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

• US 6,110,752 A
• Filed: 08/27/1997
• Issued: 08/29/2000
• Est. Priority Date: 09/17/1992
• Status: Expired due to Fees

• 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:
  US08/918,907
• Time in Patent Office: 1,098 Days
• Field of Search: 216/85, 216/60, 216/88, 216/89, 438/691, 438/692, 438/7, 438/8, 438/16
• US Class Current: 438/8
• 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. During the processing of a semiconductor structure including a substrate, a patterned layer carried thereby and a dielectric layer extending across the patterned layer with an uneven exposed dielectric surface that is raised over remaining portions of the patterned layer and low therebetween, a method of monitoring a process of planarizing said exposed surface while it is occurring, comprising:

directing a radiation beam through the substrate and the dielectric layer to strike at least the low portion of the exposed surface to reflect at least a portion of said beam from said low surface portion and back through the dielectric layer and the substrate, and

detecting, from at least the reflected portion of the radiation beam, a commencement of material being removed from the low portion of the dielectric layer, thereby indicating when the raised portions have been removed and the exposed surface is planarized.

2. The method of claim 1, wherein the remaining portions of the patterned layer are opaque to the radiation beam.

3. The method of claim 1, wherein detecting the commencement of material being removed from the low portion of the dielectric layer includes monitoring an intensity which results from an interference between said reflected portion of the radiation beam and another portion of said beam that is reflected from a boundary surface within the semiconductor structure that underlies said exposed surface.

4. The method of claim 3, wherein detecting the commencement of material being removed from the low portion of the dielectric layer additionally includes detecting a change from a substantially constant intensity over time to a cyclic variation of the intensity over time.

5. The method of claim 3, wherein the remaining portions of the patterned layer are opaque to the radiation beam.

6. The method of claim 1, wherein directing the radiation beam includes directing a radiation beam against the exposed surface that includes a multi-wavelength spectrum, and wherein detecting the commencement of material being removed from the low portion of the dielectric layer includes monitoring levels of the reflected radiation as a function of wavelength.

7. The method of any one of claims 1-5 or 6, wherein the planarization is accomplished by chemical-mechanical-polishing of the exposed surface.

8. The method of claim 7, additionally comprising terminating the chemical-mechanical-polishing of the exposed surface in response to detecting commencement of material being removed from the low portion of the dielectric layer.

9. The method of claim 7, wherein the semiconductor substrate is held by a wafer carrier having a transparent window therein, and wherein directing a radiation beam through the substrate includes directing the radiation beam through the window.

10. The method of claim 6, wherein the remaining portions of the patterned layer are opaque to the radiation beam.

11. During the processing of a semiconductor structure including a substrate, a patterned layer carried thereby and a dielectric layer extending across the patterned layer with an uneven dielectric surface, a method of monitoring a process of planarizing said dielectric surface while it is occurring, comprising:

directing a radiation beam including a multi-wavelength spectrum through the substrate and dielectric layer against the surface to reflect at least a portion of said beam from said surface and back through the dielectric layer and the substrate,

monitoring relative intensities across the wavelength spectrum of at least the reflected portion of the radiation, and

detecting from the relative intensities across the monitored wavelength spectrum when the dielectric surface has become planarized.

12. The method of claim 11, wherein detecting when the dielectric has become planarized includes monitoring an intensity which results from an interference between said reflected portion of the radiation beam and another portion of said beam that is reflected from a boundary surface within the semiconductor structure that underlies said exposed surface.

13. The method of either of claims 11 or 12, wherein the planarization is accomplished by chemical-mechanical-polishing of the exposed surface.

14. The method of claim 13, additionally comprising terminating the chemical-mechanical-polishing of the exposed surface in response to detecting when the dielectric layer has become smooth.

15. A method of monitoring the processing of a semiconductor wafer structure while it is occurring, comprising:

directing a radiation beam having a multi-wavelength spectrum against the wafer structure in a manner to obtain therefrom a radiation beam with its spectrum modified according to a stage of the processing of the wafer being monitored,

during processing of the wafer structure, monitoring a profile of relative intensities across the wavelength spectrum of at least the wafer structure modified beam, and

detecting from the relative intensity profile of the monitored spectrum a state of the wafer structure being processed.

16. The method of claim 15, wherein detecting a state of the wafer structure being processed includes monitoring relative intensities which result from an interference between said portion of the radiation beam that is reflected from a surface of the wafer structure being processed and another portion of said beam that is reflected from another boundary surface.

17. The method of either of claims 15 or 16, wherein the state of the wafer structure detected is an endpoint to its processing.

18. The method of either of claims 15 or 16, wherein the process includes planarization of an exposed surface of the wafer structure by chemical-mechanical-polishing of the exposed surface.

19. The method of claim 18, additionally comprising terminating the chemical-mechanical-polishing of the exposed surface in response to detecting from the relative intensity profile when the dielectric layer has become planarized.

20. A method of monitoring a change in thickness of a top layer of material of an integrated circuit being formed on a front side of a substrate during processing of the layer, comprising:

directing a beam of electromagnetic radiation against a back side of the substrate and to the layer through the substrate, said first beam of electromagnetic radiation including a wavelength band to which each of said substrate and said layer is substantially transparent,

receiving and detecting a portion of the radiation beam within said wavelength band after reflection from boundary surfaces of said integrated circuit, including a front surface of said layer, and said substrate, and

monitoring a varying intensity over time of a component of the reflected radiation which results from an interference between a portions of the radiation reflected from the front surface of the layer and another of the boundary surfaces while the thickness of the layer is being changed.

21. The method according to claim 20, wherein the processing of the layer includes removing material from the layer.

22. The method according to claim 20, additionally comprising determining an end point of the processing from monitoring the varying intensity of the reflected radiation.

23. The method according to claim 20, wherein substrate is a semiconductor wafer.

24. The method according to claim 20, wherein the beam of radiation is directed to the back side of the substrate from a laser.