| 摘要 |
PROBLEM TO BE SOLVED: To control the etching depth with high accuracy by detecting the intensity of diffraction light precisely, while reducing variation of in-plane etching rate of a workpiece.SOLUTION: An etching mask including a pattern of diffraction grating is formed on the surface 22 of a wafer 20. While irradiating the surface 22 of a wafer 20 with laser light L1 and supplying an etching liquid E onto the wafer 20, the etching liquid E is held on the wafer 20. Supply of the etching liquid E is stopped after recognizing the fact that the etching liquid E has reached a predetermined level from the fact that the optical axis of diffraction light L2 from the surface 22 has reached a predetermined position. Intensity of the diffraction light L2 is measured while irradiating the surface 22 with the laser light L1, and the etching liquid E is removed after recognizing the fact that the etching depth of the wafer 20 has reached a predetermined depth from the fact that the intensity of the diffraction light L2 has reached a predetermined intensity. |
