bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Properties and Power Considerations of a Piezoelectric Actuator
Authors: Jordan T. , Ounaies Z. , Tripp J. , Tcheng P.
Published: April 2011

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.
High-Temperature Thermoelectric Properties of Silicon Boride Ceramics as a Smart Material
Authors: Takashima Noriyuki , Azuma Yasuo , Matsushita Jun-Ichi
Published: April 2011

Several silicon boride phases such as SiB4, SiB6, SiB6-x, SiB6+x, and Si11B31, were previously reported. Among them, SiB6has proved to be a potentially useful material because of its excellent electrical conductivity, high degree of hardness, moderate melting point, and low specific gravity. The sintering conditions and thermoelectric properties of silicon boride (SiB6) ceramics produced by hot pressing were investigated in order to determine the suitability of this material for high-temperature thermoelectric applications as a smart material. The relative density increased with increasing sintering temperature. With a sintering temperature of 1923 K, a sintered body having a relative density of more than 99% was obtained. X-ray diffraction analysis showed no crystalline phase other than SiB6 in the sintered body. The specimens were prepared for measurement of the electrical conductivity and Seebeck coefficient by the D.C. four-terminal method. The thermal conductivity of SiB6 was obtained by calculation from the thermal diffusivity and specific heat capacity of the specimen. The electrical conductivity of SiB6 increased with increasing temperature. The electrical conductivity of the polycrystalline SiB6 (99% dense) was 0.5 to 1.1 × 103 S/m at 298 to 1273 K. The thermal conductivity decreased with increasing temperature in the range of room temperature to 1273 K. The thermal conductivity was 9.1 to 2.5 W/mK in the range of room temperature to 1273 K. The Seebeck coefficient of SiB6 increased with increasing temperature. The Seebeck coefficient of SiB6 was 140 × 10−6 V/K at 1273 K. The figure of merit Z of SiB6 increased with increasing temperature. The Z of SiB6 reached 8.1 × 10−6/K at 1273 K. The ZT value is useful to evaluate the ability of thermoelectric materials. The ZT value reached 0.01 at 1273 K. Based on the results, SiB6 showed very good thermoelectric material characteristics at high temperature.
Force Capability of a Planar Peristaltic Terfenol-D Motor
Authors: Gerver M. J. , Goldie J. H. , Kim Won-Jong , Kiley Jerome , Swenbeck J. R.
Published: April 2011

A magnetostrictive peristaltic motor, similar to an INCHWORM® motor, was designed, built, and tested, using Terfenol-D® as the active element. Unlike the Kiesewetter motor, which uses a rod of Terfenol-D in a closely fitting cylindrical channel, in our design the Terfenol-D is in the form of a flat slab, held between two spring-loaded plates. With this configuration the motor is not affected by wear of the Terfenol-D surface. In order to avoid eddy currents, we used laminated Terfenol-D. Operating at 1600 Hz with a peak field of 430 oersteds, the speed at no load was observed to be 12 mm/sec, which is 65% of the theoretical value (the peak strain times the peristaltic phase velocity), probably because the surface flatness of the Terfenol-D slab was only a few times smaller than the height of the peristaltic bumps. The measured stalling force was 90 newtons, corresponding to 350 kPa load stress in the Terfenol-D, only 3.5% of the peak strain times the stiffness of the Terfenol-D. This force was in almost exact agreement with a model which took into account the force from the spring-loaded plates (needed to avoid slippage), the transverse stiffness of the Terfenol-D slab, and the finite bending stiffness of the stator. The model can be used to design optimized motors with improved force capability. We tried using composite Terfenol-D, consisting of Terfenol-D particles in an epoxy binder, but the speed and stalling force were lower, perhaps because it did not have a very uniform distribution of particles, and was not machined as flat as the laminated Terfenol-D. The motor was driven by a specially designed 3-phase power inverter and digital controller, and the large reactive power inherent in this kind of motor was reduced by putting it in series with resonant capacitors.
The Design of Organic Gelators Based on a Family of Bis-Ureas
Authors: Meléndez Rosa E. , Carn Andrew J. , Sada Kazuki , Hamilton Andrew D.
Published: April 2011

The use of organic molecules as gelators in certain organic solvents has been the target of recent research in materials science. The types of structures formed in the gel matrix have potential applications as porous solids that can be used as absorbents or in catalysis. We will present and discuss the organogelation properties of a family of bis-ureas. Studies presented will include a molecule structure activity relationship, thermodynamic properties, comparison to x-ray crystallographic data and potential functionalization of the gels formed by this class of compounds
Fluxless Microjoining by Au-In-Ni Isothermal Solidification
Authors: Waelti M. , Schneeberger N. , Brand O. , Baltes H.
Published: April 2011

A reliable, fluxless microjoining technique based on isothermal solidification is reported. The Au-In-Ni system has been chosen for bonding, because gold is often applied for wafer bumping, and Ni is commonly used for substrate plating. To demonstrate the potential of this microjoining scheme, optical filter have been directly attached to a smart CMOS thermoelectric IR system. Since further packaging of the microsystem includes SMT assembly, the bond has to withstand subsequent SnPb reflow-soldering.

