Future on-chip interconnect metallization and electromigration

Electromigration and resistivity of Cu, Co and Ru on-chip interconnections have been investigated. Non-linered Co and Ru interconnects can have better interconnect resistance than Cu, if the Cu liner cannot be scaled down below 2 nm in future interconnect technologies. A similar resistivity size effect increase was observed in Cu, Co, and Ru. Multi-level Cu, Co or Ru back-end-of-line interconnects were fabricated using 7 and 10 nm node technology wafer processing steps. EM in 18 nm to 88 nm wide Co lines, 18–24 nm wide Cu with a thin Co cap and 18 to 24 nm wide Ru lines were tested. The electromigration activation energies for Cu with Co cap, Co and Ru were found to be 1.5–1.7 eV, 2.4–3.1 eV and 1.9 eV, respectively. These data showed that Cu with Co cap, Co and Ru interconnects all had highly reliable electromigration.