bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsed Plasma Enhanced Chemical Vapor Deposition from CH2F2, C2H2F4, and CHCIF2
Authors: Labelle Catherine B. , Lau Kenneth K. S. , Gleason Karen K.
Published: April 2011

Pulsed plasma enhanced chemical vapor deposition films have been grown from C2H2F4, CH2F2, and CHCLF2. C-Is x-ray photoelectron spectroscopy (XPS) indicates a prevalence ofC-CF species in the films from C2H2F4and CH2F2, whereas CF2species dominate the films from CHC1F2. The CFxspecies distributions for the films are largely controlled by the competition between CF2-producing and HF elimination reactions in the pulsed plasmas. Dominance by HF elimination produces films with highC-CF and CF concentrations (e.g., CH2F2), whereas dominance by CF2-producing reactions leads to films with higher CF2concentrations (e.g., CHCIF2). The % CF3in the film is lowest for the precursor having the lowest F:H ratio, CH2F2. Little or no hydrogen was detected in the deposited films. Thermal degradation of films from C2H2F4and CH2F2, as probed by solid-state nuclear magnetic resonance (NMR) spectroscopy, shows a loss through CF3detachment and HF elimination. Pulsed plasma films from all three precursors gave dielectric constants of 2.4, with loss tangents on the order of 10−2. Dielectric measurements of pulsed plasma films from hexafluoropropylene oxide (HFPO) gave a dielectric constant of 2.0 ± 0.1 with a loss tangent of 0.009.
Phase Separation Behaviors Of Polyimide Blends
Authors: Ryu C. H. , Bae Y. C.
Published: April 2011

We investigated phase behaviors of polyimide blends such as polyethermide(PEI)/polystyrene(PS), PEI/polyamideimide(PAI), PEI/polyethyleneoxide(PEO), and PAI/PEO systems. Our sample systems exhibited lower critical solution temperature(LCST) phase behaviors. In the PEI/PS system, phase transition occurred near or above the glass transition temperature(Tg) of PS and the critical temperature of the system increased with decreasing molecular weight of PS. For PEI/PAI and PEI/PEO systems, the critical temperature of PEI/PAI system is higher than that of PEI/PEO system. Phase transition temperatures of PAI/PEO systems appeared near or below the melting point of PEO.
The Closed-Form Solutions For The Breakdown Voltages Of 6H-SiC Reachthrough Diodes
Authors: Lee You-Sang , Byeon D.-S. , Choi Y.-I. , Park I.-Y. , Han Min-Koo
Published: April 2011

The closed-form analytic solutions for the breakdown voltage of 6H-SiC RTD, reachthrough diode, having the structure of p+-n-n+, are successfully derived by solving the impact ionization integral using effective ionization coefficient in the reachthrough condition. In the region of the lowly doped epitaxial layer, the breakdown voltages of 6H-SiC RTD nearly constant with the increased doping concentration. Also the breakdown voltages of 6H-SiC RTD decrease, in the region of the highly doped epitaxial layer, which coincides with Baliga'seq. [1].
Hot Spots In 4H Sic P+N Diodes Studied By The Optical Beam Induced Current Technique
Authors: Frischholz M. , Nordgren K. , Rottner K. , Seidel J. , Schöner A. , Bakowski M.
Published: April 2011

The optical beam induced current (OBIC) technique allows a direct imaging of high voltage PN junctions at a microscopic level under reverse operating conditions by measuring the local variation of the photocurrent. In this paper we focus on the application of the UV-OBIC technique for failure analysis of 4H SiC high voltage P+N diodes.

4H SiC P+N diodes with a 2-zone junction termination extension were used. The diodes were characterized in terms of reverse leakage current and breakdown voltage. Various devices were chosen for failure analysis on the base of early breakdown and/or excessive leakage current for OBIC measurements to study extrinsic failures. As a reference we selected diodes that blocked more than 2 kV with a leakage current density of typically less than 0.1 μA/cm2.

OBIC measurements have been used to detect failures in devices that manifest themselves as peaks or “hot spots” in the photocurrent distribution. Early breakdown of diodes could be attributed to formation of hot spots in the periphery of the diodes. The appearance of a hot spot preceded any noticeable increase in reverse leakage current and is thus a very sensitive tool to identify defective diodes already at low voltage levels.

The photocurrent generated by illumination of hot spots has been measured as a function of reverse bias voltage and the current multiplication factor has been determined.
Study of Stimulated Emission in InGaN/GaN Multi-Quantum Wells in the Temperature Range of 175 k to 575 k
Authors: Bidnyk S. , Cho Y. H. , Schmidt T. J. , Krasinski J. , Song J. J. , Keller S. , Mishra U. K. , Denbaars S. P.
Published: April 2011

We present the results of an experimental study on stimulated emission (SE) in optically pumped InGaN/GaN multi-quantum well (MQW) structures in the temperature range of 175 K to 575 K. Samples used in this work consisted of 12 QWs and the GaN barriers were intentionally doped with different Si concentrations. The effect of doping on the SE thresholds of the MQWs were investigated. We observed that the SE spectra were comprised of many narrow peaks of less than I Å full width at half maximum (FWHM). No broadening of the FWHMs of the peaks occurred as the temperature was raised from 175 to 575 K. The SE threshold was measured as a function of temperature and compared with that of a thin GaN film. Low SE thresholds were attributed to high quantum efficiency of the MQWs, possibly associated with large carrier localization. A characteristic temperature of 162 K was derived from the temperature dependence of the SE threshold. The integrated emission intensity versus pumping density was examined for different temperatures. This study shows that InGaN/GaN MQWs are suitable for the development of laser diodes that can operate well above room temperature.
Reaction Processes At The Initial Stage of Diamond Nucleation on The Surface of Si(111)
Authors: Xie Fangqing , Chen Youcun , Zhang Qingzhe , Lin Zhangda
Published: April 2011

