Study on the Weakly Alkaline Slurry of Copper Chemical Mechanical Planarization for GLSI

Copper has been widely used as the most fundamental interconnection metal material for Gita-large scale integrated circuits(GLSI). During the chemical mechanical polishing (CMP) process, the stability of slurry is crucial to copper polishing performance. Through selecting the important factors of influence slurry such as pH, surfactant and pH-regulator, the weakly alkaline copper slurry was investigated in this paper. As the weakly alkaline slurry becomes very promising and stringent to fit for the requirement of integrated circuits development, and according to the investigation of removal rate results, pH 8.5-9.5 was selected as the appropriate pH range. Comparing with nonionic surfactant, anionic surfactant exhibited preferable performance for stability of silica sol such as ammonium dodecyl sulfate (ADS) due to its unique structure and charged property in weakly alkaline solution. Meanwhile, using tetraethylammonium hydroxide (TEAH) as pH-regulator instead of KOH, the copper slurry exhibited the stability for 7 days with H2O2. In order to examine the effectiveness of such copper slurry, the copper blanket and pattern wafer were polished by the slurry settling for 7 days. The pH-value, mean particle size, zeta potential and viscosity of the slurry fluctuated slightly with the aging time. And from the results of copper removal rate, roughness of copper blanket wafer and the step height values of pattern wafer it indicates that the weakly alkaline copper slurry has stability and which has a guiding significance to the development of microelectronics industry. (C) 2017 The Electrochemical Society. All rights reserved.