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

The plasma enhanced chemical vapour deposition of tungsten and tungste n silicide thin films onto GaAs has been investigated over a range of deposition conditions using a modified parallel plate radial flow reac tor. The tungsten films deposited from WF6 and H-2 were typically smoo th 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 pr operties for diodes fabricated from the as-deposited layers showed cur rent-voltage characteristics governed by thermionic emission with idea lity factors (n) as low as 1.04. WSix films deposited from WF6 and SiH 4 were typically smooth and adherent with a grain size < 200 Angstrom. Schottky diodes fabricated from these layers also exhibited good Scho ttky properties. It was possible to deposit films ranging from nearly pure tungsten to nearly pure silicon using this technique by varying t he WF6:SiH4 gas flow ratio.