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

Abstract

Thermal nanoimprint lithography (NIL) of the cyclic olefin copolymeric thermoplast Topas® is demonstrated. Topas® 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® is suitable for micro systems made for optical bio-detection since waveguides for UV-light can be made directly in Topas®. In this article full process sequences for spin coating Topas® onto 4 in. silicon wafers, NIL silicon stamp fabrication with micro and nanometer sized features, and the NIL process parameters are presented. The rheological properties of Topas® are measured and the zero shear rate viscosity is found to be 2.16×104 Pa s at 170 °C and 3.6×103 Pa s at 200 °C while the dominant relaxation time is found to be 4.4 s and 0.9 s, respectively. The etch resistance of Topas® 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® film patterned by NIL is demonstrated. This exploits the chemical resistance of Topas® to sodium hydroxide and acetone. The demonstrated UVL and lift-off on top of an imprinted Topas® film opens new possibilities for post-NIL processing.

Stretching DNA in polymer nanochannels fabricated by thermal imprint in PMMA

“…Thermal imprint was performed in PMMA (MicroChem Corp., 50 k PMMA dissolved in pure anisole to give a 30 wt% solution) which is a well known thermoplastic polymer introduced for NIL by Chou et al in their pioneering work [9]. PMMA has a water absorption of 0.3% [21], a glass transition temperature of T g = 105…”

Surface modification of thermoplastics—towards the plastic biochip for high throughput screening devices

“…The hydrogenation step is necessary for increasing the thermal stability of the plastic by removing carbon-carbon double bonds that are necessarily formed during the polymerisation process. [6][7][8] Although there exist poly(cyclic olefins) that contain ethers, esters and aromatic groups, a number of commercial poly-(cyclic olefins) are saturated hydrocarbons. Consequently, it is difficult to introduce suitable functional groups at the surface of these chemically inert plastics which are expected to have a low intrinsic fluorescence background.…”

Nanoimprint lithography of topology optimized photonic crystal devices

“…The nanoimprinted patterns are transferred into the top 320 nm thick silicon layer of a SOI substrate by using an optimized SF 6 -based inductively coupled plasma (ICP) etch. The etch selectivity of silicon over mr-I T85 is 9:1 (Silicon:mr-I T85) [4] which allows for pattern transfer of the imprinted holes through the device silicon layer of the SOI substrate. The lithographic result of our imprint process is compared to devices fabricated by direct electron beam writing of the etch mask.…”