With increasing ambient temperature the time to thermal
breakdown in the studied n-p-n ESD protection structures
shortens in a step-wise way. At temperatures up to 100 ◦C the
device fails at one of the device ends. At a specific transition
temperature (TB→C) the time to TB is shortened by one CF
round trip time (transition of mode B to C, see Table I). For even
higher ambient temperatures up to 180 ◦C the failure mode at
device end (mode C) changes to a mode where the TB occurs at
the initial position of CF (mode D). The transition temperatures
decrease with current increase, which indicates that the thermal
breakdown can be induced either by increasing ambient temperature
or by increasing current. By measuring failure current
as a function of device width (transition of mode A to B) and
using thermal simulations we have confirmed that the device
end preheating by CF and the increase in ambient temperature