A light-leakage-proof storage capacitor structure with global exposure pixel and its forming method

Abstract

The invention discloses a lightproof storage capacitor structure employing a global exposure picture element and a forming method of the lightproof storage capacitor structure. A hood-shaped shielding layer comprising an annular contact hole and a metal layer covers the periphery of an upper electrode plate of an MOS capacitor; and a composite structure which extends to surround a lower electrode plate is formed by over etching of the contact hole to shield an incident light. The metal layer and the contact hole have light-tight characteristics, so that the incident light is completely reflected by the composite structure of the shielding layer; the incident light is prevented from entering a charge signal storage area of the MOS capacitor from a polycrystal side wall of the upper electrode plate and a source-drain region of the lower electrode plate; and storage signal distortion caused by the light leakage phenomenon can be prevented.

Description

technical field [0001] The present invention relates to the technical field of integrated circuit manufacturing, and more particularly, to a light-leakage-proof storage capacitor structure and a forming method of a global exposure pixel in a CMOS image sensor. Background technique [0002] An image sensor refers to a device that converts optical signals into electrical signals. Generally, large-scale commercial image sensor chips include charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) image sensor chips. [0003] Compared with traditional CCD sensors, CMOS image sensors have the characteristics of low power consumption, low cost, and compatibility with CMOS technology, so they are more and more widely used. Now, CMOS image sensors have not only been used in the field of consumer electronics, such as miniature digital cameras (DSC), mobile phone cameras, video cameras and digital single-lens reflex (DSLR), but also in the fields of automotive el...

AI Technical Summary

Problems solved by technology

Since the dielectric layer used in the side wall is usually silicon oxide or silicon nitride, and silicon oxide and silicon nitride are fully transparent to incident light, therefore, incident light (such as figure 2 Indicated by the oblique dotted arrow) can penetrate the side wall, N-type polycrystalline and N+ source and drain regions into the polycrystalline upper plate and N-well lower plate area of ​​the capacitor, causing distortion of the charge signal stored in the MOS capacitor , resulting in distortion of the output signal of the CMOS image sensor

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