Imprint lithography for curved cross-sectional structure using replicated Ni mold

Fabrication of patterns with curved cross-sectional profiles for diffractive optical elements are demonstrated by imprint lithography using replicated Ni mold. The master mold pattern is fabricated by an electron beam lithography, where dosage distribution is automatically optimized by a computer aided design (CAD) system taking the proximity effects and resist development process into account. Utilizing the CAD system, a modulated pitched resist pattern with polynomial shaped cross-sectional profiles are successfully obtained by poly (methylmethacrylate) (PMMA) on Si substrate. Using the PMMA resist as a master pattern, replicated mold is fabricated by Ni electroforming followed by Ni electroless plating. Fine and curved cross-sectional patterns are successfully transferred to a resist on Si substrate by imprint lithography using the Ni replicated mold. In the same way, fabrication of sine waved and circular curved structures are demonstrated. This method is exceedingly useful for fabrication of integrated diffractive optical elements with a cross-sectional profile. (C) 2002 American Vacuum Society.