Low Loss, 3.7GHz Wideband BAW Filters, Using High Power Single Crystal AlN-on-SiC Resonators

Bulk acoustic wave (BAW) filters operating at center frequency of 3.7GHz, comprising of BAW resonators utilizing single crystal aluminum nitride (AlN) piezoelectric films epitaxially grown on silicon carbide (SiC) substrates, are reported. Metal-organic chemical vapor deposition (MOCVD) growth was used to obtain single crystal AlN films on 150-mm diameter c-plane semi-insulating SiC substrates with (0004) X-ray diffraction (XRD) rocking curve full-width half-maximum (FWHM) of 0.025◦. The fabricated filters (1.25x0.9 sq.mm) had a center frequency of 3.71GHz and a 3dB bandwidth of 100MHz, an insertion loss of 2.0dB and narrow band rejection of 40dB and out-of-band rejection in excess of 37dB to 8GHz. Individual resonators on the same wafer show an electro-mechanical coupling as high as 7.63% and maximum quality-factors up to 1572. Insertion loss of 5ohm resonators configured as individual 2-port devices changed by 0.15dB after high power survival test at 10W. This is the first demonstration of single crystal AlN-on-SiC based BAW resonator and filter technology at 3.7GHz and illustrates the potential of a single crystal AlN-on-SiC based BAW technology platform enabling compact, high power and high performance filter solutions for high frequency mobile, Wi-Fi and infrastructure applications.