111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US007309870B2
`
`(12) United States Patent
`Omura
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,309,870 B2
`Dec. 18, 2007
`
`(54) PROJECTION OPTICAL SYSTEM,
`EXPOSURE APPARATUS, AND EXPOSURE
`METHOD
`
`(75)
`
`Inventor: Yasuhiro Omura, Kumagaya (JP)
`
`(73) Assignee: Nikon Corporation, Tokyo (lP)
`
`( *) Notice:
`
`Subject to any disclaimer, the tenn of this
`patent is extended or adjusted under 35
`U.S.c. 154(b) by 0 days.
`
`EP
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`8/1982 Tabarelli et al.
`4,346,164 A
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`1 069448 Al
`112001
`(Continued)
`
`(21) Appl. No.: 111583,934
`
`(22)
`
`Filed:
`
`Oct. 20, 2006
`
`(65)
`
`Prior Publication Data
`
`US 2007/0037080 Al
`
`Feb. 15, 2007
`
`Related U.S. Application Data
`
`(63) Continuation of application No. 11/266,288, filed on
`Nov. 4, 2005, which is a continuation-in-part of
`application No. PCT/lP2004/006417, filed on May 6,
`2004.
`(60) Provisional application No. 60/721,582, filed on Sep.
`29,2005.
`
`(30)
`
`Foreign Application Priority Data
`
`May 6, 2003
`Oct. 9, 2003
`Oct. 24, 2003
`
`(JP)
`(JP)
`(JP)
`
`............................. 2003-128154
`............................. 2003-350647
`............................. 2003-364596
`
`(51)
`
`Int. Cl.
`(2006.01)
`G02B 17/00
`(2006.01)
`G02B 3/00
`(52) U.S. Cl. ............................... 250/492.2; 250/492.3;
`359/730; 359/364; 359/365; 359/726; 359/649;
`359/350; 355/53
`(58) Field of Classification Search ..................... None
`See application file for complete search history.
`
`OTHER PUBLICATIONS
`Switkes et al; "Resolution Enhancement of 157 -nm Lithography by
`Liquid Immersion"; Massachusetts Institute of Technology; 7 pages.
`Primary Examiner-lack 1. Bennan
`Assistant Examiner-Zia R. Hashmi
`(74) Attorney, Agent, or Firm-Oliff & Berridge, PLC
`
`(57)
`
`ABSTRACT
`
`A catadioptric projection optical system for fonning a
`reduced image of a first surface (R) on a second surface (W)
`is a relatively compact projection optical system having
`excellent imaging perfonnance as well corrected for various
`aberrations, such as chromatic aberration and curvature of
`field, and being capable of securing a large effective image(cid:173)
`side numerical aperture while suitably suppressing reflection
`loss on optical surfaces. The projection optical system
`comprises at least two reflecting mirrors (CM1, CM2), and
`a boundary lens (Lb) whose surface on the first surface side
`has a positive refracting power, and an optical path between
`the boundary lens and the second surface is filled with a
`medium (Lm) having a refractive index larger than 1.1.
`Every transmitting member and every reflecting member
`with a refracting power forming the projection optical
`system are arranged along a single optical axis (AX) and the
`projection optical system has an effective imaging area of a
`predetermined shape not including the optical axis.
`
`49 Claims, 21 Drawing Sheets
`
`RST
`
`PL
`
`2
`
`110
`IL
`
`RSTD
`
`CONT
`
`-- 1 --
`
`ZEISS 1002
`
`

`

`US 7,309,870 B2
`Page 2
`
`u.s. PATENT DOCUMENTS
`6,473,243 B1
`1012002 Omura
`6,600,608 B1
`7/2003 Shafer et al.
`1012003 Schuster
`6,631,036 B2
`1012003 Shafer et al.
`6,636,350 B2
`6,829,099 B2
`12/2004 Kato et al.
`3/2005 Shafer
`6,873,476 B2
`200210024741 Al
`212002 Terasawa et al.
`2003/0197922 Al
`1012003 Hudyma
`2004/0130806 Al
`7/2004 Takahashi
`2004/0240047 Al
`1212004 Shafer et al.
`2005/0036213 Al
`212005 Mann et al.
`2005/0190435 Al * 912005 Shafer et al.
`
`............... 359/365
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`
`A 6-188169
`
`7/1994
`
`JP
`A 10-163099
`JP
`A 10-214783
`JP
`A 10-303114
`JP
`A 2000-505958
`JP
`A 2001-228401
`JP
`B23246615
`JP
`A 2002-208551
`JP
`A 2003-114387
`WO 98/28665
`WO
`WO WO 2004/019128 A2
`WO WO 2005/015316 A2
`WO WO 2005/015316 A3
`WO WO 2005/098505 Al
`WO WO 2006/005547 Al
`
`* cited by examiner
`
`6/1998
`8/1998
`1111998
`5/2000
`8/2001
`1112001
`7/2002
`4/2003
`7/1998
`3/2004
`212005
`212005
`10/2005
`112006
`
`-- 2 --
`
`

