0779528-A2 is referenced by 100 patents and cites 4 patents.

An optical projection reduction system used in photolithography for the manufacture of semiconductor devices having a first mirror pair (M1, M2; M1', M2'; M1'', M2''), a second field mirror pair (M3, M4; M3', M4'; M3'', M4''), and a third mirror pair (M5, M6; M5', M6'; M5'', M6''). Electromagnetic radiation form a reticle or mask (10) is reflected by a first mirror pair to a second field mirror pair forming an intermediate image (24, 24', 24''). A third mirror pair re-images the intermediate image to an image plane at a wafer (22). All six mirrors are spherical or aspheric and rotationally symmetrical about an optical axis (OA). An annular ring field is obtained, a portion of which may be used in a step and scan photolithography system.; In another embodiment, weak refracting elements (R1, R2, R3) are introduced to further reduce residual aberrations allowing a higher numerical aperture. In the catoptric embodiment of the present invention, a numerical aperture of 0.25 is obtained resulting in a working resolution of 0.03 microns with electromagnetic radiation having a wavelength of 13 nanometers. The optical projection reduction systems are intended for use at extreme ultraviolet to the soft X-ray wavelength range. The present invention, provides a relatively high numerical aperture and uses substantially all reflective elements, greatly facilitating the manufacture of semiconductor devices having feature sizes below 0.25 microns.

High numerical aperture ring field optical reduction system
Application Number
EP19960118465 19961118
Publication Number
0779528 (A2)
Application Date
November 18, 1996
Publication Date
June 18, 1997
Williamson David M
Svg Lithography Systems
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