CVD tungsten and tungsten silicide for multilevel metallization

The authors describe a WSi_x process using SiH₂ Cl₂ chemistry, which is characterized by higher deposition rate, better film adhesion and integrity on polysilicon, and lower impurity concentration compared to the conventional SiH₄ chemistry. The nonselective W process (WF₆+H ₂) developed for deposition on dielectric material is characterized by simplicity, excellent adhesion, and low resistivity without the need for a sticking layer. A selective W process (WF₆ +H₂) developed for TiSi₂ contacts is characterized by high deposition rate, low contact resistance, low junction leakage, no lateral encroachment, and no silicon consumption in the vertical direction. The problems of silicon consumption and lateral encroachment associated with the tungsten deposition by hydrogen reduction is eliminated by the use of silane reduction. The silane reduction also leads to high deposition rates at low temperatures suitable for W deposition on aluminum layers. Blanket W deposition using silane reduction has good step coverage