Youngki Hong

Synergistic Roles of Dodecyl Sulfate and Benzotriazole in Enhancing the Efficiency of CMP of Copper

Slurries used for chemical mechanical planarization (CMP) of copper generally contain certain dissolution inhibiting chemicals that help to improve the planarization efficiency (PE) of CMP by selective removal of Cu from protrusion regions of patterned wafers. Benzotriazole (BTAH) is a widely employed inhibitor in this category, but its use often leads to defects on the finished surface by generating insoluble debris on the polishing pad. We show how this problem can be addressed by using an environmentally friendly surfactant, ammonium dodecyl sulfate (ADS), as a primary dissolution inhibitor of Cu in the CMP slurry. Incorporation of ADS in the CMP slurry allows for a substantial reduction in the use of defect-causing BTAH in the slurry. The mixed inhibitors exhibit excellent performance both in suppressing Cu dissolution and in enhancing the PE of CMP. The individual and synergistic effects of ADS and BTAH on Cu dissolution were examined using a background slurry of 1 wt % glycine, 5 wt % H 2 O 2 , and 3 wt % fumed silica. Incorporation of 3 mM ADS + 0.5 mM BTA in this slurry yielded significantly lower dissolution rates (≤ 1 nm/min at 40°C) of Cu than that (∼40 nm/min) obtained with 10 mM BTAH. The PE of CMP, evaluated using 15 μm wide and 5000 A deep topographies on a Cu wafer, also is considerably higher (97%) for the ADS-BTAH mixed slurry than that (75%) for the slurry containing 10 mM BTA without ADS.