Interaction Forces Between Silica Particles and Wafer Surfaces during Chemical Mechanical Planarization of Copper

Abstract

This study aims to investigate the interaction forces between silica particles and wafer surfaces during chemical mechanical planarization of copper. Silica slurry is most commonly used in the final step of Cu polishing to reduce scratches, Cu dishing, and oxide erosion. This study measures and calculates the interaction forces between silica particles and tetraethylorthosilicate oxide, TaN, Cu, and low-dielectric constant material surfaces. The Derjaguin-Landau-Verwey-Overbeek theory was used to calculate these forces by measuring the zeta potentials of the particles and the surfaces. The interaction force was obtained directly by measuring the force on the particles as a function of the distance between the particle and the surface. An atomic force microscope was used. Likewise, the magnitude of particle contamination on the wafers was measured by field-emission scanning electron microscope after the wafers were polished. The weakest repulsion force was measured between silica particles and the TaN surface. Similarly, the highest number of particles was observed on TaN surfaces after they were polished. © 2003 The Electrochemical Society. All rights reserved.