Zhao Yong-wu

Effect of the number of layers on the bond strength for multi-layer brittle coating-substrate system

Finite element method (FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition, which has not been addressed previously. The maximum shear stress was used to act as the criterion of the bonded strength. This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface. Firstly, the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model. It was found that with the increase in the number of coating layers, the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating. Finally, the increase in the number of layers contributes to the decrement of the stress along the x axis.

Modeling and experimental research on a removal mechanism during chemical mechanical polishing at the molecular scale

In order to understand the fundamentals of the chemical mechanical polishing (CMP) material removal mechanism, the indentation depth of a slurry particle into a wafer surface is determined using the in situ nanomechanical testing system tribo-indenter by Hysitron. It was found that the removal mechanism in CMP is most probably a molecular scale removal theory. Furthermore, a comprehensive mathematical model was modified and used to pinpoint the effects of wafer/pad relative velocity, which has not been modeled previously. The predicted results based on the current model are shown to be consistent with the published experimental data. Results and analysis may lead to further understanding of the microscopic removal mechanism at the molecular scale in addition to its underlying theoretical foundation.