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A new run-to-run control method for oxide CMP process

The main objective of the CMP run-to-run controller is to reduce the lot-to-lot variation in the post-polish oxide film thickness. Besides tool-induced variation, product-induced variation is also a significant source of variation to the CMP process. But the need to compensate for device pattern dependencies has not been addressed until recently. In this work, two removal rate models (topography factor model and sheet film equivalent model) are compared and the equivalency between them is derived. A new control method is proposed based on the sheet film equivalent model, which shows significant improvement compared to the traditional control method based on topography factor model. The performance of the proposed control algorithm is demonstrated using both simulated and industrial examples.