Surface acoustic wave micro-sensors based on ALuminium nitride/Sapphire Structures for high-temperature Applications – SALSA

The SALSA partnership involves the company Arcelor-Mittal (AMMR) as an end-user, a high-tech start-up “frec|n|sys” exploiting technological equipment consisting of a whole industrial fabrication line allowing for the fabrication of SAW resonators, filters and sensors addressing almost any kind of RF application requiring such components, an SME “SENSeOR” as a subcontractor, with a strong experience in the field of wireless SAW sensors, and four academic laboratories IJL, IMN, LMOPS and SYMME bringing their strong knowledge and experience in the material field, an essential building block for the achievement of such project, but also in devices including SAW sensors. Scientific and technologic challenges of SALSA project concern:
- The study and the optimization of the different materials composing the micro-sensor (piezoelectric film, metallic electrodes, substrate) and the associated antenna, to meet requirements for an optimal behavior at elevated temperatures.
- The design of high performances SAW resonators and delay lines based on AlN/Sapphire structure.
- The development of a packaging solution allowing operation at temperatures in excess of 600°C for several hundred hours integrating antennas connection and assembly.
- The customization of the transceiver for wireless interrogation to match the performances of sensors in high-temperature environments.
Thanks to the SALSA project the end-user partner “ArcelorMittal” is expecting an improvement of product quality (fewer scraps and new warranty), a time-to-market reduction, and a cost diminution (through energy saving). This will give ArcelorMittal a great advantage in term of product quality, price and services in
comparison to its competitors.

The results of laboratory characterizations made on the first devices show that it is possible to use the Al/ AlN/Saphir multilayer structure as a sensor at high temperature up to 600 ° C. This unexpected result is very promising to address Arcelor monitoring problematic. We have therefore realized an optimized design for the fabrication of high-performance wireless sensors. The achievement of optimized sensors is in progress.

In parallel with this work, we have developed a sputtering deposition process to grow high-quality Sc(x)Al(1-x)N layers. Very interesting results have been obtained up to x = 0.14. As a reminder, these layers will allow the development of the packageless WLAW AlN / Sc (x) Al (1-x) N / Sapphire folding solution. They could also ultimately be used instead of the AlN layer if, as expected, the electromechanical coupling coefficient is higher than that of the AlN.higher than that of the AlN but also if the quality factor Q obtained proved to be larger and thus more favorable for wireless interrogation.

The use of SAW devices as passive and wireless sensors allows them to operate in extreme conditions such as those with high levels of radiation, high temperatures, or electromagnetic interference, in which no other wireless sensor can operate. The results of the SALSA project can contribute in the future to the development of similar SAW devices capable of operating in high-temperature environments for applications in aerospace, power, nuclear, chemical, and petrochemical processes plants. For instance, the sensor developed for ArcelorMittal applications may be directly transportable not only to the glass industry, but also to control the temperature of high-voltage cables to optimize the transport of energy, and in automotive applications for the control of combustion in engines. Hence, the SALSA project will give frec|n|sys and SENSeOR an innovative product and an opportunity to be able to propose new measurement devices and to do a huge step forward in the measurement services they can offer.

Initial dissemination actions have been carried out through papers at international conferences [2-6] and published in an international peer-reviewed journal [1]. Other papers were submitted for presentations at the IEEE IUS 2017 conference. It should be noted that the original results obtained with the Al / AlN / Saphir structure are not yet communicated to maintain an advance within the consortium.
[1] A. Taguett, T. Aubert, M. Lomello, O. Legrani, O. Elmazria, J. Ghanbaja, A. Talbi ; Ir-Rh thin films as high-temperature electrodes for SAW sensor applications validation ; Sensors and Actuators A, Vol 243, pp 35-42 (2016).

