Analysis of oxide trap characteristics by random telegraph signals in nMOSFETs with HfO₂-based gate dielectrics

This letter investigates the oxide trap properties in n-channel metal-oxide-semiconductor field-effect transistors with HfO₂ and Hf_1-xZr_xO₂/metal gate-stacks by an analysis of random telegraph signals. According to the multiphonon emission theory, the extracted relaxation energies show gate voltage dependence in devices with HfO₂-based stacks. This dependence results from the different strengths of vibrations of the nearest neighbor Hf atoms of the oxygen vacancy in the immediate vicinity of the oxide trap. Furthermore, this dependence also induces an abnormal gate voltage dependence in terms of the activation energy required for electron capture. These results are confirmed by comparisons between two HfO₂-based devices (HfO₂ and Hf_1-xZr_xO₂).