MEASUREMENT METHOD AND MEASUREMENT DEVICE FOR THICKNESS

摘要

PROBLEM TO BE SOLVED: To provide a measurement method and device capable of highly quickly measuring the thickness of an inspected object in a non-destructive manner.SOLUTION: Light from a light source 10 is divided into reference light and inspected light, and the thickness of an inspected object 80 is measured by interference measurement causing interference between the inspected light transmitted through the inspected object and the reference light. A medium 70 having group refractive index equal to the group refractive index of the inspected object 80 with specific wavelength is arranged on the optical path of the inspected light and the reference light, and interference light causing interference between the inspected light transmitted through the inspected object 80 and the medium 70 and the reference light transmitted through the medium 70 is measured, and the specific wavelength is determined on the basis of the wavelength dependency of a phase difference between the inspected light and the reference light, and the group refractive index of the medium 70 corresponding to the specific wavelength is set to the group refractive index of the inspected object 80. The optical path length of the inspected object 80 corresponding to the specific wavelength is measured, and the thickness of the inspected object 80 is calculated by using the group refractive index corresponding to the specific wavelength and the optical path length corresponding to the specific wavelength.