Metal-organic Chemical Vapor Deposition Precursors Research Articles

Trimethylphosphite stabilized disilver(I) methanedisulfonates as MOCVD precursors

New disilver(I) methanedisulfonates complexes {CH 2(SO 3) 2Ag 2·[P(OMe) 3] n } ( n = 2, 2a; n = 4, 2b; n = 6, 2c) were prepared by reacting [CH 2(SO 3) 2Ag 2], which could be synthesized from methanedisulfonic acid and Ag 2CO 3 in water, with trimethylphosphite in dichloromethane. The molecular structure of 2a was determined using X-ray single crystal analysis. Complex 2a exhibits an infinite chain structure with eight-membered rings (AgOSOAgOSO) fully interconnected by the third sulfonic O atoms. Complex 2b was used to deposit silver films by metal organic chemical vapor deposition (MOCVD) for the first time. The silver film obtained was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersion X-ray analysis (EDX).

Organophosphine/phosphite stabilized disilver(i) methanedisulphonates: synthesis, solid state structures and their potential use as MOCVD precursors

New disilver(I) methanedisulphonate complexes [CH(2)(SO(3))(2)Ag(2)·L(n)] (L = PPh(3); n=2, 2a; n=3, 2b; n=4, 2c; n=5, 2d; n=6, 2e; L=P(OEt)(3); n=2, 2f; n=4, 2g; n=6, 2h) were prepared by the reaction of [CH(2)(SO(3))(2)Ag(2)], which could be synthesized from methanedisulphonic acid and Ag(2)CO(3) in water, with triphenylphosphine or triethylphosphite in dichloromethane under a nitrogen atmosphere. The solid state structures of three complexes 2c, 2d and 2f were determined by single X-ray structure analysis. Hot-wall metal organic chemical vapor deposition (MOCVD) experiments were carried out at 395 °C, 420 °C and 450 °C using 2g as precursor for the deposition of silver films, respectively. The silver film with high purity obtained at 420 °C is dense and homogeneous, which is composed of many well isolated, granular particulates spreading all over the substrate surface.

Heteroleptic Guanidinate‐ and Amidinate‐Based Complexes of Hafnium as New Precursors for MOCVD of HfO2

AbstractThe synthesis and characterization of four new heteroleptic complexes [Hf{η2‐(iPrN)2CNMe2}2Cl2] (1), [Hf{η2‐(iPrN)2CNMe2}2Me2] (2), [Hf{η2‐(iPrN)2CMe}2Cl2] (3), and [Hf{η2‐(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1–3 were further examined by single‐crystal X‐ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine‐free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300–700 °C. The as‐deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 °C, and the composition analysis determined by Rutherford back‐scattering (RBS) and X‐ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen.

New Tantalum Amido Complexes with Chelate Ligands as Metalorganic (MO) Precursors for Chemical Vapor Deposition (CVD) of Tantalum Nitride Thin Films

Four new tantalum amido precursors (η2-RN(CH2)nNR)Ta(NMe2)3 (where R = Me, n = 2, 1; R = Et, n = 2, 2; R = Me, n = 3, 3; R = Et, n = 3, 4) with chelate diamide ligands and one new tantalum amido precursor (η2-tBuNC(NMe2)NEt)Ta(NMe2)4) (5) with a chelate guanidinate ligand were prepared and characterized. Their thermal behavior, especially (NMe2)3Ta(η2-MeN(CH2)2NMe) (1), were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) experiments to demonstrate the enhancement of their thermal stability and preservation of the volatility as metalorganic chemical vapor deposition (MOCVD) precursors as compared to Ta(NMe2)5 (PDMAT). Introduction of the asymmetric chelate guanidine ligand in complex 5 gave improved volatility as compared with its known isomer [(η2-iPrNC(NMe2)NiPr)Ta(NMe2)4 (6). The crystal structures of 5 and 6 were measured to investigate the correlation between the volatility and intermolecular interactions. The MOCVD of tantalum nitride thin films was successfully achieved using 1. The films are based on field emission scanning electron microscopy (FESEM) and show good adhesion properties. Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) data suggest that the film deposited using 1 at 500 °C under ammonia has a composition of TaN1.22±0.14 with negligible carbon and oxygen levels. It also shows low resistivity of 1.4 × 103 μΩ cm on SiO2/Si and broad X-ray diffraction (XRD) peaks for the stoichiometric cubic refractory TaN, indicating the potential of 1 becoming an alternative MOCVD precursor for barrier applications.

