(12)
`
`United States Patent
`Shafer et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,636,350 B2
`Oct. 21, 2003
`
`US006636350B2
`
`(54) MICROLITHOGRAPHIC REDUCTION
`PROJECTION CATADIOPTRIC OBJECTIVE
`
`5,212,588 A
`5,220,590 A
`
`5/1993 Viswanathan et al. .... .. 359/355
`6/1993 Bruning et al. ............. .. 378/34
`
`5,241,423 A
`
`8/1993 Chiu et al. . . . . . . . . . .
`
`. . . .. 359/727
`
`
`
`(75) Inventors: David R. Shafer, Fair?eld, CT (US); 1255563)
`
`
`
`, , 2 5,353,322 A 10/1994 Bruning 61 al. ............. .. 378/34 156K611 @1411: ~~~~~~~~~~~~ c oenma ers
`
`
`
`
`
`
`
`
`
`’
`
`’
`
`5,401,934 A
`
`3/1995 Ainsworth, Jr.
`
`Assignee: Carl-Zeiss-Stiftung, ObCI'kOCheII
`
`
`
`5,410,434 A 5,515,207 A
`
`
`
`et a1‘ ~~~~~~~~~~~~~~~~~~~ n 5/1996 F .......................... .. 359/731
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 42 days.
`
`(21) Appl- NO-I 09/761,562
`.
`_
`(22) Med
`(65)
`
`Jan- 16’ 2001
`Prior Publication Data
`
`US 2001/0043391 A1 Nov. 22, 2001
`
`Related US, Application Data
`(60) Provisional application No. 60/176,190, ?led on Jan. 14,
`ZOOQ
`
`00
`(List continued on neXt page.)
`
`FOREIGN PATENT DOCUMENTS
`
`4/1998
`196 39 586 A
`6/1997
`0 779 528 A 2
`11/1997
`0 604 093
`0 869 383 A 10/1998
`0 816892A2 A3
`6/1999
`1 069 448 A1
`7/2000
`1 067 448
`1/2001
`1 067 448 A 1
`1/2001
`
`......... .. GO2B/17/08
`G02B/17/08
`GO2B/17/08
`G02B/17/08
`G02B/17/08
`......... .. G02B/17/08
`
`........... .. G06F/1/04
`
`OTHER PUBLICATIONS
`
`DE
`EP
`EP
`EP
`EP
`EP
`EP
`EP
`
`_
`7
`(51) Int. Cl. ...................... .. G02B 17/00,
`
`_
`
`US. patent application Ser. No. 09/759,806, Shafer et al.,
`?led Jan‘ 16, 2001'
`
`(52) US. Cl. ................... .. 359/366; 359/731; 359/733
`
`Primary Examiner ; {ark A‘ Robinson
`
`Fleld of Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
`
`359/366, 726, 727, 728, 729, 730, 731,
`857, 858, 859, 732, 733, 734
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`4,171,871 A 10/1979 Dill et al. ................. .. 350/199
`4,232,969 A 11/1980 WilcZynski
`356/401
`4,595,295 A
`6/1986 WilcZynski
`356/401
`4,685,777 A
`8/1987 Hirose ........ ..
`350/505
`4,701,035 A 10/1987 Hirose ........ ..
`350/505
`5,052,763 A 10/1991 Singh et a1. .... ..
`359/355
`
`5,063,586 A 11/1991 Jewell et al. . . . . . . . .
`
`. . . .. 378/34
`
`359/366
`5,071,240 A 12/1991 Ichihara et al.
`359/366
`5,078,502 A
`1/1992 Cook ............ ..
`359/727
`5,089,913 A
`2/1992 Singh et al. .... ..
`5,153,898 A 10/1992 Suzuki 618.1. ............... .. 378/34
`5,159,172 A 10/1992 Goodman et al.
`219/151.68
`
`Attorney)
`
`Or Firm_Darby & Darby
`
`ABSTRACT
`(57)
`Aphotolithographic reduction projection catadioptric objec
`tive includes a ?rst optical group having an even number of
`at least four mirrors and having a positive overall magnify
`ing poWer, and a second substantially refractive optical
`group more image forWard than the ?rst optical group
`having a number of lenses. The second optical group has a
`negative overall magnifying poWer for providing image
`reduction. The ?rst optical group provides compensative
`aberrative correction for the second optical group. The
`objective forms an image With a numerical aperture of at
`least substantially 0.65, and preferably greater than 0.70 or
`still more preferably greater than 0.75.
