Plasma processing apparatus and plasma processing method
A plasma processing apparatus for processing a substrate using plasma includes a first electrode configured to mount the substrate, a second electrode disposed to face the first electrode with a predetermined space, a chamber containing the first electrode and the second electrode, the chamber being capable of adjusting an inside atmosphere, a first electric power source device configured to apply a first RF voltage for controlling a self-bias voltage generated on the substrate to the first electrode, the first electric power source device applying a substantially constant width and a substantially constant value in a peak-to-peak voltage of an RF voltage of a first frequency at intervals, and a second electric power source device configured to apply a second RF voltage of a second frequency for generating plasma between the first and second electrodes to one of the first electrode and the second electrode.
1. A plasma processing apparatus for etching a substrate using plasma, comprising:
a first electrode configured to mount the substrate;
a second electrode having a ground potential and disposed to face the first electrode with a predetermined space;
a chamber containing the first electrode and the second electrode, the chamber being capable of adjusting an inside atmosphere;
a first electric power source device connected to the first electrode to apply a first RF voltage to the first electrode for controlling a self-bias voltage generated on the substrate, the first RF voltage having:
a first frequency and a first period,
a varying negative-potential waveform during a first portion of each of the first periods, and
a ground potential value during each of the first periods other than the first portions; and
a second electric power source device connected to the first electrode to apply a second RF voltage of a second frequency for generating plasma between the first and second electrodes, the second frequency being higher than the first frequency,
wherein the first electric power source device includes:
an RF electric power source to generate a signal having a periodic waveform comprising the varying negative-potential waveform, and
a switching unit connected between the RF electric power source and the first electrode to output the signal during the first portion of the first period, the first portion being periodically repeated with a second period corresponding to a natural number of times as long as the first period; and
wherein the first portion of the first period is one fourth or less of the first period.
2. The plasma processing apparatus according to claim 1 , wherein the second RF voltage is continuously applied.
3. The plasma processing apparatus according to claim 1 , wherein the second RF voltage is applied at intervals in synchronization with the first RF voltage.
4. The plasma processing apparatus according to claim 1 , wherein the first frequency is higher than an ion frequency ω pi (=e 2 Ni/(∈ 0 M) 1/2 [Hz], where Ni is ion density (ions/m 3 ), ∈ 0 is dielectric constant of vacuum, M is mass of ion (kg), e is elementary charge of an electron) of the generated plasma.
5. The plasma processing apparatus according to claim 1 , wherein a potential of the first RF voltage becomes minimum at a middle of the first portion of the first period.