Overall Elastic Properties of Polysilicon Films: A Statistical Investigation of the Effects of Polycrystal Morphology

Mariani, Stefano; Martini, Roberto; Ghisi, Aldo; Corigliano, Alberto; Beghi, M.

doi:10.1615/intjmultcompeng.v9.i3.50

Cited by 36 publications

(55 citation statements)

References 24 publications

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“…Since an SVE is not statistically representative by definition, the homogenized meso-scale responses change with the SVE size, with the applied Boundary Conditions (BCs) on the SVE, but also for different SVE realizations of the same size. This last property of SVEs has been used to up-scale the uncertainties at the micro-scale to the meso-scale, for example to define the probability convergence criterion of RVE for masonry [10], to study the scale-dependency of homogenization for random composite materials [42], to obtain the property variations of poly-silicon film [25], to extract effective properties of random two-phase composites [39], or again to capture the stochastic properties of the parameters in a constitutive model [47]. The problem of finite elasticity was also considered through the resolution of composite material elementary cells in [4,24], which allows defining a meso-scale potential as proposed in [4].…”

Section: Introductionmentioning

confidence: 99%

A stochastic multi-scale approach for the modeling of thermo-elastic damping in micro-resonators

Lucas

Nguyễn

et al. 2016

Computer Methods in Applied Mechanics and Engineering

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The aim of this work is to study the thermo-elastic quality factor (Q) of micro-resonators with a stochastic multi-scale approach. In the design of high-Q micro-resonators, thermo-elastic damping is one of the major dissipation mechanisms, which may have detrimental effects on the quality factor, and has to be predicted accurately. Since material uncertainties are inherent to and unavoidable in micro-electromechanical systems (MEMS), the effects of those variations have to be considered in the modeling in order to ensure the required MEMS performance. To this end, a coupled thermo-mechanical stochastic multi-scale approach is developed in this paper. Thermo-mechanical micro-models of polycrystalline materials are used to represent micro-structure realizations. A computational homogenization procedure is then applied on these statistical volume elements to obtain the stochastic characterizations of the elasticity tensor, thermal expansion, and conductivity tensors at the meso-scale. Spatially correlated meso-scale random fields can thus be generated to represent the stochastic behavior of the homogenized material properties. Finally, the distribution of the thermo-elastic quality factor of MEMS resonators is studied through a stochastic finite element method using as input the generated stochastic random field.

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Section: Introductionmentioning

confidence: 99%

A stochastic multi-scale approach for the modeling of thermo-elastic damping in micro-resonators

Lucas

Nguyễn

et al. 2016

Computer Methods in Applied Mechanics and Engineering

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“…Each grain is modelled as an elastic orthotropic body, with an in-plane crystal orientation assigned randomly. For comparison purposes, the beam film has been also modelled as in-plane isotropic, like the other moving parts of the device, with the following overall elastic properties: Young's modulus 149.3 GPa and Poisson's ratio 0.172, see [3]. The simulations have been carried out in two steps.…”

Section: Numerical Simulationmentioning

confidence: 99%

Assessment of overetch and polysilicon film properties through on-chip tests

Mirzazadeh

Ghisi

Mariani

2015

Proceedings of 2nd International Electronic Conference on Sensors and Applications

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Due to the increasing demand of miniaturization of MEMS devices, the characteristic size (e.g. the width) of some mechanical components may become comparable to that of a silicon grain. Therefore, the relevant effective mechanical properties can vary significantly from one device to another. In this work, through on-chip tests we investigate the behavior of polysilicon films using standard electrostatic actuation/sensing. The outcomes of the experimental campaign are then compared to those obtained with an analytical reduced-order model of the moving structure, and to coupled electro-mechanical simulations accounting for the polycrystalline morphology of the silicon film. These two models are adopted to bilaterally bound the experimental data up to pull-in, and to assess the scattering induced by the random orientation of the crystal lattice of each grain in slender parts of the devices.

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“…The beam width cannot be known deterministically, as overetch might induce scattering around the target or design value ̅ . Since information is rather poor concerning the possible pdf of the overetch Recent analyses [4] showed that, in the case of slender vibrating beams, the polycrystalline morphology may affect much the resulting structural response through its overall Young's modulus. In fact, if the beam width in on the same length-scale of the characteristic size or diameter of a single Si grain, the local arrangement (hence, the film morphology) gives rise to a bending stiffness which cannot be appropriately described through an average, characteristic value only, to be obtained e.g.…”

Section: Stochastic Analysis: Sensitivity To Imperfectionsmentioning

confidence: 99%

“…Accordingly, to catch high order statistics of the pdf of , a Monte Carlo analysis has been run to obtain the data reported in Figure 2(b). Due to the target beam width m and to the standard size m of the Si grains, in order to attain objective statistical properties 1,000 numerical homogenization analyses [4] have been run, each one featuring its own film morphology. Accounting for the number of realizations adopted in the former homogenization step to build the pdf, 1,000 analyses have been run here as well.…”

Section: Stochastic Analysis: Sensitivity To Imperfectionsmentioning

confidence: 99%

Stochastic Effects on the Dynamics of a Resonant MEMS Magnetometer: A Monte Carlo Investigation

Bagherinia

Mariani

Corigliano

2014

Proceedings of International Electronic Conference on Sensors and Applications

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Abstract:In the design of Lorentz force MEMS magnetometers, the coupled thermoelectro-magneto-mechanical fields governing the dynamics of the relevant compliant structures can be appropriately exploited to enhance their performances. In recent works, we showed that reduced-order models for the dynamics of the said movable structures can be recast in the form of the Duffing equation, where nonlinear terms arise from the multiphysics governing the problem. As stochastic effects may play a role due to the micrometric dimensions of the device, an investigation of the link between the statistics of sensor imperfections and output is here carried out. The said imperfections at the microscopic length-scale are modeled in terms of: overetch thickness, assumed to feature a uniform distribution in a proper interval matching available experimental data; and elastic properties of the vibrating polycrystalline silicon film, as obtained through a numerical homogenization procedure over a representative film volume. To get insights into the effects of the parameters governing the nonlinear dynamics of the resonant structure, a Monte Carlo analysis is adopted.

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Overall Elastic Properties of Polysilicon Films: A Statistical Investigation of the Effects of Polycrystal Morphology

Cited by 36 publications

References 24 publications

A stochastic multi-scale approach for the modeling of thermo-elastic damping in micro-resonators

A stochastic multi-scale approach for the modeling of thermo-elastic damping in micro-resonators

Assessment of overetch and polysilicon film properties through on-chip tests

Stochastic Effects on the Dynamics of a Resonant MEMS Magnetometer: A Monte Carlo Investigation

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