Ex situ wafer surface cleaning by HF dipping for low temperature silicon epitaxy

Abstract

Ex situ silicon wafer cleaning by HF dipping has been studied in terms of cleaning efficiency. Silicon epitaxial layers were deposited in the MC-CVD (Multi-Chamber Chemical Vapor Deposition) reactor, which had a Load Lock Chamber. In situ cleaning was performed with an ECR (Electron Cyclotron Resonance) hydrogen plasma exposure. The XTEM (Cross-sectional Transmission Electron Microscopy) was performed to investigate the structural qualities of the epitaxial layer and the epilayer/substrate interface. The SIMS (Secondary Ion mass Spectroscopy) was performed to investigate their interfacial carbon and oxygen concentrations. HF dipping without water rinsing, followed by thermal heating up to 660°C provided the best results in terms of contamination. Rinsing seemed to help the surface natural oxide grow, but it improved the surface smoothness of the epitaxial layer. Blow-drying by nitrogen was important in reducing the interfacial oxygen concentration of the deposited epitaxial layer. Spin-drying turned out to be efficient in removing hydrocarbons or organic species. The ex situ cleaning played a major role in reducing the amounts of surface contaminants.