bluuebunny/crossref_metadata_2025 huggingface dataset:
Excimer Laser Deposition of HighlY Oriented PLZT Thin Films
Authors: Petersen G.A. , Zou L.C. , Van Buren W.M. , Boyer L.L. , Mcneil J.R.
Published: March 2011

Laser ablation provides a suitable technique of ferroelectric thin film deposition. We have used this technique to produce films of Pb1−xLax(Zr1−y Tiy)1−x/4O3 (PLZT), a class of ceramic materials which has a wide range of composition dependent electro-optical properties. PLZT films of (7/0/100) and (28/0/100) composition have been deposited onto both crystalline Si <100> and amorphous fused silica substrates. Laser ablation provides high deposition rates and good crystal structure of thin ferroelectric films on silicon. The methods required to achieve proper stoichiometry in the films are also discussed.
Ferroelectric Films-Growth, Properties and Applications
Authors: Francombe M.H. , Krisknaswamy S.V.
Published: March 2011

Thin films of ferroelectric and piezoelectric materials are playing a growing role as critical elements in microwave acoustic devices, infrared imagers, integrated optic circuits, optical displays and high-performance semiconductor memories. In this review, we discuss recent progress in the control of growth, structure and properties of the main candidate materials, such as piezoelectric ZnO and AlN, and ferroelectric PZT-based solid solutions, KNbO3, bismuth titanate (Bi4Ti3O12), LiNbO3, LiTaO3 and KNO3. Brief mention is also made of the role and status ferroelectric polymers and of the BaMF4 class of fluorides. The emphasis of the review is primarily on vacuum-processed films, and optimization of characteristics required for integration into solid-state or semiconductor components.
Study of Diffusion Barriers for PZT Deposited on Si for Non-Volatile Random-Access Memory Technology
Authors: Parikh Nalin R. , Stephen J. Todd , Swanson Max L. , Myers Edward R.
Published: March 2011

Thin film ferroelectric structures are being investigated for use as storage capacitors for Non-volatile Random-Access Memories. To integrate ferroelectrics with standard silicon semiconductor processing, a great deal of effort must be spent identifying compatible materials. These materials must be able to withstand both ferroelectric and silicon processing steps involving different temperatures and environments.

In this paper we have used Rutherford backscattering spectrometry (RBS) to study the diffusion of ferroelectric Pb(Zr.5Ti.5)O3 elements into thin films of TiOx, TiNx, ZrNx and ZrOx deposited onto thermally grown SiO2. The sample matrix was annealed at various temperatures in argon ambient and analyzed using 2 MeV He+. Diffusion profiles (concentration vs. depth profiles) of the ferroelectric constituents were determined for the different barrier films. Results indicated that ZrN is the most promising barrier layer so far, having shown the least interdiffusion at 700°C.
Characterization of Lead Zirconate Titanate (PZT) - Indium Tin Oxide (ITO) Thin Film Interface
Authors: Sreenivas K. , Sayer M. , Laursen T. , Whitton J. L. , Pascual R. , Johnson D. J. , Amm D. T. , Sproule G. I. , Mitchell D. F. , Graham M. J. , Gujrathi S. C. , Oxorn K.
Published: March 2011

The interface between ultrathin sputtered lead zirconate titanate (PZT) films and a conductive electrode (indium tin oxide-ITO) is investigated. Structural and compositional changes at the PZT-ITO interface have been examined by surface analysis and depth profiling techniques of glancing angle X-ray diffraction, Rutherford backscattering (RBS), SIMS, Auger electron spectroscopy (AES), and elastic recoil detection analysis (ERDA). Studies indicate significant interdiffusion of lead into the underlying ITO layer and glass substrate with a large amount of residual stress at the interface. Influence of such compositional deviations at the interface is correlated to an observed thickness dependence in the dielectric properties of PZT films.
Processing of Stoichiometric and Ti Doped LiNbO3 Films with Preferred Orientation from Metal Alkoxides
Authors: Hirano S. , Kikuta K. , Kato K.
Published: March 2011

Stoichiometric and Ti-doped LiNbO3 films could be synthesized by the organometallic route. The films were epitaxially crystallized at temperatures around 400°C on sapphire substrates. The reaction control of alkoxides in solvent was found to be very critical for adjusting the stoichiometry and the low temperature crystallization, as well as the crystallization in water vapor stream.
Characteristics of Metal/PZT/p—Si MIS Capacitors
Authors: Kalkur T.S. , Argos George , Kammerdiner Lee
Published: March 2011

Lead Zirconate Titanate (PZT) thin films have been sputter deposited on p–Si. The patterned PZT films were annealed in a furnace as well as in a rapid thermal annealer. The high frequency characterization of metal–PZT– p– Si capacitors show good Capacitance–Voltage characteristics. The effective dielectric constant of PZT on Si was found to be very low and depends on the thickness of the PZT film and the annealing conditions. The high frequency C–V shows hysteresis which is due to the injection of charges across the interface.
Crystalline BaTiO3 Thin Film Prepared from Ti Metal by Hydrothermal-Electrochemical Method
Authors: Ishizawa Nobuo , Yoo Seung-Eul , Hayashi Motoo , Yoshimura Masahiro
Published: March 2011

