Effects of Gas-Dissolved Water for Ceria Nanoparticles on the SiO2Film 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 SiO2film surface became much more challenging. We investigated the reduction/oxidation of ceria nanoparticles (CNPs) by hydrogen gas-dissolved water (H2GDW), carbon dioxide gas-dissolved water (CO2GDW), and oxygen gas-dissolved water (O2GDW). The concentration of Ce3+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 H2GDW, CO2GDW, and O2GDW for 3 to 12 h. Following the Ce3+concentration of the CNP surface, adhesion energies between CNPs immersed in H2GDW, CO2GDW, and O2GDW for 6 h with SiO2surface were 6.06E-16 J, 6.18E-16 J, and 4.83E-16 J. Cleaning experiments under megasonic conditions revealed the efficacy of H2GDW and O2GDW in removing residual CNPs from SiO2surfaces. The residual cerium (Ce) ion concentrations remaining on the SiO2film surface after cleaning, were 0.06, 0.41, and 0.10 ppb for H2GDW, CO2GDW, and O2GDW, respectively.