Externally excited multiple torroidal plasma source

• US 6,494,986 B1
• Filed: 08/11/2000
• Issued: 12/17/2002
• Est. Priority Date: 08/11/2000
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Tanaka, Tsutomu, Ye, Yan, Ramaswamy, Kartik, Hanawa, Hiroji, Nguyen, Andrew, Collins, Kenneth S
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): HASSANZADEH, PARVIZ
• Application Number:
  US09/636,435
• Time in Patent Office: 858 Days
• Field of Search: 156/345.35, 156/345.48, 156/345.49, 118/723.IR, 118/723.I, 118/723.ER, 118/723.E, 118/723.AN, 315/111.51, 315/111.71, 315/111.21
• US Class Current: 156/345.35
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma

Abstract

A plasma reactor for processing a workpiece, including an enclosure defining a vacuum chamber, a workpiece support within the enclosure facing an overlying portion of the enclosure, the enclosure having at least first and second pairs of openings therethrough near generally opposite sides of the workpiece support. At least first and second hollow conduits are connected to respective pairs of the openings to provide at least first and second closed torroidal paths through the respective conduits and extending between respective pairs of the openings across the wafer surface. A process gas supply is coupled to the interior of the chamber for supplying process gas to the torroidal paths. Coil antennas are coupled to RF power sources and inductively coupled to the interior of the hollow conduits and capable of maintaining a plasma in the torroidal paths.

Claims

1. A plasma reactor for processing a workpiece, said plasma reactor comprising:

an enclosure;

a workpiece support within the enclosure facing an overlying portion of the enclosure, said workpiece support and the overlying portion of said enclosure defining a process region therebetween extending generally across the diameter of said wafer support;

said enclosure having at least first and second openings therethrough near generally opposite sides of said workpiece support;

at least one hollow conduit outside of said process region and connected to said first and second openings, providing a first torroidal path extending through said conduit and across said process region;

a first coil antenna adapted to accept RF power, and inductively coupled to the interior of said hollow conduit and capable of maintaining a plasma in said torroidal path;

at least third and fourth openings therethrough near generally opposite sides of said workpiece support and disposed along an axis transverse to an axis of said first and second openings extending therebetween;

a second hollow conduit generally transverse to said one hollow conduit and disposed outside of said process region and connected to said third and fourth openings, whereby to provide a second closed torroidal path, said second torroidal path extending outside of said process region through said second conduit and extending across said process region between said third and fourth openings in a direction transverse to said first torroidal path.

2. The reactor of claim 1 wherein:

the axis of said third and fourth openings is orthogonal to the axis of said first and second openings and wherein said first and second torroidal paths extend across said wafer surface in mutually orthogonal directions.

3. The reactor of claim 1 further comprising:

a second coil antenna capable of being coupled to an RF power source and inductively coupled to the interior of said second hollow conduit and capable of maintaining a plasma current in said second torroidal path.

4. The reactor of claim 3 further comprising:

a second RF power source coupled to said second coil antenna.

5. The reactor of claim 4 wherein said first and second RF power sources provide RF signals that are of the same frequency and of different phases.

6. The reactor of claim 5 wherein the phase difference between said RF signals is such that the plasma currents across the surface of said workpiece support rotate in the plane of said workpiece support at said same frequency.

7. The reactor of claim 4 wherein said RF signals are of different frequencies.

8. The reactor of claim 7 wherein said different frequencies are high frequencies on the order of about 10 MHz and separated from one another by about 1 MHz.

9. The reactor of claim 3 further comprising:

first and second magnetic cores between said enclosure and respective ones of said first and second conduits.

10. The reactor of claim 9 wherein said first and second coil antennas are wound around respective ones of said first and second magnetic cores.

11. The reactor of claim 1 wherein each of said first and second conduits has a width along an axis parallel with the plane of said wafer support which is at least as great as the diameter of said wafer support.

12. The reactor of claim 11 wherein each of said first and second conduits has a height along an axis perpendicular to the plane of said wafer support which is less than said width.

