Novel low-temperature CMOS-compatible full-wafer-bonding process for the fabrication of 3D embedded microchannels using SU-8

This article describes a novel low temperature full wafer adhesive bonding process to fabricate three-dimensional (3-D) embedded microchannels using SU-8 photoresist as structural material. The technology development includes an improvement of the SU-8 photolithography process in order to produce high uniformity films using Taguchi methodology. After that, 3-D embedded microchannels are fabricated by a low temperature adhesive bonding of the the SU-8 thick-films. The process parameters have been chosen in order to achieve a strong and void-free bond. Different examples using this new technology are shown, including bonding between Silicon, Pyrex and combinations of them, in order to obtain 3-D interconnected microchannels between the wafers. Microchannels with vertical smooth walls and aspect ratios up to five have been obtained. Channels depth from 40 to 60 μm and 10 to 250 μm width have been achieved. Liquid has been introduced into the channels verifying a good sealing of the 3-D microchannels. The fabrication procedure described in this article is fast, reproducible, CMOS compatible and easily implemented using standard photolithography and bonding equipment.