The thermal behavior of CHx(x=2–3) radicals and H atoms adsorbed on Si(111) surface was investigated using high-resolution electron-energy-loss spectroscopy (HREELS), quadrupole mass spectrometry (QMS), and low-energy electron diffraction (LEED). We found that CHx(x=2–3) radicals in the top adlayers of saturate adsorption were not stable, and the loose structures among a few top adlayers broke up completely till 550K. TDMS(thermal desorption mass spectrometry) analysis showed significant desorption of atomic hydrogen, CH2 and CH3. In the region of 550K-750K, only H2 was detected by TDMS, and we speculate that the CHx(x=2–3) species catenate each other, and form a network of hydrocarbon, which is possibly the initial stage of diamond nucleation on Si. This formed network was not stable above 800K, C2 hydrocarbon species were observed after the thermal desorption temperature was over 800K. HREELS measurement demonstrated that no H atoms existed when substrate temperature reached 980K. Compared with the result reported by S.-Tong Lee for diamond(Ref. 12), we conclude that low stability of hydrocarbon species on Si is the dominant reason that results in the difficulty of diamond nucleation on perfect Si surface.
Spatial characterization of Doped Sic Wafers
Authors: Burton J. C. , Sun L. , Pophristic M. , Li J. , Long F. H. , Feng Z. C. , Ferguson I.
Published: April 2011

Raman spectroscopy has been used to investigate wafers of both 4H-SiC and 6H-SiC. The wafers studied were semi-insulating and n-type (nitrogen) doped with concentrations between 2.1 × 1018 cm−3 and 1.2 × 1019 cm−3. Significant coupling of the A1 longitudinal optical (LO) phonon to the plasmon mode was observed. The position of this peak shows a direct correlation with the carrier concentration. Examination of the Raman spectra from different positions on the wafer yielded a rudimentary spatial map of the carrier concentration. This data is compared with a resistivity map of the wafer. These results suggest that Raman spectroscopy of the LO phonon-plasmon mode can be used as a noninvasive, in situ diagnostic for SiC wafer production and substrate evaluation.
Phase Separation and Ordering in InGaN alloys
Authors: Doppalapudi D. , Basu S. N. , Moustakas T. D.
Published: April 2011

We investigated phase separation and long-range atomic ordering in InGaN alloys grown on (11–20) sapphire substrates by molecular beam epitaxy (MBE). Compositional inhomogeneities were found in films grown at substrate temperatures ranging from 650 – 675°C when the indium content was larger than 20%. Upon annealing to 725°C, these films underwent phase separation, similar to films grown at 725° C.These InGaN films also showed the evidence of long-range atomic ordering, with the order parameter being a function of film composition and the growth parameters. A competition between ordering and phase separation has been observed, suggesting that the driving force for both phenomena is lattice strain in the alloy.
Low-Temperature Homoepitaxial Growth of Gan Using Hyperthermal Molecular Beams
Authors: Michel A. , Chen E. , Thomson D. , Nam O. , Davis R. F. , Lamb H. H.
Published: April 2011

In situ cleaning of MOCVD-grown GaN/AlN/6H-SiC substrates using NH3-seeded supersonic molecular beams was investigated. Removal of surface carbon and oxygen contaminants was achieved by heating at 730°C under a hyperthermal NH 3 beam. Oxygen is removed primarily by thermal desorption; however, carbon removal requires an NH3 flux. Atomically smooth surfaces with regular steps are obtained after NH3 beam cleaning. Homoepitaxial growth of smooth, highly textured GaN films was accomplished at 700°C by employing a 0.61-eV NH3 beam and an effusive Ga source.
GaN Etching in BCl3/Cl2 Plasmas
Authors: Shul R. J. , Ashby C. I. H. , Willison C. G. , Zhang L. , Han J. , Bridges M. M. , Pearton S. J. , Lee J. W. , Lester L. F.
Published: April 2011

GaN etching can be affected by a wide variety of parameters including plasma chemistry and plasma density. Chlorine-based plasmas have been the most widely used plasma chemistries to etch GaN due to the high volatility of the GaClx and NClx etch products. The source of Cl and the addition of secondary gases can dramatically influence the etch characteristics primarily due to their effect on the concentration of reactive Cl generated in the plasma. In addition, high-density plasma etch systems have yielded high quality etching of GaN due to plasma densities which are 2 to 4 orders of magnitude higher than reactive ion etch (RIE) plasma systems. The high plasma densities enhance the bond breaking efficiency of the GaN, the formation of volatile etch products, and the sputter desorption of the etch products from the surface. In this study, we report GaN etch results for a high-density inductively coupled plasma (ICP) as a function of BCl3:Cl2 flow ratio, dc-bias, chamber pressure, and ICP source power. GaN etch rates ranging from ∼100 Å/min to > 8000 Å/min were obtained with smooth etch morphology and anisotropic profiles.
The Role of the In Source IN InN Growth from Molecular Beams
Authors: Donovan S. M. , Gila B. , MacKenzie J. D. , Lee K. N. , Abernathy C. R. , Wilson R. G. , Muhr G. T.
Published: April 2011

