Analysis and application of miniature 3D inductor

The structure of the miniature 3D inductors is presented in this paper. The proposed miniature 3D inductors have been fabricated in a standard 0.35-μm one-poly-four-metal (1P4M) CMOS process. According to the measurement results, the self-resonance frequency (f_SR) of the proposed miniature 3D inductor is at least 34% higher than the conventional stacked inductor. Moreover, the proposed miniature 3D inductor occupies only 16% area of the conventional planar spiral inductor with the same inductance. The analytical equations are derived and the capacitances distribution model is proposed to elucidate why the miniature 3D inductor has the higher self-resonance frequency. A CMOS voltage controlled oscillator (VCO), which utilized the proposed miniature 3D inductors, has also been demonstrated.