DEVICE AND METHOD FOR MEASURING FILM THICKNESS, MAKING USE OF IMPROVED FAST FOURIER TRANSFORMATION

摘要

PURPOSE: A device and a method for measuring film thickness, making use of improved fast Fourier transformation are provided to secure fast analysis speed and high precision. CONSTITUTION: A device for measuring film thickness, making use of improved fast Fourier transformation comprises a light-receiving part(10) including a light source(12), an optical fiber(20), and a lens(26); a detection part(40) including a spectrograph(42) and a light-measuring element array(44); a transformation part(46) transforming spectrum data by wavelengths detected through the detection part into an analog signal and transforming the analog signal into a digital signal; a calculation part(52) finding frequency through fast Fourier transformation reflecting refractive index dispersion by the data transformed through the transformation part; and an analysis part(54) measuring and analyzing film thickness by the frequency found through the calculation part and displaying the film thickness. In the light-receiving part, the optical fiber focuses the light emitted from the light source and the applies the light to one side, and accepts the light reflected from the surface of a sample of a substrate with a thin film and then makes the light exit to the other side. The lens adjusts the magnification of the light emitted from the optical fiber and the light reflected from the surface of the sample. The spectrograph divides the reflected light exiting to the other side according to the optical intensity of each wavelength. The light-measuring element array offers the intensity of radiation of each wavelength.