Flow behaviour of thin polymer films used for hot embossing lithography

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 > 100 degreesC above T-g with viscosities in the range 300 to 3000 Pa s. Two fill mechanisms have been observed: simple how of the PMMA 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. (C) 2000 Elsevier Science B.V. All rights reserved.