Chemical patterning of sub-50-nm half pitches via nanoimprint lithography Sunggook Park, Sina Saxer, Celestino Padeste, Harun H. Solak, Jens Gobrecht, Helmut Schift * Laboratory of Micro- and Nanotechnology, Paul Scherrer Institut, Villigen PSI 5232, Switzerland Available online 19 January 2005 Abstract We report on a fabrication method of achieving local chemical modification of a surface at the sub-50-nm scale by a process sequence of nanoimprint lithography, gas phase surface modification and lift-off. This was combined with a new stamp fabrication via extreme ultraviolet interference lithography to produce extremely small patterns of high density and large area. In this method, we have demonstrated chemical patterns of a fluorinated silane on an unprecedented feature size of as small as 25-nm half pitch. However, chemical contrast of high quality needed for biological and sens- ing applications was still difficult to achieve due to the contamination on the background surface areas, which is asso- ciated with the lift-off process. This will be discussed with results obtained by subsequently immobilizing a fluorescence labeled protein on the chemical patterns using different lift-off conditions and process sequences. Ó 2005 Elsevier B.V. All rights reserved. Keywords: Nanoimprint lithography; Chemical patterns; Silanes; Protein patterns 1. Introduction Spatial control over chemical functionality (chemical patterning) on a surface has become a major challenge for electronic, optoelectronic, bio- logical, and sensing applications [1–4]. In many cases, the reduction of the spatial resolution helps to improve the device performance. For example, the sensitivity of sensing elements increases by miniaturization of the pattern sizes, leading to an improved detection limit in the sensing devices [1]. In biological applications, the immobilization of a low number of molecules, e.g., single protein or DNA molecules would provide a means to broaden the understanding of a variety of sur- face-mediated biological recognition events. In general, local modification of surface chemistry re- quires the process sequence of nanofabrication via 0167-9317/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2004.12.085 * Corresponding author. Tel.: +41 56 310 2839; fax: +41 56 310 2646. E-mail address: helmut.schift@psi.ch (H. Schift). Microelectronic Engineering 78–79 (2005) 682–688 www.elsevier.com/locate/mee