bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Dielectric Films and Post-Metal Etch Wet Treatment on Charge-Induced Corrosion of Tungsten Vias
Authors: Lee Szetsen , Ni Chi-Jung 
Published: April 2011

ABSTRACTThe prevention of charge-induced corrosion of tungsten vias after metal etch has been stud-ied with several types of commonly used wet chemical solutions and two kinds of dielectric film materials, silicon dioxide and silicon oxynitride. It was found that one of the solutions, leaving essentially no polymer residue on metal lines, could effectively prevent corrosion of tungsten vias. Other solutions either produced minor residues or severe sidewall erosion on metal lines. This study has shown that the combination of wet treatment with oxynitride as the dielectric charge shielding film was as effective as other conventional methods for preventing tungsten vias corrosion. However, for metal lines capped with silicon dioxide, significant sidewall ero-sion, surface roughness, and polymer residue were observed. Chemical reaction mechanisms are proposed for the preservation of tungsten vias after metal etch.
A Low Temperature Photonic Crystal Technology for Integration with Modern CMOS Technologies
Authors: Bayat Khadijeh , Farrokh Baroughi Mahdi , Chaudhuri Sujeet K. , Safavi-Naeini Safieddin 
Published: April 2011

ABSTRACTIn this paper, low temperature amorphous silicon oxynitride (a-SixOyNz:H) thin film technology is proposed for implementation of CMOS compatible photonic crystal (PC) based optical integrated circuits (OICs). The a-SixOyNz films of different refractive indices were developed by plasma enhanced chemical vapor deposition (PECVD) technique using silane, nitrous oxide, and ammonia as gas phase precursors at 300°C. The films with refractive index between 1.43 − 1.75 were obtained by changing gas flow ratios. Such thin films can be used as cladding and core layers in photonic crystal structure.The bandgap and guiding properties of the a-SixOyNz based PCs were simulated and was shown that the a-SixOyNz:H based PC technology offers larger feature sizes than a conventional silicon based photonic crystals.
Engineered Solder-Directed Self-Assembly Across Length Scales
Authors: Knuesel Robert , Bose Shameek , Zheng Wei , Jacobs Heiko O 
Published: April 2011

ABSTRACTWe report on recent progress in the directed self-assembly of discrete inorganic semiconductor device components. Different from prior research, the goal is to enable the integration of increasingly small dies while supporting unique-angle orientation and contact pad registration. The process is based on the reduction of surface free energy between liquid solder coated areas on the substrate and metal-coated binding sites on the semiconductor dies. Recent advances include flip-chip assembly with unique angular orientation accomplished using “two-element” docking sites that contain pedestals that act as chaperones for the solder directed assembly to take place. The scale reduction to 20 μm sized components involves the use of a liquid-liquid interface to concentrate component delivery and speed up the self-assembly process to prevent oxidative dissolution of the solder sites prior to completion.
Improved Electromigration Lifetime for Copper Interconnects using Tantalum Implant
Authors: Gambino Jeff , Sullivan Timothy D. , Gill Jason , Chen Fen , Mongeon Steve , Adams Edward D. , Burnham Jay , Pokrinchak Phil , Rodbell Kenneth P. 
Published: April 2011

ABSTRACTIn this study, a novel method is explored for improving the electromigration lifetime of Cu wires, using Ta implantation into Cu. For high implant doses (2E15 cm−2), the electromigration lifetime is improved by over 5X using this method. An increase in lifetime is achieved, even for an average surface concentration of Ta on the order of 0.1 atm%. We propose that the improvement in electromigration lifetime is due to the reduction of defects at the SiN/Cu interface due to the presence of Ta. The line-to-line leakage at high voltages (> 5V) increases with the Ta implant, with higher leakage at higher Ta concentrations, so the Ta dose must be limited to avoid excessive leakage.
Impact of Fabrication Process, Layout Variation and Packaging Process on Cu/Low-k Interconnect Reliability
Authors: Karmarkar Aditya , Xu Xiaopeng , Pramanik Dipu , Lin Xi-Wei , Rollins Greg , Lin Xiao 
Published: April 2011

