bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid State Interaction and Nano-Scale Silicide Formation for Co/Ti Multilayers on Silicon
Authors: Hong Feng , Patnaik Bijoy K. , Rozgonyi George A.
Published: March 2011

The formation of a 12nm thick, continuous and thermally stable COSi2 layer was described in our previous work [MRS Proc. 238, 587 (1992)]. Interdiffusion in the Co/Ti-Si multilayer system has been further studied and the initial Ti(O) thickness is shown to be a critical parameter in controlling its effectiveness as a diffusion barrier, and in modulating the Co-Si and Ti-Si compctctive reactions. Three Ti(O) and three Co layers with thickness from ∼5nm 20nm were deposited sequentially, with Ti(O) as the first layer, on Si-(100) substrates by dual source thermal evaporation. The morphology of the CoSix/Si interface was strongly influenced by Ti(O) thickness from ∼5nm to ∼10nm, and a 12nm thick uniform CoSi2 layer with ∼28μΩ-cm resistivity was produced as decribed previously. When the initial Ti(O) thickness was increased to ∼20nm and the Co thickness set at -10nm, Co diffusion was suppressed and Ti reacted with Si yielding an ∼10nm amorphous TiSix layer at 550°C. This amorphous layer transformed to a 15nm thick uniform C-54 TiSi2 layer after selective removal of upper layers and a 750°C plus 800°C annealing. A flat silicide/Si interface and a ∼58μΩ-cm resistivity were obtained. The significance of both thermodynamic and kinetic factors in the compctetive reactions is discussed.
Self-Aligned, Metal-Masked Dry Etch Processing of III-V Electronic and Photonic Devices
Authors: Pearton S. J. , Katz A. , Feingold A. , Ren F. , Fullowan T. R. , Lothian J. R. , Abernathy C. R.
Published: March 2011

Electron Cyclotron Resonance (ECR) plasma etching of a variety of III-V devices, including heterojunction bipolar transistors (HBTs), and lasers will be reviewed. In many of these devices, the metal contacts also perform as self-aligned, dry etch masks, so that mask erosion must be addressed. Sidewall smoothness is also an issue for most etched mesa lasers, and conditions for achieving the requisite smoothness will be discussed. The use of stencil masks for pattern transfer of large (∼100μm) features during cluster-tool, single wafer integrated processing raises the possibility of a completely in-situ fabrication technology without the need for lithography. The dry etching of a variety of ohmic and Schottky metallizations and also of dielectrics deposited in a low pressure, rapid thermal CVD system lays the foundation for integrated III-V device processing.
Junction Formation in Silicon Using a Phosphorus Vapor Source and Rapid Thermal Drive-In
Authors: White Eric R. , Ashok S. , Allara D. L.
Published: March 2011

n+-n and n+-p junctions were formed on n-type and p-type Si using a thin film of phosphorus obtained from a simple vapor source, and driving in the dopant atoms in a rapid thermal processing (RTP) system. The vapor treatment consisted of heating powdered red phosphorus in a nitrogen ambient and allowing the resulting phosphorus vapor to deposit on the Si samples. This was done in an inexpensive apparatus constructed from flasks and test tubes. Following the vapor treatment, an SiOxfilm was sputtered over the phosphorus coating in order to serve as a capping layer during subsequent RTP drive-in that forms the junction. The junction properties were characterized by spreading resistance and electrical (IV and CV) measurements after deposition of metal contacts layers.
A Study of the Copper Wire Ball Bonding Processes
Authors: Hongyuan Fang , Yiyu Qian , Yihong Jiang
Published: March 2011

Copper ball bonding is a new technology which is expected to replace the traditional gold ball bonding and paid attention in woled recently, the technology is very important to reduce cost and improve reliability of microelectronic components. In this paper, the copper wire ball bonding processes have been studied by means of the MW-EFO metal wire ball forming device and the JWYH-2 thermosonic ball bonder. The bond strength of the ball bond under varied ultrasonic power and bonding time have been tested. The tested results show that the maximal strength of copper ball bond can be over 20g, it has advantage over the gold wire ball bonding. In this paper, the deformation process of the copper ball bond has been analyzed and viewed by SME.
The Effect of Xe Ion Beam Treatment on the Interaction Between Gold and GaAs
Authors: Pécz B. , Radnóczi G. , Horváth Zs. J. , Barna P. B. , Jároli Erika , Gyulai J.
Published: March 2011

The effect of the defective nature of the substrate on the alloying behaviour of Xe implanted Au(55 ran)/n-GaAs system was studied using cross sectional transmission electron microscopy.

Low dose Xe implantation (700 keV, 1*1014 ions/cm2) caused the formation of about SO nm thick polycrystalline region of GaAs beneath the gold layer. Annealing the implanted sample at 450°C gold diffused through the polycrystalline GaAs region and formed large pits of Au(Ga) solid solution in the defective area of GaAs having stacking faults and twins. The formation of a regrown GaAs covering layer was observed on the top of the reacted metallization simultaneously.

