bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of Field Emission from Cubic Boron Nitride Coated Molybdenum Emitters
Authors: Schlesser R. , Mccarson B.L. , Sitar Z. 
Published: April 2011

AbstractA combination of classical I-V characterization and voltage-dependent field emission energy distribution (V-FEED) analysis was employed to investigate the mechanisms that dominate field emission from tip-shaped Mo emitters electrophoretically coated with nominally intrinsic, cubic boron nitride (c-BN) powders. I-V characterization of Mo emitters before and after coating showed that the c-BN coating enhanced the field emission current by 2 orders of magnitude. V-FEED analysis revealed a voltage drop proportional to the applied voltage across the c-BN coating due to field penetration. This voltage drop was typically in the order of several Volts for applied voltages of several 100 Volts, and a cathode-to-anode distance of 500 μm. Extrapolation of V-FEED data to flat band condition identified the conduction band minimum of c-BN as the origin of field emitted electrons. At larger field emission currents, an additional voltage drop was observed and was found to be proportional to the emission current. This observation was interpreted in terms of an ohmic resistance at the Mo/c-BN interface and was estimated to be in the order of 10 MΩ.
Structural and Electronic Properties of Negative Electron Affinity Epitaxial Diamond (110) Films Studied Using Atomic Resolution UHV STM
Authors: Lim S.C. , Stallcup R.E. , Akwani I. , Perez J.M. 
Published: April 2011

AbstractWe report ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) studies of the structural and electronic properties of epitaxial diamond (110) films. We observe that epitaxial diamond (110) films grow very rough due to striations. The striations are found to be due to the appearance of(111) faces and contain (100) steps. UHV STM atomic resolution images of the diamond (110) films show a (lxi) zigzag structure that measures 1.5 ± 0.1 Å × 1.5 ± 0.1 Å, in agreement with theoretical predictions for the hydrogen terminated diamond (110) surface. Ultraviolet spectroscopy shows that the epitaxial films have a photoelectric threshold of 5.3 ± 0.1 eV, providing evidence that the films have a negative electron affinity surface.
Electron Emission from Nano-Structured Diamond
Authors: Zhu W. , Kochanski G. P. , Jin S. 
Published: April 2011

AbstractStrong and sustained electron emission at low electric fields has been observed in undoped, nano-structured diamond. The cold cathode emitters consist of a layer of nanometer-size diamond particulates coated on a silicon substrate which is subsequently heat treated in a hydrogen plasma for activation. Electron emission for a current density of 10 mA/cm2is observed at an applied field of 3-5 V/μm. We attribute this excellent emission property to the high defect density in the nano-structured diamond particles and the low electron affinity associated with the diamond surface. The emitters are useful for applications such as flat panel displays as, in addition to the very low fields required, they can easily be deposited on large area substrates by low-cost coating techniques and do not require complicated microtip fabrication processes.
Porous Silica: A Potential Material for Low Dielectric Constant Applications
Authors: Birdsell Edward D. , Gerhardt Rosario A. 
Published: April 2011

ABSTRACTHighly porous (15% dense) silica thin films with k < 2.2 have been produced using a colloidal sol-gel process. This process uses relatively inexpensive, commercially available colloidal silica and potassium silicate. These films were deposited by spin coating. The parameters for spin coating (spin speed, gelation time, gel composition, etc.) have been optimized and coherent films with thicknesses ranging from 0.7–2.0 μm can be reproducibly fabricated. Preliminary work shows that the porosity of these films ranges from a few rn to < 1 μm. The dielectric properties were examined for frequencies up to 1 MHz. Compatibility of the films with IC processing was also investigated.
Fundamental Aspects Of Polymer Metallization
Authors: Faupel F. , Strunskus T. , Kiene M. , Thran A. , Bechtolsheim C. V. , Zaporojtchenko V. 
Published: April 2011

