bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsed Laser Interactions With Condensed Matter
Authors: Bloembergen N.
Published: March 2011

The primary interaction is the absorption of photons by electrons. In metals free-free transitions increase the energy of the electron gas. In semiconductors and insulators electron-hole pairs are created, if the photon energy exceeds the band gap. If it is less, only multiphoton processes can initiate energy transfer from the light beam. In nearly all solid materials Auger processes and electron-phonon interactions occur on a picosecond time scale for the high density and energy of the carrier gas created by intense short laser pulses. Thus melting and evaporation of the material can occur on this time scale. These processes may be considered as the initial phases in the creation of laser produced plasmas. They have been studied by time-resolved measurements of the complex index of refraction, by electron and ion emission, by second harmonic generation, by electrical conductivity and other techniques. Fast time resolution is essential. The dynamic behavior of atoms and phase transitions in the picosecond and femtosecond regime has been opened up for experimental investigation.
Enhancement of Grain Growth In Ultra-Thin Germanium Films By Ion Bombardment
Authors: Atwater Harry A. , Smith Henry I. , Thompson Carl V.
Published: March 2011

We report the enhancement of grain growth in 50 nm-thick Ge films during Ge ion bombardment, or self-implantation, at 500-600 ° C. Conventional and cross-sectional transmission electron microscopy (TEM) indicate that normal grains grow to a columnar structure at considerably lower temperatures than during ordinary thermal annealing. Furthermore, self-implantation-enhanced normal grain growth is found to be very weakly dependent on temperature. The time dependence and temperature dependence of grain growth during self-implantation were compared with data for thermal annealing experiments and suggest that the enhancement results from elastic collisions between ions and atoms located at the grain boundaries.
Impurity Diffusion, Crystallization And Phase Separation In Amorphous Silicon.
Authors: Elliman R.G. , Poate J.M. , Williams J.S. , Gibson J.M. , Jacobson D.C. , Sood D.K.
Published: March 2011

Diffusion, crystallization and phase separation processes in indium implanted amorphous silicon are examined for low temperature annealing (600°C). Both diffusion and crystallization are shown to be extremely sensitive to the indium concentration. Diffusion coefficients more than 10 orders of magnitude higher than tracer diffusion coefficients in crystalline silicon are measured, and amorphous to crystalline silicon transitions at temperatures as low as 350°C are reported. Phase separation is also observed.
Phase Transformations In Nickel-Aluminum Alloys During Ion Beam Mixing
Authors: Eridon James , Rehn Lynn , Was Gary
Published: March 2011

The effect of ion beam mixing of nickel-aluminum alloys with 500 keV krypton ions has been investigated over a range of temperature, composition, ion dose, and post-irradiation thermal treatments. Samples were formed by aternate evaporation of layers of aluminum and nickel. A portion of these samples was subsequently annealed to form intermetallic compunds. Irradiations were performed at both room temperature and 80 K using the 2 MV ion accelerator at Argonne National Laboratory. Phase transformations were observed during both in situ irradiations in the High Voltage Electron Microscope(HVEM) at Argonne and also in subsequent analysis of an array of irradiated samples. Electron diffraction indicates the presence of metastable crystalline structures not present in the conventional nickel-aluminum phase diagram. Transformations occur at doses as low as 5×1014 cm−2 and continue to develop as the irradiation progresses up to 2×l016 cm−2. Layer mixing is followed through Rutherford Backscattering analysis. Samples are also checked with x-rays and Electron Energy Loss Spectroscopy (EELS). A thermodynamic argument is presented to explain the phase transformations in terms of movements on a free energy diagram. This analysis explains the interesting paradox concerning the radiation hardness of the NiAl[l] phase and the amorphous structure of mixed Ni-50% Al layers[2].
Electron Ream-Induced Phase Transformation In MgA1204SPINEL
Authors: Shaibani S.J. , Buckley S.N.
Published: March 2011

Bombardino stoichiometric MgAl204spinel at elevated temperatures with hiqh energy electron beams ciradually converts the irradiated area into γ-alumina. This phase transformation, which involves the diffusion of maginesium out of the irradiated area, shrinks the oxygen ion sublattice, thereby generating internal stresses which cause localised crystal fractures.

Three categories of crack are observed:type 1, the majority, are straiciht and lie at the centre of the irradiated area; type 3 are circular and they are located near the edge of the irradiated area in the spinel matrix: and, type 2 are hybrids. A quantitative model which explains the development of all types of crack is presented.

The proportion of γ-alumina produced, the fractional loss of magnesium and the extent of crackino are found to depend on the electron beam energy, the electron dose, the beam profile and the irradiation temperature.
Rapid Thermal Annealing of B or N Implanted Monocrystalline 1-SiC Thin Films and its Effect on Electrical Properties and Device Performance
Authors: Ryu Jae , Kim H. J. , Davis R. F.
Published: March 2011

The annealing behavior of B or N dual implants in 1-SiC thin films has been studied using cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectroscopy (SIMS), and four point probe electrical measurements. A high resistivity layer was produced after annealing the B implanted-amorphous layer in the temperature range from 1000°C to 1500°C for 300 a; however, the resistivity rapidly decreased as a result of annealing at higher temperatures. The reasons for these changes in resistivity and the lack of p-type conduction at all annealing temperatures in these B implants include: (1) possible compensation of the native n-type carriers, (2) reduction in the B concentration via formation of B-containing precipitates between 1300°C and 1600°C and out diffusion of this species at and above 1600°C, and (3) creation of additional n-type carriers.