`
`26 Claims, 4 Drawing Sheets
`
`Conjugate stop
`
`Elements E4-El5
`
`Group G2
`
`Group G1
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 1
`
`

`
`US 6,636,350 B2
`Page 2
`
`US. PATENT DOCUMENTS
`_
`_
`7/1996 W1~ll18ms0n ............... .. 359/727
`5,537,260 A
`2723273; 2 lé/iggg 153mm‘? (Eml- ------ ~~i ---- -- 22/525
`7
`7
`/
`‘Won a‘ Ore 6‘ a‘
`/
`5,686,728 A 11/1997 Shafer ................... .. 250/4922
`5,742,436 A
`4/1998 Furter
`359/727
`5,805,357 A
`9/1998 Omura
`359/727
`
`5,835,275 A 11/1998 Takahashi et a1. ........ .. 359/629
`5,940,222 A * 8/1999 816616116161.
`359/689
`5,956,192 A
`9/1999 Williamson
`_ 359/859
`6,014,252 A
`1/2000 Shafer ...................... .. 359/355
`6,033,079 A
`3/2000 Hudyma ................... .. 359/857
`
`6,142,641 A 11/2000 Cohen et a1. ..
`6 169 627 B1
`12001 S h t
`7
`7
`/
`C “5 er """""""""" "
`
`. 359/859
`359 364
`/
`
`5,805,365 A
`
`9/1998 Sweatt . . . . . . . . .
`
`. . . .. 359/858
`
`5,815,310 A
`
`9/1998 Williamson ............... .. 359/365
`
`* cited by examiner
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 2
`
`

`
`U.S. Patent
`
`0a.
`
`FIG. 1
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 3
`
`

`
`U.S. Patent
`
`Oct. 21, 2003
`
`Sheet 2 of 4
`
`US 6,636,350 B2
`
`2
`
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`5
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`
`I150
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`
`CARL ZEISS v. NIKON
`|PR2013-00362
`
`EX. 2015, p. 4
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 4
`
`

`
`U.S. Patent
`
`Oct. 21, 2003
`
`Sheet 3 of 4
`
`US 6,636,350 B2
`
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`CARL ZEISS v. NIKON
`|PR2013-00362
`
`EX. 2015, p. 5
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 5
`
`

`
`U.S. Patent
`
`0a. 21, 2003
`
`Sheet 4 0f 4
`
`US 6,636,350 B2
`
`NU 5.9.0
`
`2:
`
`v.07
`
`~O 9.9.0
`
`
`
`no; 3%:750
`
`\ #
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 6
`
`

`
`US 6,636,350 B2
`
`1
`MICROLITHOGRAPHIC REDUCTION
`PROJECTION CATADIOPTRIC OBJECTIVE
`PRIORITY
`This application claims the bene?t of priority to United
`States provisional patent, application No. 60/176,190, ?led
`Jan. 14, 2000.
`
`2
`It has long been realiZed that catadioptric optical systems
`have several advantages, especially in a step and scan
`con?guration and various organiZations have developed, or
`proposed development, of such systems for Wavelengths
`beloW 365 nm. One catadioptric system concept relates to a
`Dyson-type arrangement used in conjunction With a beam
`splitter to provide ray clearance and unfold the system to
`provide for parallel scanning (e.g., US. Pat. Nos. 5,537,260,
`5,742,436 and 5,805,357). HoWever, these systems have a
`serious draWback since the siZe of this beam splitting
`element becomes quite large as the numerical aperture is
`increased up to and beyond 0.65 to 0.70, making the
`procurement of bulk optical material With suf?cient quality
`(in three-dimensions) a high risk endeavor. This problem is
`exacerbated as Wavelengths are driven beloW 193 nm
`because the selection of material that can be manufactured
`to lithographic quality is severely limited.
`To circumvent this problem, attempts have focused on the
`development of systems Without beamsplitters. HoWever,
`this prior art has either failed to achieve an adequately high
`numerical aperture (e.g., US. Pat. Nos. 4,685,777, 5,323,
`263, 5,515,207 and 5,815,310), or failed to achieve a fully
`coaxial con?guration, instead relying on the use of folding
`mirrors to achieve parallel scanning (e.g., U.S. Pat. No.
`5,835,275 and EP 0 816 892) and thereby complicating the
`alignment and structural dynamics of the system. In
`addition, these designs generally utiliZe mtoo any lens
`elements, greatly increasing the mass of the optical system.
