bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Ohmic Contact Formation Mechanism in the Au/Te/N-GaAs System
Authors: Wuyts K. , Langouche G. , Vanderstraeten H. , Silverans R.E. , Van Hove M. , Van Rossum M. , Münder H. , Lüth H. 
Published: March 2011

ABSTRACTAlloyed Au/Te/n–GaAs ohmic contacts, with contact resistivities comparable to those of the AuGe device standard, have been developed and studied by Mässbauer spectroscopy, Raman scattering and X-Ray Diffraction. The formation of Au-doped Ga2Te3 crystallites, grown epitaxially on a defectively GaAs surface was observed. No evidence for the formation of an n++–GaAs surface layer could be derived. The interpretation of all experimental results leads to a description of the ohmic conduction mechanism based on a resonant tunneling process assisted by defect/impurity related deep levels through low barrier metal/Te/(Au)Ga2Te3/GaAs interfaces
The Effects of Ion Beam Mixing on Rapid Thermal Annealed Ohmic Contacts to N-GaAs
Authors: Kazmi Seemi , Kruzelecky Roman V. , Thompson David A. 
Published: March 2011

ABSTRACTNi/Ge/Au and Ni/Ge/Pd contacts have been made on 1018 cm-3 n-type GaAs. The contacts were subjected to ion beam mixing through the metallization using 70-130 keV Se+ ions and subsequently subjected to rapid thermal annealing (RTA). These are compared with unimplanted contacts produced by RTA techniques on the same substrate. The specific contact resistance ,pc, has been measured for the two systems. In addition, the contacts have been studied using Auger depth profiling and SEM studies have been used to determine surface morphology. Values of pc ∽ 10-6 -10-7 ohm-cm2 have been measured. It is observed that ion beam mixing or the addition of a Ti overlayer (to the Ni/Ge/Au) improves the contact morphology.
Ni-Ge Intermixing on GaAs Produced by Temperature Standardized Rapid Thermal Annealing
Authors: Brooks Michael B. , Sigmon Thomas W. 
Published: March 2011

ABSTRACTA new Rapid Thermal Annealing technique has been developed which uses very small samples of low melting elements and eutectic alloys to standardize temperature measurements. Temperatures of thin films during anneal are shown to lie within −3°C to +13°C of nominal for measured short anneal times using a special sample geometry. Results of annealing Ge/Ni/GaAs and Au/Ge/Ni/GaAs at 200°C and 250°C are presented. Rutherford backscattering is used to analyze the films and the resulting channeling spectra show that Ge consumption follows parabolic kinetics, with an activation energy estimate of ≈ 0.7eV. The data is consistent with a controlling process of fast Ni diffusion through grain boundaries at these low temperatures. We expect that a Ni2Ge phase is being formed preferentially, along with a NixGaAs phase at the GaAs/Ni interface. In this contact metal system Au interacts only minimally for the times and temperatures studied. Our results agree with those of previous workers who studied Ni diffusion during NixGaAs phase formation at comparable temperatures.
Au-Ge-Ni-Ti Ohmic Contacts on Gallium Arsenide
Authors: Alexander K. B. , Stobbs W. M. 
Published: March 2011

ABSTRACTThe influence of titanium additions on the microstructure of Au-Ge-Ni ohmic contacts on gallium arsenide has been evaluated. Sequentially deposited layers of Ge, Au and Ni were topped with a titanium layer. The titanium formed a native titanium oxide on the upper surface of the contact which helped to maintain a continuous film during the anneal. Both the as-deposited and the annealed microstructures were studied with the use of electron microscopy techniques. In order to examine thoroughly the various phases which form in the annealed contact, unique specimen preparation procedures were used to fabricate a single plan-view specimen in which it was possible to examine the microstructure at various depths.
Correlation Between the Interfacial Nonuniformity and the Specific Contact Resistance of Ohmic Contacts to Gaas
Authors: Tuy T. Q. , Mojzes I. , Tuyen V. V. , Cseh I. 
Published: March 2011

