| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure the thickness of a wafer even in the case the wafer is inclined. SOLUTION: A tank 18 is formed by installing a diaphragm 17 so as to cover an upper aperture of a base member 15 shaped like a cylindrical vessel, and the lower edge of shaft 25 of a sensor head 16 is installed on the diaphragm 17. A receiving member 24 shaped like a shallow vessel, which is disposed in close proximity to the under surface of the wafer 12, is set on the sensor head 16, and a thickness sensor 26, which detects the thickness of the wafer 12 without contact, is set at the center of the bottom of the receiving member 24. A liquid channel 28, which links the tank 18 and the receiving member 24, is disposed in the shaft 25. Demineralized water 22 is supplied from a liquid inlet 20 into the tank 18 and fills the tank 18. Then, the demineralized water 22 is introduced into the receiving member 24 through the liquid channel 28, fills the receiving member 24 and overflows from the upper edge of an outer wall 24a. In this condition, the under surface of the wafer 12 is in contact with the demineralized water 22, and the thickness of the wafer 12 is measured.
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