Wet chemical processing of (0001)_Si 6H-SiC. Hydrophobic and hydrophilic surfaces

The wetting characteristics of polished or polished and thermally oxidized, on- and off-axis (0001)_Si 6H-SiC [the silicon-terminated surface of SiC] surfaces in selected acids and bases have been determined and compared with that of (111)Si. Auger electron and X-ray photoelectron spectroscopies and low energy electron diffraction were used to characterize the chemical state and order of these surfaces. The oxidized SiC surfaces were hydrophilic after oxide removal with a 10:1 HF solution and were terminated with approximately a monolayer containing OH, CO, CH, and F species. The same effects were observed for the similarly treated (0001̄)_C [the carbon-terminated surface of SiC], (112̄0), and (101̄0) surfaces. The as-polished SiC surfaces were hydrophobic and covered with a thin (5-10 angstroms) contamination layer composed primarily of C-C, C-F, and Si-F bonded species. Removal of this layer using an RCA SC1 etch or Piranha clean resulted in a disordered hydrophilic SiC surface. A 20 angstroms amorphous Si capping layer both passivated the SiC surfaces and provided a better alternative to the aforementioned contamination layer for producing hydrophobic surfaces on this material.