ICMCTF2007 Session F2: In Situ Characterization

Wednesday, April 25, 2007 1:30 PM in Room Royal Palm 4-6

Wednesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	F2-1 Local Strains in Micro and Nanostructures using Synchrotron Radiation O. Thomas (Universite Paul Cezanne, France) Very high stresses arise in thin films and in the nanopatterned structures (lines, dots) that are made from them due to the constraint of the substrate to which they are attached. The mechanical behavior of these small structures can deviate significantly from scaling laws developed for bulk materials. Moreover, the origins and magnitudes of these stresses are of great interest in technology as many fabrication and reliability problems are stress related. X-ray diffraction has at least three distinct advantages with respect to strain measurements: 1) it is very sensitive to atomic displacements; 2) it is non destructive; 3) it can yield the six elements of the strain tensor. I will give examples from recent work where x-ray diffraction has been used to investigate average strains in lines, films or multilayers. However, the variations in stress within such structures can be very large. These stress gradients can arise from the proximity of surfaces or interfaces, from dislocation structures, from grain-to-grain interactions, etc. The knowledge of strain distributions in such objects is necessary in order to understand their properties. The need to characterize displacement fields in nanostructures together with the advent of third generation synchrotron radiation sources has generated new and powerful methods (anomalous diffraction, coherent diffraction, micro-diffraction). I will review some of the recent and promising results in the field of strain measurements in small dimensions via X-ray diffraction. Most examples I will give will be taken from the microelectronics industry: Silicon On Insulator (SOI) structures, Cu damascene lines, NiSi films.
2:10 PM		F2-3 Mechanical Behaviour and Micro Structural Evolution of ZrO₂ Thin Films Subjected to an External Tensile Loading at High Temperatures B. Benali, M. Herbst Ghysel (Université Paris-Sud, France); I. Gallet (CNRS, France); M. Ignat (INP Grenoble, France); A.M. Huntz, M. Andrieux (Université Paris-Sud, CNRS, France) Zironia thin films were deposited by MOCVD (organo-metallic injection chemical vapour deposition) at various temperatures and oxygen pressures on stainless steel substrates with a zirconium beta-diketonate as precursor. The 250 nm thin as deposited zirconia films presented a microstructure consisting of two phases: the monoclinic expected one and also, an unexpected tetragonal phase. According to the literature, the stabilization of the tetragonal phase (metastable in massive zirconia) can be related to the grains size and/or, to the generated internal compressive stresses. To analyse the effect of internal and external stresses on the behaviour in the film, in-situ experiments were performed, applying external tensile stresses at room temperature and high temperature (500°C). Depending on the process parameters, in-situ phase transformations and damage evolution in the films were observed. Our results are discussed with respect to the observed microstructural and chemical changes, and also with respect to XRD (X-ray diffraction) analyses, used to determine phase ratios and residual stresses within films before and after the mechanical experiments.
2:30 PM		F2-4 Activation Characterization of Non-Evaporable TiZrV Getter Films by Synchrotron Radiation Photoemission Spectroscopy C.-C. Li, J.-L. Huang (National Cheng-Kung University, Taiwan); R.-J. Lin (Intellectual Property Exchange Limited, Taiwan); D.-F. Lii (Cheng Shiu University, Taiwan) In order to upgrade and sustain the vacuum inside the cavity of the vacuum-type devices, the non-evaporable getter (NEG) materials, such as titanium or titanium alloys, have been widely used due to their high chemical activity, large solubility and high diffusivity on the adsorbed gases. The essential requirements for the non-evaporable getter (NEG) material are the high pumping speed (high surface area, high solubility and diffusion rate for the absorbed molecules), short activation time and low activation temperature. These properties are strongly related to the composition and microstructure of the NEG materials. We characterized the effects of activation temperatures on the oxidation state of surface layer of the air-exposed dense and porous TiZrV films on (100) Si substrates in a ultra-high-vacuum chamber by the synchrotron radiation photoemission spectroscopy (SRPES) with beam energy of 600 eV. Dense and porous TiZrV films were grown by the dc magnetron sputtering method with zero and 70° glancing angle between substrate and target, respectively. The dense and porous TiZrV films have similar composition and thickness, and their specific surface areas are 2 m²/g and 13 m²/g, respectively. The surface oxides of air-exposed TiZrV films are consisted of TiO₂, V₂O₅ and ZrO₂ for both films. The highly oxidized state of surface layer are gradually decomposed into sub-oxides and pure metallic state with increasing the activation temperature from 160°C to 350 C. For both films, the reduced degree of surface oxide is similar at the same activation temperature. The surface of the dense and porous TiZrV films, activated at 350 C , comprises metallic Ti, Zr, V and sub-oxides of Zr and Ti. The detailed results of photoemission spectra of the activated TiZrV films and discussion of evolution of surface oxides during consecutive activation processes will be presented.
