Wetting properties of silicon surfaces

The wetting properties of silicon surfaces are believed to be important for the process of silicon-silicon direct bonding, and for the broader issue of biocompatibility. The authors have investigated 14 different surface treatments, including several etching and surface modifying agents, and the contact angles to water were measured for each surface treatment. It was shown that the contact angle could be controlled almost continuously between 5 degrees and 96 degrees by varying the surface treatment. Removing the native oxide layer in hydrofluoric acid results in a hydrophobic surface, whereas hydrophilic surfaces are obtained by inserting the wafer in, e.g. boiling NH/sub 3/:H/sub 2/O/sub 2/:H/sub 2/O. Protein compatibility was investigated by measuring the degree of interaction with insulin. The hydrophobic surfaces showed a relatively strong interaction, whereas hydrophilic surfaces are almost completely inert towards insulin.<>