Hf Composition Research Articles

ToF-SIMS depth profiling of Hf and Al composition variations in ultrathin mixed HfO 2/Al 2O 3 oxides

Ultrathin (a few nm) mixed HfO 2/Al 2O 3 oxides deposited by ALCVD on Si substrates were analyzed with low energy (250 eV) Cs + and Xe + ions by ToF-SIMS in the dual beam mode. The analysis beam was 15 keV Ga +. Several layers were measured, with different metal ratios (Hf:Al) and different number of deposition cycles. We observed a significant enhancement of the Al (and AlO x clusters) signal at the surface along with a Hf (and HfO x clusters) depletion at the film surface. However, the thinnest films were found to contain much more Hf than the thickest ones. Several ion ratios were used (e.g. HfO +/AlO + or HfO 2 −/AlO 2 −) in order to quantify the Hf:Al concentration ratio in the films. We found that these ratios correlate well with each other, with the metal deposition ratio, and with XPS ratios, enabling us to reconstruct the Al and Hf composition variation in the film.

Low temperature UV/ozone oxidation formation of HfSiON gate dielectric

Physical and electrical properties of hafnium silicon oxynitride (HfSi x O y N z ) dielectric films prepared by UV ozone oxidation of hafnium silicon nitride (HfSiN) followed by annealing to 450 °C are reported. Interfacial layer growth was minimized through room temperature deposition and subsequent ultraviolet/ozone oxidation. The capacitance–voltage ( C– V) and current–voltage ( I– V) characteristics of the as-deposited and annealed HfSi x O y N z are presented. These 4 nm thick films have a dielectric constant of ∼8–9 with 12 at.% Hf composition, with a leakage current density of 3×10 −5 A/cm 2 at V fb+1 V. The films have a breakdown field strength >10 MV/cm.

Growth and characterization of hafnium silicate films prepared by UV/ozone oxidation

Physical and electrical properties of hafnium silicate (HfSixOy) dielectric films prepared by room-temperature UV/ozone (O3) oxidation of hafnium silicide (HfSi2) are reported. Angle-resolved x-ray photoelectron spectroscopy was used to determine chemical bonding at the film interface and within the bulk film. These films, with 12 at. % Hf composition, have a dielectric constant (κ) of ∼8–9 and exhibit a flat-band voltage shift of 60 mV. The leakage current density at VFB+1 V is 4.7×10−5 A/cm2 for a 4.7-nm-thick film (capacitance equivalent thickness=2.6 nm) and breakdown strength was >8 MV/cm.

The dependence of etch rate of photo-CVD silicon nitride films on NH 4F content in buffered HF

The influence was studied of the concentration of ammonium fluoride (NH 4F) on the etch rates of silicon nitride films deposited by the mercury-sensitized photochemical vapour deposition method. The composition of the buffered HF was varied between 0 and 40 weight percent (wt%) NH 4F with 2 to 12wt% hydrofluoric acid (HF). The etch rates as a function of buffered HF composition were measured for films deposited under various process parameters, viz. reactant gas ratio, substrate temperature and chamber pressure. The results of etch rates as a function of process parameters were correlated to variations in material density and silicon content (Si/N ratio) in the films.

Crystallization Exotherms of Zirconia‐Hafnia Mixtures

Differential scanning calorimetry was used to study the crystallization behavior of ZrO2‐HfO2 mixtures. The materials prepared by admixing Zr(NO3)4 and Hf(NO3)4 exhibited a peak at 40 wt% Hf composition in the exothermic‐heat‐versus‐mixed‐oxide composition curve. In contrast, the materials prepared by precipitation from a solution prepared from anhydrous HfCl4 and ZrC14 exhibited a gradual decrease in exothermic behavior with increasing Hf content. The temperature for the exotherm increased with increasing Hf content. The data indicate that the exotherm is due to the formation of a crystalline material and not due to a phase transformation.

Catalytic conversion of alcohols. Relation of hafnium-zirconium mixed oxide catalytic selectivity to surface composition measured by Raman spectroscopic methods

The Raman spectra obtained for a series of mixed Hf-Zr oxide catalysts, prepared by coprecipitation, indicate that the surface composition is similar to the bulk composition. Hf, impregnated on calcined zirconia, remains on the surface following calcination at 600/sup 0/C but migrates into the bulk if calcination is effected at 1000/sup 0/C. The catalytic selectivity abruptly changes from that of pure hafnia to that of pure zirconia at a composition corresponding to Hf:Zr = ca. 1:9 rather than that undergoing a gradual change that follows the surface composition. Surface Hf may produce a significant background in the Raman spectra that increases for higher Hf compositions; the extent of the background depends upon both calcination temperature and Hf composition.

Thin film dielectric capacitors formed by reactive sputtering : R. M. Goldstein and F. W. Leonhard, Proc. 1967 Electron. Compon. Conf., Washington DC, p. 312

Ultrathin (a few nm) mixed HfO2/Al2O3 oxides deposited by ALCVD on Si substrates were analyzed with low energy (250 eV) Cs+ and Xe+ ions by ToF-SIMS in the dual beam mode. The analysis beam was 15 keV Ga+. Several layers were measured, with different metal ratios (Hf:Al) and different number of deposition cycles. We observed a significant enhancement of the Al (and AlOx clusters) signal at the surface along with a Hf (and HfOx clusters) depletion at the film surface. However, the thinnest films were found to contain much more Hf than the thickest ones. Several ion ratios were used (e.g. HfO+/AlO+ or HfO2−/AlO2−) in order to quantify the Hf:Al concentration ratio in the films. We found that these ratios correlate well with each other, with the metal deposition ratio, and with XPS ratios, enabling us to reconstruct the Al and Hf composition variation in the film.