CVD Co and its application to Cu damascene interconnections

Fundamental material interactions as pertinent to nano-scale copper interconnects were studied for CVD Co with a variety of micro-analytical techniques. Native Co oxide grew rapidly within a few hours (XPS). Incorporation of oxygen and carbon in the CVD Co films (by AES and SIMS) depended on underlying materials, such as Ta, TaN, or Ru. Copper film texture (by XRD) and agglomeration resistance (by AFM) showed correlations with amounts of in-film oxygen/carbon. Cobalt diffused through copper at normal processing temperatures (by SIMS). CVD Co demonstrated diffusion barrier performance to Cu (by Triangular Voltage Sweep, TVS), but not to O₂. CVD Co was applied to 32 nm/22 nm damascene Cu interconnect fabrication in a scheme defined by the material studies. Lower post-CMP defect density and longer electromigration lifetimes were obtained.