High dose implantation of Xe++ ions resulted in the formation of amorphous GaAs layer with a thickness of about 750 nm. Twinned regions of GaAs were observed at the amorphous - crystalline GaAs interface by high resolution electron microscopy. Ion beam caused phase transition was observed in this sample. The amorphous GaAs region recrystallized to single crystalline GaAs due to annealing at 400°C.
Effect of Interfacial Oxide Thickness on Titanium Silicide Formation
Authors: Donnelly J. , Brun N. , Pantel R. , Normandon P.
Published: March 2011

TiSi2 formation on various substrates has been widely investigated in the past and one of the critical parameters has been found to be the quality of the interface before deposition. In this paper the quality of the suicide formed on a range of oxides, from lnm to 15nm, has been systematically studied using sheet resistance measurements, Scanning Electron Microscopy, Atomic Force Microscopy and Auger Electron Microscopy. The critical thickness, above which the quality of the suicide formed is affected, was found to be 2.2nm and no suicide was detected > 13.0nm. A notable difference in the suicide formation occured in a narrow band around 5.0nm. It is proposed that this is the transition region in which the oxide becomes the main source of Si for TiSi2 formation rather than the substrate.
Plasma Etching Characteristics of Sputtered Tungsten Films
Authors: Franssila S. , Molarius J. M. , Saarilahti J.
Published: March 2011

The relationship between microstructure of tungsten thin films and plasma etching properties has been studied. Rutherford backscattering, nuclear reaction analysis 16O(α,α)16O, X-ray diffraction, and resistivity measurements have been used to characterize the sputter deposited films. Independent of deposition pressure, the films were all high density, low oxygen (<1 at%), low resistivity and bccot-phase. Etch rate differences of 40% were measured in pure SF6, whereas only 10% differences were seen in SF6/Cl2 and SF6/O2BCi3 plasmas. Intentional oxygen doping (up to 2 at-%) increases the etch rate in pure SF6 plasma by 75%, wherasthe etch rate in SF6/O2/BCl3 plasma only increases 25%. The role of film density (porosity) and oxygen incorporation on etching mechanism are discussed.
Role of Teos in Improved Quality Pteos and O3-TEOS CVD SiO2 Films
Authors: Bourgeois Mark A. , Ramkumar K. , Saxena Arjun N.
Published: March 2011

The effects of TEOS (Tetra-ethyl-ortho-silicate) concentration on the physical, chemical and electrical characteristics of undoped SiO2 films deposited by plasma (PECVD) and thermal CVD (ThCVD) processes, are described. It is shown that the (TEOS/O3) or (TEOS/O) ratio strongly influences the various film properties. The uniformity of film thickness is better at higher (TEOS/O3) or (TEOS/O2) ratios in both processes. In ThCVD the SiO2 films are denser (low etch rate) when deposited at low (TEOS/O3 ) ratio. This study has shown that the TEOS concentration can be used to tailor film properties.
Interface Reaction and Atomic Transport During COSi2 Film Formation
Authors: Xiao Z. G. , Honeycutt J. W. , Rozgonyi G. A.
Published: March 2011

The formation process of COSi2 films grown from Co deposited on a Si single crystal was investigated as a function of very short annealing times by transmission electron microscopy and x-ray diffraction. Information on the interfacial reactions and atomic transport phenomena was obtained from a microstructural analysis of the CoxSiy layers formed. It was demonstrated that Co is the dominant diffusion species during COSi2 formation. Co atoms are generated at the COSi2/COSi2 interface via the reaction 2CoSi=CoSi2+Co and diffuse to the COSi2/Si interface, where they react with Si by Co+2Si=CoSi2. Direct microscopic evidence indicates that diffusivity of Co atoms along a COSi2 grain boundary greatly exceeds that through the COSi2 lattice. The grain boundary diffusion coefficient is estimated to be up to 100 times larger than the lattice diffusion coefficient. On this basis the influence of grain size on COSi2 film formation is discussed.
Interaction of A12O3-CAPPED Au/Zn/Au and Au/Te/Au Contacts With (001)GaAs Substrates
Authors: Lin X. W. , Liliental-Weber Z. , Washburn J. , Piotrowska A. , Kaminska E.
Published: March 2011

HREM,TEM, and EDX were employed to study the cross sections of Au/Zn/Au and Au/Te/Au contacts to [001]-oriented GaAs substrates. The metal contacts fabricated by sequential vapor deposition were capped with an A12O3 thin film to form a closed system when subjected to a 420°C anneal for 3 min. For an as-deposited Au/Zn/Au/GaAs specimen, Zn was found to react with Au to form ordered phases of Au3Zn. These phases were found to be stable upon annealing. The interface between the annealed metallization and GaAs exhibited the same degree of uniformity and planarity as that of the as-deposited specimen. For a Au/Te/Au/GaAs specimen, annealing resulted in epitaxial growth of Ga2Te3 grains, forming a basically flat interface with GaAs, while Au single-crystal grains were found to protrude rather extensively into GaAs to form a facetted interface with the substrate.
Refractory Ohmic Contacts Formed by Electroless Deposition of Palladium and Nickel Onto N-InP
Authors: Stremsdoerfer G. , Wang Y. , Martin J. R. , Souteyrand E.
Published: March 2011

Ni and Pd layers have been elaborated from chemical process on (100) oriented and 1018 doped n-InP substrates. The electrical and structural characteristics of these contacts have been investigated. Good refractory ohmic contacts were obtained by the annealing of these heterostructures. The ohmic quality of chemical contacts as well as those obtained with evaporated contacts is attributed to both the presence of crystallized compounds (NiP; Ni2P; PdIn3 and Pdln) and to superficial degenerescence of InP due to a phosphorus excess laying in the interphase.
Reactions of (100) Multilayered Metal Structures Containing Fe Grown on (100) Si
Authors: Chang Chin-An , Coleman Grant
Published: March 2011

