Dependence of pattern printability on thicknesses of absorber and cap layers of Mo/Si mask blank for EUV lithography

Minoru Sugawara; Akira Chiba; Hiromasa Yamanashi; Iwao Nishiyama

doi:10.1117/12.504376

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28 August 2003 Dependence of pattern printability on thicknesses of absorber and cap layers of Mo/Si mask blank for EUV lithography

Minoru Sugawara, Akira Chiba, Hiromasa Yamanashi, Iwao Nishiyama

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Proceedings Volume 5130, Photomask and Next-Generation Lithography Mask Technology X; (2003) https://doi.org/10.1117/12.504376
Event: Photomask and Next Generation Lithography Mask Technology X, 2003, Yokohama, Japan

Abstract

The dependence of printability on the thicknesses of the TaN absorber and Ru buffer layers is investigated using 22-nm-wide semi-dense line patterns. Simulations are carried out using two sets of thicknesses corresponding to optical densities (OD) of 2 and 3. Thicker layers (i.e. larger OD) are found to yield a smaller linewidth variation when the exposure light is focused on the wafer. However, they also enhance the shadowing due to off-axis illumination on a mask, which degrades the pattern edge contrast of the aerial image under defocused conditions. Estimations of the linewidth variation and the pattern position shift for a focal latitude of ± 50 nm show that thinner absorber and buffer layers (i.e. OD = 2) are more practical than thicker ones. An examination of the reflectance loss of the Si cap layer on a multilayer blank due to oxidation reveals that it is essential to select an appropriate initial thickness of the Si to ensure sufficient reflectance after the Si is oxidized by contaminants.

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Minoru Sugawara, Akira Chiba, Hiromasa Yamanashi, and Iwao Nishiyama "Dependence of pattern printability on thicknesses of absorber and cap layers of Mo/Si mask blank for EUV lithography", Proc. SPIE 5130, Photomask and Next-Generation Lithography Mask Technology X, (28 August 2003); https://doi.org/10.1117/12.504376

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