The Role of Stress in Nanoimprint Lithography

摘要

The thermal embossing form of nanoimprint lithography is used to pattern arrays of nanostructures into several different polymer films. The shape of the imprinted patterns is characterized with nm precision using both X-ray scattering and reflectivity techniques. By studying the time dependent response of the pattern shape at temperatures near the glass transition temperature, we are able to perceive large levels of residual stress induced by the imprinting process. The large shear fields that result as the viscous polymer flows into the mold leads to residual stresses. At elevated temperatures in the freestanding structures (once the mold has been separated from the imprint), there is an accelerated reduction in pattern height in the reverse direction from which the material originally flowed into the mold. Two factors that influence this residual stress include the molecular mass of the polymer resist and the amount of time the pattern is annealed at high temperature in the presence of the mold.