Tratamentos térmicos em filmes dielétricos de HfSiO e HfSiON para a tecnologia do silício

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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 Al2O3 /Si

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

Disgerminoma bilateral e hiperplasia endometrial cística com piometra em cadela

Background:  :  : Ovarian tumors are considered rare both in dogs and cats. Germ cell neoplasms correspond to approximately 15% of the cases and can be classified into dysgerminomas, teratomas and teratocarcinomas. Reports of bilateral dysgerminoma in dogs and cats are rare. The aim of this work was to describe a case of bilateral dysgerminoma and cystic endometrial hyperplasia with pyometra in a bitch by presenting the clinical, surgical, pathological and immunohistochemical findings. Case: A 10-year-old female crossbred dog was presented with a history of vomiting, apathy and purulent vulvar discharge. Physical examination revealed hyperthermia and pain was observed on abdominal palpation. Ultrasound examination revealed cystic formation and increased echogenicity inside the uterus. The animal underwent ovariohysterectomy (OHE). Macroscopically, the ovaries were multinodular, spherical to ovoid in shape, measuring 6 cm in diameter, and with a dark red color; they exhibited a firm consistency and a hemorrhagic cut surface with cystic areas and foci of necrotic tissue. At microscopic evaluation of both ovaries, the neoplasm consisted of large and polyhedral cells with amphophilic cytoplasm which were arranged in cords separated by connective tissue. The cells exhibited an anaplastic appearance, with central nuclei, large amounts of granular chromatin and one or more evident nucleoli. Several mitotic figures, often incomplete and with consequent formation of multinucleated cells similar to giant cells, were observed. Immunohistochemical detection of cytokeratin and vimentin was performed for further examination. The ovarian tumor exhibited positive staining for cytokeratin and negative staining for vimentin. Discussion: Most ovarian tumors are asymptomatic and many times are considered incidental findings during spaying surgeries. On physical examination, affected animals may show palpable abdominal masses, ascites and systemic signs caused by hormonal disturbances. The macroscopic and microscopic findings seen in this case are in accordance with those found in the literature and confirm the diagnosis of bilateral dysgerminoma and cystic endometrial hyperplasia-pyometra. Dysgerminoma should be differentiated from other neoplasias as lymphosarcoma, solid adenocarcinoma, solid granulosa cell tumor, theca cell tumor and teratoma. Diagnosis is performed by histopathological analysis. Immunohistochemistry can be performed to identify the origin of tumoral cells in order to assist the differential diagnosis for other neoplasias. Even though the immunohistochemical result can be positive for cytokeratin, this is not considered usual for dysgerminomas. The positive result for cytokeratin is related to the anaplastic characteristic of the tumor. Most cases of dysgerminomas are described in older dogs and cats, yet it can develop in younger animals. Dysgerminoma is a tumor that is typically unilateral and is hardly ever found in both ovaries. The rarity with which this neoplasia is observed in bitches can be related to the premature age at which OHE is performed

Físico-química do hidrogênio em óxidos e silicatos de háfnio para aplicação como dielétrico de porta

