Plasma delivery system for modulated plasma systems
Plasma processing systems and methods are disclosed. The plasma processing system includes a high-frequency generator configured to deliver power to a plasma chamber and a low-frequency generator configured to deliver power to the plasma chamber. A filter is coupled between the plasma chamber and the high-frequency generator, and the filter suppresses mixing products of high frequencies produced by the high-frequency generator and low frequencies produced by the low-frequency generator.
1. A plasma processing system comprising:
a high-frequency generator configured to deliver power to a plasma chamber;
a low-frequency generator configured to deliver power to the plasma chamber; and
a filter coupled between the plasma chamber and the high-frequency generator, the filter configured to suppress power outside of a bandwidth around a frequency of the high-frequency generator,
wherein the suppression of power at the frequency of the high-frequency generator is at most 2 dB,
and wherein the suppression of power at frequencies more than the frequency of the low-frequency generator from the frequency of the high-frequency generator is at least 2 dB higher than the suppression of power at the frequency of the high-frequency generator.
2. The system of claim 1 , wherein the filter is configured for ground-connected water cooling.
3. The system of claim 1 , wherein the bandwidth of the filter is 2% or less of the frequency of the high-frequency generator.
4. The system of claim 1 , wherein the bandwidth of the filter is 1.2 MHz or less.
5. The system of claim 1 , wherein the filter is configured to operate in the 1 kW to 30 kW power range.
6. The system of claim 1 , wherein the filter is configured to be at least 75% efficient.
7. The system of claim 1 , wherein a fixed or variable time delay is inserted between the filter and the plasma chamber.
8. The system of claim 1 , wherein the high frequency generator is configured to supply power at 60 MHz.
9. The system of claim 1 , wherein the low frequency generator is configured to supply power at 400 kHz.
10. The system of claim 1 , wherein the filter is tunable to compensate for manufacturing tolerances.
11. The system of claim 1 , wherein the filter is tunable to compensate for drift due to self-heating of the filter.
12. The system of claim 1 , further comprising a wideband power measurement system on the plasma chamber side of the filter.
13. A plasma processing system comprising:
a high-frequency generator configured to deliver power to a plasma chamber;
a low-frequency generator configured to deliver power to the plasma chamber;
a filter coupled between the plasma chamber and the high frequency generator, the filter including two or more helical resonators connected in parallel; and
a fixed or variable time delay coupled between the filter and the plasma chamber.
14. The system of claim 13 , wherein the filter is configured for ground-connected water cooling.
15. The system of claim 13 , wherein the helical resonators are potted.
16. The system of claim 13 , wherein the helical resonators are configured to capacitively couple to the rest of the filter.
17. A method for filtering power in a plasma processing system comprising:
supplying power to a plasma chamber with a high-frequency generator to ignite and sustain a plasma;
supplying power to a plasma chamber with a low-frequency generator that is connected to the plasma; and
suppressing power mixing products with a filter to limit variation of a time-varying load reflection coefficient presented to the high frequency generator.
18. The method of 17 , including:
cooling the filter using ground-connected water cooling.
19. The method of 17 , including:
delaying a power signal between the filter and the plasma chamber to enable impedances presented to the filter to be matched by frequency tuning the high-frequency generator.
20. The method of claim 17 , including:
tuning the frequency of the high-frequency generator for impedance matching.
21. The method of claim 17 , including:
adjusting the impedance presented to the filter by the plasma chamber to optimize efficiency of power transfer from the high frequency generator to the plasma chamber.
22. The method of claim 21 , including:
minimizing the time-average of the absolute value of load reflection coefficient presented to the filter measured with a measurement system with a bandwidth at least equal to the frequency of the low-frequency generator.
23. The method of claim 21 ,
wherein a time-average of a load reflection coefficient is optimized away from 0+j0.