Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy

We present a method for characterizing ultrathin films using sensitivity-enhanced atomic force acoustic microscopy, where a concentrated-mass cantilever having a flat tip was used as a sensitive oscillator. Evaluation was aimed at 6-nm-thick and 10-nm-thick diamond-like carbon (DLC) films deposited, using different methods, on a hard disk for the effective Young's modulus defined as E/(1 - ν2), where E is the Young's modulus, and ν is the Poisson's ratio. The resonant frequency of the cantilever was affected not only by the film's elasticity but also by the substrate even at an indentation depth of about 0.6 nm. The substrate effect was removed by employing a theoretical formula on the indentation of a layered half-space, together with a hard disk without DLC coating. The moduli of the 6-nm-thick and 10-nm-thick DLC films were 392 and 345 GPa, respectively. The error analysis showed the standard deviation less than 5% in the moduli

Film deposition by laser and arc technologies

Physical Vapor Deposition (PVD) based on laser pulses or vacuum arc discharges are distinguished by the highly (often completely) ionization of the plasma beam with high ion energies. Hence, with comparable plasma parameters both processes give comparable films. However, from the technological point of view there are essential differences, especially themuch easier control of the laser processes and the much higher productivity of the arc technologies. The pecularities of the laser and of the arc processes, their similarities and their differences are discussed in general terms. Their particular potential is demonstrated for actual applications including the preparation of nanometer precision films (e.g. for X-ray mirrors), the deposition on special geometries (e.g. for copper metalization of microelectronic structures) and the deposition of special film qualities (e.g. for preparation of superhard amorphous carbon)

Superharte Kohlenstoffschichten durch Nanometer-Schichtdesign

Schutzschichten werden gewöhnlich mit dickeren Schichten von mindestens einigen Mikrometern Dicke in Verbindung gebracht. Bei solchen Schichtdicken ist eine hinreichende Tragfähigkeit gegenüber mechanischer (z.B. abrasiver) Beanspruchung und eine hinreichende Barriere z.B. gegenüber korrodierenden Medien zu erwarten. Die Weiterentwicklung der Schutzschichtsysteme erfordert die umfassende Nutzung der neueren Möglichkeiten der Nanotechnologie: · Für wichtige Anwendungen in der Mikroelektronik und der Mikrosystemtechnik müssen Schutzwirkungen bereits mit Schichtdicken um oder weniger als zehn Nanometern erfüllt werden. Beispiele: Schutzschichten bei Computer-Festplatten, Diffusionsbarrieren für die Kupferleitungsbahnen in Silizium-Chips. · Die Grundvoraussetzung für jede (Schutz-)Beschichtung ist eine hinreichende Haftung. Die Festigkeit der Verbindung mit dem Substrat wird gewöhnlich in der Übergangsschicht von wenigen Nanometern entschieden. Die empirische Optimierung des Inter face stellt oft einen entscheidenden Teil des Beschichtungs-know-hows dar. Eine solche Empirie (manchmal auch Alchemie) ist aber nur bedingt zu verallgemeinern und gibt damit keine technologische Sicherheit bei der Skalierung oder der Übertragung auf andere Anlagen. Hier ist die strukturelle Aufklärung der Nanometer-Zwischenschicht und ihre gezielte Einstellung (in Sinne eines Interface-Engineering) erforderlich. · Auch Mikrometer-Schichten sind oft keineswegs homogen. Häufig weisen sie aufgrund des Wachstumsprozesses eine nanodisperse Struktur oder infolge technologischer Variationen (z.B. durch Substratrotationen) einen feinlamellierten Aufbau aus Nanometerschichten auf. Einerseits können damit scheinbar belanglose geometrische und/oder kinematische Modifikationen über eine geänderte Nanostruktur zu unbeabsichtigten, wesentlichen Veränderungen der Schichteigenschaften führen. Andererseits lassen sich durch gezielt eingestellte Nanostrukturen beträchtliche Verbesserungen (z.B. Härte steigerungen) erreichen

