Various 3-D integrated inductors and transformers based on stressed metal technology have been designed, fabricated, and characterized for high frequency applications. 3-D inductors with very high quality factors (Q > 100) and also high self resonant frequencies (fsr ∼ 40 GHz) are demonstrated. A 1.2 nH inductor on micromachined substrate achieves a record high quality factor of 138 at 12GHz, with Q > 100 for frequencies between 8 to 20GHz. Using the same technology, 3-D transformers with very high coupling coefficients (K > 0.8) and also high self resonant frequencies (fsr ∼ 15 GHz) are achieved. A 4:4 turn ratio transformer on high resistivity Si substrate achieves a coupling coefficient k of 0.84 at 5 GHz, with k over 0.7 for frequencies from 1.6 to 6.6 GHz and with power gain Pout/Pin over 75% up to 20 GHz. Moreover, toroidal inductors with very high inductance values and high quality factors have been developed. A 62-turn inductor on high-resistivity Si has inductance value of 81.4 nH and peak quality factor of 9.7. Toroidal transformers with 8:8, 14:14, and 30:30 turn ratio have been also developed and characterized for high frequency applications.;Through EM simulation (HFSS) and equivalent circuit modeling (ADS), it is shown that by varying the geometry and design parameters, one can achieve an optimized performance in terms of inductance value, quality factor, self-resonant frequency, and transformer coupling. The availability of high-Q 3-D integrated inductors and high performance 3-D integrated transformers will open up new design directions for RF and microwave integrated circuits. Such circuits will have improved performance in terms of RF power loss, RF noise, phase noise, DC power consumption, RF gain bandwidth and power gain.
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