Feedback Control By RF Waveform Tailoring for Ion Energy Distribution

• US 20170062186A1
• Filed: 08/27/2015
• Published: 03/02/2017
• Est. Priority Date: 08/27/2015
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: COUMOU, David J., REINHARDT, Ross, ELNER, Yuiry, GILL, Daniel M., PHAM, Richard
• Granted Patent: US 10,395,895 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32091 the radio frequency energy being capacitively coupled to the plasma
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32155 Frequency modulation
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01J 37/32972 Spectral analysis
• CPC Class Codes: H01J 37/3299 Feedback systems

Abstract

A system for controlling RF power supplies applying power to a load, such as a plasma chamber, includes a master power supply and a slave power supply. The master power supply provides a control signal, such as a frequency and phase signal, to the slave power supply. The slave power supply receives the frequency and phase signal and also receives signals characteristic of the spectral emissions detected from the load. The slave RF power supply varies the phase and power of its RF output signal applied to the load. Varying the power controls the width of an ion distribution function, and varying the phase controls a peak of the ion distribution. Depending upon the coupling between the RF generators and the load, different spectral emissions are detected, including first harmonics, second harmonics, and, in the case of a dual frequency drive system, intermodulation distortion.

Claims

1. A radio frequency (RF) generator system comprising:

a power source that generates an RF output signal applied to a load;

a sensor that detects spectral emissions from the load, the spectral emissions including at least one of harmonics and intermodulation distortion (IMD); and

a control module that varies the output signal in accordance with one of the harmonics or the IMD detected in the spectral emissions.

2. The RF generator system of claim 1 wherein the control module adjusts one of a current or a voltage of the RF signal to vary a width of an ion energy distribution (IED) or a phase of the RF signal to vary a peak of the IED.

3. The RF generator system of claim 1 wherein the load is inductively coupled plasma (ICP) system.

4. The RF generator system of claim 3 wherein the control module varies the output signal in accordance with a selected harmonic detected in the spectral emissions.

5. The RF generator system of claim 4 wherein the control module varies a current or a voltage of the RF output signal in order to control a width of an ion energy distribution (IED) or a phase of the RF signal to vary a peak of the IED

6. The RF generator system of claim 1 wherein in a CCP system, the control module varies the output signal in accordance with a selected harmonic and a selected IMD detected in the spectral emissions.

7. The RF generator system of claim 6 wherein the control module varies a current or a voltage in the RF output signal in order to control a width of an ion energy distribution (IED) or a phase of the RF signal to vary a peak of the IED.

8. The RF generator system of claim 1 wherein the sensor is disposed in one of at an input to a matching network, at an output of a matching network, or within a RF generator.

9. The RF generator system of claim 1 wherein the control module further comprises:

a harmonic/IMD module that receives output signals from the sensor in accordance with the spectral emissions from the load; and

a phase determination module that generates a frequency or a phase to control at least one of a frequency or a phase of the power source.

61. The RF generator system of claim 1 wherein the load is a capacitively coupled plasma (CCP) system.

62. The RF generator system of claim 61 wherein the control module varies a current or a voltage of the RF output signal in order to control a width of an ion energy distribution (IED) or a phase of the RF signal to vary a peak of the IED.

10. A radio frequency (RF) power delivery system comprising:

a first power supply that generates a first RF output signal;

a second power supply that generates a second RF output signal;

a sensor that detects spectral emissions from a load, the spectral emissions including at least one of a harmonic of the first or second power supply and intermodulation distortion (IMD) between the first RF signal and the second RF signal; and

a controller that varies the second RF output signal in accordance with at least one of a control signal from the first power supply, or at least one of the harmonic or the IMD.

11. The power delivery system of claim 10 wherein the controller varies one of a current or a voltage of the second RF signal to vary a width of an ion energy distribution (IED) or a phase between the first and second RF signal to vary a peak of the IED.

12. The power delivery system of claim 11 wherein the controller varies the phase to minimize the at least one harmonic.

13. The power delivery system of claim 12 wherein when a selected harmonic is minimized, a peak occurs in the IED.

14. The power delivery system of claim 12 wherein varying the phase varies a position of a peak of the IED.

15. The power delivery system of claim 11 wherein the controller varies the phase to minimize the IMD.

16. The power delivery system of claim 15 wherein when the IMD is minimized, a peak occurs in the IED.

17. The power delivery system of claim 15 wherein varying the phase varies a position of a peak in the IED.

18. The power delivery system of claim 10 wherein one of the first power supply or second power supply is a master power supply, and the other of the first power supply or the second power supply is a slave power supply.

19. The power delivery system of claim 10 wherein the load is an inductively coupled plasma (ICP) system.

20. The power delivery system of claim 10 wherein the first power supply and the second power supply operate at substantially the same frequency.

21. The power delivery system of claim 20 wherein the controller varies the second RF output signal in accordance with the harmonic.

22. The power delivery system of claim 10 wherein the first power supply and the second power supply operate at different frequencies.

23. The power delivery system of claim 22 wherein the controller varies the second RF output signal in accordance with the harmonic and the IMD.

24. The power delivery system of claim 22 wherein one of the first power supply or the second power supply operate at a harmonic frequency of the other of the first power supply or the second power supply.

25. The power delivery system of claim 24 wherein the controller varies the second RF output signal in accordance with the harmonic and the IMD.

63. The power delivery system of claim 10 wherein the load is a capacitively coupled plasma (CCP) system.

26. A radio frequency (RF) system comprising:

a first RF generator including a first power source, the first RF generator generates a control signal; and

a second RF generator including a second power source, the second RF generator receives the control signal from the first RF generator, the control signal including phase and frequency information, the second RF generator including a signal processing unit, the signal processing unit generating at least one of a phase or a power command applied to the second power source.