Synthesis, Characterization, and Mass Transport Properties of a Self-Generating Single-Source Magnesium Precursor for MOCVD of MgF2Films

The diglyme [CH3O(CH2CH2O)2CH3] adduct of the magnesium bis-hexafluoroacetyl-acetonato [Mg(hfa)2·2H2O·2diglyme] has been synthesized in a single-step reaction. It has been characterized by elemental analyses, IR spectroscopy, and 1H and 13C NMR. Single-crystal X-ray diffraction studies provide evidence of a mononuclear hexa-coordinated complex with an octahedral structure for the Mg(hfa)2·2H2O moiety and diglyme coordinated in the outer sphere (triclinic system, space group= P1̅; a = 8.952(3) Å, b = 9.036(3) Å, c = 11.98(1) Å, α = 110.44(5)°, β = 108.64(4)°, γ = 97.06(3)°, Z = 1). The “thermal robustness” and mass transport properties of the adduct have been investigated by thermogravimetric analysis and chemical vapor deposition experiments. Thermal analysis data revealed high volatility and good thermal stability with a residue left lower than 1%. The Mg(hfa)2·2H2O·2diglyme has been successfully applied to the low-pressure metal-organic chemical vapor deposition (MOCVD) of MgF2 films. The good quality of the deposited films indicates that the adduct is a very attractive single-source precursor for deposition of MgF2 films.

Lanthanide amidinates and guanidinates: from laboratory curiosities to efficient homogeneous catalysts and precursors for rare-earth oxide thin films

For decades, the organometallic chemistry of the rare earth elements was largely dominated by the cyclopentadienyl ligand and its ring-substituted derivatives. A hot topic in current organolanthanide chemistry is the search for alternative ligand sets which are able to satisfy the coordination requirements of the large lanthanide cations. Among the most successful approaches in this field is the use of amidinate ligands of the general type [RC(NR')(2)](-) (R = H, alkyl, aryl; R' = alkyl, cycloalkyl, aryl, SiMe(3)) which can be regarded as steric cyclopentadienyl equivalents. Closely related are the guanidinate anions of the general type [R(2)NC(NR')(2)](-) (R = alkyl, SiMe(3); R' = alkyl, cycloalkyl, aryl, SiMe(3)). Two amidinate or guanidinate ligands can coordinate to a lanthanide ion to form a metallocene-like coordination environment which allows the isolation and characterization of stable though very reactive amide, alkyl, and hydride species. Mono- and trisubstituted lanthanide amidinate and guanidinate complexes are also readily available. Various rare earth amidinates and guanidinates have turned out to be very efficient homogeneous catalysts e.g. for ring-opening polymerization reactions. Moreover, certain alkyl-substituted lanthanide tris(amidinates) and tris(guanidinates) were found to be highly volatile and could thus be promising precursors for ALD (= Atomic Layer Deposition) and MOCVD (= Metal-Organic Chemical Vapor Deposition) processes in materials science and nanotechnology. This tutorial review covers the success story of lanthanide amidinates and guanidinates and their transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors.

Precursors for MOCVD and ALD of Rare Earth Oxides−Complexes of the Early Lanthanides with a Donor-Functionalized Alkoxide Ligand

Complexes of the early lanthanides with the donor-functionalized alkoxide ligand mmp (Hmmp = HOCMe(2)CH(2)OMe, 1-methoxy-2-methylpropan-2-ol) are excellent precursors for Metal Organic Chemical Vapor Deposition (MOCVD) and Atomic Layer Deposition (ALD) of lanthanide oxides; however, their coordination chemistry, which is the subject of this paper, is rather complex. Precursors for MOCVD and ALD of lanthanide oxides are prepared by the reaction of [Ln{N(SiMe(3))(2)}(3)] with 3 equiv of the alcohol Hmmp in toluene in the presence of 1 equiv of tetraglyme and are indefinitely stable in solution. Reaction of [Ln{N(SiMe(3))(2)}(3)] with 3 equiv of Hmmp in the absence of stabilizing Lewis bases gives complex condensed products with empirical formula [{Ln(mmp)(3-n)}(2)O(n)]. These condensed products show poor volatility and are unsatisfactory precursors for MOCVD or ALD of oxides. The cluster complex [La(3)(mu(3),kappa(2)-mmp)(2)(mu(2),kappa(2)-mmp)(3)(mmp)(4)] has been prepared by careful reaction of [La{N(SiMe(3))(2)}(3)] with 4 equiv of Hmmp and has been characterized by single-crystal X-ray diffraction. Salt metathesis reactions using M(mmp) (M = Li or Na) are unreliable routes to [Ln(mmp)(3)]. Crystals of the heterometallic cluster complex [NaLa(3)(mu(3)-OH)(mu(3),kappa(2)-mmp)(2)(mu(2),kappa(2)-mmp)(4)(mmp)(3)] were isolated from the reaction of [La(NO(3))(3)(tetraglyme)] with 3 equiv of Na(mmp), and crystals of [Li(kappa(2)-Hmmp)Pr(mu(2),eta(2)-mmp)(4))LiCl] were isolated from the reaction of PrCl(3) with 3 equiv of Li(mmp); both of these complexes have been characterized by single-crystal X-ray diffraction.

