Reaction Of Tetraethylorthosilicate Research Articles

Synthesis and Catalytic Properties of Silicate-Intercalated Layered Double Hydroxides Formed by Intragallery Hydrolysis of Tetraethylorthosilicate

AbstractLayered double hydroxides (LDH's) interlayered with silicate anions were prepared by reaction of tetraethylorthosilicate (TEOS) with synthetic meixnerite-like precursors of the type [Mg1−xAlx(OH)2][OH−]x·zH2O, where (1 − x)/x ≈ 2, 3, or 4. TEOS hydrolysis at ambient temperature occurred readily in the galleries of the hydroxide precursors with (1 − x)/x ≈ 3 or 4, but a temperature of ∼100°C was required to achieve silicate intercalation for the LDH composition with (1 − x)/x ≈ 2. On the basis of the observed gallery heights (∼7.0−∼7.2 Å) and 29Si MAS NMR spectra that indicated the presence of Q2, Q3, and Q4SiO4 sites, the intercalated silicate anions, which are formed by condensation reactions of silanol groups and partial neutralization of SiOH groups with gallery hydroxide ions, are assigned short chain structures. Also, some O3SiOH groups become grafted to the LDH layers by condensation with MOH groups on the gallery surfaces. The LDH-silicates exhibited comparable non-microporous N2 BET surface areas in the range 59–85 m2/g, but they differed substantially in acid/base reactivities, as judged by their relative activities for the catalytic dehydration/disproportionation of 2-methyl-3-butyn-2-ol (MBOH). Under reaction conditions where the LDH structure is retained (150°C), all the silicate intercalates showed mainly basic reactivities for the disproportionation of MBOH to acetone and acetylene. However, all the LDH silicates were less reactive than the corresponding LDH carbonates. Conversion of the LDH silicates to metal oxides at 450°C introduced acidic activity for MBOH dehydration, whereas the metal oxides formed by LDH carbonate decomposition were exclusivity basic under analogous conditions.

Mechanisms of Deposition of SiO2 from TEOS and Related Organosilicon Compounds and Ozone

We have studied the deposition of silicon dioxide by thermal chemical vapor deposition from tetraethylorthosilicate (TEOS) and ozone, using a unique linear gas injection configuration and operating pressures of 10 Torr to atmosphere (≈760 Torr). We have compared the experimental results with simulations incorporating finite‐difference estimation of fluid flow fields, temperature distribution, thermally initiated decomposition of ozone, and reaction of TEOS and ozone at the surface and in the gas phase. We have demonstrated that a parasitic gas‐phase reaction, which consumes TEOS without contributing to deposition on the substrate, is necessary to explain correctly results obtained at high pressures, and that at pressures of less than 200 Torr, this reaction simply contributes to the total deposited film. We propose a general scheme for surface reactions, which accounts for the discrepancies between the simple gas‐phase reaction model and the observed temperature dependence, and allows us to incorporate aspects of the behavior of other organosilane precursors; we suggest explanations for observed variations in film properties with deposition rate, conditions, and substrate surfaces.

Reaction of tetraethylorthosilicate and hexafluoroacetone trihydrate

Neat tetraethylorthosilicate reacts with neat hexafluoroacetone trihydrate to give particulate silica xerogel precipitates. Particulates formed early in the reaction have spheroidal micromorphology, and control of the reaction conditions affords particle sizes approaching 25 nm in diameter. A mixture of tetraethylorthosilicate and Ti(Oi-Pr) 4 reacts with hexafluoroacetone trihydrate as neat liquids at 5 °C to give immediate precipitation of a Si/Ti mixed-metal oxide xerogel particulate having a Si:Ti molar ratio of approximately 9:6.

