Image sensor and preparation method thereof
By designing a structure of a transmission gate and floating diffusion region with included angles and gradually smaller distances in the image sensor, a good carrier transmission path is established, and the dark current and leakage problems are solved, and the image quality and performance of the image sensor are improved.
Patent Information
- Application Number
- CN202510472601.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-07-11
AI Technical Summary
There are adverse conditions such as dark current and leakage in existing image sensors, which affect image quality.
An image sensor is designed, including a substrate, a photoelectric conversion region and a floating diffusion region. The transmission gate and the floating diffusion region are arranged at intervals. There is an angle between the surface of the transmission gate and the surface of the floating diffusion region, and the upper surface distance gradually becomes smaller along the direction of the photoelectric conversion region pointing to the floating diffusion region, forming a good carrier transmission path.
Effectively reduce dark current and leakage, improve image quality, improve image delay phenomenon, increase full well capacity, and improve signal-to-noise ratio and dynamic range.
Smart Images
Figure CN120302734A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of semiconductor manufacturing, and more particularly to an image sensor and a method for manufacturing the same. Background Art
[0002] An image sensor is a semiconductor device that converts incident light into an electrical signal and generates image information corresponding to the incident light. With the development of the computer industry and the communication industry, it has been widely used in various fields (such as smart phones, wearable devices, digital cameras, PCS (Personal Communication Systems), game consoles, security cameras, medical micro cameras, etc.).
[0003] However, with the continuous progress of image sensor technology, there are still many problems to be improved in practical applications. Summary of the Invention
[0004] Embodiments of the present disclosure provide an image sensor, including:
[0005] A substrate;
[0006] A photoelectric conversion region located on the substrate;
[0007] A floating diffusion region spaced apart from the photoelectric conversion region, the floating diffusion region including at least a first surface;
[0008] A transfer gate, the transfer gate including at least a first transfer gate, the first transfer gate including at least a second surface, the second surface being disposed adjacent to the first surface of the floating diffusion region, and in a direction from the photoelectric conversion region to the corresponding floating diffusion region, the distance from the second surface to the first surface gradually decreases, and a first preset angle is formed between the first surface and the second surface.
[0009] In some embodiments, the number of the transfer gates is multiple, the transfer gate further includes a second transfer gate adjacent to the first transfer gate, the second transfer gate further includes a third surface, the third surface of the second transfer gate is disposed opposite to the second surface of the first transfer gate, and in a direction from the photoelectric conversion region to the corresponding floating diffusion region, the distance from the second surface of the first transfer gate to the third surface of the second transfer gate gradually decreases, and a second preset angle is formed between the second surface and the third surface.
[0010] In some embodiments, the range of the first preset angle is greater than 0° and less than or equal to 10°;
[0011] And / or
[0012] The range of the second preset angle is greater than 0° and less than or equal to 10°.
[0013] In some embodiments, in a direction parallel to the plane of the substrate, the cross-sectional shape of the transfer gate includes a polygon, and the polygon includes one of a triangle, a quadrilateral, a pentagon, and a hexagon.
[0014] In some embodiments, the image sensor includes a plurality of pixel regions, and a single pixel region at least includes the floating diffusion region, the photoelectric conversion region, and the transfer gate; the number of the transfer gates includes a plurality, and on a side adjacent to the floating diffusion region, the distance between the two closest ends of adjacent transfer gates is between 1 / 5 and 1 / 3 of the dimension value of a single pixel region in a direction parallel to the substrate.
[0015] In some embodiments, the minimum distance range between adjacent two transfer gates is between 100 nm and 200 nm, and the maximum distance range is between 150 nm and 400 nm.
[0016] In some embodiments, the image sensor further includes a gate structure, and the gate structure is located on the transfer gate and is connected to the transfer gate.
[0017] The embodiments of the present disclosure further provide a method for manufacturing an image sensor, and the manufacturing method includes:
[0018] Providing a substrate;
[0019] Forming a photoelectric conversion region on the substrate;
[0020] Forming a transfer gate, and the transfer gate at least includes a first transfer gate, and the first transfer gate at least includes a second surface;
[0021] Forming a floating diffusion region, the floating diffusion region is disposed at an interval from the photoelectric conversion region, and the floating diffusion region at least includes a first surface; the first surface is disposed adjacent to the second surface of the first transfer gate, and in a direction from the photoelectric conversion region to the corresponding floating diffusion region, the distance from the second surface to the first surface gradually becomes smaller, and there is a first preset angle between the first surface and the second surface.
[0022] In some embodiments, before forming at least one transfer gate, the manufacturing method further includes:
[0023] Forming at least one trench structure, and the trench structure is located on the photoelectric conversion region;
[0024] Forming a dielectric material layer on the surface of the trench structure, and the dielectric material layer at least covers the side walls and the bottom of the trench structure;
[0025] A doping process is performed on the dielectric material layer to form a doped region.
[0026] In some embodiments, the number of the transfer gates includes a plurality. After performing the doping process, forming the transfer gates includes:
[0027] Forming a conductive material layer, the conductive material layer filling the trench structure and connecting a plurality of adjacent transfer gates;
[0028] Wherein, the transfer gate further includes a second transfer gate disposed adjacent to the first transfer gate. The second transfer gate further includes a third surface. The third surface of the second transfer gate is disposed opposite to the second surface of the first transfer gate. Along the direction from the photoelectric conversion region to the floating diffusion region corresponding thereto, the distance from the second surface of the first transfer gate to the third surface of the second transfer gate gradually becomes smaller, and there is a second preset angle between the second surface and the third surface.
