To provide an etching method capable of measuring an etching depth even when the thickness of a layer to be etched is changed due to nonuniformity in crystal growth without depending on existence of a mask.
Two lights different in wave length emitted from a light source included in a light source detector A part 10 are radiated to a substrate 30 to be etched and reflected from the substrate 30 to be etched. Two reflection lights reflected from the substrate 30 to be etched include interference lights which are generated by the reflection lights reflected from the surface of the layer to be etched and a boundary surface between the layers to be etched. A detector included in the light source detector A part 10 converts the strength of the received two interference lights into electric signals respectively so as to output them to a control unit. The control unit obtains an etching speed, based on the frequency of the interference light having the larger amplitude than the other, and calculates the etching depth, based on the obtained etching speed and time for performing the etching.
Takeshi Sugiyama
Minetarou Hirose