Packageless SAW Devices with Isolated Layer Acoustic Waves (ILAW) and Waveguiding Layer Acoustic Waves (WLAW)

We report on two novel layered structure concepts and their acoustic wave properties for efficient, mechanically isolated, temperature compensated, and technologically attractive packageless SAW device applications as RF filters and duplexers. The piezoelectric substrate is covered with a layer of SiO₂ or Pyrex that is in turn covered by a material of higher acoustical impedance creating an isolated layer acoustic wave (ILAW). Otherwise the wave inside a relatively low acoustic velocity waveguiding layer is confined by the higher velocity topmost layer made with high SAW velocity material thus ensuring the creation of waveguiding layer acoustic waves (WLAW). Modeling of acoustical properties of these waves (ILAW and WLAW) is confirmed by experimental results while useful figures of coupling, reflection and temperature stability are obtained. Extensive experiments with in-situ monitored depositions of multiple layers were performed and very good acoustical isolation of the waves was achieved.