bluuebunny/crossref_metadata_2025 huggingface dataset:
Amplification of Misorientation of Ge Films on Si (100) During Ion-Assisted Molecular Beam Epitaxy
Authors: Tsai Cho-Jen , Atwater Harry A.
Published: March 2011

We have observed significant increases in the misorientation of Ge films on Si (001) grown by ion-assisted molecular beam epitaxy. The misorientation between the Ge films and Si substrates was found to be a function of the ion-to-atom flux ratio and growth temperature. The parametric dependence of the misorientation on the growth conditions suggests that defects generated by low energy ion bombardment are responsible for the observed increase in misorientation. The amplification of misorientation produced by concurrent low energy ion bombardment during epitaxial growth was attributed to an increase in the fraction of misfit strain accommodated by threading dislocations.
Defect Generation and Suppression During the Impurity Induced Layer Disordering of Quantum Sized GaAs/GalnP Layers
Authors: Thornton R. L. , Bour D. P. , Treat D. , Ponce F. A. , Tramontana J. C. , Endicott F. J.
Published: March 2011

Impurity induced layer disordering (JILD) has been demonstrated as an extremely powerful technique for the fabrication of optoelectronic devices within the AlGaAs alloy system. The success of this technique in this material system is due in large part to the similarity of the lattice parameters between the two binary constituents in this system, AlAs and GaAs. There are many alloy systems in which it would be highly desirable to exploit the fabrication technique of JILD, but within which the binary alloy constituents are not so well matched in lattice parameter. Perhaps the most extensively explored of such systems are the AlGaInP alloy system lattice matched to a GaAs substrate and the InGaAsP alloy system lattice matched to an InP substrate.
Structural Characterization of GaP/GaAs/GaP Heterostructure by TEM
Authors: Aragón G. , Molina S. I. , García R.
Published: March 2011

The defect structure in a GaP/GaAs/GaP heterostructure deposited on a (001) GaAs substrate with a GaAs buffer layer has been characterized by cross sectional TEM. The buffer layer presents dislocations and (α-δ)-fringe contrast parallel to (001) interface plane. HREM study reveals uniformly distributed amorphous capsules in the first GaP/GaAs buffer layer interface. The dominant defects are microtwins which are propagated into the overall heterostructure. Microtwin density is different in the GaP and GaAs layers.The different stress signs may explain the density difference.
Nucleation and Heterointerface Structure of InAs Epilayers Grown on InP Substrates
Authors: Chandra Sekhar K. S. , Ballal A. K. , Salamanca-Riba L. , Partin D. L.
Published: March 2011

Heteroepitaxial growth of indium arsenide films on indium phosphide substrates is being actively pursued since the electronic properties of these films make them promising materials for optoelectronic and other high speed devices. The various structural aspects of the film that affect their electronic properties are structural defects like dislocations, film-substrate interface roughness and chemical inhomogeneities. In InAs films, electrons accumulate at the film-air interface, making surface morphology an important factor that decides the electronic properties. The InAs films used in this study were grown on InP substrates by metal organic vapor deposition, at different temperatures. A higher growth temperature not only resulted in poor surface morphology of the film, but also created a rough film-substrate interface. However, at all deposition temperatures, the film-substrate interfaces are sharp. At lower growth temperature, the interfaces were flat. Films grown at lower temperatures had good surface morphology and a flat and shaip heterointerface.
The Stress Driven Islands Formation in Epitaxial Films and Solid HE4 Films.
Authors: Grinfeld Michael A.
Published: March 2011

We discuss the static and quasi-static problems appearing in the theory of morphological instability of interfaces. The approach has allowed to predict the corrugations in He4 films and to explain the dislocation-free Stranski-Krastanow pattern of epitaxial growth of thin solid films with the critical film thickness H = σμ/τ2 (σ is a surface energy, μ- the shear modulus, and τ - the mismatch stress). In this paper we discuss possible morphological patterns of corrugations and their changes which appear in result of the stress driven “rearrangement” destabilization of originally flat interfaces.
A Comparison of Magnetic Properties of Thin Films of Fe/GaAs(100) and Ni/MICA
Authors: Andrien Bruce , Miller David
Published: March 2011

A comparison between the morphology and magnetic properties has been made with thin films of Fe grown on GaAs(lOO) and of Ni grown on natural mica in the 10Å to 1000Å thickness range, in ultra high vacuum. The films are characterized in-situ by Auger spectroscopy and by an in-situ UHV M/H hysteresis loop tracer. If the films are thermally annealed, above 550°C for less than a few seconds, the film morphology changes. The Fe films form surface assembled clusters which are epitaxial with the GaAs substrate with diameters of order of the original average film thickness, while the Ni films grow large grains. The Auger signals show that the Fe clustering exposes the GaAs substrate while the Ni films are continuous and cover the mica substrate. In-situ adsorption studies of CO on the Ni films were consistent with the continuous nature of the Ni films. Hysteresis M/H curves are taken as a function of thickness and plots of coercivity versus film thickness or average cluster size shows a maximum near 100Å for both the Ni and the Fe films. The maximum is believed to be due to a trade-off between super-paramagnetism and magnetostatic forces, but with the grains in the Ni film playing the role of the clusters in the Fe film.
Microstructural Rearrangement in PZT(52/48) Thin Film Prepared By Reactive Cosputtering on Pt on Si(100)
Authors: Choo Woong Kil , Kim Kwang Young , Kim Hyo Jin , Kim Sung Tae
Published: March 2011

