Harmonic Derived Arc Detector

• US 20080197854A1
• Filed: 02/16/2007
• Published: 08/21/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Valcore, John, Radomski, Aaron T., Smyka, Jonathan, Polizzo, Salvatore, Han, Yufeng
• Granted Patent: US 7,728,602 B2
• Time in Patent Office: Days
• US Class Current: 324/500
• CPC Class Codes: H01J 2237/0206 Extinguishing, preventing or controlling unwanted discharges
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32944 Arc detection
• CPC Class Codes: H05H 1/0062 by using microwaves

Abstract

An arc detection system includes a radio frequency (RF) signal probe that senses a RF signal at an input of a RF plasma chamber and that generates a signal based on at least one of the voltage, current, and power of the RF signal. A signal analyzer receives the signal, monitors the signal for frequency components that have a frequency greater than or equal to a fundamental frequency of the RF signal, and generates an output signal based on the frequency components. The output signal indicates that an arc is occurring in the RF plasma chamber.

Claims

1. An arc detection system, comprising:

a radio frequency (RF) signal probe that senses a RF signal at an input of a RF plasma chamber and that generates a signal based on at least one of the voltage, current, and power of the RF signal; and

a signal analyzer that receives the signal, monitors the signal for frequency components that have a higher frequency than a fundamental frequency of the RF signal, and that generates an output signal based on the frequency components wherein the output signal indicates that an arc is occurring in the RF plasma chamber.

2. The arc detection system of claim 1 wherein the frequency components include at least one or more of a second harmonic through ninth harmonic of the fundamental frequency.

3. The arc detection system of claim 1 wherein the signal analyzer generates the output signal based on a phase of the signal.

4. The arc detection system of claim 1 wherein the signal analyzer compares an amplitude of the signal to a first predetermined threshold.

5. The arc detection system of claim 4 wherein the signal analyzer compares a rate of change of the signal to a predetermined rate of change.

6. The arc detection system of claim 5 wherein the signal analyzer generates the output signal when the rate of change of the signal exceeds the predetermined rate of change and the amplitude of the signal is between the first predetermined amplitude and a second predetermined amplitude.

7. The arc detection system of claim 1 further comprising a high-pass filter that filters the signal that is communicated to the signal analyzer.

8. The arc detection system of claim 7 wherein the high-pass filter is a modified Cheybshev filter.

9. The arc detection system of claim 1 wherein the signal analyzer generates the output signal further based on a signal-to-noise ratio of the signal.

10. An arc detection system, comprising:

a radio frequency (RF) signal probe that senses a RF signal at an input of a RF plasma chamber and that generates a signal based on at least one of the voltage, current, and power of the RF signal;

an analog to digital converter that converts the signal to a digital signal; and

a signal analyzer that receives the digital signal, monitors the digital signal for frequency components of the RF signal that have a frequency greater than or equal to a fundamental frequency of the RF signal, and that generates an output signal based on the frequency components wherein the output signal indicates that an arc is occurring in the RF plasma chamber.

11. The arc detection system of claim 10 wherein the frequency components include at least one of the first nine harmonics of the fundamental frequency.

12. The arc detection system of claim 10 wherein the signal analyzer generates the output signal based on a phase of the RF signal as indicated by the digital signal.

13. The arc detection system of claim 10 wherein the signal analyzer compares an amplitude of the RF signal, as indicated by the digital signal, to a predetermined amplitude.

14. The arc detection system of claim 13 wherein the signal analyzer compares a rate of change of the RF signal, as indicated by the digital signal, to a predetermined rate of change.

15. The arc detection system of claim 14 wherein the signal analyzer generates the output signal when the rate of change of the RF signal exceeds the predetermined rate of change and the RF signal amplitude is between the first predetermined threshold and a second predetermined threshold.

16. The arc detection system of claim 10 wherein the signal analyzer performs a fast-Fourier transform on the digital signal.