ABSTRACTValuable information on the structure and formation of metal-polymer interfaces originates from radiotracer measurements of metal diffusion at the interface, structural investigations by means of transmission electron microscopy, and computer simulations on the interplay of atomic metal diffusion and aggregation. Moreover, X-ray photoemission spectroscopy has largely contributed to our present understanding of the interfacial chemistry and the early stages of interface formation. While reactive metals always form relatively sharp interfaces with polymers, metals of lower reactivity diffuse into polymers at elevated temperatures and have a very strong tendency to agglomerate. The extent of diffusion appears to be determined by the initial stage of the deposition process. Here sticking coefficients recently measured for metals on virgin polymer surfaces deviate markedly from unity. Diffusion into the polymer increases strongly at low deposition rates. No significant diffusion is expected from a continuous metal film unless metal ions are formed at the interface. Metal ions are highly mobile and do not aggregate due to electrostatic repulsion. The model emerging from these observations allows us to predict the salient features of interface formation between metals and polymers in general and particularly with respect to the new low-k polymers.
Stress-Corrosion Cracking of Spin-on Glass Thin Films
Authors: Cook Robert F , Liniger Eric G 
Published: April 2011

ABSTRACTThe crack-velocity behavior of silsesqioxane spin-on glass thin films exposed to moist environments is examined. An absolute reaction-rate model is used to predict crack velocity using a deleted-bond model and fused silica as a basis, and compared with observed steady-state crack velocities as a function of film thickness and variations in the curing process. An implication is that, on curing, the driving force for film fracture, determined by thermal expansion mismatch, increases less rapidly than the fracture resistance, determined by polymerization.
Low Dielectric Constant Materials Integration Challenges
Authors: Ray Gary W. 
Published: April 2011

ABSTRACTConsiderable effort has been expended in recent years in the development, evaluation, and integration of new low Kc dielectric materials for IC applications. Many film properties must be measured before a film can be selected for integration into an interconnect process flow. Among them are glass transition temperature, thermal stability, Young's modulus, adhesion, stress, coefficient of thermal expansion, dielectric constant, breakdown voltage, solvent resistance, dry etch characteristics, and gap fill performance. These properties must in turn be considered when developing interconnect process modules and selecting the associated equipment set. The properties of these materials differ from those of the commonly used (PE)CVD silicon dioxides to varying extents, depending upon the nature of their composition and structure. This has often resulted in substantial modifications to the modules that comprise interconnect process flows, sometimes compromising manufacturability. This paper will address some of the issues associated with the integration of low K materials into interconnect process flows and how they are related to the properties of these materials.
Chemical-Mechanical Planarization of the Polymer Interlayer Dielectrics
Authors: Murarka S. P. 
Published: April 2011

ABSTRACTLow dielectric constant polymers are being investigated for application as interlayer dielectrics with copper as the metal in a multilevel interconnect scheme. Processing of such structures willrequire the use of chemical-mechanical planarization (CMP) technologies for both the metal and the dielectric. Polymers are comparatively quite soft. They are not readily attacked by chemicals thus requiring more mechanical component dependency compared to the chemical component in the CMP. Polymers are thus prone to scratching during CMP which may lead to reliability problems both from materials and electrical points of view. In this presentation we will discuss the use of chemical engineering and chemistry principles to optimize the polishing process to minimize or eliminate the scratching and other mechanical damages. The role of CMP parameters such as velocity, pressure, particle size, viscosity, and chemistry will be discussed to elucidate the emerging “scratch-free”-CMP-concept.
Overview Of Process Integration Issues For Low K Dielectrics
Authors: Havemann R. H. , Jain M. K. , List R. S. , Ralston A. R. , Shih W-Y. , Jin C. , Chang M. C. , Zielinski E. M. , Dixit G. A. , Singh A. , Russell S. W. , Gaynor J. F. , McKerrow A. J. , Lee W. W. 
Published: April 2011

ABSTRACTThe era of silicon Ultra-Large-Scale-Integration (ULSI) has spurred an everincreasing level of functional integration on-chip, driving a need for greater circuit density and higher performance. While traditional transistor scaling has thus far met this challenge, interconnect scaling has become the performance-limiting factor for new designs. Both interconnect resistance and capacitance play key roles in overall performance, but modeling simulations have highlighted the importance of reducing parasitic capacitance to manage crosstalk, power dissipation and RC delay. New dielectric materials with lower permittivity (k) are needed to meet this challenge. This paper summarizes the process integration and reliability issues associated with the use of novel low k materials in multilevel interconnects.
Reliability and Copper Interconnections with Low Dielectric Constant Materials
Authors: Hu C-K. 
Published: April 2011

