Microelectronic Engineering 54 (2000) 229–245 www.elsevier.nl / locate / mee Flow behaviour of thin polymer films used for hot embossing lithography a, a a a b * L.J. Heyderman , H. Schift , C. David , J. Gobrecht , T. Schweizer a Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland b ¨ Institute of Polymers, Federal Institute of Technology ( ETH), CH-8092 Zurich, Switzerland Accepted 16 July 2000 Abstract The viscous flow of thin PMMA films into microcavities during hot embossing has been investigated in order to optimise the moulding process for nanostructured surfaces. The fastest embossing times were obtained at temperatures . 1008C above T with viscosities in the range 300 to 3000 Pa s. Two fill mechanisms have been observed: simple flow of the PMMA g from the borders and formation of polymer mounds. A simple theory was used to estimate the embossing time required to fill a given stamp geometry. Thin polymer ridges with aspect ratios up to 6:1 were moulded and plastic deformation during demoulding was observed.  2000 Elsevier Science B.V. All rights reserved. Keywords: Hot embossing; Nano imprint lithography; Polymer moulding; Microstructures; Nanostructures 1. Introduction The hot embossing process is a low cost, fast method for the parallel replication of structures at the micro- and nanoscale. With a single master or stamp, identical structures can be produced as required over large surfaces. This technique is well established for microstructure fabrication, for example in compact disc moulding and in the manufacture of holographic security features. Currently the use of hot embossing lithography (HEL), also known as nano imprint lithography (NIL), for the production of nanostructures is of interest as it has several advantages over other fabrication techniques. In comparison with optical lithography, it is not limited by the diffraction of light and thin resist films can be patterned down to 10 nm [1]. Other fabrication methods require slow serial processing (electron beam and SPM lithographies), cost intensive technologies (X-ray lithography), or use processes which result in a random patterning of the surface. Applications pursued by our group include large area nanoscale electrode structures [2] and calibration structures for scanning probe *Corresponding author. 0167-9317 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0167-9317(00)00414-7