Preparation,Properties And Polishing Mechanism Of Submicron CeO₂ Polishing Powder

Chemical mechanical polishing(CMP)is one of the most effective planarization techniques in high-precision optics and VLSI manufacturing.As an important rare earth oxide polishing material,CeO2 powder possesses unique chemical mechanical polishing performance and enables optical glass,wafer and other materials to obtain higher precision and ultra-flat surface.It has become an important polishing product in the field of precision optical glass precision processing.However,the effect of the particle properties and morphology of CeO2 polishing powder on its polishing performance is unclear,and there is still no unified theory in the academic field for the polishing mechanism of cerium oxide particles.Establishing the relationship between the preparation process of polishing powder and polishing performance,it is important to clarify the polishing mechanism of CeO2 to promote its application development.In this work,the CeO2 polishing particles were prepared via precursor calcination using Ce(OH)3,Ce2(CO3)3 and Ce(OH)CO3 as precursor materials.The size distribution and specific surface area of the CeO2 particles as prepared were analyzed by Malvern laser particle size analyzer and BET automatic nitrogen adsorption specific surface meter,respectively.The phase of the particles was revealed by XRD,and the morphology of the particles was characterized by SEM and TEM.The polishing experiment of K9 glass was carried out by using Rhett 9B double-sided fine polishing machine.The mass reduction amount per unit time of K9 glass was used as the particle ablation amount {MRR),and the surface roughness Ra value of the K9 glass measured by AFM was used to evaluate the polishing quality.The effects of preparation process on the morphology,particle size,specific surface area,grain size and other particle properties of the CeO2 particles were studied.The effects of particle properties,morphology and phase composition on the polishing properties of the CeO2 particles were investigated,and the corresponding polishing mechanism was also studied.The experimental results show that the increase of calcination temperature,the prolongation of holding time,as well as the decrease of heating rate will increase the particle size and grain size and decrease the specific surface area.The morphology of precursor caninherite to between that of the particles.When the median diameter D50 is about 1.5 ?m,grain size is about 60-70 nm,and the specific surface area is 5 m2/g,the CeO2 particles possess the best polishing performance.The polishing experiments display that spherical particles can obtain a higher quality polished surface,and the block and strip particles have a higher amount of ablation.The contact area of the polished particles with the polished glass surface,the contact probability and the depth of the scratch were analyzed and used to investigate the polishing mechanism.In addition,the doped cerium-based rare earth polishing powder was also prepared.For the preparation,cesium carbonate was used as the raw material,and the processes of fluorination,precipitation and calcination were carried out in order.XRD detection indicats that the product is composed of CeO2,LaOF and LaF3.The cerium-based rare earth polishing powder has a higher throwing ability than the pure CeO2 polishing powder.The higher degree of fluorination,the higher calcination temperature,there is more LaOF phase and less LaF3 phase in the particles.The presence of the LaOF phase strengthens the grain boundary of the CeO2 particles and enhances the bonding force between the CeO2 particles,resulting in a higher removal rate.The polishing content of the polishing particles with a LaOF phase ratio of 18%is the highest.The softer LaF3 phase between the higher hardness CeO2 grains is prone to stress concentration and broken during the polishing process,resulting in a significantly reduction in the polishing ability of the polishing particle and the service life of the polishing solution.Therefore,the ceriumbased rare earth polishing powder particles should avoid appearance of the LaF3 phase.