bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Performance in Monofilament Fiber Reinforced Glass Matrix Composites Through the Use of Fiber Coatings
Authors: Tredway William K. , Prewo Karl M.
Published: March 2011

The mechanical performance of glass matrix composites reinforced with large diameter (140 µm) monofilaments has been investigated. Strong interfacial adhesion between uncoated boron monofilaments and the borosilicate glass matrix resulted in composites exhibiting low failure strain and brittle fracture. The use of coated monofilaments improved composite performance considerably by reducing fiber-matrix interfacial adhesion. Auger analysis of the interface indicated that a carbon-rich layer had formed between the monofilament coating and the matrix during composite fabrication
Creep Properties and Interfacial Microstructure of SiC Whisker Reinforced Si3N4
Authors: Swan Håkan A. , O'meara Colette
Published: March 2011

Preliminary creep tests were performed on SiC whisker reinforced and matrix Si3N4 material fabricated by the NPS technique. The material was extensively crystallised in the as received material, leaving only thin amorphous films surrounding the grains. No improvement in the creep resistance could be detected for the whisker reinforced material. The deformation mechanisms were found to be that of cavitation in the form of microcracks, predominantly at the whisker/matrix interfaces, and the formation of larger cracks. Extensive oxidation of the samples, as a result of high temperature exposure to air, was observed for the materials tested at 1375°C.
R-Curve Behavior of SiC Whisker / Al2O3 Matrix Composites
Authors: Homeny Joseph , Mangin Christophe
Published: March 2011

The R-curve behavior of SiC whisker / Al2O3 matrix composites was evaluated. Composites were fabricated with Silar SC-9 and Tateho SCW-1-S SiC whiskers. The properties of the two SiC whiskers were similar in all aspects, except for significant differences in surface chemistry. These differences were found to be a key factor in determining the R-curve behavior
Mechanical Properties and Grain Growth Inhibition in The System Al2O3 : c-ZrO2
Authors: French J. D. , Chan H. M. , Harmer M. P. , Miller G. A.
Published: March 2011

The grain coarsening in a 50:50 volume percent Al2 O3 : c-ZrO2 composite is shown to be severely limited even after long heat treatments at high temperatures (100 hours at 1650°C). The strength behavior, measured by an indentation-strength-inbending (ISIB) method, shows a “rule-of-mixtures” type behavior. The microstructural stability at high temperatures yields reliability in the mechanical properties which has important implications with regard to fiber-reinforcement technology.
Bridging Processes in Metal-Reinforced Ceramics
Authors: Shaw M. C. , Marshall D. B. , Evans A. G.
Published: March 2011

In situ observations of fracture mechanisms and crack bridging effects in model copper-glass laminated composites are described and compared with measured resistance curves.
Improved Interfacial Adhesion in Metal Matrix/Metallic Glass Composites
Authors: Köster Uwe , Blank-Bewersdorff Margret
Published: March 2011

Interfacial adhesion in metal matrix/metallic glass composites can be improved by two methods: either by shifting the original interface into the glassy material by interface induced crystallization or by creating new crystalline/amorphous interfaces during glass formation by solid state reactions between two crystalline materials.
Intrinsic Material Limitations in Using Interphase Modification to Alter Fiber-Matrix Adhesion in Composite Materials.
Authors: Drzal Lawrence T.
Published: March 2011

A very large percentage of studies seeking to improve fiber-matrix adhesion to alter composite properties are directed at the formation of primary chemical bonds between the reinforcement surface and the matrix. The dynamic events that occur when the fiber-matrix interface is formed lead to the creation of an interphase which can have properties quite different from the matrix in addition to any chemical bond formation.

This study has been directed at elucidating the role of these interphase properties themselves on fiber-matrix adhesion. A reinforcement (AS-4 carbon fiber) with a quantifiable surface chemistry and an epoxy matrix have been kept constant through a series of experiments in which the distance between crosslinks of the matrix has been changed. The wettability of the fiber and the degree of chemical bonding to the fiber have not changed but the interfacial shear strength measured for each of these systems has decreased with decreasing matrix modulus. It will be shown that the properties of the matrix and the residual stresses created during processing limit the maximum interfacial shear stress that can be supported by the fiber-matrix interphase.
Elastic Modulus of the Interphase in Organic Matrix Composites
Authors: Williams J. G. , Donnellan M. E. , James M. R. , Morris W. L.
Published: March 2011

In organic matrix composites the properties of the matrix in the vicinity of the reinforcing fiber are of interest [1]. It has been suggested that a volume of material surrounding the fiber is significantly different from the bulk matrix [2–6]. Recent work has indicated that the interphase layer may be softer than the normal matrix material [6]. For a model composite with a single fiber embedded in an epoxy/amine matrix this layer was observed to be about 500nm thick and the material had an average elastic modulus of about 1/4 of that of the normal matrix material. The objective of the present work is to observe the effect of fiber treatment on the elastic properties of the interphase.
Thermomechanical Stability of Interphases in Glass Reinforced Composites
Authors: Dibenedetto A. T. , Gomez Jaime A. , Schilling C. , Osterholtz F. , Haddad G.
Published: March 2011

The thermomechanical stability of organosilane surface treatments for E-glass fibers used in fiber reinforced composites was evaluated. The effect of molecular structure of 40 to 80 namometer coatings on the force transmission across the fiber/matrix interface was measured as a function of temperature and exposure to water using a fiber fragmentation test. It was found that phenyl-substituted amino silanes exhibited better thermal stability, but were less resistant to boiling water, than the commierically available γ-amino propyl silanes. A bis-trimethoxy γ-amino propyl silane showed an increase in both the hydrolytic and thermal stability when compared to the commiercial product. A good balance of thermal and hydrolytic stability was also obtained with a methylaminopropyltrimethoxy silane coating.

