bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxide Mediated Epitaxy on Planar and Non-Planar Si
Authors: Tung R. T. , Howard D. J. , Ohmi S. , Caymax M. , Maex K. 
Published: April 2011

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

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

ABSTRACTOwing to their large band gaps and high dielectric constants, III-V nitrides are very attractive for high temperature electronics and optoelectronic device applications. Improved material properties have recently led to a variety of devices being demonstrated such as blue, green, and yellow light-emitting devices as well as laser diodes, metal-semiconductor GaN based fieldeffect transistors (MESFETs), and AlGaN/GaN based high electron mobility transistors (HEMTs). The presence of parasitic resistance can significantly limit performance such as lower speed for electronic devices and higher turn-on voltage for the optical devices. There is room for improvements for both n- and p- type ohmic contacts in order to lower parasitic resistance and improve reliability. W based contacts on GaN and InGaN have been demonstrated and show excellent thermal stability, however the contact resistivity still in the range of 10−5 Ω-cm2. By using InN and graded InGaN as the contact layers, the contact resistivity can be reduced to ∼ 10−6 Ω -cm2.Besides low resistance ohmic contacts, a low leakage current and high turn-on voltage gate contact is critical to high performance electronic devices. Nitride based materials are very inert to conventional wet chemical etching used for other III-V compound semiconductors. Currently, dry etching is widely used for the device fabrication, however, III-nitrides are sensitive to dry etching, especially in the step of the gate recess etching. In this talk, metal insulator semiconductor (MIS) gate contacts based on AIN and Ga2O3/Gd2O3 will be discussed.
In-Situ Regrowthi of GaAs Through Controlled Phase Transformations and Reactions of Thin Films on GaAs
Authors: Caldwell D. A. , Chen L.-C. , Bensaoula A. H. , Farrer J. K. , Carter C. B. , Palmstrøm C. J. 
Published: April 2011

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

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

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

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

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

ABSTRACTThe Cu metallization in future VLSI technology requires a liner or diffusion barrier. We have studied TaN thin Films of thickness from 5 nm to 3 nm as the diffusion barrier. We deposited sandwiched TaN/Cu/TaN thin films on oxidized Si wafers, annealed them in air with ramping temperature, and measured in-situ resistance changes. Scanning and transmission electron microscopes were used to characterize the surface and microstructure of the thin films and Rutherford backscattering spectrometer (RBS) was used to profile the elemental composition and after oxidation. The oxidation of the Cu sandwiched between TaN films of 5, 10, 20, and 30 nm occurs at 300, 400, 450 and 475°C, respectively. The activation energy of oxidation of Cu with the TaN barrier of 10, 20, and 30 nm are 1.73, 2.13, and 2.26 eV, respectively, but the 5 nm TaN was not calculated due to large data scattering. For comparison, the oxidation temperature and activation energy for bare Cu films in air are 250°C and 0.74 eV, respectively. It suggests that 20 nm of TaN is quite effective as a barrier layer. However, the reaction between Cu and the underlying SiO2/Si layers was also detected in RBS; this may arise as another serious reliability criterion to the system.
Interfacial reactions in multilayers intended for microelectronics devices
Authors: Federspiel X. , Voiron F. , Ignat M. , Marieb T. , Fujimoto H. 
Published: April 2011

ABSTRACTThe knowledge of the reaction kinetics which can occur at an interface of a couple of materials, remains a crucial issue to establish the structural limits of a diffusion barrier intended for microelectronic structures.In the past years, the interfacial reactions activated at an interface of a couple of materials, as for example aluminum and titanium, have been analyzed extensively using different experimental tools, as for example: Ruthreford Back Scattering (thickness determination) and Differential Scanning Calorimetry (DSC). Then, these experimental methods were useful to deduce parameters, characterizing the interfacial reactions in bulk samples: apparent activation energies, enthalpy of formation. Because in thin films, the kinetics of the reactions that can be activated at an interface will be different; we studied interfacial reactions in submicronic Al/Ti layers.Taking advantage of the accuracy of the DSC (reaction rate determinations and detection of earlier stages of intermetallic phase formation), our experimental approach consisted in a series of isothermal and non-isothermal DSC experiments on submicron Al/Ti layered structures. From the reaction rate determination, analytical methods as the Kissinger Ozawa approach were used, to determine the apparent activation energies of the phase formation. Also the results allowed to model and discuss the first steps of the interfacial reaction.
Sub-Quarter Micron Metallization Using Ionized Metal Plasma Technology
Authors: Chen Fusen , Xu Zheng , Sinha Ashok 
Published: April 2011

