Free-standing La_0.7Sr_0.3MnO₃ suspended micro-bridges on buffered silicon substrates showing undegraded low frequency noise properties

We report on the microfabrication process of free-standing suspended micro-bridges made of La_0.7Sr_0.3MnO₃ (LSMO) thin films of thicknesses in the range of 10–100 nm. LSMO films were epitaxially grown on either SrTiO₃ or CaTiO₃ buffer layers on silicon substrates by reactive molecular beam epitaxy. The micro-bridges were patterned using standard UV photolithography then etched by ion beam and released using reactive ion etching of silicon in SF₆. LSMO suspended micro-bridges 2 and 4 µm wide and of length ranging from 50 to 200 µm could be fabricated with a high fabrication yield (of about 85% as evaluated over 100 fabricated suspended micro-bridges) without degrading the electrical transport properties and in particular the low frequency noise level, as attested by the normalized Hooge parameter. The latter was measured in the 0.55–7.50  ×  10⁻³⁰ m³ range at 300 K, which is comparable to those measured in non-suspended high quality epitaxial LSMO thin films. This fabrication process could be useful for bolometer fabrication where thermal isolation is needed, or for any microelectromechanical systems devices making use of epitaxial functional oxides. (paper)