METHOD AND APPARATUS FOR MEASURING ELECTRON DENSITY OF PLASMA AND PLASMA PROCESSING APPARATUS
First Claim
1. 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.
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Abstract
An apparatus for measuring plasma electron density precisely measures electron density in plasma even under a low electron density condition or high pressure condition. This plasma electron density measuring apparatus includes a vector network analyzer in a measuring unit, which measures a complex reflection coefficient and determines a frequency characteristic of an imaginary part of the coefficient. A resonance frequency at a point where the imaginary part of the complex reflection coefficient is zero-crossed is read and the electron density is calculated based on the resonance frequency by a measurement control unit.
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Citations
11 Claims
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1. An apparatus for monitoring plasma, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification