Toroidal low-field reactive gas source

• US 6,486,431 B1
• Filed: 09/12/2000
• Issued: 11/26/2002
• Est. Priority Date: 06/26/1997
• Status: Expired due to Term

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: Applied Science & Technology, Inc. (MKS Instruments Incorporated)
• Inventors: Chen, Xing, Smith, Donald K., Holber, William M., Georgelis, Eric
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US09/659,881
• Time in Patent Office: 805 Days
• Field of Search: 219/121.54, 219/121.43, 219/121.57, 219/121.59, 315/111.51, 156/345, 156/643.1, 156/643.6, 204/298.31
• US Class Current: 219/121.57
• CPC Class Codes: H01J 27/16 using high-frequency excitation, e.g. microwave excitation
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32862 In situ cleaning of vessels and/or internal parts

Abstract

An apparatus for dissociating gases includes a plasma chamber that may be formed from a metallic material and a transformer having a magnetic core surrounding a portion of the plasma chamber and having a primary winding. The apparatus also includes one or more switching semiconductor devices that are directly coupled to a voltage supply and that have an output coupled to the primary winding of the transformer. The one or more switching semiconductor devices drive current in the primary winding that induces a potential inside the chamber that forms a plasma which completes a secondary circuit of the transformer.

Claims

1. An apparatus for dissociating gases, the apparatus comprising:

a. a plasma chamber comprising a gas;

b. a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding; and

c. a solid state AC switching power supply comprising one or more switching semiconductor devices coupled to a voltage supply and having an output coupled to the primary winding,

the solid state AC switching power supply driving an AC current in the primary winding, the current inducing an AC potential inside the chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas.

2. The apparatus of claim 1 wherein the one or more switching semiconductor devices comprises one or more switching transistors.

3. The apparatus of claim 1 wherein the output of the one or more switching semiconductor devices is directly coupled to the primary winding.

4. The apparatus of claim 1 wherein the chamber comprises an electrically conductive material and at least one dielectric region that forms an electrical discontinuity in the chamber.

5. The apparatus of claim 4 wherein the electrically conductive material comprises aluminum.

6. The apparatus of claim 5 wherein the aluminum is anodized.

7. The apparatus of claim 1 wherein the chamber comprises a dielectric material.

8. The apparatus of claim 1 further comprising an electrode positioned in the chamber that generates free charges that assist the ignition of a plasma in the chamber.

9. The apparatus of claim 1 further comprising an electrode capacitively coupled to the chamber that generates free charges that assist the ignition of a plasma in the chamber.

10. The apparatus of claim 1 further comprising an ultraviolet light source optically coupled to the chamber that generates free charges that assist the ignition of a plasma in the chamber.

11. The apparatus of claim 1 further comprising a circuit for measuring electrical parameters associated with the primary winding and the plasma, the electrical parameters including one or more of a current driving the primary winding, a voltage across the primary winding, an average power in the primary winding, and a peak power in the primary winding.

12. The apparatus of claim 11 further comprising a power control circuit having an input coupled to an output of the circuit for measuring electrical parameters associated with the primary winding and the plasma and an input coupled to the solid state AC switching power supply, the power control circuit controlling voltage and current supplied to the primary winding.

13. The apparatus of claim 1 further comprising a process chamber that is coupled to the plasma chamber and positioned to receive the dissociated gas generated by the plasma.

14. An apparatus for material processing, the apparatus comprising:

a. a plasma chamber comprising a gas;

b. a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding;

c. a solid state AC switching power supply comprising one or more switching semiconductor devices coupled to a voltage supply and having an output coupled to the primary winding,

the solid state AC switching power supply driving current in the primary winding, the current inducing an AC potential inside the chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas; and

d. a sample holder located relative to the plasma chamber and exposed to the dissociated gas.

15. The apparatus of claim 14 further comprising a power supply that is electrically coupled to the sample holder that biases the material to be processed relative to a potential of the plasma.

16. The apparatus of claim 14 wherein the sample holder is located in the plasma chamber.

17. The apparatus of claim 14 further comprising a process chamber that is coupled to the plasma chamber and that receives the dissociated gas, wherein the sample holder is located in the process chamber.

