bluuebunny/crossref_metadata_2025 huggingface dataset:
Optically Induced Condensation of Impurity Excitations in Transparent Solids
Authors: Manykin E. A. , Ojovan M. I. , Poluektov P. P.
Published: April 2011

The interaction of electromagnetic radiation with impurities in transparent solids is studied for the case when interactions between excitations become significant. It is shown that intense optical radiation leads to condensation of the excitations of impurities. The condensed excited state, consisting of excited impurities, is an energetically favourable phase, which minimises the energy of the system. Nevertheless, condensation, as a rule, causes mechanical stresses, in some cases followed by either redistribution of impurities or even breaches of solids.
Viewport Influence on Optical Pyrometry and Deposition Process in Mocvd Vertical Rotating Disc Reactors
Authors: Prokopenko Anton , Gurary Alexander , Boguslavskiy Vadim , Ramer Jeffrey , Schurman Matthew
Published: April 2011

Optical access to the wafer for the in-situ process monitoring and control is a requirement for the advanced MOCVD equipment. Depending on their location and design, viewports can affect the reactor flow dynamics and temperature distribution inside the growth chamber thus ultimately affecting the deposition process. Furthermore, deposition on the viewport can influence the accuracy of in-situ measurements.

We have investigated viewport influence on the MOCVD vertical rotating disc reactors manufactured by EMCORE Corporation. Viewport transmittance was established for different conditions and viewport types. Computational fluid dynamics was utilized to establish conditions at which viewport has no considerable influence on deposition results. The validity of model predictions was verified by examining the results of actual deposition runs on the reactor. We have demonstrated that under typical EMCORE reactor operating conditions, viewports presence on the reactor inlet flange and a purge flow through it have minimal effect on the reactor flow dynamics and ultimately on material growth rate and thickness uniformity.
Optical Integrated Waveguides Characterization by Scanning Near Field Optical Microscope
Authors: Borrisé X. , Barniol N. , Pérez-Murano F. , Abadal G. , Aymerich X. , Jiménez D.
Published: April 2011

In this work, we present (i) the development of a scanning near-field optical microscope (SNOM) for the characterization of optical integrated devices and (ii) the description of a new lithographic technique for the modification of standard integrated optical waveguides. SNOM images of rib waveguides allow to characterise the distribution of the guided modes for up to 1 mm of propagation distance. Some of the characterised waveguides present a periodical modulation of the light in the direction of propagation which is attributed to the Tien effect. In addition, we have performed high resolution modifications on the rib waveguide with an atomic force microscope combined with standard microelectronics processes. We demonstrate that the combination of this new lithographic technique with SNOM characterization allows to obtain new information about the propagation of the light in low dimensional structures.
Light-Excitation-Based Spectroscopy of Electronic Defects in Novel Materials
Authors: Castaldini A. , Cavallini A. , Polenta L.
Published: April 2011

In recent years several spectroscopic methods based on deep level photoionization have been developed because of the demand to investigate materials spreading over a wide range of resistivities. This paper deals with some capacitance- and current-based analyses, that are mature techniques for the characterization of semiconducting as well as semi-insulating materials with respect of deep level identification as well as spatial distribution. Results relevant to novel materials are also reported.
Low Temperature Photoluminescence and Photoinduced Current Spectroscopy on CdZnTe Grown by High-Pressure Bridgman Technique
Authors: Zerrai A. , Cherkaoui K. , Mergui S. , Zumbiehl A. , Hage-Ali M. , Marrakchi G. , Brémond G.
Published: April 2011

Low temperature photoluminescence (PL), photoinduced current spectroscopy (PICTS) and thermoelectric effect spectroscopy (TEES) measurements have been carried out on several CdZnTe samples, taken from the same ingot, grown by the High Pressure Bridgman Technique. The PL bandgap edge luminescence allowed us to study the quality of the CdZnTe material. We have also determined the zinc segregation through the ingot. A broad luminescence band at lower energies was observed and correlated with PICTS results. The behavior of the defects through the ingot was studied by PICTS. Finally, these results are used to implement the resistivity model.
A Study of the Origin of Band-A Emission in Homoepitaxial Diamond Thin Films
Authors: Takeuchi Daisuke , Watanabe Hideyuki , Yamanaka Sadanori , Okushi Hideyo , Kajimura Koji , Sawada Hidetaka , Ichinose Hideki , Sekiguchi Takashi
Published: April 2011

The band-A emission (around 2.8 eV) observed in high quality (device-grade) homoepitaxial diamond films grown by microwave-plasma chemical vapor deposition (CVD) was studied by means of scanning cathodoluminescence spectroscopy and high-resolution transmission electron microscopy. Recent progress in our study on homoepitaxial diamond films was obtained through the low CH4/H2 conditions by CVD. These showed atomically flat surfaces and the excitonic emission at room temperature, while the band-A emission (2.95 eV) decreased. Using these samples, we found that the band-A emission only appeared at unepitaxial crystallites (UC) sites, while other flat surface parts still showed the excitonic emission. High-resolution transmission electron microscopy revealed that there were grain boundaries which contained π-bonds in UC. This indicates that one of the origin of the band-A emission in diamond films is attributed to π bonds of grain boundaries.
Spectrally Resolved Cathodoluminescence Determination of Dopant Diffusion In InP/InGaAsP Based Multi Quantum Well Fabry-Perot Lasers
Authors: Zanotti-Fregonara C. , Ferrari C. , Lazzarini L. , Salviati G. , Meliga M. , Bertone D. , Fang R. Y. , Morello G. , Paoletti R.
Published: April 2011

