Abstract
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 on-wafer 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.
Highlights
T HE increasing demand for miniaturized, efficient and low-cost microwave integrated systems requires the development of new technologies offering high-Q interconnections and inductive passive devices
The Z67 probe is based on a tapered coplanar waveguide sloped by 30◦ while 45◦ coaxial waveguides are used on T40 and Infinity RF probes
A model of the Cascade Infinity RF probe is added into the EM modeling to improve the agreement of this modeling with the measurement environment, and to investigate interactions that occur between the RF probe and DUT
Summary
T HE increasing demand for miniaturized, efficient and low-cost microwave integrated systems requires the development of new technologies offering high-Q interconnections and inductive passive devices. Mismatches between measurements and simulations may be observed which are usually resulting from the probing setup surrounding the inductor These disagreements depend on the nature of the problem and they are noticed on the shape of the extracted Q-factor versus frequency, with unexpected ripples and/or resonances. As a parasitic dipole antenna structure is set up, Q-factor values from experiment are well below values extracted from EM simulations This issue has been observed above few GHz, when the Q-factor of inductors exceeds the range 25 to 35. They are based on a better confinement of the field by properly setting the DUT surrounding metal ring
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