`

`-....l = = N
`00
`W = \C
`
`-....l
`rJl
`d
`
`N ....
`0 ....
`....
`.....
`rFJ =- ('D
`
`('D
`
`~ ....
`c ('D
`
`-....l
`0
`0
`N
`~CIO
`
`~ = ~
`
`~
`~
`~
`•
`7Jl
`
`e •
`
`WSTD
`
`WST
`
`kCONT
`
`55
`
`53
`
`yLX
`
`Z
`
`COLLECTOR)
`
`(SECOND
`
`COLLECTOR
`
`LIQUID
`
`1
`I
`
`RSTD
`
`EX r
`
`3
`
`t---:-AX
`
`EL--'i
`
`PL
`
`R
`
`IL
`
`,110
`
`r------(cid:173)
`_______ -1
`
`'----.--'~~ ~ 100
`
`2
`
`Fig. 1
`
`-- 3 --
`
`

`

`u.s. Patent
`
`U.S. Patent
`
`Dec. 18, 2007
`Dec. 18, 2007
`
`Sheet 2 of 21
`Sheet 2 of 21
`
`US 7,309,870 B2
`US 7,309,870 B2
`
`Fig. 2
`Fig.2
`
`AR
`
`y
`
`voov
`ow...
`
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`
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`
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`
`x
`
`-- 4 --
`
`
`
`
`
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 3 of 21
`
`US 7,309,870 B2
`
`..c rn
`
`C")
`
`• . ~ u.:
`
`
`
`-- 5 --
`
`
`

`

`u.s. Patent
`
`U.S. Patent
`
`Dec. 18, 2007
`Dec. 18, 2007
`
`Sheet 4 of 21
`Sheet 4 of 21
`
`US 7,309,870 B2
`US 7,309,870 B2
`
`..0
`00
`
`
`
`-- 6 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 5 of 21
`
`US 7,309,870 B2
`
`Fig. 5
`
`Gl
`
`K -'i.U---\---r---
`
`~-L23
`
`L24
`
`AX
`
`.\U--\\t---'-1\\-'-., --L25
`
`-I.--L26
`
`G2
`
`AS
`
`L216
`~. - - L217(Lb)
`
`-- 7 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 6 of 21
`
`US 7,309,870 B2
`
`Fig. 6
`
`TRANSVERSE ABERRATION
`
`MERIDIONAL
`
`0.0010
`
`Y=17.Dmm
`
`.-
`
`SAGITTAL
`
`0.0010
`
`...
`
`...
`
`...
`
`...
`
`...
`
`..
`
`...
`
`... - -
`
`-0.0010
`
`-0.0010
`
`0.0010
`
`Y=14.25mm
`
`0.0010
`
`-0.0010
`
`-0.0010
`
`0.0010
`
`Y=11.5mm
`
`0.0010
`
`- ... - - ...
`
`.-
`
`---- ... _--
`
`-0.0010
`
`-O.OOlO(mm)
`
`- - - - - - - - - - - - 193.306lnm
`------193.3060nm
`-
`. -
`. -
`. -
`. -
`·193.3059nm
`
`-- 8 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 7 of 21
`
`US 7,309,870 B2
`
`Fig. 7
`
`Gl
`
`L12
`
`L23
`
`r----AX
`
`L25
`
`G2
`
`JJ.=.:=.---t'---~~- L29
`L210
`
`~--11__ ,---L215
`L216
`L217(Lb)
`W __ ..J==~~-Lp
`
`-- 9 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 8 of 21
`
`US 7,309,870 B2
`
`Fig. 8
`
`TRANSVERSE ABERRATION
`
`MERIDIONAL
`
`0.0010
`
`SAGITTAL
`
`0.0010
`
`Y=17.0mm
`
`.
`- ..
`
`.....-:
`.. -
`
`-0.0010
`
`-0.0010
`
`0.0010
`
`Y=14.25mm
`
`0.0010
`
`- - - - - ... -
`
`- .-
`
`- .-
`
`..... - ";"
`
`-0.0010
`
`0.0010
`
`-0.0010
`
`0.0010
`
`Y=11.5mm
`
`.-
`
`... - - - - .. -
`
`.. .. - -
`
`-
`
`-0.0010
`
`-O.OOlO(mm)
`
`- - - - - - - - - - - - 193.3061nm
`- - - - - - 193.3060nm
`-
`. -
`. -
`. -
`. -
`.193.3059nm
`
`-- 10 --
`
`

