US007385756B2
`
`(12)
`
`United States Patent
`Shafer et a].
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 7,385,756 B2
`Jun. 10, 2008
`
`(54) CATADIOPTRIC PROJECTION OBJECTIVE
`
`FOREIGN PATENT DOCUMENTS
`
`(75) Inventors: David Shafer, Fair?eld, CT (US);
`Wilhelm Ulrich, Aalen (DE); Aurelian
`Dodoc, Heidenheim (DE); Rudolf Von
`Buenau, Jena (DE); Hans-Juergen
`Mann, Oberkochen (DE); Alexander
`Epple’ Aalen (DE)
`
`DE
`
`1064734 B
`
`9/1959
`
`(Continued)
`OTHER PUBLICATIONS
`
`(73) Asslgneez Carl Zeiss SMT AG’ Oberkochen (DE)
`
`M. H. Freeman, Innovative Wide-Field Binocular Design, OSA
`
`( >x< ) NoticeZ
`
`Subject to any disclaimer’ the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`512003653315; oxfotlhezlznternational Optical Design Conference, 1994,
`'
`’
`'
`'
`
`(Continued)
`
`(21) Appl. No.: 11/035,103
`_
`(22) Flled?
`
`Jan- 141 2005
`
`(65)
`
`PI‘iOI‘ Publication Data
`US 2005/0190435 A1
`Sep. 1, 2005
`
`Primary ExamineriStephone B. Allen
`Assistant ExamineriLee Fineman
`(74) Attorney, Agent, or FirmiFish & Richardson RC.
`
`(57)
`
`ABSTRACT
`
`A catadioptric projection objective for imaging a pattern
`Related US. Application Data
`PmYided in an Object 131211,“: O_f the Pr°j‘?°?°n objéctive Onto
`(60) Provisional application No. 60/617,674, ?led on Oct.
`an image plane ofthe projectlon objective comprises: a ?rst
`13, 2004, provisional application NO‘ 60/612’823’
`?led on Sep 24 2004 provisional application NO objective part for imaging the pattern provided in the object
`60/587’504s ?led on JUL 14, 2004, provisional app1i_
`plane into a ?rst intermediate image;~a secondobjective part
`Cation No_ 605363248, ?led on Jan 14, 2004'
`for lmaglng the ?rst lntermedlate lmaglng 1nto a second
`intermediate image; a third objective part for imaging the
`second intermediate imaging directly onto the image plane;
`wherein a ?rst concave mirror having a ?rst continuous
`mirror surface and at least one second concave mirror
`having a second continuous mirror surface are arranged
`upstream of the second intermediate image; pupil surfaces
`are formed between the object plane and the ?rst interme
`diate image, between the ?rst and the second intermediate
`image and between the second intermediate image and the
`image plane; and all concave mirrors are arranged optically
`remote from a pupil surface. The system has potential for
`very high numerical apertures at moderate lens material
`mass consumption.
`
`(51) Int. Cl.
`(2006.01)
`G02B 17/00
`(2006.01)
`G02B 21/00
`(52) US. Cl. ..................................... .. 359/365; 359/730
`(58) Field of Classi?cation Search ................... .. None
`See application ?le for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`2,380,887 A
`3,244,073 A
`
`7/1945 Warmisham
`4/1966 Bouwers et al.
`
`(Continued)
`
`109 Claims, 33 Drawing Sheets
`
`1701
`1712
`
`1711
`P1
`
`1703
`
`1710
`
`1720
`
`1730
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 1
`
`