ABSTRACTThe materials, process integration, and reliability issues in the development of multilevel electroplated Cu/polyimide on-chip interconnections are described. A combination of: good diffusion/adhesion barrier layers consisting of a metal liner plus the insulator Si3N4, and W stud/Si contacts resulted in a highly reliable IC chip. Electromigration of Cu damascene lines in both SiO2 and polyimide structures was investigated. Similar void growth was observed at the cathode ends of both the interconnect systems. However, the shapes of protrusions at the anode ends of the lines were different. Although the activation energies for both near bamboo-like Cu/SiO2 and Cu/polyimide were both 1.1 eV, the electromigration lifetime of the former was significantly longer. The difference is largely attributable to the poorer thermal conductivity of polyimide.
Aluminum Wiring Reliability of Fluorinated Amorphous Carbon Interlayer
Authors: Iguchi M. , Matsubara Y. , Ito S. , Endo K. , Koyanagi K. , Kishimoto K. , Gomi H. , Tatsumi T. , Horiuchi T. 
Published: April 2011

ABSTRACTWe investigated the aluminum wiring reliability of fluorinated amorphous carbon (a-C:F) interlayer dielectrics (ILD) using electromigration tests at the wafer level under accelerated stress conditions with current density ranging from 25–32 MA/cm2 and a the substrate temperature of 300 K. The a-C:F film is one of the low-k organic materials with a dielectric constant of 2.5. The thermal conductivity of the a-C:F film (0.108 W/m·K) is about one order lower than that of SiO2 (1.2 W/m.K). We found that joule heating effect is enhanced by the lower thermal conductivity of a-C:F and that the wiring lifetime for a-C:F ILD is about one order lower than that for SiO2 ILD under high current stress. However, when the wiring lifetime is plotted as a function of the wiring temperature, the wiring lifetimes for both a-C:F ILD and SiO2 ILD became almost the same. The degradation of the wiring lifetime for a-C:F ILD is explained by the increase of the wiring temperature which is caused from joule heating. Moreover, the activation energy of the electromigration for a-C:F ILD has the same value as that of SiO2 LD at a temperature.
Reliability of Cu/WN thin Films Deposited on Low Dielectric Constant SiOF ILD
Authors: Lee Seoghyeong , Kim Dong Joon , Yang Sung-Hoon , Park Jeongwon , Sohn Seil , Oh Kyunghui , Kim Yong-Tae , Park Jong-Wan 
Published: April 2011

ABSTRACTThe effect of the post plasma treatment on the dielectric properties and reliability of fluorine doped silicon oxide (SiOF) films was studied. Also, the thermal stability of a Cu/WN interconnect system with SiOF intermetal dielectrics was examined by RTA. The surface roughness of SiOF films increased with the increasing plasma treatment power due to ion bombardment effect during the plasma treatment. As the plasma treatment power increased, the dielectric constant increased from 3.16 to 3.43, while the change in the relative dielectric constant of the plasma treated films by the boiling treatment was decreased in magnitude. Furthermore, the chemical properties of the plasma treated SiOF films near the top layer tend to resemble those of thermal oxides by the plasma treatment of sufficient power because of the reduction in the Si-F bonding in the films. In the case of Cu/WN/SiOF/Si multilayer structure, surface oxidation and densification due to the plasma treatment seemed to play an important role in protecting the interdiffusion between SiOF and metal interconnects.
Adhesion Study in Aluminum/Polyimide System
Authors: Yoo S. H. , Heo S. J. , Kim Y.-H. , Han B. J. , Yoon J. H. 
Published: April 2011

ABSTRACTThe effects of RF plasma precleaning and polyimide curing conditions on the peel strength have been studied. polyimide precursors of BG-2480 (Toray) and PI-2611 (Du Pont) were spincoated and cured under the various conditions. Cured polyimide substrates were in-situ Ar+ RF plasma cleaned prior to metal deposition. Al-2%Si or Al-0.5%Cu-1%Si thin films were deposited onto polyimide substrates using DC magnetron sputtering.The peel strength was enhanced by RF plasma treatment. The Al/modified PI specimen failed cohesively in the polyimide. The polyimide curing condition strongly affects the peel strength in the Al/modified PI system.
Newly Developed Low-K and Low-Stress Fluorinated Silicon Oxide Utilizing Temperature-Difference Liquid-Phase Deposition Technology
Authors: Yeh Ching-Fa , Lee Yueh-Chuan , Lee Su-Chen 
Published: April 2011

