Abstract
A method of cleaning silicon substrates after chemical-mechanical polishing (CMP) for the planarization of tungsten-plug patterned silicon wafers is discussed. A phosphoric acid solution with fluoroboric acid (PFM) is used for the post treatment process to replace the conventional scrubbing process. The optimum chemical composition for the new solution is found to be the mixing ratio of 1:50 (fluoroboric acid:phosphoric acid in volume) at a phosphoric acid concentration of 40 vol%. Its oxide selectivity over metals and particle removing power are good enough for the cleanup process after CMP. The contact resistance of vias treated by the PFM solution exhibits a good distribution compared to that of vias treated by conventional scrubbing. In conclusion, the PFM solution shows promising results as a post-treatment to W CMP of via contact formation.
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