Surface Topography of Ion-Etched Si Wafers Studied by Electron Microscopy

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Abstract
Wafers of 111 and 100 Si which had been mirror-finished and then scratched by #1500–3000 grit abrasive paper were ion-etched and their surfaces were investigated by SEM and cross-sectional high-resolution TEM techniques. Ion etching was carried out at incident angles of 75°, 65°, 55° at 5 kV Ar+ ion beam by rotating the specimens around the axis normal to the wafer surface. The etched surface of the mirroe-finished Si wafer stayed smooth for 4 hours of ion etching. After more than 4 hours of ion etching, round projections of 1–10 µm in diameter were generated. Cross-sectional observation showed small pyramidal protuberances of 5–20 nm in height on the 100 surface with facets of (111). No protuberances were observed on the 111 surface. The thickness of the amorphous layer formed on the 111 surface was different from the one on the 100 surface.