Mechanical behaviour of a multilayer system for microelectronic applications

Abstract
Thin PLT (Pb_0.9La_0.1TiO₃) ferroelectric films have been deposited by a PVD process on SrTiO₃ (STO) substrates and on a superconducting interlayer. Cross sections of the different films were observed by TEM and it allowed to determine the thickness of the coatings and to characterise their microstructure. Vickers microindentation and nano-indentation tests were performed on the substrate, on the PLT films and on the PLT/YBa₂Cu₃O₇/STO system. All these tests showed an anisotropy in the mechanical behaviour, with peculiar fracture distribution and cleavage. The Young's modulus and the hardness of these systems were measured using the nano-indentation, with different imposed depths. These experiments show a very interesting phenomenon with the superconducting interlayer addition : the film delamination observed without an interlayer during indentation experiments disappears for the multilayered material, due to the presence of the superconducting ceramic. This work offers the advantage to characterise for the first time peculiar mechanical properties of multilayered ceramics.