Study On Prepration Of Alumina/Silica Composite Abrasive And Its CMP Performance

Chemical mechanical polishing as a kind of surface treatment technology is widely used in large scale integrated circuit, optical glass, sapphire and diamond, and is recognized as the only technology which provides global planarization. Abrasive is an important part of the chemical mechanical polishing process, affecting the planarization strongly. Compared with the traditional single inorganic abrasive, coated composite abrasive has the advantages of adjustable hardness and controllable morphology. In this thesis, we introduce the synthesis of coated composite abrasive with the cheap and highly hard α-Al2O3 as core and the soft SiO2 and mesoporous SiO2 as shell. The as-prepared coated composite abrasive is then used to polish the K9 optical glass. The effects of the polishing process parameters and slurry formulations on the material removal rate are studied. The regularities of the material removal rate are investigated.Al2O3/SiO2 coated composite nano-powders are successfully prepared by a heterogeneous nucleation method. Instruments such as TEM, XRD, FT-IR are used to characterize the composite powders which suggest that Al2O3 and SiO2 are connected together by chemical bonds and the SiO2 shell is amorphous. When the solid content is 5 wt%, PVP content is 0.6 wt% and ball milling time is 2 hours, the suspension and dispersion property of Al2O3/SiO2 composite slurry are best and the scratch of K9 optical glass decreases significantly and the surface roughness is 1.875 nm after polishing.Al2O3/SiO2/mesoporous SiO2 coated composite nano-powders are prepared by template self-assembly method using Al2O3/SiO2 coated composite nano-powders as core. The mesoporous structure and elemental composition of the as-prepared product are characterized by TEM, EDS and N2 adsorption-desorption methods. When the polishing pressure is 29.22 kPa, the rotating speed is 120 r/min, the slurry supplying rate is 60 mL/min, the time is 90 min, the slurry formulations includes 7.5 wt% solid and 0.6 wt% dispersant, the pH is 10, the material removal rate of K9 optical glass can reaches 137.17 nm/min and the surface roughness is 0.793 nm.