Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    An in situ tensile test device for thermo-mechanical characterisation of interfaces between carbon nanotubes and metals
    ( 2016)
    Hartmann, S.
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    Bonitz, J.
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    Heggen, M.
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    Hermann, S.
    ;
    Hölck, O.
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    Schulz, S.E.
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    Gessner, T.
    ;
    Wunderle, B.
    In this paper we present our recent efforts to develop an in situ tensile test device for thermo-mechanical characterization of interfaces between single-walled carbon nanotubes (SWCNTs) and metals. For the mechanical tests, the chosen loading condition is a pull-out test. After summarizing results of maximum stresses calculated from molecular dynamics simulations and obtained from in situ scanning electron microscope experiments we outline the requirement for an in situ experimental method with atomic resolution to study the mechanics of SWCNT-metal interfaces in further detail. To this purpose, we designed, fabricated and characterized a silicon-based micromechanical test stage with a thermal actuator for pull-out tests inside a transmission electron microscope. The objective is to obtain in situ images of SWCNT-metal interfaces under mechanical loads at the atomic scale for fundamental structure investigation. The design of this MEMS test stage permits also the integration of SWCNTs by wafer level technologies. First experiments with this MEMS test stage confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements that allow for a defined load application of SWCNTS. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope. The presented system may be also used and further developed for in situ characterization of other materials.
  • Publication
    Towards nanoreliability of CNT-based sensor applications: Investigations of CNT-metal interfaces combining molecular dynamics simulations, advanced in situ experiments and analytics
    ( 2015)
    Hartmann, S.
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    Shaporin, A.
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    Hermann, S.
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    Bonitz, J.
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    Heggen, M.
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    Meszmer, P.
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    Sturm, H.
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    Hölck, O.
    ;
    Blaudeck, T.
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    Schulz, S.E.
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    Mehner, J.
    ;
    Gessner, T.
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    Wunderle, B.
    In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (CNTs) embedded in metal matrices. We conducted experimental pull-out tests of CNTs embedded in Pd or Au and found maximum forces in the range 10-102 nN. These values are in good agreement with forces obtained from molecular dynamics simulations taking into account surface functional groups (SFGs) covalently linked to the CNT material. The dominant failure mode in experiment is a CNT rupture, which can be explained with the presence of SFGs. To qualify the existence of SFGs on our used CNT material, we pursue investigations by means of fluorescence labeling of surface species in combination with Raman imaging. We also report of a tensile test system to perform pull-out tests inside a transmission electron microscope to obtain in situ images of CNT-metal interfaces under mechanical loads at the atomic scale.
  • Publication
    Molecular dynamic simulations of maximum pull-out forces of embedded CNTs for sensor applications and validating nano scale experiments
    ( 2014)
    Hartmann, S.
    ;
    Hölck, O.
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    Blaudeck, T.
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    Hermann, S.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    We present investigations of pull-out tests on CNTs embedded in palladium by means of molecular dynamics (MD) and compare our results of maximum pull-out forces with values of nano scale in situ pull-out tests inside a scanning electron microscope (SEM). Our MD model allows the investigation of crucial influencing parameters on the interface behaviour, like CNT diameter, intrinsic CNT defects and functional groups. For the experiments we prepared simple specimens using silicon substrates and wafer level compliant technologies. We realised the nano scale experiment with a nanomanipulation system supporting an AFM cantilever with known stiffness as a force sensing element inside a SEM. Greyscale correlation has been used to evaluate the cantilever deflection. From simulations derived maximum pull-out forces are approximately 17 nN and depend on the existence of intrinsic defects or functional groups and weakly on temperature. Experimentally obtained maximum pull-out force s with values between 16-29 nN are in good agreement with the computational predictions. Our results are of significant interest for the design and a failure-mechanistic treatment of future mechanical sensors with integrated single-walled CNTs showing high piezoresistive gauge factor or other nano scale systems incorporating CNT-metal interfaces.
  • Publication
    Development of transfer Electrostatic Carriers (T-ESC®) for thin 300mm wafer handling using seal glass bonding technology
    ( 2012)
    Balaj, I.
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    Raschke, R.
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    Baum, M.
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    Uhlig, S.
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    Wiemer, M.
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    Gessner, T.
    ;
    Grafe, J.
  • Publication
    Sensornetzwerk zum Monitoring von Hochspannungsleitungen
    ( 2012)
    Voigt, S.
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    Wolfrum, J.
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    Pfeiffer, M.
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    Keutel, T.
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    Brockmann, C.
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    Grosser, V.
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    Lissek, S.
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    During, H.
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    Rusek, B.
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    Braunschweig, M.
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    Kurth, S.
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    Gessner, T.
    In diesem Beitrag wird ein autarkes Sensornetzwerk zur Überwachung und Optimierung der Auslastung von Hochspannungsleitungen vorgestellt sowie Ergebnisse aus Tests im Hochspannungslabor und auf 110-kV-Hochspannungsleitungen diskutiert. Das Sensornetzwerk besteht aus zahlreichen Sensorknoten, die direkt am Leiterseil der Freileitung montiert sind. Zusätzliche Komponenten am Mast werden nicht benötigt. Das System arbeitet autark. Die Energieversorgung der Sensorknoten erfolgt aus dem elektrischen Streufeld der Hochspannungsleitung. Die Knoten nehmen die Temperatur, die Neigung des Leiterseils sowie den Strom, der durch die Leitung fließt, auf. Diese Messdaten werden anschließend von Sensorknoten zu Sensorknoten bis zur Basisstation per Funk im 2,4 GHz-ISM-Band übertragen. In der Basisstation, welche sich im Umspannwerk befindet, werden die Daten aufbereitet und in Form eines Webservers mit Datenbanksystem der Leittechnik zur Verfügung gestellt.
