Solidly mounted BAW filters for the 6 to 8 GHz range based on AlN thin films

Bulk acoustic wave (BAW) resonators and filters have been fabricated in the frequency range between 7 and 8 GHz. Resonators with quality factors of 400 to 600, and coupling factors k/sup 2/ of 4 to 5.5% have been achieved. The obtained resonator characteristics theoretically yield filters of 3.5% 3 dB bandwidths with flat channel characteristics, and insertion losses of -6 dB. The trade-offs related to the use of aluminum or platinum bottom electrodes is investigated theoretically. While aluminum is expected to yield filters with lower insertion loss, Pt is expected to yield larger bandwidths.