CN-122002927-A - Image sensor and method of manufacturing the same

CN122002927ACN 122002927 ACN122002927 ACN 122002927ACN-122002927-A

Abstract

The application provides an image sensor and a manufacturing method thereof, wherein in the manufacturing method, grid-shaped deep trenches are formed in a first epitaxial layer, then N-type ion implantation regions are formed in the first epitaxial layer of each grid among the deep trenches, and finally a cross-shaped P-type isolation region is formed in the N-type ion implantation regions of each grid so as to divide the N-type ion implantation regions in each grid into four pixel blocks. According to the application, through carrying out deep trench etching and filling isolation on the periphery of four pixel blocks, the grid-shaped second epitaxial layer and the cross-shaped P-type isolation region are utilized to jointly form an isolation structure, so that the difficulty of grid-shaped deep trench etching on a smaller area is reduced, the situation that the deep trench etching of a small-size photodiode is easy to cause lattice damage of a PD photosensitive area is avoided, the dark current of the photodiode is increased, the dark current of a single PD imaging process can be improved, and the crosstalk between pixels can be effectively improved in the four-in-one imaging process of the pixels.

Inventors

YAN JIAXIANG
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 first epitaxial layer and a mask layer are sequentially formed on the substrate; Forming a patterned photoresist layer on the mask layer, wherein grid-shaped deep groove patterns are defined on the patterned photoresist layer; Etching the mask layer and the first epitaxial layer with partial thickness by taking the patterned photoresist layer as a mask so as to form grid-shaped deep trenches; Removing the patterned photoresist layer; forming a second epitaxial layer which is positioned in the deep trench and covers the mask layer, wherein an air gap is formed in the second epitaxial layer of the deep trench; grinding to remove the second epitaxial layer on the surface of the mask layer; removing the mask layer; grinding to remove the second epitaxial layer beyond the surface of the first epitaxial layer; forming an N-type ion implantation region in the first epitaxial layer through an ion implantation process, wherein the N-type ion implantation region is positioned in each grid between the deep trenches; And forming a cross-shaped P-type isolation region in the N-type ion implantation region in each grid through an ion implantation process so as to divide the N-type ion implantation region in each grid into four blocks.
2. The method of manufacturing an image sensor according to claim 1, wherein the opening width of the deep trench in the X direction is reduced at a position near a node where the deep trenches cross each other, and the opening width of the deep trench in the Y direction is reduced at a position near a node where the deep trenches cross each other.
3. The method according to claim 2, wherein the opening widths of the deep trenches far from the node positions of the deep trenches crossing each other in the X-direction or in the Y-direction are 150nm to 400nm.
4. The method of manufacturing an image sensor according to claim 3, wherein an opening width of the deep trench near a node position of the deep trench crossing each other is 50nm to 100nm smaller than an opening width of the deep trench far from the node position of the deep trench crossing each other in an X direction or in a Y direction.
5. The method according to claim 1, wherein ions are implanted As, P or a combination of both in the process of forming the N-type ion implantation region in the first epitaxial layer by an ion implantation process, the ion implantation time is 1 to 8 times, the ion implantation energy is 200 to 4000kev each time, and the ion implantation dose is 2E11/cm 2 ~2E13/cm 2 each time.
6. The method according to claim 1, wherein in forming the cross-shaped P-type isolation region in the N-type ion implantation region in each of the grids by an ion implantation process, ions are implanted B1 to 8 times with an ion implantation energy of 10 to 2000kev each time, and an ion implantation dose of 2 e11/cm 2 ~2 E13/cm 2 each time.
7. The method of manufacturing an image sensor of claim 1, wherein the first epitaxial layer is an intrinsic epitaxial layer or a doped epitaxial layer.
8. The method of manufacturing an image sensor according to claim 1, wherein the material of the second epitaxial layer is one or a combination of a plurality of polysilicon, silicon oxide, and P-type doped monocrystalline silicon.
9. The method of manufacturing an image sensor according to claim 1, wherein the deep trench has a depth of 1.5 μm to 5 μm.
10. An image sensor is provided, which is capable of detecting a light source, characterized by comprising the following steps: A substrate; the first epitaxial layer is formed on the substrate, the first epitaxial layer is positioned on the substrate; Grid-shaped deep trenches, wherein the deep trenches are positioned in the first epitaxial layer with partial thickness; the second epitaxial layer is positioned in the deep groove, wherein an air gap is formed in the second epitaxial layer of the deep groove; an N-type ion implantation region located in the first epitaxial layer and in each grid between the deep trenches, the N-type ion implantation region being formed by an ion implantation process; and the P-type isolation regions are positioned in the N-type ion implantation regions in the grids and divide the N-type ion implantation regions in the grids into four blocks, and the P-type isolation regions are formed through an ion implantation process.

