Chemical Mechanical Polishing of Glass Substrate with α-Alumina-g-Polystyrene Sulfonic Acid Composite Abrasive

Abrasive is the one of key influencing factors during chemical mechanical polishing（CMP） process. Currently, α-Alumina （α-Al2O3） particle, as a kind of abrasive, has been widely used in CMP slurries, but their high hardness and poor dispersion stability often lead to more surface defects. After being polished with composite particles, the surface defects of work pieces decrease obviously. So the composite particles as abrasives in slurry have been paid more attention. In order to reduce defect caused by pure α-Al2O3 abrasive, α-alumina-g-polystyrene sulfonic acid （α-Al2O3-g-PSS） composite abrasive was prepared by surface graft polymerization. The composition, structure and morphology of the product were characterized by Fourier transform infrared spectroscopy（FTIR）, X-ray photoelectron spectroscopy（XPS）, time-of-flight secondary ion mass spectroscopy（TOF-SIMS）, and scanning electron microscopy（SEM）, respectively. The results show that polystyrene sulfonic acid grafts onto α-Al2O3, and has well dispersibility. Then, the chemical mechanical polishing performances of the composite abrasive on glass substrate were investigated with a SPEEDFAM-16B-4M CMP machine. Atomic force microscopy（AFM） images indicate that the average roughness of the polished glass substrate surface can be decreased from 0.835 nm for pure α-Al2O3 abrasive to 0.583 nm for prepared α-Al2O3-g-PSS core-shell abrasive. The research provides a new and effect way to improve the surface qualities during CMP.

Preparation of composite abrasives by electrostatic self-assembly method and its polishing properties in Cu CMP

The adsorption characteristics of cationic polyelectrolyte poly dimethyl diallyl ammonium chloride （PDADMAC） and anionic polyelectrolyte poly （sodium-p-styrenesulfonate） （PSS） on benzoguanamine formal- dehyde （BGF） particles are investigated. The charging characteristics of BGF particles are changed and con- trolled using electrostatic self-assembly method. A variety of PE,-BGF/SiO2 composite abrasives are obtained. The as-prepared samples are analyzed by zeta potential analysis, transmission electron microscope （TEM） and thermogravimetric （TG） analysis. The composite abrasive slurries are prepared for copper polishing. The poli- shing results indicate that it is SiO2 abrasives, not only coated SiO2 abrasive on polymer particles but also free SiO2 abrasive in slurry, that offer the polishing action. The material removal rates of copper polishing are 264 nm/min, 348 nm/min and 476 nm/min using single SiO2 abrasive slurry, PE0-BGF/SiO2 mixed abrasive slur- ry and PE3-BGF/SiO2 composite abrasive slurry, respectively. The surface roughness Ra of copper wafer （with 5μm×5μm district） is decreased from 0.166 μm to 3.7 nm, 2.6 nm and 1.5 nm, and the surface peak-valley values Rrv are less than 20 nm, 14 nm and 10 nm using these kinds of slurries, respectively. Key words ： chemico-mechanical polishing; polishing slurry; composite abrasives ; polyelectrolyte ; copper

New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.