ABSTRACTThe industry trend towards smaller feature size and higher integration density leads to multi-level Cu/low-k interconnect schemes with reduced line width and spacing. Mechanical stress is generated during interconnect fabrication. The spatial distribution of the stress is strongly affected by the layout variation. The packaging process generates a global chip level stress that permeates to the local interconnect level. Stress related failures and yield loss are major areas of concern for Cu/low-k interconnects. The effects of fabrication process, layout variation, and packaging process on the final stress distributions in Cu/low-k interconnect structures are examined and the reliability impact of mechanical stress is assessed.
Metal-Organic Chemical Vapor Deposition (MOCVD) of GeSbTe-based Chalcogenide Thin Films
Authors: Tompa Gary S. , Sun Shangzhu , Rice Catherine E , Cuchiaro Joe , Dons Edwin 
Published: April 2011

AbstractChalcogenide Random Access Memory (C-RAM) has shown significant promise in combining the desired attributes of an ideal memory, including: nonvolatility, fast read/write/erase speed, low read/write/erase voltage/power, high endurance, and radiation hardness. Current C-RAM production technology relies on sputtering to deposit the active chalcogenide layer. The sputtering process leads to difficulties in meeting requirements for device conformality (in particular – filling vias), film adherence, compositional control, wafer yield, and surface damage. Ultimately, a viable CVD manufacturing process is needed for high-density products to realize the full potential of C-RAM. In this work, we discuss the Metal-Organic Chemical Vapor Deposition (MOCVD) tool technology used to produce the films and report the materials properties of GeSbTe-based chalcogenide thin films grown in small research scale and in large production scale MOCVD reactors. Films were grown at low pressures at temperatures ranging from 350 C to 600 C. X-Ray Fluorescence (XRF) and Auger Electron Spectroscopy (AES) were performed and determined that the film composition is controllable and uniform.
Energetics of Both Minority and Majority Carrier Transitions through Deep Defects in Wide Bandgap Pentenary Cu(In,Ga)(Se,S)2 Thin Film Solar Cells
Authors: Halverson Adam , Nishiwaki Shiro , Shafarman William , Cohen J. David 
Published: April 2011

AbstractWe report and electronic and optical characterization of three wide-bandgap alloys of the Cu(InxGa1-x)(SeyS1-y)2 pentenary material system. Devices were characterized using admittance spectroscopy as well as drive-level capacitance profiling. The devices showed activated defect behavior typical of thin-film solar cell devices. Optical characterizations were carried out with Transient Photocapacitance and Transient Photocurrent spectroscopies. These data showed broad exponential bandtails with large Urbach energies, indicative of a moderately high degree of compositional and/or structural disorder. The temperature dependence of the TPC spectra was examined in detail and we were able to observe the thermal emission of electrons from defects into the conduction band. The emission energy of these features corresponds well with the measured optical threshold and the known bandgap of the cells. Thus we infer an upper bound of about 50meV for the lattice relaxation energy following the optical transition into the defect.
Exploring Back Contact Technology to Increase CdS/CdTe Solar Cell Efficiency
Authors: Fahrenbruch Alan L. 
Published: April 2011

AbstractThe primary routes for increasing CdS/CdTe solar cell efficiency involve increasing free carrier density, reducing bulk and interface recombination, and/or reducing back contact barrier height. This paper focuses on the role of the back contact barrier in increasing cell efficiency. Measurement of barrier height and back surface recombination are outlined and three CdTe/MX/M back contact prototypes, each with particular strengths, are discussed to bring out important issues.
A Neutral Barrier at CGS Grain Boundaries - Compositional and Structural Dependencies
Authors: Hafemeister Michael , Siebentritt Susanne , Sadewasser Sascha , Frank-Rotsch Christiane , Lux-Steiner Martha Ch. 
Published: April 2011

AbstractUnlike other photoactive layers (e.g. Si) polycrystalline chalcopyrite layers achieve higher efficiency than monocrystalline ones. Although grain boundaries may play an important role for this phenomenon, there is currently no commonly accepted model for the electronic structure of grain boundaries. First experimental results on CuGaSe2 absorbers indicated a small neutral barrier for majority carriers (20-40meV) at sigma 3 grain boundaries, which is the predominant grain boundary in polycrystalline chalcopyrite absorbers [1]. These results are in discrepancy with theory, which predicts a 10 times higher barrier; we suspect that the copper excess might reduce the barrier height.Here we present a study using Hall-effect and Kelvin Probe Force Microscopy (KPFM) measurements to investigate the composition dependence of the barrier height of epitaxially grown CuGaSe2 layers containing a sigma 3 grain boundary as a function of the Cu/Ga ratio. First results show that the barrier height is independent of the copper content. In addition, we present initial results on sigma 9 grain boundaries which are observed to occur in high efficiency absorbers.
Electronic Defects and Device Performance in CuGaSe2 Solar Cells
Authors: Rembold J. Jedediah , Curtis Todd W. , Heath Jennifer T. , Young David L. , Johnston Steve W. , Shafarman William N. 
Published: April 2011

