A new on chip nanomechanical testing concept applied to brittle and ductile thin films materials

Pardoen, Thomas [UCL] Safi, A. Coulombier, Michaël [UCL] Carbonnelle, Pierre [UCL] Raskin, Jean-Pierre [UCL] Gravier, S.

A novel, versatile concept of micromachines has been developed to measure the mechanical response of films, beams or tubes, with thickness ranging between 10 to 1000 ran. Its capacity to study large strains and fracture is one of its key advantages. This new technique has been used to characterize the elastic modulus and fracture stress of two types of brittle films: polysilicon and silicon nitride. The Young's modulus agrees with the literature data. The fracture stress of polysilicon is shown to increase with decreasing specimen surface size, in agreement with the recent literature. In addition, uniaxial tensile tests have been performed on 210 nm-thick Al films up to fracture. These results show that large ductility can be obtained in very thin freestanding films, which is important for many micro- and nano-systems developments.