bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial reactions in multilayers intended for microelectronics devices
Authors: Federspiel X. , Voiron F. , Ignat M. , Marieb T. , Fujimoto H.
Published: April 2011

The 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

Ionized 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

The 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

We 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

This 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

The 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

It 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

For 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

Internal 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

Electromigration-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.
On the Interaction Between Indentation Cracks on Metallized Silicon
Authors: Manoharan M. , Muralidharan G.
Published: April 2011

The metallization of Si represents a important industrial process and produces a bi-layered composite of a ductile metal film on a brittle substrate. The mechanical properties of such a composite are determined by the properties of the two layers and the interface and influenced by the fact that the metallized layer, being a very thin film, possesses properties different from those of a bulk material. The fracture toughness is also influenced by the nature and distribution of defects which may be generated during use of these materials, even if the manufacturing process produces a reasonably defect free material. Indentation cracking has been extensively used for the measurement of fracture toughness due to its small sample size requirements as well as a relatively good correlation with values obtained from traditional fracture mechanics tests. The indentation process, with its associated cracks, produces permanent plastic deformation and also introduces a residual stress field. This field influences the crack pattern generated in an adjacent indent and can be used as a methodology to model the influence of multiple defect sources.

The present study was aimed at understanding the effect of a thin Ti alloy metallization layer sputtered on a Si wafer on the sizes of the cracks associated with the indents. It was also aimed at studying the interaction between cracks emanating from sequentially placed indentations. The distance between the indents which generated these cracks was varied from a level comparable to the crack size to a level where interaction could be ignored. This paper discusses the changes in the nature as well as the sizes of cracks due to the presence of the metallization layer as well as the interaction between the stress fields of the indents in this ductile thin film – brittle substrate composite and possible methodologies for delineating these effects.
Interface Effect on the Transverse Thermal Conductivity of SiO2 Films Deposited on Silicon
Authors: Zhao W. , Brotzen F. R. , Hehn L. , Loos P. J.
Published: April 2011

Earlier work revealed that the transverse thermal conductivity of thin films of amorphous SiO2 deposited on monocrystalline silicon decreased substantially when the film thickness was less than about 1 µm. When multiple interfaces were created by the intercalation of thin intermediate layers of polycrystalline silicon into the SiO2 film, the thickness effect was enhanced. This observation pointed to an interfacial effect. A model accounting for the interface effect is discussed.
Diffusion and Electromigration of Cu in Single Crystal Al Interconnects
Authors: Srikar V. T. , Thompson C. V.
Published: April 2011

The electromigration-induced transport properties of Cu in Al-Cu alloys, and their effect on electromigration lifetimes in interconnects with bamboo grain structures are not well understood. To isolate and study the mechanisms and kinetics of Cu diffusion and electromigration in interconnects for which grain boundary transport is not dominant, we have developed a test structure consisting of parallel Al single crystal lines, with every alternate line terminating in contact pads. Cu is locally added to the same regions in all the lines, and the effect of temperature and electric field can be simultaneously characterized by analyzing the Cu concentration profile measured using electron-probe microanalysis. Comparison of the calculated values of diffusivities with the diffusivity of Cu through the Al lattice, and through dislocation cores in Al, suggests that the path of diffusion of Cu in Al single crystals is along the Al/AlOx interface.
Grain Growth by Digm in Ni Thin Film Under High Tensile Stress
Authors: Jia Zhengyi , Pan G. Z. , Tu K. N.
Published: April 2011

Electron beam evaporated Ni thin films are found to have tensile stress of 1.2 Gpa. The stress is relieved upon heating, accompanied by grain growth. The calculated stress matches the experimental result and a mechanism of grain growth is proposed.
A Novel Technique for the Fabrication of Free-Standing Adhesive Films Using a Polymer Template
Authors: Hansford D. J. , Lee L. P. , Ferrari M.
Published: April 2011