[0029] The image sensor and its manufacturing method provided by the embodiments of the present disclosure. Wherein, the image sensor includes: a substrate; a photoelectric conversion region located on the substrate; a floating diffusion region spaced apart from the photoelectric conversion region. The floating diffusion region at least includes a first surface; a transfer gate at least including a first transfer gate. The first transfer gate at least includes a second surface. The second surface is disposed adjacent to the first surface of the floating diffusion region. Along the direction from the photoelectric conversion region to the floating diffusion region corresponding thereto, the distance from the second surface to the first surface gradually becomes smaller, and there is a first preset angle between the first surface and the second surface. In the embodiments of the present disclosure, due to the first preset angle between the second surface of the provided first transfer gate and the first surface of the floating diffusion region, and along the direction from the photoelectric conversion region to the floating diffusion region corresponding thereto, the setting method of the distance from the second surface to the first surface gradually becoming smaller is adopted. In the embodiments of the present disclosure, during the process of the electrons generated in the photoelectric conversion region being transferred from the photoelectric conversion region to the floating diffusion region, in the region between the first surface and the second surface, the electric potential on the side adjacent to the floating diffusion region can be greater than the electric potential on the side adjacent to the photoelectric conversion region. That is, a good carrier transfer path is established between the floating diffusion region and the first transfer gate, so that the photo-generated carriers generated in the photoelectric conversion region can be transferred to the floating diffusion region to a greater extent or even tend to be completely transferred, so as to reduce the occurrence of adverse conditions such as dark current and leakage, thereby improving phenomena such as image delay and improving image quality.
[0030] Details of one or more embodiments of the present disclosure are set forth in the following drawings and description. Other features and advantages of the present disclosure will become apparent from the specification and drawings. Description of the Drawings
[0031] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0032] Figures 1a to 1c Schematic structural diagram of an image sensor provided by an embodiment of the present disclosure; wherein, Figure 1a Top view schematic diagram of the image sensor, Figure 1b is along Figure 1a Detail cross-sectional view in the A1 - A2 direction of Figure 1c is along Figure 1a Detail cross-sectional view in the B1 - B2 direction of
[0033] Figures 2a to 2c Schematic structural diagram of another image sensor provided by an embodiment of the present disclosure; wherein, Figure 2a Top view schematic diagram of the image sensor, Figure 2b is along Figure 2a Detail cross-sectional view in the A1 - A2 direction of Figure 2c is along Figure 2a Detail cross-sectional view in the B1 - B2 direction of
[0034] Figures 3a to 3c Schematic structural diagram of yet another image sensor provided by an embodiment of the present disclosure; wherein, Figure 3a Top view schematic diagram of the image sensor, Figure 3b is along Figure 3a Detail cross-sectional view in the A1 - A2 direction of Figure 3c is along Figure 3a Detail cross-sectional view in the B1 - B2 direction of
[0035] Figure 4 Flow chart of the method for manufacturing an image sensor provided by an embodiment of the present disclosure;
[0036] Figures 5 to 10 Process flow chart of the method for manufacturing an image sensor provided by an embodiment of the present disclosure;
[0037] Figure 11 is Figure 10 Top view schematic diagram of the image sensor provided. Detailed Description of the Embodiments
[0038] Exemplary embodiments disclosed herein will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.
[0039] In the following description, numerous specific details are given to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without one or more of these details. In other instances, well-known features have not been described in order to avoid obscuring the present disclosure; that is, not all features of actual embodiments are described here, and well-known functions and structures are not described in detail.
[0040] In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. Like reference numerals denote like elements throughout.
[0041] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not imply that a first element, component, region, layer, or part necessarily exists in the present disclosure.
[0042] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein for convenience of description to describe the relationship of one element or feature shown in the figure with other elements or features. It should be understood that, in addition to the orientation shown in the figure, the spatial relationship terms are also intended to include different orientations of the device in use and operation. For example, if the device in the drawing is flipped, then the element or feature described as "under other elements" or "beneath it" or "under it" will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "beneath" can include both the upper and lower orientations. The device can be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.
[0043] The purpose of the terms used herein is only to describe specific embodiments and not to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, identify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the related listed items.
[0044] A CMOS (Complementary Metal-Oxide-Semiconductor) image sensor (CIS) is a semiconductor device that converts an incident light signal into an electrical signal and generates image information corresponding to the incident light, and has been widely used in fields such as consumer electronics, security, and industry. An image sensor typically includes structures such as a floating diffusion region, a photoelectric conversion region, and a transfer gate. Although great progress has been made in technology for image sensors with the development of the computer industry and the communication industry, there are still occurrences of dark current and leakage, etc.
[0045] Based on this, the following technical solutions of the embodiments of the present disclosure are proposed:
[0046] The embodiments of the present disclosure provide an image sensor, including:
[0047] A substrate;
[0048] A photoelectric conversion region, the photoelectric conversion region being located on the substrate;
[0049] A floating diffusion region, the floating diffusion region being spaced apart from the photoelectric conversion region, the floating diffusion region including at least a first surface;
[0050] The transfer gate includes at least a first transfer gate, and the first transfer gate includes at least a second surface. The second surface is disposed adjacent to the first surface of the floating diffusion region. Along the direction from the photoelectric conversion region to the correspondingly disposed floating diffusion region, the distance from the second surface to the first surface gradually decreases, and there is a first preset angle between the first surface and the second surface.