Synthesis and Characterization of Pr(DPM) 3 Served as Precursor for MOCVD

Praseodymium β-diketone chelate, Pr(DPM)3 [DPM = 2,2,6,6-tetramethyl-3,5-heptanedionato], was successfully synthesized from the inorganic salt praseodymium chloride and HDPM(2,2,6,6-tetramethyl-3,5-heptane-dione) in an ethanol/aqueous solution followed distillation at low pressure and recrystallization from toluene. The physical and thermal properties of the chelate, including volatility, stability, and thermal decomposition, were investigated by elemental analyses, 1H NMR spectroscopy, XRD, TG/DTG/DTA analysis, infrared spectroscopy, and mass spectroscopy. The chelate with high purity prepared by the authors of this study also shows sufficient volatility and stability in inert gases, which could be used as the precursor for metal-organic chemical vapor deposition (MOCVD).

LOW TEMPERATURE CRYSTALLIZATION OF Pb(Zr,Ti)O3 AND PbTiO3 MOCVD THIN FILM BY HYDROTHERMAL TREATMENT AT 240°C

ABSTRACT The Pb(Zr, Ti)O3 and PbTiO3 precursor films formed on Pt/TiOx/SiO2/Si substrate below 400°C by metal-organic chemical-vapor-deposition (MOCVD) method were treated hydrothermally in Ba(OH)2-Pb(OH)2 mixture alkaline solution at 240°C and successfully transformed into (Pb, Ba)(Zr,Ti)O3 and (Pb, Ba)TiO3 ferroelectric thin film. This low temperature preparation method is compatible with the ULSI process becouase thermal damage to the circuit is avoidable. XRD χ − 2θ reciprocal space mapping measurements, shows that orientation of the thin film treated hydrothermally is influenced much by crystallite states of MOCVD precursor film. When the PbTiO3 precursor film is pre-crystallized having small (001) peak in XRD, the (Pb, Ba)TiO3 thin film has clear (001) orientation after hydrothermal treatment. The (Pb, Ba)TiO3 thin film treated at 240°C for 3 h in 0.2 M Ba(OH)2 − 0.1 M Pb(OH)2 solution has a hysteresis loop with good shape, and the polarization at zero electric field of the treated thin film is 8 μC/cm2.

Magnesium hydrotris(1-pyrazolyl)borate as a promising single source MOCVD precursor of magnesium borate phases

The magnesium(II) hydrotris(1-pyrazolyl)borate, Mg[BH(pz) 3] 2, complex has been, for the first time, tested as a precursor for the metal organic chemical vapor deposition (MOCVD) of borate phase thin films. The thermal analyses of this source reveal high volatility and good thermal stability with a low residue left despite its relatively high melting point. In particular, the compound has been successfully applied to the MOCVD fabrication of Mg 2B 2O 5 films, and therefore it represents a suited and reliable single source precursor of borate phases. Mg[BH(pz) 3] 2 provides constant evaporation rates even for very long deposition times and, hence, highly homogeneous films of carefully controlled thickness.