(100) Fe films deposited on (100) Pd, Ag, Au and Pt seed layers, with the latter metals deposited on (100) Si with proper respective seed layers, have been heated to 600°C, and their thermal stabilities assessed. The Fe layers were found to stay little changed, both structurally and magnetically, up to an anneal of 30 min around 400°C. At higher temperatures, the Fe layers change in structure and degrade magnetically, but with different mechanisms for different structures. For the ones with Pt or only with Pd, the consumption of the metal layers for the suicide formation below 400°C causes less changes of the Fe layers than those in the other structures. For the one with Ag, Fe apparently mixes with Ag above 400°C, with Ag being nearly intact up to 600°C, resulting in a rapidly decreasing magnetic moment of Fe. For the structure with Au, the formation of the Au-Si eutectic melt at 363°C completely destroys the structure and magnetic moment of Fe above 400°C.
Silicon Precipitate Detection in Al-Si and Al-Si-Cu Metal Interconnect by Thermal Wave Imaging
Authors: Ritz K. N. , Welles C. G. , Smith W. L. , Bivas A.
Published: March 2011

Controlling the size and distribution of silicon precipitates in aluminum alloy depositions is important for yield enhancement and reliability of small geometry metal interconnects. A non-contact and non-destructive thermal wave imaging technique is used to detect and evaluate size and density of silicon precipitates in AISi and AlSiCu alloys. The thermal wave results are corroborated with SEM and Auger data.
CVD of Copper from (β-Diketonate)CuLn Copper(I) Precursors
Authors: Chi Kai-Ming , Jain A. , Hampden-Smith M. J. , Kodas T. T.
Published: March 2011

Selective chemical vapor deposition (CVD) of copper is the focus of recent research interest as a result of possible applications as vertical interconnect material in multilevel metallization. A variety of copper(I) and copper(II) compounds have been used to deposit copper. In some cases, the compounds selectively deposit copper on various different surfaces. However, the origin of this selectivity is not unambiguously established at this stage. In order to derive a better understanding of the CVD processes, a series of copper(I) compounds (β-diketonate)CuLn have been synthesized and used as CVD precursors. The new species (fod)CuL, where fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionate and L = PMe3, 1,5-COD, 2-butyne, BTMSA and VTMS (as defined below) are described. The CVD of copper and factors affecting selective copper deposition are discussed here.
Electrical and Microstructural Characteristics of Ti Contacts on (001)Si
Authors: Liauh H. R. , Chen M. C. , Chen J. F. , Chen L. J.
Published: March 2011

An investigation of the electrical and microstructural characteristics of the Ti contact on silicon has been carried out. The presence of As in Ti/n+-Si samples was found to retard the formation of poly crystalline silicides compared with that in Ti/p+-Si samples with BF2+ implantation. The variations of Schottky barrier height, contact resistance and junction leakage current were correlated with microstrucxtural changes. The influences of the formation of amorphous interlayer between Ti and Si on the elctrical characteristics are discussed.
Shallow Junction Formation in Silicon: Dopant Incorporation and Diffusion Through Tungsten Silicide Films Using Gas Immersion Laser Doping (Gild)
Authors: Ishida Emi , Kramer K. -Josef , Talwar Somit , Sigmon Thomas W. , Weiner Kurt H. , Lynch William T.
Published: March 2011

We have demonstrated a new method of doping suicide films which uses a pulsed excimer laser and a wafer cell which is filled with dopant gas species, e.g. BF3, ASF5, PF5. A spatially homogenized 308nm XeCl pulsed laser is used as a heating source to drive adsorbed dopant gas species into the suicide, as well as to outdiffuse dopants into the silicon substrate. The total dose, interface concentration, and junction depth, are controlled by varying the number of laser pulses. High interface concentrations (Cint >1020 atoms/cm3) and shallow junctions (Xj < 1500Å) are obtained using this technique. Laser irradiation also results in smoothing of the suicide film.
Studies on the Nucleation Behaviors of Precipitation in Aluminum Metallization
Authors: Wang Jen-Ren , Lin Jian-Yang , Hwang Huey-Liang
Published: March 2011

In order to simulate the precipitation effect during the aluminum metallization in the VLSI processing, an analytical model was constructed in this work. The nucleation behaviors of the silicon and copper precipitates within the aluminum - 1.0 weight percent silicon - 0.5 weight percent copper were studied. The volume free energies and interfacial energies were estimated, and the activation energy barriers for the precipitate formation were calculated. Silicon precipitate is more likely to nucleate than copper precipitate due to its lower interfacial energy and strain energy. The mechanical and electrical properties of the aluminum interconnects can be improved by the precipitate hardening.
Reliable Metallization System for Flip-Chip Optoelectronic Integrated Circuits
Authors: Wada Osamu
Published: March 2011

Thermal stability of evaporated Pd, Pt and Rh films as reaction barriers to Au-Sn solder was studied for the application to fl1p-ch1p optoelectronic integration. Sn 1n the solder diffused preferentially Into a barrier metal uniformly to produce more stable IntermetalUc phases for all three metals. Pt and Rh exhibited sufficiently samll 1nterd1ffus1on coefficients with high activation energies 1n the temperature range of device operation (Pt: 1.35 eV, Rh: 1.95 eV). This result demonstartes the usefulness of Pt and Rh 1n practical flip-chip Integrated circuit fabrication. Aging test was conducted on fl1p-ch1p GalnAs/InP p-1-n photodiodes with Au-Sn/Pt metallization and no severe degradation was observed over 3400 h at 180 ° C. The same metallization techniques were applied 1n the fabrication of 10 Gbps optoelectronic Integrated receivers as well as quad p-i-n photodiodes for coherent optical receivers.
Effects of Line Width, Thickness and Alloy Temperature on the Breakdown Energy of thin Aluminum Lines
Authors: Jairath Rahul , Gadepallu Katnesh , Bradford Brad , Shibley James , Castel Egil , Lahri Rajeeva
Published: March 2011

