Nanoimprint lithography in the cyclic olefin copolymer, Topas®, a highly ultraviolet-transparent and chemically resistant thermoplast

Thermal nanoimprint lithography (NIL) of the cyclic olefin copolymeric thermoplast Topas((R)) is demonstrated. Topas((R)) is highly UV-transparent, has low water absorption, and is chemically resistant to hydrolysis, acids and organic polar solvents which makes it suitable for lab-on-a-chip applications. In particular, Topas((R)) is suitable for micro systems made for optical bio-detection since waveguides for UV-Iight can be made directly in Topas((R)). In this article full process sequences for spin coating Topas((R)) onto 4 in. silicon wafers, NIL silicon stamp fabrication with micro and nanometer sized features, and the NIL process parameters are presented. The theological properties of Topas((R)) are measured and the zero shear rate viscosity is found to be 2.16 x 10(4) Pa s at 170 degreesC and 3.6 x 10(3) Pas at 200 degreesC while the dominant relaxation time is found to be 4.4 s and 0.9 s, respectively. The etch resistance of Topas((R)) to two different reactive ion etch processes, an oxygen plasma, and an anisotropic silicon etch, is found to be 12.6 nm/s and 0.7 nm/s, respectively. The etch rates are compared to the similar etch rates of 950 k PMMA, cross-linked SU-8, and standard AZ5214E photoresist. Finally, UV-lithography (UVL) followed by metal deposition and lift-off on top of a Topas((R)) film patterned by NIL is demonstrated. This exploits the chemical resistance of Topas((R)) to sodium hydroxide and acetone. The demonstrated UVL and lift-off on top of an imprinted Topas((R)) film opens new possibilities for post-NIL processing. (C) 2004 American Vacuum Society.