Image pixel sensor pixel structure of hole transmission

Abstract

The invention discloses an image pixel sensor pixel structure of hole transmission. Each group of pixel unit transistors of the structure is a PMOS transistor. Since a PMOS transistor has smaller output noise, the output noise can be reduced, and since PMOS transistors are placed inside an N well, the noise of peripheral devices can be isolated. Each group of pixel unit transistors can effectively reduce dark current and increase anti-irradiation capability. In the hole transmission image sensor 2D pixel array, two layers of metal lines are used to connect metal connecting lines, and only the zero layer of metal lines and the first layer of metal lines are used for serving as control lines of a device to acquire image information, and the second layer or higher layer of metal lines are not used as control lines of the device, so that the height of the medium on the surface of the photodiode Si and more light can radiate to the photodiode, and light usage efficiency and transition gain of small-area pixel sensor can be increased and sensitivity can be increased; in addition, the structure can effectively increase image quality of the small-area pixel sensor.

Description

technical field [0001] The present invention relates to the technical field of image sensors, in particular to an image sensor pixel structure for transporting holes. 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 technologies for manufacturing CMOS (Complementary Metal Oxide Semiconductor) image sensors and CCD (Charge Coupled Device) image sensors has made people have higher requirements for the output image quality of 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 sharing) as an example, due to the dependence on the structural characteristics of the pixel itself, the transistors in the prior art are all NMOS The output noise of the NMOS tube itself is higher than that of the PMOS tube, and the dark curren...

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Problems solved by technology

[0005] Since the output noise of the NMOS tube itself is relatively high, and it is also connected to the entire P substrate, the noise of the peripheral circuit is easily conducted to the transistor through the substrate, which aggravates the output noise and affects the output image effect; the dark photodiode in the prior art The current is large, and white spots will be generated when the image sensor outputs the image, which will affect the output image effect

[0006] 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 line blocks 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

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