bluuebunny/crossref_metadata_2025 huggingface dataset:
Stresses in UHV Planar Magnetron Sputtered Films
Authors: Hudson C , Somekh R. E.
Published: March 2011

A method has been developed to measure the stress in films which have been sputtered using a planar magnetron in a small-scale UHV chamber. The stress has been measured for diffent materials as a function of the sputtering gas pressure P and the substrate-target distance d. It is found that the stress in films of the same material deposited at different values of d is dependent only on the pressure-distance product (Pd), except at short (less than about 30mm) distances. The value of Pd required to produce a stress-free film is found to increase with the more extreme ratios between the atomic masses of the film material and the sputtering gas for the case of metals. However, the required Pd product is higher for the case of amorphous semiconductors. The stress in alloy films is also investigated.
Finite Element Analysis of the Mechanical Performance of Benzocyclobutene Structures in Multichip Modules.
Authors: Shaffer E. O. , Townsend P. H. , Radler M. J. , Carriere C. J.
Published: March 2011

Polymeric materials are used as interlayer dielectrics for multichip modules. One of the central challenges for these structures is management of the large stresses induced by the differences in the thermal properties of the inorganic component structures and the organic film during processing.

Finite clement analysis has been used to model the stresses in the dielectric material in practical structures used in multilayer microelectronic architecture, such as interlayer vias and the associated internal metal patterns. Calculations have been performed on the stress field at the corner of square vias in benzocyclobutcne based interlayer dielectrics and related polymeric materials. The effects of the thermal and mechanical properties of the polymeric coating on the stress fields in metal patterns have been calculated and provide insight for design and process optimization.
Measurement of Residual Stress-Induced Bending Moment of P+ Silicon Films
Authors: Chu W. H. , Mehregany M. , Ning X. , Pirouz P.
Published: March 2011

This paper presents results from measurements of residual stress-induced bending moment of heavily-boron-doped (p+) silicon films. Microfabricated free-standing cantilever beams of p+ silicon were fabricated by using anisotropie etching of (100) silicon wafers in ethylene-diamine and pyrocatechol. The p+ etch stops forming the cantilevers were created by diffusion from a solid source at 1125°C for one and two hour time durations. The nonuniform residual stress distribution through the thickness of the p+ silicon cantilevers resulted in a deflection of the beams. The as-diffused p+ silicon films had a residual stress distribution through the film thickness which resulted in negative bending moments. Thermal oxidation subsequent to the diffusion step modified the residual stresses near the top surface or, perhaps, plastically deformed the near surface region of the p+ thin film. As a result, thermally oxidized p+ silicon films exhibited a positive bending moment. Measurements of the deflection curves of the beams in conjunction with beam theory were used to calculate the residual stress-induced bending moments.
Characterization of Stress and Texture in Rtcvd Poly-Si Layers by X-Ray Diffraction
Authors: Bársony István , Klappe Jos G.E. , Ryan Tom W.
Published: March 2011

The properties of polycrystalline silicon layers deposited by RTCVD have been studied by texture, stress and electrical analyse. The intrinsic layers intended for applications in integrated IC processing are very much textured with the preferred orientation depending on deposition temperature and atmosphere. Very low residual film stress in the order of 10 dyn/cm2 was detected, and a transition from compressive to tensile stress with increasing deposition temperature around 800°C was observed. This was associated with the development of the columnar structure by the (110) orientation becoming dominant at the expense of the (100) texture. Also the effect of post-deposition anneal ambience on the grain structure has been studied. Grain size and grain-boundary trapping in after doped layers have been evaluated in P-implanted RTA activated layers.
Re-Examining the Bulge Test: Methods for Improving Accuracy and Reliability
Authors: Small Martha K. , Vlassak Joost J. , Nix William D.
Published: March 2011

Since its first application to thin films in the 1950's, the bulge test has had a prominent place in the field of thin film mechanical properties. The major appeal of the technique is that it is analogous to the familiar uniaxial tension test, which is commonly applied to bulk materials. At the same time, it avoids the sample tearing and alignment problems associated with micro-tensile tests. Unfortunately, bulge test results have been sometimes controversial and difficult to reproduce. In this paper we address possible causes for mese inconsistencies and describe a method by which the bulge test technique can be made to produce accurate and reliable results.
Mechanical Testing of Bonded Silicon on Insulator Wafers.
Authors: Farrepi S. N. , Roberds B. , Boettcher M. C. , Ismail M. S. , Bower R. W. , Desmond C. A. , Hunt C. E.
Published: March 2011

A series of mechanical tests have been conducted on bonded silicon to silicon (native oxide present only) and oxide to oxide wafers at several times and temperatures. Tensile tests have been designed to evaluate the strength of the bond. Tensile tests have been conducted over the full range of bond strengths ranging from the weak van der Waals forces to the full silicon bonds.
Mechanical Properties of Microsensor Materials: How to Deal with the Process Dependences?
Authors: Senturia Stephen D.
Published: March 2011

Microsensors are measurement devices fabricated using planar integrated circuit technology together with enhancements generically called “micromachining”. It is well known that the thin-film materials used in microelectronics can have properties which differ from their bulk counterparts. In addition, thin-film materials exhibit residual stress, which is known to be strongly process dependent. The sensor designer must understand how the detailed process used to fabricate a particular device impacts the specific mechanical properties, hence, the expected mechanical device performance. This paper illustrates the problem of process-dependent material properties using examples of residual stress of several materials, and then presents an object-oriented material-property database which is being developed as part of a CAD system for microelectromechan-ical systems (MEMCAD).
The Anomalous Behavior of Silicon During Nanoindentation
Authors: Pharr G. M.
Published: March 2011