ABSTRACTConsidering the effect of the simultaneous presence and interaction of the different phases at the contact, a modification of the model presented by Wu and coworkers (Solid-St. Electron. 29 (1986) 489] for explanation of ohmic contact resistance of n-GaAs was developed. The modified model combines the existence of the mixed phase structure of AuGeNi/n-GaAs contact with assumptions proposed by Wu et al. that the specific contact resistance Rc contains two parts Rcl and Rc2, where Rc1 is the specific contact resistance of the alloyed and underlaying doped contact region, and Rc2, is that of the high-low junction between the heavily doped contact region and the bulk semiconductor. The Rc1 depends strongly on the apparent barrier height and the effective impurity concentration formed by doping from the contact alloys during annealing. In the present paper a new theoretical model for Rc1 is proposed and compared with the experimental results.
Interfacial Microstructure and Carrier Conduction Process in Pt/Ti Ohmic Contact to P-In0.53Ga0.47As Formed by Rapid Thermal Processing
Authors: Chu S.N.G. , Katz A. , Boone T. , Thomas P.M. , Riggs V.G. , Dautremont-Smith W.C. , Johnson W.D. 
Published: March 2011

ABSTRACTThe strong dependence of electrical properties of Pt/Ti ohmic contact to p–In0.53Ga0.47 As (Zn: 5 × 1018 cm−3) on the interfacial microstructure formed by rapid thermal processing (RTP) were intensively studied by transmission electron microscopy, Auger Spectroscopy, and transmission line model (TLM) measurements. The rapid decrease of the specific contact resistance with an increase in RTP temperature was correlated with the development of an interfacial reaction zone. Significant interdiffusion of Ti, In and As across the interface occurred at temperature above, 350°C for a 30 second of RTP. A minimum specific contact resistance (3.4 × 10−6 Ω-cm2) was achieved at RTP temperature of 450°C. The corresponding interfacial microstructure revealed a complicated solid state reaction zone with InAs as one of the major interfacial compounds. The low contact resistance is attributed to the carrier conduction through the InAs regions. This is also consistent with the results of Pt/Ti contact experiments to p-type InAs, InP and GaAs binary surfaces, where the lowest contact resistance was achieved on InAs (3.0 × 10−7 Ω-cm2at Zn: 5 × 1018 cm−3). The temperature dependence of specific contact resistance of as-deposited Pt/Ti contact to InGaAs agrees very well with the thermionic emission dominated carrier transport mechanism with an effective barrier height, φb, of 0.13V. The rapid decrease in the contact resistance as well as its reduced temperature dependence after RTP treatment at elevated temperatures suggesting a partial conversion of thermionic emission dominated contact area to field emission dominated regions. A phenomenological theory of multiple parrallel carrier conduction processes was proposed to analyse the temperature dependence of specific contact resistance for contacts with complicated interfacial microstructure. It was found that, for low resistance contacts, majority of the carriers conducted through only a fraction of the contact area via a tunneling mechanism.
Submicron Pseudomorphic Hemt’S Using Non-Alloyed Ohmic Contacts with Contrast Enhancement.
Authors: Jansen Ph. , De Raedt W. , Van Hove M. , Jonckheere R. , Pereira R. , Van Rossum M. 
Published: March 2011

ABSTRACTWe report for the first time the realization of submicron pseudomorphic Al.15, Ga.85As-In.20Ga.80As HEMT’s with non-alloyed Pd/Ge ohmic coi tacts. Best results of contact resistance were obtained at a sintering temperature of 340°C with values as low as 0.057 Ωmm. Enhanced contrast, needed for accurate alignment of the gate by electron-beam lithography, was obtained by using Pd/Ge/Ti/Pd and Pd/Ge/Ti/Pt metal sequences. These contacts exhibited even lower contact resistances than the standard Pd/Ge contacts. Although Pd/Ge/Ti/Pd exhibits good morphology, reaction is witnessed at the edges, reducing the accuracy of alignment.Processed enhancement mode devices exhibit maximum transconductances in excess of 520 mS/mm and currents of 300 mA/mm for 0.3 micron gatelength. This study shows that the contact resistance is no longer a restriction for obtaining very high transconductances in high performance devices.
Role of in-Situ Rapid Isothermal Processing (Rip) in the Metallization and Passivation of Indium Phosphide Devices
Authors: Singh R. , Thakur R. P. S. , Katz A. , Nelson A. J. 
Published: March 2011