`

`u.s. Patent
`
`Fig. 9
`
`G1l
`
`G22
`
`G23
`
`Dec. 18,2007
`
`Sheet 9 of 21
`
`US 7,309,870 B2
`
`Rl
`
`/PLl
`
`Gl
`
`M4
`
`.-
`"
`L6 "",'/
`
`,,' -_ ....
`.... - L7
`
`L8
`L9
`L1D
`Lll
`L12
`AS1
`L13
`L14
`LIS
`L16
`
`G2
`
`-- 11 --
`
`

`

`u.s. Patent
`
`Dec. 18,2007
`
`Sheet 10 of 21
`
`US 7,309,870 B2
`
`Fig. 10
`
`G31
`
`M23
`
`G42
`
`G43
`
`R2
`
`/
`
`PL2
`
`G3
`
`M24
`,/ "
`,,/
`... ,..
`...
`...
`"[25
`
`L26
`L27
`L28
`
`L30
`AS2
`L31
`L32
`L33
`L34
`
`G4
`
`-- 12 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 11 of 21
`
`US 7,309,870 B2
`
`Fig. 11
`
`y
`
`OPTICAL H
`AXIS
`
`-- 13 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 12 of 21
`
`US 7,309,870 B2
`
`Fig. 12
`
`MERIDIONAL
`0,0020
`
`----
`
`-----
`
`-------
`
`-0.0020
`
`0.0020
`
`. -0.0020
`
`0.0020
`
`Y=18MM
`- --
`
`Y=16MJYl
`
`- --..:::::
`
`Y=14MJYl
`
`SAGITTAL
`0.0020
`
`-
`---
`
`.--/
`
`-0.0020
`
`0.0020
`
`-0.0020
`
`0.0020
`
`--
`--
`
`---
`
`-0.0020
`
`-0.0020
`
`-------- 193.3063NM
`193.3060NM
`- - - - - 193.3057NM
`
`-- 14 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 13 of 21
`
`US 7,309,870 B2
`
`Fig. 13
`
`MERIDIONAL
`0,0020
`
`-----
`
`-0,0020
`
`0,0020
`
`-0,0020
`
`0,0020
`
`---
`
`-
`
`Y=17,5Mr'l
`---
`- ......
`-
`
`Y==15,5P1M
`
`---
`----
`
`Y=13,5Mr'l
`
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`
`SAGITTAL
`0,0020
`
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`
`---....--.
`
`-0,0020
`
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`
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`
`0,0020
`
`--
`- --
`
`---
`--
`
`-0,0020
`
`-0,0020
`
`-------- 193.3063NM
`- - - - 193,3060NM
`- - - - - 193.3057NM
`
`-- 15 --
`
`

`

`u.s. Patent
`
`Dec. 18,2007
`
`Sheet 14 of 21
`
`US 7,309,870 B2
`
`Fig. 14
`
`/PLl
`
`Rl
`
`Gl
`
`M3
`
`G2
`
`L5
`L6
`L7
`L8
`L9
`LtO
`
`L12
`L13
`L14
`L1S
`AS1
`L16
`L17
`L18
`L19
`L20
`
`G21
`
`G23
`
`G24
`
`-- 16 --
`
`

`

`u.s. Patent
`
`Dec. 18,2007
`
`Sheet 15 of 21
`
`US 7,309,870 B2
`
`Fig. 15
`
`G31
`
`AX2.-/
`L25
`Ml1
`
`/PL2
`
`R2
`
`L21
`L22
`L23
`:1 - - - L24
`M12
`
`M14
`
`G3
`
`M13
`
`G41
`
`G42{
`
`G43
`
`G44
`
`G4
`
`L26
`L28 L27
`--L29
`L30
`L31
`L32
`k:::::==:P::=:::::!:Jr-- L 33
`L34
`L35
`'\-----==--1---=----r~;t2
`L37
`L38
`L39
`L40
`L41
`
`-- 17 --
`
`

