Plasma processing system

A plasma processing system for carrying out a plasma process for processing a substrate by using a plasma produced by ionizing a process gas, said plasma processing system comprising:

• a processing vessel;
• a process gas supply system for supplying a process gas into the processing vessel;
• an evacuating system for evacuating the processing vessel;
• an electrode for ionizing the process gas in the processing vessel;
• a RF power generating means for supplying RF power to the electrode to produce a plasma by ionizing the process gas in the processing vessel;
• a conversion means for relating the pressure in the processing vessel and the frequency of the RF power with the electronegativiy of the plasma produced in the processing vessel;
• and
• a control means for on trolling at least either the pressure in the processing vessel or the frequency of the RF power with reference to the conversion means so that the electronegativiy of the plasma is adjusted to a value, where the electronegativiy of the plasma is negative ion number density/plasma number density.

A controller for controlling a plasma processing system for processing a substrate by a plasma process using a plasma produced by RF power in a processing vessel, said controller comprising:

• a conversion means for relating the pressure in the processing vessel and the frequency of the RF power with the rate of the negative ion number density of the plasma produced in the processing vessel;
• a selecting means for selecting a combination of a value for the pressure in the processing vessel and a value for the frequency of the RF power, suitable for adjusting the rate of the negative ion number density of the plasma to a value determined beforehand according to conditions for the plasma process;
• and
• an output means for providing control signal for adjusting the pressure in the vessel and/or the frequency of the RF power to the values selected by the selecting means.