Effects of phosphoric acid stabilizer on copper and tantalum nitride CMP

Abstract

The effects of phosphoric acid addition on slurry for chemical–mechanical planarization (CMP) of copper and tantalum nitride were investigated. It is generally known that the slurry for copper CMP consists of alumina or colloidal silica as an abrasive, organic acid as a complexing agent, an oxidizing agent, a film forming agent, a pH control agent and additives. Hydrogen peroxide (H 2O 2) is one of the materials that are commonly used as an oxidizing agent in copper CMP. However, hydrogen peroxide needs some stabilizers to prevent decomposition. We evaluated phosphoric acid (H 3PO 4) as an accelerator of the tantalum nitride CMP as well as process a stabilizer of the hydrogen peroxide. We also estimated dispersion stability and zeta potential of the abrasive slurry with the contents of phosphoric acid. An acceleration of the tantalum nitride CMP was verified through the electrochemical test. This approach may be useful for the development of the second step copper CMP slurry or in general stabilization of hydrogen peroxide in abrasive slurry.