glass substrate. For example, in this embodiment, the semiconductor substrate 100 is a silicon wafer.

[0048] In this embodiment, the image sensor is, for example, a CMOS image sensor, which may include a pixel region and a peripheral circuit region (not shown). The pixel region may include multiple pixel structures arranged in an array. Each pixel structure is used to convert incident light into an electrical signal output, and therefore includes a photodiode with photoelectric conversion function and multiple transistors (not shown) for controlling electronic readout. For example, the pixel structure of the CMOS image sensor in this embodiment of the invention can be a pixel structure with 4 pixels sharing a floating diffusion point. In the pixel structure with 4 pixels sharing a floating diffusion point, the gate of the transmission transistor TX is the patterned gate structure 110 described in this invention, and the source / drain on both sides of it serves as the photodiode region PD and the floating diffusion region FD of the pixel structure with 4 pixels sharing a floating diffusion point, respectively. Since the device region of the CMOS image sensor can contain multiple pixel structures, a trench isolation structure (not shown) for isolating two adjacent pixel structures can also be formed on the semiconductor substrate 100 provided in this invention, for example, a shallow trench isolation structure (STI).

[0049] It should be noted that, in another embodiment, the photodiode region 110 can also be used to connect to a charge-coupled device (CCD) image sensor. For numerous pixel structures distributed in the pixel region, this embodiment of the invention will describe one pixel structure, whose cross-sectional structure employs the following... Figure 2b The structure may be shown as 2c, 2d, or 2e. It is understood that among the many pixel structures in a pixel region, some pixel structures may also adopt a design different from the structure described in this invention.

[0050] Furthermore, after step S100 above and before step S200 below, when at least a portion of the surface region of the photodiode region and the floating diffusion region is implanted with ions of the first conductivity type using a preset ion implantation mask, the method for forming an image sensor provided by the present invention may further include forming sidewall structures (not shown) on both sides of the patterned gate structure 110.

[0051] In step S200, a first conductivity type ion implantation is performed on at least a portion of the surface region of the photodiode region PD and the floating diffusion region FD using a preset ion implantation mask. The preset ion implantation mask defines the position of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD for the first conductivity type ion implantation.

[0052] In this embodiment, three optimized photomasks (preset ion implantation photomasks) proposed by the researchers of this invention for implanting the first conductivity type ions into specific areas of the image sensor pixel structure can be used to maximize the adsorption capacity of the implanted first conductivity type ions on the metal ions diffused into the image sensor pixel structure during the first conductivity type ion implantation into the semiconductor substrate 100. The first conductivity type ion is a p-type ion. Preferably, the first conductivity type ion can be a carbon ion. The researchers of this invention have discovered that by injecting carbon compounds under the metal plug CT in the image sensor pixel structure to absorb metal ions, the impact of metal ion contamination on the pixel can be reduced, that is, the problem of white pixels in CIS devices can be improved, especially for the absorption of tungsten W, the metal material of the metal plug CT.

[0053] Specifically, the present invention provides a method for performing first conductivity type ion implantation on at least a portion of the surface region of the photodiode region PD and the floating diffusion region FD using three types of photomasks, as detailed in the following description.

[0054] Example 1, specifically as follows: Figure 2b As shown, carbon ion implantation can be performed on the entire surface region of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD using the first photomask. Specifically, this can include the following steps:

[0055] First, a first photomask is formed, which shields the patterned gate structure 110 and simultaneously exposes the entire surface of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD.

[0056] Next, using the first photomask as a mask, the semiconductor substrate 100 is subjected to ion implantation of the first conductivity type to form a first implantation layer 120a on the entire surface of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD.

[0057] Example 2, specifically as follows: Figure 2c As shown, the second photomask can be used to perform carbon ion implantation on the surface layer of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD, which is used to form the conductive plug CT in the future. Meanwhile, all other areas of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD, except for the area used to form the conductive plug CT, are covered up; that is, carbon ion implantation is not performed. Specifically, this can include the following steps:

[0058] First, a second photomask is formed, which shields all areas on the surface of the semiconductor substrate 100 corresponding to the patterned gate structure 110, the photodiode region PD, and the floating diffusion region FD, except for the areas used to form the conductive plug, while simultaneously exposing the areas on the surface of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD used to form the conductive plug.

