Effect of Sodium Dodecyl Sulfate on Copper Anodic Dissolution in Phosphoric Acid Solution

In Electrochemical Mechanical Planarization process (ECMP), concentrated phosphoric acid is usually used as electrolyte. Role of sodium dodecyl sulfate (SDS) in anodic dissolution of Cu in concentrated phosphoric acid was studied by Cyclic Voltammetry (CV), inhibition efficiency (IE) calculation and in-situ observation of the Cu electrode surface at anodic overpotentials. It was found that presence of SDS enhances surface passivation of Cu in both active and passive potential regions. Moreover, in the passive region, introduction of SDS results in fine, close-packed and stable layers of oxygen bubbles, which can effectively inhibit anodic dissolution of Cu. A correlation was established between the electrochemical impedance spectroscopy and the structure of the passive film. The values of Rct,Yct,Rf,Yf increase with the addition of SDS indicate that SDS is helpful to form the film of oxide copper. Therefore, SDS can be used as an additive to achieve excellent planarization efficiency for ECMP.