Novel α-amine-functionalized silica-based dispersions for selectively polishing polysilicon and Si(1 0 0) over silicon dioxide, silicon nitride or copper during chemical mechanical polishing

We modified silica abrasives using the coupling agent n-(trimethoxysilylpropyl)isothiouronium chloride and found that both the polysilicon and Si(1 0 0) removal rates can be enhanced to >1 μm/min when polished using these modified silica-based dispersions at pH 10 and 4 psi down pressure. On adding arginine, lysine or ornithine in these dispersions and maintaining the same pH, both silicon dioxide and silicon nitride removal rates were suppressed to <2 nm/min without affecting the polysilicon and Si(1 0 0) removal rates. All these observed polysilicon, silicon, silicon dioxide and silicon nitride removal rates can be explained based on zeta potential and thermogravimetric data. Interestingly, when abrasive-free solutions which contain only the additives arginine, lysine, guanidine or ornithine were used, polysilicon and Si(1 0 0) removal rates were still >650 nm/min while both silicon dioxide and silicon nitride removal rates were ∼0 nm/min. In addition, removal rate of copper films was <1 nm/min in all the cases.