Improved thermal stability of ruthenium oxide metal gate electrode on hafnium oxide gate dielectric

This study focused on the detailed understanding of the thermal stability of ruthenium oxide metal gate electrode for hafnium oxide gate dielectric. A sample with ruthenium oxide electrode shows reduction of capacitance and flatband voltage shift after high temperature annealing. The degradation of device parameter can be explained by the reduction of amorphous ruthenium oxide phase into ruthenium metallic phase and oxygen. With the introduction of an additional ruthenium metal layer between ruthenium oxide and hafnium oxide, the authors can minimize oxygen diffusion from ruthenium oxide electrode toward silicon/hafnium oxide interface which in turn improves the thermal stability of hafnium oxide devices.