Cluster tool soft etch module and ECR plasma generator therefor

• US 5,280,219 A
• Filed: 04/16/1993
• Issued: 01/18/1994
• Est. Priority Date: 05/21/1991
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Materials Research Corporation (Linde Plc)
• Inventors: Ghanbari, Ebrahim
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US08/050,726
• Time in Patent Office: 277 Days
• Field of Search: 315/111.21, 315/111.41, 315/111.81, 313/231.31, 204/298.38, 204/298.37, 204/298.16
• US Class Current: 315/111.41
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32623 Mechanical discharge control means
• CPC Class Codes: H01J 37/32678 Electron cyclotron resonance
• CPC Class Codes: H01J 37/32688 Multi-cusp fields
• CPC Class Codes: H05H 1/18 wherein the fields oscillate at very high frequency, e.g. in the microwave range , e.g. using cyclotron resonance

Abstract

An electron cyclotron resonance plasma generator is provided in a semiconductor wafer plasma processing apparatus and cluster tool module, particularly for use in soft etching. The generator generates a uniform plasma by rotating a plasma producing resonance supporting magnetic field about the axis of a resonance cavity within the vacuum chamber of a plasma processor. The rotated field preferably is a single-cusp or multicusp field. Gas uniformly flows into and through the cavity from a gas distribution shower. Microwave energy is evenly divided and coupled into the cavity in a TM₀₁ mode by a plurality of axially and radially aligned loops.

Claims

1. A silicone wafer plasma processing apparatus comprising:

a sealed chamber containing a gas and having a wafer transferring port in a wall thereof communicating with a vacuum transfer chamber of a wafer transfer module of a wafer processing cluster tool, the port having a valve therein for sealing the sealed chamber from the transfer chamber;

a high vacuum pump having an inlet communicating with the sealed chamber so as to produce a vacuum pressure level in the gas in the sealed chamber;

a plasma generation cavity in the sealed chamber;

a wafer holder to support the wafer with a side thereof facing the cavity;

a source of microwave energy;

means for coupling the microwave energy from the source into the cavity;

a magnet assembly including a plurality of magnets positioned around the cavity, the magnets having a strength and configuration for producing a plurality of magnetic field portions each sufficient in strength to produce electron cyclotron resonance in the cavity to generate a plasma of the gas, the field portions defining regions at which the plasma the plasma is located within the cavity; and

,

means for rotating the assembly, including the magnets, as a unit around the cavity to rotate the field portions, the regions and the plasma therewith within the cavity.

2. The etch apparatus of claim 1 wherein:

the magnets are configured, positioned and oriented to produce at least one cusp in the magnetic field that defines the location of plasma generation, the rotation of the magnets causing a rotation of the cusp and rotation of the plasma about an approximate centerline of the cavity.

3. The apparatus of claim 2 wherein:

the magnets are configured, positioned and oriented to produce a single-cusp magnetic field in which the cusp separates two annular longitudinally spaced plasma generation field portions, the rotation of the magnets causing the rotation of the cusp and the rotation of the plasma about the approximate centerline of the cavity.

4. The apparatus of claim 3 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of the cavity, each with a polar axis that generally intersects the centerline of the cavity, and each oriented with the same pole toward the centerline of the cavity, to produce the single-cusp magnetic field in the cavity.

5. The apparatus of claim 2 wherein:

the magnets are configured, positioned and oriented to produce a multicusp magnetic field having a plurality of cusps, each separating a plurality of longitudinal axially spaced plasma generation regions, the rotation of the magnets causing rotation of the cusps, rotation of the longitudinal plasma generation regions and rotation of the plasma about the approximate centerline of the cavity.

6. The apparatus of claim 5 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of a tubular wall of the cavity, each with a polar axis that generally intersects the centerline of the cavity, the orientation of the magnets alternating an even number of times about the centerline of the cavity, to produce the multicusp magnetic field in the cavity.

7. The apparatus of claim 1 wherein:

the cavity has a closed end having a gas introduction port therein and a plurality of gas inlet holes in fluid communication with the gas introduction port, the holes being distributed in a pattern so as to uniformly introduce gas into the cavity uniformly across the closed end of the cavity.

8. The apparatus of claim 1 wherein:

a cavity is cylindrical and has an axis constituting the centerline thereof, the magnets rotation means being operative to rotate the magnets about the axis of the cylindrical cavity, the wafer holder being positioned so as to center the wafer held thereby on the axis.

