In Situ Fabrication, Manipulation, and Mechanical Characterization of Free‐Standing Silica Thin Films Using Focused Ion Beam Scanning Electron Microscopy

Abstract

are different from their bulk counterparts. [10][11][12][13] However, experimental determination of the mechanical properties of micro and nanoscale thin films, including silica, remains an extremely challenging task. [10,14] Amongst available approaches, nanoindentation is most commonly used for measuring small scale silica thin films. [15][16][17] It requires simple specimen preparation and is comparatively easy to perform while the Young's modulus and hardness of the thin film materials are measurable. [18,19] Nevertheless, several limitations still exist related to the effect of the substrate, particularly relevant for films thinner than a micrometer, such as an indentation maximum of only about 10% of the depth, as well as, the lack of in situ observation during deformation, which all restrict general applicability of conventional nanoindentation. [20][21][22] Taken together, above limitations point to the need for a more versatile approach that eliminates substrate effects, that is, by realizing free-standing silica films/beams in the appropriate respective length scales. Subsequently, performing mechanical testing via indentation in real-time with high resolution force and displacement information becoming available would enable the monitoring of the specimen deformation behavior and concurrent phenomena in great detail.Currently available top down procedures for fabricating micro and nano-objects with well-defined patterns and structure, [23,24] may be employed to obtain free standing silica films Determination of mechanical properties of (silica) thin films is important for the development of new applications. However, a versatile approach for smallscale sample fabrication and in situ mechanical testing of these materials is currently lacking which can overcome the existing difficulties in conventional testing approaches. Here, it is shown that by combining focused ion beam scanning electron microscopy (FIB-SEM) with micromanipulators freestanding silica beams of the desired dimensions can be fabricated. Using in situ bending tests on such beams inside the SEM and finite element method simulations, the Young's modulus of thin-film silica and the effects of gallium ion beam radiation on Young's modulus are determined. Furthermore, the effects of controlled relative humidity on the mechanical behavior of silica beams are investigated. The demonstrated FIB-SEM approach can be extended to other materials and preparation conditions to measure, model, and optimize mechanical properties of thin films for a wide range of (coating) applications.

Mechanical Property Measurement of Micro/Nanoscale Materials for MEMS: A Review

“…It can be used as a plastic reshaping tool like an "origami" on a sub-microscale. Si related materials, such as SiO x [57,[93][94][95], SiN x [55,[96][97][98][99], and SiC [49,[100][101][102][103][104] have been tested so far on a micrometer scale. Those mechanical characteristics depend on the deposition conditions or post-process conditions.…”

“…Si related materials, such as SiO x [57,93–95], SiN x [55,96–99], and SiC [49,100–104] have been tested so far on a micrometer scale. Those mechanical characteristics depend on the deposition conditions or post‐process conditions.…”