Time-dependent dielectric breakdown (TDDB) for Co0.65Ti0.35 as a single barrier/liner in local Co interconnects

As an interconnect metal, cobalt (Co) has been employed in state-of-the-art CMOS technology to substitute conventional Copper (Cu) or Tungsten (W) due to its surplus advantages. A single layer of Co–Ti alloy would replace the relatively thick Ta/TaN or Ti/TiN bilayer as both barrier and liner layer to match the Co interconnects, which strengthens the advantages for Co interconnects. In this article, the reliability of Co0.65Ti0.35 as both barrier and liner layer in Co interconnects is further evaluated through time-dependent dielectric breakdown experiment which is critical for its practical application in devices. It is found that the Co0.65Ti0.35 indeed can act as a single barrier/liner layer in a long-term operation. Co0.65Ti0.35 effectively prevents the diffusion of a part of Co ions, delays the formation of conducting path, and allows the SiO2 dielectric layer to withstand tremendous voltage stress. What’s more, the characteristic lifetime of devices with Co0.65Ti0.35 predicted by the √E model is significantly prolonged from 116 days to 32 years, greatly satisfying the reliability requirements of the barrier layer.