Improved etching method for microelectronic devices with supercritical carbon dioxide

Aqueous etchants used in traditional wet etching for the production of integrated circuits and MEMS devices hinder the processes and pose environmental difficulties. Therefore, we developed an improved dry etching method with HF/Pyridine (7:3) in supercritical carbon dioxide. Etch rates of BPSG, P-TEOS, Thermal SiO2 and SiN with dry etching method were several times higher than those in wet etching. Etch rates were found to be a function of temperature, HF concentration, and the kind of co-solvents. The presence of alcoholic co-solvents, especially IPA with HF/Pyridine etchant greatly increased the etch rate of BPSG. Etch selectivity could be controlled with the etchant concentration.