The Research On Rare Earth Polishing Powder’s Polishing Efficiency And Polishing Mechanism

Chemical mechanical polishing(CMP) is the only technology to provide surface global planarization and plays important role in the high-tech industry in the future, also the rare earth oxide powder is the most material used in this technology. While with the wide application of the CMP technology, high properties and great amount of rare earth cerium oxide polishing powder are required. Therefore, preparation of high efficient CeO2polishing slurry is very important for saving resources and improvement the added value. The dispersion properties of CeO2polishing slurry is the key factor to affect the polishing performance. In present paper, effect of the polymer dispersant and electrolyte on dispersion properties and suspension stability of the slurry was discussed. Polishing experiment was carried out with the slurries to the mobile phone glass substrates, finally, the formula of slurry and its polishing mechanism was discussed. Some interesting results were obtained.1Influence of different polymer dispersants on the Zeta potential of CeO2powder surface were studied. Results showed that when polyethyleneimine (PEI) was introduced to modify the ceria nano-particles, the iso-electric point of the CeO2powder moved toward high pH value. The value of Zeta potential equaled to49mV when pH was8, the dispersion stability of CeO2polishing slurry was improved clearly. In this condition, the dispersion mechanism was static electricity and steric stabilization synergism work; The material removal rate (MRR) increased from330.0nm/min to381.6nm/min as the modification of PEI can improve the valid particles amount of polishing powder in slurry.2Suspension stability and polishing performance of cerium oxide slurry were investigated when both sodium tripolyphosphate and sodium citrate mixed electrolyte mixture were used as dispersing agent. Results showed that zeta potential of CeO2particles became negative when mixed electrolyte added, and the value of Zeta potential were higher than pure CeO2particles when pH value ranged between4-10, and maximum value of52.4mV was obtained when pH equaled to8. It indicated that the dispersion stability and polishing efficiency of slurry were improved, which may due to the strengthened static repulsion interaction of double electrical layer.3Effect of CeO2particles morphology on the polishing performance was investigated. Results showed that particles with horns owned better performance than spherical particles. In addition, particles with moderate size can meet the requirements of glass planarization and thickness. 4Effect of concentration of polishing power in slurry, dispersing agent and additives on the polishing rate were discussed. Compared with mixed electrolyte of sodium tripolyphosphateand and sodium citrate, PEI provided the slurry with better suspension stability and polishing efficiency as dispersant. The addition of Zn(NO3)2·6H2O and boric acid can increase the polishing efficiency by4.4%and5.9%, respectively. The optimum conditions was obtained as follows(wt%):5%CeO2+0.025%PEI+0.1%Zn(NO3)2·6H2O,pH=8.