| 摘要 |
PURPOSE:To bring attracting force in the case when an object to be attracted is taken away of an attracting base to approximately zero by measuring the attracting force of the object and generating erased charges corresponding to the measuring value in the attracting base. CONSTITUTION:A wafer 1 is placed on electrodes 4, 5, the surfaces thereof are coated with insulating layers 4a, 5a, and voltage is applied to the electrodes 4, 5 from a voltage generating section 10, thus attracting and fixing the wafer 1 to the electrodes 4, 5. Voltage applied to the electrodes 4, 5 is brought to zero when removing the wafer 1, and the attracting force of the wafer 1 is measured by an exfoliating-force generating section 13, a displacement member 12, a positional detector 14 and a chucking control section 15. Voltage of polarity reverse to one in case of attraction is applied to the electrodes 4, 5 so that attracting force is minimized in response to the measuring value. Accordingly, charges charged to an insulating layer 3 such as silicon oxide coating the surface of the wafer 1 are removed, and the wafer 1 is not subject to stress and can be removed. The wafer 1 is not attracted to an arm for carrying, etc. by residual charges. |
