Optimization of Au mask fabrication process for LIGA applications

This paper presents approaches to fabricate Au masks for LIGA process. The proposed fabrication process starts with deposition of a thick layer of Au film, then followed by electron cyclotron resonance (ECR) Ar⁺ etching and coating of a polymer material that is used as a membrane. Finally the ICP DRIE etching is applied from backside to figure out the membrane. The profiles of the Au microstructures on the mask have been improved thanks to the optimization of etching process and photoresist material. The fabricated masks have been used in the X-ray lithography and demonstrated a well acceptable performance. A nickel mold has been successfully realized by electroplating and used in a hot embossing process for forming optical components. Au masks made by using conventional Au-electroplating technique have also been demonstrated for a comparison.