`

`U.S. Patent
`
`Dec. 18,2007
`
`Sheet 16 of 21
`
`US 7,309,870 B2
`
`Fig. 16
`
`/PL3
`
`G51
`
`AX3--
`M21
`M26
`
`G61
`
`G63
`
`G64
`
`R3
`
`L5I
`L52
`L53
`L54
`M22
`M24
`
`G5
`
`G6
`
`M23
`
`L55
`L56
`L57
`L58
`L60 L59
`L61
`L62
`L63
`L64
`L65
`AS3
`L66
`L67
`L68
`L69
`L70
`
`-- 18 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 17 of 21
`
`US 7,309,870 B2
`
`Fig. 17
`
`MERIDIONAL
`0.0020
`
`----......---
`----
`
`-0.0020
`
`0,0020
`
`-0,0020
`
`0,0020
`
`::------- -
`
`-----
`
`---
`
`SAGITIAL
`0,0020
`
`- - - - - "
`
`-0.0020
`
`-0,0020
`
`0.0020
`
`-----
`
`Y=17PiM
`
`----.."
`-----.."
`
`Y=15MM
`
`------
`
`Y=13MM
`
`--..---
`------
`
`-0,0020
`
`-0,0020
`
`-------- 193.3063NM
`- - - - 193.3060NM
`- - - - - 193.3057NM
`
`-- 19 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 18 of 21
`
`US 7,309,870 B2
`
`Fig. 18
`
`MERIDIONAL
`0.0020
`
`-"....---
`
`-----
`-------
`
`------
`
`-0.0020
`
`0.0020
`
`-0.0020
`
`0.0020
`
`Y=17MM
`
`-----
`
`Y=15MM
`---
`
`Y=131"'lM
`
`----~
`
`SAGITTAL
`0.0020
`
`-0.0020
`
`0,0020
`
`------
`
`---------
`
`-0.0020
`
`0.0020
`
`----------
`
`-0.0020
`
`-0.0020
`
`-------- 193.3063NM
`193.3060NM
`- - - - - 193.3057NM
`
`-- 20 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 19 of 21
`
`US 7,309,870 B2
`
`Fig. 19
`
`MERIDIONAL
`0.0020
`
`SAGITTAL
`0,0020
`
`.---- -
`
`-------
`
`------ ......
`
`-0.0020
`
`0.0020
`
`-0.0020
`
`0,0020
`
`-----
`
`----
`
`----.----
`
`-0,0020
`
`0.0020
`
`-------
`
`-0.0020
`
`0.0020
`
`---
`
`Y=15MI"I
`
`---
`
`Y=13MM
`
`---- -
`
`-0.0020
`
`-0.0020
`
`-------- 193.3063NM
`193.3060NM
`- - - - - 193.3057NM
`
`-- 21 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 20 of 21
`
`US 7,309,870 B2
`
`Fig. 20
`
`START
`
`FORM EVAPORATED METAL FILM
`ON WAFER
`
`STEP 301
`
`APPLY PHOTORESIST ONTO THE METAL FILM
`
`TRANSFER IMAGE OF PATTERN ON RETICLE
`ONTO EACH SHOT AREA ON WAFER.
`USING EXPOSURE APPARATUS OF EMBODIMENT
`
`STEP 303
`
`PERFORM DEVELOPMENT OF PHOTORESIST
`ON WAFER
`
`---STEP 304
`
`PERFORM ETCHING WITH
`RESIST PATTERN AS MASK ON WAFER
`
`STEP 305
`
`NEXT STEP
`
`-- 22 --
`
`

`

`u.s. Patent
`
`Dec. 18, 2007
`
`Sheet 21 of 21
`
`US 7,309,870 B2
`
`Fig. 21
`
`START
`
`PATTERN FORMING STEP
`
`STEP 401
`
`COLOR FILTER FORMING STEP
`
`STEP 402
`
`CELL ASSEMBLY STEP
`
`STEP 403
`
`MODULE ASSEMBLY STEP
`
`STEP 404
`
`END
`
`-- 23 --
`
`

