Chemical mechanical planarization (CMP) of Ru barrier lines is expected to become a critical processing step in the fabrication of the new interconnect-structures. However, due to its noble metal characteristics, Ru induces galvanic corrosion in its adjacent Cu lines in the wet CMP environment, and resists chemical surface modifications that are necessary to support CMP. The present work reports a slurry formulation to address these challenges of Ru-CMP, and explores the considerations for residual Cu removal using the same slurry. This alkaline (pH = 10) slurry with colloidal silica abrasives uses sodium percarbonate as an oxidizer/complexing agent in the CMP of both Ru and Cu. L-ascorbic acid is employed as a surface modifier to regulate the material removal rates of CMP, and benzotriazole is used to control galvanic corrosion of the Ru-Cu couple. With this slurry, wafer polish rates of ∼10 and ∼80 nm min−1 are measured for Ru and Cu, respectively, resulting in defect-free processed samples. Electrochemical measurements of open circuit potentials, potentiodynamic polarization and impedance spectroscopy are performed to investigate the detailed surface reactions of Ru and Cu that facilitate material removal and control corrosion during the CMP of these metals.

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Ruthenium (Ru) films deposited on either TiN or TaN/Ta have been proposed as a barrier stack in advanced interconnects. Here, we investigated their polishing behavior using colloidal silica-based slurries containing guanidine carbonate (GC) or hydrogen peroxide (H2O2) or both. Neither GC nor H2O2 alone enhanced the Ru removal rates (RRs) but their combination did, presumably, due to the formation of Ru oxide-guanidinium complexes which can be polished by silica abrasives suggesting that the oxidation of Ru to its oxides is a crucial first step. Ethylenediamine and 2, 2–bipyridine that were reported to form complexes with halides of Ru in various oxidation states also enhanced the RRs of Ru films, similar to GC. Furthermore, even though both types of Ru films were deposited at same conditions, RRs of Ru on TiN were enhanced more compared to those on TaN/Ta, likely a consequence of the difference in the crystalline structure of the oxide films formed due to a difference in the structure of the Ru films themselves. Using X-ray diffraction, X-ray photoelectron spectroscopy, nanoindentation, zeta potential measurements, thermo gravimetric analysis and contact angle measurements, the role of GC and crystalline structure in enhancing the RRs of the films is discussed.