SAW sensors for high temperature applications

The technology of surface acoustic wave (SAW) devices allows the integration of signal processing and sensor functions within one product. In the past, SAW sensors have been operated at room temperature or 100 to 200°C at most. Materials related problems become obvious if one attempts to increase this operating temperature to a value as high as 1000°C. First experimental results are presented based on a variation of the metallization and the use of diffusion barriers. It is expected that the use of these specially tailored materials with particular functional properties will lead to a considerable improvement of the lifetime and reliability of SAW sensors and the development of devices resistant to high temperatures as well as high pressures and chemically aggressive environments. The high-temperature characteristics of such novel devices are investigated by finite element simulation and by experimental deformation analyses. It is also discussed which assembly, interconnection and packaging techniques are applicable at 1000°C