`

`US 7,309,870 B2
`
`1
`PROJECTION OPTICAL SYSTEM,
`EXPOSURE APPARATUS, AND EXPOSURE
`METHOD
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This is a continuation of U.S. patent application Ser. No.
`11/266,288 filed Nov. 4, 2005, which in tum is a continu(cid:173)
`ation-in-part application of application Ser. No. PCTI
`JP2004/006417 filed on May 6, 2004. Application Ser. No.
`11/266,288 also claims a priority of the Provisional Appli(cid:173)
`cation No. 601721,582 filed on Sep. 29, 2005. The disclo(cid:173)
`sures of these prior applications are incorporated herein by
`reference in their entirities.
`
`FIELD OF THE INVENTION
`
`The present invention relates to a catadioptric projection
`optical system, exposure apparatus, and exposure method
`and, more particularly, to a high-resolution catadioptric
`projection optical system suitable for exposure apparatus
`used in production of semiconductor devices, liquid-crystal
`display devices, etc. by photolithography.
`
`RELATED BACKGROUND ART
`
`The photolithography for production of the semiconduc(cid:173)
`tor devices and others is implemented using a projection
`exposure apparatus for projecting a pattern image of a mask
`(or a reticle) through a projection optical system onto a
`wafer (or a glass plate or the like) coated with a photoresist
`or the like. The resolving power (resolution) required for the
`projection optical system of the projection exposure appa(cid:173)
`ratus is becoming increasingly higher and higher with
`increase in integration degree of the semiconductor devices
`and others.
`As a result, in order to satisfY the requirements for the
`resolving power of the projection optical system, it is
`necessary to shorten the wavelength A of illumination light
`(exposure light) and to increase the image-side numerical
`aperture NA of the projection optical system. Specifically,
`the resolution of the projection optical system is expressed
`by kANA (where k is the process coefficient). The image(cid:173)
`side numerical aperture NA is represented by n'sin8, where
`n is a refractive index of a medium (normally, gas such as
`air) between the projection optical system and the image
`plane and 8 a maximum angle of incidence to the image
`plane.
`In this case, if the maximum incidence angle 8 is
`increased in order to increase the numerical aperture NA, it
`will result in increasing the input angle to the image plane
`and the output angle from the projection optical system, so
`as to increase reflection loss on optical surfaces and thus fail
`to secure a large effective image-side numerical aperture.
`For this reason, there is the known technology of increasing
`the numerical aperture NA by filling a medium like a liquid
`with a high refractive index in the optical path between the
`projection optical system and the image plane.
`However, application of this technology to the ordinary
`dioptric projection optical systems caused such disadvan(cid:173)
`tages that it was difficult to well correct for chromatic
`aberration and to satisfY the Petzval's condition to well
`correct for curvature of field, and that an increase in the scale
`of the optical system was inevitable. In addition, there was
`another disadvantage that it was difficult to secure a large
`
`2
`effective image-side numerical aperture while well sup(cid:173)
`pressing the reflection loss on optical surfaces.
`
`SUMMARY OF THE INVENTION
`
`A first object of the embodiment is to provide a relatively
`compact projection optical system having excellent imaging
`performance as well corrected for various aberrations, such
`as chromatic aberration and curvature of field, and being
`10 capable of securing a large effective image-side numerical
`aperture while well suppressing the reflection loss on optical
`surfaces.
`In the case where the projection optical system is com(cid:173)
`posed of only reflecting optical members and in the case
`15 where the projection optical system is composed of a
`combination of refracting optical members with reflecting
`optical members, with increase in the numerical aperture, it
`becomes more difficult to implement optical path separation
`between a beam entering a reflecting optical member and a
`20 beam reflected by the reflecting optical member and it is
`infeasible to avoid an increase in the scale of the reflecting
`optical member, i.e., an increase in the scale of the projection
`optical system.
`In order to achieve simplification of production and
`25 simplification of mutual adjustment of optical members, it is
`desirable to construct a catadioptric projection optical sys(cid:173)
`tem of a single optical axis; in this case, with increase in the
`numerical aperture, it also becomes more difficult to achieve
`the optical path separation between the beam entering the
`30 reflecting optical member and the beam reflected by the
`reflecting optical member, and the projection optical system
`increases its scale.
`A second object of the embodiment is to achieve a large
`numerical aperture, without increase in the scale of optical
`35 members forming a catadioptric projection optical system.
`A third object of the embodiment is to provide an expo(cid:173)
`sure apparatus and exposure method capable of performing
`an exposure to transcribe a fine pattern with high accuracy
`through a projection optical system having excellent imag-
`40 ing performance and having a large effective image-side
`numerical aperture and therefore a high resolution. In order
`to achieve the above-described first object, a projection
`optical system according to a first aspect of the embodiment
`is a catadioptric projection optical system for forming a
`45 reduced image of a first surface on a second surface,
`the projection optical system comprising at least two
`reflecting mirrors, and a boundary lens whose surface on the
`first surface side has a positive refracting power,
`wherein, where a refractive index of an atmosphere in an
`50 optical path of the projection optical system is 1, an optical
`path between the boundary lens and the second surface is
`filled with a medium having a refractive index larger than
`1.1,
`wherein every transmitting member and every reflecting
`55 member with a refracting power constituting the projection
`optical system are arranged along a single optical axis, and
`the projection optical system having an effective imaging
`area of a predetermined shape not including the optical axis.
`In order to achieve the above-described second object, a
`60 projection optical system according to a second aspect of the
`embodiment is a catadioptric projection optical system for
`forming an image of a first surface on a second surface, the
`projection optical system comprising:
`a first imaging optical system comprising two mirrors, for
`65 forming an intermediate image of the first surface; and
`a second imaging optical system for forming the inter(cid:173)
`mediate image on the second surface,
`
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`
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`

