Optical techniques of measuring endpoint during the processing of material layers in an optically hostile environment

• US 6,077,452 A
• Filed: 04/14/1999
• Issued: 06/20/2000
• Est. Priority Date: 09/17/1992
• Status: Expired due to Term

• Current Assignee: LumaSense Technologies Holdings, Inc. (Advanced Energy Industries, Inc. (China))
• Original Assignee: Luxtron Corp. (Advanced Energy Industries, Inc. (China))
• Inventors: Litvak, Herbert E.
• Primary Examiner(s): DANG, THI D
• Application Number:
  US09/291,831
• Time in Patent Office: 433 Days
• Field of Search: 216/85, 216/88, 216/89, 216/60, 438/692, 438/693, 438/8, 438/7, 438/16
• US Class Current: 216/85
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 41/061 axially supporting turning workpieces, e.g. magnetically, pneumatically
• CPC Class Codes: B24B 49/02 according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent B24B49/12 takes precedence
• 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: 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
• CPC Class Codes: G03F 7/70483 Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

In a process of selectively removing material from an exposed layer carried by a substrate, a technique for determining endpoint by monitoring the intensity of a radiation beam that is passed through the substrate and any intervening layers to be reflected off the layer being processed. This monitoring technique is used during photoresist developing, wet etching, and mechanical planarization and polishing during the manufacture of integrated circuits on semiconductor wafers, flat panel displays on glass substrates, and similar articles. Planarization and polishing processes are alternatively monitored by monitoring temperature.

Claims

1. A method of monitoring a reducing thickness of a film carried by a substrate during chemical-mechanical-polishing of an exposed surface of the film, comprising:

directing electromagnetic radiation to said layer to interact with the film during said chemical-mechanical-polishing and produce radiation modified by the film,

receiving and detecting the modified radiation,

determining an emissivity of the film from the detected modified radiation, and

using the determined emissivity to monitor a changing thickness of the film resulting from the chemical-mechanical-polishing.

2. The method of claim 1, wherein a back side of the substrate opposite to the film is held and the exposed surface of the film and a chemical and mechanical film removing surface are urged together while relative motion is provided between them.

3. The method of claim 2, wherein directing the electromagnetic radiation to the layer includes directing said electromagnetic radiation through a widow transparent thereto that is provided in a moving element, and wherein receiving the modified radiation includes receiving said modified radiation through said window.

4. The method of claim 3, wherein the back side of the substrate is held by the moving element over the transparent window, whereby the electromagnetic radiation is directed in a path to the film through the window and the substrate and the modified radiation passes in a path through the substrate and the window.

5. The method of any one of claims 1-4, wherein directing the electromagnetic radiation includes producing the modified radiation with at least a partial reflection of the electromagnetic radiation from said layer.

6. The method of claim 5, wherein said film is transparent to said electromagnetic radiation and the detected modified radiation varies in amplitude as the thickness of the film changes during the processing as a result of interference between a first portion of the electromagnetic radiation being reflected from a front side of the film being removed from the substrate and a second portion of the electromagnetic radiation reflected from another surface.

7. The method of claim 5, wherein said film includes a metal.

8. The method according to any one of claims 1-4, wherein the determined emissivity is used to control some aspect of the chemical-mechanical-polishing process.

9. The method according to claim 8, wherein the controlled aspect of the chemical-mechanical-polishing process includes termination of any further changing of the thickness of the film.

10. The method according to any one of claims 1-4, additionally comprising determining from the monitored changing film thickness an endpoint of the chemical-mechanical-polishing when the film has been substantially totally removed from the substrate.

11. The method according to any one of claims 1-4, wherein the substrate includes a semiconductor wafer.

12. The method according to any one of claims 1-4, wherein the substrate includes a flat panel display.

13. The method according to claim 1, which additionally comprises:

receiving a portion of the electromagnetic radiation directed to the layer before reaching said layer, and

detecting said electromagnetic radiation portion, and

wherein monitoring the changing thickness of the film includes using the detected electromagnetic radiation portion.

14. The method according to claim 13, wherein the layer modified radiation and the electromagnetic radiation portion are received by positioning ends of first and second optical light pipes adjacent the film.

