Direct and quantitative study of ceria–SiO2 interaction depending on Ce3+ concentration for chemical mechanical planarization (CMP) cleaning

Abstract

The importance of chemical mechanical planarization (CMP) and post-CMP cleaning is highly critical because both directly affect the yields and performance of semiconductor devices. Ceria nanoparticles are widely used as abrasives for SiO2 CMP because strong ceria–SiO2 interaction enhances CMP performance. However, the interaction is a major drawback in post-CMP cleaning processes where residual ceria nanoparticles must be completely removed from the SiO2 surface. The interaction depends on the cerium oxidation state of the ceria nanoparticles surface. In this study, the ceria–SiO2 interaction was investigated systemically using an atomic force microscope and a quartz crystal microbalance. The analysis revealed that the adhesion energy between ceria and SiO2 and the adsorption rate of ceria nanoparticles on a SiO2 surface increased with the surface concentration of Ce3+. This is direct evidence showing that the ceria–SiO2 interaction becomes stronger as the surface Ce3+ concentration of ceria nanoparticles increases, suggesting that the surface Ce3+ concentration should be reduced for effective post-CMP cleaning.