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ABSTRACT: Several experiments have been performed to evaluate the nucleation, growth, structure and microstructure of aluminum induced catalytically activated low temperature crystallization of amorphous Si. TEM and in-situ XRD investigations on hydrogenated amorphous silicon (alpha-Si:H) grown by PECVD and coated with a thin layer of aluminum on it revealed the beginning of solid state transformation of polycrystalline Si (poly-Si) in the form of heterogeneously evolved nuclei in alpha-Si:H at 140degC and significant nano-scaled dendrites at 150degC.
Physics of Semiconductor Devices, 2007. IWPSD 2007. International Workshop on; 01/2008
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ABSTRACT: Solid phase crystallization of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (alpha-Si:H) in alpha-Si:H/Al and Al/alpha-Si:H structures has been investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Radiative heating has been used to anneal films deposited on carbon-coated nickel (Ni) grids at temperatures between 200 and 400 degrees C for TEM studies. alpha-Si:H films were deposited on c-Si substrates using high vacuum (HV) PECVD for the XRD studies. TEM studies show that crystallization of alpha-Si:H occurs at 200 degrees C when Al film is deposited on top of the alpha-Si:H film. Similar behavior was observed in the XRD studies. In the case of alpha-Si:H deposited on top of Al films, the crystallization could not be observed at 400 degrees C by TEM and even up to 500 degrees C as seen by XRD.
Microscopy and Microanalysis 05/2005; 11(2):133-7. · 3.01 Impact Factor
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ABSTRACT: Large grain poly-Si thin films on glass substrates have been successfully fabricated. The film thickness was 400 nm and the grains sizes were in excess of several microns. The films were fabricated using aluminum-induced crystallization of a-Si:H in the presence of a silicon oxide layer at the AI/a-Si:H interface. The a-Si:H film was deposited on glass substrates and the annealing temperatures and annealing times were kept below 450 °C and 30 minutes, respectively. The resulting poly-Si was heavily Al-doped.
Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE; 02/2005
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Journal of Vacuum Science and Technology 05/2003; A20(3).
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Journal of Materials Science Letters 03/2002; 21(8):647-648.
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R.K. Ulrich,
W.D. Brown,
S.S. Ang,
F.D. Barlow,
A. Elshabini,
T.G. Lenihan, H.A. Naseem,
D.M. Nelms,
J. Parkerson,
L.W. Schaper,
G. Morcan
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ABSTRACT: The circuit boards of many mixed-signal and digital systems are
now dominated by individually placed discrete passive (DP) components.
This article looks at thin-film integrated passives (IPs) as an
alternative to DPs in the effort to save board space and improve
electrical performance and system reliability. Integrated passive
components have been utilized successfully with ceramic substrate
technology for over 50 years in the form of thick-film resistive and
dielectric firable pastes. However, this considerable infrastructure
cannot be transferred to FR4 and flex substrates due to the high firing
temperatures required, and these board materials make up the vast
majority of interconnect substrates, in consumer and commercial systems.
Mmat has been lacking is thin-film IP materials and fabrication
processes that are compatible with organic boards
IEEE Circuits and Devices Magazine 10/2000; · 1.18 Impact Factor
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ABSTRACT: The provision of adequate decoupling capacitance in the power
distribution system for integrated circuits (ICs) is an increasing
concern. As clock rates and the IC gate density increase, discrete chip
capacitors do not satisfy the decoupling requirements for high current
switching at very high frequencies. Thin film capacitors not only
exhibit better high frequency performance than discrete ceramic
capacitors, but also provide the possibility for passive component
integration. In this work, the high frequency performance of thin film
capacitors was investigated using Maxwell Eminence, a high frequency
structure simulator based on the finite element method. Good agreement
between the calculated impedance and experimental results was obtained.