The strain energy released from the glass fibers upon decoupling from the poxy matrix or silane coating was found to be in the range of 145 to 186 g/m2 and varied no more than 20 percent over a temperature range of 25 to 75°C or when exposed to boiling water and then redried. It also varied very little with the silane coating used. In addition, the average shear stress attained at the fiber-matrix interface in an imbedded single fiber test at 25°C was as much as two times higher than the shear strength of the epoxy matrix and as much as five times higher at elevated temperature. These data lead one to the conclusion that the interphase failure in these composites is controlled by a plane strain fracture in the constrained region of the organic phase, near the fiber surface, rather than by the maximum shear strength in the interphase.
Effect of Ti+, Ar+, N+ and He+ Ion Implantation on Aramid Fiber Adhesive Properties
Authors: Kalantar J. , Grummon D. S. , Drzal L. T. , Loh I. H. , Moody R. A.
Published: March 2011

Composites made with high performance polymer fibers can achieve axial properties comparable to those which use inorganic reinforcements, but with somewhat inferior interfacial properties. A high degree of chain alignment in polyaramids, such as Kevlar, produces weak interactions between adjacent polymers, resulting in poor transverse strength in the fiber, and low interfacial shear strength in composite systems. The latter controls many composite properties, such as transverse, shear and flexural strengths. Also, by reducing the tendency to form weak interfacial boundary layers, good fiber-matrix adhesion can enhance environmental stability. For these reasons, modifications to reinforcement fiber surfaces that promote fiber-matrix adhesion are frequently used to improve the performance of composites.
Toughening of Intermetallics by Coated Ductile Reinforcements
Authors: Deve H. E. , Evans A. G. , Mehrabian R.
Published: March 2011

The effects of reinforcement debonding and work hardening on ductile reinforcement toughening of γ-TiAl have been examined. Debonding has been varied by either the development of a brittle reaction product layer or by depositing a thin oxide coating between the reinforcement and matrix. The role of work hardening has been explored by comparing Nb reinforcements that exhibits high work hardening with solution hardened Ti-Nb alloy that exhibits negligible work hardening. It is demonstrated that a high work of rupture is encouraged by extensive debonding when the reinforcement exhibits high work hardening. Conversely, debonding is not beneficial when the reinforcement exhibits low work hardening.
Determination of Flexible Interlayer Thickness for Fiber Reinforced Composites
Authors: Lo King H. , Schmitz Robert W. , Gottenberg William G.
Published: March 2011

The influence of flexible interlayers/interphases on the performance of unidirectional fiber reinforced composites is studied. Micromechanical analysis based on the embedded composite cylinders model is used to study the stiffness as well as the internal stress distributions within the matrix phase of composites. Based on the results of the analysis, a criterion is proposed for the selection of optimal interlayer thickness for fiber composites. The proposed criterion gives results which seem to correlate well with the experimental data published in the literature.
Effects of a Frictional Interface on the Load Diffusion from a Broken Filament in a Fibrous Composite
Authors: Aksel Bulent , Lagoudas Dimitris C. , Hui Chung-Yuen
Published: March 2011

The effects of a frictional interface on the load diffusion from a broken fiber to the surrounding matrix material and the extent of debonding near the fiber break in a single-fiber reinforced composite of infinite extent are studied by using the finite element method. The normal and shear stresses on the interface, the extent of the slip zone and the axial load of the fiber are evaluated for different frictional coefficients and material parameters for both the fiber and the matrix. A shear-lag analysis is also carried out to obtain a closed form approximate solution of the fiber load diffusion problem. The extent of the slip zone and the stresses predicted by the shear-lag model are compared with the finite element method results.
Filament Fragmentation Phenomena
Authors: Figueroa Juan C. , Schadler Linda S. , Laird Campbell
Published: March 2011

The effect of fiber surface treatments on the relationship between the tensile strength of a filament and the shear strength of its interphase is one of the central issues facing composite materials technologists today. We demonstrate here that analysis of fragmentation phenomena in monofilament composites can simultaneously yield information about these two parameters. Characterization of shear stress transfer zones in non-critical fragments has led us to the determination of interphase strength.

A phenomenological treatment that highlights the role of the matrix in the fragmentation process is presented here. This analysis considers issues such as the strain energy exchange between a failing fiber and the matrix, as well as interphase relaxation due to the viscoelastic nature of the matrix. Our observations of the fragmentation phenomena in AU4/polycarbonate monofilament composites indicate that the fiber/matrix interaction in this system is governed by micromechanical locking.
Interaction of Cu and CoSi2
Authors: Shepard C. L. , Lanford W. A. , Shy Y-T. , Murarka S.
Published: March 2011

Interaction of thin film Cu and CoSi2 has been studied using Rutherford backscattering spectroscopy and sheet resistance measurements. For temperatures ≤ 600° C. , no measurable diffusion of Cu into CoSi2 is observed.
Growth and Characterization of Epitaxial CoSi2-Contacts
Authors: Adamski C. , Meiser S. , Uffmann D. , Niewöhner L. , Schäffer C.
Published: March 2011

The growth of epitaxial CoSi2 by means of SPE on heavily ion implanted Si(111) was investigated with LEED, RBS and TEM. After silicide formation, the dopant distribution in silicide and silicon was determined by means of SIMS. In a self-aligned process epitaxial CoSi2/Si p+ contacts have been produced. The specific contact resistance was found to be lower than for polycrystalline CoSi2 contacts.
Structure of the Ti-Single Crystal Si Interface
Authors: Ogawa S. , Kouzaki T. , Yoshida T. , Sinclair R.
Published: March 2011

