Sensorless rf impedance matching network

A non-transitory computer readable storage medium having stored thereon instructions that when executed by a processor perform a method for plasma processing a substrate, comprising:

• supplying from an RF power source RF power at a first power level suitable for igniting and maintaining a plasma within a processing volume of a plasma processing chamber;
• measuring at the RF power source a reflected power at the first power level;
• comparing the measured reflected power to a first threshold;
• transmitting a result of a comparison to the first threshold to a controller of a matching network;
• setting at the matching network at least one variable capacitor to a first position based on the comparison of the measured reflected power at the first power level to the first threshold;
• supplying from the RF power source the RF power at a second power level different from the first power level, the second power level for plasma processing the substrate disposed within the plasma processing chamber;
• measuring at the RF power source the reflected power at the second power level;
• comparing the measured reflected power at the second power level to a second threshold different from the first threshold;
• transmitting a result of a comparison of the second threshold to the controller of the matching network;
• setting at the matching network the at least one variable capacitor to a second position based on the comparison of the measured reflected power at the second power level to the second threshold;
• and
• continuing supplying the RF power at the second power level for plasma processing the substrate.

A system for processing a substrate, comprising:

• an RF power source configured to supply RF power;
• a gas source configured to supply a process gas into a processing volume of a plasma processing chamber;
• a matching network configured to set at least one variable capacitor based on a result of a comparison received from the RF power source;
• and
• a controller configured to:
• supply from the RF power source RF power at a first power level suitable for igniting and maintaining a plasma within the processing volume of the plasma processing chamber;
• measure at the RF power source a reflected power at the first power level;
• compare the measured reflected power to a first threshold;
• transmit the result of the comparison to the first threshold to a match controller of the matching network;
• set at the matching network at least one variable capacitor to a first position based on the comparison of the measured reflected power at the first power level to the first threshold;
• supply from the RF power source the RF power at a second power level different from the first power level, the second power level for plasma processing the substrate disposed within the plasma processing chamber;
• measure at the RF power source the reflected power at the second power level;
• compare the measured reflected power at the second power level to a second threshold different from the first threshold;
• transmit a result of the comparison of the second threshold to the match controller of the matching network;
• set at the matching network the at least one variable capacitor to a second position based on the comparison of the measured reflected power at the second power level to the second threshold;
• and
• continue supplying the RF power at the second power level for plasma processing the substrate.