Pattern Printability for Variation in Thickness of a Mo/Si Mask Blank in Extreme Ultraviolet Lithography

Abstract

Pattern printability was examined while varying the thickness of a multilayer mask blank by simulation. The variations were related to the total thickness and the monolayer thickness of 40 Si/Mo bilayers. Printability was evaluated by using the pattern edge contrast for a binary mask and an attenuated phase shift mask (att-PSM). The total thickness variation degrades pattern edge contrast with decreasing exposure energy on a wafer. The phase shift between multilayer and absorber on a mask differs depending on the total thickness variation. The phase shift due to the total thickness variation gives rise to the focal position shift as a function of exposure wavelength for both the binary mask and the att-PSM. The phase shift and the focal position shift of the binary mask are different from those of the att-PSM. Monolayer thickness variation did not affect the printability of both the binary mask and the att-PSM.