InN has been grown in a gas-source MBE system using an RF nitrogen plasma source and standard TMI, solution TMI and solid In. Both solid and solution TMI produce InN with electron and carbon concentrations ≥ 1020 cm−3. Solution TMI-derived material, however, contains significantly less oxygen (8 × 1018 cm−3 vs. ≥ 1020 cm−3 for solid TMI). While the amine used to liquefy the TMI helps to displace the ether believed to be responsible for the oxygen contamination, it also appears to interfere with the growth, resulting in poorer morphology than for standard TMI. While solid In produced the lowest carrier concentration (≤ mid-1018 cm−3), it also produced the worst morphology of the sources examined, presumably due to poor surface mobility. Based on this data, it appears that carbon can play a significant role in the electrical properties of InN, and that the In source is critical in determining the structural quality.
Double Channel AlGaN/GaN Heterostructure Field Effect Transistor
Authors: Gaska R. , Shur M. S. , Yang J. W. , Fjeldly T. A.
Published: April 2011

We report on a Double Channel A1GaN/GaN Heterostructure Field Effect Transistor, where the bottom channel is formed by a GaN-AlGaN-GaN Semiconductor-Insulator-Semiconductor structure. The series resistance for the bottom channel is strongly dependent on the drain bias. This new design demonstrates that the current carrying capability of AlGaN/GaN HFETs can be enhanced using multi channel structures.
A New Method Of Measuring Hydrogen Diffusivity By Hydrogen Permeation Technique I: Theoretical Modeling
Authors: Zhang Tong-Yi , Zheng Yong-Ping
Published: April 2011

A new model on hydrogen permeation is proposed, considering absorption and desorption processes on the sample surfaces. Analytical solution, satisfying the flux continuity rather than the concentration boundary conditions, is derived from the model. Drift velocity through surface and drift velocity in bulk are introduced and their ratio determines the validity of the time-lag model. When the ratio of drift velocity through surface over that in bulk approaches infinity, the proposed model is reduced to the time-lag one. The diffusivity and the drift velocity through surface can be evaluated by fitting the entire normalized permeation curve. The obtained results can predict the effects of temperature, sample thickness and energy barriers of absorption and desorption on the permeation process. The thickness effect occurred in using the time-lag model is well explained by the effects of absorption and desorption on the permeation process.
Hydrogen Local Vibrational Modes in Compound Semiconductors
Authors: Mccluskey M. D.
Published: April 2011

Local vibrational mode (LVM) spectroscopy of hydrogen and deuterium in GaP, AlSb, ZnSe, and GaN has provided important information about the structures of dopanthydrogen complexes and their interaction with the host lattice. In GaN:Mg, for example, hydrogen binds to a host nitrogen which is adjacent to the magnesium acceptor. In GaP and ZnSe, it has been demonstrated that the temperature dependent shifts of LVM's are proportional to the lattice thermal energy, a consequence of the anharmonic coupling of the local mode to acoustical phonons.

Large hydrostatic pressures have been applied to semiconductors to probe the vibrational properties of hydrogen-related complexes. In GaAs, the pressure dependent shifts of the 12C-H and 13C-H stretch modes have positive curvatures, while the shift of the S-H stretch mode has a negative curvature. This may be related to the fact that in the bond-centered C-H complex, the hydrogen is compressed between the carbon acceptor and one gallium host atom, whereas in the S-H complex, the hydrogen occupies an interstitial position and is not crowded by neighboring atoms. If these trends are general, then hydrostatic pressure may be a powerful tool in determining the position of the hydrogen atom(s) in a complex.

In AISb. pressure was utilized to resolve a mystery as to why the Se-D complex gives rise to one stretch mode peak while the Se-H stretch mode splits into three peaks. This anomalous splitting is explained in terms of a new resonant interaction between the stretch mode and combination modes involving a wag mode harmonic and extended lattice phonons. The interaction gives rise to vibrational modes with both localized and extended components. When the temperature or hydrostatic pressure is varied, the modes exhibit anti-crossing behavior.
Hydrogen in GaN-Experiments
Authors: Pearton S. J. , LEE J. W. , Wilson R. G. , Zavada J. M. , Weinstein M. G. , Song C. Y. , Stavola M.
Published: April 2011

Hydrogen is an important component of the gas phase growth chemistry for GaN (eg. NH3, (CH 3)3 Ga)and the processing environment for subsequent device fabrication (eg. SiH4 for dielectric deposition, NH3 or H2 annealing ambients), and is found to readily permeate into heteroepitaxial material at temperatures ≤200°C. Its main effect has been the passivation of Mg acceptors in p-GaN through formation of neutral Mg-H complexes, which can be dissociated through minority-carrier (electron) injection or simple thermal annealing. Atomic hydrogen is also found to passivate a variety of other species in GaN, as detected by a change in the electrical or optical properties of the material. An example is the increase in luminescence efficiency of Er3+ ions in AIN after hydrogenation, through passivation of non-radiative states that would be an alternative path for de-excitation. The injection of hydrogen during a large variety of device fabrication steps has been detected by SIMS profiling using 2H isotopic labeling. Basically all of the acceptor species in GaN, namely Mg, C, Ca and Cd are found to form complexes with hydrogen.
Surface Passivation Of Metal Hydrides For Applications
Authors: Suda S. , Li Z. -P. , Sun Y.-M. , Liu B.-H. , Gao X.-P.
Published: April 2011

Properties and characteristics of hydriding alloys are strongly dependent on surface compositions and morphologies. For instance, oxides such as La203 on AB5 alloys and ZrO2 on AB2, AB, and body-centered-cubic (BCC) alloys act as the barriers for the conversion of molecular and ionic hydrogen to atomic hydrogen at the surface, thus reducing the kinetics in both the gas-solid and electrochemical reactions.

Alloy surfaces chemically treated by an aqueous F-ion containing solution have been developed to solve such problems. F-treated surfaces exhibit significantly improved characteristics in regard to the hydrogen uptakes and the protection against impurities and electrolyte solution. In addition, highly conductive metallic Ni layers can be formed on the surface of the alloy particles by the fluorination.

