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Modeling of Pattern Density Dependent Pressure Non-Uniformity at a Die Scale for ILD Chemical Mechanical Planarization
Published online by Cambridge University Press: 15 March 2011
Abstract
Local material removal rate is inversely proportional to the local pattern density in ILD CMP. With the assumption that the local velocity and Preston coefficient are constant across a chip, local MRR non-uniformity is mainly attributed to the local pressure non-uniformity. Pressure distributions on two different test patterns consisting of five different pattern density sections were obtained with a finite element model. These pressure distributions were compared with output from a semi-empirical pattern dependent oxide CMP model (MIT model) with three different weighting functions. Result showed that pressure distribution could be well approximated with the pattern density dependent oxide CMP model. This FEM model was further taken to evaluate the effects of thickness and material properties of each layer on the degree of pattern dependant pressure non-uniformity at a die scale for a typical polishing pad made up of a hard and a soft layer. The analysis shows that the degree of pressure nonuniformity at a die scale increases with the combination of a stiff hard layer and a thick soft layer, while it decreases with the combination of a stiff soft layer and a thick hard layer.
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- Copyright © Materials Research Society 2004
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