Methods and apparatus for electrically detecting characteristics of a microelectronic substrate and/or polishing medium Number:7,134,934 from the United States Patent and Trademark Office (PTO) owispatent Methods and apparatuses for detecting characteristics of a microelectronic substrate. A method in accordance with an embodiment of the invention includes positioning the microelectronic substrate proximate to and spaced apart from the first and second spaced apart electrodes, contacting the microelectronic substrate with a polishing surface of a polishing medium, removing conductive material from the microelectronic substrate by moving the substrate and/or the electrodes relative to each other while passing a variable electrical signal through the electrodes and the substrate, and detecting a change in the variable electrical signal or a supplemental electrical signal passing through the microelectronic substrate. The rate at which material is removed from the microelectronic substrate can be changed based at least in part on the change in the electrical signal.<H microelectronic, characteristics, Methods, and, app, 7134934.html, Patent, pto, 7134934

Title: Methods and apparatus for electrically detecting characteristics of a microelectronic substrate and/or polishing medium

Abstract: Methods and apparatuses for detecting characteristics of a microelectronic substrate. A method in accordance with an embodiment of the invention includes positioning the microelectronic substrate proximate to and spaced apart from the first and second spaced apart electrodes, contacting the microelectronic substrate with a polishing surface of a polishing medium, removing conductive material from the microelectronic substrate by moving the substrate and/or the electrodes relative to each other while passing a variable electrical signal through the electrodes and the substrate, and detecting a change in the variable electrical signal or a supplemental electrical signal passing through the microelectronic substrate. The rate at which material is removed from the microelectronic substrate can be changed based at least in part on the change in the electrical signal.

Patent Number: 7,134,934 Issued on 11/14/2006 to Lee, et al.

Inventors: Lee; Whonchee (Boise, ID), Moore; Scott E. (Meridian, ID), Meikle; Scott G. (Gainesville, VA)
Assignee: Micron Technology, Inc. (Boise, ID)

Appl. No.: 10/230,972

Filed: August 29, 2002

Current U.S. Class: 451/8 ; 451/41

Current International Class: B24B 49/00 (20060101)

Field of Search: 451/41,6,8,9 438/692,693

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Primary Examiner: Nguyen; Dung Van
Attorney, Agent or Firm: Perkins Coie LLP

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of the following pending U.S. Patent Applications, all of which are incorporated herein by reference: Ser. No. 09/651,779, filed Aug. 30, 2000; Ser. No. 09/888,084, filed Jun. 21, 2001; Ser. No. 09/887,767, filed Jun. 21, 2001; and Ser. No. 09/888,002, filed Jun. 21, 2001. Also incorporated herein by reference are the following U.S. Patent Applications, filed simultaneously herewith: Ser. No. 10/230,970 and 10/230,973; Ser. No. 10/230,463; and Ser. No. 10/230,628.

Claims

We claim:

1. A method for detecting electrical characteristics of a microelectronic substrate, comprising: positioning the microelectronic substrate proximate to and spaced apart from a first electrode and a second electrode, wherein the first and second electrodes are spaced apart from each other; contacting the microelectronic substrate with a polishing surface of a polishing medium; removing conductive material from the microelectronic substrate by moving at least one of the microelectronic substrate and the electrodes relative to the other of the microelectronic substrate and the electrodes, while passing a variable first electrical signal through the first and second electrodes and at least a portion of the microelectronic substrate, and while the microelectronic substrate contacts the polishing surface; passing a second electrical signal through at least part of the microelectronic substrate, the second electrical signal being different than the first electrical signal; detecting a change in the second electrical signal corresponding to a change in the amount of conductive material remaining on the microelectronic substrate; and changing a rate at which material is removed from the microelectronic substrate based at least in part on the change in the second electrical signal.

2. The method of claim 1, further comprising ceasing to remove conductive material from the microelectronic substrate when a rate of change of an electrical current provided by the second electrical signal is at least approximately constant.

3. The method of claim 1 wherein changing a rate at which material is removed from the microelectronic substrate includes ceasing to remove material from the microelectronic substrate.

4. The method of claim 1 wherein passing the second electrical signal through the microelectronic substrate includes passing the second electrical signal from a first surface of the microelectronic substrate through the microelectronic substrate to a second surface of the microelectronic substrate facing opposite from the first surface.

