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

• US 20130193867A1
• Filed: 03/06/2013
• Published: 08/01/2013
• 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 9,124,248 B2
• Time in Patent Office: Days
• US Class Current: 315/240
• 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 having a bipolar junction transistor, the bipolar junction transistor comprising:

a collector;

an emitter;

a base coupled between the collector and the emitter;

a collector terminal coupled to the collector, the collector terminal configured to pass a collector current with an alternating current component having a first amplitude;

a base terminal coupled to a base, the base terminal configured to pass a base current with an alternating current component having a second amplitude; and

an emitter terminal coupled to an emitter, the emitter terminal configured to pass an emitter current with an alternating current component having a third amplitude, the second amplitude being greater than the third amplitude.

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 and 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 the 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. A bipolar junction transistor having:

a collector having a collector terminal;

an emitter having an emitter terminal;

a base having a base terminal, the base being coupled between the collector and the emitter; and

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

16. The impedance-matching apparatus of claim 15, further comprising a fixed impedance-matching section in cascade with the bipolar junction transistor 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.

17. The impedance-matching apparatus of claim 16, wherein the one or more shunt elements and the one or more series elements operate as a one or multi-port network, and 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. A variable reactance element of an impedance-matching apparatus comprising at least one bipolar junction transistor configured to selectively connect at least one reactive element between a first and second terminal of the variable reactance element, thereby altering a reactance between the first terminal and the second terminal, the at least one bipolar junction transistor comprising:

an emitter having an emitter terminal;

a collector having a collector terminal; and

a base having a base terminal, the base coupled between the emitter and the collector via a base-emitter junction and a base-collector junction, the at least one bipolar junction transistor configured to forward bias the base-emitter junction in an on-state such that an AC component of a first current through the base terminal is greater than an AC component of a second current through the emitter terminal.

20. The variable reactance element of claim 19, wherein the at least one bipolar junction transistor is further configured to reverse bias the base-emitter junction and the base-collector junction in an off-state.

21. A method comprising:

conducting a first current through a bipolar junction transistor between a collector terminal and a base terminal; and

conducting a second current through the bipolar junction transistor between the collector terminal and an emitter terminal, the first current having an alternating current component with a first amplitude,

the second current having an alternating current component with a second amplitude,

the second amplitude being less than the first amplitude.