Lithographic performance evaluation of a contaminated extreme ultraviolet mask after cleaning Available to Purchase

The effect of surface contamination and subsequent mask surface cleaning on the lithographic performance of an extreme ultraviolet (EUV) mask is investigated. SEMATECH’s Berkeley microfield exposure tool printed 40 and 50 nm line and space (L/S) patterns are evaluated to compare the performance of a contaminated and cleaned mask to an uncontaminated mask. Since the two EUV masks have different absorber architectures, optical imaging models and aerial image calculations were performed to determine any expected differences in performance. The measured and calculated Bossung curves, process windows, and exposure latitudes for the two sets of L/S patterns are compared to determine how the contamination and cleaning impacts the lithographic performance of EUV masks. The observed differences between the two masks are shown to be well within the expected process variation of 10%, indicating that the cleaning process did not appreciably affect the mask performance.