The influence of bonding time and temperature on the bond was investigated. Phase formation and transformation were analyzed by light and scanning electron microscopy (SEM). Bonding performed at temperatures below 200°C remained stable even after multiple soldering cycles with peak temperatures of 235°C. The shear strength of the bonds was found to be more than 70 MPa. Long term stability was confirmed by extended anneal at 160°C. The method is generally well suited for processes involving sequences of joining steps, and for bonds demanding high strength and high thermal stability at low bonding temperature.
Deposition and Characterization of In-Situ Boron Doped Polycrystalline Silicon Films for Microelectromechanical Systems Applications
Authors: McMahon J. J. , McMahon J. J. , Melzak J. M. , Zorman C. A. , Chung J. , Mehregany M.
Published: April 2011

In an effort to develop thick, p-type polycrystalline silicon (polysilicon) films for microelectromechanical systems (MEMS) applications, in-situ boron-doped polysilicon films were deposited by a single-step APCVD process at susceptor temperatures ranging from 700°C to 955°C. The process produces boron-doped films at a deposition rate of 73 nm/min at 955°C. Spreading resistance measurements show that the boron doping level is constant at 2 × 1019 /cm3 throughout the thickness of the films. Doped films deposited at the low temperatures exhibit compressive stress as high as 666 Mpa; however films deposited at 955°C exhibited stress as low as 130 MPa. TEM and XRD show that the microstructure strongly depends on the deposition conditions. Surface micromachined, singly clamped cantilevers and strain gauges were successfully fabricated and used to characterize the residual stress of 5.0 µm-thick doped films deposited at a susceptor temperature of 955°C.
Maskless Patterning and Structuring on Ultra-Hard Film Materials
Authors: Park J.K. , Ayres V.M. , Asmussen J. , Mukherjee K.
Published: April 2011

Ultra-hard film materials such as chemical vapor deposited (CVD) diamond are uniquely qualified for applications where superior tribological and electronic properties are required. Patterning of the film materials is essential to produce functional micro devices. Conventional lithography-based chemical etching is difficult or impossible on the ultra-hard diamond film materials, which have a high chemical resistance. Investigations on maskless patterning of the CVD diamond film are presented. Focused excimer laser pulses are used for dry etching on the film materials, and a micro computer numerical control (micro-CNC) stage is used for patterned translation of a target. The laser ablation of CVD diamond is observed to set up relationships among the processing parameters, such as the gas processing environments, the laser energy fluence and the number of laser pulses. The extent of the ablation-induced plasma is observed by time integrated image capturing. A cell-patterned structure, fabricated by the innovative maskless process, is presented for discussion.
SU-8 Processing on a Variety of Substrates
Authors: Chiang Yuh-Min , Bachman Mark , Chang Hung-Pin , Chu Charles , Li G. P.
Published: April 2011

SU-8 has become a popular material for micromachining high aspect ratio structures. Typically, SU-8 is spun on a polished silicon wafer for processing. After patterning, the SU-8 is used for micromachined structures directly (such as fluidic channels) or as a mold for electroforming. Non-silicon substrates offer the possibility of cheaper processing, improved mold designs, and multi-material devices. Successful SU-8 processing depends strongly on surface properties of the substrate itself as well as environmental conditions during the processing. We explore the issues involved in transferring SU-8 technology to non-silicon substrates such as glass, plastics and metals. Issues such as wettability, adhesion, and surface tension are explored in this study. The findings indicate the merits of non-spinning approaches, such as dipping, spraying, and brushing and point to new SU-8 processes.
Metal Organic Chemical Vapor Deposition of Co-, Mn-, Co-Zr and Mn-Zr Oxide Thin Films
Authors: Barreca D. , Benetollo F. , Bozza M. , Bozza S. , Carta G. , Cavinato G. , Rossetto G. , Zanella P.
Published: April 2011

Deposition of thin films of Co- and Mn- oxides as well as of their mixtures with ZrO2 have been carried out by MOCVD using Co(C5H5)2, Mn(C5F6HO2)2(THF)2and (C5Hs)2Zr(CH3)2as precursors. XRD and XPS analyses of the obtained deposits are reported. Introduction of water vapor into the reactor chamber during the flow of the precursors improved their decomposition efficiency and the quality of the films.
Auger Suppression in and Noise Performance of “Hot” HgCdTe IR Detectors
Authors: Benjaminsen F. , Rheenen A. D.van , Chen X.-Y.
Published: April 2011

The carrier concentration in narrow-gap semiconductors operating at room temperature is usually determined by thermal generation, not by doping. By reverse biasing a specially designed HgCdTe P+ - π - N+ heterostructure, the carrier concentrations in the narrow-gap π layer are held below the intrinsic concentration. Temperature dependent measurements of the reverse-bias current-voltage characteristics reveal that the devices operate as "usual" diodes below approximately 225 K. Above this temperature, the intrinsic carrier concentration increases, and the suppression mechanism appears in the I-V curves as negative differential resistance regions. The low-frequency noise performance of these devices, both in the forward bias and the reverse bias regime, as a function of temperature will be presented.
The Growth of InAsSb/InAs/InPSb/InAs Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition
Authors: Biefeld R. M. , Phillips J. D. , Kurtz S. R.
Published: April 2011

