CN-122002928-A - Image sensor and method for manufacturing the same

CN122002928ACN 122002928 ACN122002928 ACN 122002928ACN-122002928-A

Abstract

The application provides an image sensor and a preparation method thereof, wherein in the preparation method, a groove is formed in an interlayer dielectric layer, then an N-type doped epitaxial layer filling the groove and covering the interlayer dielectric layer is formed, and then the epitaxial layer at the top end of the interlayer dielectric layer is subjected to inverse doping through an ion implantation process to obtain a P-type ion implantation region, wherein the P-type ion implantation region and the interlayer dielectric layer form a stacked isolation structure (photodiode isolation region), the N-type doped epitaxial layer in the groove and at the top end of the groove form an N-type region of a photodiode, so that the limitation of the traditional isolation structure on the extremely high depth of ion implantation can be broken through, namely, the photoetching and ion implantation process limitation of a pixel unit with smaller size can be broken through, and the process of deep trench etching at the back of a back-illuminated image sensor can be omitted, thereby greatly reducing the manufacturing difficulty of the image sensor.

Inventors

LI JIALONG
ZHANG DONG
WANG HAN

Assignees

华虹半导体(无锡)有限公司

Dates

Publication Date: 20260508
Application Date: 20260107

Claims (10)

1. A method of manufacturing an image sensor, comprising: providing a substrate, wherein a liner oxide layer, an interlayer dielectric layer and a hard mask layer are sequentially formed on the substrate; Etching the hard mask layer, the interlayer dielectric layer and the liner oxide layer to the surface of the substrate to form a plurality of grooves which are arrayed; Forming a repair oxide layer, wherein the repair oxide layer covers the bottom wall of the groove; Removing the repair oxide layer and the hard mask layer; forming an N-type doped epitaxial layer, wherein the epitaxial layer fills the groove and covers the interlayer dielectric layer; Forming a sacrificial oxide layer, wherein the sacrificial oxide layer covers the epitaxial layer; Forming a patterned photoresist layer, wherein the patterned photoresist layer is positioned on the sacrificial oxide layer, a pattern for defining a P-type ion implantation area of the photodiode is formed in the patterned photoresist layer, and the pattern for defining the P-type ion implantation area of the photodiode opens the epitaxial layer at the top end of the remained interlayer dielectric layer; Performing inversion doping on the epitaxial layer at the top end of the remaining interlayer dielectric layer by taking the patterned photoresist layer and the sacrificial oxide layer as masks to obtain a P-type ion implantation region, wherein the P-type ion implantation region and the interlayer dielectric layer at the bottom of the P-type ion implantation region jointly form an isolation structure; Removing the patterned photoresist layer and the sacrificial oxide layer; And forming a cap layer, wherein the cap layer covers the P-type ion implantation region and the N-type doped epitaxial layer.
2. The method of claim 1, wherein the patterned photoresist layer and the sacrificial oxide layer are used as masks, and the epitaxial layer on top of the remaining interlayer dielectric layer is inversely doped to obtain a P-type ion implantation region, wherein the ion implantation energy is 480kev to 1250kev, and the ion implantation dose is 1E17atoms/cm 3 ~5E17atoms/cm 3 .
3. The method of manufacturing an image sensor of claim 1, wherein the N-doped epitaxial layer is formed using a selective epitaxy process.
4. The method for manufacturing the image sensor according to claim 1, wherein in the process of forming the N-type doped epitaxial layer by adopting a selective epitaxial process, the gases involved in the selective epitaxial process at least comprise a silicon source gas, an HCl gas and H 2 , wherein the flow rate of the silicon source gas is 1000 sccm-160 sccm, the flow rate of the HCl gas is 50 sccm-100 sccm, the flow rate of the H 2 is 20 sccm-40 sccm, the process temperature is 800 ℃ to 900 ℃, and the pressure of a process chamber is 50 Torr-100 Torr.
5. The method for manufacturing an image sensor according to claim 1, wherein a ratio of a thickness of the epitaxial layer to a thickness of the interlayer dielectric layer at a top end of the remaining interlayer dielectric layer is (4:3) - (2:1).
6. The method of manufacturing an image sensor according to claim 1, wherein after forming the trenches arranged in an array, a width of the remaining interlayer dielectric layer between two adjacent trenches is less than 0.24 μm.
7. The method of manufacturing an image sensor according to claim 6, wherein after forming the trenches arranged in an array, a sum of a lateral opening size of each of the trenches and a width of the remaining interlayer dielectric layer between two adjacent trenches is less than 1 μm.
8. The method of manufacturing an image sensor of claim 1, wherein the repair oxide layer is formed using a thermal oxidation process.
9. The method of manufacturing an image sensor according to claim 1, wherein after forming the N-doped epitaxial layer and before forming the sacrificial oxide layer, the method of manufacturing an image sensor further comprises: and grinding and removing the epitaxial layer with a certain thickness by adopting a chemical mechanical grinding process.
10. An image sensor is provided, which is capable of detecting a light source, characterized by comprising the following steps: A substrate, on which a liner oxide layer and an interlayer dielectric layer are sequentially formed; the grooves are arranged in an array manner and are positioned in the interlayer dielectric layer and the liner oxide layer; an N-type doped epitaxial layer, wherein the epitaxial layer fills the groove and extends out of the top end of the groove by a certain height; The P-type ion implantation region is positioned on the interlayer dielectric layer between the grooves, the upper surface of the P-type ion implantation region is flush with the upper surface of the epitaxial layer, and the P-type ion implantation region and the interlayer dielectric layer at the bottom of the P-type ion implantation region jointly form an isolation structure; And the cap layer covers the P-type ion implantation region and the N-type doped epitaxial layer.

