Oxygen transport and reaction mechanisms in rhenium gate contacts on hafnium oxide films on Si

Oxygen transport and incorporation were investigated following postdeposition annealing of metal-oxide-semiconductor structures having ultrathin rhenium films as metal electrode and HfO2 films as dielectric on Si(001). Isotopic tracing, nuclear reaction analysis, narrow resonant nuclear reaction profiling, and x-ray photoelectron spectroscopy were used to pursue this investigation. For annealing temperatures below 400 deg. C, oxygen from the gas phase incorporates mainly in near-surface regions of the overlying Re cap. Significant oxygen incorporation into the HfO2 films is observed only after annealing at 500 deg. C. The present results are discussed considering that supplying oxygen to the metal/dielectric interface can cause device threshold voltage shifts