The experimental conditions which render the exact stoichiometry of PZT(52/48) thin films deposited on Pt thin film on Si(100) by reactive cosputtering have been investigated. As-deposited PZT is amorphous containing α-PbO2microcrystallites. As annealing temperature increases, the amorphous PZT films crystallize into pyrochlore and perovskite with pseudo-cubic structure in sequence. The perovskite PZT annealed above 750 °C evolves into a phase of morphotropic phase boundary. In the perovskite PZT thin films, the leakage current increases with annealing time. Also, the dielectric constant increases with film thickness and annealing temperature, which is discussed in conjunction with PZT/Pt interfacial morphology.
Influence of Preferred Orientation in Indium Tin Oxide.
Authors: Taniguchi H. , Ushiro T. , Okamoto Y. , Akagi Y. , Koba M.
Published: March 2011

We investigated the electrical and optical properties, the chemical composition, the surface morphology and the crystallinity of sputtered Sn-doped In2O3 films deposited on different substrate positions. Both the electric conductivity and the optical transparency are related to the free carrier density and moreover the preferred crystal orientation. The former relation is attributed to the Burstein-Moss effect and the latter suggests the Sn doping mechanism.
Surface Diffusion of Sulfur on Nickel (110) and the Effect of Carbon on the Diffusivity
Authors: Ladna Barbara , Birnbaum Howard K.
Published: March 2011

The surface diffusion coefficient of sulfur on the (110) surface of nickel was determined at temperatures of 623, 673 and 723 K by measurement of surface diffusion profiles using an Auger Electron Spectrometer. A half-plane monolayer of segregated sulfur was used as a source and the analysis was done by a Boltzmann-Matano method. The activation energy for surface diffusion of sulfur was determined to be about 106 kJ/mol and pre-exponential Do to be about 6×10-3 m2/s from the Arrhenius plot of D versus 1/T. The presence of carbon on the surface of nickel was shown to decrease the surface diffusion of sulfur. Also, the mechanism of spreading from the half-plane source changed from a classic surface diffusion on clean surfaces to a linear mobility of the sulfur-carbon interface on surfaces covered with carbon.
Initial Growth of Metastable Titanium Disilicide at Amorphous Silicide/Crystalline Silicon Interface
Authors: Ma Z. , Allen L. H. , Lee S.
Published: March 2011

Initial stage of growth of metastable titanium disilicide (C49-TiSi2) was investigated by annealing Ti/doped polycrystalline Si bilayers deposited on oxidized Si wafers at 530°C and at a constant heating rate of 10°C/min. Morphological evolution of the C49-TiSi2 phase was studied by cross-sectional transmission electron microscopy (XTEM) and local chemistry was probed with a scanning transmission electron microscope (STEM) equipped with a nanoprobe. At the early stage, the C49-TiSi2 phase nucleates discontinuously along the amorphous silicide (a-TiSix )/crystalline Si (c-Si) interface and then exhibits simultaneous lateral growth and vertical growth. The results are interpretated using a model based upon preferential Si diffusion along interphase boundaries to the growth front.
Solid Phase Heteroepitaxy of Barium Ferrite on Sapphire
Authors: Parker Michael A. , Hylton T. L. , Coffey K. R. , Howard J. K.
Published: March 2011

A new process for the crystallization of amorphous films on chemically dissimilar substrates, solid phase heteroepitaxy (SPHE), is described. Unlike SPE in Si, it is found that the kinetics can be modeled by nucleation and multi-dimensional growth with Johnson-Mehl kinetics modified for the effects of a finite film thickness and nucleation initiated at the interface with the substrate.
Structure and Morphology of PD Overlayers on Epitaxial SNO2 Films Studied with the Atomic Force Microscope
Authors: Lad R. J. , Matthews M. J. , Antonik M. D. , Cavicchi R. E. , Semancik S.
Published: March 2011

The structure and morphology of clean and Pd-doped epitaxial SnO2 films were studied with the atomic force microscope (AFM). The SnO2 films were grown by reactive sputter deposition on three different substrates yielding epitaxial orientations: (101) SnO2 / r-cut sapphire, (100) SnO2 / basal sapphire, and (110) SnO2 / TiO2 (110). AFM imaging of monolayer amounts of Pd deposited onto the epitaxial SnO2 films shows that the Pd is dispersed at 300 K and forms clusters after annealing to 500 K in vacuum.
Effect of Si Addition on the Reaction Growth and Morphology of an Aluminide Compound in Al-Cu-Si/Ti-W Bilayers
Authors: Park M. , Krause S. J. , Wilson S. R.
Published: March 2011

The effect of the addition of Si to an Al alloy on the reaction morphology of Al12W in Al-Cu-Si/Ti-W bilayers was studied with plan-view and cross-section transmission electron microscopy (TEM). The addition of 0.5 wt.% Si to an Al-0.5Cu alloy film increases multiple spiked growths of the Al12W compound by the reaction of the Al-0.5Cu-0.5Si film with the Ti-W sublayer after heat treatment at 450°C for 30 min. Increasing the Cu and Si content from 0.5 to 1.5% significantly reduced the spiked growth of Al12W into the Al-1.5Cu-1.5Si film. However the spike number density remained high compared to the reaction of a binary Al-1.5Cu film with the Ti-W layers. The result indicates that the addition of Si to form a ternary Al-Cu-Si film results in a more irregular, less planar Al12W morphology. This morphology can have a detrimental effect on thermal stability and electromigration resistance.
Effects of Substrate Pretreatments on Growth of Polycrystalline Diamond Thin Films on Si(100) Substrates
Authors: Lai C. , Wachtman J. B. , Sigel G. H. , Lu P. , Cosandey F. C. , Rudd G. , Oliver J. L. , Garofalini S. H.
Published: March 2011

