Low pressure chemical vapor deposition (LPCVD) was carried out to deposit tungsten silicide films (WSix) from WF6 and SiH4 in a low temperature range from 80 to 390 °C, using a tubular reactor system. Drastic decrease of the deposition rate occurred at an extinction temperature Tex. Increase of the reactor size in the range from 4 to 22 mmφ decreased Tex from 140 to 80 °C. Above Tex, the sticking probability of the film forming species (η) and the film composition, x of WSix , did not depend on the reactor diameter. Dependence of Tex on the reactor diameter and independence of η and x above Tex from the reactor diameter indicates that a radical chain process dominates CVD-WSix process to form film forming species.

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WSi x films were formed on a substrate from thermal chemical vapor deposition (CVD) of WF6 and SiH4. Chemical reactions were initiated upstream of the substrate by a preheater, and chemical reactions are radical chain reactions which produce preactivated cursors that are deposited, causing film growth. Because chemical reactions occur upstream of the substrate, film formation occurred even at temperatures as low as 40° C. Compared with films deposited at the same substrate temperature, without preheating, the Si content increased by 50%, the interfacial concentration of residual fluorine decreased by one order of magnitude, and the sticking probability of the precursors on the substrate was the same. The sticking probability was shown to depend solely on the substrate temperature, even for varying degrees of preheating. Deposition on a low-temperature substrate of the preactivated precursors provides a means to deposit conformal WSi x films with low interfacial concentration of fluorine.

Tungsten silicide films (WSix) were deposited from WF6 and SiH4 by low pressure chemical vapor deposition (LPCVD) using a tubular reactor system. At the deposition temperature of 150 °C, films having low concentrations of residual fluorine (∼1.5×1021 cm−3) deposited quite conformally on micron-sized trenches. The sticking probability of the film precursor was determined from the step coverage quality, as a function of deposition temperature ranging from 120 to 390 °C. While the sticking probability remained constant above 270 °C, it changed with an activation energy of 7±2 kcal/mol in the temperature range 120–240 °C. The decreased probability of sticking improved the step coverage quality at low temperatures.

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