ENDPOINT METHOD USING PEAK LOCATION OF SPECTRA CONTOUR PLOTS VERSUS TIME

• US 20110104987A1
• Filed: 11/02/2010
• Published: 05/05/2011
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Benvegnu, Dominic J., David, Jeffrey Drue, Lee, Harry Q., Swedek, Boguslaw A.
• Granted Patent: US 8,977,379 B2
• Time in Patent Office: Days
• US Class Current: 451/5
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24B 37/205 provided with a window for inspecting the surface of the work being lapped
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: G05B 19/418 Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM]
• CPC Class Codes: G05B 2219/45232 CMP chemical mechanical polishing of wafer

Abstract

In one aspect, a method of polishing includes polishing a substrate, and receiving an identification of a selected spectral feature and a characteristic of the selected spectral feature to monitor during polishing. The method includes measuring a sequence of spectra of light reflected from the substrate while the substrate is being polished, where at least some of the spectra of the sequence differ due to material being removed during the polishing. The method of polishing includes determining a value of a characteristic of the selected spectral feature for each of the spectra in the sequence of spectra to generate a sequence of values for the characteristic, fitting a function to the sequence of values, and determining either a polishing endpoint or an adjustment for a polishing rate based on the function.

Claims

1. A computer program product, tangibly embodied on a computer readable medium, comprising instructions to:

receive an identification of a selected spectral feature and a characteristic of the selected spectral feature to monitor during polishing;

measure a sequence of spectra of light reflected from a substrate while the substrate is being polished, at least some of the spectra of the sequence differing due to material being removed during the polishing;

determine a value of a characteristic of the selected spectral feature for each of the spectra in the sequence of spectra to generate a sequence of values for the characteristic;

fit a function to the sequence of values; and

determine at least one of a polishing endpoint or an adjustment for a polishing rate based on the function.

2. The computer program product of claim 1, wherein the selected spectral feature comprises a spectral peak, a spectral valley, or a spectral zero-crossing.

3. The computer program product of claim 2, wherein the characteristic comprises a wavelength, a width, or an intensity.

4. The computer program product of claim 3, wherein the selected spectral feature comprises a spectral peak and the characteristic comprises a peak width.

5. The computer program product of claim 1, wherein determining a polishing endpoint includes calculating an initial value of the characteristic from the function, calculating a current value of the characteristic from the function, and calculating a difference between the initial value and the current value, and ceasing polishing when the difference reaches a target difference.

6. The computer program product of claim 1, wherein the sequence of spectra of light is from a first portion of the substrate, and further comprising instructions to measure a second sequence of spectra of light reflected from a second portion of the substrate while the substrate is being polished, determine a value of the characteristic of the selected spectral feature for each of the spectra in the second sequence of spectra to generate a second sequence of values for the characteristic, and fit a second function to the sequence of values.

7. The computer program product of claim 6, wherein determining an adjustment for a polishing rate includes calculating a first estimated polishing endpoint time for a first portion of the substrate using a slope of the first function, calculating a second estimated polishing endpoint time for a second portion of the substrate using a slope of the second function, and adjusting a polishing rate of the first or second portion such that the first and second portions complete polishing closer to the same time.

8. The computer program product of claim 1, wherein the function is a linear function of time.

9. The computer program product of claim 1, wherein receiving an identification includes receiving user input.

10. The computer program product of claim 1, further comprising instructions to apply a high-pass filter to the spectra.

11. The computer program product of claim 1, wherein determining a polishing endpoint includes calculating an initial value of the characteristic from the function, calculating a current value of the characteristic from the function, calculating a first difference between the initial value and the current value, calculating a second difference between the initial value and a target value, generating a weighted combination of the first difference and the second difference, and ceasing polishing when the weighted combination reaches a target value.

12. A method of polishing, comprising:

polishing a substrate;

receiving an identification of a selected spectral feature and a characteristic of the selected spectral feature to monitor during polishing;

measuring a sequence of spectra of light reflected from the substrate while the substrate is being polished, at least some of the spectra of the sequence differing due to material being removed during the polishing;

determining a value of a characteristic of the selected spectral feature for each of the spectra in the sequence of spectra to generate a sequence of values for the characteristic;

fitting a function to the sequence of values; and

determining at least one of a polishing endpoint or an adjustment for a polishing rate based on the function.

13. The method of claim 12, wherein the selected spectral feature comprises a spectral peak, a spectral valley, or a spectral zero-crossing.

14. The method of claim 13, wherein the characteristic comprises a wavelength, a width, or an intensity.

15. The method of claim 14, wherein the selected spectral feature comprises a spectral peak and the characteristic comprises a peak width.

16. The method of claim 12, wherein determining a polishing endpoint includes calculating an initial value of the characteristic from the function, calculating a current value of the characteristic from the function, and calculating a difference between the initial value and the current value, and ceasing polishing when the difference reaches a target difference.

17. The method of claim 12, wherein the sequence of spectra of light is from a first portion of the substrate, and further comprising measuring a second sequence of spectra of light reflected from a second portion of the substrate while the substrate is being polished, determining a value of the characteristic of the selected spectral feature for each of the spectra in the second sequence of spectra to generate a second sequence of values for the characteristic, and fitting a second function to the sequence of values.

18. The method of claim 17, wherein determining an adjustment for a polishing rate includes calculating a first estimated polishing endpoint time for a first portion of the substrate using a slope of the first function, calculating a second estimated polishing endpoint time for a second portion of the substrate using a slope of the second function, and adjusting a polishing rate of the first or second portion such that the first and second portions complete polishing closer to the same time.

19. The method of claim 12, wherein the function is a linear function of time.

20. The method of claim 12, wherein receiving an identification includes receiving user input.

21. The method of claim 12, further comprising applying a high-pass filter to the spectra.

22. The method of claim 12, wherein determining a polishing endpoint includes calculating an initial value of the characteristic from the function, calculating a current value of the characteristic from the function, calculating a first difference between the initial value and the current value, calculating a second difference between the initial value and a target value, generating a weighted combination of the first difference and the second difference, and ceasing polishing when the weighted combination reaches a target value.

23. A method to assist in identifying a spectral feature and a characteristic of the selected spectral feature to monitor during polishing, comprising:

polishing a test substrate;

measuring a sequence of spectra of light reflected from a substrate while the substrate is being polished, at least some of the spectra of the sequence differing due to material being removed during the polishing;

visually displaying the sequence of spectra as a contour plot.

24. The method of claim 23, wherein the contour plot comprises color coding of intensity values.

25. The method of claim 23, wherein the contour plot comprises a 3-D plot of intensity values.