Study of bipolar transistor action during ESD stress in smart power ESD protection devices using interferometric temperature mapping

Thermal dynamics, temperature distribution and bipolar transistor triggering during electrostatic discharge (ESD) events are studied in smart-power technology ESD protection devices by a backside inteiferometric technique. Temperature changes in the device active area are monitored via ns-time scale measurements of optical phase shift. The bipolar transistor action under snapback operation is identified by a dominant phase shift signal arising in the n+-emitter region. Hot spot formation and temperature inhomogeneities due to current crowding are studied as a function of device layout and power.