`US 7,309,870 B2
`
`4
`Further scope of applicability of the embodiment will
`become apparent from the detailed description given here(cid:173)
`inafter. However, it should be understood that the detailed
`description and specific examples, while indicating pre(cid:173)
`ferred embodiments of the invention, are given by way of
`illustration only, since various changes and modifications
`within the spirit and scope of the invention will be apparent
`to those skilled in the art from this detailed description.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`3
`wherein the second imaging optical system comprises the
`following components in order of passage of a ray from the
`intermediate image side:
`a first field mirror of a concave shape;
`a second field mirror;
`a first lens unit comprising at least two negative lenses and
`having a negative refracting power;
`a second lens unit having a positive refracting power;
`an aperture stop; and
`a third lens unit having a positive refracting power.
`In order to achieve the above-described second object, a
`projection optical system according to a third aspect of the
`embodiment is a catadioptric projection optical system for
`forming an image of a first surface on a second surface, the
`projection optical system comprising:
`a first unit disposed in an optical path between the first
`surface and the second surface and having a positive refract(cid:173)
`ing power;
`a second unit disposed in an optical path between the first
`unit and the second surface and comprising at least four
`mirrors;
`a third unit disposed in an optical path between the second
`unit and the second surface, comprising at least two negative
`lenses, and having a negative refracting power; and
`a fourth unit disposed in an optical path between the third
`unit and the second surface, comprising at least three posi(cid:173)
`tive lenses, and having a positive refracting power,
`wherein an intermediate image is fonned in the second
`unit and wherein an aperture stop is provided in the fourth
`unit.
`In order to achieve the above-described second object, a
`projection optical system according to a fourth aspect of the
`embodiment is a catadioptric projection optical system for
`forming an image of a first surface on a second surface, the
`projection optical system comprising:
`a first imaging optical system comprising at least six
`mirrors, for fonning a first intennediate image and a second
`intermediate image of the first surface; and
`a second imaging optical system for relaying the second
`intermediate image onto the second surface.
`In order to achieve the above-described third object, an
`exposure apparatus according to a fifth aspect of the embodi(cid:173)
`ment is an exposure apparatus for effecting an exposure of
`a pattern fonned on a mask, onto a photosensitive substrate,
`the exposure apparatus comprising:
`an illumination system for illuminating the mask set on
`the first surface; and
`the projection optical system according to anyone of the
`above-described aspects, for forming an image of the pattern
`formed on the mask, on the photosensitive substrate set on 50
`the second surface.
`In order to achieve the above-described third object, an
`exposure method according to a sixth aspect of the embodi(cid:173)
`ment is an exposure method of effecting an exposure of a
`pattern fonned on a mask, onto a photosensitive substrate,
`the exposure method comprising:
`an illumination step of illuminating the mask on which the
`predetermined pattern is fonned; and
`an exposure step of perfonning an exposure of the pattern
`of the mask set on the first surface, onto the photosensitive 60
`substrate set on the second surface, using the projection
`optical system as set forth in the above.
`The present invention will be more fully understood from
`the detailed description given hereinbelow and the accom(cid:173)
`panying drawings, which are given by way of illustration
`only and are not to be considered as limiting the embodi-
`ment.
`
`15
`
`FIG. 1 is an illustration schematically showing a configu(cid:173)
`ration of an exposure apparatus according to an embodiment
`of the embodiment.
`FIG. 2 is an illustration showing a positional relation
`between the optical axis and an effective exposure area of
`arcuate shape formed on a wafer in the embodiment.
`FIG. 3 is an illustration schematically showing a configu(cid:173)
`ration between a boundary lens and a wafer in the first
`20 example of the embodiment.
`FIG. 4 is an illustration schematically showing a configu(cid:173)
`ration between a boundary lens and a wafer in the second
`example of the embodiment.
`FIG. 5 is an illustration showing a lens configuration of a
`25 projection optical system according to the first example of
`the embodiment.
`FIG. 6 is a diagram showing the transverse aberration in
`the first example.
`FIG. 7 is an illustration showing a lens configuration of a
`30 projection optical system according to the second example
`of the embodiment.
`FIG. 8 is a diagram showing the transverse aberration in
`the second example.
`FIG. 9 is an illustration showing a lens configuration of a
`35 catadioptric projection optical system according to the third
`example.
`FIG. 10 is an illustration showing a lens configuration of
`a catadioptric projection optical system according to the
`fourth example.
`FIG. 11 is an illustration showing an exposure area on a
`wafer in the third and fourth examples.
`FIG. 12 is a transverse aberration diagram showing the
`transverse aberration in the meridional direction and in the
`45 sagittal direction of the catadioptric projection optical sys(cid:173)
`tem in the third example.
`FIG. 13 is a transverse aberration diagram showing the
`transverse aberration in the meridional direction and in the
`sagittal direction of the catadioptric projection optical sys(cid:173)
`tem in the fourth example.
`FIG. 14 is an illustration showing a lens configuration of
`a catadioptric projection optical system according to the fifth
`example.
`FIG. 15 is an illustration showing a lens configuration of
`55 a catadioptric projection optical system according to the
`sixth example.
`FIG. 16 is an illustration showing a lens configuration of
`a catadioptric projection optical system according to the
`seventh example.
`FIG. 17 is a transverse aberration diagram showing the
`transverse aberration in the meridional direction and in the
`sagittal direction of the catadioptric projection optical sys(cid:173)
`tem in the fifth example.
`FIG. 18 is a transverse aberration diagram showing the
`65 transverse aberration in the meridional direction and in the
`sagittal direction of the catadioptric projection optical sys(cid:173)
`tem in the sixth example.
`
`40
`
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`
`

