Toroidal low-field reactive gas source

• US 6,664,497 B2
• Filed: 05/10/2002
• Issued: 12/16/2003
• Est. Priority Date: 06/26/1997
• Status: Expired due to Term

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: Applied Science and Technology, Inc. (MKS Instruments Incorporated)
• Inventors: Chen, Xing, Smith, Donald K., Holber, William M., Georgelis, Eric
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US10/143,070
• Publication Number:
  US 20020125226A1
• Time in Patent Office: 585 Days
• Field of Search: 219/121.57, 219/121.54, 219/121.52, 219/121.48, 219/121.43, 219/121.4, 219/121.41, 219/121.59, 315/111.51, 156/643.1, 156/646.1, 156/345, 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. A method for dissociating gases comprising:

a) confining a gas in a plasma chamber at a pressure;

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

c) generating an AC current using a solid state AC switching power supply comprising one or more switching semiconductor devices and having an output that is coupled, without requiring an impedance matching network, to the primary winding of the transformer; and

d) inducing an AC potential inside the plasma chamber by supplying the current, without requiring the impedance matching network, to the primary winding of the transformer, the induced AC potential forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas.

2. The method of claim 1 further comprising generating the current using a solid state AC switching power supply comprising one or more switching transistors.

3. The method of claim 1 wherein the output of the AC switching power supply is coupled, without using the impedance matching network, to the primary winding of the transformer and wherein the AC switching power supply supplies, without using the impedance matching network, the current in the primary winding.

4. The method of claim 1 wherein the output of the AC switching power supply is coupled, without requiring a conventional impedance matching network, to the primary winding of the transformer and wherein the AC switching power supply supplies, without requiring the conventional impedance matching network, the current to the primary winding.

5. The method of claim 4 wherein the output of the AC switching power supply is coupled, without using the conventional impedance matching network, to the primary winding of the transformer and wherein the AC switching power supply supplies, without using the conventional impedance matching network, the current to the primary winding.

6. The method of claim 1 further comprising measuring the current supplied to the primary winding;

comparing the measured current to a predetermined setpoint representative of a desired operating condition; and

adjusting one or more electrical parameters of the AC switching power supply to control the current supplied to the primary winding of the transformer.

7. The method of claim 6 wherein the one or more electrical parameters include of pulse amplitude, frequency, pulse width and phase.

8. The method of claim 1 further comprising measuring the power in the plasma;

comparing the measured power to a predetermined setpoint representative of a desired operating condition; and

adjusting frequency of the AC switching power supply to control the power delivered to the plasma.

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

a) confining a gas in a plasma chamber at a pressure;

b) generating an AC current using a solid state AC switching power supply comprising one or more switching semiconductor devices having an output that is coupled, without requiring an impedance matching network, to a primary winding of the transformer having a magnetic core surrounding a portion of the plasma chamber; and

c) inducing an AC potential inside the plasma chamber by supplying the current, without requiring the impedance matching network, to the primary winding of the transformer, the induced AC potential directly forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas.

10. The method of claim 9 wherein the output of the AC switching power supply is coupled, without using the impedance matching network, to the primary winding of the transformer, and wherein the AC switching power supply supplies, without using the impedance matching network, the current to the primary winding.

11. The method of claim 9 wherein the output of the AC switching power supply is coupled, without requiring a conventional impedance matching network, to the primary winding of the transformer, and wherein the AC switching power supply supplies, without requiring the conventional impedance matching network, the current to the primary winding.

12. The method of claim 9 further comprising measuring the current supplied to the primary winding;

the measured current to a predetermined setpoint representative of a desired operating condition; and

adjusting one or more electrical parameters of the AC switching power supply to control the current supplied to the primary winding of the transformer.

13. The method of claim 12 wherein the one or more electrical parameters include of pulse amplitude, frequency, pulse width and phase.

14. The method of claim 9 further comprising measuring the power in the plasma;

comparing the measured power to a predetermined setpoint representative of a desired operating condition; and

adjusting frequency of the AC switching power supply to control the power delivered to the plasma.

