Patent ID: 8226802

Claim:
A method for measuring a film thickness in which a thickness of a thin film formed on a surface of a film forming object from a starting time of growing of the thin film to a current time is calculated based on a measurement result at the current time and a measurement result at the starting time of the growing of the thin film by making particles of a thin film material emitted from a thin film material source attach onto the surface of the film forming object and a surface of a crystal oscillator to measure a resonance frequency of the crystal oscillator, the method for measuring a film thickness comprising the steps of: during the growing of the thin film, obtaining a frequency change value which is a difference between the measurement result at the current time and a measurement result at a past time immediately before the current time; and when an exfoliation of the thin film on the surface of the crystal oscillator occurs: calculating a thickness value of an exfoliated film based on the frequency change value; obtaining a corrected film thickness value by adding the thickness value of the exfoliated film to an increased film thickness value which is obtained based on a measurement result at a future time after the current time and the measurement result at the starting time of the growing of the thin film; and converting the corrected film thickness value to the thickness value of the thin film on the surface of the film forming object.