Bulk and surface micromachined MEMS in thin film SOI technology

Raskin, Jean‐Pierre; Iker, F.; André, Nicolás; Olbrechts, Benoit; Pardoen, Thomas; Flandre, Denis

doi:10.1016/j.electacta.2006.09.021

Cited by 16 publications

(5 citation statements)

References 22 publications

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“…2b). When two different materials are consecutively deposited to form a linear beam in microfabrication processes, strain mismatch across the layers causes internal stresses that force the beam to bend out-of-plane after release, resulting in a spontaneous curvature κ s (refs 8, 23, 24). When the same process is used to fabricate a bilayered ring of radius R (before release), the release adds a supplementary curvature κ s perpendicular to the original one (1/ R ), which amounts to overcurve the ring with a pre-set overcurvature (Supplementary Methods; Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

Overcurvature describes the buckling and folding of rings from curved origami to foldable tents

et al. 2012

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Daily-life foldable items, such as popup tents, the curved origami sculptures exhibited in the Museum of Modern Art of New York, overstrained bicycle wheels, released bilayered microrings and strained cyclic macromolecules, are made of rings buckled or folded in tridimensional saddle shapes. Surprisingly, despite their popularity and their technological and artistic importance, the design of such rings remains essentially empirical. Here we study experimentally the tridimensional buckling of rings on folded paper rings, lithographically processed foldable microrings, human-size wood sculptures or closed arcs of Slinky springs. The general shape adopted by these rings can be described by a single continuous parameter, the overcurvature. An analytical model based on the minimization of the energy of overcurved rings reproduces quantitatively their shape and buckling behaviour. The model also provides guidelines on how to efficiently fold rings for the design of space-saving objects.

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Section: Resultsmentioning

confidence: 99%

Overcurvature describes the buckling and folding of rings from curved origami to foldable tents

et al. 2012

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“…These testing stages are amenable to in situ TEM characterization by performing the back etching of the wafer under the test specimen, see [354] and also [356,357] for applications to fatigue analysis. A MEMS based testing frame based on a concept of ''on chip'' actuation of elementary tensile testing structures through internal stress has recently been developed and applied to different deformation and fracture investigations of freestanding metallic thin films [358][359][360][361][362]. This method schematically depicted in Fig.…”

Section: Fracture Testing Methods Of Freestanding Specimensmentioning

confidence: 99%

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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a b s t r a c tPushing the internal or external dimensions of metallic alloys down to the nanometer scale gives rise to strong materials, though most often at the expense of a low ductility and a low resistance to cracking, with negative impact on the transfer to engineering applications. These characteristics are observed, with some exceptions, in bulk ultra-fine grained and nanocrystalline metals, nano-twinned metals, thin metallic coatings on substrates and freestanding thin metallic films and nanowires. This overview encompasses all these systems to reveal commonalities in the origins of the lack of ductility and fracture resistance, in factors governing fatigue resistance, and in ways to improve properties. After surveying the various processing methods and key deformation mechanisms, we systematically address the current state of the art in terms of plastic localization, damage, static and fatigue cracking, for three classes of systems: (1) bulk ultra-fine grained and nanocrystalline metals, (2) thin metallic films on substrates, and (3) 1D and 2D freestanding micro and nanoscale systems. In doing so, we aim to favour cross-fertilization between progress made in the fields of mechanics of thin films, nanomechanics, fundamental researches in bulk nanocrystalline metals and metallurgy to impart enhanced resistance to fracture and fatigue in high-strength nanostructured systems. This involves exploiting intrinsic mechanisms, e.g. to enhance hardening and rate-sensitivity so as to delay necking, or improve grain-boundary cohesion to resist intergranular cracks or voids. Extrinsic methods can also be utilized such as by hybridizing the metal with another material to delocalize the deformation -as practiced in stretchable electronics. Fatigue crack initiation is in principle improved by a fine structure, but at the expense of larger fatigue crack growth rates. Extrinsic toughening through hybridization allows arresting or bridging cracks. The content and discussions are based on experimental, theoretical and simulation results from the recent literature, and focus is laid on linking microstructure and physical mechanisms to the overall mechanical behavior.

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“…As thin films are deposited on substrate surfaces either by physical or chemical vapour deposition techniques, intrinsic stresses are likely to build inside the film. If the surface onto which the film adheres were to be removed, intrinsic stresses inside the film would cause either shrinkage (if stress is tensile) or elongation (if stress is compressive) of the released film [11][12][13][14][15]. The actual deposition method and experimental factors such as temperature, pressure, and gas chemistry are effective in determining the type and magnitude of film stress.…”

Section: Concept Of Intrinsic Stress-induced Self-assemblymentioning

confidence: 99%

Intrinsic stress-induced bending as a platform technology for controlled self-assembly of high-Q on-chip RF inductors

Bajwa

Yapıcı

2019

J. Micromech. Microeng.

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This work reports on the modelling and process technology development for the design and fabrication of vertical, 3D, monolithic RF-MEMS inductors based on self-assembly via intrinsic stresses otherwise referred to as residual or internal stresses in thin films. Stressinduced bending in different cantilever designs were modelled at various film thicknesses using finite element analysis method and bending conditions were optimized. Intrinsic stress-induced bending mechanism is verified by fabrication of bi-layer metallic micro cantilever structures with varying stress conditions which reach bending angles of up to 137° and possibly more upon release. By modulating the loading mode (tensile or compressive) along the beam length, complex out-of-plane wavy cantilevers with multiple upward and/ or downward bends were realized. The fabrication and modelling results display large overlap which further demonstrates the applicability of intrinsic stress-induced bending as a controllable technology towards fabrication of out-of-plane 3D micro components. Additionally, as a potential application to RF-MEMS inductors, stress-induced self-assembly of patterned thin film stacks into out-of-plane inductor topologies of varying geometries was investigated. Electromagnetic modelling tools were used to study the effect of bending on inductor performance (primarily the Q factor and self-resonance frequency-f SR ), and results were evaluated by comparison to planar inductors of the same number of turns and dimensions, which revealed Q factor and f SR improvement of more than 100% upon bending away from substrate surface.

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Bulk and surface micromachined MEMS in thin film SOI technology

Cited by 16 publications

References 22 publications

Overcurvature describes the buckling and folding of rings from curved origami to foldable tents

Overcurvature describes the buckling and folding of rings from curved origami to foldable tents

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

Intrinsic stress-induced bending as a platform technology for controlled self-assembly of high-Q on-chip RF inductors

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