Electrical Breakdown and Reliability of Metal Gate - La2O3 Thin Films after Post Deposition Annealing in N2

Abstract

We report the electrical characteristics and reliability of Metal-La2O3 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 La2O3, 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.