Two separate phenomena occur during the low-load indentation of silicon which make its behavior distinctly different from that of most materials. First, silicon is one of only a very few materials whose hardness exceeds the pressure needed to transform it to a denser crystalline (or amorphous) form, and because of this, a reversible, pressure-induced phase transformation occurs during indentation. The transformation enhances the electrical conductivity of the material and creates a region around the indenter which flows like a soft metal. Second, silicon cracks when indented by a Berkovich or Vickers indenter at loads of less than 100 mN, i.e., loads typically used in nanoindentation experiments. These two phenomena, which account for a number of unusual features in the indentation load-displacement behavior, are documented and discussed.
Monitoring Time-Dependent Deformation in Small Volumes
Authors: Weihs T P , Pethica J B
Published: March 2011

Time-dependent deformation (TDD) in small volumes was monitored using an alternating (AC) force technique and a Nanoindenter. The AC technique provides a continuous measure of contact stiffness during an indentation. By holding the force constant and monitoring the stiffness, the applied pressure and an effective strain rate were measured. Reasonable strain rate sensitivities were obtained for permanent indentations involving significant plastic strains. Time-dependent recovery due to residual strain energy is also reported. For reversible, elastic indentations, TDD was seen when the applied force was held constant. The deformation is attributed to atomic diffusion.
Scanning Tunneling Microscopy of Nanoindentations
Authors: Castell Martin R. , Weihs Timothy P.
Published: March 2011

A scanning tunneling microscopy (STM) study of low load indentations into Si, GaAs and Au is presented. Compared with standard micrographs obtained through optical microscopy and scanning electron microscopy, the STM images show greatly improved resolution in and around the indentation. The effects of relaxation and pile-up may be observed through contour plots which show inward bowing of the indentation faces in Si.
Microhardness Characterization of 80/20 MOL % TiO2/SiO2 Sol-Gel Films
Authors: Melpolder S. M. , West A. W. , Bauer C. L.
Published: March 2011

Knoop hardness and nanoindentation studies were performed on single and multilayered 80/20 mol % TiO2/SiO2 films spin-coated onto [100] silicon wafers. The Knoop microhardness results indicated that a total sol-gel thickness (h) to indentation depth (h*) ratio of >2 was sufficient to obtain reliable thin film properties independent of substrate influence. Electron microscopy techniques were used to determine the sample's absolute film thickness, to examine the morphology of the indentations, and to determine the phase of the sol-gel thin films.
The Roles of Stress, Geometry and Orientation on Misfit Dislocations Kinetics and Energetics in Epitaxial Strained Layers.
Authors: Hull R. , Bean J. C. , Ross F. , Bahnck D. , Pencolas L. J.
Published: March 2011

The geometries, microstructures, energetics and kinetics of misfit dislocations as functions of surface orientation and the magnitude of strain/stress are investigated experimentally and theoretically. Examples are drawn from (100), (110) and (111) surfaces and from the GexSi1–x/Si and InxGa1–x/GaAs systems. It is shown that the misfit dislocation geometries and microstructures at lattice mismatch stresses < - 1GPa may in general be predicted by operation of the minimum magnitude Burgers vector slipping on the widest spaced planes. At stresses of the order several GPa, however, new dislocation systems may become operative with either modified Burgers vectors or slip systems. Dissociation of totál misfit dislocations into partial dislocations is found to play a crucial role in strain relaxation, on surfaces other than (100) under compressive stress.
In Situ Deformation Studies of Fe/Al and Fe/Si Multi-Layered Films Prepared by Ion Beam Sputtering
Authors: Kubota K. , Naoe M.
Published: March 2011

In situ deformation measurements of Fe/Al and Fe/Si multi-layered films on thin substrates were made by detecting the curvature of substrates during deposition. The deformation inside of Fe layers corresponding to the compressive and tensile stresses was detected for the Fe/Al and Fe/Si multi-layered films, respectively. For the Fe/Si multi-layered films, the internal stress in Fe layers became from tensile to compressive during deposition under bombardment of Ar Jons. These stresses in Fe layer were closely related to the soft magnetic properties of these multi-layered films. In situ deformation studies may be useful to make sure the effect of internal stress on the magnetic properties of these multi-layered films.
Yield Strength Enhancement in Multilayer Thin Films by Modulus Hardening
Authors: Krzanowski James E.
Published: March 2011

The modulus hardening mechanism for yield strength enhancement in multilayer materials is theoretically investigated. The multilayer composition profile used in the analysis has a general trapezoidal shape with allowance for two different layer thicknesses and two interface widths. The image force method is used to determine effective stresses on dislocations in the multilayer structure. Analytical expressions are derived for the effective stresses in terms of the shear elastic moduli. Calculations are carried out for representative composition profile shapes. It is found that the dislocation experiences the maximum effective stress when it is in the interface between layers, and that the effective stress increases dramatically with decreasing interface width. However, the effective stress is not strongly affected by either the multilayer wavelength or the relative thickness of the layers.
Using Weibull Statistics to Analyze Ion Beam Enhanced Adhesion as Measured by the pull Test
Authors: Pawel J. E. , Lever W. E. , Downing D. J. , Mchargue C. J. , Romana L. J. , Wert J. J.
Published: March 2011

