Impedance-Matching Network Using BJT Switches in Variable-Reactance Circuits

• US 20120188007A1
• Filed: 01/20/2011
• Published: 07/26/2012
• Est. Priority Date: 01/20/2011
• Status: Active Grant

• Current Assignee: AES Global Holdings Pte Ltd. (Advanced Energy Industries, Inc. (China))
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Van Zyl, Gideon J., Gurov, Gennady G.
• Granted Patent: US 8,416,008 B2
• Time in Patent Office: Days
• US Class Current: 327/574
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H03H 11/30 Automatic matching of source impedance to load impedance
• CPC Class Codes: H03H 5/12 with at least one voltage- or current-dependent element
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H03K 17/16 Modifications for eliminating interference voltages or currents
• CPC Class Codes: H03K 17/60 the devices being bipolar transistors bipolar transistors having four or more electrodes H03K17/72
• CPC Class Codes: H03K 17/68 specially adapted for switching ac currents or voltages
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 2242/26 Matching networks

Abstract

This disclosure describes systems, methods, and apparatuses for impedance-matching radio frequency power transmitted from a radio frequency generator to a plasma load in a semiconductor processing chamber. Impedance-matching can be performed via a match network having a variable-reactance circuit. The variable-reactance circuit can comprise one or more reactive elements all connected to a first terminal and selectively shorted to a second terminal via a switch. The switch can comprise a bipolar junction transistor (BJT) or insulated gate bipolar transistor (IGBT) controlled via bias circuitry. In an on-state, the BJT base-emitter junction is forward biased, and AC is conducted between a collector terminal and a base terminal. Thus, AC passes through the BJT primarily from collector to base rather than from collector to emitter. Furthermore, the classic match network topology used with vacuum variable capacitors can be modified such that voltages do not overload the BJT'"'"'s in the modified topology.

Claims

1. A switch circuit comprising:

a bipolar junction transistor comprising;

a collector terminal connected to a collector of the bipolar junction transistor, the collector terminal configured to pass a collector current with an alternating current component having a first amplitude;

a base terminal connected to a base of the bipolar junction transistor, the base terminal configured to pass a base current with an alternating current component having a second amplitude;

an emitter terminal connected to an emitter of the bipolar junction transistor, the emitter terminal configured to pass an emitter current with an alternating current component having a third amplitude;

a base-collector junction; and

a base-emitter junction; and

a biasing circuit that;

establishes an on-state of the bipolar junction transistor by forward biasing the base-emitter junction, wherein the second amplitude is greater than the third amplitude; and

establishes an off-state of the bipolar junction transistor by reverse biasing the base-emitter junction and the base-collector junction.

2. The switch circuit of claim 1, wherein the switch circuit is series-connected to a reactive element that is connected to a first terminal, wherein the switch circuit selectively couples the reactive element to a second terminal thereby altering a reactance between the first terminal and the second terminal.

3. The switch circuit of claim 2, wherein the base terminal of the bipolar junction transistor is connected to the second terminal.

4. The switch circuit of claim 2, wherein a capacitor between the base terminal and the second terminal conducts more than half of the alternating current component of the collector current when the bipolar junction transistor is in the on-state.

5. The switch circuit of claim 1, wherein the bipolar junction transistor is an n-p-n bipolar junction transistor.

6. The switch circuit of claim 1, wherein the bipolar junction transistor is a p-n-p bipolar junction transistor.

7. The switch circuit of claim 1, wherein the bipolar junction transistor has a collector-base breakdown voltage greater than 1000 V when the base is shorted to the emitter.

8. The switch circuit of claim 1, wherein the second amplitude is greater than a magnitude of a direct current component of the base current.

9. The switch circuit of claim 1, wherein magnitudes of direct current components of the collector, base, and emitter currents, are less than 20% of the first amplitude.

10. The switch circuit of claim 1 wherein the bipolar junction transistor is one of a plurality of such bipolar junction transistors each configured to selectively shunt a portion of an alternating current through one of a plurality of reactance elements to the second terminal a id wherein a first set of the plurality of reactance elements have identical reactance give or take a twenty percent component tolerance.

