Sughrue Mion, PLLC
Catadioptric projection objective
A catadioptric projection objective for imaging an off-axis effective object field arranged in an object surface of the projection objective onto an off-axis effective image field arranged in an image surface of the projection objective has: an optical axis; an effective object field situated entirely outside the optical axis and having a length A in a first direction and a width B in a second direction perpendicular to the first direction such that a circular area of minimum size enclosing the effective object field defines a radius REOF of the effective object field according to:and a circular design object field centered around the optical axis having a design object field radius RDOF, where the projection objective is essentially corrected with respect to image aberrations in zones having radial coordinates smaller than RDOF and wherein the projection objective is not fully corrected in zones having radial coordinates larger than RDOF. The conditions: RDOF=γ REOF and 1≦γ<1.4 are fulfilled. Very high image-side numerical apertures NA>1 are possible with a compact design. Arcuate effective object fields are preferably used.
Carl Zeiss SMT AG
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Alexander
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