ESD-level circuit simulation-impact of gate RC-delay on HBM and CDM behavior

Abstract

An extraction method for the effective gate RC-delay of MOS single- and multi-finger structures is introduced by deducing a rule of thumb for the effective poly resistance. In addition to the wiring and parasitic capacitance connected to a gate, this distributed poly resistance in conjunction with the nonlinear gate capacitance can cause an appreciable gate delay (RC/spl sim/1 ns). It is demonstrated for a CMOS output driver circuit that this effect is HBM relevant. Here, circuit simulations are compared to the corresponding TLP measurements. Furthermore, a general CDM-level circuit simulation methodology is presented. To our knowledge for the first time, a CDM current source model accounts for the single pin event character of CDM. Under such stress, the simulation reveals an unexpected large impact of the gate PC-delay formed by the metal interconnects in a CMOS double input inverter. Voltage overshoots occur at internal gates and lead to oxide breakdown, which was validated by CDM stress tests and physical failure analysis.