Method and apparatus for in-situ end-point detection and optimization of a chemical-mechanical polishing process using a linear polisher

• US 6,146,248 A
• Filed: 05/28/1997
• Issued: 11/14/2000
• Est. Priority Date: 05/28/1997
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Lam Research Corporation
• Inventors: Pecen, Jiri, Chadda, Saket, Krusell, Wilbur C., Cutini, Jerauld J., Engdahl, Erik H., Jairath, Rahul
• Primary Examiner(s): Rose, Robert A.
• Assistant Examiner(s): Nguyen, George
• Application Number:
  US08/869,655
• Time in Patent Office: 1,266 Days
• Field of Search: 451/5, 451/9, 451/10, 451/41, 451/285-289
• US Class Current: 451/41
• CPC Class Codes: B24B 21/04 for grinding plane surfaces
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 49/04 involving measurement of the workpiece at the place of grinding during grinding operation
• CPC Class Codes: B24D 7/12 with apertures for inspecting the surface to be abraded
• 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 linear polishing belt for use in chemical-mechanical polishing (CMP) of a substrate comprises an opening and a flexible monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt. A plurality of monitoring channels can also be used. A film thickness monitor comprising an interferometer can be disposed alongside the belt or at least partially within a region bound by it. The monitoring channel and the film thickness monitor can be used in the CMP process to determine the end point of the CMP process, determine removal rate at any given circumference of a substrate, determine average removal rate across a substrate surface, determine removal rate variation across a substrate surface, and optimize removal rate and uniformity.

Claims

1. A chemical mechanical polishing element comprising:

a belt comprising a layer of polishing material, the belt formed in a closed loop and having an opening formed therein; and

a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the window comprising a flexible material adapted to flex with the belt as the belt moves in use.

5. The invention of claim 1, 2, or 3, wherein the window in the belt is substantially transparent to light within a selected range of optical wavelengths.

6. The invention of claim 5 wherein the window in the belt is substantially transparent to light within the range of about 200 nm to about 2000 nm.

7. The invention of claim 1, 2, or 3, wherein the belt comprises inner, outer, and first and second side surfaces, and wherein the opening in the belt and the window in the belt extend between the inner and outer surfaces.

8. The invention of claim 1, 2, or 3, wherein the belt comprises inner, outer, and first and second side surfaces, and wherein the opening in the belt and the window in the belt extend between the outer and the first side surfaces.

9. The invention of claim 8 wherein the window in the belt comprises a flexible fiber optic element.

10. The invention of claim 1, 2, or 3 further comprising a plurality of additional openings in the belt and a plurality of additional monitoring windows in the belt, each additional monitoring window closing a respective one of the additional openings.

11. The invention of claim 10 wherein the opening in the belt and additional openings in the belt are arranged in a crossing pattern.

12. The invention of claim 11 wherein the pattern is repeated more than once along the belt.

13. The invention of claim 10 wherein the opening in the belt and additional openings in the belt are arranged in a linear pattern.

14. The invention of claim 13 wherein the pattern is repeated more than once along the belt.

15. The invention of claim 13 wherein the belt comprises inner, outer, and first and second side surfaces, and wherein the linear pattern is skewed with respect to the first side surface.

16. The invention of claim 1, 2, or 3, wherein the belt further comprises a base layer beneath the layer of polishing material, the base layer selected from the group consisting of aramid, cotton, metal, metal alloys, and polymers.

17. The invention of claim 1, 2, or 3, wherein the belt comprises a surface comprising polishing agent transport channels.

18. The invention of claim 1, 2, or 3, wherein the layer of polishing material comprises a plurality of fillers dispersed throughout the layer of polishing material, the fillers having an average particle size less than about 100 microns.

19. The invention of claim 1, 2, or 3, wherein the layer of polishing material comprises a plurality of abrasive particles dispersed throughout polishing material, the abrasive particles having an average particle size less than about 100 microns.

23. The invention of claim 11 wherein a second monitoring window secures to the platen and closes the opening formed in the platen.

24. The invention of claim 23 wherein the second monitoring window is substantially transparent to light within a selected range of optical wavelength.

27. The invention of claim 23 further comprising:

a plurality of additional openings in the platen and a plurality of additional monitoring windows, each additional monitoring window closing a respective one of the additional openings in the platen; and

a plurality of additional film thickness monitors aligned with each respective additional opening in the platen.

28. The invention of claim 27 wherein the opening and the additional openings in the platen are arranged so the opening in the belt passes over the opening and the additional openings in the platen.

29. The invention of claim 27 further comprising a plurality of additional openings in the belt and a plurality of additional monitoring windows in the belt, each additional monitoring window in the belt closing a respective one of the additional openings in the belt, the opening in the belt and the additional openings in the belt corresponding to the opening in the platen and the additional openings in the platen.

35. The invention of claim 1, 2, or 3, wherein the monitoring window in the belt comprises urethane.

36. The invention of claim 23 or 27 wherein the monitoring window in the platen comprises sapphire.

2. In a linear chemical mechanical polishing device of the type comprising:

at least two rollers;

a belt comprising a layer of polishing material and mounted to extend between the rollers such that rotation of the rollers drives the belt; and

a substrate carrier positioned adjacent the belt to press a substrate into contact with the belt intermediate the rollers;

the improvement comprising;

the belt having an opening formed therein, the opening positioned to move intermittently into alignment with the substrate as the belt is driven by the rollers; and

the belt further comprising a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the window comprising a flexible material adapted to flex with the belt as the window moves around and between the rollers in use.

