Carlos Eduardo Driemeier

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.

Room temperature interactions of water vapor with HfO2 films on Si

HfO2∕SiO2∕Si(001) thin film structures were exposed at room temperature to water vapor isotopically enriched in H2 and O18 followed by quantification and profiling of these nuclides by nuclear reaction analysis. We showed (i) the formation of strongly bonded hydroxyls at the HfO2 surface; (ii) room temperature migration of oxygen and water-derived oxygenous species through the HfO2 films, indicating that HfO2 is a weak diffusion barrier for these oxidizing species; (iii) hydrogenous, water-derived species attachment to the SiO2 interlayer, resulting in detrimental hydrogenous defects therein. Consequences of these results to HfO2-based metal-oxide-semiconductor devices are discussed.

Oxygen species in HfO2 films: An in situ x-ray photoelectron spectroscopy study

The chemical bonding of O atoms in HfO2 films on Si was investigated by in situ x-ray photoelectron spectroscopy in the O 1s spectral region. In addition to trivial O forming only O-Hf bonds, O 1s signals corresponding to nontrivial secondary O (Osec) were also observed. By ruling out possible roles of impurities as well as by comparing O 1s signals for different thermochemical processing routes, Osec chemical origins were inferred. Moreover, angle-resolved photoelectron analysis was employed to quantitatively separate surface and bulk Osec contributions. Surface Osec was assigned to surface O-H groups generated either by room temperature water vapor exposure or by 600 °C H2 annealing. Bulk Osec was assigned to O-O or O-H bonds and, as indicated by thermodynamic calculations and complementary structural analysis, is located in HfO2 amorphous regions and grain boundaries. This bulk Osec can be partly removed by annealing in reducing atmospheres. For some of the processing routes employed here, we observed ...

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in H1- and H2-containing atmospheres was investigated. H1 profiling was accessed by means of nuclear resonant reaction profiling, whereas H2 incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of H1 and H2 from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated H1, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

Atomic Transport in LaAlO3 Films on Si Induced by Thermal Annealing

LaAlO 3 films sputter-deposited on Si were submitted to rapid thermal annealing at 800 and 1000°C. Atomic transport and chemical changes were investigated using ion beam analysis and X-ray photoelectron spectroscopy. Annealing induced La and Al losses or their migration into a newly formed interracial layer and Si migration into the film. The mechanism of Si incorporation into the film is influenced by the annealing atmosphere. These instabilities were hampered by a thermal nitridation in NH 3 at 700°C performed prior to rapid thermal annealing, indicating a possible route for producing a thermally stable La-based high-K gate dielectric.

Interaction of SiC thermal oxidation by-products with SiO2

We investigated oxygen incorporation and exchange during thermal growth of silicon oxide films on silicon carbide. This investigation was carried out in parallel with the thermal growth of silicon oxide films on silicon for comparison. We provide experimental evidence that oxidation by-products of silicon carbide out-diffuse and interact with the silicon oxide overlayer, incorporating C and O. This and other results are in sharp contrast to those obtained for silicon samples, constituting a key issue in the stability of any dielectric material used on silicon carbide.

Compositional stability of hafnium aluminates thin films deposited on Si by atomic layer deposition

We have used nuclear reaction analyses and Rutherford backscattering spectrometry to investigate quantitatively the compositional stability of hafnium aluminate thin films deposited on Si(001) by atomic layer deposition using HfCl4∕H2O and Al(CH3)3∕H2O precursors. It was found that increasing Al∕Hf deposition cycles ratio leads to increasing oxygen deficiency in the as-deposited films as well as to increasing metal losses (up to ∼15%) from the films after rapid thermal annealing at 1000 °C. Furthermore, isotopic substitution experiments, showed that incorporation of oxygen from the gas phase is eased in the cases where deposition conditions failed to supply enough oxygen to complete oxides stoichiometry.

Interaction of HfO2∕SiO2∕Si structures with deuterium gas

HfO2 films (2.5 to 12 nm) deposited on thermal SiO2 (1.5 nm) on Si were annealed in deuterium gas at 400–600 °C and incorporated D amounts were quantified using the D(He3,p)He4 nuclear reaction. We found ∼1013Dcm−2 in the SiO2 interlayer region and up to 2.2×1014Dcm−2 near the HfO2 surface, whereas D amounts in the bulk of the HfO2 films were determined to be below 1013cm−2. However, analyses employing the H1(N15,αγ)C12 nuclear resonant reaction showed much more spurious H present in the bulk of HfO2 films. Mechanisms of D incorporation and desorption as well as contribution of the present results to the understanding of HfO2-based devices are discussed.

Thermal stability of plasma-nitrided aluminum oxide films on Si

The effect of post-deposition rapid thermal annealing in vacuum and in dry O2 on the stability of remote plasma-assisted nitrided aluminum oxide films on silicon is investigated. The areal densities of Al, O, N, and Si were determined by nuclear reaction analysis and their concentration versus depth distributions by narrow nuclear reaction resonance profiling, with subnanometric depth resolution. Annealing in both vacuum and O2 atmospheres produced partial loss of N from the near-surface regions of the films and its transport into near-interface regions of the Si substrate. Oxygen from the gas phase was incorporated in the AlON films in exchange for O and N previously existing therein, as well as in the near-interface regions of the Si substrate, leading to oxynitridation of the substrate. Al and Si remained essentially immobile under rapid thermal processing, confirming that the presence of nitrogen improves the thermal stability characteristics of the AlON/Si structures in comparison with non-nitrided A...