bluuebunny/crossref_metadata_2025 huggingface dataset:
Lattice Orientations of Evaporated Metals onto Uniaxially Oriented, Semicrystalline, Ultra thin Polymer Films
Authors: Jandt Klaus D. , Buhk Maren , Petermann Jürgen , Eng Lukas M. , Fuchs Harald
Published: March 2011

The textured oriented overgrowth (epitaxy) of certain metals evaporated onto substrates consisting of highly oriented ultra thin polymer films of polyethylene (PE), polypropylene (PP) and polybutene-1 (PB-1) has been well known since a few years. However, the origin of the observed epitaxy is not clear at all: graphoepitaxy (i. e. orientation induced by nucleation onto oriented topographic features of the substrate), the formation of a chemical layer (i. e. of metal-methyl groups building up the polymer-metal interface, or simply classic epitaxy (i.e. lattice matching) seem all to be possible explanations for the observed orientations. Here, we used Transmission Electron Microscopy (TEM) and Scanning Force Microscopy (SFM) to investigate the possibility of graphoepitaxial growth on polymeric surfaces. Our investigations show that the morphology of polymeric bulk material determine the topographic properties observed at the polymer surface. The semicrystalline nature of the polymer films leads to polymeric surface steps which are suitable as locations for graphoepitaxial growth. Artificial epitaxy (graphoepitaxy) seems to be the most likely orientation mechanism.
Mass Flow and Stability of Nanoscale Features on AU(111)
Authors: Cooper B. H. , Peale D. R. , Mclean J. G. , Phillips R. , Chason E.
Published: March 2011

We present the use of an STM to make quantitative observations of time-dependent mass flow associated with the decay of two-dimensional clusters on the Au(111) surface. When formed and observed in air, layered islands with well-defined edges located on larger terraces are generally found to decay in such a way that their areas decrease linearly in time over periods ranging from minutes to several hours depending on the island size. This is in contrast to the behavior of similar features formed and observed under ultra high vacuum conditions, which do not appear to decay over experimental periods of several days. The linear decay is consistent with models that have been used previously to describe growth of 2-dimensional clusters on surfaces. We discuss possible decay mechanisms, and the role that adsorbates may play in influencing the decay.
Surface Diffusion in Interactive Overlayers:
Authors: Tringides M. C.
Published: March 2011

The analysis of surface diffusion in interactive overlayers deviates from the simple picture of diffusion as a random walk. Non-equilibrium processes (the growth of ordered or the disordering of already ordered islands) under constant coverage or deposition rate, can be easily used to measure surface diffusion. For the 0/W(110) system, such experiments measured an ordering activation energy ED=0.6±0.05 eV which is different from the one measured in disordering experiments ED=1 ± 0.05 eV. The difference can be accounted for by the interactions. Ordering experiments in the Ag/Si(111)-√3x√3R30 system under constant deposition, suggest the presence of non-thermal mobility.
Changes in Electronic Device Properties During the Formation of Dislocations
Authors: Ross F. M. , Hull R. , Bahnck D. , Bean J. C. , Peticolas L. J. , Kola R. R. , King C. A.
Published: March 2011

We describe the results of an investigation into the formation and properties of dislocations in electronic devices. We have made electron transparent specimens from metastable GeSi/Si p-n junction diodes and introduced dislocations into the devices by heatingin situin the electron microscope. A modification made on the specimen holder for our microscope enables us to measure the characteristics of these devices while they remain under observation in the microscope. We can therefore observe the changes in the electrical properties of the devices as dislocations form. We confirm that the introduction of dislocations has a deleterious effect on parameters such as the reverse leakage current through a diode. However the magnitude of the effect we observe can not be explained by a generation-recombination process and instead we suggest a model based on the creation of point defects or the diffusion of metals during the formation of dislocations. We also consider the kinetics of dislocation formation, and in particular how the extent of dislocation formation in a device depends on the subsequent processing steps which it undergoes.
Seeded Heteroepitaxy and the Overgrowth of InN Films: Nucleation with Lattice Mismatched AIN
Authors: Kistenmacher Thomas J. , Ecelberger Scott A. , Bryden Wayne A.
Published: March 2011

The growth and properties of thin films of InN on a variety of substrates nucleated by a 400Å layer of AIN have been shown to be dependent on the lattice mismatch (LMM) with the substrate. Examples are drawn from growth of InN thin films by reactive magnetron sputtering on high symmetry faces of a variety of crystalline substrates [(00.1) sapphire, (111) silicon and (111) yttria-stabilized zirconia, and (001) mica] and amorphous fused quartz. Striking is a comparison of the electrical transport properties for nucleated and unnucleated InN films. For example, the ratio of the Hall mobilities for nucleated and unnucleated InN films deposited on (00.1) sapphire (LMM for AIN and InN of 13.0% and 29.0%, respectively) is ∼102, while this ratio for nucleated and unnucleated InN films on (111) zirconia (LMM for AIN and InN of −14.8% and −7.8%, respectively) is ∼10−2. While all the factors underlying these results are not necessarily obvious, it is rather apparent that this trend in Hall mobility stems from a contrasting trend in film resistivity at a more nearly constant value for the carrier concentration.
Evolution of Electrical Properties with Thermal Annealing for Seeded Heteroepitaxial InN Thin Films
Authors: Bryden Wayne A. , Ecelberger Scott A. , Kistenmacher Thomas J.
Published: March 2011

