Copper/Benzocyclobutene Interconnects for Sub‐100 nm Integrated Circuit Technology: Elimination of High‐Resistivity Metallic Liners and High‐Dielectric Constant Polish Stops

This work explores improving scalability by eliminating both high-resistivity metallic liners as well as high-dielectric constant polish stops in copper/benzocyclobutene (Cu/BCB) damascene interconnects, focusing on Cu/BCB adhesion during fabrication of Damascene interconnects as well as electrical characterization of the Cu/BCB interface. Adhesion of blanket dc magnetron sputtered Cu films on BCB was improved by use of a thin carbon-doped Cu (Cu-C) layer (<2 atom %) with a resistivity of < 3.5 μΩ-cm. In Damascene-patterned samples, a SiN x hard etch mask was used during BCB patterning but was removed by reactive ion etching (RIE) plasma etching prior to Cu deposition. The RIE removal of the SiN x etch mask modifies the BCB surface both chemically and mechanically with a resulting improvement in Cu and Cu-C adhesion. Single-level Damascene interconnect structures were successfully fabricated with and without a thin Cu-C layer between Cu and BCB. Electrical characterization of Cu/BCB and Cu-C/BCB interfaces using metal polymer oxide semiconductor (MPOS) capacitor structures shows that Cu drift does not occur at temperatures up to 200°C for 30 min with a bias of up to 1 MV/cm. Room temperature leakage current measurements of Cu/BCB/Al and Cu-C/BCB/Al (MPM) structures show the leakage behavior is ohmic up to I MV/cm, the highest applied bias used. During I-V sweeps of MPM and MPOS structures, instabilities were observed at the Cu/BCB interface, at extremely low currents, which did not appear at the Al/BCB or at the Cu-C/BCB interface.