The effect of benzotriazole (BTA) on copper electroplating for ultra large-scale integrated circuits interconnection was investigated. BTA exhibited both strong suppressing and brightening effects by modifying the nucleation and growth steps. Electroplating in the presence of BTA followed a random deposition mechanism rather than a selective or preferential deposition mechanism. As a result, the crystal orientation intensity and mean aggregates size of the electroplated copper with BTA were much smaller than those of BTA-free, which resulted in an increase in resistivity. The increased resistivity of the electroplated copper in the presence of BTA was recovered to approximately 2 muOmega-cm through annealing at 400 degreesC in a nitrogen atmosphere by grain growth and recrystallization. The amounts of carbon and nitrogen impurities from the BTA were below the detection limit of Auger electron spectroscopy.