`

`US 7,385,756 B2
`Page 2
`
`US. PATENT DOCUMENTS
`
`8/1978 Yam?da
`41103990 A
`4,241,390 A 12/1980 Markle et a1.
`4,293,186 A 10/1981 Offner _
`4,346,164 A
`8/1982 Tabarelll er a1~
`4,398,809 A
`8/1983 CanZek
`4,443,068 A
`4/1984 Itoh
`4,469,414 A
`9/1984 Shafer
`4,482,219 A 11/1984 CanZek
`4,666,259 A
`5/1987 IiZuka
`4,685,777 A
`8/1987 Hirose
`4,711,535 A 12/1987 Shafer
`4,757,354 A
`7/1988 Sam 91 91-
`4,779,966 A 10/1988 Friedman
`4,812,028 A
`3/1989 Matsumoto
`4,834,515 A
`5/1989 Mercado
`4,861,148 A
`8/1989 Sam eta1~
`4,951,078 A
`8/1990 Okada
`5,004,331 A
`4/ 1991 Haseltlne eta1~
`5,031,976 A
`7/1991 Shafer
`5,063,586 A 11/1991 Jewell er 91-
`5,114,238 A
`5/1992 Sigler
`5,153,898 A 10/1992 $114119 er 91-
`5,212,588 A
`5/1993 vlswanathan eta1~
`5,220,590 A
`6/1993 Bruning er 91-
`5,315,629 A
`5/1994 Jewell er 91-
`5,353,322 A 10/1994 Bruning er 91-
`5,410,434 A
`4/1995 Shafer
`5,477,304 A 12/1995 Nishi
`5,488,229 A
`V1996 Elliott er 91-
`5,515,207 A
`5/1996 F00
`5,636,066 A
`6/1997 Takahashi
`5,650,877 A
`7/1997 Phillips, Jr er a1
`5,652,679 A
`7/1997 Freeman
`5,686,728 A 11/1997 Shafer
`5,717,518 A
`2/1998 Shafer er a1~
`5,729,376 A
`3/1998 116116161.
`5,734,496 A
`3/1998 Beach
`5,802,335 A
`9/1998 $111116s16161.
`5,805,346 A
`9/1998 TOIIliIIlatSu
`5,805,365 A
`9/1998 Sweatt
`5,815,310 A
`9/1998 W11116111s611
`5,861,997 A
`1/1999 161161166111
`5,917,879 A
`6/1999 MaShiIIla
`5,956,192 A
`9/1999 W11116111s611
`5,999,310 A 12/1999 $116161 6161.
`6,033,079 A
`3/2000 Hudyma
`6,097,537 A
`8/2000 1616166111 6161.
`6,169,627 B1
`1/2001 $61111s161
`6,169,637 B1
`1/2001 TSuIlaShiIIla
`6,172,825 B1
`1/2001 161161166111
`6,188,513 B1
`2/2001 Hudyma 61 61.
`6,195,213 B1
`2/2001 01111116 6161.
`6,213,610 B1
`4/2001 1616116611 6161.
`6,259,510 B1
`7/2001 $11Z111<1
`6,262,845 B1
`7/2001 $w6611
`6,285,737 B1
`9/2001 $w6611 6161.
`6,353,470 B1
`3/2002 D111g61
`6,426,506 B1
`7/2002 Hudyma
`6,473,243 B1
`10/2002 01111116
`6,600,608 B1
`7/2003 $1161616161.
`6,631,036 B2 10/2003 $61111s161
`6,636,350 B2 10/2003 $1161616161.
`6,750,948 B2
`6/2004 01111116
`6,757,051 B2
`6/2004 T6k6h6shi 6161.
`6,822,727 B2 11/2004 $1111116
`6,829,099 B2 12/2004 K616 6161.
`6,842,298 B1
`1/2005 $116161 6161.
`6,873,476 B2
`3/2005 $116161 6161.
`6,912,042 B2
`6/2005 $116161
`6,995,886 B2
`2/2006 HendfikS
`6,995,918 B2
`2/2006 TefaSaWa
`
`355/67
`
`4/2006 T6k6h6shi
`7,030,965 B2
`7/2006 Terasawa et al.
`7,075,726 B2
`7/2006 $116116g6 6161.
`7,079,314 B1
`g/2006 Mann et 31‘
`7,085,075 B2
`8/2006 TefaSaWa 6161.
`7,092,168 B2
`3/2007 ROStalSki 6161.
`7,187,503 B2
`3/2007 M611116161.
`7,190,530 B2
`5/2007 $1161616161.
`7,218,445 B2
`5/2007 M11611611
`7,224,520 B2
`7/2007 Hudyma
`7,237,915 B2
`7/2007 TefaSaWa 6161.
`7,239,453 B2
`2/2002 TefaSaWa 6161.
`2002/0024741 A1
`2002/0176063 A1* 11/2002 01111116 ................... ..
`2003/0197922 A1 10/2003 Hudyma
`2003/0234912 A1 12/2003 01111116
`2003/0234992 A1 12/2003 $116161
`2004/0012866 A1
`1/2004 M611116161.
`2004/0130806 A1
`7/2004 161161166111
`2004/0160677 A1
`8/2004 15151516 6161.
`2004/0240047 A1 12/2004 $1161616161.
`2005/0036213 A1
`2/2005 M611116161.
`2005/0082905 A1
`4/2005 GfOIlau 6161.
`2005/0179994 A1
`8/2005 W6bb
`2005/0190435 A1
`9/2005 $1161616161.
`2005/0225737 A1 10/2005 WeiSSeIlfiedef 6161.
`2006/0012885 A1
`1/2006 B6616161 61.
`2006/0066962 A1
`3/2006 TOtZeCk 6161.
`2006/0077366 A1
`4/2006 $116161
`2006/0119750 A1
`6/2006 15151516 6161.
`2006/0198018 A1
`9/2006 $116161
`2006/0221456 A1 10/2006 $1161616161.
`2006/0244938 A1 11/2006 $61111s161
`2006/0256447 A1
`11/2006 DOdOC
`2007/0037079 A1
`2/2007 01111116
`2007/0091451 A1
`4/2007 $61111s161
`2007/0109659 A1
`5/2007 ROStalSki 6161.
`2007/0165198 A1
`7/2007 K116616161.
`
`FOREIGN PATENT DOCUMENTS
`
`DE
`DE
`EP
`EP
`EP
`EP
`EP
`EP
`EP
`EP
`EP
`EP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`JP
`SU
`
`103 32 112
`102005056721
`0267766
`0 951 054
`0 962 830
`1059550
`1 069 448 B1
`1098215 A1
`1318 425 A2
`1318425 B1
`1 336 887
`1 336 887 A1
`5475098
`6488169
`8466542
`8-330220
`9448241
`10463099
`10-214783
`10484408
`10303114
`2000505958
`2001428401
`3246615
`2002408551
`2002208551 A
`2002372668
`2003114387
`2003-307680
`2004-333761
`2004317534
`2005003982 A
`124665
`
`V2005
`11/2006
`5/1988
`10/1999
`12/1999
`12/2000
`V2001
`10/2001
`6/2003
`6/2003
`8/2003
`8/2003
`7/1993
`7/1994
`6/1995
`12/1996
`6/1997
`6/1998
`8/1998
`10/1998
`11/1998
`5/2000
`8/2001
`11/2001
`7/2002
`7/2002
`12/2002
`4/2003
`10/2003
`11/2004
`11/2004
`1/2005
`3/1959
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 2
`
`

