Structure of active pixel of CMOS (Complementary Metal Oxide Semiconductor) image sensor and manufacturing method thereof

Abstract

The invention relates to a structure of an active pixel of a CMOS (Complementary Metal Oxide Semiconductor) image sensor and a manufacturing method thereof. The structure comprises an active pixel circuit region, a floating node and a photosensitive element, wherein the photosensitive element comprises an optical filter and a P-type epitaxial layer for receiving light filtered by the optical filter; an N-type doped U-shaped buried layer is injected in the P-type epitaxial layer; a P+ type doped layer is inserted in the N-type buried layer; the P+ type doped layer comprises two subregions consisting of different dosage concentration substances; and the doped subregion with high concentration is surrounded by the doped subregion with low concentration, or the doped subregion with high concentration is surrounded by the doped subregion with low concentration and the boundary of the N-type buried layer together. According to the invention, when the full well capacity of a photodiode can be improved, a dark current of a silicon-silicon oxide interface is also reduced.

Description

technical field [0001] The present invention relates to the field of semiconductor devices and processing and manufacturing, more specifically, to a structure and method for improving the performance of a complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS for short) image sensor. Background technique [0002] Compared with a charge coupled device image sensor (Charge Coupled Device, CCD for short), a CMOS image sensor (Contact Image Sensor, CIS for short) has superior performance in its manufacturing process and compatibility with existing integrated circuit manufacturing processes. The CMOS image sensor can integrate the driving circuit and the pixels together, which simplifies the hardware design and greatly reduces the power consumption of the system; CIS can take out the electrical signal while collecting the optical signal, and can process the image information in real time, which is faster than the CCD The image sensor is fast; and, ...

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Problems solved by technology

However, if this structure has no obvious improvement effect on the completely depleted photodiode, it can only increase the concentration of N-type doping to improve the full well capacity, which will also increase the N-type doping in the photodiode region and the surface P+ type. Dark current at the interface of doped pinned layer

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