Processing end point detection method, polishing method, and polishing apparatus
A processing end point detection method detects a timing of a processing end point (e.g., polishing stop, changing of polishing conditions) by calculating a characteristic value of a surface of a workpiece (an object of polishing) such as a substrate. This method includes producing a spectral waveform indicating a relationship between reflection intensities and wavelengths at a processing end point, with use of a reference workpiece or simulation calculation, based on the spectral waveform, selecting wavelengths of a local maximum value and a local minimum value of the reflection intensities, calculating the characteristic value with respect to a surface, to be processed, from reflection intensities at the selected wavelengths, setting a distinctive point of time variation of the characteristic value at a processing end point of the workpiece as the processing end point, and detecting the processing end point of the workpiece by detecting the distinctive point during processing of the workpiece.
1. A processing end point detection method for detecting a processing end point based on a characteristic value with respect to a surface of a workpiece, the characteristic value being calculated using a spectral waveform of reflected light obtained by applying light to the surface of the workpiece, said method comprising:
producing a reference spectral waveform indicating a relationship between reflection intensities and wavelengths at a processing end point of a surface of a reference workpiece;
based on the reference spectral waveform, selecting wavelengths of a local maximum value and a local minimum value of the reflection intensities at the processing end point of the reference workpiece prior to processing a workpiece;
calculating a characteristic value with respect to the surface of the reference workpiece from the reflection intensities at the selected wavelengths;
setting a distinctive point of time variation of the characteristic value at the processing end point of the reference workpiece as a processing end point of a workpiece;
processing a surface of the workpiece that corresponds to the surface of the reference workpiece while monitoring a characteristic value of the surface of the workpiece; and
detecting the processing end point of the workpiece by detecting the distinctive point of time variation during the processing of the workpiece.
2. The processing end point detection method according to claim 1 , further comprising:
averaging the reflection intensities at each of the wavelengths over a processing time of the reference workpiece to determine an average reflection intensity at each of the wavelengths,
wherein said producing of the reference spectral waveform comprises producing the reference spectral waveform by dividing each of the reflection intensities, obtained at the processing end point of the reference workpiece, by a corresponding one of the average reflection intensities.
3. The processing end point detection method according to claim 1 , further comprising:
defining a weight function having a weight centered on the selected wavelength of the local maximum value,
wherein said calculating of the characteristic value comprises determining the characteristic value with respect to the surface of the reference workpiece by multiplying the reflection intensities, obtained by application of light to the surface of the reference workpiece, by the weight function and integrating the resultant reflection intensities.
4. The processing end point detection method according to claim 1 , further comprising shifting the selected wavelengths to shorter or longer wavelengths.
5. A processing end point detection method of detecting a processing end point based on a characteristic value with respect to a surface of a workpiece, the characteristic value being calculated using a spectral waveform of reflected light obtained by applying multiwavelength light to the surface of the workpiece, said method comprising:
averaging reflection intensities at each of a plurality of wavelengths over a processing time to determine an average reflection intensity at each of the wavelengths of a surface of a reference workpiece;
producing a reference spectral waveform by dividing each of reflection intensities, obtained by application of multiwavelength light to a surface of the workpiece that corresponds to the surface of the reference workpiece during processing of the surface of the workpiece, by a corresponding one of the average reflection intensities from the reference workpiece; and
detecting a processing end point of the workpiece by monitoring the reference spectral waveform during the processing of the surface of the workpiece that corresponds to the surface of the reference workpiece.
6. A processing apparatus comprising:
a light source configured to apply light to a surface of a workpiece;
a light-receiving unit configured to receive reflected light from the surface of the workpiece;
a spectroscope unit configured to divide the reflected light received by said light-receiving unit into a plurality of light rays and convert the light rays into electrical information; and
a processor configured to process the electrical information from said spectroscope unit,
wherein said processor is configured to
average reflection intensities at each of a plurality of wavelengths over a processing time of a surface of a reference workpiece to determine an average reflection intensity at each of the wavelengths,
produce a reference spectral waveform by dividing each of the reflection intensities, obtained at a processing end point of the reference workpiece, by a corresponding one of the average reflection intensities,
select wavelengths of a local maximum value and a local minimum value of the reference spectral waveform at the processing end point of the reference workpiece,
calculate a characteristic value with respect to the surface of the reference workpiece from the reflection intensities at the selected wavelengths,
set a distinctive point of time variation of the characteristic value at the processing end point of the reference workpiece as a processing end point of the workpiece, and
detect the processing end point of the workpiece by detecting the distinctive point of time variation during processing of a surface of the workpiece that corresponds to the surface of the reference workpiece.
7. The processing apparatus according to claim 6 , wherein said processor is configured to shift the selected wavelengths to shorter or longer wavelengths.
8. The processing apparatus according to claim 6 , wherein said processor is further configured to define a weight function having a weight centered on the selected wavelength of the local maximum value, and determine the characteristic value with respect to the surface of the reference workpiece by multiplying the reflection intensities, obtained by application of the light to the surface of the workpiece, by the weight function and integrating the resultant reflection intensities.
9. A processing apparatus comprising:
a light source configured to apply multiwavelength light to a surface of a workpiece;
a light-receiving unit configured to receive reflected light from the surface of the workpiece;
a spectroscope unit configured to divide the reflected light received by said light-receiving unit into a plurality of light rays and convert the light rays into electrical information; and
a processor configured to process the electrical information from said spectroscope unit,
wherein said processor is configured to
average reflection intensities at each of a plurality of wavelengths over a processing time of a surface of a reference workpiece to determine an average reflection intensity at each of the wavelengths,
produce a reference spectral waveform by dividing each of reflection intensities, obtained by application of the multiwavelength light to a surface of the workpiece that corresponds to the surface of the reference workpiece during processing of the surface of the workpiece, by a corresponding on of the average reflection intensities from the reference workpiece, and
detect a processing end point of the workpiece by monitoring the reference spectral waveform during the processing of the surface of the workpiece that corresponds to the surface of the reference workpiece.