The integration of RF passives using thin-film technology on high-ohmic Si in combination with thick-film interconnect

A technology platform is presented for the integration of passive components in RF circuits. The platform consists of a thin film process on high-ohmic Si combined with thick film technology. The thin film process is used for sections in RF circuit where a relatively high degree of component accuracy is needed, e.g. for impedance matching. The thin film process uses p >4 kΩ.cm Si substrates on which IC compatible layers, such as sputtered Al and CVD silicon nitride and oxide, are deposited and structured. This process is capable of fabricating inductors and capacitors with a performance that does not differ significantly from inductors and capacitors processed on an insulating substrate, such as glass and alumina. Inductors with a Q-factor between 40 to 60 and capacitors with an ESR < 200 mΩ in the 1-2 GHz frequency range are realized. Using the thin film process in combination with thick film interconnect a 2 Q to 50 Ω impedance matching circuit is realized with an insertion loss of 0.8 dB at 900 MHz.