5. The method of claim 1 wherein passing the second electrical signal through the microelectronic substrate includes passing the second electrical signal from a first surface of the microelectronic substrate through the microelectronic substrate to a second surface of the microelectronic substrate facing opposite from the first surface, then to the second electrode positioned at least proximate to the second surface.

6. The method of claim 1 wherein passing the second electrical signal includes passing the second electrical signal simultaneously with passing the first electrical signal.

7. The method of claim 1 wherein passing the second electrical signal includes passing the second electrical signal after passing the first electrical signal.

8. The method of claim 1 wherein passing the second electrical signal includes passing the second electrical signal from one of the first and second electrodes, through the microelectronic substrate to the other of the first and second electrodes.

9. The method of claim 1, further comprising positioning the microelectronic substrate proximate to and spaced apart from a third electrode and a fourth electrode, wherein the third and fourth electrodes are spaced apart from each other and wherein passing the second electrical signal includes passing the second electrical signal from one of the third and fourth electrodes, through the microelectronic substrate to the other of the third and fourth electrodes.

10. A method for detecting electrical characteristics of a microelectronic substrate, comprising: positioning the microelectronic substrate proximate to and spaced apart from a first electrode and a second electrode, with the first and second electrodes spaced apart from each other; removing conductive material from the microelectronic substrate by moving at least one of the microelectronic substrate and the electrodes relative to the other of the microelectronic substrate and the electrodes while passing a variable first electrical signal through the first and second electrodes and at least a portion of the microelectronic substrate; passing a second electrical signal through the first and second electrodes and at least part of the microelectronic substrate simultaneously with passing the first electrical signal by superimposing the first and second electrical signals; and detecting a change in the second electrical signal corresponding to a change in the amount of conductive material remaining on the microelectronic substrate.

11. The method of claim 10, further comprising positioning the microelectronic substrate in contact with a polishing surface of a polishing medium while removing the conductive material.

12. The method of claim 10, further comprising changing a rate at which material is removed from the microelectronic substrate based at least in part on the change in the second electrical signal.

13. The method of claim 10, further comprising ceasing to remove material from the microelectronic substrate based at least in part on the change in the second electrical signal.

14. The method of claim 10 wherein superimposing the second electrical signal includes superimposing a variable second electrical signal.

15. The method of claim 10 wherein detecting a change in the second electrical signal includes detecting a change in at least one of a voltage, current and power of the second electrical signal.

16. A method for detecting characteristics of a microelectronic substrate, comprising: positioning the microelectronic substrate proximate to and spaced apart from a pair of spaced apart electrodes; contacting the microelectronic substrate with a polishing surface of a polishing medium; after contacting the microelectronic substrate with the polishing surface and before polishing the microelectronic substrate with the polishing medium, passing a variable electrical signal through the pair of electrodes and the microelectronic substrate while the microelectronic substrate contacts the polishing surface; and detecting a characteristic of the electrical signal corresponding to a characteristic of the microelectronic substrate.

17. The method of claim 16 wherein the electrical signal is the second of two electrical signals and wherein the method further comprises determining the presence of an exposed conductive layer of the microelectronic substrate based on the characteristic of the second electrical signal and removing at least a portion of the conductive layer by passing the first electrical signal through the electrodes and the conductive layer after passing the second electrical signal.

18. The method of claim 16 wherein the electrical signal is the second of two electrical signals, and wherein the pair of electrodes is the second of two pairs of electrodes, and wherein the method further comprises determining the presence of a conductive layer on the microelectronic substrate based on the characteristic of the second electrical signal passing through the second pair of electrodes and removing at least a portion of the conductive layer by passing the first electrical signal through a first pair of electrodes and through the conductive layer after passing the second electrical signal.

19. The method of claim 16 wherein detecting a characteristic of the electrical signal includes detecting at least one of a current, voltage and power of the electrical signal.

20. The method of claim 16, further comprising moving at least one of the microelectronic substrate and the pair of electrodes relative to the other while passing the electrical signal.

21. The method of claim 16, further comprising fixing the location of the microelectronic substrate relative to the pair of electrodes while passing the electrical signal.

