Development of Post Ru CMP Cleaning Solutions

Ru (ruthenium) has been suggested as an electrode in DRAM and a Cu diffusion barrier metal for Cu interconnection. To planarize deposited Ru layer, chemical mechanical planarization (CMP) was suggested. However, abrasive particles can be easily contaminated on the Ru surface after polishing. In this study, zeta potentials of abrasive particle were measured as a function of pH. The etch rate and oxidation behavior of Ru were observed as a function of concentration of various acidic and alkaline chemicals. PRE (particle removal efficiency) was also evaluated in different cleaning solutions. Zeta potentials of abrasive particle decreased as a function of pH in these chemicals. Ru layer was etched and oxidized in a selected chemical. The highest particle removal efficiency was observed in a solution with citric acid at pH 9.