Multi-stage heterodyne control circuit
View Patent ↗A circuit for controlling an RF generator, the circuit including first and second heterodyne stages. The first heterodyne stage receives an input signal, which is based on a characteristic of an RF signal generated by the RF generator, and is configured to: mix the input signal with a first mix signal to generate a first heterodyne signal and to filter the first heterodyne signal through a low pass filter. The second heterodyne stage receives the filtered first heterodyne signal and is configured to: mix the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal and to filter the second heterodyne signal through a band pass filter. A detection stage converts the filtered second heterodyne signal to a DC signal, and a power control stage receives the DC signal and controls the RF signal in response to the DC signal.
1. A circuit for controlling an RF generator, the circuit comprising:
a first heterodyne stage receiving an input signal, the input signal being based on a characteristic of an RF signal generated by the RF generator, with the first heterodyne stage configured to:
mix the input signal with a first mix signal to generate a first heterodyne signal; and
filter the first heterodyne signal through a low pass filter;
a second heterodyne stage receiving the filtered first heterodyne signal, the second heterodyne stage configured to:
mix the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal; and
filter the second heterodyne signal through a band pass filter;
a detection stage configured to convert the filtered second heterodyne signal to a DC signal; and
a power control stage receiving the DC signal and configured to control the RF signal in response to the DC signal.
2. The circuit of claim 1 , wherein the RF signal is a pulsed RF signal.
3. The circuit of claim 1 , wherein the characteristic is a voltage of the RF signal.
4. The circuit of claim 1 , wherein the characteristic is a current of the RF signal.
5. The circuit of claim 1 , wherein the frequency of the RF signal output from the RF generator is variable.
6. The circuit of claim 1 , wherein the first heterodyne stage down-converts the input signal.
7. The circuit of claim 6 , wherein the second heterodyne stage up-converts the filtered first heterodyne signal.
8. The circuit of claim 1 , wherein the first heterodyne stage down-converts the input signal by at least an order of magnitude, and the second heterodyne stage up-converts the filtered first heterodyne signal by at least an order of magnitude.
9. A method for controlling an RF generator, the method comprising:
sensing a characteristic of an RF signal output from the RF generator and outputting a sensor signal in response to the sensed characteristic;
mixing the sensor signal with a first mix signal to generate a first heterodyne signal;
filtering the first heterodyne signal through a low pass filter;
mixing the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal;
filtering the second heterodyne signal through a band pass filter;
detecting the filtered second heterodyne signal to generate a DC signal; and
controlling the RF signal in response to the DC signal.
10. The method of claim 9 , wherein the RF signal is a pulsed RF signal.
11. The method of claim 9 , wherein the characteristic is a voltage of the RF signal.
12. The method of claim 9 , wherein the characteristic is a current of the RF signal.
13. The method of claim 9 , wherein the frequency of the RF signal output from the RF generator is variable.
14. The method of claim 9 , wherein mixing the sensor signal includes down-converting the sensor signal.
15. The method of claim 14 , wherein mixing the filtered first heterodyne signal includes up-converting the filtered first heterodyne signal.
16. The method of claim 9 , wherein:
mixing the sensor signal includes down-converting the sensor signal by at least one order of magnitude; and
mixing the filtered first heterodyne signal includes up-converting the filtered first heterodyne signal by at least one order of magnitude.
17. An RF generator comprising:
an RF generator configured to generate an RF signal;
a signal sensor configured to sense a characteristic of the RF signal and output a sensor signal in response thereto; and
a control circuit operationally coupled to the RF generator, the control circuit comprising:
a first heterodyne stage receiving the sensor signal, with the first heterodyne stage configured to:
mix the sensor signal with a first mix signal to generate a first heterodyne signal; and
filter the first heterodyne signal through a low pass filter;
a second heterodyne stage receiving the filtered first heterodyne signal, the second heterodyne stage configured to:
mix the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal; and
filter the second heterodyne signal through a band pass filter; and
a detection stage configured to convert the filtered second heterodyne signal to a DC signal;
wherein the control circuit is configured to control the RF signal in response to the DC signal.
