Nanoindentation behavior of UV-curable resist and its correlation with patterning defect in nanoimprint lithography

Abstract

Nanoimprint lithography (NIL) is a useful technique for nano/micropattern replication. For ultraviolet-NIL (UV-NIL), the volume shrinkage of the resist upon curing is strongly affected by the applied UV exposure, possibly due to the various degrees of cross-linking. The applied UV intensity also influences the mechanical behaviors of the cured resist and the demolding force separating between the mold and the cured resist. The mechanical properties of the resists cured at different levels are studied in detail by nanoindentation. The statistically derived defect rate of the replicated pattern strongly depends on the demolding process and the mechanical strength of the cured resist. By simply decreasing the applied UV exposure during curing, the volume shrinkage can be reduced to ∼3%. Such low volume shrinkage also induces high plasticity of the cured resist and low demolding force, which yield a low defect rate of replicated patterns (e.g. ∼1E-4) even with a blank silicon mold without surfactant coating. Several different types of patterning defects are found to be linked to the mechanical properties of the cured resists. The quantitative guidance on the tailoring of the mechanical properties of the cured resist for a targeting defect rate is provided. The information gained in this work will bring insights into resist formulation design and nanoimprint process optimization to improve the fidelity and mitigate the defect rate of the pattern transfer in UV-NIL.