bluuebunny/crossref_metadata_2025_split huggingface dataset:
Classification of the Modes of Dissociation in Immiscible Cu-Alloy Thin Films
Authors: Barmak K. , Lucadamo G. A. , Cabral C. , Lavoie C. , Harper J. M. E. 
Published: April 2011

AbstractWe have found the dissociation behavior of immiscible Cu-alloy thin films to fall into three broad categories that correlate most closely with the form of the Cu-rich end of the binary alloy phase diagrams. The motivation for these studies was to use the energy released by the dissociation of an immiscible alloy, in addition to other driving forces commonly found in thin films and lines, to promote grain growth and texture evolution. In this work, the dissociation behavior of eight dilute (3.3 ± 0.5 at% solute) binary Cu-systems was investigated, with five alloying elements selected from group VB and VIB, two from group VillA, and one from group 1B. These alloying elements are respectively V, Nb, Ta, Cr, Mo, Fe, Ru and Ag. Several experimental techniques, including in situ resistance and stress measurements as well as in situ synchrotron x-ray diffraction, were used to follow the progress of solute precipitation in approximately 500 nm thick films. In addition, transmission electron microscopy was used to investigate the evolution of microstructure of Cu(Ta) and Cu(Ag). For all eight alloys, dissociation occurred upon heating, with the rejection of solute and evolution of microstructure and texture often occurring in multiple steps that range over several hundred degrees between approximately 100 and 900°C. However, in most cases, substantial reduction in resistivity of the films took place at temperatures of interest to metallization schemes, namely below 400°C.
Electroplated Cu Recrystallization in Damascene Structures at Elevated Temperatures
Authors: Jiang Qing-Tang , Thomas Michael E. , Bersuker Gennadi , Foran Brendan , Mikkola Robert , Carpenter Brad , Ormando John 
Published: April 2011

AbstractTransformations in electroplated Cu films from a fine to course grain crystal structure (average grain sizes went from ∼0.1 µm to several microns) were observed to strongly depend on film thickness and geometry. Thinner films underwent much slower transformations than thicker ones. A model is proposed which explains the difference in transformation rates in terms of the physical constraint experienced by the film since grain growth in thinner films is limited by film thickness. Geometrical constraints imposed by trench and via structures appear to have an even greater retardation effect on the grain growth. Experimental observations indicate that it takes much longer for Cu in damascene structures to go through grain size transformations than blanket films.
Improved Al-Via Fill Process Technology for Sub-0.251µm Interconnect
Authors: Sengupta S. S. , Narasimhan M. , Lee S. , Abburi M. , Yao G. 
Published: April 2011

AbstractIn this paper, a simple and improved method for Al via fill is demonstrated. The ALPS (Aluminum Low Pressure Seed) technique was used to deposit a smooth, highly conformal Al seed layer over an all-IMP (ionized metal plasma) Ti/TiN/Ti stack. Subsequent warm Al deposition was carried out in a conventional warm Al chamber. The ALPS method was compared to standard hot Al deposition. Physical SEM characterization and electrical data showed lower via resistances, with better yield for ALPS. No voiding was observed even within unlanded vias. With the ALPS seed layer, the IMP Ti/TiN/Ti liner stack provided a superior wetting surface compared to an IMP Ti-only liner which resulted in voids within unlanded vias. Electrical data obtained for ALPS- and hot Al-deposited Kelvin vias and via chains with various via/metal underlaps were compared with conventional CVD W plugs (using IMP TiN as the glue layer). Both Al fill methods gave lower via resistance compared with W plugs, as expected.
A Study on the Effect of Post Metal Etching Polymer Strip Process on Via Resistance
Authors: Koh Leong-Tee , Chooi Simon Y. M. , Chok Kho-Liep , Li He-Ming , Gn Fang-Hong 
Published: April 2011

AbstractCorrosion of the titanium glue layer in a Ti/TiN/Al(Cu) /TiN ARC metal stack is observed during post metal etching polymer stripping in an alkaline chemical stripper. This novel corrosion only occurs when the underlying tungsten via plug is exposed, and leads to high resistance in vias. Investigation of the mechanism is attempted through variation of the polymer stripping duration, the deposition of the titanium and the polymer stripper, and the nitridization of the titanium layer. The high via resistance effect is solved by using analternate polymer stripper which is considered to be an inactive electrolyte for the galvanic reaction between the titanium glue layer and the exposed tungsten via.
In-Situ Study of Ti/TiN Stability under Nitrogen Anneal
Authors: DeHaven P. W. , Rodbell K. P. , Gignac L. 
Published: April 2011

