Chemical treatment effects of silicon surfaces in aqueous KF solution

The physical and chemical properties of Si(1 1 1), (1 1 0) and (1 0 0) surfaces treated in aqueous KF solution have been studied by means of spectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and wettability measurements. The SE data indicate that the solution causes the removal of the silicon native oxide upon immersing the sample in the solution. The KF-treated Si(1 1 0) and (1 1 1) surfaces are nearly flat even after long-time etching. By contrast, the Si(1 0 0) surface is found to be considerably etched and roughened even if the etching time is shorter than the native oxide is completely etch-removed (t < 30 min). The SE-estimated surface roughness is in reasonable agreement with the AFM rms value. The XPS data suggest that the KF-treated surface is cleaner than that etched in an HF solution. The as-degreased silicon surface is hydrophilic (θ ∼ 35°), while the KF-treated surface is hydrophobic (θ ∼ 80°). The properties of the KF-treated surface have also been discussed as compared to those obtained in aqueous NaF and HF solutions.