2:50 PM		F2-5 Characterization and Modelling of the Elastic Properties of Nano-Structured Thin Films E. Le Bourhis, P.O. Renault, Ph. Goudeau, B. Girault, G. Geandier, P. Villain, P. Guerin (Université de Poitiers, France); O. Castelnau, R. Chiron (CNRS, France); D. Thiaudiere (SOLEIL, France) Understanding the mechanical behaviour of nano-structured thin films in relation with their microstructure is of high importance for the development of technological applications. We are focussing our research on the investigation of the elastic properties of such materials. Model nanometric multilayer W/Cu systems exhibiting different microstructures are elaborated, the microstructure of which being characterized by TEM (grain shape, layer thickness) and XRD (crystallographic texture). These films are supported by a (thin) polyimide substrate. Films mechanical response is characterized experimentally by X-ray diffraction (XRD) based in-situ techniques to assess the orientation and depth dependences of elastic strain and stress. Results are interpreted by an appropriated mechanical modelling accounting for the material microstructure, based on homogenization schemes. For doing this, an in-situ biaxial tensile apparatus is currently developed and will be installed on the new French synchrotron SOLEIL. This machine will alloy exploring many different configurations of applied stress together with a high resolution characterization by diffraction.
3:10 PM		F2-7 Spectroscopic Ellipsometry Study of Silver Thin FIlms Deposited by High Power Pusled Magnetron Sputtering J. Li, S.R. Kirkpatrick (University of Nebraska-Lincoln); D.M. Mihute (University of Nebraska -Lincoln); S.L. Rohde (University of Nebraska-Lincoln) Thin silver films have been deposited on silicon, glass and oxide-coated glass by High Power Pulsed Magnetron Sputtering (HPPMS) and the growth processes have been studied in-situ using spectroscopic ellipsometry. HPPMS generates a very high fraction of metal ions (up to 95%) as compared to conventional DC magnetron sputtering (less than 10%), and thus provides a more energetic deposition flux. In an effort to control the nucleation and growth kinetics, both the ion flux and substrate temperature have been varied in the present study of Ag coalescence. It has been determined that this combination can result in lower coalescence thicknesses with decreasing substrate temperature. In addition, the deposited ultra thin silver films (1-10nm) have been shown to be unstable after the deposition is stopped. The silver islands in the ultra thin films tend to migrate with both increasing time and substrate temperature. The coalescence process on several substrates has also been compared.
3:30 PM		F2-8 Arc Deposition of Amorphous Carbon and Ti/C Multilayers Studied with In-Situ Ellipsometry L. Ryves, P.O. Persson (The University of Sydney, Australia); M. James (Bragg Institute, Australian Nuclear Science & Technology Organisation, Australia); J.E. Bradby (Australian National University, Australia); M.M.M. Bilek (The University of Sydney, Australia) Spectroscopic ellipsometry (SE) has been used to monitor the evolution of the structure and optical properties of thin films during deposition. Ex-situ analyses with transmission electron microscopy and X-ray reflectometry provided further structural information. A high current pulsed cathodic arc system equipped with multiple cathodes was used, which allows for deposition of multilayers, composites and alloys. Amorphous carbon(a-C)/Ti multilayers with periods from 1.5nm to 20nm were deposited. In-situ ellipsometry revealed a very low percolation threshold for Ti films nucleated on a-C layers, allowing for sub-nanometre continuous layers to be deposited. On the other hand, the initial few nanometres of a-C grown on a Ti surface were found to exhibit a different structure to thicker a-C films. The implications of this carbon structure on the nanoindentation response of these multilayer films will be discussed.