Reliability issues have assumed greater importance as critical dimensions in microelectronic devices have entered the sub-micron regime. Wafer level reliability tests have been performed to study the breakdown energy of aluminum. 1500Å, 3500Å, 5500Å aluminum films were sputter deposited at 400 °C on oxide-on-silicon substrates. Test structures with line widths varying from 1 μm to 10 μm were defined on the metal film. The aluminum lines were then passivated using a stacked layer of silicon dioxide and silicon nitride. Finally, the substrates were alloyed at temperatures from 400°C to 450 °C. An attempt has been made to minimize process variability effects by processing the substrates through the same process conditions as far as possible. Failure was induced by stressing the metal lines with high DC current densities and at a constant slew rate. The samples were characterized using optical and scanning electron microscopy. Failure analysis of the samples processed under the different conditions will be discussed.
Ion Implantation to Inhibit Corrosion of Copper
Authors: Dmg P. J. , Lanford W. A. , Hymes S. , Murarka S. P.
Published: March 2011

Ion implantation of boron and aluminium is used to passivate copper surfaces. Such a process modifies the copper only near its surface without affecting copper's desirable bulk properties. The present experiments show that implant doses as low as 1015 ions/cm2 of either boron or aluminium can reduce the oxidization rate by one order of magnitude or more compared to non-implanted samples.
Etitanium Nitride Barrier Metallization Techniques for ULSI Semiconductor Devices
Authors: Chiang Sunny , Hendel Rudi , Zhang Fang
Published: March 2011

High quality barriers of sputter deposited titanium nitride (TiN) are critical elements of advanced ULSI integrated circuits. We have examined the effect of eight variables on eight parameters which may affect device characteristics and the ability to incorporate TiN into the production process. We will discuss the interaction of the variables with the properties of the deposited TiN and indicate in particular the combination of variables which lead to optimum barrier properties.
Co/SixGe1-x Alloy Formation on Strained SixGe1-x Layers
Authors: Ridgway M. C. , Elliman R. G. , Hauser N. , Baribeau J. -M. , Jackman T. E.
Published: March 2011

The thermally-induced Co/SixGe1-x reaction has been studied for a series of isochronal (25–600°C/20 min) and isothermal (600°C/u-240 min) annealing sequences using Rutherford backscattering spectrometry, transmission electron microscopy and sheet resistance measurements. Annealing at 600°C yields a reacted surface layer comprised of Si-rich CoSixGe1-x, Ge-rich SiyGe1-y and possibly CoSi2, with the two former constituents exhibiting a degree of epitaxial alignment with the substrate. The formation of Co/SiSixGe1-x alloys is discussed in terms of the ternary phase diagram.
Detection of Surface Response to Chemical/Mechanical Planarization of Silica Films
Authors: Trogolo Jeffrey A. , Rajan Krishna
Published: March 2011

Chemical/mechanical (C/M) planarization is a technique that has received attention lately due to the industry-wide trend toward multilevel device processing. In most multilevel schemes, the most commonly planarized layer is the interlevel dielectric, usually an oxide. In order to understand the response of this oxide layer to the planarization process, the authors have addressed the issues of chemical and structural effects of C/M planarization on silicon dioxide films. Transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) spectroscopy were used to examine the films and revealed that there are chemical and structural changes that occur within 200 nm of the film surface.
Stability of Sputter Deposited Al-Cu Bilayers on SiO2.
Authors: Nandan R. , Murarka S. P. , Pant A. , Shepard C. , Lanford W. A.
Published: March 2011

An investigation of the stability and electrical characteristics of Aluminum-Copper bilayer films on SiO2 has been carried out. In this investigation, a thin layer of sputtered aluminum is used as a diffusion barrier/adhesion promoter between the copper and SiO2. The electrical performance of these structures when subjected to thermal cycles and applied biases is determined. The interactions and diffusion of copper through aluminum into SiO2 was investigated using both blanket films and MOS capacitors. Results are compared with those obtained from structures of Al and Cu metallization on SiO2. Samples were annealed at various temperatures in the range of 200°C to 500°C. Analysis using four-point probe resistivity measurements, X-ray diffraction, and Rutherford Back Scattering were carried out. MOS capacitors are used to establish performance under applied bias. Capacitance-Voltage characteristics of formed alloys are discussed. These results will be presented and discussed in view of the applicability of aluminum as the adhesion promoter for copper interconnections on SiO2.
Transient Response and Space Charge Effects in Extrinsic Photoconductors
Authors: Haegel N. M. , Latasa C. A. , Fong G. L. , White A. M.
Published: March 2011

Transient response times for extrinsic photoconductors under constant voltage bias have been calculated using a variable finite-difference technique. We find that the transient response to a step function increase in photon signal is determined by the build-up of a space charge barrier to counteract out-diffusion and sweep-out. Transient times on the order of 10−2 – 10−4 s are found for 20–500 μm thick detectors under the photon backgrounds typical of infrared astronomy and other low background spectroscopy applications.
Photoinduced Space Charge Effects on Current Noise in Photoconducting Insulators
Authors: Carbone A. , Mazzetti P.
Published: March 2011