`

`US 7,385,756 B2
`Page 3
`
`WO 92/05462 A2
`W0
`WO94/ 06047
`WO
`WO 94/06047 A1
`W0
`WO 98/28665
`W0
`WO 99/26097
`W0
`WO 99/42905
`W0
`WO 99/57596
`W0
`WO 01/04682 A1
`W0
`WO 01/55767 A2
`W0
`WO 01/55767 A3
`W0
`W0 WO 2003/088330 A1
`W0 WO 2004/010200
`W0 WO 2004/019128
`W0 WO 2004/107011 A1
`W0 WO 2005/015316
`W0 WO 2005/059055
`WO
`2005/098506
`W0 WO 2005/098504
`W0 WO 2005/098505
`W0 WO 2006/005547
`W0 WO 2007/025643
`W0 WO 2007/086220
`
`4/1992
`3/1994
`3/1994
`7/1998
`5/1999
`8/1999
`11/1999
`1/2001
`8/2001
`8/2001
`10/2003
`1/2004
`3/2004
`12/2004
`2/2005
`7/2005
`10/2005
`10/2005
`10/2005
`1/2006
`3/2007
`8/2007
`
`OTHER PUBLICATIONS
`
`Tomoyuki Matsuyama et al., Nikon Projection Lens Update, Pro
`ceedings of SPIE, 2004, vol. 5377, No. 65.
`
`Donald DeJager, Camera view?nder using tilted concave mirror
`erecting elements, International Lens Design Conference (OSA),
`SPIE, 1980, pp. 292-298, vol. 237.
`US. Appl. No. 60/511,673, ?led Oct. 17, 2003.
`US. Appl. No. 60/530,623, ?led Dec. 19, 2003.
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`1984.
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`al., Applied Optics, vol. 23, No. 17, Sep. 1, 1984.
`“Thermal expansion and length stability of Zerodur in dependence
`on temperature and time”, Lindig et al., Applied Optics, vol. 24, No.
`20, Oct. 15, 1985.
`M. SWitkes et al., Resolution Enhancement of 157-nm Lithography
`by Liquid Immersion, Proc. SPIE vol. 4691, Optical
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`Tomoyuki Matsuyama et al., “Microlithographic Lens for DUV
`Scanner,” SPIE vol. 4832, Dec. 2003, Conference Jun. 3-7, 2002,
`pp. 170-174.
`Tomoyuki, Matsuyama et al., “High NA and Low Residual Aber
`ration Projection Lens for DUV Scanner,”PSIE, vol. 4691 2002, pp.
`687-695.
`Ulrich, W. et al., “Trends in Optical Design of Projection Lenses for
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`(1980), pp. 310-320.
`* cited by examiner
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 3
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 1 0f 33
`
`US 7,385,756 B2
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 4
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 2 0f 33
`
`US 7,385,756 B2
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 5
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 3 0f 33
`
`US 7,385,756 B2
`
`7-431! u
`
`a
`N
`
`X
`
`I
`
`FIG. 6
`
`FIG. 5
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 6
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 4 0f 33
`
`US 7,385,756 B2
`
`mom
`
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`
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`
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`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 7
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 5 0f 33
`
`US 7,385,756 B2
`
`220 ‘/ 204 222M
`
`/A 230
`
`221
`
`/A 203
`
`FIG 9
`
`202
`
`201
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 8
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 6 0f 33
`
`US 7,385,756 B2
`
`FIG. 10
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 9
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 7 0f 33
`
`US 7,385,756 B2
`
`302
`
`@402
`
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`
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`
`FIG. 11
`
`322
`
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`
`403
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 10
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 8 0f 33
`
`US 7,385,756 B2
`
`FIG. 12
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 11
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 9 0f 33
`
`US 7,385,756 B2
`
`FIG. 14
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 12
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 10 0f 33
`
`US 7,385,756 B2
`
`FIG. 15
`
`FIG. 15A
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 13
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 11 0f 33
`
`US 7,385,756 B2
`
`502
`
`530 /
`
`552 504
`520 /
`
`FIG. 16
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 14
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 12 0f 33
`
`US 7,385,756 B2
`
`N
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`Q
`
`FIG. 17
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 15
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 13 0f 33
`
`US 7,385,756 B2
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`FIG. 18
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 16
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 14 0f 33
`
`US 7,385,756 B2
`
`Now
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 17
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 15 0f 33
`
`US 7,385,756 B2
`
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`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 18
`
`

`

`U.S. Patent
`
`Jun. 10, 2008
`
`Sheet 16 0f 33
`
`US 7,385,756 B2
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`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 19
`
`

`

`US. Patent
`
`Jun. 10, 2008
`
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`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 20
`
`

`

`US. Patent
`
`Jun. 10, 2008
`
`Sheet 18 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS V. NIKON
`|PR2013-00362
`
`EX. 2020, p. 21
`
`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 21
`
`

`

`US. Patent
`
`Jun. 10, 2008
`
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`Us 7,385,756 B2
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`IPR2013-00362
`Ex. 2020, p. 22
`
`