We report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InAs/InPSb/InAs as well as mid-infrared optically pumped lasers grown using a high speed rotating disk reactor (RDR). The devices contain AlAsSb cladding layers and strained, type I, InAsSb/InAs/InPSb/InAs strained layer superlattice (SLS) active regions. By changing the layer thickness and composition of the SLS, we have prepared structures with low temperature (<20K) photoluminescence wavelengths ranging from 3.4 to 4.8 µm. The optical properties of the InAsSb/InPSb superlattices revealed an anomalous low energy transition that can be assigned to an antimony-rich, interfacial layer in the superlattice. This low energy transition can be eliminated by introducing a 1.Onm InAs layer between the InAsSb and InPSb layers in the superlattice. An InAsSb/InAs/InPSb/InAs SLS laser was grown on an InAs substrate with AlAs0.16Sb0.844cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80 through 250 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T0 = 39 K, from 80 to 200 K.
Control of the Intermixing of InGaAs/InGaAsP Quantum Well in Impurity Free Vacancy Disordering by Changing NH3 Flow Rate During the Growth of SiNx Capping Layer
Authors: Choi W.J. , Yi H.T , Woo D.H. , Lee S. , Kim S.H. , Kang K.N. , Cho J.
Published: April 2011

The dependence of impurity free vacancy disordering (IFVD) of InGaAs/InGaAsP QW structure on the characteristics of dielectric capping layer was studied using SiNx film as capping layers. The characteristics of the SiNx capping layer were varied by changing the NH3 flow rate during SiNx deposition by plasma enhanced chemical vapor deposition (PECVD). The degree of quantum well intermixing (QWI) with SiNX capping layer grown at higher NH3 flow rate was larger than that with SiNx film grown at lower NH3 flow rate. This implies that QWI can be easily controlled by simply changing the reactive gas ratio in the growing process of SiN, capping layer. It was also shown that this method to control QWI is better than the method of using two different capping layers such as SiNx film and SiO2 film in order to get spatially selective QWI on the same substrate.
Theoretical and Experimental Investigation of Disordering Effects on Photoluminescence Spectra of InGaAs/InGaAsP Quantum Wells
Authors: Yi J. C. , Choi W. J. , Lee S. , Woo D.H. , Kim S. H.
Published: April 2011

The effect of disordering on photoluminescence spectra of InGaAs/InGaAsP quantum wells has been investigated experimentally and theoretically taking into account the valence band intermixing, strain, exciton effects, and the non-identical diffusion constants for group III and V materials. The disordering profile of 1.55Q InGaAs/InGaAsP quantum wells lattice matched to InP has been controlled by choice of the cap layer materials as well as the diffusion time and diffusion temperature. By comparing the experimental data and theoretical calculations, the diffusion constant for each material has been extracted.
Photoluminescence of Eu3+ in Si/SiO2 Nanostructure Films
Authors: Liu Huimin , Mahfoud Aziz , Nery G. A. , Resto O. , Fonseca Luis F. , Weisz Zvi S.
Published: April 2011

Eu3+ -doped Si/SiO2 nanocomposites were successfully prepared by Ar sputtering deposition on quartz substrates. The optical properties were studied using time-resolved photoluminescence spectroscopy. Excited by intense picosecond laser pulses with energy greater than1GW/cm2 and wavelength at 532nm the observed photoluminescence consists of a rapidly decaying component with life time of ∼1 s and a slowly component with life time of ∼ 2 ms. The former was recognized as coming from Si/SiO2 nanostructures matrix while the latter as coming from the impurity Eu3+ ions. Using the intense laser excitation a two-photon absorption by silicon matrix occurred, resulting in photo-induced carriers produced in conduction band. A direct recombination from Si/SiO2 nanostructure host gives a weak but fast emission, and creates a large number of nonequilibrium phonon. For Eu3+ emission a set of 5D0 to 7F multiplet transitions were identified. In addition to the direct excitation by 532nm the excited state 5D0 of Eu3+ ions was also found to be populated due to energy transfer from silicon matrix. The mechanism of phonon-assisted energy transfer is discussed.
Non Linear Optical Gain in Bulk Barrier Amorphous Silicon Phototransistor
Authors: Caputo D. , de Cesare G. , Nascetti A. , Palma F.
Published: April 2011

In this work we report studies on the non linear dependence of the optical gain with the incident power in an amorphous silicon bulk barrier phototransistor based on a n-i-p-i-n structure. The optical gain shows a quasi-hyperbolic dependence on the illumination intensity. The non-linear behavior was predicted by an analytical device model which takes into account the properties of both material and structure, which lead to the amplification mechanism of the device.
Amorphous Crystalline Silicon Heterojunction with Silicon Nitride Buffer Layer
Authors: Claudio G. , Rosa R. De , Roca F. , Caputo D. , Tucci M.
Published: April 2011