A set of experimental measurements concerning both current noise and conductance relaxation curves in CdS and CdSe photoconductors has shown the existence of a relationship between the noise power spectrum and the Fourier transform of the phototransient curve. Some of these experimental results have already been published. It appears that at least two different noise components contribute to the total power spectrum. The first component, which dominates the low frequency part of tile spectrum, is strictly related to the behaviour of the relaxation curve. Indeed, it can be attributed to the fluctuation of the photoinduced positive trapped charge and consequently of the potential barrier at the interface electrode-photoconductive material. The second component, on the contrary, is practically independent of the light wavelength, and represents an intrinsic noise component related to the generation-recombination and trapping processes within the photoconductor. In this paper we present a theory accounting for both the photoinduced and the intrinsic noise component. This theory fits well to the experimental data concerning the dependence of noise on light intensity and wavelength, using the parameters obtained from the phototransient and photoconductance measurements performed on thle same specimens. It also gives tile correct order of magnitude of the measured absolute value of the noise power spectrum.
Ion-Implanted Germanium Far-Infrared Photodetectors
Authors: Wua I. C. , Hailer E. E.
Published: March 2011

Germanium Blocked Impurity-Band (BIB) detectors, which have potential applications for space-born far infrared astrophysics observations, have been fabricated by means of boron ion implantation on high-purity Ge substrates. These devices are sensitive beyond the cutoff wavelength of Ge photoconductors doped with shallow acceptors. The extended cutoff wavelength increases with applied bias and can reach up to 200μm at very low dark currents of less than 100 electrons/sec. In order to enhance the photo-response, high-energy (3MeV) implantation has been used to form a thicker infrared-active layer. The influence of both ion-implant energies and post-implant anneals on the performance of detectors will be presented. Generation of excess donors in the boron implanted region has been observed. Their origin and effect of device performance will be discussed.
Applications of Optoelectrochemical Impedance Measurements on Electrolyte/Dielectric/Semiconductor Structure:Cartographic Analysis
Authors: Martin J. R. , Royer P. , Souteyrand E.
Published: March 2011

The use of a weak modulated illumination with above-bandgap light energy as a probe scanning a Electrolyte/Dielectric/Semiconductor structure under electrochemical potentiostatic polarization gives an opportunity to obtain qualitative cartographies of different electrical parameters characterizing the Semiconductor/Dielectric interface.
The Confining Potential for Carriers in Planar Doped GaAs and the Effect of Photoexcitation
Authors: Richards D. , Wagner J. , Ploog K. , Fischer A.
Published: March 2011

Single Be and Si δ-doped layers in GaAs have been investigated by Raman spectroscopy. GaAs/AlxGa1-xAs heterointerfaces, placed 30nm from the dopant spike on either side, facilitate optical measurements by the confinement of photogenerated minority carriers. Self-consistent subband calculations have been performed to compute the subband structure of the two-dimensional electron or hole gas which is confined by the space-charge induced potential well at the δ-doping layer. Upon increasing photoexcitation, the increase in density of photocreated electrons in the Be structure is clearly seen in the polarised Raman scattering spectrum by the appearance, and subsequent increase in frequency, of the electron plasmon modes. The electric field at the top GaAs/AlxGa1-xAs interface is monitored by measuring the strength of electric field induced LO phonon scattering.
Exciton Transitions in Narrow GaAs/AlxGal-x As Quantum Wells
Authors: Russo O. L. , Rehn V. , Nee T. W. , Cole T. L. , Theis W. M. , Schwartz C.
Published: March 2011

Electroreflectance (ER) measurements were made on GaAs/AxGal-x As coupled quantum wells at room temperature and at 77K. The close coupling of the narrow (28.3 A) barriers resulted in splitting of the hole and electron subband levels which was observed at both temperatures. As a first approximation, the confining potential was assumed to be due to the barrier alone; electric field effects of the modulating potential and trapped interfacial charge were considered to be negligible. The dominant heavy holeconduction and light hole-conduction transitions observed at 300K were at 1523meV and 1539 meV respectively, although other weaker transitions were also resolved.
A Theoretical Study of Band Offset Modification at the InAs/GaAs Interface
Authors: Shen T-H. , Matthai C. C.
Published: March 2011

We present the results of pseudopotential calculations on the InAs/GaAs system with and without interlayers of Ge at the interface. We find that the band alignment depends critically on the positioning of the interlayer at the interface and on the number of monolayers substituted. The results can be explained with recourse to a simple model based on charge transfer between the atoms across the interface.
Transmission Electron Microscopy Study of Epitaxial Co/Au and Co/Pd (111) Multilayers
Authors: de Veirman A.E.M. , Hakkens F. , Coene W. , Den Broeder F.J.A.
Published: March 2011

The results of a transmission electron microscopy study of Co/Au and Co/Pd multilayers are reported. Special emphasis is put on the epitaxial growth and the relaxation of the misfit strain of these high misfit systems. In bright-field cross-sectional images, periodic contrast fringes are observed at the interfaces, which are the result of Moiré interference and which allow determination of the degree of misfit relaxation at the interface. It was established that 80-85% of the misfit is relaxed. From high resolution electron microscopy images the Burgers vector of the misfit dislocations was derived, being a/2<110> lying in the (111) interface plane. The results obtained for the Co/Au and Co/Pd multilayers will be discussed in comparison with those obtained for a bilayer of Co and Au.
Films Grown on Vicinal GaAs(111) Substrates By Molecular Beam Epitaxy
Authors: Yang K. , Schowalter L. J.
Published: March 2011

