Printing-based performance analysis of the engineering test stand set-2 optic using a synchrotron exposure station with variable sigma

Abstract

While interferometry is routinely used for the characterization and alignment of lithographic optics, the ultimate measure of performance for these optical systems is the transfer of an image or pattern into photoresist. Simple yet flexible exposure systems play an important role in this task because they allow complex system-dependent effects to be isolated from the printing results. One such tool has been implemented for alpha-class extreme ultraviolet (EUV) optics at Lawrence Berkeley National Laboratory using a synchrotron-based illumination source with programmable coherence. This static microfield exposure system has been used to characterize a four-mirror optical system designed for the EUV engineering test stand prototype stepper. Here we present a detailed performance analysis based on the large volume of lithographic data collected from this 0.1 NA system. Process window results are presented for dark field and bright field nested features down to a half pitch of 70 nm (k1 factor of 0.52) where a depth of focus of approximately 1 μm with 10% exposure latitude is demonstrated.