United States Patent [19]
`Williamson
`
`[54] HIGH NUMERICAL APERTURE RING
`FIELD OPTICAL REDUCTION SYSTEM
`
`[75] Inventor: David M. Williamson, West Malvern,
`United Kingdom
`
`[73] Assignee: SVG Lithography Systems, Inc.,
`Wilton, Conn.
`
`1] Appl. No.: 571,081
`[22]
`Filed:
`Dec. 12, 1995
`
`[51]
`
`Int. C1.6 ......................... .. G02B 17/00; G02B 21/00;
`G02B 23/00; G02B 5/10
`[52] us. Cl. ......................... .. 359/365; 359/730; 359/858
`[58] Field of Search ................................... .. 359/365, 366,
`359/729, 858, 859, 730, 731
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,226,501 10/1980 Shafer ................................... .. 359/366
`4,241,390 12/1980 Markle et a1.
`362/299
`4,701,035 10/1987 Hirose ............ ..
`359/366
`4,747,678
`5/1988 Shafer et a1. .
`.. 359/366
`5,063,586 11/1991 Jewell et a1. ..
`.. 378/34
`5,153,898 10/1992 Suzuki et al. .
`.. 378/34
`5,315,629
`5/1994 Jewell et al. ............................ .. 378/34
`
`OTHER PUBLICATIONS
`
`JeWell et al, Re?ective 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.
`
`US005815310A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,815,310
`Sep. 29, 1998
`
`Primary Examiner—Thong Nguyen
`Assistant Examiner—Mark A. Robinson
`Attorney, Agent, or Firm—Paul A. Fattibene; Arthur T.
`Fattibene; Fattibene & Fattibene
`
`[57]
`
`ABSTRACT
`
`An optical projection reduction system used in photolithog
`raphy for the manufacture of semiconductor devices having
`a ?rst mirror pair, a second ?eld mirror pair, and a third
`mirror pair. Electromagnetic radiation from a reticle or mask
`is re?ected by a ?rst mirror pair to a second ?eld mirror pair
`forming an intermediate image. A third mirror pair
`re-images the intermediate image to an image plane at a
`Wafer.A1l six mirrors are spherical or aspheric and rotation
`ally symmetrical about an optical axis. An annular ring ?eld
`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 numeri
`cal 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 projec
`tion 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 re?ective elements, greatly facilitating
`the manufacture of semiconductor devices having feature
`siZes beloW 0.25 microns.
`
`18 Claims, 3 Drawing Sheets
`
`RETICLE
`
`/
`
`R1
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 1
`
`

`

`U.S. Patent
`
`Sep. 29, 1998
`
`Sheet 1 of3
`
`5,815,310
`
`mjurrwm
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 2
`
`

`

`U.S. Patent
`
`Sep. 29, 1998
`
`Sheet 2 of3
`
`5,815,310
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 3
`
`

`

`US. Patent
`
`Sep. 29, 1998
`
`Sheet 3 0f3
`
`5,815,310
`
` RETICLE
`
`CARL ZEISS v. NIKON
`|PR2013-00362
`
`Ex. 2013, p. 4
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 4
`
`

