METHOD OF DETECTING ETCHING DEPTH ON REAL TIME BASIS

PROBLEM TO BE SOLVED: To provide a method of detecting an etching depth on a real time basis which can accurately calculate the etching depth of a substrate even when the substrate is transparent. SOLUTION: The method of detecting an etching depth on a real time basis includes steps of irradiating a substrate 2 and a mask 3 provided on the surface of the substrate 2 as a member to be etched with a laser beam; detecting the intensity of an interference wave on the basis of reflected light 6c, 6d on the surface 2a of the substrate 2, and on a surface 3a of the mask 3; calculating a difference in optical path length of the reflected light 6c, 6d in the surface 2a of the substrate 2 and the surface 3a of the mask 3, on the basis of the detected intensity of the interference wave; and calculating an etching depth of the substrate 2. An inner bottom surface 2b of the used substrate 2 is already subjected to surface roughening treatment. COPYRIGHT: (C)2008,JPO&INPIT