Abstract: Aimed at the problem of device short circuit caused by MEMS step etching, a method based on Bosch is proposed by analyzing the reason for silicon grass formation and the main process parameters of deep silicon step etching, such as etching passivation and Ar physical bombardment, which adopts periodic etching-passivation-pre-etching to form the precision step structure. The method greatly improves the bias power and time of reasonably allocating etching. The results show that, under the process conditions of pre-etching bias power of 100W and pre-etching time of 0.8s, the production of silicon grass can be effectively suppressed. After step etching is completed, SF₆ etching gas is used to clean the step silicon grass for 10s to ensure that the silicon grass is completely removed. At this time,the step drop structure obtained is flat and smooth, and the verticality of the etched comb teeth is better than 90°±1°. This method has the characteristics of good repeatability and simple process.

Key words: step etching, high aspect ratio, pre-etching, Si grass, Bosch