111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US007372538B2
`
`c12) United States Patent
`Bin nard
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,372,538 B2
`May 13,2008
`
`(54) APPARATUS AND METHOD FOR
`MAINTAINING IMMERISON FLUID IN THE
`GAP UNDER THE PROJECTION LENS
`DURING WAFER EXCHANGE IN AN
`IMMERSION LITHOGRAPHY MACHINE
`
`(75)
`
`Inventor: Michael Binnard, Belmont, CA (US)
`
`(73) Assignee: Nikon Corporation, Tokyo (JP)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 111237,721
`
`(22) Filed:
`
`Sep. 29, 2005
`
`(65)
`
`Prior Publication Data
`
`US 2006/0023186 Al
`
`Feb. 2, 2006
`
`Related U.S. Application Data
`
`(63) Continuation of application No. PCT/IB2004/
`001259, filed on Mar. 17, 2004.
`
`(60) Provisional application No. 60/462,499, filed on Apr.
`11, 2003.
`
`(51)
`
`Int. Cl.
`(2006.01)
`G03B 27152
`(2006.01)
`G03B 27142
`(2006.01)
`G03B 27132
`(52) U.S. Cl. ............................. 355/30; 355/53; 355/77
`(58) Field of Classification Search .................. 355/30,
`355/53, 72, 77; 430/30, 311; 359/509
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
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`4,480,910 A
`4,509,852 A
`5,528,100 A
`5,528,118 A
`
`8/1982 Tabarelli et a!.
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`(Continued)
`
`FOREIGN PATENT DOCUMENTS
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`DE
`
`221 563 A1
`
`4/1985
`
`(Continued)
`
`OTHER PUBLICATIONS
`
`English Translation of the German patent DD 211 563 A1 (dated
`Apr. 24, 1985) cited by Applicant in his IDS.*
`
`(Continued)
`
`Primary Examiner-Alan Mathews
`(74) Attorney, Agent, or Firm-Oiiff & Berridge, PLC
`
`(57)
`
`ABSTRACT
`
`An apparatus and method maintain immersion fluid in the
`gap adjacent to the projection lens during the exchange of a
`work piece in a lithography machine. The apparatus and
`method include an optical assembly that projects an image
`onto a work piece and a stage assembly including a work
`piece table that supports the work piece adjacent to the
`optical assembly. An environmental system is provided to
`supply and remove an immersion fluid from the gap between
`the optical assembly and the work piece on the stage
`assembly. After exposure of the work piece is complete, an
`exchange system removes the work piece and replaces it
`with a second work piece. An immersion fluid containment
`system maintains the immersion liquid in the gap during
`removal of the first work piece and replacement with the
`second work piece.
`
`106 Claims, 9 Drawing Sheets
`
`+s 312
`
`3~[
`
`16
`
`26
`
`324
`
`/
`
`308
`
`Wafer Table 0NT)
`
`Wafer Stage 0/IJS)
`I
`300~ ' - - - - - - - - - - - '
`
`Nikon Exhibit 1016 Page 1
`
`

`
`US 7,372,538 B2
`Page 2
`
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`DE
`A-57-153433
`JP
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`JP
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`JP
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`JP
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`JP
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`JP
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`7/1985
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`1/2005
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`6/2005
`6/2005
`
`Nikon Exhibit 1016 Page 2
`
`

