二維矽基聲子晶體之全頻溝驗證

Abstract

In recent years, there are studies aimed at phononic crystals, both experimentally and theoretically. However, the smallest scale of the phononic structures considered is in the millimeter scale and the frequency is limited in the MHz range. For the purpose toward the applications of phononic crystals to micro electromechanical system (MEMS) related components, it is necessary to reduce the lattice size to micrometer or even in nanometer scale. Moreover, for further integrating with the complementary metal-oxide semiconductor (CMOS) processing techniques, silicon is chosen to be the base material of the two dimensional phononic crystals in this thesis. From the simulated results by plane wave expansion (PWE) method, the total band gap of 2-D Air/Si phononic crystal appears at high filling fraction. This result inspires us to employ not only partial band gap but also total band gap in MEMS related components. The purpose of this thesis is to verify the phenomenon of total band gap of 2-D Air/Si phononic crystal by MEMS process. Then comparing the insertion loss of surface wave (SAW) passing through phononic crystal structures within/without the total band gap frequency. In order to generate SAW in the silicon substrate, piezoelectric thin film is sputtered on top of the wafer. Moreover, the 2-D phononic crystals is fabricated by ICP etching (inductively coupled plasma-reactive ion etching) process. Finally, the total band gap of 2-D air/silicon phononic crystals in micrometer-scale are successfully verified by the layered IDT devices, and this experimental result agrees with the theoretical prediction by PWE method.