The authors report the properties and characteristics of fluorinated hydriding alloys, mainly of a typical AB2 Laves phase material which represents the difficult activation characteristics and poor long-term durability during electrochemical charge/discharge cycles.
Hydrogen induced plastic deformation of stainless steel
Authors: Gadgil V. J. , Keima E. G. , Geijselaers H. J. M.
Published: April 2011

Hydrogen can influence the behaviour of materials significantly. The effects of hydrogen are specially pronounced in high fugacities of hydrogen which can occur at the surface of steels in contact with certain aqueous environments. In this investigation the effect of high fugacity hydrogen on the surface of stainless steel was investigated using electrochemical cathodic charging. Microhardness was measured on the cross section. Transmission electron microscopy was used to investigate the dislocation substructure just below the surface. Computer simulation using finite element method was carried out to estimate the extent and severity of the deformation. The significance of the results are discussed in relation to the loss of ductility due to hydrogen.
Gas Atomization Processing of LaNi5-x.Mm, Modified with Silicon and Tin
Authors: Ting J. , Pecharsky V. K. , Anderson I. E. , Witham C. , Bowman R. C. , Fultz B.
Published: April 2011

A high pressure gas atomization (HPGA) process has been employed to study microsegregation in LaNi4.75 Sn0.25 and LaNi4.6Si0.4 alloy powders to serve as a basis for further investigations of low cost production of multicomponent alloys in combination with mishmetal (Mm). This investigation is an attempt to produce high quality powders for battery cathode fabrication that can be used in an as-atomized condition without prolong annealing, hydridingdehydriding, and grinding. Argon atomizing gas was used in the HPGA process of the LaNi4.75Sn0.25 and LaNi4.6Si0.4 alloys to investigate rapid solidification effects on microsegregation. Short annealing treatments of 5 minutes at 900°C were able to homogenize both alloy compositions, eliminating solidification micro-segregation along the grain boundaries phases. The rapid homogenization can be attributed primarily to the refined cell structures in gas-atomized particles that provide short diffusion pathways for the dissolving elements.
Hydrogen/Deuterium Interaction With CMOS Transistor Device Structure: Sintering Process Studied by Sims
Authors: Chen P. J. , Wallace R. M.
Published: April 2011

Passivation of the SiO2-Si interface by hydrogen/deuterium in MOS transistors serve to ensure their operating reliability against channel hot carriers. Physical characterization of device sintering process in deuterated forming gas (10%D2:90%N2) is carried out by dynamic SIMS on planar CMOS gate stack structures, in conjunction with device hot carrier electrical testing. It is found that incorporation of deuterium in the doped poly-Si/SiO2/Si interfacial region readily occurs under typical post-metallization sintering conditions, demonstrating that transport of deuterium through CMOS gate is an effective pathway in an encapsulated device structure with silicon nitride sidewalls. The measured Si-D areal densities in the interfacial region depend on gate poly-Si doping type, but in both cases, appear to be sufficient to achieve complete interface Si dangling bond (˜1012 cm−2) passivation for the SiO2-Si system.
Interaction of Deuterium with the Simox Oxide
Authors: Zimmerman L. , Riveral A. , De Nijs J. M. M. , Van Veen A.
Published: April 2011

The interaction of deuterium with silicon-implanted-with-oxygen (SIMOX) was studied for samples with and without silicon top layer using thermal desorption measurements. Deuterium is incorporated in the buried oxide by disruption of the Si-O bridging bonds. The data reveal that the top layer reduces the uptake at 1073K. Furthermore, it retards release; a moderate (≈125K) and a high-temperature (≈1400K) retention were observed. It is proposed that release is accompanied by the reconstruction of the Si-O bonds and that the bare oxide surface constitutes an abundant source for defects thus enhancing the generation and elimination of Si-O bridging bond defects.
Hydrogen Passivation and Ozone Oxidation of Silicon Surface
Authors: Kurokawa Akira , Nakamura Ken , Ichimura Shingo
Published: April 2011

The oxidation of H/Si(100) and H/Si(111) with high concentration ozone gas was investigated with X-ray photoelectron spectroscopy(XPS). The ozone oxidation of partially hydride-covered surface was observed. The hydrogen termination reduced the rate of oxygen insertion into silicon backbond. The reduction of oxygen insertion rate by the H-termination for H/Si(100) was larger than that for HSi(111). The dissociation rate of ozone molecule on H/Si was estimated to be ≃0.2 with a directional mass analyzer.
Infrared Spectroscopy of Sub-Surface Defects induced by Remote Hydrogen Plasma exposure of Silicon(100)
Authors: Lamb H. H. , Bedge S. G. , Wan Z.
Published: April 2011

Infrared multiple internal reflection (MIR) spectroscopy was used to investigate the local chemical bonding in sub-surface defects induced by remote hydrogen plasma exposure (RHPE) of Si(100) wafers. Exposure of very lightly doped n-type Si ([P] =; 5 × 1013 cm−3) to a remote hydrogen plasma for 2 min at 200°C results in the formation of Si monohydride species. An intense narrow band at 2078 cm−1 (FWHM = 7 cm−1) and a small shoulder at 2065 cm−1 are observed. The data are consistent with monohydride termination of Si{111} platelet defects with a weak interaction between H atoms on opposing internal surfaces. In contrast, platelet nucleation at 200°C followed by growth at 300°C selectively generates Si dihydride species, as evidenced by a single broad infrared band at 2109 cm−1. The P concentration was found to have a marked influence on the areal density and chemical bonding of sub-surface hydrogen. The MIR spectrum of lightly doped Si ([P] = 2 × 1014 cm−3) after RHPE at 200°C contains broad peaks at 2078 and 2130 cm−1 consistent with Si monohydride and trihydride species. We infer that hydrogen saturates broken bonds along Si{111} Type I glide planes (one bond per Si atom) and along Si{111} Type II glide planes (three bonds per Si atom). The Si-H peak area indicates a H areal density ∼2 times higher than in very lightly doped Si.
Theory of Hydrogen in Semiconductors
Authors: van de walle Chris G.
Published: April 2011

