High density plasma CVD and etching reactor

• US 5,614,055 A
• Filed: 08/27/1993
• Issued: 03/25/1997
• Est. Priority Date: 08/27/1993
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Nowak, Romuald, Fairbairn, Kevin
• Primary Examiner(s): Breneman, R. Bruce
• Assistant Examiner(s): MCDONALD, RODNEY GLENN
• Application Number:
  US08/113,776
• Time in Patent Office: 1,306 Days
• Field of Search: 156/345, 156/643, 156/643.1, 204/192.32, 204/298.31, 204/298.33, 204/298.34, 204/298.37, 204/298.39, 118/715, 118/723 R, 118/723 MP, 118/723 MW, 118/723 ME, 118/723 MR, 118/723 MA, 118/723 AN, 118/723 E, 118/723 I, 118/723 IR, 427/569, 427/571, 427/585, 427/598, 427/574, 216/68, 216/71, 216/70
• US Class Current: 156/345.33
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

In one aspect, the invention is embodied in an RF inductively coupled plasma reactor including a vacuum chamber for processing a wafer, one or more gas sources for introducing into the chamber reactant gases, and an antenna capable of radiating RF energy into the chamber to generate a plasma therein by inductive coupling, the antenna lying in a two-dimensionally curved surface. In another aspect, invention is embodied in a plasma reactor including apparatus for spraying a reactant gas at a supersonic velocity toward the portion of the chamber overlying the wafer. In a still further aspect, the invention is embodied in a plasma reactor including a planar spray showerhead for spraying a reactant gas into the portion of the chamber overlying the wafer with plural spray nozzle openings facing the wafer, and plural magnets in an interior portion of the planar spray nozzle between adjacent ones of the plural nozzle openings, the plural magnets being oriented so as to repel ions from the spray nozzle openings. In yet another aspect, the invention is embodied in a plasma reactor including a conductive dome-shaped electrode overlying the wafer and being connectable to an electrical potential. In a still further aspect, the invention is embodied in a plasma process, including the steps of providing a vacuum processing chamber having a dome-shaped antenna, feeding a processing gas including an electronegative gas into the chamber, resonantly coupling an RF electrical signal to the antenna, and non-resonantly and inductively coupling electromagnetic energy from the antenna into a plasma formed in the processing chamber from the processing gas.

Claims

1. An RF inductively coupled plasma reactor for the processing of a wafer, said reactor comprising:

a vacuum chamber;

one or more gas sources for introducing into said chamber reactant gases;

an antenna capable of radiating RF energy into said chamber to generate a plasma therein by inductive coupling, said antenna comprising a substantially domed-shaped portion at least partially surrounding said plasma and a vertical cylindrical portion which underlies said substantially domed-shaped portion.

2. The reactor of claim 1 wherein a concave surface of said antenna is facing and symmetrically disposed relative to the top surface of said wafer.

3. The reactor of claim 1 wherein an axial height of the dome-shaped portion of the antenna is not less than 20% of the diameter of said vertical cylindrical portion.

4. The reactor of claim 3 wherein said vacuum chamber comprises a ceiling comprising a vertical cylindrical portion and an overlying dome-shaped portion corresponding respectively to the shapes of said vertical cylindrical and dome-shaped portions of said antenna and wherein said antenna comprises an elongate conductor embedded within said ceiling and coiled around a rotational axis of symmetry of said ceiling.

5. The reactor of claim 4 wherein said ceiling comprises a plurality of ceiling sections having decreasing radii of curvature from a top of said ceiling and being smoothly joined to each other.

6. The reactor of claim 1, wherein said substantially dome-shaped portion of the antenna has a circular void centered at the apex thereof.

7. The reactor of claim 6 wherein said void has a diameter on the order of between 25% and 100% of the diameter of said wafer.

8. The reactor of claim 6 further comprising:

an electrode insulated from said antenna and disposed in said void, said electrode being connectable to an electrical source.

9. The reactor of claim 8 wherein said electrode is connectable to an RF source during cleaning of said chamber.

10. The reactor of claim 4 wherein said coiled conductor has a length corresponding to a quarter wavelength of an RF signal applied to said antenna.

11. The reactor of claim 10 wherein said RF signal has an RF frequency between 400 kHz and 20 MHz.

12. The reactor of claim 1 wherein at least one of said reactant gases contributes both (a) ions to said plasma for sputter etching and (b) chemical species for chemical vapor deposition, and wherein plasma ion density across said wafer is sufficient so that the rate of said sputter etching on surfaces of the wafer which are not substantially one of (I) parallel, or (ii) perpendicular to an angle of incidence of the ions on the wafer is at least on the order of the rate of said chemical vapor deposition.

