Polymer issues in nanoimprinting technique

We have studied the suitability of poly(methylmethacrylate) (PMMA) of diffe rent molecular weight for large area pattern transfer by embossing structur es above the glass transition temperature (T-g,) of the specific polymer. T he molecular weight covers a range of one order of magnitude (M-w, similar to 5.0 x 10(4)-8.1 x 10(5)). This range was chosen in order to obtain infor mation regarding the flow properties that we expect to depend strongly on t he molecular weight at a specific temperature. Large area pattern transfer were tested by applying a stamp with both densely packed and isolated featu res. The feature size ranged from 100 mu m down to 450 nm. At a processing temperature of 90 degrees C above T-g we found clear indications that flow is sufficient to transfer large, isolated features even into the polymer wi th the highest M-w. Problems of incomplete material transport can be relate d to local inhomogeneities of the imprint due to a lack of parallelism betw een the stamp and the sample. At 50 degrees C above T-g,incomplete flow eff ects were observed over the whole area and for all molecular weights. This was observed only with large, isolated structures whereas small, periodic f eatures showed a well defined transfer. (C) 1999 Elsevier Science Ltd. All rights reserved.