Low capacitance ESD protection circuits for GaAs RF ICs

We present a novel electrostatic discharge (ESD) protection circuit for GaAs radio frequency (RF) integrated circuits (ICs), which are targeted for 10 Gb/s fiber-optic communication applications. The robustness, parasitic impedance, and loading effect of the new ESD protection circuit are studied and compared with the conventional diode-based ESD protection technique. Two versions of this type of ESD protection circuit were fabricated with a 60-GHz InGaP heterojunction bipolar transistor (HBT) technology. These two circuits can withstand, respectively, 2700 and 5000 V human body model (HBM) ESD stress and provide a similar level of ESD protection to RF ICs. The corresponding impedances of the off state are represented by an equivalent shunt capacitance and shunt resistance of 0.22 pF and 500 Ω, and 0.5 pF and 250 Ω, at 10 GHz. This ESD protection circuit can protect the 10 Gb/s RF ICs against much higher level ESD stress than conventional diode-based ESD protection circuits even with smaller size.