AbstractThe effectiveness of a TiN capping layer to prevent the conversion of α-titantium to titanium nitride when annealed in a nitrogen ambient has been studied over the temperature range 300–700°C using in-situ high temperature diffraction and transmission electron microscopy. Over the time range of interest (four hours), no evidence of Ti reaction was observed at 300°C. At 450°C. nitrogen was found to diffuse into the Ti to form a Ti(N) solid solution. Above 500°C the titanium is transformed to a second phase: however this reaction follows two different kinetic paths, depending on the annealing temperature. Below 600°C. the reaction proceeds in two stages, with the first stage consisting of Ti(N) formation, and the second stage consisting of the conversion of the Ti(N) with a transformation mechanism characteristic of short range diffusion (grain edge nucleation). Above 600°C, a simple linear transformation rate is observed.
The Formation of C54 TiSi2 in The Presence of Implanted or Deposited Molybdenum
Authors: Roux M. , Mouroux A. , Zhang S.-L. 
Published: April 2011

AbstractThe presence of Mo, either implanted in Si substrate prior to Ti deposition or deposited at the interface between Ti and Si, leads to the formation of C54 TiSi2 at 600 °C. Without Mo, the C54 TiSi2 does not form below 700 °C. It is shown that the C54 TiSi2 formed with the implanted Mo of a nominal dose of 5x1014 at./cm2 and that formed with the deposited Mo of 0.09 nm average thickness, display similar microstructure properties. The preferential orientation of the C54 TiSi2 is <110> in the samples with implanted Mo or with 0.09 nm Mo interlayer, as well as in the reference sample without any Mo. It becomes <010> when the Mo interlayer is 0.73 nm thick. The silicide surface and Si/silicide interface are appreciably rougher for the silicides formed with 0.09 nm Mo interlayer, with implanted Mo or in the absence of Mo, than for the silicide formed with 0.73 nm Mo interlayer. The experimental results indicate that the enhanced formation of C54 TiSi2 is caused by the same effect, i.e. template mechanism, irrespective of the means of Mo addition to the Ti-Si system.
Diffusion Barriers for Fluorinated Low-k Dielectrics
Authors: DelaRosa M. , Kumar A. , Bakhru H. , Lu T.-M. 
Published: April 2011

AbstractThe fluorinated low-k dielectrics SiO:F and Teflon AF were investigated for process integration with aluminum and copper interconnects. To minimize fluorine diffusion, several potential barrier materials were deposited onto the fluorinated dielectrics and characterized after heat treatment at temperatures up to 450°C. The barrier layers studied include conventional materials such as Ta, TaN, and TiN, in addition to several novel materials. Barrier layer materials were deposited using evaporation, and sputtering. The materials were characterized using nuclear reaction analysis (NRA) to determine the fluorine concentration profile. A reaction zone was noted at the dielectric-barrier interface on several samples, corresponding to the formation of a fluoride complex. hI some instances, this fluoride layer was self-limiting and prevented further fluorine diffusion through the remainder of the barrier layer.
Reliability Characterization of Moisture-Induced Degradation of Low-K Dielectric Behavior for Advanced Interconnects
Authors: Ionescu A. M. , Mondon F. , Blachier D. , Morand Y. , Reimbold G. 
Published: April 2011

AbstractThis paper reports degradation characteristics of low-k dielectric (FOX) in multi-level metal structures (comb-type capacitors) submitted to moisture stress. A large increase of leakage current (>105) and capacitance (up to ×3) is observed after moisture stress when only FOX is used as lateral dielectric, while moderate degradation takes place when an oxide liner is placed between FOX and metal lines. Enhanced moisture induced degradation is found on previously probed dices with respect to virgin devices. Systematic electrical measurements, combined with SEM analysis, are performed to find out the moisture diffusion path. When contact pads are damaged by previous probing (owing to the mechanical weakness of FOX in the pad stack), they provide a direct entry path for enhanced humidity intake. Humidity is also shown to enter through wafer border. Using a SiO2 liner combined with FOX improves considerably the resistance to moisture degradation.
The Effects of Environment and Fatigue on the Adhesion and Subcritical Debonding of Dielectric Polymers
Authors: Snodgrass J. M. , Pantelidis D. , Bravman J. C. , Dauskardt R. H. 
Published: April 2011

