Evolution of the interface structure of bonded Si wafers after high temperature annealing

The evolution of the interfaces of bonded Si wafers and the corresponding low-angle twist boundary have been analysed in dependence on thermal annealing. Two orientation relations were investigated: i) Si(001)/SiO2/Si(001) and ii) Si(110)/SiO2/Si(001). The interfaces were analysed by TEM and STEM/EDX and EELS. It is found that the decomposition rate of the intermediate oxide layer and the formation of a Si-Si bonded interface depend very much on the lattice mismatch and on the twist angle. A dissolution of the oxide and the formation of Si-Si boundaries occur much faster in the case of Si(110)/Si(001) bonding than in Si(001)/Si(001). The process of interface fusion and the dissolution of the oxide layer are discussed.