Electrode material dependent breakdown and recovery in advanced high-κ gate stacks

In this paper, the mechanism and physics governing the breakdown and recovery in metal-gated high-κ (MG-HK) dielectric stacks is investigated. Postbreakdown recovery is observed in NiSi and TiN-gated, but not TaN-gated, HfO₂-based logic devices in voltage-stress tests. Failure analysis studies reveal that metal-filamentation, besides oxygen vacancies, is responsible for the breakdown of these MG-HK dielectrics. First-principle studies show that the 5d orbitals of Hf and migrated metal atoms in the filamentation process reduce the band gap and increase the leakage current, eventually causing percolative breakdown of the dielectric. Postbreakdown recovery is feasible only for gate stacks with a low enough defect formation energy, which can be realized by selecting appropriate gate electrode materials, such as NiSi and TiN.