Preparation method of semiconductor device

Abstract

The invention provides a preparation method of a semiconductor device. The method comprises the steps of providing a substrate, and forming a photodiode region and a floating diffusion region in the substrate; forming a patterned mask layer on the substrate; and taking the patterned mask layer as a mask to etch partial depth of the substrate, so as to form a gate trench located between the photodiode region and the floating diffusion region in the substrate, at least partial depth of the gate trench being formed by a cyclic etching process. The circular etching process comprises a first etching process and a second etching process which are circularly carried out, the first etching process is used for etching the substrate, the second etching process is used for etching a polymer formed in the first etching process, and the side wall of the part, formed by adopting the circular etching process, of the gate trench is vertical. According to the invention, the generation of white pixels is reduced, and the electrical performance of the device is improved.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing a semiconductor device. Background technique [0002] CMOS image sensors are semiconductor devices that convert optical images into electrical signals. CMOS image sensors are widely used in mobile phone camera, industrial inspection, security and other fields. With the continuous shrinking of the pixel size in CMOS image sensors, in order to obtain better full well capacity, the ion implantation depth of the pixel area is getting deeper and deeper, which will lead to a decrease in the electron transmission efficiency in the deeper part of the photodiode, and the CMOS image sensor reads The speed is slow, which leads to image smearing and other phenomena that affect the image quality. The proposal of the vertical gate process can effectively improve the electron transmission efficiency. The vertical gate process is to change the traditional planar cha...

AI Technical Summary

Problems solved by technology

However, in the etching process of the gate trench, if the sidewall uniformity of the gate trench is poor or the bottom is not smooth enough, the electric field distribution of the gate trench will be uneven, resulting in tip discharge and white pixels. Thus affecting the electrical performance of semiconductor devices

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