Electrochemical and material study of electroless ternary barriers for copper interconnects

Electroless cobalt-rich CoWP ternary alloys with a low weight percent of tungsten (approx. 2 percent) and a high phosphorus content (approx. 11 weight percent) have been deposited in basic solution onto copper and cobalt in integrated Cu damascene structures. A capability of the electroless CoWP deposition to form conformal barrier/protection films was demonstrated. Conformal 10 nm thick CoWP layer was also formed on the sidewalls of 30-40 nm wide seam of aspect ratio about 5:1 on the top of 0.4 μm wide in-laid Cu line.