This paper treats the subject of hydrogen in semiconductors from various perspectives. First, a brief historical overview is given. Then, some basic principles governing the interaction between hydrogen and semiconductors are outlined. Finally, specific examples will emphasize the impact of hydrogen on technological applications. While the general treatment applies to interactions of hydrogen with any semiconductor, the applications will focus mainly on hydrogen interacting with silicon.
Effect of Helium on the Electronic Structure of Palladium Tritide
Authors: Gupta R. P. , Gupta M.
Published: April 2011

Tritium is usually stored in the form of a metal tritide since it is safe to handle in this form, easily recoverable, and further large quantities of tritium can be stored. However, since tritium is radioactive it decays into 3He and an electron. Helium recoil energy in this reaction is very small, and not enough to create defects. We have performed ab-initio electronic structure calculations that show that in PdT, a considerable amount of 3He can be accommodated at the 3He results in an overall enhancement in the strength of the metal- tritium bonding that leads to the lowering of the plateau pressure. We also find that there is a weakening of the metal-metal bonds due to the repulsive interaction with 3He.
Hydrogen Solubility in Inhomogeneous PD Alloys
Authors: Flanagan Ted B. , Wang D. , Clewley J. D.
Published: April 2011

As-cast, arc-melted Pd-Ni alloys are inhomogeneous and the H2 isotherms for these differ from their homogeneous counterparts in the two phase, (dilute + hydride), regions but not in the dilute phase regions. Pd-Ni alloys, which become inhomogeneous via a ternary (Pd + Ni + H) equilibrium phase change, have H2 isotherms which differ from those of the homogeneous alloy in both the two-phase and the dilute phase regions. These results are discussed with respect to the expected type of inhomogeneities.
Microstructure and Lifetime Study of Al/Y Films
Authors: Vedula L. , Pillai V. , Nimmagadda V. S. , Singh R. , Poole K. F. , Gao H. , Pennycook S. J.
Published: April 2011

Thin Al films alloyed with three different compositions (0.1%, 1%, 5% by weight) of Yttrium were deposited by D.C. Magnetron Sputtering onto oxidized Si wafer substrates. The samples were furnace annealed at 425 °C for 30 minutes. Resistivity measured for the as-deposited and annealed Al(0. lwt% Y) were 3.07 and 2.57+/−0.25 μΩcm respectively. Al(0. lwt% Y) was also annealed by furnace annealing (FA), rapid thermal annealing (RTA) and rapid photothermal annealing (RPA). RPA gave a residual resistivity of 2.67μΩcm in 5 minutes and at a temperature of 350 C for Al(0. lwt% Y). Mean time to failure for AI(0. lwt% Y) samples at a current density of 3.2+/−0.5×106A/cm2 at 30 C was 50 hours. TEM results showed grain size variation from 0.5 to 2 μm.
A Novel Low Temperature Self-Aligned Ti Silicide Technology for Sub-0.18 μm CMOS Devices
Authors: Ren L. P. , Liu P. , Pan G. Z. , Woo Jason C. S.
Published: April 2011

A novel low temperature self-aligned Ti silicidation with Ge+ pre-amorphization implant (PAI) is presented. Compared to conventional high temperature PAI silicidation, the advantages of Ti salicidation at temperatures below the recrystallization of a pre-amorphized layer are: (1) C49 TiSi2 silicide formation occurs only in the pre-amorphized layer so that the silicide depth can be well controlled, forming a very sharp interface between the silicide and the Si substrate; (2) Ti just reacts with the amorphous layer, avoiding the so-called bridging issue in which the silicide grows laterally over the isolation or spacer; (3) the effects of metal thickness and substrate doping on silicide formation are suppressed.
Copper Electroplating for Damascene ULSI Interconnects
Authors: Dubin V. M. , Lopatin S. , Chen S. , Cheung R. , Ryu C. , Wong S. S.
Published: April 2011

Copper was electroplated on sputtered Cu seed layer with Ta diffusion barrier. We achieved enhanced Cu deposition at the bottom of trenches/vias and defect-free filling sub-0.5 μm trenches (down to 0.25 μm width) of high aspect ratio (up to 4:1). Large grains occupying the entire trench were observed. Bottom step coverage of electroplated copper in sub-0.5 μm trenches was estimated to be about 140%, while sidewalls step coverage was about 120%. Via resistance for sub-0.5 μm vias was measured to be below 0.55 Ω. Strong <111> texture, large grains, and low tensile stress were observed in electroplated Cu films and in-laid Cu lines after low temperature anneal.
Extendibility of Cu Damascene to 0.1 μm Wide Interconnections
Authors: Hu C-K. , Lee K. Y. , Gignac L. , Rossnagel S. M. , Uzoh C. , Chan K. , Roper P. , Harper J. M. E.
Published: April 2011