Microstructures of polycrystalline diamond thin films deposited on silicon (100) substrates which were pretreated by (a) wet polishing, (b) dry polishing, (c) sonication and (d) acid etching, respectively, have been studied by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HREM). The thin films were deposited by using a Hot Filament Assisted Chemical Vapor Deposition (HFCVD) technique, with a methane to hydrogen ratio of 0.5%. Atomic Force Microscopy (AFM) was used to characterize substrate surfaces after the different pretreatments. The wet and dry polishing produced substrates with scratch type of defects while the sonication and acid etching caused pit type of defects. Planar and cross-sectional SEM studies indicated that diamond films on the wet and dry polished surfaces were continuous and had a high density of nucleation sites while the films on the sonicated and acid etched surfaces were discontinuous in nature under the same deposition time (8 hours) and condition. Cross-sectional HREM studies did not reveal any intermediate layers such as SiC and amorphous carbon between the thin films and substrates. Tungsten carbide nano-sized crystals, however, were observed to be dispersed at the interface region. These particles were believed to be formed during carburizing a fresh tungsten filament and deposited on the substrate during initial stage of growth.
Morphology of Diamond Films Produced by ECR-PACVD
Authors: Jin S. , Moustakas T. D.
Published: March 2011

Diamond films were produced at a relatively low pressures (<1 Torr) by the ECR-PACVD method of gas mixtures containing CO (5%), H2 (95%) and traces of oxygen at substrate temperatures from ambient (no intentional heating) to 1050°C. Faceted surface morphologies were observed even at the lowest temperature of growth. The microstructure is dominated by octahedral crystals below 600°C, by cubic crystals at 800–900°C, and by multiply twined (111) crystals at temperatures higher than 950°C. The weak temperature dependence of the growth rate is consistent with hydrogen abstraction from the growing surface being the rate controlling step.
Surface Reconstruction and Strain Relief in Si1−x-Gex Films on Si(100)
Authors: Yu Qiuming , Clancy Paulette
Published: March 2011

The equilibrium structure of a variety of Si1−xGex/Si heterostructures have been simulated by Molecular Dynamics, modeled by the Stillinger-Weber potential, to investigate the effect of strain on the surfaces of SiGe thin Alms. It was found that the strain in SiGe/Si(100) thin films was relaxed by the segregation of Ge to the surface. Rebonding of sub-surface atoms into dimers in the presence of a vacancy or cluster of vacancies above them was observed in the ensuing surface reconstruction. For SiGe/Si, the amount of “re-bonded missing dimers” in the top two layers increased with increasing Ge composition. But for Ge/Si(100), a V-shaped twinning defect was observed in the Ge thin film. To further investigate the effect of strain on surface reconstruction, bulk Si and Ge structures were also studied. For bulk Si, several rebonded missing dimers were found at the surface, while for bulk Ge(100), the surface showed a typical 2×1 reconstruction. All these findings corroborate recent experimental studies and theoretical predictions.
The Use of Novel Organometallic Sources in Metal Organic Chemical Vapor Deposition (MOCVD)
Authors: Biefeld R. M.
Published: March 2011

In metal organic chemical vapor deposition (MOCVD), the most commonly used sources are the trimethyls of Al, Ga, In, and Sb, and PH3 and ASH3. New organometallic sources are being developed as the understanding of the deposition process improvesand allows for the determination of the effects of source type and growth condition on the properties of the grown films. These new sources are safer and allow for the growth of higher purity materials using more favorable growth conditions. InSb and AlSb prepared using these trimethyl-sources are not of high enough quality to be used in many current device applications. Alternate organometallic Sb sources are being investigated to improve the materials characteristics of InSb grown by MOCVD.InSb grown using trimethylindium (TMIn) and trimethylantimony (TMSb) or triethylantimony (TESb) yielded similar quality materials under similar growth conditions. InSb grown using triethylindium (TEIn) and TESb under similar growth conditions yielded very poor quality n-type material. Three new organometallic Sb sources, triisopropylantimony (TIPSb), tris(dimethylamino)antimony (TDMASb), and tertiarybutyldimethylantimony (TBDMSb) are being investigated. The growth of InSb using TIPSb, TDMASb, or TBDMSb and TMIn was investigated over a temperature range of 350 to 475 °C. InSb grown from TDMASb had similar properties to InSb grown from TMIn and TMSbwhen using a similar temperature and V/III ratio range. The growth rates of InSb using TMIn and either TIPSb or TBDMSb at temperatures <= 425 °C were proportional to both the TMIn flow rate and the temperature. The surface morphology of InSb grown using eitherTIPSb or TBDMSb was very rough for growth temperatures <=425 °C. This may be due to the complex decomposition mechanisms involved and the presence of methyl groups on the surface. The InSb with the highest mobility was grown at 400 °C and a V/III ratioof 3 using TIPSb. It was n-type with a carrier concentration of 2.5 × 1015 cm−3 and a mobility of 78,160 cm2/Vs at 77 K. Both n- and p-type InSb were grown using TBDMSb with mobilities up to 67,530 and 7773 cm2/Vs, respectively at 77 K. The mobility for InSb using either TIPSb or TBDMSb was optimized by going to lower temperatures, pressures and V/III ratios. The opposite was truefor surface morphology which improved with higher temperature, pressure, and V/III ratio. The growth of high mobility InSb with smooth surfaces at T<=425 °C was not achieved with TIPSb or TBDMSb and TMIn under the conditions investigated in this work.
Crystal Surface Stoichiometry and the Fermi Level Effects on Outdiffusion of Si in GaAs
Authors: You Horng-Ming , GöSele Ulrich M. , Tan Teh Yu
Published: March 2011

GaAs samples doped with Si to a concentration of ∼2.7×10 18cm−3 were annealed at temperatures between 800 and 1000°C for 3 to 20 hours under As-rich and As-poor conditions for Si outdiffusion which were then measured using the capacitance-voltage method employing an electrochemical profiler. The deduced Si diffusivity showed strong dependencies on the As4 vapor phase pressure, PAs4 and on the electron concentration, n. When reduced to that under intrinsic conditions, activation enthalpies of 3.91 eV and 4.19 eV were obtained for As-rich and As-poor annealing cases, respectively. From these results, it is concluded that Si outdiffusion in GaAs is governed by the triply-negatively-charged Ga vacancies, .
Laser Assisted CVD of Aluminum from a Novel Liquid Alane Precursor
Authors: Han Jaesung , Senzaki Yoshihide , Gladfelter Wayne L. , Jensen Klavs F.
Published: March 2011

