Excimer laser micromachining with half-tone masks for the fabrication of 3-D microstructures

Excimer laser micromachining by mask projection with half-tone masks has been used to define deep structures with complex surface profiles in cross-linked SU-8 photoresist. A simple algorithm has been developed to derive the required mask transmission function given the material etch characteristics and the desired surface profile. This algorithm has been shown to give reasonable profile accuracy for structures with heights of up to about 150 μm. The technique has been used in the fabrication of the rotor blades for an axial-flow microturbine.