| 摘要 |
PURPOSE:To accurately determine the end point of an etching without reception of influence of a variation in an emitting light intensity due to a loading effect by differentiating a voltage signal responsive to a light intensity, and determining the end point of the etching based on the fact that the differentiated value becomes a predetermined range larger than a predetermined value after it becomes smaller than the set value smaller than a predetermined value. CONSTITUTION:When a plasma discharge is generated in a vacuum chamber 1 in which an etching is started, an emitting light intensity of the discharge initially becomes high. In this case, a photoelectric converter 5 receives a light having a wavelength passed through a spectral filter 4 of the emitting light of the discharge and outputs a voltage signal (v) responsive to the intensity. A microcomputer 7 differentiates a stored digital voltage signal V, and stores the differentiated value (dV/dt). Simultaneously, whether dead time DT is elapsed from the start of the etching or not is judged, and then whether the value (dV/dt) of the signal V becomes lower than a threshold value (a) or less or not is judged. Thereafter, when the value (dV/dt) becomes zero, it is determined as an etching end point, and an etching end signal is output. As a result, the etching is finished. |
