Plasma processing apparatus and high frequency generator

1. A plasma processing apparatus that performs a processing on a processing target object using plasma, the plasma processing apparatus comprising:

a processing container configured to perform a processing by plasma therein; and

a plasma generating mechanism including a high frequency generator disposed outside of the processing container to generate high frequency waves, the plasma generating mechanism being configured to generate plasma in the processing container using the high frequency waves generated by the high frequency generator,

wherein the high frequency generator includes:

a high frequency oscillator configured to oscillate the high frequency waves;

a power supply unit configured to supply a power to the high frequency oscillator;

a waveguide path configured to propagate the high frequency waves oscillated by the high frequency oscillator to the processing container side which becomes a load side; and

a voltage standing wave ratio variable mechanism configured to vary a voltage standing wave ratio of voltage standing waves formed in the waveguide path by the high frequency waves, according to the power supplied from the power supply unit, and

wherein the voltage standing wave ratio variable mechanism is further configured to perform a control to increase the voltage standing wave ratio when the power supplied from the power supply unit to the high frequency oscillator is lower than a predetermined value such that in a fundamental frequency waveform of the high frequency oscillator, a slope of a peak of the fundamental frequency waveform is increased and a skirt region of the peak of the fundamental frequency waveform is decreased.

2. The plasma generating apparatus of claim 1 , wherein the voltage standing wave ratio variable mechanism includes a stub mechanism provided in the waveguide path and including a rod-shaped member movable in a radial direction, a driver configured to move the rod-shaped member, and a control mechanism configured to control the movement of the rod-shaped member.

3. The plasma processing apparatus of claim 2 , wherein a plurality of rod-shaped members are provided to be spaced apart from each other in a direction where the high frequency waves travel.

4. The plasma processing apparatus of claim 2 , wherein the high frequency generator includes a directional coupler installed in the waveguide path, the directional coupler being configured to branch some of travelling waves that travel in the waveguide path and reflected waves from the load side, and

the control mechanism controls the movement of the stub member based on a travelling wave power signal and a reflected wave power signal which are obtained from the directional coupler.

5. The plasma processing apparatus of claim 1 , wherein the plasma generating mechanism includes a 4E tuner provided with four movable short-circuit plates, the four movable short-circuit plates being provided to be spaced apart from each other in the travelling direction of the high frequency waves.

6. The plasma processing apparatus of claim 2 , wherein the waveguide path includes a launcher from which the high frequency waves oscillated by the high frequency oscillator are taken out, and an isolator provided at a downstream side of the launcher, the isolator being configured to transmit a frequency signal in one direction from the high frequency oscillator to the load side, and

the stub mechanism is provided on the launcher or at the downstream side of the launcher and at an upstream side of the isolator.

7. The plasma processing apparatus of claim 1 , wherein the plasma generating mechanism includes a dielectric window configured to transmit the high frequency waves generated by the high frequency oscillator into the processing container, and a slot antenna plate having a plurality of slot holes formed therein to radiate the high frequency waves to the dielectric window.

8. The plasma processing apparatus of claim 7 , wherein the plasma generated by the plasma generating mechanism is produced by the radial line slot antenna.

9. A high frequency generator comprising:

a high frequency oscillator configured to oscillate high frequency waves;

a power supply unit configured to supply a power to the high frequency oscillator;

a waveguide path configured to propagate the high frequency waves oscillated by the high frequency oscillator to the processing container which becomes a load side; and

a voltage standing wave ratio variable mechanism configured to vary a voltage standing wave ratio of voltage standing waves formed in the waveguide path by the high frequency waves, according to the power supplied from the power supply unit,

wherein the voltage standing wave ratio variable mechanism is configured to perform a control to increase the voltage standing wave ratio when the power supplied from the power supply unit to the high frequency oscillator is lower than a predetermined value such that in a fundamental frequency waveform of the high frequency oscillator, a slope of a peak of the fundamental frequency waveform is increased and a skirt region of the peak of the fundamental frequency waveform is decreased.