Patent ID: 9266214
Filing Date: 2016-02-23
CPC Classification: B24B,H01L

Claim Text:
1. A method of polishing a substrate having a film, the method comprising: polishing the substrate by pressing the substrate against a polishing tool on a rotating polishing table; irradiating the substrate with light when polishing the substrate; receiving the light reflected from the substrate; measuring intensity of the reflected light at respective wavelengths; calculating relative reflectance by dividing the measured intensity of the light by predetermined reference intensity; producing spectral waveform representing relationship between the relative reflectance and wavelength of the light; performing a Fourier transform process on the spectral waveform to determine a thickness of the film and a corresponding strength of frequency component; determining that the determined thickness of the film is a reliable measured value if the strength of frequency component is higher than a predetermined threshold value; determining that the determined thickness of the film is an unreliable measured value if the strength of frequency component is equal to or lower than the predetermined threshold value; determining a polishing end point of the substrate based on a point of time when the reliable measured value has reached a predetermined target value; calculating a defective data rate representing a proportion of the number of unreliable measured values to the total number of reliable measured values and unreliable measured values that have been obtained previously; and changing the predetermined threshold value based on the defective data rate.