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.