bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Solid State Phase Transformation from Co to Epitaxial CoSi2 in Co / Thin Ti / (100) Si Structure and its Application for Shallow Junction Formation
Authors: Ogawa Shinichi , Fair James A. , Kouzaki Takashi , Sinclair Robert , Jones Erin C. , Cheung Nathan W. , Fraser David B. 
Published: September 2012

ABSTRACTDirect epitaxial CoSi2 formation from Co, which is contrary to the reported silicidation process : Co→Co2 Si→CoSi→CoSi2, has been found during anneal of Co / Ti / (100) Si system. 2 nm thick Ti and 15 nm thick Co films were sputter deposited, and then annealed for 30 min at temperatures between 375°C and 900°C. At room temperature, the 2 nrm Ti immediately forms an amorphous Ti-Si-Co layer between the Co and Si. Epitaxial CoSi2 begins to form at 400°C, while the amorphous layer continues to act as both a Co diffusion retardant and Si diffusion suppressant even at 900°C. This retarded diffusion of Co reduces the growth rate of the CoSi2 over the entire temperature range studied. Superiority of the epitaxial to polycrystalline silicide has been demonstrated. In self aligned structures, an epitaxial CoSi2 film is formed by a single-step anneal without any overgrowth onto adjacent field oxide areas utilizing the amorphous diffusion controlling layer. A p+/n junction of 40 nm depth with reduced leakage and low ideality factor has been obtained by impurity diffusion from epitaxial CoSi2.
Kinetics and Mechanism of the C49 to C54 Titanium Disilicide Polymorphic Transformation
Authors: Ma Z. , Ramanath G. , Allen L.H. 
Published: September 2012

ABSTRACTThe kinetics and mechanism of the C49 to C54 TiSi2 polymorphic transformation have been investigated in a temperature range from 660 to 720°C using in situ sheet resistance measurement and transmission electron microscopy. The kinetics results were correlated with the microstructural changes during the phase transformation. The main structural characteristics demonstrating the mechanism of the transformation were established by examining the nucleation and growth of the C54-TiSi2 in the polycrystalline C49-TiSi2 thin films. It was found that the C54 nuclei predominantly formed at grain edges (three-grain junctions) of the C49 phase and grew very fast by moving its incoherent interphase boundaries. Preliminary results have not revealed rigorous orientation relationships between the two phases. It is suggested that the C49 to C54 structural transition is massive in nature.
Local Structural Studies of TiSi2 and ZrSi2 Thin Films on Si(111) Surfaces
Authors: Dao Y. , Edwards A.M. , Sayers D.E. , Nemanich R.J. 
Published: September 2012

ABSTRACTThis study explores the local structures of TiSi2 and ZrSi2 films on Si. The strain effect on the surface morphologies and phase stability of the films is investigated. Titanium silicide and zirconium silicide films were fabricated on atomically clean Si(111) substrates in UHV using electron gun evaporation followed by in situ annealing. A quantitative X-ray absorption spectroscopy analysis was performed to study the formation of epitaxial TiSi2 and ZrSi2 films on the Si surfaces, as well as the phase transition of TiSi2 from the metastable C49 structure to the stable C54 structure. The surface morphologies and the surface roughness of the films were studied using atomic force microscopy (AFM). The strains of these films were determined by comparing the calculated bond lengths with the measured bond lengths using the extended X-ray absorption fine structure (EXAFS) technique. The final stable C54 structure of TiSi2 has less strain than the initially formed metastable C49 phase. While the surface and interface free energies and the bulk free energy are critical to the structural formations and phase changes of the films, the energy associated with the lattice strain is another important factor.
Interactions of Cu with PtSi and TiSi2 with and without Como Barrier Layers
Authors: Hong Stella Q. , Mayer J. W. 
Published: September 2012

ABSTRACTInteractions of Cu with PtSi and TiSi2 films grown on Si (100) substrates have been studied in the temperature range of 250-500°C with Rutherfold backscattering spectrometry, Auger electron spectrometry, and x-ray diffraction. Upon annealing Cu migrates across the intermediate PtSi or TiSi2 layers and reacts with Si substrates to form Cu silicides. Unlike what were reported in the literature, no indications of the reaction of Cu with PtSi or TiSi2 have been observed. Both PtSi and TiSi2 retain their original thicknesses and compositions during Cu penetration. The structural integrity of the metal suicides in contact with Cu films is attributed to low formation energies of Cu-silicides. A 50-nm thick amorphous CoMo barrier impedes Cu diffusion up to 550°C, but fails as a diffusion barrier at higher temperatures due to CoMo-Si reaction.
Thermal Stability Study on Cu/Tin/TiSi2/Si
Authors: Chang Tzong-Sheng , Wang Wen-Chun , Wang Lih-Ping , Hwang Jenn-Chang , Huang Fon-Shan 
Published: September 2012

