Removal of surface contamination after reactive ion etching of silicon dioxide

Abstract

Reactive Ion Etching (RIE) during semiconductor device fabrication can cause surface and near-surface damage or contamination which may degrade electrical performance. We have investigated methods of removing this damage and contamination prior to further device processing. Using X-ray photoelectron spectroscopy we have analysed the surface residue remaining after a CHF 3-based RIE process used for the removal of thermal oxide on Si substrates. The dry etched wafer surface was studied before and after wet chemical cleaning or UV/O 3 exposure. Surface morphology was investigated using atomic force and scanning optical microscopy. Thickness of thermal oxides grown upon dry etched and subsequently treated wafer surfaces were measured. The results indicate the formation of a modified Si surface region underlying a residue layer formed during the RIE process. We report an investigation of the composition and oxidation behaviour as a function of depth through this near-surface region. This was performed by chemical depth profiling using a sequence of room temperature UV/O 3 oxidation and dilute HF oxide removal steps.