Plasma etching of thermoset polymer films for microchannels

Abstract

A technique is presented for fabricating, microchannels for flow investigation with fluorescent particles. The channels were fabricated using plasma etching of a thermoset polymer film, UV 15 from Master Bond. The UV15 was spun on different substrates to give a depth of 120 mu m. A 100 nm thick patterned aluminium film was sputtered and patterned on the polymer surface for the etch pattern mask. Sputtering conditions were obtained to prevent damage to the polymer layer. Curing conditions were optimized to prevent wrinkling of the Al/UV 15 surface during etching. A high glass transition temperature T-g is important to prevent the Al/UV 15 surface front wrinkling during etching. T-g is examined using differential scanning calofimetry. There is a wide variation in the polymer etch rate, which can be attributed to many factors, and one of the most significant is the energy dos c (mW cm(-2)) to cure the polymer. For etch depths greater than 20 mu m the channel cross section shape varied from rectangular by undercutting on the walls and deeper etching at the bottom of the channel walls. Conditions for obtaining uniform microchannels of width 100 mu m, depth up to 70 mu m and length of 5 cm are presented. The channels were sealed and fluid flow observed under a microscope using fluorescent nanoparticles.