Surface Cleaning of SiGe(100) and Passivation of Ge(100) with Aqeuous Ammonium Sulfide

Abstract

The effect of standard aqueous cleans including SC-1, HCl, HF, and HCl/HF mixtures on SiGe(100) surfaces with 50, 75 and 85% Ge molar ratios was characterized with x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. HF was most effective at removing both Ge and Si oxides and reduced the carbon contamination. SC-1 selectively depleted Ge from the surface. Passivation of Ge(100) surfaces with aqueous (NH4)2S was characterized with XPS as a function of the solution concentration and with the addition of H2O2. The passivation process was independent of the (NH4)2S concentration and approximately 3 Å of S was deposited or about one layer based on XPS. Addition of H2O2 to very dilute (NH4)2S oxidized the surface while addition to higher concentrations showed similar effects as a sequential HCl/H2O2 treatment.