Fraunhofer Institute for Silicon Technology
Fraunhofer Institute for Silicon Technology

Surface Acoustic Wave Sensors

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Sensors based on the modulation of surface acoustic waves (SAW) can be used to measure various physical phenomena: In addition to mass absorption, elastic, viscoelastic, or electrical effects can also be exploited. Dedicated functional layers enable a wide range of applications with pressure, humidity, electric field, vibration, gas, bio, or magnetic field sensors.

A special feature shared by all SAW sensors is that they are suitable for measuring both static and rapidly changing conditions. Based on the SAW technology platform, ISIT is currently developing a high-performance current sensor with a dynamic range of 6 orders of magnitude and a bandwidth of up to 20 MHz in cooperation with Christian-Albrechts-Universität zu Kiel and the Fraunhofer Institute for Applied Solid State Physics. This sensor is designed to precisely measure the very fast switching processes (~kA/ns) of modern switching power supplies, thereby enabling highly efficient power conversion. The functional layer of this sensor consists of a magnetostrictive layer that causes field-dependent modulation of the SAW wave by changing the elastic modulus.

The special feature of SAW sensor technology at ISIT is that it is not based on bulk crystals such as quartz. Instead, ISIT's SAW sensor elements are manufactured entirely using CMOS and MEMS-compatible silicon technology. This is made possible by the use of the high-performance piezoelectric thin-film material AlScN. In addition to high technological compatibility, further advantages include greater process flexibility with regard to the integration of functional layers, a reduced chip size, and the possibility of merging different sensors on a single chip.

Efficient energy conversion:

  • Electromobility
  • Renewable energies
  • Lighting

Feedback and control:

  • Smart home
  • Motors
  • Industry
  • Monitoring of data centers

Functional diagram of an acoustic surface wave sensor:

  • Wide range of applications thanks to various functional layers
  • High precision in measuring static and dynamic states
  • Compact and integrated solution thanks to CMOS and MEMS technology
  • High process flexibility and reduced chip size
  • Possibility of merging different sensors on one chip