Ruthenium Polishing Using Potassium Periodate as the Oxidizer and Silica Abrasives

Abstract

Silica-based slurries containing potassium periodate (KIO4)(KIO4) at 0.015M0.015M concentration, close to its solubility limit of 0.018M0.018M , polished ruthenium at ∼20nm∕min∼20nm∕min at an applied pressure of 2psi2psi . Moreover, by utilizing the increase in the solubility of KIO4KIO4 achieved by the addition of potassium hydroxide, ruthenium removal rates (RRs) were enhanced to ∼65nm∕min∼65nm∕min at pHpH 9. At this pHpH , the toxic RuO4RuO4 does not form, making it potentially attractive for a manufacturing environment. The RRs obtained with silica abrasives are higher than those obtained with alumina abrasives at 0.015M0.015M KIO4KIO4 . A removal mechanism with KIO4KIO4 as the oxidizing agent is proposed based on the formation of several ruthenium oxides, some of which formed residues on the polishing pad below a pHpH of ∼7∼7 . The removal rate selectivities of ruthenium to copper and silicon dioxide are ∼1.3:1∼1.3:1 and ∼30:1∼30:1 , respectively.