Pixel structure of single-photon avalanche detector and manufacturing method thereof
By designing RGB and IR filter arrays on the SPAD array, the problem that traditional RGB pixel structures cannot be compatible with IR channels is solved, and color and depth information is obtained simultaneously, which improves detection efficiency and is suitable for applications such as mobile, XR/VR and vehicle navigation.
Patent Information
- Application Number
- CN202510680182.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-26
- Publication Date
- 2025-08-26
AI Technical Summary
The prior art is difficult to obtain color image information and depth information at the same time in the same pixel structure. The traditional RGB pixel structure is not compatible with IR channels, resulting in solutions such as in-vehicle automatic navigation.
Different RGB and IR filter arrays are designed on traditional SPAD arrays. By adding an IR translucent layer on the top of the deep SPAD pixels and an RGB filter layer on the top of the color SPAD pixels, a multi-layer dielectric film structure is formed to achieve simultaneous acquisition of color and depth information.
It realizes the output of RGB color information and depth information simultaneously in the same single-photon avalanche detector pixel array, improves detection efficiency, and is suitable for applications such as mobile, XR/VR and vehicle navigation.
Smart Images
Figure CN120547951A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of image sensors, and in particular to a single-photon avalanche detector pixel structure and a manufacturing method thereof. Background Art
[0002] Imaging technologies include using pixels from CCD and CMOS image sensors to generate grayscale images. By applying RGB filters to these pixels, three corresponding channels are generated, resulting in color image information. In applications like spatial modeling, obtaining depth information of the corresponding scene requires completely different technologies. Currently, more mature technologies include PDAF (Phase Detection Autofocus) image sensors, as well as structured light and time-of-flight (TOF) technologies that require complex algorithms and architectures.
[0003] At present, the above two technologies are completely independent and difficult to be compatible. Among them, the traditional single-photon imaging technology can only realize depth information based on the infrared band, and cannot obtain color image information at the same time. It is difficult to use the same polymer filter layer structure as RGB on the RGB pixels in the related technology to realize the IR channel. The reason is that there is currently no mature IR (infrared ray) polymer, and the conventional hard mask coating method is difficult to achieve a small pixel IR filter structure. For example, the current debate on the in-vehicle automatic navigation technology in the market is that on the one hand, there is a pure vision solution, and on the other hand, there is a pure lidar solution. These two solutions are incompatible. Summary of the Invention
[0004] To address these issues, the present invention provides a single-photon avalanche detector pixel structure and its fabrication method. By designing different RGB and IR filter arrays on a traditional SPAD array, the present invention enables the array pixels to simultaneously generate both color and depth information, outputting images in RGBD format.
[0005] To achieve the above-mentioned objectives, the present invention mainly adopts the following technical solutions: In the first aspect, the present invention provides a single-photon avalanche detector pixel structure, wherein the single-photon avalanche detector pixel structure includes multiple filtering units, wherein each filtering unit includes: multiple SPAD pixels, and an isolation groove structure located between each adjacent SPAD pixel; wherein the multiple SPAD pixels include at least depth SPAD pixels and color SPAD pixels; an IR transparent layer located on the top of the depth SPAD pixels; and an RGB filter layer located on the top of the color SPAD pixels.
[0006] Preferably, each SPAD pixel includes: a substrate; an absorption well located on the substrate, wherein the absorption well is arranged at the bottom of the SPAD pixel; wherein the isolation trench structure is located on both sides of the absorption well and runs through the SPAD pixel.
[0007] Preferably, the color SPAD pixels include a first color SPAD pixel, a second color SPAD pixel, and a third color SPAD pixel, and correspondingly, the RGB filter layer includes a red filter layer, a green filter layer, and a blue filter layer.
[0008] Preferably, the RGB filter layer is located above the IR light-transmitting layer.
[0009] Preferably, the filter unit further comprises: a first flat layer located between the IR light-transmitting layer and the RGB filter layer; and a second flat layer located above the RGB filter layer and extending laterally across the entire top of the filter unit.
[0010] Preferably, the IR transparent layer is a multi-layer dielectric film.
[0011] In a second aspect, the present invention provides a method for manufacturing a single-photon avalanche detector pixel structure as described above, the method comprising: providing a wafer, the wafer comprising a plurality of SPAD pixels, and performing a planarization treatment on the top of the wafer; depositing a multilayer dielectric film on the top of the wafer, etching the multilayer dielectric film according to an etching pattern, and forming an IR light-transmitting layer on the top of the depth SPAD pixel; depositing a first dielectric layer on the top and around the IR light-transmitting layer, and forming a first flat layer located on the top of the IR light-transmitting layer and extending to the top of the entire wafer through a planarization treatment; coating an RGB filter layer material on the surface of the first flat layer, and forming an RGB filter layer on the top of the color SPAD pixel through exposure and development; depositing a second dielectric layer on the top and around the RGB filter layer, and forming a second flat layer located on the top of the RGB filter layer and extending to the top of the entire wafer through a planarization treatment.
