Improvement of silicon direct bonding using surfaces activated by hydrogenplasma treatment

The plasma surface treatment, using: hydrogen gas, of silicon wafers was st udied as a pretreatment for silicon direct bonding. Chemical reactions of t he hydrogen plasma with the surfaces were used for both surface activation and removal of surface contaminants. Exposure of the silicon wafers to the plasma formed art active oxide layer on the surface. This layer was hydroph ilic. The surface roughness and morphology were examined as functions of th e plasma exposure time and power. The surface became smoother with shorter plasma exposure time and lower power. In addition, the plasma surface treat ment was very efficient ill removing the carbon contaminants on the silicon surface. The value of the initial surface energy, as estimated by using th e crack propagation method, was 506 mJ/m(2), which was up to about three ti mes higher than the value for the conventional direct bonding method using wet chemical treatments.