SURFACE CLEANING FOR SI EPITAXY USING PHOTOEXCITED FLUORINE-GAS

We have demonstrated surface cleaning for Si epitaxy using photoexcited fluorine gas diluted with argon (F2/Ar). We found that F2/Ar cleaning removed native Si oxide, as well as carbon contaminants. The method lowered the surface preannealing temperature needed to grow single-crystal Si films to 690-degrees-C. This preannealing is equivalent to annealing in a hydrogen ambient in conventional chemical vapor deposition. The temperature is low because the native Si oxide is thinned by F2/Ar cleaning. F2/Ar cleaning also reduced interfacial impurities, such as oxygen and carbon, between the epitaxial layer and the substrate for preannealing temperatures above 730-degrees-C. We found that F2/Ar cleaning works on bulk features near the Si surface, including the elimination of point defects by fluorine atoms and/or removing carbon and oxygen near the surface. F2/Ar cleaning has good potential for cleaning in Si epitaxy.