Optimizing pad groove design and polishing kinematics for reduced shear force, low force fluctuation and optimum removal rate attributes of copper CMP

The effect of polisher kinematics on average and standard deviation of shear force and removal rate in copper CMP is investigated. A 'delamination factor' consisting of average shear force, standard deviation of shear force, and required polishing time is defined and calculated based on the summation of normalized values of the above three components. In general, low values of the 'delamination factor' are preferred since it is believed that they 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 PSI with different wafer rotation rates and slurry flow rates. Results indicate that at the slurry flow rate of 200 ml/min, 'delamination factor' is lower by 14 to 54 percent than at 400 ml/min. Increasing wafer rotation rate from 23 to 148 RPM reduces 'delamination factor' by approximately 50 percent and improves removal rate within-wafer-non-uniformity by appx. 2X. In the second part of this study, polishing is performed at the optimal slurry flow rate of 200 ml/min and wafer rotation rate of 148 RPM with different polishing pressures and platen rotation rates. Results indicate that 'delamination factor' is reduced significantly at the higher ratio of wafer to platen rotation rates.