Issues and requirements of polymers for thermal NIL

The requirements of polymers best suitable for thermal nanoimprint lithography are derived from the processing demands. Therefore characteristics of this type of mechanical process are discussed, and typical results obtained from rheological characterization of polymers are addressed. The main effort is laid on the impact of processing temperature and molecular weight of the polymer for the imprint result, namely residual layer uniformity and defect avoidance, when realistic stamps with different pattern sizes and pattern densities are imprinted. Under such conditions a polymer for T-NIL should feature a mean molecular weight of about 200-300 kg/mol as well as a medium broad molecular weight distribution. In addition a hybrid process is addressed, where T-NIL defines the nanometer pattern and UV-Lithography the micron sized patterns. For such a purpose polymers with UV-crosslink without need for a post exposure bake are beneficial to enable the use of conventional photomasks.