Ultrahigh-frequency surface acoustic wave transducers on ZnO/SiO₂/Si using nanoimprint lithography.

Area of Science:

• Materials Science
• Electrical Engineering
• Acoustics

Background:

• Surface acoustic wave (SAW) devices are crucial for high-frequency electronics.
• Advancements in fabrication techniques are needed to push operating frequencies higher.
• Zinc oxide (ZnO) is a promising material for piezoelectric SAW devices.

Purpose of the Study:

• To fabricate ultrahigh-frequency SAW devices on a ZnO/SiO₂/Si substrate.
• To achieve excellent critical dimension control for nanoscale interdigital transducers.
• To demonstrate the highest operating frequency for ZnO-based transducers on silicon.

Main Methods:

• Utilized step-and-flash nanoimprint lithography for device fabrication.
• Employed hydrogen silsesquioxane (HSQ) for substrate planarization.
• Excited and detected fundamental and higher-order Rayleigh modes.

Main Results:

• Achieved critical dimension control for interdigital transducers down to 65 nm finger electrode widths.
• Successfully excited and detected Rayleigh modes up to 16.1 GHz.
• Demonstrated the highest frequency for ZnO-based transducers on silicon to date.

Conclusions:

• The fabricated ZnO/SiO₂/Si SAW devices exhibit ultrahigh-frequency performance.
• Nanoimprint lithography and HSQ planarization are effective for nanoscale transducer fabrication.
• The results represent a significant advancement in ZnO-based SAW device technology on silicon.