The Ti-single crystal Si interfaces, before and after annealing in argon, were examined by cross section high resolution transmission electron microscopy (HRTEM) combined for the first time with 2nmΦ probe for energy dispersive spectrometry (EDS). HRTEM shows that there is amorphous alloy formation at the Ti-Si interface. The thickness of the reacted layer is ∼1.7nm for single crystal Si, independent of doping level and impurity species such as As and B, and is ∼2.5nm for back sputter-amorphized Si. After annealing at 430°C for 30min, the thickness of the amorphous alloy increases up to ∼11.5nm. High spatial resolution EDS microanalysis has been obtained. The results show that reliable compositions can be deduced at this level since some of the layers are only about 2nm thick. The amorphous alloy formed at the deposition step was found to be Ti55Si45. After annealing, the composition across the amorphous layer varied from about 70%Si near the substrate to about 30%S1 close to the Ti interface. The substrate interface is atomically flat. Interpretation of the behavior in terms of the metastable Ti-Si phase diagram calculated by Holloway and Bormann will be discussed.
Initial Phase Formation and Distribution in the Pt-GexSi1−x and Cr-GexSi1−x Systems
Authors: Hong Q. Z. , Mayer J. W.
Published: March 2011

Metal-GeSi reactions have been investigated in the Pt-GeSi and Cr-GeSi systems. Pt started to diffuse into and react with the alloys at 250 °C. The reacted region consisted of a uniform mixture of Pt2Si and Pt2Ge, with the same ratios of Ge to Si as those in the unreacted region. On the other hand, the Cr-GeSi reaction was induced by Ge motion at 375 °C. As a result a two-layer phase separation was observed. A Si-rich ternary layer was sandwiched between a germanide layer and the unreacted alloy
Thermal Stability of CoSi2 on Single Crystal and Polycrystalline Silicon
Authors: Phillips J. R. , Revesz P. , Olowolafe J. O. , Mayer J. W.
Published: March 2011

The thermal stability of Co silicide on single crystal and polycrystalline Si has been investigated. Co films were evaporated onto (100) Si and undoped polycrystalline Si and annealed in vacuum. Resulting silicide films were examined using Rutherford backscattering spectroscopy, scanning electron microscopy, electron-induced x-ray spectroscopy, and sheet resistivity measurements. We find that CoSi2 on single crystal (100) Si remains stable through 1000°C. In contact with undoped polycrystalline Si, intermixing begins at temperatures as low as 650°C for 30min annealing. The Co silicide and Si layers are intermixed after 750°C 30min annealing, giving islands of Si surrounded by silicide material, with both components extending from the surface down to the underlying oxide layer. The behavior of CoSi2 contrasts with results reported for TiSi2 which agglomerates on single crystal Si around 900°C but is stable on polycrystalline silicon as high as 800°C. Resistivity measurements show that the Co silicide remained interconnected despite massive incursion by Si into the silicide layer.
Tisi2 Thin Films Formed on Crystalline and Amorphous Silicon
Authors: Xiao Z.G. , Jiang H. , Honeycutt J. , Osburn C.M. , McGuire G. , Rozgonyi G.A.
Published: March 2011

TiSi2 thin films were formed on crystalline and amorphous silicon substrates obtained by Ge+ and Ge++B+ implantation and optional subsequent annealing. Transmission electron microscopy, X-ray diffraction and electrical resistivity analysis revealed that the silicide formed on amorphous Si has more tendency to have a C54 structure rather than the metastable C49 structure. Also, the grain size is smaller and the silicide/silicon interface is smoother for silicides formed on amorphous Si. Comparison between implanted and unimplanted, (100) and (111) Si substrates indicated that the origin of the differences can be attributed to the latent energy stored in amorphous silicon, which favors the silicide with fine grains and promotes the transformation to the C54 phase. Non-random distribution of planar defects in C49 grains has been observed by plan-view TEM. A proposal that these defects are transformation stress induced microtwins is presented.
The Effect of Amorphous Silicon Layer in Pe-Cvd Titanium Polycide Gate Dielectrics
Authors: Chen Shih-Chang , Sakamoto Akihiro , Tamura Hiroyuki , Yoshimaru Masaki , Ino Masayoshi
Published: March 2011

Titanium silicide (TiSix), used as polycide gate consists of TiSi1.1 and amorphous silicon (a-Si), was deposited by Plasma Enhanced Chemical Vapor Deposition method (PE-CVD). The effect of a-Si layer in PE-CVD Ti polycide gate dielectrics has been studied. In order to evaluate the a-Si layer effect, three types of samples were prepared on gate SiO2 film with following structures : a) a-Si / TiSi-1.1 / a-Si / phosphorus (P) doped poly-Si, b) a-Si / TiSi-1.1 / non-doped poly-Si / P doped poly-Si and c) a-Si / TiSi1.1 / P doped poly-Si, respectively. Furthermore, in order to avoid the influence of native oxide existence at the interface, the pre-cleaning treatment was performed in-situ on the poly-Si film surface before TiSi1.1 film deposition. The gate dielectric strengths of these samples indicate that the gate dielectric degradation in PE-CVD Ti polycide gate is greatly dependent on Si under layer crystallization. It is effective using a-Si film as the under layer in decreasing the gate dielectric degradation . This is due to the Ti oxide interlayer, formed at the interface of TiSi2.0 and poly-Si films, which restrains the TiSix local penetration.
Microanalysis of Tungsten Silicide/Polysilicon Interface: Effectiveness of