[0051] In the embodiment of the present disclosure, since there is a first preset angle between the second surface of the provided first transfer gate and the first surface of the floating diffusion region, and along the direction from the photoelectric conversion region to the correspondingly disposed floating diffusion region, the distance from the second surface to the first surface gradually decreases, in the embodiment of the present disclosure, when the electrons generated in the photoelectric conversion region are transferred from the photoelectric conversion region to the floating diffusion region, in the region between the first surface and the second surface, the electric potential on the side adjacent to the floating diffusion region can be greater than the electric potential on the side adjacent to the photoelectric conversion region. That is, a good carrier transfer path is established between the floating diffusion region and the first transfer gate, so that the photo-generated carriers generated in the photoelectric conversion region can be transferred to the floating diffusion region to a large extent or even tend to be completely transferred, thereby reducing the occurrence of adverse conditions such as dark current and leakage, and thus improving phenomena such as image delay and improving image quality.
[0052] To make the above objects, features, and advantages of the present disclosure more obvious and understandable, the following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. When describing the embodiments of the present disclosure in detail, for the convenience of explanation, the schematic diagrams will be enlarged locally not in accordance with the general scale, and the schematic diagrams are only examples and should not limit the protection scope of the present disclosure here.
[0053] Figures 1a to 1c It is a schematic structural diagram of an image sensor provided by an embodiment of the present disclosure; wherein, Figure 1a It is a top view schematic diagram of the image sensor, Figure 1b It is along Figure 1a A detailed cross-sectional view in the A1 - A2 direction of Figure 1c It is along Figure 1a A detailed cross-sectional view in the B1 - B2 direction of Figures 2a to 2c It is a schematic structural diagram of another image sensor provided by an embodiment of the present disclosure; wherein, Figure 2a It is a top view schematic diagram of the image sensor, Figure 2b It is along Figure 2a A detailed cross-sectional view in the A1 - A2 direction of Figure 2c It is along Figure 2a A detailed cross-sectional view in the B1 - B2 direction of Figures 3a to 3c It is a schematic structural diagram of yet another image sensor provided by an embodiment of the present disclosure; wherein, Figure 3a It is a top view schematic diagram of the image sensor, Figure 3b It is along Figure 3aDetailed cross-sectional view in the A1 - A2 direction, Figure 3c which is Figure 3a a detailed cross-sectional view in the B1 - B2 direction along...
[0054] As Figures 1a to 1c shown, the image sensor includes:
[0055] a substrate 10;
[0056] a photoelectric conversion region PD, which is located on the substrate 10;
[0057] a floating diffusion region FD, which is spaced apart from the photoelectric conversion region PD, and the floating diffusion region FD at least includes a first surface S1;
[0058] a transfer gate VTG, which at least includes a first transfer gate VTG1, the first transfer gate VTG1 at least includes a second surface S2, the second surface S2 is disposed adjacent to the first surface S1 of the floating diffusion region FD, and along the direction from the photoelectric conversion region PD to the correspondingly disposed floating diffusion region FD, the distance from the second surface S2 to the first surface S1 gradually decreases, and there is a first preset angle a between the first surface S1 and the second surface S2.
[0059] Here, the substrate 10 can be made of materials such as germanium, silicon germanide, silicon carbide, gallium arsenide, or indium gallium, but is not limited thereto. The substrate 10 can also be a silicon substrate 10 on an insulator surface or a germanium substrate 10 on an insulator surface, etc. In some embodiments, the substrate 10 can be a silicon substrate 10.
[0060] In some specific embodiments, the substrate 10 can be a lightly doped substrate.
[0061] The photoelectric conversion region PD can be formed in the semiconductor substrate 10 and generate charges (e.g., photo charges) based on incident light. For example, electron - hole pairs can be generated based on incident light, and the photoelectric conversion region PD can collect these electrons or holes.
[0062] In some embodiments, the photoelectric conversion region PD can be a photodiode, but is not limited thereto. In another embodiment, in addition to being a photodiode, the photoelectric conversion region PD can also be a pinned photodiode (abbreviation: PPD), a phototransistor, a photogate, or a combination thereof, which is not specifically limited herein.
[0063] In some embodiments, the transfer gate VTG extends in the vertical direction on the substrate 10 and is connected to the photoelectric conversion region PD, and the floating diffusion region FD is disposed in the substrate 10 and is spaced apart from the photoelectric conversion region PD in the vertical direction. The charges generated in the photoelectric conversion region PD can be transmitted through the transfer gate VTG and stored in the floating diffusion region FD.
[0064] In one embodiment, the floating diffusion region FD can be formed by doping impurities of a preset conduction type (e.g., n-type).
[0065] In some embodiments, in a direction parallel to the plane of the substrate 10, the cross-sectional shape of the transfer gate VTG includes a polygon, and the polygon includes one of a triangle, a quadrilateral, a pentagon, and a hexagon.
[0066] In some specific embodiments, in a direction parallel to the plane of the substrate 10, the cross-sectional shape of the transfer gate VTG can be a hexagon.
[0067] Continuing to refer to Figure 1a , in some embodiments, the first transfer gate VTG1 is disposed on one side of the floating diffusion region FD, and the first transfer gate VTG1 may further include a fourth surface S4. Among them, there is a first preset angle a between the first surface S1 and the second surface S2, and there is a third preset angle c between the fourth surface S4 and the first surface S1.
