| 摘要 |
PURPOSE: To provide a film-thickness measuring method which uses spectrometry and can be used for a double film, constituted of a plurality of layers having different refractive indexes. CONSTITUTION: On the basis of a special feature of waveform of interference spectrum, a measurement spectrum waveform can be expressed approximately, by using a linear combination of a plurality of base spectra. By using base spectra, wherein the period is fixed previously as a variable, approximate spectrum wherein square spread to measurement spectrum becomes a minimum is found for each period, and the relation between the minimum square spread and periods is obtained as a graph. Correspondence between the respective layers of the double film and extremum dots of a minimum square spread which appear plurally in the case of a double film is obtained. The film thickness is calculated from the period, which gives extremum dots to each layer and the refractive index of the layer.
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