A High Q and High Coupling SAW Resonator on Multilayer Polymide Substrate

We propose a new multilayer substrate structure (LiTaO 3 /Polymide/Si) for I.H.P SAW technology. The electrical characteristics with different thickness of polymide and 42°YX-LiTaO 3 have been investigated. We found that the coupling factor ( $k^{2}$ ) could reach 15%, which is 50% larger than the conventional substrate structure I.H.P SAW (LiTaO 3 /SiO 2 /Si). The impedance ratio at resonant frequency and anti-resonant frequency could reach 95dB, which is 11dB larger than conventional substrate structure I.H.P SAW. We analyzed the transverse modes and proposed an effective method to suppress the high order spurious response. When we use two kinds of metals with different density as IDT electrode material and busbar material, the high order transverse modes could be effectively suppressed.