The low pressure chem. vapor deposition (LPCVD) of Cu from its bis-hexafluoroacetylacetonate was studied on oxidized Si substrates partially covered with a Pt seeding layer. With a known concn. of water vapor in the gas mixt., almost equal Cu film growth rates were obtained when using either H or He as carrier gas. For both carrier gases, an increase of the Cu growth rate was obsd. with an increasing amt. of water vapor added to the gas mixt., and deposition rates above 500 .ANG./min were obtained. The chem. purity and elec. cond. of the Cu deposit are as high in the case of a He carrier gas as in the case of a H carrier gas. Implications for the mechanism of Cu LPCVD are discussed.