Thin film of crystalline barium titanate, BaTiO3, has been prepared from Ti metal at 100–200°C by a new technique called “hydrothermal-electrochemical method” which could be categorized into a variety of the extended hydrothermal method. The reaction was carried out in an electrolytic cell containing 0.1–0.5N Ba(OH)2 aqueous solutions at temperatures of 100–200°C and under saturated vapor pressures. Titanium metal substrate or Ti-deposited glass substrate was used for the anode and a Pt plate for the cathode. Between the electrodes, a constant current density up to 100 mA/cm2 was applied galvanostatically for 10–80 min. Surface of the BaTiO3 film was lustrous and free from any visible defects. Thickness of the BaTiO3 films ranged from 70nm to 300nm. The adhesion between the film and substrate was so strong that no exfoliation was observed. Similar BaTiO3 thin films with thickness less than 70 nm were also formed even in simple hydrothermal conditions without applying any electric current.
High-Speed Epitaxy Using Supersonic Molecular Jets
Authors: Eres Djula
Published: March 2011

This paper discusses the use of supersonic jets of gaseous source molecules in thin film growth. Molecular jets in free form with no skimmers or collimators in the nozzle-substrate path were used in the investigation of basic film growth processes and in practical film growth applications. The Ge growth rates were found to depend linearly on the digermane jet intensity. Furthermore, the film thickness distributions showed excellent agreement with the distribution of digermane molecules in the jet. High epitaxial Ge growth rates were achieved on GaAs (100) substrates by utilizing high-intensity pulsed jets. The practical advantages and limitations of this film growth technique are evaluated, based on the results of microstructural and electrical measurements of heteroepitaxial Ge films on GaAs (100) substrates.
Surface Processes which Control the Deposition and Etching in the Sih4/H2/Si(S)-Glow Discharge System: The Competition Between Atoms, Ions and Electronics
Authors: Vepřek Stan , Ratz Günter , Meindl Klaus , Möler Wolfhard
Published: March 2011

Depending on the glow discharge conditions, silicon can be either deposited or etched in the SiH4/H2/Si(s)-system. At floating potential and close to the Partial Chemical Equilibrium (PCE), the etching<--> deposition process is controlled by the temperature of the sample which, in turn, determines the local departure of the system from the PCE. At a constant temperature and under PCE-conditions, low energy ion and electron bombardment of the surface promotes the deposition and etching, respectively. At ion energies above the threshold for displacement damage, decrease of the deposition and etch yield is observed. A possible mechanistic explanation is suggested.
Oxygen Bubble Formation and Transformation During High-Dose Oxygen Implantation and Annealing of Silicon
Authors: Krause S. J. , Seraphin S. , Chen B. L. , Cordts B. , Roitman P.
Published: March 2011

The formation of bubbles during high dose implantation of oxygen into silicon, and the subsequent transformation of the bubbles during annealing, were studied with transmission electron microscopy (TEM). There was a threshold for bubble formation at a minimum dose of 0.3 × 1018 oxygen/cm2 and a lower temperature of 550°C. As dose increased the bubbles grew larger and the bubble trails lengthened. However, increasing beam current by a factor of 10 or increasing temperature to 700°C did not affect bubble formation. Bubble evolution during intermediate temperature annealing was also studied using TEM techniques. For 2 hour anneals between 1000 and 1100°C the oxygen bubbles transform into SiO2 particles by first forming a “shell” of SiO2, which then facets, grows inward, and finally completely transforms the bubble into an oxide particle. At temperatures greater than 1100°C the oxide particles dissolve by outdiffusion of the oxygen to the wafer surface.
Anisotropic Etching of Heavily Doped Polysilicon by a Hot Cl2 Molecular Beam
Authors: Ono T. , Hiraoka S. , Suzuki K.
Published: March 2011

Anisotropic etching of n+ poly-Si is achieved using a hot Cl2 molecular beam and a sidewall protection technique. A hot molecular beam is produced by a free jet expansion of a gas heated in a furnace. A nitrogen radical beam is used to prevent the sidewall etching. The etch rate of n+ poly-Si is 4.3 nm/min at the anisotropic etching condition.
Defect Reduction and Defect Engineering in Silicon-on-Sapphire Material Using Ge Implantation
Authors: Namavar F. , Cortesi E. , Kalkhoran N. M. , Manke J. M. , Buchanan B. L.
Published: March 2011

Substantial reduction of defect density in silicon-on-sapphire (SOS) material is required to broaden its range of applications to include CMOS and bipolar devices. In recent years, solid phase epitaxy and regrowth (SPEAR) and double solid phase epitaxy (DSPE) processes were applied to SOS to reduce the density of defects in the silicon. These methods result in improved carrier mobilities, but also in increased leakage current, even before irradiation. In a radiation environment, this material has a large increase in radiation induced back channel leakage current as compared to standard wafers. In other words, the radiation hardness quality of the SOS declines when the crystalline quality of the Si near the sapphire interface is improved.

