RF induction plasma source for plasma processing

• US 5,430,355 A
• Filed: 07/30/1993
• Issued: 07/04/1995
• Est. Priority Date: 07/30/1993
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Paranjpe, Ajit P.
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US08/100,501
• Time in Patent Office: 704 Days
• Field of Search: 315/111.21, 315/111.41, 315/111.51, 315/111.81, 313/231.31
• US Class Current: 315/111.21
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

Plasma generator (10) includes chamber (14) for containing the plasma source and a plurality of coils (12) located inside of chamber (14). Located external to chamber (14) are a plurality of permanent multipolar magnets (34) operable to establish a magnetic field in the plasma source along the surface of chamber (14) and a set of electromagnets (36) located outside of chamber (14), which define a preferred propagation direction for a whistler wave in chamber (14). Coils (12) resonantly inductive couple RF power to the whistler wave so as to transfer a sufficient amount of energy to the plasma source to induce a plasma state in the plasma source. Coils (12) also generate time varying electromagnetic fields which also sustain the plasma state in the plasma source.

Claims

1. A plasma source for generating a plasma, comprising:

a chamber operable to confine the plasma and process gases;

a coil operable to generate a whistler wave in said chamber, said coil comprising a plurality of coils located inside of said chamber and positioned substantially parallel to sidewalls of said chamber, said plurality of coils shaped to match the contour of said chamber and connected by a connecting coil traversing a vertical axis of said chamber;

at least one set of electromagnets located outside of said chamber, said electromagnets operable to define a preferred propagation direction of the whistler wave in said chamber;

said coil further operable to inductively couple RF power to the whistler wave to excite the whistler wave and to transfer a sufficient amount of energy to the process gases in said chamber to induce a plasma state in the process gases.

2. The plasma source of claim 1, wherein said coil is further operable to resonantly inductive couple the RF power to the whistler wave to excite the whistler wave.

3. The plasma source of claim 1, wherein said coil is located inside of said chamber and positioned substantially parallel to sidewalls of said chamber.

4. The plasma source of claim 1, wherein said coil further comprises:

a first coil routed outside said chamber along a bottom of said chamber; and

a plurality of coils located outside of said chamber and substantially parallel to sidewalls of said chamber, said plurality of coils located between said electromagnets and said chamber.

5. The plasma source of claim 1, wherein said RF power is selected to be at a frequency between the ion and electron cyclotron frequencies of the process gases, the ion and electron cyclotron frequencies being less than the electron plasma frequency of the process gases.

6. The plasma source of claim 1, wherein said coil is operable to provide antennas of varying lengths for resonant inductive coupling of the RF power to the whistler wave over a range of conditions impacting the resonant inductive coupling of the RF power to the whistler wave, said coil further operable to generate time-varying magnetic fields which sustain the plasma state of the process gases.

7. The plasma source of claim 1, further comprising a plurality of permanent multipolar magnets located outside of said chamber, said magnets operable to establish a magnetic field along the surface of said chamber for confining the plasma.

8. The plasma source of claim 1, wherein said coil further comprises a passage for circulating coolant through said coil so as to cool said coil.

9. The plasma source of claim 1, wherein said coil is segmented with capacitors placed between adjacent coils operable to reduce the impedance of said coil.

10. A chamber operable for performing a plasma based process, the chamber containing process gases and securing a semiconductor wafer relative to a plasma source, comprising:

a plurality of permanent multipolar magnets located outside of the chamber, said magnets operable to establish a magnetic field along the surface of the chamber for confining a plasma;

a coil operable to generate a whistler wave in the chamber;

a set of electromagnets located outside of the chamber, said electromagnets operable to define a preferred propagation direction of the whistler wave in the chamber; and

said coil further operable to inductively couple RF power to the whistler wave to excite the whistler wave and transfer a sufficient amount of energy to the process gases to induce a plasma state in the process gases.

11. A method of inducing a plasma state in process gases in a chamber, comprising the steps of:

generating a whistler wave with a coil, said coil including a first coil outside the chamber and along a bottom of the chamber, and a plurality of coils outside the chamber and along and substantially parallel to sidewalls of the chamber;

generating a variable static electromagnetic field defining a preferred propagation direction of the whistler wave in the chamber; and

exciting the whistler wave by inductively coupling RF power to the whistler wave with the coil, the excited wave transferring sufficient energy to the process gases to induce the plasma state in the process gases.

12. The method of claim 11, further comprising the step of generating time-varying electromagnetic fields with the coil to sustain the plasma state in the process gases.

