Plasma processing method and apparatus, and autorunning program for variable matching unit

A plasma processing method comprising:

• a first step of disposing a dummy substrate at a specified position in a depressurizable chamber, depressurizing the inside of the chamber to a predetermined vacuum level under the substantially same conditions as a desired process recipe, supplying a processing gas into the chamber, applying a radio frequency power of a predetermined frequency at a level from the radio frequency power supply to a radio frequency electrode via a variable matching unit to generate a plasma in the chamber, and variably controlling the impedance of the variable matching unit such that a measured value of a load impedance is matched to a plurality of reference impedance which are determined in advance;
• a second step of measuring a power of a reflected wave obtained at the side of the radio frequency power supply under the respective reference impedances and recording the measured values;
• a third step of registering a reference impedance at a time when the measured value of the reflected wave power becomes a minimum value or a value close to it among the plurality of reference impedances;
• a fourth step of disposing a substrate to be processed at the specified position in the chamber, depressurizing the inside the chamber to the predetermined vacuum level under the conditions of the process recipe, supplying a processing gas into the chamber, applying a predetermined magnitude of the radio frequency power from the radio frequency power supply to the radio frequency electrode via the variable matching unit to generate a plasma in the chamber, and variably controlling the impedance of the variable matching unit such that the measured value of the load impedance is matched to the registered reference impedance, thereby performing a plasma process on the substrate.

A plasma processing apparatus comprising:

• a chamber having a depressurized space in which a plasma process is performed on a substrate to be processed;
• a first radio frequency electrode for a plasma generation disposed inside or outside the chamber;
• a processing gas supply source for supplying a processing gas into the chamber;
• a gas exhaust unit for evacuating the inside of the chamber;
• a first radio frequency power supply for outputting a first radio frequency power of a first frequency for generating a plasma;
• a first variable matching unit electrically connected between the first radio frequency power supply and the first radio frequency electrode;
• and
• a first matching controller for variably controlling the impedance of the first variable matching unit such that the application of the first radio frequency power to the first frequency electrode is initiated under a first impedance where a peak value of a radio frequency voltage obtained at the first radio frequency electrode becomes a maximum value or a value close to it among variable impedances in the first variable matching unit in order to ignite the plasma in the chamber, and a load impedance is matched to an impedance at the side of the first radio frequency power supply after the ignition of the plasma in the chamber.

An autorunning program for determining an off preset value of impedance positions in a variable matching unit which is connected between a radio frequency power supply and a radio frequency electrode for application of a radio frequency power for generating a plasma from the radio frequency power supply to the radio frequency electrode, the program comprising:

• a module for depressurizing the inside of a chamber, applying to the radio frequency electrode a radio frequency power of a level at which no electric discharge is caused and changing the impedance of the variable matching unit to a plurality of impedance positions determined within a variable range step by step;
• a module for measuring a peak value of a radio frequency voltage obtained in a waveguide line from an output terminal of the variable matching unit to the radio frequency electrode under the respective impedance positions and recording the measured value;
• and
• a module for setting an impedance position at a time when the measured voltage peak value becomes a maximum value or a value close to it among the plurality of impedance positions as the off preset value.