Abstract: In order to obtain good etching effect, parameters as working pressure and ratio of gas flux for etching processes with and without Al mask were studied. The results are as follows: under the same conditions, etching rate varies little; whether or not having Al mask on a: CH films have no effect on etching rate; when gas flux is fixed, etching rate descends with bulk ratio of argon and oxygen increasing. In this study, the best etching conditions are using pure oxygen gas, flux of 4 mL·s-1, working pressure of 9.9×10-2 Pa, microwave current of 80 mA, bias of -90 V. Under these conditions, fabricated micro-gear has vertical sidewall, small degree of distortion. Micro-gear could be released from the substrate using HF solution.