Characterization of Different Cobalt Surfaces and Interactions with Benzotriazole for CMP Application

Different cobalt surfaces (as-received, metallic, and oxidized Co) were characterized by contact angle measurements, FTIR (Fourier-transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy) and EIS (electrochemical impedance spectroscopy) to investigate the interaction of these surfaces with benzotriazole (BTA). A new sequential EIS technique was used to study the inhibition capabilities of BTA on the cobalt surface and its stability under de-ionized (DI) water rinsing. It was found that a Co-BTA complex passive layer was formed when exposed to a BTA solution for all types of Co surfaces. It was hypothesized that BTA could actively form a Co-BTA complex on metallic Co as well as on the Co oxide surface. Interestingly, most Co-BTA complexes could be easily removed by simply rinsing with DI water, which indicates that BTA might not produce an organic residue issue after the chemical mechanical planarization (CMP) process. This was also well supported by potentiodynamic studies.