Low capacitance and high isolation bond pad for high-frequency RFICs

A bond pad structure using semi-insulating porous silicon (PS) is proposed for the purpose of reducing the parasitic pad capacitance and increasing the crosstalk isolation characteristics on low resistivity p/sup -//p/sup +/ epi substrates for high-performance CMOS. Our results show that reducing the parasitic pad capacitance by using PS results in a high bond pad resonant frequency of up to 56.2 GHz (assuming wire bond inductance is 2 nH). In addition, the crosstalk reduction is as much as 6/spl sim/31 dB at frequencies up to 40 GHz even when compared to that on conventional p/sup -/ bulk substrate. Such a high-performance bonding pad structure is important for high-frequency RFICs which require high operation frequency and low substrate effect.