[0012] Preferably, an RGB filter layer material is coated on the surface of the first flat layer, and an RGB filter layer is formed on the top of the color SPAD pixel through exposure and development, including: coating a red filter layer material on the surface of the first flat layer, and forming a red filter layer on the top of the first color SPAD pixel through exposure and development; coating a green filter layer material on the surface of the first flat layer, and forming a green filter layer on the top of the second color SPAD pixel through exposure and development; coating a blue filter layer material on the surface of the first flat layer, and forming a blue filter layer on the top of the third color SPAD pixel through exposure and development.
[0013] Preferably, each of the SPAD pixels includes: a substrate and an absorption well located on the substrate, wherein the absorption well is arranged at the bottom of the SPAD pixel; and an isolation groove structure located on both sides of the absorption well and penetrating the SPAD pixel.
[0014] This invention provides a novel single-photon avalanche detector pixel structure. This architecture adds a pixel filter that transmits infrared (IR) wavelengths to the traditional RGB monochrome pixel structure, enabling simultaneous acquisition of RGB color information and depth information. This technology utilizes the same single-photon pixel array to produce a two-dimensional image of both color and spatial depth. This technology holds great value in applications such as mobile, XR / VR, and in-vehicle navigation. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 A schematic diagram of the pixel structure of a single-photon avalanche detector provided in Example 1 of the present application;
[0016] Figures 2 to 8 This is a structural schematic diagram of the single-photon avalanche detector pixel structure manufacturing process provided in Example 2 of this application. DETAILED DESCRIPTION
[0017] In order to more clearly understand the above-mentioned objectives, technical solutions and advantages of the present application, the following is a detailed description with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features therein can be combined with each other unless there is a conflict. The specific embodiments described below are only used to explain the present application and are not intended to limit the present application.
[0018] The following description sets forth many specific details to facilitate a full understanding of the present application. The embodiments described are only a portion of the embodiments of the present application, not all of the embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present application without creative effort are intended to fall within the scope of protection of the present application.
[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application.
[0020] Example 1
[0021] The present invention provides a single-photon avalanche detector pixel structure. Figure 1 Schematic diagram of the single photon avalanche detector pixel structure provided in the embodiment of the present application, see Figure 1The single-photon avalanche detector pixel structure includes a plurality of filter units 100, wherein each of the filter units 100 includes:
[0022] A plurality of SPAD pixels and an isolation trench structure 150 located between each adjacent SPAD pixel; wherein the plurality of SPAD pixels include at least a depth SPAD pixel 120 and a color SPAD pixel 110; an IR transparent layer 130 located on top of the depth SPAD pixel 120; and an RGB filter layer 140 located on top of the color SPAD pixel 110.
[0023] Here, the SPAD pixel can be manufactured by a conventional FSI (Front side illumination) process or a BSI (Backside illumination) process. The isolation groove structure 150 can be formed into a groove by depositing, patterning, and etching silicon through a silicon nitride mask, and the isolation groove structure 150 is filled with deposited oxide. The IR light-transmitting layer on the top of the depth SPAD pixel is used as an IR pixel channel to obtain depth information; the RGB filter layer on the top of the color SPAD pixel is used to obtain RGB color information. By adding a pixel filter structure that transmits the infrared target wavelength to the traditional color RGB monochrome pixel structure, the RGB color information and depth information Depth can be obtained simultaneously, so that a two-dimensional picture of color and spatial depth can be obtained using the same single-photon pixel array, which is of great value in applications such as mobile, XR / VR, and in-car navigation.
[0024] In an embodiment of the present application, each SPAD pixel includes: a substrate; an absorption well located on the substrate, the absorption well being disposed at the bottom of the SPAD pixel; wherein the isolation trench structure is located on both sides of the absorption well and runs through the SPAD pixel. Taking the depth SPAD pixel 120 as an example, it includes: a substrate 111; an absorption well 112 located on the substrate 111, the absorption well 112 being disposed at the bottom of the SPAD pixel; wherein the isolation trench structure 150 is located on both sides of the absorption well 112 and runs through the SPAD pixel. Here, the material of the substrate 111 is any semiconductor material selected from silicon, silicon germanium, gallium arsenide, gallium nitride, or indium gallium arsenide. The substrate can be a p-type substrate or an n-type substrate, and correspondingly, the active well can be p-type doped or n-type doped.