In Situ

Rie Clean on Removal of Native Oxide
Authors: Nowicki Ronald S. , Geraghty Patrice , Harris David W. , Lux Gayle
Published: March 2011

The presence of a thin (10-30Å) oxide (“native oxide”) layer on a silicon surface prior to the deposition of another film on that surface can contribute to difficulties with subsequent device processing steps, e.g. contact metallization and high-temperature annealing or oxidation. Thus, the in situ process capability of “native oxide” removal affords an advantage over the conventional method of aqueous hydrofluoric acid cleaning prior to a film deposition step. This study describes such a technique, in which an in situ pre-deposition clean with C2F6 gas, using reactive ion etching (RIE) prior to tungsten silicide deposition, is employed. This technique allows post-silicide deposition high-temperature heat treatment and wet oxidation without loss of film adhesion or other obvious degradative effects. We also report the use of Secondary Ion Mass Spectrometry (SIMS) to show that this procedure has been effective in the removal of the oxide layer prior to silicide deposition. This study includes definition of the RIE etch parameters which provide acceptable etch selectivity of the oxide to silicon, and avoidance of excessive fluoropolymer formation on the silicon surface.
Rapid Thermal Annealed Tiw/Ti Contact Metallization for Advanced Vlsi Si Circuits
Authors: Chung Henry W , Yao Agnes T.
Published: March 2011

Rapid thermal annealed (RTA) bilayers of TiW/Ti were evaluated for contact metallization in advanced VLSI Si circuits. It was found that RTA and a minimum thickness of Ti are necessary to achieve consistently low p+ contact resistance. RTA has little effect on n+ and polysilicon contact resistances. With RTA, TiSi2 is formed at the Ti/Si interface and a thin nitrogen-containing layer is formed on the TiW surface. By controlling RTA temperature and time, the interaction between Si and TiW during RTA could be minimized while the gain factor of p-channel MOSFETs was not degraded. Moreover, the leakage currents of n+ and p+ contact chains did not increase after 30 minute anneals up to 525C
Selective Oxidation and Etching of Reacted Pt Films on Gaas
Authors: Weiss Eliezer , Keller Robert C. , Kniffin Margaret L. , Helms C.R.
Published: March 2011

The oxidation of prereacted Pt films on (100)-oriented n-GaAs substrates was studied in the temperature range between 550 and 750°C using Auger electron spectroscopy and Xe+ ion profiling. The GaPt/PtAs2/GaAs structure formed during annealing in hydrogen was oxidized using a mixture of water vapor and hydrogen. The GaPt phase can be oxidized completely, whereas the inner PtAs2 and GaAs interfaces are left unoxidized. The oxidation of the platinum-gallium phase is self limited by the diffusion of the Ga through the gallium oxide overlayer. The oxide can be etched off to leave a structure consisting only of platinum-arsenide on the GaAs substrate.
Thermal Behaviour of Au/Pd/GaAs Contacts
Authors: Pécz B. , Veresegyházy R. , Mojzes I. , Radnóczi G. , Sulyok A. , Malina V.
Published: March 2011

Au(85nm)/Pd(55nm)/GaAs(100) samples were heat treated in the 325-425°C temperature range. The annealed samples have been investigated using Rutherford Backscattering Spectrometry, Auger Electron Spectroscopy and Transmission Electron Microscopy. The gold layer remained largely unreacted up to 300°C. Significant Pd diffusion into GaAs consuming a 50–60 nm thick layer of GaAs .is evident in the case of sample annealed at 325°C and a slight Au diffusion is also noticeable. In the sample annealed at 350°C the spreading of palladium was very quick. A strong reaction took place between the GaAs and the metallization in the case of sample heat treated at 375°C. At this temperature we have identified the PdGa phase using electron diffraction.
Thermoelectric Power in Quantum Confined Optoelectronic Materials under Classically Large Magnetic Field
Authors: Ghatak Kamakhya P. , De B. , Mondal M. , Biswas S. N.
Published: March 2011

We shall study the thermoelectric power under classically large magnetic field (TPM) in optoelectronic materials of quantum wells (QWs), quantum well wires (QWW’s), quantum dots (QDs) and compare the same with the hulk specimens of optoelectronic materials by formulating the respective electron dispersion law. The TPM increases with decreasing electron concentration in an oscillatory manner in all the cases, taking n-Hg1-xC dxTe as an example. The TPM in QD is greatest and the least for quantum wells respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.
The Effect of Microstructure and Processing Procedures on the Resistivity of Co-Sputtered W-Si Layers on GaAs Substrates
Authors: Carter S. , Staton-Bevan A. E. , Allan D. A. , Herniman J.
Published: March 2011

The relationship between microstructure, composition, resistivity and processing procedures of W-Si layers on (100) GaAs was examined for both “as deposited” specimens and specimens annealed at temperatures between 100°C and 1000°C. TEM, EDAX, SIMS, AUGER and four point probe resistivity measurements were employed.

The layers, exhibiting a columnar growth structure typical of sputter deposition, are amorphous below ≈ 800°C. At 700°C, the formation of pits, attributed to the outdiffusion of Ga and As into the W-Si layer, is observed at the W-Si/GaAs interface. The Ga and As outdiffusion was confirmed for temperatures above 700°C. The layers annealed between 800°C and 1000°C consist of a polycrystalline mixture of αW, βW and W5Si3 with coarse particles, thought to be W5Si3 precursors, formed along the W-Si/GaAs interface and protruding into the substrate. As the frequency of these protrusions increases with increasing temperature, the resistivity of the W-Si layers decreases.

