FOREIGN SUBSTANCE INSPECTION APPARATUS

摘要

PURPOSE:To enable detection of a foreign substance which scatters light so feebly that it cannot be discriminated from a pattern, by extracting a pattern edge portion from a transmitted light detection signal of a sample and discriminating light scattered by a foreign substance from said signal. CONSTITUTION:A pattern edge extracting circuit 23 processes a transmitted light detection signal and extracts a pattern edge on a photomask from said signal. A foreign substance dlscriminating circuit 24 removes a scattered light detection signal from the pattern edge from a detection signal supplied from a scattered light detection section 16 and determines whether any foreign substance is detected or not based on the data of said pattern edge. In this manner, minute foreign substances can be detected indenpendently from scattered light from the pattern edge. A flat-type foreign detection circuit 30 differentiates a detection signal given by illumination of transmitted light to emphasize the edge portions of a foreign substance if any and determines whether a foreign substance is detected or not.