[0025] The color SPAD pixel 110 includes a first color SPAD pixel 111, a second color SPAD pixel 112, and a third color SPAD pixel 113. Correspondingly, the RGB filter layer 140 includes a red filter layer 141, a green filter layer 142, and a blue filter layer 143. The order of the positions of the first color SPAD pixel 111, the second color SPAD pixel 112, and the third color SPAD pixel 113 is not limited and is shown for illustrative purposes only.
[0026] In the embodiment of the present application, the RGB filter layer 140 is located above the IR transparent layer 130. In some embodiments, the RGB filter layer 140 and the IR transparent layer 130 may be located on the same plane.
[0027] In the embodiment of the present application, the filter unit 100 further includes a first planar layer 160 located between the IR-transmitting layer 130 and the RGB filter layer 140, and a second planar layer 170 located above the RGB filter layer 140 and extending laterally across the entire top of the filter unit. The first and second planar layers can be made of dielectric layers such as silicon oxide and silicon nitride.
[0028] The IR-transmitting layer is a multilayer dielectric film, perhaps composed of stacked layers of silicon dioxide and silicon nitride. This layer modifies the transmission characteristics of light passing through the filter element, enabling the design of a transmission spectrum with arbitrarily narrow linewidths to match the SPAD's emitting laser. The IR-transmitting layer is fabricated using a plasma deposition process, with a bandwidth controllable down to 10nm. Compared to traditional absorptive resin materials, it can filter out ambient light to the greatest extent possible, ensuring detection efficiency.
[0029] An embodiment of the present application provides a single-photon avalanche detector pixel structure, which uses traditional and reliable CMOS micro-nano processing technology to add an IR channel to the traditional RGB pixel architecture to produce a new type of SPAD pixel. The pixel can simultaneously output RGB and depth distance information. The use of a multi-layer dielectric film as an IR filter layer can easily control the transmission band, and the bandwidth can be controlled to a 10nm band. Compared with traditional absorption resin materials, it can filter out ambient light to the greatest extent and ensure detection efficiency.
[0030] Example 2
[0031] This embodiment of the present application provides a method for manufacturing the single-photon avalanche detector pixel structure as described in Example 1. Figures 2 to 8 Schematic diagram of the single photon avalanche detector pixel structure manufacturing process provided in the embodiment of the present application, see Figures 2 to 8 , the method comprising:
[0032] Step S1: providing a wafer 10 , wherein the wafer 10 includes a plurality of SPAD pixels, and performing a planarization process on the top of the wafer 10 .
[0033] Here, the SPAD pixels include color SPAD pixels 111, 112, and 113, and a depth SPAD pixel 120. The SPAD pixels can be manufactured using conventional methods, such as FSI or BSI, and a flat surface is obtained through planarization. In the embodiment of the present application, each of the SPAD pixels includes: a substrate 121 and an absorption well 122 located on the substrate 121, the absorption well 122 being disposed at the bottom of the SPAD pixel; and an isolation trench structure 150 located on both sides of the absorption well 122 and extending through the SPAD pixel.
[0034] Step S2: Depositing a multilayer dielectric film 131 on top of the wafer 10, etching the multilayer dielectric film 131 according to the etching pattern to form an IR transparent layer 130 on top of the depth SPAD pixel 120. Here, the IR transparent layer 130 can be manufactured using a plasma deposition process. According to the IR transmittance window specification, a multilayer dielectric film deposition process is used to form the IR transparent layer on the entire wafer, so that the bandwidth can be controlled to the 10nm band. Compared with traditional absorption resin materials, it can filter out ambient light to the greatest extent and ensure detection efficiency.
[0035] Step S3 , depositing a first dielectric layer on the top and around the IR transparent layer 130 , and performing a planarization process to form a first planarization layer 160 located on the top of the IR transparent layer 130 and extending to the top of the entire wafer 10 .
[0036] Step S4: coating the RGB filter layer material on the surface of the first flat layer, and forming the RGB filter layer on top of the color SPAD pixel through exposure and development. Here, step S4 further includes:
[0037] Step S41 : coating a red filter layer material on the surface of the first planar layer 160 , and forming a red filter layer 141 on top of the first color SPAD pixel 111 through exposure and development.
[0038] Step S42 : coating a green filter layer material on the surface of the first planar layer 160 , and forming a green filter layer 142 on top of the second color SPAD pixel 112 through exposure and development.
[0039] Step S43 : coating a blue filter layer material on the surface of the first planar layer 160 , and forming a blue filter layer 143 on top of the third color SPAD pixel 113 through exposure and development.
[0040] In the embodiment of the present application, there is no specific order for step S41, step S42, and step S43, and they can be performed in sequence as required. Figures 6 and 7 The formation process of the red filter layer 141 is taken as an example for description, and the manufacturing process of the blue filter layer 142 and the blue filter layer 143 is corresponding.
