Analyse of Protection Devices´ Speed Performance against ESD under CDM Using TCAD

Speed performance plays a critical role in protection devices against ESD (Electro-Static Discharge) overstress under CDM (Charged Device Model). It is too demanding to obtain speed performance of protection devices under CDM accurately by testing. Therefore we have to resort to TCAD (Technology Computer Aided Design) method to evaluate speed performance under CDM. This TCAD methodology is based on mix-mode transient circuit simulation, which depicts ESD events better. Two time constants, T_trigger and T_recover, and two key coefficients, F_trigger and C_recover, are provided to characterize and evaluate speed performance of ESD protection devices. The results show that this TCAD methodology has a good ability of convergence and is a good tool to evaluate speed performance of ESD protection devices quantificationally. Anlayse results show that speed performance of SCR is superior over ggNMOS in not only triggering but also bypassing ESD currents to recover the voltage towards a safe level.