Characteristics of Metal Etching Using Catalyst-Referred Etching Assisted by Anode Oxidation

Abstract

In a previous study, we developed an abrasive-free polishing method called catalyst-referred etching (CARE). By using water and Pt as an etchant and a catalyst, respectively, atomically smooth surfaces were realized on Si, SiO₂, and SiC substrates. OH generated on the Pt catalyst surface via water molecule dissociative adsorption attaches to a step edge atom, forming a hypervalent state. This hypervalent state reduced the activation energy, leading to cleavage of the back bond of the step edge atom. According to this mechanism, provided surface oxidation, metal materials with chemical stability and high hardness can be etched efficiently using the CARE method. In this study, we demonstrated Ru etching using the CARE method with oxidation. Anode oxidation was employed as surface oxidation. When 0.4 V was applied to the Ru, an atomically smooth surface without an oxidation layer was obtained. Ru is a promising next-generation wiring material. However, in the conventional polishing technique, because of chemicals added to the etchant, Ru wiring on the patterning substrate is over-polished. This phenomenon, which is called erosion and dishing, degrades the device performance. In contrast, CARE preferentially etches the topmost site of the sample surface. Therefore, the pattered substrate with Ru wiring can be planarized without erosion and dishing. The proposed method can produce a high-performance electric device with Ru wiring.