Influence of silicon oxide on the morphology of HF-etched Si(111) surfaces: Thermal versus chemical oxide

Infrared reflection-absorption measurements of the Si-H stretching vibrations of HF-etched Si(111) surfaces show that the structure of the H-passivated surfaces depends strongly on the nature of the initial silicon-oxide layer. For similar etching conditions, thermal oxides lead to much flatter surfaces than chemical oxides. A new processing sequence involving the removal of thermal oxide by buffered HF (pH=5), followed by etching in a 40% ammonium-fluoride solution, produces a remarkably homogeneous H/Si(111)-(1×1) surface, characterized by a 0.05 cm−1 broad Si-H stretch-mode.