Fabrication of ruthenium thin film and characterization of its chemical mechanical polishing process

• Published in: Materials chemistry and physics 2015-07, Vol.162, p.477-486
• Main Authors: Chou, Yi-Sin, Yen, Shi-Chern, Jeng, King-Tsai
• Format: Article
• Language: English
• Subjects: Atomic force microscopy (AFM); Electrochemical properties; Electropolishing; Thin films
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2015.06.017

The fabrication of Ru thin film is conducted on titanium (Ti)-based rotating disk electrodes (RDE) by electrodeposition and characteristics of its chemical mechanical polishing (CMP) are investigated to be employed for copper diffusion layer applications in various semiconductor-device interconnects. The electrodeposits obtained under different electrodeposition conditions are characterized using atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). Experimental results indicate that the Ru electrodeposition exhibits a Tafel behavior with a 2e metal ion reduction process. Both exchange current density and cathodic transfer coefficient are determined. A quasi Koutecky–Levich analysis is proposed to analyze the electrodeposition processes under different applied current density conditions and the activation overpotentials together with electrodeposition rate constants are obtained. For Ru CMP operations, slurries containing metal-free 2wt% ammonium persulfate and 2wt% silica abrasive at various pH values are employed. Potentiodynamic polarization studies indicate that the corrosion current density varies in the presence of ammonia while the static etch rate remains low. Both chemical and mechanical effects are investigated and analyzed, and the CMP efficacy factors are obtained. •Ru electrodeposition is a 2e metal ion reduction process with Tafel behavior.•Ru electrodeposition on Ti RDE fits a quasi Koutecky–Levich equation.•Metal-free slurry is employed for CMP operation to avoid contamination.•The Ru CMP process is affected by the surface condition and the pH of slurry.•The CMP efficacy factor should be high in order to obtain a smooth surface.