Polishing method and apparatus

• US 6,663,469 B2
• Filed: 06/01/2001
• Issued: 12/16/2003
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Kimura, Norio, Kohama, Tatsuya
• Primary Examiner(s): Wilson, Lee D.
• Application Number:
  US09/870,479
• Publication Number:
  US 20020002029A1
• Time in Patent Office: 928 Days
• Field of Search: 451/11, 451/8, 451/5, 451/41, 451/37, 451/36, 451/57, 451/285-288
• US Class Current: 451/41
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: H01L 21/02074 the processing being a planarization of conductive layers
• CPC Class Codes: H01L 21/3212 by chemical mechanical polishing [CMP]
• CPC Class Codes: H01L 21/7684 Smoothing; Planarisation

Abstract

A semiconductor substrate having a Cu layer formed so as to fill wiring grooves formed in the substrate surface and to cover regions of the substrate surface where no wiring groove is formed is brought into sliding contact with a polishing surface on a turntable to carry out polishing until the Cu layer is polished to a predetermined thickness. Then, the semiconductor substrate is brought into sliding contact with a polishing surface on a turntable to carry out polishing until the Cu layer on the substrate surface is removed, except for portions of the Cu layer formed to fill the wiring grooves, and a barrier metal layer is also removed. Thus, the Cu layer on the substrate surface can be removed uniformly, and the Cu wiring portions formed in the wiring grooves can be planarly and uniformly polished without giving rise to problems of over-polishing such as dishing or erosion.

Claims

1. A method for polishing a copper layer on a substrate, comprising:

providing a substrate having a copper layer on a surface thereof;

first polishing said copper layer;

stopping the first polishing when an eddy current sensor determines that said copper layer has been polished to a predetermined thickness;

second polishing said copper layer; and

stopping the second polishing when an optical sensor determines that said copper layer has been removed from said surface.

2. The method according to claim 1, wherein

providing a substrate having a copper layer on a surface thereof comprises providing a semiconductor substrate having grooves in a surface thereof, such that copper is on said surface and in said grooves of said semiconductor substrate,

first polishing said copper layer comprises first chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool,

second polishing said copper layer comprises second chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool, and

stopping the second polishing when an optical sensor determines that said copper layer has been removed from said surface comprises stopping the second chemically mechanically polishing when said optical sensor determines that said copper has been removed from said surface of said semiconductor substrate but not from said grooves, whereby said copper in said grooves defines wiring on said semiconductor substrate.

3. The method according to claim 2, further comprising:

providing a barrier metal layer on said surface of said semiconductor substrate such that said copper is on said barrier metal layer,

wherein stopping the second chemically mechanically polishing when said optical sensor determines that said copper has been removed from said surface of said semiconductor substrate but not from said grooves comprises stopping the second chemically mechanically polishing when said optical sensor determines that said copper and said barrier metal layer have been removed from said surface of said semiconductor substrate.

4. The method according to claim 3, wherein

first chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a first polishing liquid to said polishing surface, and

second chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a second polishing liquid to said polishing surface,

with said first polishing liquid being different than said second polishing liquid.

5. The method according to claim 4, further comprising:

cleaning said semiconductor substrate between the first chemically mechanically polishing and the second chemically mechanically polishing.

6. The method according to claim 4, wherein

providing a barrier metal layer on said surface of said semiconductor substrate comprises providing a layer of one of Ta and TaN on said surface of said semiconductor substrate.

9. The method according to claim 3, wherein

stopping the first polishing when an eddy current sensor determines that said copper layer has been polished to a predetermined thickness comprises stopping the first chemically mechanically polishing when said eddy current sensor determines that said copper on said barrier metal layer has been polished to a thickness within a range of 500 A to 2000 A.

10. The method according to claim 3, wherein

stopping the first polishing when an eddy current sensor determines that said copper layer has been polished to a predetermined thickness comprises stopping the first chemically mechanically polishing when a resonance frequency of said eddy current sensor reaches a predetermined threshold value.

11. The method according to claim 10, wherein

stopping the first chemically mechanically polishing when a resonance frequency of said eddy current sensor reaches a predetermined threshold value comprises stopping the first chemically mechanically polishing when a resonance frequency of said eddy current sensor reaches a value within a range of from 6400 Hz to 6500 Hz.

12. The method according to claim 3, wherein

stopping the second chemically mechanically polishing when said optical sensor determines that said copper layer and said barrier metal layer have been removed from said surface of said semiconductor substrate comprises operating said optical sensor to utilize dispersal of light reflected from said semiconductor substrate to determine when said copper layer and said barrier metal layer have been removed from said surface of said semiconductor substrate.

13. The method according to claim 12, wherein

operating said optical sensor to utilize dispersal of light reflected from said semiconductor substrate to determine when said copper layer and said barrier metal layer have been removed from said surface of said semiconductor substrate includes causing the dispersal of light via a diffraction grating.

