An image sensor forming method and an image sensor
By designing an ion implantation method in an image sensor where phosphorus ion-doped regions surround arsenic ion regions, and combining this with a deep trench isolation structure, the problem of flickering white spots was solved, high-temperature performance and optical performance were improved, and fabrication costs were reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GALAXYCORE SHANGHAI
- Filing Date
- 2024-12-17
- Publication Date
- 2026-06-19
AI Technical Summary
In the existing technology for forming photodiodes for image sensors, arsenic-containing ion implantation combined with deep trench technology results in a high proportion of scintillation white spots, which affects the image output quality.
An ion implantation method is used to surround an arsenic-doped region with a phosphorus-doped region, combined with a deep trench isolation structure, to create an environment where phosphorus acts as a donor, thereby reducing the proportion of scintillation white spots. High-temperature performance is also improved through a high-temperature defect repair process.
It effectively reduces flickering white spots, improves the high-temperature performance and optical performance of image sensors, and reduces manufacturing costs.
Smart Images
Figure CN122248822A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to an image sensor forming method and an image sensor. Background Technology
[0002] Ion implantation is a common technique used in the fabrication of image sensors. Ion implantation involves injecting an ion beam into a solid material. The ion beam's velocity gradually decreases due to resistance from the solid material, eventually settling within it. Through ion implantation, regions doped with specific elements can be formed at specific locations within a semiconductor material, enabling special functions or improving substrate performance.
[0003] Currently, in the process of forming photodiodes for image sensors, in order to pursue better high-temperature performance and optical performance, arsenic-containing ion implantation combined with deep trench technology is usually used. However, this combination will produce a high proportion of flickering white spots, which will affect the image output effect of the image sensor. Summary of the Invention
[0004] The purpose of this invention is to provide an image sensor forming method, comprising: When performing ion implantation on the first surface of a semiconductor substrate, the phosphorus ion-doped region surrounds the arsenic ion-doped region to improve high-temperature performance and reduce flickering white spots.
[0005] Preferably, the ion implantation includes: The first photoresist layer and the second photoresist layer are formed by exposure corresponding to the preset mask layer. Phosphorus doped ion implantation and arsenic doped ion implantation are performed on the semiconductor substrate respectively, so that the phosphorus ion doped region surrounds the arsenic ion doped region.
[0006] Preferably, the ion implantation region corresponding to the first photoresist layer completely covers the ion implantation region corresponding to the second photoresist layer. Preferably, the ion implantation includes: Arsenic-doped ion implantation is performed on the semiconductor substrate based on the second photoresist layer; The second photoresist layer is subjected to plasma treatment to expand the corresponding ion implantation region and form the first photoresist layer. Phosphorus-doped ion implantation is performed on the semiconductor substrate based on the first photoresist layer.
[0007] Preferably, the ion implantation region corresponding to the first photoresist layer is annular in shape, and the inner ring edge of the ion implantation region corresponding to the first photoresist layer at least surrounds the outer edge of the ion implantation region corresponding to the second photoresist layer.
[0008] Preferably, after ion implantation, the procedure further includes: A deep trench isolation structure is formed on the second surface of the semiconductor substrate opposite to the first surface.
[0009] Preferably, the implantation depth of the arsenic ion doped region and / or the phosphorus ion doped region is more than 0.2 μm from the first surface.
[0010] The present invention also provides an image sensor formed using the image sensor forming method described above.
[0011] This invention proposes a novel image sensor formation method through the above-mentioned scheme. By designing different ion implantation schemes, arsenic and phosphorus elements are simultaneously present in the photodiode, and the phosphorus implantation area surrounds the arsenic element, thereby creating an environment with phosphorus as the donor around the deep trench structure. This can effectively reduce the proportion of flickering white spots. At the same time, the ion implantation host in the photodiode is arsenic element, which, combined with a higher temperature defect repair process, results in better high-temperature performance. Attached Figure Description
[0012] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. Figure 1 This is a top cross-sectional view of an image sensor forming method in one embodiment of the present invention; Figure 2 , Figure 3 This is a schematic diagram of the ion implantation process in the image sensor formation method in different embodiments of the present invention; Figures 4-6 This is a schematic diagram of the image sensor formation process in different embodiments of the present invention. Throughout the figures, the same or similar reference numerals denote the same or similar devices (modules) or steps. Detailed Implementation
[0013] The purpose of this invention is to provide an image sensor forming method, comprising: When ion implantation is performed on the first surface A of the semiconductor substrate 100, the phosphorus ion-doped region 200 surrounds the arsenic ion-doped region 300, such as... Figure 1 As shown, this is to improve high-temperature performance and reduce flickering white spots.
[0014] This invention effectively improves high-temperature performance and reduces the number of flickering white spots caused by process damage by designing phosphorus-doped regions surrounding arsenic-doped regions. At the same time, arsenic can be combined with higher defect repair and element activation temperatures, resulting in lower bulk defects and thus achieving better high-temperature pixel performance. Figure 1The diagram illustrates a typical implementation, showing the ion implantation doping distribution within a pixel unit, separated from other pixel units by a deep trench isolation structure 500. Preferably, the phosphorus ion-doped region 200 may completely encompass the arsenic ion-doped region 300, or may only surround the arsenic ion-doped region 300. Preferably, there should be at least a partial overlap between the phosphorus ion-doped region 200 and the arsenic ion-doped region 300. Furthermore, the implantation depth of the arsenic ion-doped region and / or the phosphorus ion-doped region is preferably at least 0.2 μm from the first surface.
