Anisotropic Etching of Crystalline Silicon in Alkaline Solutions II . Influence of Dopants

摘要: The etching behavior of highly boron doped silicon in aqueous solutions based ethylenediamine, KOH, NaOH, and LiOH was studied. For all etchants, a strong reduction the etch rate for concentrations exceeding approximately 2 �9 10 ~9 cm -3 observed. This value is good agreement with published data onset degeneracy p-type silicon. found to be inversely proportional fourth power concentration. given high concentration, stop effect most effective ethylenediamine-based low concentration KOH least concentrated KOH. On basis these results, model proposed attributing phenomenon electrical effects holes rather than chemical boron. Due dopant width space charge layer on surface shrinks drastically. Therefore, electrons injected into conduction band by an oxidation reaction cannot confined rapidly recombine from valence band. lack impedes water thereby formation new hydroxide ions at surface. Since transfer four required dissolution one atom observed law decrease can explained. germanium or phosphorus much smaller follows different mechanism.