Triisobutylaluminum Research Articles

(η5‐Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene

AbstractAn equimolar mixture of Cp*Ti(CH3)3 (2) and Ph3C+[B(C6F5)4]− (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 107 g PS (mol Ti)−1 (mol styrene)−1 h−1. Both activity and syndioselectivity can be increased using tri–isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl3/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.

Growth of aluminium films by low pressure chemical vapour deposition using tritertiarybutylaluminium

The new aluminium precursor, tritertiarybutylaluminium (TTBA), has been used successfully for the growth of high purity aluminium films by low pressure chemical vapour deposition (LPCVD). The aluminium films were grown over the temperature range 300–450°C on Si(111) substrates and had growth rates of up to 2 μm min -1. A comparison with aluminium films grown using triisobutylaluminium (TIBA) is made.

Chemical modification of neodymium high cis‐1,4 polybutadiene with styreneoxide

AbstractThe polymerization of 1,3‐butadiene (BD) was carried out in the presence of a catalyst composed of neodymium 2‐ethylhexanoate, triisobutyl aluminum, diisobutyl aluminum hydride (DIBAH), ethylaluminum sesquichloride and acetylacetone. The molecular weight of the BR could be controlled with DIBAH. The reactive polymer was then chemically modified with styreneoxide (STO). The STO content of BR increased with the decrease in the molecular weight of the BR. This polymer was modified by the STO at the chain terminal end. The physical properties of the vulcanizates with the modified BR were measured. The abrasion resistance and the tensile strength were found to be improved.

The growth of InAlP using trimethyl amine alane by chemical beam epitaxy

The growth of InAlP and related compounds such as InGaP lattice matched to GaAs has attracted a great deal of interest for optoelectronic devices emitting in the range from 638 to 700 nm and for electronic devices such as the heterojunction bipolar transistor. Although some gas source MBE work has been performed in this material system, very little CBE work has been done, largely attributable to the lack of a suitable aluminum source. This is the first report of trimethyl amine alane (TMAA) being used to grow InAlP. TMAA offers advantages of less carbon incorporation and less oxygen sensitivity compared to triethyl aluminum, tri-isobutyl aluminum, or trimethyl aluminum. Trimethyl amine alane has been used to grow AlGaAs HBTs and more recently to grow InAlAs/InGaAs HEMTs by CBE. One of the principal strengths of CBE is its ability to handle phosphorus based compounds efficiently, offering excellent interface control. InAlP films with carbon concentrations below 7×10 17 cm -3 lattice matched |δa a|<2×10 -3 with good surface morphology have been grown. Double crystal X-ray diffraction exhibits a single epi-peak with a full width at half max of 46 arc sec with multiple Pendellösung fringes. The epitaxial films are semi-insulating, completely depleted for thicknesses up to 1.6 μm. Oxygen levels measured by secondary ion mass spectroscopy are comparable to levels measured in InAlAs films (∼2.5×10 18 cm -3) lattice matched to InP. The likely source of this oxygen is the hydride precursor as has been shown for the growth of InAlAs. As the substrate temperature is raised, the films become increasingly indium-rich. Breaking the growth rate down into its constituent binaries indicates an enhanced TMI incorporation rate. The quality of the films as measured by X-ray full width at half max and the surface morphology is extremely sensitive to substrate temperature. A very narrow window exists for the growth of good quality material in the range from 535 to 545°C.

Mass spectrometric study of laser induced pyrolytic decomposition of TIBA and TMAA

The composition of the gaseous phases during pyrolytic laser-induced chemical vapor deposition (LCVD) of aluminium from triisobutylaluminium (TIBA) and trimethylamine alane (TMAA) (aluminium trihydride trimethylamine) was determined. The analysis was carried out by means of quadrupole mass spectrometer (QMS) in closed reaction cell. The developed arrangement for sampling allowed in situ analyses during the LCVD process. The decomposition of the aluminium precursors was induced by copper bromide vapor laser on the surface of (111) silicon monocrystalline wafer at different process parameters (partial pressure, laser power and scanning speed). The analyses showed usual gaseous products for the pyrolysis of TIBA and TMAA and additional species. The occurred pyrolysis products were probably due to different ways of decomposition of the precursors caused by pulsed laser irradiation. The results from this study combined with surface analysis of the deposit could help for better understanding of LCVD and for obtaining of high purity aluminium layers

