Substrate polishing metrology using interference signals

• US 7,841,926 B2
• Filed: 06/03/2010
• Issued: 11/30/2010
• Est. Priority Date: 03/28/1995
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Pyatigorsky, Grigory, Birang, Manoocher
• Primary Examiner(s): Wilson; Lee D
• Application Number:
  US12/793,438
• Publication Number:
  US 20100240281A1
• Time in Patent Office: 180 Days
• Field of Search: 451/6, 451/7, 451/41, 451/288, 451/533, 451/537, 451/527, 451285-287, 451/28, 451/5
• US Class Current: 451/6
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/205 provided with a window for inspecting the surface of the work being lapped
• CPC Class Codes: B24B 47/12 by mechanical gearing or electric power B24B47/16 takes precedence
• CPC Class Codes: B24B 49/04 involving measurement of the workpiece at the place of grinding during grinding operation
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: B24B 51/00 Arrangements for automatic control of a series of individual steps in grinding a workpiece if applicable to other machine tools, G05B takes precedence
• CPC Class Codes: G01B 11/06 for measuring thickness ; e.g. of sheet material thickness measurement by thermal means G01B21/085
• CPC Class Codes: G01B 11/0683 measurement during deposition or removal of the layer

Abstract

A method of polishing a substrate includes holding the substrate on a polishing pad with a polishing head, wherein the polishing pad is supported by a platen, creating relative motion between the substrate and the polishing pad to polish a side of the substrate, generating a light beam and directing the light beam towards the substrate to cause the light beam to impinge on the side of the substrate being polished. Light reflected from the substrate is at a detector to generate an interference signal. A measure of uniformity is computed from the interference signal.

Claims

1. A method of polishing a substrate, comprising:

holding the substrate on a polishing pad with a polishing head;

creating relative motion between the substrate and the polishing pad to polish a layer on the substrate;

directing a light beam from the side of the substrate with the layer towards the substrate to cause the light beam to impinge on the layer being polished;

receiving light reflected from the substrate at a detector to generate an interference signal; and

computing a measure of uniformity of the thickness of the layer from the interference signal.

2. The method of claim 1, wherein creating relative motion between the substrate and the polishing pad includes rotating the polishing head.

3. The method of claim 2, wherein creating relative motion between the substrate and the polishing pad includes rotating a platen supporting the polishing pad.

4. The method of claim 1, further comprising generating relative lateral motion between the light beam and the carrier head.

5. The method of claim 4, wherein generating relative lateral motion between the light beam and the carrier head comprises laterally translating the carrier head across the polishing pad.

6. The method of claim 1, wherein the light beam is a laser beam.

7. The method of claim 1, further comprising:

comparing the measure of uniformity to a reference; and

generating an alert when the measure of uniformity diverges from the reference by more than a predetermined amount.

8. The method of claim 1, wherein the interference signal includes a low frequency component and wherein computing the measure of uniformity includes measuring an amplitude of the low frequency component.

9. The method of claim 8, further comprising filtering the interference signal to obtain the low frequency component.

10. The method of claim 8, wherein the interference signal includes a high frequency component and wherein computing the measure of uniformity includes measuring an amplitude of the high frequency component.

11. The method of claim 10, further comprising filtering the interference signal to obtain the high frequency component.

12. The method of claim 10, wherein computing the measure of uniformity includes calculating a ratio of the amplitude of the high frequency component and the amplitude of the low frequency component.