Plasma process for selectively etching oxide using fluoropropane or fluoropropylene

Abstract

A plasma etch process, particularly applicable to an self-aligned contact etch in a high-density plasma for selectively etching oxide over nitride, although selectivity to silicon is also achieved. In the process, a fluoropropane or a fluoropropylene is a principal etching gas in the presence of a substantial amount of an inactive gas such as argon. Good nitride selectivity has been achieved with hexafluoropropylene (C F ), octafluoropropane (C F ), heptafluoropropane (C HF ), hexafluoropropane (C H F ). The process may use one or more of the these gases in proportions to optimize selectivity and a wide process window. Difluoromethane (CH F ) or other fluorocarbons may be combined with the above gases, particularly with C F for optimum selectivity over other materials without the occurrence of etch stop in narrow contact holes and with a wide process window.