Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Crack and damage in low-k BEoL stacks under assembly and CPI aspects
    ( 2010)
    Auersperg, J.
    ;
    Vogel, D.
    ;
    Lehr, M.D.
    ;
    Grillberger, M.
    ;
    Michel, B.
    Miniaturization and increasing functional integration as the electronic industry drives push the development of feature sizes down to the nanometer range. Moreover, harsh operational conditions and new porous or nano-particle filled materials introduced on both chip and package level - low-k and ultra low-k materials in Back-end of line (BEoL) layers of advanced CMOS technologies, in particular - cause new challenges for reliability analysis and prediction. The authors show a combined numerical/experimental approach and results towards optimized fracture and fatigue resistance of those BEoL structures under manufacturing/packaging (during lead-free reflow-soldering, in particular) as well as chip package interaction (CPI) aspects by making use of bulk and interface fracture concepts, in multi-scale and multi-failure modeling approaches with several kinds of failure/fatigue phenomena. Probable crack paths and interactions between material damaging and interface fracture will be investigated and sensitivities with regard to structural modifications studied. Complementary to the simulation side of reliability estimations, serious issues are connected with the collection of appropriate material properties in the miniaturized range addressed - Young's modulus initial yield stress, hardening. Nano-indentation, AFM, FIB and EBSD provide these desired properties, in particular. In addition, manufacturing induced residual stresses in the Back-end layer stack have an essential impact on damage behavior, because they superpose functional and CPI loads. Their determination with a spatial resolution necessary for typical BEoL structure sizes is a critical issue. The nano-scale stress relief technique (fibDAC) makes use of tiny trenches placed with a focused ion beam (FIB) equipment at the position of stress measurement. Digital image correlation algorithms applied to SEM micrographs captured before and after ion milling allows to conclude on stresses released. Residual stresse
  • Publication
    fibDAC stress relief - A novel stress measurement approach with high spatial resolution
    ( 2010)
    Vogel, D.
    ;
    Maus, I.
    ;
    Michel, B.
    fibDAC stress relief is a new method developed to measure stresses on micro and nanotechnology devices. The classical macroscopic technique of stress relief by material removal has been adopted to determine stress with very high spatial resolution and marginal restrictions regarding the material under test. Focused Ion Beam (FIB) milling is used to remove locally material. Cross correlation algorithms on high resolution SEM images captured in the same FIB equipment reveal tiny stress relief deformations. Their analysis allows computation of stresses present at the place of ion milling. Thorough qualification of the approach resulted in a stress measurement accuracy of 1-5·10-4E, where E is the Young's modulus of the material tested. Lateral resolution of stresses can be reduced to a value around 200 ... 500 nm. Although the method needs finite element stress modeling, it is free of basic assumption upon the kind of stress and the stress built-up history.
  • Publication
    Localized high-resolution stress measurements on MEMS structures
    ( 2010)
    Vogel, D.
    ;
    Gollhardt, A.
    ;
    Michel, B.
    Three different methods of stress measurement with strong spatial resolution are presented. They base on stress relief techniques caused by focused ion beam milling, on altered electron backscattering by deformed lattices and on Stokes line shift measurements by Raman spectroscopy. The capability of these methods is demonstrated by their application to typical MEMS structures. A comparison between the methods is performed in order to outline potentials and limitations.
  • Publication
    Verfahren zur Bestimmung von Deformationen im Mikro- und Nanobereich
    ( 2010)
    Keller, J.
    ;
    Vogel, D.
    ;
    Maus, I.
    ;
    Gollhardt, A.
    ;
    Michel, B.
  • Publication
    Crack and damage evaluation in low-k BEoL stacks under assembly and CPI aspects
    ( 2010)
    Auersperg, J.
    ;
    Vogel, D.
    ;
    Lehr, M.U.
    ;
    Grillberger, M.
    ;
    Michel, B.
