Requirements on resist layers in deep-etch synchrotron radiation lithography

Abstract

To fabricate microstructures with heights of several hundred micrometers and great aspect ratios by the LIGA (German acronym for LIthographie, Galvanoformung, Abformtechnik) process thick poly(methylmethacrylate) (PMMA) resist layers are produced on a metallic base plate. The requirements these resist layers must fulfill are reported. It is shown that it is possible to achieve defect-free structuring with high accuracy using cross-linked PMMA with little content of residual monomer. Good adherence of microstructures with extremely small diameters, even on polished surfaces, is achieved by using an internal coupling agent which establishes a chemical bond between the substrate surface and the PMMA layer. By modifying the resist composition requirements dependent on product specifications can be fulfilled.