Low temperature monochromatic cathodoluminescence (CL) spectral analyses and imaging were used to determine the widths of resistive regions (due to Fe diffusion) in multi-quantum-well (MQW) InP-based laser devices and to detect the different amount of damage induced by alternative In-situ Etching (ISE) and Reactive Ion Etching (RIE) techniques. The widths of the resistive regions were estimated by comparing the 5 K CL emission width from the MQW and the actual width as obtained by SEM investigations. Monochromatic CL also did not reveal any emission from the InP:Sn layer between semi-insulating material (Fe-doped lnp) and p-type layer (Zn-doped InP), indicating interdiffusion of Fe and Zn laterally the MQW, and the presence of substantial Sn diffusion (up to 2500 nanometers) into the substrate.
x-ray Surface Scattering Studies of Molecular Ordering at Liquid-Liquid Interfaces
Authors: Schlossman Mark L. , Li Ming , Mitrinovic Dragoslav M. , Tikhonov Aleksey M.
Published: April 2011

We present our recent progress in using synchrotron x-ray surface scattering techniques to study several different aspects of ordering at liquid-liquid interfaces. (1) We present measurements of the interfacial width at the water-alkane interface for a series of different chain length alkanes. The width for the shortest chain length studied is in agreement with capillary wave theory. However, significant deviations occur for longer chain lengths, indicating the presence of molecular ordering at the interface. (2) Under appropriate conditions, a surfactant monolayer forms at the interface between water and a hexane solution of a fluorinated surfactant. Reflectivity measurements that probe the electron density profile normal to the interface provide information about the surfactant ordering. This monolayer undergoes a solid to gas transition as a function of temperature. Diffuse scattering near the transition reveals the presence of islands. (3) Equilibrium interfaces between two aqueous phases containing PEG (polyethylene glycol) and potassium phosphate salts can be studied. We present studies of coherent capillary wave fluctuations between two interfaces of a thin film of this biphase system. We also demonstrate that biological macromolecules can be trapped and studied at this aqueous-aqueous interface.
The Incorporation of Lung Surfactant Specific Protein SP-B Into Lipid Monolayers at the Air-Fluid Interface: A Grazing Incidence x-ray Diffraction Study
Authors: Lee K.Y.C. , Majewski J. , Kuhl T.L. , Howes P.B. , Kjaer K. , Lipp M.M. , Waring A.J. , Zasadzinski J.A. , Smith G.S.
Published: April 2011

Grazing incidence x-ray diffraction (GIXD) measurements were performed to determine the effects of SP-B1.25, the N-terminus peptide of lung surfactant specific protein SP-B1.25, on the structure of palmitic acid (PA) monolayers. In-plane diffraction shows that the peptide fluidizes a portion of the monolayer, but does not affect the packing of the residual ordered phase. This implies that the peptide resides in the disordered phase, and that the ordered phase is essentially pure lipid. The quantitative insights afforded by this study lead to a better understanding of the lipid/protein interactions found in lung surfactant systems.
Synchrotron x-ray Scattering Study on Oxidation of AIN/Sapphire
Authors: Kang H. C. , Seo S. H. , Noh D. Y.
Published: April 2011

We present an x-ray scattering study of the oxidation of AIN/sapphire films into λ-A12O3 upon annealing. Epitaxial AIN/Sapphire(0001) transforms into nano-crystalline epitaxial λ-A12O3 during annealing at temperatures above 800°C in air. The crystalline orientational relation between the λ-Al2O3 and AIN are < 111 > // < 0001 > in the film normal direction, and < 110 > // < 1120 > in the film plane direction. The domain size of the spinel λ-A1203 crystalline is smaller than 50 Å in both out-of-plane and in-plane directions. The XPS depth profiles of the oxide film showed that the film is composed of aluminum and oxygen, and the atomic concentration ratio is about 2:3.
Study of the Buried Interface Behavior of Liquid Crystal Thin Films Using Synchrotron Radiation and Grazing Incidence x-ray Scattering Mode
Authors: Hu Y. , Martínez-Miranda L.J.
Published: April 2011

We have used the intensity and tunability of a synchrotron x-ray source in order to access the buried interface between a glass substrate and a liquid crystal thin film. We find that for energy of 9.4kev, the x-rays can penetrate a 0.22mm substrate. Grazing Incidence x-ray Scattering has been used to study the alignment of the films as a function of depth and temperature. Our results indicate the presence of both a chevron structure and a structure similar to the helical twist-grainboundary (TGB) phase. Some films have a disordered interfacial layer. This technique can be applied in the study of semiconductor devices as well as surfactant film interfaces.
Investigation of Inhomogeneous In-Plane Strain Relaxation in Si/SiGe Quantum Wires by High Resolution x-ray Diffraction
Authors: Zhuang Y. , Schelling C. , Roch T. , Daniel A. , Schäffler F. , Bauer G. , Grenzer J. , Pietsch U. , Senz S.
Published: April 2011

