BEOL interconnects for 45 nm node and beyond

Increased copper resistivity and the associated impact on RC delays in sub-45 nm node BEOL interconnects are emerging as key focus issues for future high performance microprocessor applications. Lack of readiness of advanced optical lithographic capabilities to fabricate interconnects at such fine ground rules is a limiting factor in addressing this challenge early in the R&D mode. To circumvent this obstacle and enable early learning of process, microstructural and reliability aspects of this critical interconnect issue, a hybrid lithography scheme combining e-beam and 248 nm deep ultraviolet (DUV) lithography has been employed to fabricate Cu interconnects in various low k (LK) and ultra low k (ULK) dielectrics. Preliminary results from these studies are presented.