文摘
The real-time shape evolution of nanoimprinted polymer patterns is measured as a function of annealing time and temperature using criticaldimension small-angle X-ray scattering (CD-SAXS). Periodicity, line width, line height, and sidewall angle are reported with nanometer resolutionfor parallel line/space patterns in poly(methyl methacrylate) (PMMA) both below and above the bulk glass transition temperature (TG). Heatingthese patterns below TG does not produce significant thermal expansion, at least to within the resolution of the measurement. However, aboveTG the fast rate of loss in pattern size at early times transitions to a reduced rate in longer time regimes. The time-dependent rate of polymerflow from the pattern into the underlying layer, termed pattern "melting", is consistent with a model of elastic recovery from stresses inducedby the molding process.