[0059] Next, using the second photomask as a mask, a first conductivity type ion implantation is performed on the region on the surface of the semiconductor substrate 100 corresponding to the exposed photodiode region PD and the floating diffusion region FD, which is used to form the conductive plug, so as to form a second implantation layer 120b on the surface region on the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD, which is used to form the conductive plug.

[0060] Example 3, specifically as follows: Figure 2d or Figure 2e As shown, carbon ion implantation can be performed on the surface layer of the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD, as well as on the surface layer of the semiconductor substrate 100 located on either side of the conductive plug CT, using the third photomask. Specifically, this can include the following steps:

[0061] First, a third photomask is formed, which shields the patterned gate structure 110 and the portion of the semiconductor substrate 100 surface corresponding to the photodiode region PD and the floating diffusion region FD that is used to form the conductive plug, while simultaneously exposing the portion of the semiconductor substrate 100 surface corresponding to the photodiode region PD and the floating diffusion region FD that is used to form the conductive plug and the adjacent side region.

[0062] Next, using the third photomask as a mask, a first conductivity type ion implantation is performed on the region on the surface of the semiconductor substrate 100 corresponding to the exposed photodiode region PD and the floating diffusion region FD, which is used to form the conductive plug and the adjacent side region, so as to form a third implantation layer 120c on the surface region on the semiconductor substrate 100 corresponding to the photodiode region PD and the floating diffusion region FD, which is used to form the conductive plug and the adjacent side region.

[0063] It should be noted that, regardless of which example of carbon ion implantation is used, the semiconductor substrate 100 needs to be annealed after carbon ion implantation, for example, by an RTA process, to remove the lattice loss caused by ion implantation to the semiconductor substrate.

[0064] In step S300, please refer to the following for details. Figure 2f As shown, a metal layer is deposited on the surfaces of the photodiode region PD and the floating diffusion region FD, which have been implanted with ions of the first conductivity type, to form corresponding conductive plugs 130 on the surfaces of the photodiode region PD and the floating diffusion region FD. Preferably, the material of the deposited metal layer is tungsten W.

[0065] In this embodiment of the invention, after ion implantation of the photodiode region PD and the floating diffusion region FD in the three examples used in step S200 above, a conductive plug 130 can be formed on the corresponding carbon ion implantation layer (first implantation layer, second implantation layer or third implantation layer). For example, the present invention uses the structure of forming the second implantation layer 120b in Example 2 as an example, and then forms the conductive plug 130.

[0066] Based on the image sensor pixel structure formation method described above, this embodiment of the invention also provides an image sensor, which includes multiple pixel structures, wherein each pixel structure can be formed using the image sensor pixel structure formation method described above.

[0067] In summary, the present invention provides a method for forming an image sensor pixel structure. Specifically, before forming the conductive plugs of the image sensor pixel structure, surface implantation of first-type conductive ions is performed at the positions corresponding to the conductive plug regions in the semiconductor substrate. This reduces the diffusion and contamination of metal ions in the pixel structure through the adsorption effect of the implanted ions, thereby reducing the number of white pixels in the image sensor pixel structure.

[0068] Furthermore, the present invention provides three optimized photomasks for implanting the first conductivity type ions into specific regions of the image sensor pixel structure, so as to maximize the adsorption capacity of the implanted first conductivity type ions on the metal ions diffused into the image sensor pixel structure when implanting the first conductivity type ions into the semiconductor substrate.

[0069] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the 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 present invention shall still fall within the scope of protection of the present invention.

[0070] It should also be understood that, unless otherwise specified or indicated, the terms “first,” “second,” “third,” etc., in the specification are used only to distinguish the various components, elements, and steps in the specification, and not to indicate the logical or sequential relationships between the various components, elements, and steps.

