IC Process Compatible Preparation of Silicon Interfaces Using the Silicon-to-Silicon Direct Bonding Method

Silicon/silicon interfaces were prepared by wafer bonding using the silicon-to-silicon direct bonding method. Silicon/silicon interfaces (n/n-type) with excellent electric properties were prepared, by using hydrophobic wafer surfaces, at temperatures in the range of 7000° C to 1000° C. The influence of the bonded interface on device characteristics of bonded p⁺n junctions prepared at low temperatures was seen as n-factors larger than 2 at forward bias. A correlation between n-factors and the density of states in the bandgap was found. In hydrophilic samples, the density of voids at the bonded interface was determined mainly in the contacting of the wafer surfaces at room temperature. Compared to hydrophilic samples, hydrophobic samples were held together at a smaller fraction of the area before heat treatment. After the heat treatments, no difference in the density of voids was found.