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Qualitative new mechanical properties of microstructured metallic systems

: Schreiber, J.; Melov, V.G.

Green, R.E.; Djordjevic, B.B.; Hentschel, M.P ; Bundesanstalt für Materialforschung und -prüfung -BAM-, Berlin; Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. -DGZfP-, Berlin; Center for Nondestructive Evaluation -CNDE-:
Nondestructive Characterization of Materials XI : Proceedings of the 11th International Symposium on Nondestructive Characterization of Materials
Berlin: Springer, 2003
ISBN: 3-540-40154-7
International Symposium on Nondestructive Characterization of Materials <11, 2002, Berlin>
Fraunhofer IZFP ()
mechanical property; metallic system

Different micro-systems have been developed which only have in common that they are fabricated by processes know from semiconductor technology. The knowledge of used materials that has been gathered in mechanical engineering cannot be used very often in micro-systems technology because is often deals with thin structured layers whose properties are rather different from those of bulk material and even of lateral extended thin films.
In this contribution results of bending tests for various metallic stripes and lines sputtered on Si- substrates are presented. The analysis of their deformation structure during bending reveals anomalous plastic-elastic mechanical properties of the metallic systems of micro- and sub-micrometer dimensions. Just from the beginning the mechanical behaviour is characteristic for a quasi-linear elastic chain coupled to a two-dimensional viscous system. When straining the lines perpendicular to their extension no elastic resistance is observed. Only after achieving a critical strain the normal 3D elastic-plastic behaviour re-entries.
The peculiar mechanical behaviour results in strong stress migration. After annealing at 200°C originally rectangular cross sections of Cu-lines showed a clear doubling peak structure. Such effects are observed also after few cycles of load. Other practical consequences are discussed concerning the reliability of metallic interconnects, the quality of micro-mirror materials as well as a new approach of micro-material tailoring by surface treatment.