Após quatro décadas de sucesso do SiO2 (e SiOxNy), as novas gerações de Transistores de Efeito de Campo Metal-Óxido-Semicondutor utilizarão dielétricos de porta de materiais alternativos, dentre os quais se destacam o óxido (HfO2) e os silicatos de háfnio (HfSixOy). Para implementar esses novos dielétricos, é crucial controlar seus defeitos, em particular aqueles relacionados a hidrogênio, que é um elemento químico onipresente e que influencia as características elétricas dos transistores. Nesse contexto, esta Tese investiga a físico-química do hidrogênio em filmes de HfO2 e HfSixOy (2,5–73 nm) depositados sobre silício. Tratamentos térmicos, substituição isotópica, Análise por Reação Nuclear e Espectroscopia de Fotoelétrons Induzidos por Raios-X são algumas das técnicas que foram utilizadas. Observouse que as superfícies dos filmes de HfO2 são particularmente reativas, incorporando H com tratamentos em H2 a 400–600 °C e formando hidroxilas de superfície por exposição a vapor de água à temperatura ambiente. Além disso, no volume dos filmes de HfO2 e HfSixOy foram detectados 1021–1022 H cm-3 (comparados a 1018–1019 H cm-3 no volume de SiO2 crescido sobre Si) cujas origens são os precursores metalorgânicos das deposições por vapor químico, H residual da deposição por sputtering ou absorção de vapor de água. Pelo menos parte desse H no volume do HfO2 e do HfSixOy foi atribuída a hidroxilas, que são parcialmente removidas com tratamento em H2 a 500–600 °C. No caso particular das interações com vapor de água, observou-se que espécies derivadas da água difundem através do HfO2 a temperatura ambiente. Absorção de água no volume dos filmes só foi observada para HfO2 com regiões amorfas ou para HfO2 cristalizado do qual O fora previamente removido. Além disso, em filmes de HfSixOy, foi estabelecida uma relação entre incorporação de H e pré-existência de deficiência de O. Essa relação também foi explorada por cálculos de primeiros princípios, os quais mostraram que vacâncias de O em HfSixOy capturam átomos de H exotermicamente, embasando a relação entre incorporação de H e deficiência de O que fora observada experimentalmente.After four successful decades employing SiO2 (and SiOxNy), new generations of Metal- Oxide-Semiconductor Field-Effect Transistors will employ gate dielectrics of alternative materials, among which hafnium oxide (HfO2) and hafnium silicates (HfSixOy) are prominent. In order to implement these novel gate dielectrics, it is crucial to control their defects, particularly those related to hydrogen, which is a ubiquitous chemical element and influences the transistors electrical characteristics. In this scenario, this Thesis investigates the physical chemistry of hydrogen in HfO2 and HfSixOy films (2.5–73 nm thick) deposited on silicon. Thermal treatments, isotopic substitution, Nuclear Reaction Analysis, and X-Ray Photoelectron Spectroscopy are a few techniques that were employed. It was observed that HfO2 film surfaces are particularly reactive, incorporating H by annealing in H2 at 400– 600 °C and forming surface hydroxyls by exposing to water vapor at room temperature. Moreover, 1021–1022 H cm-3 were detected in bulk regions of the HfO2 and HfSixOy films (compared with 1018–1019 H cm-3 in bulk regions of SiO2 grown on Si). The origins of this H are the metalorganic precursors from the chemical vapor depositions, residual H from the sputtering deposition, or water vapor absorption. At least part of this H in bulk regions of HfO2 and HfSixOy was assigned to hydroxyls, which are partially removed by annealing in H2 at 500–600 °C. Particularly in the case of water vapor interactions, it was observed that waterderived species diffuse through HfO2 at room temperature. Water absorption in bulk regions of the films was only observed for HfO2 with amorphous regions or for crystallized HfO2 from where O had been previously removed. In addition, in HfSixOy films a relation between H incorporation and pre-existent O deficiency was established. This relation was further explored by first-principles calculations, which showed that oxygen vacancies in HfSixOy exothermically trap H atoms, supporting the relation between H incorporation and O deficiency that had been experimentally observed

Thermochemical behavior of hydrogen in hafnium silicate films on Si

HfSiO films on Si were sequentially annealed in vacuum, oxygen, hydrogen, or deuterium atmospheres followed by quantification of H and D by nuclear reaction analysis. The observed H D incorporation and desorption behaviors are discussed in terms of two H bonding states in the films. Si–H bonds are easier to break thermally and formation of these bonds can be suppressed by annealing in O2 to fully oxidize Si atoms. O–H bonds are harder to break thermally. However, hydrogen atmospheres ease desorption of H in O–H species. The results indicate possible paths to achieve low H content in HfSiO gate dielectrics

Metal transport and loss in ultrathin hafnium aluminate films on silicon studied by low, medium, and high energy ion beam analyses

Metal transport and loss induced by thermal annealing in ultrathin HfAlxOy films deposited on Si by atomic layer deposition were investigated by ion beam analysis. It was observed that rapid thermal annealing at 1000 °C induces decomposition of the aluminate films leading to Hf and Al losses mainly into the gas phase. It was possible to avoid this undesired decomposition effect by performing a postdeposition nitridation in NH3 at 850 °C prior to the rapid thermal annealing step. The role of nitridation is discussed in terms of the profiles of incorporated N, before and after rapid thermal annealing, as determined by narrow resonant nuclear reaction profiling

Tratamentos térmicos em filmes dielétricos de HfSiO e HfSiON para a tecnologia do silício

35

Oxygen species in HfO/sub 2/ 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 additional, water-induced bulk Osec, which was attributed to dissociative water absorption in HfO2 amorphous regions and O-depleted grain boundaries

Changes in Nanoscale Porosity by Wet Pressing Pulps from Sugarcane Bagasse

Nanoscale porosity is critical for cellulose reactivity and can be detrimentally affected by wet pressing. The present study evaluated how wet pressing reduced the nanoscale porosity of a set of pulps produced from sugarcane bagasse. The pulps were produced using hydrothermal treatments, followed by either 160 °C alkaline (sodium hydroxide) or 190 °C organosolv (ethanol-water) pulping. Pulping times (20, 40, 60, 80, and 100 min) and applied pressures in the pressing step (21, 43, 64, 85, and 107 MPa) were varied, and the resulting samples had their nanoscale porosity characterized using calorimetric thermoporometry. The lowest applied pressure (21 MPa) collapsed a considerable fraction of the nanoscale porosities. Otherwise, when additional pressure (up to 107 MPa) was applied, a much lower reduction in porosity was observed. The findings indicate that nanoscale porosity of pulps can be separated into compressible and incompressible components