Plasma treatment apparatus and method

A plasma treatment apparatus for plasma-treating a substrate in a reduced-pressure atmosphere, comprising:

• an electrically grounded chamber;
• a first electrode located inside the chamber;
• a second electrode located inside the chamber and facing the first electrode, said second electrode having a surface on which the substrate to be plasma-treated is placed;
• gas supply means for supplying a plasma generating gas into the chamber from a region where the first electrode is located;
• exhaust means for exhausting gas from the chamber, said exhaust means and said gas supply means controlling the chamber to have an internal pressure which is within 10 to 250 mTorr;
• and
• a plasma generating circuit for generating a high-frequency electric field between the first and second electrodes,
• said plasma generating circuit including:
• a high-frequency signal source for generating a high-frequency signal;
• a phase controller for controlling a phase of the high frequency signal and producing first and second high-frequency output signals;
• a first circuit including a first amplifier for amplifying the first high-frequency output signal produced by phase control, said first circuit applying the amplified first high-frequency output signal to the first electrode;
• a second circuit including a second amplifier for amplifying the second high-frequency output signal produced by phase control, said second circuit applying the amplified second high-frequency output signal to the second electrode;
• and
• a detector for detecting products generated by chemical reaction in the chamber, and for supplying a detection signal to the phase controller,
• wherein said phase controller controls phases of the signals such that:
• in an initial period of processing, the first and second high-frequency output signals applied to the first and second electrodes have a phase difference of anisotropic etching, and
• when a change in the products in the chamber has reached a threshold value, the first and second high-frequency output signals applied to the first and second electrodes have a phase difference of high isotropic etching tendency.