In this paper, we will demonstrate that Ge implantation, rather than Si implantation normally employed in DSPE and SPEAR processes, is an efficient and more effective way to reduce the density of defects near the surface silicon region without improving the Si/sapphire interface region. Ge implantation may be used to engineer defects in the Si/sapphire interface region to eliminate back channel leakage problems.
Radiation Induced Grain Growth in Transition Metals
Authors: Børgesen P. , Lilienfeld D. A. , Msaad H.
Published: March 2011

Nanocrystalline self supporting thin films of Ni, Co, Cr, V, and Ti were irradiated with 600 keV Xe ions at liquid nitrogen temperature and the resulting grain growth was measured by transmission electron microscopy. Average grain sizes were seen to increase from about 10 nm to 18–35 nm, depending on the metal. Systematic variations did not support current thermal spike models.
Laser-Induced Growth of In-Sb-Se Thin Films
Authors: Kolev K. , Laude L. D.
Published: March 2011

Three-elements (In-Sb-Se) alloy thin films are synthesized by laser irradiation of multi-layered films. Optical characterization of the films is performed function of laser fluence which helps defining optimized conditions for the production of good quality, homogeneous alloy films. Such films exhibit particularly high reflectiviy contrast (4:1) for the alloy SeSb2 25 In1.75·.
An In-Situ Study of Laser-Induced Plume Radiance and Thermal Effects of Laser Irradiated Polycarbonate and Poly(Methyl Methacrylate) Samples
Authors: Yip Pearl W.
Published: March 2011

Threats of lasers to human eyes and electro-optics on the modern battlefield has been significantly increased due to the rapid growth of laser technology in military applications. Currently polycarbonate (PC) and poly [methyl methacrylate] (PMMA) are being used as transparencies for aircraft and goggle materials for aircrews and combat soldiers [Ref 1,2]. A carefully monitored laser test was conducted on these two particular polymers using a medium-power, continuous-wave CO2 laser to determine the brightness of the laser-induced plume radiance and how much luminance was transmitted to the back of the sample. Plume luminance for photopic (daytime) and scotopic (nighttime) visual conditions, as well as the recovery times for human eyes exposed to these levels of luminance were calculated. Our test results demonstrated that the plume induced by the CW CO2 laser irradiation can be an ocular hazard to soldiers operating behind these conventional transparent materials.
Thermocapillary Effects in Laser Direct-Write Metallization
Authors: Price Peter E. , Stuke Michael , Jensen Klavs F.
Published: March 2011

A model describing melting and thermocapillary (or Marangoni) flow in laser irradiated thin films is presented. The free surface formulation leads to predictions of surface profiles that are in qualitative agreement with experimental observations. Additional experimental results for direct-writing of palladium from palladium acetate films demonstrate the influence of thermocapillary effects on the dynamics of the process.
Photo-Induced Reversible Modification of II-VI Semiconductor Surface Composition and Structure
Authors: Brewer P. D. , Zinck J. J. , Olson G. L.
Published: March 2011

It is shown that the composition and structure of CdTe and CdS surfaces can be reversibly controlled by excimer laser irradiation at fluences below the melting threshold. The removal rate is observed to depend exponentially on laser fluence up to the melting threshold. The translational energies of products desorbed from laser-irradiated CdTe surfaces were determined using time-of-flight spectrometry and are well-described by a Maxwellian velocity distribution. The dynamics of the photo-stimulated desorption process are correlated with the laser-induced changes in composition, and it is shown that the data are consistent with a thermal mechanism for desorption. A model is introduced which describes the reversible, fluence-dependent changes in composition and structure in terms of the kinetic competition between formation and desorption processes at the semiconductor surface.
Strain Modification and Thermal Stability of SixGe1−x Films Grown by Ion-Assisted Molecular Beam Epitaxy
Authors: Tsai C. J. , Atwater H. A. , Vreeland T.
Published: March 2011

Significant changes in strain are produced in SixGe1−x epitaxial films grown on Si and Ge (001) substrates as a result of low energy ion beam assisted molecular beam epitaxy (IAMBE). Films grown with concurrent Ar+ or Xe+ ion bombardment are coherent and uniformly strained in the growth direction by up to 1.5% in Ge films and 0.5% in Si films and contain no dislocations. The dependence of the films strain perpendicular to the growth surface on ion-atom flux ratio, and ion energy can be explained by the injection of uniformly distributed point defects. Post-growth isochronal annealing of SixGe1−x films suggests that the existing defects in the IAMBE films are defect complexes and that the strain relaxation path is determined by the overall thermodynamic driving force toward the strain-relieved state.
Atomic Absorption Spectroscopy: An In Situ Diagnostic for Sputter Deposition of Y-Ba-Cu-Oxide
Authors: Metzger G. , Blair A. J. , Fleddermann C. B.
Published: March 2011

Atomic absorption spectroscopy (AAS) has been used as an in situ diagnostic tool to study sputtering of high-temperature superconductors. Hollow-cathode lamps were used as line sources to measure relative atomic species concentrations during sputtering of Y-Ba-Cu-oxide targets using a Kaufman ion gun. The AAS measurements showed that the fluxes of ground state Ba and Cu ejected from a composite target during argon- and oxygen-ion bombardment varied greatly with sputtering parameters. Measurements were made of the effects of changes in ion-beam energy, ion flux to the target, and target temperature. In addition, the variation in atomic densities of Ba and Cu with distance from the target were measured. For comparison, AAS measurements during argon- and oxygen-ion sputtering of a pure copper target were also performed. The AAS results were verified by measuring stoichiometry variations of thin films deposited under identical conditions.
Scanning Tunneling Microscopic Study of the Growth Process in Photochemical Vapor Deposition of Aluminum Film
Authors: Hanabusa Mitsugu , Sahara Kouji
Published: March 2011

