Photocopying – Projection printing and copying cameras – Methods
Patent
1997-12-19
1999-07-06
Metjahic, Safet
Photocopying
Projection printing and copying cameras
Methods
355 71, G03B 2732, G03B 2772
Patent
active
059203803
ABSTRACT:
The present invention relates an apparatus and method for creating a bright, uniform source of partially coherent radiation for illuminating a pattern, in order to replicate an image of said pattern with a high degree of acuity. The present invention introduces a novel scatter plate into the optical path of source light used for illuminating a replicated object. The scatter plate has been designed to interrupt a focused, incoming light beam by introducing between about 8 to 24 diffraction zones blazed onto the surface of the scatter plate which intercept the light and redirect it to a like number of different positions in the condenser entrance pupil each of which is determined by the relative orientation and the spatial frequency of the diffraction grating in each of the several zones. Light falling onto the scatter plate, therefore, generates a plurality of unphased sources of illumination as seen by the back half of the optical system. The system includes a high brightness source, such as a laser, creating light which is taken up by a beam forming optic which focuses the incoming light into a condenser which in turn, focuses light into a field lens creating Kohler illumination image of the source in a camera entrance pupil. The light passing through the field lens illuminates a mask which interrupts the source light as either a positive or negative image of the object to be replicated. Light passing by the mask is focused into the entrance pupil of the lithographic camera creating an image of the mask onto a receptive media.
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Sweatt, W.C., Chow, W.W., "Investigation of Image Defects in EUV Lithography Experiments" Optical Society of America, Proceedings vol. 23, pp. 126-131, 1995.
Evans Timothy
Metjahic Safet
Nguyen Hung Henry
Sandia Corporation
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