Electroless Deposition of Copper-Manganese for Applications in Semiconductor Interconnect Metallization.

Manganese-doped copper interconnects are known to provide superior electromigration resistance and thus are attractive for further downscaled interconnect metallization in future high-performance microprocessors. In the present study, we report on Cu-Mn (copper-manganese) fabricated by electroless deposition. Using tartrate-complexed electrolytes, we achieved electroless plating of Cu-Mn with (4.0 ± 0.5) at.% Mn. Electrochemical studies determined the most likely oxidation state of the Mn in the deposit to be +2. This suggests incorporation of MnO or Mn(OH)₂ during deposition. After heat-treatment of the Cu-Mn films, X-ray photoelectron spectroscopy indicated Mn segregation at the film surface. Moreover, transmission electron microscopy demonstrates Mn segregation at Cu-substrate interface. These observations suggest that Mn transport in electroless-deposited Cu-Mn can be exploited to engineer future interconnects with improved reliability and 'self-forming' barrier properties. Challenges to be addressed in future studies are highlighted. [ABSTRACT FROM AUTHOR]