Micromachining applications of a high resolution ultrathick photoresist

This article describes a new negative-tone photoresist, SU-8, for ultrathick layer applications. An aspect ratio of 10:1 has been achieved using near-ultraviolet lithography in a 200-μm-thick layer. The use of this resist for building tall micromechanical structures by deep silicon reactive-ion etching and electroplating is demonstrated. Using SU-8 stencils, etched depths of ≳200 μm in Si and electroplated 130-μm-thick Au structures with near-vertical sidewalls have been achieved.