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