Micro Fabrication of Au Thin-Film by Transfer-Printing Using Atomic Diffusion Bonding

Transfer printing of a thin film is a great candidate technique for micro/nanofabrication for microelectromechanical system (MEMS) elements. The authors propose a technique to apply atomic diffusion bonding to transfer printing of a gold (Au) thin film. When a substrate is previously coated with Au thin film as an adhesive, another Au thin film can be transfer-printed from a h-PDMS stamp to the substrate. It enables 50 μm-wide line patterns of the Au thin film located on the Au-coated Si substrate, whereas the Au thin film cannot be transfer-printed on a bare (uncoated) Si surface. The interface between two Au thin films disappears after transfer printing; hence, the Au atoms can interdiffuse from one to another to make a strong bonding. This process can be performed with a soft contact without any pressure in atmospheric and vacuum conditions. In the case of Au, the atoms can interdiffuse around a contacted area at room temperature. Moreover, one can make 50 μm-wide line patterns by 1 min of transfer printing and that of 24 h. The proposed process makes the line patterns of the Au thin film transfer-printed to be a bridged microbeam over the grooves when a prestructured (grooved) substrate is prepared.