`

`US. Patent
`
`Jun. 10, 2008
`
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`CARL ZEISS V. NIKON
`|PR2013-00362
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`Ex.2020,p.23
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`US. Patent
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`Jun. 10, 2008
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`Sheet 21 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS V. NIKON
`|PR2013-00362
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`CARL ZEISS V. NIKON
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`US. Patent
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`Jun. 10, 2008
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`Sheet 22 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS V. NIKON
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`US. Patent
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`Jun. 10, 2008
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`US. Patent
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`Jun. 10, 2008
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`Sheet 24 0f 33
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`CARL ZEISS V. NIKON
`|PR2013-00362
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`US. Patent
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`Jun. 10, 2008
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`Sheet 25 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS V. NIKON
`|PR2013-00362
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`US. Patent
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`Jun. 10, 2008
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`Sheet 26 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS V. NIKON
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`US. Patent
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`Jun. 10, 2008
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`Sheet 27 0f 33
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`Us 7,385,756 B2
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`CARL ZEISS v. NIKON
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`US. Patent
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`Jun. 10, 2008
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`Sheet 28 0f 33
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`US 7,385,756 B2
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`CARL ZEISS v. NIKON
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`US. Patent
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`Jun. 10, 2008
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`Sheet 29 0f 33
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`Us 7,385,756 B2
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`US. Patent
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`Jun. 10, 2008
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`Sheet 30 0f 33
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`Us 7,385,756 B2
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`US. Patent
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`Jun. 10, 2008
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`Sheet 31 0f 33
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`CARL ZEISS v. NIKON
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`Jun. 10, 2008
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`CARL ZEISS v. NIKON
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`Jun. 10, 2008
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`Sheet 33 0f 33
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`

