Mechano-oxidation during cobalt polishing.

Abstract The synergetic effects of chemical-mechanical interactions are key to generate atomically flat surfaces during polishing. The mechanisms need to be further understood. Here we report the influence of pH values on chemical-mechanical interactions during cobalt chemical-mechanical polishing (CMP). Using an in situ approach combining polishing and electrochemical measurement, we found that the single frequency electrochemical impendence Z value reflected the nature and thickness of the surface oxide. Specifically, the oxide thickness grew when the pH was increased from 5.0 to 8.0 and reduced while in 8.0–9.0. The variation of pH not only affected cobalt chemical reactions but also abrasive effects, along with mechanical input through contact pressure, as well as surface speed. It is interesting that the pH value affects both the chemical reaction and mechanical wear. Specifically, oxidation enhances with the increase in pH from 5.0 to 8.0 resulting in a thicker film. Subsequently the mechanical wear becomes stronger, over oxidation in the range of pH 8.0–9.0. As a result, the thickness of oxide is reduced. This investigation is beneficial to understanding metal CMP process and polishing mechanism. Highlights • The influences of pH values and mechanical power on chemical-mechanical interactions were studied in situ. • The variation of pH not only affected cobalt chemical reactions but also abrasive effects along with mechanical input. • Oxidation enhanced from pH 5.0 to 8.0 but the Mechanical abrasion became stronger in the range of pH 8.0- 9.0. [ABSTRACT FROM AUTHOR]