A technique has been developed that allows the application of free-standing membranes of polymer adhesives used in microfabricated structures. The film is made free-standing by the application of the adhesive to a polymer template, followed by an adhesion step to a microfabricated substrate, and the final release of the film by the removal of the polymer template. It was found that the surface treatment used to treat the Teflon template made it adhere too strongly to the adhesive film for this application. The results show that Gel-Paks make a suitable template for the transference of polymer films over holes of at least micron size.
Adhesion of Polysilicon Microbeams in Controlled Humidity Ambients
Authors: de Boer M. P. , Clews P. J. , Smith B. K. , Michalske T. A.
Published: April 2011

We characterize in-situ the adhesion of surface micromachined polysilicon beams subject to controlled humidity ambients. Beams were freed by supercritical CO2drying. Consistent adhesion results were obtained using a post-treatment in an oxygen plasma which rendered the microbeams uniformly hydrophilic. Individual beam deformations were measured by optical interferometry after equilibration at a given relative humidity (RH). Validation of each adhesion measurement was accomplished by comparing the deformations with elasticity theory. The data indicates that adhesion increases exponentially with RH from 30% to 95%, with values from 1 mJ/m2 to 50 mJ/m2. Using the Kelvin equation, we show that the data should be independent of RH if a smooth interface is considered. By modeling a rough interface consistent with atomic force microscopy (AFM) data, the exponential trend is satisfactorily explained.
Buckling Evolution of Microelectromechanical Structures
Authors: Zhang Xin , Zhang Tong-Yi , Zohar Yitshak
Published: April 2011

This study reports in-situ observations of the buckling evolution of microelectromechanical structures during etching of their underneath sacrificial layers. As the etching went on, the buckling pattern evolved from mode I, the sinusoidal half-waves, to mode II, the constrained sinusoidal half-waves, to mode III, the conventional mode, and finally to mode IV, the blister- like local buckling. Closed formulae were derived from theoretical analysis, and the experimental results agreed well with the theoretical ones.
Silicon-Framed Tensile Specimens: Techniques and Results
Authors: Read D. T.
Published: April 2011

The silicon-framed tensile specimen design has been used in tensile tests of thin films of a variety of metals and epitaxial silicon. A piezo-actuated microtensile test device holds the specimen while the silicon frame is cut just before testing, imposes the tensile displacement, and provides voltages proportional to force and displacement. This technique is appropriate for films that are hundreds of micrometers long, tens to a few hundred micrometers wide, and from 0.3 to 15 micrometers thick. The specimen film must be amenable to lithographic patterning, must adhere well to the silicon substrate, and must resist a silicon etchant. The specimen fabrication is a bulk-micromachining process, because the silicon substrate is etched through underneath the specimen film. Uniaxial yield strength, ultimate tensile strength, and elongation to maximum load can be measured using the microtensile tester. The addition of laser illumination and digital photography allows implementation of electronic speckle pattern interferometry, for accurate measurement of local displacement. This addition allows evaluation of the tensile Young's modulus. Compared to bulk material, thin films of copper and aluminum have lower apparent Young's moduli, higher yield and ultimate tensile strengths because of their fine grain size, and lower elongation to failure. Correlation between properties measured by indentation and by tensile testing needs further study.
Internal Stress of ZnO thin Films Caused by Thickness Distribution and Crystallinity
Authors: Takeuchi M. , Inoue K. , Yoshino Y. , Ohwada K.
Published: April 2011

The improvement of thickness distribution and crystallinity in ZnO thin films prepared by radio frequency (rf) planer magnetron sputtering has been studied. Optimum thickness distribution of less than ± 2.2% in a 3-inch wafer is obtained by changing the substrate angle to the ZnO target and is in accordance with cosine law. The c-axis orientation perpendicular to the silicon substrate is confirmed by x-ray diffraction. The stress of ZnO thin films is larger than 0.3GPa and its distribution is independent of the substrate angle that is set at a slant to the optimum angle for thickness distribution. These results indicate that thickness distribution of ZnO thin films heavily depends on the substrate angle, while the stress and its distribution are independent of the setting angle of the substrate. Stress distribution is attributed to the distribution of argon ions and sputtered molecules impinging a wafer.
Mechanical Property Measurement of 0.5-µm CMOS Microstructures
Authors: Lu M. S.-C. , Zhu X. , Fedder G. K.
Published: April 2011