The structural properties of Si/SiGe quantum wires, which were grown by local solid source molecular beam epitaxy through a Si3N4/SiO2 wire-like shadow mask, were investigated by means of high resolution x-ray coplanar and x-ray grazing incidence diffraction, as well as by transmission electron microscopy. High resolution x-ray coplanar diffraction was used to obtain the average in-plane strain in Si/SiGe wires before and after removing the Si3N4/SiO2 shadow mask. x-ray grazing incidence diffraction measurements were performed to obtain information on the shape of the wires and on the depth-dependent strain relaxation. A finite element method was used to calculate the strain distribution in the Si/SiGe wires and in the Si substrate which clearly show the influence of the Si3N4/SiO2 shadow masks on the strain status of the Si/SiGe wires in agreement with the experimental data.
A High-Resolution Angle-Resolved Photoemission Study of the Temperature Dependent Electronic Structure of the Pentatelluride ZrTe5
Authors: McIlroy D. N. , Zhang Daqing , Kempton Bradley , Wharton J. , Littleton R. T. , Tritt T. M. , Olson C. G.
Published: April 2011

The temperature dependent band structure of the pentatelluride ZrTe5 has been examined using the technique of high-resolution angle-resolved photoemission in conjunction with synchrotron radiation. Specifically, the band dispersion along the X-Γ-X high symmetry axis was mapped at 20K (TTc), where Tc≃160K. One electron band and two hole bands within 0.5eV of the Fermi level have been identified. The dispersion of the bands indicates that they have extremely small electron and hole effective masses. The hole bands were observed to distort and shift in energy upon raising the sample temperature above Tc, indicative of a surface distortion.
The Role of Structure-to-Property-Relationships in Materials Characterization
Authors: Morgner W.
Published: April 2011

The paper deals with questions concerning the material characterization for steels in the field of engineering and metallurgy. Based on the structure-to-property-relationships, a procedure is proposed to strengthen the systematical development of methods for nondestructive characterization of materials. The state of the nondestructive characterization of metals is reviewed and applications are described in which adequate macroscopic physical properties are measured in order to characterize the materials state and properties nondestructively. The materials characterization of ball bearing steel and cast iron using multiparametrical approaches is discussed in detail.
Microscopic Techniques for Characterization of Magnetic Layers
Authors: Meyendorf N. , Altpeter I. , Netzelmann U. , Hoffmann J. , Nichtlpecher W. , Grimm H.
Published: April 2011

In recent years increasing interest in magnetic materials especially amorphous and nano crystalline layers has arised. Due to the magnetostrictive and magnetoresistive properties magnetic materials obtained high importance in sensor, actuator and memory applications. Therefore new methods to characterize magnetic and mechanical properties of magnetic materials are required. Two new microscopic techniques will be presented in this paper.
Three-Dimensional, Nondestructive Imaging of Low Density Materials
Authors: Kinney J.H. , Haupt D.L. , Lemay J.D.
Published: April 2011

The goal of this study was to develop a three–dimensional imaging method for studies of deformation in low-density materials during loading, and to implement finite element solutions of the elastic equations based on the images. Specimens of silica–reinforced polysiloxane foam pads, 15 mm in diameter by 1 mm thick, were used for this study. The nominal pore density was 50%, and the pores approximated interconnected spheres. The specimens were imaged with microtomography at ∼16µm resolution. A rotating stage with micrometer driven compression allowed imaging of the foams during deformation with precise registration of the images. A finite element mesh, generated from the image voxels, was used to calculate the mechanical properties of the structure, and the results were compared with conventional mechanical testing. The foam exhibited significant nonlinear behavior with compressive loading. The finite-element calculations from the images, which were in excellent agreement with experimental data, suggested that nonlinear behavior in the load displacement curves arises from buckling of the cell walls during compression and not from any nonlinear properties of the base elastomer. High–resolution microtomography, coupled with efficient finite–element modeling, shows promise for improving our understanding of the deformation behavior of cellular materials.
IR Tomography of the Lifetime and Diffusion Length of Charge Carriers in Semiconductor Silicon Ingots
Authors: Akhmetov V.D. , Fateev N.V.
Published: April 2011

A nondestructive method for estimating quality of single-crystal Si ingots is proposed. The method provides a three-dimensional pattern of the lifetime and diffusion length of charge carriers inside Si ingots up to 300 mm in diameter and I m in length. The method employs optical probing of ingots with laser-emitted radiation and includes laser-induced photoinjection of charge carriers followed by laser-assisted monitoring of their spatial distributions and time evolution in any part of the ingot about 1 cm in size.
Small Signal AC-Surface Photovoltage Technique for Non-Contact Monitoring of Near Surface Doping and Recombination-Generation in the Depletion Layer
Authors: Marinskiy D. , Lagowski J. , Wilson M. , Savtchouk A. , Jastrzebski L. , DeBusk D.
Published: April 2011

