Low-Temperature Chemical-Vapor Deposition of Tungsten from Tungsten Hexacarbonyl

摘要

Chemical vapor deposition (CVD) of tungsten from W(CO) sub 6 has been investigated below 670 exp 0 K as an alternate process to WF sub 6 CVD for coating glass microspheres. The major advantages of W(CO) sub 6 CVD are the elimination of the HF damage to the glass microspheres and potentially a lower deposition temperature for coating DT-filled microspheres. W(CO) sub 6 CVD can be utilized, in principle, to coat the microspheres with 1 to 5 mu m of tungsten or to flash coat the microspheres for further coating by WF sub 6 CVD. Test coatings were deposited in a fluidized-bed reactor with a hydrogen carrier gas. The coatings were found to contain nearly-equal portions of carbon and oxygen, ranging from 16 to 25 at. % for each element. The high carbon and oxygen concentrations are believed to result principally from the physical entrapment of chemisorbed CO molecules at the surface of the growing deposit. (ERA citation 07:003484)