bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Beam Treatment of Ohmic Contacts to n-TYPE Hg1-xCdxTe
Authors: Leech Patrick W. , Reeves Geoffrey K. , Li Yuan H. 
Published: March 2011

ABSTRACTThe application of ion beam mixing and ion implantation techniques in the formation of ohmic contacts to n-Hg1-xCdxTe (x = 0.6, 0.7) has been investigated. For experiments in ion beam mixing, an indium layer (15nm thick) on Hg1-xCdxTe wasbombarded with 45keV Te+ ions at doses ranging from 1 × 1013 to 1 × 1016 cm2. Minimum values of specific contact resistance, pc, of 4 × 10-4Ωcm-2 were measured for a dose of 1 × 1016 cm-2 after 200°C annealing; pc was independent of dose in this range. Analysis of the interfaces by Auger depth profile and Rutherford backscattering spectrometry has shown that ion beam mixing produced an enhanced indiffusion of indium. In comparison, samples which were ion implanted with In+ at 50keV prior to metalisation showed a reduction in pc which was strongly dependent on dosage.
A Photoemission Investigation of the Interfacial Electronic Properties of Mo and Ni Schottky Barriers to CuInSe2(112)
Authors: Niles David W. , Nelson Art J. , Richard Schwerdtfeger C. , Höchst Hartmut , Rioux Dennis 
Published: March 2011

ABSTRACTWe studied Mo and Ni contacts to p-type CuInSe2(112) with angular-resolved synchrotron radiation ultraviolet photoemission spectroscopy in the range 40 eV hv < 120 eV. By varying the photon energy, we determined that emission from the CuInSe2 Г-point in the Brillouin zone occurs for hv = 60 eV, and identified emission from the valence band maximum. After depositing Ni and Mo, we found that the conduction band minimum of the CuInSe2 very nearly aligned to the Fermi edges of both metals, giving Schottky barriers Vsb = 1.05 ±0.1 eV. The interfaces are not atomically abrupt, as seen by the outdiffusion of Se into the refractory metal overlayers and the formation of In-Mo and In-Ni alloys.
Barrier Inhomogeneities Dominating Low-Frequency Excess Noise of Schottky Contacts
Authors: Rau Uwe , Güttler Herbert H. , Werner Jürgen H. 
Published: March 2011

ABSTRACTWe introduce a new quantitative description for electronic noise at Schottky contacts. The model combines spatially inhomogeneous current transport across the interface with the modulation of the local barrier height due to trapping dynamics of charged states located at or close to the interface. The experimentally observed increase of noise power with decreasing temperature is explained by the inhomogeneity of the interface. Our model fits experimental data obtained from different silicide/silicon Schottky contacts and the detailed analysis of measured noise spectra yields information about the interfacial potential fluctuations.
Au-GaAs Reaction Kinetics: Its Role in Fabrication of Ohmic Contacts
Authors: Barcz Adam J. 
Published: March 2011

ABSTRACTAnnealing of Au/GaAs leads to vaporization of As species and migration of Ga atoms into Au. These processes are simultaneous only on a macro-scale. A simple kinetic model is developed in which they are treated sequential by introducing specific fluxes F(Ga) and F(As). F(Ga) is calculated assuming linear flow at the phase boundary. F(As) is set constant for a given external pressure of arsenic. The model accurately describes the observed reaction rate in both capped and open configuration. It is shown that instantaneous composition of GaAs surface adjacent to the metal evolves from initially As-rich to Ga-rich when Au becomes saturated with Ga. The model is consistent with common observation that short-time heating of Au(dopant)/GaAs activates dopant species preferentially on Ga vacant sites. To activate dopants in As sublattice longer times and/or higher temperatures are needed.
Estimating Local Deposition Conditions and Kinetic Parameters Using Film Profiles
Authors: Cale T. S. , Chaara M. B. , Hasper A. 
Published: March 2011

ABSTRACTEVREST, a program which uses film profile data in features obtained from low pressure chemical vapor deposition (LPCVD) processes to estimate the local partial pressures, temperature, and kinetic parameters is demonstrated for blanket tungsten deposition by the hydrogen reduction of tungsten hexafluoride. EVREST uses EVOLVE, a physically based process simulator for ballistic transport and heterogeneous reactions in features on patterned wafers, to compute film profiles for a given set of deposition conditions and kinetic parameters. Calculated film profiles are compared with the experimental film profile and the free parameters are adjusted to minimize the sum of squared differences between points on the calculated and experimental profiles. EVREST uses Marquardt's method to determine the set of deposition parameters which provide the best calculated profile. Simulated and experimental profiles are in very good agreement.
Formation of Nickel Silicides on Ion-Amorphized Silicon
Authors: Mohadjeri B. , Linnros J. , Svensson B. G. , ÖStling M. , Johanssons S. , D'Heurle F. M. 
Published: March 2011

