Model alumina slurries for chemical-mechanical planarization (CMP) of copper have been studied using fundamental electrochemical concepts together with modification of surface tension and zeta-potential. A model slurry was established containing 3 wt% alumina (50 nm nominal size), 2 wt% potassium dichromate (K2Cr2O7) and 1 vol % DOWFAX, as abrasive, oxidizer and anionic surfactant, respectively, which resulted in blanket copper removal rates of 130 nm/min with smooth, low-particulate defect density surfaces without aggressive post-CMP cleaning. When used with a model silica-abrasive slurry to remove the Ta liner, well-defined damascene-patterned structures were achieved with low-particulate defect densities.
Open circuit potential measurement, potentiodynamic polarization, surface tension measurement, and zeta-potential measurement were used in developing the model slurries. The variations obtained with alternative abrasives, alternative oxidizers and alternative surfactants illustrate the principles of synthesizing slurries for Cu and Ta.