Novel phosphate-functionalized silica-based dispersions for selectively polishing silicon nitride over silicon dioxide and polysilicon films

We prepared and characterized novel phosphate-functionalized silica particles, and showed that, by using them during chemical mechanical polishing, both silicon dioxide and polysilicon removal rates can be suppressed while simultaneously enhancing silicon nitride removal rates. We achieved a silicon nitride:silicon dioxide:polysilicon removal rate selectivity of (>20):1:1. The measured removal rates of silicon dioxide, silicon nitride, and polysilicon are related to the electrostatic interactions and chemical reactivity between these films and the modified-silica abrasives.

Novel phosphate-functionalized silica abrasives were prepared using diethylphosphato-ethyltriethoxysilane (DPTS) as the coupling agent. Possible binding of DPTS to both silicon dioxide and silicon nitride surfaces is shown above. These novel abrasives can be used to suppress both silicon dioxide and silicon nitride removal rates to <2 nm/min and simultaneously enhance silicon nitride removal rates to >50 nm/min at pH 5.Figure optionsDownload high-quality image (53 K)Download as PowerPoint slide