Low temperature direct bonding of silicon and silicon dioxide by the surface activation method

Low temperature bonding of Si and SiO₂ by the surface modification in a vacuum was examined. For the bonding of Si wafers, surface cleaning by Ar beam etching was effective to improve the bonding prepared in the vacuum at room temperature. The strength was equivalent to that of conventional wafer bonding with high temperature annealing. For the bonding of SiO₂ both Ar beam and H₂O beam treatment were applied. SiO₂ bonding strength was about a half of Si bonding. The influence of surface oxidation was also examined by exposing etched Si surface to residual gas in a vacuum chamber. Long time exposure before bonding caused the reduction of bonding strength. These results mean that oxidized surface has less bonding ability than clean surface etched by Ar beam at the room temperature