No precipitates or defect structure was observed in N implanted-annealed samples. The resistivity of this non amorphous n-type layer decreased with increasing annealing temperatures from 700°C to 1800°C. Furthermore n-p junction diodes were fabricated for the first time in β-SiC via N implantation into samples previously in situ doped with 8 × 1018/cm3 Al coupled with rapid thermal annealing at 1200°C for 300 a. A typical diode ideality constant and a saturation current for these diodes was 3.4 and 9 × 10-10 A/cm2, respectively.
Temperature Measurement and Control in a Rapid Thermal Processor
Authors: Sheets Ronald E.
Published: March 2011

Rapid Thermal Processing (RTP) of silicon or other semiconductor materials requires accurate measurement and control of temperature. In a typical RTP cycle, heating of the wafer takes place in seconds, making accurate control of the wafer temperature very critical. Non contact wafer temperature sensing is achieved using an optical pyrometer. Precise temperature control from 400° C to 1350° C is maintained with a closed loop control system consisting of an optical pyrometer and a computer. Sources of errors due to variations in emissivity as a function of wafer temperature, surface conditions and background radiation are discussed. Calibration of the system is achieved by using a thermocouple instrumented wafer.
Rapid Thermal Anneaung of Arsenic-Phosphorus(N+-N-) Double-Diffused Shallow Junctions
Authors: Kwong D. L. , Alvi N. S. , Ku Y. H. , Cheung A. W.
Published: March 2011

Double-diffused shallow junctions have been formed by ion implantation of both phosphorus and arsenic ions into silicon substrates and rapid thermal annealing. Experimental results on defect removal, impurity activation and redistribution, effects of Si preamorphization, and electrical characteristics of Ti-silicided junctions are presented.
Silicides and Rapid Thermal Annealing
Authors: d'Heurle F. M. , Hodgson R. T. , Ting C. Y.
Published: March 2011

In the first part of this paper the role of rapid thermal annealing in sulicide processing is viewed from a theoretical point of view with respect to what is known about metal-silicon reactions. The second part is a brief survey of the quickly expanding literature on the rapid thermal annealing of silicides. Whereas RTA does not appear to solve all, or perhaps even any, of the problems encountered in the use of silicides, it is concluded that RTA presents a number of definite advantages.
Limited Reaction Processing of Silicon: Oxidation and Epitaxy
Authors: Gronet C. M. , Sturm J. C. , Williams K. E. , Gibbons J. F.
Published: March 2011

Limited reaction processing has been used to grow thin, high quality layers of epitaxial silicon, silicon dioxide, and polycrystalline silicon. Multiple layers of these materials were deposited in – situ to demonstrate control of layer thicknesses, interface transition regions, and interface cleanliness. MOS and p-n junction structures were fabricated which exhibit electrical characteristics comparable to those of devices produced by conventional techniques.
A Study of Se+ Implants into Encapsulated GaAs
Authors: Gwilliam R. , Shahid M. A. , Sealy B. J.
Published: March 2011

The effects of implanting Se+ ions through Si N4 layers have been compared with implants into uncapped GaAs. Through nitride implants have a higher residual damage, lower carrier concentration and lower mobility following rapid thermal annealing between 850 and 975 °C. The effect is believed to be due to the interface strain between the encapsulant and the amorphous GaAs.
Rapid Thermal Annealing of Be Implanted in 0.53Ga 0.47As
Authors: Lam Christine S. , Fonstad Clifton G.
Published: March 2011

Rapid thermal annealing (RTA) techniques have been developed to activate shallow, high dose implants in InGaAs. Activation of deep, multiple energy high dose beryllium implants was also investigated. Two-step RTA cycles which peaked at a high temperature momentarily and then held at a lower temperature for 3 to 10 seconds were used to activate the implanted dopants. Over 80% activation was achieved. The results are superior to furnace anneal results, and at least comparable to graphite strip heater results. Increasing the anneal temperature on higher dose implants, however, type conversion was observed when the peak temperature exceeded a certain value.
Multi-Step Rapid Thermal Annealing of Si-Implanted Gaas for Microwave Discrete Devices and Monolithic Integrated Circuits Fabrication
Authors: Yu Tan-Hua , Kong W. M. , Lester L. F. , Smith P. M. , Duh K. H. G. , Hwang J. C. M.
Published: March 2011

In this paper, we report a multi-step rapid thermal annealing process for microwave discrete devices and monolithic integrated circuits fabrication. 2” diameter undoped liquid encapsulated Czochralski GaAs wafers were implanted with 29 Si+ and annealed without capping using incoherent light from high intensity halogen lamps. The annealing was carried out in multiple temperature steps to achieve optimum damage removal and dopant activation. As a result, wafers implanted with mid 1012 cm−2 dose exhibited 85–90% activation efficiency for 100kV implant and nearly 100% activation for 300 kV implant. In comparison with single-stepannealed wafers, multi-step-annealed wafers showed not only higher activation efficiency, but also more uniform activation, higher electron mobility and better device performance.
Zone Melting Recrystallization of GaAs Films on Oxidized Si
Authors: Zhu Weiwen , Wang Weiyuan
Published: March 2011

