High-sensitivity cmos image sensor shared pixel structure

Abstract

The invention discloses a sharing type pixel structure of a high-sensitivity CMOS image sensor. The sharing type pixel structure of the high-sensitivity CMOS image sensor comprises a plurality of photodiodes, charge transfer transistors and a first floating active area, wherein the number of the photodiodes is the same as the number of the charge transfer transistors. The sharing type pixel structure of the high-sensitivity CMOS image sensor further comprises a reset transistor, a source following transistor, a column selection transistor and a second floating active area. The first floating active area and the second floating active area are spaced through a switch transistor. The source following transistor detects a potential signal of the second floating active area. The stray capacitance of the second floating active area does not change along with the number of shared pixels. By the sharing type pixel structure, the photovoltaic conversion gains of the shared pixels are effectively increased, and the luminous sensitivity of the CMOS image sensor with the sharing type pixel structure adopted is effectively improved.

Description

technical field [0001] The invention relates to an image sensor, in particular to a shared pixel structure of a high-sensitivity CMOS image sensor. Background technique [0002] Image sensors have been widely used in digital cameras, mobile phones, medical devices, automobiles and other applications. In particular, the rapid development of the technology for manufacturing CMOS (Complementary Metal Oxide Semiconductor) image sensors has made people have higher requirements for the output image quality of the image sensor. [0003] CMOS image sensors in the prior art, especially CMOS image sensors using small-area pixel units, generally use a shared pixel structure, such as sharing two pixels, sharing four pixels, or sharing more pixels. The important reason for using pixel sharing is to save transistors in order to expand the area of ​​the photodiode, thereby improving the photosensitivity of the pixel; however, this way of improving photosensitivity sacrifices the photoelec...

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Problems solved by technology

[0009] The larger n in the above equation, the more transistors the pixel saves on average, and the more the photodiode area of ​​the pixel is enlarged, the higher the pixel sensitivity will be; however, the larger n in the equation, the total floating active area The higher the capacitance CFDn, the lower the photoelectric conversion gain and the lower the photosensitive sensitivity of the pixel, which is contrary to the original intention of increasing the photosensitive sensitivity by enlarging the photodiode area.

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