[0068] As Figure 1b and Figure 1c shown, the transfer gate VTG, that is, the first transfer gate VTG1, is connected to the photoelectric conversion region PD. The photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can reach the region where the floating diffusion region FD is located after being transferred in the region around the first transfer gate VTG1. Specifically, the photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can be transmitted to the position where the floating diffusion region FD is located via the paths between the first surface S1 and the second surface S2 and between the first surface S1 and the fourth surface S4 as shown in Figure 1a .
[0069] Here, the ranges of the first preset angle a and the third preset angle c can be between greater than 0° and less than or equal to 10° (including the end values), for example, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc.
[0070] It can be understood that in the embodiments of the present disclosure, when the shape of the transfer gate VTG is a hexagon, it has two non-parallel surfaces at a position adjacent to the floating diffusion region FD, namely the second surface S2 and the fourth surface S4. Since the plane where the fourth surface S4 is located is in a state that is more inclined to be parallel to the first surface S1 relative to the plane where the second surface S2 is located. Therefore, in the direction from the photoelectric conversion region PD to the floating diffusion region FD, the third preset angle c between the fourth surface S4 and the first surface S1 is less than the first preset angle a between the second surface S2 and the first surface S1.
[0071] As a result, it can be ensured that when the electrical signal generated in the photoelectric conversion region PD is transferred to the floating diffusion region FD, not only can the electric potential at the first region C1 adjacent to the floating diffusion region FD be greater than the electric potential at the second region C2 adjacent to the photoelectric conversion region PD, but also, further, the electric potential between the first surface S1 and the fourth surface S4 can be further greater than the electric potential at the position of the first region C1. In this way, a good transmission path can be established for the transfer of the electrical signal (including but not limited to electrons, etc.) generated in the photoelectric conversion region PD, and the photo-generated charges can be effectively transferred to the floating diffusion region FD to a large extent or even tend to be completely transferred, so as to reduce the occurrence of adverse conditions such as dark current and leakage, thereby improving phenomena such as image delay and enhancing image quality.
[0072] It can be seen that in the embodiment of the present disclosure, by optimizing the shape of the transfer gate VTG, the included angle between the surfaces, etc., the photo-generated carriers (such as electrons) generated in the photoelectric conversion region PD are more likely to be transferred from the photoelectric conversion region PD to the floating diffusion region FD, reducing the residue of the photo-generated carriers (such as electrons) in the photoelectric conversion region PD. Therefore, the dark current and leakage caused by the residue of the photo-generated carriers (such as electrons) in the photoelectric conversion region PD can be reduced. Thus, phenomena such as image delay and leakage can be improved to enhance image quality.
[0073] In some embodiments, as Figures 2a to 2c shown, the number of the transfer gates VTG includes multiple. The transfer gate VTG further includes a second transfer gate VTG2 adjacent to the first transfer gate VTG1. The second transfer gate VTG2 further includes a third surface S3. The third surface S3 of the second transfer gate VTG2 is disposed opposite to the second surface S2 of the first transfer gate VTG1. Along the direction from the photoelectric conversion region PD to the corresponding floating diffusion region FD, the distance from the second surface S2 of the first transfer gate VTG1 to the third surface S3 of the second transfer gate VTG2 gradually decreases, and there is a second preset angle b between the second surface S2 and the third surface S3.
[0074] As Figure 2b and Figure 2c shown, both the first transfer gate VTG1 and the second transfer gate VTG2 included in the transfer gate VTG are connected to the photoelectric conversion region PD. The photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can reach the region where the floating diffusion region FD is located after being transferred in the regions around the first transfer gate VTG1 and the second transfer gate VTG2. Specifically, the photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can pass through such as Figure 2aThe paths between the first surface S1 and the second surface S2, between the first surface S1 and the fourth surface S4, and between the second surface S2 and the third surface S3 are transmitted to the position where the floating diffusion region FD is located.
[0075] In some embodiments, the range of the second preset angle b is greater than 0° and less than or equal to 10° (including the end values). For example, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc.
[0076] In this embodiment, in addition to forming a good transmission path between the first transfer gate VTG1 and the floating diffusion region FD, further, due to the addition of the second transfer gate VTG2, a path for the transfer of photo-generated carriers can also be established between the first transfer gate VTG1 and the second transfer gate VTG2. At the same time, since the distance from the second surface S2 of the first transfer gate VTG1 to the third surface S3 of the second transfer gate VTG2 gradually becomes smaller, and the second surface S2 and the third surface S3 are arranged with the second preset angle b, in this embodiment, the electric signal generated in the photoelectric conversion region PD, during the process of transferring to the floating diffusion region FD, the electric potential at the first region C1 adjacent to the floating diffusion region FD can be further greater than the electric potential at the second region C2 adjacent to the photoelectric conversion region PD. In this way, a better transmission path can be established for the transfer of the electric signal (including but not limited to electrons, etc.) generated in the photoelectric conversion region PD, and the photo-generated charges can be further effectively transferred to the floating diffusion region FD to a large extent or even tend to be completely transferred, so as to reduce the occurrence of adverse conditions such as dark current and leakage, thereby further improving phenomena such as image delay and further improving the image quality.
[0077] In some embodiments, as Figures 3a to 3c shown, in embodiments where the number of transfer gates VTG includes multiple, in addition to the first transfer gate VTG1 and the second transfer gate VTG2, the transfer gate VTG also includes a third transfer gate VTG3 arranged adjacent to the second transfer gate VTG2. The second transfer gate VTG2 also includes a fifth surface S5 opposite to the third surface S3. The third transfer gate VTG3 includes a sixth surface S6, and the sixth surface S6 is opposite to the fifth surface S5. Along the direction from the photoelectric conversion region PD to the corresponding floating diffusion region FD, the distance from the fifth surface S5 of the second transfer gate VTG2 to the sixth surface S6 of the third transfer gate VTG3 gradually becomes smaller, and there is a fourth preset angle d between the fifth surface S5 and the sixth surface S6.
