Focused ion beam induced Ga-contamination—An obstacle for UV-nanoimprint stamp repair?

Abstract

Ultravoilet (UV)-nanoimprint lithography (NIL) master stamps are subject to wear due to the mechanical nature of the imprint process. To extend the useful lifespan of expensive NIL master stamps, a focused ion beam repair process is highly desirable. Due to the inevitable Ga-staining induced by the focused ion beam processing the transmissivity of repaired NIL stamps is locally degraded. In this work, the authors investigate the impact of Ga-induced transmission losses on the imprint process. Experimental results indicate that the reduced transparency mainly impacts the amplitude of bow deformations in the imprint. These deformations are strongly enhanced by Ga-staining of the master stamp. The authors present a method for quantification of such bow-deformations. The introduced bowing-factor allows to make a qualified decision on whether the occurring deformation is acceptable for the target application. The authors have achieved control over the extent of the Ga-induced bow-deformation by tuning the UV-dose applied during NIL resist exposure. The bowing-factor provides excellent guidance for adapting the required exposure-dose of the NIL resist to reduce the bow-deformation to an acceptable level. With the presented approach, the mitigation of Ga-staining induced defects in the imprint is successfully achieved.