We describe pyrolytic laser assisted chemical vapor deposition of Al from dimethylethylamine-alane with 514 nm radiation from an Ar+ laser. Results from deposition on different substrates, including Pt, Au, W, and Si, provide insight into to thermal and nucleation effects in the laser writing process. High purity Al lines with resistivity close to bulk Al are reported for a range of operating conditions. The relationship between operating parameters and the resulting properties of the deposited lines is investigated. We also demonstrate a two-step fast writing process based on fast laser nucleation of lines followed by selective chemical vapor deposition of Al on the nucleated pattern.
The Reduction of CuII Compounds by Excimer Laser Irradiation for Copper Metal Deposition
Authors: Suys M. , Moffat B. , Bernier M.-H. , Izquierdo R. , Poulin S. , Meunier M. , Sacher E.
Published: March 2011

The short (UV) wavelength and the large beam cross-section of excimer lasers are expected to permit high resolution projection patterning and, for this reason, excimer laser deposition of Cu from organometallic precursors appears to be an interesting alternative for metallization in ULSI circuits. Unfortunately, the photolytic decomposition of those precursors leads to strong carbon contamination of the deposits. However, the valence state of the Cu in such deposits is unknown. In this paper, the reduction of two Cu (II) compounds, Cu(hmac)2 and Cu(hfac)2, under excimer laser irradiation in a hydrogen ambient is discussed. It is shown, with X-ray Photoelectron Spectroscopy, that, under our experimental conditions, Cu(hmac)2 is reduced to a Cu (I) compound while some of the Cu(hfac)2 appears to be reduced to the metallic state. Furthermore, reaction of the SiO2 substrate with the carbon from the Cu(hmac)2 precursor is observed.
Laser-Assisted Low Temperature Deposition of WSix from WF6 and SiH4
Authors: Izquierdo R. , Desjardins P. , Elyaagoubi N. , Meunier M.
Published: March 2011

A laser direct writing system has been developed for low temperature deposition of WSix on TiN from a gas mixture of WF6 and SiH4-. An Ar+ laser (488 nm, 1.5 W) and a diode laser (796 nm, 1.0 W) are used as photon sources. Lines are written at scan speeds of up to 100 μ/s from a flowing gas mixture of WF6 and SiH4 diluted in Ar. Lines 1.5 to 11 nm wide and 20 to 180 nmthick are obtained at a writing speed of 100 μ/s with the Ar+ laser. Lines written using the diode laser are typically 4 to 12 μm wide and 160 to 860 nm thick. W/Si ratio in the deposits, as measured by Auger electron spectroscopy (AES), isbetween 1.5 and 1.8.

Surface analysis of the interaction of this gas mixture with the TiN surface without laser irradiation shows that W, Si and F are adsorbed on the surface when exposed simultaneously to WF6 and SiH4 producing an adsorbed layer where W/Si ratio is 1.3 and F/W ratio 1.7.
Chemical Vapor Deposition of Copper Alloys
Authors: Smart Christopher J. , Reynolds Scott K. , Stanis Carol L. , Patil Arvind , Kirleis J. Thor
Published: March 2011

Chemical vapor deposition of metals is becoming a desirable alternative to physical deposition techniques (e.g. sputtering, evaporation) for applications in chip wiring. This is due to the possibility of achieving highly conformal coverage and low processing temperatures. Additionally, it is convenient to be able to enhance the physical properties (e.g. corrosion resistance, adhesion, electromigration resistance) of metal films used for chip interconnection by incorporation of an alloying agent. We have investigated the possibility of extending our current copper deposition process to allow for the deposition of copper alloys. By careful selection of the precursors and reactor conditions, simultaneous decomposition of the two compounds to give clean alloy films is effected. Using this co-deposition method, Cu-Co and Cu-Te alloy films were prepared. Precursor and reaction chemistry are discussed as well as some properties of the resulting films.
Organometallic CVD of CoGa and Related Bimetallic thin Films from Novel Single Source Precursors
Authors: Fischer Roland A.
Published: March 2011

A series of volatile heterodinuclear organometallic compounds of the general formula L(CO)nM-ER1R2(D) (L = CO, η5-C5H5, P(CH3)3; n = 1–4; M = Mn, Fe, Co, Ni; E = Al, Ga, In; R = H, alkyl; D = O- or N-donor ligand) was syndiesized and characterized. These compounds exist either as low melting solids or liquids with vapor pressures typically around 10–50 mTorr at room temperature. The possibility to grow bimetallic thin films ME (e.g. CoAl, CoGa, Coin, Niln etc.) from those single source molecular precursors by thermally induced low pressure OMCVD was investigated. It was shown that the thin film composition, namely the metal stoichiometry, can be controlled by the ligand set at the metal atoms.
Alternative Organometallic Precursors for CVD of Tungsten
Authors: Kirss Rein U. , Gordon Douglas , Kirlin Peter S.
Published: March 2011

Two solid, air stable, volatile tungsten complexes, tris(methylvinylketone) tungsten, I, and tris(butadiene)tungsten, II, have been investigated as precursors for chemical vapor deposition (CVD) of tungsten containing films. Thermal gravimetic analysis, (TGA), of I and II under argon showed the onset of decomposition at 140°C and 150°C, respectively. A rapid weight decrease corresponding to loss of all three ligands, methylvinyl ketone or butadiene, was observed.