`

`1
`HIGH NUMERICAL APERTURE RING
`FIELD OPTICAL REDUCTION SYSTEM
`
`FIELD OF THE INVENTION
`
`This invention relates generally to projection lithography,
`and more particularly to a catoptric and catadioptric optical
`system for use With short Wavelengths in the near and
`extreme ultraviolet or soft X-ray region.
`
`BACKGROUND OF THE INVENTION
`
`In the manufacture of semiconductor devices, photoli
`thography is often used. Projection optics are used to image
`a mask or reticle onto a Wafer. Optical systems using
`refractive elements have achieved resolutions approaching
`0.25 micrometers operating With illumination sources hav
`ing Wavelengths of 248 or 193 nanometers. As the element
`or feature siZe of semiconductor devices become smaller, the
`need for optical projection systems capable of providing a
`resolution less than 0.25 micrometers are needed. In order to
`decrease the feature siZe Which the optical projection sys
`tems used in photolithography can resolve, shorter Wave
`lengths of electromagnetic radiation must be used to project
`the image of a reticle or mask onto a photosensitive
`substrate, such as a semiconductor Wafer. Because very feW
`refractive optical materials are able to transmit signi?cant
`electromagnetic radiation beloW a Wavelength of 193
`nanometers, it is necessary to reduce to a minimum or
`eliminate refractive elements in optical projection systems
`operating at Wavelengths beloW 193 nanometers. An optical
`system that is usable in the deep ultraviolet portion of the
`spectrum is disclosed in US. Pat. No. 4,747,678 entitled
`“Optical Relay System With Magni?cation” issuing to
`Shafer, et al, on May 31, 1988, Which is herein incorporated
`by reference. HoWever, the desire to resolve ever smaller
`features makes necessary optical projection systems that
`operate at the extreme ultraviolet Wavelengths, beloW 200
`nanometers, to the soft X-ray Wavelengths, around 13
`nanometers. While there are several optical projection sys
`tems that operate Within this Wavelength region, they are
`limited to a relatively loW numerical aperture of less than 0.1
`at the image or Wafer. Increasing the numerical aperture of
`these designs Will result in unacceptably large residual
`aberrations and obscuration of the light beams by the edges
`of the mirrors. While these projection optical systems per
`form adequately for their intended purpose, there is a need
`for optical projection systems having a higher numerical
`aperture for use at Wavelengths in the extreme ultraviolet or
`soft x-ray Wavelengths, or for resolutions substantially less
`than 0.1 micrometers or microns.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`SUMMARY OF THE INVENTION
`
`The present invention comprises three mirror pairs. The
`?rst mirror pair includes a positive poWer mirror imaging an
`entrance pupil onto a second mirror of the ?rst mirror pair
`providing an accessible, real aperture stop. A second mirror
`pair receives electromagnetic radiation from the ?rst mirror
`pair and includes a positive poWer mirror relaying the
`aperture stop to a second real pupil and forming an inter
`mediate image. A third mirror pair receives electromagnetic
`radiation from the second mirror pair, and includes a positive
`poWer mirror relaying the second real pupil to an exit pupil
`at in?nity and imaging the intermediate image to a real ?nal
`image. A six mirror reduction system of relatively high
`numerical aperture is thereby obtained that provides a
`reduced image of an object, such as a reticle or mask, onto
`a photosensitive substrate, such as a semiconductor Wafer.
`
`55
`
`60
`
`65
`
`5,815,310
`
`2
`The second mirror pair acts as a ?eld mirror element
`providing a relatively high numerical aperture With good or
`acceptable image quality. All six mirrors may be aspheric to
`obtain the smallest possible residual aberrations.
`Accordingly, it is an object of the present invention to
`provide a projection optical system for use With Wavelengths
`loWer than approximately 200 nanometers and having a
`relatively high numerical aperture.
`It is a further object of the present invention to increase
`resolution permitting imaging of small element features as
`required in semiconductor manufacture.
`It is an advantage of the present invention that the object
`and image are accessible for parallel scanning of a reticle
`and Wafer stage as used in step and scan photolithography.
`It is another advantage of the present invention that a
`relatively large ?eld is obtained.
`It is a feature of the present invention that an aperture stop
`is accessible.
`It is a further feature of the present invention that a ?eld
`mirror element is used.
`These and other objects, advantages, and features Will
`become readily apparent in vieW of the folloWing detailed
`description.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic illustration of one embodiment of
`the present invention.
`FIG. 2 is a schematic illustration of a second embodiment
`of the present invention.
`FIG. 3 is a schematic illustration of a third embodiment of
`the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 schematically illustrates a ?rst embodiment of the
`present invention. The light from a reticle or mask 10 is
`collected by concave mirror M1. Dashed line 12 represents
`the extended curvature of mirror M1. Mirror M1 re?ects
`electromagnetic radiation to concave mirror M2. An aper
`ture stop 14 is positioned at or near mirror M2. An entrance
`pupil is positioned a ?nite distance from the reticle or mask
`10 and imaged at mirror M2 by mirror M1. Electromagnetic
`radiation is re?ected from mirror M2 to concave mirror M3.
`Dashed line 16 illustrates the extended curvature of concave
`mirror M3. Electromagnetic radiation from mirror M3 is
`received and re?ected by concave mirror M4. Dashed line
`18 illustrates the extended curvature of concave mirror M4.
`Electromagnetic radiation is re?ected from mirror M4 and
`received by convex mirror M5. Dashed line 20 illustrates the
`extended curvature of convex mirror M5. Electromagnetic
`radiation is re?ected from mirror M5 and received by
`concave mirror M6, and re?ected by concave mirror M6 to
`an image location at a Wafer 22. All of the mirrors M1—M6
`are substantially rotationally symmetric about the optical
`axis OA. An intermediate image 24 is formed betWeen the
`mirrors M4 and M3 or at an off-axis location betWeen the
`?rst mirror pair, M1 and M2, and the third mirror pair, M5
`and M6. This intermediate image is re-imaged at the Wafer
`22 by mirrors M4, M5, and M6. The ?rst mirror pair, M1 and
`M2, re?ects electromagnetic radiation to a second mirror
`pair, M3 and M4. The second mirror pair, M3 and M4,
`functions as a ?eld mirror element and takes the chief ray
`leaving mirror M2 diverging aWay from the optical axis OA,
`and converts it to a chief ray converging toWard the optical
`axis OA for acceptance by a third mirror pair, M5 and M6.
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 5
`
`

