Switching circuit for RF currents

1. A switching circuit comprising:

a first switch coupled to a first switch terminal, the first switch comprising at least one gallium nitride high-electron mobility transistor (GaN HEMT);

a second switch coupled in series with the first switch and a second switch terminal, the second switching comprising a GaN HEMT; and

at least one power source configured to provide power to the first switch and the second switch;

wherein the second switch is configured to drive the first switch ON and OFF.

2. The switching circuit of claim 1 wherein the first switch comprises four GaN HEMTs connected in series.

3. The switching circuit of claim 1 wherein the first and second switches are turned ON and OFF at the same time.

4. The switching circuit of claim 1 wherein each GaN HEMT of the first switch is driven by a gate driver, the gate driver comprising:

a diode coupled to the gate of the Gan HEMT;

a capacitor having a first terminal coupled to the gate of the Gan HEMT and a second terminal coupled to the source of the Gan HEMT; and

a resistor coupled in parallel to the capacitor.

5. The switching circuit of claim 1 further comprising:

a monitoring circuit configured to:

receive an indication that a switching circuit voltage exceeds a predetermined amount and, in response, reduce a power provided to the driving switch; or

receive an indication that a switching circuit current exceeds a predetermined amount and, in response, reduce a power provided to the driving switch.

6. The switching circuit of claim 5 wherein:

the indication that the switching circuit voltage has exceeded a predetermined amount is provided by a voltage sensing circuit, the voltage sensing circuit comprising (a) a first transformer operably coupled to the second terminal and (b) a first diode operably coupled to the monitoring circuit; and

the indication that the switching circuit current has exceeded a predetermined amount is provided by a current sensing circuit, the current sensing circuit comprising (a) a second transformer operably coupled to the second terminal and (b) a second diode operably coupled to the monitoring circuit.

7. The switching circuit of claim 1 wherein the first and second switches are configured to pass an RF current between the first switch terminal and the second switch terminal when ON, and to not pass the RF current when OFF.

8. The switching circuit of claim 1 wherein there is no inductor between the first switch and the second switch.

9. A method of controlling a switching circuit, the method comprising:

coupling a first switch to a first switch terminal, the first switch comprising at least one gallium nitride high-electron mobility transistor (GaN HEMT);

coupling a second switch in series with the first switch and a second switch terminal, the second switching comprising a GaN HEMT, wherein the second switch configured to drive the first switch ON and OFF;

coupling at least one power source to the first switch and the second switch;

driving the first switch ON to thereby drive the first and second switches simultaneously ON, and thereby pass an RF current between the first switch terminal and the second switch terminal; and

driving the first switch OFF to thereby drive the first and second switches simultaneously OFF, and thereby not pass the RF current between the first switch terminal and the second switch terminal.

10. The method of claim 9 wherein the first switch comprises four GaN HEMTs connected in series.

11. The method of claim 9 wherein each GaN HEMT of the first switch is driven by a gate driver, the gate driver comprising:

a diode coupled to the gate of the Gan HEMT;

a capacitor having a first terminal coupled to the gate of the Gan HEMT and a second terminal coupled to the source of the Gan HEMT; and

a resistor coupled in parallel to the capacitor.

12. The method of claim 9 further comprising:

receiving an indication that a switching circuit voltage exceeds a predetermined amount and, in response, reducing a power provided to the driving switch; or

receiving an indication that a switching circuit current exceeds a predetermined amount and, in response, reducing a power provided to the driving switch.

13. A method of fabricating a semiconductor, the method comprising:

placing a substrate in a plasma chamber configured to deposit a material layer onto the substrate or etch a material layer from the substrate;

energizing plasma within the plasma chamber by coupling RF power from an RF source into the plasma chamber to perform a deposition or etching; and

while energizing the plasma, carrying out an impedance match by an impedance matching network coupled between a load and an RF source, wherein the impedance matching network comprises:

a first variable component providing a first variable capacitance or inductance; and

a second variable component providing a second variable capacitance or inductance; and

wherein each of the first variable component and the second variable component has a plurality of switching circuits configured to provide the first variable capacitance or inductance and the second variable capacitance or inductance, respectively, each of the plurality of switching circuits comprising:

a first switch coupled to a first switch terminal, the first switch comprising at least one gallium nitride high-electron mobility transistor (GaN HEMT);

a second switch coupled in series with the first switch and a second switch terminal, the second switching comprising a GaN HEMT; and

at least one power source configured to provide power to the first switch and the second switch;

wherein the second switch is configured to drive the first switch ON and OFF.

14. The method of claim 13 wherein the first switch comprises four GaN HEMTs connected in series.

15. The method of claim 13 wherein the first and second switches are turned ON and OFF at the same time.

16. The method of claim 13 wherein each GaN HEMT of the first switch is driven by a gate driver, the gate driver comprising:

a diode coupled to the gate of the Gan HEMT;

a capacitor having a first terminal coupled to the gate of the Gan HEMT and a second terminal coupled to the source of the Gan HEMT; and

a resistor coupled in parallel to the capacitor.

17. The method of claim 13 further comprising:

a monitoring circuit configured to:

receive an indication that a switching circuit voltage exceeds a predetermined amount and, in response, reduce a power provided to the driving switch; or

receive an indication that a switching circuit current exceeds a predetermined amount and, in response, reduce a power provided to the driving switch.

18. The method of claim 17 wherein:

the indication that the switching circuit voltage has exceeded a predetermined amount is provided by a voltage sensing circuit, the voltage sensing circuit comprising (a) a first transformer operably coupled to the second terminal and (b) a first diode operably coupled to the monitoring circuit; and

the indication that the switching circuit current has exceeded a predetermined amount is provided by a current sensing circuit, the current sensing circuit comprising (a) a second transformer operably coupled to the second terminal and (b) a second diode operably coupled to the monitoring circuit.

19. A semiconductor processing tool comprising:

a plasma chamber configured to deposit a material onto a substrate or etch a material from the substrate; and

an impedance matching circuit operably coupled to the plasma chamber, the matching circuit comprising:

a first variable component providing a first variable capacitance or inductance; and

a second variable component providing a second variable capacitance or inductance;

wherein each of the first variable component and the second variable component has a plurality of switching circuits configured to provide the first variable capacitance or inductance and the second variable capacitance or inductance, respectively, each of the plurality of switching circuits comprising:

a first switch coupled to a first switch terminal, the first switch comprising at least one gallium nitride high-electron mobility transistor (GaN HEMT);

a second switch coupled in series with the first switch and a second switch terminal, the second switching comprising a GaN HEMT; and

at least one power source configured to provide power to the first switch and the second switch;

wherein the second switch is configured to drive the first switch ON and OFF.