Improved Phosphoric Acid Mixtures for Nitride Strip

摘要

Wet chemical etching using hot phosphoric acid at high temperature is commonly used for the removal of nitride films during silicon wafer processing. The nitride-to-oxide etch selectivity using H_3O_4 at 160℃ typically amounts to 50:1. As rather high over-etch times are employed to ensure complete removal of the nitride films and because thinner and/or faster etchable oxide films are used for future generations of technologies, a more reproducible and higher etch selectivity is demanded. In this paper it will be demonstrated that the nitride-to-oxide etch selectivity can be significantly improved by using a Si-based additive in the bath.