Molecular Dynamics Simulation of the Resist Filling Process in UV-nanoimprint Lithography

The selection and design of appropriate resist materials is indispensable for a successful nanoimprint lithography (NIL) technique. Currently, the pattern resolution of NIL is below 10 nm. Therefore, atomic-scale analysis of the NIL process is required for further development in this field. In this study, we performed all-atom molecular dynamics (MD) simulations of the filling process of resist molecules in ultraviolet NIL (UV-NIL). To simulate the filling process, silicon molds with different trench widths (1, 2, and 3 nm) were pressed into different resist materials composed of two or four molecular species with different viscosities (viscosity range 4 to 5,566 mPa.s) under constant pressure (100 atm). In the MD simulations, resists with viscosities lower than 10 mPa.s were successfully filled into the 3-nm wide trench. Lowering the resist viscosity shortened the time required for complete filling. In the resist consisting of four molecular species, the 1-nm-wide trench was preferentially filled by the lower-viscosity molecules; consequently, the resist molecules were non-uniformly distributed in the system. This inhomogeneity would lead to defects after the UV curing process. The MD simulations also showed that when mixed with small resist molecules, the multi-functional resist molecules can more easily enter a narrow cavity, which is advantageous for fabricating high-resolution patterns by UV-NIL. The molecular behaviors during the filling process observed in the MD simulations provide useful information for the future design of defect-free resists.