EBIRCH Localization for Low-Current Soft Fails

An experimental study was undertaken to determine the minimum level of leakage or shorting current could be detected by EBIRCH. A 22 nm SRAM array was overstressed with a series gradually increasing bias, followed by EBIRCH scans with 1 V applied bias and 2 kV SEM imaging, until fins were observed. The result was that with only 12 nA of shorting current, the fins of a pulldown device could be imaged by EBIRCH. Higher stresses created an ohmic short, and careful consideration of experiments with current direction provide additional evidence that EBIRCH is largely a temperaturedriven, or Seebeck effect.