In the literature, the Schottky emission equation is widely used to describe the conduction mechanism in perovskite-type titanate thin films. Though the equation provides a good fit to the leakage current data, the extracted values of the Richardson and dielectric constants are inconsistent with their experimental values. In this work, a modified Schottky equation is applied. This equation resolves the difficulties associated with the standard Schottky equation. Also, the electronic mobility in thin films of barium strontium titanate is reported.

Over the years, the development of epitaxial oxides on silicon has been a great technological challenge. Amorphous silicon oxide layer forms quickly at the interface when the Si surface is exposed to oxygen, making the intended oxide heteroepitaxy on Si substrate extremely difficult. Epitaxial oxides such as BaTiO3 (BTO) and SrTiO3 (STO) integrated with Si are highly desirable for future generation transistor gate dielectric and ferroelectric memory cell applications. In this article, we review the recent progress in the heteroepitaxy of oxide thin films on Si(001) substrate by using the molecular beam epitaxy technique at Motorola Labs. Structural, interfacial and electrical properties of the oxide thin films on Si have been characterized using in situ reflection high energy electron diffraction, x-ray diffraction, spectroscopic ellipsometry, atomic force microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, high-resolution transmission electron energy loss spectroscopy, capacitance–voltage and current–voltage measurement. We also present the transistor results and address the impact of the epitaxial oxide films on future generation metal-oxide-semiconductor field effect transistors.

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In this study, the authors investigated the addition of zirconium (Zr) into HfO2 to improve its dielectric properties. HfxZr1−xO2 films were deposited by atomic-layer deposition at 200–350°C and annealed in a nitrogen ambient environment at 1000°C. Extensive physical characterization of the impact of alloying Zr into HfO2 is studied using vacuum ultraviolet spectroscopy ellipsometry, attenuated total reflectance Fourier transform infrared spectroscopy, secondary-ion mass spectrometry, transmission electron microscopy, atomic force microscopy, x-ray diffraction, Rutherford backscattering spectrometry, and x-ray reflectometry. HfxZr1−xO2 transistors are fabricated to characterize the impact of Zr addition on electrical thickness, mobility, and reliability. Zr addition into HfO2 leads to changes in film microstructure and grain-size distribution. HfxZr1−xO2 films have smaller and more uniform grain size compared to HfO2 for all deposition temperatures explored here. As Zr content and deposition temperature are increased, stabilization of the tetragonal phase is observed. A monotonic decrease in band gap is observed as ZrO2 content is increased. The chlorine impurity in the films is strongly dependent on deposition temperature and independent of film composition. TEM images of transistors showed excellent thermal stability as revealed by a sharp HfxZr1−xO2∕Si interface and no Zr silicide formation. Significant improvement in device properties such as lower electrical thickness (higher permittivities), lower threshold voltage (Vt) shift after stress (improved reliability), and higher mobilities are observed with Zr addition into HfO2. All of these results show HfxZr1−xO2 to be a promising candidate for SiO2 replacement.