In this work we study the possibility to use amorphous silicon nitride, grown by plasma, as an alternative way to realize buffer layer in a-Si:H/c-Si heterostructure. We experimented several growing condition for silicon nitride depending on deposition parameters, obtaining samples highly transparent and with optical gap varying in the range 2.4 – 5.2 eV. We found evidence that the gap of the material is principally due to the NH3/N2 ratio. The very low absorption obtainable on this material was successfully utilized to increase the short circuit current density of the device respect to the standard cell with intrinsic amorphous silicon buffer, particularly in the low wavelength region as confirmed by quantum yield measurements. We optimized the thickness of the SiNx buffer layer respect to the photovoltaic parameters of the solar cell. A 0.5 nm thick SiNx ensures good photogeneration in blue region of the visible spectrum and does not appreciably degrade the transport mechanism of the heterojunction.
Amorphous Silicon Microbolometer Technology
Authors: Syllaios A. J. , Schimert T. R. , Gooch R. W. , McCardel W. L. , Ritchey B. A. , Tregilgas J. H.
Published: April 2011

Highly sensitive hydrogenated amorphous silicon (a-Si:H) microbolometer arrays have been developed that take advantage of the high temperature coefficient of resistance (TCR) of aSi:H and its relatively high optical absorption coefficient. TCR is an important design parameter and depends on material properties such as doping concentration. Ultra-thin (∼2000 Å) aSiNx:H/a-Si:H/ a-SiNx:H membranes with low thermal mass suspended over silicon readout integrated circuits are built using RF plasma enhanced chemical vapor deposition (PECVD) and surface micromachining techniques. The IR absorptance of the bolometer detectors is enhanced by using quarter-wave resonant cavity structures and thin-film metal absorber layers. To ensure high thermal isolation the microbolometer arrays are vacuum packaged using wafer level vacuum packaging. Imaging applications include a 120×160 a-Si:H bolometer pixel array IR camera operating at ambient temperature. Non-imaging applications are multi-channel detectors for gas sensing systems.
Si-H Vibration Only at 2000 CM-1 in Fully Polycrystalline Silicon Films Made by Hwcvd
Authors: Rath J.K. , Schropp R.E.I.
Published: April 2011

The Si-H vibration in IR spectra of our device quality poly-Si films grown by hot-wire chemical vapour deposition (HWCVD) made at low wire temperature (Tw=1800 °C) is at 2000 cm−1 whereas in a poly-Si film made at high wire temperature (Tw=1900 °C) both 2000 cm−1 vibrations as well as 2100 cm−1 are observed. On the other hand, the Raman spectra (probing the upper part of the film) of Si-H stretching vibration measured for both these samples show only 2000 cm-1 mode. XTEM micrographs of these films show that whereas the low Tw film has a structure made of closely packed crystalline columns, the high Tw film has conical crystalline structures with amorphous region between them. The crystal cones meet each other towards the top of the film and form a closed structure. This is confirmed by Raman spectrum at 520 cm−1. We attribute the 2100 cm−1 mode to the Si-H bonds at the surface of the cones touching the amorphous regions. The Si-H vibration shifts to 2000 cm-1 when the crystalline cones coalesce with each other, as is the case in the upper part of both types of films.
Modeling of Beta Conductivity in Tritiated Amorphous Silicon
Authors: Costea Stefan , Gaspari Franco , Kosteski Tome , Zukotynski Stefan , Kherani Nazir P. , Shmayda Walter T.
Published: April 2011

The change with time in the electrical conductivity of a hydrogenated-tritiated amorphous silicon film (a-Si:H:T) has been studied. The conductivity decreased with time after deposition. A model is developed to account for the decrease. The radioactive decay of tritium into helium produces energetic beta particles. Each β particle creates over 1500 electron-hole pairs in the film thereby increasing the conductivity of the film. The 3He atoms diffuse away leaving dangling bonds behind. We find that neutral dangling bonds (D0) are responsible for the decrease in conductivity by acting as recombination centers in the material.
Laser Processing of Amorphous Silicon for Polysilicon Devices, Circuits and Flat-Panel Imagers
Authors: Boyce J. B. , Fulks R. T. , Ho J. , Lu J. P. , Mei P. , Street R. A. , Schuylenbergh K. F. Van , Wang Y.
Published: April 2011

Pulsed excimer-laser processing of amorphous silicon on non-crystalline substrates allows for the fabrication of high-quality polysilicon thin-film transistors (TFTs). It also provides procedures for doping self-aligned amorphous silicon TFTs. In addition, laser-crystallized polysilicon exhibits some interesting materials properties, such as, large lateral grain growth with a corresponding enhancement in the electron mobility. Under optimized processing conditions, excellent polysilicon TFTs with high mobilities, sharp turn on, low off-state leakage currents and good spatial uniformity have been achieved. These improved parameters, particularly the low off-state leakage currents and good uniformity, enable not only displays but also the moredemanding flat-panel imaging arrays to be fabricated in polysilicon. Results on both polysilicon CMOS circuits and a polysilicon flat-panel imager are presented.
Methods of Suppressing Cluster Growth in Silane RF Discharges
Authors: Shiratani Masaharu , Maeda Shinichi , Matsuoka Yasuhiro , Tanaka Kenichi , Koga Kazunori , Watanabe Yukio
Published: April 2011

