Pattern fidelity in nanoimprinted films using critical dimension small angle x-ray scattering

The primary measure of process quality in nanoimprint lithography (NIL) is the fidelity of pattern transfer, comparing the dimensions of the imprinted pattern to those of the mold. Routine production of nanoscale patterns will require new metrologies capable of nondestructive dimensional measurements of both the mold and the pattern with subnanometer precision. In this work, a rapid, nondestructive technique termed critical dimension small angle x-ray scattering (CD-SAXS) is used to measure the cross sectional shape of both a pattern master, or mold, and the resulting imprinted films. CD-SAXS data are used to extract periodicity as well as pattern height, width, and sidewall angles. Films of varying materials are molded by thermal embossed NIL at temperatures both near and far from the bulk glass transition (T _G). The polymer systems include a photoresist and two homopolymers. Our results indicate that molding at low temperatures (T-T _G<40°C) produces small-aspect-ratio patterns that maintain periodicity to within a single nanometer, but feature large sidewall angles. While the observed pattern height does not reach that of the mold until very large imprinting temperatures (T-T _G = 70°C), the pattern width of the mold is accurately transferred for T-T _G>30°C.