Screening Study on Frictional Force Analysis in Relation to Silica Abrasive and Slurry Properties
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Screening Study on Frictional Force Analysis in Relation to Silica Abrasive and Slurry Properties Yun Zhuang1,2, Yasa Adi Sampurno2, Fransisca Sudargho1,2, Geoff Steward2, Herbert Barthel3, Erwin-Peter Mayer3, Torsten Gottschalk-Gaudig3, Michael Stintz4, Uwe Kaetzel4, Andre Nogowski4, Michael Goldstein5, and Ara Philipossian1,2 1 Araca, Inc., 6655 North Canyon Crest Drive, Suite 1205, Tucson, AZ, 85750 2 Department of Chemical and Environmental Engineering, University of Arizona, 1133 James E. Rogers Way, Tucson, AZ, 85721 3 Wacker Chemie AG, Johannes-Hess-Strasse 24, Burghausen, 84489, Germany 4 Institute of Process Engineering and Environmental Technology, University TU Dresden, Helmholtzstr. 10, Dresden, 01062, Germany 5 Intel Corporation, 2200 Mission College Boulevard, Santa Clara, CA, 95052 ABSTRACT In this study, different amounts of standard fumed silica and fumed silica contaminated by coarse particles was added as powder to a standard copper CMP slurry to investigate their effects on large particle count, mean particle size, slurry viscosity, frictional force during wafer polishing, and copper removal rate. Standard silica powder consisted of the same particles used in the standard slurry while contaminated silica powder consisted of the same particles used in the standard slurry and additional large size particles. Large particle count analysis indicated that slurry dispersion itself generated large size particles in the slurries. The addition of 0.3% and 1% contaminated silica to the standard slurry caused significant increases in large particle count, and the mean particle size increased with the amount of contaminated silica added to the standard slurry. The slurry viscosity generally increased with the amount of standard and contaminated silica added to the standard slurry under the shear rate of 100 s-1. The standard slurry and slurries added with 0.3% and 1% contaminated silica were used to polish 200-mm blanket copper wafers on the APD-500 polisher that has the unique ability to measure frictional force in real time during polishing. The coefficient of friction increased with the amount of contaminated silica added to the standard slurry. In general, the removal rates for the slurry added with 1% contaminated silica were higher than the standard slurry and slurry added with 0.3% contaminated silica.
INTRODUCTION It is well known that slurry abnormalities resulting from large abrasive particles and abrasive particles agglomeration can cause defects on wafer surfaces during CMP processes. In this study, different amount of standard and contaminated fumed silica powder was added to a standard copper CMP slurry to create such abnormalities. Large particle count, mean particle size, and slurry viscosity were measured and compared among the standard slurry and slurries added with standard and contaminated silica. The standard slurry and slurries added with 0.3% and 1% contaminated silica were used to polish 200-mm blanket copper wafers, and the effects of contaminated silica on frictional f
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