The effects of gas temperature gradient, pulse discharge modulation, hydrogen dilution, gas flow, and substrate materials on growth of clusters below about 10 nm in size in silane parallelplate RF discharges are studied using a high-sensitivity photon-counting laser-light-scattering (PCLLS) method. Thermophoretic force due to the gas temperature gradient between the electrodes drives neutral clusters above a few nm in size toward the cool RF electrode. Pulse discharge modulation is much more effective in reducing the cluster density when it is combined with the gas temperature gradient, and clusters above a few nm in size cannot be detected by the PCLLS method even for the discharge over a few hours. Hydrogen dilution and gas flow are also effective in suppressing growth of clusters, when the H2/SiH4 concentration ratio is above about 5 and the flow velocity is above about 6 cm/s, respectively. Cluster growth rate with a glass or Si substrate is found to be considerably higher than that without the substrate.
Effect of Hydrogen Radical on Properties of Hydrogen in Hydrogenated Microcrystalline Silicon
Authors: Itoh Takashi , Yamana Noriyuki , Inouchi Hiroki , Yoshida Norimitsu , Harada Hidekuni , Kondo Hiroaki , Yamamoto Kanta , Nonomura Shuichi , Nitta Shoji
Published: April 2011

Hydrogenated microcrystalline silicon (μc-Si:H) films are prepared by hot-wire assisted plasma enhanced chemical vapor deposition, which controls the hydrogen radical density by filament temperatures, Tf, without changing other conditions. The effect of hydrogen radical on the properties of incorporated hydrogen into μc-Si:H films is studied using infrared absorption and gas effusion spectroscopies. The hydrogen concentration decreases with increasing Tf. The crystalline volume fraction, Xc, increases with Tf and shows a peak at Tf of 1850 °C. Integrated intensities of the modes near 2000 and 2100 cm-1 decrease with increasing Tf. Integrated intensity of the mode near 880 cm-1 shows almost same tendency of Xc. The effect of hydrogen radical on the properties of incorporated hydrogen into μc-Si:H films is discussed.
Control of Amorphous Silicon Crystallization Using Germanium Deposited by Low Pressure Chemical Vapor Deposition
Authors: Toita Masato , Kalavade Pranav , Saraswat Krishna C.
Published: April 2011

Crystallization behavior of 100nm amorphous silicon film with and without a 160nm poly-Ge layer on top was investigated. Ge was observed to increase the nucleation rate as well as to increase the incubation time for nucleation in a-Si. Activation energy for nucleation was 2.3eV for Ge-covered Si films as compared to 2.7eV for the control a-Si films with no poly-Ge. Activation energy for incubation is almost unchanged for both the films (-3.3eV). An alternative seeding technique for a-Si films using the increase in the incubation time for nucleation due to presence of poly-Ge is proposed.
A Percolative Approach to Electromigration Modelling
Authors: Pennetta C. , Reggiani L. , Trefán Gy. , Fantini F. , Scorzoni A. , DeMunari I.
Published: April 2011

We present a stochastic model which simulates electromigration damage in metallic interconnects by biased percolation of a random resistor network. The main features of experiments including Black's law and the log-normal distribution of the times to failure are well reproduced together with compositional effects showing up in early stage measurements made on Al-0.5%Cu and Al-1%Si lines.
Study of SiH4-based PECVD Low-k Carbon-doped Silicon Oxide
Authors: Yang Hongning , Tweet Douglas J. , Stecker Lisa H. , Pan Wei , Evans David R. , Hsu S.-T.
Published: April 2011

In previous studies, low-k carbon-doped silicon oxide (SiOC) films were deposited using organosilicon precursor: (CH3)xSiH4−x. In this paper, we present the properties of PECVD low-k SiOC films produced by using conventional SiH4 based gas precursors. The SiH4 based SiOC films have similar gross physical and electrical characteristics to those of (CH3)xSiH4−x based SiOC. Since the precursors are inexpensive, commercially available and convenient to operate for existing tools, the process should not require additional cost as compared with that of PECVD silicon dioxide. We demonstrate the feasibility of integrating Cu with SiOC on damascene interconnection. The evaluation on electrical performance of the Cu/SiOC based damascene structure will be discussed.
Backside Copper Contamination Issues in CMOS Process Integration – A Case Study
Authors: Prasad K. , Tee K.C. , Chan L. , See A. K.
Published: April 2011

NMOS and PMOS transistors of various (W/L) ratios, down to 0.24µm channel length, have been used to investigate the effects of copper diffusion (from the backside) on their electrical parameters. A thin layer of copper film was deposited on the back surface of the wafer. Over 10 hours of annealing at 4000C was carried out. Electrical parameters such as the threshold voltage (VT0), the drain saturation current (IDsat) and the off-current (Ioff), for transistors, and the leakage current for large diodes were measured. Secondary Ion Mass Spectroscopy (SIMS) was used to monitor the copper diffusion. Even after 10 hours of annealing at 400°C, electrical parameters of both NMOS and PMOS devices and leakage currents of diodes showed no significant degradation.
The Integration of Low-k Dielectric Material Hydrogen Silsesquioxane (HSQ) with Nitride Thin Films as Barriers
Authors: Zeng Yuxiao , Chen Linghui , Alford T. L.
Published: April 2011

