Quality Factor Improvement of a 2.4GHz AlN Checker Patterned Lamb Wave Resonator by Novel Distributed Anchor Design

In a checker patterned lamb wave resonator, electrode patches with the square, diamond or round shape are usually arranged in the way that one electrode is surrounded by a group of four patches with an opposite electrical polarity to excite two-dimensional (2D) lamb waves. This arrangement of the electrodes makes the signal routing quite challenging. The existing approach is to supply the electrical signal from a thin anchor, then go to a long and narrow wire at the edge of the resonator plate before it is distributed to multiple rows/columns of the electrode patches. The drawback of this approach is firstly high resistive loss of the long wire which degrades the Q factor and secondly the distorted acoustic field excitation due to the non-uniform distribution of the electric signal. This work presents a novel distributed anchor design which does not only improve the mechanical strength of the thin film resonator, but also reduce the resistive loss by embedding the electrical routing in each anchor. This concept is applied to a checker patterned resonator operating at 2.4GHz. The measurement results show the reduction of series resistance from 16Ω for the corner anchor design to 5.6Ω for the distributed anchor design, corresponding to a significant quality factor improvement.