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Slurry Particle Agglomeration Model for Chemical Mechanical Planarization (CMP)

Published online by Cambridge University Press:  01 February 2011

Joy Marie Johnson
Affiliation:
joyj@mit.edujoymariejohnson@gmail.com, Massachusetts Institute of Technology, Electrical Engineering & Computer Science, Cambridge, Massachusetts, United States
Duane Boning
Affiliation:
boning@mtl.mit.edu, Massachusetts Institute of Technology, Electrical Engineering & Computer Science, Cambridge, Massachusetts, United States
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Abstract

In this work we propose a particle agglomeration model for chemical mechanical planarization (CMP) under the primary motivation of understanding the creation and behavior of the agglomerated slurry abrasive particles during the CMP process, which are a major cause of defectivity and poor consumable utility due to sedimentation.

The proposed model considers the slurry composition as a colloidal suspension of charged colloidal silica in an electrically neutral aqueous electrolyte. First, a theoretical relationship between the measurable chemical parameters of the slurry's aqueous electrolyte, the surface potential of the abrasive particles, and corresponding zeta potential between the agglomerated abrasive particles is presented. Secondly, this zeta potential is used in a modified DVLO interaction potential model to determine the particle interaction potentials due to both the attractive van Der Waals forces and repulsive electrostatic interactions. Finally, the total interaction potential created is then used to define a stability ratio for slow versus fast agglomeration and corresponding agglomeration rate equations between particles; these are used in a discrete population balance framework to describe the final particle size distribution with respect to time and agglomerate composition.

The proposed model will provide both a qualitative and quantitative description of agglomeration of abrasive slurry particles during CMP that can be extended to account for slurry composition or abrasive particle type, enabling more accurate process control, increased consumable utility, and possible defectivity reduction.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

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