FILM THICKNESS MEASURING APPARATUS USING INTERFERENCE AND METHOD OF MEASURING FILM THICKNESS USING INTERFERENCE

摘要

Disclosed is a film thickness measuring apparatus in which a substrate (103) having a transparent film (16) on the surface is placed on a table (100), light emitted from a light source (101) is divided by a half mirror (102) and irradiated onto the surface of the substrate and a reference surface while interfering light is formed by the mixing of reflected light from the surface of the substrate and the reference surface, the interfering light is imaged with an image pickup apparatus (105), and the film thickness of the transparent film is calculated by a processing unit (106) on the basis of the imaging results. The processing unit comprises a spectrum variation database (106s) generated by compiling in advance a database of the variation of a first phase spectrum between light incident onto and light reflected from the transparent film, a second phase spectrum calculating unit (106b) calculating a second phase spectrum of the transparent film by applying a Fourier transform to an interference signal of the transparent film imaged by the image pickup apparatus, and a film thickness calculating unit (106d) measuring the film thickness of the transparent film by selecting the first phase spectrum, which has the highest degree of coincidence with the second phase spectrum in the database, and using the selected first phase spectrum.