`
`US 7,372,538 B2
`Page 3
`
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`wo
`
`WO 2005/054955 A2
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`OTHER PUBLICATIONS
`
`Emerging Lithographic Technologies VI, Proceedings of SPIE, vol.
`4688 (2002), "Semiconductor Foundry, Lithography, and Partners",
`B.J. Lin, pp. 11-24.
`Optical Microlithography XV, Proceedings of SPIE, vol. 4691
`(2002), "Resolution Enhancement of 157 nm Lithography by Liquid
`Immersion", M. Switkes eta!., pp. 459-465.
`
`J. Microlith., Microfab., Microsyst., vol. 1 No.3, Oct. 2002, Society
`of Photo-Optical Instrumentation Engineers, "Resolution enhance(cid:173)
`ment of 157 nm lithography by liquid immersion", M. Switkes eta!.,
`pp. 1-4.
`Nikon Corporation, 3'd 157 nm symposium, Sep. 4, 2002, "Nikon
`F2 Exposure Tool", Soichi Owa eta!., 25 pages (slides 1-25).
`Nikon Corporation, Immerison Lithography Workshop, Dec. 11,
`2002, 24 pages (slides 1-24).
`Optical Microlithography XVI, Proceedings of SPIE vol. 5040
`(2003), "Immersion lithography; its potential performance and
`issues", Soichi Owa et al., pp. 724-733.
`Nikon Corporation, Immersion Workshop, Jan. 27, 2004, "Update
`on 193 nm immersion exposure tool", S. Owa eta!., 38 pages (slides
`1-38).
`Nikon Corporation, Litho Forum, Jan. 28, 2004, "Update on 193 nm
`immersion exposure tool", S. Owa eta!., 51 pages (slides 1-51).
`Nikon Corporation, NGL Workshop, Jul. 10, 2003, :Potential per(cid:173)
`formance and feasibility of immersion lithography, Soichi Owa et
`a!., 33 pages, slides 1-33.
`* cited by examiner
`
`Nikon Exhibit 1016 Page 3
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 1 of 9
`
`US 7,372,538 B2
`
`N
`
`co
`
`co
`N
`
`~I
`
`~I
`
`~I
`
`C)
`i..L..
`
`Nikon Exhibit 1016 Page 4
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 2 of 9
`
`US 7,372,538 B2
`
`216
`
`212
`
`16
`
`26
`
`208
`
`214
`222~
`
`220
`
`202
`
`Wafer Table 0NT)
`
`204 224
`
`Wafer Stage 0/VS)
`
`~
`200
`
`206
`
`\226
`
`Fig. 2
`
`Nikon Exhibit 1016 Page 5
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 3 of 9
`
`US 7,372,538 B2
`
`316
`
`312
`
`16
`
`302
`
`___.,..
`300
`
`Wafer Table 0NT)
`
`Wafer Stage (WS)
`
`Fig. 3A
`
`26
`
`308
`
`324
`
`/
`
`Pad
`
`326
`
`328
`
`306
`
`Motor
`
`--r----- 322
`
`Motor
`
`308
`
`302 r
`
`326
`
`324
`
`I 328
`
`300
`~
`
`320
`
`+ 16 -+---+--1
`
`26
`
`322
`
`306
`
`330
`
`304
`
`Control
`System
`
`Motor
`Fig. 38
`
`Nikon Exhibit 1016 Page 6
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 4 of 9
`
`US 7,372,538 B2
`
`416
`~
`
`428
`
`410
`
`418
`
`420
`
`412
`
`424
`
`16 ~ l o(
`
`)>
`
`402
`
`Wafer Table (WT)
`
`406 -----t---....
`
`Wafer Stage 0JVS)
`
`Fig. 4A
`
`\~ 430
`
`400
`
`416
`~ 410 428
`418
`
`408
`
`26
`
`16
`
`420
`
`402
`
`400~
`
`Wafer Table 0/VT)
`
`Wafer Stage 0fVS)
`
`011111(
`
`------432
`
`Fig. 48
`
`430
`
`404
`406
`
`Nikon Exhibit 1016 Page 7
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 5 of 9
`
`US 7,372,538 B2
`
`Motor
`
`16
`
`502
`
`Motor
`
`Motor
`
`WS1
`
`WS2
`
`504
`
`Motor
`
`Fig. SA
`
`Motor
`
`16
`
`Motor
`
`Fig. 58
`
`502
`
`WS2
`
`Motor
`
`504
`
`Motor
`
`WS1
`
`502
`
`504
`
`Nikon Exhibit 1016 Page 8
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 6 of 9
`
`US 7,372,538 B2
`
`602
`
`Motor
`
`606
`
`604
`
`Motor
`
`WS1
`
`Motor
`
`Fig. 6A
`
`16
`
`602
`
`602
`
`Motor
`
`~
`600
`
`Nikon Exhibit 1016 Page 9
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 7 of 9
`
`US 7,372,538 B2
`
`606
`
`602
`
`606
`
`,16
`
`602
`
`604
`
`Fig. 68
`
`Fig. 6C
`
`604
`
`Fig. 60
`
`604
`
`Fig. 6E
`
`Nikon Exhibit 1016 Page 10
`
`