The faceted surface morphology of films grown on on-axis GaAs(111) substrates in the reconstruction regime is studied with an atomic force microscope. It reveals that facets are vicinal surfaces. Surface morphologies of films grown on substrates tilted toward different directions have been compared. An explanation is given for all observed surface morphologies. Smooth films can only be obtained on substrates tilted toward [211] in the surface reconstruction regime.
In-Situ Growth of Three-Dimensionally Confined Structures on Patterned GaAs (111)B Substrates
Authors: Rajkumar K. C. , Kaviani K. , Chen J. , Chen P. , Madhukar A. , Rich D. H.
Published: March 2011

The potential of realizing quantum box structures via in-situ molecular beam epitaxical growth on the (111)B face of GaAs is explored. Growth is carried out on patterned (111)3B substrates with an array of truncated triangular pyramidal mesas. The mesa tops with arbitrarily small areal dimensions are used as templates for quantum box realization. Under appropriate conditions of growth along with the attendant interfacet migration, a mesa top growth profile characterized by monotonically shrinking lateral dimensions resulting in 'pinch-off is achieved.
Effect of Biaxial Stress on Solid Phase Epitaxy of Silicon
Authors: Lu Guo-Quan , Gupta Tapan K.
Published: March 2011

The effect of biaxial stress on solid phase epitaxial growth (SPEG) rate of crystalline Si(100) into self-implanted amorphous surface layer has been measured. Biaxial stresses in the crystalline and amorphous phases were generated by bending the silicon wafer using the residual stresses in Ge films deposited on the back side of the wafer. Stresses were determined at SPEG temperatures by optical measurements of wafer bending curvatures. Tensile stresses up to 13 MPa in the crystalline phase and 34 MPa in the amorphous phasewere achieved during SPEG at 530ºC. An optical system based on the time-resolved reflectivity (TRR) technique was devised to measure the growth rates of two adjacent samples during a single SPEG run. This enables a direct comparison of the growth rates under different stress conditions without concern for run-to-run temperature variations. We found that the growth kinetics in all the samples were retarded as the c/a interface approached the free surface. However, the extent of this rateretardation was reducedin the stressed samples, leading to stress-enhanced growth kinetics. We speculate that the application of the biaxial tensile stresses might slow down the incorporation of hydrogen into the amorphous phase, a mechanism for the rate-retardation.
Epitaxial Lateral Overgrowth of Silicon on SiO2 Investigated by X-Ray Topography
Authors: Jenichen B. , Köhler R. , Nagel N. , Bergmann R. , Bauser E.
Published: March 2011

Silicon lamellae grown laterally over silicon dioxide by liquid phase epitaxy are investigated using X-ray double crystal topography. The lamellae are grown from Indium solution. All of the lamellae show growth striations with indium concentration differences of about 1016...4x1017 cm−3 Overgrowth widths up to 320μm are obtained on sides of the seeding window by growth under conditions of low supersaturation. Facetting of the lamella edges then becomes less pronounced and, therefore,striations are detected farther away from the windows.

About 60% of the lamellae are free of crystallographic defects. In the defective lamellae single dislocations parallel to the sample surface are detected. They extend between seeding window edges and re—entrant corners at the lamella edges. Dislocations probably form during the cooling process due to strains near the edges of the seeding windows, and as a result of indium incorporation in high concentration.
In Situ Monitoring of the Smear-Out of the Ge Profile in GAS Source SiGe MBE Using Rheed Intensity Oscillations
Authors: Werner K. , Butzke S. , Maes J.W. , Schannen O.F.Z. , Trommel J. , Radelaar S. , Balk P.
Published: March 2011

We have studied the deposition of GexSi1−x layers on (100) Si substrates by gas source molecular beam epitaxy (GSMBE) using disilane and germane.

The investigation of RHEED intensity oscillations during growth reveals the well known rate enhancement obtained when adding a small amount of germane to the disilane flux. However, when exposing a previously deposited Ge layer to a pure disilane flux the growth rate during the first few monolayers remains at an enhanced value but returns to its homoepitaxial value after about 10 to 15 monolayers. This behaviour was observed under a variety of growth conditions. It is in marked contrast to the experience obtained in conventional Si/Ge MBE and suggests a catalytic effect of the particular surface present during GSMBE growth. We propose that this effect is caused by the surface segregation of Ge species and leads to a smear-out of the Ge profile in the layer.
Heteroepitaxial Growth of Transition-Metal Nitride Films
Authors: Shinn M. , Mirkarimi P.B. , Barnett S.A.
Published: March 2011

The nucleation of epitaxial transition-metal nitride films with different lattice mismatch and growth of the corresponding supcrlattices were studied. In-situ Auger electron spectroscopy (AES) was used to characterize the nucleation mechanisms of V0.3Nb0.7N films on TiN (1.7% mismatch), TiN films on VN (2.4% mismatch), TiN films on NbN (3.6% mismatch), NbN films on VN (5.7% mismatch), and VN films on NbN grown by ultra-high vacuum reactive magnetron sputtering. The initial growth mechanism was layer-by-layer for mismatch values up to 3.6%, but three-dimensional island nucleation occurred for 5.7% mismatch. Scanning tunneling microscopy (STM) observations of NbN films showed threedimensional islands, confirming the AES results. X-ray diffraction spectra from the corresponding superlattices showed strong superlattice reflections except for the large-mismatch NbN/VN combination. Cross-sctional transmission electron microscopy studies showed that the superlattice layers were.velldefined and planar for low mismatch, but were irregular and non-planar for VN/NbN, in agreement with the X-ray, AES, and STM results. The maximum lattice mismatch for epitaxial nitride superlattice growth was thus limited by island nucleation and in the range from 3.6 - 5.7%.
Characterisation of Extended Defects in Si and Si1−x Gex Alloys: The Influence of Transition Metal Contamination
Authors: Higgs V. , Lightowlers E.C.
Published: March 2011