Measurements are reported on the mechanical properties of high-aspect-ratio micromechanical structures formed using a conventional 0.5-µm CMOS process. Composite structures are etched out of the CMOS dielectric, aluminum, and gate-polysilicon thin films using a post-CMOS CHF3:O2 reactive-ion etch and followed by a SF6 :O2silicon etch for release. Microstructures have a height of 5 µm and beam widths and gaps down to 1.2 µm. Properties are strongly dependent on the relative metal and dielectric content of the beams. Beams with three metal conductors and polysilicon have an effective Young's modulus of 62 GPa, residual stress of -29 MPa, and an average out-of-plane radius of curvature of 1.9 mm. Maximum Young's modulus variation is 3 GPa die-todie, and is 9 GPa between two runs. Die-to-die variation of stress and stress gradient is poor for many beam compositions, however local matching on a die is very good. Cracking is induced in a resonant fatigue structure at 620 MPa of repetitive stress after over 50 million cycles.
Synthesis of Sol-Gel Matrices for Encapsulation of Enzymes Using an Aqueous Route
Authors: Bhatia R.B. , Brinker C.J. , Ashley C.S. , Harris T.M.
Published: April 2011

Sol-gel matrices are promising host materials for potential chemical and biosensor applications. Previous studies have focused on modified sol-gel routes using alkoxides for encapsulation of enzymes. However the formation of alcohol as a byproduct during hydrolysis and condensation reactions poses limitations. We report the immobilization of glucose oxidase and peroxidase in silica prepared by an aqueous route which may provide a more favorable environment for the biomolecules. A two step aqueous sol-gel procedure using sodium silicate as the precursor was developed to encapsulate the enzymes and the dye precursor, o-dianisidine. Glucose oxidase catalyzes the oxidation of glucose to give gluconic acid and hydrogen peroxide. Peroxidase then catalyzes the reaction of the dye precursor with hydrogen peroxide to produce a colored product. The kinetics of the coupled enzymatic reactions were monitored by optical spectroscopy and compared to those occurring in tetramethyl orthosilicate (TMOS) derived silica matrices developed by Yamanaka et al. [1]. Enhanced kinetics in the aqueous silicate matrices were related to differences in the host microstructures as elucidated by microstructural comparisons of the corresponding aerogels.
Polymeric Based Conducting Nanocomposites: Controlling The Distribution of the Conducting Phase
Authors: Vaia Richard. A. , Lee Jar-Wha , Click William , Price Gary , Wang Chyi-Shan
Published: April 2011

The optimization of bulk properties of polymeric based nano– and mesoscale composites require the ability to spatially control phase distribution. In this study, electrical conductivity is introduced by incorporation of a metal precursor via infiltration into the polymer host and subsequent conversion in–situ by a reducing agent, templating the morphology of the polymer matrix. Distribution of nano– and mesoscale metal particles in isotropic and anisotropic swollen polymer hosts is discussed relative to metal precursor and reducing reagent diffusion and their in–situ bimolecular reduction reaction. The swelling and infiltration procedure employed to form the composites is generally applicable to rigid–rod, semi–flexible and flexible polymer matrices and not restricted to special synthesis of metal containing or complexing polymers. As an example, high–performance rigid–rod polymer fibers containing an interpenetrating network of polymer microfibrils and silver are produced with d.c. conductivities in excess of 104 S/cm and tensile
Organic-Inorganic Crystals for Optical Devices
Authors: Ibanez A. , Zaccaro J. , Baldeck P. L. , Masse R.
Published: April 2011

Two routes of crystal engineering and elaboration of optical materials are described. The former applied to the design of organic-inorganic crystals for quadratic nonlinear optics is supported by a strategy of deliberately engineered noncentrosymmetric structures built-up from herringbone motifs of 2-amino-5-nitropyridinium chromophore. The original crystal growth of a solid solution of a member of this family is presented and discussed. The latter is a simple and generic elaboration of stable organic nanocrystals embedded in sol-gel matrices. Several molecules and characterization techniques have been involved to demonstrate the validity of this preparation.
Carboxylate-Substituted Oxotitanium and Oxozirconium Clusters as Structural Models for Titania- and Zirconia-Based Inorganic-Organic Hybrid Materials
Authors: Kickelbick Guido , Schubert Ulrich
Published: April 2011