Tungsten film growth under hydrogen using I was investigated on Si, SiO2, Cu, TiN, Si, and Pt substrates. Selective tungsten film growth on platinum using a hydrogen carrier was observed at temperatures above 200°C. No appreciable tungsten deposition was observed on clean Si, SiO2. Cu or TiN surfaces below 400°C. No oxygen or carbon was detected in these films to the level of EDX analysis (∼1%) for depositions at 200°C. Increased growth temperatures resulted in increasing amounts of oxygen incorporation. The films grown at 200°C were smooth whereas cracking was observed in films grown at 300°C. The volatile products from the deposition were identified by a combination of gas chromatography and mass spectrometry. Small amounts of methylvinylketone. and methylethylketone were observed. Higher molecular weight species are as yet unidentified, but constituted the majority of the products.
Single-Source Precursors to Titanium Nitride Thin Films
Authors: Winter Charles H. , Lewkebandara T. Suren , Sheridan Philip H. , Proscia James W.
Published: March 2011

The syntheses of the first single-source precursors to gold-colored titanium nitride films are reported. The precursors have the empirical formula [TiCl2(NHR)2(NH2R)0–2] and [TiCl4(NH3)2] and are obtained upon treatment of titanium tetrachloride with alkylamines or ammonia in nonpolar organic solvents. Both precursors sublime without decomposition between 80–120 °C and 0.01–0.1 mmHg. Deposition of titanium nitride films on glass and silicon substrates was achieved using either precursor at substrate temperatures of 475–600 °C. The films were characterized by x-ray diffraction, resistivity measurements, and X-ray photoelectron spectroscopy. In particular, low levels of carbon and chlorine contaminants were observed in the films.
Alternate Titanium Source Compounds for CVD of Ti/TiC Coatings
Authors: Groshens Thomas J. , Lowe-Ma Charlotte K. , Scheri Richard C. , Dalbey Robert Z.
Published: March 2011

CVD experiments were conducted using (Me3SiCH2)4Ti, Bis(2,4-dimethylpentadienyl) titanium, Cl3TiMe, (Me3SiCH2TiCl3 to evaluate their potential as Ti precursor compounds. Only Me3SiCH2TiCl3 was suitable for atmospheric CVD applications. Uniform thin films of polycrystalline TiC were deposited using Me3SiCH2TiCl3 in an argon ambient between 700 °C and 800 °C. A mechanism involving initial loss of Me3SiCl to generate a titanium carbene intermediate is proposed. Thin films of TiC deposited on Si[111] were characterized using XRD and AES. Depth profile line shape analysis showed only TiC and elemental Si in the interfacial region. XRD indicates some titanium silicide is formed at 800 °C. In a hydrogen ambient, hydrogenolysis of the alkyl group occurs and very poor film growth results were obtained.
Aluminum Particle Formation in the GaS Phase of a Low Pressure Chemical Vapor Deposition Reactor Using Dimethylethylamine Alane (AlH3) as a Precursor
Authors: Simmonds Michael G. , Gladfelter Wayne L. , Li Haojiang , McMurry Peter H.
Published: March 2011

Particle formation in the gas phase during the chemical vapor deposition of Al using dimethylethylamine alane was studied. Typical sizes of the crystalline Al particles monitoredwere in the range 20 nm to 1000 nm. Introducing trace amounts of H2O, CO and O2 into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that Al particle formation was induced by impurities in the gas phase although competing mechanisms could not be ruled out.
Metal Organic Chemical Vapor Deposition of Al and CuAl Alloy Films in a Vertical, High-Speed, Rotating Disk Reactor
Authors: Tompa G. S. , Wolak E. , Stall R. A. , George M. A. , Lippitt M. , Norman John A.T.
Published: March 2011

A vertical high-speed, rotating disk reactor has been used to produce Al and CuAl alloy films on 125 mm diameter Si (100) wafers. Trimethylamine-alane and Cu (hexafluoroacetylacetonate) trimethylvinylsilane (CupraSelect™) were used as metal precursors. Aluminum films were deposited over the temperature range from ∼100 C to 700 C. Aluminum sheet resistance measurements showed the films to have resistance 2 to 3 times that of bulk Al films. CuAl alloy films were deposited sequentially and by codeposition. At 30 Torr, deposition rates as high as 3.7 um/hr, 0.024 um/hr, and 1 um/hr for Al, Cu, and CuAl films, respectively, were demonstrated. Auger analysis showed the deposited films to be free of contaminants.
Low Temperature Selective Area Chemical Vapor Deposition of Gold Films: Growth and Characterization
Authors: Seidler Paul F. , Kowalczyk Steven P. , Holl Mark M. Banaszak , Yurkas John J. , Norcott Maurice H. , Read F.
Published: March 2011

Substrate-selective, low-temperature chemical vapor deposition of high quality gold filmswas obtained with the new precursor ethyl(trimethylphosphine)gold(I) in an ultrahigh vacuum reactor designed to handle wafers up to 3 inches in diameter. Growth behavior at temperatures as low as room temperature as well as substrate pre-cleaning procedures are presented. Activation energies of 35.1 ± 0.4 kcal mol−1 and 18.3 ± 0.7 kcal mol−1 were found for growth of gold films on gold and copper substrates, respectively.
Copper CVD Reactions of Cu(I)(hfae)(vtms) Adsorbed on TiN
Authors: Guinn K. V. , Donnelly V. M. , Gross M. E. , Baiocchi F. A. , Petrov I. , Greene J. E.
Published: March 2011

