Tungsten CMP—Contact Wear Model

Chekina et al. [8] have applied contact wear methods to the modeling of surface evolution in both oxide and dual material (tungsten-oxide) CMP to predict erosion and dishing or recess. The formulation uses calculation of 

Because the local pressure distribution depends on the surface shape, and the evolution of the surface shape depends on the local pressure distribution, a discretization in space of the shape profile combined with a time-step approach can be used to predict the progress of the polish process. 

An example application of the contact wear model to simulation of the polish of an embedded array (assuming no material in the trenches within the array) is shown in Fig. 29. One can also observe the evolution of the pressure distribution, where clear sharp pressure concentrations at the edges of the features can be seen. Such localized pressures work to rapidly round the corners of features undergoing polish. 

The contact wear approach is also applicable to modeling dual material systems such as tungsten polish. The calculated shape evolution is shown in 

The contact wear calculations appear to hold great promise for detailed feature-level simulation. The die-level simulation approaches discussed earlier can be viewed as approximations to the contact-wear approach that focus on the polish or planarization results over large length scales rather than over feature-length scales. 

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