The adhesion of iron films to single crystal Al2O3 substrates was investigated using a pull test. Chromium (300 keV) or nickel (340 keV) ions were implanted to a fluence of 1 × 1015 ions-cm-2 after film deposition. The adhesion test results were widely scattered due to a random distribution of interfacial flaw sizes controlling the failure nucleation. Because Weibull statistics were developed to describe the failure probability due to a population of flaw-initiated cracks, the Weibull distribution was chosen to analyze the data. Modifications in the adhesion strength due to the ion implantation were reflected in the failure distributions. It was found that the chromium ions improved the adhesion of the Fe/Al2O3 system while the implantation of nickel did not.
Tribological Propertees of Carbon thin Films Prepared by Plasma-Free Sputtering Method
Authors: Hirata T. , Naoe M.
Published: March 2011

Amorphous “Diamond-like” carbon films were deposited on plasma-free substrates at low temperature by the Facing Targets Sputtering (FTS) method. Tribological characteristics determined by tap, scratch and slide tests were much better than those for amorphous carbon films deposited by the conventional Magnetron Sputtering (MS) method. Consequently, these films deposited by the FTS method were surely useful for protective layers in rigid magnetic disk.
Microstructure and Tribological Properties OF Co-Cr thin Films Deposited by Facing Targets Sputtering and Magnetron Sputtering Methods
Authors: Kadokura Sadao , Naoe Masahiko
Published: March 2011

The tribological properties and the slid surface profiles of Co-Cr thin films deposited by Facing Targets sputtering and Magnetron sputtering methods were investigated in regard to the durability of flexible disks. Co-Cr thin films with columnless microstructure and homogeneously packed particles were much tougher than ones with columnar microstructure for tribological test. The Co-Cr films deposited by conventional Magnetron sputtering method revealed typically columnar structure, while ones deposited by Facing Target sputtering method did columnless microstructure. This indicates probably homogeneous distribution of strong bonding forces between grain boundaries throughout the films, because no brittle fracture was observed even after the delamination between a plastic substrate and the CoOx/ Co-Cr / Ni-Fe triple layers took place by application of excess stresses. It was found that difference in morphology of Co-Cr thin film between Facing Target sputtering and conventional Magnetron sputtering methods was much significant.
Effeci of Stresses on Void Nucleation During Electromigration
Authors: Brotzen F. R. , Rosenmayer C. T. , Dunn C. F. , McPherson J. W.
Published: March 2011

Based on experimental findings obtained earlier by the authors [1], a model is devised in which the divergence of the vacancy flow created in the grain boundaries of Al-Si(1%) metallizations by high-density DC is attributed to temperature gradients and structural features. Void nuclei of critical size are created in areas of high vacancy concentration. These nuclei grow, fed by the electromigrational vacancy current. It is shown that stresses have only a negligible' effect on the vacancy diffusion but influence the nucleation process dramatically. Results expressed in terms of fraction of void area are calculated and then correlated with experimental results. Certain material parameters, whose values are not known, are derived from the experimental data. The physical significance of these parameters is discussed.
Thermal Stress Induced Void Formation in Narrow Passivated Cu Lines
Authors: Brown D. D. , Børgesen P. , Lilienfeld D. A. , Korhonen M. A. , Li C.-Y.
Published: March 2011

0.75–3 μm wide copper lines encased in a thin adhesion layer of Al or Cr were passivated at 300°C and annealed at 400°C. The passivation was then removed and the lines examined in a scanning electron microscope. The development of thermal stress induced voiding was found to depend primarily on aging conditions and adhesion.
Dielectric Loss in Li- and Na-Swept α-Quartz and the Effect of Irradiation
Authors: Toulouse J. , Nowick A.S.
Published: March 2011

Alkali ions, which compensate for substitional Al3+, play an important role in the frequency stability of α-quartz crystals. In this work, low temperature dielectricloss measurements (between 2.9 and 300 K) are carried out on crystals that have been “swept” so as to introduce either Li+ or Na+. High quality synthetic crystals as well as natural crystals are employed. The well known loss peaks due to Al-Na pairs are further explored and similar peaks due to Al-Li are sought after but not found. It is concluded that the Al-Li pair is oriented along the C2 -axis of the A104 distorted tetrahedron. After irradiation, large peaks are observed at very low temperatures both in Li+- and Na+-containing crystals. These peaks, which are distorted below ∼6 K due to the onset of quantum effects, may originate in alkali centers produced when alkali ions are liberated by the irradiation.
Order and Disorder in the Oxygen-Deficient Fluorite-Related Oxides
Authors: Eyring Leroy
Published: March 2011

The fluorite-related oxides have many uses in applied materials science and they present an excellent subject for study in solid state science. They exhibit examples of nonstoichiometric phases of wide composition range and series of ordered intermediate phases. Some details of the ordering of oxygen vacancies in the nonstoichiometric fluorite-related phases of the rare earth oxides are presented, including imaging of the process at high resolution in the electron microscope. Other highresolution studies of the ordered intermediate phases have revealed the structural principles that relate members of the homologous series RnO2n−2 Other ordered structures not belonging to the series are also discussed and the whole related to the zirconia and hafnia systems stabilized by calcia and yttria.
The Influence of Cation Stoichiometry on the Electrical Conductivity and High-Temperature Stability of MgO.nAl203 Spinel
Authors: Sonder E. , Darken L. S.
Published: March 2011