AbstractThe adhesion of thin film polymers will be critical in the integration of low-κ materials into microelectronic processing. This study describes the adhesion of two promising low-κ polymers (polyimide and benzocyclobutene) to a silicon dioxide surface. Critical adhesion values were measured using interface fracture mechanics samples in a double cantilever beam geometry. The effect of subcritical (time-dependent) delamination was also evaluated for these systems. Subcritical debonding data are important in understanding the effect of environment and temperature on interface reliability. To that end, experiments were conducted over a range of humidities to elucidate the effect of moisture on interface delamination. The important effect of the acceleration of debond growth rates due to cyclic loading is also described. In addition, XPS studies are presented to characterize the debond path in these layered systems.
Evaluation of Copper Penetration in Low-κ Polymer Dielectrics by Bias-Temperature Stress
Authors: Loke Alvin L. S. , Wong S. Simon , Talwalkar Niranjan A. , Wetzel Jeffrey T. , Townsend Paul H. , Tanabe Tsuneaki , Vrtis Raymond N. , Zussman Melvin P. , Kumar Devendra 
Published: April 2011

AbstractThe industry is strongly interested in integrating low-κ dielectrics with Damascene copper. Otherwise, with conventional materials, interconnects cannot continue to scale without limiting circuit performance. Integration of copper wiring with silicon dioxide (oxide) requires barrier encapsulation since copper drifts readily in oxide. An important aspect of integrating copper wiring with low-κ dielectrics is the drift behavior of copper ions in these dielectrics, which will directly impact the barrier requirements and hence integration complexity.This work evaluates and compares the copper drift properties in six low-κ organic polymer dielectrics: parylene-F; benzocyclobutene; fluorinated polyimide; an aromatic hydrocarbon; and two varieties of poly(arylene ether). Copper/oxide/polymer/oxide/silicon capacitors are subjected to bias-temperature stress to accelerate penetration of copper from the gate electrode into the polymer. The oxide-sandwiched dielectric stack is used to overcome interface instabilities occurring when a low-κ dielectric is in direct contact with either the gate metal or silicon substrate. The copper drift rates in the various polymers are estimated by electrical techniques, including capacitance-voltage, current-voltage, and current-time measurements. Results correlate well with timeto-breakdown obtained by stressing the capacitor dielectrics. Our study shows that copper ions drift readily into fluorinated polyimide and poly(arylene ether), more slowly into parylene-F, and even more slowly into benzocyclobutene. A qualitative comparison of the chemical structures of the polymers suggests that copper drift in these polymers may possibly be retarded by increased crosslinking and enhanced by polarity in the polymer.
Diffusion Barriers For Fluorinated Low-k Dielectrics
Authors: DelaRosa M. , Kumar A. , Bakhru H. , Lu T.-M. 
Published: April 2011

AbstractThe fluorinated low-k dielectrics SiO:F and Teflon AF were investigated for process integration with aluminum and copper interconnects. To minimize fluorine diffusion, several potential barrier materials were deposited onto the fluorinated dielectrics and characterized after heat treatment at temperatures up to 450°C. The barrier layers studied include conventional materials such as Ta, TaN, and TiN, in addition to several novel materials. Barrier layer materials were deposited using evaporation, and sputtering. The materials were characterized using nuclear reaction analysis (NRA) to determine the fluorine concentration profile. A reaction zone was noted at the dielectric-barrier interface on several samples, corresponding to the formation of a fluoride complex. In some instances, this fluoride layer was self-limiting and prevented further fluorine diffusion through the remainder of the barrier layer.
The Study of Fluorinated Amorphous Carbon as Low-K Dielectric Material and its Interface with Copper Metallization
Authors: Ariel N. , Eizenberg M. , Tzou E. Y. 
Published: April 2011

