Imprinted optical device and its reliability

Although imprint technology has made considerable progress in recent times, there are certain limitations on its use because of several problems. One of these is the reliability caused by the dimensional change of the imprinted structure. In particular, a hot-embossed structure is inherently involved in residual stress due to the temperature and pressure cycle during the fabrication process. A structure with residual stress undergoes stress relaxation, which leads to dimensional change. Therefore, we have conducted research on its dimensional stability by using an annealing process. To evaluate the reliability of an imprinted structure, it is necessary to measure changes in the mechanical properties, such as elastic modulus, micro-hardness, residual stress, and dimensional change. Through these measurements, we propose a way of controlling the level of residual stress. Before annealing, the dimension of an imprinted structure changes by 0.9 μm during one month. However, after annealing, a dimensional change of 0.3 μm was observed over the same period.