| 摘要 |
PROBLEM TO BE SOLVED: To provide a thickness measuring device for measuring the thickness of a semiconductor wafer while wet etching is being executed, a wet etching device using it, and a wet etching method. SOLUTION: Measurement light from a measurement light source 11 is branched by a photocoupler 12, one branched light is applied from a probe head 13 to a semiconductor wafer W and an etching liquid layer E as reflection light, and the other is guided to a reference light generation part 14 as reference light. The reflection light and the reference light are coupled by the photocoupler 12, and interference light is detected by a photo detector 15. Then, a light intensity distribution according to the correlation between the light intensity of interference light and a reference light path is obtained by a thickness calculation part 16, and the thickness of the semiconductor wafer W is obtained according to the light path length difference between the second and third light intensity peaks from a side with a smaller reference light path length.
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