Projection lens system

Abstract

This invention relates to a projection lens system used for transferring circuit or other patterns from masks, etc. on which the circuit patterns are drawn onto semiconductor wafers by projection photolithography, and provides a projection lens system which makes high resolving power of the order of a few micrometers and wide exposure coverages compatible with each other. This projection lens system includes at least two sets of lens groups, each built up of lenses having concave surfaces located opposite to each other, and includes at least one lens surface of positive refractive power between said two sets of lens groups, said two sets of lens groups all satisfying the following conditions: (1) 1/L<.vertline..phi..sub.1 .vertline.<20/L (2) 1/L<.vertline..phi..sub.2 .vertline.<20/L wherein .phi..sub.1 and .phi..sub.2 stand for the respective negative refractive powers of said oppositely located concave surfaces, and L is the distance between object and image.

Dependencies are inferred from the claim text.