ABSTRACTAs compared to a stand alone rapid isothermal annealing unit, the integration of deposition system and rapid isothermal processing unit is very attractive for the next generation of micro, opto and cryoelectronics. We have used in-situ rapid isothermal processor for in-situ rapid isothermal chemical cleaning of InP, solid phase epitaxial growth of II-A fluorides, and in-situ metallization of InP capacitors. As compared to ex-situ annealed films, SrF2 films deposited on InP by in-situ rapid isothermal processed films show less thermal stress and lower thermal hysteresis for the identical thermal budget. Similarly, as compared to ex-situ annealing, in-situ cleaning of InP before metallization followed by in-situ annealing results into improved high frequency capacitance-voltage (C-V) characteristics of Al-SrF2-InP capacitors.
Anti-Reflection Coatings (Arc) for use with Aluminum Metallizations on GaAs ICs
Authors: Brady Michael F. , Helms Aubrey L. 
Published: March 2011

ABSTRACTThe need for an Anti-Reflection Coating (ARC) on aluminum metallizations is well known. A new class of materials based on tungsten-silicide and tungsten-silicon-nitride has been developed Tor use as an ARC. It has been shown that the reflectivity (relative to aluminum = 100%) can be decreased to −55% for the tungsten-silicide material and to −6% for the tungsten-silicon-nitride materials. These materials are easily etched in fluorine containing plasmas and are not as sensitive to thickness uniformity issues as dyed resists or amorphous silicon ARC materials. The option of leaving these ARC materials on the aluminum lines may lead to an increase in the electromigration resistance. The dependence of the reflectivity on nitrogen content has been investigated. Additionally, the reflectivity reducing properties have been studied on a variety of substrates such as aluminum, gold, tungsten, tantalum, and silicon.
Vapour Deposited Nanocomposite Thin Films
Authors: Wen L. S. 
Published: March 2011

ABSTRACTFundamental principles of nanocomposites are discussed. The basic features of nanocomposites are low dimensionality of their composition components, widespreadness of the electronic interactions between the components and the great variety of microstructure of nanocomposites ranging from high level ordered 3-dimensional periodic structure to stochastically dispersed medium of superfine particle. All these offer much more potential for tailoring the property of materials than by formation of chemical compound or mixture including microcomposites. Vapour deposition enhanced by ion beam and electrical discharge plasma provides a class of versatile processes both for preparing low dimensional components of nanocomposites and for synthesizing nanocomposite film itself. Elements of designing nanocomposite thin films and their preparing by ion beam and plasma enhanced vapour deposition are also discussed. Examples of nanocomposite films are given.
Electrical and Metallurgical Characteristics of PtSix and TiSix/GaAs Schottky Contacts
Authors: He Qian , Jinsheng Luo 
Published: March 2011

ABSTRACTElectrical properties, metallurgical properties and their relationship of PtSix/GaAs formed by sputter deposition and TiSix/GaAs formed by e-gun multilayer evaporation have been studied. It has been found that TiSix/GaAs contacts exhibit excellent Schottky electrical propcrties and good metallurgical stability after RTA (975°C , 12 sec) but some interface unstability and degradation of electrical properties after conventional FA (800°C ,20 min). The electrical and metallurgical properties of PtSix/GaAs contacts begin to degrate after annealed at 500°C.
Chemical Stability of Vb2 and ZrB2 with Aluminum
Authors: Halperin L. E. , Kolawa E. , Fu Z. , Nicolet M-A. 
Published: March 2011

ABSTRACTThe chemical stability of boride thin films with aluminum is investigated. Only two diborides, VB2 and HfB2 have a positive heat of reaction which makes them potential candidates for thermodynamically stable diffusion barriers between Al and Si. Thin films of VB2, and ZrB2 for comparison, prepared by rf sputtering of composite targets were chosen for this study. Multilayer samples of these borides and aluminum were investigated by differential scanning calorimetry to determine if, according to calculations, a reaction between Al and the borides takes place, and to measure the heat of reaction. We find that an exothermic chemical reaction occurs between ZrB2 and Al and that an exothermic crystallization reaction takes place in the VB2 and Al sample. The reaction products were determined using X-ray diffraction.
Multilayer Metallization Structures in a Gate Array Device Shown by Cross-Sectional Transmission Microscopy
Authors: Gong S. F. , Hentzell H. T. G. , Robertsson A. 
Published: March 2011

