Progress in the Development of Miniature Thin Film BAW Resonator and Filter Technology

Fundamental mode bulk acoustic wave resonators and filters have been fabricated from ZnO/Si composite thin films prepared by sputter depositing c-axis oriented polycrystalline ZnO onto single crystal silicon. Resonant frequencies of these devices, which are compatible with silicon IC technology, can be readily controlled in the 100 MHz to 1000 MHz range. Development of improved fabrication procedures is described, emphasizing the importance of smooth resonator surfaces and precise control of ZnO sputtering conditions. Chemical etch treatments of the ZnO is shown to markedly reduce spurious resonances. Device modeling theory is described and the good agreement between experimental data and theory is discussed. Filter insertion loss as low as 4.1 dB and bandwidths between 0.5 and 5 percent have been achieved, Q values as high as 2700 were observed, and out of band rejection of 45 dB was realized. (Author This article is from the Proceedings of the Symposium on Frequency Control (36th Annual), 2-4 Jun 82, Philadelphia, PA., AD-A130 811, p537-548.