The optical properties of monolayer amorphous Al2O3-TiO2 composite films used as HT-APSM blanks for ArF immersion lithography

Abstract

Amorphous (Al2O3)(x)-(TiO2)(1-x) composite films are prepared using r.f. unbalanced magnetron sputtering in an atmosphere of argon and oxygen at room temperature. The optical constants of (Al2O3)(x)-(TiO2)(1-x) composite films are linearly dependent on the Al2O3 mole fraction in the Al2O3-TiO2 composite film. The optical constants of these Al2O3-TiO2 Composite films can be made to meet the optical requirements for a high transmittance attenuated phase shift mask (HT-APSM) blank by tuning the Al2O3 mole fraction. The Al2O3 mole fraction range that would allow the films to meet the optical requirements of an HT-APSM blank for ArF immersion lithography is calculated to be between 76% and 84%. One Tu-phase-shifted Al2O3-TiO2 composite thin film to be used as an HT-APSM blank for ArF immersion lithography is fabricated and is shown to satisfy the optical requirements. (c) 2007 Elsevier B.V. All rights reserved.