A novel ESD super-clamp structure for TVS applications

This paper presents a new ESD clamp structure for transient voltage suppressor (TVS) applications that combines the advantages of avalanche diode and bipolar transistor clamps. The device structure consists of a non-snapback avalanche diode triggered vertical NPN transistor. The avalanche diode provides the fast trigger and current conduction path at low currents, while the vertical NPN bipolar transistor turn-on provides alternate low resistance path for current conduction at high currents. The snapback in the IV characteristics is minimized by matching the avalanche diode breakdown voltage V _BD and the vertical NPN transistor open base collector-emitter breakdown voltage, BV _CEO- Measurements on fabricated devices show consistent results with the theory. The TVS has low leakage currents (< 25 nAmps), negligible snapback in the output characteristics (<0.5 Volts) and excellent clamping voltage at high currents (13.1 Volts @ 30 Amps of TLP current). The presence of low doped base region also results in 35 % decrease in the TVS capacitance.