Accelerated corrosion and oxidation of tungsten plug during tungsten CMP

Tungsten CMP process involves an electrochemical alteration of metal surface and mechanical removal of the modified film. Electrochemical alteration means oxidation and corrosion of tungsten surface, so some extent of tungsten dishing and recess is very natural phenomena of tungsten CMP. Recently, there have been some reports that show excessive corrosion and oxidation of tungsten plug and device failure caused by these phenomena. This excessive corrosion and oxidation of tungsten plug is far worse than the normal static etch and dishing of tungsten. These phenomena show that some other factors, not just oxidizer, accelerate the oxidation of tungsten at specific area. This study tries to explain why abnormal acceleration of corrosion and oxidation occurred, why recently this failure appeared, and how to minimize this undesirable problem and prevent it from causing device failure.