Low Velocity I.H.P. SAW Using Al/Pt Electrodes for Miniaturization

In this paper, we study a velocity reduction of incredible high performance (I.H.P.) surface acoustic wave (SAW). First, variations of I.H.P. SAW velocity and fractional bandwidth with thickness of Pt layer in Al/Pt electrode are estimated using a finite element method simulator, and specific conditions where the SAW velocity can be reduced maintaining the fractional bandwidth equivalent to that of the conventional structure are determined. Then some one-port resonators under the determined conditions are fabricated and their velocity, fractional bandwidth, quality factor, and temperature stability are evaluated. As the result, it is indicated that, by using Al/Pt electrode and by adjusting the film thicknesses of a multilayer substrate, the velocity of I.H.P. SAW is successfully reduced while keeping other important characteristics.