At high frequencies, the performance of thin film capacitors is related
to contact configurations, dielectric and metal layer thicknesses, and
capacitor shapes. The influence of these factors on the impedance
behavior was examined. Equivalent circuits of a thin film capacitor for
use in a circuit simulator at high frequencies are discussed
IEEE Transactions on Advanced Packaging 06/2000; · 1.12 Impact Factor
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ABSTRACT: CdCl<sub>2</sub>-doped CdS films have been prepared using a vacuum evaporation technique with a goal of providing a low resistivity, large grain size, window layer for CdTe-CdS solar cells. CdS films with 0.05, 0.1 and 0.2% CdCl<sub>2</sub> doping have been grown. The effects of doping on the optical transmission, XRD, resistivity, carrier concentration, Hall mobility and microstructure have been investigated. N-type CdS films with resistivities of 2 to 10 Ωcm and Hall mobilities from 1 to 5 cm<sup>2</sup>/V-sec have been grown using this technique. The XRD patterns show that <002> is the preferred orientation. SEM analyses reveal that the grains in the films are columnar and their size increases from 70 nm for undoped CdS films to 150 nm for 0.2% CdCl<sub>2</sub>-doped films
Photovoltaic Specialists Conference, 2000. Conference Record of the Twenty-Eighth IEEE; 02/2000
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ABSTRACT: Scaling down on-chip interconnect cross-sectional dimensions
results not only in higher circuit wiring density, but also in the long
lossy line problem, wherein the long lines become highly resistive and
have unacceptable delays. One possible solution to the problem of long
lossy lines is to transfer these lines off-chip using seamless high
off-chip connectivity (SHOCC) technology. In this work, me modeled and
studied the electrical performance of SHOCC signal lines. The
performance of SHOCC interconnects was compared with that of typical
on-chip interconnerts. Modeling and simulation results, along with
recommendations with regards to driver sizes and the type of
interconnect that should be used, are presented
IEEE Transactions on Advanced Packaging 09/1999; · 1.12 Impact Factor
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ABSTRACT: Parallel and floating plate decoupling capacitors, which exhibit
extremely low effective series inductance, have been modeled and their
high frequency performance simulated. Simulations compare well with
measurement. The effects of various design variations on capacitor
performance is reported, as are accurate equivalent circuit models which
correctly describe the performance of these devices over a wide
frequency range
Electronic Components and Technology Conference, 1999. 1999 Proceedings. 49th; 02/1999
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ABSTRACT: Since 1979, the Department of Electrical Engineering, University
of Arkansas, Fayetteville, AR has offered the courses, IC Fabrication
Technology (ELEG 5213) and its laboratory sequel, IC Fabrication Lab
(ELEG 5293), as technical elective courses for seniors and graduate
students interested in a microelectronic processing emphasis. The IC Fab
Tech course covers silicon crystal growth, epitaxy, oxidation,
diffusion, ion implantation, CVD and PVD growth, and metallization
processes and their underlying mechanisms. In the IC Fab Lab, students
start with polished Si wafers and use a six level mask set to fabricate
various test structures. These include planar four probe resistors,
capacitors, p-n junctions, bipolar transistors, MOS devices, and other
process control and alignment structures. This lab is conducted in the
Teres Instruments Solid State Laboratory of the Department of Electrical
Engineering and is equipped with an RO system for the de-ionized water
and Class 100 laminar flow workbenches
University/Government/Industry Microelectronics Symposium, 1999. Proceedings of the Thirteenth Biennial; 02/1999
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Diamond and Related Materials 01/1999; 8:1083-1090. · 1.91 Impact Factor
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ABSTRACT: We report the development of a new metal-to-metal antifuse with amorphous carbon as the dielectric. Amorphous carbon antifuses have several characteristics making them superior to amorphous silicon antifuses, including lower values of OFF-state leakage current, ON-state resistance, dielectric constant, and breakdown voltage. Most importantly, amorphous carbon antifuses do not show ON-OFF switching, which is observed in amorphous silicon antifuses. A new model is proposed to explain the breakdown mechanism and ON-state reliability of amorphous carbon antifuses.
IEEE Electron Device Letters 10/1998; · 2.85 Impact Factor
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ABSTRACT: A study was performed on electroplating of an extended eutectic
solder structure. The use of electroplating technology enabled firm
control over the size and shape of grains in the deposit. Grain size and
shape in turn affected the diffusion of lead and tin through bulk phases
as well as along grain boundaries. The control over diffusion affected
the reflow properties of the final solder structure. The reflow
properties affected the strength of the flip-chip bond, as well as the
self-alignment properties of the solder. The structures were then tested
for their electrical resistance
Multichip Modules and High Density Packaging, 1998. Proceedings. 1998 International Conference on; 05/1998
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ABSTRACT: Diamond-coated tools can greatly improve the productivity of machining highly abrasive materials such as high silicon–aluminium alloys used in the automotive industry. Cemented-carbide diamond-coated tool inserts have not become an off-the-shelf product owing to several difficulties including insufficient adhesion of diamond to the substrate and questionable reproducibilty in their machining performance in the manufacturing. In order to overcome these difficulties, a better understanding of the effects of the chemical vapour deposition (CVD) conditions such as methane concentration, reactor pressure and substrate temperature is important. In this work, cemented tungsten carbide tool inserts with 6 wt% Co (WC–Co) were coated with diamond films deposited at five different methane concentrations (1–9 vol%). Here we present preliminary results of the effect of methane concentration variation on the following physical properties of the diamond coating: surface morphology; crystal structure; chemical quality; surface roughness; residual stress. The results indicate that the best physical properties of diamond-coated tool inserts using hot-filament CVD are achieved with diamond coatings deposited at methane concentrations ranging from 1 to 3%.