Small signal non-contact ac-SPV method for monitoring near surface doping (NSD) in silicon has recently been introduced in commercial diagnostic tools. High chopping frequency light with a submicron penetration depth is used to generate small SPV signal and this signal is in turn monitored using a transparent pickup electrode. This technique has the advantage of producing fast, non-destructive full wafer measurement. Under certain conditions, the magnitude of this ac-SPV signal is inversely proportional to the depletion layer capacitance. If a depletion layer barrier height is known this allows the calculation of the concentration of ionized donors or acceptors in the depletion layer. NSD measurements by ac-SPV method were typically done for doping concentrations up to about 1016 cm−3. Only recently this range has been extended to 1018 cm−3, making it a very attractive technique for monitoring low and medium dose implants and especially for wafer scale mapping of implant uniformity and activation efficiency. In addition, the frequency dependence of the SPV signal provides a mean for evaluating the minority carrier lifetime in the near surface region of bulk and epitaxial wafers.

The influence of surface/interface traps upon small ac-SPV signal has never been fully understood. This paper quantifies the role of interface traps in the monitoring of NSD. The effect of typical surface treatments such as HF, SCI and SCI+SC2 wafer cleans are examined.
Image-Guided Failure Assessment of Porous Materials
Authors: Tantillo M. , Müller R.
Published: April 2011

Lightweight metallic cellular materials have the potential for use in composite structures such as plates, shells, and tubes. In order to evaluate the usefulness of these porous materials, an understanding of their failure mechanisms is essential. We have developed a technique called image-guided failure assessment that allows for the 3-dimensional analysis of fracture initiation and progression on the microscopic level. The technique has already been used to study trabecular bone failure, and the objective of this study was to use the technique to study porous aluminum alloys. Image-guided assessment involves the use of a novel micro-compression device to apply and maintain loads, and the use of micro-computed tomography, providing 68 µm isotropic resolution in this application, to image the specimens. Specimens were compressed and imaged at intervals of increasing strain (0%, 0.8%, 4%, 8%, 16%, and 32% strain). The advantage of using a nondestructive approach to assess failure is that subsequent images of increasing strain can be animated to give visual information regarding fracture initiation and progression. In our tests, damage was seen to accumulate and propagate in local bands rather than being evenly distributed throughout the structure. This implies that local strains may be much larger than the apparent strain. These preliminary results demonstrate the usefulness of image-guided failure assessment in obtaining both visual and mechanical data regarding fracture initiation and progression. The technique is applicable to a multitude of porous materials and might, in the future, become a new standard in the mechanical assessment of these structures.
Nondestructive Measurement of In-Plane Residual Stress in Silicon Strips
Authors: Zheng Tieyu , Danyluk Steven
Published: April 2011

This paper reports the development of a shadow moiré technique to measure the in-plane residual stresses of thin, flat strips. This is an extension of prior work on the measurement of in-plane residual stresses in silicon plates and wafers. Phase stepping shadow moir6 and digital image processing techniques are employed to measure the deflections of the silicon plate specimens subjected to three-point-bending at several different loads. The measured deflections over the area of the silicon plates are fitted with an equation represented by a 2-D polynomial. With the theory of thin plates with large deflection, the fitting coefficients are used to extract the in-plane stresses at the different bending load. The residual stress is resolved by linear regression of the in-plane stresses versus bending loads.
Interfacial Diffusion in a MOCVD Grown Barium Titanate Film
Authors: Datta A. , Chattopadhyay Soma , Richter A.G. , Kmetko J. , Lee C. B.
Published: April 2011

A combination of two nondestructive techniques, Grazing Incidence X-ray Reflectivity and High Resolution X-ray Diffraction, is used to study (at around 10Å resolution) the composition profile across a 500Å thick film of BaTiO3 grown epitaxially on (100) MgO by MOCVD. Results from both studies indicate diffusion of Mg to about 250Å into the film at film-substrate interface, consistent with the diffuse ferroelectric phase transition observed in this film. The lattice parameter a shows a progressive decrease as we move into the film from the interface, and an anomalously low value in the Mg-free portion of the film.
Impedance Spectroscopy Investigation on the Low-Temperature Degradation of Tetragonal Zirconia: Influence of Measurement Conditions
Authors: Santos A. P. , Domingues R. Z.
Published: April 2011

Impedance spectroscopy has been used for the characterization the low-temperature degradation of yttria-stabilized tetragonal zirconia polycrystals in a non-destructive assay. Superficial transformations resulting from annealing in air lead to the appearance of an extra relaxation in the impedance spectra which evolves with degradation extent. It has been demonstrated that in situ electrical characterization cannot be performed because the electrode layers retard the degradation phenomenon. The ideal temperature/time condition to record spectra is also discussed.
A Study of Quasi-Breakdown Mechanism in Ultrathin Gate Oxide Under Various Types of Stress
Authors: Guan Hao , Xu Zhen , Cho Byung Jin , Li M. F. , He Y. D.
Published: April 2011