In this paper, GaAs SOI consisting of MBE deposited GaAs films on oxidized Si was recrystallized by narrow-zone melting in a RF induction graphite strip heater at a rate of 1–1.2 mm/s. The original grain size of MBE GaAs SOI films is smaller than 800 Å, and the electron diffraction patterns appear as typical polycrystalline rings as determined by SEM and ED, respectively. After zone melting recrystallization, the grain size of GaAs SOI films increases to 1 µm, the prefered ˂111˃ diffraction spots appear apparently, and the carrier concentrations and electron mobility amount to 3×1017cm−3 and 1.1×103cm2/v.s as determined by Hall measurement. The AES Ga/As signal ratio of the GaAs SO before and after recrystallization is the same as that of the GaAs single crystal. The possible application of GaAs SOI to devices is discussed.
Formation of Epitaxial Soi Structures Using Alkaline Earth Fltuoride Films
Authors: Ishiwara Hiroshi , Asano Tanemasa
Published: March 2011

Recent progress in the research of heteroepitaxial SOI structures such as Si/CaF2/Si and Ge/CaF2/Si structures is reviewed. Structural and electrical properties of alkaline earth fluoride films on Si substrates are first discussed. Growth conditions, structural properties, and device applications of the Si/CaF2/Si structures are then presented. It is shown that a predeposition technique, in which a thin Si layer is deposited at room temperature prior to the growth of a thick film at elevated temperature, is effective to improve the crystalline quality and the surface morphology of the film. Usefulness of solid phase epitaxy to obtain high quality films is also demonstrated. Finally, it is shown that the predeposition technique is also useful in formation of Ge/CaF2/Si structures.
Comparison of Structural and Electrical Characteristics of Solid-Phase Epitaxial Films Recrystallized By Rapid Thermal Annealing and Furnace Annealing
Authors: Sundaresan R. , Chang P.-H. , Malhi S.D.S. , Lam H.W.
Published: March 2011

Solid-phase epitaxial regrowth of polysilicon films. amorphized by a room-temperature silicon implant. has been achieved using a (low temperature) furnace anneal or a (high temperature) rapid thermal anneal. Lateral extension of the growth onto an oxide layer, 4 μm wide, has also been observed. The electrical properties of the films were examined by building MO2S devices in them. Average electron mobilities of 520 cm2/v-sec and 200 cm2/v-sec have been measured for films regrown on top of silicon and oxide respectively.
Epitaxial Regrowth of a-GaAs/(100) Silicon By Excimer Laser Annealing at 248 nm
Authors: Christou A. , Efthimiopoulos T. , Kyriakidis G. , Varmazis C.
Published: March 2011

Excimer laser annealing at 248 nm has resulted in the recrystallization of a-GaAs on (100) silicon. An AlAs encapsulation layer was found to be necessary to prevent the loss of arsenic during laser annealing. An energy density of 105 mJ/cm2 was the critical energy density which gave optimum results. Field effect transistors were fabricated on the regrown (100) GaAs utilizing ion implantation for the n-type channel, and resulted in a transconductance of 70–80 mS/mm.
Formation of Facets at the Solid-Melt Interface in Silicon
Authors: Arnold Emil , Landman Uzi , Ramesh S. , Luedtke W. D. , Barnett R. N. , Cleveland C. L. , Martinez A. , Baumgart H. , Khan B.
Published: March 2011

We have done experimental and theoretical studies of the origins of facet formation at the solid-liquid interface in laser-beam-melted silicon films. Two laser beams were used to produce a molten zone with a closely controlled thermal profile in a thin single-crystal film of silicon, and the liquid-solid interface was observed in situ. A transition to a faceted structure was found to occur under conditions of near thermal equilibrium. The solidliquid interface was also studied theoretically by means of molecular dynamics simulations, incorporating pair- and three-body terms in the interaction potential. Similarly to the experimental system, the solid-melt interface in the simulated system breaks up into facets defined by (111) planes. The melt region in the vicinity of the faceted planes exhibits a certain degree of ordering due to the influence of the crystalline potential.
Formation of Buried Sio2 By High Dose Implantation of Oxygen at Room and Liquid Nitroeen Temperatures
Authors: Namavar F. , Budnick J. I. , Sanchez F. H. , Hayden H. C.
Published: March 2011

We have carried out a study to understand the mechanisms involved in the formation of buried SIO2 by high dose implantation of oxygen into Si targets. Oxygen ions were implanted at 150 keV with doses up to 2.5 X 1018 ions/cm2 and a current density of less than 10 μA/cm2 into Si 〈100〉 at room and liquid nitrogen temperatures. In-situ Rutherford backscattering (RBS) analysis clearly indicates the formation of uniform buried SIO2 for both room and liquid nitrogen temperatures for doses above 1.5 X 1018/cm2.

Oxygen ions were implanted at room temperature into crystalline quartz to doses of about 1018 ions cm2 at 150 keV, with a current density of 〈10〉10 μA/cm2. The RBS spectra of the oxygen implanted quartz cannot be distinguished from those of unimplanted ones. Furthermore, Si ions were implanted into crystalline quartz at 80 keV and dose of 1 X 1017 Si/cm2, and a current aensity of about 1 μA/cm2. However, no signal from Si in excess of the SiO2 ratio could be observed. Our results obtained by RBS show that implantation of either Si+ or O into SiO2 under conditions stated above does not create a layer whose Si:O ratio differs measurably from that of SiO2.
Donor Creation During Oxygen Implanted Buried Oxide Formation
Authors: Delfino M. , Chu P.K.
Published: March 2011

Enhanced electron conductivity is observed in silicon that has been implanted with oxygen ions to form a buried oxide layer. The conductivity is attributed to donors that are created in the silicon both above and below the oxide. Secondary ion mass spectrometry and Rutherford backscattering spectroscopy show that, during subsequent annealing, oxygen accumulates only in the silicon surface. This causes the donors in the silicon surface to be easily activated to high concentrations and, unlike donors beneath the oxide, to be extremely resistant to thermal annihilation.
Reduced Subboundary Misalignment in SOI Films Scanned at Low Velocities
Authors: Pfeiffer Loren , West K. W. , Joy D. C. , Gibson J. M. , Gelman A. E.
Published: March 2011

