HYDROPHILICITY OF SILICON-WAFERS FOR DIRECT BONDING

The hydrophilicity of the silicon wafer surface caused by hydroxylgroups and physisorbed water plays an essential role in silicon wafer direct bonding. Different wafer pretreatments from the literature are tested applying the contact angle method for the estimation of the hydrophilicity. Special attention is paid to the RCA clean and ageing processes of the surface. The doping and the orientation of the silicon wafers influence the desorption of water during ageing. The best hydrophilization method forming fully hydrated surfaces with very good long time stability is the plasma activation.