Both the composition and the resistivity of the W-Si thin films are affected by the processing procedure. The Si/W ratio of the W-Si thin films decreases whilst their resistivity significantly increases as a result of etching away the Si3N4 capping layer using HF. It is thought that this is due to the removal of Si-oxides formed within the layer during the W and Si sputtering. The decrease in the Si/W ratio and the increase in resistivity are not observed if an A1N capping layer is used.
The Relationship Between Microstructure and Contact Resistance in NiAuGe/ZrB2/Au Ohmic Contacts to GaAs.
Authors: Grimshaw M. P. , Staton-Bevan A. E. , Herniman J. , Allan D. A.
Published: March 2011

The microstructure and contact resistance of NiAuGe contacts to n-type GaAs were determined as a function of initial contact composition. The contact microstructures were found to contain varying amounts of of α, α’ and β (or Au7Ga2) Au-Ga, epitaxial Ge, NiGe and NiGeAs phases. A previously unidentified NiAsx (Zr,B) phase was also observed. The contact resistance was found to vary between 0.22-0.38±0.03Ωmm. Comparison of the microstructural and contact resistance data revealed that the ohmic formation models based on (i) the formation of a recrystallised n+ GaAs layer and (ii) the presence of a graded Ge/GaAs heterojunction were not applicable to this contact system.
Process Design for Non-Alloyed Contacts to InP-Based Laser Devices
Authors: Katz A. , Dautremont-Smith W. C. , Chu S. N. G. , Pearton S. J. , Geva M. , Weir B. E. , Thomas P. M. , Kimerling L. C.
Published: March 2011

Pl/Ti and W thin films on n- and p- type InP and related materials have been investigated for potential use as a refractory ohmic contacts for conventional, single-side coplanar contacted and self-aligned barrier hetcrostructurc laser devices. Pt and Ti films were deposited sequentially by electron gun evaporation, while the W layer was rf sputtered, both onto p+ -In0.53Ga0.47As (Zn doped 5×l018cm−3) and n−- InP (S doped, 5×l018cm−3). The deposition parameters of the two metal systems were optimized to produce adherent films with the lowest possible induced stress. Almost all the studied systems performed as ohmic contacts already as-deposited and were heat treated by means of rapid thermal processing in the temperature range of 300–900°C. The final contact processing conditions were tuned to provide the lowest possible contact resistance values accompanied by low mechanical stress and stable microstructure.
Tantalum and Tantalum Nitride as Diffusion Barriers Between Copper and Silicon
Authors: Holloway Karen , Fryer Peter
Published: March 2011

We have investigated the effectiveness of thin tantalum layers as diffusion barriers to copper. Fifty nm Ta films were sputtered onto unpatterned single crystal Si wafers and overlaid with 100 nm Cu. Material reactions in these films were followed as a function of annealing temperature by in-situ resistance measurements, and characterized by by Rutherford Backscattering and cross-section TEM. The effect of the incorporation of nitrogen was explored by reactively depositing Ta(5 at.% N) and Ta2N. Pure Ta prevents Cu - silicon interaction to at least 600 °C. At higher temperatures, reaction of the Si substrate with Ta forms a planar TaSi2 layer. Cu rapidly penetrates to the Si substrate, forming Cu silicide precipitates at the TaSi2 - Si interface. A study performed on the Si/Ta(N)/Cu film had very similar results. Ta2N is an even more effective barrier to copper penetration, preventing Cu reaction with the substrate for temperatures up to at least 700 °C.
Lateral Spreading of Au Contacts on InP
Authors: Fatemi Navid S. , Weizer Victor G.
Published: March 2011

We have investigated the contact spreading phenomenon observed when small area Au contacts on InP are annealed at temperatures above about 400 C. We have found that the rapid lateral expansion of the contact metallization which consumes large quantities of InP during growth is closely related to the third stage in the series of solid state reactions that occur between InP and Au, i.e., to the AU3In-to-AugIn4 transition. We present detailed descriptions of both the spreading process and the Au3In-to-AugIn4 transition along with arguments that the two processes are manifestations of the same basic phenomenon.
Preparation and Characterization of LPCVD TiB2Thin Films
Authors: Choi Chang , Ruggles G. A. , Osburn C. M. , Shea P. , Xing G. C.
Published: March 2011

Titanium diboride is an interesting new candidate for VLSI interconnection applications due to its high electrical conductivity and its excellent chemical inertness at high temperatures.

A thermodynamic analysis of the chemical vapor deposition of TiB2from gaseous mixtures of TiCl4, B2H6and H2onto silicon or SiO2substrates was performed using the SOLGASMIX computer program. Results indicate that at an input gas ratio corresponding to stoichiometry, TiB2should form in the solid phase. For non-stoichiometric input gas mixtures, other solid phases, including oxides and silicides, are expected to result from the reaction with the Si or SiO2substrate. Both the addition of hydrogen to the system and increased deposition temperature are expected to enhance the deposition efficiency of TiB2.