Effect of Substrate Temperature on the Selectivity in Low Pressure Chemical Vapor Deposition of Aluminum

Selective deposition of aluminum was carried out by the low pressure chemical vapor deposition (LPCVD) method. Selectivity between silicon and silicon dioxide was investigated in a cold wall LPCVD system with tri‐isobutyl‐aluminum (TIBA) source. It has been found that the substrate temperature is the most important variable in determining the selectivity among other variables such as TIBA flow rate and TIBA pressure. Growth activation energy and nucleation activation energy for the aluminum deposition were determined from Arrhenius plot, and it could be concluded that the temperature dependence of the selectivity of aluminum between Si and came from the large difference (∼1 eV) in nucleation activation energies. It was suggested that topology improvement in chemically vapor deposited films could be made by pretreatment of the substrate which reduces the nucleation activation energy.

Asymmetric functionalization of conformationally distinctive Cs-symmetric cis-[n.3.1] bicyclic ketones. Definition of the absolute course of enantio- and diastereodifferentiation

The four C s -symmetric cis[n.3.1] bicyclic ketones where n=3,5,7, and 9 were acetalized with (R,R)-2,4-pentanediol, and the resulting derivatives were cleaved with triisobutylaluminum (TRIBAL). The first three examples, all of which have their polymethylene chain rigidly fixed in a diaxial orientation, undergo ring opening with very high diastereoselectivity. In the fourth case (n=9), the chain is sufficiently long to be attached in a diequatorial manner

Growth of Al films by gas-temperature-controlled chemical vapor deposition

Epitaxial single-crystal aluminum (Al) films were deposited on 4-in.-diam silicon (Si) substrates by gas-temperature-controlled chemical vapor deposition using tri-isobutyl aluminum (TIBA). The TIBA was preheated just prior to the deposition by a gas-temperature controller (GTC). The crystallographic orientation of Al films was determined by the gas flow rate and the degree of thermal decomposition of TIBA. The GTC was thought to work in such a manner as to efficiently generate a desirable intermediate of unknown composition. Four kinds of Al single-crystalline epitaxial films on Si substrates were obtained: Al(001)/Si(001), Al(001)/Si(111), Al(111)/Si(111), and Al(110)/Si(115). The common epitaxial relationship in these films was Al[11̄0]∥Si[11̄0] in the interfacial plane. Along this direction, four lattice spacings of Al matched three lattice spacings of Si at the interface.

MOMBE growth characteristics of antimonide compounds

This paper describes the MOMBE (metalorganic molecular beam epitaxy) growth characteristics of antimonide compounds using TMIn (trimethylindium), TEGa (triethylgallium) and TIBAl (triisobutylaluminium) as group III sources, and As 4, Sb 4, TEAs (triethylarsine) and TESb (triethylstibine) as group V sources. Large differences in the growth characteristics of GaAs and GaSb MOMBE are observed. These are explained, using a theoretical consideration of the growth mechanism, by the difference in the effective surface coverage of excess As and Sb atoms during the growth. The use of TEAs and TESb instead of As 4 and Sb 4 alters the growth rate variation of both GaAs and GaSb with substrate temperature ( T sub), which results from the interaction of alkyl Ga species with the alkyl radicals coming from the thermally cracked TEAs and TESb. The alkyl exchange reaction process is observed in the growth of AlGaSb using TIBAl and TEGa, where the incorporation rate of Al is suppressed by the coexistence of TEGa on the growth surface, in the low T sub region. This is caused by the formation of an ethyl-Al bond which is stronger than the isobutyl-Al bond. The composition and the growth rate variations of InGaSb with T sub are similar to those of InGaAs, which are closely related to the MOMBE growth process and are quite different from those of MBE (molecular beam epitaxy) and MOVPE (metalorganic vapor phase epitaxy) growth. In the MOMBE growth of InAsSb and GaAsSb using TEAs and TESb, the composition variation with T sub is weaker than that of MBE. This is a superior point of MOMBE growth for the composition control. The electrical and optical properties of MOMBE grown films as well as the quantum well structures are also described.

