Microfabrication of a nickel mold insert by a modified deep X-ray lithography process and its application to hot embossing

In the present study, a modified deep X-ray lithography process is utilized for an efficient fabrication of precise metallic mold insert. A bare bulk polymethylmethacrylate (PMMA) sheet is used without any substrate as an X-ray photoresist in order to achieve a stable fabrication by avoiding a generation of a secondary radiation during a deep X-ray lithography process. The patterned PMMA sheet after development is then bonded on a metallic substrate using adhesive layers. The adhesive layers on the opened region of the patterned PMMA sheet are subsequently removed by X-ray exposure of short duration time. The next procedure is an electroplating process onto the opened area in the PMMA sheet, consequently resulting in the final mold insert. In this manner, a robust metallic mold insert for a mass replication of microstructures could be realized quite efficiently. The present fabrication method is confirmed by an example with a replication of microchannels via hot embossing process.