Platinum/AlN/Sapphire SAW resonator operating in GHz range for high temperature wireless SAW sensor

The temperature responses of aluminum nitride (AlN) based surface acoustic wave resonator (SAWR) are modeled and tested. The modeling of the electrical performance is based on a modified equivalent circuit model introduced in this work. For SAWR consisting of piezoelectric film and semiconducting substrate, parasitic parameters from the substrate is taken into consideration for the modeling. By utilizing the modified model, the high temperature electrical performance of the AlN/Si and AlN/6H-SiC based SAWRs can be predicted, indicating that a substrate with a wider band gap will lead to a more stable high temperature behavior, which is further confirmed experimentally by high temperature testing from 300 K to 725 K with SAWRs having a wavelength of 12 μm. Temperature responses of SAWR’s center frequency are also calculated and tested, with experimental temperature coefficient factors (TCF) of center frequency being −29 ppm/K and −26 ppm/K for the AlN/Si and AlN/6H-SiC based SAWRs, which are close to the predicted values.

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Section: Modelingmentioning

confidence: 99%

Modeling and Experimental Analysis on the Temperature Response of AlN-Film Based SAWRs

Chen

You

2016

“…The electromechanical coupling factors k 2 indicate the effectiveness with which a piezoelectric material converts electrical energy into mechanical energy or vice versa. The k 2 was determined using measured and simulated data for the

parameter (reflection) and the following Equation (18) derived from [ 18 ]:

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Section: Resultsmentioning

confidence: 99%

“…At room temperature (23 • C), the value of the electromechanical coupling coefficient of our modeled device is 1.812% and the measured value is 1.868%. Figure 7 presents a comparison of the variation in electromechanical coupling as a function of the temperature obtained from the experimental measurements and the simulations of the Pt/AlN/Sapphire sensor [18]. Figure 7 shows that the k 2 coefficient increases with temperature.…”

Section: Electromechanical Coefficient Factor Kmentioning

confidence: 99%

“…However, it has a number of limitations, the most important being the excessive damping (propagation losses) of surface waves when the operating frequency exceeds 1 GHz [15]. Recently, efforts have been devoted to the development of a SAW sensor heterostructure for high and very high temperature applications such as AlN/Pt/LiNbO 3 [16] and AlN/Sapphire [17][18][19][20][21]. The AlN/Sapphire SAW structure can also operate at very high frequencies [18].…”

Section: Introductionmentioning

confidence: 99%

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FEM Modeling of the Temperature Influence on the Performance of SAW Sensors Operating at GigaHertz Frequency Range and at High Temperature Up to 500 °C

Ondo

Blampain

Mbourou

et al. 2020

In this work, we present a two-dimensional Finite Element Method (2D-FEM) model implemented on a commercial software, COMSOL Multiphysics, that is used to predict the high temperature behavior of surface acoustic wave sensors based on layered structures. The model was validated by using a comparative study between experimental and simulated results. Here, surface acoustic wave (SAW) sensors consist in one-port synchronous resonators, based on the Pt/AlN/Sapphire structure and operating in the 2.45-GHz Industrial, scientific and medical (ISM) band. Experimental characterizations were carried out using a specific probe station that can perform calibrated measurements from room temperature to 500 °C. In our model, we consider a pre-validated set of physical constants of AlN and Sapphire and we take into account the existence of propagation losses in the studied structure. Our results show a very good agreement between the simulation and experiments in the full range of investigated temperatures, and for all key parameters of the SAW sensor such as insertion losses, resonance frequency, electromechanical factor of the structure (k2) and quality factor (Q). Our study shows that k2 increases with the temperature, while Q decreases. The resonance frequency variation with temperature shows a good linearity, which is very useful for temperature sensing applications. The measured value of the temperature coefficient of frequency (TCF) is equal to −38.6 ppm/°C, which is consistent with the numerical predictions.

“…Moreover, because of its wide bandgap of 6.2 eV, AlN has outstanding dielectric properties, superior to those of langasite by several orders of magnitudes at any temperature [15]. In addition, SAW velocities in AlN are close to 5500 m/s, making this material suitable for applications in the most promising industrial, scientific, and medical (ISM) 2.45 GHz band [16]. In this context, sapphire substrates are highly compatible with AlN films as they show concurrently high temperature stability, high dielectric properties, comparable SAW velocities, and they enable the growth of highly textured AlN films [17].…”

Section: Introductionmentioning

confidence: 99%

Epitaxial Growth of Sc0.09Al0.91N and Sc0.18Al0.82N Thin Films on Sapphire Substrates by Magnetron Sputtering for Surface Acoustic Waves Applications

Bartoli

Streque

Ghanbaja

et al. 2020

Scandium aluminum nitride (ScxAl1-xN) films are currently intensively studied for surface acoustic waves (SAW) filters and sensors applications, because of the excellent tradeoff they present between high SAW velocity, large piezoelectric properties and wide bandgap for the intermediate compositions with an Sc content between 10 and 20%. In this paper, the growth of Sc0.09Al0.91N and Sc0.18Al0.82N films on sapphire substrates by sputtering method is investigated. The plasma parameters were optimized, according to the film composition, in order to obtain highly-oriented films. X-ray diffraction rocking-curve measurements show a full width at half maximum below 1.5°. Moreover, high-resolution transmission electron microscopy investigations reveal the epitaxial nature of the growth. Electrical characterizations of the Sc0.09Al0.91N/sapphire-based SAW devices show three identified modes. Numerical investigations demonstrate that the intermediate compositions between 10 and 20% of scandium allow for the achievement of SAW devices with an electromechanical coupling coefficient up to 2%, provided the film is combined with electrodes constituted by a metal with a high density.