ABSTRACTA multilayer metallization structure in a gate array circuit has been investigated by cross-sectional transmission electron microscopy. Microstructures of thin films, interfaces, contacts, dislocations and step coverage are revealed. Good step coverage was observed when polyimide was used as an insulator between two metal layers.
Formation of Cosi2-Shallow Junctions By Ion Beam Mixing and Rapid Thermal Annealing
Authors: Niewöhner L. , Depta D. 
Published: March 2011

ABSTRACTFormation of CoSi2 using the technique of ion implantation through metal (ITM) and subsequent appropriate rapid thermal annealing is described. Silicide morphology is investigated by SEM and TEM. SIMS and RBS are used to determine dopant distribution and junction depth. Self-aligned CoSi2/n+p diodes produced in this technique are presented.
Deposition of Tungsten Silicide Barrier Layers and Tungsten in Rectangular Vias
Authors: Cale Timothy S. , Raupp Gregory B. , Jain Manoj K. 
Published: March 2011

ABSTRACTDiffusion-reaction analysis of a two step process in which a tungsten silicide barrier layer is deposited in a rectangular trench by low pressure dichlorosilane reduction of tungsten hexafluoride followed by a complete tungsten fill by low pressure hydrogen reduction of tungsten hexafluoride reveals that high step coverage and high deposition rate can be readily achieved with logical selection of process parameters. This fact, coupled with the potential for accomplishing these deposition steps in the same single wafer reactor, suggests that this two step process may offer a high throughput alternative to blanket tungsten deposition by silane reduction.
Characterization of the Al/RuO2 Interface Upon Thermal Annealing
Authors: Vu Quat T. , Kolawa E. , Nicolet M-A. 
Published: March 2011

ABSTRACTWe have characterized the Al/RuO2 interface after annealing at temperatures in the range 450° C-550° C for durations up to several hours by backscattering spectrometry, cross-sectional transmission electron microscopy, and electrical four point probe measurement of specially designed structures. The electrical measurement yields the specific contact resistance of the interface by applying a transmission line type model developped for this purpose. An interfacial aluminum-oxygen polycrystalline compound is shown to grow with annealing temperature and duration, with a concurrent reduction of a thin layer of RuO2. However, the specific contact resistance between Al and RuO2 is found to decrease with annealing duration at 500°C. This last result indicates that the interfacial reaction does not lead to an insulating interface as could have been expected if the growth were pure and dense A12O3.
The Effects of SI Addition on the Properties of AICu Films used in Multilevel Metal Systems
Authors: Wilson S. R. , Weston D. , Kottke M. 
Published: March 2011

ABSTRACTThis paper reports a systematic study of the properties of Al(Cu 0.5-1.5%) and Al(Cu 0.5-1.5%, Si 0.5-1.5%)alloys. The effects of deposition temperatures ranging from room temperature to 475°C were studied as well as whether the films were deposited on Ti-W or SiO2. The Cu and Si profiles were measured as well as the presence of Al2Cu and Si precipitates. The effects of post deposition bake treatments are also discussed.
Low Temperature Processing for Multilevel Interconnection and Packaging
Authors: Lu T.-M. , McDonald J. F. , Dabral S. , Yang G.-R. , You L. , Bai P. 
Published: March 2011

ABSTRACTThe future high density multilevel interconnection and packaging requires that the combination of the insulator and conductor layers has a low RC value. Thermal stress and diffusion during processing are issues of great concern in the high density multilevel structures. The problem can be alleviated by a proper choice of materials and processes that do not require high temperature. In this paper we propose to use parylene and its derivatives (dielectric constant 2.3–2.6) as the possible interlayer dielectrics and Cu (bulk resistivity ∼1.7 μ Ω-cm) as the conductor. Parylene can be vapor-deposited and cured at room temperature. The metallization of Cu has been achieved at room temperature using the newly developed partially ionized beam deposition technique. This technique has been shown to grow high quality metal films with low resistivity at low substrate temperatures. The interaction between Cu and parylene, including adhesion and diffusion, is also discussed.
The Effect of Aqueous Chemical Cleaning Procedures on Schottky Contacts to N-Type Gaas
Authors: Kniffin M. L. , Helms C.R. 
Published: March 2011

