Carbon-doped copper as a high-conductivity liner for copper/benzocyclobutene (BCB) interconnects

This work explores the use of carbon-doped copper (Cu-C) as a high-conductivity liner for copper/benzocyclobutene (Cu/BCB) damascene interconnects, focusing on fabrication of damascene interconnects without polish stops and electrical characterization of the Cu/BCB interface. Single-level-damascene interconnect structures were successfully fabricated with and without a 60 nm Cu-C (<2 at %) liner (resistivity <3.5 μΩ-cm). The RIE removal of the SiN_x etch mask modified the BCB surface both chemically and mechanically with an improvement in adhesion. Electrical characterization of Cu/BCB and Cu-C/BCB interfaces using metal-polymer-oxide-semiconductor (MPOS) structures shows that Cu migration does not occur at temperatures up to 200°C for 30 minutes with a bias of up to 1 MV/cm. During I-V sweeps of metal-polymer-metal (MPM) and MPOS structures, instabilities are observed at the Cu/BCB interface, which do not appear at either the Al/BCB or the Cu-C/BCB interface