Aluminum thin films were photodeposited on silicon wafer from dimethyl-aluminum hydride under illumination of the ultraviolet photons generated by a deuterium lamp with a distinguished wavelength dependence. Namely, the growth rates increase linearly with vapor pressure under illumination of the l60-nm vacuum ultraviolet band from the lamp, while the growth starts above 0.3 mTorr only with the 240-nm band. To study the early stage of photo-deposition of Al, we constructed a scanning tunneling microscope and observed Al, islands. Steep sides were observed on islands with the distinguished boundary between vertical and horizontal growth. The shape of islands formed in the illuminated region and in the dark area was identical, thus indicating the absence of photo-induced migration effects.
Use of Ion Scattering Spectroscopy to Monitor the Nb target Nitridation during Reactive Sputtering
Authors: Lichtenwalner D. J. , Anderson A. C. , Rudman D. A.
Published: March 2011

Ion scattering spectroscopy (ISS) has been used to directly monitor the nitrogen coverage of a niobium target during ion-beam reactive sputtering. This measurement shows that the fully reacted target is nearly completely covered with nitrogen. The functional dependence of the nitrogen coverage on the N2pressure has also been obtained. By taking the fractional target coverage to be a steady-state equilibrium between nitrogen sputter removal and thermal N2arrival, the measured target coverage has been accurately modeled. The results indicate that the nitridation reaction is controlled by the thermal N2molecules, which stick to the target with a high probability. This firmly establishes the fact that the molecular N2flux can control the target reaction. This target coverage model has also been applied to fit the measured deposition rate as a function of the N2pressure and shows that the deposition rate does not accurately reflect the target coverage. By modifying an existing reactive sputtering model, we show that the deposition rate can be modeled accurately by taking into account both the gettering reaction at the growing film and the target reaction.
Secondary Electron Emission Spectroscopy of Crystalline and Non-Crystalline Carbon Allotropes
Authors: Hoffman Alon , Prawer Steven
Published: March 2011

The Secondary Electron Emission (SEE) spectra of type Ha diamond, highly oriented pyrolytic graphite (HOPG), amorphous carbon (e-beam evaporated), glassy carbon and amorphic-diamond (filtered arc evaporated) were measured in the 0–80 eV electron kinetic energy range, and found to be very distinctive for the different carbon allotropcs. The sensitivity of SEE spectroscopy to crystal damage for the type Ha diamond surface was studied by performing SEE measurements as function of 1 keV argon ion irradiation dose. Two examples of the use of SEE in the characterization of diamond surfaces are presented. In the first, the crystalline quality of the back and front surfaces of a chemically vapour deposited diamond thin film which had dclaminated from a fused quartz substrate were compared using SEE and, in the second, SEE was used to provide a qualitative estimate of the damage induced by mechanical polishing of a natural diamond surface.
Evolution of Semiconductor Thin Film and Surface Microstructure During Ion Bombardment
Authors: Atwater H. A.
Published: March 2011

Defects created by ion irradiation can enable new modes of microstructural development at interfaces and surfaces in semiconductor thin films. Two examples are described. First, novel kinetic paths for microstructural evolution via MeV ion beam modification of amorphous-crystal interface motion in Si are discussed. At intermediate temperatures, amorphous layer formation is initiated at interfaces such as surfaces and grain boundaries in polycrystalline Si. Irradiation at higher temperatures during the early stages of Si crystallization leads to a significant enhancement of the crystal nucleation rate, while nearly complete suppression of crystal nucleation during crystal growth can be achieved by a cyclic irradiation-induced amorphization and thermal growth process. Second, a new development in misfit strain accommodation in epitaxial semiconductor films is described in which ion-induced injection of point defect complexes can produce coherent, uniformly strained epitaxial thin films. Measurement of strain in epitaxial films can be used to distinguish between surface and sub-surface atomic displacements generated by a low energy ion beam.
In Situ Stress Measurements during the reaction of WF6 with Si(100)
Authors: Leusink G. J. , Heerkens C. Th. H. , Janssen G. C. A. M. , Radelaar S.
Published: March 2011

We present measurements on the intrinsic stress developing during chemical vapour deposition of W and WSi2 from the reaction between WF6 and Si (100). It will be shown that depending on temperature and WF6 partial pressure, three growth modes, corresponding with three different stress developments, can be distinguished. The results can be explained with three basic processes. The intrinsic tensile stress during the deposition of self limited W can be as high as 2 GPa.
Intrinsic Growth Stress in Thermally Grown and Annealed SiO2 Thin Films: Control of Stress-Induced Electronically Active Defects at Si/SiO2 Interfaces
Authors: Bjorkman C. H. , Lee D. R. , Lucovsky G.
Published: March 2011

We find that the density of electronically active defect states, formed close to the Si/SiO2 interface during high temperature oxidation (Tox > 800°C), is proportional to the thickness-averaged stress or strain in the oxide layer. This was established by measuring the midgap interface state density, Dit, and correlating it with: i) a direct measurement of the stress, using a beam deflection technique; and ii) a determination of the oxide strain, using infrared (IR) spectroscopy and a model that relates the frequency of the Si-O bond-stretching vibration to the microscopic strain in the oxide.In addition, the elastic stress at the Si/SiO2 interface has been modified by film deposition onto the SiO2 surface of Si:3N4 film or a variable thickness of an Al gate metal. The additional elastic stress introduced by these depositions did not influence Dit. These observations lead us to conclude that interface traps are generated by “local plastic deformations” that occur during the oxidation process, and are localized in the immediate vicinity of the Si/SiO2 interface.
Electroless Deposition and Characterization of Pd Thin Films on Hydrogenated Amorphous Silicon
Authors: Chou M. L. , Manning N. , Chen Haydn
Published: March 2011