Reaction of Ti(OR)4 or Zr(OR)4 with carboxylic acids resulted in the formation of crystalline carboxylate-substituted oxotitanium and oxozirconium clusters with different Ti/Zr : carboxylate ratios. Structural investigations showed that the cluster cores are rutile- or zirconia-like if the carboxylate : metal ratio does not exceed 1.33 (for Ti) or 2 (for Zr), respectively. When the carboxylate : metal ratio is increased beyond these values, more open clusters and eventually polymeric structures are obtained.
Self-Organization in Nanoparticle Titanium Dioxide Thin Films
Authors: Burnside S.D. , Shklover V. , Barbe C.A. , Brooks K. , Comte P. , Arendse-Duriaux F. , Jirousek M. , Graetzel M.
Published: April 2011

Nanocrystalline titanium dioxide has been synthesized using a sol-gel technique followed by hydrothermal growth at temperatures in the range 190-270°C. Thin films of these colloids were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption/desorption. Self-organization of the nanocrystalline particles in regular arrays was observed in films made from colloids autoclaved at lower temperatures. We present herein initial photovoltaic performance of these semiconducting films used as working electrodes in a dye-sensitized solar cell.
Characterization of Electrically Pulsed Chromium Disilicide Fusible Links
Authors: Domenicucci A.G. , Cunningham B. , Tsang P.
Published: April 2011

Fusible links, fabricated from silicon rich chromium disilicide thin films, were subjected to voltage pulses in the 3–6 volt range. An optimum voltage existed at which the fuses blew. Transmission electron microscopy (TEM) was used to study the microstructural characteristics of the fuses both before and after the application of the voltage pulses. The TEM characterization, coupled with electrical and physical measurements, revealed that the mechanism underlying the fuse blow was hole current induced Si electromigration. Below the optimum voltage, the amount of Si transported was insufficient to cause fuse rupture. Above the optimum voltage, the current- voltage characteristics of the fuses became nonlinear and a unique sequence of material phases was formed. The composition of the phases suggests that both thermomigration and electromigration processes were operating at voltages above the optimum voltage.
Aluminum Spiking Mechanism in Contact Holes Studied by High-Resolution Analytical TEM
Authors: Cerva H. , Klüppel V. , Barth H. J. , Helneder H.
Published: April 2011

Al-spiking in contacts to Si were studied on a microscopic scale by a detailed cross sectional TEM analysis. Electron spectroscopic imaging and energy dispersive x-ray microanalysis with a I nm high-current electron probe formed by a field emission gun helped to identify the Al-diffusion paths and the reaction mechanisms which lead to contact failure. Combinations of advanced PVD-Ti/TiN barrier layers and cold/hot or high-pressure AlSiCu-fills revealed that the highly rugged TiN barrier sidewalls and thick Ti sidewall layers are the weak points which cause Al-spiking.
Electron Microscopic Studies of Co- and Ti-Germanosilicide Films Formed on SiGe Layers
Authors: Jin S. , Donaton R. A. , Bender H. , Maex K.
Published: April 2011

Cobalt films are sputter deposited on Si0.8Ge0.2 layers grown epitaxially on Si substrates. Compared with the silicidation on pure silicon, there is a retardation of the disilicide formation in the SiGe case. The conversion of the monosilicide into the disilicide strongly depends on the thickness of the initial SiGe layers. For the silicidation of titanium on poly-SiGe layers, the increase of the Ge content favours the nucleation of C54 titanium germanosilicide, hence helping the transition from the C49 to the C54 phase on the blanket layers. The thickness of the final C54 Ti-germanosilicide layers formed on narrow poly-Sil-×Gex runners is independent of the line width and the Ge concentration.
Tem Studies of Polysilicon Emitter Bipolar Materials & Devices: Increased Interfacial Oxide Break-Up and Polysilicon Regrowth and Decreased Emitter Resistance by Fluorine Implantation
Authors: Marsh C. D. , Moiseiwitsch N. E. , Schiz J. , Booker G. R. , Ashburn P.
Published: April 2011

