Patent ID: 8342907

Claim:
A method of polishing a film formed on a workpiece, said method comprising: moving a workpiece relative to a polishing table; rotating the polishing table and the workpiece respectively, wherein a sensor provided on the polishing table detects a rotation angle of the polishing table during said rotating; applying pulse lighting from a pulsed light source to a surface, being polished, of said workpiece at the timing based on a trigger signal, wherein said applying pulse lighting starts after elapse of a predetermined time from the time when said rotation angle of the polishing table becomes a predetermined angle; receiving reflected light from said surface of said workpiece; dividing the reflected light into light rays having respective wavelengths and generating spectral data from the divided light rays having the respective wavelengths; and monitoring the progress of polishing of said surface of said workpiece using a characteristic value calculated from said spectral data.