Performance comparison of 5GHz VCOs integrated by CMOS compatible high Q MEMS inductors

In this paper, we report the performance comparison of 5 GHz CMOS VCOs fabricated by 0.18 /spl mu/m six-metal mixed-mode RF CMOS processes with respect to the same VCOs integrated with high Q MEMS inductors. The CMOS inductors implemented by a top-level 2 /spl mu/m-thick Al/Cu metal layer typically show Q factors of about 10, while the MEMS inductors can give much higher Q factors over 25. Differential CMOS VCO circuits have been optimally designed for the respective Q factors of both CMOS and MEMS inductors. Phase noise has been measured and compared for the fabricated VCOs, demonstrating that the VCOs with MEMS inductors can give better phase noise by more than 7 dB in the offset frequency range from 30 kHz to 3 MHz.