Trench etching method

Abstract

The invention discloses a trench etching method, and relates to the field of semiconductor manufacturing. The method comprises the steps of forming a hard mask layer on a substrate, forming a layer ofphotoresist on the surface of the hard mask layer, forming a trench opening pattern in the photoresist, and the feature size of the trench opening pattern being smaller than the target feature size of a trench opening; etching according to the trench opening pattern, forming a trench opening pattern on the hard mask layer, forming a groove with a predetermined depth in the top of the substrate, increasing the feature size of the trench opening pattern in the hard mask layer, the feature size of the trench opening pattern in the hard mask layer being equal to a target feature size, etching thesubstrate according to the increased trench opening pattern; and forming a trench in the substrate. The problem that after a groove is etched at present, the top of the side wall of the groove is likely to be laterally hollowed out is solved. And the effects of avoiding the side hollowing phenomenon at the top of the side wall of the groove and optimizing the groove forming process are achieved.

Description

technical field [0001] The present application relates to the field of semiconductor manufacturing, in particular to a trench etching method. Background technique [0002] The trench of a conventional MOS device is formed on the surface of the substrate. When the MOS device is turned on, the source-drain current flows through the channel in a direction parallel to the gate oxide. With the continuous improvement of device breakdown voltage and integration requirements, the structure of MOS devices has changed, and power MOSFETs have appeared. [0003] The MOSFET with trench gate structure changes the channel from horizontal to vertical, which eliminates the influence of planar parasitic JFET. At the same time, the reduced cell size increases the current gain and reduces the on-resistance. When fabricating trench-gate MOSFET devices, trenches need to be formed in the substrate. The steps of making the trench are: forming a hard mask on the surface of the substrate, defining ...

AI Technical Summary

Problems solved by technology

[0004]However, during the etching process, due to the relatively high selection of silicon to the hard mask, the sidewall at the top of the trench is prone to undercut11 phenomenon, As shown in Figure 1, it is easy to affect the performance of the device

Images