Local mass transport and its effect on global pattern replication during hot embossing

Thickness and uniformity of the residual layer are major global quality criteria for nanoimprint lithography. When the total area of a stamp used in a mechanical replication process like hot embossing is composed of sections with different pattern density, the specific local stamp layout strongly affects residual layer uniformity. Taking the example of a positive stamp with sections of well-defined pattern density the effect of initial layer thickness on uniformity of the residual layer was investigated on the centimetre scale. Long-range uniformity is shown to be a result of local polymer flow in particular between sections of different pattern density. We found the effect to be independent of pattern size. It turned out, that initial layer thickness has to be chosen with regard to the polymer volume locally required for filling of the stamp cavities. Whereas overfilling should be avoided, underfilling may be beneficial for specific applications. (C) 2003 Elsevier Science B.V. All rights reserved.