Two related studies of the effects of elevated temperature annealing on reactive rf magnetron sputtered InN films have been conducted. In the first study, thin films of InN were deposited and annealed in 5 mTorr of nitrogen gas using a conventional high-vacuum (HV) magnetron sputtering system. Films were grown at 100°C and following annealing at an elevated temperature (Ta) for 4 hours were removed from the system for physical characterization. The physical properties of the annealed films improved with thermal treatment and were strikingly coincident with the properties of a second set of films grown at Ta. In the second study, films were deposited at 400°C in 5 mTorr of nitrogen gas using an ultrahigh-vacuum (UHV) sputtering system. Samples were annealed (at 550°C) and electrically characterized under UHV conditions using a custom designed annealing furnace with an integral Van der Pauw probe. Contrary to expectations, the carrier concentration of these films showed a steady decrease with extended annealing and the carrier mobility nearly doubled after 15 hours of treatment.
Interfacial Morphology of Selicides Formed Via Rta of Sputtered Bi- and Multi-Layer Co/Ti(O,C) on Si
Authors: Hong Feng , Patnaik Bijoy K. , Li Bingzong , Liu Ping , Sun Zen , Rozgonyi George A.
Published: March 2011

Cobalt silicide formed by diffusion of Co through a Ti compound has been reported for both bilayer and multilayer Co/Ti-Si structurest[2-4]. To compare the bilayer and multilayer systems in terms of the Co silicide interfacial morphology, both bilayers and six layers of 20nm Co and lOnm Ti were sputter deposited on (100)Si in a system where background. oxygen and carbon were gettered by each Ti layer. The samples were annealed from 550°C to 800°C for 60 sec by lamp RTA in N2 ambient. XTEM micrographs revealed that significant differences in interfacial morphology existed between bilayer and multilayer samples. The interfacial amorphous Ti(O.C) diffusion barrier layer was found to be more effective in the multilayer system producing uniform CoSix layers as thin as ∼5nm after 550°C RTA, whereas the silicide formed in the bilaver samples under the same condition was rough. RBS analysis showed that the transformation temperature from CoSi to CoSi2 was 800°C in bilayers and even higher for multilayers. The higher transformation temperature is attributed to the additional Co available in the multilayer system and its effect on Co monosilicide phase stability as previously reported[10].
Some Comparisons of Ag Deposits on Ge and Si(111)
Authors: Metcalfe F. L. , Venables J. A.
Published: March 2011

Crystal growth and surface diffusion have been studied in the Ag/Ge(lll) system using UHV-SEM based techniques, biassed secondary electron imaging (b-SEI), micro-AES and RHEED. Ag was deposited through and past a mask of holes held close to the substrate at 300<Td< 775K. Under certain conditions, the Ag patches were observed to split into two regions corresponding to the √3×√3R30° (hereafter √3) and a lower coverage 4×4 structure, each of which were easily observable using b-SEI. These patch widths were measured as a function of Td, and of annealing times at temperatures Ta, and effective diffusion coefficents extracted. The diffusion length of adatoms over the 4×4 structure is larger than that over the √3 structure. These observations are modelled using kinetic rate equations, and the results are compared with previous studies of Ag/Si(111). We find that energies characterising processes on top of the √3 layers of both systems are very similar, but that processes involved in the formation of the layers are quite different. The coverage of the √3 Ag/Ge(111) layer is close to 1 ML for all Td studied, unlike √3 Ag/Si(111). where it depends on deposition and annealing conditions.
Non-Destructive X-Ray Diffraction Analysis of the Under-Film Corrosion Processes in Zinc-Coated Steel Sheets by Synchrotron Radiation
Authors: Nose K. , Kawasaki K. , Hayashi K. , Morikawa H. , Sasaki S.
Published: March 2011

A highly brilliant x-ray beam from a synchrotron radiation source is a powerful tool to perform non-destructive x-ray diffraction analysis of an under-film corroded region of zinc-coated steel sheets. Investigations to identify corrosion products under the outdoor salt-spray test condition and to reveal their one-dimensional distribution were carried out Simonkolleite (ZnCl2•4Zn(OH)2 ) was identified for the first time at the tip of the under-film corroded region. By the one-dimensional analysis, it was shown that the x-ray diffraction intensity of simonkolleite increased, where that of metal zinc decreased. It was suggested that simonkolleite was formed as the first corrosion product under the outdoor salt-spray test condition.
Observation and Characterization of the Pseudomorphic to Stable Phase Transitions of Fe1-xSi on Si(111)
Authors: Onda N. , Sirringhaus H. , Goncalves-Conto S. , Schwarz C. , Muller-Gubler E. , Von Kanel H.
Published: March 2011

Pseudomorphic Fe1-x Si films have been grown on Si(111) by molecular beam epitaxy (MBE) at room temperature (RT). Structural investigations revealed that the phase crystallizes in the cubic CsCl structure with a lattice constant close to half that of Si. Upon annealing, films thicker than 15Å undergo a phase transition to the stable bulk ε-FeSi, either in epitaxial or in polycrystalline form at temperatures around 300°C. Thinner films do not transform to the ε-FeSi phase. Instead they exhibit a continuous increase of the Si content up to the stoichiometry of FeSi2 The CsCl symmetry persists, exept for prolonged annealing close to the transition to βFeSi2, where γ-FeSi2 (CaF2 ) forms as an intermediate phase.
Formation Mechanism of Epitaxial CoSi2 Films on (001) Si Using Ti-Co Bimetallic Layer Source Materials
Authors: Hsia S. L. , Tana T. Y. , Smith P. L. , Mcguire G. E.
Published: March 2011