13. The reactor of claim 12 wherein each of said first and second conduits has a rectangular cross-section whereby to produce first and second wide belts of plasma in said closed torroidal path that intersect over said workpiece support.

14. The reactor of claim 1 wherein the heights of said first and second closed torroidal paths along an axis generally perpendicular to a plane of said wafer support in a process region overlying said workpiece support is less than elsewhere in said first and second closed torroidal paths respectively, whereby to enhance the plasma density in said process region relative to the density elsewhere in said first and second closed torroidal paths.

15. The plasma reactor of claim 1 wherein said first and second hollow conduits comprise a continuous plenum extending around the axis of symmetry of said chamber and wherein said first and second openings are comprised within a continuous opening in said enclosure extending around the axis of symmetry of said chamber.

16. The plasma reactor of claim 15 wherein said plenum and said continuous opening extend 360 degrees around the axis of symmetry of said chamber.

17. The reactor of claim 16 further comprising:

a second coil antenna capable of being coupled to an RF power source and inductively coupled to the interior of said plenum and capable of maintaining a plasma current in said second torroidal path, said first and second coil antennas being located between said plenum and said vacuum enclosure of said chamber.

18. The plasma reactor of claim 17 wherein said plenum is formed of a metal material, said plenum having an insulating gap extending transversely to said torroidal path and separating said plenum into two portions so as to prevent formation of a closed electrical path along the length of said plenum.

19. The plasma reactor of claim 17 wherein each of said first and second coil antennas is wound around an axis generally parallel with the axis of a respective one of said first and second closed torroidal paths.

20. The plasma reactor of claim 17 wherein said first and second coil antennas are driven by respective RF power signals of at least nearly the same frequency and of different phases so as to produce a rotating plasma current in the process region overlying said workpiece support.

21. The plasma reactor of claim 20 wherein the phase difference between the two RF power signals is 90 degrees.

22. The plasma reactor of claim 21 further comprising:

a third coil antenna capable of being coupled to an RF power source and inductively coupled to the interior of said plenum and capable of maintaining a plasma current in a third torroidal path transverse to said first and second torroidal paths, said first and second and third coil antennas being located between said plenum and said vacuum enclosure of said chamber.

23. The plasma reactor of claim 22 wherein said first, second and third antennas are driven by respective RF signals of at least nearly the same frequency and of different phases so as to produce a rotating plasma current in the processing region overlying said workpiece support.

24. The plasma reactor of claim 17 wherein said coil antenna comprises n separately driven windings wound about n axes disposed at respective angles of 360/n degrees about the axis of symmetry of said chamber.

25. The plasma reactor of claim 24 wherein said n windings are driven by respective RF signals of at least nearly the same frequency and of different phases to produce a rotating plasma current in the process regions overlying said workpiece support.

26. The plasma reactor of claim 25 further comprising:

a central access conduit extending through said plenum from an exterior wall of said plenum to an interior wall of said plenum to provide access to said windings located between said plenum and said vacuum enclosure.

27. The plasma reactor of claim 26 further comprising conductors connected to said windings for coupling said windings to RF power signals.

28. The plasma reactor of claim 27 further comprising n magnetic cores having respective horizontal sections lying along respective directions in a lateral plane parallel to the plane of said wafer support and respective longitudinal section extending from corresponding horizontal sections up through said access conduit and having external sections extending above said access conduit.

29. The plasma reactor of claim 28 wherein said n windings are wound around the external sections of respective ones of said n magnetic cores.

30. The plasma reactor of claim 29 wherein the respective horizontal sections of said n magnetic cores are disposed at uniformly distributed angular directions within said horizontal plane.

31. The reactor of claim 1 wherein said conduits are non-intersecting whereby the torroidal paths intersect only within the process region.

32. The reactor of claim 1 further comprising a pair of plural radial vanes between each of said openings and an adjacent edge of said workpiece support for guiding a plasma current between said process region and the respective opening.