We have studied the thermal decomposition of a Cu MOCVD precursor, hexafluoroacetylacetonate copper vinyl trim ethylsilane (CuI (hfac)(vtms)), on both air-oxidized and N2 ion beam sputter-annealed single crystal (100) and polycrystalline TiN surfaces. Dosing TiN with CuI(hfac)(vtms) at 25°C results in chemisorption of CuIhfac) and desorption of vtms. On oxidized surfaces, litle or no decomposition of CF3 groups is detected at room temperature, while on sputter-annealed polycrystalline and single crystal surfaces, a small amount of decomposition is indicated by a CF2 feature in the C(1s) X-ray photoelectron spectroscopy (XPS) spectrum, and a low-binding energy fluoride in the F(1s) spectrum. Between 100 and 250°C, CuI(hfac) decomposes to evolve gaseous products and leaves Cu, F, and C on the surface. Further heating leads to diffusion of Cu into the TiN, apparently enhanced by simultaneous diffusion of F. Decomposition of the hfac CF3 groups at elevated temperature is independent of the nature of the TiN surface (i.e. polycrystalline vs. (100), or clean vs. oxidized). However, Cu diffusion depends strongly on the surface preparation. The onset of Cu diffusion into oxidized polycrystalline, clean polycrystalline, and clean single crystal (100) TiN occurs at 250, 320, and 430°C, respectively.
Substrate Pretreatments and Strength Limiting Factors in Cu-AlN Direct Bonds
Authors: Chiang Wan-Lan , Greenhut Victor A. , Shanefield Daniel J. , Johnson Lois A.
Published: March 2011

Cu-AlN direct bonds were made by the gas-metal eutectic method. Two kinds of AlN substrates from different suppliers were used for the research. The AlN surfaces were preoxidized in O2 at three different temperatures. An optional “anneal” in Ar was applied following the oxidation procedure. Two processes were used for the bonding.

The bond strengths and the failure modes were found to depend on the substrate used, the pretreatment of the AlN and bonding conditions. There was an optimum thickness for the Al2O3 layer on the AlN surface. High temperature annealing in Ar was demonstrated to effectively promote bond strength. The highest peel strength measured was 50 N/cm.

A thermal expansion mismatch between Al2O3 and AlN was considered to be the main factor which dominated the ultimate bond strength. This mismatch resulted in a residual stress in the Al2O3 layer. A measurement by XRD indicated a 300 MPa tensile stress existed in the surface Al2O3 after AlN oxidation. This made Al2O3/AlN the weakest interface and limited the bond strength rather than the eutectic bond.
Comparison of Trichlorosilane and Trichlorogermane Decomposition on Silicon Surfaces Using FTIR Spectroscopy
Authors: Dillon A. C. , Robinson M. B. , George S. M.
Published: March 2011

Fourier transform infrared (FTIR) transmission spectroscopy was used to compare the decomposition of trichlorosilane (SiHCl3) and trichlorogermane (GeHCl3) on silicon surfaces. Chlorosilanes, such as SiHCl3 are employed in silicon chemical vapor deposition (CVD). Chlorosilanes and chlorogermanes are also possible molecular precursors for the controlled atomic layer growth of silicon and germanium. GeHCl3 may be useful for the deposition of germanium on silicon surfaces and the growth of Si1−xGex heterostructures. The FTIR studies were performed in-situ in an ultra-high vacuum chamber on high surface area, porous silicon samples. The FTIR spectra revealed that SiHCl3 dissociatively adsorbs at 200 K to form SiH, SiClx, ClSiH and Cl2SiH surface species. The presence of ClxSiH species is revealed by ClxSiH stretching (2196 cm−1) and bending (775, 744 cm−1) vibrations. The presence of these modes indicates that there is incomplete decomposition of SiHCl3 upon adsorption at 200 K. GeHCl3 also dissociatively adsorbs at 200 K to form SiH and SiClx species. An infrared absorption feature in the Ge-H stretching region (1970–1995 cm−1) was not detected in the FTIR spectrum. The absence of a Ge-H absorption feature argues that there is a complete transfer of hydrogen from germanium to surface silicon atoms at 200 K. The thermal stabilities of the surface species were studied with annealing experiments. The Clx SiH formed upon initial SiHCl3 exposures at 200 K were observed to decompose between 200–590 K and form additional surface SiH and SiCl species. For both GeHCl3 and SiHCl3 dissociative adsorption on porous silicon, the SiCL. (x = 2 or 3) surface species were converted to silicon monochloride surface species between 200–600 K. In addition, SiH surface species were lost upon annealing between 680–780 K as H2 desorbed from the surface. The adsorption kinetics of SiHCl3 and GeHCl3 were also monitored on porous silicon at various isothermal temperatures. These experiments provide insight into the surface chemistry of chlorosilanes and chlorogermanes during CVD and atomic layer controlled growth.
Germanium Deposition on Silicon: Surface Chemistry of (CH3CH2)2GeH2 and GeC14
Authors: Coon P. A. , Wise M. L. , Dillon A. C. , George S. M.
Published: March 2011

Diethylgermane, (CH3CH2)2GeH2, and germanium tetrachloride, GeCl4 may be useful precursors for chemical vapor deposition (CVD) or atomic layer controlled deposition of germanium. To explore the surface chemistry of these alternative precursors, the adsorption and desorption kinetics of (CH3CH2)2GeH2 (DEG) and GeCl4 on Si(111) 7×7 have been examined using laser-induced thermal desorption (LITD), and temperature programmed desorption (TPD) techniques. Fourier transform infrared (FTIR) spectroscopy has also been employed to monitor the decomposition of DEG on porous silicon surfaces. The FTIR spectra revealed that DEG dissociatively adsorbs on porous silicon surfaces at 200 K to form SiH, GeH, and SiCH2CH3 surface species. No spectral features were observed for GeCH2CH3 surface species. The TPD studies following DEG exposures on Si(111) 7×7 observed CH2=CH2 and H2 desorption products at 700 and 800 K, respectively. The production of CH2=CH2 (ethylene) was consistent with a βhydride elimination mechanism from surface ethyl species, i.e. SiCH2CH3(ad) → SiH(ad) + CH2=CH2 (g). Similar TPD experiments following GeCl4 exposures monitored the desorption of only SiCl2 at approximately 920 K. Desorption of SiCl2 indicates that the chlorine on GeCl4 has transferred to the silicon surface. Atomic Ge was also observed to desorb at 1200 K following both DEG and GeCl4 adsorption. LITD experiments measured initial reactive sticking coefficients of So ∼0.05 for DEG and So ∼1.0 for GeCl4 at 200 K. As expected from a precursor-mediated adsorption model, the sticking coefficients decreased versus increasing surface temperature. The sticking coefficients for these germanium containing precursors were higher than the corresponding sticking coefficients for (CH3CH2)2SiH2 and SiCl4. Possible recipes for the CVD or atomic layer controlled deposition of germanium on silicon can be proposed based on the surface chemistry and adsorption and desorption kinetics for DEG and GeCl4.
Investigation of the Hydrogen Content of Silicon in an Integrated Rapid Thermal Processing Reactor
Authors: George M. A. , Beck S. E. , Bohling D. A. , Hames G. A. , Wortman J. J. , Melzak J. A.
Published: March 2011

