TWI807057B

A film thickness measurement device according to one aspect of the present disclosure includes: a first computing unit configured to, for each location on a first wafer having a known thickness other than a reference location on the first wafer, calculate a relative reflectance of a reflection spectral signal of reflected light detected by a collection probe, with respect to a reference reflection spectral signal of reflected light detected by the collection probe at the reference location on the first wafer; a specifying unit configured to specify a relationship between the relative reflectance calculated by the first computing unit and distance data representing a distance between the location on the first wafer and the collection probe; a second computing unit configured to calculate relative reflectances each corresponding to distance data representing a distance between the collection probe and a corresponding location on a second wafer to be measured, based on the relationship specified by the specifyin