The state of etched semiconductor surfaces as revealed by electron diffraction

Germanium and silicon (100) and (111) surfaces have been etched with a variety of reagents and subsequently examined by reflection electron diffraction. No oxide layers were detected on surfaces etched with the common mixtures containing hydrofluoric and nitric acids. When metal ions were present, either as essential components or as impurities in the etchants, deposits, either of the metals or of compounds, were sometimes found; in particular, contamination from materials commonly used for making contacts to devices has been found. No preferential deposition was found on either side of an etched p-n junction. Details of the sensitivity of electron diffraction are included as an Appendix.