Physics / mechanism
TiN and TaN are refractory metal nitrides deposited by PVD or ALD as thin films (2–10 nm typical) between copper interconnects and surrounding dielectrics or silicon. Their function is kinetic: they present a thermodynamically unfavorable diffusion path for Cu atoms, which would otherwise migrate into SiO₂ or low-k dielectrics and create trap states or junction leakage. TaN is preferred at the seed-layer interface (better adhesion to Cu); TiN dominates gate and contact applications. Resistivity runs 50–200 µΩ·cm depending on stoichiometry and deposition conditions. ALD enables conformal coverage into high-aspect-ratio vias at sub-3 nm nodes; thickness control below 1 nm is now production-relevant. Key failure mode is pinhole formation at ultrathin regimes, driving research into amorphous alternatives.
Competitive landscape
TiN/TaN face substitution pressure from three directions. Ruthenium liners (used by Intel at sub-5 nm) offer lower resistivity and direct-plate Cu without a seed layer. Cobalt fill eliminates the barrier/seed stack entirely for narrow lines but has electromigration limits. Manganese self-forming barriers (diffusion from CuMn alloy) are low-volume but eliminate deposition steps entirely.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.