9. The apparatus of claim 8 wherein:

the source includes a transmission line connected to the cavity; and

the coupling means includes a plurality of loops, each electrically connected to the transmission line so as to couple equal amounts of microwave energy into the cavity, the loops being spaced around the axis of the cavity, the loops being shaped and oriented to produce a TM₀₁ mode of excitation by the microwave energy in the cavity.

10. The apparatus of claim 9 wherein:

the cavity is shaped and dimensioned such that the microwave energy, when coupled into the sealed chamber, forms a TM₀₁₁ mode of excitation in the cavity.

11. A silicone wafer plasma processing apparatus comprising:

a sealed chamber;

means for supplying gas to the chamber;

vacuum pump means for reducing the gas within the chamber to a vacuum pressure level;

a plasma generation cavity in the chamber;

a wafer holder mounted in the chamber for supporting thereon a wafer to be processed;

a source of microwave energy coupled into the cavity;

rotatable magnet means positioned around the cavity, the magnet means including a rotatable assembly of a plurality of magnets, the rotatable assembly having magnets of a strength and configuration for producing a magnetic field within the cavity having a sufficient strength to produce electron cyclotron resonance at regions within the cavity to thereby produce a plasma in the regions; and

,

means for rotating the entire assembly and magnets thereof as a unit around the cavity to rotate the fields, the regions at which the electron cyclotron resonance is produced and the plasma in the regions within the cavity.

12. The wafer processing apparatus of claim 11 wherein:

the magnets are configured, positioned and oriented to produce at least one cusp in the magnetic field that defines the location of the regions in which the electron cyclotron resonance is produced, the rotation of the magnets causing a rotation of the cusp, the rotation of the regions and rotation of the plasma about an approximate centerline of the cavity.

13. The apparatus of claim 12 wherein:

the magnets are configured, positioned and oriented to produce a single-cusp magnetic field in which the cusp separates two annular longitudinally spaced plasma generation field portions, the rotation of the magnets causing the rotation of the cusp and the rotation of the plasma about the approximate centerline of the cavity.

14. The apparatus of claim 13 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of the cavity, each with a polar axis that generally intersects the centerline of the cavity, and each oriented with the same pole toward the centerline of the cavity, to produce the single-cusp magnetic field in the cavity.

15. The apparatus of claim 12 wherein:

the magnets are configured, positioned and oriented to produce a multicusp magnetic field having a plurality of cusps, each separating a plurality of longitudinal axially spaced plasma generation regions, the rotation of the magnets causing rotation of the cusps, rotation of the longitudinal plasma generation regions and rotation of the plasma about the approximate centerline of the cavity.

16. The apparatus of claim 15 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of a tubular wall of the cavity, each with a polar axis that generally intersects the centerline of the cavity, the orientation of the magnets alternating an even number of times about the centerline of the cavity, to produce the multicusp magnetic field in the cavity.

17. The apparatus of claim 11 wherein:

the cavity has means at one end thereof for introducing an axial flow of gas into the cavity uniformly distributed therein.

18. The apparatus of claim 11 wherein:

the cavity is cylindrical and has an axis constituting a centerline thereof, the magnets rotation means being operative to rotate the magnets about the axis of the cylindrical cavity, the wafer holder being positioned to center the wafer on the axis.

19. The apparatus of claim 18 further comprising:

coupling means for coupling microwave energy from the source into the cavity, including a plurality of loops, each electrically connected between the source and the cavity so as to couple equal amounts of microwave energy into the cavity, the loops being spaced around the centerline of the cavity, the loops being shaped and oriented to produce a TM₀₁ mode of excitation by the microwave energy in the cavity.

20. A plasma generator for a semiconductor wafer plasma processor comprising:

a vacuum chamber having a tubular side wall, a gas introduction port, a gas evacuation port, and a plasma generating cavity surrounded in part by the tubular wall thereof;

a microwave energy source having an output connected to thereto;

means for coupling from the output into the cavity microwave energy from the source;

a rotatable assembly including a plurality of magnets spaced outside of the tubular wall of the cavity and rotatably mounted with respect thereto, the magnets being oriented and configured to generate a magnetic field within the cavity, the magnetic field being of sufficient strength and configuration to produce electron cyclotron resonance within the cavity in a plurality of distinct plasma generation regions where the plasma is produced, the field having magnetic lines of force defining the shape and location of the regions; and

,

means for rotating the assembly, including the magnets as a unit to rotate the magnetic field, the regions and the plasma about an approximate centerline of the cavity.

21. The plasma generator of claim 20 wherein:

the magnets are configured, positioned and oriented to produce at least one cusp in the magnetic field that defines the position of the plasma generation regions, the rotation of the magnets causing rotation of the cusp, rotation of the plasma generation regions and rotation of the plasma about the approximate centerline of the cavity.

