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

Abstract

A polishing method includes: detecting, by an acoustic sensor, an environmental sound including 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 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.

What is claimed is: 
     
         1 . A polishing method comprising:
 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.   
     
     
         2 . The polishing method according to  claim 1 , further comprising:
 generating a differential spectrum map indicating over-time changes in the differential spectrum by arranging the differential spectrum along a time axis, wherein   the monitoring the polishing progress comprises monitoring the polishing progress based on a change in the sound pressure level in the differential spectrum map.   
     
     
         3 . The polishing method according to  claim 1 , wherein
 the monitoring the polishing progress comprises detecting a polishing endpoint of the substrate, and   the polishing method further comprises ending polishing of the substrate based on the polishing endpoint.   
     
     
         4 . The polishing method according to  claim 1 , wherein
 the environmental sound spectrum is generated by performing a Fourier transform on the environmental sound signal, and   the polishing sound spectrum is generated by performing a Fourier transform on the polishing sound signal.   
     
     
         5 . The polishing method according to  claim 1 , wherein
 the environmental sound is a sound detected after start of polishing of the substrate.   
     
     
         6 . The polishing method according to  claim 1 , wherein
 the environmental sound is a sound detected when a polishing apparatus performing polishing of the substrate is operated before polishing the substrate.   
     
     
         7 . The polishing method according to  claim 1 , wherein
 the generating the environmental sound spectrum comprises: generating a plurality of environmental sound spectra from the environmental sound signals outputted from the acoustic sensor in a predetermined period, calculating a representative value of a sound pressure level for each frequency from the plurality of environmental sound spectra, and generating the environmental sound spectrum indicating a relationship between the frequency and the representative value of the sound pressure level.   
     
     
         8 . The polishing method according to  claim 1 , further comprising:
 monitoring the polishing environment based on the environmental sound spectrum.   
     
     
         9 . 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. 
   
     
     
         10 . The polishing apparatus according to  claim 9 , wherein
 the processing system is configured to:
 arrange the differential spectrum along a time axis to generate a differential spectrum map indicating over-time changes in the differential spectrum, and 
 monitor the polishing progress based on a change in the sound pressure level in the differential spectrum map. 
   
     
     
         11 . The polishing apparatus according to  claim 9 , wherein the processing system is configured to:
 monitor the polishing progress to detect a polishing endpoint of the substrate, and   end polishing of the substrate based on the polishing endpoint.   
     
     
         12 . The polishing apparatus according to  claim 9 , wherein the processing system is configured to:
 generate the environmental sound spectrum by performing a Fourier transform on the environmental sound signal, and   generate the polishing sound spectrum by performing a Fourier transform on the polishing sound signal.   
     
     
         13 . The polishing apparatus according to  claim 9 , wherein the processing system is configured to issue a command to the acoustic sensor to detect the environmental sound after start of polishing of the substrate. 
     
     
         14 . The polishing apparatus according to  claim 9 , wherein the processing system is configured to issue a command to the acoustic sensor to detect the environmental sound when the polishing apparatus is operated before polishing the substrate. 
     
     
         15 . The polishing apparatus according to  claim 9 , wherein
 the processing system is configured to:   generate a plurality of environmental sound spectra from the environmental sound signals outputted from the acoustic sensor in a predetermined period,   calculate a representative value of a sound pressure level for each frequency from the plurality of environmental sound spectra, and   generate the environmental sound spectrum indicating a relationship between the frequency and the representative value of the sound pressure level.   
     
     
         16 . The polishing apparatus according to  claim 9 , wherein the processing system is configured to monitor the polishing environment based on the environmental sound spectrum. 
     
     
         17 . 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.   
     
     
         18 . The non-transitory computer-readable recording medium according to  claim 17 , wherein the program is configured to cause the computer to further execute: generating a differential spectrum map indicating over-time changes in the differential spectrum by arranging the differential spectrum along a time axis, and
 the monitoring the polishing progress comprises monitoring the polishing progress based on a change in the sound pressure level in the differential spectrum map.