Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Comparative film thickness determination by atomic force microscopy and ellipsometry for ultrathin prepolymer films
    ( 1995)
    Gesang, T.
    ;
    Fanter, D.
    ;
    Höper, R.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    Ellipsometry and Atomic Force Microscopy (AFM) were utilized to study the film thickness of continuous and discontinuous polymer films in the 1 to 20 nm thickness range on smooth silicon wafers and on structured aluminum substrates. The methods of exploiting AFM for thickness measurements with a high spatial resolution are described. For continuous films, the AFM method is a direct one, i.e. it does not rely on any model. There is excellent agreement between AFM and ellipsometry in the 1 to 10 nm thickness range. Very small systematic deviations in this range, but big deviations above 10 nm occur and are discussed. The film preparation method, spin coating, was characterized to result in prepolymer films with a very homogeneous thickness. Discontinuous films with 2 to 9 nm thickness were also evaluated by both methods of thickness determination. In this case, for one of the AFM approaches a model has to be utilised, too. The agreement between both methods ranged from very good to poor depending on the kind of sample and on the kind of AFM determination method
  • Publication
    Prepolymer film growth by adsorption out of solution on silicon and aluminium. An atomic force microscope study
    ( 1995)
    Gesang, T.
    ;
    Höper, R.
    ;
    Dieckhoff, S.
    ;
    Hartwig, A.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    A cyanurate prepolymer was applied to smooth silicon wafers or to distinctly structured aluminum coatings. The surface composition of the substrates was investigated by X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Ellipsometry. The application methods, spin coating and dip coating represent adsorption by a technical process exerting significant shear stresses or nearly equilibrated conditions, respectively. The mean thickness of the prepolymer film was adjusted by variation of the concentration of the solution and checked by ellipsometry. Atomic Force Microscopy (AFM) monitored the development of the respective film morphologies of all 4 systems (silicon / aluminum, spin / dip coating) in the mean film thickness range from 1 to 50 nm.
  • Publication
    Quantitative Erfassung von Oberflächentopographien
    ( 1995)
    Gesang, T.
    ;
    Höper, R.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    Some applications of Atomic Force Microscopy in adhesion science and technology are presented. The essential advantage of AFM over mere imaging methods is the capability of quantitatively acquiring the topography of the sample surface. This in turn allows a number of useful quantitative evaluations of the surface. The examples described are fluorination and oxygen plasma treatment of a polypropylene foil for improvement of adhesion. Moreover it is evidenced that AFM can provide nanoscopic insight into adhesion phenomena by imaging the islands of adsorbed adhesive molecules. They show specific characteristics of their geometric shape depending on the kind of adhesive molecule and on the type of substrate.
  • Publication
    Imaging elastic sample properties with an atomic force microscope operating in the Tapping Mode
    ( 1995)
    Höper, R.
    ;
    Gesang, T.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    ;
    Boseck, S.
    Many delicate samples cannot be imaged without artefacts by contact-mode AFM. However, tapping-mode AFM is well suited for topographic imaging of this kind of sample. When the delicate samples laterally consist of different ,material phases, ambiguities in the interpretation of the topographic image can occur. Unfortunately, at present for tapping-mode imaging there is no technique available for the acquisition of material-contrast images. In this paper we present a way for tapping-mode material-contrast imaging. The material property utilized is the differing deformability of distinct material phases. Therefore, the controlled elastic deformation of the sample in the tapping mode is the first investigation carried out in this study. The novel method of tapping-mode material-contrast imaging has been validated for two different kinds of samples, both consisting of hard substrates partially covered by deformable organic adsorbates. In both cases deformabilities could be measured and mat erial-contrast images have been acquired. The smallest visible adsorbed objects in the material-contrast images had a width of about 5 nm.
  • Publication
    Organic film formation investigated by atomic force microscopy on the nanometer scale
    ( 1995)
    Gesang, T.
    ;
    Höper, R.
    ;
    Dieckhoff, S.
    ;
    Schlett, V.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
  • Publication
    AFM investigations of the initial stages of prepolymer film growth on aluminium
    ( 1995)
    Gesang, T.
    ;
    Höper, R.
    ;
    Dieckhoff, S.
    ;
    Fanter, D.
    ;
    Hartwig, A.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    A cyanurate prepolymer was applied to aluminium coated silicon wafers by adsorption out of solution. Film growth from the initial stages to closed films was studied by Atomic Force Microscopy (AFM). Sample preparation in the presence of external forces (spin coating) leads to film morphologies very different from adsorption near equilibrium (dip coating). The edge of the non closed films can be characterized by means of a borderline angle. The influence of specific prepolymer - substrate interactions, external forces and substrate topography is discussed. The formation of ultrathin, amorphous organic films on solids is studied for an application oriented model system. A prepolymer or a copolymer of a cyanate based high temperature adhesive is spin cast or dip coated onto silicon wafers or aluminium coatings to produce films as thin as possible. The mean thickness ranges from 1 - 4 nm. After a thorough substrate characterization by imaging and spectroscopic methods, the various films we re investigated by atomic force microscopy. Besides imaging, for discontinuous films atomic force microscopy was also utilized to measure the 'borderline angle' introduced in this paper. The borderline angle characterizes the slope of the surface of an isolated adsorbed organic object near the substrate. Thus, it is the geometric equivalent to the classical contact angle of a lying liquid drop. However, the phenomena leading to these angles are different. Nevertheless, the borderline angle is related to the affinity of the organic phase to the substrate an d thus will play an important role in future investigations of film formation and adhesion on the nanometer scale.
  • Publication
    AFM - Abbildung feinster Strukturen
    ( 1995)
    Gesang, T.
    ;
    Höper, R.
    ;
    Possart, W.
    ;
    Hennemann, O.-D.
    Atomic Force Microscopy allows novel investigations into birth and growth of ultrathin polymeric films. This bears relevance both for coatings and for adhesive bonding technology. The article describes the initial stages of prepolymeric film growth on silicon wafers and aluminum evaporation layers which have been selected for their application orientation. The prepolymer chosen is based on the dicyanate of bisphenole A and is a potential ingredient for high temperature adhesives. The initial stages of film growth have been accomplished by adsorption out of solution. The application techniques either realize adsorption with significant centrifugal forces ("Spin Coating`) or in nearly equilibrated condition ("Dip-Coating"). The investigations reveal the respective kind of growth which highly depends on the type of substrate and on the application technique.