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EP0744664A2
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Hybrid illumination system for use in photolithography
Assignee: ASML Holding NV
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Filing: 1996-05-15
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Granted: —
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Expires: 2016-05-15
Abstract
Abstract An illumination system for use in photolithography having an array optical element near the formation of a desired illumination field. Light or electromagnetic radiation from an illumination source is expanded and received by a multi-image optical element forming a plurality of secondary illumination sources in a plane. A condenser receives the light from the plurality of illumination sources. A array or diffractive optical element is placed on or near the focal point of the condenser. The illumination plane formed at the focal point of the condenser is within the near field diffraction pattern of the array or diffractive optical element. There is no condenser following the array or diffractive optical element. The use of the array or diffractive optical element permits the use of a condenser between the multi-image optical element and the array or diffractive optical element having a smaller numerical aperture than the emergent numerical aperture of the diffractive optical element, and generates a desired angular distribution with little dependance on the illumination source profile. When a relay is used, intermediate illumination planes may be spatially separated to form separate X and Y planes that facilitate the formation of a rectangular illumination field. The relay, unlike a condenser, simply conjugates the illumination plane with another plane or a reticle. Additionally, the use of a diffractive optical element makes possible an illumination field that has a substantially uniform illumination intensity profile along one axis and a trapezoidal illumination profile along a perpendicular axis. This illumination field profile being particularly advantageous in a scanning photolithography operation. In one embodiment, a plurality of optical multiplexers are used to condition the beam prior to being directed through the multi-image optical element. Multiplexing to create secondary beams with small lateral coherence and no mutual coherence enhances the uniformity of spacial and angular profiles. This permits efficient use of the electromagnetic radiation.
Inventors
- 👤 Stuart Stanton
- 👤 Mark Oskotsky
- 👤 Gregg Gallatin
- 👤 Fritz Zernike
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 11:35
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70058; G03F7/70091; G03F7/20; G03F7/701; G03F7/70108; G03F7/7015; G03F7/70158; G03F7/70216; G03F7/70358
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
71 words
An illumination system comprising: an illumination source generating a beam of electromagnetic radiation; a multi-image optical element receiving the beam of electromagnetic radiation from said illumination source; and an array optical element receiving the beam of electromagnetic radiation from said multi-image optical element and providing an emerging predetermined angular distribution of electromagnetic radiation, whereby electromagnetic radiation from said illumination source forms an illumination field for projecting an image of a reticle.
Claim 2
Dependent Claim
17 words
An illumination system as in claim 1 wherein: said array optical element is a diffractive optical element.
Claim 3
Dependent Claim
17 words
An illumination system as in claim 1 wherein: the predetermined angular distribution is a uniform circular illumination.
Claim 4
Dependent Claim
16 words
An illumination system as in claim 1 wherein: the predetermined angular distribution is an annular illumination.
Claim 5
Dependent Claim
16 words
An illumination system as in claim 1 wherein: the predetermined angular distribution is a quadrupole illumination.
Claim 6
Dependent Claim
22 words
An illumination system as in claim 1 further comprising: a condenser placed between said multi-image optical element and said array optical element.
Claim 7
Dependent Claim
22 words
An illumination system as in claim 6 further comprising: a beam conditioner placed between said illumination source and said multi-image optical element.
Claim 8
Dependent Claim
20 words
An illumination system as in claim 1 wherein: said array optical element causes controlled spacial redistribution of the electromagnetic radiation.
Claim 9
Dependent Claim
37 words
An illumination system as in claim 6 wherein: a first numerical aperture formed on the entrance side of said condenser is less than a second numerical aperture formed on the emergent side of said array optical element.
Claim 10
Dependent Claim
71 words
An illumination system comprising: an illumination source generating a beam of electromagnetic radiation; a multi-image optical element receiving the beam of electromagnetic radiation from said illumination source; a condenser receiving the beam of electromagnetic radiation from said multi-image optical element; and a diffractive optical element receiving the beam of electromagnetic radiation from said condenser, whereby electromagnetic radiation from said illumination source forms an illumination field having predetermined angular and spacial properties.
