Combining nano-scale imprint lithography and reactive ion etching to fabricate high-quality surface relief gratings

In this study, we present a novel approach combining nano-scale imprint lithography (NIL) and reactive ion etching (RIE) to fabricate high-quality surface relief gratings (SRGs). This study provides valuable insights into the challenges and optimizations in fabricating SRGs from TiO₂ layers using the combination of NIL and RIE. The work was performed with SCHOTT RealView® substrates coated with a 100 nm TiO₂ layer and a NIL mask with pattern widths of 200 nm and a pitch of 400 nm. The substrates were processed using the SmartNIL® method to prepare the NIL mask. The advantage of removing the residual layer before the actual structuring of the TiO₂ using argon plasma was demonstrated in our research. This led to a significant increase in the selectivity between TiO₂ and the NIL resist UV/OA R18. Through the employment of a two-step etching process, which involved the removal of the residual layer with argon plasma and the use of a BCl₃-based reactive process with high ion energy, TiO₂ structures with a height of 100 nm and a sidewall angle of 75° were successfully created. An effective selectivity of 0.84 was achieved for this two-step process.