Effect of Slurry Additives on Co-BTA Complex Stability and Inhibition Property During Co CMP Process

Abstract

The stability of the cobalt surface after the chemical mechanical planarization process is crucial to prevent the corrosion of the surface during the wafer transfer step. The stability of the Co-BTA complex is investigated in this work by using various experimental and surface analysis techniques. The higher inhibition efficiency of the Co-BTA complex observed at pH 7 was further investigated, and a more passive Co surface was observed during the de-ionized water (DIW) rinsing step. The low stability of the Co-BTA complex in the presence of slurry additives was confirmed from the accelerated oxidative dissolution of the Co surface compared to the adsorption of BTA. Ex-situ electrochemical impedance spectroscopy was further performed to analyze the stability of the Co-BTA complex to confirm the passivation of Co during the DIW rinsing step. The corrosion resistance of the Co surface during the rinsing step is further enhanced by reducing the dissolved oxygen content.