The quasi-breakdown (QB) in ultra thin gate oxide is investigated through the observation of defect generation during high field F-N stress and substrate hot hole and hot electron stresses. The interface trap density increases during stress and reaches to a same critical amount at the onset point of QB regardless of stress current density and stressing carrier type. The experiments also show that hot carriers are much more effective to trigger QB than F-N electrons at the same current level. This can be ascribed to the fact that hot carrier has much higher interface state generation rate than F-N electron does. All results consistently support the interface damage model for the QB occurrence.
Ultrathin NO/N2O Oxynitride Dielectric For Advanced Flash Memory Application: Single Wafer and Batch Technology
Authors: Zonca R. , Crivelli B. , Polignano M. L. , Cazzaniga F. , Alessandri M. , Caricato A. P. , Bersani M. , Sbetti M. , Vanzetti L. , Xing G. C. , Miner G. E. , Astici N. , Kuppurao S. , Lopes D. , Nesso S.
Published: April 2011

In this paper a systematic investigation of nitrided oxides obtained by Rapid Thermal Oxidation/Nitridation (RTO/RTN) in AMAT Centura System is reported. Two different aspects were considered: first the comparison between single wafers and batch technology, second the different possible oxide architecture achievable with RTO/RTN system (i.e. RTO + RTN, RTN + RTO, RTN + RTO + RTN). Both morphological and patterned wafers were processed. Physical and chemical characterizations were carried out by means of SIMS, XPS, ELYMAT, AFM and Etching Rate studies. Morphological results were then correlated to electrical data obtained on MOS capacitors. The film obtained performing a NO RTN nitridation of the native oxide followed by a ISSG (In Situ Steam Generation) oxidation exhibited very promising electrical properties that made it an appealing candidate as gate dielectric in CMOS and Flash memories applications.
Microscopic and Theoretical Investigations of the Si-SiO2 Interface
Authors: Duscher G. , Buzcko R. , Pennycook S. J. , Pantelides S. T. , Müllejans H. , Rühle M.
Published: April 2011

Z-contrast imaging and electron energy-loss spectroscopy with a spatial resolution at the atomic scale provide evidence of an atomically abrupt Si-SiO2, interface. Th micrographs revealed no indication for an interface layer of crystalline oxide at this thermally grown interface. Theoretical ab-initio calculations of two different interface structures showed that even in the most ideal interface the local density of states extends into the region of the oxide band gap. The O-K energy-loss near-edge structure was simulated for both interface models. The comparison of theoretical and experimental results of the O-K near-edge structure agreed and showed that states below the conduction band of the oxide are caused by the dimer-like SiO-Si bridges present in all structural models.
Room Temperature Ultraviolet Photoluminescence from 800°C Thermally Oxidized Si1−x−yGexCy Thin Films on Si(100) Substrate
Authors: Cheng X. M. , Zheng Y. D. , Zang L. , Liu X. B. , Zhu S. M. , Lo Z. Y. , Han P. , Jiang R.L.
Published: April 2011

The thermally oxidized Si1−x−yGexCy thin films were grown on silicon substrates by Plasma-enhanced Chemical Vapor Deposition (PECVD) and then wet oxidized at 800°C for 20 minutes. Photoluminescence spectra of the samples were measured at room temperature under 250nm excitation. Two ultraviolet photoluminescence bands with the peaks at ∼370nm and ∼396nm were observed in the oxidized samples. Possible mechanism of this photoluminescence is discussed.
Characterization of the Pb1 Interface Defect in Thermal (100)Si/SiO2 by Electron Spin Resonance: 29Si Hyperfine Structure and Electrical Relevance
Authors: Stesmans A. L.
Published: April 2011

Optimized electron spin resonance investigation resulted in the observation of the fuill angular dependence of the hyperfine (hi) spectra of the Pb1 interface defect in thermal (100)Si/SiO2, showing that the dominant hf interaction of the associated unpaired electron arises from a single Si site. The defect is identified as a prototype Si dangling bond defect with, much remarkably, the unpaired sp3-orbital pointing closely along a <211> direction at 35.26° with the [100] interface normal. If O is excluded as an immediate part of the defect, the key part of the Pb1 defect is uncovered as a tilted Si3≡Si unit. The incorporation of this defect kernel into a larger defect structure is analyzed within the framework of theoretical insight, suggesting the moiety to be part of a strained interfacial Si-Si dimer. ESR has been combined with electrical measurements to monitor the defect's behavior under thermal treatment, including postoxidation annealing in various ambients. No electrical activity of Pb1 as a detrimental interface trap could be traced, suggesting the defect to be of little relevance for device performance. The results are reviewed and discussed in the light of the defect's characteristic appearance at the (100)Si/SiO2 interface.
Challenges in Interface Trap Characterization of Deep Sub-Micron MOS Devices Using Charge Pumping Techniques
Authors: Autran J.L. , Masson P. , Ghibaudo G.
Published: April 2011

This work surveys some of our recent experimental and theoretical advances in charge pumping for the electrical characterization of interface traps present in MOSFET architectures. The first part of this paper is devoted to an improved time-domain analysis of the charge pumping phenomenon. This approach presents the main advantage to use the same formalism to describe the charge pumping contribution of a single trap or a continuum of traps at the Si-SiO2 interface. The implications for deepsubmicron MOSFET characterization are illustrated. Some experimental aspects are then presented, including the adaptation of the technique to ultra-thin oxides, non-planar oxides and DRAM memory cells. Finally, recent charge pumping characterization results are reported concerning the electrical behavior of the Si-SiO2 interface submitted to particular technological treatments, electrical and radiation stresses, or post-degradation anneals.
Surface and Interfacial Topography of Oxides on Si(111) With Ultra-Low Atomic Step Density
Authors: Oliver Antonio C. , Blakely Jack M.
Published: April 2011

