Physical Modeling of Monolithic Self-Rolled-Up Microtube Interdigital Capacitors

This article presents a physical model for monolithic self-rolled-up microtube interdigital capacitors and elaborates their working mechanisms in comparison to on-chip planar interdigital capacitors. Besides the high-frequency phenomena such as the skin effect in thin, wide metal films, the model accounts for the complexities resulting from all possible 3-D electrode configurations, such as the inner diameter-dependent overlapping capacitances and edge capacitances between electrodes, as well as parasitic inductances within the rolled-up structure between the fingers, for integer and noninteger number of turns. The model is validated by the measured results of fabricated self-rolled-up membrane (S-RuM) interdigital capacitors over a wide range of layout and process parameters. This fully enables the structural design optimization for electrical performance of this 3-D device architecture.