High-Q 3D embedded inductors using TSV for RF MEMS tunable bandpass filters (4.65–6.8 GHz)

This paper presents the optimization design of 3D integrated inductors exploiting through silicon vias (TSV) technology to improve the quality (Q) factor in the 2-20 GHz range. The embedded inductor allows the heterogeneous integration with CMOS and MEMS components in a size-compact and low-cost manufacturing process. Results limited to our manufacturing possibilities (5.5×15 μ m-area tungsten TSVs, high resistivity (HR) silicon substrate) show Q-factor values as high as 35 at 8 GHz for 4.8 nH inductance, and design methods to improve them. These inductors are attractive to be used with MEMS capacitors for reconfigurable RFICs, as proposed for a tunable passband filter in the range 4.65 - 6.8 GHz. The filter shows 15% continuous linear center frequency tuning and over 45% in a digital fashion. The filter is also continuously tunable in bandwidth (up to 40%) while keeping constant the center frequency.