ABSTRACTWe have investigated TiN/TiSi2 films as diffusion barriers between copper and silicon. The TiN/TiSi2 films were formed by annealing Ti/Si via rapid thermal process at a temperature of 850'C for 30 seconds in N2 ambient. The contact resistance and leakage current of the Cu/TiN/TiSi 2/n+-p Si contact system were measured after sintering at 350-600°C for 30 minutes in an N2 ambient. We found an abrupt increase of contact resistance occurred at a sintering temperature of 600°C. From the leakage current of n+-p diode, we observed that the thermally stable temperature was about 475ycC. Meanwhile, XTEM photographs showed small Cu3Si crystallites with size of about 0.25 μm precipitated in the n+Si substrate at a sintering temperature 500°C. The formation of Cu3Si increases the occupied volume, generates the gap between TiSi2 and n+Si, and gradually increases the specific contact resistance. SIMS profiles also showed that a certain amount of Cu atoms diffused into the n+-p Si junction and that Si atoms existed in the Cu film. The Cu3Si formation across the n+-p junction can explain the abrupt increase in the leakage current measurement at 500°C. So the failure mechanisms for contact resistance and leakage current are different.
Phase Formations in Co/Si, Co/Ge, and Co/Si1−xGex by Solid Phase Reactions
Authors: Wang Z. , Chen Y. L. , Ying H. , Nemanich R. J. , Sayers D. E. 
Published: September 2012

ABSTRACTPhase formations in Co thin films (200Å in thickness) reacting with atomically clean Si(100), Ge(100), and Si0.80Ge0.20 epitaxial layer (800Å in thickness on Si(100) substrates) in UHV have been investigated. For the Co/Si system, it is found that CoSi (FeSi structure) is formed at 375°C through a very disordered CoSi phase, and the final CoSi2 phase is formed at 575°C. On the other hand, the Co5Ge7 phase was identified for the Co/Ge samples annealed at 300°C and 450°C and the final CoGe2 phase is formed at 600°C. For the Co/Si0.8 Ge0.20 samples annealed from 400°C to 600°C, Co(Si1−yGey) phases with y∼0.10 were detected, and for annealing at 700°C, only the CoSi2 phase was formed. These results indicate a preferential Co- Si reaction when annealing the Co/SiGe structure. It was also found that the sheet resistance of the reacted thin films depend strongly on annealing temperature.
Laser Induced Epitaxial CoSi2 Formation
Authors: Comrie C.M. , Hoffman V. 
Published: September 2012

ABSTRACTWhile it is possible to grow epitaxial CoSi2 films of a high quality using UHV technology it is much more difficult to produce films of similar quality under high vacuum and non-“clean room” conditions. Tung et al.1 have however shown that films of a good quality can be produced under these poorer conditions with the aid of a laser anneal of an appropriate power followed by a short thermal anneal. In this paper the role of the laser anneal, and of the (post laser) thermal anneal, in the production of epitaxial films is examined. It appears that the principle role of the laser anneal is to induce the epitaxial CoSi2 formation at the silicon / silicide interface, and that this epitaxial layer then acts as a seed for epitaxial film growth during the subsequent thermal anneal.
Multilevel Contact System with a Thin Silicide Reaction Controlling Interlayer
Authors: Fenske F. , Schulze S. , Selle B. , Lange H. , Wolke W. 
Published: September 2012

ABSTRACTTaking advantage of controllable interdiffusion and reaction processes by using a 50 nm thin Ti interlayer an annealing step in the temperature range from 450 to 475°C transforms the TiNiAg layer sequence on silicon into a stable final state, whereby a contamination free, homogeneous nanoscale NiSi contact layer arises with low values of the contact resistance. Intercalating a thin Ti layer the nickel silicide growth rate is lowered by 2 orders of magnitude. Low sheet resistance and a good bondability are preserved by the remaining Ni-Ag top layer sequence which does not interact during the contact formation process.
Silicon-Silicide Eutectic Composites
Authors: Ditchek Brian M. , Nguyen Quang V. , Rossoni Philip G. 
Published: September 2012

