PLASMA PROCESS FOR SELECTIVELY ETCHING OXIDE USING FLUOROPROPANE OR FLUOROPROPYLENE

摘要

A plasma etch process, particularly applicable to a 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 (C3F6), octafluoropropane (C3F8), heptafluoropropane (C3HF7), hexafluoropropane (C3H2F6). The process may use one or more of these gases in proportions to optimize selectivity and a wide process window. Difluoromethane (CH2F2) or other fluorocarbons may be combined with the above gases, particularly with C3F6 for optimum selectivity over other materials without the occurrence of etch stop in narrow contact holes and with a wide process window.