HSQ (hydrogen silsesquioxane) is one of the promising low-k materials used in VLSI technology as an intra-metal dielectric to reduce capacitance-related issues. Like any other dielectrics, the integration of HSQ in multilevel interconnect schemes has been of considerable importance. In this study, the compatibility of HSQ with different nitride barrier layers, such as PVD and CVD TiN, PVD TaN, and CVD W2N, has been investigated by using a variety of techniques. The refractory metal barriers, Ti and Ta, are also included for a comparison. The degradation of HSQ films indicates a strong underlying barrier layer dependence. With CVD nitrides or refractory metals as barrier, HSQ exhibits a better structural and property stability than that with PVD nitrides. The possible mechanisms have been discussed to account for these observations.
Energetic Inert Gas Atom Impact Effects During Ion Beam Multilayer Deposition
Authors: Zhou X. W. , Zou W. , Wadley H. N. G.
Published: April 2011

New magnetic field sensors and non-volatile magnetic random access memories can be built from giant magnetoresistive multilayers with nanoscale thickness. The performance of these devices is enhanced by decreasing the atomic scale interfacial roughness and interlayer mixing of the multilayers. During ion beam sputtering, inert gas neutrals with energies between 50 and 200 eV impact the growth surface. A molecular dynamics method has been used to study the effects of these impacts on the surface roughness and interlayer mixing of model nickel/copper multilayers. The results indicate that impacts with energy above 50 eV cause mixing due to the exchange of Ni atoms with Cu atoms in an underlying Cu crystal. The extent of the mixing increases with impact energy, but decreases as the number of the Ni monolayers above the Cu crystal increases. While Xe and Ar impacts have a similar mixing effect at low energies, heavier Xe ions/neutrals induce more significant mixing at high energies.
Diamond CVD Growth Mechanisms and Reaction Rates From First-Principles
Authors: Oleinik I.I , Pettifor D.G. , Sutton A.P. , Battaile C.C. , Srolovitz D.J. , Butler J.E. , Dandy D.S. , Harris S.J. , D'evelyn M.P.
Published: April 2011

CVD diamond is an enabling material for diverse applications. In recent years, multiscale modelling of CVD growth in conjunction with experimental studies of the deposition processes has made a substantial progress towards our understanding of the fundamental growth chemistry and material quality. Macroscopic gas phase simulations of the CVD reactor, the mesoscale kinetic Monte-Carlo (KMC) modelling of the crystal growth and nanoscale modelling of the surface chemistry are three main legs in the multiscale hierarchy. In the framework of this methodology we have performed first-principles quantum mechanical calculations of bonding and reaction kinetics of the elementary growth processes and provided critical input in the form of atomistic growth mechanisms and reaction rates for the mesoscale KMC modelling of CVD diamond growth. A key success was achieved by combining first-principles and Monte Carlo studies to elucidate (100) growth mechanisms that have perplexed the diamond growth community for many years.
Chemical Vapor Deposition Coating for Micromachines
Authors: Mani S. S. , Fleming J. G. , Sniegowski J. J. , Boer M. P. De , Irwin L. W. , Walraven J. A. , Tanner D. M. , Dugger M. T.
Published: April 2011

Two major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, we will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF6, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleans prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.
Synthesis and Characterization of α-Alumina Films Via Combustion Chemical Vapor Deposition
Authors: Grandinetti G. , Shanmugham S. , Hendrick M.R. , Hampikian J.M.
Published: April 2011

α-Alumina films are useful for high-temperature, wear, and semiconductor device applications because of their good oxidation resistance, high hardness values, and electrical properties. α-Alumina films have been previously synthesized using techniques such as chemical vapor deposition, sol-gel, physical vapor deposition, and plasma spraying. This paper presents an alternative approach for producing high quality dense α-alumina coatings using a flame-assisted process called combustion chemical vapor deposition (CCVD). This process is an open atmosphere technique that does not require the use of a reaction chamber. In this work alumina films were grown on YSZ at temperatures ranging from 900 to 1500°C. At lower temperatures only amorphous alumina was grown, but as the deposition temperature increased different alumina phases were formed. At 1100°C, a thin highly crystalline θ-Al2O3 coating was formed. At temperatures higher than 1100°C thick θ-Al2O3 coatings were deposited on the YSZ. Coatings were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD).
Vapor Phase Synthesis of II-IV Semiconductor Nanoparticles in a Counterflow Jet Reactor
Authors: Sarigiannis D. , Peck J.D. , Mountziaris T.J. , Kioseoglou G. , Petrou A.
Published: April 2011

The vapor-phase synthesis of polycrystalline ZnSe nanoparticles is reported. The particles were grown at room temperature and at a pressure of 125 torr in a counterflow jet reactor and were collected by impact on a Si watler. The precursors used in this study were vapors of (CH3)2Zn:[N(C2H5)3)]2 and H2Se gas diluted in hydrogen. These precursors have been used in the past for Metalorganic Vapor Phase Epitaxy (MOVPE) of ZnSe thin films. The particles were characterized by Transmission Electron Microscopy (TEM). electron diffraction. and Raman spectroscopy. The reactor was operated in a continuous, steady-state mode using a gas delivery system that is typical flor MOVPII systems.
A Parallel Detecting, Spectroscopic Ellipsometer for Intelligent Process Control of Continuously Deposited CIGS Films
Authors: Simpson L. J. , Joshi B. S. , Gonzales L. A. , Verley J. , Furtak T. E.
Published: April 2011

