A study on electrochemical metrologies for evaluating the removal selectivity of AlCMP

Abstract

The in-situ electrochemical measurements were performed for the Al and Ti disks in the various slurries under the polishing or static condition. The slurries used contained Al2O3 abrasive, phosphoric acid, citric acid and hydrogen peroxide. The results showed that the addition of H2O2 could help to form an effective passivating layer on the Al surface. Besides, the addition of H2O2 enhanced Al dissolution. The maximum corrosion potential drop between the abraded and non-abraded Al electrodes corresponded to the possible maximum polishing rate of Al. The novel equipment for in-situ galvanic measurements was designed for evaluating the Al/Ti galvanic couple. It was found that Al dissolution could be suppressed in the slurry with the addition of 6 vol% H2O2 at pH 4. As regards the Al/Ti removal selectivity, the polishing with the addition of 6 vol% H2O2 at pH 4 would mitigate the Al dishing, since the polishing and dissolution of Al could be suppressed while those of Ti could be enhanced.