AbstractThe electronic and materials properties of two series of wide-bandgap solar cells with Cu-poor CuGaSe2 (CGS) absorbers have been studied, to better understand limitations on the device performance. One series of samples displayed distinct lateral non-uniformities in Cu/Ga ratio, Na content, and thickness, likely due to a limited supply of Se during CGS growth. The second series of samples appeared uniform. The most prominent electronic difference was the presence of a distinct band of near-interface defect states in the more non-uniform set of samples. The device performance did not appear to be limited by defects in the bulk CGS film until the defect density was larger than 2×1016 cm-3. Instead, interface recombination appears to be a significant factor limiting Voc in both sets of samples.
The Mechanism of J-V “Roll-Over” in CdS/CdTe Devices
Authors: Zhou Jie , Wu Xuanzhi , Yan Yanfa , Asher Sally , Da Silva Juarez , Wei Suhuai , Weinhardt Lothar , Bar Marcus , Heske Clemens 
Published: April 2011

AbstractThe “roll-over” phenomenon in current-voltage (J-V) curves of CdS/CdTe devices is recognized as a result of the formation of a higher back barrier. When Cu has not been intentionally added to the back contact, roll-over is understandable. However, the mechanism was unclear for forming J-V roll-over in a CdTe cell with a back contact containing Cu. We did extensive characterizations, including XRD, XPS, SIMS, TEM, and EDS, and “recontact” experiments to understand this phenomenon. The results show that the roll-over comes from the formation of Cu-related oxides at the back side of the device during processing, rather than the diffusion of Cu to the front side of the device. Discussions related to the J-V roll-over mechanisms will also be presented.
Pressure Dependent Rapid Thermal Processing of CuInS2 Thin Films Investigated by In-Situ Energy Dispersive X-ray Diffraction
Authors: Kötschau Immo Michael , Rodriguez-Alvarez Humberto , Streeck Cornelia , Weber Alfons , Klaus Manuela , Denks Ingwer Asmus , Gibmeier Jens , Genzel Christoph , Schock Hans-Werner 
Published: April 2011

AbstractThe rapid thermal processing (RTP) of Cu-rich Cu/In precursors for the synthesis of CuInS2 thin films is possible within a broad processing window regarding leading parameters like top temperature, heating rate, and Cu excess. The key reaction pathway for the CuInS2 phase formation has already been investigated by in-situ energy dispersive X-ray diffraction (EDXRD) for various precursor stoichiometries, heating rates and top temperatures at sulphur partial pressure conditions which are typical for physical vapour deposition processes. According to the phase diagrams of the binary sulphide phases, the sulfur partial pressure strongly determines the occuring crystalline phases. However, a controlled variation of the maximum sulphur partial in a typical RTP experiment has not been carried out yet. In order to study the influence of this parameter a special RTP reaction chamber was designed suitable for in-situ EDXRD experiments at the EDDI beamline at BESSY, Berlin. In a typical in-situ RTP/EDXRD experiment sulphur and a Cu/In/Mo/glass precursor are placed in an evacuated graphite reactor. The amount of sulphur determines the maximum pressure available at the top temperature of the experiment. As the RTP process proceeds a complete EDXRD spectrum is acquired every 10 seconds and thus the various stages of the reaction path and the crystalline phases can be monitored. The first experiments show already a significant change in the reaction pathway and the secondary Cu-S phases which segregate on top of the CuInS2 thin film during the reaction.
Synthesis and Sintering of Aluminium Nitride Nano-particles
Authors: HAN Zhao , YANG Mei , ZHU Hongmin 
Published: April 2011

