Photocopying – Projection printing and copying cameras – Methods
Patent
1978-12-01
1980-07-22
Moon, Charlie T.
Photocopying
Projection printing and copying cameras
Methods
29559, 29569R, 51235, 269 21, 430396, G03B 2900
Patent
active
042136989
ABSTRACT:
An apparatus and method for holding a thin workpiece such as a semiconductor wafer for operations which require the workpiece to have a high degree of planarity such as photolithographic printing includes positioning the workpiece onto a planar holding face comprising the points of a multiplicity of regularly spaced-apart substantially parallel pins with a thin rim encompassing all pins to contain a vacuum in the region adjacent to the workpiece. The small abutting area of each pinpoint abutment reduces the probability of dirt particles collecting on the holding face and provides a high thrust pressure to dislodge dirt particles interposed between the abutment and the workpiece. A small amount of lateral motion is imparted to the workpiece when it first contacts the holding face to brush off any dirt particles on the abutments.
REFERENCES:
patent: 1121452 (1914-12-01), Bagnall
patent: 3627338 (1971-12-01), Thompson
patent: 3747282 (1973-07-01), Katzke
patent: 3765289 (1973-10-01), Gerber
patent: 3815221 (1974-06-01), Pearl
patent: 3853313 (1974-12-01), Appenzeller
patent: 4046474 (1977-09-01), Lee
patent: 4088312 (1978-05-01), Frosch et al.
Firtion Victor A.
Herriott Donald R.
Poulsen Martin E.
Rongved Leif
Saunders Thomas E.
Bell Telephone Laboratories Incorporated
Canepa Lucian C.
Moon Charlie T.
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