Unique Rise Time Sensitivity Leading to Air Discharge System-Level ESD Failures in Bidirectional High Voltage SCRs

Abstract

This article discloses a unique failure mode in high-voltage bidirectional (Bi-Di) silicon-controlled rectifier (BDSCR) cells during International Electrotechnical Commission (IEC) air discharge electrostatic discharge (ESD) events. Failure was found to be sensitive to IEC measurement conditions or variabilities such as the speed of IEC gun and angle of approach, which causes different stress rise times. Hence, observed failure was a peculiar function of the rise times of the discharge current waveform. Remarkably, failure in high-voltage BDSCR was observed only for a window of current rise times. A new approach is presented using 3-D TCAD simulations of multifinger BDSCR to study and probe the failure mechanism dependent on these system-level stress parameters and variabilities. By emulating the experimental conditions in a 3-D TCAD environment, physical insights are developed to probe the root cause of the observed air discharge failures. Furthermore, a device engineering approach has been proposed, with the help of 3-D TCAD simulations of multifinger BDSCR, which computationally demonstrated improved robustness of BDSCR multifinger cells against IEC air discharge failures. The proposed design mitigates the nonuniform turn-on and failure due to IEC stress or rise time variability at the cost of a negligibly small area overhead.