[0078] As Figure 3b and Figure 3cAs shown, the transfer gate VTG includes a first transfer gate VTG1, a second transfer gate VTG2, and a third transfer gate VTG3, all of which are connected to the photoelectric conversion region PD. The photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can reach the region where the floating diffusion region FD is located after being transferred in the regions around the first transfer gate VTG1, the second transfer gate VTG2, and the third transfer gate VTG3. Specifically, the photo-generated carriers (including but not limited to electrons e-) generated in the photoelectric conversion region PD can pass through the paths between the first surface S1 and the second surface S2, between the first surface S1 and the fourth surface S4, between the second surface S2 and the third surface S3, and between the fifth surface S5 and the sixth surface S6 as shown in Figure 3a to be transferred to the position where the floating diffusion region FD is located.
[0079] In some embodiments, the range of the fourth preset angle d is greater than 0° and less than or equal to 10° (including the end values). For example, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc.
[0080] Thus, in the embodiments of the present disclosure, based on the embodiment in which a better transmission path can be established when the transfer gate VTG shown in the previous embodiment ( Figures 2a to 2c ) includes the first transfer gate VTG1 and the second transfer gate VTG2, in the embodiment shown in Figures 3a to 3c , since the transfer gate VTG includes not only the first transfer gate VTG1 and the second transfer gate VTG2 but also the third transfer gate VTG3, the introduction of the third transfer gate VTG3 further increases the number of transmission paths, so that in the direction from the photoelectric conversion region PD to the corresponding floating diffusion region FD, the photo-generated charges can be more effectively transferred to the floating diffusion region FD to a greater extent or even tend to be completely transferred, so as to reduce the occurrence of adverse situations such as dark current and leakage, thereby improving the image delay and other phenomena to a greater extent and further improving the image quality.
[0081] In any of the above embodiments, the image sensor includes a plurality of pixel regions P. A single pixel region P includes at least a floating diffusion region FD, a photoelectric conversion region PD, and a transfer gate VTG. The number of transfer gates VTG includes a plurality. On the side adjacent to the floating diffusion region FD, the distance between the two closest ends of adjacent transfer gates VTG is between 1 / 5 and 1 / 3 (including the end values) of the size value of a single pixel region P in the direction parallel to the substrate 10. For example, 1 / 4, 3 / 10, etc.
[0082] In some embodiments, the minimum distance D1 between two adjacent surfaces of the transmission gates VTG opposite to each other (e.g., the second surface S2 and the third surface S3, the fifth surface S5 and the sixth surface S6) ranges from 100 nm to 200 nm (including the endpoint values), such as 120 nm, 150 nm, 180 nm, 200 nm, etc. The maximum distance D2 ranges from 150 nm to 400 nm (including the endpoint values), such as 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, etc.
[0083] In this way, the embodiment of the present disclosure not only constrains the shape of the transmission gate VTG and the value of the angle between the adjacent structure, but also further constrains the maximum distance and the minimum distance between adjacent transmission gates VTG, so that the technical solution provided in the embodiment of the present disclosure can not only provide a good transmission path for the transmission of photogenerated carriers (such as electrons), but also effectively avoid the interference between adjacent transmission gates VTG that affects the performance of the image sensor, which helps to improve the performance of the image sensor.
[0084] In conventional technology, in order to reduce the difficulty of transferring photogenerated carriers from the photoelectric conversion region to the floating diffusion region, a region where the transmission path of photogenerated carriers from the photoelectric conversion region to the floating diffusion region is located is usually located (it can be understood that Figure 1b , Figure 2b and Figure 3b The electron e-shown in the figure (the area where the arrow near the electron e- is located) is subjected to two doping processes, and the two doping processes form a concentration difference in the area to reduce the difficulty of transferring photogenerated carriers.
[0085] In the embodiment of the present disclosure, Figure 1b , Figure 2b and Figure 3b As shown, since the transmission gate VTG in the embodiment of the present disclosure is constrained in the cross-sectional shape parallel to the plane of the substrate 10, the distance between it and other structures, and the angle between them, in the region where the transmission path of the photogenerated carriers in the photoelectric conversion region PD to the floating diffusion region FD is located (it can be understood that Figure 1b , Figure 2b and Figure 3b(in the area where the arrow is near the electron e- shown in the figure), when performing the doping operation, there is no need to pass through the two doping operations in this area, that is, there is no need to adopt a structure with a doping concentration difference to achieve the reduction of the difficulty of photo-generated carrier transfer. Instead, only by adopting the method of performing a single doping process, that is, only by adopting an operation involving a single photomask, a doping area with the effect of reducing the difficulty of photo-generated carrier transfer can be obtained. In this way, the number of photomasks can be effectively saved and the production cost can be saved. At the same time, it can also directly avoid the phenomenon of electron overflow under the transmission path when the transistor structure based on the transmission gate VTG is turned off.
