Role of hydrogen in silicon wafer bonding: an infrared study

Infrared absorption spectroscopy (IRAS) is used to probe the chemical purity of joint silicon wafer surfaces immediately prior to bonding and the wafer interface right after joining. The IRAS technique can give partial chemical information, particularly for hydrogen, and can also indicate the nature of the interactions. Experimentally, the surfaces of Si wafers are probed in two ways: either with multiple internal reflections (MIR) using the wafer itself to trap the IR radiation, or with MIR using a germanium plate to trap the IR radiation. To probe the interface of joined wafers, the technique of multiple internal transmission is used using the joined Si wafers themselves to trap the IR radiation. This configuration is again limited to frequencies above 1500 cm^-2, but its sensitivity to vibrations perpendicular to the interface is 20 times that of MIR.