ABSTRACTIonized Metal Plasma (IMP) technology has been developed for liners and wetting layer deposition of sub-quarter-micron devices. Numerical modeling showed the unique advantages of IMP source over ECR source and long throw sputtering in enhancing bottom coverage. Ti and TiN bottom coverage up to 70% were demonstrated on 0.18μm contact holes. The deposition rate, uniformity, bottom coverage and film stress were optimized by tuning RF and DC powers, process pressure and bias power. In situ TiSi2 were formed in high aspect ratio contacts by depositing IMP Ti at an elevated temperature. The precisely controlled microstructure of IMP TiN film enabled low temperature aluminum planarization. The extendibility to 0.13μm technology node was demonstrated, and the application in copper metallization was revealed.
Effect of Ar Sputtering Pretreatment on the Electromigration Resistance in Al-Cu/TiN/Ti Interconnects
Authors: Wang L.P. , Chuang A. , Lin L.T. , Huang F.S. , Perng K. , Hwang J. 
Published: April 2011

AbstractThe 1 µm-wide Al-0.5wt%Cu/TiN/Ti interconnect, on the oxidized Si(100) wafer without Al sputtering pretreatment on the SiO2 surface prior to Ti deposition, failed after stressing with a current density of 1 × 106 A/cm2 for 190 hr at 175°C. In contrast, the interconnect with Ar sputtering pretreatment did not fail after stressing under the same condition for 550 hr. X-ray diffraction spectra indicated that the Ar sputtering pretreatment lowered Al(111) peak intensity down to 1/46 of its magnitude. This result suggests that the improvement of electromigration resistance by Ar sputtering pretreatment is not due to Al(111) texture, which is opposite to the result of Shibata et al. (Jpn. J. Appl. 32, 4479 (1993)). The elemental concentration distribution in depth was characterized on Al-Cu/TiN/Ti multilayers with and without Ar sputtering pretreatment by using secondary ion mass spectroscopy and Auger electron microscopy. A fairly large amount of oxygen and nitrogen was found to segregate near the Al-Cu/TiN interface. The phenomenon associated with the large amount of segregated oxygen and nitrogen is attributed to the enhancement of electromigration resistance.
Defect Generation and Diffusion Mechanisms in Al and Al-Cu
Authors: Liu C. - L. , Liu X.-Y. , Borucki L. J. 
Published: April 2011

AbstractWe describe a newly-developed defect generation mechanism, namely the grain boundary Frenkel pair (GBFP) model, and corresponding diffusion mechanisms during electromigration developed using atomic molecular statics (MS), Monte Carlo (MC), and molecular dynamics (MD) simulation techniques in Al and Al-Cu. We contend that large numbers of interstitials and vacancies exist at grain boundaries and both contribute to mass transport. Cu preferentially segregates to the interstitial sites at grain boundaries via a Frenkel pair generation process and reduces the overall grain boundary diffusivity due to the strong binding in the Al-Cu dimer. Predictions from our models are in excellent agreement with available experimental data and observations.
Stress- and Electromigration-Induced Voiding and Its Correlation to Macroscopic Stress Changes
Authors: Schroeder Herbert 
Published: April 2011

AbstractThis paper reviews experimental data on stress- and electromigration (EM)-induced voiding in passivated Al- and AlSiCu-lines under different experimental conditions (thermal cycling, iso-thermal annealing without and with EM-current). The data are deduced from measured changes of average metal strain or stress and from in-situ observations in a transmission electron microscope. There are excellent correlations between corresponding data sets showing stress induced voiding during cycling and isothermal annealing without EM-current, but nearly no changes in stresses or void volume during EM-testing. The implications of these results on EM-modelling are discussed.
The Effects of Passivation Thickness and Initial Aluminum Line Stress on Electromigration Behavior
Authors: Lee Samantha , Bravman John C. , Flinn Paul A. , Marieb Tom N. 
Published: April 2011

AbstractThe electromigration behavior of pure Al lines passivated with oxides of different thicknesses and passivation deposition temperatures was studied. The initial hydrostatic stress states of the passivated Al lines were modeled with finite element modeling (FEM), and, when possible, measured with X-ray diffraction. Conventional wafer-level electromigration tests showed a clear passivation thickness effect, but no detectable effect of initial stress on electromigration lifetimes. Increasing the passivation thickness increased the electromigration lifetimes, which has been observed by other researchers. However, in a sample set where the Al lines were covered with a thin (0. 1µm) oxide layer, the lifetimes were much longer than expected. Differences in the damage morphology and the failure mechanism between the thin and thicker oxides accounted for this unexpected result.
Copper Versus Magnesium as an Alloying Element in Aluminum Interconnects: Effects on Electromigration
Authors: Spolenak R. , Mason J. , Kraft O. , Arzt E. 
Published: April 2011

