KRYPTON SPUTTERING OF THIN TUNGSTEN LAYER FOR INTEGRATED CIRCUITS

摘要

A method of depositing a bilayer of tungsten (28) over tungsten nitride (42) by a plasma sputtering process in which krypton is used as the sputter working gas during the tungsten deposition. Argon may be used as the sputtering working gas during the reactive sputtering deposition of tungsten nitride. The beneficial effect of reduction of tungsten resistivity is increased when the thickness of the tungsten layer is less than 50nm and further increased when less than 35nm. The method may be used in forming a gate stack including a polysilicon layer (20) over a gate oxide layer (16) over a silicon gate region of a MOS transistor in which the tungsten nitride acts as a barrier. A plasma sputter chamber (50) in which the invention may be practiced includes gas sources of krypton (110), argon (62), and nitrogen (90).