An Unassisted, Low Trigger-, and High Holding-Voltage SCR (uSCR) for On-Chip ESD-Protection Applications

A new silicon-controlled rectifier (SCR) is proposed and realized in a 0.35-mum/3.3-V fully salicided BiCMOS process for electrostatic-discharge (ESD) applications. Without using an external trigger circuitry, the unassisted SCR has a trigger voltage as low as 7 V to effectively protect deep-submicrometer MOS circuits, a holding voltage higher than the supply voltage to minimize transient influence and avoid latch-up issue, and a second snapback current density exceeding 60 mA/mum to provide robust ESD-protection solutions.