Pattern Transfer Process Using Innovative Polymers in Combined Thermal and UV Nanoimprint Lithography (TUV-NIL)
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1002-N03-01
Pattern Transfer Process Using Innovative Polymers in Combined Thermal and UV Nanoimprint Lithography (TUV-NIL) Francesca Brunetti1,2, Stefan Harrer1, Giuseppe Scarpa1, Paolo Lugli1, Mike Kubenz3, Christine Schuster3, and Freimut Reuther3 1 Institute for Nanoelectronics, Technische Universit‰t M¸nchen, Arcisstrasse 21, Munich, 80333, Germany 2 Electronic Engineering Department, University of Rome "Tor Vergata", Viale del Politecnico 1, Rome, 00133, Italy 3 Micro Resist technology GmbH, Berlin, 12555, Germany
ABSTRACT We performed combined thermal and ultraviolet nanoimprint lithography (TUV-NIL) using a recently developed nanoimprint polymer (mr-NIL 6000 from Micro Resist technology GmbH) and achieved an imprinted feature size of 50 nm. We used commercially available 2inch-diameter transparent quartz molds (NIL Technology, Denmark and Obducat, Sweden) comprising 150 nm to 190 nm-deep features of various shapes and aspect ratios with lateral dimensions ranging between 50 nm and 300 nm. The imprint polymer was spun onto a silicon substrate, covered with an oxide layer. After the TUV-NIL step, residual polymer layers at the bottom of the imprinted features were removed by oxygen plasma etching. Imprinted patterns were then transferred into the silicon oxide layer underneath by reactive ion etching (RIE). In a final step the residual polymer was stripped off the silicon oxide surface in an oxygen asher. All imprinted features as well as the corresponding pattern transfer results showed good surface and sidewall characteristics. INTRODUCTION The introduction of deep UV lithography with improved quartz lenses and high-output light sources brought major improvements to conventional lithography techniques [1] [2]. Milestones of the development of UV Lithography (UVL) were the invention of UV-zone-platearray lithography (UV-ZPAL) [3] and immersion ZPAL [4]. Recently reported results show that UV-nanoimprint lithography (UV-NIL) in general has reached a level that allows the fabrication of electronic devices (such as amorphous silicon thin-film transistors (TFT) [5]) and structures reaching the 40-nm-scale [6]. In order to further extend the success of the UV-NIL technique, its resolution, overlay, and throughput need to be improved [7]. This can be done by developing new imprint polymers, looking in particular at critical parameters such as sensitivity to UV light, thermal stability, surface tension, shrinkage, modulus, viscosity, and etch resistance. A novel version of NIL uses UV radiation in addition to thermal treatment [8]. Combined thermal NIL and UV-NIL (TUV-NIL) uses the effect that a polymer patterned by thermal NIL can be cured by exposing it to UV radiation while keeping it at its imprint temperature Timprint before stamp release. This enables a complete isothermic imprint cycle at Timprint [9] [10]. Therefore TUV-NIL has the potential of significantly shorter process times than conventional
thermal NIL processes. Additionally, TUV-NIL imprint polymers can be designed in such a way that their impri
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