High Q metal strip SSBW resonators using a SAW design

Area of Science:

• Acoustic physics
• Materials science
• Electrical engineering

Background:

• Surface acoustic wave (SAW) resonators are widely used in electronic devices.
• Surface skimming bulk wave (SSBW) resonators offer potential advantages but require optimization.

Purpose of the Study:

• To experimentally investigate and compare the characteristics of SSBW and SAW resonators.
• To identify optimal design parameters for high-performance SSBW resonators.

Main Methods:

• Fabrication of SSBW and SAW resonators using identical photolithographic masks.
• Systematic variation of interdigital transducer distance (L), metal thickness (h/lambda), and finger-to-gap ratio.
• Performance characterization including unloaded Q factor and insertion loss.

Main Results:

• SSBW resonators achieved high unloaded Q (5820) and low insertion loss (7.8 dB) at 766 MHz.
• Optimal SSBW performance was obtained at L=nλ/2-λ/4, h/λ=1.6%, and finger-to-gap ratio near 1.
• SSBW resonant frequency exhibited higher sensitivity to metal thickness, addressable by CF(4) plasma etching.

Conclusions:

• Optimized SSBW resonators fabricated with a SAW design demonstrate excellent performance.
• Frequency trimming via plasma etching effectively compensates for metal thickness variations in SSBW devices.
• SSBW resonators show promise for advanced electronic applications requiring high Q and low loss.