Oxidation to mitigate dry etch and/or wet etch fluorine residue

Abstract

In some implementations, fluorine is oxidized after dry etching an oxide layer above a source/drain contact and before cleaning. Accordingly, less hydrofluoric acid is formed during cleaning, which reduces unexpected wet etching of the source/drain contact. This allows for forming a recess in the source/drain contact with a depth to width ratio in a range from approximately 1.0 to approximately 1.4 and prevents damage to a layer of silicide below the source/drain that can be caused by excessive hydrofluoric acid. Additionally, or alternatively, the recess is formed using multiple wet etch processes, and any residual fluorine is oxidized between the wet etch processes. Accordingly, each wet etching process may be shorter and less corrosive, which allows for greater control over dimensions of the recess. Additionally, less hydrofluoric acid may be formed during cleaning processes between the wet etch processes, which reduces the etching of the source/drain contact between processes.