Optical-constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices for attenuated phase shift mask in ArF lithography

(ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices composed of ten film stacks with ∼9 nm thickness in each stack, which includes the stoichiometric ZrO2, Cr2O3, and Al2O3 layers, are obtained by using rf unbalanced magnetron sputtering in an atmosphere of argon and oxygen. Binding energies of Cr 2p3/2, Al 2p3/2, and Zr 3d5/2 identified by x-ray photoelectron spectroscopy (XPS) are consistent with those of the theoretical Al2O3, Cr2O3, and ZrO2 XPS spectrum, respectively. The dielectric constants of (ZrO2)0.4/(Cr2O3)y/(Al2O3)0.6−y and (ZrO2)x/(Cr2O3)0.6/(Al2O3)0.4−x optical superlattices are illustrated to satisfy the effective medium approximation. By controlling the thickness percentage of ZrO2, Cr2O3, and Al2O3, the optical constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices can meet the optical requirements of a material blank for an attenuated phase shift mask (APSM). A quadrangular area of thickness percentage of (ZrO2, Cr2O3) that meets the requirement of optical constants for an ...