Title :
Micromachined high-Q inductors in a 0.18-μm copper interconnect low-k dielectric CMOS process
Author :
Lakdawala, Hasnain ; Zhu, Xu ; Luo, Hao ; Santhanam, Suresh ; Carley, L. Richard ; Fedder, Gary K.
Author_Institution :
Dept. of Electr. & Comput. Eng., Carnegie Mellon Univ., Pittsburgh, PA, USA
fDate :
3/1/2002 12:00:00 AM
Abstract :
On-chip spiral micromachined inductors fabricated in a 0.18-μm digital CMOS process with 6-level copper interconnect and low-K dielectric are described. A post-CMOS maskless micromachining process compatible with the CMOS materials and design rules has been developed to create inductors suspended above the substrate with the inter-turn dielectric removed. Such inductors have higher quality factors as substrate losses are eliminated by silicon removal and increased self-resonant frequency due to reduction of inter-turn and substrate parasitic capacitances. Quality factors up to 12 were obtained for a 3.2-nH micromachined inductor at 7.5 GHz. Improvements of up to 180% in maximum quality factor, along with 40%-70% increase in self-resonant frequency were seen over conventional inductors. The effects of micromachining on inductor performance was modeled using a physics-based model with predictive capability. The model was verified by measurements at various stages of the post-CMOS processing. Micromachined inductor quality factor is limited by series resistance up to a predicted metal thickness of between 6-10 μm
Keywords :
CMOS analogue integrated circuits; Q-factor; field effect MMIC; inductors; integrated circuit interconnections; integrated circuit modelling; micromachining; 0.18 micron; 6-level copper interconnect; 7.5 GHz; Cu interconnect low-k dielectric CMOS process; RFIC; digital CMOS process; maximum quality factor; metal thickness; micromachined high-Q inductors; on-chip spiral micromachined inductors; parasitic capacitances; physics-based model; post-CMOS maskless micromachining; predictive capability; quality factors; self-resonant frequency; series resistance; substrate losses; CMOS process; Copper; Dielectric materials; Dielectric substrates; Frequency; Inductors; Micromachining; Predictive models; Q factor; Spirals;
Journal_Title :
Solid-State Circuits, IEEE Journal of