Characterization of low-temperature wafer bonding by infrared spectroscopy

We present the results of an infrared (IR) spectroscopic investigation of i nterfaces between two hydrophilic Si wafers bonded at low temperature. Mult iple internal transmission IR spectra were recorded of the bonds, with diff erent chemical pretreatments of Si surfaces employed before bonding. The an alysis of IR spectra shows that the number of O-H and H-Si-O-x species at t he interface depends strongly on the chemical pretreatment type, which dete rmines the bonding energy. The annealing procedure used in the bonding proc ess leads to dissociation of water molecules, oxidation of silicon st the i nterfaces, and diffusion of hydrogen into silicon oxide layer formed at the interface. The difference in bonding processes is discussed. (C) 2000 Amer ican Vacuum Society. [S0734-211X(00)12403-5].