Silicon-on-Insulator (SOI) films on SiO2 scan-melted at low velocities (20 to 300 µm/sec) with reduced thermal gradients at the melt-freezing interface are found to have qualitatively different properties from similar films melt-scanned at higher gradients and scan velocities. The transition between the two regimes appears to be abrupt. Scanning at intermediate velocities often results an admixture of patches containing one or the other type of material. The slow scan regime is characterized by long straight non-branched subboundaries having a lateral spacing 50-60 µm, and very small tilt misalignments of 0.1° or less. These slow scan subboundaries are found to consist largely of threading dislocations in contrast conventional subboundaries which are tilt boundaries of up to 3° and typically consist of edge dislocations running in the plane of the film.
Photoconduction in Thin-Film Transistors Fabricated from Lasercrystallized Silicon on Fused Quartz
Authors: Chiang A. , Zarzycki M. H. , Johnson N. M.
Published: March 2011

Photoconduction with optical gain in excess of 3000 is achieved in depletion-mode MOSFETs fabricated from laser-crystallized silicon thin-films on fused quartz. Devices operated with a reverse gate bias show responsivity of ≥ 300 Amp/Watt for radiation in the visible spectrum and dynamic range of > 106. This process occurs by spatial separation of photogenerated electron-hole pairs across a p-n junction in the device body, collection of holes in the floating substrate, and conduction of electrons in a buried channel in the bulk of the nearly defect-free silicon film. This study explores the influence of channel dopant profile on the photoconduction process and the latitude for optimized photodetector performance. The effect of post-crystallization residual structural defects on performance uniformity is also evaluated.
A Method to Determine the Density of Surface States and Interfacial Charge Density in N-Channel Sos Mosfet's
Authors: Annamalai N.K. , Khondker A.N.
Published: March 2011

A method to determine the density of surface states NSS and interfacial charge density QSAP in n-channel silicon-on-sapphire MOS transistors from back channel leakage current measurements is presented. A rigorous theory to determine this current as a function of drain-to-source bias, VDS and as a function of body-to-source bias, VBS is also discussed. The evaluation of leakage current is more rigorous in this work because the surface potential is explicitly calculated from the charge neutrality equation of the device. The surface potential, being dependent on interfacial surface state density and the doping density, is more accurate when evaluated from the charge neutrality equation than from assuming a simple a priori value (ɸs={3/2}ɸF). Applying the present theory to experimentally reported leakage current values, the following were obtained:
A Comprehensive Analytic Model of Accumulation-Mode Mosfet's in Polysilicon Thin Films
Authors: Ahmed S. S. , Kim Dae M.
Published: March 2011

The performance of MOSFET's fabricated in LPCVD polysilicon thin films and operating in accumulation mode is modeled analytically. The model quantitatively explains reported device characteristics. Specifically, measured temperature coefficient of current, drive and leakage current, transconductance, drain admittance and ON/OFF current ratio are described in terms of inherent structural and electronic properties of polysilicon. The role of grain boundary hydrogenation in effectino the device performance is highliohted and ouantified.
Addressing the Problems of Agglomeration, Surface Roughness and Crystal Imperfection in Soi Films
Authors: Ramesh S. , Martinez A. , Petruzzello J. , Baumgart H. , Arnold Emil
Published: March 2011

We have designed and experimentally tested, under a wide variety of laser recrystallization conditions, a reliable encapsulation structure that prevents agglomeration and enables recrystallization of SOT films over a 100% wafer area. Our experiments indicate that the wetting characteristics of the structure can also improve the surface planarity of the recrystallized silicon. We also report a dramatic reduction in defect density and the non - occurrence of the characteristic branched subgrain boundary pattern under appropriate conditions of laser recrystallization.
Low Temperature Gate Dielectrics for Tft Applications
Authors: Jones B L , Meakin D B
Published: March 2011

A series of low temperature CVD films of oxide (VAPOX and LTO) and nitride (PECVD ∝-SixNy:H) have been compared and optimised for use as gate dielectrics for TFT on insulator technology. The method of investigation involves the fabrication of MIS capacitor structures using the deposited insulator on single crystal n+ Si. I-V and C-V analyses yield information of the interested electronic stability parameters which are compared for the various insulators.
Twin Stabilzed Planar Growth of Soi Films
Authors: Baumgart H. , Phillipp F. , Ramesh S. , Khan B. , Martinez A. , Arnold E.
Published: March 2011

The microstructure of beam recrystallized silicon-on-insulator (SOI) films is strongly dependent on nucleation and growth processes during zone-melt propagation. In general, the recrystallization takes place along the (100) plane and in the <001> direction and in this case subgrain boundaries form the only major defects in the material. We have, however, identified stable growth regimes that produce predominantly twin boundaries, when the SOl films recrystallize with their surface parallel to the (110) planes. The twin formation process is attributed to growth twinning characteristic for f.c.c. and diamond structures. It has been established that the majority of these boundaries consist of coherent twins. In this manner (110) textured SOl films can be grown which contain almost entirely twin boundaries as structural defects. The crystallography of coherent twin boundaries in SOI films and their dependence on growth parameters is presented.
˂100˃ Single Crystal Soi Films Obtained on 4. In Wafers Using Halogen Lamps
Authors: Haond M. , Dutartre D. , Bensahel D.
Published: March 2011