Thin films of TiB2, 50 – 120 nm thick, were experimentally deposited on thermally grown SiO2by low pressure CVD using various gas mixtures in the temperature range 400 – 700°C. Depth profiling of the deposited films, using XPS and RBS, indicated the successful growth of a uniform, stoichiometric TiB2film. After deposition, the films were rapid thermal annealed at various temperatures in an effort to reduce their resistivity. Resistivity was reduced by 80 % after an 1150°C, 10 sec RTA in Ar to a value as low as 40μΩ-cm, only 4 times larger than that reported for hot pressed polycrystalline TiB2. X-ray diffraction of as-deposited samples showed no crystalline peaks; however, annealed films exhibited the expected TiB2peaks as well as those of Ti3O5and TiO2. The titanium oxide was most likely produced during annealing due to trace amounts of oxygen in the Ar atmosphere. The average grain size measured 0.1μm via TEM. More careful control of growth and annealing conditions is expected to result in even lower resistivity TiB2films.
Instabilities in the Mechanical Stress in Deposited SiO2 Films Caused by Thermal Treatments
Authors: Bhushan Bharat , Murarka S.P.
Published: March 2011

Using an in-situ stress measurement technique that measures stress as a function of annealing temperature, instabilities in mechanical stress induced by heat treatment in a variety of doped/undoped SiO2 films deposited by APCVD, LPCVD and PECVD techniques have been investigated. A large hysteresis in mechanical stress, caused by first heat treatment to which the as-deposited films are subjected, has been observed in films deposited by APCVD/LPCVD techniques. No such hysteresis is obsesrved in films deposited by PECVD technique. Hysteresis in APCVD/LPCVD films is found to vanish once the films are heat treated at or above 800°C. The results are discussed in terms of oxide densification, the presence of hydrogenous species, and phosphorous.
Acceptor Delta-Doping for Schottky Barrier Enhancement on n-Type GaAs
Authors: Pearton S. J. , Ren F. , Abernathy C. R. , Katz A. , Hobson W. S. , Chu S. N. G. , Kovalchick J.
Published: March 2011

The incorporation of thin C- or Zn-doped layers under metal Schottky contacts on n-type GaAs can lead to significant enhancements in the effective barrier height. A single C δ-doped layer (p = 1.3 × 1020 cm–3) within 100 Å of the surface leads to a barrier height of ∼0.9 eV, a significant increase over the value for a control sample (∼0.75 eV). The use of two sequential δ-doped layers can lead either to a further enhancement in barrier height, or a decrease depending on whether these layers are fully depleted at zero applied bias. The temperature dependence of current conduction in barrier-enhanced diodes was measured. Both the ideality factor and breakdown voltage degrade with increasing temperature. Zinc δ-doping in a similar fashion produces barrier heights of 0.81 eV for one spike and 0.95 eV for two spikes.
Metal/Silicide Interactions in the Ti-Co-Si System.
Authors: Setton M. , Van Der Spiegel J. , Madar R. , Thomas O.
Published: March 2011

Confirming the results obtained for Ti-Co bilayers on Si and in accordance with the phase diagram, the high temperature formation and stability of three ternary silicides Ti0.75Co0.25Si2 (T phase), TiCoSi (E) and Ti4Co4Si7 (V) is reported. The Si rich T phase grows for Ti / CoSi2 and Co / TiSi2 structures. The tetragonal V compound is obtained by annealing Ti (400 Å) / Co (250 Å) / Si (900 Å) / SiO2 whereas orthorhombic TiCoSi is prepared using Ti / CoSi / Si3N4 samples.
Reactive Ion Beam Assisted Evaporation of Tin Films for Use as Diffusion Barriers in GaAs MMICs
Authors: Kazior T. E. , Brooks R. C.
Published: March 2011

We report on the development of an evaporated diffusion barrier for incorporation into the metallizations currently used in GaAs MMICs. Results indicated that TiN films formed by reactive ion beam assisted evaporation - the simultaneous evaporation of metal atoms and bombardment with reactive ions - were as stable as TiN films formed by reactive sputter deposition and far superior to films formed by reactive evaporation. In addition the formation of these films is compatible with photoresist lift-off techniques. Chemical and electrical analysis has shown that these films are effective barriers against Au, Ga and As diffusion under extensive (up to 1500 hrs) elevated temperature storage (280°C). TiN-Au gate electrodes whose electrical characteristics are comparable to conventional Ti-Pt-Au gates have also been fabricated.
Phase Stability of Molybdenum-Silicon Nitride-Silicon Mis Schottky Diode at High Temperatures
Authors: Park Heungsoo , Helms C.R.
Published: March 2011

Previously our group[1,2] has demonstrated metal-thin insulator- silicon Schottky diode structures which allow the Si Schottky barrier height to be adjusted over nearly the full range of the silicon band gap by appropriate choice of insulator thickness and metal. However, previous attempts to achieve a structure with a high barrier height to p-type that is stable above 400C(using primarily Titanium) have failed. In this paper we report on results for a metal, Molybdenum, which has a stable tie line to Sio2 and Si3N4 in metal-silicon-oxygen(nitrogen) ternary phase diagram which leads to a more stable system.
Characterization of a Rapid Thermal Annealed TiNxOy/TiSi2 Barrier Layer
Authors: Chittipeddi Sailesh , Kelly Michael J. , Dziuba Charles M. , Oates Anthony S. , Cochran William T.
Published: March 2011

In this paper we characterize the thin film formed by rapid thermal anneal of a magnetron sputtered titanium film in a nitrogen atmosphere. The barrier properties of this material have been characterized for both n- and p-type junctions in our CMOS technology. We have characterized the physical properties of the film using Auger, RBS and TEM analysis in the same range of temperatures, and find that as the annealing temperature is increased a better quality TiNxOy film is formed. The electromigration characteristics for Aℓ/TiNxOy/TiSi2 runners, as well as the role that this system plays in minimizing failures due to stress induced voiding are examined in this study.
Metal Surface Morphology Characterization Using Laser Scatterometry
Authors: Gaspar S. M. , Hickman K. C. , McNeil J. R. , Jacobson R. D. , Lindauer G. P. , Strausser Y. E. , Krosche E. R.
Published: March 2011

