Multi-stage heterodyne control circuit

Patent metadata

Field	Value
Publication number	US-9591739-B2
Application number	US-201514702863-A
Country	US
Kind code	B2
Filing date	May 4, 2015
Priority date	May 2, 2014
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

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.

First claim

What is claimed is:

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 heterodyn

Assignees

• Reno Tech Inc

Inventors

• Bhutta Imran Ahmed

Classifications

• H05H1/46 Primary

  using applied electromagnetic fields, e.g. high frequency or microwave energy (H05H1/26 takes precedence) · CPC title

• H01J37/32183

  Matching circuits · CPC title

• H04B10/40

  Transceivers · CPC title

• H04B10/50

  Transmitters · CPC title

• H04B10/60

  Receivers · CPC title