A method for process monitoring includes receiving a sample having a first
layer that is at least partly conductive and a second layer formed over
the first layer, following production of contact openings in the second
layer. A beam of charged particles is directed along a beam axis that
deviates substantially in angle from a normal to a surface of the sample,
so as to irradiate one or more of the contact openings in each of a
plurality of locations distributed over at least a region of the sample.
A specimen current flowing through the first layer is measured in
response to irradiation of the one or more of the contact openings at
each of the plurality of locations. A map of at least the region of the
sample is created, indicating the specimen current measured in response
to the irradiation at the plurality of the locations.