Electroless palladium thin films have been successfully deposited on hydrogenated amorphous Si from a palladium-ammine bath. The d.c. magnetron reactive sputtered 18% hydrogenated amorphous silicon (a-Si:H) possessed a hydrogen passivated surface, using an activation step prior to the electroless deposition to obtain a film with good uniformity. The specially prepared hypophosphite-based dilute metal ion bath exhibited good stability at low operating temperatures of 35–50 °C. The morphology and microstructure of the Pd aggregates were characterized by scanning transmission electron microscopy (STEM) and energy dispersive x-ray spectroscopy (EDX), while the Pd aggregates and as-deposited films from the citrate and NH3/NH4Cl baths were examined by scanning electron microscopy (SEM). Marked differences in morphology and distribution of the Pd aggregates on activated a-Si:H and c-Si substrates were observed and discussed. The as-deposited films with higher coverage from the NH3/NH4Cl bath were typically more uniform and crack-free, while those from the citrate bath suffered from incorporated hydrogen, resulting in bare spots, microcracks and local a-Si film peeling. Auger Electron Spectroscopy (AES) revealed a higher amount of co-deposited phosphorus in NH3/NH4Cl bath films than citrate bath films.
Microscopic Determination of Stress Distribution in Gaas Grown at Low Temperature on GaAs (100)
Authors: Liliental-Weber Zuzanna , Ishikawa A. , Teriauchi M. , Tanaka M.
Published: March 2011

A microscopic strain distribution across commensurate interfaces between GaAs layers grown on semi-insulating GaAs substrates was observed by means of convergent beam electron diffraction (CBED) and large angle convergent beam methods (LACBED). Strain relaxation at a specific distance from the interface was observed in these layers without formation of misfit dislocations. It was proposed that specific point defects distributed close to the interface can explain the asymmetric broadening of high-order Laue zone (HOLZ) lines in the CBED patterns.
Reflection Electron Diffraction and Structural Behavior of GaAs/GaAs (111)B Grown Via MBE
Authors: Rajkumar K. C. , Chen P. , Madhukar A.
Published: March 2011

Homoepitaxy on the {1ll} face of GaAs has been long known to give films with surfaces marred with macroscopic features. We have identified this problem to be tied to the surface phase regime. We have used Reflection High Energy Electron Diffraction (RHEED) to identify a phase regime wherein specular-surfaced GaAs films can be grown. We have found that it is possible to glean information regarding the macroscopic surface morphology by monitoring the variation in the RHEED specular spot intensity during growth. This has allowed in situ monitoring of the macroscopic surface morphology of a growing film in real time which has made it possible to grow specular-surfaced films reproducibly.
X-Ray Diffraction Study of Cubic Boron Nitride Grown Epitaxially on Silicon
Authors: Doll G. L. , Sell J. A. , Wims A. , Taylor C. A. , Clarke R.
Published: March 2011

We report the growth of boron nitride films on (001), (110), and (111) faces of silicon using the method of pulsed excimer laser ablation. The structure of the Alms grown on the (001) and (110) orientations of Si is cubic zincblende with a lattice constant of 3.619 Å. The films were found to be heteroepitaxial on silicon (001) with the cubic BN (100) axes parallel to Si (100), as characterized by x-ray diffraction and high-resolution transmission electron microscopy. In that system, we find evidence for an unusual 3:2 commensurate lattice matching. The films appear to cubic but randomly oriented on the Si (110), and no evidence for crystallinity is found for films grown on Si (111).
The Creation of Misfit Dislocations; A Study of InGaAs Alloys on GaAs Substrates
Authors: Goodhew Peter J , Kightley Philip
Published: March 2011

Growth onto vicinal substrates causes 60° misfit dislocations to adopt line directions away from <110> in order for them to maintain their presence within the substrate to strained layer interface. Observations show that for the growth of an on-axis [001]wafer the dislocations have a line direction, within measurement error, exactly [110] or [-110] and two sets of orthogonal dislocations are generated. When grown onto a wafer that is cut off-axis toward [010] four sets of dislocations are generated. The two sets of dislocations in each direction converge to form low angle intersections from which edge dislocations are formed. These edge dislocations can become very long by the glide out of the interface plane of the component 60° dislocations. This ‘zipping-up’ to form the edge components only occurs in one direction from the low angle point of intersection and the edge segments are exclusively generated in the buffer layer. Their density and penetration are a function of thickness and composition of the mismatched epilayer. The mechanisms by which the dislocations adopt line directions away from <110> and why they zip-up from the intersection in only one direction are discussed.
Initial Stages of Molecular Beam Epitaxical Growth of Highly Strained Inxga1-XAs on Gaas (100)
Authors: Guha S. , Madhukar A. , Kapre R. , Rajkumar K. C.
Published: March 2011

We have studied the initial stages of highly mismatched InxGa1-x As growth on GaAs (100) by transmission electron microscopy (TEM). We find direct evidence of (i) deformation in the substrate below each island to depths of about 150 A and (ii) strain relief in the islands at their lateral edges. Growth morphology as a function of growth temperature is studied and it is found that the tendency for islanding for x as high as 0.5 can be supressed to a large extent by a reduction in the growth temperature. We also present results of correlation between TEM determined different growth morphologies (brought about by different growth temperatures ) and the electrical characteristics of AlAs/InxGa1-xAs resonant tunneling diode structures grown on GaAs (100).
Molecular Dynamics Study of Pb Overlayer on Cu(100)
Authors: Karimi M. , Tibbits P. , Ila D. , Dalins I. , Vidali G.
Published: March 2011

