Stability of flexible composite stamps with thermal nanoimprint

Flexible composite stamps are commonly used in low pressure and low temperature processes, e.g., UV-assisted nanoimprint, as they provide a good conformal contact between stamp and substrate. The composite stamps investigated here consist of two layers, a thin hard top layer to enable stable nanometre-scaled structures with high aspect ratio and a soft backplane to ensure conformal contact. Stamps with two different material combinations were investigated, OrmoStamp /PDMS (polydimethylsiloxane) and h-PUA/s-PUA (polyurethane acrylate). The stability of both composite stamps was tested under harsh imprint conditions in a process at elevated temperature and pressure. Temperature and pressure loading results in strain in the top layer and may lead to break when the tensile strength is exceeded. To vary the stress level in the top layer, two different stamp designs were investigated, one with a thin backplane and one with a thicker backplane. The experimental results clearly show that a thin stamp (low stress level) is more stable than a thick stamp. Moreover, composite stamps are also suitable for a thermal imprint process when temperature and pressure remain limited.