We demonstrate the extendibility of the Cu damascene process to 0.1 μm wide lines. Cu interconnects, 0.1 - 1 μm wide, were fabricated by a damascene process that produced planarized lines and vias, imbedded in insulators. This process was defined by 1) trench and via formation in blanket dielectrics using e-beam lithography and reactive ion etching, 2) trench fill using a series of metal depositions, and 3) chemical mechanical polishing to remove the field metals. Physical vapor and ionized physical vapor deposition techniques were used to deposit the adhesion/diffusion barrier liner and the Cu seed layer, respectively. The main Cu conductor was deposited by an electroplating method. The width of lines and vias were varied from 0.1 μm to 1 μm while the thicknesses were held constant at 0.45 μm. A near bamboo-like structure was observed in the sub-μm wide lines. The effective resistivity of the Cu lines was found to be about 2.3 μΩ-cm and was independent of width after annealing at 400 °C.
Microstructure and Texture of Electroplated Copper in Damascene Structures
Authors: Gross M. E. , Lingk C. , Siegrist T. , Coleman E. , Brown W. L. , Ueno K. , Tsuchiya Y. , Itoh N. , Ritzdorf T. , Turner J. , Gibbons K. , Klawuhn E. , Biberger M. , Lai W. Y. C. , Miner J. F. , Wu G. , Zhang F.
Published: April 2011

The transition from Al to Cu for advanced ULSI interconnects involves changes in architecture and deposition technique that will influence the microstructure and texture of the metal. Cu interconnects are typically formed within the confines of pre-patterned trenches and vias using an electroplating process with a sputtered Cu conduction layer deposited over a refractory metalbased diffusion barrier layer. In this paper, we focus on the influence of the barrier layer (PVD Ti/TiN, Ta, TaN, CVD TiN) and the effect of a vacuum break between barrier and conduction layer depositions, on the texture of the Cu lines, as examined by X-ray diffraction pole figure analysis.

A preferred (111) orientation was observed for all samples. The samples with no vacuum break between barrier and conduction layer deposition exhibited in plane anisotropy that was particularly pronounced for the Ta and TaN samples compared with the Ti/TiN sample. Focused ion beam images and transmission electron micrographs showed Cu grain size to be on the order of the trench width with a high degree of twinning, and no boundary could be distinguished between the PVD Cu conduction layer and the electroplated Cu.
Mocvd of Copper from the Solution of New and Liquid Precursor (hfac)Cu(1-pentene)
Authors: Shin H.-K. , Cho Y.-H. , Yoo D.-J. , Shin H.-J. , Lee E.-S.
Published: April 2011

In an attempt to increase the deposition rate, new Cu (I) compounds, (hfac)Cu(1-pentene)(1) and (hfac)Cu(VTMOS)(2) have been synthesized. These species are chartreuse liquids and exhibit sufficient vapor pressures to allow high transport rates.

In order to avoid the premature decomposition of the copper precursors during CVD processes, the 50% of free 1-pentene, and VTMOS was added to the compounds 1 and 2 respectively. These mixtures 1 and 2 were used in this study. Approximately 2gm of precursor was used for each experiment. No premature decomposition of the precursor in the source reservoir was observed during CVD processes. It is a sufficiently important result to expect the use of these mixtures in copper CVD to achieve the reproducible deposition.

The copper films using these mixtures were deposited in a hot-wall pyrex reactor at a pressure of approximately 10–2 torr under dynamic vacuum. The films deposited at 100°C, 150°C and 200°C from the mixture 1. Pure copper films were deposited from these species. The resistivities 1.8 ∼ 2.1 μΩcm were obtained in the deposition temperature range. SEM revealed that the surface morphology of the films grown in these depositon temperature range was composed of dense film and grains were well connected. The deposition rate at 200°C was 3,500 Å/min.
Sensitive Analysis of Deposition Chemistry of Cu From (Hfac)Cu(Tmvs) Using Well Characterized Test Structure
Authors: Chae Y. K. , Shimogaki Y. , Komiyama H.
Published: April 2011

The chemistry of Cu-CVD from the precursor (hfac)Cu(tmvs) on sputtered TiN films was investigated using a simple tubular reactor analysis. In the present study, the validity of a proposed reaction mechanism and its rate constants were investigated using a well characterized test structure (Macrocavity). The macrocavity was prepared by stacking silicon wafers with spacing ranging from 0.1–0.5mm, and placing the stacked structure in the tubular reactor. The growth rate profile within a macrocavity is simulated from a derived equation using the reaction mechanism and rate constants obtained from previous work. The variation of the absolute growth rate around the center of a macrocavity with varying wafer spacing indicates that the Cu deposition is proceeded via gas phase reaction to produce a reaction intermediate. As a whole, the simulated growth rate profiles agree very well the experimental data. Therefore, we conclude that the mechanism and reaction rate constants from our research are valid and can be applied to the prediction of growth rate of Cu from the (hfac)Cu(tmvs) system.
Pre-Treatment Effect on Aluminum Thin Films Deposition from Cvd Using Dimethylethylamine Alane
Authors: Jang Tae Woong , Rhee Hwa Sung , Ahn Byung Tae
Published: April 2011

To study the effect of pre-treatment of substrates on the deposition behavior of Al films, the surfaces of TiN and SiO2 substrates were exposed to hydrogen plasma or Ar plasma before Al deposition. The Al films were deposited by the pyrolysis of dimethylethylamine alane (DMEAA). A uniform Al film was deposited by the hydrogen plasma exposure of SiO2 substrate, while island grains were grown by the Ar plasma exposure. The pre-treatments of TiN substrate did not affect the deposition rate of Al film. The concentration of OH radicals at the SiO2 surface was increased by the hydrogen plasma treatment. We suggest that the OH radicals enhance the adsorption of DMEAA on SiO2 surface, resulting in the larger number of nucleation sites.
Ion Beam Induced Metallorganic Chemical Vapor Deposition of Titanium Nitride Films as a Diffusion Barrier Between Cu and Si
Authors: Park Ki-Chul , Kim Soo-Hyun , Kim Ki-Bum
Published: April 2011

