Low Loss Acoustic Waveguide Based on Aluminum Nitride Thin Film

In this work, we conduct a series of acoustic waveguide analyses built on a 400 nm suspended aluminum nitride (AlN) thin film. The two port acoustic waveguide with different structure are simulated and analyzed using the finite element method (FEM) to validate the transmission performance. The implemented devices are measured using a vector network analyzer (VNA), and the insertion losses of different waveguide structures are evaluated. The results reveal that a 5 μm wide acoustic waveguide supports a relatively pure fundamental symmetric (S0) Lamb wave, while a 10 μm wide waveguide supports an S0 mode affected by spurious modes. For a straight waveguide with a 10 μm width and 40 μm length, the minimum insertion loss is 16.85 dB at 858 MHz. The curved waveguide with a height difference of 20 μm has a minimum insertion loss of 15.24 dB at 859 MHz. Both of these configurations show an insertion loss reduction of 10 dB compared to the 5 μm wide waveguide. These analyses pave the way for high-frequency and compact acoustic manipulation, providing guidance for low loss piezoelectric integrated circuits (PnIC).