Atomic force microscopy has been used to study the morphology of the oxide surface and the Si-SiO2 interface after oxidation of Si(111) surfaces that are either totally free of atomic steps or have well characterized low step density. The step-free areas were formed by thermally processing a patterned Si surface in which flat areas are enclosed by a square array of ridges; flow of the atomic steps into the surrounding ridge barriers produces a regular array of step-free areas each of which can be up to ∼50µm×50µm. Arrays of widely spaced steps (e.g. 5µm) can also be produced in the step-free areas. AFM scans of the same areas were taken prior to (dry) oxidation, after oxidation, and after chemical removal of the oxide. It was found that at an oxide thickness in the 5-13nm range, the initial step structure of the underlying Si substrates is translated through the oxide to the surface after oxidation with the oxide surface being somewhat rougher than the initial substrate. Furthermore, the initial step morphology of the substrate remains at the Si-SiO2 interface after etching away the oxide by HF. The interface roughness is less than that of the oxide surface. The results suggest that the initial oxidation of silicon proceeds in a ‘layer by layer’ manner and not through a preferential step-flow oxide growth mode.
Influence of Pre and Post Process Conditions on the Composition of Thin Si3N4 Thin Films (3 nm) Studied by XPS and TOFSIMS
Authors: Conard T. , Witte H. De , Vandervorst W. , Houssa M. , Heyns M. , Pomarede C. , Werkhoven C.
Published: April 2011

With the downscaling of the electronic devices and the increase in the frequency of the electronic circuits, a large search for new gate dielectric is ongoing. The exact composition and element distribution in the dielectric film have a large impact on the electrical characteristics of these films. We studied here the formation of ultrathin Si3N4 films (3 nm) under different conditions and concentrated on their composition analysis. The Si substrates were cleaned using RCA and/or HF dip. The Si3N4 films were subsequently fabricated either by RTCVD (SiH4/NH3) either by remote plasma (SiH4/N2) with or without a pre-anneal to form a 0.5 nm SiO2 layer. Post annealing was made using NO, N2O or NH3 at various temperatures and for various times. The quantification of the composition was realized using XPS and elemental distribution was analyzed using TOFSIMS with Ar+ sputtering and positive ion detection mode.

The results show that the fabrication method of the nitride film has only a very limited influence on the O/N content of the films. However, both the preparations of the substrate (HF last or RCA last) and the post-annealing influence strongly the film composition. The presence of an interfacial oxide increases significantly the oxygen content of the film. Post-annealing with N2O also increases the oxygen content of the film while the NH3 post-annealing leads to a significant decrease. The results are compared with electrical characterization of the same films.
Highly Reliable Thin Hafnium Oxide Gate Dielectric
Authors: Kang Laegu , Lee Byoung-Hun , Qi Wen-Jie , Jeon Yong-Joo , Nieh Renee , Gopalan Sundar , Onishi Katsunori , Lee Jack C.
Published: April 2011

HfO2 is the one of the potential high-k dielectrics for replacing SiO2 as a gate dielectric. HfO2 is thermodynamically stable when in direct contact with Si and has a reasonable band gap (∼5.65eV). In this study, MOS capacitors (Pt/HfO2/Si) were fabricated by depositing HfO2 using reactive DC magnetron sputtering in the range of 33∼135Å followed by Pt deposition. During the HfO2 deposition, O2 flow was modulated to control interface quality and to suppress interfacial layer growing. By optimizing the HfO2 deposition process, equivalent oxide thickness (EOT) can be reduced down to ∼11.2 Å with the leakage current as low as 1X10−2 A/cm2 at +1.0V and negligible frequency dispersion. HfO2 films also show excellent breakdown characteristics and negligible hysteresis after high temperature annealing. From the high resolution TEM, there is a thin interfacial layer after annealing, suggesting a composite of Si-Hf-O with a dielectric constant of ≈ 2 X K SiO2.
Nanoindentation Study of Amorphous Metal Multilayered Thin Films
Authors: Vella J. B. , Cammarata R. C. , Weihs T. P. , Chien C. L. , Mann A. B. , Kung H.
Published: April 2011

Nanoindentation studies were preformed on amorphous metal, multilayered thin films containing alternating layers of Fe50Ti50 and Cu35Nb65 in order to investigate the mechanism for plastic deformation in metallic glass. Films with a total thickness of 1μm and bilayer repeat lengths ranging from 2 to 50 nm were magnetron sputter-deposited onto sapphire substrates. In contrast to many crystalline multilayered systems, where large hardness enhancements have been observed when the bilayer repeat length is reduced below about 10 nm, no significant hardness enhancement as a function of bilayer repeat length was observed in the Fe50Ti50/ Cu35Nb65 amorphous metal system. This result suggests that a dislocation–like mechanism for plastic deformation may not be appropriate for these amorphous metals.
Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)
Authors: Bhatia C. S. , Chen C.-Y. , Fong W. , Bogy D. B.
Published: April 2011

Tribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carboncoated Al2O3-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated Al2O3/TiC sliders, forming CF3 (69) and C2F5 (119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation.
Fabrication and Characterization of Functionally Gradient Diamondlike Carbon Coatings
Authors: Wei Q. , Sharma A.K. , Yamolenko S. , Sankar J. , Narayan J.
Published: April 2011

Pure diamondlike carbon thin films largely bonded by four-fold coordination suffer from a large internal compressive stress that gives rise to a serious adhesion problem. In this work, functionally gradient (FG) diamondlike carbon thin coatings were prepared by pulsed laser deposition in a high vacuum chamber as an alternative approach to address the adhesion problem of diamondlike films. Copper, silver and titanium were incorporated into the growing films with their concentration as a function of the distance from the substrate surface. The top of the thin coating is pure DLC of about 400 nm in thickness. The total thickness of the functionally graded superhard DLC coatings can exceed 1.0 μm without buckling. Visible micro-Raman spectroscopy was used to characterize the bonding structure of the layers which contain alloy atoms. High resolution transmission electron microscopy was employed to study the microstructure of the coatings. Nanoscale mechanical characterizations using Nanoindenter XP™ were carried out to study the mechanical behavior of the functionally gradient DLC films.
A Brittle to Ductile Transition (BDT) in Adhered Thin Films
Authors: Gerberich W. W. , Volinsky A. A. , Tymiak N. I. , Moody N. R.
Published: April 2011

It has been long recognized that the BDT in bulk materials may be associated with enhanced plastic energy dissipation. This can be achieved by either changing the state of stress (plane strain to plane stress) or by raising the test temperature (lowering the yield stress). The situation is somewhat different in thin films where the BDT can be achieved by increasing film thickness or perhaps, even in a limited temperature range, by raising the test temperature. To study the latter we use a superlayer technique with a 1 μm tungsten film on top of thin copper films bonded to SiO2/Si wafers. This involves indenting into the superlayer which stores and then releases large amounts of elastic energy into the thin film/substrate interface. Here, preliminary data on 500 nm thick Cu demonstrates more than an order of magnitude increase in fracture energy from about 10 to 200 J/m2 as the test temperature is raised from 20°C to 130°C. As the amount of plastic energy absorption would appear to be limited by film thickness, this relatively large value was unanticipated. This interfacial fracture energy translates to a stress intensity of 5 MPa-m1/2. In context of the highest possible nanocrystalline Cu yield strength, this still represents a plastic zone of nearly 30 μm. This illustrates the quandary associated with explaining such high apparent toughness values as one generally expects plasticity to be truncated by film thickness. Is this associated with:

–some artifact of assessing local stresses during nanoindentation at elevated temperature:

–extending the plastic zone in the direction of crack growth much further than the film thickness;

–a shielding mechanism from an organized dislocation array in a ductile film sandwiched between a brittle substrate and a higher yield strength superlayer;

–some plastic energy dissipation in the superlayer;

–or by enhanced mode II at higher temperatures?

A few of these will be addressed in some detail with a goal of narrowing the field of the most promising candidates.
Modified Edge Lift-Off Test: Experimental Modifications for Multifilm Systems
Authors: Hay J. C. , Liniger E. G. , Liu X-H
Published: April 2011

In developing an adhesion test for a microelectronics fabrication facility there are many criteria which must be met. Some of these include (i) sample prep must be simple, (ii) deformations should be elastic so the problem can be easily modeled, (iii) mechanics are ideally analytical, and (iv) the test end-point must be unambiguous and easy to obtain. A testing method in the literature which meets many of these criteria is the modified edge liftoff test (MELT). Delamination is induced through the release of strain energy stored in an elastic superlayer which results from a large mismatch in CTE between the film and substrate. In this work we consider details of the energy release rate calculation, effects of plate bending, and initial flaw size.
Superlayer Residual Stress Effect on the Indentation Adhesion Measurements
Authors: Volinsky Alex A. , Moody Neville R. , Gerberich William W.
Published: April 2011

The practical work of adhesion has been measured in thin aluminum films as a function of film thickness and residual stress. These films were sputter deposited onto thermally oxidized silicon wafers followed by sputter deposition of a one micron thick W superlayer. The superlayer deposition parameters were controlled to produce either a compressive residual stress of 1 GPa or a tensile residual stress of 100 MPa. Nanoindentation testing was then used to induce delamination and a mechanics based model for circular blister formation was used to determine practical works of adhesion. The resulting measured works of adhesion for all films between 100 nm and 1 μm thick was 30 J/m2 regardless of superlayer stress. However, films with the compressively stressed superlayers produced larger blisters than films with tensile stressed superlayers. In addition, these films were susceptible to radial cracking producing a high variability in average adhesion values.
The Mechanical Properties of Common Interlevel Dielectric Films and Their Influences on Aluminum Interconnect Extrusions
Authors: Chen Fen , Li Baozhen , Sullivan Timothy D. , Gonzalez Clara L. , Muzzy Christopher D. , Lee H. K. , Levy Mark D. , Dashicll Michael W. , Kolodzcy James
Published: April 2011

