Numerical Investigation of Defect Printability in Extreme Ultraviolet (EUV) Reflector: Ru/Mo/Si Multilayer System

The defect printability of Mo/Si and Ru/Mo/Si multilayer (ML) systems for extreme ultraviolet (EUV) reflectors was quantitatively investigated by monitoring aerial images on a wafer. The aerial image intensity of the Ru/Mo/Si model was calculated and compared with that of the Mo/Si model for various defect widths, heights, and positions. The aerial image characteristic of the defective ML structure turned out to be mainly dependent on defect height, which is related to the phase shift of the reflected field. Peak intensity and peak position shift according to the lateral position were calculated on an ML mask with a 50 nm L/S pattern. Through the investigation of the aerial image characteristics of the two models, it can be concluded that the Ru/Mo/Si model seems to be consistent with the Mo/Si model for all cases within ∼6%.