Distortion current mitigation in a radio frequency plasma processing chamber
Embodiments provided herein generally include apparatus, plasma processing systems and methods for distortion current mitigation. An example plasma processing system includes a voltage source coupled to an input node, which is coupled to an electrode disposed within a processing chamber, wherein the voltage source is configured to generate a pulsed voltage signal at the input node; a signal generator having an output, wherein the RF signal generator is configured to deliver a first RF signal at a first RF frequency to the input node; a bandpass filter coupled between the output of the signal generator and the input node, wherein the bandpass filter is configured to attenuate second RF signals that are outside a range of frequencies including the first RF frequency of the first RF signal; and an impedance matching circuit coupled between the bandpass filter and the input node.
1. A method of processing a substrate, comprising:
generating, by a voltage source, a pulsed voltage signal at an input node coupled to an electrode disposed within a processing chamber; and
delivering, by a radio frequency (RF) plasma generator, a first RF signal through at least a bandpass filter to the input node, wherein:
the first RF signal comprises a first RF frequency,
the bandpass filter is disposed between the RF plasma generator and the input node,
an impedance matching circuit is disposed between the bandpass filter and the input node,
the bandpass filter is configured to attenuate second RF signals that are outside of a range of frequencies that include the first RF frequency of the first RF signal; and
tuning a center frequency of the bandpass filter with at least one capacitor to match the first RF frequency of the RF signal allowing a peak power for the first RF signal at the first RF frequency.
2. The method of claim 1 , wherein a signal filter is disposed between the impedance matching circuit and the input node.
3. The method of claim 1 , wherein the bandpass filter includes a capacitor and an inductor coupled in parallel.
4. The method of claim 1 , wherein the bandpass filter includes a distributed-element filter.
5. The method of claim 1 , wherein the bandpass filter includes a first shunt capacitor, a second shunt capacitor, and a capacitor coupled in series with an inductor, wherein the capacitor and the inductor are coupled between the first shunt capacitor and the second shunt capacitor.
6. The method of claim 1 , wherein the bandpass filter has a quality factor greater than or equal to fifty.
7. The method of claim 1 , further comprising tuning a bandwidth of the bandpass filter to attenuate the second RF signals reflected from the processing chamber, wherein tuning the bandwidth of the bandpass filter comprises adjusting the bandwidth to be within ±5% from the first RF frequency of the first RF signal.
8. The method of claim 1 , wherein generating the RF signal comprises:
sweeping through a range of output frequencies for the RF signal;
selecting a frequency from the range of output frequencies that provides a peak power for the RF signal through the bandpass filter; and
generating the RF signal at the selected frequency.
9. The method of claim 1 , wherein generating the RF signal comprises generating the RF signal through at least an RF circulator and the bandpass filter.
10. The method of claim 9 , further comprising:
monitoring a power of signals reflected from the processing chamber at the RF circulator; and
stopping generation of the RF signal if the monitored power is greater than or equal to a threshold for a duration.
11. A plasma processing system, comprising:
a voltage source coupled to an input node, which is coupled to an electrode disposed within a processing chamber, wherein the voltage source is configured to generate a pulsed voltage signal at the input node;
a radio frequency (RF) signal generator having an output, wherein the RF signal generator is configured to deliver a first RF signal at a first RF frequency to the input node;
a bandpass filter coupled between the output of the RF signal generator and the input node, wherein the bandpass filter is configured to attenuate second RF signals that are outside a range of frequencies that include the first RF frequency of the first RF signal, wherein a center frequency of the bandpass filter is tuned with at least one capacitor to match the first RF frequency of the RF signal allowing a peak power for the first RF signal at the first RF frequency; and
an impedance matching circuit coupled between the bandpass filter and the input node.
12. The plasma processing system of claim 11 , further comprising a signal filter disposed between the impedance matching circuit and the input node.
13. The plasma processing system of claim 11 , wherein the bandpass filter includes a capacitor and an inductor coupled in parallel.
14. The plasma processing system of claim 11 , wherein the bandpass filter includes a distributed-element filter.
15. The plasma processing system of claim 11 , wherein the bandpass filter includes a first shunt capacitor, a second shunt capacitor, and a capacitor coupled in series with an inductor, wherein the capacitor and the inductor are coupled between the first shunt capacitor and the second shunt capacitor.
16. The plasma processing system of claim 11 , wherein the bandpass filter has a quality factor greater than or equal to fifty.
17. The plasma processing system of claim 11 , wherein:
the RF signal generator is configured to sweep through a range of output frequencies for the RF signal;
the plasma processing system further comprises:
a memory; and
a processor coupled to the memory, the processor and the memory being configured to select a frequency from the range of output frequencies that provides a peak power for the RF signal through the bandpass filter; and
wherein RF signal generator is configured to generate the RF signal at the selected frequency.
18. The plasma processing system of claim 11 , further comprising:
a memory; and
a processor coupled to the memory, the memory including instructions that when executed by the processor is configured to:
monitor a power of signals reflected from the processing chamber at an RF circulator; and
stop generation of the RF signal at the RF signal generator if the monitored power is greater than or equal to a threshold for a duration.
19. A plasma processing system, comprising:
a voltage source coupled to an input node coupled to an electrode disposed within a processing chamber, wherein the voltage source is configured to generate a pulsed voltage signal at the input node;
a radio frequency (RF) signal generator having an output, wherein the RF signal generator is configured to generate a RF signal overlaid on the pulsed voltage signal at the input node;
an RF circulator coupled between the output of the RF signal generator and the input node;
a memory; and
a processor coupled to the memory, the processor and the memory being configured to:
monitor a power of signals reflected from the processing chamber at the RF circulator; and
stop generation of the RF signal at the RF signal generator if the monitored power is greater than or equal to a threshold for a duration.