Substrate processing apparatus and substrate processing method
There are provided a substrate processing apparatus and a substrate processing method realizing an effective reduction of a voltage change of a substrate on an electrode to reduce the variation of incident energy of ions entering the substrate. The substrate processing apparatus includes: a first electrode holding a substrate on a main surface of the first electrode; a second electrode facing the first electrode; a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and a pulse voltage applying unit applying to the first electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage.
1. A substrate processing apparatus, comprising:
a chamber;
an inlet configured to introduce a gas for etching into the chamber;
a first electrode disposed in the chamber and having a main surface for placing a substrate thereon;
a second electrode disposed in the chamber and facing the first electrode;
a radio frequency (RF) power source configured to apply a RF voltage to the first electrode to generate ions of the gas, the RF voltage having a frequency of 40 MHz or higher; and
a voltage pulse generator configured to superimpose a voltage waveform on the RF voltage applied to the first electrode to lead the ions onto the substrate for its etching,
the voltage waveform having a first period and a second period alternately repeated,
the first period including N1 negative voltage pulses with a frequency of ω1 and break times t1 of 0.2 μsec or less between the voltage pulses,
the second period being a break time t2 lacking a voltage pulse, the break time t2 being longer than each break time t1, and
the voltage waveform having a voltage level of zero in the break times t1 and t2.
2. The apparatus according to claim 1 , further comprising:
a voltage monitor configured to measure a voltage of the first electrode; and
a controller configured to control at least one of the number N1, the frequency co1, and the break times t1, t2 in correspondence with the measured voltage.
3. The apparatus according to claim 1 , further comprising:
a plasma monitor configured to measure an electron density of plasma; and
a controller configured to control at least one of the number N1, the frequency co1, and the break times t1, t2 in correspondence with the measured electron density.
4. The apparatus according to claim 1 , wherein the break time t1 is determined based on the expression t1<1/ωp [second], where
ω p =( e 2 N 0 /(ε 0 mi )) 1/2 :
plasma ion frequency, where
e: electron elementary quantum,
ε 0 : vacuum permittivity,
mi: mass of ions,
N 0 : plasma density.