[0015] To achieve the above structure, several specific implementation methods are given below.
[0016] In one optional embodiment, during ion implantation, phosphorus-doped ion implantation and arsenic-doped ion implantation are performed on the semiconductor substrate 100 corresponding to the preset first photoresist layer 410 and second photoresist layer 420, respectively, so that the phosphorus-doped region surrounds the arsenic-doped region.
[0017] That is, during ion implantation, two mask layers of different shapes or sizes are used, and after exposure, two photoresist layers are formed on the surface of the semiconductor substrate 100 to achieve differences in the implantation regions for different elements. For example, a second photoresist layer 420 can be formed first based on the mask layer exposure for arsenic doping ion implantation, then the second photoresist layer 420 can be removed, and a first photoresist layer 410 can be formed using a new mask layer exposure for phosphorus doping ion implantation. Optionally, such as Figure 2 As shown, the ion implantation region corresponding to the first photoresist layer 410 can completely cover the ion implantation region corresponding to the second photoresist layer 420; or as shown Figure 3 As shown, the ion implantation region corresponding to the first photoresist layer is annular in shape, and the inner ring edge of the ion implantation region corresponding to the first photoresist layer 410 at least surrounds the outer edge of the ion implantation region corresponding to the second photoresist layer 420.
[0018] In another alternative implementation, ion implantation can also be performed using the following steps: Step S1: Based on the second photoresist layer 420, arsenic-doped ion implantation is performed on the semiconductor substrate 100, such as... Figure 4 As shown; Step S2: Perform plasma treatment on the second photoresist layer 420 to expand the corresponding ion implantation region, thereby eliminating the need for another mask layer to form the first photoresist layer 410, and directly forming the first photoresist layer 410, as shown below. Figure 5 As shown; Step S3: Phosphorus doped ion implantation is performed on the semiconductor substrate 100 based on the first photoresist layer 410.
[0019] In this embodiment, only one mask layer is needed. By plasma processing of the second photoresist layer 420, the injection range is expanded, thereby forming the first photoresist layer 410, achieving an ion-doped structure of phosphorus element encapsulating arsenic element.
[0020] This implementation method can achieve the same structure with fewer mask layers, effectively reducing the cost of the fabrication process.
[0021] In an optional embodiment, after ion implantation, a deep trench isolation structure 500 can also be formed on the second surface B of the semiconductor substrate 100 opposite to the first surface A, such as... Figure 6 As shown. Furthermore, the back-side process can be further completed in subsequent process steps to construct structures such as microlenses, forming a back-illuminated image sensor.
[0022] The present invention also provides an image sensor formed using the image sensor forming method described above.
[0023] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and not restrictive in any way. Furthermore, it is clear that the word "comprising" does not exclude other elements and steps, and the word "a" does not exclude a plural. Multiple elements recited in the apparatus claims may also be implemented by a single element. The terms "first," "second," etc., are used to denote names and do not indicate any particular order.
Claims
1. A method for forming an image sensor, characterized in that, include: When performing ion implantation on the first surface of a semiconductor substrate, the phosphorus ion-doped region surrounds the arsenic ion-doped region to improve high-temperature performance and reduce flickering white spots.
2. The image sensor forming method as described in claim 1, characterized in that, The ion implantation includes: The first photoresist layer and the second photoresist layer are formed by exposure corresponding to the preset mask layer. Phosphorus doped ion implantation and arsenic doped ion implantation are performed on the semiconductor substrate respectively, so that the phosphorus ion doped region surrounds the arsenic ion doped region.
3. The image sensor forming method as described in claim 2, characterized in that, The ion implantation region corresponding to the first photoresist layer completely covers the ion implantation region corresponding to the second photoresist layer.
4. The image sensor forming method as described in claim 3, characterized in that, The ion implantation includes: Arsenic-doped ion implantation is performed on the semiconductor substrate based on the second photoresist layer; The second photoresist layer is subjected to plasma treatment to expand the corresponding ion implantation region and form the first photoresist layer. Phosphorus-doped ion implantation is performed on the semiconductor substrate based on the first photoresist layer.
5. The image sensor forming method as described in claim 2, characterized in that, The ion implantation region corresponding to the first photoresist layer is annular in shape, and the inner ring edge of the ion implantation region corresponding to the first photoresist layer at least surrounds the outer edge of the ion implantation region corresponding to the second photoresist layer.
6. The image sensor forming method as described in claim 1, characterized in that, Following ion implantation, the procedure further includes: A deep trench isolation structure is formed on the second surface of the semiconductor substrate opposite to the first surface.
7. The image sensor forming method as described in claim 1, characterized in that, The implantation depth of the arsenic ion doped region and / or the phosphorus ion doped region is more than 0.2 μm from the first surface.
8. An image sensor, characterized in that, It is formed using the image sensor forming method as described in claims 1 to 7.