Theelectrical conductivityof MgO:nAl2O3spinelhas been measured for 1 < n < 3.6 for temperatures between 500 and 1400°C. The results for nonstoichiometric spinel are significantly different from those of stoichiometric material. Spinel with n up to 2 was found to be stable at temperatures above 1000°C, whereas, MgO:3.6Al2O3exhibited multiple indications of instability and disproportionation.
Cathodoluminescence from Therimochemically reduced MgO Crystals
Authors: Ballesteros C. , Piqueras J. , Llopis J. , Gonzalez R.
Published: March 2011

Cathodoluminescence of thermochemically reduced MgO crystals has been studied in the scanning electron microscope. Two peaks at around 3.0eV (410nm) and 2.4eV (520nm) have been detected. The intensity evolution of these two peaks with temperature and electron beam irradiation has been recorded. The results are analyzed on the basis of emission from anion vacancies (F and F+ centers)
Permeability of Filter Pressed Monosized SiO2
Authors: Danforth S.C. , Velazquez M.
Published: March 2011

The feasibility of slip casting monosized ceramic powders has been investigated using colloidal (spherical) SiO2particles. Pertinent aspects of powder syntheses, particle characteristics, and slip preparation are discussed. Processing variables affecting thepermeabilityof the cast compact to fluid flow are discussed in relation to forming cast bodies with near ideal (ordered) particle packing.
Sinterability of Agglomerated Powders
Authors: Lange F.F.
Published: March 2011

Powdered compacts that do not have periodic, particulate arrangements exhibit nonperiodic density variations and are, by definition, agglomerated. The void phase in the compact can be separated into pores. The pore coordination number distribution and the critical coordinated number (Rc) governs the volume fraction of pores that can spontaneously disappear by diffusion, and therefore, the compact's sinterability. The pore coordination number distribution is favorably influenced by increasing the compact's initial density and decreasing the size of the multiple particle packing unit (for example, agglomerate size). During heating the pore coordination number distribution is unfavorably shifted by local sintering, which is produced by the spontaneous disappearance of pores with favorable coordination numbers (R < Rc). Local densification produces a dense, polycrystalline skefetal network. Grain growth during densification, supported by dense regions, favorably alters the coordination number of pores within the skeletal network and improves sinterability. The configuration and microstructure of the dense, skeletal network will control its compliance to deformation by either effective or applied (hot pressing) compressive stresses. Deformation of the dense, skeletal network will improve the coordination number distribution and thus sinterability. From this thinking, one concludes that the ideal situation requires either a periodic particle arrangement (which requires monodispersed powders), or lacking this arrangement, alterations in surface chemistry (or structure) such that Rc → ∞.
Hydrothermal Preparation and Sintering of Fine Ceramic Powders
Authors: Sōmiya Shigeyuki
Published: March 2011

Hydrothermal preparation is one of the methods to make fine ceramic powders. There are: (1) hydrothermal oxidation, (2) hydrothermal precipitation, (3) hydrothermal synthesis, (4) hydrothermal decomposition, (5) hydrothermal crystallization, etc. Starting materials for hydrothermal oxidation is mainly metal. Reaction between metal and high temperature-high pressure solution occurs to form oxide. Therefore, starting materials for very fine powders are: (1) metal powders or chips, (2) gel, solutions, etc., (3) oxides and solutions, (4) solids, and (5) hydrous material. This paper describes hydrothermal crystallization and oxidation. Fine powders of ZrO2, Al2O3, HfO2, and Al2O3-ZrO2 are described.

Sintered bodies are also able to get under hydrothermal conditions with reactions. Hydrothermal reaction sintered bodies of iron oxides, Cr2O3, ZrO2 and HfO2 were obtained under 100 MPa above 1000°C with 1–5 μm grains.
Short-Circuit Diffusion Processes in Oxidation Films
Authors: Hughes A.E. , Atkinson A. , Chadwick A.T.
Published: March 2011

The rate ofoxidation of metalsat high temperatures is usually controlled by the transport of metal ions or oxygen through the growing film of oxide on the surface. Since many technologically useful alloys (eg steels, nickelbased alloys) are based on the 3d transition metals, the transport properties of the oxides of these elements are of particular interest. In the temperature range 500–1000°C, where these alloys are used, the important transport paths in the oxide are not those that involve diffusion in the bulk crystal lattice, but other “short-circuit” paths. Basic experiments on the oxidation of nickel and direct tracer measurements of diffusion coefficients show that rain boundaries are the most important short-circuit paths under protective oxidation conditions. Similar conclusions can be drawn for other metals including chromium. The methods used in this work have been extended to study the way in which a surface treatment withCeO2reduces the oxidation rate of nickel, apparently by inhibiting the outward transport of metal ions along grain boundaries. Segregation of cerium ions to grain boundaries increases the diffusion coefficient of nickel; the inhibition is caused instead by particulates of CeO2in the middle region of the scale.
The Occurrence of Defects in Silicon Carbides as a Result of Processing Mode and Applied Stress
Authors: Carter C. H. , Bentley J. , Davis Robert F.
Published: March 2011