`

`5,815,310
`
`3
`Accordingly, a ?eld mirror element may be a mirror pair that
`converts a chief ray diverging away from the optical axis OA
`to a chief ray converging towards the optical axis OA. In this
`?rst embodiment the residual aberrations are small enough
`to permit use at a Wavelength of approximately 13 nanom
`eters. The numerical aperture in the image space near the
`Wafer 22 in this ?rst embodiment is approximately 0.25.
`This provides a Working resolution of 0.03 micrometers or
`
`.
`
`.
`
`.
`
`5
`
`TABLE 1A
`
`Aspheric
`
`Curv
`
`K
`
`A
`
`B
`
`C
`
`D
`
`A(1)
`A(2)
`A(3)
`A(4)
`A(5)
`A(6)
`
`—0.00204178 0.000000 6.26871E - 10 -1.09535E - 15
`—0.00248086 0.000000 1.05970E - O8
`4.81436E - 13
`—0.0004828O 0.000000 2.18257E - 11
`2.87915E - 15
`0.00101457 0.000000 3.42885E - 11 —4.85608E - 16
`0.00355137 0.000000 1.77414E - O8
`1.15815E - 12
`0.00258825 0.000000 1.36198E - 10
`1.22849E - 15
`
`1.29067E - 20
`-1.10750E - 15
`6.04832E - 20
`-3.57675E - 22
`7.13212E - 17
`8.27928E - 21
`
`8.68980E - 26
`7.52743E - 19
`3.68423E - 25
`1.81445E - 26
`-4.35391E - 21
`1.16903E - 25
`
`FIG. 2 illustrates a second embodiment of the present
`microns.An annular image ?eld having aradius betWeen 29 20
`invention, In this einbodiinent, the entrance pupil is at
`and 31 millimeters from the optical axis OA has aberrations,
`in?nity, resulting in the system being telecentric at the reticle
`1nC1ud1_ng dlstomons Small ellough for use m a Step and Scan
`10. Electromagnetic radiation from the reticle 10 is collected
`PhC?tPhthOgYaPhY System Wlth a 539mm‘? ?el? S1Zhe_ Of?30
`by concave mirror M1‘ and re?ected to convex mirror M2‘.
`m1 ?ngers In t 6 Cross Scan . Heqmn' . n t 15. rst
`.
`,
`.
`embodiment, a four to one reduction is obtained. Mirrors 25
`Dashed line 12 represents the extended curvature of mirror
`M1_M6 ma b
`h -
`1
`h -
`d f b -
`t d b
`M1‘ M,
`M1‘ d M2‘ f
`? t
`,
`, E1 t
`y e sp er1ca or asp er1c an a r1ca e
`y any
`'
`mors _
`_ an
`Orm a rs mlrror Pam 66f?‘
`conventional means, including the placement of coatings
`magnenc radlanon re?ected from Convex mlrror M2 15
`thereon such as disclosed in Us. Pat. No. 5,153,898 entitled
`collected by concave mirror M3‘. Dashed line 16‘ represents
`“X_Ray Reduction Projection Exposure System of Reiiec-
`tion Type” issuing to Fukuda et al on Oct. 6, 1992, Which is 30 the extended curvature of mirror M3‘. Electromagnetic
`herein incorporated by reference. Aspheric mirrors may be
`radiation is re?ected from mirror M3‘ to concave mirror M4‘.
`used to Obtaln the Smallest P055191e resldual abefratlOnS
`Dashed line 18‘ represents the extended curvature of mirror
`The construction data for the opticalsystem‘illustrated in
`M4‘_ Mirrors M3‘ and M4‘ form a Second mirror pair acting
`FIG. 1 according to the present invention is given in Table
`as a ?eld mirror element Electromagnetic radiation is
`1 below‘
`35 re?ected from mirror M4‘ and is collected by convex mirror
