APPARATUS FOR DETECTING END POINT OF SURFACE TREATMENT

摘要

PURPOSE:To provide an apparatus for detecting the end point of the surface treatment which can accurately detect a end point of the surface treatment of a substrate of a liquid crystal display or the like without detecting optical noise components generated at the time of the surface treatment. CONSTITUTION:A light projecting mechanism 31 takes out, by means of a filter 42a and a filter selecting mechanism 42b, the light of the wavelength enabling the detection of a reflecting light of a substrate G of a liquid crystal display with good sensitivity. The light is turned to a parallel beam by a collimator lens 45 which is then projected at right angles to the sample surface of the substrate G. The light cast to the sample surface is reflected from each surface of the substrate G to be a reflecting light. The reflecting light is condensed by an image forming lens 48 and received by a photodetecting surface Q of a photodetecting device 49. The radius D of the image forming lens 48 and the radius H of the photodetecting surface Q are set large enough to detect also a reflecting light when the sample surface of the substrate G is inclined theta. Moreover, a curtain forming mechanism 33 forms a curtain of an etching solution in the periphery of the projecting area during the measurement, thereby to prevent the pulsation of the etching solution and the entry of air bubbles.