Micromachined high-Q inductors in 0.18 /spl mu/m Cu interconnect low-K CMOS

摘要

Spiral inductors fabricated in a 0.18 /spl mu/m 6-level copper interconnect low-K dielectric process are described. A post-CMOS maskless micromachining process compatible to copper interconnect and low-k dielectric CMOS has been developed to create inductors suspended 100 /spl mu/m above the substrate with sidewall oxide removed. Such inductors have higher quality factors as substrate losses are eliminated by silicon removal and have higher self-resonant frequency due to removal of inter-turn dielectrics. Micromachined inductors have the potential to extend the useful operational frequency range of CMOS RF circuits. Quality factors of greater than 7 were obtained at 5.5 GHz for inductors with silicon undercut and inter-turn oxide removed, compared to a Q of 4 for inductors having only their inter-turn oxide removed but without silicon undercut.