The role of fluorine (F) in the break-up of the native oxide and the regrowth of As doped poly-Si layers on unpatterned Si wafers and on patterned regions of Si device wafers at temperatures of 900°C to 1000°C are investigated by TEM and by the fabrication of npn poly-Si emitter bipolar devices. Results for unpatterned wafers with F show i) a 950°C dopant drive-in anneal causes oxide break-up and regrowth after a time suitable for the fabrication of devices, ii) a pre-anneal, before the As implant, further enhances the break-up and regrowth and iii) there is an optimum F dose of 5×1015/cm2. Based on these results poly-Si emitter bipolar devices were fabricated using F=5×1015/cm2, a pre-anneal and a 900°C As drive-in anneal. The results establish quantitatively the relationship between the interface structures and the specific emitter resistance, i.e. with no F there is no break-up or regrowth and the emitter resistance is high (114Ωμm2) while with F there is break-up and regrowth and the emitter resistance is low (17Ωμm2).
Electron Microscopy, Electrical Activity, Artefacts and the Assessment of Semiconductor Epitaxial Growth
Authors: Brown Paul D. , Humphreys Colin J.
Published: April 2011

The characterisation of semiconductor thin films and device structures increasingly requires the use of a variety of complementary electron microscope-based techniques as feature sizes decrease. We illustrate how layer electrical and structural properties can be correlated: firstly averaged over the bulk and then on the individual defect scale, e.g. scanning transmission electron beam induced conductivity can be used to image the recombination activity of orthogonal <110> misfit dislocations within relaxed MBE grown Si/Si1-xGex/Si(001) heterostructures on the sub-micrometre scale. There is also need for improved understanding of sample preparation procedures and imaging conditions such that materials issues relevant to ULSI development can be addressed without hindrance from artefact structures. Hence, we consider how point defects interact under the imaging electron beam and the relative merits of argon ion milling, reactive ion beam etching, focused ion beam milling and plasma cleaning when used for TEM sample preparation. Advances in sample preparation procedures must also respect inherent problems such as thin foil surface relaxation effects, e.g. cleaved wedge geometries are more appropriate than conventional cross-sections for the quantitative characterisation of δ-doped layers. Choice of the right imaging technique for the problem to be addressed is illustrated through consideration of polySi/Si emitter interfaces within bipolar transistor structures. The development of microscopies for the rapid analysis of electronic materials requires wider consideration of non-destructive techniques of assessment, e.g. reflection high energy electron diffraction in a modified TEM is briefly described.
Applications of Plasma Cleaning for Electron Microscopy of Semiconducting Materials
Authors: Isabell T. C. , Fischione P. E.
Published: April 2011

As semiconductor device sizes continue to decrease, the degree of accuracy needed for electron microscopy and microanalyis of such materials increases. To achieve such accuracy, small electron probes with high beam currents are needed. The combination of these two factors results in an increase in the amount of carbonaceous contamination formed on the specimen under the electron beam. Recently, the use of low energy plasmas has been shown to be effective in preventing such contamination from occurring [1–7]. For TEM, the simultaneous placement of the specimen holder and specimen into such a plasma for short periods of time results in the ability to hold a converged probe on the specimen for analysis without contamination becoming an problem. Furthermore, in this presentation we show that existing contamination from prior TEM analysis can be removed from the specimen by plasma cleaning. The benefits of plasma cleaning are not solely limited to TEM. SEM specimens, as well as SEM specimen holders, aperture strips, tweezers and other electron microscopy accessories can readily be inserted into the plasma chamber for cleaning.
Application of Electron Microscopy Towards the Analysis of Submicron Particles and Microcorrosion
Authors: Rice Larry , Carpenter B. , Johnston L. , Chen Wei
Published: April 2011