`US 7,385,756 B2
`
`1
`CATADIOPTRIC PROJECTION OBJECTIVE
`
`The present application claims priority benefit to U.S.
`Provisional 60/536,248 filed Jan. 14, 2004; U.S. Provisional
`60/587,504 filed Jul. 14, 2004; U.S. Provisional 60/617,674
`filed Oct. 13, 2004; and U.S. Provisional 60/612,823 filed
`Sep. 24, 2004. The disclosures of all of these Provisional
`applications are incorporated into his ap olication by refer-
`ence.
`
`
`BACKGROUND OF THi INViNTION
`
`
`
`
`1. Field of the Invention
`The invention relates to a catadioptric projection objective
`for imaging a pattern arranged in an object plane onto an
`image plane.
`2. Description of the Related Art
`Projection objectives of that type are employed on pro-
`jection exposure systems,
`in particular wafer scanners or
`wafer steppers, used for fabricating semiconductor devices
`and other types of microdevices and serve to project patterns
`on photomasks or reticles, hereinafter referred to generically
`as “masks” or “reticles,” onto an object having a photosen—
`sitive coating with ultrahigh resolution on a reduced scale.
`In order to create even finer structures, it is sought to both
`increase the image-end numerical aperture (NA) of the
`projection objective to be involved and employ shorter
`wavelengths, preferably ultraviolet light with wavelengths
`less than about 260 nm,
`in particular,
`However,
`there are very few materials,
`synthetic quartz glass and crystalline fluorides,
`that are
`sufiiciently transparent in that wavelength region available
`for fabricating the optical elements required. Since the Abbe
`numbers of those materials that are available lie rather close
`to one another,
`it is diflicult to provide purely refractive
`systems that are sufficiently well color—corrected (corrected
`for chromatic aberrations).
`In view of the aforementioned problems, catadioptric
`systems that combine refracting and reflecting elements, i.e.,
`in particular, lenses and mirrors, are primarily employed for
`configuring high-resolution projection objectives of the
`aforementioned type,
`The high prices of the materials involved and limited
`availability of crystalline calcium fluoride in sizes large
`enough for fabricating large lenses represent problems,
`particularly in the field of microlithography at 157 nm for
`very large numerical apertures, NA, of,
`for example,
`NA70.80 and larger. Measures that will allow reducing the
`number and sizes of lenses employed and simultaneously
`contribute to maintaining, or even improving, imaging fidel-
`ity are thus desired.
`least two
`Catadioptric projection objectives having at
`concave mirrors have been proposed to provide systems
`with good color correction and moderate lens mass require—
`ments. The patent U.S. Pat. No. 6,600,608 B1 discloses a
`catadioptric projection objective having a
`first, purely
`refractive objective part for imaging a pattern arranged in
`the object plane of the projection objective into a first
`intermediate image, a second objective part for imaging the
`first intermediate image into a second intermediate image
`and a third objective part for imaging the second intenne—
`diate image directly, that is without a further intermediate
`image, onto the image plane. The second objective part is a
`catadioptric objective part having a first concave mirror with
`a central bore and a second concave mirror with a central
`bore, the concave mirrors having the mirror faces facing
`each other and defining an interrnirror space or catadioptric
`
`20
`
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`
`61 U!
`
`40
`
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`
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`
`60
`
`2
`cavity in between. The first intermediate image is formed
`within the central bore of the concave mirror next to the
`object plane, whereas the second intermediate image is
`formed within the central bore of the concave mirror next to
`the object plane. The objective has axial symmetry and
`provides good color correction axially and laterally. How-
`ever, since the reflecting surfaces of the concave mirrors are
`interrupted at the bores, the pupil of the system is obscured.
`The Patent EP 1 069 448 B1 discloses another catadioptric
`projection objective having two concave mirrors facing each
`other. The concave mirrors are part of a first catadioptric
`objective part imaging the obj ect onto an intermediate image
`positioned adjacent to a concave mirror. This is the only
`intermediate image, which is imaged to the image plane by
`a second, purely refractive objective part. The object as well
`as the image of the catadioptric imaging system are posi-
`tioned outside the intennirror space defined by the mirrors
`facing each other. Similar systems having two concave
`mirrors, a common straight optical axis and one intermediate
`image formed by a catadioptric imaging system and posi—
`tioned besides one of the concave mirrors are disclosed in
`Japanese patent application JP 2002208551 A and U.S.
`patent application Ser. No. U.S. 2002/00241 Al.
`European patent application PIP 1 336 887 (corresponding
`to U.S. 2004/0130806 A1) discloses catadioptric projection
