Tungsten CMP Modeling

A number of works have focused on the pattern dependencies in tungsten (both tungsten via and local interconnect) polishing [12,19,21]. To first order, empirical results seem to suggest that dishing is dominated by the width or size of the metal feature being polished wide lines tend to suffer 

Elbel et al. [12] have studied the polish of tungsten lines in a damascene-style process. The focus of the study and model is to relate the degree of dishing and erosion to the layout patterns, including both density and line-width dependencies. A simple model is used to relate the amount of erosion (e) to the density of metal and the overpolishing time  

In addition to erosion, an interesting model for dishing within metal features is proposed, based on the concept of a maximum dishing, which 

Maximum dishing within an array of contacts (of size 0.5 fim) observed in tungsten CMP overpolish [12]. Reproduced by permission of the Electrochemical Society, Inc. 

The physical mechanisms (e.g., chemical interactions, slurry interactions, and pad mechanics) governing dishing and erosion remain unclear, and accurate modeling awaits further experimental studies both to empirically characterize and physically identify important effects. 

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