Modeling the Effect of Bumpy Abrasive Particles on Chemical-Mechanical Polishing

Modeling the Effect of Colloidal Forces on Chemical-Mechanical Polishing

Clarkson Distinguished Professor Goodarz Ahmadi and his group are preparing a model for the effect of colloidal forces on CMP. It is well known that the variation of slurry pH could significantly affect the chemical-mechanical polishing process. In this study, a particle-scale mechanical model for the surface removal rate (that includes the double layer forces of abrasives and the wafer surface) is being developed. Results show that the van der Waals force and the electrical double layer attraction and repulsion play a major role in the chemical-mechanical polishing process. Furthermore, the magnitudes and signs of the zeta potential of the surface and the abrasives significantly affect the removal rates. The results show that the removal rate increases sharply in cases where the zeta potentials of the surface and abrasive have an opposite sign. On the other hand, the removal rate decreases when the zeta potentials have the same sign. The removal rates for the polishing of tantalum with silica and alumina abrasives were compared with the available data and qualitative agreements were observed.

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