Method for improving breakdown voltage of gate oxide layer of groove-type VDMOS device

Abstract

The invention provides a method for improving a breakdown voltage of a gate oxide layer of a groove-type VDMOS device. The method comprises the following steps of providing a silicon substrate with an epitaxial layer; forming an initial oxide layer on the epitaxial layer of the silicon substrate; photoetching and etching so as to form an active region pattern on the initial oxide layer; injecting ions, and forming an active region in the epitaxial layer below the active region pattern; photoetching, sequentially performing wet etching and dry etching, and forming a loop region pattern and a grid pattern on the initial oxide layer, wherein the initial oxide layer is reserved above the loop region pattern and the grid pattern; injecting ions, and forming a loop region in the epitaxial layer below the loop region pattern; forming a gate above the grid pattern. The method is capable of effectively protecting the surface of the epitaxial layer below the gate oxide layer from being damaged by processes such as etching and injection, thus obviously improving the breakdown voltage of the gate oxide layer and effectively improving an IGSS failure ratio.

Description

technical field [0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a method for increasing the breakdown voltage of a gate oxide layer of a trench type VDMOS device. Background technique [0002] For trench VDMOS devices, the breakdown voltage of the gate oxide layer is a very important performance parameter. If the breakdown voltage of the gate oxide layer is low, it will lead to an increase in the failure ratio of gate-source leakage (IGSS), and even lead to the scrapping of the entire device in severe cases. [0003] In the manufacturing process of the initial ring region of the trench VDMOS device, operations such as ion implantation and etching are usually required, and the etching process includes wet etching and dry etching. Wet etching usually immerses the etching material in the etching solution for etching, which has good selectivity and isotropy, and the width of lateral etching is close to the depth o...

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Problems solved by technology

Wet etching usually immerses the etching material in the etching solution for etching, which has good selectivity and isotropy, and the width of lateral etching is close to the depth of vertical etching, but the distance between adjacent rings is relatively small. It is not applicable in small cases; dry etching uses plasma for etching, which has good anisotropy, but cannot be selectively etched. In order to ensure that the initial oxide layer is etched clean, usually in dry etching overetch

[0004] These operations in the process of making the initial ring area can easily cause damage to the surface of the epitaxial layer of the silicon substrate, resulting in a decrease in the quality of the gate oxide layer grown on the damaged site, a decrease in the breakdown voltage, and ultimately the failure of the device IGSS

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