Wafer stage apparatus for attracting and holding semiconductor w

Details Wafer stage apparatus for attracting and holding semiconductor w Wafer stage apparatus for attracting and holding semiconductor w

1996-04-17

1998-01-13

Watson, Robert C.

Work holders

With fluid means

Vacuum-type holding means

269329, B25B 1100

Patent

active

057070512

ABSTRACT:
A wafer stage is provided with a plurality of through holes in its central and peripheral portions. To each of the through holes is coupled an end of a vacuum line the other end of which is coupled to a vacuum pump. With each of the vacuum lines is associated a respective one of electromagnetic valves. A controller controls the timing of opening of the electromagnetic valves. When a wafer placed on the stage is warped so that its central portion is higher than its peripheral portion, the electromagnetic valves associated with the vacuum lines coupled to the peripheral portion of the stage are opened first and the electromagnetic valves associated with the vacuum lines for the central portion of the stage are opened next. When a wafer placed on the stage is warped so that its central portion is lower than its peripheral portion, on the other hand, the electromagnetic valves associated with the vacuum lines coupled to the central portion of the stage are opened first and the electromagnetic valves associated with the vacuum lines for the peripheral portion of the stage are opened next. This permits a greatly warped wafer to be attracted to the stage in a state where it is made flat.

REFERENCES:
patent: 3729206 (1973-04-01), Cachon et al.
patent: 4131267 (1978-12-01), Ono et al.
patent: 4684113 (1987-08-01), Douglas et al.
patent: 4693458 (1987-09-01), Lewecke et al.
patent: 5249785 (1993-10-01), Nelson et al.
patent: 5372357 (1994-12-01), Blaimschein

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