Mechanical characterization of ultrahard and ultrathin films by laser acoustics

The mechanical properties are often the main topic, but at least a necessary precondition in the application of thin films. The indentation methods with monitoring of load and penetrating depth yield local stress-strain curves. Devices are now available with depth resolution down to the manometer range. They are very valuable tools for mechanical characterization for many film systems. But the indentation methods have some intrinsic limitations. Apart from such problems as uncertainties of the tip shape and influence of surface roughness, there are two classes of thin films, which are especially critical: ultra-hard and ultra-thin films. For ultra-hard films (with Vickers hardness HV > 50 GPa) the deformabilities of indenter and film become comparable. For ultra-thin films (with thickness below 100 nm) the plastic zone induced even by very shallow indentations is usually not restricted on the film material but reaches into the underlying substrate. Thus the measured values represent a certain average of the film-substrate composite, where the film properties cannot extracted from in a reliable manner due to the high complexity and non-linearity of the indentation test. The film characterization by Young's modulus determined by surface ultrasonic waves helps to overcome these problems. The laser-acoustic method has proved to be very suitable as reliable, quick and robust technique for testing thin films. The surface acoustic wave method is based on linear-elastic phenomena. Hence, even for deformation fields reaching deep into the substrate, the film properties may be deciphered by strong mathematics. Furthermore, high film hardness is not limiting. (There is only another unavoidable restriction: the attenuation of the substrate material for the high frequency ultrasonic surface waves must be sufficient low.) The measuring method and some representative results are given in chapter 3 and 4, respectively. But at first the basic question must be discussed, if the Young's modulus is suitable for mechanical characterization at all

Identifikationselement

DE 102006017155 A1 UPAB: 20071119 NOVELTY - The identification unit has a structural unit formed as a coating on a substrate. The identification unit is detected by an electromagnetic radiation in a tera-hertz frequency region. The coating has a thickness smaller than 50 nanometer and an electrical conductivity of 100 siemens per meter. The maximum thickness of the coating is kept at 15 nanometer. The coating is composed of aluminum, copper, gold, silver, cobalt, nickel, iron and alloy of metals. The structural unit has a substructure for producing diffraction and interference effects. USE - Used in a label for identifying an article e.g. valuable piece of luggage or parcel and high-quality textile. ADVANTAGE - The coating has a thickness smaller than fifty nanometer and the electrical conductivity of hundred siemens per meter, thus improving falsification and manipulation security of the identification unit to provide a safe detection of the identification unit for identifying the articles

DLC-Schichtabscheidung mit dem Laser-Arc und Eigenspannungsuntersuchungen

The Laser-Arc is a controlled pulsed arc plasma source combining advantages of the pulsed laser deposition (PLD) technique with the high energy efficiency of a vacuum arc (VAD). The influence of deposition temperature on DLC-film properties will be shown by the results of mechanical and optical studies. Elastic modulus (E) was measured by means of ultrasonic surface waves. E-values up to 230 GPa were obtained for substrate temperatures bellow 150 Cel. The very small modulus for T > 150 Cel suggests a drastic decrease of sp (exp 3)/sp (exp 2) onding ratio in the amorphous DLC structure. These results correlate with optical studies, by means of ellipsometry and the behaviour of the complex refractive index. The optical absorption at 10.6 micrometres ranges from 200 to 900 cm (exp -l) and depends on the film thickness and on the substrate material. The results demonstrate that the Laser-Arc is suitable for the preparation of DLC-coatings with optical quality

Tribological behavior of superhard amorphous carbon films

Due to their unique combination of low adhesion, high abrasive resistance and chemical inertness, the amorphous carbon films are increasingly becoming established as optimum tribological coatings for many applications. The breakthrough for protective carbon coatings on components was achieved by their application in Diesel injection systems. Application on tools is limited at higher temperatures, especially in the case of steel machining, because of the high solubility of carbon in steel. Hence, carbon coated tools are preferably to be used for machining of non-iron materials and for forming processes. Up to now only hydrogenated carbon films (a-C:H and related systems), are commercially available. A great potential for future applications is offered by the ta-C films with their markedly higher hardness and their specific interaction with lubricants. Fraunhofer IWS has developed coating technology for deposition of ta-C films in the industrial scale. The tribological behavior of amorphous carbon films is determined by monomolecular covering layers strongly attached to the surface. They cause the very low friction in normal humid air, their absence in dry air or vacuums leads to high friction. Lubricants usually do not improve the tribological behavior in comparison to air. However with non-hydrogenated ta-C films a marked reduction of friction is possible by attaching specially adapted lubricants