Plasma processing apparatus and plasma processing method
View Patent ↗A plasma processing apparatus includes a plasma-generation high-frequency power supply which generates plasma in a processing chamber, a biasing high-frequency power supply which applies high-frequency bias electric power to an electrode on which a sample is placed, a monitor which monitors a peak-to-peak value of the high-frequency bias electric power applied to the electrode, an electrostatic chuck power supply which makes the electrode electrostatically attract the sample, a self-bias voltage calculating unit which calculates self-bias voltage of the sample by monitoring the peak-to-peak value of the high-frequency bias electric power applied to the electrode, and an output voltage control unit which controls output voltage of the electrostatic chuck power supply based on the calculated self-bias voltage.
1. A plasma processing apparatus comprising:
a processing chamber in which a sample is processed by plasma generated therein; a first radio-frequency power supply which supplies a first radio-frequency electric power for generating the plasma in the processing chamber;
a second radio-frequency power supply which applies a second radio-frequency bias electric power to a stage on which the sample is placed;
a monitor which monitors a peak-to-peak value of the second radio-frequency bias electric power applied to the stage;
an electrostatic chuck power supply which makes an electrode disposed inside the stage electrostatically attract the sample;
a self-bias voltage calculating unit which calculates self-bias voltage of the sample by monitoring the peak-to-peak value of the ratio-frequency bias-electric power applied to the electrode; and
an output voltage control unit which is configured to control output voltage of the electrostatic chuck power supply based on the calculated self-bias voltage,
wherein the output voltage control unit is configured to set the output voltage of the electrostatic chuck power supply unit at a first negative value during an initial period of generating plasma which is from after plasma ignition until a plasma potential becomes stable, and thereafter set the output voltage at a second negative value for processing of the sample which is greater than both of a self-bias voltage of the sample and the first negative value, the second negative value being determined based upon an output from the monitor.
2. The plasma processing apparatus according to claim 1 , wherein when an absolute value of the self-bias voltage is smaller than electrostatic chuck voltage necessary for the attraction of the sample after the initial period, the output voltage control unit sets the output voltage at (self-bias voltage)−(electrostatic chuck voltage).
3. The plasma processing apparatus according to claim 1 , wherein when an absolute value of the self-bias voltage is larger than electrostatic chuck voltage necessary for the attraction of the sample after the initial period, the output voltage control unit sets the output voltage at (self-bias voltage)+(electrostatic chuck voltage).
4. The plasma processing apparatus according to claim 3 , wherein when an absolute value of the obtained output voltage is smaller than a prescribed value at plasma ignition, the output voltage control unit sets the output voltage at a value which is on the negative side of the self-bias voltage and capable of achieving the electrostatic chuck voltage necessary for the attraction of the sample only at plasma ignition.
5. The plasma processing apparatus according to claim 1 , further comprising a control unit which is configured to stop supply of gas to the back of the sample while processing of the sample shifts from a step to the next step in cases where the processing of the sample includes multiple steps which are executed successively and electrostatic chuck voltage varies from step to step.
6. The plasma processing apparatus according to claim 1 , wherein the output voltage control unit is configured to set the output voltage of the electrostatic chuck power supply unit, during the predetermined period after the plasma ignition, less than the plasma potential.