Photoluminescence (PL) spectroscopy, cathodoluminescence (CL) spectroscopy and imaging, transmission electron microscopy (TEM), and preferential defect etching and optical microscopy have been used to characterise dislocations in plastically deformed Si and in Si1−x Gex alloys. The PL spectra from plastically deformed Si produced under clean conditions, contained no dislocation related luminescence features. However, after deliberated Cu contamination and annealing, the PL spectra were dominated by the four main D-bands (D1-D4). CL spectroscopy and imaging revealed that the D3 and D4 bands originate on the slip lines, whereas D1 and D2 are dominant between the slip lines. Pseudomorphic Si1−x Gex layers grown by molecular beam epitaxy (MBE) and forced to relax by Cu contamination and annealing have also been examined. Both the PL and CL spectra were dominated by the D1-D4 bands, and monochromatic CL imaging showed that the D3 and D4 bands originate at the misfit dislocations with the location of the Dl and D2 bands being much less well defined. PL spectra from Si1−x Gex capping layers, grown by MBE on linearly compositionally graded buffer layers, were dominated by bound exciton luminescence features, identical with those observed in bulk grown alloys, and showed relatively weak D-band features. PL spectra obtained after chemical step etching, and CL spectra obtained with different beam energies, showed that the D-bands originated in the buffer layers which contained high densities of misfit dislocations. Well defined monochromatic CL images of the misfit dislocations could only be obtained using a narrow band pass filter centred on the D4 band. No D-band luminescence was observed from Si1−x Gex layers grown by high temperature chemical vapour deposition (CVD). However, after deliberate contamination with Ni, the D-bands became the dominant features and CL imaging clearly showed that the D4 band originates at the misfit dislocations and the D2 band predominantly between the misfit dislocations.
Tem Structure Investigations of Low-Temperature MBE Grown Inalas Layers on INP<001> Substrate
Authors: Werner P. , Liliental-Weber Z. , Yu K.M. , Weber E.R. , Rek Z. , Metzger R.
Published: March 2011

The real crystal structure of In0.52A10.48As layers grown on InP<001> substrate as a function of the growth temperature (between 150°C and 450°C) was investigated. The following structural / electrical analyses were applied to the samples: transmission electron microscopy (TEM), x-ray diffraction and particle induced x-ray emission (PIXE). In the temperature range between 200°C and 450°C good epitaxial growth of InAlAs layers can be achieved with a low density of dislocations and stacking faults. Ordering of group-III elements on {111} planes was observed for these layers. Structure models of such ordered domains are discussed. At growth temperatures below 300 °C additional As (≈2%) is incorporated in the lattice. Growth at temperatures below 200°C leads to the formation of pyramidal defects with As grains in their cores. As-grown as well as annealed InAlAs layers show a nearly constant, high electrical resistance (106-107Ωcm) in the whole temperature range.
The Dependence of Defect Density in GexSi1−x/Si Heterostructures Grown by Remote Plasma-Enhanced Chemical Vapor Deposition on Deposition Parameters
Authors: Kinosky D. , Qian R. , Hsu T. , Irby J. , Mahajan A. , Thomas S. , Banerjee S. , Tasch A. , Magee C. , Grove C.L.
Published: March 2011

The density of misfit dislocations in GexSi1−x films has been measured as a function of deposition temperature and r-f plasma power in Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD). The misfit dislocation density decreases as the deposition temperature is lowered from 450°C to 410°C. As the plasma power is increased from 6.6 to 16W, the dislocation density peaks at lOW and then decreases with increasing power.
Sticking and Desorption Coefficients of As4 and As2 During Group V and Group III Controlled MBE Growth
Authors: Fernandez Rouel
Published: March 2011

Reflection High Energy Electron Diffraction (RHEED) oscillations under arsenic and gallium-controlled Molecular Beam Epitaxy (MBE) growth conditions have been used to measure the sticking and desorption coefficients of As2 and As4. The coefficients are obtained from measurements of the arsenic incorporation rates. Comparisons are made with measurements obtained from desorption rates using modulated beam mass spectroscopy. The transition from gallium to arsenic-controlled growth is observed to occur after excess gallium atoms accumulate on the surface. The maximum intrinsic arsenic sticking coefficients occur when the maximum number of gallium atoms can be incorporated for a given arsenic flux. The intrinsic maximum arsenic sticking coefficients are found to be 0.75 and 0.50 for As2 and As4, respectively. During galliumcontrolled growth, the arsenic sticking coefficients are independent of substrate temperature as long as the sticking coefficient of gallium is equal to one. However, a temperature dependent maximum gallium-controlled arsenic sticking coefficient exists. It can be measured by the maximum Ga to As4 flux ratio that produces specular film surfaces. During gallium-controlled growth, the Ga to As flux ratios are shown to be equal to the gallium-controlled arsenic sticking coefficients. The activation energy for arsenic desorption during arsenic-controlled growth conditions was measured as -0.50 eV for independent As4 and As2 incident fluxes. During gallium-controlled growth with incident As4 fluxes, an activation energy for arsenic desorption of -0.70 eV was measured for the maximum gallium-controlled arsenic sticking coefficients.
Initial Studies on The Heteroepitaxial Growth of Thin Films of (AI/In)N on Ain-Seeded (00.1) Sapphire by Single-Target Reactive Magnetron Sputtering
Authors: Kistenmacher T. J. , Ecelberger S. A. , Bryden W. A.
Published: March 2011