ABSTRACTThe formation of NiSi and NiSi2 upon annealing of an ion-amorphized Ni/Si structure has been studied by various surface analytical techniques to characterize the morphology, stoichiometry and interface sharpness of the NiSi2 layer. In comparison with reactions of nickel on crystalline silicon (c-Si), sharpening 0ofthe NiSi2/C-Si interface is obtained for appropriate amorphization depths. Moreover, the surface roughness of the NiSi2 films is significantly reduced by implantation. The NiSi2 formation temperature is, however, not reduced as observed for structures with nickel deposited on amorphous silicon prepared by evaporation. This dissimilarity can be explained by an unexpected low crystallization temperature or the ion-amorphized structure, where Ni-ennanced solid phase epitaxy occurs at a temperature as low as 425°C.
Recent Progress of Alloyed Ohmic Contacts to GaAs Compound Semiconductors
Authors: Murakami Masanori , Otsuki A. , Tanahashi K. , Tarata H. J. , Callegari A. , Lustig N. 
Published: March 2011

ABSTRACTLow resistance, alloyed AuGeNi Ohmic contacts have been extensively used in the current manufacturing GaAs devices. However, extension of usage of these devices to Very Large Scale Integration levels requires the contacts with excellent thermal stability, shallow diffusion depth, and smooth contact surface in addition to low contact resistance. In the present paper recent studies for development of “non-gold” Ohmic contacts which improve the poor contact properties of the alloyed Ohmic contacts are rev i ewed.
Low Au Content Ohmic Contacts to n-GaAs Incorporating Sputtered Tungsten Oxide
Authors: Lustig Naftali , Schad R. G. , Fleischman A. 
Published: March 2011

ABSTRACTElectron-beam (e-beam) evaporated low Au content NiGe(Au)W ohmic contacts with a contact resistance (Rc) as low as 0.15 Ω-mra have been reported. Due to the high melting point of W it is desirable to deposit this layer by means other than e-beam evaporation. However, the use of nearly oxygen-free sputtered W, yields contact resistances in excess of 0.7 Ω-mm. By replacing the sputtered W by a reactively sputtered metallic W oxide, containing ∼25 at. % oxygen, the low contact resistance (Rc < 0.15 Ω-mm) is restored. Contacts employing a reactively sputtered W nitride in place of W oxide also yield high Rc's (∼0.75 Ω-mm). Auger depth profiles of the reacted contacts show a significant outdiffusion of Ga from the GaAs substrate in the presence the oxygenated W but not in the low oxygen and the W nitride contacts. These results and the fact that our previously reported e-beam evaporated W contacts also contain ∼25 at. % oxygen, suggest an oxygen assisted ohmic contact formation mechanism.
Ti/Pt Based Contacts to Heterojunction Bipolar Transistors
Authors: Kalkur T. S. , Wright P. D. , Ko S. K. , Lu Y. C. , Casas L. , Jones K. A. 
Published: March 2011

ABSTRACTTi/Pt metallization was used to form contacts on both n+-InAs emitter cap and p+ base layers of heterojunction bipolar transistors (HBTs). The as-deposited contacts were found to be ohmic for both the base and emitter cap layers. Rapid thermal processing of the contact metallizations was performed in the temperature range of 3 00–500 C for 30 seconds. Minimum contact resistivities of l×10-6 ohm-cm2 for the base and 3×l0-7 ohm-cm2 for the emitter layer were achieved. The influence of heat treatment on contact morphology was also examined.
Thermal Stability of Reactively Sputtered TiN on InP as a Diffusion Barrier
Authors: Pang Zhengda , Boumerzoug Mohamed , Kruzelecky Roman V. , Mascher Peter , Simmons John G. 
Published: March 2011

ABSTRACTThe stability of rcactively sputtered TiN films on InP for application as a diffusion barrier has been examined using electrical measurements, Auger profiling and scanning electron microscopy (SEM). The samples were subjected to rapid-thermal-annealing (RTA) in a N2 atmosphere at temperatures between 400°C and 900°C. The SEM pictures of “as deposited” and RTA stoichiometric films show that the morphology is smooth, fine-grained and stable until 800°C. Auger depth profiling shows little interdiffusion between TiN and InP for RTA below 800°C. Annealing at temperatures of about 700°C reduces the sheet resistance of TiN relative to the “as-deposited” films by about 50%. Annealing at temperatures above 800°C results in a large sheet resistance. This may be associated with the deterioration of the TiN/InP morphology at high anneal temperatures as observed by SEM.
Hillock Formation in Platinum Films
Authors: Hren Philip D. , Al-Shareef H. , Rou S. H. , Kingon A. I. , Buaud P. , Irene E. A. 
Published: March 2011