13. The reactor of claim 1 wherein at least one gas source comprises:

a plurality of elongate spray nozzles located within and thermally coupled to a vacuum containment wall of said vacuum chamber and extending toward said wafer with respective nozzle tips near the edge of said wafer.

14. The reactor of claim 13 wherein gas flow out of said nozzles is supersonic.

15. The reactor of claim 1 wherein at least one gas source comprises:

a closed tube inside said vacuum chamber and symmetrically disposed relative to said wafer and following an edge contour of said wafer so as to not overlie a substantial portion of said wafer, said closed tube having a plurality of spray openings therein facing an interior portion of said vacuum chamber overlying said wafer.

34. The plasma process of claim 1, wherein said RF electrical signal has a frequency within the range of 400 kHz to 20 MHz.

35. The plasma process of claim 34, wherein a pressure of said processing gas within said chamber is within a range of 1 to 30 milliTorr.

36. The reactor of claim 1 further comprising:

means for suppressing a capacitive coupling of the RF energy radiating from the antenna into the chamber.

37. The reactor of claim 36 wherein said suppressing means comprises:

a grounded Faraday shield disposed between the antenna and the plasma generated inside the vacuum chamber, said shield suppressing capacitive coupling between the antenna and the plasma.

38. The reactor of claim 37 wherein the shield comprises a dome-shaped shield corresponding to the shape of the antenna.

39. The reactor of claim 38 wherein the shield comprises:

a ring comprising a conductive film strip and forming a bottom of the dome-shaped shield, said ring positioned so as to be between a bottom portion of the antenna and the plasma; and

,

a plurality of conductive film strips, individual ones of which project periodically from the ring along a circumference thereof in a perpendicular direction and forming a top portion of the dome-shaped shield.

40. The reactor of claim 39 wherein each of the plurality of conductive film strips projecting from the ring is approximately 1 cm in width, and wherein a spacing between each of the plurality of strips along the circumference of the ring is approximately 0.1 cm.

41. The reactor of claim 1 wherein said vacuum chamber comprises a dome-shaped ceiling corresponding to the shape of the antenna.

42. The reactor of claim 41 wherein the dome-shaped ceiling comprises a heat-resistant interior layer and an exterior cooling layer.

43. The reactor of claim 42 wherein said antenna comprises an elongate conductor embedded within said exterior cooling layer and coiled around a rotational axis of symmetry of said ceiling.

44. The reactor of claim 41 wherein the heat resistant interior layer comprises quartz and the exterior cooling layer comprises a dielectric thermally conductive material.

16. A plasma reactor including means for holding a wafer in a vacuum chamber, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma in a portion of said chamber overlying said wafer; and

means for spraying a reactant gas at a supersonic velocity toward said portion of said chamber overlying said wafer, so as to produce a substantially uniform distribution of the reactant gas in said portion of the chamber.

17. The reactor of claim 16 wherein said means for supersonically spraying comprises a plurality of elongate supersonic spray nozzles.

18. The reactor of claim 17 wherein each one of said nozzles has an inner portion tapering radially inwardly and an outer portion tapering radially outwardly.

19. The reactor of claim 17 wherein said nozzles extend toward said wafer with respective nozzle tips having gas distribution inlet orifices up to but not overlying the edge of said wafer.

20. The reactor of claim 19 wherein said spray nozzles are thermally coupled to a vacuum containment wall of said vacuum chamber.

21. The reactor of claim 19 wherein supersonic gas flow from each nozzle forms an gas diffusion center displaced from the nozzle tip thereof to a location overlying said wafer.

22. The reactor of claim 19 wherein said orifices each have a size on the order of 10 mils and said chamber has a vacuum between 1 and 30 milliTorr.

23. A plasma reactor including means for holding a wafer in a vacuum chamber, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma in a portion of said chamber overlying said wafer;

a plurality of elongate spray nozzles thermally coupled to a vacuum containment wall of said vacuum chamber and extending away from said containment wall toward said wafer such that a distal end of each of said spray nozzles is disposed no closer to the wafer than an edge thereof, each spray nozzle comprising a nozzle tip having a gas distribution orifice at the distal end.

24. A plasma reactor including means for holding a wafer in a vacuum chamber, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma in a portion of said chamber overlying said wafer, said antenna comprising a substantially domed-shaped portion at least partially surrounding said plasma and a vertical cylindrical portion which underlies said substantially domed-shaped portion; and

,

a closed tube inside said vacuum chamber for spraying a reactant gas into said portion of said chamber overlying said wafer and symmetrically disposed relative to said wafer and following an edge contour of said wafer so as to not overlie a substantial portion of said wafer, said closed tube having a plurality of spray openings therein facing an interior portion of said vacuum chamber overlying said wafer.