Silicon carbide (SiC) possesses extreme hardness, very good electrical, thermal and mechanical properties as well as excellent resistance to corrosion and thermal shock. As such, it is one of the primary candidate materials for use in systems for the production and conversion of energy at elevated temperatures. It is currently employed in or being considered for use in heat exchangers or waste heat recouperators in various prototype fossile fuel systems. Specific examples of its potential use include (1) indirectly fired turbine engines wherein the turbine section is separated and protected from the combustor by a SiC heat exchanger; (2) coal fired systems which heat air in a fluidized bed containing aSiCheat exchanger; (3) coal gasifiers wherein the outlet channels will be of SiC because of the particle erosion, high temperatures (1673K) and pressures on these systems; (4) critical parts for gas turbines, the Sterling engine and adiabatic diesel engines; (5) high temperature bearings and (6) first wall materials for fusion reactors.
Planar Waveguides Formation Process in Linbo3 by Ti IN-Diffusion and H-Li Ion Exchange: A Structural Study
Authors: CANALI C. , CARNERA A. , CELOTTI G. , DELLA MEA G. , MAZZOLDI P.
Published: March 2011

The interactions and compounds formed between Ti and LiNbO3, occurring before the true Ti in-diffusion process for optical wa veguides production,have been studied by using different analysis techniques.The relationship between lattice modifications and H concentration profile in proton exchanged LiNbO3 waveguides are also reported.
Cation Distribution in Transition Metal Oxide Spinels: Thermodynamic and Kinetic Considerations
Authors: Dorris S. E. , Erickson D. S. , Mason T. O.
Published: March 2011

The point defect reaction which governs the magnetic and electrical properties of transition metal oxide spinels is the distribution of cations between tetrahedral and octahedral sublattices. Two types of redistribution occur -- ionic and electronic. The thermodynamics and kinetics of these processes can be studied via the electrical properties, thermoelectric coefficient and conductivity.
Aspects of the Reliability of Ceramics
Authors: Evans A. G.
Published: March 2011

Failure processes in brittle solids have been described. Particular emphasis has been placed upon a distinction of the various flaw populations that dictate failure and their relation with the dominant manufacturing (or environmental) variables. Micromechanics models of failure from the more significant flaws, and considerations of their relative roles in the failure process, have been cursorily presented. The fracture toughness, its significance in failure, and its dependence upon microstructure, have been examined, in conjunction with considerations of crack shielding and enhanced toughness. Finally, the role of statistical processes has been outlined, within the context of the important flaw populations.
Growth and Characterization of Ternary and Quaternary Compounds of Iny (AlxGa1−x)1-yAs on (100) InP
Authors: Tseng W. F. , Comas J. , Steiner B. , Metze G. , Cornfeld A. , Klein P. B. , Gaskill D. K. , Xia W. , Lau S. S.
Published: March 2011

The acquisition of RHEED oscillation information on (100) GaAs substrates is described for use in the growth of “lattice-matched] Iny (AlxGa1−x)1-Y As layers on (100) InP substrates with 0.52 < y < 0.53 and 0.00 < x < 1.00. The observed frequency of the RHEED oscillations on GaAs is the same as on InP, however, the measured lattice parameters of the grown layers are less than that of InP. The x-ray diffraction images show that the misfit dislocations perpendicular to the primary flats of 2” round (100) InP wafers are denser than the parallel ones. Photoluminescence (at 10K) and photoreflectance (at 300K) measurements on a composite layer structure of x=0, 0.2, 0.4, 0.6, 0.8 and 1 clearly show six distinct peaks with narrow FWHMs of less than 20 meV. The measured bandgaps increase linearly with the Al content.
Non-Destructive Measurements of III-V Semiconductor Device Structure by a Hard X-ray Microprobe
Authors: Uchida F. , Shigeta J. , SUZUKI Y.
Published: March 2011

A non-destructive characterization technique featuring a hard X-ray Microprobe is demonstrated for lll-V semiconductor device structures. A GaAs FET with a 2 μm gate length is measured as a model sample of a thin film structure. X-ray scanning microscopic images of the FET are obtained by diffracted X-ray and fluorescence X-ray detection. Diffracted X-ray detection measures the difference in gate material and source or drain material as a gray level difference on the image due to the X-ray absorption ratio. Ni Ka fluorescence detection, on the other hand, provides imaging of 500 Å thick Ni layers, which are contained only in the source and drain metals, through non-destructive observation.
Novel Growth Techniques for the Fabrication of Photonic Integrated Circuits
Authors: Coudenys G. , Vermeire G. , Zhu Y. , Moerman I. , Buydens L. , Van Daele P. , Demeester P.
Published: March 2011

INTRODUCTION:

The fabrication of Photonic Integrated Circuits (PIC) requires the development of advanced growth and processing techniques. One of the major problems in the fabrication of PICs is the monolithic integration of passive and active waveguiding structures with a different bandgap. This is schematically shown in figure 1 where a laser, waveguide and detector are integrated on the same substrate. The following relationship between the different bandgaps is required : Eg (detector) < Eg (laser) < Eg (waveguide). One of the most advanced PICs is certainly a coherent receiver chip where a local DFB laser oscillator is integrated with a Y-junction, 3-dB splitter and balanced photodetector pair [1,2,3]. Current integration schemes are mostly based on the use of different epitaxial growth steps to obtain the different bandgap materials on the same substrate. In order to improve yield and performance it is required to reduce the number of growth steps by using special growth techniques. In this paper we will briefly describe some of the recent developments in advanced growth techniques. A more detailed description will be given of our recent work based on selective growth and shadow masked growth using Metal Organic Vapour Phase Epitaxy (MOVPE).
A Comparison Between Dry Etching with an Electron Cyclotron Resonance Source and Reactive Ion Etching for GaAs and InP
Authors: Pang S. W.
Published: March 2011

