Model for Al etch-rate enhancement at low temperatures

A surface reaction model for aluminum etching by chlorine is proposed, which takes into account the temperature dependence of the thermal processes and the ion-assisted processes simultaneously. In the model, chlorine physisorption and chemisorption are treated separately, based on the previous work on chlorine adsorption on aluminum. In particular, cluster formation was introduced into the chlorine physisorption process to allow physisorbed species to exist on the Al surface. The model reproduced the measured Al etch rate, including the Al etch-rate enhancement in the low-temperature regime. This etch-rate enhancement was found to be brought about by the increase in physisorbed chlorine on the Al surface, followed by ion-assisted reaction and desorption.