Effects of Gas-Dissolved Water for Ceria Nanoparticles on the SiO 2 Film Surface in Post-CMP Cleaning

As a trend of using colloidal and smaller ceria nanoparticles (CNPs) at the shallow trench isolation (STI) chemical mechanical polishing (CMP) in semiconductor manufacturing, post-CMP cleaning challenges in the removal of residual CNPs on the SiO 2 film surface became much more challenging. We investigated the reduction/oxidation of ceria nanoparticles (CNPs) by hydrogen gas-dissolved water (H 2 GDW), carbon dioxide gas-dissolved water (CO 2 GDW), and oxygen gas-dissolved water (O 2 GDW). The concentration of Ce 3+ on the CNPs changed from 18.64% to 19.48%, 20.31% to 21.94%, and 21.27% to 19.22%, respectively, after immersion in H 2 GDW, CO 2 GDW, and O 2 GDW for 3 to 12 h. Following the Ce 3+ concentration of the CNP surface, adhesion energies between CNPs immersed in H 2 GDW, CO 2 GDW, and O 2 GDW for 6 h with SiO 2 surface were 6.06E-16 J, 6.18E-16 J, and 4.83E-16 J. Cleaning experiments under megasonic conditions revealed the efficacy of H 2 GDW and O 2 GDW in removing residual CNPs from SiO 2 surfaces. The residual cerium (Ce) ion concentrations remaining on the SiO 2 film surface after cleaning, were 0.06, 0.41, and 0.10 ppb for H 2 GDW, CO 2 GDW, and O 2 GDW, respectively.