An Approach for Correlating Friction Force and Removal Rate to Pad Topography during Tungsten Chemical Mechanical Planarization

Abstract

The evolution of coefficient of friction (COF) and removal rate (RR) during 8.5 h of tungsten CMP is correlated to pad surface topography via a novel pad surface descriptor termed ‘pad surface abruptness’. Interferometric analysis indicates that during the first 2.5 h of polishing, pad surface abruptness remains stable and after 5.5 h, pad surface abruptness decreases (i.e. surface becomes smoother). Results from polishing show similar trends whereby RR and COF are stable during the first 2.5 h period and decrease significantly thereafter. The coefficient of correlation between pad surface abruptness and COF as well as between pad surface abruptness and RR are 0.98 and 0.77, respectively.