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 °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 °C. The present results are discussed considering that supplying oxygen to the metal/dielectric interface can cause device threshold voltage shifts

Effect of oxide overlayer formation on the growth of gold catalyzed epitaxial silicon nanowires

A direct dependence between the inadvertent formation of SiO2 on gold films deposited on silicon 111 substrates, and the nucleation and yield of epitaxial, gold catalyzed, silicon nanowires grown on such substrates is reported. The unintended SiO2 layer formed due to the diffusion of silicon from the underlying substrate through the gold film is observed to be 0.5 nm with medium energy ion scattering after brief exposures of 10–15 min in air. Silicon nanowires grown at 500 °C on such samples show reduced nucleation and growth. A remarkable improvement in nanowire nucleation density and epitaxy is observed on removing the SiO2 overlayer prior nanowire growth

Reduction of hafnium oxide and hafnium silicate by rhenium and platinum

We report chemical interactions of Hf-based dielectrics with Re and Pt overlayers during annealing. Reduction of the Hf to a suboxide is observed by x-ray photoelectron spectroscopy, along with a decrease in total oxygen content measured by medium-energy ion scattering. For Re, this unanticipated reaction is highly dependent on the premetallization history of the sample. The presence of hydroxyl groups, observed by infrared absorption, is thought to be responsible. In addition, substantial electrostatic core-level shifts are observed, even in the absence of Hf reduction. The electrostatic shifts are symptomatic of altered threshold voltages for devices

Aluminum mobility and interfacial segregation in fully silicided gate contacts

The mobility of aluminum implanted as a dopant of fully silicided nickel for advanced metal gates has been investigated following rapid thermal annealing at temperatures ranging from 160 to 700 °C. Resonant nuclear reaction profiling using the 27Al p, 28Si reaction was used for aluminum quantification and depth profiling. The results indicate that there is no significant aluminum loss in the whole annealing temperature interval. Furthermore, aluminum is seen to segregate near the interface with silicon oxide during metal silicidation, forming a stable layer of aluminum oxide