The mechanism of formation of epitaxial CoSi2 film on (001) Si substrate, produced using sequentially deposited Ti-Co bimetallic layer source materials for which Ti was deposited onto the Si substrates first, has been studied by observing the Co silicide formation processes and structures in samples prepared by isochronal annealing and by isothermal annealing. The results demonstrated that, in leading to epitaxial CoSi2 film formation, Ti has played two roles. It has served as a barrier material to Co atoms and thus preventing Co2Si from forming. More importantly, it has allowed nucleation and growth of epitaxial-CoSi2 to dominate the Co silicide film formation process, apparently because it has served as a cleanser to remove native oxide from the Si substrate surface.
Stm Observation of Solid Phase Epitaxy Processes of Ar-Sputtered Si(100) Surfaces
Authors: Uesugi Katsuhiro , Yoshimura Masamichi , Yao Takafumi , Sato Tomoshige , Sueyoshi Takashi , Iwatsuki Masashi
Published: March 2011

Scanning tunneling microscopy (STM) is used to investigate the surface morphology of Ar+-ion bombarded Si(100) surfaces and to elucidate the very beginning stages of solid phase epitaxy (SPE) processes of the Ar+-ion bombarded Si surfaces. The Ar+-ion bombarded Si surface consists of hillocks of 1–2 nm in diameter and 0.35–0.75 nm in height. The onset of SPE initiates at around 590°C, at which temperature a (2×2) structure surrounded by amorphous regions is partially observed on terraces of the surface. During annealing at 590–620°C, the areas of the c(2×2) and c(4×4) reconstruction surrounded by amorphous regions develops. New defect models for the (2×2) and c(4×4) structures are proposed w here alternating arrangements of the buckled dimers together with missing dimer defects are considered. On the other hand, after thermal annealing of the Ar+-ion bombarded Si at 830°C for 10 sec, terraces of (2×1) and (1×2) orientations arc observed on the surface, and pyramidal structures on a nanometer-scale which consists of double-layer step edges (dimer rows perpendicular to terrace edge) arc observed.
High Resolution X-Ray Diffraction of Hg1-xMnx Te Epitaxial Films
Authors: Tanner B K , Hallam T D , Funaki M , Brinkman A W
Published: March 2011

Epitaxial films of Hg1-xMnxTe (MMT) have been grown by direct alloy growth MOVPE. Perfection of layers grown on CdTe buffered GaAs, and unbuffered CdZnTe substrates has been assessed by double axis X-ray diffraction. No significant difference was observed in the rocking curve full width at half maximum (FWHM) between layers grown on the two types of substrate. Rocking curves taken as a function of position across the layer showed substantial variation, there being a very good correlation between layer thickness determined from the intensity of the substrate peak, layer rocking curve FWHM and Mn composition determined from the substrate and layer peak splitting. The contour maps of these parameters are discussed in terms of depletion of the DIPTe precursor.
Dynamic Film Composition Transition Phenomena in the Copper Oxide Metal Organic Chemical Vapor Deposition (MOCVD) Studied by Scanning Electron Microscopy (Sem)
Authors: Chang Yu-neng
Published: March 2011

In this report, the impact of deposition temperature variation on the evolution of film morphology and microstructure was studied. In the copper oxide metal organic chemical vapor deposition (MOCVD) process, a temperature gradient was created on the substrate surface. By using a specific design of the heating susceptor, the local temperature of the leading edge (upstream) on the substrate surface was maintained at 70°C lower than the temperature of the ending (downstream) edge. The evolution of local composition and microstructure in deposited films were analyzed by X-ray diffraction (XRD), transmission Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and SEM. From XPS and XRD results, Cu2O rich phase was deposited at the low temperature area, while CuO rich phase was deposited at the high temperature area. These two areas were divided by a phase intermixing (transition) zone of 40–100 ums wide. The temperature of this abrupt Cu2O->CuO deposition product transition was determined to be 390°C -400°C. As indicated by SEM results, the low temperature favorite Cu2O continuous phase, collapsed into coarse grains (with the scale of 10 urn) first, then became fine grains among channels of CuO phase, and finally diminished into the high temperature favorite CuO continuous phase. Spatially resolved XPS results also indicated that the film composition changed abruptly through the transition zone. A nucleation-growth competition mechanism, between the Cu2O rich phase and the CuO rich phase, was suggested to occur in this zone. In this model, this dynamic deposition product transition is interpreted by the temperature dependency of nucleation rates for the specific CuO phase or Cu2O phase.
Deposition and Characterization of MgO Thin Films on SrTiO3 and LaAlO3 Substrates
Authors: Chang Bertha P. , Sonnenberg Neville , Cima Michael J.
Published: March 2011

MgO thin films have been deposited on SrTiO3 and LaA1O3 substrates using both off-axis rf magnetron sputtering and electron beam evaporation techniques. The effects of substrate material, temperature, film thickness, deposition rate, sputtering gas, and pressure on the quality of the MgO films produced have been studied. Films deposited on (100) SrTiO3 at temperatures > 300°C display only the (h00) reflections in their X-ray diffraction traces, with narrow X-ray rocking curve measurements indicating that these films are epitaxial. Epitaxy has been confirmed with grazing incidence diffraction. MgO films deposited on (100) LaAlO3 are crystalline, but have varying orientations depending on the film thickness. From scanning electron microscopy, MgO films on SrTiO3 substrates appear smooth and dense while those deposited on LaAlO3 substrates possess rougher surfaces. Surface morphologies have been analyzed using atomic force microscopy.
Structural Instability of the Ceramic Coating in a Metal-Ceramic Composite Induced Through Control of Chemistry of the Bonding Atmosphere
Authors: Ray Abhijit
Published: March 2011

