Micro-bias-tees using micromachined flip-chip inductors

In order to reduce the circuit area required by bias-tees in active circuits, an approach using a micromachined suspended inductor is presented in this paper. The inductor is fabricated using a commercial silicon micromachining process and then integrated with a microwave circuit using flip-chip assembly. Suspending the inductor above the substrate greatly reduces the parasitic capacitances associated with the substrate. The inductor has a measured self-resonant frequency of 18 GHz. A tethered approach allows "pre-releasing" of the structure, which makes integration possible on any substrate. 4-mm/sup 2/ bias-tees on both alumina and TMM6 substrates are presented in this work with comparable performance to commercially available bias-tees, but with a significant reduction in circuit area.