`objectives having one common straight optical axis and, in
`that sequence, a first catadioptric objective part for creating
`a first intermediate image, a second catadioptric objective
`part for creating a second intermediate image from the first
`intermediate image, and a refractive third objective part
`forming the image from the second intermediate image.
`Each catadioptric system has two concave mirrors facing
`each other. The intennediate images lie outside the inter—
`mirror spaces defined by the concave mirrors. Concave
`mirrors are positioned optically near to pupil surfaces closer
`to pupil surfaces than to the intermediate images of the
`projection objectives.
`In the article “Nikon Projection Lens Update” by T.
`Matsuyama, T. Ishiyama andY. Ohmura, presented by B. W.
`Smith in: Optical Microlithography XVII, Proc. of SPIE
`5377.65 (2004) a design example of a catadioptric projec-
`tion lens is shown, which is a combination of a conventional
`dioptric DUV system and a 6-mirror EUV catoptric system
`inserted between lens groups of the DUV system. A first
`intermediate image is formed behind he third mirror of the
`catoptric (purely reflective) group upstream of a convex
`mirror. The second intermediate image is formed by a purely
`reflective (catoptric) second objective part. The third obj ec—
`tive part is purely refractive featuring negative refractive
`power at a waist of minimum beam diameter within the third
`objective part for Petzval sum correction.
`Japanese patent application JP 2003114387 A and inter—
`national patent application WO 01/55767 A disclose cata-
`dioptric projection objectives having one common straight
`optical axis, a first catadioptric objective part for forming an
`intermediate image and a second catadioptric objective part
`for imaging the intermediate image onto the image plane of
`this system. Concave and convex mirrors are used in com-
`bination.
`U.S. provisional application with Ser. No. 60/511,673
`filed on Oct. 17, 2003 by the applicant discloses catadioptric
`projection objectives having very high NA and suitable for
`immersion lithography at NA>1. In preferred embodiments,
`exactly three intennediate images are created. A cross-
`shaped embodiment has a first, refractive objective part
`creating a first intermediate image from the obj ect, a second,
`catadioptric objective part for creating a second intermediate
`
`
`
`CARL ZEISS V. NIKON
`|PR2013-00362
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`Ex.2020,p.37
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`CARL ZEISS V. NIKON
`IPR2013-00362
`Ex. 2020, p. 37
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`US 7,385,756 B2
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`
`
`3
`image from the first object, a third, catadioptric objective
`part for creating a third intermediate image from the second
`intermediate image and a fourth, refractive objective part for
`imaging the third intermediate image onto the image plane.
`The catadioptric objective parts each have one concave
`mirror, and planar folding mirrors are associated therewith.
`The concave mirrors are facing each other with the concave
`mirror surfaces. The folding mirrors are arranged in the
`middle or the interrnirror space defined by the concave
`mirrors. The concave mirrors may be coaxial and the optical
`axes of the catadioptric parts may be perpendicular or at an
`angle with respect to the optical axis defined in the refractive
`imaging systems.
`lie full disclosure of the documents mentioned above is
`incorporated into this application by reference.
`"he article “Camera View finder using tilted concave
`mirror erecting elements” by D. DeJager, SPIE. Vol. 237
`(1980) p. 292-298 discloses camera View finders comprising
`two concave mirrors as elements ofa lzl telescopic erecting
`relay system. The system is designed to image an object at
`infinity into a real image, which is erect and can be viewed
`through an eyepiece. Separate optical axes of refractive
`
`
`system parts upstream and downstream of the catoptric relay
`
`
`system are parallel 0 set to each other. In order to build a
`system having concave mirrors facing each other mirrors
`must be tilted. The authors conclude that physically realiz-
`able systems of this type have poor image quality.
`Intemational patent applications WO 92/05462 and WO
`94/06047 and the article “Innovative Wide—Field Binocular
`Design” in OSA/SPIE Proceedings (1994) pages 3891f dis-
`close catadioptric optical systems especially for binoculars
`and other viewing instrtunents designed as in-line system
`having a single, unfolded optical axis. Some embodiments
`have a first concave mirror having an object side mirror
`surface arranged on one side of the optical axis and a second
`concave mirror having a mirror surface facing the first
`mirror and arranged on the opposite side of the optical axis
`such that the surface curvatures of the concave mirrors
`define and intermirror space. A front refractive group forms
`a first intermediate image near the first mirror and a second
`intermediate image is formed outside of the space formed by
`the two facing mirrors. A narrow field being larger in a
