Measurement and application of vertical inductors in high-speed broadband circuit

The measurement results and a practical application of vertical inductors (VIs) are presented. VIs are on-chip inductors designed to save chip area. In VI the spiral plane is oriented perpendicularly with respect to the substrate. An inductance of 318 pH with a self-resonance frequency of 66.5 GHz is implemented in a 130 nm bipolar complementary metal-oxide semiconductor (BiCMOS) technology and results are compared with three-dimensional (3D) planar EM (ground-signal-ground) simulations. The inductance per unit area is 424 nH/mm², more than 1.7 times higher than other simulated spiral horizontal inductors. Moreover, VIs have been applied in the design of a broadband amplifier leading to a 25% bandwidth enhancement.