Leonardo Miotti

Oxygen reaction-diffusion in metalorganic chemical vapor deposition HfO2 films annealed in O2

Composition, atomic transport, and chemical reaction were investigated following annealing in O2 of ultrathin HfO2 films deposited on Si substrates thermally nitrided in NO. The as-prepared thin film composition was established by Rutherford backscattering spectrometry, nuclear reaction analysis, and x-ray photoelectron spectroscopy as a HfO2 film on an intermediate layer containing silicon oxynitride, hafnium silicate, and possibly hafnium–silicon oxynitride. O penetration, incorporation in the bulk of the HfO2/SiOxNy structure, and oxidation of the substrate forming SiO2 were observed.

Nitrogen bonding, stability, and transport in AlON films on Si

The chemical environment of N in nitrided aluminum oxide films on Si(001) was investigated by angle-resolved x-ray photoelectron spectroscopy. Two different bonding configurations were identified, namely N–Al and N–O–Al, suggesting the formation of the AlN and AlO2N compounds. The near-surface region is N-rich and AlN compounds therein are more abundant than AlO2N, whereas in bulk regions the proportions of these two compounds are comparable. Rapid thermal annealing at 1000 °C for 10 s in vacuum or in low-pressure oxygen atmosphere led to the breakage of N–Al bonds in AlN, releasing N and Al. The mobile N is partly lost by desorption from the surface and partly fixed by reacting with the network to form AlO2N. The released Al atoms, which remain immobile, react with oxygen from the film or from the gas phase. Characterization of the films outermost surfaces by low-energy ion scattering revealed that the migration of Si atoms from the substrate across the films, reaching the surface and being oxidized ther...

Effects of post-deposition annealing in O2 on the electrical characteristics of LaAlO3 films on Si

LaAlO3 films were deposited on p-type Si(100) by sputtering from a LaAlO3 target. C×V characteristics were determined in nonannealed and O2-annealed capacitors having LaAlO3 films as dielectric and RuO2 as top electrode. Thermal annealing in O2 atmosphere reduced flat band voltage to acceptable values for advanced Si-based devices. O16–O18 isotopic substitution was characterized by Rutherford backscattering spectrometry and nuclear resonant reaction profiling. Chemical analysis of the films was accomplished by x-ray photoelectron spectroscopy. The electrical improvements observed after thermal annealing in O2 were attributed to the incorporation of oxygen from the gas phase, possibly healing oxygen vacancies in the films and providing mobile oxygen to the interface.

Integrity of hafnium silicate/silicon dioxide ultrathin films on Si

Rapid thermal annealing at 1000 °C of (HfO2)1−x(SiO2)x pseudobinary alloy films deposited on Si were performed in N2 or O2 atmospheres. The effects on the atomic transport, structure, and composition were investigated using isotopic substitution of oxygen, high-resolution transmission electron microscopy, nuclear reaction analyses, narrow nuclear reaction resonance profiling, and grazing angle x-ray reflection.

Stability of zirconium silicate films on Si under vacuum and O2 annealing

The effect of postdeposition annealing in vacuum and in dry O2 on the atomic transport and chemical stability of chemical vapor deposited ZrSixOy films on Si is investigated. Rutherford backscattering spectrometry, narrow nuclear resonance profiling, and low energy ion scattering spectroscopy were used to obtain depth distributions of Si, O, and Zr in the films. The chemical environment of these elements in near-surface and near-interface regions was identified by angle-resolved x-ray photoelectron spectroscopy. It is shown that although the interface region is rather stable, the surface region presents an accumulation of Si after thermal annealing.

Characterization of nanoparticles through medium-energy ion scattering

In this work we review the use of the medium-energy ion scattering (MEIS) technique to characterize nanostructures at the surface of a substrate. We discuss here how the determination of shape and size distribution of the nanoparticles is influenced by the energy loss at the backscattering collision, which leads to an asymmetrical energy-loss line shape. We show that the use of a Gaussian line shape may lead to important misinterpretations of a MEIS spectrum for nanoparticles smaller than 5 nm. The results are compared to measurements of gold nanoparticles adsorbed on a multilayered film of weak polyelectrolyte.

Effects of nitrogen incorporation on the interfacial layer between thermally grown dielectric films and SiC

C-containing interlayers formed between the SiC substrate and dielectric films thermally grown in O2, NO, and in O2 followed by annealing in NO were investigated. X-ray reflectometry and x-ray photoelectron spectroscopy were used to determine N and C incorporation in dielectric films and interlayers, as well to determine their mass densities and thicknesses. The thickest C-containing interlayer was observed for films thermally grown in O2, whereas the thinnest one was observed for films directly grown in NO, evidencing that the presence of N decreases the amount of carbonaceous compounds in the dielectric/SiC interface region.

Thermal stability and diffusion in gadolinium silicate gate dielectric films

Gadolinium silicate films on Si(100) annealed in oxygen and vacuum at temperatures up to 800 °C were analyzed by Rutherford backscattering and narrow resonance nuclear profiling. Oxygen diffused into the film eliminating oxygen vacancies, but Si diffusion, previously observed in Al and Y oxides and in La and Zr silicate films, was absent. Higher-temperature annealing in oxygen resulted in the formation of an interfacial layer observable in high-resolution electron micrographs. Gd0.23Si0.14O0.63 films crystallize at temperatures between 1000 and 1050 °C. These observations combined with recent electrical measurements show that gadolinium silicate films may be a good candidate for the replacement of SiO2 in deep submicron metal–oxide–semiconductor gates.

Annealing of ZrAl x O y Ultrathin Films on Si in a Vacuum or in O 2

ZrAl x O y films deposited on Si were submitted to thermal annealings in a vacuum or an oxygen atmosphere. Elemental compositions as functions of depth were established using ion beam techniques such as Rutherford backscattering spectrometry and narrow nuclear resonance profiling. In addition, chemical composition profiles were obtained by angle-resolved X-ray photoelectron spectroscopy. The as-deposited film is amorphous, has an abrupt interface with the Si substrate, and its chemical composition is a double oxide with approximate stoichiometry Zr 4 AlO 9 . Atomic transport and chemical reaction induced by thermal annealing were investigated by the above mentioned techniques and by low energy ion scattering spectroscopy. We have observed that Al, O, and Si migrate during annealing, whereas Zr is essentially immobile. Oxygen from the gas phase was heavily incorporated into the oxide films during annealing in O 2 , mostly in exchange for previously existing oxygen.

Environment of hafnium and silicon in Hf-based dielectric films: An atomistic study by x-ray absorption spectroscopy and x-ray diffraction

The atomic structure of HfSiO and HfSiON was investigated before and after thermal annealing using x-ray diffraction and x-ray absorption spectroscopy. In HfSiO, the Hf atoms are arranged in a monoclinic HfO2 structure with Hf as second nearest neighbors, while Si is in a SiO2 environment. Thermal annealing induces crystallization of HfSiO with subtle changes in Hf–Hf distances. In the case of HfSiON, a stable structure is observed around the Hf atoms, which remains unaffected after annealing. Nitrogen is present in the first coordination shell of the Hf atoms, with Si in a SiON environment.