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

Abstract

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 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 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 1 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. © 1999 The Electrochemical Society. All rights reserved.