High-isolation bonding pad with depletion-insulation structure for RF/microwave integrated circuits on bulk silicon CMOS

Bonding pads for RF/microwave integrated circuits on bulk silicon CMOS is designed with a simple depletion-insulation (DI) structure. Experimental results show high isolation and low substrate loss. An inter-pad isolation of more than 40dB at 10GHz is obtained for a 90-μm separation distance. The isolation is about two orders of magnitude higher than that of the conventional structure. The return loss is also less than 1.5dB at 10GHz. The high Q factor of the DI pad is achieved a few times greater that of the conventional type. The low pad capacitance of about 0.013fF/μm² is attained. This will increase the resonant frequency of the bond-wire-pad connection. The application of the useful DI structure is extendable to interconnect and planar spiral inductor to reduce the substrate loss and increase the Q factor.