Journal of Materials Science 12/1997; 33(1):173-182. · 2.02 Impact Factor
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ABSTRACT: The presence of undesirable hydrogen-related impurities and the resulting stress instability in chemical vapor deposited silicon dioxide films are important issues. In this work, the bonding nature and stress behavior of relatively low-temperature deposited silicon dioxide films deposited at high rates were investigated. Films were deposited at 1000 Å/min and at a substrate temperature in the 250–350 °C range. A considerable change in stress was observed in these films upon annealing in the 250–400 °C temperature range. Both as-deposited and annealed films were then stored in a cleanroom environment for long periods of time, and their stress was monitored intermittently. In parallel, Fourier transform infrared studies were performed on an identical set of as-deposited and annealed films to investigate changes in the bonding nature of the films during aging. Thus, film stress and their bonding nature were studied concurrently over an extended period of time. Si–H and silanol (Si–OH) were identified as impurities responsible for the observed stress instability of the deposited films. Initial concentrations of these impurities have been observed to vary depending on the deposition conditions. Also, depending on the concentrations of these impurities, both reversible and irreversible bond reconstruction were observed in the films upon annealing. Concomittantly, reversible and irreversible changes in stress were observed in annealed films, the amount of change depending on the impurity type and content. Impurities responsible for reversible and irreversible bond reconstruction were identified. Good correlation between film stress and bonding was observed. © 1997 American Institute of Physics.
Journal of Applied Physics 09/1997; 82(6):2922-2932. · 2.17 Impact Factor
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ABSTRACT: Electroplating is a vital component of MCM-technology because it
is the most cost effective method available for deposition of thick
copper interconnects. A vital issue in the use of electroplated copper
is the uniformity of the deposit. Thickness uniformity of 5% is
desirable but often difficult to obtain. A rotating disk electroplating
process that consistently achieves the required uniformity has been
developed. It is an extremely robust system, capable of reproducing the
required uniformity in spite of great variations in electroplating
conditions. The parameters that have been studied include uneven
rotation rate, wobble, and fluctuating current. Studies have also been
done on the effect that rotation speed has on both uniformity and
deposition rate
Multichip Modules, 1997., 6th International Conference on; 05/1997
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ABSTRACT: Residual stress in thin silicon dioxide films has been studied as a function of storage time. Films of varying microstructure and impurity content were deposited by plasma-enhanced chemical vapor deposition. Initially, all the films exhibited compressive stress, the magnitude of which was found to increase rapidly with time for the first few hours after deposition. For all the deposited thin films, this increasing compressive stress eventually saturates and then begins to decrease with time. The time at which the transition occurs depends on film thickness and quality, whereas, for relatively thicker films deposited under identical conditions, a saturation in compressive stress after long aging time was observed. No existing model of thin oxide films successfully explains the observed time variation of stress. In this paper, the variation of film stress as a function of storage time and film properties, such as porosity and impurity content, is discussed. Three driving forces, namely, surface reactivity, silanol buildup, and water dipole interaction, each of whose contribution varies depending on film thickness and quality, have been identified as potential mechanisms behind stress change in oxide films. A unified model consisting of these driving forces can explain the time variation of stress behavior in oxide films, irrespective of film quality and thickness. © 1997 American Institute of Physics.
Journal of Applied Physics 03/1997; 81(7):3129-3133. · 2.17 Impact Factor
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ABSTRACT: Aluminum metal‐induced crystallization and doping of hydrogenated amorphous silicon (a‐Si:H) have been investigated. Aluminum was evaporated onto device quality a‐Si:H films deposited in an ultrahigh vacuum plasma‐enhanced chemical vapor deposition system. These Al/a‐Si:H structures were annealed in the 100–300 °C range. Electrical, surface morphological, and chemical characterizations of the material were performed. The transmission line model technique was used for electrical characterization. Raman spectroscopy showed that crystallization of the interacted a‐Si:H film underneath Al pads initiates at temperatures as low as 180 °C. X‐ray diffraction analysis showed very good polycrystallinity of the interacted film. Electrical measurement, Hall measurement and x‐ray photoelectron spectroscopy analysis results revealed that a‐Si:H film in contact with Al becomes heavily doped by Al during crystallization as a result of annealing at relatively low temperatures. © 1996 American Institute of Physics.
Journal of Applied Physics 06/1996; · 2.17 Impact Factor
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ABSTRACT: This paper presents the University of Arkansas High Density Electronics Center’s (HiDEC) most recent developments in diamond processing, high‐temperature superconductors (HTS), and MCM power distribution technologies. Each of these technologies not only can be used for conventional MCMs, but are also candidate technologies for an ongoing development effort of highly integrated, intelligent, high‐power solid‐state power controllers, hereafter termed, multichip power modules (MCPMs). © 1996 American Institute of Physics.
AIP Conference Proceedings. 02/1996; 361(1):1335-1338.