Etching with an electron cyclotron resonance (ECR) source provides several advantages over conventional reactive ion etching (RIE). In this work, the results of GaAs and InP etching using a multipolar ECR source are presented and compared to RIE. The effects of microwave and rf power, gas composition, pressure, and source to sample distance on the etch characteristics of GaAs and InP were evaluated. Three different etch gases were used including CCl2F2, BCl3, and Cl2. The influence of microwave power on etch characteristics is compared to conventional parallel plate system using rf power alone.
Electron Cyclotron Resonance Plasma Processing of GaAs-AlGaAs Hemt Structures
Authors: Pearton S. J. , Ren F. , Lothian J. R. , Fullowan T. R. , Kopf R. F. , Chakrabarti U. K. , HUI S. P. , Emerson A. B. , Pei S. S.
Published: March 2011

The damage introduced into GaAs/AlGaAs HEMT structures during pattern transfer (O2 plasma etching of the PMGI layer in a trilevel resist mask) or gate mesa etching (CCl2F2/O2 or CH4/H2/Ar etching of GaAs selectively to AlGaAs) has been studied. For etching of the PMGI, the threshold O+ ion energy for damage introduction into the AlGaAs donor layer is ∼200 eV. This energy is a function of the PMGI over-etch time. The use of ECR-RF O2 discharges enhances the PMGI etch rate without creating additional damage to the device. Gate mesa etching produces measurable damage in the underlying AlGaAs at DC negative biases of 125–150V. Substantial hydrogen passivation of the Si dopants in the AlGaAs occurs with the CH4 /H2 /Ar mixture. Recovery of the initial carrier concentration in the damaged HEMT occurs at ∼400°C, provided the maximum ion energies were dept to ≤400 eV. Complete removal of residual AIF3 on the CCl2F2/O2 exposed AlGaAs was obtained after H2O and NH4 OH:H2O rinsing while chlorides were removed by H2O alone.
Selective Gate Recessing of GaAs/AIGaAs/lnGaAs Pseudomorphic HEMT Structures Using BCl3 Plasmas
Authors: Kazior T. E. , Patel B. I.
Published: March 2011

Wet chemical gate recessing of GaAs based devices suffers from poor control and uniformity of the recess etch depth. Electrical variability can be particularly severe for heterojunction devices that contain thin highly doped layers. This problem can be addressed by the use of etch stop layers and the appropriate etch chemistry. In this paper, results on the selective plasma etching of GaAs from InGaAs and AIGaAs etch stop layers are presented. Using a BCl3 plasma, GaAs layers were removed from thin lnxGa(1-X)As (0.12<x<0.25) layers with selectivities >1000 to 1 due to the poor volatility of indium chlorides. With the addition of SFe, the etch process becomes selective to AlxGa (1-X)As due to the formation of a non-volatile AlFX layer. By the judicious choice of etch conditions (high pressure and low power resulting in low DC bias and optimal BCl3/SF6 ratio), isotropie etch profiles with minimal substrate damage and GaAs to Al0.25Ga0.75As selectivities >1000 to 1 have been achieved. Using these etch conditions, pseudomorphic HEMT wafers were selectively plasma gate recessed yielding saturated current uniformities across a 3 inch wafer of <±1.0mA/100μm of gate periphery. Device characteristics and uniformities that are dependent upon the material structure and epitaxial layer thickness and dopant uniformities rather than upon the gate recess process are realized.
Investigation of Gaas Deep Etching by Using Reactive Ion Etching Technique
Authors: Din Kuen-Sane , Chi Gou-Chung
Published: March 2011

RIE is an important technique in obtaining anisotropie etch profile. This is a critical requirement for very deep etching which needs long etch duration. Among many factors which affect RIE characteristics in deep etching, the following are most concerned: (1) the etch mask: needs suitable plasma resistance without significant plasma attack for extended etch time; (2) Long time stability in etch rate and surface conditions for the sample; (3) Etch profile: should be anisotropie with tolerable undercut In this work, CCl2F2 and SiCl4 were used with CCl2F2 as the main etchant. Ar was used in the initial stage for sputtering away surface residues prior to actual etching was performed. Three types of etch masks were prepared and their performance such as plasma was investigated. Multilayer metal etch mask has very low etch rate in plasma and its etch rate selectivity is around 300. The etch selectivities of GaAs to Si3N4 and to photoresist are 35 and 23, respectively. Etch mask can be chosen depending on the thickness of etch mask and the required GaAs etch depth. The etch rate of GaAs was found significantly increased when metal mask was applied. While PR mask is easier for inducing surface coating.
Novel ECR Reactor for Plasma Processing of III-V Semiconductor Compounds
Authors: Lane Baxton , Smatlak Donna
Published: March 2011

A novel electron cyclotron resonance (ECR) reactor for plasma processing of III-V compound semiconductors is presented. The reactor is appropriate for processes which are damage sensitive or for applications in which direct overhead access to the wafer is advantageous. The reactor uses an axisymmetric magnetic geometry provided by electromagnets and locates the source region below the wafer; there is no direct line of sight to the wafer from the plasma discharge region. The geometry allows more flexible neutral gas handling capabilities and frees the area above the wafer for diagnostics, neutral gas manifolds, energetic ion beam injection, laser irradiation of the wafer or vacuum pumping access. The combination of auxiliary processing with beams or laser light simultaneous with the plasma processing step opens possibilities for new processes, increased throughput and reduced wafer handling.
Rapid Growth Kinetics, Mechanical Properties and Thermal Stability of Siox Thin Films Grown by Rapid Thermal Low Pressure Chemical Vapor Deposition
Authors: Feingold A. , Katz A. , Pearton S. J. , Chakrabartl U. K. , Jones K. S.
Published: March 2011

