Measurements of variable capacitance using single port radio frequency reflectometry.

Area of Science:

• Electrical Engineering
• Materials Science
• Computer Engineering

Background:

• Adiabatic reversible computing offers energy-efficient computation by reducing heat dissipation.
• Micro-electromechanical systems (MEMS) variable capacitors are crucial components for digital gates in reversible computing architectures.
• Characterizing these variable capacitors is essential for optimizing circuit performance and energy efficiency.

Purpose of the Study:

• To present a radio frequency (RF) reflectometry technique for measuring device capacitances.
• To characterize MEMS variable capacitor devices for reversible computing applications.
• To assess the feasibility of RF reflectometry for measuring variable capacitors within a specific capacitance range.

Main Methods:

• Utilized single-port RF reflectometry with a custom-made RF probe featuring an on-board matching network.
• Calibrated the RF probe using a capacitive bank to observe frequency shifts indicative of capacitance changes.
• Measured static capacitors and MEMS variable capacitors to evaluate the technique's performance and limitations.

Main Results:

• The RF reflectometry technique successfully measured static capacitors without significant parasitic resistance.
• A high in-series parasitic resistance (approximately 80 kΩ) in MEMS variable capacitors masked the frequency shift, hindering accurate measurement.
• RF reflectometry demonstrated potential for measuring MEMS variable capacitors in the 0-30 fF range when parasitic resistance is not a limiting factor.

Conclusions:

• RF reflectometry is a potentially fast and versatile method for characterizing variable capacitors.
• The technique's effectiveness is significantly impacted by parasitic resistance in the devices under test.
• Further development is needed to overcome challenges associated with measuring high-resistance MEMS variable capacitors for energy-efficient computing applications.