Breakdown and reliability of metal gate-la₂o₃ thin films after post-deposition annealing in N₂

We report the electrical characteristics and reliability of Metal-La ₂O₃ stacks on silicon after Post Deposition Annealing (PDA) of La₂O₃ in N₂. MIS capacitors were fabricated and their C-V and I-V characteristics before and after applying a Constant Voltage Stress (CVS) in the substrate injection condition were evaluated. By using 2 different physical thickness for La₂O ₃, the same Equivalent Oxide Thickness EOT ∼ 1.5nm is obtained for Al-gated and W-gated La₂O₃ stacks. This is explained by the presence of an already existent Al₂O₃ interfacial layer IL at the Al-La₂O₃ interface which results in a lower k for the total oxide stack. It is speculated that the physical thickness of this IL slightly increases after stress, which can be seen as degradation in the C-V characteristics of the Al-La₂O₃-nSi structure. This can be explained by the use of a modified Reaction-Diffusion (R-D) model, which is based on the Electric Stress-Induced Defect Generation (ESIDG) mechanism (1). Finally, longer lifetimes before breakdown were obtained for W-gated La₂O₃ MIS capacitors and a 10 years operation is guaranteed by using both the linear or reciprocal Vg models. copyright The Electrochemical Society.