Peak-based endpointing for chemical mechanical polishing

• US 9,799,578 B2
• Filed: 12/12/2016
• Issued: 10/24/2017
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Benvegnu, Dominic J., Swedek, Boguslaw A., Lischka, David J.
• Primary Examiner(s): Tran, Binh X
• Application Number:
  US15/376,312
• Publication Number:
  US 20170092551A1
• Time in Patent Office: 316 Days
• Field of Search: 216 84, 216 85, 438692, 438693
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: B24D 7/12 with apertures for inspecting the surface to be abraded
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step
• CPC Class Codes: H01L 21/3212 by chemical mechanical polishing [CMP]
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

A method of polishing includes storing a predetermined location and a predetermined number as criteria for detecting an end point, polishing a substrate, measuring a sequence of current spectra of light reflected from the substrate while the substrate is being polished, identifying a plurality of peaks or valleys that persist with an evolving location through at least some of the sequence of current spectra, counting a number of peaks or valleys that were identified that pass the predetermined location as polishing progresses, and ceasing to polish the substrate when the number counted reaches the predetermined number.

Claims

1. A method comprising:

storing a predetermined location and a predetermined number as criteria for detecting an end point;

polishing a substrate;

measuring a sequence of current spectra of light reflected from the substrate while the substrate is being polished;

identifying a plurality of peaks or valleys in the sequence of current spectra, wherein the peaks or valleys persist with an evolving location through at least some of the sequence of current spectra;

counting a number of peaks or valleys that were identified that pass the predetermined location as polishing progresses; and

ceasing to polish the substrate when the number counted reaches the predetermined number.

2. The method of claim 1, wherein the current location comprises a wavelength value of the selected peak or valley.

3. The method of claim 1, wherein the plurality of peaks or valleys comprise peaks.

4. The method of claim 1, wherein the plurality of peaks or valleys comprise valleys.

5. The method of claim 1, wherein measuring the sequence of current spectra comprises directing a beam of white light onto the substrate.

6. The method of claim 1, wherein polishing the substrate comprises contacting the substrate with a polishing pad, and wherein measuring the sequence of current spectra comprises directing a light beam through a window in the polishing pad.

7. The method of claim 1, comprising applying a low pass filter to the current spectra.

8. The method of claim 1, comprising normalizing the current spectra.

9. The method of claim 1, comprising, for each current spectrum in the sequence of current spectra, combining at least one additional spectrum with the current spectrum.

10. The method of claim 1, wherein counting the number of peaks or valleys comprises measuring a first location of a peak or valley in a first current spectrum of the sequence of current spectra, and measuring a second location of the peak or valley in a second current spectrum of the sequence of current spectra.

11. The method of claim 10, wherein counting the number of peaks or valleys comprises determining whether the first location is on one side of the predetermined location and the second location is on an opposite side of the predetermined location.

12. The method of claim 11, wherein the first current spectrum is measured during a first rotation of a platen and the second current spectrum is measured during an immediately subsequent second rotation of the platen.