A Novel Structure of Reflective Type Attenuated Phase-Shifting-Masks for Sub-25 nm Extreme Ultraviolet ExposureTools

摘要

Phase-shifting-masks are vital resolution enhance technique that will be used in extreme ultraviolet (BUY) lithography beyond the 25 nm node. In this paper, we demonstrated a novel structure for a reflective type attenuated phase-shifting-mask, which is based on a Fabry-Perot structure with common materials in EUV masks. The mask structure not only performs 180° phase-shift with high-reflectance at EUV wavelength but also has high inspection-contrast at deep ultraviolet (DUV) wavelength. The top layer of mask structures exhibits good conductivity, which can alleviate the charging effect during electron-beam patterning. The reflectance ratio of the absorber stack could be tuned from 32.6% (TaN/SiO{sub}2/Mo) to 4.4% (TaN/SiO/TaN) by choosing different bottom layers and thickness. The inspection contrast could be raised to 99% with large thickness-control-tolerance.