Thick-Film Deposition of High-Viscous Liquid Photopolymer
There are high interests among the researchers and industries for effective deposition of thick layer liquid photo-resists with applications such as fabrication of microfluidics and polymeric membranes using lithography. In this paper, we study performance of different techniques of coating for thick layers of SU-8 using spin coating, self planarization and a technique of sandwiching the resin between two parallel solid plates. Deposition using spin coaters for SU-8 2075 is limited hardly to around 250 µm with some irregularities such as edge-beads. Self-planarization requires enough resting time. We have achieved a thickness of around 1 mm in a single coating but is limited to only thick layers in reasonable time. The sandwich technique can be used for any thickness and is very fast. We present here a comparison of the three mentioned methods according to our observed data of the coating time, uniformity of the coating surface and capability of coating thick layers for a high viscosity SU-8 2075 that is employed in fabrication of microfluidics micro-structures.
Lynn Khine and Julius M. Tsai
J. Alvankarian et al., "Thick-Film Deposition of High-Viscous Liquid Photopolymer", Advanced Materials Research, Vol. 254, pp. 5-8, 2011