The effects of H2 and H atoms on electronic properties of crystalline silicon is of great interest to many scientists and technologists involved in developing and manufacturing of microelectronic devices. Hydrogen is of interest because of its ability to interact with defects and impurities in single crystal silicon, its abundance in many processing steps, and its effect on electronic structure of the interface between Si and SiO2. Here we present results of experiments examining the gas phase concentration of impurities during thermal oxidation and annealing of p(100) silicon. These experiments reveal that a significant quantity of hydrogen is contained in virgin wafers, which may have significant impact on thermal processing. A brief review of studies done on hydrogen diffusion in p-type silicon is provided with a perspective to the process investigated here.
Chemical Vapor Cleaning of Sodium from SiO2
Authors: Bohling David A. , Felker Brian S. , George Mark A.
Published: March 2011

Chemical vapor cleaning (CVC) is an emerging technology which has been used to remove transition metal contamination from wafer surfaces. CVC is a gas phase/surface reaction which does not incorporate any wet steps nor condensation of reagents onto the wafer surface. In previous work, we reported the effective removal of trace iron and copper from native oxide surfaces using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HFAC) and other chelating or coordination compounds. In general, surface metal contaminants form volatile reaction products with these CVC reagents at relatively low temperatures (<300°C). In this paper, we report the extension of that work to include the facile removal of sodium from silicon oxide surfaces. Wafers doped with sodium from aqueous sodium hydroxide can be cleaned in a fully gas phase process at temperatures below 225°C.We will describe our preliminary process results, which have led to a surface sodium concentration reduction of roughly one order of magnitude. Current understanding related to the mechanisms controlling mobile ion removal will also be described.
Divinylmercury as a Precursor in the Metalorganic Molecular Beam Epitaxy of Hg Containing II-VI Materials
Authors: Zinck J. J. , Rajavel D.
Published: March 2011

We have used x-ray photoelectron spectroscopy, temperature programmed desorption, and epitaxial growth experiments to study the feasibility of using divinylmercury (DVHg) as a precursor for metalorganic molecular beam epitaxial (MOMBE) growth of Hg-containing II-VI materials. The surface chemistry associated with the interaction of DVHg and Te was investigated using polycrystalline Te (poly-Te) films as the substrates for DVHg adsorption. nDVHg dissociatively adsorbed on a poly-Te surface at temperatures as low as -118°C. However, the DVHg dissociation probability was temperature dependent and substantially less than unity when extrapolated to typical Hg1−xCdx Te growth temperatures of 150–200°C. Preliminary results from MOMBE growth experiments showed that successful MOMBE growth of HgTe on CdTe//ZnTe//GaAs using DVHg and thermally precracked diethyltellurium was only possible when the DVHg was also thermally precracked. Simultaneous exposure of atomic H and DVHg to a poly-Te surface significantly enhanced the dissociative adsorption of DVHg, indicating that the presence of atomic H in the growth environment may be an effective alternative to precracking DVHg for MOMBE growth.
IR Diagnostics of MOCVD Reaction Chemistry
Authors: Weiller Bruce H.
Published: March 2011

The gas-phase chemical reactions in the Metallorganic Chemical Vapor Deposition (MOCVD) of A1N and TiN have been studied using IR spectroscopy. The products formed from the reaction of trimethyl aluminum (TMA) and NH3 were compared to those from the reaction of TMAwith NF3 using a static gas-phase IR cell. Reaction with NH3 is rapid at 25 °C, and the IR spectrum of the product is consistent with the acid-base adduct (CH3)3Al-NH3. At 25 °C, no reaction between TMA and NF3 was observed. However, at 58 °C a slow reaction occurredto give (CH3)2AlF. The reaction of Ti(N(CH3)2)4 with NH3 was also studied using a flow-tube reactor with a sliding injector port that provides control over the reaction time between two reactive flows. By monitoring the disappearance of Ti(N(CH3)2)4 as a function of NH3 partial pressure and reaction time, we have obtained a preliminary estimate of the rate constant as ∼ 10−16 cm3 molecule−1 s−1 at 25 °C. This result confirms that the reaction is rapid even at room temperature and demonstrates the utility of the flow-tube reactor and FTIR spectrometer for studies of MOCVD chemistry.
Formation of TiO2 Thin Films by Oxidation of TiN
Authors: Truman J. K. , Ballentine P. H. , Terzioglu E. , Kadin A. M.
Published: March 2011

TiN thin films were deposited by reactive sputtering onto Si substrates. TiO2 films were formed by subsequent oxidation of the TiN films, using either conventional furnace heating or rapid thermalprocessing (RTP). The materials properties of the resulting films were characterized by x-ray diffraction and Rutherford backscattering, and indicate conversion of the TiN to fully-oxidized rutile TiO2 by a diffusion-limited process. Electrical measurements of the insulating properties of the TiO2 films indicated a relative dielectric constant greater than 100, although the leakage current was greater than optimum. A fully in-situ process for the fabrication of microcapacitors is proposed, which involves the sputter deposition of TiN, the formation of TiO2 by RTP, and the deposition of a top TiN counterelectrode. This can be carried out under conditions that are compatible with Si microelectronic device processing.
Some Theoretical Aspects of Carbon Incorporation into III-V“s
Authors: Weyers Markus
Published: March 2011

