Abstract-A cost-effective technology is proposed for the integration of very compact and high-performance 3-D solenoid inductors. Based on a two metal level process, it involves a 3-D copper electroplating step for simultaneous integration of vertical and upper sections of coils. Several solenoids fabricated on a glass substrate and ranging from 2.3 nH to 9.5 nH are presented. The best performance is experimentally achieved by a 3-turn 3 nH inductor showing a maximum Q-factor of 58 at 5.6 GHz and a self-resonant frequency of 19 GHz. The best inductance density of 63 nH/mm 2 is reached by an 8-turn 9.5 nH solenoid.
This paper investigates the disagreements that may occur between on-wafer measurements and electromagnetic (EM) simulations of high-Q inductive devices. Such disagreements are highlighted on a planar spiral inductor and a 3-D solenoid which exhibit measured maximum Q-factors of 27 and 35 respectively, while 42 and 45 were expected from EM simulations. Both devices are fabricated on high-resistivity substrates. A radiative interaction is identified between RF probe and inductive device under test. By using EM simulations, extra-losses associated with this parasitic effect are fully modeled through the calculation of radiation and dissipation related Q-factors. Adjustments of onwafer probe setup are proposed to reduce this parasitic effect. Finally, the 3-D solenoid inductor is characterized using a new experimental fixture, and the maximum Q of 45 predicted by EM simulation is retrieved.
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