3:50 PM		F2-9 Mechanical Characterization of Multilayer Nitride Coatings K. Rzepiejewska-Malyska, J. Michler (EMPA, Switzerland); H. Wrzesinska (Institute of Electron Technology, Poland) Mechanical properties of ultrathin multilayer coatings TiN/NbN, NbN/CrN and CrN/TiN, deposited on silicon <100> by dc magnetron sputtering process were investigated. Thin films with different thickness of the single layers (range between 2 - 25 nm) and different number of periods, as well as reference coatings were synthetized. Ellipsometrical measurements allowed a calibration of the deposition time during the sputtering process. Stochiometry of the reference coatings was characterized by the GDOS technique. Hardness and Young's modulus were determined by nanoindentation experiments with a Berkovich indenter. To asses toughness and adhesion of the coatings in-situ SEM indentation experiments were performed. This technique allows for observation of pile-up or sinking-in phenomena and crack propagation during the loading cycle. The reference coatings of pure materials exhibited very different mechanical behavior. NbN had a tendency to pile-up already at low applied loads (<15 mN). Adhesion between coating and the substrate was weak - delamination and spalling off for higher forces were observed. TiN coatings showed sink-in and crack propagation for similar low applied loads. The CrN coating had a tendency to pile-up that was observable for about 15 mN, and shear band formation around the indent as well as longer cracks compared to the other materials, were visible for higher loads. Based on the crack morphology, the fracture toughness of the coatings was estimated. For the study of multilayer samples that require indentation depths below 100nm a Hysitron PicoIndenter® was integrated into a high resolution SEM. First observations with this new type of setup will be presented at the conference.
4:10 PM		F2-10 Deformation of Ti₃SiC₂ MAX Phase Material using High Temperature Nanoindentation and In-Situ Deformation within TEM F. Giuliani (Linköping University, Sweden); J. Emmerlich (RWTH Aachen University, Germany); L. Johnson (Linköping University, Sweden); W.J. Clegg (University of Cambridge, United Kingdom); L. Hultman (Linköping University, Sweden) Work elsewhere has shown that MAX phase materials can deform by the formation and movement of kink bands. Furthermore, these kink bands have been observed beneath nanoindents in thin film MAX phase material. The aim of this paper is to investigate whether such effects can also be observed at elevated temperature and to study the effects of temperature on the deformation patterns under the indent. The hardness of Ti₃SiC₂ MAX phase material has been studied at temperatures from room temperature up to 400°C. These measurements have been correlated with changes in deformation patterns using cross-sectional transmission electron microscopy, where sections have been prepared directly through the centre of the indents. Furthermore, the presence of kink bands as a deformation mechanism has been linked to anelastic effects during the deformation process; this is investigated by deforming the material within the transmission electron microscope using an in-situ nanoindenter.
4:30 PM		F2-11 Novel In-Situ Characterization of Micro-Scale Wear Behavior R. Wheeler, J. Hu (UES, Inc.); A.A. Voevodin, J. Zabinski (Air Force Research Laboratory) Materials applications in the vacuum environment of space often require very demanding tribological thin film properties. The study of such behavior is ideally suited for the chamber environment of electron and ion beam microscopes. Here, micro and nano-scaled microstructural features can be captured via electron imaging using in-situ techniques. Using specialized testing equipment operating within a dual beam FIB microscope chamber, small spherical contact tips, tens of microns in diameter, produce wear tracks in flat coating samples under vacuum. Interruptions of these reciprocal motion micro-tribometer tests enable monitoring of time dependent buildup of wear debris. Termination of the microscale test, while maintaining unbroken contact between tip and surface, allows the tip/debris/film microstructure to remain "frozen" in time. Subsequent sectioning using the FIB yields intact TEM cross sections as well as serial cross sections which can be used for 3-D reconstruction of local structure.