SU8 resist plasma etching and its optimisation

The thick photoresist SU8, by virtue of its good mechanical durability, water impermeability and dielectric properties on polymerisation, is widely used as a resin for making high aspect ratio, functional MEMS device structures and packaging parts. However, the difficulty associated with removal, stripping or repatterning of the polymerised SU8 remains a serious issue. This paper presents a novel process, based on O/sub 2//SF/sub 6/ plasma etching, for patterning or removal of fully cross-linked SU8. The Taguchi methodology is used to optimise the O/sub 2//SF/sub 6/ mix for a high etch rate and low under cut.