System-Level IEC ESD Failures in High-Voltage DeNMOS-SCR: Physical Insights and Design Guidelines

A unique failure mechanism for International Electrotechnical Commission (IEC) stress through a common-mode (CM) choke is investigated. The presence of a CM choke in the stress path was found to change the current waveform shape that the electrostatic discharge (ESD) protection device experiences on-chip. Minor variations in the stress current waveform shape for specific IEC stress levels are found to cause an unexpected window failure in drain-extended nMOS silicon controlled rectifier (DeNMOS-SCR). The 3-D technology computer-aided (TCAD) simulations are used to understand the device behavior and failure under the peculiar two-pulse-shaped IEC current waveform attributed to the presence of a CM choke. DeNMOS-SCR failure sensitivity to different components of the unique pulse shape is studied in detail. A novel device architecture is proposed to increase the DeNMOS-SCR robustness against the peculiar two pulse stimuli. The proposed DeNMOS-SCR was found to eliminate the window failures against system-level IEC stress through a CM choke in communication pins in automotive ICs. The proposed concept is universal and can be extended to all high-voltage DeNMOS-SCRs. A detailed physical insight is provided for the operation of the engineered structure.