AbstractIt is well known that the addition of Cu improves the electromigration resistance of Al conductor lines. However, the underlying mechanisms are not entirely understood. As Mg has also been found to have a beneficial effect, a thorough comparison between these two alloying elements may result in new insights. In this work, we present results of drift velocity experiments on Al-2wt%Cu and A1-3wt%Mg, where the edge drift was measured in-situ as a function of temperature. Additionally, the concentration profile of either alloying element was measured as a function of testing time using an electron probe micro-analysis technique. For both alloys an incubation time for stripe drift was observed. The activation energies of edge drift after this depletion were determined to be 0.83 eV and 1.01 eV for Al-Cu and Al-Mg, respectively. Both activation energies seem to agree with the activation energy of electromigration of the alloying element rather than the activation energy of drift in pure Al, which was determined separately to be 0.5 eV.
Effect of Poly-Si on Electromigration Behaviors and Microstructure Characteristics of Au Metallization
Authors: Lee T. , York B.R. , Lindgren B. , Kentzinger H. , Lee J. , Christenson C. , Varker C. , Evans K. 
Published: April 2011

AbstractFor BJT and MOSFET, poly-Si is the most critical layer used as an emitter to improve the current gain in BJT and as a gate to improve the gate oxide reliability in MOSFET. In both cases, the poly-Si is then connected to the conductor. It is very important to understand how poly-Si affects the microstructure and the electromigration behavior of conductor. NIST test structures (length = 800μ, thickness = 0.7μ, widths = 1, 5, 10 μ) with Au conductor and TiW/TiWN/TiW barrier were used to study the impact of poly-Si. Two groups of samples were used: one with poly-Si under the barrier and the other without poly-Si. Thermal oxide was used to isolate the substrate from the conductor and Si3N4, was used as passivation. DC stress was performed at 175, 200, and 225°C. Microbeam X-ray Diffraction (μ XRD) was used to characterize the microstructure of the TiW barrier and Au metallization layers as a function of line length and width. The data indicates that samples with poly-Si have lower electromigration resistance for Au conductors for all widths and temperatures, with higher initial deformation fault densities on poly-Si.
Cracking and Debonding in Integrated Microstructures
Authors: Liu X.H. , Suo Z. , Ma Q. , Fujimoto H. 
Published: April 2011

AbstractInternal stresses inevitably arise in integrated microstructures. This paper reviews a fracture mechanics approach to devising design rules to avert cracking. The smallness of the feature size permits a strategy different from that conventionally used to analyze the fracture of bulk materials. In an integrated microstructure, high tensile stress is localized in small regions. The elastic energy stored in each region scales with its volume. The surface energy associated with the creation of a crack scales with the surface area of the crack. Thermodynamics dictates that a flaw cannot grow if the stored elastic energy is lower than the created surface energy. Consequently, for a sufficiently small feature size, the volume-to-area ratio is small, and no flaw can grow. Our design rules do not depend on flaw size. They are deterministic, and rely on well-specified geometric and physical parameters. Furthermore, the stress singularity at corners does not cause any particular difficulty. As an example, the thermal misfit cracking in a multilevel interconnect test structure is investigated.
Quantitative Measure of EM-Induced Drift in Sub-Micron Al Lines
Authors: Witt C. , Volkert C.A. 
Published: April 2011

AbstractElectromigration-induced drift in sub-micron wide Al segments has been measured using energy dispersive x-ray analysis in a scanning electron microscope. This technique, which works on both passivated and unpassivated samples, is sensitive to uniform Al displacements as small as 100 nm. The samples were 0.3 and 0.5 µm wide runners consisting of a continuous Ti/TiN line on top of which were patterned 0.4µm thick Al (0.5wt% Cu) segments of lengths varying between 5 and 100 µm. The microstructure, as determined by focused ion beam imaging, was predominantly bamboo. We have measured the Al depletion at the cathode ends of these segments after stressing for various times at 2 MA/cm2 at 200'C. For segments shorter than roughly 15 µm, no depletion occurred during the entire 100 hours of the experiment, yielding a value of the current-length threshold product of roughly 3000 A/cm, in agreement with previously published data. Longer segments (20-25 µm) depleted at a roughly constant rate for the duration of the experiment, yielding a drift velocity of around 3 nm/hr in the 0.5 µm wide lines, also in good agreement with published data for near-bamboo lines. However, the 0.3 µm wide lines drifted faster at roughly 6.5 nm/hr. The longest segments (50-100 µm), which started drifting at the same rate as the shorter segments, accelerated after 50 hours of testing to drift velocities in excess of 40 nm/hr. This may be associated with the depletion of Cu from the drifting end.