25. A plasma reactor including means for holding a wafer in a vacuum chamber, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma in a portion of said chamber overlying said wafer;

a planar spray showerhead for spraying a reactant gas into said portion of said chamber overlying said wafer, said planar spray showerhead overlying an interior portion of said vacuum chamber over said wafer and having plural spray nozzle openings facing said wafer; and

plural magnets in an interior portion of said planar spray showerhead between adjacent ones of said plural nozzle openings, said plural magnets being oriented so as to repel ions from said spray nozzle openings.

26. The reactor of claim 25 wherein said nozzle openings are located in a range of about 25% to 50% of a wafer diameter from said wafer.

27. A plasma reactor including means for holding a wafer in a vacuum chamber for containing a processing gas, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma, said antenna comprising a substantially domed-shaped portion at least partially surrounding said plasma and a vertical cylindrical portion which underlies said substantially domed-shaped portion; and

,

a conductive dome-shaped electrode insulated from said antenna and overlying said wafer and being connectable to an electrical potential.

28. The reactor of claim 27 wherein said dome-shaped electrode comprises a portion of a ceiling of said chamber and is connected to ground during processing.

29. The reactor of claim 28 further comprising means for connecting said dome-shaped electrode to an RF power source during cleaning of said chamber.

30. A plasma process, comprising the steps of:

providing a vacuum processing chamber holding a workpiece to be processed and having on one side thereof an antenna comprising a substantially dome-shaped portion at least partially surrounding a plasma generating region and a vertical cylindrical portion which underlies said substantially domed-shaped portion;

feeding a processing gas including an electronegative gas into said processing chamber;

resonantly coupling an RF electrical signal to said antenna;

non-resonantly and inductively coupling electromagnetic energy from said antenna into a plasma formed in said plasma generating region of said processing chamber from said processing gas, whereby said workpiece is processed by said plasma.

31. The plasma process of claim 30, wherein said electronegative gas comprises oxygen gas.

32. The plasma process of claim 30 wherein said electronegative gas comprises a halogen.

33. The plasma process of claim 31, wherein said processing gas additionally comprises a precursor gas for silicon oxide.

45. A plasma reactor including means for holding a wafer in a vacuum chamber for containing a processing gas, comprising:

an antenna capable of radiating RF energy into said chamber to generate a plasma comprising ions; and

a ceiling overlying the wafer comprising at least two ceiling sections having decreasing radii of curvature from a top of the ceiling and being smoothly joined to each other thereby imparting a dome-shape to the ceiling, wherein the ceiling is further away from a center of the wafer than edges of the wafer so as to enhance a density of the plasma over the center of the wafer by providing more volume for diffusion of ions within the plasma thereby providing for a uniform distribution of ions throughout the plasma; and

wherein,

the ceiling is conductive and is connectable to ground during a sputter etching of the wafer so as to increase a rate of sputter etching.

46. The plasma reactor of claim 45 wherein the ceiling is further connectable to a RF power source during cleaning of the vacuum chamber.

47. An RF inductively coupled plasma reactor including means for holding a wafer in a vacuum chamber, said reactor comprising:

one or more gas sources for introducing into said chamber reactant gases;

an antenna capable of radiating RF energy into said chamber to generate a plasma therein by inductive coupling, said antenna comprising a substantially domed-shaped portion at least partially surrounding said plasma and a circular void centered at the apex of the domed-shaped portion, said. circular void further having a diameter in excess of 33% of the diameter of said wafer; and

an electrode insulated from said antenna and disposed in said void, said electrode being connectable to an electrical source.

48. The reactor of claim 47 wherein said electrode is connectable to an RF source during cleaning of said chamber.

49. An RF inductively coupled plasma reactor including means for holding a wafer in a vacuum chamber, said reactor comprising:

one or more gas sources for introducing into said chamber reactant gases;

an antenna capable of radiating RF energy into said chamber to generate a plasma therein by inductive coupling, said antenna comprising a substantially domed-shaped portion at least partially surrounding said plasma and a vertical cylindrical portion which underlies said substantially domed-shaped portion; and

,

a grounded Faraday shield disposed between the antenna and the plasma generated inside the vacuum chamber, said shield suppressing capacitive coupling between the antenna and the plasma.

50. The reactor of claim 49 wherein the shield comprises a dome-shaped shield corresponding to the shape of the antenna.

51. The reactor of claim 50 wherein the shield comprises:

a ring comprising a conductive film strip and forming a bottom of the dome-shaped shield, said ring positioned so as to be between a bottom portion of the antenna and the plasma; and

,

a plurality of conductive film strips, individual ones of which project periodically from the ring along a circumference thereof in a perpendicular direction and forming a top portion of the dome-shaped shield.

52. The reactor of claim 51 wherein each of the plurality of conductive film strips projecting from the ring is approximately 1 cm in width, and wherein a spacing between each of the plurality of strips along the circumference of the ring is approximately 0.1 cm.