A novel processing technique has been developed to coat Al2O3 on Nb in an argon atmosphere with very low O2 content. It has been proposed1 that the low O2 content helped to increase the defect concentration in the ceramic phase resulting in an enhanced diffusion of Nb into Al2O3 at the metal-ceramic interface at a relatively low bonding temperature. A mathematical model has been developed1 to understand the effect of purified bonding atmosphere on interfacial diffusion. While diffraction studies in the transmission electron microscope revealed1 extensive amorphization at the metal-ceramic interface, EDX analysis showed1 that the interfacial amorphous phase has a very high concentration of O. Additionally, this phase is found to contain Al and Nb. The interfacial phase is formed due to the diffusion of Nb into the ceramic phase. The paradoxical phenomenon of O enrichment of the interfacial amorphous phase in a low O2 containing bonding atmosphere is due to the loss of gaseous oxides of Al from this phase. These oxides have relatively less proportion of O compared to Al2O3. Continuous loss of such oxides from the amorphous phase to the gaseous phase will, therefore, result in an O to Al ratio (in the amorphous phase) far exceeding that in Al2O3 (3:2).
Detailed Characterisations of GaAs Films on Si Obtained by Conformal Growth.
Authors: Gerard B. , Pribat D. , Bisaro R. , Costard E. , Nagle J. , Ricciardi J. , Dupuy M.
Published: March 2011

Conformal growth is a confined epitaxial lateral overgrowth technique capable of yielding low dislocation density GaAs films on Si. This technique makes extensive use of selective epitaxy and crystal growth is confined by a dielectric cap as well as by the self-passivated Si surface itself.

In this paper, we have performed a detailed characterisation of the state of stress of the GaAs films in various configurations (after conformal growth and removal of the seed regions, and after the regrowth of an MBE layer) by photoluminescence measurements at 5K and X-ray diffraction experiments. Although the as-grown conformal films are found in the same state of stress than reference MOCVD GaAs epilayers on Si, we report a significant decrease of this stress after MBE regrowth on conformal films.
Mechanism for Step Growth on Diamond (100)
Authors: Zhu Mei , Hauge Robert H. , Margrave John L. , D'Evelyn Mark P.
Published: March 2011

A model for diamond growth on stepped diamond (100)2×1 surfaces is proposed, involving adsorption and reaction of CH3 and H on a dimer-reconstructed surface. Surface rearrangments and the breaking of C-C dimer bonds by H and/or H2 are suggested to be important The energetics were estimated by molecular mechanics (MM3). Growth is concluded to occur predominantly by extension of dimer rows, yielding a smooth surface, due to steric and bond-strain constraints on the positions of precursor-addition reactions and the kinetic stability of type SB steps against etching.
Diamond Nucleation During Biased Chemical Vapor Deposition
Authors: Csencsits Roseann , Rankin Janet , Boekenhauer Rachel E. , Kundmann Michael K. , Sheldon Brian W.
Published: March 2011

The initial stages of bias-enhanced chemical vapor deposition (CVD) of diamond were investigated in a microwave-plasma system. Samples were characterized with TEM and concurrent electron energy loss spectroscopy (EELS) to characterize chemical bonding in the deposited material. The results show that a thin amorphous carbon film is deposited during biasing, and that diamond nucleation occurs on this amorphous film. Isolated regions of crystalline SiC within the amorphous layer were also observed at longer bias times. These regions apparently form by a reaction between the amorphous carbon layer and the silicon substrate.
Metastable Structural Surface Excitations and Concerted ad Atom Motions: A Stm Study of Atomic Motions Within a Semiconductor Surface
Authors: Golovchenko Jene , Hwang Ing-Shouh , Ganz Eric , Theiss Silva K.
Published: March 2011

Knowledge about atomic scale motions is essential to the understanding of dynamical phenomena on surfaces, such as diffusion, phase transitions, and epitaxial growth. We demonstrate that the addition of a very small number of Pb atoms to a Ge(111) surface reduces the energy barrier for activated processes, thus allowing one to observe concerted atomic motions and metastable structures on this surface near room temperature using a tunneling microscope. The activation energy for surface diffusion of isolated substitutional Pb atoms in Ge(111)-c(2×8) was measured by observing individual atomic interchanges from 24°C to 79°C. We also observed the formation and annihilation of metastable structural surface excitations, which are associated with large numbers of germanium surface atoms in one row of the c(2×8) reconstruction shifting along that row like beads on an abacus. The effect provides a new mechanism for atomic transport on semiconductor surfaces and can explain a number of other observed phenomena associated with Ge(111) surfaces, including the surface diffusion of Pb atoms.
Dry Surface Cleaning of Plasma-Etched Hemts
Authors: Pearton S. J. , Ren F. , Katz A. , Chakrabarti U. K. , Lane E. , Hobson W. S. , Kopf R. F. , Abernathy C. R. , Wu C. S. , Bohling D. A. , Ivankovits J. C.
Published: March 2011

Fabrication of sub-micron high electron mobility transistors (HEMTs) involves dry etch removal of GaAs from an underlying AlGaAs or InGaAs stop layer. The etch selectivity is achieved by formation of AlF3 on AlGaAs, or InCl3 and InF3 on InGaAs, which must be removed before processing can proceed. Wet chemical cleaning has difficulty in such a situation because of surface tension effects. We have investigated use of Electron Cyclotron Resonance (ECR) H2 or Ar discharges, or hexafluoroacetylacetone (HFAC) vapor, for in-situ dry etch cleaning of HEMTs exposed to low bias BCl3/SF6 discharges. The HFAC vapor can remove most of the remnant fluorine, but is effective only when the sample is heated above ∼250°C. This relatively high temperature is not compatible with in-situ cleaning of the etched device. Low-bias(−75V) sputter cleaning with an Ar discharge removes all remnant Cl and ∼40% of the F, but dc biases above -125V are required for complete cleaning, and this ion bombardment can lead to damage in the HEMT. ECR H2 discharge exposure is effective in removing all Cl- and F-related residues in a short period (∼5 mins) with low dc biases (−25 V) on the sample.
Disordering of a Short Period GaAs-AlGaAs Superlattice by C Diffusion
Authors: Jamal Z. , Goodhew P. J.
Published: March 2011