Synthesis of New Donor-functionalized Alcohols as Organic Ligands for Metal Precursors of Metal Organic Chemical Vapor Deposition

Recently, the development and use of single precursors for metal organic chemical vapor deposition (MOCVD) has been extensively focused on application to electronic devices. However, systematic design and synthesis of organic ligands appropriate for preparation of metal complexes with relevant chemical and physical properties, such as stability, volatility, and resistance to air and moisture have not received much attention. Generalization to prepare organic ligands for MOCVD precursors is especially important because the large scale synthesis of the metal complexes exclusively depends on the potential usefulness of the ligands. It is desirable for metal complexes to be in monomeric forms because mononuclear complexes generally show high vapor pressures and low sublimation or boiling temperatures. To do so, the coordinated atom of ligands should be crowded in its own environment with some substituents by keeping the coordinated atoms from bonding to another metal through bridging configuration. Therefore, pendant groups should be introduced into organic ligands. Some research results have been reported on the synthesis and application of organic ligands containing pendant groups. Herrmann reported his pioneering works on the synthesis of donor-functionalized alcohols and their application as bidentate ligands for the preparation of metal complexes. A variety of donor-functionalized alcohols which contain two alkyls on the α–carbon of the hydroxyl group were prepared and used to give metal complexes such as M(mmp)4 (mmp = 1-methoxy-2-methyl-2-propanolate; M = Zr, Hf), M(mmp)3 (M = Cr, Bi), 9 M(dmamp)3 (dmamp = 1-dimethylamino-2-methyl-2-propanolate; M = Y, Lu), Cu(dmamp)2. 12 The ligands in the complexes have pendant groups capable of coordinating to metals as bidentate ligands. Some of trifunctional alcohols have been used for the preparation and homoleptic complexes of alkaline-earth elements as well as transition metals. For larger cations such as Ba and Sr, it is necessary to introduce a neutral ancillary ligand possessing a sufficient number of donor sites or to incorporate a donor-functionalized feature into the anionic ligand to satisfy the multiple coordination requirement. Chi reported the successful preparation of alkalineearth metal complexes using a multi-donor site monoalcohol. Herein we disclose the synthesis and characterization of novel alcohols, which have pendant groups to stabilize the metal compounds by coordinating to the metal center in the formation of metal complexes. New alkoxyalcohols were prepared by the nucleophilic addition ring opening reaction between alkoxide anions and a highly reactive alkene oxide (epoxide).

Real-time acoustic sensing and control of metalorganic chemical vapor deposition precursor concentrations delivered from solid phase sources

We have investigated the performance and potential benefit of acoustic sensing for real-time monitoring and closed loop control of binary gas mixture compositions delivered from low vapor pressure metalorganic sources. Two solid phase sources were investigated in the presence of H2 as a carrier gas: (1) trimethylindium (TMI) and (2) bis(cyclopentadienyl) magnesium (Cp2Mg), which have room temperature (25°C) vapor pressures of 2.5 and 0.04Torr, respectively. An acoustic sensor was implemented on the gas feed line to measure the concentration-dependent speed of sound in the gas mixture. This enabled sensitivity and control at precursor levels as low as 0.6ppm in H2. Closed loop process control was implemented to maintain TMI and Cp2Mg concentration target in the presence of intentionally introduced long term temperature drifts. Despite induced variations of the precursor vapor pressure up to 50%, the delivered composition was controlled to within ±0.15% for TMI (at 0.5mol% set point) and ±0.3% for Cp2Mg (at 0.01mol% set point). Short term variability could also be substantially reduced by the control scheme. This work demonstrates the feasibility of sensor-driven control systems for stable delivery of low vapor pressure, normally problematic precursor materials. In turn, this opens the door to utilization of a broader range of species which can be synthesized as chemical precursors.

Synthesis and characterization of Sm(DPM) 3 used as precursor for MOCVD

High pure Sm(DPM) 3 (DPM=2,2,6,6-tetramethyl-3,5-heptanedionato) powder was successfully synthesized from Sm(NO 3) 3 and HDPM in ethanol/aqueous solution followed by reduced pressure distillation and recrystallization from toluene. This metal β-diketonate complex used as precursor for metal-organic chemical vapor deposition (MOCVD) of Sm 2O 3 film has been characterized by elemental analyses, 1H-NMR spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA analysis), infrared spectroscopy and mass spectroscopic analysis. The thermal decomposition behavior of the complex is sensitive to the ambient gases and Sm(DPM) 3 is sufficiently stable after it being exposed to air for 30 days. The chemical bonds in the complex are decomposed in the sequence of C–O>SmO>C–C(CH 3) 3>C–C and C–H at elevated temperatures. At 400°C this complex thoroughly converts into Sm 2O 3 and Sm 2(CO 3) 3 in air. The decomposition mechanism may be somewhat different at different operation conditions.

