Method and apparatus for electrically endpointing a chemical-mechanical planarization process

• US 6,319,420 B1
• Filed: 06/21/2000
• Issued: 11/20/2001
• Est. Priority Date: 07/29/1998
• Status: Expired due to Fees

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Dow, Daniel B.
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): GOUDREAU, GEORGE A
• Application Number:
  US09/599,077
• Time in Patent Office: 517 Days
• Field of Search: 216/84, 216/86, 216/88, 216/89, 216/100, 438/692, 438/693, 438/5, 438/10, 438/13, 438/17
• US Class Current: 216/86
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/04 designed for working plane surfaces
• CPC Class Codes: B24B 49/10 involving electrical means B24B49/02, B24B49/08 take precedence
• CPC Class Codes: H01L 21/30625 With simultaneous mechanical treatment, e.g. mechanico-chemical polishing

Abstract

A method and apparatus for endpointing a planarization process of a microelectronic substrate. The apparatus can include a source of electrical power having first and second electrical contacts coupled to the microelectronic substrate to form a conductive path through the substrate. An impedance of the conductive path changes as conductive material is removed from the substrate during planarization. In one embodiment, one contact can be attached to an upper surface of the substrate and the other contact can be attached to an intermediate surface between the upper surface and a lower surface of the substrate. In another embodiment, both contacts are connected to the intermediate surface and in still another embodiment, one contact can be connected to a retainer adjacent the substrate. In yet another embodiment, the power source induces a current in the conductive material, and the endpoint is detected by detecting a change in the induced current as the conductive material is removed.

Claims

1. A method for detecting removal of a conductive material from a surface of a microelectronic substrate where the surface of the microelectronic substrate is the second of two surfaces and the microelectronic substrate has an intermediate surface between the two surfaces, the method comprising:

monitoring the impedance between at least two spaced apart locations coupled to the conductive material, where at least one of the spaced apart locations includes a first location of the intermediate surface;

removing the conductive material from the microelectronic substrate; and

terminating removal of the conductive material when the monitored impedance drops to a value corresponding to removal of substantially all of the conductive material from the surface of the substrate.

2. The method of claim 1 wherein the microelectronic substrate has a conductive structure extending between and electrically coupled to the two surfaces, and monitoring the impedance includes monitoring the impedance between a point on a first of the two surfaces and a planarizing medium adjacent the second of the two surfaces.

3. The method of claim 1 wherein monitoring the impedance includes monitoring a current through the conductive material.

4. The method of claim 1 wherein monitoring the impedance includes monitoring a voltage across the conductive material.

5. The method of claim 1 wherein removing the conductive material includes engaging the conductive material with a planarizing medium and moving at least one of the planarizing medium and the microeelctronic substrate relative to the other of the planarizing medium and the microelectronic substrate.

6. The method of claim 5 wherein engaging the conductive material with a planarizing medium includes engaging the conductive material with a polishing pad.

7. The method of claim 5 wherein engaging the conductive material with a planarizing medium includes engaging the conductive material with a planarizing liquid disposed on a surface of a polishing pad.

8. A method for detecting removal of a conductive material from a microelectronic substrate having first and second surfaces, the second surface being in electrical contact with a planarizing liquid disposed on a polishing pad, the method comprising:

removing conductive material from the second surface of the microelectronic substrate thereby changing an impedance of a conductive path extending from the first surface of the microelectronic substrate to the second surface of the microelectronic substrate, through the planarizing liquid and through an electrical contact engaged with the planarizing liquid and spaced apart from the polishing pad; and

detecting the change in the impedance of the conductive path.

9. The method of claim 8 wherein detecting the change in impedance of the conductive path includes measuring a decrease in current through the conductive path as the resistance of the conductive path increases.

10. The method of claim 8 wherein the conductive material includes a first material and the microelectronic substrate includes a second material adjacent the first material, the second material having an impedance greater than an impedance of the first material and changing the impedance of the conductive path includes increasing the impedance of the conductive path by exposing the second material to the planarizing liquid.

11. The method of claim 8 wherein detecting the change in impedance includes measuring a change in a voltage drop across at least a portion of the conductive path.

12. The method of claim 8 wherein the microelectronic substrate includes a via that extends from the first surface through the microelectronic substrate to the second surface and detecting the change in impedance includes applying a voltage through the via.

