Experimental Investigation on Effects of Passivants in the Abrasive-Free Polishing of Copper Film

Abrasive Free Polishing (AFP) is a polishing technology without abrasives and widely employed in copper-base semiconductor fabrications. This paper investigates the effect of passivants, added to the slurry, on the material removal rate (MRR) and the non-uniformity (NU) via experiments. Two kinds of passivants, Benzotriazole (BTA) and citric acid (CA) are added to the slurry for the experiments. Experimental results showed that the MRR increases when polishing pressure increases while NU decreases at the same time. Both MRR and NU tends to increase when rotational speed increases, though MRR and NU at 40 rpm are lower than that at 30 and 50 rpm in the slurry with CA. Experimental data also showed that AFP using the slurry with CA performs better than that with BTA.