Image sensor and method of forming the same

Abstract

The invention provides an image sensor and a forming method thereof. The image sensor comprises a silicon-on-insulator (SOI) substrate, wherein the SOI substrate comprises a wafer back absorption layer, a bottom layer substrate, a buried oxide layer and a top layer substrate; the buried oxide layer is located at the upper part of the bottom layer substrate; the top layer substrate is located at the upper part of the buried oxide layer and comprises a pixel region and an absorption region; the absorption region is located on the periphery of the pixel region; the pixel region comprises a photoelectric diode PD and a transistor unit; an absorption structure is arranged in the absorption region and comprises polycrystal layers and covering layers; the covering layers ares located on the surfaces of the polycrystal layers; and the absorption layer is in a laminated structure which is formed by alternate arrangement of the polycrystal layers and the covering layers; the covering layers are used for inhibiting recrystallization of the polycrystal layers; and the absorption structure can effectively absorb metal impurities in the top layer substrate, reduces the dark current and improves the image quality.

Description

technical field [0001] The invention relates to the technical field of semiconductor manufacturing, in particular to an image sensor and a forming method thereof. Background technique [0002] Image sensors are devices that convert light signals into electrical signals, and are widely used in digital TV and visual communication markets. [0003] CMOS Image Sensors (CMOS Image Sensors, CIS) is an image sensing element manufactured using the principle of photoelectric technology. The composition of its photosensitive pixels is an array structure, which is mainly composed of MOS capacitors or p-n junction photosensitive diodes. CIS is formed by integrating light-sensitive light unit array (photodiode), transfer transistor, reset transistor, source follower transistor and selection transistor on a silicon chip board by traditional chip technology. [0004] Manufacturing a CMOS image sensor by using a silicon-on-insulator (Silicon-On-Insulator, SOI) substrate can effectively re...

AI Technical Summary

Problems solved by technology

Metal impurities in the top substrate are easily diffused into the semiconductor device in the pixel area during heat treatment, and are trapped to form metal impurity energy levels, resulting in dark current and affecting image quality

[0006] It can be seen that the CIS formed by the silicon-on-insulator substrate in the prior art has the disadvantages of large dark current and poor image sensor performance.

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