Anti-adhesive characteristics of CHF3/O2 and C4F8/O2 plasma-modified silicon molds for nanoimprint lithography

The anti-adhesive characteristics of a plasma-modified silicon mold surface for nanoimprint lithography are presented. Both CHF3/O2 and C4F8/O2 plasma were used to form an anti-adhesive layer on silicon mold surfaces. The gas mixing ratios of CHF3/O2 and C4F8/O2 were experimentally changed between 0% and 80% to optimize the plasma conditions to obtain a low surface energy of the silicon mold. The plasma characteristics were examined by optical emission spectroscopy (OES). In order to investigate the changes in surface energy and surface chemistry of the anti-adhesive layer during repeated demolding cycles, contact angle measurements and X-ray photoelectron spectroscopy (XPS) were performed on the plasma-modified silicon mold surface. Simultaneously, the surface morphology of the demolded resists was evaluated by field-emission scanning electron microscope (FE-SEM) in order to examine the effect of the anti-adhesive layers on the duplicated patterns of the resists. It was observed that the anti-adhesive layer formed by CHF3/O2 plasma treatment was worn out more easily during repeated demolding cycles than the film formed by C4F8/O2 plasma treatment, because CHF3/O2 gas plasma formed a thinner plasma-polymerized film over the same plasma treatment time.