| 摘要 |
PURPOSE:To enable to accurately detect the endpoint of an etching by a method wherein one beam of a plurality of laser beams are projected on the film to be etched and a mask film, another beam is projected on the mask film only, and the difference of both signals is observed, thereby enabling to measure the thickness of the film to be etched. CONSTITUTION:The laser beam 7, sent from a laser beam source 6 and passed through a beam splitter 8, is projected on the etching part located on the surface of a wafer 1, the interference between an incident beam and a reflected beam is generated on an SiO2 film 2 and a mask film 3 respectively, it is reflected in the state wherein the interference light is mixed and received by a detector 12. The laser beam 11 reflected by a beam splitter 8 and a half-mirror 10 is projected to the mask film 3 located on the circumferential part of the wafer 1, and the reflected beam and the interference light are received by a detector 13 through the half mirror 10. The difference between detectors 12 and 13 is calcurated by an arithmetic operational processing part 15, the signal of an SiO2 film 2 only is led out and the film thickness of the SiO2 is worked out. |
