The effect of the neutral ligand W on the characteristics of hexafluoroacetylacetonate (hfac)Cu(I)-L precursor and on the copper deposition process was studied. It was found that the property of the ligand has an influence on the properties of the precursor such as vapor pressure and dissociation temperature and also on the deposition characteristics such as deposition temperature, deposition rate and film properties. Copper films were deposited at substrate temperatures ranging from 70 to 300 degreesC. When the dissociation temperature of the Cu(I)-L bond of the (hfac)Cu(l)-L was low, low-temperature deposition below 100 degreesC was possible, and lower resistivity of the copper film was obtained. The thermal stability of the precursor, however, was low in this case. Regardless of the molecular weight of L, the resistivity of the film was almost the same at substrate temperatures ranging from 125 to 175 degreesC. However, the resistivity increased as the molecular weight of L became higher above 225 degreesC. The vapor pressure of the (hfac)Cu(I)-L was higher when the molecular weight of L is low. Also the L had a strong influence on the morphology and texture of the copper film.