Characterization and modeling of second breakdown in NMOST´s for the extraction of ESD-related process and design parameters

A technique is presented to determine the effective process and design-related parameters from the high-current I-Vcharacteristics of NMOSTs, for use in the development of electrostatic discharge (ESD) protection circuits. Test structures from a fully salicided, LDD MOS process were characterized with a transmission line pulse generator to obtain the snapback voltages and the second-breakdown trigger currents (I_t2) Good correlations are shown between I_t2 and the human body model (HBM) ESD damage thresholds. It was seen that homogeneous current injection in the avalanching diffusions is imperative for good second breakdown behavior. A simplified thermal model, with second breakdown as the boundary condition for damage, was used in the extraction of the effective junction depth, depletion width, and transistor width under high-current conditions. Experimental data obtained for the power-to-failure as a function of the time-to-failure showed a good fit to the model. A possible extension of the technique for the use of DC characterization to monitor ESD behavior is presented