We have deposited TiN films by using ion-beam-induced chemical-vapor-deposition (IBICVD). Tetrakis-dimethyl-amido-titanium (TDMAT) was used as a precursor. N2 and Ar gas were used to generate the plasma and the ions in the plasma were extracted by using two electrically isolated grids. The energy of ion beam was about 115–127 eV. The use of N-ion beam significantly lowers the resistivity and carbon content of TiN film (∼320 μΩ-cm, 15 at.%), compared with the thermally decomposed film (∼6000 μΩ-cm, 36 at.%). The use of Ar ion beam also considerably lowers the resistivity of films (∼800 μΩ-cm), but does not reduce the carbon content. The step coverage of the thermally-decomposed film was about 70 %, while the step coverages of the films deposited using N2 and Ar ion beams were about 0 and 30 %, respectively, in 0.5 μm x 1.5 μm contacts. The etch-pit test showed that 50-nm-thick films deposited by using N2 and Ar ion beams prevent the diffusion of Cu into the Si substrate up to annealings at 550 °C and 600 °C for 1 hour, while the thermally decomposed film fails at 500 °C.
Oxide Mediated Epitaxy on Planar and Non-Planar Si
Authors: Tung R. T. , Howard D. J. , Ohmi S. , Caymax M. , Maex K.
Published: April 2011

The recently developed oxide mediated epitaxy (OME) technique involves the growth of epitaxial CoSi2 through a thin layer of silicon oxide grown in peroxide baths. Here we report improvements of the OME technique from the use of in-situ grown thermal oxide as the barrier layer and post-growth oxygen anneals. Growth of uniform epitaxial CoSi2 layers by OME on non-planar surfaces of selectively deposited CVD Si layers with oxide and nitride patterns was also demonstrated. Both the epitaxial orientation of CoSi2 and the thickness of the CoSi2 layer, measured along the deposition direction, remained unchanged across facet boundaries. OME appears well suited for shallow-junction silicidation application in devices involving raised source/drain structures.
Is Selective Cvd an Improvement for the Titanium Silicide Process in Sub-Quarter Micron Technology? A Phase Formation Study Using X-Ray Diffraction
Authors: Roy Ronnen , Cabral Cryil , Lavoie Christian , Jordan-Sweet Jean , Viswanathan R. , Ozturk Mehmet , Fang Hua , Swenberg Johanes , Achutharaman Raman
Published: April 2011

The C54 phase formation process of titanium silicide was studied after selective chemical vapor despostion (CVD) onto very small silicon structures, to ascertain the efficacy of CVD to form low resistance contacts in sub-quarter micron technology. Because the selective CVD process forms silicide on any exposed silicon in a CMOS device, the process was studied on both polysilicon and Si (100) chips. The structures consisted of arrays of about 106 identical lines, 0.1 2.0 μm in width, depending on the chip. The CVD process employed TiCl4 and SiH4 for the most part as process gases and the depostion temperature ranged from 730–825°C. X-ray diffraction (XRD) was used to document the amount of C54 phase present after deposition. In some cases samples were annealed after deposition and the phase transformation behavior studied by in-situ XRD. The latter technique employed a synchrotron radiation source providng for rapid XRD spectra collection, so that the C49-C54 phase transformation could be examined with great precision in real time during rapid thermal annealing. The results of CVD depositions were compared to titanium silicide formed by sputter deposition of Ti on identical silicon chips, followed by a typical salicide protocol. Although the phase formation is affected by both film thickness and substrate temperature during CVD, the general result is that the C54 formation is more facile using the CVD process, especially for the smallest line dimensions. The findings are discussed with respect to nucleation processes occurring during growth and post-deposition thermal processing.
Metal Contact On Nitride Based Materials
Authors: Ren E. , Abernathy C. R. , Shurman M. , Hong M. , Pearton S. J. , Lothian J. R.
Published: April 2011

Owing to their large band gaps and high dielectric constants, III-V nitrides are very attractive for high temperature electronics and optoelectronic device applications. Improved material properties have recently led to a variety of devices being demonstrated such as blue, green, and yellow light-emitting devices as well as laser diodes, metal-semiconductor GaN based fieldeffect transistors (MESFETs), and AlGaN/GaN based high electron mobility transistors (HEMTs). The presence of parasitic resistance can significantly limit performance such as lower speed for electronic devices and higher turn-on voltage for the optical devices. There is room for improvements for both n- and p- type ohmic contacts in order to lower parasitic resistance and improve reliability. W based contacts on GaN and InGaN have been demonstrated and show excellent thermal stability, however the contact resistivity still in the range of 10−5 Ω-cm2. By using InN and graded InGaN as the contact layers, the contact resistivity can be reduced to ∼ 10−6 Ω -cm2.

Besides low resistance ohmic contacts, a low leakage current and high turn-on voltage gate contact is critical to high performance electronic devices. Nitride based materials are very inert to conventional wet chemical etching used for other III-V compound semiconductors. Currently, dry etching is widely used for the device fabrication, however, III-nitrides are sensitive to dry etching, especially in the step of the gate recess etching. In this talk, metal insulator semiconductor (MIS) gate contacts based on AIN and Ga2O3/Gd2O3 will be discussed.
In-Situ Regrowthi of GaAs Through Controlled Phase Transformations and Reactions of Thin Films on GaAs
Authors: Caldwell D. A. , Chen L.-C. , Bensaoula A. H. , Farrer J. K. , Carter C. B. , Palmstrøm C. J.
Published: April 2011

In-situ depositions and reactions are utilized in the study of phase formation from solid phase reactions. We report on the formation of epitaxial GaAs and the formation of NiAs or Ni2Ga3 by the exposure of Ni3GaAs to As4 or Ga fluxes. In-situ annealing of Ni on MBE-grown GaAs leads to Ni3GaAs, and subsequent reaction with As4 or Ga drives regrowth of GaAs. The structures were analyzed by RBS, XRD, TEM, and in-situ electrical measurements.
Carbon Nanotubes: Molecular Electronic Devices and Interconnects
Authors: Srivastava Deepak , Menon Madhu
Published: April 2011