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

a) flowing a gas in a plasma chamber at a pressure;

b) generating an AC current with a solid state AC switching power supply comprising one or more semiconductor transistors;

c) coupling an output of the solid state AC switching power supply, without requiring an impedance matching network, to a primary winding of a transformer having a magnetic core surrounding a portion of the plasma chamber

d) inducing an AC potential inside the plasma chamber by supplying the current, without requiring the impedance matching network, to the primary winding of the transformer, the induced AC potential directly forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas forming chemically active species; and

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

16. The method of claim 15 further comprising coupling the output of the AC switching power supply, without using the impedance matching network, to the primary winding of the transformer;

and inducing the AC potential inside the plasma chamber by supplying the current, without using the impedance matching network, to the primary winding.

17. The method of claim 15, further comprising coupling the output of the AC switching power supply, without using a conventional impedance matching network, to the primary winding of the transformer;

and inducing the AC potential inside the plasma chamber by supplying the current, without using the conventional impedance matching network, to the primary winding.

18. An apparatus for dissociating gases 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 gas inlet for providing a feed gas to the plasma chamber; and

d) a solid state AC switching power supply comprising one or more switching semiconductor devices and having an output coupled to the primary winding without requiring the use of an impedance matching network, the AC switching power supply supplying an AC current to the primary winding without requiring the use of the impedance matching network, 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.

19. The apparatus of claim 18 wherein the plasma chamber comprises an electrically conductive material and at least one dielectric region that forms an electrical discontinuity in the plasma chamber.

20. The apparatus of claim 18 the plasma chamber comprises at least one of a metallic material and dielectric material.

21. The apparatus of claim 18 wherein the output of the AC switching power supply is coupled to the primary winding without the use of the impedance matching network.

22. The apparatus of claim 21 the AC switching power supply supplies the AC current to the primary winding without the use of the impedance matching network.

23. The apparatus of claim 18 wherein the output of the AC switching power supply is coupled to the primary winding without the use of a conventional impedance matching network, and wherein the AC switching power supply supplies the AC current to the primary winding without the use of the conventional impedance matching network.

24. The apparatus of claim 18 comprising a circuit for measuring the current supplied to the primary winding, comparing the measured current to a predetermined setpoint representative of a desired operating condition, and adjusting one or more electrical parameters of the AC switching power supply to control the current supplied to the primary winding of the transformer.

25. The apparatus of claim 24 wherein the one or more electrical parameters include pulse amplitude, frequency, pulse width and phase.

26. The apparatus of claim 24 comprising a circuit for measuring the power in the plasma, comparing the measured power to a predetermined setpoint representative of a desired operating condition;

and adjusting frequency of the AC switching power supply to control the power delivered to the plasma.

27. 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) a solid state AC switching power supply comprising one or more switching semiconductor devices and having an output coupled to the primary winding without requiring the use of an impedance matching network, the AC switching power supply an AC current to the primary winding without requiring the use of the impedance matching network, 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.

28. The apparatus of claim 27 wherein the output of the AC switching power supply is coupled to the primary winding of the transformer without using the impedance matching network and wherein the AC switching power supply supplies the current to the primary winding without using the impedance matching network.

29. The apparatus of claim 27 wherein the output of the AC switching power supply is coupled to the primary winding of the transformer without using a conventional impedance matching network, and wherein the AC switching power supply supplies the current to the primary winding without using the conventional impedance matching network.

30. A method for reducing surface erosion in a plasma chamber of a reactive gas source, the method comprising:

confining a gas in a plasma chamber;

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

inducing an AC potential inside the plasma chamber by supplying an AC current generated by a solid state AC switching power supply, without requiring the use of a conventional impedance matching network, to the primary winding of the transformer;

forming a toroidal plasma inside the plasma chamber that completes a secondary circuit of the transformer and that dissociates the gas; and

operating the reactive gas source with an electric field of the plasma being substantially between 1 and 100 volts per centimeter in the plasma chamber.