`horizontal direction than in a vertical direction is arranged
`ofilset to the optical axis. The object side refractive group
`has a collimated input and the image side refractive group
`has a collimated output and entrance and exit pupils far from
`telecentric are formed. The pupil shape is semi-circular
`unlike pupil surfaces in lithographic projection lenses.
`which have to be circular and centered on the optical axis.
`The PCT application W0 01/044682 Al discloses cata-
`dioptIic UV imaging systems for wafer inspection having
`one concave mirror designed as Mangin mirror.
`
`SUMMARY OF THE INVENTION
`
`It is one object of the invention to provide a catadioptric
`projection objective suitable for use in the vacuum ultravio-
`let (VUV) range having potential for very high image side
`numerical aperture which may be extended to values allow-
`ing immersion lithography at numerical apertures NA>1. It
`is another object of the invention to provide catadioptric
`projection objectives that can be build with relatively small
`amounts of optical material.
`As a solution to these and other objects the invention.
`according to one fomiulation, provides a catadioptric pro-
`jection objective for imaging a pattern provided in an object
`
`20
`
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`
`40
`
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`
`u. m
`
`60
`
`4
`plane of the projection objective onto an image plane of the
`projection objective comprising:
`
`a first objective part for imaging the pattern provided in the
`object plane into a first intermediate image;
`
`a second objective part for imaging the first intermediate
`image into a second intermediate image;
`
`a third objective part for imaging the second intermediate
`image onto the image plane;
`
`wherein a first concave mirror having a first continuous
`mirror surface and at
`least one second concave mirror
`having a second continuous mirror surface are arranged
`upstream of the second intermediate image;
`
`pupil surfaces are formed between the object plane and the
`first intermediate image, between the first and the second
`intermediate image and between the second intermediate
`image and the image plane; and all concave mirrors are
`arranged optically remote from a pupil surface.
`In designs according to this aspect of the invention a
`circular pupil centered around the optical axis can be pro-
`vided in a centered optical system. Two or more concave
`mirrors in the system parts contributing to forming the
`second intermediate image are provided, where the used area
`of the concave mirrors deviates significantly from an axial
`symmetric illumination. In preferred embodiments exactly
`two concave mirrors are provided and are sufiicient for
`obtaining excellent imaging quality and very high numerical
`aperture. Systems having one common unfolded (straight)
`optical axis can be provided which facilitate manufacturing.
`adjustment and integration into photolithographic exposure
`systems. No planar folding mirrors are necessary. However.
`one ore more planar folding mirrors can be utilized to obtain
`more compact designs.
`All concave mirrors are arranged “optically remote” from
`pupil surfaces which means that they are arranged outside an
`optical vicinity of a pupil surface. They may be arranged
`optically nearer to field surfaces than to pupil surfaces.
`Preferred positions optically remote from a pupil surface
`(i.e. outside an optical vicinity of a pupil surface) may be
`characterized by the ray height ratio H:hC/hM>l, where hC
`is the height of a chief ray and 11M is the height of a marginal
`ray ofthe imaging process. The marginal ray height hMis the
`height of a marginal ray running from an irmer field point
`(closest to the optical axis) to the edge of an aperture stop,
`whereas the chief ray height hC is the height of a chief ray
`running from an outermost field point (farthest away from
`the optical axis) parallel to or at small angle with respect to
`the optical axis and intersecting the optical axis at a pupil
`surface position where an aperture stop may be positioned.
`With other words: all concave mirrors are in positions where
`the chief ray height exceeds the marginal ray height.
`A position “optically remote” from a pupil surface is a
`position where the cross sectional shape of the light beam
`deviates significantly from the circular shape found in a
`pupil surface or in an immediate vicinity thereto. The term
`“light beam” as used here describes the blmdle of all rays
`rumring from the object plane to the image plane. Mirror
`positions optically remote from a pupil surface may be
`delined as positions where the beam diameters of the light
`beam in mutually perpendicular directions orthogonal to the
`propagation direction of the light beam deviate by more than
`50% or 100% from each other. In other words, illuminated
`areas on the concave mirrors may have a shape having a
`form strongly deviating from a circle and similar to a high
`aspect ratio rectangle corresponding to a preferred field
`
`CARL ZEISS V. NIKON
`|PR2013-00362
`
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`IPR2013-00362
`Ex. 2020, p. 38
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`