`It is desired to develop a compact, coaxial, catadioptric
`projection system for deep ultraviolet and/or vacuum ultra
`violet lithography that uses no beamsplitters or fold mirrors
`in its optical path.
`It is an object of the invention to provide an objective for
`microlithographic projection reduction having high chro
`matic correction for typical bandWidths of excimer laser
`light sources, Which permits a high image-side numerical
`aperture, and Which reduces complexity With respect to
`mounting and adjusting.
`
`SUMMARY OF THE INVENTION
`
`In accordance With the above object, a photolithographic
`reduction projection catadioptric objective is provided
`including a ?rst optical group having an even number of at
`least four mirrors, and a second substantially refractive
`optical group more image forWard than the ?rst optical
`group having a number of lenses. The second optical group
`provides image reduction. The ?rst optical group provides
`compensative aberrative correction for the second optical
`group. The objective forms an image With a numerical
`aperture of at least substantially 0.65, and preferably greater
`than 0.70 or still more preferably greater than 0.75.
`The ?rst optical group preferably produces a virtual
`intermediate image. The more image forWard mirror is
`preferably convex, although a concave ?nal mirror may
`produce the virtual image. In addition, optical surfaces of
`each mirror of the objective are preferably at least sections
`of revolution each having a common optical axis, and more
`preferably optical surfaces of each mirror and each lens of
`the objective are at least sections of revolution each having
`this common axis.
`The objective preferably has an unobscured system aper
`ture located Within the second optical group, and there are
`preferably no folding mirrors in the objective. The second
`group preferably more lenses that the number of mirrors in
`the ?rst group, and more preferably includes at least eight
`lenses.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`BACKGROUND
`1. Field of the Invention
`The invention relates to a microlithographic projection
`catadioptric objective, and particularly including an even
`number of four or more mirrors and an unobscured aperture,
`and excluding any planar folding mirrors.
`2. Description of the Related Art
`Microlithographic reduction projection catadioptric
`objectives, such as that shoWn and described With respect to
`FIG. 3 of European patent no. EP 0 779 528 A2, are knoWn
`as variants of pure catoptric objectives. FIG. 3 of the ’528
`application shoWs a system having six mirrors and three
`lenses. The optical surfaces are generally symmetric to a
`common axis, and the object plane and the image plane are
`situated on this same axis upstream and doWnstream of the
`objective, respectively. As described in the ’528 application,
`the system of FIG. 2 has a numerical aperture of only 0.55
`and that of FIG. 3 only 0.6. In addition, all but one of the six
`mirrors shoWn at FIG. 3 are cut off sections of a bodies of
`revolution, yielding mounting and adjustment face dif?cul
`ties. Also, the lenses shoWn in FIG. 3 serve only as correct
`ing elements having minor effect. The most image forWard
`(or optically closest to the image plane) mirror is concave.
`It is desired to have an objective With a higher numerical
`aperture, and Which is constructed for easier mounting and
`adjustment.
`A similar objective to that described in the ’528 applica
`tion (above) is disclosed at US. Pat. No. 4,701,035. The
`objective shoWn at FIG. 12, for example, has nine mirrors,
`tWo lenses and tWo intermediate images. The object plane
`and image plane are situated Within the envelope of the
`objective. The objective described in the ’035 application
`also exhibits a loW numerical aperture and offers similar
`mounting and adjustment dif?culties as described above
`With respect to the ’528 application. In both the ’528 and
`’035 applications, the image ?eld is an off-axis ring sector.
`An axially symmetric type of catadioptric objective is
`45
`disclosed in German patent document DE 196 39 586 A
`(US. patent application Ser. No. 09/263,788). The ’788
`application discloses an objective having tWo opposing
`concave mirrors, an image ?eld centered at the common axis
`and a central obscuration of the aperture. It is desired to have
`an axially objective having an unobscured aperture.
`Another type of catadioptric objective for microlitho
`graphic reduction projection has only one concave mirror
`and a folding mirror, as is described at U.S. Pat. No.
`5,052,763 and European patent application no. EP 0 869 383
`A.
