In our research, we are investigating the manufacturing of phase gratings using soft nanoimprint lithography (NIL). NIL is a nanostructuring process in which a master structure is replicated via a stamp. In the soft NIL method, the stamp structure is molded from the master structure using liquid photoresist followed by ultraviolet (UV) light curing. Once a working stamp is created, it can be used to directly stamp multiple replicas. This makes the nanostructuring process time and cost efficient. The quality and reproducibility of the replicated structures are critical for the application of the nanostructures. Here, for the evaluation of the resolution, a test pattern (grating structures in the shape of a USAF 1951 Resolution Test Chart) is used as master structure. For stamp production, we use various polymers (Micro Resist Technology, EV Group and DELO) as stamp materials, spin coated on 4-inch wafers. These photoresists differ in their properties, such as the refractive index, which affects the quality of the nanostructures. The imprinted phase gratings are investigated with respect to their shape deviations and surface properties. We present a comprehensive analysis of the different stamp materials. Based on our evaluation, an optimal material can be selected to fulfill specific requirements of an application. This work provides insights into the manufacturing of nanostructures with soft NIL. Our research contributes to the further development of the NIL process and thus the fabrication of precise phase gratings.
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