Gallium nitride MEMS resonators: how residual stress impacts design and performances

Morelle, Christophe; Théron, Didier; Derluyn, Joff; Degroote, Stefan; Germain, Marianne; Zhang, Victor; Buchaillot, L.; Grimbert, B.; Tilmant, Pascal; Vaurette, Francois; Roch‐Jeune, Isabelle; Brändli, Virginie; Avramovic, Vanessa; Okada, Étienne; Faucher, M.

doi:10.1007/s00542-017-3293-0

Cited by 10 publications

(7 citation statements)

References 23 publications

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“…The resonant frequency

of the PMUT can be expressed as [ 29 ]

where

is the radius of the PMUT diaphragm,

is the average plate modulus,

is the average density,

is the total layer thickness, and

is the stress induced by the DC bias voltage. As can be seen in the equation, the resonant frequency of the PMUT is sensitive to

when the ratio (

) is large [ 30 ]. It provides a way to manipulate the resonant frequency via the modification of

by applying a voltage to the piezoelectric films of PMUT devices, which is also beneficial to extend the bandwidth.…”

Section: Results and Analysismentioning

confidence: 99%

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Zhang

Geng

et al. 2023

Micromachines

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Due to their excellent capabilities to generate and sense ultrasound signals in an efficient and well-controlled way at the microscale, piezoelectric micromechanical ultrasonic transducers (PMUTs) are being widely used in specific systems, such as medical imaging, biometric identification, and acoustic wireless communication systems. The ongoing demand for high-performance and adjustable PMUTs has inspired the idea of manipulating PMUTs by voltage. Here, PMUTs based on AlN thin films protected by a SiO2 layer of 200 nm were fabricated using a standard MEMS process with a resonant frequency of 505.94 kHz, a −6 dB bandwidth (BW) of 6.59 kHz, and an electromechanical coupling coefficient of 0.97%. A modification of 4.08 kHz for the resonant frequency and a bandwidth enlargement of 60.2% could be obtained when a DC bias voltage of −30 to 30 V was applied, corresponding to a maximum resonant frequency sensitivity of 83 Hz/V, which was attributed to the stress on the surface of the piezoelectric film induced by the external DC bias. These findings provide the possibility of receiving ultrasonic signals within a wider frequency range, which will play an important role in underwater three-dimensional imaging and nondestructive testing.

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“…The resonant frequency

of the PMUT can be expressed as [ 29 ]

where

is the radius of the PMUT diaphragm,

is the average plate modulus,

is the average density,

is the total layer thickness, and

is the stress induced by the DC bias voltage. As can be seen in the equation, the resonant frequency of the PMUT is sensitive to

when the ratio (

) is large [ 30 ]. It provides a way to manipulate the resonant frequency via the modification of

by applying a voltage to the piezoelectric films of PMUT devices, which is also beneficial to extend the bandwidth.…”

Section: Results and Analysismentioning

confidence: 99%

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Zhang

Geng

et al. 2023

Micromachines

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“…During the growth of multi-layer films, it is inevitable to bring residual stress in the process, resulting in the WCR having the tensile prestress of the material layer [ 65 ]. The model is considered as shown in Figure 5 c. When the initial prestress

gradually increases from 0 to 4 MPa, the elastic anisotropy energy density

increases, making

decrease and reduces the

consequently.…”

Section: Resultsmentioning

confidence: 99%

Modeling and Parameter Sensitivity Improvement in ΔE-Effect Magnetic Sensor Based on Mode Localization Effect

Lyu

Wang

et al. 2022

Micromachines

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A mode-localized ΔE-effect magnetic sensor model is established theoretically and numerically. Based on the designed weakly coupled resonators with multi-layer film structure, it is investigated how the ΔE-effect of the magnetostrictive film under the external magnetic field causes the stiffness perturbation of the coupled resonators to induce the mode localization effect. Using the amplitude ratio (AR) as the output in the mode-localized ΔE-effect magnetic sensor can improve the relative sensitivity by three orders of magnitude compared with the traditional frequency output, which has been verified by simulations based on the finite element method (FEM). In addition, the effects of material properties and geometric dimensions on sensor performance parameters, such as sensitivity, linear range, and static operating point are also analyzed and studied in detail, providing the theoretical basis for the design and optimization of the mode-localized ΔE-effect magnetic sensor in different application scenarios. By reasonably optimizing the key parameters of the weekly coupled resonators, a mode-localized ΔE-effect magnetic sensor with the sensitivity of 18 AR/mT and a linear range of 0.8 mT can be achieved.

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“…Currently, both our COMSOL simulations and analytic model assume the global damping to be characterized by a Q-factor that does not explicitly depend on the stress, without considering any specific physical mechanisms of dissipation. a See [29] for experimental setup and studies in more detail.…”

Section: Results Of Highly Stressed Resonators Obtained By Different ...mentioning

confidence: 99%

Improved analytical modelling and finite element verification of stressed GaN microbeam resonators by piezoelectric actuation

Zhang¹,

Faucher²,

Théron³

et al. 2017

J. Micromech. Microeng.

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The characteristics of piezoelectric micro-resonators based on vibrating beams essentially depend on two basic physical coefficients, an effective Young’s modulus (Ye) and a piezoelectric coupling factor (e31e). An improved analytic model is proposed with newly derived expressions of Ye and e31e that account for the anisotropic properties of the III-nitride materials and beam width, W. The analytic model applicable to the only axial stress is completed by finite element (FE) simulations that allow any spatial patterns of pre-stress in wafers to be studied. The value of e31e for wider beams is analytically demonstrated to be much higher than the usual e31, and a strong dependence of e31e on W is also confirmed by FE simulations. Resonance frequency (fr) and actuation efficiency (η) are numerically studied for several pre-stress patterns and beam dimensions. The fr is found to be sensitive to the beam width only for resonators under 2D pre-stress while the η to the stress magnitude regardless of stress pattern. Compared with measurements published for some fabricated resonators, both analytic and FE approaches agree well quantitatively for the resonance frequency and qualitatively for the dynamic amplitude. The results of this study can help design optimization, such as appropriate electrode length and suitable beam width, to gain better performance for this type of resonators.

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Gallium nitride MEMS resonators: how residual stress impacts design and performances

Cited by 10 publications

References 23 publications

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Modeling and Parameter Sensitivity Improvement in ΔE-Effect Magnetic Sensor Based on Mode Localization Effect

Improved analytical modelling and finite element verification of stressed GaN microbeam resonators by piezoelectric actuation

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