Addition of yttrium in HfO 2 thin films prepared on silicon by metal organic chemical vapor deposition is investigated in a wide compositional range ͑2.0-99.5 at. % ͒. The cubic structure of HfO 2 is stabilized for 6.5 at. %. The permittivity is maximum for yttrium content of 6.5-10 at. %; in this range, the effective permittivity, which results from the contribution of both the cubic phase and silicate phase, is of 22. These films exhibit low leakage current density ͑5 ϫ 10 −7 A/cm 2 at −1 V for a 6.4 nm film͒. The cubic phase is stable upon postdeposition high temperature annealing at 900°C under NH 3 .

This work focuses on the etching of different porous methylsilsesquioxane materials (spin on SiOCH, k=2.2) with different porosity (30%, 40% and 50%) in fluorocarbon-based plasmas (CF4∕Ar). The etching of these materials is performed on blanket wafers in a magnetically enhanced reactive ion etcher. The surface and bulk modification after partial etching are studied using different surface analysis techniques such as quasi-in-situ x-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), and attenuated total reflection spectroscopy (FTIR-ATR). Similar to nonporous SiOCH materials, a decrease in etch rate of porous SiOCH films is observed with either increasing Ar dilution or polymerizing gas addition (CH2F2), which can lead in this last case to an etch stop phenomenon. The etch rate increases with higher porosity in the SiOCH film, since less material per unit thickness needs to be removed as the porosity increases. The XPS results show that a fluorocarbon layer is formed at the surface of the porous material and complementary angle resolved XPS analyses reveal that fluorocarbon species diffuse through the pores into the material. After partial etching, FTIR and ATR analyses reveal a carbon depletion in the remaining film, which indicates that the porous material is altered during plasma exposure. The film degradation is more important as the porosity increases. The etch rate evolution and film degradation are discussed and interpreted in terms of etching mechanisms and plasma surface interaction.

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.