ABSTRACTMany silicides, including TaSi2, CoSi2, TiSi2and others, form eutectics with silicon. Directional solidification of melts with the eutectic composition and controlled doping of the silicon matrix results in two-phase electronic composites with oriented structures. Such composites have unusual microstructures and interesting properties resulting from the high density of Schottky junctions. In this paper, the growth, microstructure, transport properties and device applications of silicon-silicide composites are reviewed, concentrating mostly on the benchmark Si-TaSi2system. The Si-TaSi2interface, formed upon solidification, is characterized electrically as well as structurally by electron-beam induced current techniques, x-ray diffraction and high resolution TEM. It is shown that the interface is of remarkably good quality allowing the fabrication of very high quantum efficiency (80%) photodiodes and high voltage (up to 6kV) transistors.
Silicided P-N Junction Diodes Fabricated by Silicidation through Silicon Buffer Layer and Dopant Drive-Out Process
Authors: Chen W. M. , Lee J. C. , Frost M.R. 
Published: September 2012

ABSTRACTThis study investigates characteristics of p-n junction diodes fabricated by silicidation through a silicon buffer layer and dopant drive-out process. The purpose of using the buffer silicon layer is to reduce silicon consumption from the Si substrate during silicidation, and thus reduce the effective junction depth. The resulting structure is suitable for elevated CoSi2 source/drain contact in a metal-oxide-semiconductor field effect transistor or a silicided polysilicon emitter in a bipolar junction transistor. It was found that boron diffusion is enhanced by these buffer layers comparing to silicided diodes without silicon buffer layers. The sheet resistance of the CoSi2/polysilicon/Si structure does not degrade as seriously as CoSi2/polysilicon/oxide structure. The diode leakage current density is higher compared to diodes without buffer layers, especially when thinner buffer layers and high temperature 1000°C anneal are used.
Electrical Conductivity of Silicides
Authors: Ottaviani G. , Nava F. 
Published: September 2012

ABSTRACTElectrical transport properties of thin film and single crystal silicides will be reviewed and discussed. The presentation will be made by considering that most of the compounds behave as metals, with the resistivity which increases with the temperature, and few of them are semiconductors. Semiconductor silicides have band-gaps which span between 0.1 and 1.2 eV for ReSi2 and IrSil.75, respectively. Several metallic silicides show, expecially in the high-temperature limit, a resistivity-temperature dependence different from the classical linearity. The deviation, related to the intrinsic properties of the compound, can be affected by the presence of structural defects and impurities. The role played of such defects on the residual resistivity at low temperature will also be considered. Anisotropic effects will be discussed in relation with the shape of the Fermi surfaces.
Tunable Infrared Detection Using Epitaxial Silicide/Silicon Heterostructures
Authors: Sagnes I. , Campidelli Y. , Chevalier F. , Bodnar S. , Renard C. , Badoz P. A. 
Published: September 2012

ABSTRACTA new silicide/silicon IR detector is presented which has the potential for multicolour detection due to the tunability of its photoresponse. This tunable internal photoemission sensor (TIPS) fabricated using the Ir/Si/ErSi2 system, consists of two back–to–back Schottky diodes separated by a thin undoped Si layer. The two metals have different Schottky barrier heights so that the depleted Si forms an asymmetrical potential barrier to the carriers photocreated in each metallic film. The photocurrent flowing between the two metallic films is therefore strongly dependent on the shape and height of the effective potential barrier that can be varied by a bias applied between the two metallic electrodes. The Ir/Si/ErSi2 photoresponse and cut–off wavelength are indeed dramatically modulated when a small bias (less than 1 volt) is applied between the Ir and ErSi2 electrodes. The quantum efficiencies, measured in the 1 to 3 μm range, are comparable to the best obtained in Schottky and SiGe/Si internal photoemission detectors. A quantitative model derived from the Fowler formalism (by taking into account (i) the hole and electron photocurrents and (ii) the wavelength dependence of the photon absorption in each metallic film) fits all the experimental data over the whole range of photon energy and applied biases. The effective barrier heights thus measured as a function of applied bias are in good agreement with those deduced from activation energy analysis of the TIPS dark current and show that the cut–off wavelength can be modulated from 2.5 μm to more than 6 μm. Finally, electrical and photoresponse measurements on Cr/Si/SiGe(p+) structures (using the same TIPS mode of operation) also demonstrate the photoresponse tunability, thus combining the TIPS tunability with the extended wavelength range of operation (up to 10 μm) of SiGe/Si detectors.
Formation of β-and α-FeSi2 Films on (100) Silicon using Fe-Si and Fe-Ti-Si Diffusion Couples
Authors: Larsen K. Kyllesbech , Lauwers A. , Maex K. , Van Rossum M. 
Published: September 2012