We have applied angle-resolved laser scatterometry to characterize the morphology of metals deposited under various conditions. Scatterometry is a rapid, noncontact and nondestructive diagnostic which yields surface statistics including rms roughness and power spectral density of the microstructure.
The Effect of Chemical Treatment of the GaAs Surface on the Ohmic Contact Properties
Authors: Kovács Balázs , Németh-Sallay Margit , Mojzes Imre
Published: March 2011

Electrical properties of metal/GaAs system are known to be influenced very much by GaAs surface condition before the metal deposition. The surface condition of GaAs epitaxial layer can be affected by the wet chemical treatment of the surface. The influence of different processes were compared to choose the best technique for a high quality ohmic contact technology. Applying a chemical treatment which contains degreasing process, a light surface etching and a rinsing process, the carbon contaminations, 20-25 nm GaAs surface layer and the native oxide layer are removed from the GaAs surface. The benefit of the rinsing step is to produce a reproducible, stable surface condition before the metallization. Since the importance of the finishing step was assumed, the investigated processes differed in this step. The compared methods finished with either alkaline, like NH4OH, or acidic, like HCl, etchants resulted higher specific contact resistance than the process finished with neutral, high purity (18 MΩcm) water. In the latest case the obtained specific contact resistance was (6.4 ± 2.7) ×10−6 Ωcm2 on a GaAs epitaxial layer with the doping concentration 1.5 × 1017cm−3.
Parameters Affecting the Process Window for Laser Planarization of Aluminum.
Authors: Raaijmakers Ivo J , Chu Harren , Ong Edith , Wang Shi-Qing , Ritz Ken
Published: March 2011

Irradiation with excimer laser pulses is demonstrated as a technique to fill contact/via holes for integrated circuits with Al-(1 wt.%)Cu. We discussed the influence of the size, shape and aspect ratio of the contact hole, and the metal thickness on the process (attitude for laser planarization. The most dominant parameters found to influence the planariza-tion process are the shape of the contact, and the shape of the as-deposited metal surface (“step coverage”). The application of a Cu anti-reflection coating increased the process window substantially. Although a planar Al-Cu surface was easily formed with laser irradiation, void free filling of contact holes was a more demanding task. Conditions for which completely filled contacts can be obtained were discussed.
Interface Morphology, Nucleation and Island Formation of Tisi2 on Si(111).
Authors: Jeon Hyeongtag , Sukow C. A. , Honeycutt J. W. , Humphreys T. P. , Nemanich R. J. , Rozgonyi G. A.
Published: March 2011

In this study we investigate the formation mechanisms and morphology of TiSi2 formed by deposition of Ti on atomically clean silicon substrates. Ti films of 50–400 Å thickness were deposited in ultra-high vacuum on Si (111) wafers and annealed to temperatures between 500–900°C. Films were monitored in situ with AES and LEED, and post preparation characterization was accomplished with SEM, TEM and Raman scattering. The results show that for films of thickness ≤, 100 Å the C49 TiSi2 phase is stable over the entire 600-800°C temperature range. However, for films of 200-400 Å thickness, the C49 to C54 phase transition occurs at temperatures varying from 700 to 800°C dependent upon film thickness. The high temperature annealing results in flat interface structures, and island formation is observed for all films with the C54 structure. The interface morphology and the mechanisms of TiSi2 island and phase formation are discussed in terms of surface and bulk free energies considerations based on nucleation theory.
Structural and Substructural Analysis of Glass Surface
Authors: BochyŃskia Zenon
Published: March 2011

A structure of surface and near surface layers in inorganic glasses used as substrated in metallization was studied. The analysed samples were made of melted quartz, technical and optical quartz glass and sodium-silicate glass.

The sample surface were at first treated mechanically ground and polished and then chemically etched.

In the investigation we applied the following methods:

- X-ray and electron/mean voltages 35…65 kV/diffraction,

- electron emission microscopy,

- optical/UV-VIS/and infrared/IR/microspectrophotometry and microscopy.

For the studied series of quartz based/SiO2/glasses we determined the size of inhomogeneous. regions and the distortion degree of the elementary tetrahedra/basic structural elements/and estimated the thickness of surface and near-surfaoe layers.

The obtained structural parameters enabled us to propose structural models of the surface of real glasses uaed in elec-trotechnology, electronics and microelectronics.
Low Resistance α-Ta Film For Large Area Electronic Devices
Authors: Yamamoto Shigeru , Hikichi Takehito , Hamano Toshihisa
Published: March 2011

A New method of the low resistivity α-Ta deposition technique has been developed. The sputtered Ta film deposited on TaMo alloy has bcc structure (α-Ta) in contrast to tetragonal of the Ta mono layer (β-Ta), and shows the resistivity as low as 22μΩ cm. The mechanism of this transformation is not explained by simple epitaxial growth. X-ray diffraction analysis and RBS analysis indicated that the TaMo alloy layer, due to Mo diffusion from the under layer, acts as a seed plane of growth. The Ta/TaMo layered film is suitable for Large Area Electronic devices for its low resistivity.
Properties of Laser Planarized Aluminum Alloy Films
Authors: Ramaswami Seshadri , Smith Jonathan
Published: March 2011

An excimer laser (XeCl, 308 nm) has been used to locally melt and reflow aluminum alloy films into contacts of VLSI device structures resulting in contact filling and local planarization. This technique has the potential to be the answer to the ‘poof’ aluminum step coverage problem. The first order problems are that of ablation and voids. Voids have been categorised as ‘line voids’ and ‘contact voids’. Various processing conditions of the barrier, Al-Si-Cu alloy and Al-Cu alloy metallizations were explored to obtain the optimum process with the desired film characteristics.
Effects of Dwell Time and Current Density on Ion-Induced Deposition of Tungsten
Authors: Tran Khanh Q. , Madokoro Yuuichi , Ishitani Tohru , Yang Cary Y.
Published: March 2011