Advanced materials processing involves active control of fabrication and real-time monitoring of the final product. Sensors must be an integral part of the overall material processing system. ITN Energy Systems, Inc. and the Colorado School of Mines have developed a Parallel Detection, Spectroscopic Ellipsometer (PDSE) sensor for in-situ, real-time characterization and process control of multi-layered vapor deposited films. By measuring changes in the polarization state of reflecting light as a function of wavelength (250 to 5000 nm), the PDSE sensor determines the complex reflectance and/or the ellipsometric amplitude and phase. The PDSE provides cost-effective in-line sensing for film process control through detection of critical product variables that directly relate to film performance including: film thickness, optical excitation states, impurity concentrations, conductivity/resistance, intermixing at interfaces, microstructure, surface roughness, void fraction, defects, and grain size. The PDSE sensor is an optical probe with no moving parts that can measure the optical properties of thin films in as little as 3 msec with sensitivity to films less than a monolayer in thickness. We will use this PDSE system to provide real time process control of vapor deposited CuInGaSe2 (CIGS) films on a continuous flexible substrate. Initial results from CIGS films indicate that the PDSE has the sensitivity and accuracy to provide intelligent process control. The remaining challenge is to develop interpretive algorithms; the amount and quality of information required will determine their complexity. In addition, with the inception of in-situ, real-time monitoring, we hope to enable minimal data analysis approaches1 that provide extremely useful information with minimum interpretive algorithm development.
Atomic Layer Deposition of thin Films Using Sequential Surface Reactions
Authors: George S. M. , Ferguson J.D. , Klaus J.W.
Published: April 2011

Thin films can be deposited with atomic layer control using sequential surface reactions. The atomic layer deposition (ALD) of compound and single-element films can be accomplished using the appropriate surface chemistry. This paper reviews the ALD of dielectric alumina (Al2O3) films and conducting tungsten (W) films. The Al2O3 films are deposited on submicron BN particles and the surface chemistry is monitored using Fourier transform infrared (FTIR) spectroscopy. Additional transmission electron microscopy (TEM) studies investigated the conformality of the Al2O3 growth on the BN particles. FTIR investigations of the surface chemistry during W ALD are performed on nanometer-sized Si02 particles. Additional in situ spectroscopy ellipsometry studies of W ALD on Si(100) established the W ALD growth rates. Al2O3 and W ALD both illustrate the potential of ALD to obtain conformal and atomic layer controlled thin film growth using sequential surface reactions.
Investigation On Laser-Induced Effects In Nanostructure Fabrication With Laser-Irradiated Scanning Tunneling Microscope Tips in Air Ambient
Authors: Mai Z. H. , Lu Y. F. , Song W. D. , Chim W. K.
Published: April 2011

In this paper, we report our investigation on the kinetics of nanostructure fabrication on gold films and on H-passivated Ge surfaces. The relationship between the current and the tip-sample distance of the STM junction was measured for both gold films and H-passivated Ge surfaces. The tip-sample distance for gold films under a electrochemically etched W tip is approximately 2 nm, while that for H-passivated Ge sufaces is more than 27 nm. The thermal expansion length of the tip under laser irradiation was calculated. From the comparison of the thermal expansion length and the tip-sample distance, we can reach the conclusion that for gold films, thermal mechanical indention is the primary reason of nanostructure formation, while for H-passivated Ge surfaces, optical enhancement is the only reason.
Preparation Of Superhard Functionally Graded Tetrahedral Amorphous Carbon Coatings By Pulsed Laser Deposition
Authors: Wei Q. , Yamolenko S. , Sankar J. , Sharma A. K. , Narayan J.
Published: April 2011

The internal compressive stress as large as 10 GPa has been the major stumbling block for preparation of relatively thick superhard tetrahedral amorphous carbon (Ta-C) films. We have successfully deposited Ta-C films as thick as 1000 nm by mechanical doping to reduce and alleviate the level of internal compressive stresses. In this paper, we reported the preparation of functionally graded Ta-C coatings by pulsed laser deposition. The thickness of the Ta-C films with significantly improved adhesion was measured to be up to 1500 nm. The concentration of foreign atoms such as silver, copper, silicon and titanium was decreased away from the coating/substrate interface, and the surface layer was pure Ta-C. Nanoindentation measurements were performed on the coatings. Nanohardness as high as 65 GPa and Young‘s modulus as large as 600 GPa were obtained for the functionally graded Ta-C films. Micro-Raman measurements and microstructural analysis by transmission electron microscopy was carried out to acquire information about the bonding environment and atomic structure of the coatings as a function of foreign atoms. The results were discussed in combination with theoretical models associated with the prediction of elastic properties of amorphous carbon networks.
The Kinetics of Calcite Growth: Interpreting Chemical Affinity-Based Rate Laws Through the Lens of Direct Observation
Authors: Teng Henry H. , Dove Patricia M. , Yoreo James J. De
Published: April 2011