13. The method of claim 8 wherein the first surface of the microelectronic substrate is opposite the second surface and detecting the change in impedance includes applying a voltage to the first surface.

14. The method of claim 8 wherein the microelectronic substrate includes an intermediate surface between the first and second surfaces, the conductive material extends over the intermediate surface and detecting the change in impedance includes applying a voltage between the first surface and the conductive material extending over the intermediate surface.

15. The method of claim 8 wherein detecting the change in impedance includes passing an electrical current through a retaining ring positioned adjacent the microelectronic substrate when the microelectronic substrate engages the planarizing liquid.

16. The method of claim 8, further comprising halting removal of the conductive material in response to detecting the change in impedance.

17. A method for endpointing a planarization process of a microelectronic substrate having a first surface and a second surface opposite the first surface, the method comprising:

detecting a characteristic of power provided to a first conductive path extending from a point proximate to the first surface of the microelectronic substrate, through the microelectronic substrate to a conductive region of the second surface of the microelectronic substrate, and through a planarizing liquid adjacent the microelectronic substrate to an electrical contact engaged with the planarizing liquid and spaced apart from a polishing pad beneath the planarizing liquid;

removing material from the conductive region of the second surface of the microelectronic substrate;

detecting a characteristic of power provided to a second conductive path that extends from the first surface of the microelectronic substrate, through the microelectronic substrate and directly to the planarizing liquid, then to the electrical contact engaged with the planarizing liquid and spaced apart from the polishing pad; and

halting removal of the material in response to detecting the characteristic of power provided to the second conductive path.

18. The method of claim 17 wherein detecting the characteristic of power provided to at least one of the first and second conductive paths includes detecting an impedance of the at least one conductive path.

19. The method of claim 17 wherein detecting the characteristic of power provided to at least one of the first and second conductive paths includes detecting an electrical current passing through the at least one conductive path.

20. The method of claim 17 wherein the conductive region includes a first material and the microelectronic substrate includes a second material adjacent the first material, the second material having an impedance greater than an impedance of the first material, further wherein removing material from the conductive region of the second surface of the microelectronic substrate includes exposing the second material to the planarizing liquid.

21. The method of claim 17 wherein detecting a characteristic of power provided to the first conductive path includes detecting a characteristic of power provided to a retaining ring positioned adjacent the microelectronic substrate when the microelectronic substrate engages the planarizing liquid.

22. A method for detecting removal of conductive material from a surface of a microelectronic substrate during planarization, the method comprising:

detecting a characteristic of power provided to a first conductive path extending through at least a portion of the microelectronic substrate and through both the conductive material of the surface of the microelectronic substrate and a polishing pad adjacent the surface of the microelectronic substrate to an electrical contact adjacent the polishing pad;

removing at least a portion of the conductive material from the second surface of the microelectronic substrate; and

detecting a characteristic of power provided to the second conductive path extending through the microelectronic substrate directly to the polishing pad adjacent the microelectronic substrate.

23. The method of claim 22, further comprising halting removal of the conductive material from the microelectronic substrate upon detecting the characteristic of power provided to the second conductive path.

24. The method of claim 22 wherein the polishing pad is generally electrically non-conductive and detecting the characteristic of power provided to the second conductive path includes detecting an electrical current with a value of approximately zero.

25. The method of claim 22, further comprising comparing the characteristic of power provided to the first conductive path with the characteristic of power provided to the second conductive path.

26. The method of claim 22 wherein detecting the characteristic of power provided to at least one of the first and second conductive paths includes detecting an impedance of the at least one conductive path.

27. The method of claim 22 wherein detecting the characteristic of power provided to at least one of the first and second conductive paths includes detecting a current passing through the at least one conductive path.

28. A method for detecting the removal of conductive material from a microelectronic substrate during planarization, the microelectronic substrate having a first surface, a second surface opposite the first surface, and an intermediate surface between the first and second surfaces, the method comprising removing material having a first conductivity from the second surface of the microelectronic substrate to expose material having a second conductivity less than the first conductivity until an impedance of a conductive path initially extending from a point proximate to the first surface of the microelectronic substrate, through the microelectronic substrate to a point, proximate to the second surface of the microelectronic substrate and through a planarizing medium adjacent the microelectronic substrate to the intermediate surface of the microelectronic substrate increases.

