Method for etching 111 silicon surface on 001 surface silicon wafer

The method discloses a method for etching a 111 silicon surface on a 001 surface silicon wafer, and relates to a semiconductor MEMS device. The method comprises following steps: after the (001) surface silicon wafer is washed; removing a surface oxide layer by BOE; growing a layer of SiO2 thin film on the surface of the (001) surface silicon wafer as a mask film; photoetching and developing rectangle and square figures along a (110) crystal orientation; then postbaking; placing the silicon wafer in the BOE to remove partial SiO2 mask film which is not protected by photoresist; removing the photoresist; placing a sample in a KOH solution for etching; placing the etched silicon wafer in sulfuric acid hydrogen peroxide solutions; reacting; and then washing by water, thus etching the 111 silicon surface on the 001 surface silicon wafer. The etched surface roughness resulted from the low concentration KOH is overcome; the negative factor of low etching rate resulted from the high concentration KOH is overcome; the side etching can be ignored; the technology cycle is shortened effectively; and the cost is reduced.