Pad Conditioning and Removal Rate in Oxide Chemical Mechanical Polishing

摘要

Polish rate and corresponding pad surface morphology data are presented over a range of pressure-velocity space in oxide chemical-mechanical polishing. Pad surface data are obtained using vertical scanning optical interferometry. The pad surface state is manipulated through the use of a range of pad conditioners with different cutting characteristics at redundant process conditions. Under some conditions, significant deviations from idealized polish behavior are observed. The most significant deviations from ideal behavior correspond to pad surfaces exhibiting the highest degree of asperity deformation as exhibited by changes in the pad height probability distribution. Extremes of velocity induce more significant deviations from idealized polish behavior than extremes in pressure. Extremes of pressure induce more significant levels of pad asperity deformation than extremes of velocity. The data presented here suggest that the stability of oxide polishing is highly dependent on the pad surface state and the nature of the pad-wafer interface. The choice of pad conditioner has a dramatic effect on the pad surface state and hence the dynamics of the polishing process. These data can be interpreted in terms of the effect of frictional loading on polish rate. Based on the analysis presented here, polish behavior that closely mimics idealized behavior occurs in the boundary lubrication regime and is therefore dominated primarily by pad-wafer contact mechanics. The most significant deviations from ideality can be explained by the influence of hydrodynamic effects as the forces at the pad-wafer interface push the behavior into the mixed lubrication regime.