Room-Temperature Wafer Bonding Using Smooth Au Thin Films for Integrated Plasmonic Devices

Room-temperature wafer bonding of 4-inch Si wafers with a few tens of nanometers thick Au films using Ar plasma surface activation was demonstrated for integrated plasmonic devices. Thermal stability of Cr/Au multilayer thin films was investigated by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that annealing at 200 °C for 10 min resulted in considerable Cr diffusion and this indicates that low-temperature bonding is desirable for the integration of multilayer metal thin films.