Method and apparatus for measuring electron density of plasma

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

1994-09-15

1995-11-28

Pascal, Robert J.

Electric lamp and discharge devices: systems

Discharge device load with fluent material supply to the...

Plasma generating

31511181, 31511141, 31511171, H01J 724

Patent

active

054711150

ABSTRACT:
A method for measuring electron density n.sub.p of a plasma in a plasma reaction chamber for semiconductor fabrication processes is capable of an accurate measurement without time-drifting of measuring values and metal contamination to semiconductor wafers. The method comprises injecting electrons in the plasma to generate a plasma oscillation, getting a plasma oscillation frequency .omega..sub.p by antenna and frequency analyzer, and easily computing n.sub.p by a well-known formula using the value of .omega..sub.p. A plasma generating apparatus for semiconductor fabrication processes is capable of keeping the electron density in a plasma reaction chamber constant. The apparatus comprises feed-back circuits for feeding back a deviation signal of the computed (n.sub.p) from a presetting value to an RF oscillator or a gas control unit so as to control RF power or pressure of a source gas, respectively.

REFERENCES:
patent: 5086255 (1992-02-01), Okamoto et al.
patent: 5274306 (1993-12-01), Kaufman et al.
patent: 5339039 (1994-08-01), Carlile et al.
Jpn. J. Appl. Phys. vol. 32 (1993), pp. 5129-5135, Part 1, No. 11A, Nov. 1993, T. Shirakawa et al., "Plasma Oscillation Method for Measurements of Absolute Electron Density in Plasma".

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