| 摘要 |
<p>PURPOSE: To minimize the wear of holding surface by controlling applied voltage, adjusting attraction force and attracting a wafer with optimum suction force using an A/D converter and a processing unit, and observing the suction status of the wafer. CONSTITUTION: In an electrostatic attraction device of the wafer, applied voltage is controlled and attraction force is adjusted by using an A/D converter 5 and a processing unit 2, and observing the attracted status of a wafer 1. AC current value, at which the wafer 1 is held with optimum attraction force, is registered to the processing unit 2. From the next time, in attraction the wafer 1, minimum DC voltage is applied from a DC power supply 3 to electrode parts 4 and the wafer is held with minimum attraction force. The AC current value at it is A/D converted by an A/D converter 5 and the output is input to the processing unit 2. Then the present AC current value is compared with the previously registered AC current value by the processing unit 2 and if these are different, the DC power supply 3 is controlled by the signal from the processing unit 2 and the DC voltage is increased.</p> |
