Published online by Cambridge University Press: 21 February 2011
The use of an aqueous HF dip as the final ex situ cleaning step following a modified RCA clean before growth of epitaxial Si layers by Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) has been found to cause haze. Two approaches have been employed to eliminate the haze: addition of alcohol to lower the surface energy of the HF solution, and the application of the HF solution by a spin etch technique. We have studied final ex situ treatments with water/HF, ethanol/HF and methanol/HF solutions applied by both dip and by spin methods, and their effects on haze in low temperature Si homoepitaxy by RPCVD. The ratios of solvent to 49% HF (aq) were 40:1, 10:1 and 5:1. Surface carbon and oxygen levels, as measured by Auger Electron Spectroscopy (AES) after the HF solution treatments were found to be comparable for the alcohol/HF and water/HF dips. For the spin application, methanol/HF resulted in higher surface carbon coverage than for ethanol or water HF solutions. Epitaxial silicon films, 2000–4000Å thick, were grown on the wafers at 450°C using RPCVD. Secondary Ion Mass Spectroscopy (SIMS) measurements showed elevated levels of oxygen and carbon contamination at the epi-substrate interface to result when the wafers were treated with water/HF solutions rather than alcohol/HF, but no advantage was observed for the spin versus the dip technique. Films which were cleaned by water/HF exhibited patterns of haze over the wafer surface showing flow lines where the liquid drained from the surface for both dip and spin applications. The alcohol/HF solutions resulted in substantial reduction in haze for the dip application and elimination of haze for the spin application.