Method and apparatus for depositing tungsten after surface treatment to improve film characteristics

摘要

A method and system to form a refractory metal layer over a substrate includes introduction of a reductant, such as PH₃ or B₂H₆, followed by introduction of a tungsten containing compound, such as WF₆, to form a tungsten layer. It is believed that the reductant reduces the fluorine content of the tungsten layer while improving the step coverage and resistivity of the tungsten layer. It is believed that the improved characteristics of the tungsten film are attributable to the chemical affinity between the reductants and the tungsten containing compound. The chemical affinity provides better surface mobility of the adsorbed chemical species and better reduction of WF₆ at the nucleation stage of the tungsten layer. The method can further include sequentially introducing a reductant, such as PH₃ or B₂H₆, and a tungsten containing compound to deposit a tungsten layer. The formed tungsten layer can be used as a nucleation layer followed by bulk deposition of a tungsten layer utilizing standard CVD techniques. Alternatively, the formed tungsten layer can be used to fill an aperture.