Degradation of silicon dioxide films is shown to occur primarily near interfaces with contacting metals or semiconductors. This deterioration is shown to be accountable through two mechanisms triggered by electron heating in the oxide conduction band. These mechanisms are trap creation and band-gap ionization by carriers with energies exceeding 2 and 9 eV with respect to the bottom of the oxide conduction band, respectively. The relationship of band-gap ionization to defect production and subsequent degradation is emphasized. The dependence of the generated sites on electric field, oxide thickness, temperature, voltage polarity, and processing for each mechanism is discussed. A procedure for separating and studying these two generation modes is also discussed. A unified model from simple kinetic relationships is developed and compared to the experimental results. Destructive breakdown of the oxide is shown to be correlated with ‘‘effective’’ interface softening due to the total defect generation caused by both mechanisms.

The high dielectric constant of insulators currently investigated as alternatives to SiO2 in metal–oxide–semiconductor structures is due to their large ionic polarizability. This is usually accompanied by the presence of soft optical phonons. We show that the long-range dipole field associated with the interface excitations resulting from these modes and from their coupling with surface plasmons, while small in the case of SiO2, for most high-κ materials causes a reduction of the effective electron mobility in the inversion layer of the Si substrate. We study the dispersion of the interfacial coupled phonon-plasmon modes, their electron-scattering strength, and their effect on the electron mobility for Si-gate structures employing films of SiO2, Al2O3, AlN, ZrO2, HfO2, and ZrSiO4 for “SiO2-equivalent” thicknesses ranging from 5 to 0.5 nm.

The thermal stability, microstructure, and electrical properties of xZrO2⋅(100−x)SiO2 (ZSO) and xHfO2⋅(100−x)SiO2 (HSO) (x=15%, 25%, 50%, and 75%) binary oxides were evaluated to help assess their suitability as a replacement for silicon dioxide gate dielectrics in complementary metal–oxide–semiconductor transistors. The films were prepared by chemical solution deposition using a solution prepared from a mixture of zirconium, hafnium, and silicon butoxyethoxides dissolved in butoxyethanol. The films were spun onto SiOxNy coated Si wafers and furnace annealed at temperatures from 500 to 1200 °C in oxygen for 30–60 min. The microstructure and electrical properties of ZSO and HSO films were examined as a function of the Zr/Si and Hf/Si ratio and annealing temperature. The films were characterized by x-ray diffraction, mid- and far-Fourier transform infrared (FTIR), Rutherford backscattering spectroscopy, and Auger electron spectroscopy. At ZrO2 or HfO2 concentrations ⩾50%, phase separation and crystallization of tetragonal ZrO2 or HfO2 were observed at 800 °C. At ZrO2 or HfO2 concentrations ⩽ 25%, phase separation and crystallization of tetragonal ZrO2 or HfO2 were observed at 1000 °C. As the annealing temperature increased, a progressive change in microstructure was observed in the FTIR spectra. Additionally, the FTIR spectra suggest that HfO2 is far more disruptive of the silica network than ZrO2 even at HfO2 concentrations ⩽25%. The dielectric constants of the 25%, 50%, and 75% ZSO films were measured and were observed to be less than the linear combination of ZrO2 and SiO2 dielectric constants. The dielectric constant was also observed to increase with increasing ZrO2 content. The dielectric constant was also observed to be annealing temperature dependent with larger dielectric constants observed in nonphase separated films. The Clausius–Mossoti equation and a simple capacitor model for a phase separated system were observed to fit the data with the prediction that to achieve a dielectric constant larger than 10 doping concentrations of ZrO2 would have to be greater than 70%.

Impact of metal gates on remote phonon scattering in titanium nitride/hafnium dioxide -channel metal-oxidesemiconductor field effect transistors-low temperature electron mobility study

A combination of two complementary depth profiling techniques with sub-nm depth resolution, nuclear resonance profiling and medium energy ion scattering, and cross-sectional high-resolution transmission electron microscopy were used to study compositional and microstructural aspects of ultrathin (sub-10 nm) Al2O3 films on silicon. All three techniques demonstrate uniform continuous films of stoichiometric Al2O3 with abrupt interfaces. These film properties lead to the ability of making metal-oxide semiconductor devices with Al2O3 gate dielectric with equivalent electrical thickness in the sub-2 nm range.

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Epitaxial growth of SrTiO₃ on silicon by molecular beam epitaxy has opened up the route to the integration of functional complex oxides on a silicon platform. Chief among them is ferroelectric functionality using perovskite oxides such as BaTiO₃. However, it has remained a challenge to achieve ferroelectricity in epitaxial BaTiO₃ films with a polarization pointing perpendicular to the silicon substrate without a conducting bottom electrode. Here, we demonstrate ferroelectricity in such stacks. Synchrotron X-ray diffraction and high-resolution scanning transmission electron microscopy reveal the presence of crystalline domains with the long axis of the tetragonal structure oriented perpendicular to the substrate. Using piezoforce microscopy, polar domains can be written and read and are reversibly switched with a phase change of 180°. Open, saturated hysteresis loops are recorded. Thus, ferroelectric switching of 8- to 40-nm-thick BaTiO₃ films in metal-ferroelectric-semiconductor structures is realized, and field-effect devices using this epitaxial oxide stack can be envisaged.

Leakage currents introduced in the low-field, direct-tunneling regime of thin oxides during high-field stress are related to defects produced by hot-electron transport in the oxide layer. From these studies, it is concluded that the "generation" of neutral electron traps in thin oxides is the dominant cause of this phenomenon. Other mechanisms due to anode hole injection or oxide nonuniformities are shown to be unrealistic for producing these currents. Exposure of thin oxides to atomic hydrogen from a remote plasma is shown to cause leakage currents similar to those observed after high-field stress, supporting the conclusion that these currents are related to hydrogen-induced defects.