AbstractIn order to achieve better performance of devices, the interconnects RC delay time, the limiting factor of the device speed today, must be reduced. This calls for a new interconnect stack: lower resistivity Copper and low k materials (k<3) as dielectrics.Fluorinated amorphous carbon (a-F:C) prepared by HDP- CVD is an attractive candidate as a low-k material. In this work we have studied the film, its stability and its interface with Copper metallization. The high density plasma CVD process resulted in a film which contains C and F at a ratio of 1:0.6 as determined by Nuclear Reactions Analysis. XPS analysis of the Cls transition indicated four types of bonds: C-C, C-CF, CF, and CF2. X-ray diffraction as well as high resolution TEM analyses proved that the film was amorphous at least up to 500°C anneal. For various applications, the advantage of adding a thin bi-layer of a-SiC/SiOx for adhesion promotion purposes was demonstrated. In addition, the interface of a-F:C and the adhesion promoter layer with Ta, TaN and Cu was studied. No interdiffusion was observed by SIMS after 400°C annealing. 500°C annealing caused F outdiffusion from the film and Cu diffusion into the adhesion promoter layer.
Phenyl Silica Glass for Formation of Porous Dielectric Film
Authors: Endo Kazuhiko , Shinoda Keisuke , Tatsumi Toru 
Published: April 2011

AbstractPhenyl and alkyl groups were introduced into silica glass in order to prevent the formation of a Si-O network and reduce its density and to reduce the dielectric constant of the glass. In this regard, the phenyl group was more effective than the alkyl group. The measured Si-O intensity of FTIR spectrum of the glass with introduced phenyl was only 14% of thermal SiO2 film, however, the thermally stable carbon component prevented further reduction in density after 400°C annealing.
Low-K Porous Spin-On-Glass
Authors: Kohl Paul A. , Padovani Agnes , Wedlake Michael , Bhusari Dhananjay , Ann Sue , Allen Bidstrup , Shick Robert , Rhodes Larry 
Published: April 2011

AbstractPreviously, the fabrication of air-gap structures for electrical interconnections was demonstrated using a sacrificial polymer encapsulated in conventional dielectric materials. The air-gaps were formed by thermally decomposing the sacrificial polymer and allowing the by-products to diffuse through the encapsulating dielectric. The diffusivity of the polymer decomposition products is adequate at elevated temperatures to allow the formation of air-gaps. This process was extended to form low dielectric constant, porous silica from commercially available methylsilsesquioxane (MSQ) by the addition of the sacrificial polymer to the MSQ. The porous MSQ film was thermally cured followed by decomposition of the NB at temperatures above 400°C. The dielectric constant of the MSQ was lowered from 2.7 to 2.3 by creating 70 nm pores in the MSQ. The voids created in the MSQ appeared to exhibit a closed-pore structure.
Film Properties of Low-Density and Ultra-Low-Dielectric-Constant Material
Authors: Muraguchi Ryo , Egami Miki , Arao Hiroki , Tounai Atsushi , Nakashima Akira , Komatsu Michio 
Published: April 2011

AbstractWe studied the effect of pore diameter on the film properties of low-density porous material with special interest in the pore diameter range below 5nm. A novel low-density material, Interpenetrated SOG (IPS), was designed to realize such porous character. It is composed of a pyrolic template, which is an organic olygomer, and framework, made from SOG polymer and silica sol, forming an interpenetrated structure. Thermal decomposition of the organic component successfully resulted in films with pore diameter range below 5nm. It is found that the dielectric constant and the pore diameter depended on the density and the film strength was affected by the average pore diameter. Practically, films with the average pore size below 5nm possessed dielectric constants as low as 2.2–2.0 and sufficient strength.
Calculation of Pore Size Distribution in the Ellipsometric Porosimetry: Method and Reliability
Authors: Mogilnikov K. P , Polovinkin V. G , Dultsev F. N , Baklanov M. R 
Published: April 2011

AbstractEllipsometric porosimetry allows measurement of the pore size distribution in a thin porous film deposited on top of any solid substrate. The most important concept of this technique is the use of in-situ ellipsometry to determine the amount of adsorbate adsorbed/condensed in the film. Changes in refractive index and film thickness are used for calculation of the amount of adsorbate. A room temperature porosimetry based on adsorption of vapours of some organic solvents has been developed. In this paper, a method of calculation of the pore size distribution and reliability of the ELP results is discussed and the validity of the Gurvitsch rule for organic adsorbates (toluene, heptane, CCl4) is examined. Porous silica films on top of Si wafers were used for this analysis.
Uniform Quantum Wire and Quantum Dot Arrays by Natural Self-Faceting on Patterned Substrates
Authors: Nötzel Richard , Fricke Jörg , Niu Zhichuan , Jahn Uwe , Friedland Klaus-Jürgen , Ramsteiner Manfred , Schönherr Hans-Peter , Trampert Achim , Ploog Klaus H. 
Published: April 2011

