FIB Voltage Contrast
An array structure containing failing contacts has been parallel lapped to reveal the top of the contacts. FIB (focused ion beam) passive voltage contrast imaging lights up good contacts, while failing contacts (red circles) remain dark. Marginal contacts (yellow circles) appear darker than good contacts.
A site-specific TEM specimen prepared by FIB through the center of a failing contact reveals a contaminant layer of residual photoresist at the bottom of the contact which prevents electrical connection of the contact to the silicide.