`M5‘. Dashed line 20‘ represents the extended curvature of
`mirror M5‘. Electromagnetic radiation is re?ected from
`mirror M5‘ and collected by mirror M6‘. Mirrors M5‘ and
`M6‘ form a third mirror pair. The electromagnetic radiation
`40 re?ected from the concave mirror M6‘ is imaged at a Wafer
`22. All of the mirrors M1‘—M6‘ are rotationally symmetrical
`about the optical axis OA. The ?eld mirror element mirror
`pair M4‘ and M3‘ form an intermediate image plane 24‘ after
`Re? 45 mirror M4‘ and close to mirror M6‘ or at an off-axis location
`betWeen the mirrors of the third mirror pair M5‘ and M6‘.
`This is advantageous at~h1gh numerical apertures to mini
`mize the electromagnetic radiation beam size that has to
`clear the edge of mirror M6‘. The third mirror pair, mirrors
`Re? 50 M5‘ and M6‘, re-image the image at the intermediate image
`Re?
`,
`.
`.
`plane 24 to a ?nal image at the Wafer 22. In this second
`embodiment the image space is telecentric, that is the exit
`pupil is at in?nity. This second embodiment has a four to one
`reduction ratio, and the numerical aperture into the image
`Re?
`Re? 55 space near the Wafer 22 is 0.55. At this relatively high
`numerical aperture, the residual aberrations are small
`enou h that the o tical ro'ection s stem ma be used at
`g
`p
`_ p 1
`y
`y _
`Wavelengths of approximately 193 nanometers. This alloW
`_
`_
`_
`_
`_
`ing a Working resolution of 0.25 microns or micrometers. An
`In the above table, positive ‘radius ~1I1d'1Cat'6S the center of 60 annular ?eld formed between a radius of 295 and 305
`clflrvature Is to ‘he Ugh: nelgitlvii_radlus,lndlcates th? centfzr
`millimeters from the optical axis OA at the Wafer 22 is
`O _ ‘,mrvature ,15 to t, e 8 t’ _ lmenslons are glven 1n
`suf?cient for use in a step and scan lithography system With
`millimeters, thickness is ax1al distance to next surface, and
`-
`-
`-
`-
`-
`-
`.
`.
`.
`.
`.
`a ?eld size of 30 millimeters in the cross-scan direction.
`the image diameter shoWn above is a parax1al value and is
`not a ray traced value.
`Additionally, aspheric constants are given by the equation
`and Table 1A beloW.
`
`Aperture Diameter
`F t
`B k G1
`
`IOI'I
`
`3C
`
`ass
`
`.
`
`.
`
`.
`
`Re?
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`2369146
`2334582
`46.3098
`45.7172
`452145
`
`334-0156
`503.2223
`2400123
`
`261-2488
`86 6738
`227.7070
`72-1652
`
`62.0000
`
`65
`
`The construction data for the optical system illustrated in
`FIG. 2 according to the present invention is given in Table
`2 beloW.
`
`Element
`N b
`
`um er
`
`Radius of
`Curvature
`F t
`B k
`
`IOI'I
`
`3C
`
`Obie/Ct
`
`In?nity
`
`1
`
`2
`
`3
`4
`
`5
`6
`
`A0)
`
`Ac)
`
`A6)
`A(4)
`
`A6)
`A(6)
`
`TABLE 1
`
`Th_ kn
`
`1C ess
`
`571-0624
`192 0526
`_192:O526
`Aperture Stop
`0.0000
`
`432.1152
`‘4905496
`490.5496
`
`—62.8918
`320 6990
`_32O'699O
`320.6990
`
`Image
`
`Image Distance :
`INF
`
`223092
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 6
`
`

