Graphene-All-Around Cobalt Interconnect with a Back-End-of-Line Compatible Process.

The graphene-all-around (GAA) structure has been verified to grow directly at 380 °C using hot-wire chemical vapor deposition, within the thermal budget of the back end of the line (BEOL). The cobalt (Co) interconnects with the GAA structure have demonstrated a 10.8% increase in current density, a 27% reduction in resistance, and a 36 times longer electromigration lifetime. X-ray photoelectron spectroscopy and density functional theory calculations have revealed the presence of bonding between carbon and Co, which makes the Co atom more stable to resist external forces. The ability of graphene to act as a diffusion barrier in the GAA structure was confirmed through time-dependent dielectric breakdown measurement. The Co interconnect within the GAA structure exhibits enhanced electrical properties and reliability, which indicates compatibility applications as next-generation interconnect materials in CMOS BEOL.

MoS2 as an Effective Cu Diffusion Barrier with a Back-End Compatible Process.

This study demonstrates molybdenum disulfide (MoS2) as a superior candidate as a diffusion barrier and liner. This research explores a newly developed process to show how effectively MoS2 can be applied. First, a new approach is developed to prepare molybdenum disulfide (MoS2) by microwave plasma-enhanced sulfurization (MW-PES). MW-PES can rapidly and directly grow on the target substrate at low temperatures, which is compatible with the back-end-of-line (BEOL) technology. Second, the performance of MW-PES MoS2 as a diffusion barrier and liner is reported in the subsequent section. Through time-dependent dielectric breakdown (TDDB) measurements, MoS2 is shown to have a barrier property better than that of the current material, Ta, with the same thickness. According to the model fitting, the lifetime of the device is about 45.2 times the lifetime under normal operating conditions. Furthermore, MoS2 shows its superior thermal stability in maintaining the barrier properties. MoS2 is proven to be an excellent interface as a liner as it can provide sufficient adhesion and wettability to further effectively reduce the surface scattering of copper (Cu) and significantly lower the circuit resistance.