Effects of Gas-Dissolved Water for Ceria Nanoparticles on the SiO₂ Film Surface in Post-CMP Cleaning

Abstract

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 SiO2 film surface became much more challenging.
We investigated the reduction/oxidation of ceria nanoparticles (CNPs) by hydrogen gas-dissolved water (H2 GDW), carbon dioxide gas-dissolved water (CO2 GDW), and oxygen gas-dissolved water (O2 GDW). 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 H2 GDW, CO2 GDW, and O2 GDW for 3 to 12 h. Following the Ce3+ concentration of the CNP surface, adhesion energies between CNPs immersed in H2 GDW, CO2 GDW, and O2 GDW for 6 hours with SiO2 surface were 6.06E-16 J, 6.18E-16 J, and 4.83E-16 J. Cleaning experiments under megasonic conditions revealed the efficacy of H2 GDW and O2 GDW in removing residual CNPs from SiO2 surfaces. The residual cerium (Ce) ion concentrations remaining on the SiO2 film surface after cleaning, were 0.06, 0.41, and 0.10 ppb for H2 GDW, CO2 GDW, and O2 GDW, respectively.