Modeling Of Capacitance-Voltage And Tunneling Current Of Mos Structure With Ultrathin HfO₂ Gate Dielectric

HfO2 has emerged as an attractive high-k material because of its relatively high permittivity and its thermal stability. However, there is a high interface state density between hafnium oxide and silicon substrate interface, which may greatly affect the device performance. Due to the dielectric constant mismatch between hafnium oxide and silicon substrate,which results in the interface image potential effect near the interface.For ultra-thin hafnium gate oxide, electronic state in strong inversion is often an focus of research, at this moment the electronic exchange-correlation effect is relatively strong.To simulate static capacitance of MOS structure acculately, In the parabolic effective mass approximation including exchange-correlation effect and image potential effect, taking into quantum tunneling effect and effect of interface states account, Poisson and Schrodinger equation self-consistency are solved, according to the simulation data analysis show that the interface state energy distribution in the band gap is reasonable, but the physical meaning of the most important thing is get through this model,and analyzed HfO2 gate nMOS capacitance-voltage relationship under different interface state density. In this article, HfO2 gate pMOS tunneling current is simulated. In the kp approximation effective mass theory, three-band model and single-band model are proposed to study the structure of ultra-thin oxide gate pMOS hole direct tunneling current.By comparison, the effective single-band model used to simulate the hole tunneling current is reasonable. In addition, the electron tunneling current from metal electrode is also considered, numerical simulation found that when hole is in the inversion, the electron tunneling current is not negligible, and different mechanis of HfO2 gate pMOS structure tunneling current may also occur.