Abstract
The attractiveness of Cu dual damascene technology arises from a lower resistance capacitance (RC) delay due to higher electrical conductivity of Cu and its superior electro-migration performance. The damascene process eliminates residual metal by using chemical mechanical polishing (CMP) for field Cu and barrier removal.Standard Cu CMP process involves two steps; step one involves polishing of Cu and stopping on the barrier layer, and step two requires removal of the barrier layer and planarization of the entire surface (Cu/Barrier/Ox). Additive abrasives in slurry sometimes scratched the surface in step one.Abrasive free polishing (AFP) technology is one of promising alternatives for low-stress material removal to avoid scratching or film peeling during polishing. While Benzotriazole (BTA) as an inhibitor formulated with nitric acid (HNO3) as an oxidizer for Cu AFP process, it can provide high planarization efficiency based on formation of a strong BTA-Cu surface passivation during polishing, but in trade of low removal rates and large pattern-dependent planarization effect. In this study, the BTA derivatives such like (Benzotriazole-5-carboxylic acid, 5-Methyl-1H-benzotriazole) are investigated for reduced packing density of planar BTA-Cu complex compound for improving removal rate and pattern effect. In this study, HNO3 fixed at 1.11M functions as oxidizer for Cu removal and BTA derivatives (Benzotriazole-5-carboxylic acid, 5-Methyl-1H-benzotriazole) chemistry as a corrosion inhibitor by forming a surface passivation on Cu surface. Electrochemical AC impedance technique was carried out to investigate surface passivation, which would be related to planarization. Furthermore, contact angle measurement’s results show the wetting effect and packing condition of a surface passivation formed during polishing. The planarization efficiency at various feature size of Cu interconnects with BTA derivatives(Benzotriazole-5-carboxylic acid, 5-Methyl-1H-benzotriazole) as inhibitors during Cu AFP are also discussed.