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

Abstract

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 polycrystalline aluminum nitride (AIN) 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) AIN and polycrystalline Physical Vapor Deposition (PVD) AIN piezoelectric materials, showing that power handling capability of single crystal MOCVD AIN XBAW technology exceeds PVD AIN 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 AIN XBAW filters far exceed survival times of PVD-AIN 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.