Oxide removal by remote plasma treatment with fluorine and oxygen radicals

Abstract

Oxides (e.g., native or thermal silicon oxide) are etched from underlying silicon with a mixture of fluorine and oxygen radicals generated by a remote plasma. The oxygen radicals rapidly oxidize any uncovered bare silicon areas, preventing the pitting that can result from fluorine etching bare silicon more rapidly than it etches the surrounding oxide. A very thin (few Å), highly uniform passivation layer remaining on the silicon after the process may be left in place or removed. An oxygen-impermeable layer may be formed in-situ immediately afterward to prevent further oxidation. A pre-treatment with oxygen radicals alone fills pores and gaps in the oxide before etching begins.