Optimization of broadband RF performance and ESD robustness by π-model distributed ESD protection scheme

Large electrostatic discharge (ESD) protection devices close to the I/O pins, beneficial for ESD protection, have an adverse effect on the performance of broadband RF circuits for impedance mismatch and bandwidth degradation. A new proposed ESD protection structure, pi-model distributed ESD (pi-DESD) protection circuit, composed of one pair of ESD devices near the I/O pin, the other pair close to the core circuit, and a coplanar waveguide with under-grounded shield (CPWG) connecting these two pairs, can successfully achieve both excellent ESD robustness and good broadband RF performance. Cooperating with the active power-rail ESD clamp circuit, the experimental chip in a 0.25-mum CMOS process can sustain the human-body-model (HBM) ESD stress of 8 kV.