The Anisotropic Deposition of Doped Silicate Glass

In this letter we present initial results for the anisotropic deposition of doped silicate glass. The deposition was performed in a previously described low pressure chemical vapor deposition reactor by the reaction of tetraethylorthosilicate, triethyl borate, phosphine, and oxygen. The depositions were performed over a nominal temperature range of 973 to 1023 K. Results presented here indicate that the glass deposits anisotropically over polysilicon structures on silicon substrates favoring high surface density corners to lower surface density flat areas of the silicon substrates.

Dielectric Planarization with Spin-On Glass Films: Characterization and Application

Spin-on glass (SOG) materials were prepared from the acid catalyzed hydrolysis-condensation reaction of tetraethylorthosilicate and methyltriethoxysilane in organic solvents. Siloxane products of d...

Application of computational fluid modeling to the development of semiconductor chemical vapor deposition systems

A computational fluid dynamics model was developed to simulate atmospheric pressure chemical vapor deposition of silicate glasses. The model is used to examine chamber geometry and substrate placement effects on fluid flow and temperature profiles. The reaction of tetraethyl orthosilicate (TEOS) and ozonated oxygen to form undoped silicate glass is modeled. Comparison between model predictions and experimental data suggests that ozone is essential for initiating the overall reaction at deposition temperatures between 300 and 550 °C. At deposition temperatures over 300 °C, no ozone is present at the wafer surface. A correlation is found between deposition rate and the time that TEOS is combined with ozone in the gas stream at temperatures below 200 °C.

The Effects of Silicon Source Gas on PECVD SiO2 Properties

ABSTRACTSilicon dioxide was plasma-deposited at 300C using either the reaction of silane and nitrous oxide or the reaction of tetraethylorthosilicate with oxygen. The structural and electronic properties of films produced by both reactions were studied as functions of post-deposition heat treatments. The former reaction produced films which were more dense and less conductive than the latter. A model was developed to determine the amount and location of charge in the deposited films. The charge was found to be dependent on the reaction and the post-deposition anneal.

Low Temperature Interlevel SiO2 Layers by Photoinduced Processing

ABSTRACTPolysiloxane layers were deposited from the gas phase by photoinduced polymerization reaction of tetraethylorthosilicate (TEOS) and 02/N20. The deposition kinetics can be described by a gas phase polymerization and the subsequent condensation of the siloxane molecules. As UV light sources an ArF excimer laser (193 nm) anda 185/253 nm low pressure Hg—discharge lamp were used, the polysiloxane deposition rates are 2000 Å/min or 1200 Å/min respectively. Ina second thermal or combined thermal/ photoinduced process step the as deposited siloxane layers are transformed by hydrolysis and condensation reactions to pure Si02. The composition of the as deposited and transformed polysiloxane layers were investigated by FTIR spectroscopy. Typical examples of the step coverage and planarizing properties of the SiO2 layers for the use as interlevel dielectrics are presented.

Low Pressure Deposition of Phosphosilicate Glass Films

Phosphosilicate glass films have been deposited on silicon substrates by the reaction of tetraethyl orthosilicate (TEOS), phosphine, and oxygen. The depositions are carried out at 630°–700°C in a low pressure CVD reactor. The dependence of the deposition rate, the phosphorus oxide concentration, the thickness uniformity across a wafer, and the depletion in the deposition rate across the deposition zone upon the deposition conditions have been investigated. The step coverage obtained in the reaction is conformal. The refractive index, the etch rate, and the film stress are reported.

Reaction of silica with tetraethyl orthosilicate

AbstractThe reaction of tetraethyl orthosilicate with fumed silica at various temperatures was investigated by means of infra‐red spectroscopy and gas chromatography. It was found that essentially no reaction occurred at 25° while at 100°, traces of reaction by‐products were detected after short reaction periods. When the reaction temperature was raised to 165°, the condensation reaction proceeded with both hydrated and predried silica glass. It was shown that silanol sites on the glass do take part in a reaction which results in the formation of new siloxane bonds. These sites can be rehydrated after thermal degradation of the treated surfaces in vacuum.