`In extending DUV lithography to sub 100-nm feature
`siZes or lineWidths, it is desired to have a projection system
`With a numerical aperture of 0.65 or larger and more
`preferably of 0.75 or larger at a Wavelength of 157 nm. As
`optical lithography is extended into the vacuum ultraviolet
`(VUV), issues surrounding the laser lineWidth and material
`availability could cause substantive delays to the develop
`ment of lithography tools for the most extreme VUV Wave
`lengths. Therefore, it is desired to investigate optical con
`?gurations that minimiZe the use of available VUV optical
`materials.
`
`55
`
`60
`
`65
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 7
`
`

`
`US 6,636,350 B2
`
`3
`The objective also preferably has parallel axes of sym
`metry of curvatures of each optical element of the ?rst and
`second optical groups. In addition, preferably no more than
`tWo and more preferably no more than one of the optical
`elements are cut to deviate in a substantially non-rotationally
`symmetric form.
`Also preferably, the objective includes in sequence, in an
`optical direction from an object side to an image side of the
`objective, a ?st catadioptric sub group for producing a real
`intermediate image, a second sub group including catoptric
`components for producing a virtual image, and a third
`dioptric group for producing a real image. The objective
`may include in sequence, in an optical direction from the
`object side to the image side of the objective, a ?rst ?eld lens
`sub group, a second catadioptric sub group comprising one
`or more negative lenses and a concave mirror for generating
`aXial chromatic aberration, and a third sub group including
`an odd number of catoptric components, and a fourth
`positive lens sub group.
`The objective may also include in sequence, in an optical
`direction from the object side to the image side, a ?rst
`catadioptric sub group comprising a single mirror and hav
`ing a negative reduction ratio, a second sub group compris
`ing an odd number of mirrors and having a positive reduc
`tion ratio, and a third dioptric lens sub group having a
`negative reduction ratio. In the latter case, the ?rst catadiop
`tric sub group may include a positive ?eld lens group and a
`negative lens group neXt to the single mirror, and the third
`dioptric lens sub group may include a larger number of
`positive than negative lenses.
`The most image forWard mirror of said ?rst optical group
`is conveX. An intermediate image is preferably formed
`before the tWo most image forWard mirrors of the ?rst
`optical group.
`An image ?eld may be betWeen substantially 5 mm><20
`mm to 8 mm><30 mm. Each lens of the objective is prefer
`ably unobstructive of a beam path of a beam incident at the
`objective. The objective also preferably includes at least one
`spherical mirror.
`The optical surfaces of each mirror of the objective are
`preferably at least sections of revolution each having a
`common optical aXis. The ?rst optical group preferably
`includes four mirrors, and Wherein in sequence, from an
`object side to an image side of the objective, the ?rst and
`third mirrors are concave and the fourth.mirror is conveX.
`An aperture plane is preferably located Within a sub group
`of the ?rst optical group for generating catadioptric chro
`matic aberration and has at least one negative lens and a
`concave mirror. The ?rst optical group preferably includes a
`?eld lens group proXimate to and after an object plane Which
`produces object side telecentricity. The objective is prefer
`ably doubly telecentric.
`All lenses of the objective are preferably located Within a
`cylindrical envelope of a radius of a largest of the lenses of
`the objective, and all but one mirror of the objective is
`located Within the same envelope.
`A virtual image is preferably formed Within the ?rst
`optical group, and more preferably betWeen the second and
`the third mirror of the ?rst optical group. Each optical
`element of the ?rst optical group is preferably substantially
`spherical.
`The optical elements of the objective are preferably
`aligned along a common optical aXis of symmetry of cur
`vatures of each optical element of the ?rst and second optical
`groups. Preferably, a largest distance from the common
`optical aXis of symmetry of any ray of a beam incident upon
`the objective is not more than 370 mm.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`55
`
`60
`
`65
`
`4
`The ?rst mirror of the ?rst optical group is preferably
`concave, and the ?rst optical group also preferably further
`includes at least one, and more preferably at least tWo,
`concave lens(es) before the ?rst concave mirror.
`The second optical group may include several lenses
`Wherein each is a positive lens. A diameter of the beam
`incident upon each of these multiple lenses is preferably at
`least half of a diameter of each respective lens.
`The third mirror of the mirrors of the ?rst optical group is
`preferably a substantially spherical mirror. This substantially
`spherical third mirror is preferably concave. The fourth
`mirror of the ?rst optical group is preferably conveX.
`A projection eXposure apparatus is also provided includ
`ing an eXcimer or EUV light source, an illumination system,
`a reticle handling, positioning and scanning system, a pro
`jection objective according to the above and a Wafer
`handling, positioning and scanning system.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 schematically shoWs a front end of a microlitho
`graphic projection reduction objective according to a pre
`ferred embodiment.