Isothermal-isobaric Molecular Dynamics (MD) simulation of a submonolayer Pb film in c(2×2) ordered structure adsorbed on a Cu(100) substrate showed retention of order to high T. The Embedded Atom Method (EAM) calculated the energy of atoms of overlayer and substrate. The time-averaged squared modulus of the two dimensional structure factor for the Pb overlayer measured the order of the overlayer. The results are for increasing T only, and require verification by simulated cooling.
Elastic Energies of Coherent Germanium Islands on Silicon
Authors: Vanderbilt David , Wickham L. K.
Published: March 2011

Motivated by recent observations of coherent Ge island formation during growth of Ge on Si (100), we have carried out a theoretical study of the elastic energies associated with the evolution of a uniform strained overlayer as it segregates into coherent islands. In the context of a two-dimensional model, we have explored the conditions under which coherent islands may be energetically favored over both uniform epitaxial films and dislocated islands. We find that if the interface energy (for dislocated islands) is more than about 15% of the surface energy, then there is a range of island sizes for which the coherent island structure is preferred.
Effect of Nonhydrostatic Stress on Crystal Growth Kinetics
Authors: Aziz Michael J. , Sabin Paul C. , Lu Guo-Quan
Published: March 2011

The effect of nonhydrostatic stresses on the solid phase epitaxial growth rate of crystalline Si(100) into self-implanted amorphous surface layers has been measured. Uniaxial stresses of up to 6 kbar (0.6 GPa) were attained by bending wafers over SiO2 rods and annealing at a temperature too low for plastic deformation to relieve the stress in the crystal, but high enough for solid phase epitaxial growth to proceed. The growth rate on the tensile side was greater than that on the compressive side of the wafer, in marked contrast to the enhancement observed from hydrostatic pressure. The phenomenology of an “activation strain”, the nonhydrostatic analogue of the activation volume, has been developed to characterize the results. Combined with the measurement of the activation volume, the measurement reported here permits us to characterize to first order the entire activation strain tensor corresponding to the transition state for solid phase epitaxy of Si(lOO). We conclude that the transition state for this process is “short and fat”; that is, the fluctuation to the transition state involves an expansion in the two in-plane directions and a contraction in the direction normal to the surface large enough to make the overall volume change negative. The symmetry of the measured activation strain tensor is inconsistent with all bulk point defect mechanisms for solid phase epitaxy. The relevance of the activation strain formalism to heteroepitaxy and vapor phase epitaxy is discussed.
Ion Induced Crystallization and Growth of Nanoscale Grains in Ceramics
Authors: Pannikkat A. R. , Børgesen P. , Lilienfeld D. A. , Lappalainen R. , Msaad H. , Raj R.
Published: March 2011

Self supporting thin films of amorphous alumina and zirconia were irradiated with light and heavy ions at various temperatures(25–430°C). Irradiation was found to result in the formation of 10–30 nm large grains well below conventional crystallization temperatures. These grains were quite stable against subsequent thermal growth. Crystallization, grain size, and growth depended on ion species as well as on ‘stabilizing’ additives (yttria or Pt).
Manipulation of Nucleation Sites in Solid-State Crystallization of Amorphous Si Films
Authors: Kumomi Hideya , Yonehara Takao
Published: March 2011

Nucleation sites are manipulated in amorphous Si films to control grain location and the size distribution during the solid-state crystallization. The principle of the method is theoretically investigated. Nucleation is suppressed and the sites are periodically formed in the plane of amorphous films by 2-step Si ion implantation. Thermal annealing causes preferential nucleation of single nuclei at the artificial sites and they grow laterally in the film. Consequently, 3 μm large grains were arranged in a matrix with a narrow size distribution.
Microstructural Evolution of AI/Ni and Ni/AI Bilayer Thin Films
Authors: Barnard J. A. , Haftek E. , Waknis A. , Tan M.
Published: March 2011

The growth and microstructural evolution of Al/Ni and Ni/AI bilayer thin films have been investigated as a function of Al and Ni layer thickness and thermal treatment by transmission electron microscopy. Studies were also made of Al and Ni single layers of varying thickness. All films were grown by dc magnetron sputtering using carbon coated Cu TEM grids as substrates. For the bilayers, the Al thickness was fixed at either 3.5 or 7.0 nm while the Ni thickness was varied systematically from 3.2 to 12.8 nm. Deposition sequence significantly influenced bilayer microstructure even in as-deposited samples. Al/Ni bilayers generally exhibited a finer microstructure than Ni/AI. In the 3.5 nm Al/Ni bilayers no conclusive electron diffraction evidence was found for elemental Al while for the reverse sequence both Al and NiAl3 diffraction rings were found. In the 7.0 nm Al/Ni bilayers diffraction rings due to Al were observed. The reverse sequence again produced both Al and NiAl3 diffraction rings. Interestingly, diffraction rings due to the Ni layers were found for all samples but were consistently measured at positions corresponding to a 2.5–3.5% increase in interplanar spacing. Annealing at 385°C produced evidence for generalized grain growth and strong accentuation of the electron diffraction rings due to the NiAl3 phase. Again, deposition significantly influenced annealed bilayer microstructure. For the Al/Ni sequence annealing produced polycrystalline N1AI3 island-like structures, while for Ni/AI bilayers, annealing promoted the growth of small NiAl3 crystals uniformly distributed in the film.
Characterization of the Structure and Interfaces in Metallic Superlattices
Authors: Kim Jeha , Dutcher John R. , Lee Sukmock , Stegeman George I. , Falco Charles M.
Published: March 2011

