Tunable Ultra-Small Monolithically-Rolled-up Capacitors by Piezoelectric Actuation

The miniaturization of passive electronic components is essential for radio-frequency integrated circuits (RFICs). In addition, with the surge of wireless technologies, the need for reconfigurable and tunable radio-frequency (RF) components has grown. Enabled by strain-induced self-rolled-up membrane (S-RuM) technology, three-dimensional (3D) tubular interdigital capacitors with greatly reduced footprints can be made with diameter-dependent capacitances. By integrating piezoelectric AlScN, diameter and thus capacitance tuning is demonstrated for the prototyped capacitors, with preliminary data showing a tuning ratio of 1.41 and response of 15.75 pF/V for capacitances of over 150 pF and areal footprints of 0.18 mm
²
. These S-RuM-enabled piezoelectrically-tunable capacitors are easily redesigned to target different capacitances, frequencies, and tuning ratios, with little effect on footprint or process complexity, representing a novel capacitance tuning scheme enabling extreme miniaturization.