Finite element method investigation into nanoimprinting of aluminum/polyimide bi-layer substrates

Finite element method (FEM) simulations are performed to investigate the nanoimprinting of aluminum/polyimide bi-layer substrates at temperatures ranging from 25 to 200 °C. In constructing the FE analysis model, the mechanical properties of the aluminum and polyimide layers are obtained from thermo-mechanical micro-force tensile tests. The validity of the FE model is confirmed by comparing the results obtained for the formation height ratio in single-layer aluminum substrates with the experimental results. Thereafter, simulations are performed to investigate the effects of the aluminum-to-polyimide thickness ratio and the substrate temperature on the imprint pressure required to obtain a complete filling of the mold cavities. The simulation results show that under low temperature conditions (i.e. <100 °C), the imprint pressure reduces as the aluminum-to-polyimide thickness ratio decreases. In addition, for temperatures lower than 100 °C, the use of a polyimide layer reduces the imprinting force by around 38% compared to that required to imprint a single-layer aluminum substrate of an equivalent total thickness. However, for temperatures higher than 150 °C and a polyimide-to-substrate thickness ratio of more than 40%, the imprint force reversely enlarged due to the strain-hardening of the polyimide film at elevated temperatures. The simulation results obtained for the variation of the imprint pressure with the aluminum thickness ratio, the polyimide thickness ratio, and the substrate temperature are compiled in the form of a contour chart. The chart provides a convenient means of establishing suitable processing conditions for a variety of nanoimprinting applications.