Optical: systems and elements – Compound lens system – With curved reflective imaging element
Patent
1995-12-12
1998-09-29
Nguyen, Thong
Optical: systems and elements
Compound lens system
With curved reflective imaging element
359730, 359858, G02B 1700, G02B 2100, G02B 2300, G02B 510
Patent
active
058153101
ABSTRACT:
An optical projection reduction system used in photolithography for the manufacture of semiconductor devices having a first mirror pair, a second field mirror pair, and a third mirror pair. Electromagnetic radiation from a reticle or mask is reflected by a first mirror pair to a second field mirror pair forming an intermediate image. A third mirror pair re-images the intermediate image to an image plane at a wafer. All six mirrors are spherical or aspheric and rotationally symmetrical about an optical axis. 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 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.
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Jewell et al, Reflective Systems Design Study For Soft X-Ray Projection Lithography, Aug. 3, 1990, J. Vac. Sci. Technol B8(6), Nov./Dec. 1990;1990 American Vaccum Society; pp. 1519 to 1523.
Fattibene Arthur T.
Fattibene Paul A.
Nguyen Thong
Robinson Mark A.
SVG Lithography Systems, Inc.
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