18. The apparatus of claim 14 wherein the material to be processed comprises at least one of a solid, powder, and a gas.

19. The apparatus of claim 14 wherein the material to be processed comprises a semiconductor material.

20. The apparatus of claim 14 wherein the plasma chamber comprises an electrically conductive material and at least one dielectric region that forms an electrical discontinuity in the chamber.

21. The apparatus of claim 14 further comprising an electrode positioned in the chamber that generates free charges that assist the ignition of a plasma in the chamber.

22. The apparatus of claim 14 further comprising an electrode capacitively coupled to the chamber that generates free charges that assist the ignition of a plasma in the chamber.

23. The apparatus of claim 14 further comprising an ultraviolet light source optically coupled to the chamber that generates free charges that assist the ignition of a plasma in the chamber.

24. The apparatus of claim 14 further comprising a circuit for measuring electrical parameters associated with the primary winding and the plasma, the electrical parameters including one or more of a current driving the primary winding, a voltage across the primary winding, an average power in the primary winding, and a peak power in the primary winding.

25. The apparatus of claim 14 further comprising a power control circuit having an input coupled to an output of the circuit for measuring electrical parameters associated with the primary winding and the plasma and an input coupled to the solid state AC switching power supply, the power control circuit controlling voltage and current supplied to the primary winding.

26. A method for dissociating gases, the method comprising:

a. confining a gas in a chamber at a pressure;

b. generating a current with a solid state AC switching power supply; and

c. inducing an AC potential inside the chamber by passing the current though a primary winding of a transformer having a magnetic core surrounding a portion of the chamber, the induced AC potential directly forming a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas.

27. The method of claim 26 further comprising providing an initial ionization event in the chamber.

28. The method of claim 26 wherein the step of providing an initial ionization event in the chamber comprises applying a voltage pulse to the primary winding.

29. The method of claim 26 wherein the step of providing an initial ionization event in the chamber comprises exposing the chamber to ultraviolet light.

30. The method of claim 26 wherein the gas comprises at least one of a noble gas and a reactive gas.

31. The method of claim 26 further comprising measuring electrical parameters including at least one of the current passing though the primary winding, a voltage across the primary winding, an average power in the primary winding, and a peak power in the primary winding.

32. The method of claim 26 further comprising the step of adjusting a magnitude of the current generated by the solid state AC switching power supply from the measured electrical parameters and from predetermined operating conditions.

33. The method of claim 26 wherein the pressure is substantially between 1 mtorr and 100 torr.

34. The method of claim 26 wherein an electric field of the plasma is substantially between 1-100 V/cm.

35. A method for cleaning a process chamber, the method comprising:

a. flowing a gas in a chamber at a pressure;

b. generating a current with a solid state AC switching power supply;

c. inducing an AC potential inside the chamber by passing the current though a primary winding of a transformer having a magnetic core surrounding a portion of the chamber, the induced AC potential directly forming a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas forming chemically active species; and

d. directing the chemically active species generated by the plasma from the plasma chamber into the process chamber, thereby cleaning the process chamber.

36. The method of claim 35 wherein the reactive gas comprises at least one of an oxygen or a fluorine containing gas.

37. A method for processing materials, the method comprising:

a. flowing a gas in a chamber at a pressure;

b. generating a current with a solid state AC switching power supply;

c. inducing an AC potential inside the chamber by passing the current though a primary winding of a transformer having a magnetic core surrounding a portion of the chamber, the induced AC potential directly forming a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas; and

d. exposing material to be processed to the dissociated gas.

38. The method of claim 37 further comprising directing the dissociated gas from the plasma chamber into the process chamber containing the material to be processed.

39. An apparatus for dissociating gases comprising:

a) a plasma chamber comprising an electrically conductive material and at least one dielectric region that forms an electrical discontinuity that substantially prevents induced current flow from forming in the plasma chamber itself, the plasma chamber further comprising an inlet for providing a gas;

b) a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding; and

c) an AC power supply having an output electrically connected to the primary winding, the AC power supply driving current in the primary winding, the current inducing an AC potential inside the plasma chamber that directly forms a toroidal plasma which completes a secondary circuit of the transformer and dissociates the gas.

