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Effects of mold geometries and imprinted polymer resist thickness on ultrasonic nanoimprint lithography

This paper investigated the effects of imprinted resist thickness and mold geometries on the polymer flow and the temperature distribution of ultrasonic nanoimprint lithography (U-NIL) through numerical simulations and experiments. In simulations, the velocity fields in the imprinting stage and the temperature distributions in ultrasonic vibrations are performed under variations of convexity width, cavity width and thickness of the imprinted polymer resist. The study of the velocity field, including the lateral and vertical velocity, is significant because the velocity field can directly describe the mode of the polymer deformation, which is the key role to determine the mechanism of nanoimprint forming. Though the velocity field is crucial for the polymer deformation, it is often ignored and is rarely found in the literature. In ultrasonic vibrations, the temperature distribution of U-NIL is different from that of the thermal NIL and deserves to be investigated. Moreover, the combined effects of the imprinting stage and ultrasonic vibrations in the U-NIL process are discussed. Furthermore, experiments were conducted to verify the results performed by the numerical simulations. In this work, the simulations and experiments provide a deep understanding of polymer flow affected by the velocity field and temperature distribution during U-NIL, which should be well applied to a thermal NIL.