Polishing endpoint detecting method, device for detecting a polishing endpoint of a polishing process and chemical-mechanical polishing apparatus comprising the same

A chemical-mechanical polishing apparatus comprising:

• a light source that produces a beam of light;
• a rotational table rotatable about a central axis of rotation, the rotational table including a rotary plate including a first material that is transparent with respect to the light produced by the light source, and a polishing pad including a second material that is transparent with respect to the light produced by the light source, the polishing pad being attached to the rotary plate;
• a polishing head disposed above the polishing pad for holding a substrate such that a surface of the substrate faces the polishing pad and is pressed into contact with the polishing pad, and rotating the substrate while the surface of the substrate is in contact with the polishing pad;
• light path changing means for changing a path of the beam of light so that the beam of light scans the surface of the substrate along a horizontal line across the surface of the substrate held against the polishing pad by the polishing head through the rotary plate and the polishing pad;
• a light measuring instrument operative to produce signals representative of a characteristic of a light reflected from the surface of the substrate;
• and
• a processor connected to the light measuring instrument so as to receive the signals produced by the light measuring instrument and configured to analyze the signals to detect a polishing endpoint of the polishing process.