Electrochemical Characterizations and CMP Performance of Ru Slurry

Abstract

Currently, the manufacture of integrated circuits and fabrication of electronic devices requires the use of various types of chemical mechanical polishing compositions to selectively remove different metal, barrier, dielectric, low-k, ultra-low-k and other films at desirable rates to achieve the global planarization goal on the surfaces of patterned wafers. For more advanced node processing and applications, the copper metal lines are getting thinner and narrower, which leads to increased resistivity and causes electrical signal loss in the interconnection lines of the fabricated electronic devices. Therefore, new barrier layer materials other than Ta, TaN, Ti and TiN have been introduced in order to reduce the electrical signal loss beyond 20nm node applications. Ruthenium (Ru) has been used and tested as one of the new promising barrier layer materials. The introduction of Ru as a new barrier layer further complicates electrochemical and chemical reactions involved in a barrier chemical mechanical planarization process. Our studies focused on discovering the effects of key chemical components used in the CMP polishing compositions for polishing copper/ruthenium films and the effects of such polishing compositions on corrosion current, open circuit potential, galvanic corrosion and AC impedance on both ruthenium and copper films. The chemical mechanical polish results are reported together with these electrochemical studies. Using electrochemical studies, the effects of corrosion inhibitors on galvanic corrosion behavior at the Cu/Ru interface enables a more effective selection of suitable corrosion inhibitors for polishing Cu/Ru films.