CMOS (complementary metal oxide semiconductor) image sensor column-sharing 2X2 pixel unit and CMOS image sensor pixel array

Abstract

The invention discloses a CMOS (complementary metal oxide semiconductor) image sensor column-sharing 2X2 pixel unit and a CMOS image sensor pixel array. Four pixels are arrayed to a 2X2 pixel array to serve as a pixel unit group, and two pixels in the front column and two pixels in the rear column of each pixel unit group respectively share a selective transistor, a source following transistor, a reset transistor and a drift active region in the same column. Metal wiring in a two-dimensional pixel array of a CMOS image sensor is achieved by metal wires in two layers, the metal wires in the zero layer and the metal wires in the first layer are used as device control wires to achieve an image information acquisition function, the metal wires in the second layer or the higher layer are unused as device control wires, and the dielectric height on the Si surface of a photodiode can be decreased to enable more light to be incident to the photodiode, so that light use efficiency and conversion gain of a small-area pixel sensor can be increased, and further, sensitivity is improved, and image quality of the small-area pixel image sensor can be effectively improved.

Description

technical field [0001] The invention relates to a CMOS image sensor, in particular to a CMOS image sensor column sharing 2×2 pixel units and a pixel array. Background technique [0002] Image sensors are already widely used in digital cameras, mobile phones, medical devices, automobiles and other applications. In particular, the rapid development of CMOS (Complementary Metal Oxide Semiconductor) image sensors has made people have higher requirements for low power consumption, small size, and high resolution image sensors. [0003] The CMOS image sensor columns in the prior art share the arrangement of the 2×2 pixel unit structure. Taking 4T2S (four transistors and two pixels shared) as an example, due to the dependence on the structural characteristics of the pixels themselves, the pixel array generally requires the first layer Metal, second-level metal and third-level metal are used as device interconnection lines, and multiple rows or columns of first-level metal, second-...

AI Technical Summary

Problems solved by technology

[0005] Due to the small photosensitive area and low sensitivity of the small-area pixel sensor, the information transmitted in dark light is not clear enough

Especially when the first layer of metal, the second layer of metal and the third layer of metal are used as device interconnection lines, the dielectric height on the surface of the photodiode Si (silicon) is relatively high, and the metal lines block part of the light from entering the photodiode; Moreover, the metal line connecting the floating active area to the gate of the source follower transistor is close to the power supply metal line, and the parasitic capacitance of the floating active area is large, resulting in a small amplitude (conversion gain) for converting signal electrons into signal voltage

Images