Analysis of pads with slanted grooves for copper CMP

This investigation presents the analysis of concentric grooves with different degrees and directions of slant for the optimization of copper chemical mechanical planarization (CMP) processes. Taking into consideration the common industrial application of the concentric groove pattern, in this study pads were prepared with concentrical grooves having different degrees and direction of slant, such as 0° (zero), ±20°, and ±30°. The slanted groove pads were tested and statistically compared to each other in terms of removal rate, average coefficient of friction, and average pad leading edge temperature. Theoretical examination of the experimental data was performed to establish the mechanical and chemical contributions to the process. A three-step model, in combination with a previously developed flash heating temperature model, was proposed for copper CMP. This model presented an expression to characterize the rate of oxide growth and the addition of a third step to characterize the dissolution rate of copper oxide. The root-mean-square error after predicting the removal rate behavior with the three-step model fell between 351 and 445 Amin, while the experimental repeatability error fell in the range of 150 to 590 Amin for all pads tested in this study.