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Designed Structures of Interdigital Electrodes for Thin Film SAW Devices
Yicong Qian1, Yao Shuai1,2, Chuangui Wu1,2
1Chongqing Institute of Microelectronics Industry Technology, University of Electronic Science and Technology of China, Chongqing 401332, China.
Micromachines
|October 28, 2023
Summary
This study introduces a novel piston, dummy finger, and tilt (PDT) structure to enhance surface acoustic wave (SAW) resonator performance. The PDT structure effectively suppresses spurious modes and improves impedance ratio in SAW filters.
Area of Science:
- Materials Science
- Electrical Engineering
- Physics
Background:
- Surface Acoustic Wave (SAW) resonators are crucial components in modern electronic devices, particularly for frequency filtering.
- Optimizing the microstructure of interdigital electrodes is key to improving SAW resonator performance and suppressing unwanted spurious modes.
- Existing SAW resonator designs face challenges in achieving high impedance ratios and effectively mitigating transverse modes.
Purpose of the Study:
- To investigate the impact of interdigital electrode microstructure on SAW resonator performance.
- To propose and validate an innovative piston, dummy finger, and tilt (PDT) structure for enhanced SAW resonator quality.
- To apply the PDT structure to GLONASS L3 band filters and evaluate its effectiveness.
Main Methods:
- 3D finite element simulation (FEM) was employed to analyze resonator behavior.
- Photolithography techniques were used for fabricating the proposed structures.
- Experimental testing was conducted on an incredible high-performance surface acoustic wave (I.H.P. SAW) substrate.
Main Results:
- An optimal total aperture length of 20T (T is period) was determined for improved resonator performance.
- Adjusting piston dimensions suppressed transverse modes but did not enhance the impedance ratio.
- The proposed PDT structure was experimentally validated to effectively suppress spurious modes and achieve a high impedance ratio.
Conclusions:
- The PDT structure offers a significant improvement in SAW resonator quality by suppressing spurious modes and enhancing impedance ratio.
- A GLONASS L3 band filter utilizing the PDT structure achieved an 8 MHz bandwidth and 3.73 dB insertion loss.
- The developed resonator and filter designs are applicable to similar frequency bands, including BeiDou B2 and GPS L2/L5.