By using a halogen lamp recrystalization system, we show that a patterning of the underlying oxide of SOI structures allows a high yield of localization of the remaining defects generally encountered in zone melting recrystallization. The influence of the scan speed and grain orientation on the efficiency of the entrainment is investigated. Moreover, we show that a quasi-single crystal can be obtained if a combination of seeding and oxide patterning is used.
Microscopy of Thin Si Films During Lamp Zone Melting
Authors: Dutartre D. , Haond M. , Bensahel D.
Published: March 2011

The melting and solidification fronts of thin Silicon On Insulator (SOI) films have been observed in-situ. The melting front does not advance continuously but by bursts. This so called “explosive melting” allows to explain the appearance of defects (such as voids and surface roughness) observed in the recrystallized film. The freezing front is observed in the case where a pattern for the entrainment of the defects has been etched in the underlying oxide: we show that the entrainment effect is due to the spatial modulation of the solidification front by the structure. Furthermore, the scan speed influences the morphology of the liquid/solid interface and the defect entrainment efficiency.
Compound Formation And Silicon Behavior In Titanium And Tantalum Layered Aluminum Films
Authors: Shen B. W. , Anthony J. M. , Chang P-H. , Keenan J. , Matyi R. , Tsai H. L.
Published: March 2011

Thin film interaction in the material systems of titanium and tantalum-layered Al- 1% Si films has been studied using advanced material characterization techniques. Compound phase formation was analyzed based on results from X-ray diffraction analysis. Al3Ti was identified in the titanium-layered film after 450° C sintering. TaSi2 and unreacted Ta. however, were identified after the sintering. Silicon participated in the phase formation process by incorporating itself as a solute in the Al3Ti while transforming Ta into its silicide. This behavior is to be interpreted based on available ternary phase diagrams. Cross-sectional transmission electron microscopy results indicate that well defined layered films and columnar grains of aluminum were obtained which are believed to be the primary reasons for the observed electromigration improvement over the base metal.
Amorphous W-Zr Films As Diffusion Barriers Between Al And Si
Authors: So F. C. T. , Zhao X.-A. , Kolawa E. , Tandon J. L. , Zhu M. F. , Nicolet M-A.
Published: March 2011

Cosputtered W70Zr30 and W40Zr60 films are investigated as diffusion barriers between Al and Si. W-Zr alloys of both compositions were determined by x-ray diffraction to crystallize at 900°C on Al2O3 substrates. On <111>Si the W-Zr alloy reacts with the substrate above 700°C, forming a uniform, polycrystal line layer of W and Zr suicides. Despite the high crystallization temperatures, an Al overlayer interacts with W-Zr and the Si substrate at ∼500°C. MeV He backscattering spectrometry, SEM and EDAX indicate that this reaction is laterally nonuniform with the formation of deep pits penetrating into the Si substrate. We believe this to be a consequence of fractures in the W-Zr layer induced by reaction with Al. Electrical measurements on shallow junction diodes with /W-Zr/Al contacts show that the device junctions were thermally stable after a 30 min annealing at 450°C but were all shorted after heat treatments at 500°C or above.
A Grazing Incidence X-Ray Study Of Interfacial Reactions In Al-Cu
Authors: Heald S. M. , Chen H. , Tranquada J. M.
Published: March 2011

The Al-Cu system has been used to test the application of grazing incidence EXAFS and x-ray reflectivity measurements to interface systems. Both techniques have been found to be sensitive to compound formation and interdiffusion, and with further development of analysis procedures should be very useful complements to more traditional techniques.
Ion Beam Mixing of Alternate Layers Of Ni-Nb and Ni-Cr
Authors: Rai A. K. , Bhattacharya R. S. , Rashid M. H. , McCormick A. W.
Published: March 2011

Alternating layers of Ni and Nb with a total thickness of 1060Å, and Ni and Cr with a total thickness of 840Å were deposited by electron beam evaporation on silicon. The individual layer thicknesses were adjusted in such a way as to obtain 50/50 at% compositions of Ni-Nb and Ni-Cr; the thicknesses were around 100Å for Ni and 170Å for Nb, and 100Å of Ni and 110Å of Cr. The films were bombarded with 350 keV Cr+ions at a dose of 2 × 10 ions cm. RBS and TEM techniques were used to study the mixing and microstructure. Almost complete mixing and amorphization have been observed for the Ni-Nb system. Ni-Cr film has revealed very little mixing compared to Ni-Nb film and the microstructure remained polycrystalline. Sputter (rf) deposited Ni-Cr film also remained polycrystalline both before and after ion irradiation. The Ni-Cr System appears to be an exception to the structural difference rule for amorphous phase formation by ion irradiation.
Silicon Layers Grown on Patterned Substrates by Liquid Phase Epitaxy
Authors: Bauser E. , KÄss D. , Warth M. , Strunk H. P.
Published: March 2011

Single-crystal silicon layers and doping multilayers have been grown by liquid phase qpitaxy on silicon substrates. The substrates were either partially masked by SiO2, with via holes of various shapes and sizes, or patterned with SiO2 stripes, or profiled with grooves and ridges. The via holes and grooves were just refilled, or they acted as seeding areas for lateral overgrowth of the oxidized wafer up to 100μm. The silicon layers, interfaces and heterointerfaces were free of defects. With appropriate growth conditions the surfaces and interfaces of the epitaxial Si were outstandingly planar.
Cross-Sectional TEM Study Of Phase Separation In Reaction Of Ni-Ta Films With GaAs
Authors: Lahav A. , Eizenberg M. , Komem Y.
Published: March 2011

