By F. Giannazzo, S. Di Franco, V. Raineri, from CNR-IMM, Stradale Primosole 50, 95121 Catania, Italy.

Abstract

 In this paper, we report the results obtained by the application of the SET FC150 equipment for UV Nanoimprinting Lithography (UV-NIL), using nanostructured quartz molds, which were properly functionalized by an antisticking treatment. The used process condition, establlished after an accurate optimization of the imprint parameters (time profiles of force, substrate temperature and UV irradiation), are described in details. In order to accurately characterize the pattern transfer on a negative resist deposited on a Si substrate, optical microscopy (OM) and atomic force microscopy (AFM) were carried out both on the quartz mold and on the structures obtained on resist after UV NIL process; In particular, we show that the used process conditions allowed us to obtain a resist residual thickness inferior of 10 nm on the Si substrate at the bottom of the imprinted region, which is optimal to perform subsequent plasma treatments without degrading the features on resist. Finally, some examples of structures obtained on resist deep submicron dimensions are reported.


Introduction

 Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and low cost. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques.

Tow main implementations of NIL have been demonstrated to date, i.e. hot embossing lithography (HEL) have been demonstrated to date, i.e. hot embossing lithorgraphy and UV nanoimprint lithography (UV-NIL).

In the first apporach, a thermoplastic resist material is used, whose viscosity is greatly reduced upon heating at temperatures higher than a critical value (the glass transition temperature Tg); therefore, the hard mold is able to penetrate in this fluid material; finally, its layout remains imprinted in the resist after its coolingdown below Tg. For this application molds have to be fabricated with materials with high thermal conductivity.

In the NIL the curing of the resist materials during mold imprinting is obtained by UV light illumination. Dedicated UV curable resists have to be used for UV-NIL; however, higher resolution pattern transfer on resist can be achieved by this approach than with hot-embossing.....

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