ABSTRACTHillocks, surface protrusions from thin metal films, have been observed in Al, Al/Cu, Pb, and other materials. Platinum films are widely used as substrates for the deposition of ferroelectric thin films because of their superior oxidation resistance. However, hillock formation in platinum films has not been reported in the literature. In this work, we report the appearance of hillocks in platinum in Pt/Ti bilayers on oxidized silicon wafers. Platinum films 250 to 300 nra were deposited by ion beam sputter deposition at 25°C and 300°C onto a 70 nm Ti film on oxidized Si wafers. The wafers were then heated in flowing argon to 600°C, held 1 hr at 600°C, and cooled to room temperature while the wafer curvature (and hence the film stress) was measured with a laser beam deflection technique. At 600°C, compressive stresses of 0.1 to 0.4 GPa, due to thermal expansion mismatch, developed in the metal films. The platinum surface, initially flat, showed strong hillocking after the anneal. Cross-sectional TEM revealed that severe Ti/Pt interdiffusion occurred, in one case leading to a Ti layer on the top surface.
Fermi Level Inhomogeneities on GaAs(110) Surface Imaged with a Photoelectron Microscope
Authors: Kim Changyoung , King Paul L. , Pianetta Piero 
Published: March 2011

ABSTRACTA photoelectron microscope operating with a retarding field analyzer has been used to exploit core level energy shifts due to band bending in order to directly image Fermi level variations on n- and p-type cleaved GaAs(110) surfaces. Fermi level maps resolved to better than 10 um indicate lateral variations in the surface Fermi level which are often quite abrupt. In agreement with earlier, lower resolution work [1], Fermi level topography is found to be highly correlated with surface roughness as characterized by SEM, optical microscope and stylus profi lometer. The largest defect derived pinnings encountered to date resut in the Fermi level lying 0.5 eV above the VBM for both n- and p-type GaAs. Low coverage In evaporations have the. effect of reducing Fermi level contrast as Fermi levels in formerly unpinned regions move into the gap.
Construction of Band Profiles for Semiconductor Heterojunctions and Layered Structures
Authors: Garland J. W. , Kassel L. , Yang D. , Zhang Z. , Raccah P. M. 
Published: March 2011

ABSTRACTBand profiles specify the position of all band edges as a function of distance from a sample surface or interface. They largely determine the electrical and optoelectronic properties of semiconductor heterostructures. Neither theory nor standard transport measurements alone have been able to give reliable values for band offsets, much less entire band profiles. However, the use of electroreflectance, which reveals crossover transitions between localized states or band edges present on opposite sides of an interface, and which allows us to measure accurately built-in fields, has allowed us to determine accurate band profiles for several types of semiconductor heterostructures. The procedure used to find the band profile is elucidated in detail for two technologically important cases.
W and Related Alloys Deposited onto InP by RT-LPCVD
Authors: Katz A. , Feingold A. , Pearton S. J. , Lane E. , Nakahara S. , Geva M. 
Published: March 2011

ABSTRACTTungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapor deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogran (H2). W films of thickness 50 to 450 nm were deposited in the temperature range of 350° to 550°C, pressure range of 0.5 to 4.5 Torr and deposition rates up to 4 nm/sec with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300°C for about 800 hr and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600°C led to reduction of the resistivity with a minimum value of about 55μΩ-crn as a result of heating at 500°C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40 to 50 nm·sec-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.
Interfacial Reactions of the Pt/Ti/Si Structures
Authors: Tseng Bae-Heng , Lee Chong-Kuang , Tseng Ming-Feng 
Published: March 2011

ABSTRACTA 15rm-thick Ti-layer incorporated between Pt and Si was found to be effective in improving the structures of PtSi/Si interface. The roles of Ti-layer were to react with native oxides on the Si substrate and to form Ti-O solid solutions instead of Ti oxides which act as diffusion barrier and inhibit the reactions between Pt and Si. Auger depth profiling gave evidence that Ti and O moved outward as platinum suicides were formed. A smooth PtSi/Si interface was revealed by the transmission electron microscope.
Nonconformal Al Via-Hole Filling by Electron Beam Evaporation
Authors: Cho C.-C. 
Published: March 2011