The reaction between Ni60Ta40 amorphous alloy and (001) GaAs was studied by cross-sectional transmission electron microscopy, Auger spectroscopy, and x-ray diffraction. At 400°C formation of Ni GaAs at the interface with GaAs was observed. After heat treatment at 600°C in vacuum a layered structure of TaAs/NiGa/GaAs has been formed. The NiGa layer has epitaxial relations to the GaAs substrate. The vertical phase separation can be explained by opposite diffusion directions of nickel and arsenic atoms.
Ir Laser Assisted Grading Of Mocvd GaAsp
Authors: Wiseman T. , Juang C. , Jones K. A.
Published: March 2011

We hypothesize that a primary growth mechanism for the MOCVD growth of GaAsP is a series of surface catalyzed methane elimination reactions, and that they can be affected either thermally or photochemically by the absorption of light from a CO2 TEA laser tuned to an absorption maxima. Our preliminary results show that the laser dramatically alters the morphology and supresses the phosphorus incorporation rate when the laser is tuned to an absorption maxima for the AsH3, We interpret these results to indicate that, for the conditions used, the the primary effect of the laser is photochemical, and that the phosphorus incorporation can be increased by exciting PH3, instead of AsH3,. Once the growth mechanisms are better understood and the growth conditions are optimized GaAs1−xPx/GaAs1-yPy superlattices with atomically abrupt junctions should be able to be grown simply by turning the laser on and off.
Transmission Electron Microscope Study of Interfacial Reactions in Gold-Germanium Contact to Gallium Arsenide
Authors: Kim Taeil , Chung D.D.L.
Published: March 2011

The structure of 500 Å Au/500 A Ge/500 Å Au/GaAs (100) was studied by transmission electron microscopy after annealing at 350 – 500°C. Annealing at 350 – 450°C caused the formation of AuGeAs with a (110) texture, but this phase disappeared after annealing at 500°C. The hexagonal a-AuGa (or AuGa) was formed after annealing at 400°C, such that (111)Au // (0001)a, and [110]AU // [1120]a and there was perfect lattice match between Au (i.e., Au-rich solid solution) and a-AuGa. After annealing at 450°C or above, a phase tentatively identified as the hexagonal Au3Ga was formed and Ge (i.e., Ge-rich solid solution) became epitaxial to (100) GaAs. Annealing at 400°C caused Au to change from no texture to a (110) texture.
Interfacial Structure of In/Pt/GaAs Heterojunction Ohmic Contacts
Authors: Marvin D. C. , Ives N. A. , Leung M. S.
Published: March 2011

Graded heterojunction InGaAs ohmic contacts to n-GaAs have been prepared which show improved electrical and morphological properties compared with other diffused contacts. The improvements result primarily from the use of a thin 400 A Pt layer between the 4000 Â In layer and the substrate to control the reaction of the In and the GaAs. A study of chemically etched samples using energy dispersive x-ray (EDX) analysis has revealed the formation of a smooth In Ga, As heterojunction interface. Evidence is also presented that the heterojunction regions are epitaxial. A smooth, uniform interface of this type is not formed in other diffused contact systems, such as In/GaAs and Ni/Au-Ge/GaAs.
Schottky Barrier and Electronic States at Silicide-Silicon Interfaces
Authors: Schmid P. E. , Liehr M. , Legoues F. K. , Ho P. S.
Published: March 2011

This paper reviews the recent studies on Schottky barrier and interface states at silicide-silicon interfaces, with emphasis placed on the results obtained from the epitaxial Ni suicides. A model based on interfacial defect states has been proposed to account for the overall chemical correlation between the barrier height and the metal electronegativity. Measurements on the barrier heights of type A, B and C epitaxial Ni suicides show that these three interfaces can be formed with high degrees of perfection to yield a barrier of 0.78 eV. Similar interfaces formed under less ideal conditions or with impurity incorporation decrease the barrier to 0.66 eV. The density and distribution of the interface states measured by a capacitance spectroscopy method correlate well with the structural perfection of the single and mixed-phase interfaces. A consistent picture seems to have emerged suggesting that the barrier height at silicide-Si interfaces is formed as a result of Fermi level pinning by interfacial defect states which are controlled primarily by the degree of perfection of the interface instead of the specific epitaxy.
Deposition of Thin Insulating films by Plasma Enhanced CVD
Authors: Lucovsky G. , Richard P. D. , Tsu D. V. , Markunas R. J.
Published: March 2011

We discuss a new low temperature process for the deposition of electronic quality thin films of silicon oxide and nitride. In contrast to conventional plasma enhanced chemical vapor deposition [PECVD], this process involves the remote excitation of one of the gas reactants followed by the extraction of the active species out of the plasma region where they react to generate precursor molecules. The precursors undergo a CVD reaction at a heated substrate to form the desired thin film. The process is called remote PECVD [RPECVD]. Insulators produced in this way show significant reductions in the incorporation of impurity groups such as SiH and SiOH relative to films grown by the PECVD process at the same substrate temperatures.
Structural Investigation of Ti-N Films
Authors: Asplund M. , Korhonen A. S. , Molarius J. M. , Nykänen E. , Sulonen M. S.
Published: March 2011

