Pellicle cover for projection printing system

摘要

In a projection printing system the pattern mask, whose image is projected onto a light sensitive layer, is protected with a thin, 0.2-6 micron thick, transparent film or pellicle which is positioned an optically large distance of about 1-125 mm from the mask surface by a spacer member. Any dirt particles on the surface of the pellicle will be out of focus and are not printed in the light sensitive layer. A pellicle can also be employed to protect the light sensitive layer at the image plane.