Surface reaction of bis(tertbutylimido)bis(diethylamido)tungsten precursor on Si(100)–(2×1)

Thermal decomposition of a metal-organic chemical vapor deposition precursor, (t-BuN=)2W(–NEt2)2, (bis(tertbutylimido)bis(diethylamido)tungsten, on Si(100) has been studied by means of synchrotron radiation-based x-ray photoemission spectroscopy and temperature programmed desorption spectroscopy. The resultant thin films consist of tungsten metal, silicon carbides and silicon nitrides. Major desorption products originated from ligand decomposition include imine (C2H5N=CHCH3) that is derived from β-H elimination of diethylamido ligand, and isobutene (C4H8) that is generated from γ-H elimination of t-butylimido ligands. The transmetalation of the precursor leads to tungsten metal adsorption on Si(100); by contrast, tungsten nitrides, tungsten carbides and tungsten oxides are produced as the same precursor is decomposed on SiO2 surface.

Facile synthesis of a novel class of organometalloid-containing ligands, the sila-β-diketones: preparation and physical and structural characterization of the copper(II) complexes, Cu[R′C(O)CHC(O)SiR 3] 2

The substitution of a carbon atom by silicon provides an attractive, novel approach to modification of the thermal stability and volatility of metal-organic chemical vapor deposition precursors supported by β-diketonate ancillary ligands. The low temperature reaction of the lithium enolates of acetyltrialkylsilanes with acyl chlorides affords the sila-β-diketones, R′C(O)CH 2C(O)SiR 3 (R′=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, s-Bu, t-Bu; SiR 3=SiMe 3, SiEt 3, SiMe 2( t-Bu), SiMe 2( t-hexyl), Si( i-Pr) 3), in good yields. Multinuclear NMR studies suggest that the sila-β-diketones exist as the enolic tautomer with a vinylsilane isomeric structure. Homoleptic Cu(II) sila-β-diketonate complexes were prepared in a first pass study to evaluate how precursor performance is affected by modulation of the peripheral substituents in the ligands. Thermal analyses, (TGA, DSC) show that the silylated Cu(II) precursors (SiR 3=SiMe 3; R′= t-Bu or i-Bu) have greater volatility than the corresponding carbon analogues. Some of the new Cu(II) complexes exist as liquids or low melting solids, which are preferred states for industrial deposition processes. X-ray diffraction studies of selected copper complexes showed them to have typical, square planar geometry; calculations of molecular volumes suggest that packing in the solid-state is less efficient for the silicon-containing complexes than for the non-silylated analogues.

Zirconium silicate films obtained from novel MOCVD precursors

The potential of zirconium silicate films as an alternative gate dielectric to silicon oxide in future technology generations is demonstrated. Novel single-source precursors for metal organic chemical vapor deposition (MOCVD) of zirconium silicate films are presented. These precursors meet the demands for implementation in a MOCVD process in respect to purity, volatility, and deposition temperature. Zirconium silicate layers were deposited and metal insulator semiconductor capacitors were manufactured. Structural characterization of the films was performed by means of X-ray photoelectron spectroscopy, secondary neutral mass spectroscopy, transmission electron microscopy, and ellipsometry. It was found that the silicon content in the zirconium silicate films is less than stoichiometric and carbon free films can only be obtained at deposition temperatures above 550 °C. The permittivity of the films is about 10.5–15. Electrical characterization by capacitance as a functions of voltage and current as a function of voltage measurement techniques show very promising results: low leakage current (5 × 10 −9 A/cm 2 at −3 V), low level of bulk charge (5 to 6 × 10 11 cm −2), and small hysteresis (about 50 mV) were obtained. However, some instabilities, i.e negative charge trapping (up to 2 × 10 12 cm −2) during electrical stress, have also been encountered and further investigations should aim at reducing this charge trapping.

Synthesis and characterization of volatile, fluorine-free beta-ketoiminate lanthanide MOCVD precursors and their implementation in low-temperature growth of epitaxial CeO(2) buffer layers for superconducting electronics.

A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric Ce, Nd, Gd, and Er complexes are coordinatively saturated by a versatile, multidentate ether-functionalized beta-ketoiminato ligand series, the melting point and volatility characteristics of which can be tuned by altering the alkyl substituents on the keto, imino, and ether sites of the ligand. Direct comparison with conventional lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO(2) buffer layer films can be grown on (001) YSZ substrates by MOCVD at significantly lower temperatures (450-650 degrees C) than previously possible by using one of the newly developed cerium beta-ketoiminate precursors. Films deposited at 540 degrees C have good out-of-plane (Deltaomega = 0.85 degrees ) and in-plane (Deltaphi = 1.65 degrees ) alignment and smooth surfaces (rms roughness approximately 4.3 A). The film growth rate decreases and the films tend to be smoother as the deposition temperature is increased. High-quality yttrium barium copper oxide (YBCO) films grown on these CeO(2) buffer layers by pulsed organometallic molecular beam epitaxy exhibit very good electrical transport properties (T(c) = 86.5 K, J(c) = 1.08 x 10(6) A/cm(2) at 77.4 K).