    Miniaturization and increasing functional integration as the electronic industry drives push the development of feature sizes down to the nanometer range. Moreover, harsh operational conditions and new porous or nano-particle filled materials introduced on both chip and package level - low-k and ultra low-k materials in Back-end of line (BEoL) layers of advanced CMOS technologies, in particular - cause new challenges for reliability analysis and prediction. The authors show a combined numerical/experimental approach and results towards optimized fracture and fatigue resistance of those BEoL structures under manufacturing/packaging as well as chip package interaction (CPI) aspects by making use of bulk and interface fracture concepts, in multi-scale and multi-failure modeling approaches with several kinds of failure/fatigue phenomena. In addition, manufacturing induced residual stresses in the Back-end layer stack have an essential impact on damage behavior, because they superpose functional and CPI loads. Their determination with a spatial resolution necessary for typical BEoL structure sizes is a critical issue. The nano-scale stress relief technique (fibDAC) makes use of tiny trenches placed with a focused ion beam (FIB) equipment at the position of stress measurement. Digital image correlation algorithms applied to SEM micrographs captured before and after ion milling allows to conclude on stresses released. Residual stresses can be computed with the help of appropriate, adjusted FEA models.
  • Publication
    Comparative study of residual stress measurement techniques with high spatial resolution
    ( 2010)
    Vogel, D.
    ;
    Maus, I.
    ;
    Schindler-Saefkow, F.
    ;
    Michel, B.
    Three different methods of stress measurement with strong spatial resolution are presented. They base on stress relief techniques caused by focused ion beam milling, on altered electron backscattering by deformed lattices and on Stokes line shift measurements by Raman spectroscopy. The capability of these methods is demonstrated by their application to typical MEMS structures. A comparison between the methods is performed in order to outline potentials and limitations.
  • Publication
    Local stress measurement methods for packaging purposes- a comparison
    ( 2010)
    Gollhardt, A.
    ;
    Vogel, D.
    ;
    Michel, B.
    The paper gives a brief overview on some advanced stress measurement methods, which permit local access to semiconductor or packaging structures with a micrometer scale spatial resolution. Focusing is made on local stress relief, Raman spectroscopy and EBSD based techniques. The methods are compared with respect to their resolution limits, feasibility to be applied to different materials and their specific limitations.
  • Publication
    Deformation and stress measurement on electronic components with high spatial resolution
    ( 2008)
    Vogel, D.
    ;
    Gollhardt, A.
    ;
    Keller, J.
    ;
    Michel, B.
  • Publication
    Approaches of local stress measurement on microsystem devices
    ( 2008)
    Vogel, D.
    ;
    Auerswald, E.
    ;
    Gollhardt, A.
    ;
    Luczak, F.
    ;
    Sabate, N.
    ;
    Michel, B.
    Integration of micro and nano devices causes several new reliability issues to be analyzed and solved. Among them mechanical stresses between and in structural components covering some dimensional magnitudes are one of the concerns. The latter appear as residual stresses resulting from a multitude of different component processing steps manufacturing micro and nano components, as wells as stresses introduced by the nano-to-micro integration, e.g. by the component packaging, or by environmental loads. Unfortunately, stress determination in MEMS/NEMS and their packaging is everything else as a simple task. Finite element simulations should include modeling of complete production steps, having impact on final stress profiles. Realistically, this approach cannot be realized for complex devices. Experimentally, the choice of available stress measurement methods with micro- or even nanoscopic spatial resolution is rather limited. The authors developed a new promising stress measurement technique allowing access to stresses in microscopic and nanoscopic system areas. This method bases on the specific testing feasibilities provided by focused ion beam (FIB) equipment. Ion milling is utilized to release very locally residual stresses on components of interest. Generated this way surface deformations around the milled area are measured by digital image correlation (DIC) algorithms. As a result originally existing residual stresses are computed from measured stress release deformations. The method is being applied to semiconductor structures, MEMS components and packaging materials.
  • Publication
    Residual Stress Measurements on Semiconductor Layers Utilizing Stress Relief Techniques
    ( 2008)
    Vogel, D.
    ;
    Lehr, M.U.
    ;
    Grillberger, M.
    ;
    Jaschke, V.
    ;
    Geisler, H.
    ;
    Gollhardt, A.
    ;
    Luczak, F.
    ;
    Michel, B.