Understanding the Role of Slurry Additive Molecular Structure on Modulating the Interfacial Dynamics for Oxide CMP Applications

Abstract

As feature sizes continue to shrink well beyond the 7-nm node, understanding the delicate balance present in the chemical mechanical planarization (CMP) process is of utmost importance. In order to achieve high through-put and defect-free CMP processes it is critical to develop predictive analytical techniques that directly correlate to macroscopic STI CMP performance metrics (i.e. oxide/nitride removal, defectivity, and dishing/erosion). This work employed a suite of techniques to monitor the CeO2 nanoparticle interfacial redox processes in the presence of structurally diverse rate modulating additives. Specifically, utilizing a UV-Vis spectroscopic technique, the Ce3+/Ce4+ ratio in the presence of different slurry additives was monitored and proved to directly correlate to removal rate performance (i.e. an increase in Ce3+/Ce4+ ratio shows an increase in rate). This finding coupled with the rate of dissolved O2 evacuation and a modified QCM technique determined the mode of interaction/adsorption which validates that the mechanism of oxide removal does not strictly depend on redox capacity, but also depends on the dynamic O2 equilibrium at the CeO2 nanoparticle surface. In this work, the additives selected provide multiple modes of interaction spanning from noncovalent surface adsorbers to redox active functional groups. It was determined that the modulation of oxide removal was directly related to the distribution of interactions (i.e. steric vs redox) and was highly dependent on the slurry additive functionality.