`FIG. 2 schematically shoWs a microlithographic projec
`tion reduction objective according to a ?rst preferred
`embodiment.
`FIG. 3 schematically shoWs a microlithographic projec
`tion reduction objective according to a second preferred
`embodiment.
`FIG. 4 schematically shoWs a mnicrolithographic projec
`tion reduction objective according to a third embodiment.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`In order to meet the above object of the invention, and to
`solve problems discussed above With respect to the related
`art systems, several catadioptric projection systems are
`disclosed. Each system is comprised of tWo distinct imaging
`groups G1 and G2. Group G1 is a catadioptric group that
`provides a conjugate stop position to correction chromatic
`aberration, if desired, and Works to balance the aberrations
`of the aft group. This aft group, Group G2, is dioptric and
`enables the system to achieve numerical apertures up to and
`in eXcess of 0.75. This catadioptric system achieves high
`numerical aperture preferably using no beamsplitters or fold
`mirrors, making use of the rotational symmetry associated
`With an off-axis ring ?eld.
`FIG. 1 schematically shoWs a front end of a microlitho
`graphic projection reduction objective according to a pre
`ferred embodiment. The front end shoWn in FIG. 1 includes
`in optical sequence, from an object side to an image side, a
`?eld lens L1 Which provides object side telecentricity, a
`second lens L2 Which is concave and disposed just before a
`?rst mirror M1, a second mirror M2 preferably located on a
`portion of the ?rst lens L1, a third mirror M3 Which is shoWn
`as a cut off section of a spherical mirror located on a same
`aXis as the other elements Which may also be similarly cut
`off portions, i.e., L1, L2, M1, M2, and a conveX fourth
`mirror M4.
`The front end shoWn in FIG. 1 is preferably a part of a
`0.25 reduction, 0.75 image side numerical aperture (NA)
`system having an image ?eld siZe preferably betWeen 5
`mm><20 mm and 8 mm><30 mm, and more speci?cally 7
`mm><26 mm. The front end shoWn in FIG. 1 is preferably
`particularly designed to be part of an overall objective
`having each of its components aligned along a common
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 8
`
`

`
`US 6,636,350 B2
`
`10
`
`15
`
`20
`
`25
`
`30
`
`5
`optical axis, or having their axes of symmetry located on this
`common axis. The front end shoWn in FIG. 1 is a catadiop
`tric partial system providing an intermediate image Imi
`betWeen the second mirror M2 and the third mirror M3. The
`front end of FIG. 1 has enough axial chromatic aberration to
`compensate for a focussing lens group Which forms a
`preferably 0.65, 0.70 or more preferably at least a 0.75 NA
`image. A real pupil or aperture plane Would be preferably
`formed on the right hand end of the system Within the
`focussing lens group (not shoWn, but see beloW). The system
`shoWn preferably has enough PetZval sum so that the
`focusing lens group can be made up of mostly or even
`entirely positive poWer lenses.
`Only a single ?eld lens L1 is shoWn in FIG. 1, and is
`located near the object plane Ob end of the system. That
`location of the ?eld lens is advantageous With respect to
`providing reduced lens heating. There are preferably no
`aspherics in this front end. The mirrors M1 to M4 are
`preferably all spherical and coaxial to a common optical
`axis. It is possible to make this front end system be corrected
`for spherical aberration of the pupil, and a someWhat larger
`concave mirror than What is shoWn here Would be used to
`achieve this.
`This spherical aberration can also be corrected in the
`focusing lens group, and thus With respect to the front end
`shoWn in FIG. 1, the siZe of the concave mirror M3 is
`smaller than that Which Would be used to perform the
`spherical aberration correction. The smaller siZe of mirror
`M3 simpli?es the mechanical construction of the system. In
`the example of FIG. 1, the concave mirror M3 has an
`illuminated area that is about 165 mm Wide in the plane of
`the draWing and about 500 mm in the orthogonal direction,
`for a 7 mm><26 mm image ?eld siZe.
`Advantageously, the greatest distance of any ray from the
`common optical axis is about 370 mm in the example shoWn
`in FIG. 1. This is advantageously less than is the case for
`many designs, such as that shoWn and described in the ’788
`application described above. In the case of the design of the
`’788 application, the concave mirror thickness and mount
`thickness are added to the sideWays ray path distance after
`the fold mirror, from the axis to the concave mirror.