Carbon doping of GaAs and AlGaAs is easily carried out during chemical beam epitaxy by controlling the proportions of the precursors trimethylgallium and triethylgallium. The diffusion of C introduced at levels of up to 1020 cm−3, has been studied by SIMS and by TEM. In the latter case the destruction of short period GaAs-Al.3Ga.7As superlattices was monitored in order to assess the extent of diffusion after annealing at 800°C. The results confirm that C is quite a stable dopant. In addition, the destruction of the superlattices indicates that the diffusion mechanism of C involves group III sublattice sites.
Laser-Chemical 3-D Micromachining
Authors: Bloomstein T. M. , Ehrlich D. J.
Published: March 2011

Three-dimensional parts are machined in silicon using laser-induced chlorine etching reactions. Structures are created directly from solid-modeling computer-aided-design/computer-aided-manufacturing software. Removal rates exceeding 2×104 and 105μm3/s, several orders of magnitude faster than electrodischarge machining methods, are achieved at 1-μm, and 15-μm x-y resolution, respectively. Laser-induced metallization of resulting structures as well as replication through compression molding have been demonstrated.
Covalent Nitrides for Maskless Laser Writing of Microscopic Metal Lines
Authors: Maya Leon
Published: March 2011

Selected covalent metal nitrides with limited thermal stability, such as Sn3N4, Cu3 N, and Ni3N, were prepared in a glow discharge system by reactive sputtering in a nitrogen plasma. These compounds were characterized by chemical analysis and their thermal behavior established by temperature-programmed thermal decomposition. These materials decompose into the elements with the rate reaching a maximum at 615, 465, and 405 °C for Sn, Cu, and Ni respectively. The feasibility of using these coatings to generate metal lines by maskJess laser writing was explored. Conductingmetal lines, a few micron in width, could be generated with each of these nitrides. The resistivities of the metal lines were within an order of magnitude of those of the bulk metals for Cu and Ni and somewhat more for Sn.
Highly Reliable WGe Ohmic Contact to GaAs-AlGaAs HBTs
Authors: Fullowan T. R. , Ren F. , Tseng B. , Pearton S. J. , Abernathy C. R. , Harriott L. R. , Lane E.
Published: March 2011

We report a highly reliable, sputtered WGe emitter contact for npn heterojunction bipolartransistors. A specific contact resistance of 7.5 × 10−7 Ω-cm2 and a transfer resistance of 4.0 × 10−2 Ωmm were obtained after 380°C, 1 min alloy. The contact was patterned by SF6 dry etching at low bias using a Au mask. This novel contact has comparable resistance to conventional AuGe-based metallization while having superior thermal stability. We have studied the dependence of contact properties on the post-deposition annealing conditions by transfer length method of electrical characterization and Auger analysis, and will also report long-term reliability results in comparison to AuGe-based metallization.
Study of the Thermal Stability of the Schottky Contacts on GaInP Grown by LP-MOCVD
Authors: Chang Edward Y. , Lai Yeong-Lin , Lin Kuen-Chyuan , Chang Chun-Yen , Juang F. Y.
Published: March 2011

Thermal stability of the Schottky contacts on Ga0.51In0.49P has been made. The Ga0.51In0.49P epitaxial layer was successfully grown on the GaAs substrate by LP-MOCVD to form a lattice-matched heterostructure. In this paper, materials aspects of the Ga0.51In0.49P layers were characterized and thermal stability of three different types of films, including single-layer metal (Pt, Ni, Pd, Au, Co, Mo, W, Cr, Ti, Al, Ta, and In), metal silicides (WSi2, W5Si3, PtSi, and Pt2i), and TiW nitrides (TiWNx ) as the Schottky contacts materials on Ga0.51In0.49P were studied. Due to the high bandgap nature of Ga0.51In0.49P, the Schottky contacts on Ga0.51In0.49P demonstrate good characteristics. The barrier heights range from 0.79 to 1.19 eV depending on the selection of the materials and the annealing conditions. For single-metal contacts, Pt film shows the best thermal stability, the barrier height of 1.09 eV and the ideality factor of 1.06 were obtained for the Pt Schottky diode with furnace annealing at 500 °C for 30 min. For refractory compound films, the TiWNx film shows the best thermal stability. The TiWNx Schottky contacts demonstrate excellent electrical as well as physical characteristics, even after high temperature annealing at 850°C.
Tri-Layer Lift-off Metallization Process Using Low Temperature Deposited SiNx
Authors: Lothian J. R. , Ren F. , Pearton S. J. , Chakrabarti U. K. , Abernathy C. R. , Katz A.
Published: March 2011

A tri-level resist scheme using low temperature (<50°C) deposited SiNx ratfier than Ge for the transfer layer has been developed. This allows use of an optical stepper for lithographic patterning of the emitter-base junctions in GaAs/AlGaAs heterojunction bipolar transistors (HBTs) where a conventional lift-off process using a single level resist often leads to die presence of shorts between metallizations. The plasma-enhanced chemically vapor deposited (PECVD) SiNx shows a sligtly larger degree of Si-H bonding compared to nitride deposited at higher temperature (275°C), and is under compressive stress (-5 × 1010 dyne · cm−2) which is considerably relieved upor thermal cycling to 500°C (-1.5 × 1010 dyne · cm−2 after cool-down). This final stress is approximately a factor of two higher man conventional PECVD SiNx cycled in the same manner. The adhesion of the low temperature nitride to die underlying polydimediylglutarimide (PMGI) base layer in the tri-level resist is excellent, leading to high yields in the lift-off metallization process. These layers are etched in Electron Cyclotron Resonance (ECR) discharges of SF6 or O2, respectively, using low additional dc bias (≤-100V) on the sample. Subsequent deposition of the HBT base metallization (Ti/Ag/Au) and lift-off of the tri-level resist produces contacts with excellent edge definition and an absence of shorts between metallization.
Fundamental Studies of TiN Film Growth by CVD From Ti(N M e2)4 and Ammonia
Authors: Prybyla J. A. , Chiang C.-M. , Dubois L. H.
Published: March 2011