22. A method for detecting electrical characteristics of a polishing pad for microelectronic substrates, comprising: disposing an electrolytic liquid on the polishing pad; contacting a polishing surface of the polishing pad with a generally non-conductive surface of a planar contact member; passing an electrical signal through a first electrode, a second electrode and the electrolytic liquid while the first and second electrodes are positioned at least proximate to the polishing surface, and while the first and second electrodes are spaced apart from each other and the contact member; determining a characteristic of the electrical signal; and detecting an electrical characteristic of the polishing pad based on the characteristic of the electrical signal.

23. The method of claim 22 wherein detecting a characteristic of the polishing pad includes detecting a presence of a conductive material on or in the polishing pad.

24. The method of claim 22 wherein detecting a characteristic of the polishing pad includes detecting a presence of a conductive material removed from a microelectronic substrate.

25. The method of claim 22 wherein determining a characteristic of the electrical signal includes detecting at least one of a voltage, a current and a power of the electrical signal.

26. An apparatus for removing material from a microelectronic substrate, comprising: a carrier configured to support a microelectronic substrate; a polishing pad proximate to the carrier and having a polishing surface to contact the microelectronic substrate, at least one of the polishing pad and the carrier being movable relative to the other; first and second electrodes positioned proximate to the polishing surface; at least one electrical signal transmitter coupled to the first and second electrodes, the at least one electrical signal transmitter being configured to transmit first and second electrical signals to the microelectronic substrate via the first and second electrodes, the first signal being a varying signal to remove material from the microelectronic substrate, the second signal being a diagnostic signal; and a sensor coupled to the first and second electrodes and the at least one signal transmitter, the sensor being configured to detect a characteristic of the second signal.

27. The apparatus of claim 26 wherein the first and second electrodes are recessed from the polishing surface.

28. The apparatus of claim 26 wherein the first and second electrodes includes a first electrode pair and wherein the apparatus further comprises a second electrode pair positioned proximate to the polishing surface.

29. The apparatus of claim 26 wherein the polishing pad includes an elongated web.

30. The apparatus of claim 26 wherein the sensor is configured to detect at least one of a voltage, a current and a power.

31. The apparatus of claim 26 wherein the polishing pad is carried by a support the sensor is operatively coupled to at least one of the support and the carrier to control motion of the at least one of the support and the carrier.

32. The apparatus of claim 26 wherein the at least one electrical signal transmitter includes a first signal transmitter configured to transmit the first electrical signal and a second signal transmitter configured to transmit the second electrical signal.

33. The apparatus of claim 26, further comprising third and fourth electrodes, and wherein the at least one signal transmitter includes a first signal transmitter coupled to the first and second electrodes to transmit the first electrical signal, and a second signal transmitter coupled to the third and fourth electrodes to transmit the second electrical signal.

34. An apparatus for removing material from a microelectronic substrate, comprising: a carrier configured to support a microelectronic substrate; a polishing pad proximate to the carrier and having a polishing surface to contact the microelectronic substrate, at least one of the polishing pad and the carrier being movable relative to the other; first and second electrodes positioned at least proximate to the polishing surface; at least one electrical signal transmitter coupled to the first and second electrodes, the at least one electrical signal transmitter being configured to simultaneously transmit first and second electrical signals to the microelectronic substrate via the first and second electrodes, the first signal being a varying signal to remove material from the microelectronic substrate, the second signal being a diagnostic signal and being superimposed on the first signal; and a sensor coupled to the first and second electrodes and the at least one electrical signal transmitter, the sensor being configured to detect a characteristic of the second signal.

35. The apparatus of claim 34 wherein the first and second electrodes are recessed from the polishing surface.

36. The apparatus of claim 34 wherein the first and second electrodes include a first electrode pair and wherein the apparatus further comprises a second electrode pair positioned proximate to the polishing surface.

37. The apparatus of claim 34 wherein the polishing pad includes an elongated web.

38. The apparatus of claim 34 wherein the polishing pad is carried by a support, and wherein at least one of the support and the carrier is coupled to a drive unit, further wherein the sensor is operatively coupled to the drive unit to control motion of the at least one of the support and the carrier.

Description

TECHNICAL FIELD

This invention relates to methods and apparatuses for electrically detecting characteristics of microelectronic substrates and/or polishing media for removing material from microelectronic substrates.

