Bulk-micromachining of SrTiO3 substrates is employed to realize suspended structures made of epitaxial thin films of complex oxides such as trampoline resonators and sealed membranes with physical access from both sides. The fabrication protocol relies on wet chemical etching of SrTiO3 and uses (La,Sr)MnO3 as hard mask and device layers.
Abstract
Suspended micro-structures made of epitaxial complex oxides rely on surface micro-machining processes based on sacrificial layers. These processes prevent to physically access the microstructures from both sides, as substantial part of the substrate is not removed. In this work, a bulk micromachining protocol is developed for a commonly used substrate employed in oxide thin films deposition. Suspended oxide thin film devices are realized by fabricating pass-through holes across SrTiO3(100) or SrTiO3(110) substrates. Careful calibration of anisotropic etching rates allows controlling the final geometry of the aperture in the substrate in a predictable way. As demonstrators of possible device geometries, clamped membranes and trampolines realized from deposited thin films of (La,Sr)MnO3, a conductive magnetic oxide, and a suspended trampoline resonator carved from the SrTiO3 substrate itself are presented. Reported protocols can be readily applied to a broad variety of other complex oxides so to extend the use of membranes technology beyond those of commercially available silicon compounds.
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