Evaluation of oxygen inhibition for UV-curable resins by adhesion force measurement using scanning probe microscope

Abstract

UV nanoimprint lithography is used to fabricate nanostructure devices with high throughput, low cost, and high resolution. UV-curable resins are one important factor in UV nanoimprinting and they are mainly categorized into two reaction types: radical and cationic curing systems. A drawback of the radical curing system is curing inhibition by oxygen. To evaluate the oxygen inhibition for UV-curable resins, the authors measured the force curve transition by scanning probe microscopy with an UV irradiation system. With this system, the authors are able to measure in situ the UV dose dependence of the force curve transition on the same UV-curable resin. Measurements showed that the curing speed of radical UV-curable resin in vacuum became 800 times higher than that in air due to oxygen inhibition. Furthermore, for a cationic UV-curable resin, although the curing reaction of a cationic UV-curable resin is not affected by oxygen, the authors observed that the curing speed in vacuum at about 15 Pa became 4.5 times higher compared to that in air. The curing reaction of a cationic UV-curable resin may be inhibited by alkali.