bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real Time Optics of p-Type Microcrystalline Silicon Deposition On Specular and Textured ZnO-Coated Glass
Authors: Rovira Pablo I. , Ferlauto Andre S. , Koval Randy J. , Wronski Christopher R. , Collins Robert W. , Ganguly Gautam 
Published: April 2011

ABSTRACTIn this study, we optimize the plasma-enhanced chemical vapor deposition (PECVD) process to achieve high-density nucleation of single-phase microcrystalline silicon (µc-Si:H) p-type layers on zinc oxide (ZnO) surfaces at 200 °C for applications in amorphous silicon (a-Si:H) based p-i-n solar cells. The phase evolution of the Si:H p-layers on specular ZnO-coated glass substrates is characterized using real time spectroscopic ellipsometry (RTSE). The resulting evolutionary phase diagram depicts the accumulated film thickness at which the amorphous-to- microcrystalline (→µc) transition occurs versus the H2-dilution ratio, with all other parameters fixed. Guided by this diagram, we find that high-density microcrystallite nucleation and fully- coalesced µc-Si:H p-layers ∼100 Å thick can be obtained on specular ZnO at 200 Å using a B(CH3)3 doping gas flow ratio of D=[B(CH3)3]/[SiH4]=0.02 and an optimized H2-dilution ratio of R=[H2]/SiH4]=200. Lower H2-dilution levels (R<160) generate purely amorphous or mixed (a+µc) phases, and higher dilution levels (R>200) generate longer induction periods, low-density nucleation, and incomplete coalescence of microcrystallites even after ∼100 Å. The time evolution of the microstructure and the resulting dielectric functions as determined by RTSE are similar for optimized µc-Si:H p-layers ∼200 Å thick prepared on specular and textured ZnO surfaces, indicating that the substrate texturing does not necessitate process reoptimization.
Nanocrystalline Undoped Silicon Films Produce by Hot Wire Plasma Assisted Technique
Authors: Ferreira Isabel M.M. , Martins Rodrigo F. P. , Cabrita Ana M. F. , Fortunato Elvira M. C. , Vilarinho Paula 
Published: April 2011

ABSTRACTIn this work, we show results concerning electro-optical properties, composition and morphology of nanocrystalline hydrogenated undoped silicon (nc-Si:H) films produced by hot wire plasma assisted chemical vapour deposition process (HWPA-CVD) and exhibiting a compact granular structure, as revealed by SEM micrographs. This was also inferred by infrared spectra, which does not present the SiO vibration band located at 1050-1200 cm-1, even when samples have long atmospheric exposition. The photoconductivity measured at room temperature also does not change when samples have a long time exposition to the air or to the light irradiation. The influence of hydrogen dilution on the properties of the films was also investigated.
Roughness of TFT Gate Metallization and its Impact on Leakage, Threshold Voltage Shift and Mobility
Authors: Nathan A. , Park B. , Sazonov A. , Murthy R.V.R. 
Published: April 2011

ABSTRACTA comparison of the performance of aluminium (Al)-gated thin film transistors (TFTs) is presented in which we varied its sputter deposition conditions, such as deposition temperature, process pressure, and power. Gate films deposited at 30°C/5mTorr/300W yield TFT characteristics with low leakage current (~ 10 fA at low VDS), an ON/OFF ratio better than 108, and a mobility of 1.1 cm2/Vs. In contrast, films deposited at 150°C/10mTorr/400W, yield a significant degradation in leakage current (~ 1 pA) and mobility (0.77 cm2/Vs). The degradation stems from the high surface roughness of the a-SiNx:H gate insulator, and hence the TFT channel, caused by hillock formation on the Al gate. In addition, the high roughness leads to a correspondingly large shift in threshold voltage. After one-hour bias stress of +25 V applied to the gate, the shift in threshold voltage is ΔVT ~ 5 V, as compared to the small shift of ΔVT ~ 2.3 V associated with the smoother gate. Also included in our comparison is a TFT whose Al gate is now capped with 20 nm of molybdenum (Mo) to minimize propagation of the gate surface roughness to the active channel. Its cross sectional topography shows the interface smoothness to be as good or better, to yield improved leakage and stability characteristics.
Effect Of Nickel In Large Grain Poly-Si Film Formed By Nickel Induced Lateral Crystallization and New Grain Enhancement Method
Authors: Chan W.Y. , Myasnikov A.M. , Poon M.C. , Yuen C.Y. , Han P. G. , Chan M. , Ko P.K. 
Published: April 2011

