| 摘要 |
PURPOSE:To obtain accurate secondary differential value of light emitting intensisty and judge the end point of high precision etching by monitoring light emitting intensity of plasma in the particular wavelength and eliminating noise element of light emitting intensity by digital operation processing. CONSTITUTION:A water 3 is placed on a lower electrode 2 within an etching chamber 1, the etching gas is supplied and plasma discharge is generated by applying a high frequency signal from a high frequency signal generator 4. Only the particular wavelength is extracted with a spectrometer 6 from the spectrum of such plasma and the particular wavelength is converted into a voltage with an optoelectro converter 7. This voltage is amplifier to a predetermined value with an analog amplifier 8, an output thereof is applied to an A/D converter 10 through an isolation amplifier 9 and the light emitting intensity of particular waveform is converted to a digital value and is then applied to a microcomputer 11. The secondary differentiation values are obtained from the moving averages of sampling values of light emitting intensity of particular wavelength and moreover the moving averages of these values are compared with preset values in order to judge the end point of etching. |
