Smoothing of Plated Au Bumps Based on Template-Stripping for Low-Temperature Bonding

For low-temperature solid-state Au-Au bonding, the bonding surfaces must be smooth. In this study, we used a multiple Au thin-film transfer method based on template stripping to obtain smooth Au surfaces for low-temperature bonding. We employed and compared polyimide films and thermally oxidized Si substrates as template substrates. By transferring the Au thin film from the PI template to the surfaces of the rough-plated Au bumps, the RMS surface roughness decreased from 30 nm to 6 nm with an area of 10x10 µm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, enabling bonding at room temperature.