Effect of nanosilica abrasive properties on tungsten chemical mechanical planarization

The effect of particle size, solid content, and surface charge of nano-silica on tungsten chemical mechanical polishing was explored to clarify the mechanical action. Particle size and solid content both showed a linear relationship with tungsten material removal rate. Analyzed with coefficient friction during the process, the contact area and contact mode changed with the varying particle size and solid content. In addition, the different surface charge of nano-silica was prepared through a graft of different silane coupling agent. The positively charged A-Surf-silica improved the tungsten removal rate by 33.2% and also presented higher coefficient friction in the polishing process. Moreover, tungsten removal rate shows a linear positive correlation to the abrasives’ zeta potential. The mechanism of abrasives in tungsten chemical mechanical planarization is discussed by combining DLVO theory and coefficient friction through the contact area, contact mode, and the synergy between the abrasives and the substrate of the mechanical action.