Using magnetically enhanced dc-triode sputtering we have grown metallic multilayers of Ag/Pd and Cu/Pd with modulation wavelengths A ranging from 10 Å to 120 Å. The Ag/Pd films were prepared with two different thickness ratios of silver to palladium (1:1 and 3:1) while the Cu/Pd films all were 1:1. We observed in the Ag/Pd films that the variation with A of the (111) lattice spacing dav in the growth direction is less than 0.5%, independent of the composition. However, these films exhibited enhancements in the Rayleigh sound velocity vR of up to 22% for the 1:1 samples and 13% for the 3:1 Ag/Pd samples respectively as A decreased. The Cu/Pd films showed a slight systematic dependence of dav on A, although its variation was only approximately 0.7%. A softening in vR of up to 7% for the Cu/Pd samples was observed.
A Microfabrication Approach to Mechanical Testing of Thin Films
Authors: Read David T.
Published: March 2011

An approach to measuring the mechanical properties of thin films with in—plane and thickness dimensions comparable to those of films in VLSI electronic devices and in multi—chip modules is being developed. The guiding principles are to utilize as much as possible the technology of microelectronic fabrication and to make the design downward—scalable in size so that eventually the very smallest films and structures can be tested. The necessary components have been designed; we are in the process of building and testing them.

The specimen and associated instrumention are fabricated by semiconductor techniques on a 50 mm—diameter silicon wafer. Piezoresistors arranged as strain—sensitive Wheatstone bridges are fabricated by diffusion. One bridge, located on a grip section, is the load cell. After opening contact windows and metallization, the thin—film specimen is deposited. Then the silicon wafer is patterned and etched, leaving the specimen hanging between two instrumented grip sections linked by flexible silicon springs. Relative displacement of the grip sections is imposed by either a micrometer or a micro—stepper motor and measured by a scanned laser beam and by additional strain—sensitive bridges.
Nondestructive Measurement of Interphase Processes Using Impedance Spectroscopy
Authors: Frankovic Richard , Troyk Philip R. , Anderson James E.
Published: March 2011

Impedance spectroscopy (IS) was used as a nondestructive technique to measure the interphase processes of encapsulated microelectronic substrates exposed to high relative humidity. The advantages of IS include: sensitivity of IS to chemical kinetics, ability of in-situ testing of encapsulated packages and non-destructive nature.

Samples undergoing contamination under high relative humidity, produce frequency responses resembling those found for electrochemical cells. This suggests that the presence of hygroscopic residues induce surface water uptake resulting in the formation of surface electrochemical cells and decreased interphase impedance.

Samples undergoing a process of “supercleaning” using argon plasma and exposed to high relative humidity, produce frequency responses that more closely approach responses characteristic of dry samples than do conventionally cleaned or contaminated samples.
Removing the Barriers to Next Generation'S Dielectric Films: In Situ Void-Free Planarized Films
Authors: Monkowski J.R. , Logan M.A. , Wright L.F.
Published: March 2011

In the next generation of semiconductor devices, minimum dimensions will be smaller, aspect ratios (height to width) of devices features will be larger, and BPSG dielectrics will be challenged to deal with these changes. A new process, which integrates deposition, flow, and anneal of BPSG films, and allows void-free filling of high-aspect-ratio trenches with excellent surface planarization, is presented in this paper. Scanning electron micrographs are used to show the extent of film coverage and planarization. Additional characterization includes ion chromatography, ellipsometry, stress measurements, and breakdown field measurements.
Crosslinking and Ciiain-Scission of Photosensitive Polyimidesiloxane Under Deep UV Irradiation
Authors: Jeng S. , Xu M. , Kwok H. S. , Tang D. Y. , Acharya H. R. , Rosenfeld J. C.
Published: March 2011

Polyimides are considered as promising packaging materials in multi-layer interconnections and multi-chip modules because of their low dielectric constant and good planarizability. Photosensitive polyimidesiloxane (SIM2000XL) as a newly emerging polyimide is showing not only similar properties as conventional polyimides but also the advantages of process simplification and improved adhesion. Moreover, it is proposed that SIM2000XL can be an oxygen-plasma etching barrier in multi-level lithographic systems because of its high silicon content.

We characterized the photosensitivity of SIM2000XL thin films under excimer laser (193 nm) exposure. The sensitivity of SIM2000XL was found to be about 20 mJ/cm2. After the SIM2000XL thin films were exposed through a photomask in the contact mode, development gave the usual negative patterns. However, the remained film thickness after exposure reached a maximum of about 65 % of the initial film thickness and decreased with further irradiation. This can be attributed to the competing processes of polymer crosslinkage and chain-scission. This phenomenon is important for applications of polymers in DUV lithography. A detailed study of these two competing processes are presented.
Curing and Alignment of Liquid Crystalline Epoxy Networks
Authors: Ober C. K. , Barclay G. G. , Papathomas K I. , Wang D. W.
Published: March 2011

Liquid crystalline epoxy networks have been prepared from glycidyl terminated polyether oligomers of varying molecular weight. These oligomers were prepared by functionalizing hydroxy terminated oligomers based on 4,4'- dihydroxy-α-methylstilbene and α,ω-dibromoalkanes with glycidyl groups. Curing of these oligomers was carried out either within their nematic mesophase or in their isotropic state. Different thermal properties were observed after curing under these two sets of conditions. Extremely low values of the coefficient of thermal expansion in the range of 15 to 60 ppm/°C were achieved. To produce aligned thermosets, orientation of the liquid crystalline phase was induced during the curing process by a magnetic field. Orientation of these networks was measured by wide angle x-ray diffraction (WAXD).
Characterization of Polymer Dielectrics for High-Density Electronic Packaging
Authors: Wang David W. , Tong Ho-Ming
Published: March 2011

Because of rapid advances in semiconductor technology, polymer dielectrics are finding widespread use in high-density packaging to improve performance and processability. Notable among these materials are polyimides, benzocyclobutene resins, and fluoropolymer containing composites.

