Patent EP0779528A2 successfully refreshed from Google Patents.
EP0779528A2
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EP
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High numerical aperture ring field optical reduction system
Assignee: ASML Holding NV
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Filing: 1996-11-18
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Granted: —
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Expires: 2016-11-18
Abstract
Abstract 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.
Inventors
- 👤 David M. Williamson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 09:23
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/18; G03; G03F; G03F7/00; G03F7/70; G03F7/70216; G03F7/70225; G02B17/00; G02B17/02; G02B17/06; G02B17/0647; G02B17/0657; G03F7/70233; G03F7/70275
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
68 words
An optical reduction system for use in photolithography, from the long conjugate end to the short conjugate end, comprising: a first mirror pair; a field mirror pair positioned to receive electromagnetic radiation reflected from said first mirror pair; and a third mirror pair positioned to receive electromagnetic radiation reflected from said field mirror pair, whereby an intermediate image is re-imaged to a final image at an image plane.
Claim 2
Dependent Claim
28 words
An optical reduction system as in claim 1 wherein: the intermediate image is formed at an off-axis location between said first mirror pair and said third mirror pair.
Claim 3
Dependent Claim
25 words
An optical reduction system as in claim 1 wherein: the intermediate image is formed at an off-axis location between mirrors of said third mirror pair.
Claim 4
Dependent Claim
24 words
An optical reduction system as in claim 1 wherein: an aperture stop is formed at or near one mirror of said first mirror pair.
Claim 5
Dependent Claim
29 words
An optical reduction system as in claim 1 wherein: said first mirror pair, said field mirror pair, and said second mirror pair are rotationally symmetrical about an optical axis.
Claim 6
Dependent Claim
24 words
An optical reduction system as in claim 1 wherein: said first mirror pair, said field mirror pair, and said second mirror pair are aspheric.
Claim 7
Dependent Claim
53 words
An optical reduction system as in claim 1 further comprising: a first refractive element positioned between an object and said first mirror pair; a second refractive element positioned at or near a second mirror of said first mirror pair; and a third refractive element positioned between an image and said third mirror pair.
Claim 8
Dependent Claim
20 words
An optical reduction system as in claim 7 wherein: said first refractive element is axially movable along an optical axis.
Claim 9
Dependent Claim
33 words
An optical reduction system as in claim 7 wherein: the chromatic variation of focus introduced by said first refractive element and said third refractive element is substantially corrected by said second refractive element.
Claim 10
Dependent Claim
30 words
An optical reduction system as in claim 7 wherein: the chromatic variation of magnification is substantially corrected by balancing contributions from said first refractive element and said third refractive element.
Claim 11
Dependent Claim
90 words
An optical reduction system for use in photolithography, from the long conjugate end to the short conjugate end, comprising: a first mirror pair; a field mirror pair, said field mirror pair positioned to receive a chief ray reflected from said first mirror pair diverging away from an optical axis and converting it to a chief ray converging towards the optical; and a third mirror pair, said third mirror pair positioned to receive the chief ray reflected from said field mirror pair, whereby a reduced image of an object is formed.
Claim 12
Dependent Claim
61 words
An optical reduction system for use in photolithography, from the long conjugate end to the short conjugate end, comprising: a first concave mirror; a second mirror; a third concave mirror; a fourth concave mirror; a fifth convex mirror; and a sixth concave mirror, whereby two of said first, second, third, fourth, fifth or sixth mirrors act as a field mirror pair.
Claim 13
Dependent Claim
14 words
An optical reduction system as in claim 12 wherein: said second mirror is concave.
Claim 14
Dependent Claim
14 words
An optical reduction system as in claim 12 wherein: said second mirror is convex.
Claim 15
Dependent Claim
20 words
An optical reduction system as in claim 12 wherein: an aperture stop is formed at or near said second mirror.
Claim 16
Dependent Claim
154 words
An optical reduction system for use in photolithography, from the long conjugate end to the short conjugate end, comprising: a first concave mirror; a second mirror positioned to receive reflected electromagnetic radiation from said first concave mirror; a third concave mirror positioned to receive reflected electromagnetic radiation from said second mirror; a fourth concave mirror positioned to receive reflected electromagnetic radiation from said third concave mirror; a fifth convex mirror positioned to receive reflected electromagnetic radiation from said fourth concave mirror; and a sixth concave mirror positioned to receive reflected electromagnetic radiation from said fifth convex mirror, said first, second, third, fourth, fifth and sixth mirrors being centered on an optical axis, said third concave mirror receiving a chief ray diverging away from the optical axis, and said fourth concave mirror receiving the chief ray reflected from said third concave mirror and reflecting the chief ray causing it to converge toward the optical axis.
Claim 17
Dependent Claim
19 words
An optical reduction system as in claim 16 wherein: the electromagnetic radiation has a wavelength less than 200 nanometers
Claim 18
Dependent Claim
24 words
An optical reduction system as in claim 17 wherein: an intermediate image is formed between said third concave mirror and said fourth concave mirror.
Claim 19
Dependent Claim
24 words
An optical reduction system as in claim 17 wherein: an intermediate image is formed between said fifth convex mirror and said sixth concave mirror.
Claim 20
Dependent Claim
46 words
An optical reduction system as in claim 16 further comprising: a first refractive element located between an object and said second mirror; a second refractive element located at or near said second mirror; and a third refractive element located between an image and said fifth mirror.
References Cited (Backward Citations)
US5153898A
Cited
US4747678A
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