14. The method according to claim 3, wherein

first chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a first polishing solution to said polishing surface, and

second chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a second polishing solution to said polishing surface,

with said first polishing solution and said second polishing solution each having different polishing rates for copper and an oxide film.

15. The method according to claim 3, wherein

first chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a first polishing solution to said polishing surface, and

second chemically mechanically polishing said copper layer by bringing said copper layer into sliding contact with a polishing surface on a polishing tool includes supplying a second polishing solution to said polishing surface,

with said first polishing solution and said second polishing solution each having different polishing rates for copper and tantalum.

7. The method according to claim wherein

providing a barrier metal layer on said surface of said semiconductor substrate comprises providing said barrier metal layer on an oxide film, and

stopping the second chemically mechanically polishing comprises continuing the second chemically mechanically polishing until said oxide film is exposed.

8. The method according to claim 7, wherein

providing said barrier metal layer on an oxide film comprises providing said barrier layer on a film of SiO₂.

16. An apparatus for polishing a copper layer on a semiconductor substrate to form copper wiring on the semiconductor substrate, said apparatus comprising:

a first polishing tool having a polishing surface for first polishing a copper layer, which layer includes copper on a barrier metal layer that is in grooves and on a surface of a semiconductor substrate in which the grooves are formed, by bringing the copper layer into sliding contact with said polishing surface;

an eddy current sensor for determining when the copper layer has been polished by said first polishing tool to a predetermined thickness so as to stop the first polishing of the copper layer;

a second polishing tool having a polishing surface for second polishing the copper layer after stoppage of the first polishing of the copper layer, by bringing the copper layer into sliding contact with said polishing surface of said second polishing tool; and

an optical sensor for determining when the copper and the barrier metal layer have been removed by said second polishing tool from the surface of the semiconductor substrate, but not from the grooves, so as to stop the second polishing of the copper layer.

17. The apparatus according to claim 16, wherein the barrier metal layer comprises a layer of one of Ta and TaN.

18. The apparatus according to claim 16, wherein the barrier metal layer is on an oxide film, and said optical sensor is for determining when the copper and the barrier metal layer have been removed such that the second polishing is continued until the oxide film is exposed.

19. The apparatus according to claim 18, wherein the oxide film comprises a film of SiO₂.

20. The apparatus according to claim 16, wherein said eddy current sensor is for determining when the copper layer has been polished by said first polishing tool to a thickness within a range of 500 A to 2000 A.

21. The apparatus according to claim 16, wherein said eddy current sensor is for determining when the copper layer has been polished by said first polishing tool to a predetermined thickness by indicating when a resonance frequency of said eddy current sensor reaches a predetermined threshold value.

22. The apparatus according to claim 16, wherein said optical sensor is for determining when the copper and the barrier metal layer have been removed by said second polishing tool from the surface of said semiconductor substrate, but not from the grooves, by utilizing dispersal of light reflected from said semiconductor substrate.

23. The apparatus according to claim 22 further comprising a diffraction grating for conducting the dispersal of light reflected from the semiconductor substrate.

24. The apparatus according to claim 16, wherein

said first polishing tool is for first polishing the copper layer by bringing the copper layer into sliding contact with said polishing surface while a first polishing solution is supplied to said polishing surface, and

said second polishing tool is for second polishing the copper layer by bringing the copper layer into sliding contact with said polishing surface while a second polishing solution is supplied to said polishing surface,

with the first polishing solution and the second polishing solution each having different polishing rates for copper and an oxide film.

25. The apparatus according to claim 24, wherein

said first polishing tool is for first polishing the copper layer by bringing the copper layer into sliding contact with said polishing surface while a first polishing solution is supplied to said polishing surface, and

said second polishing tool is for second polishing the copper layer by bringing the copper layer into sliding contact with said polishing surface while a second polishing solution is supplied to said polishing surface,

with the first polishing solution and the second polishing solution each having different polishing rates for copper and tantalum.

26. An apparatus for polishing a substrate, comprising:

a polishing tool providing a polishing surface;

a top ring for holding a substrate while the substrate is in contact with and moved relative to said polishing surface so as to polish the substrate;

a first sensor to measure a film thickness of the substrate; and

a second sensor to measure a film thickness of the substrate,

wherein said first sensor is of a type that is different than that of said second sensor.

27. The apparatus according to claim 26, wherein

said first sensor is provided at a first position on a polishing surface side of said polishing tool such that while the substrate is moved relative to said polishing surface, during polishing of the substrate, a center of the substrate passes through said first position; and

said second sensor is provided at a second position on a polishing surface side of said polishing tool such that while the substrate is moved relative to said polishing surface, during polishing of the substrate, a center of the substrate passes through said second position.

28. The apparatus according to claim 27, wherein said first sensor comprises an optical thickness by emitting a light to the substrate.

29. The apparatus according to claim 28, wherein said second sensor comprises an eddy current sensor for measuring the film thickness by inducing an eddy current in a layer on the substrate.

30. The apparatus according to claim 27, wherein said first sensor comprises an eddy current sensor for measuring the film thickness by inducing an eddy current in a layer on the substrate.