Defects present in microelectronic devices are often present in test structures as well. This makes test structures useful in identifying defect mechanisms. Chain patterns consists of thousands of contacts and plugs in series. The presence of an open contact in a chain can be detected by a loss of electrical continuity. The specific site of an open contact is difficult to locate for further analysis.

The application of the focused ion beam (FIB) for passive voltage contrast (PVC) provides an effective method for contact defect location. Once the defect is located the FIB facilitates efficient site-specific specimen preparation for scanning electron microscopy (SEM), transmission electron microscopy (TEM) or Auger analysis.

The FIB is capable of PVC analysis by distinguishing electrically isolated conductors from grounded conductors. Isolated conductors charge as a result of ion beam interaction. Once charged, the quantity of secondary electrons available for detection is greatly reduced.