Polysilicon etching method

The invention provides a polysilicon etching method. The method comprises the following steps of S1, forming a SiN layer on the surface of a polysilicon layer, etching the SiN layer and patterning the SiN layer to obtain a SiN hard mask layer; S2, forming an oxide layer between SiN residual particles which are not etched thoroughly and on the periphery of the SiN hard mask layer and the polysilicon layer; S3, adopting wet etching to remove the oxide layer, and enabling the SiN residual particles to separate from the polysilicon layer due to suspension; and S4, etching the polysilicon layer taking the SiN hard mask layer as a mask layer. The invention prevents that fact that silicon nitride residual particles obstruct follow-up polysilicon etching, and greatly reduces polysilicon residual defects. With the polysilicon etching method, the photoetching time is not required to be increased, almost no influence on subsequent processes exists, disadvantages of using the traditional DARC as a hard mask layer are suc