Control method and plasma processing apparatus
A control method of a plasma processing apparatus including a first electrode that places a workpiece thereon includes supplying a bias power to the first electrode, and supplying a source power having a frequency higher than that of the bias power into a plasma processing space. The source power has a first state and a second state. The control method further includes a first control process of alternately applying the first state and the second state of the source power in synchronization with a signal synchronized with a cycle of a radio frequency of the bias power, or a phase within one cycle of a reference electrical state that represents any one of a voltage, current, and electromagnetic field measured in a power feeding system of the bias power.
1. A plasma processing apparatus comprising:
an electrode;
a low frequency (LF) radio frequency (RF) power supply configured to generate LF power at a first radio frequency (RF) frequency, a waveform of the first RF frequency having a cycle, a first half-cycle of the waveform being separated from a second half cycle of the waveform at a zero-crossing;
a high frequency (HF) RF power supply configured to generate HF power at a changeable RF frequency that is higher in frequency than the first RF frequency, the LF power and the HF power being applied to the electrode; and
a controller configured to control the HF RF power supply to provide the HF power at a first HF frequency during the first half-cycle of the waveform of first RF frequency, and provide the HF power at a second HF frequency during the second half-cycle of the waveform of the first RF frequency.
2. The plasma processing apparatus according to claim 1 , wherein
the zero-crossing being at a mid-point of the cycle of the waveform of the first RF frequency,
the waveform having an initial zero-crossing at an initial portion of the cycle of the waveform, and
the waveform having an end zero-crossing at an end of the cycle of the waveform.
3. The plasma processing apparatus according to claim 1 , further comprising:
impedance matching circuitry disposed in a power supply path between the LF RF power supply and the electrode and between the HF RF power supply and the electrode.
4. The plasma processing apparatus according to claim 3 , wherein
the controller is configured to control the HF RF power supply to change the HF power from the first HF frequency during the first half-cycle to the second HF frequency during the second half-cycle of the waveform so as to assist the impedance matching circuitry in reducing a reflection of RF power supplied to the electrode.
5. The plasma processing apparatus according to claim 3 , further comprising:
a voltage sensor that detects an output voltage of the impedance matching circuitry.
6. The plasma processing apparatus according to claim 1 , wherein
a frequency of the waveform of the first RF frequency is in an inclusive range of 200 kHz through 13.56 MHz.
7. The plasma processing apparatus according to claim 6 , wherein
the frequency of the waveform of the first RF frequency is in an inclusive range of 200 kHz and 400 kHz.
8. The plasma processing apparatus according to claim 1 , wherein
a minimum frequency of the changeable RF frequency is at least 13.56 MHz.
9. The plasma processing apparatus according to claim 1 , wherein
the LF RF power supply generates the LF power at a higher level than the HF power generated by the HF RF power supply.
10. The plasma processing apparatus according to claim 1 , wherein
the controller is further configured to progressively change the second HF frequency during the second half-cycle.
11. The plasma processing apparatus according to claim 10 , wherein
the controller is further configured to maintain the first HF frequency constant during the first half-cycle but progressively change the second HF frequency during the second half-cycle.
12. The plasma processing apparatus according to claim 1 , wherein
the controller is further configured to progressively increase the second HF frequency during a first portion of the second half-cycle and decrease the second HF frequency during a second portion of the second half-cycle, the second portion of the second half-cycle being later in time than the first portion of the second half-cycle.
13. A controller in a plasma processing apparatus comprising:
circuitry configured to
control a low frequency (LF) radio frequency (RF) power supply to generate LF power at a first radio frequency (RF) frequency, a waveform of the first RF frequency having a cycle, a first half-cycle of the waveform being separated from a second half cycle of the waveform at a zero-crossing;
control a high frequency (HF) RF power supply to generate HF power at a changeable RF frequency that is higher in frequency than the first RF frequency, the LF power and the HF power being applied to an electrode in the plasma processing apparatus; and
control the HF RF power supply to provide the HF power at a first HF frequency during the first half-cycle of the waveform of first RF frequency, and provide the HF power at a second HF frequency during the second half-cycle of the waveform of the first RF frequency.
14. The controller according to claim 13 , wherein
the zero-crossing being at a mid-point of the cycle of the waveform of the first RF frequency,
the waveform having an initial zero-crossing at an initial portion of the cycle of the waveform, and
the waveform having an end zero-crossing at an end of the cycle of the waveform.
15. The controller according to claim 13 , wherein:
the circuitry is configured to control the HF RF power supply to change the HF power from the first HF frequency during the first half-cycle to the second HF frequency during the second half-cycle of the waveform so as to assist an impedance matching circuitry in reducing a reflection of RF power supplied to the electrode.