Description

Image sensor and method of manufacturing the same Technical Field The application relates to the technical field of semiconductor manufacturing, in particular to an image sensor and a manufacturing method thereof. Background In a CMOS Image Sensor (CIS), a core device is a graded junction Photodiode (PD), and after light is irradiated into the PD, the light is converted into photo-generated electrons, and then the photo-generated electrons are converted into other types of electrical signals through some auxiliary circuit structures to be output. In recent years, mobile phone image sensors are evolving toward high pixels and smaller single pixel sizes. To meet the imaging quality of the sensor, the pixels are generally isolated by Deep Trench Isolation (DTI), so as to reduce signal crosstalk between the pixels. The mainstream mobile phone image sensor can support four-in-one pixels, and can combine four adjacent pixels into a large pixel according to illumination conditions, so that bright and clear images can be generated even in a low-light environment. Reducing the number of transistors in a pixel is advantageous for reducing the size of the pixel, and image sensors of small pixel size often use 2×2 pixels to share a set of transfer transistors, where a set of transfer transistors includes a transfer transistor TX, a reset transistor RST, a selection transistor SEL, a source follower transistor SF, and so on. However, lattice damage to the PD photosensitive area is unavoidable in the deep trench etching process of the small-sized photodiode, the dark current of the photodiode is increased, and the small-sized etching process has a great challenge as the size of a single pixel is reduced. Disclosure of Invention The application provides an image sensor and a manufacturing method thereof, which can solve the problems that in the manufacturing process of the traditional CMOS image sensor, the deep groove etching of a small-size photodiode is easy to cause lattice damage of a PD photosensitive area and dark current of the photodiode is increased. In one aspect, an embodiment of the present application provides a method for manufacturing an image sensor, including: Providing a substrate, wherein a first epitaxial layer and a mask layer are sequentially formed on the substrate; Forming a patterned photoresist layer on the mask layer, wherein grid-shaped deep groove patterns are defined on the patterned photoresist layer; Etching the mask layer and the first epitaxial layer with partial thickness by taking the patterned photoresist layer as a mask so as to form grid-shaped deep trenches; Removing the patterned photoresist layer; forming a second epitaxial layer which is positioned in the deep trench and covers the mask layer, wherein an air gap is formed in the second epitaxial layer of the deep trench; grinding to remove the second epitaxial layer on the surface of the mask layer; removing the mask layer; grinding to remove the second epitaxial layer beyond the surface of the first epitaxial layer; forming an N-type ion implantation region in the first epitaxial layer through an ion implantation process, wherein the N-type ion implantation region is positioned in each grid between the deep trenches; And forming a cross-shaped P-type isolation region in the N-type ion implantation region in each grid through an ion implantation process so as to divide the N-type ion implantation region in each grid into four blocks. Optionally, in the manufacturing method of the image sensor, the opening width of the deep trench in the X direction is reduced at a position close to a node where the deep trenches mutually intersect, and the opening width of the deep trench in the Y direction is reduced at a position close to a node where the deep trenches mutually intersect. Optionally, in the method for manufacturing an image sensor, the opening widths of the deep trenches far from the node positions of the deep trenches crossing each other in the X direction or in the Y direction are 150nm to 400nm. Optionally, in the method for manufacturing an image sensor, in the X direction or in the Y direction, an opening width of the deep trench near the node position of the deep trench crossing each other is 50nm to 100nm smaller than an opening width of the deep trench far from the node position of the deep trench crossing each other. Optionally, in the method for manufacturing the image sensor, in the process of forming the N-type ion implantation region in the first epitaxial layer by an ion implantation process, the implantation ions are As, P or a combination of the As and P, the ion implantation times are 1-8 times, the ion implantation energy is 200 kev-4000 kev each time, and the ion implantation dose is 2E11/cm 2~2E13/cm2 each time. Optionally, in the method for manufacturing an image sensor, in the process of forming the cross P-type isolation region in the N-type ion implantation region in each grid through an ion implantatio