Method for forming a plug metal layer

A method for forming a plug tungsten layer, the method comprising:

• providing a semiconductor substrate;
• forming a dielectric layer on said semiconductor substrate;
• forming a photoresist layer on said dielectric layer;
• etching said dielectric layer byway of using said photoresist layer as an etching mask to form a via hole in said dielectric layer;
• removing said photoresist layer;
• conforming a titanium layer on said dielectric layer and the sidewall and the bottom of said via hole;
• forming a first nitride titanium layer on said titanium layer by way of using a metal organic chemical vapor deposition;
• forming a second nitride titanium layer on said first nitride titanium layer by way of using a physical vapor deposition wherein said titanium layer, said first nitride titanium layer and said second nitride titanium layer stack to form a barrier layer;
• treating said barrier layer by way of using a plasma process with nitrogen/hydrogen;
• transporting a mixing gas having a hydrogen and a silane on said barrier layer to absorb said mixing gas on said barrier layer;
• performing a purge/vacuum process to remove remainder after absorption;
• transporting a reactive gas with a WF6 on said barrier layer with said mixing gas to perform a substitution reaction that reacts said reactive gas with said mixing gas, so as to form a continuous tungsten seed layer with a thickness about 20 to 40 Å on said barrier layer;
• forming a nucleation layer on said continuous tungsten seed layer;
• performing a chemical vapor deposition to form a tungsten layer on said continuous tungsten seed layer;
• and
• etching back tungsten layer to form said plug tungsten layer in said via hole.