ABSTRACTAn investigation of the influence of an intermediate titanium thin film on the silicidation reaction between an overlying iron film and the (100)-oriented silicon substrate is presented. The Fe-Ti bilayers were obtained by consecutive sputtering of a Ti layer and an Fe layer on Si substrates. In addition, single iron layers were made by sputtering for comparison with the bilayers. By subsequent rapid-thermnal processing (RTP), depending on the annealing conditions, both the semiconducting β- and the metallic α-FeSi2 thin films could be formed. The phase formation has been investigated as a function of the thickness of the titanium layer, the annealing time and temperature. In this paper the first results on iron disilicide formation through Fe-Ti-Si diffusion couples are shown. Characterisation of the FeSi2 layers using Rutherford backscattering spectrometry (RBS), channelling RBS, X-ray diffraction (XRD), sheet resistivity measurements will be presented.
Thermodynamic and Experimental Study of β-FeSi2 Lpcvd
Authors: Morand Y. , Blanquet E. , Bourhila N. , Thomas N. , Bernard C. , Madar R. , Enseeg L.T.P.C.M. 
Published: September 2012

ABSTRACTThin films of semiconducting iron sulicide β-FeSi2 have been synthetized by Low Pressure Chemical Vapor Deposition in a cold wall reactor, starting from iron chloride and silane. Optimum experimental conditions for both iron chlorination and iron disilicide deposition have been determined by classical thermodynamic calculations. Despite the narrow range of as predicted deposition parameters, it has been possible to obtain mirror like thin films of pure polycrystalline β-FeSi2 on SiO2 substrate. The structural characteristics of the as deposited layers observed by SEM, ABS and RBS are presented together with their electronic properties.
Discrimination of Surface Textures Using Fractal Methods
Authors: Card Jill P. , Hyde J. M. , Giversen T. 
Published: September 2012

AbstractThis paper investigates the use of fractal metrics for discrimination of copper surface textures. Measurements of copper surfaces, using contacting profilometry, provided the raw data for the fractal analysis. The samples tested included copper foil samples and a copper lead frame, typical of those in use in plastic electronic packages. The fractal Hausdorf dimension and upper/lower ranges of fractal scale are analyzed by the coastline method and compared using Bonferroni multiple confidence limits. Metrics show significant differences between sample couplets, indicating significant precision in the fractal approach to adequately quantify surface texture qualities.
Microstructural Fractal Dimension of AISI 316L Steel
Authors: Hinojosa M. , Rodréguez R. , Ortiz U. 
Published: September 2012

AbstractFractal dimension of the microstructure of AISI 316L steel (17 Cr, 12.7 Ni, 2.1 Mo, 1. 5 Mn, 0.01 C) with different degrees of strain were obtained from Richardson plots of grain boundary perimeter against magnification. Grain boundaries were revealed using conventional metallographic techniques and measurements were taken with the aid of an automatic image analizer (Quantimet 520) attached to an optical microscope. The magnifications used were 50, 100, 200, 400, and 1000X. The samples were obtained from a 4” diameter tubing, machined according to ASTM A370 standard test method and deformed to 5, 10, 15, and 20 % tensile strain. The results show that the fractal dimension of the grain boundaries changes as deformation is imparted to the material.These results suggest that fractal dimension may be used to describe microstructural evolution of metals during deformation processes.
The Influence of Crystallographic Orientation of the Crack Plane and Crack Front on the Fracture of Tungsten Single Crystals
Authors: Glebovsky V. , Fishmeister H. , Riedle J. , Semenov V. , Gumbsch P. 
Published: September 2012

AbstractFor fracture studies on oriented W monocrystalline specimens it is necessary to produce very sharp, stopped precracks, which presents difficulties in the case of W. The experimental procedure and technique to produce precracks is described. The fracture experiments gave strong indications for a preference of the {100} plane as cleavage plane. It was found that the {110} planes successfully resist crack propagation, although they are the planes with the lowest surface energy. The appearance of the {121} plane as a cleavage plane in our experiments makes further studies with oriented W monocrystalline samples necessary.
Critical Cluster Size: Island Morphology and Size Distribution in Submonolayer Epitaxial Growth
Authors: Amar Jacques G. , Family Fereydoon 
Published: September 2012

