Ultra-High Q-factor Through Fused-silica Via (TFV) Integrated 3D Solenoid Inductor for Millimeter Wave Applications

In this work, a substrate integrated 3D solenoid inductor with an ultra-high quality factor (Q-factor) is demonstrated using the combination of Through Fused-silica Vias (TFVs) for low substrate loss and Copper (Cu) / Cobalt (Co) metaconductors for low conductor loss for millimeter wave (mmWave) applications. Especially, a Cu/Co metaconductor based 1 turn 3D solenoid inductor is integrated on a 300 μm thick fused-silica substrate with a small form factor of 170 μm×200 μm. The Cu/Co inductor shows a peak Q-factor of 204 while a solid Cu counterpart does a Q-factor of 88.9 at 28.4 GHz, showing 130% Q-factor improvement. Modeling and optimization of the inductors has been performed using a lumped element circuit model and High Frequency Structure Simulator (HFSS) simulation. Design, fabrication, and characterization of the inductors is detailed.