Polishing apparatus, polishing method, and polishing control apparatus

A polishing method comprising:

• detecting a polishing sound of an object to be polished;
• collecting the polishing sound;
• performing frequency analysis on a power spectra of the collected polishing sound with a given time resolution to acquire first data, the first data represented by a first table in which each power spectrum of the power spectra is correlated with a time point and a frequency;
• performing an arithmetic operation between a first part of the power spectra in the first data that is correlated with a first time point and a second part of the power spectra in the first data that is correlated with a second time point to acquire second data, the second data represented by a second table in which each of a plurality of arithmetic values is correlated with the time point and a mixed frequency;
• analyzing each of parts of the arithmetic values in the second data that is correlated with a corresponding mixed frequency to determine whether or not the part of the arithmetic values of the second data satisfies changes in value;
• synthesizing two of the parts of the arithmetic values of the second data with value changes when a correlation coefficient between the two of the parts of the arithmetic values of the second data with value changes falls under a threshold value to obtain synthesized values;
• and
• determining a polishing end point of the object based on a change in the synthesized values.

A polishing control apparatus comprising:

• a processor and a memory storing data, the processor configured to:
• collect a polishing sound of an object to be polished;
• perform frequency analysis on the power spectra of the polishing sound with a given time resolution to acquire first data, the first data represented by a first table in which each power spectrum of the power spectra is correlated with a time point and a frequency;
• perform an arithmetic operation between a first part of the power spectra in the first data that is correlated with a first time point and a second part of the power spectra in the first data that is correlated with a second time point to acquire second data, the second data represented by a second table in which each of a plurality of arithmetic values is correlated with the time point and a mixed frequency;
• analyze each of parts of the arithmetic values in the second data that is correlated with a corresponding mixed frequency to determine whether or not the part of the arithmetic values of the second data satisfies changes in value;
• synthesize two of the parts of the arithmetic values of the second data with value changes when a correlation coefficient between the two of the parts of the arithmetic values of the second data with value changes falls under a threshold value to obtain synthesized values;
• and
• determine a polishing end point of the object to be polished based on a change in the synthesized values.