16. The controller according to claim 13 , wherein
the circuitry is configured to control a frequency of the waveform of the first RF frequency to be in an inclusive range of 200 kHz through 13.56 MHz.
17. The controller according to claim 16 , wherein
the circuitry is configured to control the frequency of the waveform of the first RF frequency to be in an inclusive range of 200 kHz and 400 kHz.
18. The controller according to claim 13 , wherein
the circuitry is configured to control a minimum frequency of the changeable RF frequency to be at least 13.56 MHz.
19. The controller according to claim 13 , wherein
the circuitry is configured to control the LF RF power supply to generate the LF power at a higher level than the HF power generated by the HF RF power supply.
20. The controller according to claim 13 , wherein
the circuitry is further configured to progressively change the second HF frequency during the second half-cycle.
21. The controller according to claim 20 , wherein
the circuitry is further configured to maintain the first HF frequency constant during the first half-cycle but progressively change the second HF frequency during the second half-cycle.
22. The controller according to claim 13 , wherein
the circuitry is further configured to progressively increase the second HF frequency during a first portion of the second half-cycle and decrease the second HF frequency during a second portion of the second half-cycle, the second portion of the second half-cycle being later in time than the first portion of the second half-cycle.
23. A method for controlling a plasma processing apparatus comprising:
generating, with a low frequency (LF) radio frequency (RF) power supply, LF power at a first radio frequency (RF) frequency, a waveform of the first RF frequency having a cycle, a first half-cycle of the waveform being separated from a second half cycle of the waveform at a zero-crossing;
generating, with a high frequency (HF) RF power supply, HF power at a changeable RF frequency that is higher in frequency than the first RF frequency, the LF power and the HF power being applied to an electrode in the plasma processing apparatus; and
controlling the HF RF power supply to provide the HF power at a first HF frequency during the first half-cycle of the waveform of first RF frequency, and provide the HF power at a second HF frequency during the second half-cycle of the waveform of the first RF frequency.
24. The method according to claim 23 , wherein
the controlling includes controlling
a zero-crossing to be at a mid-point of the cycle of the waveform of the first RF frequency,
the waveform to have an initial zero-crossing at an initial portion of the cycle of the waveform, and
the waveform to have an end zero-crossing at an end of the cycle of the waveform.
25. The method according to claim 23 , wherein:
the controlling includes controlling the HF RF power supply to change the HF power from the first HF frequency during the first half-cycle to the second HF frequency during the second half-cycle of the waveform so as to assist an impedance matching circuitry in reducing a reflection of RF power supplied to the electrode.
26. The method according to claim 23 , wherein
the controlling includes controlling a frequency of the waveform of the first RF frequency to be in an inclusive range of 200 kHz through 13.56 MHz.
27. The method according to claim 26 , wherein
the controlling includes controlling the frequency of the waveform of the first RF frequency to be in an inclusive range of 200 kHz and 400 kHz.
28. The method according to claim 23 , wherein
the controlling includes controlling a minimum frequency of the changeable RF frequency to be at least 13.56 MHz.
29. The method according to claim 23 , wherein
the controlling includes controlling the LF RF power supply to generate the LF power at a higher level than the HF power generated by the HF RF power supply.
30. The method according to claim 23 , wherein
the controlling includes progressively changing the second HF frequency during the second half-cycle.
31. The method according to claim 30 , wherein
the controlling includes maintaining the first HF frequency constant during the first half-cycle but progressively change the second HF frequency during the second half-cycle.
32. The method according to claim 23 , wherein
the controlling includes progressively increasing the second HF frequency during a first portion of the second half-cycle and decreasing the second HF frequency during a second portion of the second half-cycle, the second portion of the second half-cycle being later in time than the first portion of the second half-cycle.
33. A non-transitory computer readable storage device having stored therein computer readable instructions that when executed by controller circuitry cause the controller circuitry to perform a control process in a plasma processing apparatus comprising:
generating, with a low frequency (LF) radio frequency (RF) power supply, LF power at a first radio frequency (RF) frequency, a waveform of the first RF frequency having a cycle, a first half-cycle of the waveform being separated from a second half cycle of the waveform at a zero-crossing;
generating, with a high frequency (HF) RF power supply, HF power at a changeable RF frequency that is higher in frequency than the first RF frequency, the LF power and the HF power being applied to an electrode in the plasma processing apparatus; and
controlling the HF RF power supply to provide the HF power at a first HF frequency during the first half-cycle of the waveform of first RF frequency, and provide the HF power at a second HF frequency during the second half-cycle of the waveform of the first RF frequency.