[0071] Furthermore, it should be recognized that the terminology described herein is used only to describe particular embodiments and not to limit the scope of the invention. It must be noted that the singular forms “a” and “an” used herein and in the appended claims include plural bases unless the context clearly indicates otherwise. For example, a reference to “a step” or “an apparatus” means a reference to one or more steps or apparatuses, and may include secondary steps and secondary apparatuses. All conjunctions used should be understood in the broadest sense. Also, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive OR”, unless the context clearly indicates otherwise. Furthermore, implementation of the methods and / or devices in embodiments of the invention may include performing selected tasks manually, automatically, or in combination.

Claims

1. A method of forming an image sensor pixel structure, characterized by, Comprising: providing a semiconductor substrate, a patterned gate structure being formed on a surface of the semiconductor substrate, and a photodiode region and a floating diffusion region being formed in the semiconductor substrate on two sides of the patterned gate structure respectively; performing first-conductivity-type ion implantation on at least partial surface layer regions of the photodiode region and the floating diffusion region by using a preset ion implantation mask, wherein the preset ion implantation mask defines positions of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for the first-conductivity-type ion implantation; depositing a metal layer on surfaces of the photodiode region and the floating diffusion region implanted with the first-conductivity-type ions, so as to form corresponding conductive plugs on the surfaces of the photodiode region and the floating diffusion region; the first-conductivity-type ions are P-type ions; the first-conductivity-type ions include carbon ions; the step of performing first-conductivity-type ion implantation on at least partial surface layer regions of the photodiode region and the floating diffusion region by using a preset ion implantation mask comprises: forming a first mask, the first mask shielding the patterned gate structure and simultaneously exposing the entire surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region; performing first-conductivity-type ion implantation on the semiconductor substrate by using the first mask as a mask, so as to form a first implantation layer on the entire surface layer of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region; or the step of performing first-conductivity-type ion implantation on at least partial surface layer regions of the photodiode region and the floating diffusion region by using a preset ion implantation mask comprises: forming a second mask, the second mask shielding the patterned gate structure and all regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region except for regions for forming the conductive plugs, and simultaneously exposing the regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for forming the conductive plugs; performing first-conductivity-type ion implantation on the exposed regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for forming the conductive plugs by using the second mask as a mask, so as to form a second implantation layer on surface layer regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for forming the conductive plugs; or the step of performing first-conductivity-type ion implantation on at least partial surface layer regions of the photodiode region and the floating diffusion region by using a preset ion implantation mask comprises: forming a third mask, the third mask shielding the patterned gate structure and partial regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region except for regions for forming the conductive plugs, and simultaneously exposing the regions on the surface of the semiconductor substrate corresponding to the photodiode region and the floating diffusion region for forming the conductive plugs and a side region adjacent to the regions; Exposing the semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region to a third mask, and performing ion implantation of the first conductive type on the exposed semiconductor substrate surface corresponding to the photodiode region and the floating diffusion region to form a third implanted layer on the surface layer region corresponding to the photodiode region and the floating diffusion region.

2. The method for forming an image sensor pixel structure according to claim 1, wherein The material of the deposited metal layer includes tungsten.

3. The method of forming a pixel structure of an image sensor according to claim 1, wherein Before performing ion implantation of the first conductive type on at least part of the surface layer region of the photodiode region and the floating diffusion region using a preset ion implantation mask, the method further comprises forming a sidewall structure on both sides of the patterned gate structure.

4. The method of forming a pixel structure of an image sensor according to claim 1, wherein After performing ion implantation of the first conductive type on at least part of the surface layer region of the photodiode region and the floating diffusion region using a preset ion implantation mask, the method further comprises performing an annealing process on the semiconductor substrate after the ion implantation of the first conductive type.

5. An image sensor, characterized by, The image sensor comprises a plurality of pixel structures, wherein each of the pixel structures is formed by the method for forming an image sensor pixel structure according to any one of claims 1 to 4.

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