Role of Guanidine Carbonate and Crystal Orientation on Chemical Mechanical Polishing of Ruthenium Films

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.