Viscosity of a Thin Film of UV Curable Resin in Pentafluoropropane

Abstract

It is known that UV curable resin used in UV nanoimprint shows viscosity change when thin UV-curable resin films are created by spin-coating. Through the study of UV nanoimprint using pentafluoropropane (PFP), which is a promising method enabling high-throughput and reliable UV nanoimprint, it was found that PFP may reduce the viscosity of UV curable resin PAK-01. In this paper, the effect of PFP on the viscosity of spin-coated PAK-01 is carefully studied with our unique viscosity measurement apparatus using an unpatterned mold under the same conditions as in UV nanoimprint where a patterned mold is contacted with spin-coated UV curable resin on a wafer. The effect of viscosity reduction occurs by PFP exposure even for 1s and the effect is not dependent on PFP exposure time. On the other hand, the effect caused by PFP exposure is lost by air exposure for less than 1 s. Namely, the gas, which exists at the moment when a UV curable resin film is making contact with a mold, impacts the viscosity of the UV curable resin regardless of the gas exposure history. We also preliminarily investigated a patterned mold which can trap a larger amount of gas and found that a patterned mold gives the lower viscosity than unpatterned one.