Description

Image sensor and method for manufacturing the same Technical Field The application relates to the technical field of semiconductor manufacturing, in particular to an image sensor and a preparation method thereof. Background The sensitivity of the image sensor (CIS) is strongly related to the size of the Pixel (Pixel) region, and a Photodiode (PD) is the most basic unit of the Pixel structure, including an N-type region and a P-type region. While conventional photodiodes are formed in the longitudinal direction by photolithography and ion implantation processes, as CIS gradually pursues high pixels, the size of each pixel (the total lateral width of an N-type region and a P-type region) is continuously reduced, for example, the size of each pixel is 1 μm/0.7 μm/0.64 μm, and even 0.56 μm or less, and the aspect ratio and ion implantation depth and concentration of the photoresist used to fabricate the photodiodes are greatly limited, which severely limits the development of higher-order CIS products. Disclosure of Invention The application provides an image sensor and a preparation method thereof, which can solve the problem of high manufacturing difficulty of the image sensor caused by the continuous reduction of the pixel size of the image sensor required at the present stage. In one aspect, an embodiment of the present application provides a method for manufacturing an image sensor, including: providing a substrate, wherein a liner oxide layer, an interlayer dielectric layer and a hard mask layer are sequentially formed on the substrate; Etching the hard mask layer, the interlayer dielectric layer and the liner oxide layer to the surface of the substrate to form a plurality of grooves which are arrayed; Forming a repair oxide layer, wherein the repair oxide layer covers the bottom wall of the groove; Removing the repair oxide layer and the hard mask layer; forming an N-type doped epitaxial layer, wherein the epitaxial layer fills the groove and covers the interlayer dielectric layer; Forming a sacrificial oxide layer, wherein the sacrificial oxide layer covers the epitaxial layer; Forming a patterned photoresist layer, wherein the patterned photoresist layer is positioned on the sacrificial oxide layer, a pattern for defining a P-type ion implantation area of the photodiode is formed in the patterned photoresist layer, and the pattern for defining the P-type ion implantation area of the photodiode opens the epitaxial layer at the top end of the remained interlayer dielectric layer; Performing inversion doping on the epitaxial layer at the top end of the remaining interlayer dielectric layer by taking the patterned photoresist layer and the sacrificial oxide layer as masks to obtain a P-type ion implantation region, wherein the P-type ion implantation region and the interlayer dielectric layer at the bottom of the P-type ion implantation region jointly form an isolation structure; Removing the patterned photoresist layer and the sacrificial oxide layer; And forming a cap layer, wherein the cap layer covers the P-type ion implantation region and the N-type doped epitaxial layer. Optionally, in the method for manufacturing the image sensor, the patterned photoresist layer and the sacrificial oxide layer are used as masks, and the epitaxial layer at the top end of the remaining interlayer dielectric layer is subjected to inversion doping, so that in the process of obtaining the P-type ion implantation region, the ion implantation energy is 480-640 kev, and the ion implantation dose is 1E17atoms/cm 3~5E17atoms/cm3. Optionally, in the method for manufacturing the image sensor, a selective epitaxy process is used to form an N-doped epitaxial layer. Optionally, in the preparation method of the image sensor, in the process of forming the N-type doped epitaxial layer by adopting a selective epitaxial process, the gases participating in the selective epitaxial process at least comprise silicon source gas, HCl gas and H 2, wherein the flow rate of the silicon source gas is 1000 sccm-160 sccm, the flow rate of the HCl gas is 50 sccm-100 sccm, the flow rate of H 2 is 20 sccm-40 sccm, the process temperature is 800 ℃ to 900 ℃, and the pressure of a process chamber is 50 Torr-100 Torr. Optionally, in the method for manufacturing an image sensor, a ratio of a thickness of the epitaxial layer located at the top end of the remaining interlayer dielectric layer to a thickness of the interlayer dielectric layer is (4:3) - (2:1). Optionally, in the method for manufacturing an image sensor, after forming the trenches arranged in an array, a width of the remaining interlayer dielectric layer between two adjacent trenches is smaller than 0.24 μm. Optionally, in the method for manufacturing an image sensor, after forming the trenches arranged in an array, a sum of a lateral opening size of each trench and a width of the remaining interlayer dielectric layer between two adjacent trenches is less than 1 μm. Optionally, in the method