Acrylated Hyperbranched Polymer Photoresist for Ultra-Thick and Low-Stress High Aspect Ratio Micropatterns
Different photocurable acrylates, including two hyperbranched monomers, are compared with an epoxy negative-tone photoresist (SU-8) with respect to their suitability for the fabrication of ultra-thick polymer microstructures in a photolithographic process. To this end, a resolution pattern was used and key parameters, such as the maximum attainable thickness and aspect ratio, the minimum resolution and the processing time were determined. Compared to SU-8, all acrylate materials allowed the fabrication of thicker layers with a fast single layer fabrication procedure. Microstructures with thicknesses of up to 850 μm, an aspect ratio of up to 7.7, a 5.5-fold reduction in internal stress and a 6-fold reduction in processing time compared to SU-8 were demonstrated using an acrylated hyperbranched polyether. The specific development process of the hyperbranched polymer combined with channel design moreover enabled us to produce a high-performance valve for micro-battery devices.