13. The method of claim 11, wherein said generating a variable static electromagnetic field step is accomplished with at least one set of electromagnets located outside the chamber.

14. The method of claim 11, further comprising the step of generating a magnetic field along the surface of the chamber for confining the plasma.

15. The method of claim 11, wherein said exciting step is accomplished by resonant inductive coupling of the RF power to the whistler wave with the coil.

16. The method of claim 11, further comprising the steps of:

selecting a frequency of the RF power to be between ion and electron cyclotron frequencies of the process gases; and

selecting the ion and electron cyclotron frequencies to be less than an electron plasma frequency of the process gases.

17. The method of claim 11, further comprising the steps of locating a plurality of coils inside the chamber and substantially parallel to sidewalls of the chamber, and connecting the plurality of coils with a connector coil traversing a vertical axis of the chamber.

18. The method of claim 11, wherein said exciting the wave step further comprises the coil providing antennas of varying lengths for resonant inductive coupling the RF power to the whistler wave over a range of conditions.

19. A plasma source for generating a plasma, comprising:

a chamber operable to confine the plasma and process gases;

a coil operable to generate a whistler wave in said chamber, said coil including;

a first coil routed outside said chamber along a bottom of said chamber; and

a plurality of coils located outside of said chamber and substantially parallel to sidewalls of said chamber, said plurality of coils located between said electromagnets and said chamber;

at least one set of electromagnets located outside of said chamber, said electromagnets operable to define a preferred propagation direction of the whistler wave in said chamber;

said coil further operable to inductively couple RF power to the whistler wave to excite the whistler wave and to transfer a sufficient amount of energy to the process gases in said chamber to induce a plasma state in the process gases.

20. The plasma source of claim 19 wherein said coil is further operable to resonantly inductive couple the RF power to the whistler wave to excite the whistler wave.

21. The plasma source of claim 19 wherein said coil includes a plurality of coils located inside of said chamber and positioned substantially parallel to sidewalls of said chamber, said plurality of coils shaped to match the contour of said chamber and connected by a connecting coil traversing a vertical axis of said chamber.

22. The plasma source of claim 19 wherein said RF power is selected to be at a frequency between the ion and electron cyclotron frequencies of the process gases, the ion and electron cyclotron frequencies being less than the electron plasma frequency of the process gases.

23. The plasma source of claim 19 wherein said coil is operable to provide antennas of varying lengths for resonant inductive coupling of the RF power to the whistler wave over a range of conditions impacting the resonant inductive coupling of the RF power to the whistler wave, said coil further operable to generate time-varying magnetic fields which sustain the plasma state of the process gases.

24. The plasma source of claim 19 further comprising a plurality of permanent multipolar magnets located outside of said chamber, said magnets operable to establish a magnetic field along the surface of said chamber for confining the plasma.

25. The plasma source of claim 19 wherein said coil further comprises a passage for circulating coolant through said coil so as to cool said coil.

26. The plasma source of claim 19 wherein said coil is segmented with capacitors placed between adjacent coils operable to reduce the impedance of said coil.

27. A plasma source for generating a plasma, comprising:

a chamber operable to confine the plasma and process gases;

a coil operable to generate a whistler wave in said chamber;

at least one set of electromagnets located outside of said chamber, said electromagnets operable to define a preferred propagation direction of the whistler wave in said chamber;

a plurality of permanent multipolar magnets located outside of said chamber, said magnets operable to establish a magnetic field along the surface of said chamber for confining the plasma.

said coil further operable to inductively couple RF power to the whistler wave to excite the whistler wave and to transfer a sufficient amount of energy to the process gases in said chamber to induce a plasma state in the process gases.

28. The plasma source of claim 27 wherein said coil is further operable to resonantly inductive couple the RF power to the whistler wave to excite the whistler wave.

29. The plasma source of claim 27 wherein said coil is located inside of said chamber and positioned substantially parallel to sidewalls of said chamber.

30. The plasma source of claim 27 wherein said coil comprises a plurality of coils located inside of said chamber and positioned substantially parallel to sidewalls of said chamber, said plurality of coils shaped to match the contour of said chamber and connected by a connecting coil traversing a vertical axis of said chamber.

31. The plasma source of claim 27 wherein said coil further comprises:

a first coil routed outside said chamber along a bottom of said chamber; and

a plurality of coils located outside of said chamber and substantially parallel to sidewalls of said chamber, said plurality of coils located between said electromagnets and said chamber.

32. The plasma source of claim 27 wherein said RF power is selected to be at a frequency between the ion and electron cyclotron frequencies of the process gases, the ion and electron cyclotron frequencies being less than the electron plasma frequency of the process gases.