20. The invention of claim 2 further comprising:

a film thickness monitor secured with respect to the rollers in alignment with the monitoring window in the belt such that the monitoring window in the belt intermittently moves past the film thickness monitor as the belt is driven by the rollers.

21. The invention of claim 20 wherein the belt comprises inner, outer, and first and second side surfaces, wherein the opening and the window extend between the inner and outer surfaces, and wherein the film thickness monitor is disposed at least partially within a region bounded by the belt.

22. The invention of claim 20 wherein the polishing device further comprises a platen stationary with respect to the belt and having an opening formed therein, and wherein the film thickness monitor is disposed at least partially within the opening formed in the platen.

25. The invention of claim 20 wherein the belt comprises inner, outer, and first and second side surfaces, wherein the opening and the window extend between the outer and first side surfaces, and wherein the film thickness monitor is disposed alongside the belt.

26. The invention of claim 20 wherein the film thickness monitor comprises an interferometer.

37. The invention of claim 20 wherein the film thickness monitor further comprises a sensor for detecting when the monitoring window in the belt is in alignment with the film thickness monitor.

3. In a linear chemical mechanical polishing device of the type comprising:

at least two rollers;

a belt comprising a layer of polishing material and mounted to extend between the rollers such that rotation of the rollers drives the belt;

a platen stationary with respect to the belt; and

a substrate carrier positioned adjacent the belt to press a substrate into contact with the belt intermediate the rollers;

the improvement comprising;

the belt having an opening formed therein, the opening positioned to move intermittently into alignment with the substrate as the belt is driven by the rollers;

the belt further comprising a first monitoring window secured to the belt to close the opening and to create a first monitoring channel in the belt;

the platen having an opening formed therein, the opening being positioned to align with the belt opening; and

the platen further comprising a second monitoring window secured to the platen to close the opening in the platen to create a second monitoring channel in the platen;

whereby the second monitoring window secured to the platen is stationary with respect to the first monitoring window secured to the belt as the belt moves around and between the rollers in use.

4. The invention of claim 3, wherein the first monitoring window comprises a flexible material adapted to flex with the belt as the first monitoring window moves around and between the rollers in use.

30. A method for determining an end point of a chemical-mechanical polishing process with an interferometer using a linear polishing belt, the method comprising the steps of:

(a) providing a belt having an opening formed therein and a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the monitoring window comprising a flexible material adapted to flex with the belt as the belt moves in use;

(b) measuring a film thickness of a substrate during a chemical-mechanical polishing process with an interferometer when the monitoring channel in the belt aligns with a film thickness monitor; and

then

(c) repeating step (b) until the measured film thickness reaches a predefined thickness; and

then

(d) indicating that end point has been reached.

31. The invention of claim 30 further comprising the step of terminating the chemical-mechanical polishing process when the film thickness reaches a predefined thickness.

32. A method for determining removal rate per belt revolution at any given circumference of a substrate while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

(a) providing a belt having an opening formed therein and a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the monitoring window comprising a flexible material adapted to flex with the belt as the belt moves in use;

(b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the monitoring channel in the belt aligns with a film thickness monitor; and

then

(c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the monitoring channel in the belt realigns with the film thickness monitor; and

then

(d) calculating a difference between the second film thickness and the first film thickness.

33. A method for determining average removal rate per belt revolution across a substrate surface while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

(a) providing a belt having a first and second opening formed therein and a first and second monitoring window secured to the belt to close the respective first and second openings and to create a respective first and second monitoring channel in the belt, the first and second monitoring windows each comprising a flexible material adapted to flex with the belt as the belt moves in use;

(b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the first monitoring channel in the belt aligns with a first film thickness monitor; and

then

(c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the first monitoring channel in the belt realigns with the first film thickness monitor; and

then

(d) measuring a third film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt aligns with a second film thickness monitor; and

then

(e) measuring a fourth film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt realigns with the second film thickness monitor; and

then

(f) calculating a difference between the second film thickness of step (c) and the first film thickness of step (b); and

(g) calculating a difference between the fourth film thickness of step (e) and the third film thickness of step (d); and

then

(h) calculating an average of the differences of steps (f) and (g).

34. A method for determining removal rate variation per belt revolution across a substrate surface while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

(a) providing a belt having a first and second opening formed therein and a first and second monitoring window secured to the belt to close the respective first and second openings and to create a respective first and second monitoring channel in the belt, the first and second monitoring windows each comprising a flexible material adapted to flex with the belt as the belt moves in use;

(b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the first monitoring channel in the belt aligns with a first film thickness monitor; and

then

(c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the first monitoring channel in the belt realigns with the first film thickness monitor; and

then

(d) measuring a third film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt aligns with a second film thickness monitor; and

then

(e) measuring a fourth film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt realigns with the second film thickness monitor; and

then

(f) calculating a difference between the second film thickness of step (c) and the first film thickness of step (b); and

(g) calculating a difference between the fourth film thickness of step (e) and the third film thickness of step (d); and

then

(h) calculating a variation of the differences of steps (f) and (g).