Three-dimensional SU-8 structures by reversal UV imprint

In this work, three-dimensional (3D) SU-8 micro- and nanostructures were fabricated using a reversal UV imprint process at low temperature and low pressure. The SU-8 polymer was coated on a patterned glass mold and then transferred onto various substrates by reversal UV imprint at a typical temperature of 50°C, pressure of 1 MPa, and UV exposure of 1 s. The lower temperature and pressure used compared to conventional thermal imprint shorten the imprint time and alleviate pattern distortion. A combination of silanes was used to generate a medium surface energy on the imprint molds to enable polymer spin coating and mold release after imprint. In addition, an O ₂ plasma was used for glass mold treatment to improve uniformity of silane coating and to increase substrate surface energy for better polymer adhesion. Using this technology, 100 nm-1 μm wide SU-8 gratings were fabricated on flat or patterned substrates with good fidelity. By repeating this process, multiple-level nanochannels, cavities, or air-bridging polymer structures with 400 nm-10 μm widths have been demonstrated. The surface energy of SU-8 was modified using an O ₂ plasma to promote layer adhesion for 3D stacking. This reversal UV imprint technology offers versatility and flexibility to stack polymer layers and multiple-level sealed fluidic channels. © 2006 American Vacuum Society.