Monolithic planar RF inductor and waveguide structures on silicon with performance comparable to those in GaAs MMIC

The monolithic inductors and transmission lines on Si substrate with very high Q factor, low insertion loss, and high resonant frequency, are achieved by using very thick polyimide (10 μm) as dielectric material, and thick Al (4 μm) metalization system. This structure is made on the finished conventional standard two layer metalization BiCMOS wafer. For 10 nH inductor, 6 GHz resonant frequency, maximum Q factor of 5.5 at 1.2 GHz, and 1.2 dB insertion loss at 3 GHz are obtained, which are very comparable to those available in GaAs MMIC, These inductors can be used as RF choke as well as matching element. Transmission lines are also fabricated using this technology. The S₂₁ of coplanar waveguide with 1 mm length is -0.2 dB at 4 GHz, and that of microstrip line is -0.3 dB. It is expected that, using these passive elements, Si RF IC can be designed up to several GHz with performance comparable to GaAs MMIC