Formation of smooth Au surfaces produced by multiple thin-film transfer process based on template stripping for low-temperature bonding

Surface roughness plays a crucial role in the low temperature solid-state bonding. Here, we present a multiple thinfilm transfer method for the fabrication of smooth Au surfaces. The multiple thin-film transfer procedure uses a template stripping, which mechanically peeling-off the Au thin films prepared on a smooth template, and the simultaneous lowtemperature direct bonding process to target rough surfaces. By repeating this transfer process, rms surface roughness of rough Au surfaces decreased from 205 nm to 10 nm over a large area (90 × 90 μm
²
) and from 3.1 nm to 0.8 nm over a small area (1 × 1 μm
²
), respectively. Au-Au surface activated bonding of rough surface finished Si substrates with or without template stripped Au thin films was performed at a low temperature (150 °C). Strong bonds between the Au/Au were formed in the case of multiple thin-film transfer process, although bonding didn't succeed without template stripped Au.