PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION OF TUNGSTEN AND TUNGSTEN SILICIDE THIN-FILMS

The plasma enhanced chemical vapour deposition of tungsten and tungsten silicide thin films onto GaAs has been investigated over a range of deposition conditions using a modified parallel plate radial flow reactor. The tungsten films deposited from WF6 and H-2 were typically smooth and adherent with as-deposited resistivities in the range 20-100 mu Omega.cm and a grain size in the range 200-2000 Angstrom. Schottky properties for diodes fabricated from the as-deposited layers showed current-voltage characteristics governed by thermionic emission with ideality factors (n) as low as 1.04. WSix films deposited from WF6 and SiH4 were typically smooth and adherent with a grain size < 200 Angstrom. Schottky diodes fabricated from these layers also exhibited good Schottky properties. It was possible to deposit films ranging from nearly pure tungsten to nearly pure silicon using this technique by varying the WF6:SiH4 gas flow ratio.