Variable quadruple electromagnet array in plasma processing

• US 20050263389A1
• Filed: 09/23/2004
• Published: 12/01/2005
• Est. Priority Date: 05/26/2004
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Gung, Tza-Jing, Perrin, Mark A., Gillard, Andrew
• Granted Patent: US 7,527,713 B2
• Time in Patent Office: Days
• US Class Current: 204/192.120
• CPC Class Codes: H01J 37/32688 Multi-cusp fields
• CPC Class Codes: H01J 37/3408 Planar magnetron sputtering

Abstract

A quadruple electromagnetic coil array coaxially arranged in a rectangular array about a chamber axis outside the sidewalls of a plasma sputter reactor, preferably in back of an RF coil within the chamber. The coil currents can be separately controlled to produce different magnetic field distributions, for example, between a sputter deposition mode in which the sputter target is powered to sputter target material onto a wafer and a sputter etch mode in which the RF coil supports the gas sputtering the wafer. The coil array may include a tubular magnetic core, particularly useful for suppressing stray fields. A water cooling coil may be wrapped around the coil array to cool all the coils. The electromagnets can be powered in different relative polarities in a multi-step process.

Claims

1. In a plasma processing reactor having a substrate support disposed in a plane perpendicular to a central axis of a vacuum chamber, an array of separately controllable electromagnetic coils arranged about said central axis, at least two of the coils being disposed at different radii from the central axis.

2. The array of claim 1 having four coils arranged in a rectangular pattern.

3. The array of claim 2, wherein two of said coils located closer to said substrate support have at least 50% more turns than radially corresponding ones of two of said coils located farther away from said substrate support.

4. The array of claim 1, further comprising a magnetic core disposed between said at least two coils.

5. The array of claim 1, wherein said reactor includes a sputtering target arranged in opposition to said substrate support along said central axis.

6. The array of claim 5, incorporated into an adaptor forming a portion of said chamber between said target and said substrate support.

7. The array of claim 1, further comprising a multi-wrap cooling coil thermally contacting at least two of said coils.

8. The array of claim 1, wherein currents in said at least two coils circulate in opposite directions about said central axis.

9. The array of claim 8, wherein said levels of said currents are chosen to reduce stray fields outside of said chamber.

10. An array of electromagnetic coils fixed in an assembly and having both ends of all of said coils available on an outside of said assembly.

11. The array of claim 10, wherein said electromagnetic coils are fixed in said assembly by an adhesive.

12. The array of claim 10, comprising four of said electromagnetic coils arranged in a rectangular array and wrapped about an axis.

13. The array of claim 12, wherein a magnetic core separates radially inner ones of said electromagnetic coils from radially outer ones of said electromagnetic coils.

14. A quadruple array comprising four electromagnetic coils in an assembly annular about an axis in a rectangular pattern and configured for being disposed outside and around the wall of a plasma processing reactor.

15. The array of claim 14, further comprising a magnetic core disposed between radially inner ones of said coils and radially outer ones of said coils.

16. The array of claim 15, wherein all of said coils are separated from each other within said assembly to allow magnetic field to form therebetween.

17. The array of claim 14, further comprising a single helically wound fluid cooling helically wound coil in thermal contact with said four electromagnetic coils.

18. The array of claim 14, wherein all of said coils are separated from each other within said assembly to allow magnetic field to form therebetween.

19. The array of claim 14, further comprising an adapter around which said electromagnetic coils are wound and configured to form part of a vacuum chamber of said plasma processing reactor.

20. A plasma processing reactor, comprising:

a chamber body arranged generally symmetrically about a central axis;

a support for supporting within said reactor a substrate to be plasma processed on a front face thereof; and

an array of a plurality of electromagnets wound about said chamber body at at least two radii from said central axis and at a axial distance displaced above said front face, at least some of said electromagnets being independently powerable.

21. The reactor of claim 20, wherein said array comprises three of said electromagnets arranged as a triangular array.

22. The reactor of claim 20, wherein said array comprises four of said electromagnets arranged in a rectangular array.

23. The reactor of claim 24, further comprising a terminal structure including eight accessible and reconfigurable electrical connections to opposed ends of said four electromagnets.

24. The reactor of claim 22, further comprising:

a sputtering target fixed to said chamber and arranged about said central axis.

25. The reactor of claim 24, further comprising an RF coil disposed to overlap said array along said central axis.

26. The reactor of claim 21, further comprising:

a sputtering target fixed to said chamber and arranged about said central axis.

27. The reactor of claim 26, further comprising an RF coil disposed to overlap said array along said central axis.

29. An adapter and electromagnet assembly, comprising:

an adapter body generally arranged about a central axis and configured to be vacuum sealed to a plasma processing chamber with said central axis being perpendicular to a surface of a substrate to be processed; and

a plurality of electromagnetic coils wound on an exterior of said adapter body at at least two radii from said central axis and each having two leads accessible from an exterior of said coils.

30. The assembly of claim 29, comprising four of said electromagnetic coils arranged in a rectangular pattern about said central axis.

31. The assembly of claim 29, further comprising a tubular spacer arranged between an inner two of said coils and an outer two of said coils.

32. The assembly of claim 29, further comprising a fluid cooling channel formed in a body arranged around central axis and contacting at least two of said four electromagnets on a radially outer side thereof.

33. The assembly of claim 31, wherein said body comprises aluminum.

34. The assembly of claim 31, wherein said body comprises a helically wound rectangular member having said cooling channel formed therein.

35. The method of claim 34, wherein said reactor is a sputtering chamber including a sputtering target arranged in opposition to said substrate support with said coils axially disposed therebetween.

36. The method of claim 35, wherein at least one of said steps includes sputter depositing a material of said target onto said substrate.

37. The method of claim 36, wherein said array comprises four coils in a rectangular array.

38. The method of claim 34, wherein a third step includes passing counter-rotating currents through upper and lower ones of said coils and a fourth step includes passing counter-rotating currents through inner and outer ones of said coils.

34-1. A method of operating a plasma reactor including a chamber arranged around a central axis, a substrate support for supporting a substrate to be processed, and an array of a plurality of electromagnetic coils wound around said central axis in a vicinity of said chamber, said method comprising the steps of:

a first step including passing co-rotating currents through at least two of said coils to process said substrate; and

a second step including passing counter-rotating currents through said at least two coils to process said substrate.