# US 8,569,174 B2 · Using spectra to determine polishing endpoints

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- Number: US 8,569,174 B2
- Document ID: US8569174B2
- Status: Granted
- Kind: B2
- Application number: 12/036,174
- Filed: 2008-02-22
- Published: 2008-08-28
- Granted: 2013-10-29
- Earliest claimed: 2007-02-23
- Assignees: Applied Materials, Inc.
- Applicants: Harry Q. Lee; Boguslaw A. Swedek; Dominic J. Benvegnu; Jeffrey Drue David
- Inventors: Harry Q. Lee; Boguslaw A. Swedek; Dominic J. Benvegnu; Jeffrey Drue David
- Web page: https://patentgrep.com/patent/US8569174B2

## CPC

- H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects}
- B24B 37/013: Devices or means for detecting lapping completion
- B24B 49/12: involving optical means
- H10P 52/402: {of semiconductor materials}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS

## Abstract

Methods of determining a polishing endpoint are described using spectra obtained during a polishing sequence. In particular, techniques for using only desired spectra, faster searching methods and more robust rate determination methods are described.

## Claims

### Claim 1

A non-transitory computer readable storage medium comprising a computer program product that is operable to cause a data processing apparatus to perform operations comprising:
receiving a first spectrum measured from a substrate undergoing polishing during a first scan of an optical monitoring module across the substrate;
comparing the first spectrum to at least some of a plurality of reference spectra in a library to determine a best matching first matching spectrum from the at least some of the plurality of reference spectra, each reference spectrum of the plurality of reference spectra in the library having an associated index number;
determining a first index number for the first matching spectrum, wherein the first index number is N;
receiving a second spectrum measured from the substrate undergoing polishing during a subsequent second scan of the optical monitoring module across the substrate, wherein the second scan is X scans after the first scan;
comparing the second spectrum to a subset of the plurality of reference spectra in the library to determine a best matching second matching spectrum from the subset, the subset including at least two spectra and less than all of the reference spectra in the library, wherein Y degrees of freedom is a predetermined number and the subset of the plurality of reference spectra in the library are reference spectra having index numbers within (N+X)±Y; and
determining a second index number for the second matching spectrum.

### Claim 2

A method of determining a polishing endpoint comprising:
obtaining a spectrum measured from a substrate undergoing polishing during a scan of an optical monitoring module across the substrate;
determining a number N of platen rotations at which the scan of the optical monitoring module across the substrate is performed;
comparing the spectrum to a subset of a plurality of reference spectra in a library to determine a best matching spectrum from the subset, each reference spectrum of the plurality of reference spectra in the library having an index number, the subset including at least two spectra and less than all of the reference spectra in the library, wherein Y degrees of freedom is a predetermined number and the subset of the plurality of reference spectra in the library are reference spectra having index numbers within N±Y; and
determining an index number for the best matching spectrum.

### Claim 3

A non-transitory computer readable storage medium comprising a computer program product that is operable to cause a data processing apparatus to perform operations comprising:
receiving a spectrum measured from a substrate undergoing polishing during a scan of an optical monitoring module across the substrate;
determining a number N of platen rotations at which the scan of the optical monitoring module across the substrate is performed;
comparing the spectrum to a subset of a plurality of reference spectra in a library to determine a best matching spectrum from the subset, each reference spectrum of the plurality of reference spectra in the library having an index number, the subset including at least two spectra and less than all of the reference spectra in the library, wherein Y degrees of freedom is a predetermined number and the subset of the plurality of reference spectra in the library are reference spectra having index numbers within N±Y; and
determining an index number for the best matching spectrum.

### Claim 4

A method of determining a polishing endpoint comprising:
receiving a first spectrum measured from a substrate undergoing polishing during a first scan of an optical monitoring module across the substrate;
comparing the first spectrum to at least some of a plurality of reference spectra in a library to determine a best matching first matching spectrum from the at least some of the plurality of reference spectra, each reference spectrum of the plurality of reference spectra in the library having an associated index number;
determining a first index number for the first matching spectrum, wherein the first index number is N;
receiving a second spectrum measured from the substrate undergoing polishing during a subsequent second scan of the optical monitoring module across the substrate, wherein the second scan is X scans after the first scan;
comparing the second spectrum to a subset of the plurality of reference spectra in the library to determine a best matching second matching spectrum from the subset, the subset including at least two spectra and less than all of the reference spectra in the library, wherein Y degrees of freedom is a predetermined number and the subset of the plurality of reference spectra in the library are reference spectra having index numbers within (N+X)±Y; and
determining a second index number for the second matching spectrum.