Characterization of the electronic structure and thermal stability of HfO ₂2 /SiO ₂2 /Si gate dielectric stack

摘要

> X‐ray photoelectron spectroscopy was used to investigate thermal stability of HfO ₂ on SiO ₂ /Si substrate prepared by atomic layer deposition, followed by annealing at different temperature. Hf silicate and Hf silicide are formed at the interface of HfO ₂ and SiO ₂ during deposition. The Hf silicide disappears, while the amount of the Hf silicate is intensified after post‐deposition annealing treatment at 400?°C. Phase separation of the Hf silicate layer occurs when the annealing temperature is over 400?°C, resulting in the Hf silicate decomposition into Si and Hf oxides. Moreover, crystallization at high temperature leads to grain boundaries formation, which deteriorates the gate leakage current, as observed by the electrical measurements. The similar annealing temperature dependence of both internal electric field and the amount of Hf silicate implies that the Hf silicate plays a key role in building up the internal electric field, which is attributed to generation of oxygen vacancies ( V _o ) in the Hf silicate layer. Copyright ? 2017 John Wiley & Sons, Ltd.