`

`5,815,310
`
`10
`
`15
`
`20
`
`6
`mirror M3“ and collected by concave mirror M4“. Dashed
`line 18“ represents the curvature of mirror M4“. Mirrors
`M3“ and M4“ form a second mirror pair. Electromagnetic
`radiation re?ected from mirror M4“ is collected by convex
`mirror M5“. Electromagnetic radiation re?ected from mirror
`M5“ is collected by concave mirror M6“. Mirrors M5“ and
`M6“ form a third mirror pair. Electromagnetic radiation
`re?ected from mirror M6“ is directed to a lens element R3
`and is then imaged at an image plane at Wafer 22. The
`second mirror pair, mirrors M3“ and M4“, form a ?eld
`mirror element providing an intermediate image plane 24“
`between mirrors M6“ and M3“. The third mirror pair M5“
`and M6“ re-image intermediate image plane 24“ at the Wafer
`22. All of the mirrors M1“—M6“ and the refractive lens
`elements R1—R3 are rotationally symmetrical about the
`optical axis OA. The lens elements R1—R3 are refracting
`elements that reduce residual aberrations alloWing operation
`at a higher numerical aperture in the image space near the
`Wafer 22. In this third embodiment the numerical aperture at
`the image space near the Wafer 22 is 0.6. An annular ?eld
`having a radius between 29 and 31 millimeters from the
`optical axis OA is formed that may comfortably resolve
`0.225 micron features using electromagnetic radiation at a
`Wavelength of 193 nanometers. In this third embodiment
`0.18 micron feature sizes may be achievable With the
`appropriate reticles, illumination conditions, and photo
`resist. An advantage of this third catadioptric embodiment is
`that the ?rst lens element R1 may also serve as a sealing
`WindoW if desired. This is desirable When the system is used
`in a purged environment. Lens element R1 may additionally
`be moved axially along the optical axis OA to make ?ne
`adjustments to system magni?cation. While the mirror M1“
`could be used for ?ne adjustments to magni?cation, mirror
`M1“ is much more sensitive to alignment errors during axial
`.
`35 movement. Lens element R3 may also be used as a sealing
`WindoW. Additionally, lens element R3 may act as a sub
`strate on Which mirror M5“ may be formed. The lens
`element R3 may have an aspheric second surface primarily
`
`5
`
`TABLE 2
`
`Element
`
`Radius of
`Curvature
`
`Aperture Diameter
`
`Number Front
`
`Back
`
`Thickness
`
`Front
`
`Back Glass
`
`object
`
`In?nity
`
`407.8161
`
`1
`
`2
`
`3
`4
`
`5
`6
`
`A(1)
`
`A(2)
`
`A(3)
`A(4)
`
`A(5)
`A(6)
`
`Image
`
`Image Distance =
`INF
`
`264.5379
`—264.5379
`Aperture Stop
`0.0000
`0.0000
`
`390.2371
`—260.0000
`260.0000
`
`—5.6992
`
`186.2863
`—186.2863
`186.2863
`
`20.0000
`
`357.5906
`
`419.5247
`77.5026
`
`74.9379
`77.3224
`
`467.2174
`527.2466
`240.4502
`
`206.6446
`
`92.0895
`272.0463
`82.3061
`
`60.9996
`
`Re?
`
`Re?
`
`Re?
`Re?
`
`Re?
`Re?
`
`In the above table, positive radius indicates the center of
`curvature is to the right, negative radius indicates the center
