FILM THICKNESS MEASURING METHOD AND FILM THICKNESS MEASURING INSTRUMENT FOR MULTILAYER FILM

PROBLEM TO BE SOLVED: To provide an accurate film thickness measuring method of non-contact type for a thin film spread on another thin film and a film thickness measuring instrument. SOLUTION: This film thickness measuring method for a multilayer film is used for measuring the film thickness of a measuring film having a film thickness as to a multilayer film structure wherein a multilayer film comprising at least two layers including the measuring film of the film thickness are provided on a substrate, at least one layer film is provided under the measuring film, and the film thickness of the film lying under the measuring film is sufficiently thinner than the film thickness of the measuring film. The spectral reflectance of reflected light by the thin films are measured, and a finite number of spectral reflectance data are sampled and Fourier-transformed. When finding the film thickness of the measuring film from a spectrum found by transformation with the film thickness and the refraction factor of the films under the measuring film and the refraction factor of the measuring film assumed to be known, the weight of the layer films under the measuring film is added to the optical film thickness corresponding to the position of a peak of the found spectrum, and the film thickness of the measuring film is calculated with the above peak assumed to be a plurality of superposed peaks. COPYRIGHT: (C)2005,JPO&NCIPI