Preparation of the Bragg reflectors of tuneable thin film bulk acoustic wave resonators by RF sputtering

Electrically tuneable thin film bulk acoustic wave resonators have drawn much attention for their advantages of high Q factors, integrable feature and small sizes. Accurate controlling of the thickness of the Bragg reflectors directly affects the Q-factor of the resonators with solidly mounted structure. In this paper, the preparation method to precisely control the thickness of the Bragg reflectors by RF sputtering has been studied. The structure of W/SiO₂ alternated layers with different thicknesses was successfully prepared by RF sputtering method. The film thicknesses showed good linearity over time. The deposition rates of two layers under different annealing conditions were derived.