Techniques for matching spectra

• US 9,482,610 B2
• Filed: 11/12/2012
• Issued: 11/01/2016
• Est. Priority Date: 11/12/2012
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Shrestha, Kiran Lall, Swedek, Boguslaw A., David, Jeffrey Drue, Lee, Harry Q.
• Primary Examiner(s): Lee, Paul D
• Application Number:
  US13/674,667
• Publication Number:
  US 20140134758A1
• Time in Patent Office: 1,450 Days
• Field of Search: 702/189
• US Class Current: 1/1
• CPC Class Codes: B24B 37/005 Control means for lapping machines or devices
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps

Abstract

A method of controlling processing of a substrate includes measuring a spectrum reflected from the substrate, for each partition of a plurality of partitions of the measured spectrum, computing a partition value based on the measured spectrum within the partition to generate a plurality of partition values, for each reference spectrum signature of a plurality of reference spectrum signatures, determining a membership function for each partition, for each partition, computing a membership value based on the membership function for the partition and the partition value for the partition to generate a plurality of groups of membership values with each group of the plurality of groups associated with a reference spectrum signature, selecting a best matching reference spectrum signature from the plurality of reference spectra signatures based on the plurality of groups of membership values, and determining a characterizing value associated with the best matching reference spectrum signature.

Claims

1. A method of controlling processing of a substrate, comprising:

processing a substrate;

measuring a spectrum reflected from the substrate with a spectrographic monitoring system to generate a measured spectrum;

partitioning the measured spectrum into a plurality of partitions, each partition spanning a different range of wavelengths of the measured spectrum;

for each partition of the plurality of partitions of the measured spectrum, computing a partition value based on the measured spectrum within the partition to generate a plurality of partition values;

for each reference spectrum signature of a plurality of reference spectrum signatures, determining a membership function for each partition of the plurality of partitions of the measured spectrum based on the reference spectrum signature;

for each partition of the plurality of partitions of the measured spectrum, computing a membership value based on the membership function for the partition and the partition value for the partition to generate a plurality of groups of membership values with each group of the plurality of groups associated with a reference spectrum signature;

selecting a best matching reference spectrum signature from the plurality of reference spectra signatures based on the plurality of groups of membership values;

determining a characterizing value associated with the best matching reference spectrum signature; and

adjusting processing of the substrate or a subsequent substrate based on the characterizing value.

2. The method of claim 1, wherein processing the substrate comprises polishing the substrate.

3. The method of claim 2, wherein measuring the spectrum comprises monitoring the substrate with an in-situ spectrographic monitoring system.

4. The method of claim 3, comprising generating a sequence of measured spectra, determining the characterizing value for each measured spectrum of the sequence of measured spectra to generate a sequence of characterizing values, and computing a polishing endpoint or an adjustment to a polishing parameter based on the sequence of characterizing values.

5. A computer program product, tangibly embodied in a non-transitory computer readable medium, comprising instructions for causing a processor to:

receive a measured spectrum of a substrate being processed from a spectrographic monitoring system;

partition the measured spectrum into a plurality of partitions, each partition spanning a different range of wavelengths of the measured spectrum;

for each partition of the plurality of partitions of the measured spectrum, compute a partition value based on the measured spectrum within the partition to generate a plurality of partition values;

for each reference spectrum signature of a plurality of reference spectrum signatures, determine a membership function for each partition of the plurality of partitions of the measured spectrum based on the reference spectrum signature

for each partition of the plurality of partitions of the measured spectrum, compute a membership value based on the membership function for the partition and the partition value for the partition to generate a plurality of groups of membership values with each group of the plurality of groups associated with a reference spectrum signature;

select a best matching reference spectrum signature from the plurality of reference spectra signatures based on the plurality of groups of membership values;

determine a characterizing value associated with the best matching reference spectrum signature; and

adjust processing of the substrate or a subsequent substrate based on the characterizing value.

6. The computer program product of claim 5, wherein each reference spectrum signature of the plurality of reference spectrum signatures includes a code value for each partition of the plurality of partitions of the reference spectrum, the code value associating the partition of the reference spectrum with a membership function.

7. The computer program product of claim 6, wherein the instructions to determine the membership function comprise instructions to use the membership function associated with the partition of the reference spectrum that corresponds to the partition of the measured spectrum.

8. The computer program product of claim 5, wherein the instructions to compute the partition value comprise instructions to compute an average value of the measured spectrum within the partition.

9. The computer program product of claim 5, wherein the instructions to select the best matching reference spectrum signature comprise instructions to, for each group, compute a total value of the membership values in the group to provide a plurality of total values, and select a reference spectrum signature associated with a group having the largest total value of the plurality of total values.

10. The computer program product of claim 5, wherein the instructions to select the best matching reference spectrum signature comprise instructions to, for each group, determining a second-lowest value of the group of values to provide a plurality of second-lowest values, and select a reference spectrum signature associated with a group having the largest second-lowest value of the plurality of second-lowest values.

11. The computer program product of claim 5, wherein each reference spectrum signature comprises a plurality of code values, each code value of the plurality of code values is associated with one of the plurality of partitions.

12. The computer program product of claim 11, wherein the instructions to determine the membership function for each partition comprise instructions to determine the code value in the reference spectrum signature associated with the partition, and determine the membership function associated with the code value.

13. The computer program product of claim 5, wherein the plurality of membership functions include a first triangular function having a first maximum value at a midpoint of a first intensity range and a second function having a second maximum value at a midpoint of a second intensity range, and wherein the first triangular function and the second triangular function having an equal value at a boundary between the first intensity range and the second intensity range.

14. The computer program product of claim 5, comprising instructions to compute the plurality of reference spectrum signatures based on a plurality of reference spectra.

15. The computer program product of claim 14, wherein the instructions to compute the plurality of reference spectrum signatures comprise instructions to compute an average reference spectrum, the average reference spectrum being an average of the plurality of reference spectra.

16. The computer program product of claim 15, comprising instructions to determine boundary wavelengths between the partitions based on the average reference spectrum.

17. The computer program product of claim 16, wherein the instructions to determine boundary wavelengths comprise instructions to compute wavelengths of a plurality of inflection points in the average reference spectrum, and compute boundary wavelengths that are a fraction of a distance between adjacent inflection points.

18. The computer program product of claim 15, comprising instructions to determine boundary intensities between a plurality of intensity zones based on the average reference spectrum.

19. The computer program product of claim 18, comprising instructions to compute a second partition value for each partition of the average reference spectrum, and determine boundary intensities includes selecting at least some of the second partition values.

20. The computer program product of claim 19, wherein the instructions to determine boundary intensities include instructions to calculate an average of the second partition values.

21. The computer program product of claim 18, comprising instructions to, for each partition of each reference spectrum, calculate a third partition value based on the reference spectrum within the partition, and select one of a plurality of unique code values based on comparing the third partition value to the intensity zones.