The deposition and wet etching of Mg-doped ZnO films and their applications for solidly mounted resonators

In this report, a solidly mounted resonator (SMR), consisting of an Au electrode, Mg-doped ZnO (Mg X Zn 1− X O) piezoelectric film and Bragg acoustic reflector, was fabricated on a Si substrate by radio frequency (RF) magnetron sputtering. As a key processing step for the SMR, Mg X Zn 1− X O films with high c -axis orientation were fabricated and the crystalline structure, surface morphology and roughness of the films were investigated. The surface morphology, optical transmittance and shape control of Mg X Zn 1− X O films were investigated by the chemical wet-etching method with various etchants. The profiles and line patterns of Mg X Zn 1− X O films etched with FeCl 3 ·6H 2 O solutions are satisfactory and fully meet the industrial requirements. The Bragg acoustic reflector, made entirely of metal, has small internal stress and good heat conduction. An SMR based on a Mg X Zn 1− X O piezoelectric film shows a resonant frequency of 2.402 GHz, and the k eff 2 , Q S and Q P of the SMR are 3.07%, 415 and 546, respectively. In this report, a solidly mounted resonator (SMR), consisting of an Au electrode, Mg-doped ZnO (Mg X Zn 1− X O) piezoelectric film and Bragg acoustic reflector, was fabricated on a Si substrate by radio frequency (RF) magnetron sputtering.