27. The RF system of claim 26 wherein the signal processing unit includes a harmonic/IMD processor, the harmonic/IMD processor analyzes spectral emissions from a load powered by one of the first RF generator or the second RF generator.

28. The RF system of claim 27 wherein the signal processing unit further includes a phase determination processor, the phase determination processor receives a phase signal from the harmonic/IMD processor and generates a control signal to the second power source, the control signal varies the phase or frequency of a signal output by the second power source.

29. The RF system of claim 28 further comprising a sensor, the sensor detects the spectral emissions from the load, the sensor generates a sensor signal that varies in accordance with the spectral emissions, wherein the sensor signals are applied to the harmonic/IMD processor.

30. The RF system of claim 27 wherein harmonic/IMD processor outputs a phase signal to a phase module, the phase module generates a phase control signal to the second power source in accordance with the phase signal and the control signal from the first RF generator, the phase control signal varies a phase of the second power source.

31. The RF system of claim 27 wherein one of the first power source or second power source is a master power supply, and the other of the first power source or the second power source is a slave power supply.

32. A controller for a RF power supply system comprising:

a harmonic/intermodulation distortion (IMD) processor, the IMD processor receiving a frequency input signal and spectral emissions sensed from a load, the harmonic/IMD processor generating a phase setting; and

a phase determination processor, the phase determination processor receiving at least one of the frequency input signal, the phase setting, or a sensor signal characteristic of a power applied to the load, the phase determination processor generating a phase control signal in accordance with the received signals.

33. The controller of claim 32, wherein a phase of a RF power source associated with the controller is varied in accordance with the phase control signal.

34. The controller of claim 33 wherein a frequency of a RF power source associated with the controller is varied in accordance with the phase control signal.

35. The controller of claim 33 further comprising a power determination processor, the power determination processor receives the frequency input signal and the sensor signal, the power determination processor generating a power control signal.

36. The controller of claim 35 wherein the power control signal controls a power output by a RF source associated with the controller.

37. The controller of claim 32 further comprising a power determination processor, the power determination processor receives the frequency input signal and the sensor signal, the power determination processor generating a power control signal.

38. The controller of claim 37 wherein the power determination processor adjusts one of a voltage or a current output by a RF source associated with the controller to vary a width of an ion energy distribution (IED).

39. The controller of claim 37 wherein the phase determination processor adjusts a phase of a RF source associated with the controller to vary a peak in an ion energy distribution (IED).

40. The controller of claim 32 wherein controller controls power signals applied to load in an inductively coupled plasma (ICP) system.

41. The controller of claim 32 wherein the controller controls at least one of a first power supply or a second power supply, wherein the first power supply and the second power supply operate at substantially the same frequency.

42. The controller of claim 41 wherein the controller varies an output of the at least one of a first power supply or a second power supply in accordance with a harmonic.

43. The controller of claim 32 wherein the controller controls at least one of a first power supply or a second power supply, wherein the first power supply and the second power supply operate at substantially different frequencies.

44. The controller of claim 43 wherein the controller varies an output of the at least one of a first power supply or a second power supply in accordance with a harmonic and an IMD.

45. The controller of claim 43 wherein one of the first power supply or the second power supply operate at a harmonic frequency of the other of the first power supply or the second power supply.

46. The controller of claim 45 wherein the controller varies an output of the at least one of a first power supply or a second power supply in accordance with a harmonic and an IMD.

64. The controller of claim 32 wherein controller controls power signals applied to load in a capacitively coupled plasma (CCP) system.

47. A method for controlling a radio frequency (RF) generator comprising:

detecting spectral emissions from a load, the spectral emissions including at least one a harmonic and intermodulation distortion (IMD); and

varying an output signal of a RF power source in accordance with one of the harmonic or the IMD detected in the spectral emissions.

48. The method of claim 47 further comprising adjusting one of a current or a voltage of the output signal to vary a width of an ion energy distribution (IED) or a phase of the output signal to vary a peak of the IED.

49. The method of claim 47 further comprising applying the output signal to a load in an inductively coupled plasma (ICP) system.

50. The method of claim 49 wherein in an ICP system, varying the output signal in accordance with at least one selected harmonic detected in the spectral emissions.

51. The method of claim 50 further comprising varying a current or a voltage of the output signal in order to control a width of an ion electron distribution (IED) or a phase of the RF signal to vary a peak of the IED.

52. The method of claim 49 wherein in a CCP system varying the output signal in accordance with a selected harmonic and a selected IMD detected in the spectral emissions.

53. The method of claim 52 further comprising varying a current or a voltage in the RF output signal in order to control a width of an ion energy distribution (IED) or a phase of the RF signal to vary a peak of the IED.

54. The method of claim 47 further comprising sensing at an input to a matching network, at an output of a matching network, or within an RF generator.

55. The method of claim 47 further comprising operating a first power supply and a second power supply at substantially the same frequency.

56. The method of claim 55 further comprising varying operation of one of the first power supply or the second power supply in accordance with the harmonic.

57. The method of claim 47 further comprising operating a first power supply and a second power supply at different frequencies.

58. The method of claim 57 further comprising varying operation of one of the first power supply or the second power supply in accordance with the harmonic and the IMD.

59. The method of claim 57 further comprising operating one of the first power supply or the second power supply at a harmonic frequency of the other of the first power supply or the second power supply.

60. The method of claim 59 further comprising varying operation of one of the first power supply or the second power supply in accordance with the harmonic and the IMD.

65. The method of claim 47 further comprising applying the output signal to a load in a capacitively coupled plasma (CCP) system.