High-Q Micromachined Inductors for 10-to-30-GHz RFIC Applications on Low Resistivity Si-Substrate

The measured results for quality factor improvement and self-resonance frequency (f_sr) improvement of the planar inductors implemented in 0.35-mum two-poly-four-metal (2P4M) CMOS process are presented in this paper. These inductors are fabricated on a low resistivity Si-substrate with a resistance about 33 Omega-cm. It is observed that the quality factors of planar inductors can be increased by the shunt metals from metal1 (M1) to metal4 (M4) to reduce the series resistance at low frequencies and by the CMOS compatible post-process to reduce the parasitic capacitance between the inductors and the lossy Si-substrate at high frequencies. With micromachined inductors suspended above the substrate, the measured maximum quality factor is 18.6 for a 0.16-nH micromachined inductor and the improvement of quality factor is up to 107%. This is also the first report of the high-Q measured micromachined inductors above 10-GHz on low-resistivity silicon substrate