22. The plasma generator of claim 20 wherein:

the magnets are configured, positioned and oriented to produce a single-cusp magnetic field in which the cusp separates two annular plasma generation portions longitudinally spaced from each other and extending around the centerline of the cavity, the rotation of the magnets causing a rotation of the cusp and rotation of the plasma generation regions about the approximate centerline of the cavity.

23. The plasma generator of claim 22 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of the tubular wall of the cavity, each with a polar axis that generally intersects the centerline of the cavity, and each oriented with the same pole toward the centerline of the cavity to produce the single-cusp magnetic field.

24. The plasma generator of claim 21 wherein:

the magnets are configured, positioned and oriented to produce a multicusp magnetic field having a plurality of cusps in an array around the centerline of the cavity, each cusp separating two adjacent circumferentially spaced plasma generation regions, the rotation of the magnets causing rotation of the cusps, rotation of the plasma generation regions and the rotation of the plasma about the approximate centerline of the cavity.

25. The plasma generator of claim 24 wherein:

the magnets include a plurality of permanent magnets spaced around the outside of the cavity, each with a polar axis that generally intersects the centerline of the cavity, the orientation of the magnets alternating an even number of times about the centerline of the cavity to produce the multicusp magnetic field.

26. The plasma generator of claim 20 wherein:

the cavity has a closed end having the gas introduction port therein and a plurality of gas inlet holes therein distributed in a pattern about the approximate centerline of the cavity, the holes being in fluid communication with the gas introduction port, the cavity having an opening axially spaced from the closed end opposite the plasma generation regions, the cavity communicating with the gas evacuation port through the opening.

27. The plasma generator of claim 20 wherein:

the cavity is cylindrical and has an axis constituting the centerline of the cavity, the magnets rotation means being operative to rotate the magnets about the axis.

28. The plasma generator of claim 27 wherein:

the coupling means includes a plurality of loops, each electrically connected to the wall and spaced around the approximate centerline of the cavity, the loops being shaped and oriented to produce a TM₀₁ mode of excitation by the microwave energy in the cavity.

29. The plasma generator of claim 28 wherein:

the cavity is shaped and dimensioned such that the microwave energy, when coupled into the chamber, forms a TM₀₁₁ mode of excitation in the cavity.

30. The plasma generator of claim 28 wherein:

the transmission line has a power splitter connected therein to divide the microwave energy approximately equally among the loops.

31. The plasma generator of claim 28 wherein:

each of the loops lies in a different one of a plurality of radial planes each passing through and containing the axis of the cavity.

32. A method of plasma processing semiconductor wafers comprising the steps of:

supplying a gas at a vacuum pressure level within a chamber;

coupling microwave energy into a cavity within the chamber;

producing a magnetic field within the cavity with magnets located outside of the chamber;

producing, with the microwave energy and the magnetic field, electron cyclotron resonance in the gas at regions within the cavity;

generating a plasma at the regions within the cavity;

rotating the entire magnetic field with which the electron cyclotron resonance is produced, and thereby the regions and the plasma, about an axis of the cavity; and

,

processing with the rotated plasma a wafer positioned in the chamber.

33. The method of claim 32 wherein:

the magnetic field producing step includes the step of producing at least one magnetic cusp within the chamber; and

the field rotating step includes the step of rotating the magnetic cusp.

34. The method of claim 33 wherein:

the magnetic cusp producing step includes the step of producing a single magnetic cusp located in a plane through the cavity and the axis of the cavity.

35. The method of claim 33 wherein:

the magnetic cusp producing step includes the step of producing a plurality of magnetic cusps located in an array around the axis of the cavity.

36. The method of claim 32 wherein:

the cavity is dimensioned to support TM₀₁ mode of the energy within the cavity; and

the microwave energy coupling step includes the step of coupling the energy into the cavity in a TM₀₁ mode.

37. The method of claim 36 wherein:

the microwave energy coupling step includes the step of coupling the energy into the cavity through at least one loop lying in a plane containing the axis of the cavity.

38. The method of claim 36 wherein:

the microwave energy coupling step includes the step of coupling the energy into the cavity through a plurality of loops circumferentially spaced around the axis of the cavity and each lying in a plane through the axis of the cavity.

39. The method of claim 38 wherein:

the microwave energy coupling step includes the step of equally dividing the microwave energy among the plurality of loops.

40. The method of claim 32 wherein:

the gas supplying step includes the step of introducing a distribution of gas into the cavity uniformly about the axis distributed across the cross-section thereof, and causing the gas to flow parallel to the axis through the cavity in a direction toward and perpendicular to the wafer.