`of curvature is to the left, dimensions are given in
`millimeters, thickness is axial distance to next surface, and
`the image diameter shoWn above is a paraxial value and is
`not a ray traced value.
`Additionally, aspheric constants are given by the equation
`and Table 2A beloW.
`
`Z = 1 + (1
`
`gCURVgY2
`(1 HO (CURWZYZWZ + (4)1’4 +0501’6 + (C)Y8+
`
`(D)Y1” + (E)Y12 + (F)Y” + (G)Y16 + (H)Y1'3 + (J)Y2”
`
`25
`
`30
`
`TABLE 2A
`
`Aspheric
`
`Curv
`
`K
`E
`
`A
`F
`
`B
`G
`
`C
`H
`
`D
`J
`
`A(1)
`
`A(2)
`
`A(3)
`
`A(4)
`
`A(5)
`
`A(6)
`
`—0.00184131 0.000000
`0.00000E + 00
`—0.00344767 0.000000
`3.43046E - 23
`—0.00073996 0.000000
`0.00000E + 00
`0.00145483 0.000000
`0.00000E + 00
`0.00444460 0.000000
`6.03283E - 23
`0.00442274 0.000000
`5.1581OE - 28
`
`2.24506E - 12
`0.00000E + 00
`2.70239E - O8
`0.00000E + 00
`3.47651E - 10
`0.00000E + 00
`—6.10242E - 11
`0.00000E + 00
`1.67615E - 07
`0.00000E + 00
`5.24492E - 10
`0.00000E + 00
`
`-1.06529E - 15
`0.00000E + 00
`6.29102E - 12
`0.00000E + 00
`1.86467E - 16
`0.00000E + 00
`7.82453E - 16
`0.00000E + 00
`1.75232E - 11
`0.00000E + 00
`8.43072E - 15
`0.00000E + 00
`
`1.40153E - 20
`0.00000E + 00
`1.39941E - 15
`0.00000E + 00
`—3.27086E - 20
`0.00000E + 00
`—8.98158E - 21
`0.00000E + 00
`8.40253E - 16
`0.00000E + 00
`4.12933E - 19
`0.00000E + 00
`
`-1.45525E - 26
`0.00000E + 00
`—1.11823E - 19
`0.00000E + 00
`1.15234E - 25
`0.00000E + 00
`-4.15911E - 26
`0.00000E + 00
`8.38291E - 20
`0.00000E + 00
`—9.7652OE - 24
`0.00000E + 00
`
`FIG. 3 illustrates a third embodiment of the present
`invention. This third embodiment illustrates a catadioptric
`system. Electromagnetic radiation from the reticle 10 is
`refracted by a ?rst lens element R1. The electromagnetic
`radiation is then collected by concave mirror M1“ and
`re?ected, to a second lens element R2. Lens element R2 is
`near or adjacent convex mirror M2“. Mirrors M1“ and M2“
`form a ?rst mirror pair. Dashed line 12“ represents the
`extended curvature of mirror M1“. Electromagnetic radia
`tion is re?ected from mirror M2“ and collected by mirror
`M3“. Dashed line 16“ represents the curvature of concave
`mirror M3“. Electromagnetic radiation is re?ected from
`
`55
`
`60
`
`65
`
`to reduce residual distortion errors. This, the second surface
`of lens element R3, alloWs a Wider annular ?eld Width to be
`used. Lens element R2 is primarily used to correct the
`chromatic variation of focus introduced by refractive lens
`elements R1 and R3. Chromatic variation of magni?cation
`is corrected by balancing the contributions of chromatic
`variations of magni?cation from lens elements R1 and R3.
`Chromatic correction is good enough in this embodiment to
`alloW the use of an unnarroWed excimer laser source oper
`ating at 193 or 248 nanometers, or even a ?ltered mercury
`lamp operating at 248 nanometers. The optical projection
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 7
`
`

