Effect of oxygen vacancy on the electronic structure and electrical properties of HfO₂/Si interface

HfO2 is one of the alternative candidate gate materials for SiO₂ in electronic devices, because of its high dielectric constant (e 25). Space charges and defects are more favorable to be accumulated at the oxide-substrate interface, which plays a key role in the electrical properties of electronic devices. However, it is still unclear that how the defects affect the electrical performance of devices. In this paper, the effect of oxygen vacancy (V_o) on the electronic structure of the HfO₂/Si interface and electrical properties of devices was analyzed by using the density functional theory. The 2-layer model of HKVSi was built, and then the V_o was introduced into the interface through first-principles calculation method. The interfacial electronic levels, states, and localization functions of these two models were calculated with the assistance of Quantum Espresso software. It was found that the interaction between atoms such as Si-O and Hf-O at HfO₂/Si interface is weaker than that in the SiO₂ and HfO₂, respectively. It means that the point defects are easy to be formed at the HfO₂/Si interface. The interfacial state is originated from Si and Hf atoms, which is quite different from the bulk state and responsible to the electrical performance of devices. Compare with Hf, the Si near V_o processes greater electron affinity and thus has more ability to capture electrons, leading to the electrostatic breakdown eventually. Our research work revealed the reason why the interfacial states were formed and the physical mechanism of the effect of interfacial states on the electrical properties of the device from the electronic level. It is expected that these results can be benefited to the structural design and performance optimization for electronic devices.