Fabrication of X-ray masks and applications for optical switch molding

Conventional X-ray masks for LIGA process are generally fabricated using Au electroplating. In this paper, a new approach of fabricating LIGA masks for X-ray lithography was demonstrated. The fabrication process started with deposition of a layer of Au film as thick as 5 μm on silicon substrate, then followed by electron cyclotron resonance (ECR) Ar⁺ etching, coating of negative resist SU-8 as a membrane for supporting and protection of patterned Au structures, and high aspect ratio reactive ion etching (RIE) from backside of the substrate. The fabricated Au masks were used for X-ray lithography. A PMMA mold-master of optical switch with a mirror height of 210 μm and verticality of 88.9° was obtained, which demonstrated a well acceptable performance.