Vertical High-$Q$ RF-MEMS Devices for Reactive Lumped-Element Circuits

Compact reactive lumped-element circuits fabricated using a single thick metal-layer deep X-ray lithography process are presented. Vertically oriented capacitive features are combined with inductive features in >0.25-mm-thick metal layers to realize lumped-element filter and coupler microstructures operating at up to 12 GHz. Measurements for separate thick metal reactive structures are also presented, including variable capacitors and single-turn square loop inductors. Devices feature impressive vertical structure, including a 77:1 aspect ratio, 1.3-μm-wide cantilever gap structure in 100-μm-thick photoresist. A 0.6-pF capacitor has -factors of 95 at 5.6 GHz and 214 at 3.5 GHz, and a structurally compatible 1.2-nH loop inductor has a -factor of 47 at 6.8 GHz and a self-resonant frequency of 18.8 GHz. Together, these types of devices could form the building blocks for various integrated reactive lumped-element-based circuits.