Effect of ceria abrasive synthesized by supercritical hydrothermal method for chemical mechanical planarization

Scratches on the wafer surface are one of the significant issues during chemical mechanical planarization process. In order to satisfy wiring width shrinking with time, after polishing process, the presence of small scratches on the wafer is considerable issue. To reduce mechanically induced scratches, small-sized ceria particles are synthesized by a supercritical hydrothermal method. Spherical shaped nano ceria primary abrasive size is about 10 nm and secondary particles are uniformly distributed around 40 nm. The SiO₂ wafer removal rate is improved through increasing Ce³⁺ concentration by metal doping during the synthesis. The detailed principle of the material removal is introduced. The polishing test and its removal rates by the supercritical-hydrothermal-synthesized ceria slurries (SHC) are compared to a commercial ceria slurry. Removal rate of SHC catches up about 85% of the commercial one. The Ce³+ concentration of the slurry samples is compared, and the wafer surfaces are scanned for morphology characteristics. Scratch and roughness results of SHC are significantly improved against the results of commercial ceria slurry.