Monolithic transformers in a five metal CMOS process

Four monolithic transformers and an inductor are fabricated in a 5 metal CMOS process with varying number of turns and metal thicknesses. The S-parameters are measured from 500 MHz to 5.5 GHz, and equivalent lumped element models are extracted to calculate the differential quality factor vs. frequency. The transformers demonstrated significantly higher quality factors peaking at higher frequencies compared to the inductor.