Resist deformation at low temperature in nanoimprint lithography

In this work, the squeeze flow of thin polymethyl methacrylate (PMMA) films into nanocavities has been investigated in order to understand and optimise the imprint process conditions. This work was focused primarily on the PMMA flow behaviour at temperatures below the glass transition temperature Tg (<105 °C). The cavity and structure patterns were fabricated on silicon nitride molds. An ABAQUS/CAE finite element software package has been employed to simulate the squeeze flow and predict the final resist shape. Imprint at temperatures well below Tg is attributed to high localized stresses imposed on the resist surface, which exceed the yield stress, and thickness dependent Tg. The residual resist thickness is a function of pattern shape, size and initial resist thickness.