Nanosecond transient thermoreflectance imaging of snapback in semiconductor controlled rectifiers

Transient thermoreflectance imaging method has been applied for the first time to reveal current distribution in ESD protection devices through the surface temperature change due to self heating. Experimentally calibrated temperature images are obtained of a multiple finger, 80 square micron 100V NLDMOS-SCR device in snapback operation regimes for different current levels (1.15-1.47A) and at different times ranging between 100 nanoseconds to one millisecond after the ESD pulse. The novel applied methodology demonstrates a practical and straightforward way to characterize non-uniform temperature and current distribution in ESD structures, revealing effects of non-simultaneous triggering of individual fingers on the multiple finger SCR device.