`Therefore, this advantageous of the design of FIG. 1 is
`clearly seen.
`More axial chromatic aberration and PetZval curvature
`may be included over that of the front end of FIG. 1, by
`increasing the poWer of the negative lens L2 near the
`concave mirror M1. A strong lens L2, hoWever, may tend to
`put in more overcorrected spherical aberration than is
`desired, making the intermediate image aberrations be larger
`than desired. In vieW of this, a preferred alternative to the
`design shoWn in FIG.1 includes tWo concave lenses near the
`concave mirror rather than the single lens L2 shoWn.
`The ?eld lens L1 near the object plane Ob can also be split
`into tWo Weaker lenses, in an alternative embodiment, to
`improve control of pupil aberration. The convex mirror M2
`that is near the reticle (Ob) can also be split off from the ?eld
`lens L1 surface and made to be a separate optical element.
`This alternative embodiment yields a more complicated
`design, but may provide improved performance and/or an
`additional degree of freedom.
`Also advantageously, it is possible to make this system
`meet high speci?cations, as Well as to have correction for
`PetZval curvature, and axial and lateral color correction,
`With just positive lenses in the telecentric focusing group
`TFG. An example of such a focussing group is shoWn in
`FIG. 2. FIG. 2 shoWs a ?rst embodiment of an objective
`
`40
`
`45
`
`55
`
`60
`
`65
`
`6
`having similar front end components, in general, to that
`described With respect to FIG. 1, except the concave lens L2
`of FIG. 1 is split into tWo lenses L22 and L23. OtherWise,
`the front end elements L21, M21, M22, M232, and M24 of
`FIG. 2 correspond to elements L1, M1, M2, M3 and M4 of
`FIG. 1, and as such, the discussion above is incorporated
`here and not repeated.
`The focussing group (TFG) of FIG. 2 includes six lenses
`L24 through L29. Lenses L24 and L25 are disposed in a ?rst
`sub group of the focussing group and receive the beam as it
`diverges from mirror M24 of the front end (FE), or the
`virtual image formed behind mirror M24. Lenses L26, L27,
`L28 and L29 form a second sub group of the focussing lens
`group of the objective shoWn in FIG. 2. A real image Im of
`4x reduction is formed after the lens L29.
`The focussing group of FIG. 2 may be designed Without
`any other kind of aberration correction, due to the aberration
`correction performed by the front end group. Lens heating in
`the objective of FIG. 2 is advantageously uniform, as the
`beam diameter is large on all the lenses L21 to L29.
`Preferably the beam diameter is at least 50% of the diameter
`of each respective lens of the focussing group upon Which
`the beam is incident.
`FIG. 3 shoWs an objective according to a second preferred
`embodiment The details of the embodiment of FIG. 3 are set
`forth at Table 1, beloW. The front end FE‘ of the objective of
`FIG. 3 features a ?eld lens group split into 3 lenses L31 to
`L33. These lenses I31 to L33 provide advantageous tele
`centricity at the object end of the objective. The front end
`FE‘ is otherWise similar to that shoWn at FIG. 2 and its
`elements are otherWise described above and not repeated
`here.
`The focussing lens group FLG‘ of the objective of FIG. 3
`has eight lenses L36 to L44 instead of the six lenses L24 to
`L29 of the objective of FIG. 2. This focussing lens group
`FLG‘ preferably has some aspherics, and aspherics may be
`included in the catadioptric front end FE‘ of the objective of
`FIG. 3 Which simplify correction. The provision of these
`aspherics is not necessary, hoWever, to meet the above object
`of the invention. The large mirror M33 is still preferably
`made to be a sphere, and this advantageously simpli?es
`production.
`Preferred locations of the aspheric surfaces, are near an
`aperture or pupil plane, namely on mirror M-or on lenses
`L34, L35, Where the marginal ray height preferably exceeds
`80% of the height of the neighboring aperture, and alterna
`tively on some distant locations With marginal ray heights
`less than 80% of the height of the next aperture. Examples
`of the latter are surfaces of the ?eld lens group or of the last
`tWo lenses next to the image plane Im.