TiN films were grown by CVD from Ti(N M e2)4 and ammonia using a novel gas delivery system which allowed the sample to be kept in high vacuum while the reactants were mixed at elevated pressures. The object was to study fundamental chemistries and growth properties. We obtained clean (<5% carbon), near-stoichiometric (Ti:N = 1.15+/-0.1) TiN films. The gas phase chemistry was studied by mass spectrometry while the films were analyzed in situ by Auger electron spectroscopy (AES), and then removed for Rutherford backscattering (RBS) analysis. Film quality was studied as a functionof reactant ratio, substrate temperature, and reactant gas pressure. We obtained definitive information on the growth mechanism. Isotopic substituiton experiments establish that a rapid transami-nation reaction occurs in the gas phase. Mass spectrometry experiments indicate that the reactive intermediate is polymeric, consisting of Ti, N, H, arid perhapscarbon. Growth on patterned wafers shows that this intermediate has a high sticking coefficient and a low surface mobility at 300°C. These findings are considered in terms ofthe potential of this precursor system to be used in manufacturing.
Consecutive Selective Chemical Vapor Deposition of Copper and Aluminum from Organometallic Precursors
Authors: Fine Stephen M. , Dyer Paul N. , Norman John A. T.
Published: March 2011

For the next generation of integrated microcircuits, there exists a need in the electronics industry for high conductivity, electromigration resistant metallization that can be deposited selectivity by chemical vapor deposition techniques. This paper describes a new process for depositing copper/aluminum metallization selectively onto diffusion barrier surfaces in two consecutive steps. First copper is selectively deposited by OMCVD ontoa patterned diffusion barrier surface using a Cu(I)(hfac)(olefin) precursor. Selective copper deposition onto tungsten or titanium nitride is achieved at 150°C and 100 mtorr. Aluminum is then selectively deposited onto copper using trimethylaminealane as the OMCVDprecursor. Trimethylaminealane gives good selectivity for aluminum deposition onto coppersurfaces over a temperature range of 100–120°C without the use of a surface activating agent. A small amount of copper diffuses into the as deposited aluminum layer atthe low deposition temperature. Complete diffusion of copper into aluminum is achieved by a rapid thermal anneal at a higher temperature. The selectivity of aluminum deposition onto copper surfaces is far superior to that observed for aluminum deposition onto other metal surfaces.
InGaP/GaAs Based Single and Double Heterojunction Bipolar Transistors Grown by MOMBE
Authors: Ren F. , Abernathy C. R. , Pearton S. J. , Wisk P. W. , Esagui R.
Published: March 2011

Carbon-doped base InGaP/GaAs single and double heterojunction bipolar transistors (HBTs) grown by gas-source Metal Organic Molecular Beam Epitaxy (MOMBE) are reported. Large are devices (emitter diameter 70 μm) exhibited gain of 25 for high injection levels at a base doping of 5 × 1019 cm−3. Ideality factors (<1.1)were obtained for both emitter-base and base-collector junctions in both single (SHBT) and double PHBT) heterojunction devices. Vceo's of 12 V and 19 V for SHBTs and DHBTs respectively were measured.
Characterization of Palladium Acetylacetonate as a CVD Precursor for Pd Metallization
Authors: Kowalczyk Steven P. , Ldgdlund Michael , Fahlman Mats , Salaneck William R.
Published: March 2011

Palladium acetylacctonate has received much consideration as a possible precursor for chemical vapor deposition of metallic palladium films for a variety of microelectronic applications. We have studied the adsorption and decomposition of palladium acetylacetonate ongold, polyimide, silicon and silver surfaces to understand the initial mechanisms of metallic palladium film formation. In situ x-ray photoelcctron spectroscopy was used to characterized the films after adsorption and their decomposition after thermal treatment or laser irradiation.
Erbium-Doped Silicon Prepared by UHV/CVD
Authors: Beach David B. , Collins Reuben T. , Legoues Francoise K. , Chu Jack O.
Published: March 2011

Erbium-doped silicon has been prepared using Ultra High Vacuum/Chemical Vapor Deposition (UHV/CVD). An erbium mctalorganic compound, tris-1,1,1,5,5,5-hexafluoro-2,4-pentanedionato erbium (111) (Er(HFAC)3), was used as the erbium source and silane was used as the silicon source. Films were deposited at 650 °C at a total pressure of 1 mtorr. Erbium concentrations between 8×1019and 1×1018Er atoms/cm3were prepared by varying the Er source reservoir temperature. Low temperature photoluminescence measurements showed strong emission at 1.54μm. The films are single crystal, but with a high concentration of threading defects.
The Reactivity of HCI and Methyltrichlorosilane with Silicon Carbide Surfaces
Authors: Allendorf Mark D. , Outka Duane A.
Published: March 2011

This work explores the reactivity of HCI and methyltrichlorosilane (MTS) with polycrystalline β-silicon carbide (SiC) surfaces using temperature-programmed desorption (TPD) and Auger electron spectroscopy. HCl is a corrosive gas that inhibits SiC deposition. The results show that HCl is adsorbed by SiC, forming a stable surface chloride that could inhibit SiC deposition. TPD shows that chlorine desorbs as HCI or SiCl4, confirming that HCl can etch SiC surfaces. Desorption is rate-limited by the breaking of Si-Cl bonds. MTS is also adsorbed by SiC; its desorption is similar to that of HCI.
Growth of SiO2 on Si(111)7×7 Using SiCl4 and H2O
Authors: Wise Michael L. , Okada Lynne A. , Coon Peter A. , George Steven M.
Published: March 2011

The controlled atomic layer growth of SiO2 insulating layers on silicon surfaces might be achieved through the sequential reaction of SiCl4 and H2O:

(A) Si-Cl + H2O → Si-OH + HCl

(B) Si-OH + SiCl4 → Si-O-SiCl3 + HCl.