Temperature dependence of epitaxial growth of Al on Si(111) by chemical vapor deposition

Chemical vapor deposition of aluminum films using tri-isobutyl aluminum on Si(111) wafers has been studied from the viewpoint of structural and electrical properties of Al films as a function of substrate temperature (Ts). The epitaxial relation of Al on Si is found to be very sensitive to Ts, thus changing from Al(100)))Si(111) with Al[1$\overline 1$0]))Si[11$\overline 1$] to Al(111)))Si(111) with Al[1$\overline 1$0]))Si[1$\overline 1$0] around 410 °C in the course of increasing Ts. The epitaxial relation is mainly determined at the initial stage of the deposition, but in some cases the relation changes with increasing film thickness. Above 420 °C, single-crystalline Al(111) is grown on Si(111), which has resistivity as low as the bulk value, high reflectivity, and a very flat surface.

Thermal stability of alkyl groups on aluminum

The infrared spectrum of alkyl groups on Al(100) derived from the dissociative adsorption of tri-isobutylaluminum (TIBA) or 1-iodobutane are studied as a function of surface temperature. Once formed, these species maintain both their structure and orientation on the surface to temperatures in excess of 500 K. An upper bound for the activation energy to cleave the Al-C bond in adsorbed TIBA is estimated to be ≈ 13 kcal mol .

The Characteristics of LPCVD Aluminum Films: Nucleation and Selectivity

ABSTRACTGrowth kinetics of CVD Al films using TIBA(Tri-IsoButyl-Aluminum) as a source material were investigated. Nucleation activation energy of aluminum on the silicon substrate was determined to be 3.2 eV for the first time in this work. It turned out that selectivity between Si and SiO2 was very sensitive to the substrate temperature during deposition, which could be well explained from the nucleation activation energy derived in this work. It was found that the surface topology of aluminum films could be improved by reduction of nucleation activation energy through pre-treatment of the substrate.

MOMBE growth of AlGaSb

AlSb and AlGaSb single crystalline layers have been grown on GaSb substrates by metalorganic molecular beam epitaxy (MOMBE) using trimethylaluminium (TMAl), triisobutylaluminium (TIBAl), triethylgallium (TEGa) and solid antimony (Sb 4). Crystalline AlSb films have been obtained using TIBAl, while not when TMAl was used. This is related to the difference in the reaction processes. In the growth of AlGaSb using TIBAl and TEGa, a strong suppression of the growth rate of constituent binary AlSb is observed in the low substrate temperature region. This is caused by the co-existence of TEGa and the formation of ethyl-Al bonds where the ethyl radicals are supplied during the decomposition process of TEGa. GaSb/AlSb quantum well structures have been grown and their PL spectra have shown strong peaks.

High deposition rate laser direct writing of Al on Si

We report, for the first time, the direct write laser patterning of highly conductive Al from a liquid precursor, triisobutylaluminum (TIBA). Al wires were written on Si with a scanned Ar+ laser from liquid TIBA at speeds of up to several mm/s. Wires 3 μm wide by 1 μm high with a resistivity of 5.6 μΩ cm were routinely achievable.

Surface mechanisms in aluminum chemical vapor deposition

Triisobutylaluminum (TIBA) can be used to selectively grow patterned aluminum films in chemical vapor deposition. This is possible because film nucleation occurs much more rapidly on a metal or semiconductor surface than on an oxide surface. In this study we examine the adsorption and decomposition of TIBA on a silicon oxide surface. Two of the three isobutyl groups in the TIBA are removed easily upon adsorption on a silicon oxide surface, but the third isobutyl group will not decompose thermally. Ultraviolet laser irradiation has previously been shown to be effective at aiding film growth by decomposing adsorbed organometallics and creating adsorbed metal particles that act as nucleation sites for thermal growth. We show here that x rays are also effective at decomposing the isobutyl groups through some surface mediated process such as generation of hot electrons, but only when the surface is heated. Chemical changes in the surface are linked to this process.