ABSTRACTUsing electron beam evaporation, we have deposited Al on patterned SiO2 films grown on various Si(100)-based substrates and characterized the Al films by scanning electron microscopy, x-ray diffraction and transmission electron microscopy. The growth mode of Al in the via holes of the SiO2 films is found to depend on the base materials of the holes. For via holes based on Si(100) and TiSi2, Al fills the holes nonconformally, showing little Al on the side walls. The nonconformal growth of Al is useful for submicron via-hole filling because it prevents void formation caused by shadowing effect. In contrast, for holes of AlCu bases, Al grows conformally. For the Al grown in the via holes of Si(100) bases, single crystal Al with Al(110)//Si(100) epitaxial relation can be grown in the holes at a substrate temperature of 300°C.
Comparative Electrical Study of Epitaxial and Polycrystalline GdSi2/(100)p-Si Schottky Barriers
Authors: Kovács B. , Horváth Zs. J. , Mojzes I. , Molnár G. , Petó G. , Andrási M. 
Published: March 2011

ABSTRACTThe electrical and interface parameters of epitaxial orthorombic, textured orthorombic, polycrystalline orthorombic, and polycrystalline hexagonal structures with different initial thickness of the evaporated Gd layer are compared. The Schottky barrier height, the ideality factor, the series resistance, the breakdown voltage, the relative interfacial layer thickness, the energy distribution spectra of interface states, and the equilibrium interface charge have been evaluated from the current-voltage and capacitance-voltage measurements. The obtained results indicate that the initial thickness of the Gd layer influences much more stronger the obtained parameters through the perfection of the epitaxial layer than the crystal structure.
Planarized Copper Interconnects by Selective Electroless Plating
Authors: Kiang M. H. , Tao J. , Namgoong W. , Hu C. , Lieberman M. , Cheung N. W. , Kang H. -K. , Wong S. S. 
Published: March 2011

ABSTRACTElectroless deposition of planarized copper in SiO2 trenches has been carried out using Pd/Si plasma immersion ion implantation (PIII) or Pd2Si deposition to form a seed layer at the bottom of trenches. Electrical resistivity of the plated Cu is < 2 μΩ-cm for both types of seeding layers. For the PHI seeding method, we found a threshold Pd dose of 2 ×l014/cm2 is required to initiate Cu plating, and RBS analysis confirms intermixing of Pd, Si, and SiO2 improves the adhesion of the plated Cu to SiO2. Electromigration tests show both void and hillock formation under accelerated current stress testing, with an activation energy of 0.8 eV for interconnect open failure. The DC and pulse-DC median-time-to-failure (MTF) of plated Cu are found to be about two orders of magnitude longer than that of Al-2%Si at 275°C, and about four orders of magnitude longer than that of Al-2%Si when extrapolated to room temperature. Pulsed DC electromigration stressing exhibits a transition from low to high frequency behavior around 900 kHz, indicating a vacancy relaxation time much shorter than that of Al. For bipolar AC stressing, the ratio MTFAC / MTFDC of Cu is much smaller than that of Al-2%Si, indicating a different void recovery mechanism for Cu.
Reliability, Properties and Microstructure of W80Ti20 Diffusion Barriers Between Al-Based Metallizations and Si.
Authors: Dirks A. G. , Wolters R. A. M. , De Veirman A. E. M. 
Published: March 2011

ABSTRACTTungsten-rich W-Ti (or W-Ti-N) alloy films are known for their applicability as diffusion barriers in advanced silicon technology, especially in the case of aluminium-based metallizations. For a wide variety of deposition conditions and post-deposition anneal treatments these refractory-metal barriers show a columnar microstructure. In contact with aluminium the W-Ti films do not form absolute barriers, because of mutual diffusion resulting in compound formation. The reactivity of the W-Ti barriers with the Al99Si1 interconnect has been studied by in-situ resistance measurements in vacuum at temperatures of approximately 450 °C (for W-Ti alloy films) and 475 °C (for W-Ti-N alloy films). In this paper new results dealing with the relationship between deposition conditions, microstructure and barrier properties will be discussed. Furthermore, it will be shown that the actual distribution of the titanium atoms in the tungsten matrix has a substantial influence on the reactivity of the barrier film with the Al99Si1 interconnect.
Plasma Diagnostics and Modeling of TI/TIN Reactive Sputtering
Authors: Tsai W. , Fair J. , Hoddl D. , Ginzton Edward L. 
Published: March 2011

