Method and apparatus for measuring electron density of plasma and plasma processing apparatus

An apparatus for monitoring plasma, comprising:

• an insulating pipe inserted and attached into and to a chamber in or into which plasma is created or introduced;
• a coaxial cable provided with a probe portion formed by exposing a front core wire of the coaxial cable, and inserted into the insulating pipe from one end of the insulating pipe;
• an actuator for moving the coaxial cable in the insulating pipe in the axial direction thereof;
• a scalar reflection coefficient measuring unit for, while sweeping frequencies, transmitting electromagnetic signals of respective frequencies to the probe portion of the coaxial cable at certain power to be irradiated to a surrounding space, measuring reflection coefficients from the levels of signals reflected through the probe portion with respect to the respective frequencies, and obtaining frequency characteristics of the reflection coefficients;
• and
• a measurement operation unit for measuring a plasma absorption frequency based on a first frequency characteristic obtained by the reflection coefficient measuring unit in a state where the plasma does not exist in the chamber and a second frequency characteristic obtained by the reflection coefficient measuring unit in a state where plasma exists in the chamber, at a measurement location determined by a location of the probe portion, wherein the insulating pipe is hung between first and second supports provided in the sidewalls of the chamber.

An apparatus for monitoring plasma, comprising:

• an insulating pipe inserted and attached into and to a chamber in or into which plasma is created or introduced;
• a coaxial cable provided with a probe portion formed by exposing a front core wire of the coaxial cable, and inserted into the insulating pipe from one end of the insulating pipe;
• an actuator for moving the coaxial cable in the insulating pipe in the axial direction thereof;
• a scalar reflection coefficient measuring unit for, while sweeping frequencies, transmitting electromagnetic signals of respective frequencies to the probe portion of the coaxial cable at certain power to be irradiated to a surrounding space, measuring reflection coefficients from the levels of signals reflected through the probe portion with respect to the respective frequencies, and obtaining frequency characteristics of the reflection coefficients;
• and
• a measurement operation unit for measuring a plasma absorption frequency based on a first frequency characteristic obtained by the reflection coefficient measuring unit in a state where the plasma does not exist in the chamber and a second frequency characteristic obtained by the reflection coefficient measuring unit in a state where plasma exists in the chamber, at a measurement location determined by a location of the probe portion,
• wherein the apparatus further comprises a grounding conductor one end of which is connected to a grounding potential portion of the chamber and the other end of which is connected to the outer conductor of the coaxial cable, and
• wherein an electromagnetic wave absorber for absorbing a noise signal propagating along the outer conductor through electromagnetic induction is provided at a location of the probe portion side of the coaxial cable when viewed from a location where the grounding conductor and the outer conductor of the coaxial cable are in contact with each other.