Plasma processing apparatus and plasma processing method

1. A plasma processing apparatus, comprising:

a processing chamber in which a sample is processed by using a plasma;

a first radio frequency power source supplying a radio frequency power to generate the plasma;

a sample stage on which the sample is placed;

a second radio frequency power source applying a first radio frequency voltage to the sample stage;

a third radio frequency power source applying, to the sample stage, a second radio frequency voltage having a frequency which is N times a frequency of the first radio frequency voltage in a case where N is a natural number of 2 or more;

a phase controller comprising at least one variable phase shifter and configured to generate and output a first frequency pulsar control signal to said second radio frequency power source, and a second frequency pulsar control signal to said third radio frequency power source; and

a controller configured to

control the phase controller such that a phase difference between the phase of the first radio frequency voltage and the phase of the second radio frequency voltage reaches a predetermined value, the predetermined value being determined by said controller setting a phase difference of said variable phase shifter to zero followed by sweeping said phase difference from 0 to 360 degrees to obtain a characteristic curve, and selecting said predetermined value from a point on said characteristic curve based on a minimum value of a peak-to-peak voltage of a radio frequency voltage obtained by superimposing the first radio frequency voltage and the second radio frequency voltage; and

adjust a ratio of a frequency of the second radio frequency voltage to a frequency of the first radio frequency voltage such that an etching rate distribution is a desired etching rate distribution,

wherein said at least one variable phase shifter is configured to adjust a phase difference at said second frequency pulsar control signal with respect to said first frequency pulsar control signal in response to a control signal received from a voltage monitor such that a peak-to-peak voltage of a radio frequency voltage-s applied to said sample stage.

2. A plasma processing apparatus, comprising:

a processing chamber in which a sample is processed by using a plasma;

a first radio frequency power source supplying a radio frequency power to generate the plasma;

a sample stage on which the sample is placed;

a second radio frequency power source applying a first radio frequency voltage to the sample stage;

a third radio frequency power source applying, to the sample stage, a second radio frequency voltage; and

a pulse controller configured to generate and output a first frequency pulsar control signal to said second radio frequency power source, and a second frequency pulsar control signal to said third radio frequency power source; and

a controller configured to control a phase controller such that a phase difference between a phase of the first radio frequency voltage and a phase of the second radio frequency voltage reaches a predetermined value, the predetermined value being determined by said controller setting a phase difference of said variable phase shifter to zero followed by sweeping said phase difference from 0 to 360 degrees to obtain a characteristic curve, and selecting said predetermined value from a point on said characteristic curve based on a minimum value of a peak-to-peak voltage of a radio frequency voltage obtained by superimposing the first radio frequency voltage and the second radio frequency voltage.

3. A plasma processing apparatus, comprising:

a processing chamber in which a sample is processed by using a plasma;

a first radio frequency power source supplying a radio frequency power to generate the plasma;

a sample stage on which the sample is placed;

a second radio frequency power source applying a first radio frequency voltage to the sample stage;

a third radio frequency power source applying, to the sample stage, a second radio frequency voltage having a frequency which is N times a frequency of the first radio frequency voltage in a case where N is a natural number of 2 or more;

a phase controller comprising at least one variable phase shifter and configured to generate and output a first frequency pulsar control signal to said second radio frequency power source, and a second frequency pulsar control signal to said third radio frequency power source;

a voltage monitor detecting a minimum value of a peak-to-peak voltage of a radio frequency voltage obtained by superimposing the first radio frequency voltage and the second radio frequency voltage; and

a controller configured to control the phase controller such that a phase difference between a phase of the first radio frequency voltage and a phase of the second radio frequency voltage reaches a value determined by setting a phase difference of said variable phase shifter to zero followed by sweeping said phase difference from 0 to 360 degrees to obtain a characteristic curve, and selecting said predetermined value from a point on said characteristic curve based on the minimum value of the peak-to-peak voltage detected by the monitor,

wherein said at least one variable phase shifter is configured to adjust a phase difference at said second frequency pulsar control signal with respect to said first frequency pulsar control signal in response to a control signal received from the voltage monitor such that a peak-to-peak voltage of a radio frequency voltage applied to said sample stage is a minimum value.

4. The plasma processing apparatus according to claim 3 , wherein the controller is further configured to adjust a ratio of a frequency of the second radio frequency voltage to a frequency of the first radio frequency voltage such that an etching rate distribution is a desired etching rate distribution.