Researching the Aluminum Nitride Etching Process for Application in MEMS Resonators

We investigated the aluminum nitride etching process for MEMS resonators. The process is based on Cl-2/BCl3/Ar gas chemistry in inductively coupled plasma system. The hard mask of SiO2 is used. The etching rate, selectivity, sidewall angle, bottom surface roughness and microtrench are studied as a function of the gas flow rate, bias power and chamber pressure. The relations among those parameters are reported and theoretical analyses are given. By optimizing the etching parameters, the bottom surface roughness of 1.98 nm and the sidewall angle of 83 degrees were achieved. This etching process can meet the manufacturing requirements of aluminum nitride MEMS resonator.