High‐Frequency Inductors by Co‐Design Optimization of Self‐Rolled‐up Membrane Technology

Abstract

Self‐rolled‐up membrane (S‐RuM) 3D microtube inductors represent a significant advancement in miniaturization for radio frequency (RF) integrated circuit applications, particularly internet‐of‐things and 5G/6G communications. These inductors have excellent high‐frequency performance due to better confinement of the magnetic field and weak dependence on substrate conductivity. However, previously reported S‐RuM inductor frequencies are limited by the crosstalk capacitance between overlapping metal strips between rolled‐up turns. This work advances S‐RuM inductor design by co‐optimizing inductance, frequency, and footprint, leading to significant reductions in crosstalk capacitance and enhancements in maximum operating frequencies. Design intricacies tailored to the unique structure of S‐RuM inductors are thoroughly addressed, particularly by mapping the angle of the rolled‐up inductor strips with respect to the number of turns. Self‐resonance frequencies as high as 40–53 GHz (instrument testing limit) are reported for 2–5 rolled‐up turns, demonstrating increases of over 15 GHz from previous S‐RuM inductors. These designs, with footprints of 0.02–0.56 mm2 and inductances of <1 nH to >5 nH at GHz frequencies, demonstrated the effectiveness of co‐designing frequency, footprint, and inductance for RF inductors, openning a new paradigm for miniaturizing high‐frequency on‐chip passive electronic components.