`The polychromatic r.m.s. Wavefront error value in this
`design noW varies from 0.05 to 0.13 Waves over a 26><7 mm
`?eld at 0.75 NA in a 4x design. The catadioptric front end
`FE‘ of the objective of FIG. 3 is more complicated than those
`shoWn in FIGS. 1 and 2. The design is doubly telecentric,
`i.e., exhibits telecentricity on both the object side and the
`image side, and is corrected for pupil aberration and distor
`tion. The Working distance is 34 mm on the reticle end (0b)
`and 12 mm on the Wafer end
`The system length is
`about 1200 mm.
`The focusing lens group FLG‘ is preferably all positive
`lenses except lens L41, With no particularly strong curva
`tures. Avery large amount of aberration at the intermediate
`image may be included Whereby the tWo concave lenses
`L31, L35 next to the concave mirror M31 do not have
`optimum bending in this embodiment.
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 9
`
`

`
`US 6,636,350 B2
`
`7
`Mechanical construction of the focussing lens groups
`FLG, FLG‘, or lens barrel, is advantageous When compared
`With catadioptric systems having a folding mirror for folding
`the optical aXis as With the design of the ’788 application.
`Folding mirrors are generally not desirable, as folding
`mirrors cause intensity losses and quality degradation of the
`light beam, production costs and adjustment Work Without
`improving image quality.
`In the embodiments of FIGS. 2 and 3, preferably only the
`mirrors M32 and M33 are not provided as full disks. Even
`mirror M33, hoWever, may be extended to a full annular
`body Which can be mounted in a rotationally symmetric
`structure. The lens barrel is cut betWeen the lenses L33 and
`L36 at a loWer side of the draWing of FIG. 3 to provide
`passage to the light beam, and may be generally cylindrical.
`Only mirror M33 is positioned outside this cylindrical
`barrel, and even that is a moderate distance. Mirror M33
`may be provided as an annular blank. Mirror M33 may be
`
`5
`
`10
`
`15
`
`8
`mounted as this annular part in a cylindrical barrel Which is
`eXtended in diameter in this area.
`Concave spherical mirror M33 is the preferably the only
`mirror reaching outside of a cylindrical envelope de?ned by
`the focusing lens group diameters, or scribed around all the
`lenses Which has the radius of the lens of the greatest radius.
`The preferred objective, as exempli?ed above at FIGS. 2—3,
`thus has the advantage that it may be mounted in a compact
`cylindrical barrel of high intrinsic rigidity.
`The preferred lens material is calcium ?uoride, ?uorspar,
`particularly for 157 nm applications. Other materials, stand
`ing alone or in combinations, may be used, namely at other
`Wavelengths of eXcimer lasers or at EUV Wavelengths.
`Quartz glass, eventually suitably doped, and ?uoride crystals
`are such suitable materials.
`A complete optical prescription is found in Table 1,
`describing the optical surfaces in Code V format.
`
`TABLE 1
`
`CODE V> lis
`Shafer-design .75NA.4X.75 mm Obj.—hight
`RDY
`THI
`INFINITY
`34.000000
`147.23281
`21.000000
`236.79522
`1.000000
`
`RMD
`
`GLA
`
`‘CAF-UV’
`
`GLC
`
`CCY THC
`100
`100
`100
`100
`100
`100
`
`> OBJ:
`1:
`2:
`ASP:
`K:
`IC:
`A:
`AC:
`3:
`4:
`5:
`6:
`7:
`8:
`9:
`10:
`11:
`ASP:
`K:
`IC:
`A:
`AC:
`12:
`13:
`14:
`15:
`16:
`17:
`18:
`ASP:
`K:
`IC:
`A:
`AC:
`19:
`20:
`21:
`ASP:
`K:
