Silicon Surface Treatments and Their Impact on Chemical Composition and Morphology

Abstract

The smoothness of silicon wafer surfaces is defined by polishing. Subsequent cleaning steps take account of surface conditioning of the wafer and meet the demands for low metal surface contamination as well as low particle level. Wet chemical treatments, however, can also influence surface morphology. The coexistence of oxidation and etching of the Si surface has a pronounced feedback on the resulting surface roughness. This holds in particular for SC1 cleaning solutions and modified HF treatments. Buffered HF enhances surface roughness of the technological important Si (100) surface, in contrast to a smoothening effect on Si (111). The same holds for other modifications of HF treatments with an enhanced oxidation behaviour involved, like HF-H2O2 solutions. In parallel with the change of surface morphology and with the increase of surface roughness an increase in Light Point Defect (LPD) densities is also found. Small LPDs are predominantly not particle related, depend on the respective silicon substrate material and were not found to influence gate oxide integrity.