A tunable ferroelectric based unreleased RF resonator.

Area of Science:

• Solid-state physics
• Materials science
• Electrical engineering

Background:

• Radio frequency micro-electro-mechanical systems (RF MEMS) are crucial for wireless communication.
• Existing RF MEMS resonators often require complex fabrication processes and lack tunability.
• Ferroelectric materials offer unique electrical properties for device integration.

Purpose of the Study:

• To introduce the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator.
• To demonstrate monolithic integration within standard CMOS technology.
• To achieve high-quality factor (Q) and switchable resonance characteristics.

Main Methods:

• Monolithic integration of FeCAPs in CMOS back-end-of-line (BEOL) process.
• Utilizing acoustic waveguiding for vertical confinement and optimizing lateral confinement.
• Employing FeCAPs as electromechanical transducers for resonance control.

Main Results:

• Demonstrated a resonator with fundamental resonance at 703 MHz and a Q of 1012.
• Achieved a frequency-quality factor product 1.6x higher than state-of-the-art PZT resonators.
• Showcased switchable resonance, with the ability to turn off transduction at ±0.3 V.

Conclusions:

• The developed FeCAP-based RF MEMS resonator offers superior performance and tunability.
• Monolithic integration in CMOS technology simplifies fabrication and reduces cost.
• Potential applications include on-chip timing, ad-hoc radio front ends, and chip-scale sensors.