Simulation analysis of the characteristics of a high magnification imaging optics for the observation of extreme ultraviolet lithography mask to predict phase defect printability

By employing simulation, we analyzed the characteristic of the optics of high-magnification multilayer-coated mirror employed for the examination of extreme ultraviolet lithography (EUVL) mask, and we also examined the performance of phase defect printability prediction. The imaging optics comprises Schwarzschild optics and a concave mirror; and it is modeled as an imaging means with an annular-shaped pupil. In this simulation, tilted coherent illumination that was successfully applied in an EUV microscope constructed at a beamline of the NewSUBARU, was assumed. Observation images of mask patterns affected by phase defects were simulated assuming EUVL masks representing half pitches of 16 and 11nm generations; and those simulated results were compared with the simulated reduction-projection images on wafer formed by an exposure tool. Although the high-magnification observation optics does not completely emulate the printed pattern images on wafer it predicts the existence of phase defects and predict the value of their impacts.