33. The plasma source of claim 27 wherein said coil is operable to provide antennas of varying lengths for resonant inductive coupling of the RF power to the whistler wave over a range of conditions impacting the resonant inductive coupling of the RF power to the whistler wave, said coil further operable to generate time-varying magnetic fields which sustain the plasma state of the process gases.

34. The plasma source of claim 27 wherein said coil further comprises a passage for circulating coolant through said coil so as to cool said coil.

35. The plasma source of claim 27 wherein said coil is segmented with capacitors placed between adjacent coils operable to reduce the impedance of said coil.

36. A plasma source for generating a plasma, comprising:

a chamber operable to confine the plasma and process gases;

a coil operable to generate a whistler wave in said chamber, said coil being segmented with capacitors placed between adjacent coils operable to reduce the impedance of said coil;

at least one set of electromagnets located outside of said chamber, said electromagnets operable to define a preferred propagation direction of the whistler wave in said chamber;

said coil further operable to inductively couple RF power to the whistler wave to excite the whistler wave and to transfer a sufficient amount of energy to the process gases in said chamber to induce a plasma state in the process gases.

37. The plasma source of claim 36 wherein said coil is further operable to resonantly inductive couple the RF power to the whistler wave to excite the whistler wave.

38. The plasma source of claim 36 wherein said coil is located inside of said chamber and positioned substantially parallel to sidewalls of said chamber.

39. The plasma source of claim 36 wherein said coil comprises a plurality of coils located inside of said chamber and positioned substantially parallel to sidewalls of said chamber, said plurality of coils shaped to match the contour of said chamber and connected by a connecting coil traversing a vertical axis of said chamber.

40. The plasma source of claim 36 wherein said coil further comprises:

a first coil routed outside said chamber along a bottom of said chamber; and

a plurality of coils located outside of said chamber and substantially parallel to sidewalls of said chamber, said plurality of coils located between said electromagnets and said chamber.

41. The plasma source of claim 36 wherein said RF power is selected to be at a frequency between the ion and electron cyclotron frequencies of the process gases, the ion and electron cyclotron frequencies being less than the electron plasma frequency of the process gases.

42. The plasma source of claim 36 wherein said coil is operable to provide antennas of varying lengths for resonant inductive coupling of the RF power to the whistler wave over a range of conditions impacting the resonant inductive coupling of the RF power to the whistler wave, said coil further operable to generate time-varying magnetic fields which sustain the plasma state of the process gases.

43. The plasma source of claim 36 further comprising a plurality of permanent multipolar magnets located outside of said chamber, said magnets operable to establish a magnetic field along the surface of said chamber for confining the plasma.

44. The plasma source of claim 36 wherein said coil further comprises a passage for circulating coolant through said coil so as to cool said coil.

45. A method of inducing a plasma state in process gases in a chamber, comprising the steps of:

generating a whistler wave with a coil, said coil including a plurality of coils located inside the chamber and located substantially parallel to sidewalls of the chamber;

connecting the plurality of coils with a connector coil traversing a vertical axis of the chamber;

generating a variable static electromagnetic field defining a preferred propagation direction of the whistler wave in the chamber; and

exciting the whistler wave by inductively coupling RF power to the whistler wave with the coil, the excited wave transferring sufficient energy to the process gases to induce the plasma state in the process gases.

46. The method of claim 45 further comprising the step of generating time-varying electromagnetic fields with the coil to sustain the plasma state in the process gases.

47. The method of claim 45 wherein said generating a variable static electromagnetic field step is accomplished with at least one set of electromagnets located outside the chamber.

48. The method of claim 45 further comprising the step of generating a magnetic field along the surface of the chamber for confining the plasma.

49. The method of claim 45 wherein said exciting step is accomplished by resonant inductive coupling of the RF power to the whistler wave with the coil.

50. The method of claim 45 further comprising the steps of:

selecting a frequency of the RF power to be between ion and electron cyclotron frequencies of the process gases; and

selecting the ion and electron cyclotron frequencies to be less than an electron plasma frequency of the process gases.

51. The method of claim 45 further comprising the step of locating a first coil outside the chamber and along a bottom of the chamber, and a plurality of coils outside the chamber and along and substantially parallel to sidewalls of the chamber.

52. The method of claim 45 wherein said exciting the wave step further comprises the coil providing antennas of varying lengths for resonant inductive coupling the RF power to the whistler wave over a range of conditions impacting the resonant inductive coupling of the RF power to the whistler wave.