The influence of Hf-based dielectrics on the underlying SiO2 interfacial layer (IL) in high-k gate stacks is investigated. An increase in the IL dielectric constant, which correlates to an increase of the positive fixed charge density in the IL, is found to depend on the starting, pre-high-k deposition thickness of the IL. Electron energy-loss spectroscopy and electron spin resonance spectra exhibit signatures of the high-k-induced oxygen deficiency in the IL consistent with the electrical data. It is concluded that high temperature processing generates oxygen vacancies in the IL responsible for the observed trend in transistor performance.

We apply a systematic approach to identify a highk/metal gate stack degradation mechanism. Our results demonstrate that the SiO 2 interfacial layer controls the overall degradation and breakdown of the high-k gate stacks stressed in inversion. Defects contributing to the gate stack degradation are associated with the high-k/metal-induced oxygen vacancies in the interfacial layer.

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Conventional electron spin resonance measurements indicate gross processing dependent differences in the densities of paramagnetic oxygen deficient silicon sites, E′ centers, in the interfacial layer of unstressed hafnium oxide based metal-oxide-silicon structures. (E′ centers are not usually observed in unstressed oxides.) The volume densities of these centers can be quite high (∼1×1019cm−3). Electrically detected magnetic resonance measurements suggest that related oxygen deficient sites may significantly degrade device performance and reliability.