Characteristics of Abrasive-Free Micelle Slurry for Copper CMP

The need for a next-generation chemical mechanical polishing (CMP) slurry for copper planarization, to meet the requirements posed by advanced copper damascene processes, has led to the conception and development of a new type of slurry. The new micelle slurry is based on a mixture of surfactant and heteropolyacid, which takes the form of surfactant micelles enveloping the copper-reactive heteropolyacid. When used in the CMP process in place of conventional slurries, it effects copper planarization by a chemical mechanism with little or no mechanical abrasion. The mechanism enables a high rate of copper removal under low polishing pressures with minimal copper dishing, largely free from the scratching or erosion that may be encountered in CMP with conventional slurries due to their abrasive particle contents. These characteristics are advantageous for planarization of advanced copper damascene interconnects and particularly those including the relatively fragile low-k dielectrics. The micelle slurry also reduces the need for frequent dressing of foamed pads and enables a remarkably high rate of copper planarization with nonfoamed hard pads under low polishing pressures. It may therefore lengthen the pad service life and reduce the complexity and cost of CMP, particularly for copper damascene interconnects incorporating low-k dielectrics.