| 摘要 |
PROBLEM TO BE SOLVED: To exactly detect etching starting point on etching material existing in holes even if the thickness of material to be etched on substrate surface varies. SOLUTION: This detector is constituted to be used for plasma-etching the material to be etched 32 by a specific depth in holes 34 of processed substrate 30 of which surface and hole 34 are covered with the material to be etched. Provided in this case are an irradiation means 52 irradiating the holes 34 with light with wavelength longer than the width of the holes 34 and wavelength absorbed by the material to be etched 32, a light detection means 62 detecting the light intensity of reflection light reflected by the processed substrate 30, and an operation means for finding the terminal point of periodic intensity variation by interference light based on the detected light intensity and detecting the etching starting point.
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