Carbon as a constituent of some of the source molecules is always present in the metalorganic growth techniques and can potentially be incorporated into the grown layers. Unintentional carbon incorporation as well as intentional carbon doping of III-V compounds has been studied intensely, especially in the case of GaAs. However, a number of experimental findings still is not well understood. Besides the different electrical behavior of carbon in different host materials (acceptor in GaAs, donor in InAs) also the different probability of incorporation into, for example, GaAs compared to InAs is currently not well explained. Model calculations may provide useful hints to enhance the understanding of the experimentally observed trends. In this paper, two different approaches will be reviewed and their results will be discussed.

The first approach is dealing with the expected incorporation site of carbon in III-V“s. The change in total energy associated with substitutional carbon incorporation onto group III or group V lattice sites has been calculated. From this change the conduction type of carbon doped arsenides and phosphides (except for InAs) can correctly be predicted. While this method is dealing with the bulk semiconductor, the second approach attempts to model the binding energy of methyl to atoms on the growing surface. By using appropriate molecules the methyl bond strength can be estimated. Both approaches together provide a basis for a more complete understanding of carbon incorporation behavior in III-V compounds.
Pyrolysis Studies of Single-Source Precursors to Gallium Phosphide
Authors: Lee Kenneth E. , Lowe-Ma Charlotte K. , Higa Kelvin T.
Published: March 2011

New dialkylgallium dialkylphosphide compounds having the formula [(t- Bu)(R)GaPR'2]n (R = t-Bu, Me3SiC=C; R' = t-Bu, i-Pr, Et; n = 1, 2) were recently prepared and characterized. When R = R' = t-Bu, the compound is a low melting, monomeric solid. The other compounds are dimeric solids with the unsym-metrical acetylides occurring as cis and trans isomers. Polycrystalline gallium phosphide was deposited from these sources on silicon atlow pressure (0.05–0.1 Torr) and low temperature (350–600 °C) in a horizontal OMVPE reactor. The film growth was monitored by a residual gas analyzer and the by-products were trapped (N2(1)) to be later analyzed by 1H and 13C NMR. The deposited films were characterized by Raman spectroscopy, X-ray powder diffraction, and Auger emission spectroscopy.
Alternative Group V Precursors for the Growth of Al-Based III-V Epitaxial Layers by OMVPE
Authors: Hobson W. S. , Geva M.
Published: March 2011

Tertiarybutylarsine (TBAs), tris-dimethylaminoarsenic (DMAA), and tertiarybutylphosphine (TBP) were investigated as alternatives to arsine and phosphine for the growth of AlGaAs, AlInAs, and AlInP by organometallic vapor phase epitaxy. The use of TBAs led to a significant reduction in carbon and oxygen incorporation compared to ASH3 for AlGaAs. Increasing the TBAs molar flow rate reduced the oxygen (and carbon) concentration. Lower oxygen concentration was observed in AllnP grown with TBP compared to PH3. Increasing the PH3 molar flow rate decreased the oxygen incorporation in AllnP. The morphology of AllnP improved considerably as the growth temperature was increased from 650°C to 750°C, similar to the case of PH3. AlInAs and AlGaAs layers grown with DMAA exhibited rough morphology, presumably due to oxygen-containing impurities in the DMAA source.
Reaction and Transport Models of the MOVPE of Ternary III-V Semiconductors
Authors: Ingle N. K. , Mountziaris T. J.
Published: March 2011

Reaction and transport models describing the deposition of thin films of ternary compoundsemiconductors by Metalorganic Vapor Phase Epitaxy (MOVPE) are being developed. The growth of AlxGa1−x As (0≤x≤1) films from trimethyl-aluminum (TMA1), trimethyl-gallium (TMG) and arsine has been used as a typical example. A kinetic model of the process including both gas phase and surface reactions has been coupled to a two-dimensional transport model of a horizontal reactor with a flat susceptor. The model predicts reported experimental observations on growth rates and film compositions [1] using a single adjustable parameter, the activation energy of the the AlAs growth reaction. A parametric study was performed to identify operating conditions maximizing the thickness andcompositional uniformity of the deposited films. All inlet flow rates considered in this work were higher than the ones required to suppress transverse buoyancy-driven recirculations in the reactor [2,3]. Such conditions permit the growth of abrupt heterojunctions byrapidly switching various precursors on and off. Our results indicate that the most promising operating conditions coincide with the transition from kinetic limited to diffusion limited growth, which occurs at temperatures between 800 K and 850 K for typical experiments [1]. The optimal inlet mole fraction of the limiting group-III species was found to be about 6×10−4 for such cases.
PL and FTIR Absorption Study on Porous Silicon in Situ During Etching, in Oxygen Ambient, and After Chemical Oxidation
Authors: Mauckner G. , Walter T. , Baier T. , Thonke K. , Sauer Abteilung R.
Published: March 2011

Steady state and time-resolved photoluminescence (PL) and Fourier-transform infrared (FTIR) spectroscopy have been performed in situ during etching, on “as prepared” porous Si in air under laser exposure and on chemically oxidized porous Si. We suppose that PLdegradation of “as prepared” porous Si is caused by creating non-radiative defect centers during photooxidation. Chemically oxidized porous Si shows increased PL intensity and longer recombination lifetimes as compared to non-oxidized samples. We conclude, that an oxide layer with low defect density on the inner surface of chemically oxidized porous Si reduces the non-radiative recombination rate.