[0086] In the embodiments of the present disclosure, whether the number of transmission gates VTG is single or multiple, it can play a good promoting effect on the transmission process of carriers from the photoelectric conversion region PD to the floating diffusion region FD, so that the photo-generated carriers generated in the photoelectric conversion region can be transferred to the floating diffusion region to a large extent or even tend to be completely transferred, so as to reduce the occurrence of adverse conditions such as dark current and leakage, thereby improving the occurrence of phenomena such as image delay. At the same time, in the embodiments where the transmission gate VTG includes multiple ones, the full well capacity (FWC, Full Well Capacity) can be further increased. A larger full well capacity (FWC) can enable the image sensor to have a better dynamic range and signal-to-noise ratio, and reduce the occurrence of image delay.
[0087] In some embodiments, the image sensor further includes a gate structure G, and the gate structure G is located on the transmission gate VTG and is connected to the transmission gate VTG.
[0088] It can be understood that when the number of transmission gates VTG includes multiple ones, the multiple transmission gates VTG in the same pixel P can be connected to each other through the gate structure G on the side far from the photoelectric conversion region PD.
[0089] It can be understood that Figure 1a to Figure 3c and the related text, taking the cross-sectional shape of the transmission gate VTG in the direction parallel to the plane of the substrate 10 as a hexagon as an example, the technical solutions provided by the embodiments of the present disclosure are described. However, it is not limited to this. In some other embodiments, as described above, the cross-sectional shape of the transmission gate VTG in the direction parallel to the plane of the substrate 10 can also be other shapes such as triangles, quadrilaterals, pentagons and other polygons. No matter what shape the transmission gate VTG is, as long as it meets the angle setting, distance setting, size setting, etc. provided by any of the above embodiments, it can provide a good path for the transmission of photo-generated carriers from the photoelectric conversion region PD to the floating diffusion region FD.
[0090] In some cases, when the shape of the transfer gate VTG is other shapes and the number of transfer gates VTG is multiple, in a top view, among the surfaces where two adjacent transfer gates VTG are oppositely arranged, along the direction from the photoelectric conversion region PD to the floating diffusion region FD, the extension length of the boundary on the surfaces where two adjacent transfer gates VTG are oppositely arranged can be slightly greater than the extension length of the boundary on other surfaces in other directions. In this way, on the basis of providing a good transfer path with a large length, the occupied area of the transfer gate VTG on the substrate 10 can be reduced, which helps to set multiple transfer gates VTG to provide more good transfer paths.
[0091] The embodiments of the present disclosure also provide a method for manufacturing an image sensor, as Figure 4 shown, the manufacturing method includes the following steps:
[0092] Step S101: Provide a substrate 10;
[0093] Step S102: Form a photoelectric conversion region PD on the substrate 10;
[0094] Form a transfer gate VTG, the transfer gate at least includes a first transfer gate VTG1, and the first transfer gate VTG1 at least includes a second surface S2;
[0095] Step S103: Form a floating diffusion region FD, the floating diffusion region FD is arranged at an interval from the photoelectric conversion region PD, and the floating diffusion region FD at least includes a first surface S1; the first surface S1 is arranged adjacent to the second surface S2 of the first transfer gate VTG1. Along the direction from the photoelectric conversion region PD to the corresponding floating diffusion region FD, the distance from the second surface S2 to the first surface S1 gradually becomes smaller, and there is a first preset angle between the first surface S1 and the second surface S2.
[0096] Figures 5 to 10 is a process flow chart of the method for manufacturing an image sensor provided by the embodiments of the present disclosure; Figure 11 is Figure 10 a top view schematic diagram of the provided image sensor, Figures 5 to 10 respectively are detailed cross-sectional views of the image sensor provided by the embodiments of the present disclosure in the B1 - B2 direction at different process steps along Figure 2a wherein, in Figure 2a the shallow trench isolation structure STI is not shown.
[0097] Next, the method for manufacturing an image sensor provided by the embodiments of the present disclosure will be further described in detail with reference to the accompanying drawings.
[0098] First, execute step S101, as Figure 5 shown, provide a substrate 10.
[0099] Here, the substrate 10 can be made of materials such as germanium, silicon germanide, silicon carbide, gallium arsenide, or indium gallium, but is not limited thereto. The substrate 10 can also be a silicon substrate 10 on an insulator surface or a germanium substrate 10 on an insulator surface, etc. In some embodiments, the substrate 10 can be a silicon substrate 10.
[0100] In some specific embodiments, the substrate 10 can be a lightly doped substrate.
[0101] In some embodiments, a shallow trench isolation structure STI is also formed in the substrate 10. The shallow trench isolation structure STI can form a good electrical isolation effect between multiple subsequent formed photoelectric conversion regions PD, prevent phenomena such as crosstalk of photo-generated carriers, and contribute to improving the image quality of the finally obtained image sensor.
[0102] Next, step S102 is executed. As Figures 6 to 10 shown, a photoelectric conversion region PD located on the substrate 10 is formed; a transfer gate VTG is formed. The transfer gate VTG includes at least a first transfer gate VTG1, and the first transfer gate VTG1 includes at least a second surface S2.
[0103] In some embodiments, as Figure 5 shown, after the photoelectric conversion region PD is formed and before the transfer gate VTG is formed, the manufacturing method further includes:
[0104] An initial dielectric material layer La is formed, and the initial dielectric material layer La covers the surface of the substrate 10.
[0105] Multiple mask layers are formed from bottom to top. The mask layers include a first mask layer 12, a second mask layer 13, a third mask layer 141, and a fourth mask layer 142.
[0106] A mask pattern layer 15 is formed on the fourth mask layer 142, and the mask pattern layer 15 exposes a part of the surface of the fourth mask layer 142.
