Development of a pH-independent Post-CMP Cleaning Solution using Phosphoric Acid-based Surfactants for Removal of Ceria Nanoparticles

The global interest and demand for the advancement of semiconductor technology, including 3 nm generation semiconductors and gate-all-around semiconductors, continues to rise. This study presents an improvement plan aimed at enhancing performance and yield in the semiconductor manufacturing process, with particular emphasis on the post-CMP cleaning of SiO2 surface. The removal of residual ceria abrasives from SiO2 surfaces after the SiO2-chemical and mechanical planarization (SiO2-CMP) process is a sincere concern in the post-CMP cleaning process because the strong interaction between ceria nanoparticles and SiO2 makes their removal challenging. Herein, we propose a cleaning solution containing a phosphoric acid-based surfactant to address this issue. Three phosphoric-acid-based surfactants with varying numbers of phosphoric acid groups were evaluated, and etidronic acid (EA) with two phosphoric acid groups was found to be the most suitable surfactant. The EA demonstrated a reasonably negative zeta potential of the ceria nanoparticles, a key factor for efficient cleaning, despite variations in solution pH, pH adjuster cations, and surfactant and oxidizing agent (hydrogen peroxide) concentrations. Furthermore, the efficiency of the cleaning solution containing EA was evaluated, and the results confirmed the potential of EA as a promising surfactant for use in the post-CMP cleaning process.