Ti-N films were deposited by reactive ion plating on various substrates. The N/Ti-ratio was systematically varied in order to produce films of varying structure and properties from pure titanium to overstoichiometric TiN. Broad diffraction peaks typical of PVD Ti-N films were found. Metastable ct-titanium was observed over a wide range up to about 50 at. % N. No marked differences in the phase composition or in the crystallographic texture could be found in the films deposited on the various substrates. The hardness of the films was observed to increase with increasing nitrogen content, reaching a maximum around 35 – 40 at. % N corresponding to a mixed ε-Ti2N and δ-TiN structure. Extended annealing at 773 K did not result in any major phase transformations. After annealing at 1173 K, α-Ti could no longer be found in nitrogen-rich films. Also ε-Ti2 N transformed to δ-TiN after annealing at 1173 K for 2 h.
HCL Oxidation of High Dose Arsenic Implanted Silicon
Authors: Choi Seong Soo , Numan M. Z. , Finstad T. G. , Chu W. K. , Fathy D.
Published: March 2011

Thermal oxidation of high dose arsenic implanted p-type <100> silicon has been performed in order to study arsenic snowplowing. Bubble pattern formation and local oxide bowing (mound) in relation to the arsenic concentration in silicon as well as an HC1 ambient have been observed for an oxidation temperature of 1050°C. Oxide peel off at an oxidation temperature of 950°C for an atmosphere with an HC1 ambient has been observed. In addition, an anomaly in the temperature dependence of the oxidation rate independent of an HC1 ambient has been found.
Structural Evaluation of Interfaces by Electron Diffraction
Authors: Sullivan Tim D. , Ast Dieter G.
Published: March 2011

A method for extracting quantitative information from weak diffraction features at or near matrix reflections is described. The technique requires an accurate knowledge of the fall-off of the matrix reflection. This fall-off was studied both experimentally and theoretically for a wide range of coherence conditions in the microscope. Subtraction of this matrix contribution from the total intensity of an [004] reflection from a E=13 (001) twist boundary shows that the streak arises from local as well as from long range interference effects. The latter contribution varies with spatial coherence length which depends on the condenser setting of the microscope.
Strain Mapping in InGaAsP Epitaxial Films by An X-Ray Diffraction Technique
Authors: Chaudhuri Jharna , Mayo William E. , Weissmann Sigmund
Published: March 2011

A new x-ray diffraction method is developed to determine the full elastic strain tensor and its distribution about a strain center in single crystal materials. It is based on the recently developed Computer Aided Rocking Curve Analyzer and is particularly well suited for analysis of thin film structures common to electronic materials. This technique will be described in detail, and its application in measuring the non-uniform strains in InGaAsP epitaxial film on InP substrate will be presented. Also, possibility of using this method to measure the uniformity of film thickness will be discussed.
The Effects of Dopants and Crystal Perfection on the Chemical Vapor Deposition of Tungsten on Silicon by Silicon Reduction of Tungsten Hexafluoride
Authors: Green M. L. , Ali Y. S. , Davidson B. A. , Feldman L. C. , Nakahara S.
Published: March 2011

The use of CVD W as a diffusion barrier between Al and Si is becoming widespread. The initial stage of the deposition involves the Si reduction of WF6 according to the following reaction:

The reaction is thought to be self-limiting, since once a sufficiently thick W film forms, WF6 and Si are no longer able to be in contact. We have studied the effects of implanted dopant and damage on the rate of this reaction and the thickness of the self-limiting W film. To study the mechanism of W film growth, Si wafers were implanted with As, P or Sb. These wafers were either left in the as-implanted state (amorphized surface layer) or were annealed to drive-in the implant and recrystallize the Si. The reactivity with WF6 of these wafers, as well as unimplanted Si wafers, was then studied as a function of temperature between 210° C and 700° C. Si-WF6 reactivity is shown to have a strong temperature dependence, with maximum reactivity occuring at 340 °C, at which temperature a 960A thick film of W can form. Enhanced diffusion of Si through the growing W film is thought to be the mechanism responsible for thick film growth. At higher temperatures, thinner films form, due to the cessation of enhanced diffusion. Lower temperature films are also thinner, probably due to a nucleation barrier, not a kinetic barrier, to growth. Implantation lowers the temperature of the onset of enhanced reactivity between Si and WF6, when the wafers are reacted in the as-implanted state.
The Effects of Dopants on Surface-Energy-Driven Secondary Grain Growth in Ultrathin Si Films
Authors: Kim H.-J. , Thompson C. V.
Published: March 2011

Secondary or abnormal grain growth has been observed in ultrathin films of silicon (<120nm) that were heavily doped with phosphorous or arsenic. This grain growth leads to grains which are much larger than the film thickness (>50x) and which have uniform (111) texture. This abnormal grain growth is believed to be driven, in part, by surface energy minimization and hence is termed surface-energy-driven secondary grain growth.

It was found that n-type dopants, phosphorous and arsenic, markedly enhance the rate of secondary grain growth as seen through a lowering of the temperature required for significant growth. On the other hand, boron (a p-type dopant) appears to neither markedly increase nor decrease the rate of grain growth. Enhancement caused by phosphorous or arsenic is thought to stem from increases in the mobility of the grain boundaries. Enhancement of grain boundary mobility was found to be compensated (reduced or eliminated) by additional doping with boron.
Study of Molybdenum-Alusil Interdiffusion Kinetics and Contact Resistance for VLSI Applications
Authors: Singh R. N. , Brown D. M. , Kim M. J. , Smith G. A.
Published: March 2011

