High-isolation bonding pad design for silicon RFIC up to 20 GHz

A simple depletion-insulation (DI) bonding pad structure is presented for silicon radio frequency integrated circuits (RFIC). Experimental results show that DI bonding pads can achieve a 3 to 7 dB improvement in cross-talk isolation compared with an ordinary bonding pad at all measured frequencies. An improvement of up to 90% in the Q-factor is also achieved by the DI pad indicating a significantly reduced high-frequency substrate loss. When compared with a ground-shield (GS) bonding pad, the isolation and the Q-factor of the DI bonding pad is inferior. However, the DI pad has a 40% smaller pad capacitance compared with the GS pad. The DI structure can be used in interconnect optimization to achieve high cross-talk isolation and low substrate loss, with minimal increase in parasitic capacitance.