`US 7,385,756 B2
`
`5
`shape in lithographic projection objectives for wafer scan-
`ners. Therefore, small concave mirrors having a compact
`rectangular or near rectangular shape signilicantly smaller in
`one direction than in the other may be used. A high aperture
`light beam can therefore be guided through the system
`without vignetting at mirror edges.
`Wherever the terms “upstream” or “downstream” are used
`in this specification these terms refer to relative positions
`along the optical path of a light beam running from the
`object plane to the image plane of the projection objective.
`Therefore, a position upstream of the second intermediate
`image is a position optically between the object plane and
`the second intermediate image.
`According to another aspect of the invention there is
`provided a catadioptric projection objective for imaging a
`pattern provided in an objective plane of the projection
`objective onto an image plane of the projection objective
`comprising:
`
`a first objective part for imaging the pattern provided in the
`object plane into a first intemiediate image;
`
`a second objective part for imaging the first intermediate
`image into a second intermediate image:
`
`20
`
`a third objective part for imaging the second intermediate
`image onto the image plane;
`wherein the second objective part includes a first concave
`mirror having a first continuous mirror surface and a second
`concave mirror having a second continuous mirror surface,
`the concave mirror surfaces of the concave mirrors facing '
`each other and defining an intermirror space;
`wherein at
`least
`the first
`intermediate image is located
`geometrically within the intermirror space between the first
`concave mirror and the second concave mirror.
`
`Lu U!
`
`40
`
`In this specification the term “intermediate image” gen—
`erally refers to a “paraxial intermediate image” formed by a
`perfect optical system and located in a plane optically
`conjugated to the object plane. Therefore. wherever refe