ABSTRACTTo meet the requirements of low-K and low-stress intermetal dielectric (IMD) for future ULSI devices, a novel temperature-difference liquid-phase deposition (TD-LPD) method is proposed. The deposition solution of supersaturated silicic acid with high concentration of fluorine can be achieved by raising deposition temperature larger than 15 °C from dissolution temperature (0 °C). Because fluorine atoms can easily be incorporated with the technique, TDLPD fluorine-doped SiO2 (FSG) exhibits low-K (∼3.4) and low-stress (∼40MPa) property. In this paper, to study the interaction between TD-LPD FSG and moisture, the FSG is annealed and moisture stressed repeatedly as in a real process. Since K is sensitive to moisture absorption, and the stress is sensitive to the dehydration reaction between Si-OH's, the both are monitored as indices. A feasible mechanism is proposed to explain the variation in K/stress during annealing and boiling cycles.
The Origin of Nanopipes and Micropipes in Non-Cubic GaN and SiC
Authors: Pirouz P. 
Published: April 2011

ABSTRACTMicro/nanopipes are linear defects along the c-axis of hexagonal polytypes of SiC and GaN that are currently the focus of much attention. It has been shown that these defects can be very detrimental to the electronic properties of devices manufactured from, at least, 6H-SiC. In this paper, the origin of these defects is discussed in terms of Frank's theory [1] that dislocations will have a hollow core when their Burgers vector is large. Two fundamental issues about such dislocations are addressed: their formation along the c-axis of the crystal, and their stability despite their large Burgers vectors [2]. The proposed model is based on the mosaic structure of sublimation-grown 6H- or 4H-SiC, and VPE-grown 2H-GaN on sapphire substrates. The presence of unit c-axis screw dislocations is attributed to the accommodation of low-angle twist boundaries in the mosaic structure. The formation of superscrew dislocations with large Burgers vector, which empty their cores to reduce the excessive strain energy there, is shown to be the result of 3c screw dislocations in the axis of triple junctions which “getter” the neighboring unit dislocations and simultaneously increase their diameter. The predictions of the model are compared with available data in the literature, and suggestions are made for the decrease of nano/micropipe density.
The Estimation and revision of barrier heights in 4H- SiC and 6H-sic Schottky Diodes
Authors: Lee You-Sang , Kim D.-Y. , Oh J.-K. , Han M.-K. , Choi Y.-I. 
Published: April 2011

ABSTRACTThe barrier heights of various Schottky diodes in n-type 4H-SiC and 6H-SiC is estimated from published data at Si-face and C-face, respectively, employing the LSM (least square method). It is found that the barrier height in SiC Schottky diode is a linear function of metal work function as φB. =a φm + b. The a is about 0.63 ∼ 0.72. The already established analytic expression in [9] is compared with the estimated linear expression and revised by employing the empirical factor, α between the upper and lower boundary of interface state density, DIT. The values of a lie in 1.65 ∼ 32.1.
Turn-on Process in High Voltage 4H-SiC Thyristors
Authors: Dyakonova N. V. , Levinshtein M. E. , Palmour J. W. , Rumyantsev S. L. , Sing R. 
Published: April 2011

ABSTRACTThe turn-on process and the steady state current-voltage characteristics have been investigated in 4H-SiC thyristors with a forward breakover voltage close to 700 V and pulse switch current density of 16 000 A/cm2. The rise current constant, τr, has been found to decrease monotonically with temperature: τr, ≈ 10.5 nsec at T = 300 K and τr ≈ 1.2 nsec at T = 500 K at high bias Uo ≥ 300 V. The value of τr ≈ 1.2 nsec is the lowest observed value for SiC thyristors. At very high current density, j ≥ 5 103 A/cm2, the residual voltage drop for 4H-SiC thyristors is lower than for identically rated Si thyristors. The voltage drop Udo decreases monotonically with temperature.
Deep Levels In High Resistivity AlGaN Films Grown By MOCVD
Authors: Polyakov A. Y. , Smirnov N. B. , Govorkov A. V. , Redwing J. M. 
Published: April 2011