`

`5,815,310
`
`7
`system of this third embodiment is designed to operate at a
`four to one reduction ratio.
`The construction data for the optical system illustrated in
`FIG. 3 according to the present invention is given in Table
`3 beloW.
`
`8
`Accordingly, the present invention, by using three mirror
`pairs, With the second mirror pair being a ?eld mirror
`element, greatly increases the numerical aperture possible in
`an optical projection reduction system for use With electro
`magnetic radiation at Wavelengths beloW approximately 200
`
`TABLE 3
`
`Element
`
`Radius of Curvature
`
`Aperature Diameter
`
`Number
`
`Front
`
`Back
`
`Thickness
`
`Front
`
`Back
`
`Glass
`
`Object
`1
`
`INF
`528.5985 CX 560.6353 CC
`
`2
`3
`
`4
`5
`
`6
`7
`
`8
`9
`10
`
`IMAGE
`
`A(1)
`—83.4955 CX —75.5672 CC
`
`A(2)
`—75.5672 CC —83.4955 CX
`
`A(3)
`A(4)
`
`A(5)
`A(6)
`
`A(8)
`A(7)
`Image Distance =
`INF
`
`363.7117
`30.0000
`20.0000
`
`229.7508
`—209.7508
`—15.0000
`—11.6150
`Aperture Stop
`11.6150
`15.0000
`407.8622
`—635.1022
`635.1022
`
`—62.2903
`
`134.7903
`—134.7903
`134.7903
`17.5000
`10.0000
`
`369.2458 367.0565 ‘silica’
`
`364.0844
`
`414.3396
`97.0160
`79.4269
`
`Refl
`‘silica’
`
`72.1226
`Refl
`72.1226
`77.0143
`93.4487 ‘silica’
`
`Refl
`Refl
`
`691.6152
`1006.3416
`131.7841
`
`177.7085
`
`89.6331
`223.8931
`88.9023
`73.3478
`
`Refl
`Refl
`‘silica’
`
`62.0953
`
`In the above table, positive radius indicates the center of
`curvature is to the right, negative radius indicates the center
`of curvature is to the left, dimensions are given in
`millimeters, thickness is aXial distance to neXt surface, and
`the image diameter shoWn above is a paraXial value and is
`not a ray traced value.
`Additionally, aspheric constants are given by the equation
`and Table 3A beloW.
`
`35
`
`40
`
`CURV Y2
`
`nanometers. This greatly increases the ?eld siZe as Well as
`maintaining necessary resolution, permitting practical appli
`cation for use in the manufacture of semiconductor devices
`having features smaller than 0.25 microns.
`Additionally, although the preferred embodiment has
`been illustrated and described, it Will be obvious to those
`skilled in the art that various modi?cations may be made
`Without departing from the spirit and scope of this invention.
`What is claimed is:
`1. An optical reduction system for use in
`photolithography, from the long conjugate end to the short
`conjugate end, comprising:
`a ?rst mirror pair;
`
`TABLE 3A
`
`Aspheric
`
`Curv
`
`K
`E
`
`A
`F
`
`B
`G
`
`C
`H
`
`D
`J
`
`A(1)
`
`A(2)
`
`—0.00204511 0.000000
`0.00000E + 00
`0.000000
`—2.35686E — 22
`
`—0.00552141
`
`A(3)
`
`—0.00053739
`
`A(4)
`
`0.00101984
`
`A(5)
`
`0.00387779
`
`0.000000
`0.00000E + 00
`0.000000
`0.00000E + 00
`0.000000
`2.19063E — 22
`
`2.33031E — 10
`0.00000E + 00
`—3.13911E — 09
`0.00000E + 00
`
`1.97475E — 10
`0.00000E + 00
`—1.51028E — 11
`0.00000E + 00
`1.19897E — 07
`—2.90311E — 26
`
`—2.45108E — 16
`0.00000E + 00
`5.79100E — 12
`0.00000E + 00
`
`—1.92949E — 16
`0.00000E + 00
`—2.24413E — 18
`0.00000E + 00
`1.63739E — 11
`0.00000E + 00
`
`1.19279E — 20
`0.00000E + 00
`—7.42414E — 16
`0.00000E + 00
`
`—1.05508E — 21
`0.00000E + 00
`—3.43794E — 23
`0.00000E + 00
`1.80437E — 15
`0.00000E + 00
`
`7.03022E — 26
`0.00000E + 00
`1.18359E — 18
`0.00000E + 00
`
`3.23255E — 27
`0.00000E + 00
`—1.20284E — 28
`0.00000E + 00
`—5.45296E — 19
`0.00000E + 00
`
`A(6)
`
`0.00571450
`
`0.000000
`—1.62403E — 26
`
`2.26163E — 09
`7.29705E — 31
`
`8.71431E — 14
`0.00000E + 00
`
`5.66545E — 19
`0.00000E + 00
`
`3.51393E — 22
`0.00000E + 00
`
`A(7)
`
`0.00387779
`
`0.000000
`
`1.19897E — 07
`
`1.63739E — 11
`
`1.80437E — 15
`
`—5.46296E — 19
`
`2.19063E — 22
`
`—2.90311E — 26
`
`0.00000E + 00
`
`0.00000E + 00
`
`0.00000E + 00
`
`A(8)
`
`0.00280709
`
`0.000000
`0.00000E + 00
`
`—2.73857E — 08
`0.00000E + 00
`
`3.40519E — 10
`0.00000E + 00
`
`—6.15022E — 14
`0.00000E + 00
`
`—1.29049E — 17
`0.00000E + 00
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 8
`
`