AbstractThe island-size distribution scaling function fi (u) corresponding to submonolayer epitaxial growth with critical island size i is studied via kinetic Monte Carlo simulations for i = 0, 1, 2, and 3. An analytic form for fi (u) based on a conjecture for the small-u behavior is also presented. For i = 1, the scaled island-size distribution is found to depend on island morphology. In particular, for fractal islands with i = 1 there is excellent agreement with our analytical form as well as with experiments on low temperature Fe/Fe(100) deposition. However, for compact islands with i = 1, the scaled distribution is found to deviate slightly at small u. We also find excellent agreement between our analytical form, simulations, and experiment for i =- 2 and i = 3. Good agreement between our simulation results for i = 0 and recent experiments on Fe/Cu(100) deposition is also found. Results for the scaling of the island-density as well as crossover scaling forms for the transition from i = 1 to i = 2 and from i = 1 to i = 3 are also presented and used to determine the one-bond activation energy and critical island size transition temperature for Fe/Fe(100). The morphology of fractal islands for i = 2 is also studied and compared with experiments on Au/Ru(0001).
Formation of Self-Affine Surface During the Growth of Nickel Thin Films
Authors: Rao M.V.H. , Srinivas V. , Mathur B.K. , Chopra K.L. 
Published: September 2012

AbstractThin films of nickel deposited on various substrates have been investigated by using an STM. Topographic data recorded at different stages of the film growth reveal that the surface structure at one location of the film resemble that at another location of the same film. The repetitive structures are made up of a few coalescing clusters and forming exactly similar looking islands. As the film thickness increases, the shape and size of these repetitive patterns changes but the self-affinity of the surface structure is maintained.
Non-Linear Response of Self-Similar Electrodes and Active Membranes
Authors: Sapoval B. 
Published: September 2012

AbstractWe describe a simple way to compute the response of an irregular resistive interface to a Laplacian field in d=2. It permits to find the linear response of electrodes with an arbitrary geometry from the image only of the electrode. It also allows to compute the non-linear response of self similar electrodes. This method applies in principle to arbitrary irregular geometry in d=2 and it permits to predict generally that the slope of the Tafel plot is divided by the fractal dimension. These results may be transposed to the calculation of the steady state diffusion flux across an active self-similar membrane.
Step-Edge Barriers, Re-Entrant Oscillations, and Unstable Epitaxial Growth
Authors: Vvedensky Dimitri D. , Šmilauer Pavel 
Published: September 2012

AbstractThe influence of step-edge barriers that inhibit the interlayer transport of atoms is discussed in the context of several material systems by using simulations of a solid-on-solid model. We show how the combined effect of this step-edge barrier and a non-thermal short-range incorporation process of freshly-deposited atoms can be used to explain several epitaxial phenomena on metal and semiconductor surfaces: (i) re-entrant oscillations seen with He-atom scattering and high-resolution low-energy electron diffraction during Pt(111) homoepitaxy, (ii) instabilities during growth on GaAs(001) and several metal (001) and (111) surfaces in the form of multilayer features that dynamically coarsen, while maintining their shape, and (iii) re-entrant oscillations during etching of GaAs(001). In (iii), the incorporation is replaced by a short-range search for the atom to be removed.
When Interface Gets Rough…
Authors: Lu Toh-Ming , Yang Hong-Ning , Wang Gwo-Ching 
Published: September 2012

AbstractInterface roughness is one of the central features in many important thin film technologies. Roughness is a result of far from equilibrium dynamic growth process and is difficult to describe using conventional statistical mechanics. Recently a dynamic scaling hypothesis has been proposed to describe such a system in which both time and space scaling are considered simultaneously. This approach has generated tremendous interest, both theoretical and experimental, for scientists working in thin film growth/etching as well as many diverse fields. In this paper we shall discuss the origin of the formation of interface roughness, the difference between near equilibrium and far from equilibrium growth problems, the relevant parameters that are necessary to describe a rough interface, and the application of the self-affine scaling concept in growth problems. The experimental approaches to study rough interfaces and growth fronts using diffraction will be summarized. It is shown that there exist two types of dynamic scaling during growth, one with a stationary local slope and another one with a nonstationary local slope. Future directions in this new area of research are highlighted.