Hot carrier stress study in Hf-silicate NMOS transistors

Hot carrier stress (HCS) effects in NMOSFETs with HfSiO gate dielectric and poly-Si gate electrode are investigated. Both cold carriers and hot carriers contribute to the reversible V_th shift. In the case of the poly gate electrode, the stress bias dependant positive charge, attributed to the hole generation/trapping process, may complicate evaluation of the constant voltage stress and hot carrier stress. Cold carrier induced hole generation in poly-Si gate devices at high temperature is not desirable for a high-k stack. TiN metal gates show superior stress stability.