29. The method of claim 28, further comprising detecting a current passing through the conductive path to determine when the impedance of the conductive path increases.

30. The method of claim 29 wherein the planarizing medium includes a polishing pad and detecting the current passing through the conductive path includes detecting a current passing through the polishing pad.

31. The method of claim 29 wherein the planarizing medium includes a planarizing liquid and detecting the current passing through the conductive path includes detecting a current passing through the planarizing liquid.

32. The method of claim 28 wherein the microelectronic substrate includes a via that extends from the first surface through the microelectronic substrate to the second surface, further comprising passing an electrical current through the via.

33. The method of claim 28, further comprising halting removal of material having the first conductivity in response to detecting an increase in the impedance of the conductive path.

34. A method for detecting removal of a conductive material from a microelectronic substrate having, a first surface, a second surface opposite the first surface with the conductive material, and an intermediate surface between the first and second surfaces, the method comprising:

removing at least a portion of the conductive material from the second surface of the microelectronic substrate thereby changing an impedance of a conductive path that initially extends from one portion of the intermediate surface of the microelectronic substrate through the second surface of the microelectronic substrate to a second portion of the intermediate surface; and

detecting the change in impedance of the conductive path.

35. The method of claim 34 wherein the microelectronic substrate is adjacent a polishing pad and removing at least a portion of the conductive material from the second surface includes engaging the second surface with the polishing pad and moving at least one of the polishing pad and the microelectronic substrate relative to the other of the polishing pad and the microelectronic substrate.

36. The method of claim 34 wherein the microelectronic substrate is adjacent a planarizing liquid and removing at least a portion of the conductive material from the second surface includes engaging the second surface with the planarizing liquid.

37. The method of claim 34 wherein detecting the change in impedance of the conductive path includes measuring a decrease in current through the conductive path as the resistance of the conductive path increases.

38. The method of claim 34 wherein detecting the change in impedance includes measuring a change in a voltage drop across at least a portion of the conductive path.

39. The method of claim 34 wherein detecting the change in impedance includes passing an electrical current through a retaining ring positioned adjacent the microelectronic substrate when the microelectronic substrate engages a planarizing medium.

40. The method of claim 34, further comprising halting removal of the conductive material in response to detecting the change in impedance.

41. A method for detecting removal of a conductive material from a surface of a microelectronic substrate, comprising:

inducing a first electrical current in the conductive material and detecting the first electrical current;

planarizing the surface of the microelectronic substrate to remove at least a portion of the conductive material;

inducing a second electrical current in the microelectronic substrate after removing at least a portion of the conductive material; and

detecting the second electrical current.

42. The method of claim 41 wherein inducing the first electrical current includes positioning an inductive coil proximate to the microelectronic substrate and passing a third electrical current through the inductive coil.

43. The method of claim 42 wherein detecting the second electrical current includes inducing a change in the third electrical current passing through the inductive coil, the induced change being induced by the second electrical current in the conductive material.

44. The method of claim 42, further comprising halting planarization of the microelectronic substrate in response to detecting the second electrical current.

45. The method of claim 42, further comprising passing the second electrical current from the surface of the microelectronic substrate through the microelectronic substrate.

46. The method of claim 42 wherein detecting the second electrical current includes positioning an inductive probe proximate to the microelectronic substrate after removing at least a portion of the conductive material.

47. The method of claim 42 wherein inducing the first electrical current in the conductive material includes inducing the first electrical current with an inductor positioned in a polishing pad adjacent the surface of the microelectronic substrate.

48. The method of claim 42 wherein inducing the first electrical current in the conductive material includes inducing the first electrical current with an inductor positioned beneath a polishing pad adjacent the surface of the microelectronic substrate.

49. The method of claim 42 wherein planarizing the surface of the microelectronic substrate includes engaging the microelectronic substrate with a polishing pad and moving at least one of the microelectronic substrate and the polishing pad relative to the other of the microelectronic substrate and the polishing pad.

50. The method of claim 49, further comprising disposing a planarizing liquid on a surface of the polishing pad while planarizing the surface of the microelectronic substrate.