Microfluidic Channels in Polymethyl-Methacrylate by Optimizing Aluminum Adhesion

A study has been performed to determine the optimum surface treatment to adhere an aluminum hard mask to a polymethyl-methacrylate (PMMA) wafer substrate for the production of microfluidic channels. The initial process parameters of the PMMA reactive ion surface treatment included oxygen plasma, sulfur hexafluoride plasma and argon plasma designs of experiments. However, a soak in tetra methyl ammonium hydroxide (TMAH) proved to provide the most adhereable surface for an aluminum deposition. It is hypothesized that the TMAH soak allowed for the removal of the surface layer of the PMMA wafer substrate. The aluminum hard mask was deposited by evaporation after the wafers were surface treated with TMAH. Using contact photolithography, the aluminum was patterned and the PMMA wafer substrate was etched isotropically in propalene glycol mono methyl ether acetate (PGMEA) for the creation of microfluidic channels. Success of this project is based on the quality of the aluminum evaporated film and the transparency of the PMMA wafer substrates after the isotropic etch in PGMEA