Stabilizer for switch-mode powered RF plasma

• US 6,046,546 A
• Filed: 05/05/1998
• Issued: 04/04/2000
• Est. Priority Date: 04/16/1992
• Status: Expired due to Term

• Current Assignee: Advanced Energy Industries Incorporated
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Porter, Robert M., Mueller, Michael L.
• Primary Examiner(s): Shingleton, Michael B
• Application Number:
  US09/072,613
• Time in Patent Office: 700 Days
• Field of Search: 315/111.21, 315/111.51, 315/111.71
• US Class Current: 315/111.21
• 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 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters

Abstract

Circuitry and techniques designed to allow stable and continuous delivery of alternating power to a plasma with switch-mode power supply (16) include a variety of embodiments. Parallel, series, and other circuit elements connected across switching element (7) are tuned so that energy at other than the fundamental frequency is absorbed and dissipated. This energy may be only at the second harmonic or it may be across broad frequency ranges through selecting high impedance at the fundamental frequency and relatively low impedance at other frequencies. In overcoming instabilities, oscillations, and even changing class of operation of the switch-mode power supply, the stabilizing element absorbs the energy to avoid allowing it to affect switch (7) of power supply (16).

Claims

1. A method of stably delivering power to a plasma through an alternating signal comprising the steps of:

a. generating an alternating signal at a fundamental frequency by a switch-mode power supply;

b. transmitting said alternating signal into the plasma;

while

c. affirmatively absorbing energy at substantially other than the fundamental frequency by electrical circuitry.

2. A method of stably delivering power to a processing plasma through an alternating signal as described in claim 1 wherein said switch-mode power supply has at least one primary switching element and wherein said step of substantially absorbing energy at other than the fundamental frequency occurs prior to allowing said energy to affect said primary switching element.

3. A method of stably delivering power to a processing plasma through an alternating signal as described in claim 1 wherein said switch-mode power supply has at least one primary switching element and wherein said step of substantially absorbing energy at other than the fundamental frequency is accomplished at said primary switching element.

4. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of transmitting said power to said plasma is accomplished by a transmission line and wherein said step of substantially absorbing energy at other than the fundamental frequency is accomplished on said transmission line.

5. A method of stably delivering power to a plasma through an alternating signal as described in claim 4 wherein said step of substantially absorbing energy at other than the fundamental frequency comprises the step of subjecting said power transmission to more than one energy absorption element.

6. A method of stably delivering power to a plasma through an alternating signal as described in claim 5 wherein said step of substantially absorbing energy at other than the fundamental frequency further comprises the step of changing the phase of said alternating signal between at least two energy absorption elements.

7. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of substantially absorbing energy at other than the fundamental frequency comprises the step of utilizing a tuned circuit element.

8. A method of stably delivering power to a processing plasma through an alternating signal as described in claim 7 wherein said tuned circuit element has high impedance at said fundamental frequency.

9. A method of stably delivering power to a processing plasma through an alternating signal as described in claim 8 wherein said tuned circuit element has relatively low impedance at least one other frequency.

10. A method of stably delivering power to a processing plasma through an alternating signal as described in claim 8 wherein said tuned circuit element has relatively low impedance at the second harmonic.

11. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of substantially absorbing energy at other than the fundamental frequency comprises the step of subjecting said alternating signal to more than one energy absorption element.

12. A method of stably delivering power to a plasma through an alternating signal as described in claim 11 wherein said step of substantially absorbing energy at other than the fundamental frequency further comprises the step of changing the phase of said alternating signal between at least two energy absorption elements.

19. A method of stably delivering power to a plasma through an alternating signal as described in claim 3 wherein said primary switching element has a common connection, an output connection, and a control connection and wherein said step of substantially absorbing energy reflected back to said switch-mode power supply at other than the fundamental frequency is accomplished by a circuit element connected across said control connection and said common connection.

20. A method of stably delivering power to a plasma through an alternating signal as described in claim 3 wherein said primary switching element has a common connection, an output connection, and a control connection and wherein said step of substantially absorbing energy reflected back to said switch-mode power supply at other than the fundamental frequency is accomplished by a circuit element connected across said output connection and said common connection.

21. A method of stably delivering power to a plasma through an alternating signal as described in claim 3 wherein said step of substantially absorbing energy at other than the fundamental frequency at said switch is accomplished by utilizing a resistor connected in series with a capacitor and an inductor where the capacitor and inductor are connected in parallel.

22. A method of stably delivering power to a plasma through an alternating signal as described in claim 3 wherein said step of substantially absorbing energy at other than the fundamental frequency at said switch is accomplished by utilizing a resistor connected in parallel with a capacitor and an inductor where the capacitor and inductor are connected in series.

