| 摘要 |
PROBLEM TO BE SOLVED: To measure a delicate tilt angle with high accuracy, by making a wafer chuck, which reforms a wafer into a plane by vacuum or electrostatic adsorption, have a reference face which reflects light with a face parallel with a wafer adsorption face. SOLUTION: In this wafer chuck, the periphery of a chuck base is provided with a reference face 8 which reflects light, on the same plane as the pin 2 on the chuck base, that is, the same plane as a wafer adsorption face. This reference face 8 is a face, which is polished into a mirror face when the user achieves the final flatness, and it can reflect visible light or a laser beam. This reference face is used for measurement of the angle of the wafer chuck. The quantity of shifting of the wafer chuck 1 can be measured by the interference between reflected light 16 and a Y-axis laser beam 9. As a result, this can compensate for the change on standing of the tilt angle caused by the thermal expansion changes, etc., of a tilt stage, and can measure the delicate tilt angle with high accuracy. |
