Simultaneous and Sequential Triggering in Multi-Finger Floating-Base SCRs Depending on TLP Pulse Rise Time

Multi-finger floating-base silicon controlled rectifiers (SCRs) of discrete technologies are investigated by transmission line pulses (TLP) with short (300ps) and long (10ns) pulse rise times (RT). Transient interferometric mapping (TIM) is applied to study the finger triggering dynamics. The measurements are correlated with TCAD simulation. It is found that for short RT the fingers trigger simultaneously which is due to the positive influence of a voltage overshoot related to delayed conductivity modulation. For long RT the fingers trigger sequentially which is accompanied by the voltage drops near the holding voltage. The time delay between the triggering of neighboring fingers is in the 3–150ns range and depends on the actual current density in fingers. The sequential finger triggering is due to lateral carrier diffusion-limited processes and the coupling via substrate currents.