Plasma processing apparatus and plasma processing method
A plasma processing apparatus includes a microwave generation unit configured to generate a microwave, a processing vessel configured to introduce the microwave thereinto, and a gas supply mechanism configured to supply a gas into the processing vessel, plasma being generated within the processing vessel so that a plasma processing is performed on a processing target object. The microwave generation unit includes an oscillation circuit configured to oscillate the microwave, a pulse generation circuit configured to oscillate a control wave having a predetermined frequency bandwidth at a predetermined cycle, and a frequency modulation circuit configured to modulate a frequency of the microwave to a modulated wave having the predetermined frequency bandwidth by the control wave and output the modulated wave, and the frequency modulation circuit alternately and repeatedly outputs the modulated wave and a non-modulated microwave at the predetermined cycle.
1. A plasma processing apparatus comprising:
a microwave generation unit configured to generate a microwave;
a processing vessel configured to introduce the microwave thereinto through a radial line slot antenna; and
a gas supply source configured to supply a gas into the processing vessel, plasma being generated within the processing vessel so that a plasma processing is performed on a processing target object,
wherein the microwave generation unit includes an oscillation circuit configured to oscillate the microwave,
a pulse generation circuit configured to oscillate a control wave having a predetermined frequency bandwidth at a predetermined cycle, and
a frequency modulation circuit configured to modulate a frequency of the microwave to a modulated wave having the predetermined frequency bandwidth by the control wave and output the modulated wave, and
the frequency modulation circuit is configured to alternately and repeatedly output the modulated wave and a non-modulated microwave at the predetermined cycle, and
a frequency of the microwave is controlled in real time based on a state of plasma density which is monitored by monitoring a reflected wave of the modulated wave during the period in which the control wave is oscillated within the predetermined cycle,
wherein the microwave generation unit includes an arithmetic circuit,
the pulse generation circuit oscillates a synchronous wave in a same timing as the control wave,
a synchronous sampling circuit configured to receive a synchronous wave signal from the pulse generation circuit and synchronously sample reflected wave signals from a power detector and for supplying the signals to the arithmetic circuit; and
the arithmetic circuit monitors a reflected wave of the modulated wave in accordance with the timing of the synchronous wave, and controls the frequency of the microwave based on the monitored reflected wave.
2. The plasma processing apparatus of claim 1 , wherein the frequency of the microwave is controlled by a frequency at an absorption peak of the microwave at which reflection of the reflected wave is reduced.
3. The plasma processing apparatus of claim 1 , wherein an oscillation time of the control wave is 10% or less of an entire oscillation time of the microwave.
4. A plasma processing method comprising:
supplying a gas to a processing vessel configured to introduce a microwave thereinto by a radial line slot antenna; and
generating plasma within the processing vessel to perform a plasma processing on a processing target object; and
oscillating the microwave by an oscillation circuit;
oscillating a control wave by a pulse generation circuit, and having a predetermined frequency bandwidth at a predetermined cycle,
wherein a frequency of the microwave is modulated by the control wave by a frequency modulation circuit to a modulated wave having the predetermined frequency bandwidth, and the modulated wave and a non-modulated microwave are output alternately and repeatedly at the predetermined cycle, and
wherein a frequency of the microwave is controlled in real time by an arithmetic circuit based on a state of plasma density which is monitored by monitoring a reflected wave of the modulated wave during the period in which the control wave is oscillated within the predetermined cycle,
wherein a synchronous wave is oscillated by the pulse generation circuit in a same timing as the control wave, and is supplied to a synchronous sampling circuit, and
a reflected wave of the modulated wave is received from the synchronous sampling circuit and is monitored by the arithmetic circuit in accordance with the timing of the synchronous wave, and the frequency of the microwave is controlled based on the monitored reflected wave.
5. The plasma processing method of claim 4 , wherein the frequency of the microwave is controlled by a frequency at an absorption peak of the microwave at which reflection of the reflected wave is reduced.
6. The plasma processing method of claim 5 , wherein an oscillation time of the control wave is 10% or less of an entire oscillation time of the microwave.
7. The plasma processing method of claim 4 , wherein an oscillation time of the control wave is 10% or less of an entire oscillation time of the microwave.