ABSTRACTThe combination of self-organized growth on high-index substrates with lithographic patterning and atomic hydrogen assistance allows the fabrication of GaAs quantum wires and quantum dots as well as coupled wire-dot arrays with superior structural and electronic properties by molecular beam epitaxy. The selectivity of patterned growth on high-index substrates differs qualitatively from that on low-index ones thus producing quantum wire and quantum dot structures which fulfill the stringent criteria on the geometrical features to be met for useful devices.
Connection between Structure and Electronic Properties in Epitaxial Magnetic Layers
Authors: Altmann K. N. , Foo J. A. Con , Himpsel F. J. , Kelly J. F. , Lagally M. G. , MacKay J. F. , O'Brien W. L. , Ortega J. E. , Petrovykh D. Y. 
Published: April 2011

ABSTRACTThis study explores the consequences of structure on the electronic properties of magnetic multilayers. Epitaxial layers of Co and Cu are grown on Cu(100) in a new deposition system that couples sputter-deposition with MBE and contains a wide range of characterization tools, including RHEED, LEED, and Kerr effect. This system can be coupled in situ to spin-polarized, angle-resolved photoemission and to resonant, magnetic X-ray scattering, both employing synchrotron radiation. The interface structure turns out to be critical in determining the coercivity and the presence of quantum well states, which determine oscillatory magnetic coupling.
Transmission Electron Microscopy Study of Ingaas/Gaas Structural Evolution Near the Stranski-Krastanow Transformation
Authors: Wellman J. , George T. , Leon R. , Fafard S. , Zou J. , Cockayne D. J. H. 
Published: April 2011

ABSTRACTAn experimental study of the microstructure during formation and evolution of MOCVD-grown In0.6Ga0.4As/GaAs quantum dots (QDs) was undertaken to provide a more thorough understanding of the underlying growth principles. Transmission Electron Microscopy (TEM) was used to examine the evolution of the In0.6Ga0.4As/GaAs system in order to correlate photoluminescence (PL) spectra with structural data. In particular, we have examined the QD size evolution, capped and uncapped, and its possible contribution to the slight QD PL blueshift observed before QD saturation. TEM studies in the QD coalescence regime clarify the microstructural origins of the sharp decrease in QD PL due to large, incoherent islands observed in AFM and TEM images.
Compliant Substrate Processes
Authors: Doolittle W. A. , Brown A. S. 
Published: April 2011

ABSTRACTRecent results indicate that compliant substrates offer significant promise as a new approach for strain management in semiconductors. The potential applications include 1) the growth of device-quality highly mismatched materials on dissimilar substrates, and 2) the lateral control of material properties resulting from the effects of strain on bandstructure and/or growth dynamics. A significant amount of research in this area is dedicated to the reduction of extrinsic processing effects resulting from compliant substrate fabrication, and the development of simple models for understanding the observed reduction in defect density and/or strain in the epitaxial films grown on compliant substrates. A recent focus in our work has been on the growth of GaN on a novel and easily removable substrate -lithium gallate- for the regrowth on a bonded GaN template. The first step in this approach is the optimization of the growth of GaN on lithium gallate. In addition, this approach requires the use of an appropriate bonding layer to reduce the strain or defect production during growth due to coefficient of thermal expansion mismatches between the GaN sample and the handle wafer. Our work in this area will be highlighted in the context of an overview of various compliant substrate approaches and current results that indicate their efficacy.
Observation of Surfactant Properties of Thallium in the Epitaxial Growth of Indium Arsenide on Gallium Arsenide
Authors: Storm D.F. , Lange M.D. 
Published: April 2011

ABSTRACTBecause of the large lattice mismatch between InAs and GaAs, the growth of the former on the (001) surface of the latter undergoes a well-known transition from a layer-by-layer mode to an island mode at an equivalent coverage of 1–2 monolayers (ML). We have observed a suppression of this transition when growth proceeds under a simultaneous thallium flux. The thallium is not significantly incorporated into the InAs layer; however, approximately I ML may remain at the interface. The effect of the thallium on the electronic properties of the InAs is investigated.