Etching of Thermal Oxides in Low Pressure Anhydrous HF/CH₃OH Gas Mixture at Elevated Temperature

Etching of thermal oxides in HF/CH₃OH gas mixture at the pressure from 100 to 500 Torr and wafer temperatures from 25 to 120°C is studied using a commercial cluster tool compatible reactor. Pressure and temperature are selected to control condensation of reactants on the etched surfaces, and hence, the thermal oxide etch rate. Using this etching mode, controlled etching of thermal oxides at rates up to 200 A/min was achieved without any water vapor intentionally added to the input gases.