Role of oxygen vacancies in V/sub BF//V/sub t/ stability of pFET metals on HfO/sub 2/

Anomalous VFB Shift in High-k Gate Stacks - Is its Origin at the Top or Bottom Interface ? -

“…Furthermore, the dipole formation at the metal/high-k interface due to the group electronegativity difference at the interface was also proposed as a reasonable extension of the above-mentioned model for anomalous V FB (5). For poly-Si/high-k (6) and metal/high-k gate stacks (7), charged oxygen vacancy formation in HfO 2 was also proposed as the origin. results so far reported for anomalous V FB shift and discusses the models to consistently understand them.…”

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

“…This suggests that some oxygen can diffuse through the metal layer without being fixed therein, reaching the metal/dielectric interface and thus confirming the oxygen supply to this interface, which can be the cause of device threshold voltage shifts. 8 The above presented results indicate that, in contrast to platinum that is known to oxidize only above 500°C, 14 Re oxidation owing to oxygen transport and reactive incorporation from the gas phase takes place even at temperatures as low as 300°C. However, it is noteworthy that the formation of rhenium oxide in the gate contact is only of secondary concern.…”

“…21 Finally, one should not disregard the effect of a thermally grown interfacial SiO 2 , since devices annealed at 500°C showed a marked decrease of the overall effective capacitance. 8 Nevertheless, recall that any possible SiO 2 interfacial layer thermally grown at 500°C by the arrival of oxygen from the gas phase will be extremely thin, 17 most likely of the order of 0.5 nm ͑ϳ2 ϫ 10 15 oxygen/ cm 2 ͒ or less. In summary, we investigated the transport and incorporation of oxygen in ultrathin Re/ HfO 2 /Si͑100͒ structures during postdeposition annealing in oxygen-containing atmospheres at low partial pressures.…”

“…[1][2][3][4][5][6][7][8] Device downscaling based on standard materials, such as heavily doped polycrystalline Si ͑poly-Si͒ gate contacts and SiO 2 gate dielectric materials, is reaching its physical limit due to excessively high gate leakage current as well as threshold voltage shifts because of undesired boron diffusion through the gate dielectric. The use of alternative gate dielectric ͑high ͒ 1-4 and metal contact materials [5][6][7][8] is proposed to overcome these limitations.…”

Systematic study on work-function-shift in metal/Hf-based high-k gate stacks

“…The main concern about high-k gate transistors is the controllability of the work function ͑WF͒ utilizing various kinds of gate electrode materials. Fermi level pinning ͑FLP͒ in p-type poly-Si gate electrodes 2 and oxygen-pressure and temperature-dependent WF of p-metals, 3 have been reported by several groups. For these cases, the WF of the electrodes decreased, so the threshold voltage ͑V th ͒ of high-k transistors drastically increased in spite of the intrinsic high WF of the electrode materials.…”