ABSTRACTLarge grain poly-silicon film (poly-Si) with high material quality and uniformity can have numerous novel applications such as providing a low cost alternative to form silicon-on-insulator (SOI) substrates and a breakthrough technology to ultra-dense 3-dimensional multi-layer SOI like devices and circuits. Nickel Induced Lateral Crystallization (NILC) of amorphous Si (a-Si) has been studied intensively, yet the grains are still small (∼ 1 μm). Recently, we have reported a novel method by combining NILC and a new annealing (at above 900 °C) to form poly-Si film with very large grains ranging from 10 μm to 100 μm. The film has good quality and the TFTs formed are highly comparable to SOI TFTs. This work further reports the effect of Ni to the new large-grain poly-Si film.
Effect of Deposition Conditions on the Structural and Mechanical Properties of Poly SiGe
Authors: Sedky Sherif , Witvrouw Ann , Caymax Matty , Saerens Annelies , Van Houtte Paul 
Published: April 2011

ABSTRACTMicroElectroMechanical Systems (MEMS) are used in a wide variety of applications such as accelerometers [1], gyroscopes [2], infrared detectors [3],…etc. For high volume applications, fabrication costs can be possibly reduced by monolithic integration of MEMS with the driving electronics. The easiest approach for monolithic integration is post processing MEMS on top of the driving electronics, as this does not introduce any change into standard fabrication processes used for realizing the driving electronics. On the other hand, post processing imposes an upper limit on the fabrication temperature of MEMS in order to avoid any damage or degradation in the performance of the driving electronics. Polycrystalline silicon (Poly Si) has been widely used for MEMS applications [4], but the main disadvantage of this material is that it requires a high processing temperature (higher than 800°C [5]) to achieve the desired physical properties. In particular, a low tensile stress is needed for MEMS. Polycrystalline silicon germanium (Poly SiGe) seems to be an attractive alternative to poly Si as it has similar properties, while the presence of germanium reduces its melting point. Hence, the desired physical properties are expected to be realized at lower temperature. Depending on the germanium concentration and the deposition pressure, the transition temperature from amorphous to polycrystalline can be reduced to 450°C [6], or even lower, compared to 580°C for LPCVD poly Si. Also, the residual mechanical stress in poly SiGe is lower than that in poly Si [7].
Grazing Incidence Small Angle X-Ray Scattering Study on Low Dielectric Thin Films
Authors: Hsu C.-H. , Lee Hsin-Yi , Liang K.S. , Jeng U-Ser , Windover D. , Lu T.-M. , Jin C. 
Published: April 2011

AbstractHighly porous silica films with pore size in the nanometer scale are being extensively studied as potential candidates for interlevel dielectrics. Because these dielectric materials appear in the form of thin films with a thickness of only several thousand Angstroms, conventional techniques are difficult to be readily applied to study their structure and porosity. We employed small angle scattering in the grazing incidence geometry in this study. Using high resolution xray beamline with synchrotron radiation source, we demonstrate that the small angle x-ray scatteirng (SAXS) data of the porous films can be obtained. The structure of sol-gel derived silica - xerogel films on silicon substrate studied by specular reflectivity and grazing incidence small angle x-ray scattering (GISAXS) will be presented.
Processing, Characterization and Reliability of Silica Xerogel Films for Interlayer Dielectric Applications
Authors: Jain Anurag , Rogojevic Svetlana , Wang Feng , Gill William N. , Wayner Peter C. , Plawsky Joel L. , Haberl Arthur , Lanford William 
Published: April 2011

AbstractSurface modified silica xerogel films of high porosity (25-90 %) and uniform thickness (0.4-2 µm) were fabricated at ambient pressure on silicon and other substrates. Mechanical reliability of the films was determined by measuring fracture toughness (adhesive) as a function of aging time and temperature using the modified edge-lift-off technique. There is an optimum aging time at 60 °C aging to obtain maximum fracture toughness for the procedure used here.Cu/xerogel/Si and Ta/xerogel/Si structures were annealed at different temperatures and in different ambient environments were analyzed using RBS and optical microscopy to assess the extent of interaction with the xerogel film. When annealed in N2 with trace amounts of O2 (equivalent to 10-7-10-6 Torr vacuum), RBS analysis does not show diffusion of Cu or Ta through the xerogel up to 450 °C. At higher temperatures, or in the presence of larger concentrations of O2, Cu and Ta oxidize. Cu oxidation leads to significant diffusion through the xerogel. Ta oxidation also results in diffusion-like RBS spectra. Using the micron-size ion beam to probe the Ta surface, this was found to be solely due to buckling of Ta films on xerogel. A thin SiNx layer on top of Cu and Ta prevents metal oxidation up to 640 °C, Cu diffusion, and Ta buckling.
Strain Measurements from Single Grains in Passivated Aluminum Conductor Lines by X-Ray Microdiffraction During Electromigration
Authors: Hwang K. J. , Cargill G. S. , Marieb T. 
Published: April 2011

