Physical Properties of Tungsten Oxide Films Deposited by a Reactive Sputtering Method

Tungsten oxide films were deposited in ambient gas (Ar+O2) by a reactive sputtering method, and their physical properties as an X-ray mask absorber were investigated. The density, stress and structure of the films strongly depend upon the sputtering condition, especially on the total working pressure and the oxygen partial pressure. Smooth tungsten oxide films were deposited in the range of 11∼18 mTorr total working pressure and in the oxygen partial pressure of 8.3% and their density was about 13.5 g/cm3. Pressure dependence of the stress of tungsten oxide films was much smaller than that of tungsten films. The stress-free films of tungsten oxide had no fibrous structure and their surface and cross section were smooth.