Dynamical Mechanism of Chemical Mechanical Polishing Analyzed by Frictional Force Measurement

摘要

The dynamical mechanism of chemical mechanical polishing (CMP) was proposed. The relationships between removal rate and CMP parameters were evaluated by directly measuring the frictional force acting on a wafer under actual CMP conditions. According to the measurements, we devised a new experimental equation to replace Preston's empirical equation, by taking into account the dynamic frictional coefficient and the polishing efficiency. To conduct the equation, the dependences of the CMP characteristics on down force and sliding speed were analyzed quantitatively. This analysis showed that polishing efficiency decreases with increasing sliding speed, while it remains constant with changing down force. This result suggests that the removal mechanism changes with sliding speed, while it does not change with down force. Moreover, the decrease in removal efficiency was found to be less for a mechanical-effect-dominant slurry than for a chemical-effect-dominant slurry. The results suggest that Preston's empirical equation is valid for mechanical-effeet-dominant polishing.