Naoyuki Koyama

Polymer Adsorption Effects on Stabilities and Chemical Mechanical Polishing Properties of Ceria Particles

Characterization of ceria particles in the presence of poly(vinyl pyrrolidone) (PVP) was performed by the measurements of adsorbed amounts of PVP, average sizes, and back scattering intensities of the ceria particles as functions of PVP molecular weight and PVP concentration. Adsorption of PVP on the ceria particles enhanced the stability of ceria particles due to steric stabilization of the thick adsorbed layer of PVP. Moreover, SiO2 and Si3N4 films deposited on Si wafers were polished by the ceria particles in the presence of PVP in order to understand the effect of PVP adsorption on chemical mechanical polishing (CMP) technique, together with ceria particles without PVP and re-dispersed ceria particles adsorbed by PVP in water (re-dispersed ceria). Removal rates of the deposited SiO2 and Si3N4 films were decreased with an increase in the concentration of free PVP chains in the dispersion media, while the removal rates by the re-dispersed ceria were the same as those by the ceria particles in the absence of PVP.

Chemical Mechanical Polishing with Nanocolloidal Ceria Slurry for Low-Damage Planarization of Dielectric Films

New chemical mechanical polishing processes using nanocolloidal ceria slurry are proposed for high-precision and low-damage planarization of silicon-dioxide-based dielectric films. In the polishing process of a shallow trench isolation structure, a hard pad and a cationic polymer additive are used in combination with the slurry. The new process is effective in improving the planarity and reducing the microscratch count in comparison with a conventional polishing process with calcined ceria slurry and a standard pad. In the polishing process of an interconnect structure with ultralow-k interlayer dielectrics (ULK-ILDs), the standard pad should be used since the ULK-ILDs are easily damaged. By employing a spin-on-type ULK-ILD having a self-planarizing effect, a high planarity is obtained when using the nanocolloidal ceria slurry with the standard pad. The electrical measurement of the interconnect structure indicates that dielectric damage due to the process is successfully suppressed.