High quality SiOx films were deposited onto InP substrates in the temperature range of 350 to 550°C and pressure range of 5 to 15 Torr. Depositions were made by means of rapid thermal low pressure chemical vapor deposition (RT-LPCVD) using oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) gas sources, with O2:SiH4 gas ratio of 5:1 to 50:1. High deposition rates of 15–50 nm/sec were obtained, providing uniform SiOx layers, with low stresses of −5×109 to −2×109 dyne-cm−2, and thermal stability on post deposition temperatures up to 1000°C. The SiOx films had refractive indexes between 1.44 and 1.50, densities of 2.25 to 2.37grcm−3 and exhibited wet etch rates of 0.2 to 0.8 nmsec.−1 through standard p-etch process. The influence of the various process parameters on the SiOx film properties was examined.
Ohmic Contacts to Heavily Carbon-Doped p+-GaAs Using Ti/Si/Pd
Authors: Lee H. S. , Han W. Y. , Lu Y. , Cole M. W. , Lareau R. T. , Casas L. , Thompson R. J. , Deanni A. , Jones K. A. , Yang L. W.
Published: March 2011

Low specific resistance ohmic contacts have been formed on heavily carbon doped GaAs using the Ti/Si/Pd system. Suicide formation was observed in the Pd/Si layers over the temperature range 400 – 700 C using RTA. Contact resistances as low as 0.061 Ω-mm and specific contact resistances as low as 3.2 × 10−6Ω;-cm2 were measured. Silicide/Ti/GaAs interfacial information was determined using TEM and Auger depth profiling.
Fabrication of Hemt-on-Si by Movpe for Lsi Applications
Authors: Ohori Tatsuya , Kikkawa T. , Suzuki M. , Takasaki K. , Romeno J.
Published: March 2011

We grew selectively doped heterostructures on a Si substrate by metalorganic vapor phase epiaxy (MOVPE) for the first time and fabricated high electron mobility transistors (HEMTs). The conventional selective dry etching process to fabricate enhancement and depletion mode HEMTs on the same wafer, can be used without changing any process conditions. We evaluated the side-gate effect and obtained a critical voltage of 8V. This is large enough for LSI applications. We fabricated HEMTs on two kinds of GaAs-on-Si substrates. One had a small etch pit density (EPD) and poor surface morphology. The other had a large EPD, and better surface morphology. We compared the characteristics of devices on these two substrates, and the degradation of their characteristics was larger for the substrate with a small EPD and poor surface morphology. We conclude that improvement of surface morphology is more important than reduction of dis-location density. For the substrate with better surface morphology, maximum transconductance and K-value, for a gate length of 1 μm were 91% and 84% those of on-GaAs devices.
Direct Evidence for Interstitial Carbon in Heavily Carbon-Doped GaAs
Authors: HÖFler G. E. , Klatt J. , Baillargeon J. N. , Averback R. S. , Cheng K. Y. , Hsieh K C.
Published: March 2011

Carbon is a promising p-type dopant in GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBT) because of its low atomic mobility and its potential for achieving very high carrier concentrations. It is generally believed that carbon incorporates substitutionally on the column V sublattice. However, an anomalous behavior at carrier concentrations > 5 × 1019 cm−3 is observed in the electrical properties of carbon doped layers. The strain sustained in these layers may be explained by the presence of interstitial carbon.

We used Rutherford Backscattering Spectrometry in channeling geometry utilizing the nuclear reaction 12C (d,p)13C to determine the lattice locations of carbon in GaAs. The data presented unambiguously show, that up to 25% of the carbon atoms occupy interstitial sites. The presence of interstitial carbon is of importance for applications, since interstitial carbon may exhibit an enhanced diffusivity altering nominally abrupt dopant profiles.
Radiation Testing of AlInAs/lnGaAs and GaAs/AlGaAs HBTs
Authors: Witmer S. B. , Mittleman S. , Lehy D. , Ren F. , Fullowan T. R. , Kopf R. F. , Abernathy C. R. , Pearton S. J. , Humphrey D. A. , Montgomery R. K. , Smith P. R. , Kreskovsky J. P. , Grubin H. L.
Published: March 2011

The radiation hardness of small geometry (∼2 × 4 μm2), state of the art AlInAs/lnGaAs and GaAs/AlGaAs HBTs to 60Co γ-ray has been investigated up to a dose of 100 MRad. The former devices showed a small change in Ic and gain for 20 MRad, with essentially no change in IB. At 40 MRad, the gain of the devices had decreased to unity. By contrast, for GaAs/AlGaAs HBTs, the current gain actually increased up to a dose of 75 MRad. At 100 MRad, none of our devices were still operational. This was ascribed to degradation of the base-collector contact metallization (TiPtAu) and in particular to the presence of Au. Carbon-and beryllium-doped base devices showed the same response to 60Co γ-ray doses. No long transient responses in either base or collector currents were observed during irradiation of the GaAs/AlGaAs devices with 120 nsec pulses of 10 MeV electrons at rates up to 2.7 × 1010 Rad · sec−1. Results of a 2-dimensional modelling study suggest that both GaAs and InP based HBTs are relatively immune to damage by transient radiation effects up to a dose rate of 1011 Rad · sec−1, with GaAs based devices being more resistant to radiation than InP due to their shorter recombination times.
High Electron Mobility Transistors with Optically Processed Refractory Silicide Metallizations: Thermal and Microwave Analysis
Authors: Tang P. F. , Fan M. S. , Illiadis A. A.
Published: March 2011

