Effect of polisher kinematics in reducing average and variance of shear force and increasing removal rate in copper CMP

The effect of polisher kinematics on average and variance of shear force and removal rate in copper CMP is investigated. A 'delamination triangle' consisting of average shear force, variance of shear force, and required polishing time is defined, and 'delta' is calculated based on the product of the above three components. In general, low values of 'delta' are preferred to minimize defects during polishing. In the first part of this study, 200-mm blanket copper wafers are polished at constant platen rotation of 25 RPM and polishing pressure of 1.5 PS1 with different wafer rotational rates and slurry flow rates. Results indicate that at the slurry flow rate of 400 ml/min, 'delta' is higher by 50 to 290 percent than at 200 ml/min, and increasing wafer rotational rate from 23 to 148 RPM reduces 'delta' by more than 90 percent and improves removal rate within-wafer-non-uniformity by 2X. In the second part of this study, polishing is performed at the optimal slurry flow rate of 200 ml/min and wafer rotational rate of 148 RPM with different polishing pressures and platen rotational rates. Results indicate that 'delta' is reduced significantly at higher ratio of wafer to platen rotational rates.