The carbon nanotubes and carbon nanobtube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. Single wall carbon nanotubes, as molecular wires, could be used as nanoscale interconnects, where as complex junctions of nanotubes of different chirality can be used as rectifying and transiting devices. It has been shown that pentagon-heptagon defect is responsible for the creation of simple hetero-junctions. Complex junctions, such as 3-termianl T-junctions and Y-junctions require entirely different arrangement of defects. These 3-terminal junctions form prototypes of nanoscale tunnel devices made entirely of carbon. Furthermore, either n-type or p-type doping of the semiconducting portion of these complex junctions should yield Schottky barrier type devices. We also investigate simple wires and junctions of boron and nitrogen (III-V elements) and compare with those of carbon. The structural and electronic properties on nanotubes and nanotube junctions (carbon as well as BN) are studied using a generalized tight-binding molecular dynamics (GTBMD) scheme.
Self-Aligned Gate Metallization Processes with Low-Thermal Budget
Authors: Lin X. W. , Weling M.
Published: April 2011

A novel concept for CMOS transistor gate metallization is described. It is featured with Gate Cloisonné, a process consisting of dielectric deposition over frontend transistors, followed by chemical mechanical polishing to re-expose the gate pattern on a planar dielectric background. Based on this concept, two metallization schemes have been developed. One is self-aligned metal gate process, which allows for low thermal budget gate metallization with element metals such as W and Al, resulting in a very low sheet resistance (< 1 Ω/sq). The other scheme is dual self-aligned silicidation, which enables decoupling of gate silicidation from that of source/drain silicon areas. Titanium based silicidation process is implemented to form thick silicide on narrow polysilicon gates and thin one over active silicon areas. Low gate sheet resistance (≈ 1.9Ω/sq) is achieved with complete suppression of linewidth effects. Both the metallization schemes are a priori scaleable to deep submicron technologies and suitable to fabricating ultra-shallow junction devices with very low gate sheet resistance. Both of them have been implemented in a 0.25-μm CMOS technology.
Development of a Titanium Nitride Thin Film Standard
Authors: Steel Eric , Deslattes Richard , Pedulla Joseph , Lamaze George , Greenberg Robert , Armstrong John
Published: April 2011

Titanium nitride films are used in a variety of applications in the semiconductor industry, but the stoichiometry and homogeneity of the films can be difficult to control and characterize. The National Institute of Standards and Technology (NIST) is developing a TiN thin film on silicon to be used as a physical and chemical standard for the semiconductor industry. A prototype 100 nm thick film has been manufactured by dual ion beam deposition. NIST is characterizing the film by x-ray interferometry for thickness and density, neutron depth profiling for nitrogen content and homogeneity as a function of depth, neutron activation analysis for titanium content, and x-ray fluorescence spectromety, electron probe microanalysis, grazing incidence x-ray photoelectron spectroscopy, and transmission electron microscopy for homogeneity and composition. The intent of this research is to create a TiN film of known thickness, density, stoichiometry, and homogeneity that can be used by the semiconductor industry as a primary, traceable standard for characterization of industry thin films. The intent of the standard is to promote more accurate characterization and improved TiN manufacturing capabilities as well as to aid manufactures in more easily employing ISO 9000 related traceability and quality assurance practices.
Novel Diffusion Barrier with Ultra-Thin Silicon Nitride Cap Layer
Authors: Lu J. P. , Hsu W. Y. , Hong Q. Z. , Dixit G. A. , Cordasco V. T. , Zielinski E. M. , Luttmer J. D. , Havemann R. H. , Magel L. K. , Tsai H. L.
Published: April 2011

A novel type of diffusion barrier, consisting of a conducting layer whose surface is enriched with silicon nitride, was developed. The new barrier was prepared by thermal decomposition of a metal-organic precursor, tetrakis(dimethylamino) titanium (TDMAT), followed by in-situ silane anneal and subsequent surface nitridation. It combines the conformality and conductivity advantages of the underlying diffusion barrier with the good barrier properties of silicon nitride. The new barrier films were characterized by sheet resistance measurement, secondary electron micrographs (SEM) and x-ray photoelectron spectroscopy (XPS). The thermal stability of Cu/capped barrier/Si multilayer structures was demonstrated.
Ultra-Thin TaN Films As Diffusion Barriers For Cu Metallization
Authors: Huang Sharon S. , Tu K. N. , Sun Bingxi
Published: April 2011

The Cu metallization in future VLSI technology requires a liner or diffusion barrier. We have studied TaN thin Films of thickness from 5 nm to 3 nm as the diffusion barrier. We deposited sandwiched TaN/Cu/TaN thin films on oxidized Si wafers, annealed them in air with ramping temperature, and measured in-situ resistance changes. Scanning and transmission electron microscopes were used to characterize the surface and microstructure of the thin films and Rutherford backscattering spectrometer (RBS) was used to profile the elemental composition and after oxidation. The oxidation of the Cu sandwiched between TaN films of 5, 10, 20, and 30 nm occurs at 300, 400, 450 and 475°C, respectively. The activation energy of oxidation of Cu with the TaN barrier of 10, 20, and 30 nm are 1.73, 2.13, and 2.26 eV, respectively, but the 5 nm TaN was not calculated due to large data scattering. For comparison, the oxidation temperature and activation energy for bare Cu films in air are 250°C and 0.74 eV, respectively. It suggests that 20 nm of TaN is quite effective as a barrier layer. However, the reaction between Cu and the underlying SiO2/Si layers was also detected in RBS; this may arise as another serious reliability criterion to the system.