Design and fabrication of aluminum nitride Lamb wave resonators towards high figure of merit for intermediate frequency filter applications

A design guideline for one-port aluminum nitride (AlN) Lamb wave resonators (LWRs) working at S 0 mode with high performance is reported. A fabricated 252 MHz LWR, with an aperture of 200 μ m, 12 fingers, and 1.5 μ m thick AlN, is found to have a remarkably high figure of merit (FOM), which exhibits a high ratio of the resistance at parallel resonance ( R p ) to the resistance at series resonance ( R s ) of 1317 and a corresponding product of the effective coupling coefficient ( k 2 eff ) and quality factor ( Q ) exceeding 52. Consisting of such resonators, a 6-stage ladder filter with a low pass-band insertion loss (IL) of 4.5 dB and steep filter skirts is achieved, offering significant advantage of size savings.