17. The arc detection system of claim 16 wherein the FFT generates a plurality of signals that represent corresponding harmonic frequencies of the RF signal.

18. The arc detections system of claim 17 wherein the signal analyzer generates the output signal when amplitudes of the signals exceed corresponding predetermined amplitudes.

19. The arc detection system of claim 16 wherein the FTT is a sliding-window FFT.

20. The arc detection system of claim 19 wherein the sliding-window FFT includes a window size between 3 and 5 cycles of the RF signal, inclusive.

21. The arc detection system of claim 10 further comprising a digital high-pass filter that filters the digital signal that is received by the signal analyzer.

22. The arc detection system of claim 21 wherein the digital filter is an infinite impulse response (IIR) filter.

23. The arc detection system of claim 22 wherein the IIR filter is sixth-order.

24. A method of detecting an arc in a RF plasma processing system, comprising:

sensing a RF signal at an input of a RF plasma chamber;

generating a signal based on at least one of the voltage, current, and power of the RF signal;

monitoring the signal for frequency components that have a frequency at or greater than a selected fundamental frequency within the RF signal; and

generating an output signal based on the frequency components wherein the output signal indicates that an arc is occurring in the RF plasma chamber.

25. The method of claim 24 wherein the frequency components include at least one of a first harmonic through ninth harmonic of the fundamental frequency.

26. The method of claim 24 further comprising generating the output signal based on a phase of the signal.

27. The method of claim 24 further comprising comparing an amplitude of the signal to a first predetermined threshold.

28. The method of claim 27 further comprising comparing a rate of change of the signal to a predetermined rate of change.

29. The method of claim 28 wherein generating the output signal occurs when the rate of change of the signal exceeds the predetermined rate of change and the amplitude of the signal is between the first predetermined amplitude and a second predetermined amplitude.

30. The method of claim 24 further comprising high-pass filtering the signal that is communicated to the signal analyzer.

31. The method of claim 24 further comprising generating the output signal based on a signal-to-noise ratio of the signal.

32. A method of detecting an arc in a RF plasma processing system, comprising:

sensing a RF signal at an input of a RF plasma chamber;

generating a signal based on at least one of the voltage, current, and power of the RF signal;

converting the signal to a digital signal;

monitoring the digital signal for frequency components of the RF signal that have a frequency greater than or equal to a fundamental frequency of the RF signal; and

generating an output signal based on the frequency components wherein the output signal indicates that an arc is occurring in the RF plasma chamber.

33. The method of claim 32 wherein the frequency components include at least one of a harmonic of the fundamental frequency.

34. The method of claim 32 further comprising generating the output signal based on a phase of the RF signal as indicated by the digital signal.

35. The method of claim 32 further comprising comparing an amplitude of the RF signal, as indicated by the digital signal, to a predetermined amplitude.

36. The method of claim 35 further comprising comparing a rate of change of the RF signal, as indicated by the digital signal, to a predetermined rate of change.

37. The method of claim 36 further comprising generating the output signal when the rate of change of the RF signal exceeds the predetermined rate of change and the RF signal amplitude is between the first predetermined threshold and a second predetermined threshold.

38. The method of claim 32 further comprising performing a fast-Fourier transform on the digital signal.

39. The method of claim 38 wherein the FFT generates a plurality of signals that represent corresponding harmonic frequencies of the RF signal.

40. The method of claim 39 further comprising generating the output signal when amplitudes of the signals exceed corresponding predetermined amplitudes.

41. The method of claim 38 wherein the FTT is a sliding-window FFT.

42. The method of claim 41 wherein the sliding-window FFT includes a window size between 3 and 5 cycles of the RF signal, inclusive.

43. The method of claim 32 further comprising digitally filtering the digital signal that is received by the signal analyzer.

44. The method of claim 43 wherein the digital filtering is infinite impulse response (IIR) filtering.

45. The method of claim 44 wherein the IIR filtering is sixth-order.