AbstractAluminum nitride (AlN) nano-particles were synthesized from aluminum chloride by sodium reduction in liquid ammonia. A liquid solution of sodium dissolved in ammonia was employed as a reduction-nitridation agent, which enabled direct nitridation of aluminum chloride at −45°C. The synthesized particles were heat-treated at 1000°C in vacuum, and were characterized by X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area measurement. The results indicated that the product were hexagonal wurtzite AlN particles, with a specific surface area of 262 m2g−1. Spark plasma sintering (SPS) process was used to consolidate the as-prepared AlN nanoparticles, and a dense AlN ceramic (>98.5%) with average grain size of 200-400nm was obtained at 1600°C without the use of sintering additives.
Preparation of AlN thin films by means of CVD using iodide source under atmospheric pressure
Authors: Iwane Hiroki , Wakiya Naoki , Sakamoto Naonori , Nakamura Takato , Suzuki Hisao 
Published: April 2011

AbstractEpitaxial aluminum nitride (AlN) thin films were successfully prepared on the (0001) sapphire substrate by chemical vapor deposition (CVD) using aluminum iodide (AlI3) and ammonia (NH3) under atmospheric pressure at 750 ºC. The crystallographic relationship between AlN thin films and Al2O3 substrate is in the following; AlN(0001)//Al2O3(0001) and AlN[1010]//Al2O3[1120]. Lattice parameters of AlN thin film measured by X-ray diffraction revealed that c=0.498 and a=0.311 nm, respectively. Residual stress estimated by modified sin2ψ method was 0.38 GPa in compressive stress. Cross-sectional TEM observation revealed that an interlayer lies between the AlN films and the sapphire substrate. It was suggested that relaxation of residual stress caused by the mismatching of lattice parameter and thermal expansion coefficient was brought about by the interlayer.
Preparation of InN by Means of AP-HCVD Using In Buffer Layers
Authors: Yokoo Hiroaki , Wakiya Naoki , Sakamoto Naonori , Nakamura Takato , Suzuki Hisao 
Published: April 2011

AbstractWe have grown indium nitride (InN) films using In buffer layer on an a-plane sapphire substrate under atmospheric pressure by halide CVD (AP-HCVD). Growth was carried out by two steps: deposition In buffer layer at 900 °C and subsequent growth of InN layer at 650 °C. In order to compare, we also grown InN films on an a-plane sapphire. The InN films are investigated on crystal quality, surface morphology and electrical property using high-resolution X-ray diffraction (HR-XRD), X-ray pole figure, scanning electron microscope (SEM), Hall measurement. The results show that the crystal quality, surface morphology and electrical property of InN films are improved by using In buffer layer.
Predicting Efflorescence and Subflorescences of Salts
Authors: Espinosa Rosa , Franke Lutz , Deckelmann Gernod 
Published: April 2011

AbstractCrystallization of salts is a common cause of damage in porous building materials. Understanding of the crystallization mechanism of salts is important in order to prevent or avoid the problem. Subflorescence of salts (i.e., crystallization within the pores of the body) can induce scaling and cracking, while efflorescence (i.e., crystallization in a film of solution on the exterior surface of the body) does not generally affect the coherence and endurance of the building materials.In this paper, we deal with the crystallization behavior of two salts, sodium sulfate and sodium chloride, in two bricks with different capillary porosity. The results reveal quite different crystallization behavior depending on salt and substrate.The supersaturation of the solution is induced in our experiments by evaporation. Indeed, the main reason for the different behavior of these salts is the different ability for supersaturation. Thus, the sodium sulfate solution is prone to be much more supersaturated than sodium chloride. Furthermore, the solution transport, which depends on salt properties, material porosity, pore-clogging and climatic conditions, affects the position of the drying front and, with it, the crystallization front leading to the formation either of efflorescence or of subflorescence. A simulation of the experiments helps us to understand the effect of the influencing factors on the crystallization pattern. Therefore, considering both factors, supersaturation ratio and solution transport, it is possible to predict the different crystallization behavior observed in the experiments.
Defect Healing of Carbon Nanotubes by Rapid Vacuum Arc Annealing
Authors: Tsai Jeff Tsung-Hui , Li Jason , Tseng Andy 
Published: April 2011

