Lateral microwave transformers and inductors implemented in a Si/SiGe HBT process

Experimental results are presented on a set of microwave inductors and transformers fabricated in a lateral spiral design utilizing two metal layers rather than a single metal layer as used in conventional planar magnetic devices. The fabrication process utilizes a production Si-SiGe HBT technology with standard metallization and a thick polyimide dielectric. Inductors with peak Q's between 2.6-5 and inductance values between 1-3 nH are presented. Transformers with a loss of less than 5 dB when corrected for impedance mismatch and a measured coupling coefficient (k) of 0.6 at 5.5 GHz and 0.4 up to 12.5 GHz are also discussed.