31. The method of claim 30 wherein the plasma chamber comprises at least one of a metallic material and a coated metallic material.

32. The method of claim 31 further comprising electrically isolating a region of the plasma chamber using at least one dielectric spacer to prevent induced current flow from forming in the plasma chamber itself.

33. The method of claim 32 further comprising protecting the at least one dielectric spacer from the plasma by a protruded plasma chamber wall.

34. The method of claim 32 further comprising positioning a vacuum seal adjacent the at least one dielectric spacer.

35. The method of claim 30 further comprising supplying the AC current generated by the solid state AC switching power supply to the primary winding without using the conventional impedance matching network.

36. The method of claim 30 wherein the solid state AC switching power supply comprises one or more switching transistors for supplying the AC current to the primary winding without requiring the use of the conventional impedance matching network.

37. A reactive gas source for dissociating gases in a toroidal plasma comprising:

a plasma chamber for containing a gas, the plasma chamber comprising at least one of a metallic material and a coated metallic material and having at least one dielectric spacer that electrically isolates the plasma chamber into a plurality of portions to prevent induced current flow from forming in the plasma chamber itself, the dielectric spacer being protected from the plasma by a protrusion in the plasma chamber;

at least one transformer having a primary winding and having a magnetic core surrounding at least a portion of the plasma chamber; and

a solid state AC switching power supply supplying an AC current to the primary winding without requiring the use of an impedance matching network, the AC current inducing an AC potential inside the plasma chamber that forms the plasma that completes a secondary circuit of the transformer and dissociates the gas.

38. The reactive gas source of claim 37 further comprising a vacuum seal disposed adjacent the dielectric spacer.

39. The reactive gas source of claim 38 wherein the vacuum seal is located outside the dielectric spacer.

40. The reactive gas source of claim 37 wherein the dielectric spacer is disposed in a recess adjacent the protrusion in the plasma chamber.

41. The reactive gas source of claim 37 wherein the dielectric spacer is protected from the plasma by a protruded plasma chamber wall.

42. The reactive gas source of claim 37 wherein the dielectric spacer is protected the plasma by a protruded plasma chamber wall.

43. The reactive gas source of claim 37 wherein the AC switching power supply supplies the AC current to the primary winding without requiring the use of a conventional impedance matching network.

44. The reactive gas source of claim 37 wherein the AC switching power supply supplies the AC current to the primary winding without the use of a conventional impedance matching network.

45. The reactive gas source of claim 37 wherein the AC switching power supply comprises one or more switching transistors that supply the AC current to the primary winding without requiring the use of a conventional impedance matching network.

46. The reactive gas source of claim 37 further comprising cooling channels for passing a fluid that controls the temperature of the plasma chamber.

47. A plasma chamber for use with a reactive gas source comprising:

an inlet for receiving a gas;

at least one plasma chamber wall for containing the gas, the plasma chamber wall comprising at least one of a metallic material and coated metallic material;

at least one dielectric spacer that electrically isolates the plasma chamber into a plurality of portions to prevent induced current flow from forming in the plasma chamber itself, the dielectric spacer being protected from a plasma formed in the plasma chamber by a protrusion on the plasma chamber wall; and

cooling channels for passing a fluid that controls the temperature of the plasma chamber.

48. The plasma chamber of claim 47 wherein the dielectric spacer is protected from the plasma by a protruded plasma chamber wall.

49. A toroidal plasma chamber for use with a reactive gas source comprising:

an inlet for receiving a gas;

one or more chamber walls for containing the gas, the chamber walls comprising at least one of a metallic material, coated metallic material and dielectric material; and

at least one dielectric spacer that electrically isolates a region of the plasma chamber to prevent induced current flow from forming in the plasma chamber itself, the at least one dielectric spacer being protected from a plasma formed in the plasma chamber by a protrusion on the plasma chamber wall.