Electrical characterization of interfaces in unitype directly bonded silicon wafers

The effect of processing technology and oxygen contamination on the electrical characteristics of the interface of unitype directly bonded Si wafers is investigated. A study on p–p and n–n bicrystals bonded after joining in air or deionized water shows that the interface activity is defined by a contamination level of oxygen and acceptor-like impurities (probably aluminum). The activity of oxygen-free interface in the bicrystals manufactured by joining and annealing of ion-etched wafers in vacuum depends mainly on mismatching of the bonded wafer crystal lattices. The properties of bicrystals with a buried oxide layer specially grown before bonding are strongly dependent both on the homogeneity of SiO2 and contamination of SiO2/Si interface by aluminum.