Equivalent circuit model with nonlinear characteristics of zener diode extracted from SPICE model for ESD simulation

Transient analysis of an electrostatic discharge (ESD) is important for development of a highly immune device and an IC. High nonlinearity of an ESD protection circuit makes it difficult to simulate transient waveform of ESD. In this manuscript, a nonlinear model of a zener diode as ESD protection device is proposed for transient simulation of ESD. In the proposed model, voltage-dependence of a series resistance and a diffusion capacitance are represented by approximation formulae. In order to evaluate the proposed model, transient waveforms are calculated using SPICE model and the proposed model when ESD current specified by IEC 61000-4-2 is injected into the zener diode. By comparison with these waveforms, the calculation results by the proposed model is in good agreement with that by SPICE model.