[0041] Step S5: depositing a second dielectric layer on top of and around the RGB filter layer 140, and forming a second flat layer 170 on top of the RGB filter layer 140 and extending to the entire top of the wafer after a flattening process, thereby forming a complete RGB-IR four-channel filter unit.
[0042] Through the manufacturing method of the single-photon avalanche detector pixel structure of the embodiment of the present application, on the basis of the traditional reliable CMOS micro-nano processing technology, an IR channel is added to the traditional RGB pixel architecture to produce a new SPAD pixel. The pixel has the ability to simultaneously output RGB and depth distance information, has the advantages of high process maturity and low cost, and can integrate the traditional RGB pixel architecture and the infrared SPAD pixel architecture, add an IR channel, and add infrared depth sensing. The depth sensing pixel uses the IR channel, and the IR light-transmitting layer adopts an interference-type multi-layer film filter layer, which can easily control the transmission band, and the bandwidth can be controlled to a 10nm band. Compared with traditional absorption resin materials, it can filter out ambient light to the greatest extent and improve detection efficiency.
[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any person skilled in the art may make various changes, modifications, substitutions and variations to these embodiments without departing from the principles and purpose of the present invention. The scope of the present invention is defined by the claims and their equivalents.
Claims
1. A single-photon avalanche detector pixel structure, characterized in that: The single-photon avalanche detector pixel structure includes a plurality of filter units, wherein each filter unit includes: A plurality of SPAD pixels and an isolation trench structure located between each adjacent SPAD pixel; wherein the plurality of SPAD pixels include at least depth SPAD pixels and color SPAD pixels; An IR-transmitting layer on top of the deep SPAD pixel; And the RGB filter layer located on top of the color SPAD pixel.
2. The single photon avalanche detector pixel structure according to claim 1, characterized in that: Each SPAD pixel consists of: substrate; an absorption well located on the substrate, wherein the absorption well is arranged at the bottom of the SPAD pixel; The isolation groove structure is located on both sides of the absorption well and runs through the SPAD pixel arrangement.
3. The single photon avalanche detector pixel structure according to claim 2, characterized in that: The color SPAD pixels include a first color SPAD pixel, a second color SPAD pixel, and a third color SPAD pixel. Correspondingly, the RGB filter layer includes a red filter layer, a green filter layer, and a blue filter layer.
4. The single photon avalanche detector pixel structure according to claim 3, characterized in that: The RGB filter layer is located on the IR transparent layer.
5. The single photon avalanche detector pixel structure according to claim 4, characterized in that: The filter unit also includes: a first planar layer located between the IR transparent layer and the RGB filter layer; A second flat layer is located above the RGB filter layer and extends laterally across the entire top of the filter unit.
6. The single photon avalanche detector pixel structure according to claim 5, characterized in that: The IR light-transmitting layer is a multi-layer dielectric film.
7. A method for manufacturing a single-photon avalanche detector pixel structure according to any one of claims 1 to 6, characterized in that: The method comprises: Providing a wafer, the wafer including a plurality of SPAD pixels, and performing a planarization process on the top of the wafer; Depositing a multilayer dielectric film on top of the wafer, and etching the multilayer dielectric film according to an etching pattern to form an IR light-transmitting layer on top of the deep SPAD pixel; Depositing a first dielectric layer on top of and around the IR transparent layer, and performing a planarization process to form a first flat layer located on top of the IR transparent layer and extending to the entire top of the wafer; Coating RGB filter layer material on the surface of the first flat layer, and forming an RGB filter layer on top of the color SPAD pixel after exposure and development; A second dielectric layer is deposited on the top and around the RGB filter layer, and is planarized to form a second planar layer located on the top of the RGB filter layer and extending to the top of the entire wafer.
8. The method according to claim 7, characterized in that Coating RGB filter layer material on the surface of the first flat layer, and forming an RGB filter layer on top of the color SPAD pixel after exposure and development, including: Coating a red filter layer material on the surface of the first flat layer, and forming a red filter layer on the top of the first color SPAD pixel after exposure and development; A green filter layer material is coated on the surface of the first flat layer, and a green filter layer is formed on the top of the second color SPAD pixel after exposure and development; A blue filter layer material is coated on the surface of the first flat layer, and a blue filter layer is formed on the top of the third color SPAD pixel after exposure and development.
9. The method according to claim 8, characterized in that Each of the SPAD pixels comprises: A substrate and an absorption well located on the substrate, wherein the absorption well is arranged at the bottom of the SPAD pixel; And an isolation groove structure is located on both sides of the absorption well and runs through the SPAD pixel.