Forming method of CMOS image sensor

Abstract

According to a forming method of a CMOS image sensor provided by the invention, nitrogen element doping is carried out on the surface of a semiconductor substrate in a photodiode region, and the doped nitrogen element can form a silicon-nitrogen bond on the surface of the semiconductor substrate in the photodiode region, so that plasma induced damage caused by a subsequent process can be effectively reduced, the production of dark current and white pixels is reduced, the signal-to-noise ratio of the CIS is improved, the product yield and the image quality are improved, and the performance of the image sensor is improved. Besides, fluorine element doping can be carried out on the surface of the semiconductor substrate in the photodiode area after nitrogen element doping, and plasma induced damage can be further reduced through formed silicon-fluorine bonds.

Description

technical field [0001] The invention relates to a method for forming a CMOS image sensor. Background technique [0002] CMOS Image Sensor (CMOS Image Sensor, CIS), as a device unit that converts optical signals into digital electrical signals, is widely used in various emerging fields such as smartphones, tablet computers, automobiles, and medical care. The incident photons are converted into electrons by the pixel array, and when an integration period is completed, the collected electrons are converted into digital signals by analog and digital circuits, and transmitted to the output terminal of the sensor. [0003] Such as figure 1 As shown, in the current CMOS image sensor manufacturing process, the photodiode 101 is first formed in the semiconductor substrate 100, and then after the transfer transistor, reset transistor and other structures are formed, an oxide layer 106 is formed on the surface of the semiconductor substrate, usually a rich Silicon Rich Oxide (SRO), a...

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Problems solved by technology

[0004] However, during the formation of the self-aligned silicide barrier layer or in the subsequent process, plasma is often introduced to bring plasma-induced damage (Plasma Induced Damage, PID), resulting in the formation of a large number of dangling bonds on the silicon-oxygen surface. The existence of the key is easy to generate electrons in the dark field of the image sensor, and these electrons are collected by the photodiode, resulting in dark current or white pixel (White Pixel, WP) phenomenon, affecting product yield and image quality

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