ABSTRACTThe effect of interfacial oxides and impurities left by aqueous chemical cleaning procedures on the n-type Schottky barrier heights of various metal-GaAs contacts have been examined as a function of annealing temperature. The as-deposited barrier heights of metals which are expected to be reactive with respect to the native oxides of GaAs (Mn, Cr, Al and Ti) were the most sensitive to variations in the residual oxide thickness. Omitting the final oxide etch from the cleaning sequence resulted in a 50 to 60 meV reduction in the as-deposited barrier height of these metals. However annealing these contacts at temperatures as low as 175 °C results in a barrier height that is independent of the initial surface clean. In contrast, for metals which are expected to be unreactive with respect to the native oxides of GaAs (Ni, Au, Cu and Ag) the pre-deposition cleaning procedure had little effect on either the as-deposited or the annealed Schottky barrier heights.
Deposition of Tungsten Boride by Ion Beam Sputtering
Authors: Meyer F. , Bouchier D. , Stambouli V. , Gautherin G. 
Published: March 2011

ABSTRACTRefractory metal compounds, such as nitrides or borides, are attractive candidates for diffusion barrier between silicon and aluminium in VLSI technology. We studied tungsten boride films deposited on silicon (100) by ion beam sputter deposition (IBSD).The tungsten boride films were prepared by sputtering a W2B5 target by argon ions with energy ranging from 0.5 to 2keV. The substrate temperature was varied from room temperature to 630°C. Finally, the films were patterned by selective wet etching in order to characterize the resulting Schottky diodes. We observed that a boron loss occurs during deposition, probably due to the backscattering of sputtered boron on previously deposited W atoms. By in situ AES analysis, we verified that a 5 nm thick layer acts as a diffusion barrier for silicon up to about 630°C, for all deposition conditions. The films properties were found to depend weakly on the primary ion energy and on the substrate temperature. All the films have resistivity at room temperature in the range of about 250 µΩ cm. The measured density, in the range of 12 g/cm3, is very close to that of WB2 bulk material, while the intrinsic stress of the films remains compressive and in the range of -lGPa. This value is notably lower than what we measured for pure tungsten prepared under similar deposition conditions.
Effect of Residual Stress on Si-Consumption During W-Deposition by LPCVD
Authors: Lee S. H. , Lee J. J. , Kum Dong-Wha 
Published: March 2011

ABSTRACTThe effect of stress on W-deposition at low pressure by Si-reduction of WF6 has been studied on patterned wafers utilizing cross-section SEM and cross-section TEM. Si-consumption and encroachment formation at the Si/Si02 interface was analyzed as a function of the oxide thickness, which changes the residual stress of the Si-substrate beneath the SiO2-layer. At the edge of the SiO2-layer, significant enhancement of W-deposition was observed from the early stage of W-metallization. Penetration of W into the Si-substrate beneath the edge showed strong dependency upon the oxide thickness, while penetration along the SiO2/Si interface (i.e. encroachment) did not. It has been analyzed that early stage of W-deposition was strongly affected by residual stress in the Si-substrate, and contact between WF6 and Si will be much easier through porous W-film and the W/Si interface, where the existence of microvoids is expected.
The Dependence of Aluminum/Tungsten Reaction on Crystalline Phases of Cvd Tungsten
Authors: Harada Y. , Onoda H. , Madokoro S. 
Published: March 2011

ABSTRACTThe reaction between Al and CVD-W films has been studied. Al/α-W/Si and Al/β-W/Si structures were prepared by deposition on different Si substrates by changing deposition conditions using silane reduction of tungsten hexafluoride, followed by Al-Si-Cu alloy film sputter deposition. The sheet resistance of Al/α-W/Si structure is higher than that of Al/β-W/Si structure after 500°C annealing. RBS measurements show that the W diffusion into Al occurs in both structures after annealing, and the reaction between α-W and Al takes place easily compared with that between β-W and Al. This causes the sheet resistance difference. The activation energies for the W diffusion into Al, however, are almost the same in both structures. When CVD-W films are exposed to air after removal from the reactor, the sheet resistance of β-W film increases according to the exposure time, while that of α-W film does not. AES measurements indicate that the β-W film absorbs more oxygen than the α-W because of the difference of grain structures. The resistance increase of β-W film is caused by the oxygen that is absorbed from air. Our results indicate that the oxygen in the β-W layer suppresses the W diffusion into Al. Once the reaction begins, however, the diffusion into Al does not depend on crystalline phases of CVD-W.