High landing energy SEM dimensional metrology for High NA EUVL

BackgroundRecently, High Numerical Aperture Extreme Ultraviolet Lithography (High-NA EUVL) started delivering its first wafers, showing its potential by printing 18 and 16 nm pitch line/space. However, as feature sizes drop below 10 nm, questions are raised on the ability of the current metrology procedures and tools to properly characterize such small targets. In particular, it is critical to assess the impact of limited spatial resolution and identify possible ways forward.AimA high-resolution, low damage strategy based on high-landing energy (LE) is proposed.ApproachHigh-LE setting (15 keV) and standard low LE (500 eV) best-known methods are compared using both rigorous simulation and experiments. The comparison is performed for metal oxide resist (MOR) as well as for chemical amplified resist, after development inspection (ADI), and after etch inspection (AEI).ResultsOur results indicated that the 15 keV setting provides 3× better resolution and less ADI damage as compared with the 500 eV setting. AEI damages, throughput, and precision are comparable.ConclusionsUsing high LE provides the needed resolution for High-NA EUVL, with similar or better impact on damages compared with low LE.