Ba 0.5 Sr 0.5 TiO 3 ͑BST͒ thin films grown on Si by an in situ ultraviolet-assisted pulsed laser deposition ͑UVPLD͒ technique exhibited significantly higher dielectric constant and refractive index values and lower leakage current densities than films grown by conventional PLD under similar conditions. X-ray photoelectron spectroscopy ͑XPS͒ investigations have shown that the surface layer of the grown films contained, besides the usual BST perovskite phase, an additional phase with Ba atoms in a different chemical state. PLD grown films always exhibited larger amounts of this phase, which was homogeneously mixed with the BST phase up to several nm depth, while UVPLD grown films exhibited a much thinner ͑ϳ1 nm͒ and continuous layer. The relative fraction of this phase was not correlated with the amount of C atoms present on the surface. Fourier transform infrared spectroscopy did not find any BaCO 3 contamination layer, which was believed to be related to this new phase. X-ray diffraction measurement showed that although PLD grown films contained less oxygen atoms, the lattice parameter was closer to the bulk value than that of UVPLD grown films. After 4 keV Ar ion sputtering for 6 min, XPS analysis revealed a small suboxide Ba peak for the PLD grown films. This finding indicates that the average Ba-O bonds are weaker in these films, likely due to the presence of oxygen vacancies. It is suggested here that this new Ba phase corresponds to a relaxed BST surface layer.

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In this letter, we report on the low temperature (∼350°C) growth of Hf–Al–O dielectric films with improved thermal stability and electrical characteristics for gate dielectric applications. A higher capacitance and improved interfacial properties were observed in the films deposited with NH3 ambient followed by ultraviolet radiation assisted oxidation annealing. The films containing 10.6at.% Al were found to remain amorphous after a 900°C furnace anneal for 1min in flowing nitrogen. The flat-band voltage was stabilized by nitrogen incorporation with negligible shift. An equivalent oxide thickness of 19Å and a dielectric constant of 20.4 were obtained in the best samples processed in NH3 and ultraviolet radiation ambient.

Uniaxial-mechanical-stress altered gate leakage current and dielectric constant of silicon metal-oxide-semiconductor (MOS) devices with nitrided Hf-silicate (HfSiON) dielectric are measured as a function of uniaxial stress applied using four-point wafer bending along the [110] direction. The gate leakage current and dielectric constant are found to increase by ∼2% per 100MPa of tensile and compressive stresses. A decrease in hole trap activation energy in hafnium oxide-based dielectric is used to explain the mechanical stress altered gate leakage. It is proposed that the HfSiON dielectric constant increase results from band gap narrowing caused by strain induced N p band splitting.