AbstractWe describe a method for determining the local strain state of passivated aluminum metal lines from single grains within 2.6 µm × 7.0 µm × 0.75 µm sized regions along the line. X-ray microbeam diffraction is used to obtain localized measurements of thermal and electromigration-induced strain during 37 hours of electromigration in a passivated 2.6 µm-wide, 300 µm-long pure Al conductor line at a current density of 4.2×105 A/cm2 and temperature of 270°C. Diffraction from single grains is used to measure both the in-plane and normal components of strain and their evolution during electromigration at several positions along the line.
Experimental Studies of the Reliability of Interconnect Trees
Authors: Hau-Riege S.P. , Thompson C.V. 
Published: April 2011

AbstractThe electromigration resistance of simple straight-line interconnects is usually used to estimate the reliability of complex integrated circuits. This is generally inaccurate, and overly conservative at best. The shapes and connectedness of interconnects is not accounted for in standard reliability assessments. We have identified the interconnect tree as the fundamental reliability unit. An interconnect tree consists of connected conducting line segments lying within a single layer of metallization, and terminating at two or more nodes at which there is a diffusion barrier such as a W-filled via. We performed electromigration experiments on the simplest tree structures, such as ‘L’- and ‘T’-shaped interconnects, as well as straight lines with an additional via in the middle of the line, passing currents of different magnitudes and directions through the limbs of the trees. We found that metal limbs ending in other limbs can act as reservoirs for electromigrating metal atoms. Passive reservoirs, which are limbs that do not carry electrical current, are generally beneficial for reliability, whereas limbs that do carry electrical current, called active reservoirs, can be beneficial or detrimental, depending on the direction and magnitude of the current in the reservoir. However, our experiments show that bends in interconnects do not affect their reliability significantly. We also found that the reliability of an interconnect tree can be conservatively estimated by considering void-growth and void-nucleation-limited failures at the most heavily stressed junction in the tree, which can be found by analyzing the geometry and current configuration. Our experimentally verified model for tree reliability can be used with layout tools for reliability-driven computer-aided design (RCAD), through ranking of the reliabilities of trees in order to identify areas at risk from electromigration damage.
The Influence of Stress-Induced Voiding on the Electromigration Behavior of AlCu Interconnects
Authors: Zitzelsberger A.E. , Fischer A.H. 
Published: April 2011

AbstractThe influence of stress-induced voiding on the electromigration (EM) behavior has been investigated on narrow via-line structures. For this purpose the EM performance of metal lines containing stress-induced voids already before the electrical operation has been compared with samples without stress-induced voids. We found, that pre-existing stress voids in the metal lines do not affect the activation energy Ea and lead only to a small decrease of the EM median time to failure, but cause a relevant reduction of the current density exponent down to n = 1. As a consequence, a tremendous decrease of the electromigration limited life time is obtained.
Evolution of Surface Morphology During Cu(TMVS)(hfac) Sourced Copper CVD
Authors: Yang Daewon , Hong Jongwon , Cale Timothy S. 
Published: April 2011

AbstractIn this paper, we describe an experimental study of the nucleation and growth stages during Cu(TMVS)(hfac) sourced Cu CVD on TaN substrates. In particular, we have investigated the effects of water vapor as a co-reactant on evolving surface morphology. The results of short (less than 10 s) depositions without/with water vapor indicate that water vapor helps to reduce the incubation time and to enhance the nuclei formation, uniformity, and adhesion (based on AFM analysis). Introducing water vapor during only the initial stage of deposition results in lower roughnesses, larger grain sizes, and lower short-range roughnesses as compared to the films deposited without water vapor. From this study, we conclude that water vapor enhances Cu nucleation and that a relatively small amount of water vapor before or during the initial stage of deposition improves surface morphology in terms of roughness and grain size.
Modeling of Ionized Magnetron Sputtering of Copper
Authors: Bloomfield M.O. , Cale T.S. 
Published: April 2011