15. The method according to any one of claims 1-4, wherein said electromagnetic radiation is within a wavelength range including visible and near-visible electromagnetic radiation.

16. A method of reducing the thickness of a film carried by a first side of a substrate and simultaneously monitoring the film thickness, comprising

holding a second side of the substrate by a first mechanical element, the first and second sides being on opposite sides of the substrate,

providing chemical-mechanical slurry on a polishing pad carried by a second mechanical element,

providing relative motion between the first and second elements such that motion is provided between an outer surface of the film and the polishing pad when urged together, thereby to remove material from the outer surface of the film,

directing electromagnetic radiation to said layer such that at least a portion of the electromagnetic radiation is reflected from the layer,

detecting the reflected radiation,

calculating an emissivity of the film from the detected reflected radiation, and

using the calculated emissivity to quantitatively monitor a changing thickness of the film resulting from the removal of material from its outer surface.

17. The method of claim 16, wherein directing electromagnetic radiation includes passing said electromagnetic radiation through a window provided in one of the first and second elements, and the reflected radiation portion passes back through said window.

18. The method of claim 17, wherein the window is provided in the first element, and the electromagnetic radiation is directed through the window and the substrate, in that order, and said at least a portion of the electromagnetic radiation being reflected back from the layer passes through the substrate and the window, in that order.

19. The method of any one of claims 16-18, wherein first and second rotating wheels are respectively provided as said first and second mechanical elements, respectively.

20. A method of operating on a film carried by a first side of a substrate and simultaneously monitoring the film, comprising:

holding a second side of the substrate by a first mechanical element, the first and second sides being on opposite sides of the substrate,

providing relative motion between the first element and a second mechanical element such that motion is provided between an outer surface of the film and a polishing pad of the second element when urged together, thereby to remove material from the outer surface of the film,

directing electromagnetic radiation incident upon said layer such that at least a portion of the electromagnetic radiation is reflected from the layer,

detecting a portion of the incident radiation prior to being reflected from the layer,

detecting the reflected radiation,

calculating an emissivity of the film from both of the detected incident and reflected radiation, and

using the calculated emissivity to monitor the film during the operation on the film.

21. The method according to claim 20, wherein the reflected radiation and the incident radiation portion are detected by positioning ends of respective first and second optical light pipes adjacent the film, and transmitting the radiation along the respective light pipes to respective first and second photodetectors.

22. The method according to either one of claims 20-21, wherein said electromagnetic radiation is within a wavelength range including visible and near-visible electromagnetic radiation.

23. A method of monitoring a change in a characteristic of a film carried by a substrate during chemical-mechanical-polishing of an exposed surface of the film by providing relative motion between the film and a polishing pad while urged together, comprising:

directing electromagnetic radiation to said layer to interact with the film during said chemical-mechanical-polishing and produce radiation modified by the film, said electromagnetic radiation being directed through a window transparent thereto that is provided in a moving element utilized in the chemical-mechanical-polishing of the film,

receiving and detecting the modified radiation through said window, and

utilizing the detected modified radiation to monitor the change in the characteristic of the film resulting from the chemical-mechanical-polishing.

24. The method of claim 23, wherein directing the electromagnetic radiation to said layer includes producing the modified radiation with at least a partial reflection of the electromagnetic radiation from said layer.

25. The method of claim 24, wherein the characteristic being monitored is a thickness of the film.

26. The method of claim 25, wherein said film is transparent to said electromagnetic radiation and the detected modified radiation varies in amplitude as the thickness of the film changes during the processing as a result of interference between a first portion of the electromagnetic radiation being reflected from a front side of the film being removed from the substrate and a second portion of the electromagnetic radiation reflected from another surface.

27. The method of claim 25, wherein said film includes a metal.

28. The method according to claim 23, wherein the monitored characteristic is used to control some aspect of the chemical-mechanical-polishing process.

29. The method according to claim 28, wherein the controlled aspect of the chemical-mechanical-polishing process includes termination of any further processing of the film.

30. The method according to any one of claims 23-29, wherein said electromagnetic radiation is within a wavelength range including visible and near-visible electromagnetic radiation.