30-keV focused Ga+ ion beam was used for induced deposition of small-area tungsten thin films from W(CO)6 on Si and SiO2. Deposition yield, calculated assuming pure tungsten depositions, depends on dwell time (beam diameter/scan speed) and beam current density. High current density and/or long dwell time are known to cause low deposition yield because of the depletion of adsorbed gas molecules during ion beam irradiation. Based on a model taking this effect into account, numerical fitting was carried out. The reaction cross-section was estimated to be 1.4 × 10−14 cm2. For doses below 1017 ions/cm2, film resistivity decreases with increasing dose. This was confirmed for several dwell times. However, for doses above 1017 ions/cm2, film resistivity remains independent of dose. In this “high”-dose range, variation of beam current density has little effect on film resistivity. AES analyses revealed a consistency between film composition and resistivity. For a “high”-dose film with a resistivity of 190 μΩ-cm, the approximate tungsten content was 50 at%.
Low Temperature Tungsten Deposition by Arf-Laser Induced Photo-CVD
Authors: Krans Rutger L. , Berntsen Arjan , Sinke Wim C.
Published: March 2011

Laser-induced Chemical Vapor Deposition of tungsten on Si(100) using WF6 and H2 has been investigated using a high-vacuum system comprising a cold-wall reactor. The activation source is a pulsed ArF-excimer laser. The deposition rate depends linearly on the repetition rate, when H2 is used as a reducing agent. When no H2 is used the laser radiation suppresses deposition.

At deposition temperatures down to 200 °C laser deposited layers have resistivities better than 20 μΩ cm. Thick layers have resistivities down to 8 μΩ cm. There is a direct relation between layer thickness and resistivity. X-ray diffraction revealed the layers to consist of α-tungsten. β-tungsten was only obtained for those thermally deposited layers where growth was slower than expected.

Nuclear reaction analysis of fluorine showed that most fluorine is present near the W-Si interface, and that the amount of fluorine relative to the amount of tungsten in the layer decreases markedly with deposition temperature.
Modified Line-of-Sight Model for Deposition of Tungsten Silicide Barrier Layers
Authors: Cale Timothy S. , Raupp Gregory B.
Published: March 2011

A modified line-of-sight model for transport and deposition during LPCVD is used to predict step coverage and film composition uniformity of tungsten silicide barrier layers. Predictions are compared with experimental results for 2 μim wide by 6 μm deep trenches with barrier layers of 0.2 μm nominal thickness. Model predictions are in quantitative agreement with those of a diffusion-reaction model and are in qualitative agreement with experiment.
Deposition Mechanism of Tungsten Silicide Films by Low Pressure CVD
Authors: Sone Jae H. , Kim Hyeong J.
Published: March 2011

WSix thin films were deposited on SiO2/Si substrates by Low Pressure Chemical Vapor Deposition (LPCVD) using WF6 and SiH4 gases. The deposition mechanism has been studied by measuring the thickness, resistivity and composition of the films by varying deposition temperature and gas flow rate at a constant total reactant gas pressure. Below 300°C, the surface chemical reaction was the rate-limiting process and the deposition rate increased exponentially with temperature having a thermal activation energy of 3.2 kcal/mol. Meanwhile, above 300°C the reaction was governed by the mass transfer step in the gas. The deposition rate in this range is insensitive to the deposition temperature but shows dependence of the flow rate of reactant gases. AES and RBS analyses were performed to determine the stoichiometry of WSix thin film. The Si content in film gradually increased as the deposition temperature increased. The resistivity of as-deposited WSix film has dependence on both deposition temperature and Si/W ratio, and exponentially increased with a moderate slope. However, temperature insensitive behavior of resistivity appeared in the mass transfer controlled region. Such resistivity changes with temperature were discussed with the Si/W ratio and the microstructure of films.
Chemical Vapor Deposition of Copper from an Organometallic Source
Authors: Beach David B. , Kane William F. , Legoues Francoise K. , Knors Christopher J.
Published: March 2011

High purity copper has been deposited from trialkyl phosphine complexes of cyclopentadienyl and methylcyclopentadienyl copper(I) by thermal chemical vapor deposition (CVD). Films as thick as 4.4 μm have been deposited at growth rates of up to 2000 Å/min with resistivites typically 2.0 μΩ cm, just slightly higher than bulk copper. Depositions were carried out at substrate temperatures between 150 and 220 °C on a variety of substrates including Si, SiO2, polyimide, and Cr/Cu. At low substrate temperatures, copper film growth appears to show some selectivity for transition metal surfaces. An activation energy of 18 kcal/mole has been measured for film growth on Cu seeded substrates. CVD copper films have been characterized by Auger spectroscopy which showed that carbon and oxygen levels are below the limits of detection. Transmission electron microscopy revealed that the copper grain size was ∼0.6μm and the grain boundaries are free of precipitates. Films show good conformality.
In-Situ Transmission Electron Microscopy of the Formation of Metal-Semiconductor Contacts
Authors: Gibson J. M. , Loretto D. , Cherns D.
Published: March 2011

We have studied the formation of metal silicides in-situ in an ultra-high vacuum transmission electron microscope. Metals were deposited on in-situ cleaned, reconstructed silicon surfaces and annealed. For the metals Ni and Co, we find that the phase sequence in ultra-thin films is different from that seen in ≈1000 Å thick films, and attribute this to the high surface-to-volume ratio. In general reactions occur at room temperature, to form an epitaxial phase if possible. We report preliminary new results on the formation of Pd2Si.