Liquid source metalorganic chemical vapor deposition of aluminum from triethylamine alane

Low-pressure metalorganic chemical vapor deposition (MOCVD) of aluminum using triethylamine alane (TEAA) is reported. This liquid source combines the chemical advantages of adduct precursors such as solid trimethylamine alane (TMAA), with the processing and handling advantages of liquid precursors such as triisobutyl aluminum (TIBA). High-purity Al films were deposited on TiN and thin in situ evaporated Cu and Ti films, which serve as activators for nucleation of Al. The electrical resistivities of the Al films on TiN were close to the 3 μΩ cm of sputtered Al. In the case of depositions on Cu, the Cu diffuses readily into the Al and serves to improve the electromigration resistance of the latter. The Al deposition rates using TEAA are 2–4 times those using TIBA at 250 °C, although the TEAA process is not fully optimized at this point and further work is needed to improve the film morphologies.

Evidence for a Charge Transfer Mechanism in Laser Induced Chemical Vapor Deposition

Abstract Photodecomposition of triisobutylaluminum (TIBA) adsorbed on an aluminum surface by pulsed ultraviolet laser irradiation is studied by observing the photoproducts with time-of-flight mass spectroscopy. The fragmentation pattern at different laser wavelengths (193, 248, and 351nm) is very similar and the intensity of fragments at these three wavelengths is 1:0.6:0.05 even though in the gas phase, absorption drops off rapidly for wavelengths above 193nm. In addition, the translational energy of the fragments is considerably less than the photon energy. These findings support a mechanism whereby absorption of light by the surface creates hot electrons which induce desorption of the TIBA molecules, rupture isobutyl groups to create methyl radicals, and induce β-hydride elimination reactions that create isobutylene molecules which desorb from the surface.

MOMBE (metalorganic molecular beam epitaxy) growth of InGaAlAsSb system on GaSb

Abstract MOMBE (metalorganic molecular beam epitaxy) growth characteristics of materials in the InGaAlAsSb system on GaSb substrates are described. The studies on GaSb growth using TEGa (triethylgallium) and solid Sb sources show that the surface reconstructions and the excess Sb on the surface play important roles in the MOMBE growth process. This is explained by a model which includes group V chemistry. The use of TESb (triethylstibine) instead of solid Sb indicates that the alkyl species coming from thermally cracked TESb also play important roles. Crystalline AlSb films are obtained using TIBAl (triisobutylaluminium), while not when using TMAl (trimethylaluminium), which is related to the difference in the reaction process. In the growth of InAsSb using TMIn (trimethylindium), TEAs (triethylarsine) and TESb, mirror-like surfaces are obtained only in the narrow TEAs/TMIn flux ratio region close to the (2×4)-(4×2) surface reconstruction transition boundary in InAs growth, and it is found that the composition of InAsSb alloy films can be controlled precisely using TMIn, TEAs and TESb. The growth characteristics of InAs and InSb are also discussed. Finally, preliminary results on the electrical and optical properties of the layers are shown to be encouraging.

Fundamental Characteristics of Capillary-Type Cluster Ion Source and Its Application for Selective Deposition of Aluminum Film

Cluster ions of acetone and triisobutylaluminum (TIBA) are generated from an apex of a capillary tube with an innerdiameter of 5 µm and an outerdiameter of 20 µm, based on the atomization of a semiconductive liquid in high electrostatic field. The ion emission has an onset at a threshold voltage of around 2 kV, which is nearly equal to the value calculated from Taylor's argument. The averaged charge-to-mass ratio of these cluster ions is determined to be 4.0-4.7 Coulomb/kg from a time-of-flight method. Spatially selected chemical vapor deposition of aluminum films is realized by the cluster ions of TIBA.

Capillary-type cluster ion source and its application for selective deposition of aluminum film

Cluster ions of acetone and triisobutylaluminum (TIBA) are generated from an apex of a capillary tube with an inner diameter of 5 μm and outer diameter of 20 μm, based on the atomization of a semiconductive liquid in high electrostatic field. Ion emission has an onset at a threshold voltage of around 2 kV, which is nearly equal to the value calculated from Taylor’s argument. The averaged charge‐to‐mass ratio of these cluster ions is determined to be 4.0–4.7 Coulomb/kg from a time‐of‐flight method. Spatially selected chemical vapor deposition of aluminum films is realized by the cluster ions of TIBA.