[0107] In some embodiments, the material of the initial dielectric material layer La includes but is not limited to oxide materials such as silicon oxide, etc. The material of the first mask layer 12 includes but is not limited to nitride materials such as silicon nitride, etc. The material of the second mask layer 13 includes but is not limited to spin-on carbon or advanced patterning film (APF) materials, etc. The material of the third mask layer 141 includes but is not limited to dielectric anti-reflection coating (DARC) materials, and the material of the fourth mask layer 142 includes but is not limited to bottom anti-reflection coating (BARC) materials, etc. The material of the mask pattern layer 15 includes but is not limited to photoresist, etc.
[0108] In some embodiments, as Figures 6 to 9As shown, before forming at least one transfer gate VTG, the manufacturing method further includes:
[0109] First, using the mask pattern layer 15 as a mask, etch the second mask layer 13, the third mask layer 141, and the fourth mask layer 142 to remove part of the second mask layer 13, the third mask layer 141, and the fourth mask layer 142 to form an initial trench structure (not shown in the figure) in the second mask layer 13, the third mask layer 141, and the fourth mask layer 142;
[0110] Next, remove the remaining mask pattern layer 15, the third mask layer 141, and the fourth mask layer 142;
[0111] Then, using the second mask layer 13 with the initial trench structure (not shown in the figure) as a mask, etch the first mask layer 12, the substrate 10, and the photoelectric conversion region PD to form at least one trench structure T, and the trench structure T is located on the photoelectric conversion region PD (please refer to Figure 6 specifically);
[0112] Next, remove the remaining second mask layer 13 to expose the surfaces of the first mask layer 12 and the trench structure T;
[0113] Form a dielectric material layer L on the surface of the trench structure T, and the dielectric material layer L covers at least the sidewalls and the bottom of the trench structure T (please refer to Figure 7 specifically);
[0114] Perform a doping process on the dielectric material layer L to form a doped region Q (please refer to Figure 8 and Figure 9 specifically).
[0115] In some embodiments, the material of the dielectric material layer L includes but is not limited to an oxide layer, such as silicon oxide, etc.
[0116] In some embodiments, forming the dielectric material layer L further includes: performing a rapid thermal oxidation (RTO) process to obtain the dielectric material layer L, and the temperature during the RTO process can be about 850 °C.
[0117] In some embodiments,
[0118] Forming the dielectric material layer L includes:
[0119] Form the dielectric material layer L, and the dielectric material layer L covers the surface of the remaining first mask layer 12 and covers the sidewalls and the bottom of the trench structure T.
[0120] In some embodiments, such as Figure 10 , Figure 11 and Figure 3aAs shown, the number of transfer gates VTG includes multiple. After performing the doping process, forming the transfer gates VTG includes:
[0121] Forming a conductive material layer EL, the part of the conductive material layer EL filling the trench structure T constitutes multiple transfer gates VTG, and the part located above the transfer gates VTG constitutes a gate structure G. The gate structure G connects multiple transfer gates VTG in the same trench structure T;
[0122] Among them, the transfer gate VTG further includes a second transfer gate VTG2 adjacent to the first transfer gate VTG1. The second transfer gate VTG2 further includes a third surface S3. The third surface S3 of the second transfer gate VTG2 is disposed opposite to the second surface S2 of the first transfer gate VTG1. Along the direction from the optoelectronic conversion region PD to the corresponding floating diffusion region FD, the distance from the second surface S2 of the first transfer gate VTG1 to the third surface S3 of the second transfer gate VTG2 gradually decreases, and there is a second preset angle b between the second surface S2 and the third surface S3.
[0123] In some embodiments, the material of the transfer gate VTG may include but is not limited to polysilicon, metal, or metal compound, etc.
[0124] In some embodiments, as Figure 9 shown, after performing the doping process and before forming the conductive material layer EL, the preparation method further includes:
[0125] At least removing the first mask layer 12 and the part of the dielectric material layer L covering the sidewall and top of the first mask layer 12 and a part of the thickness of the initial dielectric material layer La. The remaining initial dielectric material layer La covers the surface of the substrate 10 and the shallow trench isolation structure STI, and the remaining dielectric material layer L covers the sidewall and bottom of the trench structure T.
[0126] In some embodiments, along the direction parallel to the plane of the substrate 10, the cross-sectional shape of the transfer gate VTG includes a polygon, and the polygon includes one of a triangle, a quadrilateral, a pentagon, and a hexagon.
[0127] Here, the ranges of the first preset angle a and the second preset angle b can be between greater than 0° and less than or equal to 10° (including the end values). For example, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc.
[0128] It can be understood that in the conventional technology, in order to reduce the difficulty of the transfer of photo-generated carriers from the optoelectronic conversion region to the floating diffusion region, usually on the region where the transfer path of the photo-generated carriers in the optoelectronic conversion region to the floating diffusion region is located (it can be understood as, Figure 1b 、 Figure 2b andFigure 3b The doping process is performed twice in the region where the arrow is located near the electron e- shown in [description of the figure], and the two doping processes form a concentration difference in this region to reduce the difficulty of the transfer of photo-generated carriers.
[0129] In the embodiment of the present disclosure, since the transfer gate VTG in the embodiment of the present disclosure is constrained in terms of the cross-sectional shape parallel to the plane of the substrate 10, the distance from other structures, and the included angle, the photo-generated carriers can have a good transfer path when transferring from the photoelectric conversion region PD to the floating diffusion region FD. Therefore, when doping the doping region Q, there is no need to perform two doping operations in this region during the doping operation, that is, there is no need to adopt a structure with a doping concentration difference to reduce the difficulty of the transfer of photo-generated carriers. Instead, only by performing a single doping process, that is, only by using an operation involving a single photomask, a doping region with the effect of reducing the difficulty of the transfer of photo-generated carriers can be obtained. In this way, the number of photomasks can be effectively saved, and the production cost can be saved. At the same time, it can also directly avoid the phenomenon of electron overflow under the transfer path when the transistor structure based on the transfer gate VTG is turned off.