AbstractComputer simulations are used to study ionized physical vapor deposition, with ionized magnetron sputtering of copper as the primary system of interest. The effects of sputtering-ion energy and sputtering-ion angular flux distributions on the evolution of sub-micron scale features during IPVD are explored using the EVOLVE simulator. Our goal is to develop semi- quantitative engineering relationships that accurately predict the trends in experimental responses to changes in operating conditions. A sticking- factor model is used to describe deposition by neutrals. The sticking-factor of incident Cu atoms can depend on arrival angle and energy. Copper ions can also become part of the growing film. Energy and angular dependent sputter yields for both copper and argon ions are taken alternately from MD simulation results and a semi-empirical model. Sputtered material is ejected from the surface, tracked through the gas phase, and allowed to redeposit. Redeposition is also modeled via a sticking-factor based approach. The redistribution of film material results in non-intuitive profiles and complex relationships between final profiles and process parameters such as sample bias and neutral-to-ion flux ratios.
Computational Experiment on CVD of SiC: Growth Rate, C/Si Ratio, Parasitic Phase Formation
Authors: Vorob'ev Andrei N. , Komissarov Alexandre E. , Bogdanov Maxim V. , Karpov Sergey Yu. , Bord Olga V. , Zhmakin Alexandre I. , Lovtsus Andrei A. , Makarov Yuri N. 
Published: April 2011

AbstractThe heat and mass transport model extended to describe silicon cluster formation in the gas phase is employed for a numerical analysis of SiC CVD in a commercial vertical rotating disc reactor. The growth rate is studied as a function of precursor flow rates varied in a wide range of values. It is found that the growth rate is limited by the gas mixture depletion in silicon atoms due to homogeneous nucleation. The secondary phase formation on the growing surface is analyzed. The SiC growth window depending on the precursor flow rates is calculated, and a significant effect of the homogeneous nucleation on the window width is found. The model predicts that the Si/C ratio on the wafer can considerably differ from that at the reactor inlet.
Low Temperature Growth Of Barium Strontium Titanate Films By Ultraviolet-Assisted Pulsed Laser Deposition
Authors: Craciun V. , Howard J. M. , Lambers E. S. , Singh R. K. 
Published: April 2011

AbstractBarium strontium titanate (BST) thin films were grown directly on Si substrates by an in situ ultraviolet (UV)-assisted pulsed laser deposition (UVPLD) technique. With respect to films grown by conventional (i.e. without UV illumination) pulsed laser deposition (PLD), the UVPLD grown films exhibited improved structural and electrical properties. The dielectric constant of a 40-nm thick film deposited at 650 °C was determined to be 281, the leakage current density was approximately 4×10−8 A/cm2at 100 kV/cm, and the density of interface states at the flat-band voltage was found to be approximately 5.6×1011 eV−1 cm−2 X-ray photoelectron spectroscopy investigations found that the surface of the grown films exhibited an additional Ba-containing phase, besides the usual BST perovskite phase, which was likely caused by stress and/or oxygen vacancies. The amount of this new phase was always smaller and very superficial for UVPLD grown films, which can explain their better overall properties.
Photoluminescence Charateristics of SrTiO3:Pr3+,Ga3+ Single Crystal
Authors: Byun Jaedong , Lee Yongjei , Jang Boyun , Yu Youngmoon , Ryou Sunyoun , Suh Kyungsoo 
Published: April 2011

ABSTRACTSrTiO3 crystals containing varying concentrations of Pr and Ga were grown by a standard floating zone method and their photoluminescence characteristics were investigated. It was found that only a small fraction of Pr ions added are incorporated in the lattice. When the Ga ions are co-doped, the solubility of Pr ions is increased considerably. Comparing the ionic sizes of the host and dopants, it seems that the increase of solubility of Pr by Ga co-doping is due to charge compensation achieved by the additional Ga3+. The addition of Ga in Pr - activated SrTiO3 resulted also in a considerable enhancement of Pr3+ emission band at 615 nm. This result is attributed to the hole trapping effect of Ga3+ ions.
Plastic Deformation of Thin Foil Substrates with Amorphous Silicon Islands into Spherical Shapes
Authors: Hsu Pai-hui I. , Huang Min , Wagner Sigurd , Suo Zhigang , Sturm J. C. 
Published: April 2011