Small particles in ULSI devices are one of the key causes for affecting device yield. This is especially true since modern devices are shrinking in all dimensions and the critical size for ‘killer’ particles is also shrinking. It is increasingly challenging to identify the root cause of particle contamination in terms of locating and identifying the particles. A precision cross section through the particles is required to be able to identify at which processing step the particles occurred and an energy dispersive spectroscopy (EDS) microanalysis usually helps identify the source. This paper focuses on the methodology for carrying out submicron defect and particle analysis. In addition to processing knowledge, it demonstrates the importance of techniques such as scanning electron microscopy (SEM), EDS, and focused ion beam (FIB). The analysis of microcorrosion observed after third metal deposition, and submicron titanium particles after metal etch are used as vehicles to illustrate the procedure of submicron particle analysis.
Texture Analysis of Al and Cu Metallization Materials Using Orientation Imaging Microscopy
Authors: Carpenter D. T. , Alvis R. , Morales G.
Published: April 2011

X-ray diffraction (XRD) is generally used to measure crystallographic texture, but complete analysis is rarely performed. Orientation imaging microscopy (OIM) gives similar data by electron diffraction and has potential for widespread use since it may be added to any scanning electron microscope. Analysis software has been developed to reduce QIM results into a form which may be compared directly to XRD results. OIM texture parameters measured from Al films showed good quantitative agreement with XRD parameters, however the texture in Cu films is more complex and difficult to compare. Although subject to certain limitations, OIM has several advantages over XRD including more efficient data collection, better sensitivity to minor texture components, and more flexible data analysis.
Effect of Mo Doping on Formation of Ti-Silicide Phases Studied by HRTEM
Authors: Gribelyuk M. A. , Samavedam S. B. , Kittl J. A.
Published: April 2011

The phase sequence of the RTP induced reaction at T=650°C has been studied. We found that pre-amorphization of poly-Si substrates does not change the reaction path. i.e. Ti5Si4, and C-49 TiSi2 phases were formed_ with the latter growing upon further anneal. In the Mo doped poly-Si/Ti system the C-54 TiSi2 phase has formed along with Ti5Si4 and two Mo silicide phases, MoSi2 and Mo5Si3; no C-49 TiSi2 was observed. We show that the reaction in the Mo doped system follows the template mechanism with MoSi2 and Mo5Si3 based phase acting as template phases for accelerated growth of C-54 TiSi2.
Tem Investigation of Titanium Silicide Thin Films
Authors: Myers A. F. , Steel E. B. , Struck L. M. , Liu H. I. , Burns J. A.
Published: April 2011

Titanium silicide films grown on silicon were analyzed by transmission electron microscopy (TEM), electron diffraction, scanning transmission electron microscopy (STEM), and energy dispersive x-ray spectroscopy. The films were prepared by sequential rapid thermal annealing (RTA) at 675 °C and 850 °C of 16-nm-thick sputtered Ti on Si (001) wafers. In some cases, a 20-nm-thick TiN capping layer was deposited on the Ti film before the RTA procedure and was removed after annealing. TEM and STEM analyses showed that the silicide films were less than 0.1 μm thick; the capped film was more uniform, ranging in thickness from ∼ 25 – 45 nm, while the uncapped film ranged in thickness from ∼ 15 – 75 nm. Electron diffraction was used to determine that the capped film contained C54-TiSi2, C49-TiSi2, Ti5Si3, and possibly TiSi, and that the uncapped film contained C49-TiSi2, TiSi, Ti5Si3, unreacted Ti, and possibly C54-TiSi2.
The First Synchrotron Infrared Beamlines at the Advanced Light Source: Microscpectroscopy and Fast Timing
Authors: Martin Michael C. , McKinney Wayne R.
Published: April 2011

A set of new infrared (IR) beamlines on the 1.4 bending magnet port at the Advanced Light Source, LBNL, are described. Using a synchrotron as an IR source provides considerable brightness advantages, which manifests itself most beneficially when performing spectroscopy on a microscopic length scale. Beamline (BL) 1.4.3 is a dedicated microspectroscopy beamline, where the much smaller focused spot size using the synchrotron source is utilized. This enables an entirely new set of experiments to be performed where spectroscopy on a truly microscopic scale is now possible. BL 1.4.2 consists of a vacuum FTIR bench with a wide spectral range and step-scan capabilities. The fast timing is demonstrated by observing the synchrotron electron storage pattern at the ALS.
Preliminary Results from a New Spin Spectrometer
Authors: Tobina J. G. , Bedrossiana P. J. , Cumminsb T. R. , Waddillb G. D. , Mishrac S. , Larsond P. , Negrid R. , Millerd M. , Petersond E. , Boyd P. , Gunion R.
Published: April 2011

