Materials issues of SAW sensors for high-temperature applications

The technology of surface acoustic wave (SAW) devices allows the integratio n of signal processing and sensor functions within one product. In the past , SAW sensors have been operated at room temperature or 100 degreesC-200 de greesC at most. material-related problems become obvious if one attempts to increase this operating temperature to a value as high as 1000 degreesC. F irst experimental results will be presented based on a variation of the met allization and the use of diffusion barriers. It is expected that the use o f these specially tailored materials with particular functional properties mill lead to a considerable improvement of the lifetime and reliability of SAW sensors and the development of devices resistant to high temperatures a s well as high pressures and chemically aggressive en cironments. The high- temperature characteristics of such no c et devices are investigated by fin ite-element simulation and by experimental deformation analysis. It will al so be discussed which assembly, interconnection, and packaging techniques a re applicable at 1000 degreesC.