Method and apparatus for in-situ monitoring of thickness using a multi-wavelength spectrometer during chemical-mechanical polishing
First Claim
1. In a chemical mechanical polishing device of the type comprising:
- a polishing element, means for moving the polishing element along a polishing path, and a substrate carrier positioned adjacent the polishing element to press a substrate against the polishing element during a polishing operation;
the improvement comprising;
said polishing element having at least one opening formed therein, said opening positioned to move into intermittent alignment with the substrate during the polishing operation;
said polishing element further comprising a monitoring window secured to the polishing element to close the opening and to create a monitoring channel in the polishing element; and
said device further comprising a film thickness monitor, said film thickness monitor comprising a multi-wavelength spectrometer responsive to at least two wavelengths of optical radiation reflected from the substrate through the monitoring channel during the polishing operation to provide an indication of thickness of a film carried by the substrate.
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Abstract
A method and apparatus for in-situ monitoring of thickness using a multi-wavelength spectrometer during chemical mechanical polishing (CMP) of a substrate using a polishing tool and a film thickness monitor. The tool has an opening placed in it. The opening contains a monitoring window secured in it to create a monitoring channel. A film thickness monitor views the substrate through the monitoring channel to provide an indication of the thickness of a film carried by the substrate. This information can be used to determine the end point of the CMP process, determine removal rate at any given circumference of a substrate, determine average removal rate across a substrate surface, determine removal rate variation across a substrate surface, and optimize removal rate and uniformity. The film thickness monitor comprises a spectrometer.
190 Citations
21 Claims
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1. In a chemical mechanical polishing device of the type comprising:
- a polishing element, means for moving the polishing element along a polishing path, and a substrate carrier positioned adjacent the polishing element to press a substrate against the polishing element during a polishing operation;
the improvement comprising;said polishing element having at least one opening formed therein, said opening positioned to move into intermittent alignment with the substrate during the polishing operation; said polishing element further comprising a monitoring window secured to the polishing element to close the opening and to create a monitoring channel in the polishing element; and said device further comprising a film thickness monitor, said film thickness monitor comprising a multi-wavelength spectrometer responsive to at least two wavelengths of optical radiation reflected from the substrate through the monitoring channel during the polishing operation to provide an indication of thickness of a film carried by the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- a polishing element, means for moving the polishing element along a polishing path, and a substrate carrier positioned adjacent the polishing element to press a substrate against the polishing element during a polishing operation;
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14. A method for determining thickness of a layer on a substrate during chemical-mechanical polishing, the method comprising the steps of:
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(a) performing chemical-mechanical polishing on a substrate (b) illuminating the substrate with at least two wavelengths of optical radiation during step (a); (c) using a multi-wavelength spectrometer to receive said at least two wavelengths of optical radiation after being reflected from the substrate; and (d) determining the thickness of a film carried by the substrate from said at least two wavelengths of optical radiation received in step (c).
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15. A method for determining an end point of a chemical-mechanical polishing process, the method comprising the steps of:
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(a) illuminating a substrate with at least two wavelengths of optical radiation during chemical-mechanical polishing of the substrate; (b) using a multi-wavelength spectrometer to receive said at least two wavelengths of optical radiation after being reflected from the substrate; (c) determining a thickness of a film carried by the substrate from said at least two wavelengths of optical radiation received in step (b); and (d) indicating that end point has been reached in response to the film thickness determined in step (c) reaching a predefined thickness. - View Dependent Claims (16)
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17. A method for determining removal rate per polishing element revolution at any given circumference of a substrate while performing a chemical-mechanical polishing process, the method comprising the steps of:
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(a) measuring a first film thickness of a substrate during a chemical-mechanical polishing process when a monitoring channel in a polishing element aligns with a film thickness monitor comprising a spectrometer; and
then(b) measuring a second film thickness of a substrate during a chemical-mechanical polishing process when the monitoring channel in a polishing element realigns with the film thickness monitor comprising a spectrometer; and
then(c) calculating a difference between the second film thickness and the first film thickness.
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18. A method for determining average removal rate per polishing element revolution across a substrate surface while performing a chemical-mechanical polishing process, the method comprising the steps of:
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(a) measuring a first film thickness of a substrate during a chemical-mechanical polishing process when a first monitoring channel in a polishing element aligns with a first film thickness monitor comprising a spectrometer; and
then(b) measuring a second film thickness of a substrate during a chemical-mechanical polishing process when the first monitoring channel in a polishing element realigns with the first film thickness monitor comprising a spectrometer; and
then(c) measuring a third film thickness of a substrate during a chemical-mechanical polishing process when a second monitoring channel in a polishing element aligns with a second film thickness monitor comprising a spectrometer; and
then(d) measuring a fourth film thickness of a substrate during a chemical-mechanical polishing process when the second monitoring channel in a polishing element realigns with the second film thickness monitor comprising a spectrometer; and
then(e) calculating a difference between the second film thickness of step (b) and the first film thickness of step (a); and (f) calculating a difference between the fourth film thickness of step (d) and the third film thickness of step (c); and
then(g) calculating an average of the differences of steps (e) and (f).
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19. A method for determining removal rate variation per polishing element revolution across a substrate surface while performing a chemical-mechanical polishing process, the method comprising the steps of:
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(a) measuring a first film thickness of a substrate during a chemical-mechanical polishing process when a first monitoring channel in a polishing element aligns with a first film thickness monitor comprising a spectrometer; and
then(b) measuring a second film thickness of a substrate during a chemical-mechanical polishing process when the first monitoring channel in a polishing element realigns with the first film thickness monitor comprising a spectrometer; and
then(c) measuring a third film thickness of a substrate during a chemical-mechanical polishing process when a second monitoring channel in a polishing element aligns with a second film thickness monitor comprising a spectrometer; and
then(d) measuring a fourth film thickness of a substrate during a chemical-mechanical polishing process when the second monitoring channel in a polishing element realigns with the second film thickness monitor comprising a spectrometer; and
then(e) calculating a difference between the second film thickness of step (b) and the first film thickness of step (a); and (f) calculating a difference between the fourth film thickness of step (d) and the third film thickness of step (c); and
then(g) calculating a variation of the differences of steps (e) and (f).
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20. A method of optimizing a chemical-mechanical polishing process comprising the steps of:
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(a) illuminating a substrate with at least two wavelengths of optical radiation; (b) using a multi-wavelength spectrometer to receive said at least two wavelengths of optical radiation after being reflected from the substrate, (c) determining a removal rate of a film carried by the substrate from said at least two wavelengths of optical radiation received in step (b); and
then(d) adjusting polishing process parameters to optimize the removal rate. - View Dependent Claims (21)
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Specification