A Modification to Preston’s Equation and Impact on Pattern Density Effect Modeling

We have shown that the removal rate of blanket oxide layers does not follow Preston’s law strictly. There exist two polishing regimes which are distinguished by the magnitude of the pressure and relative velocity product, pv. For large pv typically used for polishing, a constant term should be added to the Preston term for better fit to experimental data. The modified Preston’s equation has been incorporated into a closed-form analytic ILD thickness model to obtain a better agreement with experimental observations.