To explore this ABAB… binary reaction scheme, laser-induced thermal desorption, temperature-programmed desorption, and Auger electron spectroscopy techniques were utilized to measure the kinetics of H2O oxidation of a Si(111)7×7 surface that had been previously subjected to a saturation SiCl4 exposure. Reaction kinetics studies for the oxidation of the chlorinated surface revealed that the rate of oxygen gain and the rate of chlorine loss were equal at reaction temperatures between 200 K and 700 K. These results were consistent with a direct substitution reaction according to:

(A) Si-Cl + H2O → Si-OH + HCl.

Above 700 K, the amount of oxygen gain became progressively greater than the amount of chlorine loss. This behavior was associated with the thermal desorption of H2 and the resultant formation of new dangling bond sites for H2O adsorption. For all temperatures, the oxidation kinetics of the chlorinated surface were nearly equivalent to the kinetics for the oxidation of clean silicon. This surprising result indicates that chlorine sites and free dangling bond sites react with equal probability to H2O. The kinetics of SiCl4 deposition were also measured on a Si(111)7×7 surface previously exposed to a saturation H2O dose. This chlorination reaction occurred at a much slower rate and was not as amenable to UHV studies.
Control of Isotropic and Anisotropic Etching and Surface Cleaning of Silicon and Silicon Dioxide in a Hydrogen Plasma
Authors: Veprek S. , Wang Ch. , Ratz G.
Published: March 2011

We present data on the temperature dependence of the etch rate of silicon and silicon dioxide in order to elucidate optimum conditions for the selective oxygen removal from the silicon surface. Both, the etching temperature and ion bombardment have a pronounced influence on the surface morphology. The conditions yielding a minimum surface roughness will be presented. A careful control of the oxygen impurities of the hydrogen plasma in the range between about 1–3 ppm and 60 ppm allow us to control the degree of anisotropy of etching of patterned silicon wafers.
Reduction of Sidewall Roughness During Dry Etching of SiO2
Authors: Ren F. , Pearton S. J. , Lothian J. R. , Abemathy C. R. , Hobson W. S.
Published: March 2011

The appearance of striations on dry etched semiconductor laser mesas is a common feature of these structures. We describe a number of different methods of reducing the extent of this roughness, including the choice of dielectric etch chemistry, modification of the initial resist processing and deposition of a SiN sidewall to prevent additional rougheningduring the plasma etch step. SF6 is found to be preferable to CF4 for dielectric etching because of an absence of polymer formation. This produces smoother SiO2 sidewalls. Flood exposure of the initial photoresist mask and optimization of the postbake temperature also produces smoomer sidewalls on the subsequently etched SiO2. The sidewall can also be protected from roughening that occurs during the dry etch step by coating it with a low temperature SiN layer. A combination of all of these methods produces sidewalls with morphological variations of ≤500Å.
Vapor Deposition of Parylene Films from Precursors
Authors: You L. , Yang G.-R. , Lang C.-I. , Wu P. , Moore J. A. , McDonald J. F. , Lu T.-M.
Published: March 2011

Parylene films, depending on the type, are thermally stable up to 530°C and have low dielectric constants ranging from 2.35 to 3.15. One of the most interesting properties of this material is its vapor depositability. Conventional vapor deposition involves cracking the parylene dimers at temperatures from 600 to 730 °C and polymerizingthe monomers at - 35 °C to RT. We have developed a simpler and less expensive technique that directly uses the precursors from which the dimers are made. This method requires the use of metal catalysts to produce parylene films. We have used the precursors α,α'-dibromo-p-xylene and dibromotetrafluoro-p-xylene to produce N-type and F-type parylene films. FTIR, XPS, thermal stability, and electrical studies show that the F-type parylene films grown from the precursors are comparable to, or sometimes better than, the films grown from dimer, and have potential microelectronics applications.
Mechanism of Reactive Ion Etching of Polymeric Films in Oxygen-Based Plasmas
Authors: Graham Sandra W. , Steinbrüchel Christoph
Published: March 2011

The etching of polymeric films in O2 plasmas containing small amounts of CF4 has been studied at low pressures (10–60 mtorr) in an RIE reactor. The relationship between etch rate, ion flux, and O atom concentration is investigated for photoresist, polyimide, and amorphous carbon. The applicability of a surface-chemical model proposed by Joubert, et al. (J. Appl. Phys. 65(12) 1989, 5096) is explored. Modifications to the model are made to include physical sputtering and direct reactive ion etching. The modified model provides an improved description of the process, showing the various contributions of the ions and O atoms to the overall etching.
Synthesis, Characterization and Evaluation of Zinc-Amides as Potential Dopant Sources for ZnSe OMVPE
Authors: Rees William S. , Green David M. , Hesse Werner , Anderson Timothy J. , Pathangey Balu
Published: March 2011

