ELASTIC WAVE SENSORS - QUARTZ TECHNOLOGICAL CHANNEL AND SILICON TECHNOLOGY

Elastic wave sensors use the vibrating mechanical properties of materials, generally monocrystalline and piezoelectric, such as quartz crystal or lithium niobate. Within such materials, elastic waves are easy to generate and to detect after propagation by means of plate electrodes (bulk waves) or interdigital transducers (IDT) (surface waves or bulk waves). The sensitive signal of such sensors can be measured in terms of intensity (attenuation of the signal) or frequency, with oscillating electronic loop, or in-phase versus an arbitrary or out of phase reference. Among quartz crystal sensors, a particularly interesting new family has been studied: sensors using transverse horizontal waves (TH sensors). In recent years, elastic wave sensors on silicon have been studied. The piezoelectric layer deposited on the silicon substrate must be compatible with the usual silicon process used in microelectronics, and also with the micromachining made generally chemically in 3-D.