Effect of Oxidizer on the Galvanic Behavior of Cu ∕ Ta Coupling during Chemical Mechanical Polishing

The effect of oxidizer addition, namely, H 2 O 2 , KIO 3 , and Fe(NO 3 ) 3 , on the galvanic behavior of the Cu/Ta coupling in 0.01 M Na 2 SO 4 + 1 wt % Al 2 O 3 base slurry was studied. Both open-circuit potentials of the uncoupled Cu and Ta as well as galvanic current of the Cu/Ta were measured in static and under chemical mechanical polishing conditions to analyze the roles of these additives. The results showed that Fe(NO 3 ) 3 was more effective than H 2 O 2 and KIO 3 in promoting the passivation of Ta, which in turn caused the change of polarity between Cu and Ta. The effect of Cu/Ta area ratio on the galvanic behavior of the coupling was also investigated. The results showed that in Fe(NO 3 ) 3 -containing slurry, Ta was the anode with a Cu/Ta area ratio of 5:1 but became the cathode with an area ratio of 1:1.