BACKGROUND

Microelectronic substrates and substrate assemblies typically include a semiconductor material having features, such as memory cells, that are linked with conductive lines. The conductive lines can be formed by first forming trenches or other recesses in the semiconductor material, and then overlaying a conductive material (such as a metal) in the trenches. The conductive material is then selectively removed to leave conductive lines extending from one feature in the semiconductor material to another.

Electrolytic techniques have been used to both deposit and remove metallic layers from semiconductor substrates. For example, an alternating current can be applied to a conductive layer via an intermediate electrolyte to remove portions of the layer. In one arrangement, shown in FIG. 1, a conventional apparatus 60 includes a first electrode 20a and a second electrode 20b coupled to a current source 21. The first electrode 20a is attached directly to a metallic layer 11 of a semiconductor substrate 10 and the second electrode 20b is at least partially immersed in a liquid electrolyte 31 disposed on the surface of the metallic layer 11 by moving the second electrode downwardly until it contacts the electrolyte 31. A barrier 22 protects the first electrode 20a from direct contact with the electrolyte 31. The current source 21 applies alternating current to the substrate 10 via the electrodes 20a and 20b and the electrolyte 31 to remove conductive material from the conductive layer 11. The alternating current signal can have a variety of wave forms, such as those disclosed by Frankenthal et al. in a publication entitled, "Electroetching of Platinum in the Titanium-Platinum-Gold Metallization on Silicon Integrated Circuits" (Bell Laboratories), incorporated herein in its entirety by reference.

One drawback with the arrangement shown in FIG. 1 is that it may not be possible to remove material from the conductive layer 11 in the region where the first electrode 20a is attached because the barrier 22 prevents the electrolyte 31 from contacting the substrate 10 in this region. Alternatively, if the first electrode 20a contacts the electrolyte in this region, the electrolytic process can degrade the first electrode 20a. Still a further drawback is that the electrolytic process may not uniformly remove material from the substrate 10. For example, "islands" of residual conductive material having no direct electrical connection to the first electrode 20a may develop in the conductive layer 11. The residual conductive material can interfere with the formation and/or operation of the conductive lines, and it may be difficult or impossible to remove with the electrolytic process unless the first electrode 20a is repositioned to be coupled to such "islands."

One approach to addressing some of the foregoing drawbacks is to attach a plurality of first electrodes 20a around the periphery of the substrate 10 to increase the uniformity with which the conductive material is removed. However, islands of conductive material may still remain despite the additional first electrodes 20a. Another approach is to form the electrodes 20a and 20b from an inert material, such as carbon, and remove the barrier 22 to increase the area of the conductive layer 11 in contact with the electrolyte 31. However, such inert electrodes may not be as effective as more reactive electrodes at removing the conductive material, and the inert electrodes may still leave residual conductive material on the substrate 10.

FIG. 2 shows still another approach to addressing some of the foregoing drawbacks in which two substrates 10 are partially immersed in a vessel 30 containing the electrolyte 31. The first electrode 20a is attached to one substrate 10 and the second electrode 20b is attached to the other substrate 10. An advantage of this approach is that the electrodes 20a and 20b do not contact the electrolyte. However, islands of conductive material may still remain after the electrolytic process is complete, and it may be difficult to remove conductive material from the points at which the electrodes 20a and 20b are attached to the substrates 10. A further problem with the approaches described above with reference to both FIGS. 1 and 2 is that it may be difficult to accurately determine when the desired amount of material has been removed from the substrate 10.

SUMMARY

The present invention is directed toward methods and apparatuses for detecting characteristics of a microelectronic substrate and/or a polishing medium. A method in accordance with one aspect of the invention includes positioning a microelectronic substrate proximate to and spaced apart from a first electrode and a second electrode, with the first and second electrodes being spaced apart from each other. The microelectronic substrate is contacted with a polishing surface of a polishing medium, and conductive material is removed from the microelectronic substrate by moving at least one of the microelectronic substrate and the electrodes relative to the other while passing a variable electrical signal through the electrodes and at least a portion of the microelectronic substrate. The method can further include detecting a change in the electrical signal corresponding to a change in the amount of conductive material remaining on the microelectronic substrate, and changing a rate at which material is removed from the microelectronic substrate based at least in part on the change in the electrical signal.

In a further aspect of the invention, the method can include ceasing to remove conductive material from the microelectronic substrate when the electrical signal changes by or to a target value. In another aspect of the invention, two signals are transmitted to the microelectronic s