Method and apparatus of providing power to ignite and sustain a plasma in a reactive gas generator

• US 7,353,771 B2
• Filed: 11/07/2005
• Issued: 04/08/2008
• Est. Priority Date: 11/07/2005
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Alexander, Thomas, Millner, Alan, Joshi, Madhuwanti, Bystryak, Ilya, Tran, Ken
• Primary Examiner(s): Owens; Douglas W.
• Assistant Examiner(s): DUONG, DIEU HIEN
• Application Number:
  US11/268,692
• Publication Number:
  US 20070103092A1
• Time in Patent Office: 883 Days
• Field of Search: 31511121-11171, 315/326, 315/349, 315/354, 315/355, 315/356, 118/723.R, 118/715, 118/156, 427/457
• US Class Current: 118/723.00R
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32137 controlling of the discharge by modulation of energy
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

According to a first aspect, a power supply and a method of providing power for igniting a plasma in a reactive gas generator is provided that includes (i) coupling a series resonant circuit that comprises a resonant inductor and a resonant capacitor between a switching power source and a transformer, the transformer having a transformer primary and a plasma secondary; (ii) providing a substantially resonant AC voltage from the resonant capacitor across the transformer primary, thereby inducing a substantially resonant current within the transformer primary to generate the plasma secondary; and (iii) upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply. According to another aspect, bipolar high voltage ignition electrodes can be used in conjunction with inductive energy coupling to aid in plasma ignition.

Claims

1. A method of providing power for igniting a plasma in a reactive gas generator, comprising:

inductively coupling a power supply remote from a plasma chamber containing a gas capable of being transformed into a plasma, the remote power supply comprising a series resonant circuit coupled between a switching power source and a transformer, the series resonant circuit further comprising a resonant inductor in series with a resonant capacitor and the resonant capacitor in parallel with a transformer primary of the transformer;

providing a substantially resonant AC voltage from the series resonant circuit across the transformer primary to induce a substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into a plasma secondary of the transformer; and

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply.

2. The method of claim 1 further comprising:

providing a first AC voltage from the switching power source across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, providing the substantially resonant AC voltage from the series resonant circuit across the transformer primary to induce the substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into the plasma secondary of the transformer; and

modulating the frequency of the first AC voltage from the switching power source to a frequency greater than the substantially resonant frequency of the series resonant circuit to further limit the current flowing to the switching power supply subsequent to generation of the plasma secondary.

3. The method of claim 1 further comprising:

coupling a plurality of resonant inductors in series with the resonant capacitor of the series resonant circuit, such that at least one resonant inductor is coupled in series to each end of the resonant capacitor;

limiting the current flowing to the switching power supply through the plurality of inductors upon generation of the plasma secondary.

4. The method of claim 3 further comprising:

providing a first AC voltage from the switching power source across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, providing the substantially resonant AC voltage from the series resonant circuit across the transformer primary to induce the substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into the plasma secondary of the transformer; and

modulating the frequency of the first AC voltage from the switching power source to a frequency greater than the substantially resonant frequency of the series resonant circuit to further limit the current flowing through the plurality of inductors to the switching power supply subsequent to generation of the plasma secondary.

5. The method of claim 1 further comprising:

coupling a second capacitor in series between the resonant inductor and the resonant capacitor or in series between the resonant capacitor and the transformer, the second capacitor being a DC blocking capacitor or a second resonant capacitor.

6. The method of claim 1 wherein the switching power source is a half bridge inverter.

7. The method of claim 1 wherein the switching power source is a full bridge inverter.

8. The method of claim 1 further comprising:

coupling flux from the transformer primary to the plasma secondary through a magnetic core surrounding a portion of the plasma chamber and the transformer primary; and

flowing an inlet gas through the plasma secondary to convert the inlet gas into a reactive gas.

9. A method of providing power for igniting a plasma in a reactive gas generator, comprising:

coupling a series resonant circuit that comprises a resonant inductor and a resonant capacitor between a switching power source and a transformer, the transformer having a transformer primary and a plasma secondary;

providing a substantially resonant AC voltage from the series resonant circuit across the transformer primary to induce a substantially resonant current within the transformer primary for generating the plasma secondary;

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply;

coupling a secondary winding to the transformer, the secondary winding having a center tap or a substantially center tap;

grounding the center tap of the secondary winding to provide a first lead and a second lead of the secondary winding;

coupling the first lead to a first ignition electrode positioned at a first location about the plasma secondary and coupling the second lead to a second ignition electrode opposing the first ignition electrode at a second location about the plasma secondary; and

applying a voltage of a first polarity to the first lead and a voltage of a second polarity to the second lead, resulting in electric field flux traversing a cross sectional area between the first and second electrode to generate the plasma secondary.

10. The method of claim 9 further comprising:

providing a plasma chamber for containing the plasma secondary; and

coupling the first lead to the first ignition electrode on an outer surface of the plasma chamber and coupling the second lead to the second ignition electrode on the outer surface of the plasma chamber opposing the first ignition electrode; and

applying a voltage of a first polarity to the first lead and a voltage of a second polarity to the second lead, resulting in the electric field flux traversing a cross sectional area of the plasma chamber between the first and second electrode to generate the plasma secondary.