18. The RF generator of claim 17 , wherein the RF signal is a pulsed RF signal.
19. The RF generator of claim 17 , wherein the characteristic is a voltage of the RF signal.
20. The RF generator of claim 17 , wherein the characteristic is a current of the RF signal.
21. The RF generator of claim 17 , wherein the frequency of the RF signal output from the RF generator is variable.
22. The RF generator of claim 17 , wherein the first heterodyne stage down-converts the sensor signal.
23. The RF generator of claim 22 , wherein the second heterodyne stage up-converts the filtered first heterodyne signal.
24. The RF generator of claim 17 , wherein the first heterodyne stage down-converts the sensor signal by at least an order of magnitude, and the second heterodyne stage up-converts the filtered first heterodyne signal by at least an order of magnitude.
25. A semiconductor fabrication system comprising:
an RF generator configured to generate an RF signal;
a plasma chamber operationally coupled to the RF generator to receive the RF signal;
a signal sensor operationally coupled between the RF generator and the plasma chamber, the signal sensor configured to sense a characteristic of the RF signal and output a sensor signal in response thereto; and
a control circuit operationally coupled to the RF generator and to the signal sensor, the control circuit comprising:
a first heterodyne stage receiving the sensor signal, with the first heterodyne stage configured to:
mix the sensor signal with a first mix signal to generate a first heterodyne signal; and
filter the first heterodyne signal through a low pass filter;
a second heterodyne stage receiving the filtered first heterodyne signal, the second heterodyne stage configured to:
mix the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal; and
filter the second heterodyne signal through a band pass filter; and
a detection stage configured to convert the filtered second heterodyne signal to a DC signal;
wherein the control circuit is configured to control the RF signal in response to the DC signal.
26. The system of claim 25 , wherein the RF signal is a pulsed RF signal.
27. The system of claim 25 , wherein the characteristic is a voltage of the RF signal.
28. The system of claim 25 , wherein the characteristic is a current of the RF signal.
29. The system of claim 25 , wherein the frequency of the RF signal output from the RF generator is variable.
30. The system of claim 25 , wherein the first heterodyne stage down-converts the sensor signal.
31. The system of claim 30 , wherein the second heterodyne stage up-converts the filtered first heterodyne signal.
32. The system of claim 25 , wherein the first heterodyne stage down-converts the sensor signal by at least an order of magnitude, and the second heterodyne stage up-converts the filtered first heterodyne signal by at least an order of magnitude.
33. A control circuit comprising:
a first heterodyne stage receiving an input signal, the input signal being based on a characteristic of a pulsed RF signal, with the first heterodyne stage configured to:
mix the input signal with a first mix signal to generate a first heterodyne signal; and
filter the first heterodyne signal through a low pass filter;
a second heterodyne stage receiving the filtered first heterodyne signal, the second heterodyne stage configured to:
mix the filtered first heterodyne signal with a second mix signal to generate a second heterodyne signal; and
filter the second heterodyne signal through a band pass filter;
a detection stage configured to convert the filtered second heterodyne signal to a DC signal; and
a power control stage receiving the DC signal and configured to control the pulsed RF signal in response to the DC signal.
34. The circuit of claim 33 , wherein the characteristic is a voltage of the pulsed RF signal.
35. The circuit of claim 33 , wherein the characteristic is a current of the pulsed RF signal.
36. The circuit of claim 33 , wherein the first heterodyne stage down-converts the input signal.
37. The circuit of claim 36 , wherein the second heterodyne stage up-converts the filtered first heterodyne signal.
38. The circuit of claim 33 , wherein the first heterodyne stage down-converts the input signal by at least an order of magnitude, and the second heterodyne stage up-converts the filtered first heterodyne signal by at least an order of magnitude.