Patent ID: 8830590
Filing Date: 2014-09-09
Classification: G02B,G03F

Abstract:
1. A microlithographic lens for imaging over an image field at an image plane a photomask that defines a plurality of die at an object plane, comprising along an optical axis: a concave mirror having an aspheric concave surface; a positive lens group spaced apart from the concave surface of the concave mirror; first and second total-internal-reflection (TIR) prisms disposed adjacent the positive lens group opposite the concave mirror and on respective sides of the optical axis, with the first prism having a first surface adjacent the object plane and the second prism having a second surface adjacent the image plane, wherein each prism has a refractive index of 1.5357 or greater at an i-line wavelength and respective TIR surfaces each having a phase-preserving coating; wherein the positive lens group consists of either three or four air-spaced lens elements, with one of the lens elements being a most mirror-wise lens element, having a positive meniscus shape and including a prism-wise concave aspheric surface; and wherein the image field is sized to include from four to six die, with each die having a nominal size of 26 mm×34 mm, the lens having substantially unit magnification at a numerical aperture of nominally 0.32, and wherein the lens has a Strehl ratio of >0.95 over the image field for at least an i-line wavelength of light.