Design of CMOS Spiral Inductors for Effective Broadband Shielding

Design of a CMOS spiral inductor of significantly reduced coupling to the adjacent inductor is presented. The synthetic quasi-TEM transmission line (TL), or the so-called complementary-conducting-strip transmission line (CCS TL), is applied to realize the proposed inductor and simultaneously shield electromagnetic coupling from the adjacent inductor by the existing meshed ground plane of the CCS TL. Several coupled inductors at edge-to-edge spacing of 90 mum, 170 mum, and 250 mum were fabricated by the 1P6M (one poly-layer and six metal layers) 0.18 mum CMOS process, demonstrating excellent broadband shielding characteristics of approximately 30-to-40 dB improvement below 5 GHz and 15 dB improvement at 20 GHz when compared with the same spirals integrated on the CMOS substrate directly without shields