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Abstract

The present invention relates to a method of and apparatus for detecting the end point of plasma treatment. The method includes steps: selecting a plasma spectrum having a characteristic wavelength from the plasma spectrum occurring at the time of the plasma treatment reaction of a specimen; computing a secondary differential value of a function of the quantity of the plasma spectrum selected and the plasma treatment reaction time of the specimen; and detecting the end point of the plasma treatment reaction of the specimen by comparing the secondary differential value computed with preset reference values for judgment. The apparatus comprises a means of selecting plasma spectrum having a particular wavelength from the plasma spectrum occurring at the time of the plasma treatment reaction of the specimen, a means of converting the quantity of the plasma spectrum selected into an analog electric signal, a means of converting the analog electric signal into a value of digital data, a means of counting the plasma treatment reaction time of the specimen, a means of secondarily differentiating a function of the value of digital data and the plasma treatment reaction time, a means of making judgment by comparing the secondary differential value with preset reference values for judgment, and a means of giving an instruction for starting judgment to said means. Thus, accurate detection is achieved regardless of which curve is taken by the change in the reaction time of the quantity of plasma spectrum.

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First Claim