Electricity: measuring and testing – Using ionization effects – For analysis of gas – vapor – or particles of matter
Patent
1995-07-05
1997-12-30
Brown, Glenn W.
Electricity: measuring and testing
Using ionization effects
For analysis of gas, vapor, or particles of matter
324470, 324 711, 31511121, 376143, 436153, G01N 2762, G01N 2766, H05H 146
Patent
active
057034885
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an instrument for measuring a plasma excited by a high frequency, and relates to an instrument which makes possible the accurate measurement of all parameters of a plasma excited by a high frequency.
BACKGROUND ART
By applying a voltage to an extremely small electrode inserted into a stationary plasma produced by means of direct current discharge, and thus measuring the amount of current flowing from the plasma, it is possible to measure plasma parameters such as the potential, density, electron temperature and the like of the plasma; beginning with the single probe proposed in the 1920's by Langmuir et al, various probes have been employed in plasma measurement, such as the emission probe, which was proposed later and which employed thermoelectrodes, the double probe, which employed two electrodes, and the like. These probes were effective in the measurement of direct current discharge plasma in which the plasma potential did not fluctuate over time; however, when used in the measurement of high frequency discharge plasma, such probes were greatly affected by the excitation frequency of the plasma, and this caused a problem in that the accuracy of measurement of the plasma parameters declined markedly. In addition, it was difficult to obtain accurate information about the film formation atmosphere of, for example, functional thin films, or the like, and this constituted a great hindrance to the development of high quality functional thin films.
The present invention has as an object thereof to provide an instrument for measuring plasma which is capable of accurately and simply measuring all parameters of plasma, not only in direct current discharge plasma, but also in high frequency discharge plasma.
DISCLOSURE OF THE INVENTION
The measuring instrument for plasma excited by high frequencies in accordance with the present invention is a measuring instrument for measuring all values of a plasma produced within a vacuum chamber by means of a high frequency discharge having a given frequency, characterized in comprising a wire for electrically connecting a first electrode disposed within a plasma and a terminal provided outside the vacuum chamber which serves to take out signals, and a first insulator which is provided so as to cover at least a portion of the surface of the wire, and in that the absolute value of the impedance at the given frequency between the first electrode and the ground when looking into the terminal side from the first electrode is 5 times or more the absolute value of the impedance at the given frequency between the first electrode and the plasma in a state in which no direct current flows through the first electrode.
It is preferable that a second electrode be disposed within the plasma, and that the second electrode and the first electrode be connected via a capacitor.
Furthermore, it is preferable that the impedance between the terminal and the ground when looking into the side opposite the first electrode from the terminal, at the given frequency, be made variable.
Furthermore, it is preferable that at least a portion of the wire comprises a coaxial cable, that the length of the outer conductor of this coaxial cable be approximately equivalent to an odd multiple of 1/4 the wavelength within the coaxial cable at the given frequency, and that the core and the outer conductor of the coaxial cable be provided via a capacitor at the terminal side end of the coaxial cable.
Additionally, it is preferable that at least a portion of the wire comprise a coaxial cable, that a resistor be provided between the first electrode and the core of the coaxial cable, and that a measuring instrument which is capable of measuring the high frequency voltage of the terminal at the given frequency be provided.
Hereinbelow, the function of the present invention will be explained on the basis of experiments which were conducted in the process of arriving at the present invention.
FIG. 12 shows the results of the measurement of a direct current discharge
REFERENCES:
patent: 5140223 (1992-08-01), Gesche et al.
patent: 5153519 (1992-10-01), Wentworth et al.
patent: 5175472 (1992-12-01), Johnson, Jr. et al.
patent: 5537004 (1996-07-01), Imahashi et al.
Goto et al., "A Low Damage, Low Contaminant Plasma Processing System Utilizing Energy Clean Technology," IEEE Transactions on Semiconductor Manufacturing, pp. 111-121, vol. 4, No. 2, (May 1991).
Hirayama Masaki
Ohmi Tadahiro
Brown Glenn W.
Ohmi Tadahiro
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