The role of etching anisotropy in the fabrication of freestanding oxide microstructures on SrTiO3(100), SrTiO3(110), and SrTiO3(111) substrates

Abstract

The release process for the fabrication of freestanding oxide microstructures relies on appropriate, controllable and repeatable wet etching procedures. SrTiO3 is among the most employed substrates for oxide thin films growth and can be decomposed in HF:water solution. Such process is strongly anisotropic and is affected by local defects and substrate cut-plane. We analyze the etching behavior of SrTiO3 substrates having (100), (110), and (111) cut-planes during immersion in a 5% HF:water solution. The etching process over the three substrates is compared in terms of pitting, anisotropy, macroscopic etch rate and underetching effects around HF-resistant (La,Sr)MnO3 thin film micropatterns. The release of targeted structures, such as the reported (La,Sr)MnO3 freestanding microbridges, depends on the substrate crystallographic symmetry and on the in-plane orientation of the structures themselves along the planar directions. By comparing the etching evolution at two different length scales, we distinguish two regimes for the propagation of the etching front: an intrinsic one, owning to a specific lattice direction, and a macroscopic one, resulting from the mixing of different etching fronts. We report the morphologies of the etched SrTiO3 surfaces and the geometries of the underetched regions as well as of the microbridge clamping zones. The reported analysis will enable the design of complex MEMS devices by allowing to model the evolution of the etching process required for the release of arbitrary structures made of oxide thin films deposited on top of STO.

6 pages, 3 figures, 1 table, 4 supporting sections

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• Atomically flat single terminated oxide substrate surfaces
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• Large tunability of strain in WO3 single-crystal microresonators controlled by exposure to H2 gas
• Influence of thermal boundary conditions on the current-driven resistive transition in $\mathbf{V}{\mathbf{O}}_2$ microbridges

Cited by in corpus (4)

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• Integration of High-Tc Superconductors with High Q Factor Oxide Mechanical Resonators
• Oxide Membranes from Bulk Micro-Machining of SrTiO${}_3$ substrates
• Magnetic Trampoline Resonators from (La,Sr)MnO3 Single-Crystal Thin Films