| 摘要 |
PROBLEM TO BE SOLVED: To obtain a plasma etching system in which the end point of etching can be detected with a high accuracy regardless of the aging of an optical system or a measuring equipment, contamination of an observation window, or the like. SOLUTION: A high frequency power from a high frequency power supply 3 is applied to an electrode in a vacuum tank 1 and etching gas is supplied to generate plasma. The high frequency power is turned on/off in synchronism with the pulse frequency of a pulse generator 2 thus varying plasma light emission. Variation of plasma light emission is detected by a photodetector 4 as a spectrum signal. Difference of variation of plasma light emission is measured by a synchronous detector 5 in order to remove noise and the end point of etching is detected based on that difference.
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