[0130] At the same time, in the embodiment of the present disclosure, whether the number of transfer gates VTG is single or multiple, it can play a good promoting effect on the transfer process of carriers from the photoelectric conversion region PD to the floating diffusion region FD, so that the photo-generated carriers generated in the photoelectric conversion region can be transferred to the floating diffusion region to a large extent or even tend to be completely transferred, so as to reduce the occurrence of adverse conditions such as dark current and leakage, thereby improving the occurrence of phenomena such as image delay. At the same time, in the embodiment where the transfer gate VTG includes multiple ones, the full well capacity (FWC) can be further increased. A larger full well capacity (FWC) can enable the image sensor to have a better dynamic range and signal-to-noise ratio, and reduce the occurrence of image delay.
[0131] In any of the above embodiments, after performing the process of the previous step and before performing the next process step of material deposition, the preparation method further includes: performing a cleaning process to provide good conditions for the deposition of the material.
[0132] Among the technical features of the technical solutions described in the embodiments provided by the present disclosure, they can be arbitrarily combined without conflict.
[0133] The above is only a preferred embodiment of the present disclosure, and is not used to limit the protection scope of the present disclosure. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.
Claims
1. An image sensor, characterized in that, Comprising: A substrate; A photoelectric conversion region located on the substrate; A floating diffusion region spaced apart from the photoelectric conversion region, the floating diffusion region at least including a first surface; A transfer gate, the transfer gate at least including a first transfer gate, the first transfer gate at least including a second surface, the second surface being disposed adjacent to the first surface of the floating diffusion region, and in the direction from the photoelectric conversion region to the correspondingly disposed floating diffusion region, the distance from the second surface to the first surface gradually decreases, and there is a first preset angle between the first surface and the second surface.
2. The image sensor according to claim 1, wherein The number of the transfer gates includes a plurality, the transfer gate further includes a second transfer gate adjacent to the first transfer gate, the second transfer gate further includes a third surface, the third surface of the second transfer gate is disposed opposite to the second surface of the first transfer gate, and in the direction from the photoelectric conversion region to the correspondingly disposed floating diffusion region, the distance from the second surface of the first transfer gate to the third surface of the second transfer gate gradually decreases, and there is a second preset angle between the second surface and the third surface.
3. The image sensor according to claim 2, wherein The range of the first preset angle is greater than 0° and less than or equal to 10°; And / or The range of the second preset angle is greater than 0° and less than or equal to 10°.
4. The image sensor according to claim 1, wherein In the direction parallel to the plane of the substrate, the cross-sectional shape of the transfer gate includes a polygon, and the polygon includes one of a triangle, a quadrilateral, a pentagon, and a hexagon.
5. The image sensor according to claim 1, wherein, The image sensor includes a plurality of pixel regions, and a single pixel region at least includes the floating diffusion region, the photoelectric conversion region, and the transfer gate; the number of the transfer gates includes a plurality, and on one side adjacent to the floating diffusion region, the distance between the two closest ends of the adjacent transfer gates is between 1 / 5 and 1 / 3 of the size value of the single pixel region in the direction parallel to the substrate.
6. The image sensor according to claim 5, wherein, The minimum distance range between two adjacent transfer gates is between 100 nm and 200 nm, and the maximum distance range is between 150 nm and 400 nm.
7. The image sensor according to any one of claims 1-6, characterized in that, The image sensor further includes a gate structure located on and connected to the transfer gate.
8. A method for manufacturing an image sensor, characterized in that, The preparation method includes: Providing a substrate; Forming a photoelectric conversion region on the substrate; Forming a transfer gate, the transfer gate at least including a first transfer gate, the first transfer gate at least including a second surface; Forming a floating diffusion region spaced apart from the photoelectric conversion region, the floating diffusion region at least including a first surface; the first surface is disposed adjacent to the second surface of the first transfer gate, and in the direction from the photoelectric conversion region to the correspondingly disposed floating diffusion region, the distance from the second surface to the first surface gradually decreases, and there is a first preset angle between the first surface and the second surface.
9. The preparation method according to claim 8, characterized in that Before forming at least one of the transfer gates, the preparation method further includes: Form at least one trench structure, where the trench structure is located on the optoelectronic conversion region; Form a dielectric material layer on the surface of the trench structure, where the dielectric material layer covers at least the sidewalls and the bottom of the trench structure; Perform a doping process on the dielectric material layer to form a doped region.
10. The preparation method according to claim 9, characterized in that, The number of the transfer gates includes a plurality. After performing the doping process, forming the transfer gates includes: Form a conductive material layer, where the conductive material layer fills the trench structure and connects a plurality of adjacent transfer gates; Wherein, the transfer gate further includes a second transfer gate disposed adjacent to the first transfer gate. The second transfer gate further includes a third surface. The third surface of the second transfer gate is disposed opposite to the second surface of the first transfer gate. Along the direction from the optoelectronic conversion region to the corresponding floating diffusion region, the distance from the second surface of the first transfer gate to the third surface of the second transfer gate gradually decreases, and there is a second preset angle between the second surface and the third surface.