Total ionizing dose radiation effects and negative bias temperature instability on SiGe pMOS devices

Abstract

The total ionizing dose (TID) response of HfO2-SiO2/SiGe pMOS FinFETs under different irradiation biases have been evaluated. Negative bias irradiation leads to the worst-case degradation in TID response. This is attributed to the additional contributions of radiation-induced holes generated in the SiO2 interfacial layer of the bilayer insulating structure that, under negative bias, transport into and become trapped in the HfO2. This leads to a more negative threshold voltage shift compared to 0 V irradiation. During positive bias irradiation, a similar number of radiation-induced electrons are generated in the SiO2. These can similarly transport into and become trapped in the HfO2, leading to a less negative threshold voltage shift than during 0 V irradiation. Interface- and oxide-trap charge buildup during negative bias-temperature stress of SiGe0.45 pMOSFETs is also investigated. The activation energies (Ea) of the effective interface-trap and oxide-trap charge densities in SiGe0.45 pMOSFETs with SiO2/HfO2 gate dielectric stacks are compared with those of Si FinFETs with SiO2 gate dielectrics. We find similar values of Ea for oxide-trap charge buildup for the two device types, and a reduced Ea for interface-trap buildup for the SiGe0.45 pMOSFETs with high-k gate stacks, compared to the Si FinFETs with SiO2 gate dielectrics.