Ru passivated and Ru doped ε-TaN surfaces as a combined barrier and liner material for copper interconnects: a first principles study

摘要: The reduction of critical dimensions in transistor scaling means that a severe bottleneck arises from the lowest levels device interconnects. Copper is currently used as an interconnect metal, but requires separate barrier, to prevent Cu diffusion, and liner, promote deposition, materials. Advanced technology will require coating very high aspect ratio trench structures which copper barrier + liner stack should take up only small volume maintain low resistivity. current industry standard for diffusion barriers TaN Ru widely liner. In this paper we use first principles density functional theory (DFT) computations explore detail interaction atoms at models TaN, combined TaN/Ru barrier/liner This model allows us role these materials adsorption (over surface into bulk) early stage film growth. As benchmark studied behaviour adatoms index surfaces e-TaN, with (0 0 1) hexagonal Ru. These results confirm properties Ru, respectively, while also highlighting weaknesses both We then investigate Ru-passivated Ru-doped e-TaN(1 1 0) surfaces. passivated enhances binding compared bare On other hand, activation energy lower than on may agglomeration. For find decrease energy. addition, favourable migration toward doped atom, unfavourable away site, bulk. suggests doping sites can act nucleation points growth energies agglomeration electroplating Cu. Therefore propose candidate material have reduced thickness individual stacks.