40. The apparatus of claim 39 wherein the chamber comprises aluminum.

41. The apparatus of claim 40 wherein the aluminum is anodized.

42. The apparatus of claim 39 wherein the chamber comprises cooling channels for passing a fluid that controls the temperature of the chamber.

43. The apparatus of claim 39 wherein the AC power supply comprises one or more switching semiconductor devices directly coupled to a voltage supply and having an output coupled to the primary winding.

44. An apparatus for dissociating gases, the apparatus comprising:

a. a plasma chamber comprising a gas;

b. a primary winding of a transformer magnetically coupled to a portion of the plasma chamber; and

c. a solid state AC switching power supply comprising one or more switching semiconductor devices coupled to a voltage supply and having an output coupled to the primary winding of the transformer,

the solid state AC switching power supply driving an AC current in the primary winding, the current inducing an AC potential inside the chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the gas.

45. The apparatus of claim 44 herein the transformer comprises a magnetic core surrounding a portion of the plasma chamber and the primary winding surrounds a portion of the magnetic core.

46. An apparatus for activating gases, the apparatus comprising:

a. a plasma chamber comprising a gas;

b. a primary winding of a transformer magnetically coupled to a portion of the plasma chamber; and

c. a solid state AC switching power supply comprising one or more switching semiconductor devices coupled to a voltage supply and having an output coupled to the primary winding of the transformer,

the solid state AC switching power supply driving an AC current in the primary winding, the current inducing an AC potential inside the chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and activates the gas.

47. The apparatus of claim 46 wherein the transformer comprises a magnetic core surrounding a portion of the plasma chamber and the primary winding surrounds a portion of the magnetic core.

48. A downstream plasma source comprising:

a) a metallic plasma chamber coupled to a process chamber having a material disposed therein;

b) at least one dielectric region that forms an electrical discontinuity that substantially prevents induced current flow from forming in the plasma chamber itself;

c) a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding;

d) a gas inlet for providing a feed gas to the plasma chamber; and

e) an AC power supply having an output connected to the primary winding, the AC power supply driving an AC current in the primary winding, the AC current inducing an AC potential inside the plasma chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the feed gas, the dissociated feed gas flowing downstream into the process chamber for processing the material disposed therein.

49. A downstream plasma source for cleaning a process chambers the downstream plasma source comprising:

a) a metallic plasma chamber coupled to a process chamber;

b) at least one dielectric region that forms an electrical discontinuity that substantially prevents induced current flow from forming in the plasma chamber itself;

c) a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding;

d) a gas inlet for providing a feed gas to the plasma chamber; and

e) an AC power supply having an output connected to the primary winding, the AC power supply driving an AC current in the primary winding, the AC current inducing an AC potential inside the plasma chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the feed gas, the dissociated feed gas flowing into the process chamber for cleaning the process chamber.

50. A downstream plasma source for cleaning a process chamber, the downstream plasma source comprising:

a) a plasma chamber coupled to a process chamber;

b) a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding;

c) a gas inlet for providing a feed gas to the plasma chamber; and

d) an AC switching power supply having an output coupled to the primary winding, the AC switching power supply driving an AC current in the primary winding with a sinusoidal waveform, the AC current inducing an AC potential inside the plasma chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the feed gas, the dissociated feed gas flowing into the process chamber for cleaning the process chamber.

51. A downstream plasma source comprising:

a) a plasma chamber having at least one side exposed to a process chamber having a material disposed therein;

b) a transformer having a magnetic core surrounding a portion of the plasma chamber and a primary winding;

c) a gas inlet for providing a feed gas to the plasma chamber; and

d) an AC switching power supply having an output connected to the primary winding, the AC switching power supply driving an AC current in the primary winding, the AC current inducing an AC potential inside the plasma chamber that directly forms a toroidal plasma that completes a secondary circuit of the transformer and dissociates the feed gas, the dissociated feed gas and charged particles generated by the plasma flowing into the process chamber for processing the material disposed therein.