Removal of CeO2 particles for SiO2/Si3N4 post-CMP with composite cleaning solution: Performance and synergistic mechanism

In semiconductor manufacturing, CeO 2 -based slurries used for shallow trench isolation (STI) chemical mechanical polishing (CMP) tend to form strong Ce-O-Si chemical bonds with the wafer surface, resulting in strong adhesion. This significantly impacts the yield of subsequent processes and device performance, making these residues the primary target for post-CMP cleaning. However, existing cleaning solutions are unable to effectively remove residual particles from both silicon dioxide (SiO 2 ) and silicon nitride (Si 3 N 4 ) surfaces simultaneously. To address this challenge, this study focused on CeO 2 particles adhering to SiO 2 and Si 3 N 4 surfaces and systematically investigated the removal efficiency of a cleaning solution formulated by combining the nonionic surfactant AEO-9 with ascorbic acid (VC) at pH 11. Using various characterization techniques, including zeta potential measurements, contact angle analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), the residual CeO 2 particles on the surfaces before and after cleaning were thoroughly evaluated. Additionally, by integrating ultraviolet-visible (UV-Vis) spectroscopy, XPS analysis, and molecular dynamics simulations, the desorption mechanism of CeO 2 particles was further elucidated from the perspective of molecular-interface interactions. The experimental results indicate that when AEO-9 and VC are blended in a 1:1 ratio (both 750 ppm), the cleaning solution significantly reduces the adhesion between CeO 2 particles and the wafer surface. Furthermore, by forming chelates with Ce 3+ ions and aided by the physical-mechanical action of a polyvinyl alcohol (PVA) brush, it efficiently removes CeO 2 particles from the surfaces of SiO 2 and Si 3 N 4 films, achieving a removal rate exceeding 99%.