An improved voltage contrast test structure is disclosed. In general terms, the
test structure can be fabricated in a single photolithography step or with a single
reticle or mask. The test structure includes substructures which are designed to
have a particular voltage potential pattern during a voltage contrast inspection.
For example, when an electron beam is scanned across the test structure, an expected
pattern of intensities are produced and imaged as a result of the expected voltage
potentials of the test structure. However, when there is an unexpected pattern
of voltage potentials present during the voltage contrast inspection, this indicates
that a defect is present within the test structure. To produce different voltage
potentials, a first set of substructures are coupled to a relatively large conductive
structure, such as a large conductive pad, so that the first set of substructures
charges more slowly than a second set of substructures that are not coupled to
the relatively large conductive structure. Mechanisms for fabricating such a test
structure are also disclosed. Additionally, searching mechanisms for quickly locating
defects within such a test structure, as well as other types of voltage contrast
structures, during a voltage contrast inspection are also provided.