Substrate polishing apparatus and film thickness calculating method

A substrate polishing apparatus comprising:

• a polishing table which is provided with an eddy current sensor and constructed to be able to rotate,
• a polishing head which is arranged to face the polishing table, constructed to be able to rotate, and constructed to allow a substrate to be attached to a surface facing the polishing table, and
• a controller;
• wherein
• the controller is constructed to
• obtain multiple pieces of waveform data representing output signals of the eddy current sensor when the eddy current sensor has passed multiple paths on the substrate, wherein each piece of waveform data corresponds to a single path,
• make a judgment as to whether a metal structure exists on a path on the substrate, based of comparison between degrees of similarity of the multiple pieces of waveform data,
• correct a piece of waveform data corresponding to the path on that the metal structure exists, to lower a signal value of the position that has been judged as a position where the metal structure exists, and
• calculate thickness of a film on a surface of the substrate, based on the corrected piece of waveform data and the pieces of waveform data other than the corrected piece of waveform data.

A film thickness calculating method in a substrate polishing apparatus, wherein

• the substrate polishing apparatus comprises
• a polishing table which is provided with an eddy current sensor and constructed to be able to rotate, and
• a polishing head which is arranged to face the polishing table, constructed to be able to rotate, and constructed to allow a substrate to be attached to a surface facing the polishing table;
• and
• the method comprises steps for:
• obtaining pieces of waveform data of output signals of the eddy current sensor when the eddy current sensor has passed multiple paths on the substrate,
• identifying, in the multiple paths on the substrate, mutually corresponding multiple points that are in positions at same distances from the center of the substrate,
• comparing values of the output signals of the eddy current sensor obtained at the identified multiple points to thereby find a minimum value,
• correcting the pieces of waveform data based on the found minimum values, and
• calculating thickness of a film on a surface of the substrate, based on the corrected pieces of waveform data.