CMOS image sensor columns share pixel units and pixel arrays

Abstract

A column sharing pixel unit and a pixel array of a CMOS image sensor. Two column pixels form a set of pixel units. Two pixels share a selection transistor, a source follower transistor, a reset transistor, and a floating active region in the column. Multiple sets of pixel units are arranged in the vertical and horizontal directions to form a two-dimensional pixel array. In the two-dimensional pixel array, two layers of metal connection lines are used for connection. For the metal connection lines, only a 0th layer metal connection line and a 1st layer metal connection line are used as device control lines to collect image information, but a 2nd or higher layer metal connection line is not used as a device control line, so that the height of the medium on the Si surface of a photodiode is decreased, and more light can enter the photodiode, so as to increase the light utilization efficiency and conversion gain of a small-area-pixel sensor, thereby increasing the sensitivity and effectively improving the image quality of the small-area-pixel image sensor.

Description

technical field [0001] The invention relates to a CMOS image sensor, in particular to a column sharing pixel unit and a pixel array of a CMOS image sensor. 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 pixel structure arrangement of CMOS image sensors in the prior art takes 4T2S (four transistors and two pixels shared) as an example. Due to the dependence on the structural characteristics of the pixel itself, the pixel array generally requires the first layer of metal, and the second layer of metal and the third layer of metal are used as device interconnection lines, and multiple rows or columns of the first layer of metal, the second layer...

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 connection blocks part of the light from entering the photodiode ; Moreover, the metal connection between the floating active region and the gate of the source follower transistor is close to the power metal connection, and the parasitic capacitance of the floating active region is large, resulting in a small amplitude (conversion gain) for converting signal electrons into signal voltage

Images