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Open Access Publications from the University of California

Evaluation of the Effect of Pad Thickness and Stiffness on Pressure Non-Uniformity at Die-Scale in ILD CMP


In this study, 2^4 full factorial design of experiment was applied to an FEM model, which gives pattern dependant contact pressure distribution, to build a qualitative model of pad effects on within die non-uniformity (WIDNU) in CMP. Analysis of variance showed that every single effect and two-way interaction effects of hard layer stiffness and soft layer stiffness are significant compared to the round-off error from mesh change. Various regression models were built and residual analyses were done for each of them. Best model with best normality of residuals includes only the effect of hard layer stiffness, soft layer stiffness and hard layer thickness. Based on this model, basic qualitative design rule for a stacked CMP pad to minimize WIDNU were suggested.

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