Toroidal low-field reactive gas source

• US 6,559,408 B2
• Filed: 05/10/2002
• Issued: 05/06/2003
• 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:
  US10/143,061
• Publication Number:
  US 20020125225A1
• Time in Patent Office: 361 Days
• Field of Search: 219/121.54, 219/121.57, 219/121.48, 219/121.36, 219/121.43, 219/121.59, 315/111.51, 156/345, 156/646.1, 156/643.1, 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 to the primary winding of the transformer;

d) inducing an AC potential inside the plasma chamber by supplying the current to the primary winding, the induced AC potential forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas;

e) measuring the current supplied to the primary winding;

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

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

2. The method of claim 1 wherein the one or more electrical parameters are chosen from the group consisting of pulse amplitude, frequency, pulse width and phase.

3. The method of claim 1 wherein the output of the AC switching power supply is coupled, without using an 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.

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 1 wherein the output of the AC switching power supply is coupled, without using a 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. 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 to the primary winding of the transformer;

d) inducing an AC potential inside the plasma chamber by supplying the current to the primary winding, the induced AC potential forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas;

e) measuring power in the toroidal plasma;

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

g) adjusting a frequency of the AC switching power supply to control a delivered to the toroidal plasma.

7. 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 a substantially sinusoidal current using a solid state AC switching power supply comprising one or more switching semiconductor devices and having an output that is coupled to the primary winding of the transformer; and

d) inducing an AC potential inside the plasma chamber by supplying the substantially sinusoidal current to the primary winding, the induced AC potential forming a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the gas.

8. 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 having 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 that is coupled through a reactive element to the primary winding of the transformer, the AC switching power supply supplying an AC current through the reactive element to the primary winding, the current inducing an AC potential inside the plasma chamber that forms a toroidal plasma that completes a secondary circuit of the transformer and that dissociates the feed gas.

9. The apparatus of claim 8 wherein the AC switching power supply supplies the current to the primary winding without the use of the conventional impedance matching network, and wherein the AC switching power supply supplies the current to the primary winding without the use of the conventional impedance matching network.

10. The apparatus of claim 8 wherein the AC switching power supply supplying a substantially sinusoidal current.

11. The apparatus of claim 8 wherein the reactive element is an inductor.

12. The apparatus of claim 8 wherein the plasma chamber comprises at least one of a metallic material and dielectric material.

13. The apparatus of claim 8 further comprising a circuit for measuring the current supplied to the primary winding of the transformer, comparing the measured current to a predetermined setpoint representative of a desired operating condition, and adjusting one or more electrical parameters of the switching power supply to control the current supplied to the primary winding.

14. The apparatus of claim 8 wherein the one or more electrical parameters are chosen from the group consisting of pulse amplitude, frequency, pulse width and phase.

15. The apparatus of claim 8 further comprising a circuit for measuring a power in the toroidal 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 a power delivered to the toroidal plasma.