Aspects of the present disclosure describe an inspection apparatus which performs inspection on a smaller field of a wafer with structures for current collection. The defective via holes may be located based on the collected current. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.