The first preliminary results from a novel spectrometer for elementally-specific measurements of magnetic surfaces and ultrathin films are presented here. The key measurements are based upon spin-resolving and photon-dichroic photoelectron spectroscopy. True spinresolution is achieved by the use of a Mini-Mott detection scheme. The photon-dichroic measurements include the variant magnetic x-ray linear dichroism (MXLD). Both a multi-channel, energy dispersive collection scheme as well as the spin-detecting Mini-Mott apparatus are used in data collection. The [Spin Spectrometer] is based at the Spectromicroscopy Facility (Beamline7)at the Advanced Light Source.
Evidence for the Photoemission Nature of Gd 4f Resonant Photoemission
Authors: Mishra S. R. , Cummins T. R. , Gammon W. J. , Waddill G. D. , Van der-Laan G. , Goodman K. W. , Tobin J. G.
Published: April 2011

The constructive interference between direct and indirect channels above the absorption threshold of a core level leads to a massive increase in the emission cross section leading to a phenomenon called “resonant photoemission”. Using novel magnetic linear dichroism in angular distribution photoelectron spectroscopy experiment we have tried to understand the nature of the resonant photoemission process in Gd metal. The presence of dichroism in Gd 4f photoemission intensity at a photon energy corresponding to resonant photoemission clearly demonstrates the photoemission-like nature of the resonant photoemission process.
Esca Microscopy on Elettra: Chemical Characterization of Surfaces and Interfaces With Sub-Micron Spatial Resolution
Authors: Kiskinova m. , Casalis L. , Gregoratti L. , Gunther S. , Marsi M.
Published: April 2011

The chemical sensitivity, spatial resolution and data acquisition rates achieved with the scanning photoelectron microscope built at ELETTRA, a third-generation synchrotron facility in Italy has made it an indispensable tool for surface analysis of laterally heterogeneous materials. The information on the composition and evolution of coexisting phases, mass transport and other surface processes occurring on a microscopic scale can be obtained by combining elemental and chemical mapping with core and valence level photoelectron spectromicroscopy with spatial resolution better than 0.15 μm and energy resolution better than 0.5 eV. Selected recent results will be presented to illustrate the capabilities and some of the possible applications of synchrotron radiation spectromicroscopy for characterization of complex spatially heterogeneous materials and studies of dynamic processes related to the interface chemical structure.
State-of-the-Art X-Ray Photoelectron Spectroscopy (XPS): Conventional and Synchrotron X-Ray Sources for Micro-XPS
Authors: Principe E. L. , Odom R. W. , Johnson A. L. , Ackermann G. D. , Hussain Z. , Padmore H.
Published: April 2011

This paper presents preliminary data on analyses of selected materials using two state-ofthe- art XPS systems: the Physical Electronics Inc. (PHI, Eden Prairie, MN) Quantum 2000 instrument and the microXPS beamline (7.3.2.1) at the Advanced Light Source (ALS). This research compares and contrasts relevant performance characteristics of the two systems including elemental and chemical state detection sensitivity, imaging capabilities including lateral resolution and useful image fields, role of X-ray dose damage to surface, analysis speed as well as analytical throughput.
Update On Synchrotron Radiation TXRF: New Results
Authors: Brennan S. , Pianetta P. , Ghosh S. , Takaura N. , Wiemer C. , Fischer-Colbrie A. , Laderman S. , Shimazaki A. , Waldhauer A. , Zaitz M. A.
Published: April 2011

Synchrotron-based total-reflection x-ray fluorescence(SR-TXRF) has been developed as a leading technique for measuring wafer cleanliness. It holds advantages over other techniques in that it is non-destructive and allows mapping of the surface. The highest sensitivity observed thus far is 3x108 atoms/cm 2 (- 3fg) for 1000 second count time. Several applications of SR-TXRF are presented which take advantage of the energy tunability of the synchrotron source or the mapping capability.
High-Resolution X-Ray Photoemission Electron Microscopy at the Advanced Light Source
Authors: Stammler Thomas , Anders Simone , Padmore Howard A. , Stöhr Joachim , Scheinfein Michael , Ade Harald
Published: April 2011

