Photocopying – Contact printing – Methods
Patent
1974-06-24
1976-05-04
Gonzales, John
Photocopying
Contact printing
Methods
29569R, 29578, 269 21, 279 3, 355 91, G03B 2702, G03B 2720
Patent
active
039551636
ABSTRACT:
A non-planar semiconductor wafer chuck having a plurality of outwardly extending channels in the chuck face and a plurality of vacuum/pressure ports extending through the chuck and communicating with the face thereof. When a semiconductor wafer is positioned with respect to an overlying photomask by the chuck, atmospheric pressure is applied to the centrally located port or ports and a vacuum is applied to the peripheral ports of the chuck. The resulting pressure differentials acting in concert with a surrounding vacuum chamber causes the central portion of the wafer to rise against the photomask while the peripheral portions of the wafer are drawn down into the channels. At this point in the operational sequence, the normally trapped nitrogen can escape through breaks in the peripheral seal between the mask and wafer which are formed by the downwardly extending wafer surface in each channel. Thereafter, pressure is applied to all of the ports to press the wafer firmly against the overlying photomask for subsquent exposure.
REFERENCES:
patent: 3510217 (1970-05-01), Cirimele
Birch Richard J.
Gonzales John
The Computervision Corporation
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