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Modeling CMP Transport and Kinetics at the Pad Groove Scale
Published online by Cambridge University Press: 15 March 2011
Abstract
A 3-D fluid flow and kinetics model of the full pad-wafer gap of a commercial CMP machine, including both grooves and land area flow properties, was developed to research the influence of these essential pad features at a scale not previously studied. Concentric circular grooves of two different dimensions were examined. Heat transfer and chemical reaction rates at the wafer surface were studied by including a combined frictional/chemical heat release model and firstorder kinetics for slurry activity. Results revealed sharp variations in velocity between the grooves and land areas, and a strong impact of groove depth and width on transient slurry mixing in the pad-wafer gap. These effects were more pronounced at higher polish pressures. Flow patterns in individual grooves beneath the rotating wafer were highly variable from one location to another such that fluid pathlines were dissimilar point to point even within the same groove. The effects of pad and wafer rotation, amplified by the unequal flow resistances of grooves and land areas, led to features in the steady-state temperature and concentration profiles at the same spacing as the groove pitch. This unusual finding identified a direct mechanism by which polish irregularities may be formed at the scale of the grooves.
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- Copyright © Materials Research Society 2004
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