Processing method and plasma processing apparatus
A method performed by a plasma processing apparatus including a first electrode and a second electrode is provided. The method includes applying a pulsed wave of first radio frequency (RF) power to the first electrode or the second electrode; and applying a pulsed wave of second RF power having a lower frequency than the first RF power, to the first electrode with a given phase difference relative to the pulsed wave of the first RF power. A first on-period of the second RF power and a second on-period of the second RF power are controlled such that the first on-period and the second on-period do not overlap with a period of time while the first RF power is turned on. Also, the first on-period is controlled such that the first on-period ends just before the first RF power is turned on.
1. A method performed by a plasma processing apparatus including a first electrode and a second electrode, the method comprising:
applying a pulsed wave of first radio frequency (RF) power to the first electrode or the second electrode; and
applying a pulsed wave of second RF power to the first electrode, with a given phase difference relative to the pulsed wave of the first RF power, the second RF power having a lower frequency than the first RF power; wherein the applying of the pulsed wave of the second RF power includes
controlling a first on-period of the second RF power during which the second RF power is turned on and a second on-period of the second RF power during which the second RF power is turned on, such that the first on-period and the second on-period do not overlap with a period of time while the first RF power is turned on, the first on-period being different from the second on-period; and
controlling the first on-period such that the first on-period ends just before the first RF power is turned on.
2. The method according to claim 1 , wherein
a timing when the first on-period ends is within a range between 0 seconds and 200 microseconds prior to a time when the first RF power is turned on.
3. The method according to claim 1 , further comprising
setting a first duty cycle that controls the period of time during which the first RF power is turned on, the given phase difference, an off-period that divides a period of time while the second RF power is turned on into the first on-period and the second on-period, and a start timing indicating a time when the off-period starts; wherein
the applying of the pulsed wave of the first RF power includes applying the pulsed wave of the first RF power with the first duty cycle;
the controlling of the second on-period includes
controlling a start time of the second on-period of the second RF power based on the given phase difference, and
turning off the second RF power for a period corresponding to the off-period, from a time indicated by the start timing; and
the controlling of the first on-period includes
turning on the second RF power after the period corresponding to the off-period has elapsed.
4. The method according to claim 1 , further comprising
setting a first duty cycle that controls the period of time during which the first RF power is turned on, and the given phase difference; wherein
the applying of the pulsed wave of the first RF power includes applying the pulsed wave of the first RF power with the first duty cycle;
the controlling of the first on-period includes
controlling a start time of the first on-period of the second RF power based on the given phase difference, and
turning off the second RF power at a time when the first RF power is turned on; and
the controlling of the second on-period includes
turning on the second RF power at a time when the first RF power is turned off.
5. The method according to claim 1 , wherein
the second RF power applied during the first on-period is used to ignite a plasma generated during the period of time while the first RF power is turned on.