11. The switch circuit of claim 10, wherein the first set of plurality of reactance elements numbers at least thirty.

12. The switch circuit of claim 10, wherein the first set of the plurality of reactance elements are capacitive.

13. The switch circuit of claim 1, wherein the third amplitude is less than 10% of the first amplitude.

14. The switch circuit of claim 1, wherein the bipolar junction transistor is part of an insulated-gate bipolar transistor and the collector current passes primarily from the collector terminal to the emitter terminal.

15. An impedance-matching apparatus comprising:

at least one variable reactance element comprising;

a first terminal;

a second terminal;

at least one reactive element connected to the first terminal;

at least one switch circuit configured to selectively connect the at least one reactive element to the second terminal thereby altering a reactance between the first terminal and the second terminal, the at least one switch circuit comprising;

a bipolar junction transistor having;

an on-state, wherein a base-emitter junction is forward biased, and an AC component of a first current through a base terminal of the bipolar junction transistor is greater than an AC component of a second current through an emitter terminal of the bipolar junction transistor; and

an off-state, wherein the base-emitter junction is reverse biased, and a base-collector junction is reverse biased; and

a fixed impedance-matching section in cascade with the at least one variable reactance element and configured to be arranged in cascade with a plasma load, and comprising one or more shunt elements and one or more series elements, the one or more shunt elements and the one or more series elements being in a ladder network.

16. The impedance-matching apparatus of claim 15, wherein the one or more shunt elements and the one or more series elements operate as a one or multi-port network.

17. The impedance-matching apparatus of claim 15, wherein the one or more shunt elements and the one or more series elements each comprise at least one reactive and/or lossless element.

18. The impedance-matching apparatus of claim 17, wherein one of the shunt elements is a capacitor and one of the series elements is an inductor.

19. An impedance-matching apparatus comprising:

at least one variable reactance element comprising;

a first terminal;

a second terminal;

at least one reactive element connected to the first terminal;

at least one switch circuit configured to selectively connect the at least one reactive element to the second terminal thereby altering a reactance between the first terminal and the second terminal, the at least one switch circuit comprising;

a bipolar junction transistor having;

an on-state, wherein a base-emitter junction is forward biased, and an AC component of a first current through a base terminal of the bipolar junction transistor is greater than an AC component of a second current through an emitter terminal of the bipolar junction transistor; and

an off-state, wherein the base-emitter junction is reverse biased, and a base-collector junction is reverse biased; and

a fixed impedance-matching section in cascade with the at least one variable reactance element and configured to be arranged in cascade with a plasma load, and comprising at least two distinct Darlington sections.

20. A method comprising:

forward biasing a base-emitter junction of a bipolar junction transistor;

conducting a first current through the bipolar junction transistor between a collector terminal of the bipolar junction transistor and a base terminal of the bipolar junction transistor,

wherein the first current has an alternating current component with a first amplitude; and

conducting a second current through the bipolar junction transistor between the collector terminal of the bipolar junction transistor and an emitter terminal of the bipolar junction transistor,

wherein the second current has an alternating current component with a second amplitude, and

wherein the second amplitude is less than the first amplitude, and the second amplitude is equal to or greater than zero.

21. A switch circuit comprising:

means for forward biasing a base-emitter junction of a bipolar junction transistor;

means for conducting a first current through the bipolar junction transistor between a collector terminal of the bipolar junction transistor and a base terminal of the bipolar junction transistor,

wherein the means for conducting the first current includes means for conducting the first current with an alternating current component with a first amplitude; and

means for conducting a second current through the bipolar junction transistor between the collector terminal of the bipolar junction transistor and an emitter terminal of the bipolar junction transistor,

wherein the means for conducting the second current includes means for conducting the second current with an alternating current component with a second amplitude, and

wherein the second amplitude is less than the first amplitude, and the second amplitude is equal to or greater than zero.