ABSTRACTIn situ optical emission spectroscopy studies of Ti/TiN reactive sputtering were carried out in a Varian M2000 cluster tool. Deposition rates of Ti/TiN films at 4.3 mTorr are directly proportional to ratio of Ti(365)/Ar(435) emission lines. Measurement of the ratio of the N(655)/Ar(435) emission lines indicates an incubative dependence on.nitrogen flow due to nitridation of the target. TiN reactive sputtering is accurately described by a mathematical model based on the nitrogen flux balance on target and wall/shield at steady state.
Competitive Reactions in Unicomponent/Bicomponent Contact Systems
Authors: Eizenberg M. 
Published: March 2011

ABSTRACTThe advance of microelectronic devices has emphasized the important role of contact metallization. Contacts have become more and more complex in their structure. In this review we present some of our work on three different types of contact systems consisting of a unicomponent/bicomponent interface. The systems are: 1) alloy films (codeposited two metals) on Si, 2) a metal on Si1-xGex epilayers, and 3) a metal on a compound semiconductor (GaAs). Due to applied heat-treatments, competitive interfacial reactions take place between the various constituents of the contacts. These interfacial reactions can affects the properties of the contacts and their stability and reliability.
MOCVD-TiN Barrier Layers for ULSI Applications
Authors: Raaijmakers Ivo J. , Vrtis Raymond N. , Yang Jack , Ramaswami Seshadri , Lagendijk Andre , Roberts David A. , Broadbent Eliot K. 
Published: March 2011

ABSTRACTMaterial properties are reported of high quality TiN thin films, deposited by a low temperature (400 – 450 C) and low pressure (10 Torr) metalorganic chemical vapor deposition process using tetrakis(diethylamino)Ti and ammonia. Layer resistivities of less than 200 μΩ cm are achieved in 300 to 500 A thick films. The carbon and oxygen content in the films is found to be low (<3% C, <0.5% O). Conformality of the films in small contact holes is sufficient for the films to be applicable as diffusion barrier and adhesion layers in integrated circuit manufacturing at the 0.25 μΩgeneration.Integration of the MOCVD-TiN films in a Ti/TiN/Al-alloy metallization scheme is also reported. The diffusion barrier performance of the MOCVD-TiN layers is found to exceed that of PVD-TiN layers.
A Novel Technique for Characterization of Amorphous Silicon Thin Films
Authors: Malhotra V. , Weling M. 
Published: March 2011

ABSTRACTA novel technique for characterizing the variation of depletion width versus reverse bias voltage, the absorption coefficient, and the defect density in amorphous silicon thin films has been developed. The technique utilizes the fact that the rate of change of dc photocurrent with reverse voltage in a photodiode is strongly dependent upon the wavelength of light.
Photo-Hall, Pr, Pl and Photoconductivity Study On Native Defects in CuInS2
Authors: Ueng H. Y. , Cheng Y. H. , Hwang H. L. 
Published: March 2011

ABSTRACTBy correlating the results of photoreflectance, photoconductivity, photoluminescence, and differential-Hall and photo-Hall measurements with the stoichiometry, for a number of undoped single crystal samples, we could conclude two donor levels (35 meV, 70 meV) and three acceptor levels (100 meV, 155 meV, 170 meV) distributed in the forbidden ga.p for undoped CuInS2 samples.
Integration of Heterojunction Bipolar Transistors and Shallow Quantum Well Modulators for Smart Pixel Fabrication
Authors: Goossen K. W. , Cunningham J. E. , Jan W. Y. , Walker J. A. 
Published: March 2011

ABSTRACTUsing the recently developed SESHL (for Single Epitaxy Supporting HBT and Low-barrier modulator) process, we present a monolithic single-stage common-emitter amplifier with photodiode input and modulator output (or HBT-SEED), one of the simplest forms of smart pixels.
New Theoretical Treatment of Electroreflectance from Surfaces and Interfaces Having Large Built-in Fields
Authors: Garland J. W. , Zhang Z. , Kim C. , Yang D. , Raccah P. M. 
Published: March 2011

ABSTRACTWe have constructed a completely quantum-mechanical theoretical treatment of the modification of the local dielectric function by intense electric fields. It includes the numerical calculation of depletion-region bound-state energies and wavefunctions as well as band wavefunctions. We use this treatment to construct electroreflectance (ER) lineshapes. Our numerical results differ significantly from those of previously proposed ER lineshapes for GaAs with Nd >> 1016. They yield excellent fits to ER data and allow the accurate determination of doping levels and band bendings from ER data.