High Power, Wideband Single Crystal XBAW Technology for sub-6 GHz Micro RF Filter Applications

The authors report a Bulk Acoustic Wave (BAW) filter technology built using a 6-inch MEMS wafer process on a Si substrate, compatible with single crystal and polycrys-talline aluminum nitride (AlN) piezoelectric materials (denoted as XBAW), and present metrics demonstrating resonator technology
capable of highly reliable, high power, compact, high performance RF filter solutions in the sub-6 GHz spectrum, with proven high Qmax of 3685 and resonator Figure-Of-Merit (FOM) of 222 at 1.8GHz. Using the XBAW process, the authors compare power handling capability of filters built from single crystal Metal-Organic Chemical Vapor Deposition (MOCVD) AlN and polycrystalline Physical Vapor Deposition (PVD) AlN piezoelectric materials, showing that power handling capability of single crystal MOCVD AlN XBAW technology exceeds PVD AlN XBAW by 2.3x, when packaged and by 1.8x, when measured on-wafer. A first reliability study shows that survival times of single crystal MOCVD AlN XBAW filters far exceed survival times of PVD- AlN XBAW filters. As an example of high frequency capability, the authors report filters with a center frequency of 5.25 GHz, a 3dB bandwidth of 205 MHz, a minimum insertion loss of 0.83dB, excellent wide band rejection from 30 MHz to 11 GHz and attenuation greater than 50dB in the UNII 2C+3 bands.