Gas-phase etching of SiO2 layers in an HF/C2H5OH mixture

This paper describes a technique for dry etching SiO 2 layers in MEMS technologies without the moving elements sticking. Etching the sacrificial SiO 2 in anhydrous HF (hydrofluoric acid in the gas phase) allows avoiding the subsequent complex operations of cleaning and drying, which are mandatory in the case of liquid etching. Using the HF/C 2 H 5 OH anhydrous mixture under low pressures makes it possible to prevent water condensation, which is due to etching in HF vapor, and allows one to employ gas-phase etching in surface MEMS technologies. The mechanisms and physicochemical processes taking place when etching thermal SiO 2 are discussed. The rate of etching thermal SiO 2 films is investigated at temperatures ranging from 30 to 50°С and under chamber pressures ranging from 10 to 20 kPa.