ABSTRACTA rapid thermal annealing process is demonstrated for healing the defects in carbon nanotubes using a DC vacuum arc discharge system. Multi-walled carbon nanotubes (MWCNTs) grown by chemical vapor deposition at a relatively low temperature (∼650 °C) showed structural imperfections inside the tubes which are known as "bamboo-like" defects. These defects can be thermally annealed to reconstruct the graphitic structure. A vacuum arc discharge system was used to generate high temperatures (∼1800 °C) followed by rapid cooling. The MWCNTs can be rapidly annealed in such a system by several heating and cooling cycles. The annealed samples were characterized by Raman spectroscopy and transmission electron microscopy. The defects were found to be healed when the environment contained water vapor, indicating that oxygen may play an important role in breaking the imperfect graphitic structure and removing the weakly bonded defects during the rapid heating cycles. After breaking the “bamboo” segment, the graphene shell was then reconstructed during the cooling process to produce multi-shell perfection. This method produces effective defect healing and bamboo structure removal from MWCNTs.
Growth of Single Crystalline ZnO Nanotubes and Nanosquids
Authors: Prasad Abhishek , Mensah Samuel , Wang Jiesheng , Pandey Archana , Yap Yoke Khin 
Published: April 2011

ABSTRACTThe growth of ZnO nanotubes and nanosquids is obtained by conventional thermal chemical vapor deposition (CVD) without the use of catalysts or templates. Characterization of these ZnO nanostructures was conducted by X-ray powder diffraction (XRD), Field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and photoluminescence (PL). Results indicate that these ZnO nanostructures maintain the crystalline structures of the bulk wurtzite ZnO crystals. Our results show that rapid cooling can be used to induce the formation of ZnO nanotubes and ZnO nanosquids. The self-assembly of these novel ZnO nanostructures are guided by the theory of nucleation and the vapor-solid crystal growth mechanism.
Dielectrophoretic Deposition of Carbon Nanotubes with Controllable Density and Alignment
Authors: Moscatello Jason , Kayastha Vijaya , Pandey Archana , Ulmen Benjamin , Yap Yoke Khin 
Published: April 2011

ABSTRACTControlled deposition of carbon nanotubes (CNTs) across desired electrodes is important for the fabrication of nanoelectronic devices. Dieletrophoresis (DEP) has been recognized as a convenient and affordable technique for the deposition of nanotubes and nanowires on electrodes. Although DEP has been quite well studied for dielectric particles, the application for depositing nanotubes is still at the early stage of development. Here, we show that multi-walled CNTs can be deposited by DEP with controllable density and degree of alignment.
Real-Time Electrical Characterization of Dielectrophoretic Assembly of Multi-Walled Carbon Nanotubes
Authors: An Libao , Friedrich Craig 
Published: April 2011

ABSTRACTThis paper reports on a real-time monitoring method for the assembly of a small number of metallic carbon nanotubes (CNTs) by dielectrophoresis (DEP). A time-varying impedance model of the electrode gap was developed to evaluate the number of CNTs which span the gap by measuring the simultaneous variation of gap impedance during the DEP process. Sudden decreases of gap impedance signals were detected during the DEP assembly of multi-walled carbon nanotubes (MWNTs) corresponding to assembly of single or multiple tubes across the gap. The method reduces the requirement of scanning electron microscopy (SEM) inspection and could help automate DEP assembly of CNTs.
Dependence of GaN Defect Structure on the Growth Temperature of the AlN Buffer Layer
Authors: Wong Yuen-Yee , Chang Edward Yi , Yang Tsung-Hsi , Chang Jet-Rung , Chen Yi-Cheng , Ku Jui-Tai 
Published: April 2011

ABSTRACTThe defect structure of the GaN film grown on sapphire by plasma-assisted molecular beam epitaxy (PAMBE) technique was found to be dependent on the AlN buffer layer growth temperature. This buffer growth temperature controlled the defect density in GaN film but had shown contrary effects on the density of screw threading dislocation (TD) and edge TD. The density of screw TD was high on lower temperature buffer but low on the higher temperature buffer. Meanwhile the density of edge TD had shown the opposite. Further examinations have suggested that the defect structure was closely related to the stress in the GaN film, which can be controlled by the growth temperature of the AlN buffer. Using the 525°C AlN buffer, optimum quality GaN film with relatively low screw and edge TDs were achieved.