Polishing method, polishing apparatus, and non-transitory computer-readable recording medium

A polishing apparatus comprising:

• a polishing table supporting a polishing pad;
• a polishing head for pressing a substrate against a polishing surface of the polishing pad;
• an acoustic sensor attached to the polishing table or the polishing head and detecting a sound to output a signal representing the sound;
• and
• a processing system generating a frequency spectrum from the signal outputted from the acoustic sensor, wherein
• the acoustic sensor is configured to:
• detect an environmental sound comprising a sound arising from a polishing environment of the substrate to output an environmental sound signal representing the environmental sound, and
• detect a polishing sound of the substrate to output a polishing sound signal representing the polishing sound, and
• the processing system is configured to:
• generate an environmental sound spectrum indicating a relationship between a frequency and a sound pressure level from the environmental sound signal,
• generate a polishing sound spectrum indicating a relationship between a frequency and a sound pressure level from the polishing sound signal,
• calculate a difference between the polishing sound spectrum and the environmental sound spectrum to generate a differential spectrum, and
• monitor a polishing progress based on the differential spectrum.

A non-transitory computer-readable recording medium recording a program causing a computer to execute:

• detecting, by an acoustic sensor, an environmental sound comprising a sound arising from a polishing environment of a substrate to output an environmental sound signal representing the environmental sound from the acoustic sensor;
• generating an environmental sound spectrum indicating a relationship between a frequency and a sound pressure level from the environmental sound signal;
• detecting, by the acoustic sensor, a polishing sound of the substrate while pressing the substrate against a polishing surface of a polishing pad to polish the substrate, to output a polishing sound signal representing the polishing sound from the acoustic sensor;
• generating a polishing sound spectrum indicating a relationship between a frequency and a sound pressure level from the polishing sound signal;
• calculating a difference between the polishing sound spectrum and the environmental sound spectrum to generate a differential spectrum;
• and
• monitoring a polishing progress of the substrate based on the differential spectrum.