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Fundamental Studies on the Mechanisms of Oxide CMP

Published online by Cambridge University Press:  14 March 2011

Uday Mahajan ,
Seung-Mahn Lee  and
Rajiv K. Singh
Uday Mahajan
Affiliation:
Department of Materials Science and Engineering and Engineering Research Center for Particle Science and Technology, University of Florida, Gainesville, FL 32611
Seung-Mahn Lee
Affiliation:
Department of Materials Science and Engineering and Engineering Research Center for Particle Science and Technology, University of Florida, Gainesville, FL 32611
Rajiv K. Singh
Affiliation:
Department of Materials Science and Engineering and Engineering Research Center for Particle Science and Technology, University of Florida, Gainesville, FL 32611
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Abstract

In this paper, results of studies on the addition of salt to a polishing slurry, in terms of its effect on slurry stability, SiO2 polishing rate and surface roughness of the polished surface are presented. Three salts, viz. LiCl, NaCl and KCl were selected, and three concentrations were tested. Polishing rate measurements using these slurries show that adding salt leads to increased removal rate without affecting surface roughness significantly. Based on these results, we can say that the agglomerates formed by adding salt to the slurry are fairly soft and easily broken during the polishing process. In addition, turbidity and particle size measurements show that significant coagulation of the particles in the slurry occurs only at the highest salt concentration, and is fastest for LiCl and NaCl, with KCl showing the slowest coagulation. From these results, it can be concluded that the enhancement in polish rate is due to increased contact at the wafer-pad-slurry interface, and not due to formation of larger agglomerated particles in the slurry. This is because of reduced electrostatic repulsion between these three surfaces, due to the screening of their negative surface charge by the metal ions in solution, resulting in a higher wear rate.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 613: Symposium E – Chemical-Mechanical Polishing 2000 - Fundamentals… , 2000 , E1.7.1
Copyright
Copyright © Materials Research Society 2000

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References

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