Characterization of charge trapping in SiO2/HfO2 dielectrics

The techniques for characterizing HfO₂ charge traps are summarized in this paper. A defect band is present in the HfO₂ layer and located above the Si conduction band. This band can be efficiently charged and discharged by applying positive or negative gate bias respectively. The effect of the defect band can be observed by I_D-V_G characteristic. It is concluded from experiments that only the electron fluence controls the trapping, while the detrapping is controlled by oxide field in combination with the lattice temperature. Charge pumping is proven to be a suitable technique to measure the charge trapping in SiO₂/HfO₂ stacks. The trap density can be scanned by varying the gate pulse amplitude or in distance from the Si/SiO₂ interface by varying the pulse frequency.