OVL performance of HighNA stitched fields using Monte Carlo simulations

Abstract

Extreme Ultraviolet (EUV) lithography has gained maturity and is now the de facto leading edge patterning technology for advanced nodes beyond 7nm. Looking forward, the industry is exploring how to push the resolution even further. A high NA EUV scanner promises to increase the numerical aperture to capture larger diffraction orders enabling resolution improvement. The desire to use existing mask infrastructure with the anamorphic high NA projection lens project results in a half-field on wafer as compared to the currently available low NA EUV scanner. Once the high NA scanner is available, integrated devices will be manufactured with mix and match full-field and half-field lithography. This will bring its own set of challenges from an overlay error minimization standpoint, as half-field and full-field will not share the same center of gravity. Given the fact that overlay models are well known and that the high NA EUV scanner is not yet commercially available we took the approach to emulate the process through computer Monte Carlo simulations. This paper will explain the methods and assumptions used for the Monte Carlo simulation and explore how the mix and match affect the overlay correctable and none-correctable errors