A pixel unit structure for reducing dark current and its manufacturing method

Abstract

The invention discloses a pixel unit structure for reducing dark current and a manufacturing method of the pixel unit structure. An original transfer tube grid in a conventional pixel unit is concealed; a metal structure is utilized to cover the upper part of the position of the original transfer tube grid; a well region, a lower pinch-off layer, a channel layer and an upper pinch-off layer are arranged between a photodiode and a suspended drain from bottom to top to form a channel region; and the metal structure is utilized as a light blocking layer of the channel region, so that an incident ray is prevented from affecting charges in a lower conductive channel. The metal structure is taken as a control terminal for opening and closing the channel layer; and an interface state between a gate oxide layer of the original transfer tube grid and substrate silicon can be removed, so that the dark current of the pixel unit is effectively reduced.

Description

technical field [0001] The present invention relates to the technical field of image sensors, and more particularly, to a pixel unit structure capable of reducing dark current of a CMOS image sensor and a manufacturing method thereof. Background technique [0002] An image sensor refers to a device that converts optical signals into electrical signals. Image sensors generally include Charge Coupled Devices (CCD) and Complementary Metal Oxide Semiconductor (CMOS) image sensors. [0003] Compared with traditional CCD sensors, CMOS image sensors have the characteristics of low power consumption, low cost and compatibility with CMOS technology, so they are more and more widely used. Now CMOS image sensors can be used not only in the field of consumer electronics, such as miniature digital cameras (DSC), mobile phone cameras, video cameras and digital single-lens reflex (DSLR), but also in automotive electronics, monitoring, biotechnology and medical fields. . [0004] For CMO...

AI Technical Summary

Problems solved by technology

[0008] In the above-mentioned conventional pixel unit structure, since there are dangling bonds formed during the gate oxide oxidation process at the interface between the gate oxide layer 17 under the transfer tube gate 13 and the substrate silicon 10, these dangling bonds become some defects. center, which becomes the generation and recombination center of electron-hole pairs; in the process of charge transport, even under the condition of total darkness without light, this part of the charge signal generated by the dangling bonds at the interface will cause the rise of dark current, making the pixel The signal-to-noise ratio of the unit is reduced, and the image quality is reduced

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