[2] F. Bartoli, P. Pigeat, T. Aubert, O. Elmazria, F. Genty, P. Boulet, J. Ghanbaja. ; Highly-textured sputtered AlN and ScxAl1-xN thin films, for surface acoustic wave devices. ; 2016 European Materials Research Society (EMRS), Warsaw, Poland, Sept. 19-22 2016 ;

[3] F. Bartoli, S. Zhgoon, T. Aubert, P. Pigeat, A. Talbi, O. Elmazria ; Packageless WLAW devices based on Al2O3/Pt/GaN/Sapphire structure for high-temperature applications.. 2016 IEEE Intern. Ultrasonics Symposium, Tours, France Sept. 18-20 2016

[4] A. Taguett, T. Aubert, M. Lomello , O. Elmazria, High-temperature SAW electrodes based on Ir-Rh thin films. 2016 IEEE Intern. Ultrasonics Symposium, Tours, France Sept. 18-20 2016,

[5] A. Taguett, T. Aubert, M. Lomello , O. Elmazria, High-temperature SAW electrodes based on Ir-Rh thin films. 2016 IEEE Intern. Ultrasonics Symposium, Tours, France Sept. 18-20 2016,

[6] F. Bartoli, S. Zhgoon, T. Aubert, A. Talbi, P. Pigeat, O. Elmazria ; Packageless WLAW devices based on Al2O3/Pt/GaN/Sapphire structure for high-temperature applications. SAW Symposium 2016 Dresden, Germany, France Oct. 20-21 2016 ; (rencontres industriels et académiques travaillant dans le domaine des capteurs SAW),

The SALSA project aims at developing a micro-sensor enabling wireless process control in industrial applications operating at elevated temperatures (up to 1000°C) where no conventional wireless sensor can survive. The sensor consists in a surface acoustic wave (SAW) device based on AlN/Sapphire layered structure. A key issue of this development lies in the wireless and the battery-less requirement of such sensors and the good stability of the considered structure in high-temperature conditions. Since the consortium partners have already solved partially or even completely some of the problems related to the targeted environments, the real scientific advance therefore consists in the achievement of a high performances and relatively low cost micro-sensor capable to operate at high frequency and in high temperature conditions. As a backup solution but also as source of intellectual properties and high level journal production, original structures such as packageless WLAW (Waveguiding layer acoustic wave) and a new type of FBAR (film bulk acoustic resonator) will be also investigated.

The SALSA partnership involves a large company (Arcelor-Mittal) as a end user, a high-tech start-up “frec|n|sys” exploiting technological equipments consisting in a whole industrial fabrication line allowing for the fabrication of SAW resonators, filters and sensors addressing almost any kind of RF application requiring such components, an SME “Senseor” as subcontractor, with a strong experience in the field of wireless SAW sensors, and four academic laboratories IJL, IMN, LMOPS and SYMME bringing their strong knowledge and experience in material field, an essential building block for the achievement of such project, but also in devices including SAW sensors. These laboratories also exhibit strong experience concerning the characterization of materials as well as sensors, at elevated temperatures.
Scientific and technologic challenges of SALSA project concern:
- The study and the optimization of the different materials composing the micro-sensor (piezoelectric film, metallic electrodes, substrate) and associated antenna, to meet requirements for an optimal behaviour at elevated temperatures.
- The design of high performances SAW devices based on AlN/Sapphire substrates.
- The development of a packaging solution allowing operation at temperatures in excess of 600°C for several hundred hours integrating antenna connection and assembly.
- Customization of the transceiver for wireless interrogation to match the performances of sensors in high temperature environments.
Thanks to the SALSA project the end-user partner “ArcelorMittal” is expecting an improvement of product quality (less scraps and new warranty), a time-to-market reduction and a cost reduction (through energy saving). This will give ArcelorMittal a great advantage in terms of product quality, price and services in comparison to its competitors.
The use of SAW devices as passive and wireless sensors allows them to operate in extreme conditions such as those with high levels of radiation, high temperatures, or electromagnetic interference, in which no other sensors can operate. The results of the SALSA project can contribute in the future to the development of similar SAW devices able to operate in high temperature environments for applications in aerospace, power, nuclear, chemical, and petrochemical processes plants. For instance, the sensor developed for ArcelorMittal applications may be directly transportable not only to the glass industry, but also to control the temperature of high voltage cables to optimize the transport of energy, and in automotive applications for the control of combustion in engines. Hence, the SALSA project will give frec|n|sys and Senseor an innovative product and an opportunity to propose new measurement devices and to do a huge step forward in the measurement services they can offer.