Compounds of the general forms Zn[N(R)2]2, Zn(N(R)(R')2] and Zn{[N(R)2][N(R')2]} have been prepared, these new compositions have been characterized by multinuclear NMR, GC/MS, FTIR, elemental analysis and single crystal x-ray diffraction, and they have been evaluated for their potentialto serve as “designer dopants” in the epitaxial growth of p-type ZnSe. Retention of the Zn-N bond during deposition should insure selective location of the nitrogen atom on the native selenium lattice site. Precursor vapor pressures, vapor phase decomposition mechanisms, and thin film properties are presented. Results from materials characterization by XRD, SIMS, PL, Raman and SEM are presented in the context of evaluating dopantlevel.
Low-Temperature Deposition of ZrC thin films from a Single-Source Precursor
Authors: Smith David C. , Rubiano Rodrigo R. , Healy Matthew D. , Springer Robert W.
Published: March 2011

Stable zirconium carbide thin films have been deposited from a singlesource organometallic precursor, tetraneopentyl zirconium, at substrate temperatures above 500 °C. Materials deposited above this temperature are crystalline by X-ray diffraction. A metal to carbon ratioof 1:2 is observed by Auger electron spectroscopy depth profiling. X-ray photoelectron spectroscopy indicates the zirconium is single phase. The observed spectra correspond well to spectra for zirconium carbide standards. Carbon XPS reveals carbidic and graphitic or hydrocarbon species with a third unknown carbon species. Elastic recoil detection finds a large, up to 16%, hydrogen content in the thin film.
The Realization of Molecular Control Over Solid State Structure: Chemical Vapor Deposition of Gallium and Indium Sulfide Films
Authors: Power Michael B. , Macinnes Andrew N. , Hepp Aloysius F. , Barron Andrew R.
Published: March 2011

The chemical vapor deposition of cubic gallium sulfide and tetragonalindium sulfide films is reported. The structure of the deposited films was demonstrated to be defined not solely by thermodynamics, but bythe predesigned molecular motif of the precursor molecules. Analysis of the deposited films has been obtained by transmission electron microscopy (TEM), with associated energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS).
Single Source Precursors for the Growth of Metal-Chalcogenide Thin Films
Authors: Seligson Allen L. , Bonasia Philip J. , Arnold John , Yu Kin-Man , Walker Jim M. , Bourret Edith D.
Published: March 2011

We have recently reported the growth of ZnTe and CdTe thin films from the novel volatile single-source precursors Zn(sitel)2 and Cd(sitel)2 [sitel = TeSi(TeSi(siMe3)3]. In an effort to understand the role played by the bulky substituents, we have prepared a number of related compounds and have investigated their potential for the growth of II-VI materials. We now describe the synthesis and characterization of M[EX(SiMe3)3]2 (M = Zn, Cd, Hg for E = Te, X = C; M = Zn for E = Se, X = C, Si) and their use as precursors molecules for the growth of ZnSe, ZnTe, CdTe and HgTe. The thin films were characterized by Rutherford Back scattering spectrometry (RBS) and X-ray diffraction. Pyrolysis reaction conditions for the alkyl and silyl chalcogenolates are also compared.
Samarium Monosulfide Films Prepared from Organometallic Compounds
Authors: Zavyalova L. V. , Domrachev G. A. , Suvorova O. N. , Shupak E. A. , Svechnikov G. S.
Published: March 2011

The possibility of preparation SmS films by the chemical method from organic compounds has been studied. For this purpose three types of coordinatively-saturated compounds based on dithiocarbamate complexes were synthesized and studied by various methods.
Alkoxide Doping of GaAs During Organometallic Vapor Phase Epitaxy
Authors: Park Y. , Skowronski M. , Rosseel T. M.
Published: March 2011

Doping of GaAs with dimethylaluminum methoxide and its effects have been studied during metalorganic vapor phase epitaxy. Oxygen concentration decreases exponentially with increasing growth temperature and the activation energy equal to 1.8 eV.Increase of oxygen content with decrease of V/III ratio indicates that oxygen most likely occupies arsenic site. Photoluminescence intensity was observed to decrease with increasing oxygen contentand three new deep level luminescence peaks appeared at 75, 96, and 160 meV below the band gap. This, together with the fact that as-grown layers are fully depleted, indicates that oxygen is electrically active in OMVPE GaAs and forms deep non-radiative recombinationcenters.
Visible Light Emission from Porous Silicon Examined by Photoluminescence and Raman Spectroscopy
Authors: Guilinger Terry R. , Kelly Michael J. , Tallant David R. , Redman David A. , Follstaedt David M.
Published: March 2011

We describe the acquisition of Raman and photoluminescence (PL) spectra on porous silicon (PS) samples that emit visible light. Spectra were acquired in both ex situ experiments (after exposure to air) and in situ experiments (with the PS covered either with the hydrofluoric acid electrolyte used in the formation process or water). Our results generally show a correlation of blue-shifted PL with increased oxidation. In one set of ex situ experiments, however, we observed an inconsistency in the shift of the wavelengthof maximum luminescence intensity for PS samples that exhibit oxygenated character in the Raman spectra. A higher anodization current density produced a red shift in the PL spectra in one experiment, while chemical dissolution of the PS by hydrofluoric acid produced the well-known blue shift in the other case. In two in situ experiments, we observed very weak and red-shifted PL for a PS sample immersed in HF (compared to the same sample measured later in air) while in another we immersed air-exposed PS in water and observed a 15-fold increase in PL intensity along with a blue shift in the luminescence maximum.
Luminescence Properties of Porous Silicon
Authors: Peng C. , Tsybeskov L. , Fauchet P. M.
Published: March 2011

We report the results of a systematic study of the influence of the anodization and etching conditions, and chemical and thermal treatments on the properties of light-emitting porous silicon (PSI). PSI layers with stable, high efficiency photoluminescence (PL) tunable from the near infrared to the yellow have been obtained using p-type and n-type substrates. As the temperature drops below 100 K, the as-anodized PSI layers display striking changes in the PL spectra, which are absent in PSI layers that have received a post-growth treatment.