The formation of thinhyphen;film tungsten silicide annealed in ultrahigh vacuum

摘要

Thin films of tungsten silicide have been formed by sputter depositing 710 Aring; of W metal onto (100)hyphen;oriented, 3ndash;7 OHgr;thinsp;cm,phyphen;type silicon wafers. The samples were annealed in an ultrahigh vacuum ambient (pressurele;1.0times;10minus;9Torr) at temperatures ranging from 845 to 1100thinsp;deg;C for 30 s. The lack of oxygen contamination in the ambient allows the Whyphen;Si interaction to proceed, first producing both the Whyphen;rich W5Si3phase and the tetragonal WSi2phase near 900thinsp;deg;C, followed by only the tetragonal, lowhyphen;resistivity (30ndash;40 mgr;OHgr;thinsp;cm) WSi2phase above 1000thinsp;deg;C. This result is in contrast to previous work where films formed by rapid thermal processing in vacuum showed no significant Whyphen;Si interaction for temperatures below 1100thinsp;deg;C due to the formation of an interfacial oxide diffusion barrier gettered into the films from the 10minus;6Torr ambient.