EBIRCH Localization for Low-Current Soft Fails

An experimental study was undertaken to determine the minimum level of leakage or shorting current that could be detected by electron-beam induced resistance change (EBIRCH) analysis. A 22-nm SRAM array was overstressed with a series of gradually increasing voltage biases followed by EBIRCH scans at 1 V and 2-kV SEM imaging until fins were observed. It was found that the fins of a pulldown device could be imaged by EBIRCH at just 12 nA of shorting current, representative of a soft failure. Stressing the sample at higher voltages eventually created an ohmic short, which upon further investigation, strongly suggested that the Seebeck effect plays a significant role in EBIRCH analysis.