Method of and apparatus for measuring film thickness

摘要

A film thickness measuring apparatus measures the thickness of a thin film which is formed on a substrate with an excellent reproducibility regardless of inclination of a surface of a sample. Since an illumination system (20) includes a glass rod (GL) which corrects wavelength dependencies of luminance distributions of light sources (HL, DL), even when an eclipse in reflected light due to inclination of a sample (SP) decreases the energy of the reflected light, a spectral distribution of the reflected light entering a spectroscopic unit (40) is maintained with almost no change. A control unit (50) performs data conversion of multiplying an actual spectral reflectance by a ratio of an average of the actual spectral reflectance which is determined based on an output from the spectroscopic unit (40) to an average of a calibrated spectral reflectance and thereafter calculates a deviation between the two spectral reflectances. As a result, the film thickness is accurately measured while preventing an influence of inclination of the sample (SP). <IMAGE>