Claim 11
Dependent Claim
33 words
An illumination system as in claim 10 further comprising: a beam conditioner placed between said illumination source and said multi-image optical element and receiving the beam of electromagnetic radiation from said illumination source.
Claim 12
Dependent Claim
15 words
An illumination system as in claim 10 wherein: said multi-image optical element is an array.
Claim 13
Dependent Claim
18 words
An illumination system as in claim 12 wherein: the array is formed by a plurality of refractive lenses.
Claim 14
Dependent Claim
18 words
An illumination system as in claim 10 wherein: said multi-image optical element is a first diffractive optical element.
Claim 15
Dependent Claim
22 words
An illumination system as in claim 14 wherein: the first diffractive optical element is formed from a plurality of diffractive optical elements.
Claim 16
Dependent Claim
14 words
An illumination system as in claim 10 wherein: said diffractive optical element is transmissive.
Claim 17
Dependent Claim
28 words
An illumination system as in claim 10 wherein: the illumination field is created in the near field or in the Fresnel diffraction region of said diffractive optical element.
Claim 18
Dependent Claim
14 words
An illumination system as in claim 10 wherein: said illumination source is a laser.
Claim 19
Dependent Claim
25 words
An illumination system as in claim 10 further comprising: a relay placed between said diffractive optical element and the desired location of the illumination field.
Claim 20
Dependent Claim
12 words
An illumination system as in claim 19 wherein: said relay is astigmatic.
Claim 21
Dependent Claim
12 words
An illumination system as in claim 10 wherein: said condenser is anamorphic.
Claim 22
Dependent Claim
15 words
An illumination system as in claim 11 wherein: said beam conditioner is a beam expander.
Claim 23
Dependent Claim
15 words
An illumination system as in claim 11 wherein: said beam conditioner is a beam multiplexer.
Claim 24
Dependent Claim
63 words
An illumination system as in claim 23 wherein said beam multiplexer comprises: a first plane surface; a second plane surface, said second plane surface separated from said first plane surface; a reflective surface formed on said first plane surface; a plurality of partially reflective surfaces formed on said second plane surface, each of said plurality of partially reflective surfaces having a different reflectance.
Claim 25
Dependent Claim
19 words
An illumination system as in claim 24 wherein: said beam multiplexer is formed from a single block of material.
Claim 26
Dependent Claim
36 words
An illumination system as in claim 10 wherein: said condenser has an entrance numerical aperture, and said diffractive optical element has an exit numerical aperture, the exit numerical aperture being larger than the entrance numerical aperture.
Claim 27
Dependent Claim
72 words
An illumination system comprising: an illumination source generating a beam of electromagnetic radiation; a multi-image optical element receiving the beam of electromagnetic radiation from said illumination source; a condenser receiving the beam of electromagnetic radiation from said multi-image optical element; and a refractive array optical element receiving the beam of electromagnetic radiation from said condenser, whereby electromagnetic radiation from said illumination source forms an illumination field having predetermined angular and spatial properties.
Claim 28
Dependent Claim
33 words
An illumination system as in claim 27 further comprising: a beam conditioner placed between said illumination source and said multi-image optical element and receiving the beam of electromagnetic radiation from said illumination source.
Claim 29
Dependent Claim
15 words
An illumination system as in claim 27 wherein: said multi-image optical element is an array.
Claim 30
Dependent Claim
17 words
An illumination system as in claim 27 wherein: said multi-image optical element is a diffractive optical element.
Claim 31
Dependent Claim
21 words
An illumination system as in claim 30 wherein: the diffractive optical element is formed from a plurality of diffractive optical elements.
Claim 32
Dependent Claim
14 words
An illumination system as in claim 27 wherein: said illumination source is a laser.
