Characterization of spiral inductors with patterned floating structures

The impact of two different types of floating patterns on spiral inductors was investigated. Both patterned trench isolation with a floating p/n junction and floating metal poles were implemented underneath reference spiral inductors. All three types of inductors have an identical spiral geometry. Combination of patterned trench isolation with a floating p/n junction increases maximum quality factor (Q_max) by 17% compared to the reference inductors. The floating metal poles enable adjustment of the frequency at Q_max (f_max) without hampering the Q_max. A ladder-type lump-element model was employed to analyze inductor performance after it was demonstrated to precisely capture behavior of all three inductors. Enhancement of the quality factor due to patterned trench isolation with a floating p/n junction was found to result from an increment of effective resistivity in substrates. Reduction of the frequency f_max due to the floating metal poles was caused by increasing effective coupling capacitance between the spiral inductors and substrate.