# US 9,437,632 B2 · Image sensor and manufacturing method thereof

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- Number: US 9,437,632 B2
- Document ID: US9437632B2
- Status: Granted
- Kind: B2
- Application number: 14/419,888
- Filed: 2014-06-24
- Published: 2016-01-28
- Granted: 2016-09-06
- Earliest claimed: 2013-08-30
- Assignees: Galaxycore Shanghai Limited Corporation
- Applicants: GalaxyCore Shanghai Limited Corporation
- Inventors: Lixin Zhao; Wenqiang Li; Jie Li; Ze Xu
- Web page: https://patentgrep.com/patent/US9437632B2

## CPC

- H10F 39/8037: {the integrated elements comprising a transistor}
- H10F 39/014: {of CMOS image sensors}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/80377: {characterised by the channel of the transistor, e.g. channel having a doping gradient}
- H10F 39/807: {Pixel isolation structures}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An image sensor and a manufacturing method thereof are provided. The image sensor includes: a photo diode; a first-conductive-type isolating layer; a second-conductive-type lightly-doped region formed in the first-conductive-type semiconductor substrate; a first-conductive-type lightly-doped region formed under the second-conductive-type lightly-doped region, where the second-conductive-type lightly-doped region is isolated from the second-conductive-type region by the first-conductive-type lightly-doped region; a gate structure of a transfer transistor; and a floating diffusion region which is second-conductive-type heavily-doped. In the image sensor, the second-conductive-type lightly-doped region is formed to be connected with the floating diffusion region, thus, a distance between the floating diffusion region and the photo diode may be reduced which may enable photo-induced carriers to be transmitted from the photo diode to the floating diffusion region more rapidly, and further increase the transmission efficiency of the photo-induced carriers.

## Claims

### Claim 1

A method for manufacturing an image sensor, comprising:
A: forming a second-conductive-type region in a first-conductive-type semiconductor substrate to form a photo diode, wherein the second-conductive-type region serves as a region for collecting photo-induced carriers, and forming a first-conductive-type isolating layer above the photo diode in the first-conductive-type semiconductor substrate;
B: forming a second-conductive-type lightly-doped region and a first-conductive-type lightly-doped region under the second-conductive-type lightly-doped region, wherein the second-conductive-type lightly-doped region is isolated from the second-conductive-type region by the first-conductive-type lightly-doped region, wherein the second-conductive-type lightly-doped region and the first-conductive-type lightly-doped region have a self-alignment feature, and the second-conductive-type lightly-doped region and the first-conductive-type lightly-doped region do not contact the second-conductive-type region and the first-conductive-type isolating layer;
C: forming a gate structure of a transfer transistor on a surface of the first-conductive-type semiconductor substrate by a deposition process and a patterning process, wherein the gate structure covers at least a portion of the second-conductive-type lightly-doped region; and
D: forming a floating diffusion region which is second-conductive-type heavily-doped by a doping process, the floating diffusion region contacting with the second-conductive-type lightly-doped region,
wherein in the step B, photoresist is coated on the surface of the first-conductive-type semiconductor substrate, a photolithography process is performed on the photoresist using a first mask plate to expose and develop to form a patterned photoresist, an etching process is performed by taking the patterned photoresist as a mask to form a groove on the surface of the first-conductive-type semiconductor substrate, a doping process is performed to a first portion of the first-conductive-type semiconductor substrate which corresponds to the groove to form the first-conductive-type lightly-doped region, an inner side of the groove is etched to enlarge the groove, and a doping process is performed to a second portion of the first-conductive-type semiconductor substrate which corresponds to the enlarged groove to form the second-conductive-type lightly-doped region.

### Claim 2 (depends on 1)

The method according to claim 1, wherein in the step A, the second-conductive-type region and the first-conductive-type isolating layer have self-alignment feature.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the gate structure covers the first-conductive-type isolating layer and the second-conductive-type lightly-doped region.

### Claim 4 (depends on 1)

The method according to claim 1, wherein in the step C, forming the gate structure comprises: forming a gate oxide layer, a gate layer covering the gate oxide layer, gate sidewalls disposed on two sides of the gate layer in turn by a thermal oxidation process and a patterning process.

### Claim 5 (depends on 1)

The method according to claim 1, wherein when the first-conductive-type is P type, the second-conductive-type is N type; and when the first-conductive-type is N type, the second-conductive-type is P type.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the photo-induced carriers comprise electrons or electron holes.