Role of oxidizer in the chemical mechanical planarization of the Ti/TiN barrier layer

The electrochemical parameters controlling the polishing rates of Ti and TiN are investigated. In this paper, alumina containing slurry was studied at pH 4 with 5% H 2O 2 as the oxidizer. Passive film formation on the surface during chemical mechanical polishing (CMP) plays an important role. To understand the oxide growth mechanism and the surface chemistry, X-ray photoelectron spectroscopy was performed. It was found that in the absence of an oxidizer, the removal of Ti and TiN is mainly due to mechanical abrasion of oxide layer or metal layer. However, in the presence of 5% H 2O 2 as the oxidizer, different removal behavior was observed for Ti and TiN. The removal mechanism of Ti during CMP is mainly due to mechanical abrasion of the oxide layer whereas for TiN it could be attributed to the formation of metastable soluble peroxide complexes.