High contrast mark used for in-situ UV nano-imprint lithography allignment

This paper focuses on designing a high contrast alignment mark used for imprint lithography in-liquid alignment. Since the imprint resist filled in the imprint pattern will deteriorate the intensity and contrast of the Moiré fringes, it´s hard to perform alignment based on the Moiré image. Through coating optically dens materials inside the imprint mask and changing the material, thickness, etch depth and grating pitch size, higher contrast can be obtained. Simulations based on Rigorous coupled-wave analysis (RCWA) are performed to calculate the reflection efficiency and contrast of obtained Moiré fringes. Experiments demonstrated that the simulation result is correct and feasible.