`

`US 7,309,870 B2
`
`5
`FIG. 19 is a transverse aberration diagram showing the
`transverse aberration in the meridional direction and in the
`sagittal direction of the catadioptric projection optical sys(cid:173)
`tem in the seventh example.
`FIG. 20 is a flowchart of a method of producing semi(cid:173)
`conductor devices as microdevices.
`FIG. 21 is a flowchart of a method of producing a liquid
`crystal display device as a microdevice.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`In the projection optical system according to the first
`aspect of the embodiment, the medium having the refractive
`index larger than 1.1 is interposed in the optical path
`between the boundary lens and the image plane (second
`surface), thereby increasing the image-side numerical aper(cid:173)
`ture NA. In passing, "Resolution Enhancement of 157-nm
`Lithography by Liquid Immersion" reported in "Massachu(cid:173)
`setts Institute of Technology" in "SPIE2002 Microlithogra(cid:173)
`phy" by Mr. M. Switkes and Mr. M. Rothschild describes
`Fluorinert (Perfluoropolyethers: trade name of 3M, USA)
`and Deionized Water as candidates for media having the
`required transmittance for light of wavelength A of not more
`than 200 nm.
`In the projection optical system according to the first
`aspect of the embodiment, the optical surface on the object
`side (first surface side) of the boundary lens is provided with
`the positive refracting power, whereby the reflection loss is
`reduced on this optical surface and, in turn, the large
`effective image-side numerical aperture can be secured. In
`the optical system having the high-refractive-index material
`like liquid as the medium on the image side, it is feasible to
`increase the effective image-side numerical aperture to not
`less than 1.0 and, in tum, to enhance the resolution. How(cid:173)
`ever, where the projection magnification is constant, the
`object-side numerical aperture also increases with increase
`in the image-side numerical aperture; therefore, if the pro(cid:173)
`jection optical system is constructed of only refracting
`members, it will be diffIcult to satisfy the Petzval's condition
`and it will result in failing to avoid the increase in the scale
`of the optical system.
`Therefore, the projection optical system according to the
`first aspect of the embodiment adopts the catadioptric sys(cid:173)
`tem of the type comprising at least two reflecting mirrors, in
`which every transmitting member and every reflecting mem(cid:173)
`ber with a refracting power (power) are arranged along the
`single optical axis and which has the effective imaging area
`of the predetermined shape not including the optical axis. In
`the projection optical system of this type, for example,
`through action of a concave reflecting mirror, it is feasible to
`well correct for the chromatic aberration and to readily
`satisfY the Petzval's condition to well correct for the cur(cid:173)
`vature of field, and the scale of the optical system can be
`reduced.
`The projection optical system of this type has the con(cid:173)
`figuration wherein every transmitting member (lenses or the
`like) and every reflecting member with a power (concave
`reflecting mirrors or the like) are arranged along the single
`optical axis, which is preferable because the degree of
`difficulty in production is considerably lower than in a
`multi-axis configuration wherein the optical members are
`arranged along multiple optical axes. However, in the case
`of the single-axis configuration wherein the optical members
`are arranged along the single optical axis, the chromatic
`aberration tends to be difficult to well correct for, but this
`problem of correction for chromatic aberration can be over-
`
`6
`come, for example, by use of laser light with a narrowed
`spectral width like ArF laser light.
`In this manner, the first aspect of the embodiment can
`realize the relatively compact projection optical system
`having the excellent imaging performance as well corrected
`for the various aberrations such as chromatic aberration and
`curvature of field and being capable of securing the large
`effective image-side numerical aperture while well sup(cid:173)
