Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Characterisation of Cu/Cu bonding using self-assembled monolayer
    ( 2018)
    Lykova, M.
    ;
    Panchenko, I.
    ;
    Künzelmann, U.
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    Reif, J.
    ;
    Geidel, M.
    ;
    Wolf, M.J.
    ;
    Lang, K.-D.
    Purpose: Cu/Cu diffusion bonding is characterised by high electrical and thermal conductivity, as well as the mechanical strength of the interconnects. But despite a number of advantages, Cu oxidises readily upon exposure to air. To break through the adsorbed oxide-layer high temperature and pressure, long bonding time and inert gas atmosphere are required during the bonding process. This paper aims to present the implementation of an organic self-assembled monolayer (SAM) as a temporary protective coating that inhibits Cu oxidation. Design/methodology/approach: Information concerning elemental composition of the Cu surface has been yielded by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy. Two types of substrates (electroplated and sputtered Cu) are prepared for thermocompression bonding in two different ways. In the first case, Cu is cleaned with dilute sulphuric acid to remove native copper oxide. In the second case, passivation with SAM followed the cleaning step with dilute sulphuric acid. Shear strength, fracture surface, microstructure of the received Cu/Cu interconnects are investigated after the bonding procedure. Findings: The XPS method revealed that SAM can retard Cu from oxidation on air for at least 12 h. SAM passivation on the substrates with sputtered Cu appears to have better quality than on the electroplated ones. This derives from the results of the shear strength tests and scanning electron microscopy (SEM) imaging of Cu/Cu interconnects cross sections. SAM passivation improved the bonding quality of the interconnects with sputtered Cu in comparison to the cleaned samples without passivation. Originality/value: The Cu/Cu bonding procedure was optimised by a novel preparation method using SAMs which enables storage and bonding of Si-dies with Cu microbumps at air conditions while remaining a good-quality interconnect. The passivation revealed to be advantageous for the smooth surfaces. SEM and shear strength tests showed improved bonding quality for the passivated bottom dies with sputtered Cu in comparison to the samples without SAM.
  • Publication
    Nothing is as it seems - A contribution to changes in the base and filler materials during fusion brazing
    ( 2013)
    Wittke, K.
    ;
    Scheel, W.
    ;
    Kising, M.
    ;
    Rinn, A.
    The heat input and the heat control for thermal processes such as brazing usually lead to changed microstructures of the base and filler materials. The studies described in this article were performed on brazed joints which were manufactured from the X5CrNi18-10 steel (material number: 1.4301) with copper brazing materials and were prepared under reducing protective gas in a continuous furnace. On the one hand, the microstructural changes in the volume of the base material and on its brazing surface are considered and, on the other hand, chemical changes in the process gas atmosphere and in the filler material as well as liquid-metal embrittlement of the transport chain during the brazing process are discussed.
  • Publication
    Generative Fertigungstechnologien für eine Direktintegration von mikroelektronischen Komponenten und Kontaktstrukturen
    ( 2013)
    Ifland, D.
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    Ansorge, F.
    ;
    Baar, C.
    ;
    Lang, K.-D.
    The present article deals with the development ofSys-tem-in-Package (SiP) modules, which are produced by stereolithography, an additive fabrication process. During the production process of the SIP module the necessary electrical components will be integrated into the carrier substrate. Afterwards the components will be interconnected of an electrically conductive adhesive. This method is intended to demonstrate a novel three-dimensional construction and connection technology for microsystems.
  • Publication
    Anwendungen hydrophober Oberflächenmodifikationen in der Mikrosystemtechnik
    ( 2013)
    Georgi, L. von
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    Kahle, R.
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    Lang, K.-D.
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    Bauer, J.
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    Braun, T.
    ;
    Becker, K.-F.
    ;
    Jung, E.
    In this report, the principles and processes involved in surface modification to create hydrophobic/ hydrophilic surfaces for use in microsystems are set out. Two examples are used to illustrate this, the first being contactless placing of small microelectronic components and the second being the manipulation of reagent-containing water droplets for rapid micro-diagnosis.
  • Publication
    Stressmessung auf Chip-Ebene - Ein Fahrtenschreiber für die Elektronikverarbeitung
    ( 2013)
    Schreier-Alt, T.
    ;
    Fraunhofer, F.A.
    This article investigates stress measurement within electronic systems during fabrication and reliability testing. Results of an on-chip MOS stress measurement technology are investigated with a special focus on soldering and encapsulation of systems. Experimental results are compared with numerical simulations. The stress sensor is based on a MOS chip, subdivided into 60 measurement cells (300 fim grid) and needs only four electrical connections. We are able to measure the shear and both main stresses in-plane of the chip surface. The stress value of the measurement cell can be interrogated subsequently within 50 ms time steps. The main potential of this stress measurement chip is to replace selected electronic parts and to investigate all production and lifetime related loads acting on the system. The presented measurement technique enables a more accurate characterization of manufacturing processes and polymer behavior. Finally the sensor enables the choice of optimized materials minimizing production related stresses and leading to more reliable products.
  • Publication
    RFID - Theoretische Konzepte und Anwendungsbeispiele
    ( 2010)
    Fotheringham, G.
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    Ohnimus, F.
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    Maaß, U.
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    Ndip, I.
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    Guttowski, S.
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    Reichl, H.
    RFID tags are now used in the widest range of applications and this can make special demands in terms of their design. The basics of design of inductively coupled (LF or HF) RFID tags are described, and some specialised solutions to specific problems, noted. As an example, the design and manufacturing sequence for a curved HF RFID is described.
  • Publication
    Solidification and wetting behaviour of SnAgCu soldier alloyed by reactive metal organic flux
    ( 2010)
    Zerrer, P.
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    Fix, A.
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    Hutter, M.
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    Reichl, H.
    Purpose - The purpose of this paper is to develop a new alloying method for solders by using a metal organic modified flux in solder pastes. Design/methodology/approach - This paper presents the impact of six metal organic compounds (Co, Fe, Al; stearate, oxalate, citrate) on the melting and solidification behaviour in comparison to the revealed microstructure. Findings - It could be shown that Co and Al influence the supercooling whereas Fe exhibits no effect. Co reduces the supercooling of the cast of about 10 K and affects the nucleation. Al retards the solidification up to 185 degrees C. Doping of the solder by flux containing metal organic compounds is successful and the alloying elements Co and Fe are found in the microstructure. Research limitations/implications This paper provides a starting-point for the new alloying method so far only fluxes for solder pastes have been investigated. Originality/value - The reactive alloying method enables the use of new alloying elements for solder pastes in unmodified soldering processes.
  • Publication
    Gravitationsgestützte galvanische Abscheidung zur Erzeugung dreidimensional kristallin strukturierter Oberflächen
    ( 2010)
    Schmidt, R.
    ;
    Zwanzig, M.
    ;
    Moritz, H.
    Using the process known as gravitation-enhanced electrodeposition, structured metal layers can be formed without the use of masks in a specially designed cell. In this process, the depletion of metal ions at the deposition interface is avoided, by use of a rocking cell. Using this technology, encouraging results were obtained for Flip-Chip bonding, bringing advantages in the production of stacked, thinned chips in a wafer assembly.
  • Publication
    Neues modulares Anlagenkonzept für nasschemische Ätzprozesse und die Wafergalvanoformung
    ( 2009)
    Guttmann, M.
    ;
    Kaiser, K.
    ;
    Muth, S.
    ;
    Moritz, M.
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    Schmidt, R.
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    Zwanzig, M.
    ;
    Hofmann, L.
    ;
    Schubert, I.