Theoretical Evaluation of Reliability and Via Resistance of Liner-Less Co Interconnect Using Co–Ti Binary Alloy

The structural and transport properties of CoTi binary alloys were investigated using density functional theory (DFT) calculations to evaluate the potential as a single-layer liner/barrier in liner-less Co interconnects. Cohesive energies of CoTi binary phases were calculated to identify thermodynamically stable compositions, with CoTi, Co₂Ti, and Co₃Ti exhibiting the lowest values. Interface binding energies were then evaluated for multiple Co/Co_xTi_y configurations and compared with conventional Cu/TaN interfaces. We identified several Co/Co_xTi$_{\textit{y}}\vphantom{_{_{_{_{}}}}}$ interfaces with binding energies lower than ~-5 J/mTEXPRESERVE8 such as fcc-Co(100)/CoTi(110), which exceeds that of the conventional Cu(111)/TaN(0001) interface. Finally, electron transport across the via stack was analyzed. Co/Co_xTi_y/Co via structures showed consistently higher specific conductance compared to Cu/TaN/Ta/Cu, with the highest value of 4.40 × 10^-4 S/nm² observed for fcc-Co(110)/Co₂Ti(110)/ fcc-Co(110). These results support the use of CoTi alloys as reliable, high-performance alternatives to conventional liner/diffusion barrier stacks in future interconnect technologies.