ABSTRACTThere is a growing interest in the application of large area electronics on curved surfaces. One approach towards realizing this goal is to fabricate circuits on planar substrates of thin plastic or metal foil, which are subsequently deformed into arbitrary shapes. The problem that we consider here is the deformation of substrates into a spherical shape, where the strain is determined by geometry and cannot be reduced by simply using a thinner substrate. The goal is to achieve permanent, plastic deformation in the substrates, without exceeding fracture or buckling limits in the device materials.Our experiments consist of the planar fabrication of amorphous silicon device structures onto stainless steel or Kapton® polyimide substrates, followed by permanent deformation into a spherical shape. We will present empirical experiments showing the dependence of the results on the island/line size of the device materials and the deformation temperature. We have successfully deformed Kapton® polyimide substrates with 100 [.proportional]m wide amorphous silicon islands into a one steradian spherical cap, which subtends 66 degrees, without degradation of the silicon. This work demonstrates the feasibility of building semiconductor devices on plastically deformed substrates despite a 5% average biaxial strain in the substrate after deformation.
Sequential Lateral Solidification of Ultra-Thin a-Si Films
Authors: Cho Hans S. , Kim Dongbyum , Limanov Alexander B. , Crowder Mark A. , Im James S. 
Published: April 2011

ABSTRACTThis paper demonstrates that Sequential Lateral Solidification (SLS) of Si can be carried out on films as thin as – and potentially much thinner than – 250 Å. When compared to thicker Si films, however, the SLS-processed ultra-thin films contain more twins, and successful processing requires irradiation within a narrower laser energy density range and a smaller per-pulse translation distance. The physical interpretation of these findings is formulated by analyzing the details of the microstructures observed in single-pulse-irradiation-induced Controlled Super-Lateral Growth (C-SLG) experiments. SEM and TEM analyses reveal complicated microstructural details that we interpret as originating from breakdown of epitaxial growth during lateral solidification, an effect that is detrimental to the SLS process. Based on considerations of far-from- equilibrium solidification behavior of Si, it is argued that undercooling of the solidification interface below a threshold value at which solidification no longer proceeds epitaxially – arising from reduction in interfacial recalescence during lateral solidification of ultra-thin Si films, relative to that of thicker films – is responsible for the breakdown. Based on this model, we discuss how external parameters may be adjusted so as to permit optimal crystallization of ultra-thin Si films using SLS.
Field Emission from Carbon Systems
Authors: Robertson John 
Published: April 2011

ABSTRACTElectron field emission from diamond, diamond-like carbon, carbon nanotubes and nanostructured carbon is compared. It is found that in all practical cases that emission occurs from regions of positive electron affinity with a barrier of ∼5 eV and with considerable field enhancement. The field enhancement in nanotubes arises from their geometry. In diamond, the field enhancement occurs by depletion of grain boundary states. In diamond-like carbon we propose that it occurs by the presence of sp2-rich channels formed by the soft conditioning process.
Mo and Co Silicide FEAs
Authors: Lee Jong Duk , Shim Byung Chang , Jin Sung Hun , Park Byung-Gook 
Published: April 2011

ABSTRACTFor enhancement and stabilization of electron emission, Mo and Co silicides were formed from Mo mono-layer and Ti/Co bi-layers on single crystal silicon FEAs, respectively. Using the slope of Fowler-Nordheim curve and tip radius measured from SEM, the effective work function of Mo and Co silicide FEAs are calculated to be 3.13 eV and 2.56 eV, respectively. Compared with silicon field emitters, Mo and Co silicide exhibited 10 and 34 times higher maximum emission current, 10 V and 46 V higher failure voltage, and 6.1 and 4.8 times lower current fluctuation, respectively. Moreover, the emission currents of the silicide FEAs depending on vacuum level are almost same in the range of 10−9 ∼ 10−6 torr. This result shows that silicide is robust in terms of anode current degradation due to the absorption of air molecules.
Under-Gate Triode Type Field Emission Displays with Carbon Nanotube Emitters
Authors: Kang J. H. , Choi Y. S. , Choi W. B. , Lee N. S. , Park Y. J. , Choi J. H. , Kim H. Y. , Lee Y. J. , Chung D. S. , Jin Y. W. , You J. H. , Jo S. H. , Jung J. E. , Kim J. M. 
Published: April 2011

ABSTRACTA new structure of triode type field emission displays based on single-walled carbon nanotube emitters is demonstrated. In this structure, gate electrodes are situated under cathode electrodes with an in-between insulating layer, so called under-gate type triode. Electron emission from the carbon nanotube emitters is modulated by changing gate voltages. A threshold voltage is approximately 70 V at the anode bias of 275 V.