| 摘要 |
PURPOSE:To certainly sense if a wafer is attracted by allowing compressed air to jet along the inner wall of the body of a conical Bernoulli chuck, and thereby changing the pressure in the space between the Bernoulli chuck body and the wafer attracted. CONSTITUTION:When a solenoid valve 8 is opened, compressed air with a specified pressure, which is set by a pressure regulator 9, is supplied to a nozzle 3 and jets out along the inner wall of the body 1 to produce an attraction force directed upward. Thereby a wafer 5 situated in the position shown by the broken line is attracted by the body 1 and reaches the position shown by the solid line. This movement of wafer 5 changes the pressure at Point A (negative) greatly, that is transmitted to a pressure sensor 10 through a sensor tube 11. Thereby the pressure sensor 10 compares the pressure at Point A with the preset value and emits an electrically converted signal to indicate if wafer 5 is in attraction. This performance is independent from the material, surface condition and attitude of the wafer as well as eventual attachment of wafer drops to the wafer.
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