Extraneous substance inspection apparatus for patterned wafer

摘要

An extraneous substance inspection apparatus includes a level conversion circuit for converting a level of an extraneous substance detection signal obtained from a position in a first chip into one of multi-valued levels. A judging circuit determines the existence or absence of an extraneous substance by comparing a signal indicative of one of the multi-valued levels with another signal indicative of a converted level obtained by converting a detection signal detected at a similar position in another chip adjacent to the first chip.