Interdiffusion barrier characteristics of molybdenum thin films with Alusil(Al-1% Si) is studied between 733 and 7 63 K via sheet and contact resistance measurements, Rutherford backseattering spectrometry, secondary ion mass spectroscopy, and x-ray diffraction analysis. The results indicate that thermal annealing of Mo/Alusil thin film couples leads to MoAl compound formation initially as a nonplanar front, but extensive annealing results in complete transformation of Alusil to MoAl12 and a significant increase in contact resistance. The interdiffusion kinetics is studied and implications of these observations to VLSI device characteristics is discussed. Based on these results a safe time-temperature processing regime is proposed.
ELECTRICAL RESISTIVITY OF Au-Cr SUPERLATTICES
Authors: BRODSKY M. B. , SOWERS C. H. , SILL L. R.
Published: March 2011

Superlattices of Au-Cr, with Au:Cr=2:l have been prepared. Their electrical resistivities have been measured between 0.3-300 K. Whereas simple ρ-T behavior was found forλ = 30, 51, 90 and 150 Å, complicated behavior, similar to magnetic ordering is found for λ = 45 Å. No correlation is observed with the extremum wavelength for phonon velocities - a maximum occurs at 75 Å - unlike that found for most metallic superlattics.
OPTICAL IMAGING OF DISLOCATIONS IN STRAINED—LAYER SUPERLATTICES AND LATTICE—MISMATCHED EPILAYERS
Authors: GOURLEY P. L. , BIEFELD R. M. , DAWSON L. R.
Published: March 2011

We have developed a convenient photoluminescence microimaging technique to probe misfit dislocations in epitaxially grown semiconductor alloys and multilayers. Using this technique, we have examined the microscopic optical quality of thick (~ 1 μm ) III-V semiconductor epitaxial layers, mismatched to their substrates. The layers includeseveral kinds of [100] strained-layer superlattices (GaP/GaAsxP1-x on GaP and GaAs/GaAs. P on GaAs grown by MOCVD, and GaAs/In Ga1-x As on GaAs grown by MBE) and associated alloys. For each type of superlalti e, we have studied a large number of samples corresponding to different compositions and layer thicknesses. The results show that misfit dislocations can be completely eliminated in the uppermost layers of the strained-layer superlattices if these structures have thin layers, less than the critical thickness for elastic accommodation, and sufficient numbers of interfaces to block threading dislocations.
STRAIN AND REORDERING IN CaF2/Si(lll) EPITAXY
Authors: HASHIMOTO SHIN , SCHOWALTER L.J. , R.W.FATHAUER-a2  , GIBSON W.M.
Published: March 2011

Strains in CaF2 films, grown by molecular beam epitaxy at 700ºC on Si(lll) subsrates, have been measured by MeV 4He+ ion channeling. For CaF2 films thinner than 200nm, the strain parallel to the (111) plane is found to be tensile. No strain is observed for films thicker than 200nm. The observed tensile strain cannot be explained by a simple pseudomorphic growth model because the larger lattice constant of CaF2 relative to Si should result in a compressive misfit strain. The tensile strain is an indication of the relaxation of the compressive misfit strain at the growth temperature due to nucleation of interfacial defects. If these defects are not annealed out as the substrate temperature is lowered after growth, the tensile strain can result because of the larger thermal contraction of CaF2 compared to Si. The final film quality near the interface improves as the film thickness is increased. This indicates that reordering of interfacial disorder is caused by the strain energy accumulated during the cooling process.
EPITAXIAL GROWTH OF ZIRCONIA AND YTTRIA STABILIZED ZIRCONIA FILMS ON SAPPHIRE SUBSTRATES BY REACTIVE SPUTTERING
Authors: KONUSHI F. , DOI T. , MATSUNAGA H. , KAKIHARA Y. , KOBA M. , AWANE K. , NAKAMURA I.
Published: March 2011

Epitaxial single crystal growth of zirconia (ZrO2) and yttria stabilized zirconia (ZrO2 ·Y2O3) films on sapphire substrates was achieved for the first time by using reactive sputtering. And the relations of crystallographic orientations between the epitaxial films and sapphire substrates was determined. Yttria stabilized zirconia films seem to offer hiah quality SOI substrates, since the crystal structure of ZrO2·Y2O3 is cubic fluorite and its lattice constant is closely matched to those of semiconductors such as Si and GaAs.
Effects of Se implantation on the compositional disordering of GaAs-AlAs superlattices
Authors: NAKAMURA T. , KOMIYA S. , INATA T. , MUTO S. , HIYAMIZU S.
Published: March 2011

The LO phonon frequency evaluated from Raman spectra identifies two compositional disordering mechanisms in GaAs-AlAs superlattices. For a high Se dose, the LO phonons of the Al0.5Ga0.5As alloy are observed from the asimplanted samples. That means the compositional disordering occurred just by Se implantation. The probable mechanism for this disordering is the implantation of Ga atoms into the AlAs layer and of Al atoms into the GaAs layer. The superlattices implanted at a low dose are disordered by the subsequent annealing. The mechanism is the enhanced interdiffusion of both Ga and Al atoms between the GaAs and AlAs layers by Se thermal diffusion.
EQUALLY STRAINED Si/SiGe SUPERLATTICES ON Si SUBSTRATES
Authors: KASPER E. , HERZOG H.-J. , H.DAEMBKES-a1  , ABSTREITER G.
Published: March 2011

Growth of Si/SiGe superlattices on Si substrates by molecular beam epitaxy (MBE) is described. Strain symmetrization in the superlattice is achieved with an incommensurate SiGe buffer layer. The concept of strainsymmetrization is explained and properties of buffer and strained layer superlattices are investigated. A twodimensional electron gas with enhanced room temperature mobility and folded phonon modes within the reduced onedimensional Brillouin zone are observed. An n-channel Si/SiGe MODFET demonstrates the device applications of this material concept.