Manipulation of exposure dose parameters to improve production of high aspect ratio structures using SU-8

The detailed consideration of the chemistry occurring during the fabrication process is very important for SU-8 compared to other photoresists. In SU-8, the solvent does far more than just act as a carrier for the photoactive compounds: it plays a prominent role in the processing chemistry. In this paper we explain how the change of solvent from old to new formulations of SU-8 has an effect on the processing of this resist. We then show how, and why, in the modern 2000 series formulations the manipulation of the polymerization rate via variation of the exposure dose allows dark field features on a mask design to be reduced, in a controlled manner, by up to 30% while still maintaining good sidewall profiles in features. (paper)