Polyimides have been used extensively for chip passivation and first-level packaging. Benzocyclobutenes, processed as conventional thermosets, are being investigated as thin film dielectric for use in multichip modules. A silicon containing derivative can be used as a plasma etch stop. Polytetrafluoroethylene is used either as matrix or reinforcement in circuit boards to produce a low dielectric constant composite.

Knowledge of materials properties is crucial to ensure the reliability and function of products incorporating these polymers. In this article, a few selected characterization techniques for the determination of important materials properties such as solvent diffusion, plasma etch rate, and thermomechanical characteristics will be discussed.
Effects of Processing Conditions on the Material Properties of Polyimide Thin Films
Authors: Pietila Doug , DeBra Lisa , Guan John , Lee Chung
Published: March 2011

The effects of curing rate and solvent content prior to curing were examined for Hitachi PIX L110 polyimide thin films. DMA, TMA, DSC, and wafer bow measurements were used to elucidate in-plane storage modulus, Z-axis CTE, heat capacity, and residual stress dependencies on processing conditions and film position across the wafer. It was found that the residual stress and storage modulus are highly dependent on the processing conditions. Additionally, the heat capacity and storage modulus showed significant dependency on wafer position as well as processing conditions. The Z-axis CTE was found to deviate significantly from values published for the in-plane (xy) direction.
Impedance Spectroscopy of the Polymer Thick Film Resistor/Conductor Interface
Authors: Jussila S. , Stubb H. , Pienimaa S.
Published: March 2011

Impedance spectroscopy has been used to study the electric properties of screen—printed polymer thick film (PTF) resistors over the frequency range 10 Hz — 500 MHz. With a suitable test pattern it was possible to separate the impedance response of the resistor/conductor interface from that of the resistive element itself. This proved to be useful when analysing, whether the manufacturing parameters have more influence on the properties of the interface or the bulk resistor. The main varied manufacturing parameters were curing method, curing temperature and the resistor/conductor interface (pure copper vs. silver treated copper). Furthermore, the test components were kept for 600 hours in a humid environment (85ºC / 85% RH), and after this the impedance measurements were repeated. Analysis of the effects of these manufacturing and environmental conditions on the electrical properties of PTF resistors are presented.
Effect of RF Sputtering on T/H Susceptibility of Cr/Polyimide Adhesion
Authors: Kim D. G. , Oh T. S. , Molis S. , Kowalczyk S. , Kim J.
Published: March 2011

Effects of RF sputtering on the hydrothermal stability of Cr/polyimide interfaceshave been studied using FTIR, XPS, and peel test. It has been found that RF sputter-treatment of polyimnide surface prior to metal deposition leads to an enhancement of adhesion through chemical bonding of the metal with polyimide resulting in cohesive polyimide failure. The RF sputter treatment of polyimide, however, simultaneously modifies the polyimide underneath its surface. The adhesion strength of the Cr/polyimide interfaceis degraded significantly upon exposure to a temperature/humidity (T/H) environment. It is suggested this degradation results from the hydrolysis of polyimide. The hydrolysis is facilitated by the presence of modified unstable polyimide near the interface. This degradation of adhesion strength can be minimized by converting the unstablemodified polyimide to a more stable state by re-curing the Cr/polyimide interfacebefore exposure to T/H environment.
Novel Precursors for the Deposition of II-VI Semiconductor Films
Authors: Bochmann Manfred , Webb Kevin J.
Published: March 2011

Highly sterically hindered chalcogenolato complexes M(EC6H2R3-2,4,6)2 (M = Zn, Cd, Hg; E = S, Se, Te; R = Me, Pri, But) have been prepared. Compounds with R -= But are volatile under reduced pressure and are suitable as precursors for the deposition of II-VI films.
Growth and Characterization of Highly Oxygen-Doped GaAs
Authors: Goorsky M.S. , Kuech T.F. , Mooney P.M. , Cardone F. , Potemski R.M.
Published: March 2011

High levels (≃ 1018cm-3) of oxygen were introduced into GaAs by using dimethyl aluminum methoxide (DMAlM0) as an oxygen-bearing precursor during metalorganic vapor phase epitaxy. Layers co-doped with oxygen and intentionally added silicon, both to concentrations of ≃ 1018 cm-3, were depleted of free carriers and had no measurable luminescence. Deep levels were present in layers grown with lower oxygen incorporation, but the compensation mechanism due to oxygen incorporation is not apparently tied to a specific defect level. The material with the electronic deep levels also possessed deep luminescence energy lines. All layers exhibited excellent surface morphology. For comparison, other layers were grown by introducing low levels of 02 and trimethyl aluminum during GaAs growth. The surface morphology of these layers was usually hazy and the layers did not exhibit the same well defined electrical and optical characteristics as the layers grown with DMAlMO.