`pressing the reflection loss on the optical surfaces. There-
`10 fore, an exposure apparatus and exposure method using the
`projection optical system according to the first aspect of the
`embodiment are able to perform an exposure of a fine pattern
`to transcribe the pattern through the projection optical
`system having the excellent imaging performance and the
`15 large effective image-side numerical aperture and therefore
`the high resolution.
`In the first aspect of the embodiment, the projection
`optical system is preferably arranged to have an even
`number of reflecting mirrors, i.e., to form the image of the
`20 first surface on the second surface through an even number
`of reflections. When the projection optical system in this
`configuration is applied, for example, to the exposure appa(cid:173)
`ratus and exposure method, not a mirror image (a flipped
`image) but an unmirrored (unflipped) image (erect image or
`25 inverted image) of the mask pattern, is formed on the wafer,
`whereby the ordinary masks (reticles) can be used as in the
`case of the exposure apparatus equipped with the dioptric
`projection optical system.
`In the first aspect of the embodiment, the projection
`30 optical system preferably comprises: a first imaging optical
`system comprising two mirrors, which forms an intermedi(cid:173)
`ate image of the first surface; and a second imaging optical
`system, which forms the intermediate image on the second
`surface; the second imaging optical system preferably com-
`35 prises the following components in order of passage of a ray
`from the intermediate image side: a first field mirror of a
`concave shape; a second field mirror; a first lens unit
`comprising at least two negative lenses and having a nega(cid:173)
`tive refracting power; a second lens unit having a positive
`40 refracting power; an aperture stop; and a third lens unit
`having a positive refracting power.
`In this configuration, the intermediate image of the first
`surface is formed in the first imaging optical system, and it
`is thus feasible to readily and securely achieve the optical
`45 path separation between the beam toward the first surface
`and the beam toward the second surface, even in the case
`where the numerical apertures are increased of the catadiop(cid:173)
`tric projection optical system. Since the second imaging
`optical system comprises the first lens unit having the
`50 negative refracting power, the total length of the catadioptric
`projection optical system can be reduced, and adjustment for
`satisfying the Petzval's condition can be readily performed.
`Furthermore, the first lens unit relieves variation due to the
`difference of field angles of the beam expanded by the first
`55 field mirror, so as to suppress occurrence of aberration.
`Therefore, the good imaging performance can be achieved
`throughout the entire region in the exposure area, even in the
`case where the object-side and image-side numerical aper(cid:173)
`tures of the catadioptric projection optical system are
`60 increased in order to enhance the resolution.
`In the above-described configuration, preferably, the first
`imaging optical system comprises a fourth lens unit having
`a positive refracting power, a negative lens, a concave
`mirror, and an optical path separating mirror; and the first
`65 imaging optical system is arranged as follows: light travel(cid:173)
`ing in the first imaging optical system passes through the
`fourth lens unit and the negative lens, is then reflected by the
`
`-- 26 --
`
`

`

`US 7,309,870 B2
`
`7
`concave mirror, and passes again through the negative lens
`to be guided to the optical path separating mirror; the light
`reflected by the optical path separating mirror is reflected by
`the first field mirror and the second field mirror-and there(cid:173)
`after directly enters the first lens unit in the second imaging
`optical system.
`In this configuration, the projection optical system can be
`telecentric on the first surface side because the first imaging
`optical system comprises the fourth lens unit having the
`positive refracting power. Since the first imaging optical
`system comprises the negative lens and the concave mirror,
`adjustment for satisfYing