The mask technology of HgCdTe dry etching technique was investigated. Photoresist was used as etching mask for HgCdTe inductively coupled plasma (ICP) enhanced reactive ion etching (RIE) process. Because the selectivity over photoresist was very low, the photoresist mask was obviously narrow and the profile of mesa formed by ICPRIE was not smooth and vertical. Therefore, SiO2 film grown by magnetron sputtering with good selectivity was used as etching mask. Smooth and vertical HgCdTe etchedfacets were obtained with SiO2 mask. The following IV test showed that the standard growth process of SiO2 caused electrical damage to the surface of HgCdTe. By optimizing the process parameters, SiO2 mask on HgCdTe without damage was obtained finally.