Atomic force microscopy and high-resolution RBS investigation of the surface modification of magnetron sputter-etched Si(111) in an argon plasma at different pressures

The surface morphology and metallic contamination of magnetron sputter-etched Si(111) was investigated by atomic force microscopy (AFM) and high-resolution Rutherford backscattering spectroscopy (RBS) as a function of Ar plasma pressure. The root-mean-square roughness (R_rms) of plasma-etched Si decreased monotonically from 36±28 angstroms at 2×10^-3 mbar to 13±6 angstroms at 2×10^-2 mbar. High-resolution RBS showed that metallic impurity contamination increased with increasing plasma pressure, whereas Ar atom incorporation in the near-surface region of etched Si followed the opposite pressure dependence. The barrier height of Pd Schottky contacts fabricated on the etched n-Si also decreased monotonically with decreasing Ar pressure, showing that the extent of barrier height modification was not affected by metallic impurity contamination. High-resolution RBS combined with channelling experiments showed that the topmost layers of the plasma-etched samples were disordered. The thickness of the damaged layers decreased with increasing plasma pressure.