Variable output impedance RF generator
Various RF plasma systems are disclosed that do not require a matching network. In some embodiments, the RF plasma system includes an energy storage capacitor; a switching circuit coupled with the energy storage capacitor, the switching circuit producing a plurality of pulses with a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; a resonant circuit coupled with the switching circuit. In some embodiments, the resonant circuit includes: a transformer having a primary side and a secondary side; and at least one of a capacitor, an inductor, and a resistor. In some embodiments, the resonant circuit having a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV.
1. An RF system comprising:
an energy storage capacitor;
a switching circuit coupled with the energy storage capacitor, the switching circuit producing a plurality of pulses with a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts;
a resonant circuit coupled with the switching circuit, the resonant circuit comprising:
a transformer having a primary side and a secondary side; and
a circuit element selected from the group consisting a capacitor, an inductor, and a resistor,
the resonant circuit having a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV; and
an energy recovery circuit coupled with the energy storage capacitor and the secondary side of the transformer, the energy recovery circuit comprising a diode and an inductor.
2. The RF system according to claim 1 , further comprising a plasma chamber coupled with the resonant circuit.
3. The RF system according to claim 1 , wherein the switching circuit comprises either a full-bridge driver or a half-bridge driver.
4. The RF system according to claim 1 , wherein the resonant circuit comprises an inductor, and the resonant frequency comprises
f
resonant
≈
1
2
π
(
L
)
(
C
)
,
where the inductance L includes any stray inductance of the transformer and the inductance of the inductor, and the capacitance C includes any stray capacitance of the transformer.
5. The RF system according to claim 1 , wherein the resonant circuit comprises a capacitor, and the resonant frequency comprises
f
resonant
≈
1
2
π
(
L
)
(
C
)
,
where the inductance L includes any stray inductance of the transformer, and the capacitance C includes any stray capacitance of the transformer and the capacitance of the capacitor.
6. An RF plasma system comprising:
a high voltage switching power supply producing a plurality of pulses with a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; and
a resonant circuit coupled with the switching power supply, the resonant circuit having a resonant frequency substantially equal to the pulse frequency and the resonant circuit increases the amplitude of the plurality of pulses to a voltage greater than 2 kV; and
a plasma chamber coupled with the resonant circuit.
7. The RF plasma system according to claim 6 , further comprising a transformer coupled with the resonant circuit.
8. The RF plasma system according to claim 6 , further comprising a resistive output stage.
9. The RF plasma system according to claim 6 , further comprising an energy recovery stage.
10. The RF plasma system according to claim 6 , further comprising a bias compensation circuit.
11. The RF plasma system according to claim 6 , wherein either or both the inductance (L) and/or the capacitance (C) of the transformer determine the resonant frequency according to:
f
resonant
≈
1
2
π
(
L
)
(
C
)
.
12. The RF plasma system according to claim 6 , wherein the resonant frequency comprises
f
resonant
≈
1
2
π
(
L
)
(
C
)
,
where the inductance L includes any stray inductance of the transformer and the capacitance C includes any stray capacitance of the transformer.
13. The RF plasma system according to claim 6 , wherein the high voltage switching power supply comprises either a full-bridge driver or a half-bridge driver.
14. The RF plasma system according to claim 6 , wherein the switching power supply is driven with a frequency selected from the group consisting of 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, and 50 MHz.
15. An RF plasma system comprising:
a high voltage switching power supply producing a plurality of pulses with a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz;
an inductively coupled plasma source comprising a coil that is electrically coupled with the high voltage switching power supply; and
a capacitor, wherein the capacitor and the inductance of the inductively coupled plasma source resonate with a resonant frequency substantially equal to the pulse frequency.
16. The RF plasma according to claim 15 , wherein the resonant frequency comprises
f
resonant
≈
1
2
π
(
L
)
(
C
)
,
where the inductance L includes the inductance of the inductively coupled plasma source and the capacitance C includes the capacitance of the capacitor.
17. The RF plasma according to claim 15 , wherein the high voltage switching power supply comprises either a full-bridge driver or a half-bridge driver.
18. An RF plasma system comprising:
a high voltage switching power supply producing a plurality of pulses with a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz;
a capacitively coupled plasma; and
an inductor, wherein the inductor and the capacitance of the capacitively coupled plasma form a resonant circuit with a resonant frequency substantially equal to the pulse frequency.
19. The RF plasma according to claim 18 , wherein the resonant frequency comprises
f
resonant
≈
1
2
π
(
L
)
(
C
)
,
where the inductance L includes the inductance of the inductor and the capacitance C includes the capacitance of the capacitively coupled plasma.
20. The RF plasma according to claim 18 , wherein the high voltage switching power supply comprises either a full-bridge driver or a half-bridge driver.