Properties characterization of Ce(DPM) 4 served as precursor for MOCVD

High purity Ce(DPM) 4 (DPM=2,2,6,6-tetramethyl-3,5-heptanedionato) powder was successfully synthesized from Ce(NO) 3 and HDPM followed by reduced pressure distillation and recrystallization from toluene. This metal β-diketonate complex used as precursor for metal–organic chemical vapor deposition (MOCVD) of CeO 2 film has been characterized by elemental analyses, X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG–DTA) analysis, 1 H -NMR spectroscopy, and infrared spectroscopy. The structure of this complex is monocline and the sublimation temperature is 145°C. This product was sufficiently stable after it was exposed to air for 30 days, as only a few impurities such as Ce 2(CO 3) 3·8H 2O, Ce(OH) 3, and H 2O can be identified. Ce(DPM) 4 decomposes during evaporation, the chemical bonds dissociate in the sequence of CC(CH 3) 3>CH>CO and CC by heating. At 280°C this complex thoroughly decomposes to CeO 2.

Recycling of Metal-Organic Ru Precursor and the Influence of Organic Impurities on the Surface Morphology of Ruthenium Films

In order to investigate whether recycling of a metal-organic chemical vapor deposition (MOCVD) precursor, bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2), is possible, impurities of used Ru(EtCp)2 collected in a cold trap were analyzed. It became clear that several kinds of organic impurities containing ruthenium (Ru) are contained when analyzing used Ru(EtCp)2 by gas chromatography (GC) mass and liquid chromatography (LC) mass technology. The organic impurities were generated during the course of Ru film formation. When trapped Ru(EtCp)2 was reused as a MOCVD precursor, the surface of the Ru film was somewhat rough. We presumed that organic impurities included in the trapped Ru(EtCp)2 might affect the surface roughness of the Ru film. To remove the impurities, the trapped Ru(EtCp)2 was purified using a purification technology with a 70% recycle rate. The refined Ru(EtCp)2 was found to have a purity and a vapor pressure that were equivalent to those of fresh Ru(EtCp)2. The root-mean-square (rms) roughness value of the Ru film prepared using the refined Ru(EtCp)2 was similar to that of the fresh Ru(EtCp)2. In this paper, we propose that recycling of Ru(EtCp)2, as a MOCVD precursor, is possible.

Encapsulating bis(beta-ketoiminato) polyethers. Volatile, fluorine-free barium precursors for metal-organic chemical vapor deposition.

The synthesis, characterization, and incorporation in volatile metal-organic chemical vapor deposition (MOCVD) precursors of a new class of linked beta-ketoiminate-polyether-beta-ketoiminate ligands is presented. These ligands are designed to encapsulate alkaline-earth cations having low charges and large ionic radii. Barium complexes having the general formula Ba[(RCOCHC(R')N)2(R")] (R = tert-butyl or CF3; R' = tert-butyl, methyl, or CF3; R" = -(CH2CH2O)4CH2CH2- or -(CH2CH2O)5CH2CH2)-) were prepared and characterized by 1H and 13C NMR spectroscopy, elemental analysis, and mass spectrometry. Single-crystal X-ray diffraction analysis of 2,2,5,25,28,28-hexamethyl-9,12,15,18,21-pentaoxa-4,25-diene-6,24- diimino-3,27-pentacosadionatobarium(II) reveals a monomeric, nine-coordinate, tricapped trigonal prismatic coordination geometry. Single-crystal X-ray structural analysis of 1,1,1,24,24,24-hexafluoro-4,21-ditrifluoromethyl-8,11,14,17- tetraoxa-3,21-diene-5,20-diimino-2,23-tetracosadionatobarium(II).2DMSO reveals a monomeric, ten-coordinate, distorted tetracapped trigonal prismatic coordination geometry. Volatility data are presented for these barium complexes, demonstrating viability as MOCVD precursors. In addition, it is demonstrated that thin epitaxial films of BaTiO3 can be grown on (001) MgO by low-pressure MOCVD techniques using one of these barium complexes and Ti(dipivaloylmethanate)2(isopropoxide)2 as precursors.