X-ray Photoemission Electron Microscopy (X-PEEM) is a full-field imaging technique where the sample is illuminated by an x-ray beam and the photoemitted electrons are imaged on a screen by means of an electron optics. It therefore combines two well-established materials analysis techniques - photoemission electron microscopy (PEEM) and x-ray spectroscopy such as near edge x-ray absorption fine structure (NEXAFS) spectroscopy. This combination opens a wide field of new applications in materials research and has proven to be a powerful tool to investigate simultaneously topological, elemental, chemical state, and magnetic properties of surfaces, thin films, and multilayers at high spatial resolution. A new X-PEEM installed at the bend magnet beamline 7.3.1.1 at the Advanced Light Source (ALS) is designed for a spatial resolution of 20 nm and is currently under commissioning. An overview of the ongoing experimental program using X-PEEM in the field of materials research at the ALS is given by elemental and chemical bonding contrast imaging of hard disk coatings and sliders, field emission studies on diamond films as possible candidates for field-emission flat-panel displays, and the study of dewetting and decomposition phenomena of thin polymer blends and bilayers.
Anomalous X-Ray Scattering Studies of Short-, Intermediate- and Extended-Range Order in Glasses
Authors: Price David L. , Saboungi Marie-Louise , Armand Pascale , Cox David E.
Published: April 2011

We present the formalism of anomalous x-ray scattering as applied to partial structure analysis of disordered materials, and give an example of how the technique has been applied, together with that of neutron diffraction, to investigate short-, intermediate- and extended-range order in vitreous germania and rubidium germanate.
X-Ray Absorption Fine Structure (Xafs) Studies Of Cobalt Silicide Thin Films
Authors: Naftel S. J. , Coulthard I , Hu Y. , Sham T. K. , Zinke-Allmang M.
Published: April 2011

Cobalt silicide thin films, prepared on Si(100) wafers, have been studied by X-ray absorption near edge structures (XANES) at the Si K-, L2,3 and Co K-edges utilizing both total electron (TEY) and fluorescence yield (FLY) detection as well as extended X-ray absorption fine structure (EXAFS) at the Co K-edge. Samples made using DC sputter deposition on clean Si surfaces and MBE were studied along with a bulk CoSi2 sample. XANES and EXAFS provide information about the electronic structure and morphology of the films. It was found that the films studied have essentially the same structure as bulk CoSi2. Both the spectroscopy and materials characterization aspects of XAFS (X-ray absorption fine structures) are discussed.
Interfacial Electronic Charge Transfer and Density of States in Short Period Cu/Cr Multilayers
Authors: Bello A. F. , Buuren T. Van , Klepeis J. E. , Barbee T. W.
Published: April 2011

Nanometer period metallic multilayers are ideal structures to investigate electronic phenomena at interfaces between metal films since interfacial atoms comprise a large atomic fraction of the samples. The multilayers studied were fabricated by magnetron sputtering and consist of bilayers from 1.9 nm to 3.3 nm. X-ray diffraction, cross-section TEM and plan-view TEM show the Cu layers to have a BCC structure Cu in contrast to its equilibrium FCC structure. The electronic structure of the Cu and the Cr layers in several samples of thin Cu/Cr multilayers were studied using x-ray absorption spectroscopy (XAS). Total electron yield was measured and used to study the white lines at the Cu L2 and L3 absorption edges. The white lines at the Cu absorption edges are strongly related to the unoccupied d-orbitals and are used to calculate the amount of charge transfer between the Cr and Cu atoms in interfaces. Analysis of the Cu white lines show a charge transfer of 0.026 electrons/interfacial Cu atom to the interfacial Cr atoms. In the Cu XAS spectra we also observe a van Hove singularity between the L2 and L3 absorption edges as expected from the structural analysis. The absorption spectra are compared to partial density of states obtained from a full-potential linear muffin-tin orbital calculation. The calculations confirm the presence of charge transfer and indicate that it is localized to the first two interfacial layers in both Cu and Cr.