11. A power supply for igniting a plasma in reactive gas generator, comprising:

a switching power source;

a transformer comprising a transformer primary; and

a series resonant circuit coupled between the switching power source and the transformer primary, the series resonant circuit further comprising a resonant inductor in series with a resonant capacitor and the resonant capacitor in parallel with the transformer primary;

the switching power source, the series resonant circuit and the transformer primary being inductively coupled to and remote from a plasma chamber containing a gas capable of being transformed into a plasma;

the series resonant circuit providing a substantially resonant AC voltage across the transformer primary to induce a substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into a plasma secondary of the transformer;

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply.

12. The power supply of claim 11 further comprising:

a controller;

the switching power source providing a first AC voltage across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, the series resonant circuit providing the substantially resonant AC voltage from across the transformer primary to induce the substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into the plasma secondary of the transformer;

the controller providing signals to the switching power source to modulate the frequency of the first AC voltage to a frequency greater than the substantially resonant frequency of the series resonant circuit to further limit the current flowing to the switching power supply subsequent to generation of the plasma secondary.

13. The power supply of claim 11 wherein the series resonant circuit comprises:

a plurality of resonant inductors in series with the resonant capacitor, such that at least one resonant inductor is coupled in series to each end of the resonant capacitor;

the plurality of resonant inductors limiting the current flowing to the switching power supply upon generation of the plasma secondary.

14. The power supply of claim 13 further comprising:

a controller;

the switching power source providing a first AC voltage across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, the series resonant circuit providing the substantially resonant AC voltage across the transformer primary to induce the substantially resonant current within the transformer primary which transforms the gas in the plasma chamber into the plasma secondary of the transformer;

the controller modulating the frequency of the first AC voltage from the switching power source to a frequency greater than the substantially resonant frequency of the series resonant circuit to further limit the current flowing through the plurality of resonant inductors to the switching power supply subsequent to generation of the plasma secondary.

15. The power supply of claim 11 wherein the series resonant circuit further comprises:

a second capacitor being coupled in series between the resonant inductor and the resonant capacitor or in series between the resonant capacitor and the transformer, the second capacitor being a DC blocking capacitor or a second resonant capacitor.

16. The power supply of claim 11 wherein the switching power source comprises a half bridge inverter.

17. The power supply of claim 11 wherein the switching power source comprises a full bridge inverter.

18. The power supply of claim 11 further comprising:

a magnetic core surrounding a portion of the plasma chamber and the transformer primary for coupling flux from the transformer primary to the plasma secondary.

19. A power supply for igniting a plasma in reactive gas generator, comprising:

a switching power source;

a transformer comprising a transformer primary and a plasma secondary; and

a series resonant circuit comprising a resonant inductor and a resonant capacitor coupled between the switching power source and the transformer primary,

the series resonant circuit providing a substantially resonant AC voltage across the transformer primary to induce a substantially resonant current within the transformer primary for generating the plasma secondary;

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply;

a secondary winding coupled to the transformer, the secondary winding having a center tap or a substantially center tap being grounded to provide a first lead and a second lead of the secondary winding;

a first ignition electrode positioned at a first location about the plasma secondary, the first ignition electrode being coupled to the first lead; and

a second ignition electrode opposing the first ignition electrode at a second location about the plasma secondary, the second ignition electrode being coupled to the second lead;

the secondary winding applying a voltage of a first polarity to the first lead and a voltage of a second polarity to the second lead, resulting in electric field flux traversing a cross sectional area between the first and second electrode to generate the plasma secondary.

20. The power supply of claim 19 further comprising:

a plasma chamber containing the plasma secondary;

the first lead being coupled to the first ignition electrode on an outer surface of the plasma chamber and the second lead being coupled to the second ignition electrode on the outer surface of the plasma chamber opposing the first ignition electrode;

the secondary winding applying the voltage of a first polarity to the first lead and the voltage of the second polarity to the second lead, resulting in the electric field flux traversing a cross sectional area of the plasma chamber between the first and second electrode to generate the plasma secondary.

21. A power supply for igniting a plasma in reactive gas generator, comprising:

a switching power source;

a transformer comprising a transformer primary and a plasma secondary; and

a series resonant circuit comprising a resonant inductor and a resonant capacitor coupled between the switching power source and the transformer primary, and

a controller;

the switching power source providing a first AC voltage across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, the series resonant circuit providing a substantially resonant AC voltage across the transformer primary to induce the substantially resonant current within the transformer primary for generating the plasma secondary;

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply;

the controller providing signals to the switching power source to modulate the duty cycle of the first AC voltage to further limit the current flowing to the switching power supply subsequent to generation of the plasma secondary.

22. A method of providing power for igniting a plasma in a reactive gas generator, comprising:

coupling a series resonant circuit that comprises a resonant inductor and a resonant capacitor between a switching power source and a transformer, the transformer having a transformer primary and a plasma secondary;

providing a first AC voltage from the switching power source across the series resonant circuit, the first AC voltage having a frequency at a substantially resonant frequency of the series resonant circuit;

in response to the first AC voltage, providing the substantially resonant AC voltage from the series resonant circuit across the transformer primary to induce the substantially resonant current within the transformer primary for generating the plasma secondary;

upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply;

modulating the duty cycle of the first AC voltage from the switching power source to further limit the current flowing to the switching power supply subsequent to generation of the plasma secondary.