`IC:
`A:
`AC:
`22:
`23:
`ASP:
`K:
`IC:
`A:
`AC:
`24:
`ASP:
`K:
`
`KC:
`0.000000
`CUF:
`YES
`0.273300E-07 B
`100
`BC:
`145.44401
`224.64885
`—223.00016
`—184.59445
`—97.23630
`—928.69926
`—75.28503
`—116.14787
`—134.28262
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`100
`CCF:
`0.000000
`0.201130E-11 C:
`100
`CC:
`27.000000
`‘CAF-UV’
`51.185724
`25.004072
`162.666291
`12.000000
`24.980383
`15.000000
`3.000000
`—3.000000 REFL
`
`100
`—.871260E—16 D:
`100
`DC:
`100
`100
`100
`100
`100
`100
`100
`100
`100
`
`0.118100E-19
`100
`
`100
`100
`100
`100
`100
`100
`100
`100
`100
`
`0.934830E-21
`100
`
`100
`100
`100
`100
`100
`100
`100
`
`0.143630E-20
`100
`
`100
`100
`100
`
`100
`KC:
`0.000000
`CCF:
`0.000000
`CUF:
`YES
`0.506570E-12 C:
`0.474810E-08 B:
`100
`CC:
`100
`BC:
`—116.14787
`—15.000000
`‘CAF-UV’
`—75.28503
`—24.980383
`—928.69926
`—12.000000
`—97.23630
`—162.666291
`—184.59445
`—25.004072
`—223.00016
`—11.195502
`—363.91714
`11.195502 REFL
`
`100
`—284590E-17 D:
`100
`DC:
`100
`100
`100
`100
`100
`100
`100
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`KC:
`0.000000
`CUF:
`YES
`—.107960E—07 B:
`100
`BC:
`—223.00016
`—184.59445
`—96.00000
`
`100
`CCF:
`0.000000
`0.170830E-13 C:
`100
`CC:
`25.004072
`‘CAF-UV’
`162.666291
`15.000000
`
`100
`—.328180E—16 D:
`100
`DC:
`100
`100
`100
`
`—1.000000 KC:
`YES
`CUF:
`0.000000E+00 B:
`100
`BC:
`INFINITY
`—247.00000
`
`100
`CCF:
`0.000000
`0.000000E+00 C:
`100
`CC:
`24.980383
`67.808099
`
`100
`0.000000E+00 D:
`100
`DC:
`100
`100
`
`0.000000E+00
`100
`
`100
`100
`
`100
`—1.000000 KC:
`CCF:
`0.000000
`YES
`CUF:
`0.000000E+00 C:
`0.000000E+00 B:
`100
`CC:
`100
`BC:
`—237.00000
`266.861281
`
`100
`0.000000E+00 D:
`100
`DC:
`100
`
`0.000000E+00
`100
`
`100
`
`—1.000000 KC:
`
`100
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2015, p. 10
`
`

`
`US 6,636,350 B2
`
`9
`
`TABLE l-continued
`
`10
`
`CCF:
`0.000000
`CUF:
`YES
`0.000000E+00 C:
`0.000000E+00 B:
`100
`CC:
`100
`BC:
`—470.52323
`—255.861281 REFL
`—210.84570
`266.861281 REFL
`
`100
`0.000000E+00 D:
`100
`DC:
`100
`100
`
`0.000000E+00
`100
`
`100
`100
`
`KC:
`0.000000
`CUF:
`YES
`—.419940E-08 B:
`100
`BC:
`INFINITY
`1621.80000
`
`100
`CCF:
`0.000000
`—.904030E-13 C:
`100
`CC:
`35.031723
`33.000000
`
`100
`—.297400E-17 D:
`100
`DC:
`100
`100
`
`‘CAF-UV’
`
`KC:
`0.000000
`CUF:
`YES
`0.155580E-07 B:
`100
`BC:
`—747.60113
`827.21786
`—1939.50000
`197.25357
`128.31113
`—1370.10000
`
`100
`CCF:
`0.000000
`—.854090E-12 C:
`100
`CC:
`67.859320
`27.000000
`20.227637
`14.999969
`39.542169
`24.000000
`
`100
`0.123240E-1 D:
`100
`DC:
`100
`100
`100
`100
`100
`100
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`KC:
`0.000000
`CUF:
`YES
`—.164770E—07 B:
`100
`BC:
`—253.41246
`109.90063
`242.23740
`—264.99438
`—372.29467
`173.30822
`
`100
`CCF:
`0.000000
`0.155510E-11 CL
`100
`CC:
`18.476467
`30.001392
`22.529315
`46.219742
`0.998929
`24.000000
`
`100
`—.542070E-16 D:
`100
`DC:
`100
`100
`100
`100
`100
`100
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`KC:
`0.000000
`CUF:
`YES
`0.628520E-07 B:
`100
`BC:
`1411.60000
`110.28842
`160.79657
`69.10873
`—895.78799
`
`100
`CCF:
`0.000000
`—.915530E-11 C:
`100
`CC:
`4.845900
`22.740804
`13.371732
`45.185600
`11.999039
`
`100
`—.628040E-15 D:
`100
`DC:
`100
`100
`100
`100
`100
`
`‘CAF-UV’
`
`‘CAF-UV’
`
`—.106340E-21
`100
`
`100
`100
`
`—