23. A method of stably delivering power to a plasma through an alternating signal as described in claim 4 wherein said step of absorbing energy comprises utilizing a resistor connected in series with a capacitor and an inductor where the capacitor and inductor are connected in parallel.

24. A method of stably delivering power to a plasma through an alternating signal as described in claim 6 wherein said step of absorbing energy comprises utilizing a resistor connected in parallel with a capacitor and an inductor where the capacitor and inductor are connected in series.

25. A method of stably delivering power to a plasma through an alternating signal as described in claim 4 wherein said step of absorbing energy comprises utilizing a specific length of transmission line having two conducting elements connected together at one end and a resistor connected in series with one of said conducting elements.

26. A method of stably delivering power to a plasma through an alternating signal as described in claim 4 wherein said step of absorbing energy comprises utilizing a specific length of transmission line having two conducting elements unconnected at one end and a resistor connected across said specific length of transmission line at its other end.

27. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class C operation and having a relatively short active region.

28. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class D operation.

29. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class E operation.

30. A method of stably delivering power to a plasma through an alternating signal as described in claim 1 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class AE operation.

31. A method of stably delivering power to a plasma through an alternating signal as described in claim 10 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class C operation and having a relatively short active region.

32. A method of stably delivering power to a plasma through an alternating signal as described in claim 10 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class D operation.

33. A method of stably delivering power to a plasma through an alternating signal as described in claim 10 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class E operation.

34. A method of stably delivering power to a plasma through an alternating signal as described in claim 10 wherein said step of generating the alternating power signal comprises the step of utilizing a power amplifier in class AE operation.

13. A circuit for delivering power to a plasma through an alternating signal comprising:

a. a switch-mode power supply capable of generating an alternating power signal at a fundamental frequency;

b. a transmission line which transmits said alternating power signal into the plasma; and

c. at least one energy absorption element which affirmatively absorbs energy at substantially other than the fundamental frequency.

14. A circuit for delivering power to a processing plasma through an alternating signal as described in claim 13 wherein said tuned circuit element has high impedance at said fundamental frequency.

15. A circuit for delivering power to a processing plasma through an alternating signal as described in claim 14 wherein said tuned circuit element has relatively low impedance at at least one other frequency.

16. A circuit for delivering power to a processing plasma through, an alternating signal as described in claim 14 wherein said tuned circuit element has relatively low impedance at the second harmonic.

17. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 and further comprising a second energy absorption element that substantially absorbs energy at other than the fundamental frequency.

18. A circuit for delivering power to a plasma through an alternating signal as described in claim 17 and further comprising at least one phase change element wherein said phase change element is connected between said energy absorption element and said second energy absorption element.

35. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said energy absorbing element comprises a resistor connected in series with a capacitor and an inductor where the capacitor and inductor are connected in parallel.

36. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said energy absorbing element comprises a resistor connected in parallel with a capacitor and an inductor where the capacitor and inductor are connected in series.

37. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said energy absorbing element comprises a specific length of transmission line having two conducting elements connected together at one end and a resistor connected in series with one of said conducting elements.

38. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said energy absorbing element comprises a specific length of transmission line having two conducting elements unconnected at one end and a resistor connected across said specific length of transmission line at its other end.

39. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply has a primary switching element having a common connection, an output connection, and a control connection and wherein said energy absorption element which absorbs energy at other than the fundamental frequency comprises a circuit element connected across said control connection and said common connection.

40. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply has a primary switching element having a common connection, an output connection, and a control connection and wherein said energy absorption element which absorbs energy at other than the fundamental frequency comprises a circuit element connected across said output connection and said common connection.

41. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply comprises a power amplifier in class C operation and having a relatively short active region.

42. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply comprises a power amplifier in class D operation.

43. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply comprises a power amplifier in class E operation.

44. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said switch-mode power supply comprises a power amplifier in class AE operation.

45. A circuit for delivering power to a plasma through an alternating signal as described in claim 18 wherein said switch-mode power supply comprises a power amplifier in class C operation and having a relatively short active region.

46. A circuit for delivering power to a plasma through an alternating signal as described in claim 18 wherein said switch-mode power supply comprises a power amplifier in class D operation.

47. A circuit for delivering power to a plasma through an alternating signal as described in claim 18 wherein said switch-mode power supply comprises a power amplifier in class E operation.

48. A circuit for delivering power to a plasma through an alternating signal as described in claim 18 wherein said switch-mode power supply comprises a power amplifier in class AE operation.

49. A circuit for delivering power to a plasma through an alternating signal as described in claim 13 wherein said energy absorption element comprises a tuned circuit element.