Claim 33
Dependent Claim
26 words
An illumination system as in claim 27 further comprising: a relay placed between said refractive array optical element and the desired location of the illumination field.
Claim 34
Dependent Claim
12 words
An illumination system as in claim 33 wherein: said relay is astigmatic.
Claim 35
Dependent Claim
12 words
An illumination system as in claim 34 wherein: said condenser is anamorphic.
Claim 36
Dependent Claim
15 words
An illumination system as in claim 28 wherein: said beam conditioner is a beam expander.
Claim 37
Dependent Claim
15 words
An illumination system as in claim 28 wherein: said beam conditioner is a beam multiplexer.
Claim 38
Dependent Claim
63 words
An illumination system as in claim 37 wherein said beam multiplexer comprises: a first plane surface; a second plane surface, said second plane surface separated from said first plane surface; a reflective surface formed on said first plane surface; a plurality of partially reflective surfaces formed on said second plane surface, each of said plurality of partially reflective surfaces having a different reflectance.
Claim 39
Dependent Claim
19 words
An illumination system as in claim 38 wherein: said beam multiplexer is formed from a single block of material.
Claim 40
Dependent Claim
36 words
An illumination system as in claim 27 wherein: said condenser has an entrance numerical aperture, and said diffractive optical element has an exit numerical aperture, the exit numerical aperture being larger than the entrance numerical aperture.
Claim 41
Dependent Claim
120 words
An illumination system comprising: an illumination source; beam forming optics following said illumination source; a multi-image optical element following said beam forming optics; a first concave mirror following said multi-image optical element; a second concave mirror following said first concave mirror; and a diffractive optical element following said second concave mirror, whereby electromagnetic radiation from said illumination source is formed into a beam by said beam forming optics, passes through said multi-image optical element, is reflected by said first concave mirror to said second concave mirror, reflected by said second concave mirror and through said diffractive optical element forming an illumination field in the near field or in the Fresnel diffraction region of said diffractive optical element at a reticle.
Claim 42
Dependent Claim
64 words
An illumination system comprising: an illumination source; a first diffractive optical element following said illumination source; a mirror; and a second diffractive optical element, whereby electromagnetic radiation from said illumination source is propagated without transmission through said first diffractive optical element to said mirror and reflected to said second diffractive optical element forming an illumination field without transmission through said second diffractive optical element.
Claim 43
Dependent Claim
28 words
An illumination system as in claim 42 wherein: the illumination field is within the near field or in the Fresnel diffraction region of said second diffractive optical element.
Claim 44
Dependent Claim
196 words
An illumination system for projecting an image of a reticle onto a wafer as used in photolithography for the manufacture of devices comprising: an illumination source; a beam expander following said illumination source and positioned to receive electromagnetic radiation therefrom; a multi-image optical element following said beam expander and positioned to receive electromagnetic radiation transmitted through said beam expander, said multi-image optical element forming a plurality of secondary sources; a condenser following said multi-image optical element and positioned to receive electromagnetic radiation from said plurality of secondary sources, said condenser having a first and second illumination plane; a diffractive optical element following said condenser and positioned to receive electromagnetic radiation transmitted through said condenser, said diffractive optical element having a near field diffraction region, the first and second illumination planes formed by said condenser being within the near field diffraction region of said diffractive optical element; and a relay following said diffractive optical element and positioned to receive electromagnetic radiation propagating from said diffractive optical element, said relay conjugating the first and second illumination planes to a reticle plane, whereby the image of the reticle is projected through projection optics onto a photosensitive resist covered wafer.
Claim 45
Dependent Claim
17 words
An illumination system as in claim 44 wherein: the first and second illumination planes are spatially separate.
Claim 46
Dependent Claim
48 words
An illumination system as in claim 44 wherein: one of the first or second illumination planes has a first axis that has a substantially trapezoidal illumination profile and the other of the first or second illumination planes has a second axis that has a substantially constant illumination profile.
References Cited (Backward Citations)
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