Halogen-based slurries have been investigated for chemical-mechanical polishing of tungsten. Among these slurries, Bromine-methanol-water slurry gives the best results. Depending on the polishing parameters and slurry concentration, polishing rate of the slurry for W varies from 100 nm/min to 300 nm/min, while the chemical etch rate of the slurry for W and SiO2 is near zero. The W and SiO2 films after polishing with the slurry show very smooth surfaces (featureless under a high quality optical microscope). The selectivity of larger than 15 has been achieved between W and PECVD TEOS oxide. Tungsten stud formation through CMP with this slurry has been demonstrated with no significant dishing in the metal.
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