IEEE Transactions on Electron Devices vol:51 issue:3 pages:402-408
Dielectric relaxation currents in SiO2/Al2O3 and SiO2/HfO2 high-kappa dielectric stacks are studied in this paper. We studied the thickness dependence, gate voltage polarity dependence and temperature dependence of the relaxation current in high-kappa dielectric stacks. It is found that high-kappa dielectric stacks show different characteristics than what is expected based on the dielectric material polarization model. By the drain current variation measurement in n-channel MOSITET, we confirm that electron trapping and detrapping in the high-kappa dielectric stacks is the cause of the dielectric relaxation current. From substrate injection experiments, it is also concluded that the relaxation current is mainly due to the traps located near the SiO2/high-kappa interface. As the electron trapping induces a serious threshold voltage shift problem, a low trap density at the SiO2/high-kappa interface is a key requirement for high-kappa dielectric stack application and reliability in MOS devices.