  • Publication
    Electronic transport properties in copper nanowire
    ( 2008)
    Mohammadzadeh, S.
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    Pouladsaz, D.
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    Streiter, R.
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    Gessner, T.
    In present work, we study the electronic transport properties of copper nanowire using the non-equilibrium Green's function technique on the density functional tight binding method for modelling the conductance under external bias voltage. We also carried out the calculations for the Au nanowire for comparison.
  • Publication
    Investigations on via geometry and wetting behavior for the filling of through silicon vias by copper electro deposition
    ( 2008)
    Hofmann, L.
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    Küchler, M.
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    Gumprecht, T.
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    Ecke, R.
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    Schulz, S.
    ;
    Gessner, T.
    The background of this paper is the fabrication of Through Silicon Vias (TSV) for three-dimensional chip stacking. At first an adapted etching process is presented. Vias with a cross sectional area of approx. 3x10 square micron and 50 - 70 micron depth were etched. Those vias have a V-shaped entrance that is aimed to prevent a pinch-off at the via-top and a void formation during the subsequent filling process. For a better filling performance a pre-treatment of the vias is necessary, too. Therefore the wetting behavior of Cu-CVD and Cu-PVD layers as well as Au-PVD layers that have undergone several pre-treatments was investigated by contact angle measurements. Moreover two plating chemistries were investigated regarding their impact on the wetting. Copper electro deposition experiments have been performed using DC and Pulse-Reverse (PR) currents and two commercially available electrolyte systems. In this experiment the beneficial effect of the V-shaped vias could be shown as well as the impact of several pre-treatments.
  • Publication
    Reproducible reliable ausi eutectic wafer bond process with high yield
    ( 2008)
    Schwerdtner, R.
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    Froemel, J.
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    Wiemer, M.
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    Gessner, T.
    The AuSi eutectic bond process is a well known and important technique in the field of single chip packaging. When it comes to low-cost and hermetic sealed packages for MEMS/NEMS sensors and actuators this technology has its decisive merits. The AuSi bonding is a low-temperature process with an electric conductive alloy. To achieve a reliable bonding with 100% yield is quite difficult, especially for large areas. In our institute we made several analyses with different process parameters and surface properties variations. The results show that the surface condition of the silicon side of the wafer pair as well as the process parameters are very important factors in relation to the yield of the eutectic bond. We also did investigations on the thickness of the gold layer. Unlike conventional AuSi wafer bonding technologies [1] our technique does not need several m thick gold layers. We were able to achieve 100% bond yield with 1500nm and even 150nm thin gold layers. Anoth er result we found was that a good bonding process is not only depending on the value of applied temperature and time, there is also an important influence because of the heat flow and applied pressure. In the presentation we would like to introduce our results and experience, plus we will present the coherences of parameter variations for achieving 100% yield.
  • Publication
    Low-cost, fully integrated liquid handling platform for protein assays
    ( 2008)
    Nestler, J.
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    Hiller, K.
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    Morschhauser, A.
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    Bigot, S.
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    Griffiths, C.
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    Auerswald, J.
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    Gavillet, J.
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    Nonglaton, G.
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    Otto, T.
    ;
    Gessner, T.
  • Publication
    Fuel gas determination using a MEMS gas analyser
    ( 2008)
    Otto, T.
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    Saupe, R.
    ;
    Weiss, A.
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    Throl, O.
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    Stock, V.
    ;
    Gessner, T.
    Gas condition is of importance for operating industrial firing processes. Changing gas conditions, caused by a diversification of the natural gas purchase, affect combustion processes, the warmth brought into and subsequent production processes. Especially at sensitive thermal processing units a consequent adjustment of the burn attitudes is, with change of the natural gas condition, obligatory. The direct measurement of the gas condition ensures adjusting effects of variable gas conditions very fast and precisely. Thus consequent improvement advance the process and product quality. Currently available devices are mostly huge and expensive. Some inexpensive devices, which came to the market in the last years, measure only individual variables and are thereby not able to determine atypical gas compositions correctly. An answer to this problem enables the direct acquisition of clearly more gas constituents by using a MEMS analyser. Since large individual component determination of the natural gas components, disadvantages of existing systems will be avoid and the determination of a precise fuel value will be enabled. Core component of the system is a NIR-MEMS-spectrometer, which has been optimized for this purpose. The connection to the process is realized with a specific gas measuring cell. The realization of a practicable system require an exact adoption of the optical system according to efficient sample connection a high wavelength stability, which represents the condition for exact chemometric evaluation. Other challenges are MEMS design and packaging optimization regarding to vibration stability and thermal stress. The paper describes functional principle and characteristics of a novel MHMS-based gas analyser. Experimental results will demonstrate the sv stem performance.