AN ULTRA-LOW STRESS TUNGSTEN ABSORBER FOR X-RAY MASKS

A stress compensation technique for a tungsten (W) absorber for an x-ray mask has been developed. Tungsten films with a thickness of 500 nm were deposited using the magnetron dc sputtering method in an argon (Ar) working gas at a power of 1 kW. A high film density (18.0 g/cm3) was obtained at a low working gas pressure. Neon (Ne), Ar, krypton (Kr) and silicon (Si) ion implantations were performed with a projection range (R(p)) of 50 nm, at doses of 10(14)-10(15) ions/cm2 to modify the absorber stress. The ion implantation reduced the film stress to less than 5 X 10(7) dyn/cm2. Ar and Kr implanted film stress stability was less than 5 X 10(7) dyn/cm2. Ne and Si implanted film stresses were not stable.