Thin films of (AI/In)N alloys have been deposited on AIN-nucleated (00.1) sapphire by reactive (pure N2 gas) magnetron sputtering and characterized by X-ray scattering, stylus profilometry, optical spectroscopy, and electrical transport measurements. Initial efforts have concentrated on producing films with compositions near Al0.31In0.69N (bandgap tailored to GaN). The alloy sputtering targets were disks fabricated by cold pressing appropriate molar mixtures of beads of 99.99% purity Al and In. The resulting thin films are composed of heteroepitaxial grains {(00.1)InNll(00.1)sapphire; (10.0)InNll(11.0)Sapphire} and their chemical composition has been deduced from the variation in the a cell constant (as measured by the X-ray precession method) to yield equilibrium film compositions near Al0.04In0.96N and Al0.25In0.75N, respectively. Preliminary results are presented on the dependence of the quality of heteroepitaxial growth and electrical and optical properties of. these AlxIn1−xN alloy films on various growth parameters: such as chemical composition; film thickness; morphology; and substrate temperature.
Cure Studies of Fluorinated Polyamic Acids by Thermal-IR
Authors: Roginski Robert T. , Fjare Douglas E.
Published: March 2011

The thermal curing chemistry of a fluorinated polyamic acid based on 6FDA (hexafluoroisopropylidene bis(phthalic anhydride)) and APBP (4,4′-bis(4-aminophenoxy)biphenyl) was studied by thermal-IR spectroscopy. Anhydride formation was observed at intermediate cure temperatures and maximized at approximately 220°C. The degree of anhydride formation was affected by the solvent, being least in 2-methoxyethyl ether and increasing in the solvent order: 2-methoxyethyl ether < NMP < 2-(2-ethoxy)ethoxyethanol. In addition to the back reaction of amic acid to anhydride and amine, at least one additional mechanism of anhydride formation is observed. The onset of the second mechanism of anhydride formation is coincident with the onset of imidization, which leads us to propose that water generated by imidization can react with anhydride during the curing process, before escaping from the film, to form diacid. Cyclization of diacid to anhydride is proposed as the second mechanism of anhydride formation.
Cure Technology for Controlled Stress in Thin Benzocyclobutene Coatings
Authors: Townsend P. H. , Burdeaux D. C. , Stokich T. M. , Dibbs M. G.
Published: March 2011

The stress at room temperature in many typical polymer coatings used for microelectronic dielectrics is near 40 MPa. Polymer coatings derived from divinylsiloxane bisbenzocyclobutene (BCB), (CAS 117732-87-3), have a stress level of ca. 38 MPa after a conventional thermal oven cure. In this work, a novel approach based on curing the BCB polymeric network in the vitrified state has been used to achieve far field stresses of 24 MPa in the final coatings. This represents a 36% reduction in the far field stress of BCB coatings cured at 250 °C. The cure methodology and compatibility with device process design are discussed.
Stresses in Polyimide Films during Cure and Thermal Cycling
Authors: Monk David J. , He Yongxiang , Soane David S.
Published: March 2011

Several electronics packaging schemes involve polymer/inorganic interfaces, including: dual-in-line packages, tape automated bonding and multilayer interconnects. Typically, the thermal expansion coefficients are disparate, so these interfaces often cause high stress. Therefore, a phenomenological model describing transient stresses in spin-coated polyimide films was developed. The model is based on linear viscoelastic theory, and it accounts for shrinkage caused by solvent evaporation and imidization, viscoelastic relaxation, and thermal expansion mismatch. Strains have been defined from three mechanisms: thermal expansion mismatch, chemical curing, and solvent evaporation. Stress is, then, calculated by using the Classical Maxwell Model with one element. The concept of free volume is used throughout the model to estimate viscosity, modulus, and other quantities related to calculating strains. Model predictions for stress as a function of temperature during film cure and thermal cycling are fit with experimental data obtained from a bending beam apparatus.

Stress has been estimated by using the thin film approximation of the Timoshenko bilayer stress equation. Experimental data agree well with wafer bowing stress measurements. Although the technique does not yet take into account changing polyimide thickness during curing, the results still show qualitative curing dynamics. This preliminary study revealed good agreement between predicted and observed effects of material properties on stresses developed during cure and thermal cycling. Specificially, an unexpected high in-cure stress was observed for a standard low CTE polyimide. High stresses during curing can be as detrimental to an electronics device as high stress during device operation, so this technique may be useful when screening polyimides and/or prescribing curing schedules. Future work will improve the predictive capability of the model.
Thermal and Mechanical Analysis of a Multichip Module
Authors: Hu M. S.
Published: March 2011

High speed, high density packaging requirements have made multichip modules (MCM) one of the most active areas of research in the electronic industry.

High density printed wiring board (PWB) have low production cost and good electrical performance. However, the most questioned issue in application is the reliability. As a result, a thermal and mechanical analysis on a MCM has been conducted to understand its feasibility. The results indicate that with proper design, the components can operate under satisfactory conditions on PWB laminates.