Template Stripping Process Combined With Polyimide and SiO₂/Si Templates for Obtaining Smooth Au Surfaces

Surface roughness is a dominant factor for low-temperature Au-Au solid-state bonding. Here, we present a multiple Au thin-film transfer method using a template-stripping method for obtaining smooth Au surfaces to achieve bonding at low temperatures. Polyimide films and Si substrates with thermal oxide (SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) films were used as templates. By transferring Au thin films from the templates to the rough plated Au surfaces, rms surface roughness of rough plated Au surfaces decreased from 21 nm to sub-nanometers (scan area: 10 × 10 µm 2 ). Using Si chips with templated-stripped Au thin films, room-temperature Au-Au bonding was realized in air atmosphere environment.