Chemical affinity-based rate laws are used across the geochemical and materials communities to quantify mineral/material corrosion and growth kinetics. These rate expressions are founded in assumptions regarding reaction mechanism with little evidence for surface processes. Using Atomic Force Microscopy (AFM), this study demonstrates the dependence of growth kinetics upon the structures of dislocation sources. In situ observations show that the dominant mode of growth occurs by hillock development initiated at complex sources. Derivations of surface process-based rate expressions show a complex dependence of rate on chemical affinity. This dependence is approximated by second order affinity-based rate laws only under the special conditions that 1) growth proceeds by development of single sourced spirals and 2) growth occurs at very near equilibrium conditions where spiral formation is the only operative mechanism. This suggests that growth experiments that measure temporal changes in solution chemistry yield a composite rate that arises from the contributions of the different hillock types. Hence, chemical affinity-based rate laws do not generally give meaningful interpretations of growth mechanism. By combining direct observations with macroscopic methods that monitor temporal changes in solution chemistry, rate laws with greater predictive capabilities may be possible.
Templated Crystallization of Calcite on Patterned Self-Assembled Monolayers
Authors: Aizenberg Joanna
Published: April 2011

Micropatterned self-assembled monolayers (SAMs) that serve as substrates for nucleation provide a way of controlling various aspects of the crystallization process with a previously unreachable precision. We focus on crystallization of calcite (CaCO3) on SAMs of HS(CH2)nX (X = CO2H, CH3, SO3H, OH, N(CH3)3Cl) supported on Ag and Au. Fine-tuning of the crystallographic orientation of the forming crystals has been achieved by using different functional groups and metal substrates. By patterning SAMs with microregions having different nucleating activities and proper geometry, it is possible to confine crystallization to well defined, spatially delineated sites. This method provides means to fabricate arbitrarily patterned calcitic arrays with controlled density of nucleation, crystallographic orientation, and crystal sizes. The experimental conditions and the mechanisms discussed can be applied to the templated nucleation of a wide range of inorganic materials.
Nitrogen containing hydrogenated amorphous carbon prepared by integrated distributed electron cyclotron resonance for large area field emission displays
Authors: Conway N. M. J. , Godet C. , Equer B.
Published: April 2011

The field emission properties of hydrogenated amorphous carbon containing up to 29at% nitrogen (a-C:N:H), grown in an integrated distributed electron cyclotron resonance (IDECR) reactor were studied using a sphere-plane geometry. All films were smooth in character and required a high field (20-70V/νm) activation process before emission, which created micron- sized craters in the emission region. Further analysis suggested that the emission originates from activation-created geometrically enhanced areas around the crater region. Upon low-level nitrogen incorporation (N/N+C≤0.2), the field required for activation decreased from 54V/νm to a minimum value of 20V/νm. The turn-on field required for 1νA of current also decreased, reaching a minimum of 11.3V/νm. The decrease in activation and turn-on field was related to the increase in conductivity observed with increasing nitrogen content. At higher nitrogen concentrations, the increase in activation energy and turn on field for emission may be due to changes in overall material structure, as indicated by the decreasing optical gap
The Effects of Microstructure on the Brightness of Pulsed Laser Deposited Y2O3:Eu Thin Film Phosphors for Field Emission Displays
Authors: Cho K. G. , Singh R. K. , Kumar D. , Holloway P. H. , Gao H-J. , Pennycook S. J. , Russell G. , Wagner B. K.
Published: April 2011

In order to investigate the effect of microstructure on the brightness of thin film phosphors for field emission displays, Y2O3:Eu thin film phosphors were prepared using pulsed laser deposition. To deconvolute the effects experimentally, the Y2O3:Eu films of controlled thickness and microstructure were prepared on various substrate materials such as amorphous quartz, (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon wafers. Cathodoluminescent brightness and efficiency of the films were obtained in both transmission and reflection modes. The Y2O3:Eu films deposited on the quartz substrates showed the maximum brightness followed by the films on (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon substrates. The role of interface scattering of the emitted light on the film brightness will be discussed together with changing surface roughness and film thickness.
New Dendritic Materials as Potential OLED Transport and Emitter Moeities
Authors: Padmaperuma Asanga B. , Schmett Greg , Fogarty Daniel , Washton Nancy , Nanayakkara Sanjini , Sapochak Linda , Ashworth Kimba , Madrigal Luis , Reeves Benjamin , Spangler Charles W.
Published: April 2011

Traditionally, organic light-emitting devices (OLEDs) are prepared with discrete layers for hole and electron transport. Different materials must be used for these layers because most materials will preferentially transport one charge carrier more efficiently than the other. In most cases, the emitter material serves a dual purpose as both the emitter and the hole or electron transporter. One of the major failure modes of OLEDs results from thermal instabilities of the insulating organic layers caused by joule heating during device operation. The problem is most pronounced for the hole transporting layer (HTL) material which are usually tertiary aromatic amines (i.e., TPD and NPD). This has been attributed to the relatively lower glass transition temperatures (Tg) and resulting inferior thermal stabilities compared to the other materials making up the device. Many researchers have produced HTL materials with higher Tgs based on tertiary aromatic amine oligomers and starburst compounds. Starburst or model dendritic materials offer the advantages of high thermal stabilities and multi-functionality.