Thermal imprint into thin polymer layers below the critical molecular weight

Imprints into thin thermoplastic layers in thermal imprint often go along with phenomena such as physical self-assembly and recovery, which impair the resulting replication quality. To avoid recovery, in particular within larger structures, a polymer with extremely low Mw (polystyrene with a molecular weight of 1kg∕mol) is investigated. In contrast to expectations, the polymer develops a strong recovery. This occurs at such low viscosities that the imprint is also impaired by strong physical self-assembly effects. The imprint is further hampered by the fact that, due to the very low glass-transition temperature, a layer preparation without prebake is required. In addition the suitable temperature window for imprint is extremely small (T≈40°C) so that process control is hardly feasible. Polystyrene with such low Mw is not suitable for thermal imprint.