Knowledge of the mechanical properties of interlevel dielectric films and their impact on sub-micron interconnect reliability is becoming more and more important as critical dimensions in ULSI circuits are scaled down. For example, lateral aluminum (Al) extrusions into spaces between metal lines, which become a more of a concern as the pitches shrink, appear to depend partially on properties of SiO2 underlayers. In this paper, the mechanical properties of several common interlevel dielectric SiO2 films such as undoped silica glass using a silane (SiH4) precursor, undoped silica glass using a tetraethylorthosilicate (TEOS) precursor, phosphosilicate glass (PSG) deposited by plasma-enhanced chemical vapor deposition (PECVD) and borophosphosilicate glass (BPSG) deposited by sub-atmosphere chemical vapor deposition (SACVD) were studied. Among the four common interlevel layers, BPSG exhibits the smallest modulus (E), hardness (H) and the highest the coefficients of thermal expansion (CTE). BPSG again has the lowest as-deposited compressive stress and the lowest local Si-O-Si strain before annealing. Stress interactions between the various SiO2 underlayers and the Al metal film are further investigated. The impact of dielectric elastic properties on interconnect reliability during thermal cycles is proposed.
Electromigration Modeling of Blech Experiment with Comparison to Recent Experimental Data
Authors: Fan Zhineng , Korhonen M. A. , Li C.-Y.
Published: April 2011

Finite element analysis is applied to simulate electromigration in a copper line/tungsten junction, which is a typical structure in Blech experiments adopted to measure the electromigration drift velocity by edge displacement. Because the specific resistivity of tungsten is higher than that of copper, the electric current crowds at the corner where the underlying tungsten bar connects to the edge of the copper line. Therefore, material in the corner is depleted faster than that in other places of the copper/tungsten interface. Our simulation reveals that a stress that may be high enough to crack the interface is also built up in the corner. The evolution of the line resistance under various current densities is calculated from our model and compared to recent experiment results.
The Implications of Energetic and Kinetic Surface Instability for a Stress Measurement Technique
Authors: Yu H. H. , Suo Z.
Published: April 2011

It has been understood for some time that elastic energy can cause surface roughening during a solid surface motion. This instability has recently led to a novel experimental technique to determine stress state on the surface of a solid by measuring the surface profile before and after etching [1]. Along a separate line of investigation, Aziz and co-workers has recently described a different kind of instability, also driven by stress [2]. Their experiments showed that the activation energy of the surface mobility depends linearly on the stress state, and this dependence can cause surface instability. The two kinds of instabilities have very different characteristics. In this paper, we describe a linear stability analysis of a three dimensional interface evolving under stress. The interface can be destabilized either by stress-dependent activation energy or by elastic energy. The implications for the stress measurement technique are discussed. It is suggested that the same experimental procedure be used to measure surface energy and activation strains.
The Strength and Fracture of Passive Oxide Films on Metals
Authors: Pang M. , Wilson D. E. , Bahr D. F.
Published: April 2011

Passive films have been grown electrochemically on a polycrystalline titanium alloy. By varying the applied voltages, the film thickness is varied. A testing apparatus has been constructed to allow measurements of nanomechanical properties during electrochemical testing using a Ag/AgCl reference electrode in a traditional three-electrode potentiostatic scan. The stress at which oxide film fracture occurs is correlated to the applied potential. Observations of in situ film fracture measurements on single grains during immersion show the strength of the film remains constant in environments in which the film is inert, but decreases by approximately 20% in solutions which lead to corrosion. The fracture mode of the oxide has been observed using atomic force microscopy, and is shown to qualitatively match the largest tensile stresses which develop using elastic contact mechanics. A simplified model for determining the maximum tensile stress around an indentation is presented, and is used to show the stress required for fracture increases approximately linearly with increasing applied anodic polarization, from 850 MiPa to approximately 3 GPa for applied potentials between 1 and 9 V.
Wafer Curvature Studies of Strengthening Mechanisms in Thin Films on Substrates
Authors: Leung O. S. , Nix W. D.
Published: April 2011

The effects of film thickness and passivation on plasticity of thin metal films on substrates have been studied using gold films as a model system. Wafer curvature/thermal cycling measurements were used to study plasticity in films ranging in thickness from 0.2 to 2.5 micrometers. We were able to describe these stress-temperature curves using a simple phenomenological model for linear kinematic hardening. The yield stresses revealed by the modeling were inversely proportional to the film thickness for thicknesses greater than about one micrometer. This relationship is expected from a dislocation model of plasticity. However, the residual stresses in thinner films are substantially lower than this relationship would predict and on unloading, these films show stress-temperature plots not predicted by the model. Stress-temperature curves were also measured after a tungsten passivation was deposited on the gold surface. Films thinner than one micrometer were substantially strengthened by this passivation and could then be described by the linear kinematic model. The observed stresses are only minimally affected for films thicker than about a micrometer. This strengthening effect on thinner films is consistent with the complete blocking of grain boundary diffusion near the free surface of the film.