ABSTRACTDeep levels in high resistivity layers of AlGaN grown by MOCVD on sapphire were studied by means of dark current and photocurrent versus temperature measurements and by photoinduced current relaxation spectroscopy (PICTS). Strong temperature quenching of photocurrent was observed and explained by the presence of hole traps with energies 0.2 eV, 0.3 eV and 0.35 eV for films with correspondingly 5%, 15% and 25% of Al. Two hole traps with activation energies of 0.27–0.35 eV and 0.85–1.05 eV depending on composition were detected in PICTS spectra. It is suggested that the former traps are the same as observed in temperature quenching of photocurrent while the latter traps are related to the yellow luminescence band in AlGaN. The photocurrent decay is shown to have a complex form with a rapid decrease followed by a long tail associated with detrapping of holes. It is argued that, at room temperature, the ∼1 eV hole traps are mainly responsible for the amplitude of the tail.
Vacancy-Type Defects in as-Grown and Proton-Irradiated 6H-SiC
Authors: Puff Werner , Mascher Peter , Balogh Adam G. 
Published: April 2011

ABSTRACTAnnealing of defects in as-grown and proton irradiated bulk n- and p-type 6H-SiC has been investigated by positron lifetime spectroscopy and Doppler-broadening measurements. The grown-in defects do not anneal out until 1600 °C, whereas the radiation induced defects show three main annealing stages well below this temperature. During annealing, the formation of larger defect complexes can be observed.
Phonons and Holes in Magnesium Doped GaN
Authors: Demangeot F. , Frandon J. , Renucci M. A. , Smirnov D. , Létin J. , Grandjean N. , Beaumont B. , Kuball M. , Davies T. , Steeds J. W 
Published: April 2011

ABSTRACTP doping of gallium nitride by incorporation of magnesium in the layers was controlled recently. Only Popovici et al. [1] have published the results of a Raman study on p type GaN. In the present communication, we report on the interaction of the free hole gas with the axial A1(LO) or planar E1(LO) phonon modes, evidenced by Raman scattering: the observed coupled phononplasmon mode is found very different from the corresponding one evidenced in silicon doped (n type) GaN. We compare the experimental data with the lineshape calculated within a dielectric model, using the results of electrical measurements. These results are also compared with infrared reflectivity spectra.
Comparison of High Field Characteristics of SiO2 and AIN Gate Insulators in 6H SiC MOS Capacitors
Authors: Madangarli V. P. , Sudarshan T. S. , Tin C. C. 
Published: April 2011

ABSTRACTUsing a fast ramp response technique, the high field characteristics, specifically the breakdown strength, of thermally grown silicon-dioxide (SiO2) and MOCVD grown aluminum-nitride (AIN), on n-type 6H-SiC epilayers is obtained as a function of three different processing conditions for the insulator growth. Significant improvement in the breakdown strength of thermally grown SiO2 after a 30 minute post annealing at 400°C in nitrogen ambient is reported. Further, the influence of temperature profile during the AIN growth on the breakdown strength is reported.
Persistent photoconductivity in AlGaN films Grown by mocvd
Authors: Polyakov A. Y. , Smirnov N. B. , Govorkov A. V. , Redwing J. M. 
Published: April 2011

ABSTRACTPhotocurrent transients due to illumination by above-bandgap and subbandgap light were studied for Si doped and undoped films of AlGaN grown by MOCVD on sapphire and having compositions ranging from 0% to 60% of Al. It is shown that in Si doped layers the decay of photoconductivity takes extremely long time (hundreds and thousands seconds, depending on temperature, composition and illumination conditions). Both the kinetics of rise and fall of photoconductivity are best described by stretched exponents. The characteristic decay times are virtually temperature independent for temperatures below 270–290K and have activation energy of 0.14–0.26 eV (depending on composition) for higher temperatures. The decay times become longer with decreased light intensity and increase when above-bandgap light excitation is replaced by subbandgap light excitation (the photocurrent values from which the decay starts being equivalent). The results cannot be quantitatively explained by the effects of changing of the quasi-Fermi level position well known for DX-centers in AlGaAs. No persistent photoconductivity could be observed in high resistivity undoped AlGaN films with 5%, 15% and 25% of Al.