`

`9
`a ?eld mirror pair positioned to receive electromagnetic
`radiation re?ected from said ?rst mirror pair;
`a third mirror pair positioned to receive electromagnetic
`radiation re?ected from said ?eld mirror pair;
`a ?rst refractive element positioned betWeen an object and
`said ?rst mirror pair;
`a second refractive element positioned near a second
`mirror of said ?rst mirror pair; and
`a third refractive element positioned betWeen an image
`and said third mirror pairs,
`Whereby an intermediate image is re-imaged to a ?nal
`image at an image plane.
`2. An optical reduction system as in claim 1 Wherein:
`said ?rst refractive element is axially movable along an
`optical aXis.
`3. An optical reduction system as in claim 1 Wherein:
`chromatic variation of focus introduced by said ?rst
`refractive element and said third refractive element is
`substantially corrected by said second refractive ele
`ment.
`4. An optical reduction system as in claim 1 Wherein:
`chromatic variation of magni?cation is substantially cor
`rected by balancing contributions of chromatic varia
`tion of magni?cation from said ?rst refractive element
`and said third refractive element.
`5. An optical reduction system for use in
`photolithography, from the long conjugate end to the short
`conjugate end, comprising:
`a ?rst mirror pair;
`a ?eld mirror pair, said ?eld mirror pair positioned to
`receive a chief ray re?ected from said ?rst mirror pair
`diverging aWay from an optical aXis and converting it
`to a chief ray converging toWards the optical aXis; and
`a third mirror pair, said third mirror pair positioned to
`receive the chief ray re?ected from said ?eld mirror
`pair,
`Wherein said ?rst mirror pair, said ?eld mirror pair, and
`said third mirror pair are positioned betWeen a ?rst
`plane formed by the long conjugate end and a second
`plane formed by the short conjugate end While pro
`gressing in a single direction along the optical aXis,
`Whereby a reduced image of an object is formed and the
`?rst plate and the second plane are accessible for
`parallel scanning.
`6. An optical reduction system for use in
`photolithography, from the long conjugate end to the short
`conjugate end, comprising:
`a ?rst concave mirror;
`a second mirror;
`a third concave mirror;
`a fourth concave mirror;
`a ?fth conveX mirror; and
`a siXth concave mirror,
`Wherein said ?rst concave mirror, said second mirror, said
`third concave mirror, said fourth concave mirror, said
`?fth conveX mirror, and said siXth concave mirror are
`all positioned betWeen a ?rst plane formed by the long
`conjugate end and a second plane formed by the short
`conjugate end While progressing in a single direction
`along an optical aXis,
`Whereby tWo of said ?rst, second, third, fourth, ?fth or
`siXth mirrors act as a ?eld mirror pair.
`7. An optical reduction system as in claim 6 Wherein:
`
`1O
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`5,815,310
`
`10
`said second mirror is concave.
`8. An optical reduction system as in claim 6 Wherein:
`said second mirror is conveX.
`9. An optical reduction system as in claim 6 Wherein:
`an aperture stop is formed near said second mirror.
`10. An optical reduction system for use in
`photolithography, from the long conjugate end to the short
`conjugate end, comprising:
`a ?rst concave mirror;
`a second mirror, positioned to receive re?ected electro
`magnetic radiation from said ?rst concave mirror;
`a third concave mirror positioned to receive re?ected
`electromagnetic radiation from said second mirror;
`a fourth concave mirror positioned to receive re?ected
`electromagnetic radiation from said third concave mir
`ror;
`a ?fth conveX mirror positioned to receive re?ected
`electromagnetic radiation from said fourth concave
`mirror; and
`a siXth concave mirror positioned to receive re?ected
`electromagnetic radiation from said ?fth conveX
`mirror,
`said ?rst, second, third, fourth, ?fth and siXth mirrors
`having 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
`re?ected from said third concave mirror and re?ecting
`the chief ray causing it to converge toWard the optical
`aXis,
`Wherein said ?rst concave mirror, said second mirror, said
`third concave mirror, said fourth concave mirror, said
`?fth conveX mirror, and said siXth concave mirror are
`all positioned betWeen the lone conjugate end and the
`short conjugate end While progressing in a single
`direction alone the optical aXis,
`Whereby the long conjugate end and the short conjugate
`end are accessible for parallel scanning.
`11. An optical reduction system as in claim 10 Wherein:
`the electromagnetic radiation has a Wavelength less than
`200 nanometers.
`12. An optical reduction system as in claim 11 Wherein:
`an intermediate image is formed betWeen said third con
`cave mirror and said fourth concave mirror.
`13. An optical reduction system as in claim 11 Wherein:
`an intermediate image is formed betWeen said ?fth con
`veX mirror and said siXth concave mirror.
`14. An optical reduction system for use in
`photolithography, from the long conjugate end to the short
`conjugate end, comprising:
`a ?rst concave mirror,
`a second mirror positioned to receive re?ected electro
`magnetic radiation from said ?rst concave mirror;
`a third concave mirror positioned to receive re?ected
`electromagnetic radiation from said second mirror;
`a fourth concave mirror positioned to receive re?ected
`electromagnetic radiation from said third concave mir
`ror;
`a ?fth conveX mirror positioned to receive re?ected
`electromagnetic radiation from said fourth concave
`mirror; and
`a siXth concave mirror positioned to receive re?ected
`electromagnetic radiation from said ?fth conveX
`mirror,
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2013, p. 9
`
`

`

`5,815,310
`
`said ?rst, second, third, fourth, ?fth and sixth mirrors
`having a radius of Curvature On an Optical ms,
`said third concave mirror receiving a chief ray diverging
`aWay from the optical axis,
`said fourth concave mirror receiving the chief ray 5
`re?ected from said third concave mirror and re?ecting
`the chief ray causing it to converse toWard the optical
`
`a plurality of curved mirror pairs constructed according to
`the optical construction data of the folloWing Table 2
`
`TABLE 2
`
`Element
`
`Radius of
`Curvature
`
`Aperture Diameter
`
`axis;
`
`— —
`
`a ?rst refractive element located betWeen an object and 10
`Said Second mirror;
`
`Number Front
`
`Back
`
`a second refractive element located near said second
`mirror; and
`a third refractive element located betWeen an image and
`said ?fth mirror.
`15. An optical reduction system for use in photolithogra-
`phy conlpnslngZ
`a plurality of curved mirror pairs constructed according to
`the optical construction data of the folloWing Table 1
`
`TABLE 1
`
`_
`ob]ect
`
`_
`In?nity
`
`15
`
`1
`
`Ag)
`
`2O
`
`2
`
`A(2)
`
`0.0000
`
`Element
`
`Radius o