The enhanced high temperature gate metallizations consisting of sputtered TiWSi or TiWN were investigated in order to attain high temperature stability at temperatures in excess of 250°C. The TiWN/Au system resulted in a sheet resistance of only 11.5 mΩ/□ while TiWSi/Au resulted in 75.0 mΩ/□. The HEMTs and FETs processed with additional stable ohmic contacts of epitaxial Ge/Pd structures exhibited a stable transconductance of 160 -180 mS/mm at temperatures of 300°C. Thermal analysis indicated the peak junction temperature increase with an input power of 200mW to be less than 18°C at substrate temperature of 60°C.
An Optically Gated InP Based Thyristor for High Power Pulsed Switching Applications
Authors: Zhao J. H. , Lis R. , Coblentz D. , Illan J. , McAfee S. , Burke T. , Weiner M. , Buchwald W. , Jones K.
Published: March 2011

An MOCVD grown InP based optothyristor has been fabricated and tested for high power pulsed switching applications. To increase the power handling capability, the thyristor structure has a 250 μm thick Fe doped semi-insulating (SI) InP sandwiched between two pn junctions of a conventional thyristor. The turn-on of the thyristor is controlled by optical illumination on the SI-InP which creates a high concentration of electron and hole pairs. More than 1,100 V device hold-off voltage has been observed and over 66 A switched current has been realized with a di/dt rating of 1.38×1010 A/s. The switched current as a function of switch voltage and of optical illumination power has also been studied. Comparison with the switching characteristics of a bulk SI-InP photoconductive switch clearly indicates the advantage of this optothyristor in terms of power handling capability.
The Impact of the Extrinsic Device on HFET Performance
Authors: Greenberg David R. , Del Alamo Jesús A.
Published: March 2011

The extrinsic device is known to degrade the performance of heterostructure field-effect transistors (HFET's) through the introduction of a parasitic source resistance (Rs). To date, however, there has been no recognition of the fact that carrier velocity saturation (vsat) can occur in both the extrinsic source and drain, setting the ultimate limit on maximum drain current (I,D,max) and on the useful VGS swing in HFET's. In this study, we demonstrate the mechanisms through which vsat in the extrinsic device limits device performance, using AlGaAs/n+-InGaAs Metal-Insulator-Doped-channel FET's (MIDFET's) as a vehicle. These devices show that gm falls at a lower VGSthan does fT, by as much as 1 V. This reveals that there are two mechanisms at work. The approach of vsat in the extrinsic source first causes the small-signal source resistance (Ts)to rise rapidly, leading gm to decline but leaving fT unaffected. As the carrier velocity in the extrinsic device approaches Vsat more closely, there is an actual decline of the carrier velocity in the intrinsic device. This process degrades velocity-related figures of merit such as and fT.
Theoretical Studies of Defects, Impurities, and Complexes in Semiconductors
Authors: Estreicher Stefan K.
Published: March 2011

Theoretical studies of microscopic properties of localized defects, impurities, and complexes in semiconductors have greatly progressed in the past decade. Theory has advanced beyond “point” defects to include lattice relaxations and distortions, interactions between defects, complex formation, and even some extended structures. Vibrational frequencies, hyperfine parameters, and other measurable quantities are being calculated from first principles. Both the one-effective-particle density-functional approach and the all-electron Hartree-Fock methods are able to predict a variety of microscopic properties of defects at or near the ab initio level. However, despite the progress achieved, theoretical descriptions only approximate the real world. In this paper, an overview is given of the way these calculations are done and of the main approximations involved. Although some of them will be eliminated by progress in computer technology, other problems such as electron correlation or excited states are likely to require new thinking.
Dose effects in Si FIB-mixing of short period AlGaAs/GaAs superlattices
Authors: Stecki A. J. , Chen P. , Choo A. , Jackson H. , Boyd J. T. , Pronko P. P. , Ezis A. , Kolbas R. M.
Published: March 2011

Results are presented on FIB mixing of an Al0.3Ga0.7As/GaAs superlattice with equal 3.5 nm barrier and well widths. Si++ was accelerated to 100 kV and implanted parallel to sample normal at doses ranging from 1013 to 1015/cm2. The level of inter-layer disordering was measured primarily by Auger depth profiling. The mixing effect of RTA-only increased roughly linearly with annealing time at both 950 and 1000°C, with the latter exhibiting a sharper slope. At either temperature, 90 s was sufficient to produce complete mixing within the accuracy of the measurement. An anneal of 10 s at 950°C, which was utilized in subsequent post-implantation annealing, resulted in ∼ 25% thermally-induced mixing, with a corresponding PL “blue shift” of 6 meV. The level of mixing by an ion dose of 1 × 1014/cm2 yielded a mixing parameter of 0.87, where 1.0 represents complete mixing. This is the lowest ion beam dose necessary for nearly complete mixing reported to date for either FIB or BB implantation. Doubling the dose to 2 × 1014/cm2 results in an increase in mixing by only 0.05 to 0.92. Larger doses produced a diminishing increase in mixing parameter.