`
`U.S. Patent
`
`May 13, 2008
`
`Sheet 8 of 9
`
`US 7,372,538 B2
`
`701
`
`/
`DESIGN
`(FUNCTION,
`PERFORrvlANCE,
`PATTERN)
`
`702
`
`/
`
`/703
`
`WAFER
`FABRICATION
`l
`
`lr
`MASK
`f\IIAKING
`
`704
`
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`
`r
`
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`WAFER
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`
`705
`
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`
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`
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`
`DEVICE
`ASSEMBLY
`
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`
`/
`INSPECTION
`
`,,
`(DELIVERY)
`
`Fig. 7A
`
`Nikon Exhibit 1016 Page 11
`
`

`
`U.S. Patent
`
`May 13,2008
`
`Sheet 9 of 9
`
`US 7,372,538 B2
`
`..... - . - - . - - -
`
`I
`~ - - - .... - - .... - . - ... - .... - ... - .............................. - ...... - -
`
`712
`
`,
`
`ELECTRODE
`FORMATION
`
`I
`
`. . . . . . . . - . . . . . - - . . . . . . .
`
`f 715
`
`PRE-PROCESS
`lNG
`STEPS
`
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`STEPS
`
`f 716
`f 717
`
`r-
`
`718
`
`6' 719
`
`.....................
`
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`
`PHOTORESIST
`FORMATION
`
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`
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`
`It
`
`ETCHING
`
`PHOTORESIST
`REMOVAL
`.. -- .. ---.-.- .. . .. . . . .. . .. - ................... - ..
`
`Fig. 78
`
`Nikon Exhibit 1016 Page 12
`
`

`
`US 7,372,538 B2
`
`1
`APPARATUS AND METHOD FOR
`MAINTAINING IMMERISON FLUID IN THE
`GAP UNDER THE PROJECTION LENS
`DURING WAFER EXCHANGE IN AN
`IMMERSION LITHOGRAPHY MACHINE
`
`RELATED APPLICATIONS
`
`This is a Continuation of International Application No.
`PCT/IB2004/001259 filed Mar. 17, 2004, which claims the
`benefit of U.S. Provisional Application No. 60/462,499 filed
`on Apr. 11, 2003. The entire disclosures of the prior appli(cid:173)
`cations are incorporated herein by reference in their entire(cid:173)
`ties.
`
`BACKGROUND
`
`2
`stage moves away from the projection lens, for example
`during wafer exchange, is therefore needed.
`
`SUMMARY
`
`An apparatus and method maintain immersion fluid in the
`gap adjacent to the projection lens in a lithography machine.
`The apparatus and method include an optical assembly that
`projects an image onto a work piece and a stage assembly
`10 including a work piece table that supports the work piece
`adjacent to the optical assembly. An environmental system
`is provided to supply and remove an immersion fluid from
`the gap. After exposure of the work piece is complete, an
`exchange system removes the work piece and replaces it
`15 with a second work piece. An immersion fluid containment
`system is provided to maintain the immersion fluid in the
`gap when the work piece table moves away from the
`projection lens. The gap therefore does not have to be
`refilled with immersion fluid when the first work piece is
`20 replaced with a second work piece.
`
`Lithography systems are commonly used to transfer
`images from a reticle onto a semiconductor wafer during
`semiconductor processing. A typical lithography system
`includes an optical assembly, a reticle stage for holding a
`reticle defining a pattern, a wafer stage assembly that
`positions a semiconductor wafer, and a measurement system
`that precisely monitors the position of the reticle and the
`wafer. During operation, an image defined by the reticle is 25
`projected by the optical assembly onto the wafer. The
`projected image is typically the size of one or more die on
`the wafer. After an exposure, the wafer stage assembly
`moves the wafer and then another exposure takes place. This
`process is repeated until all the die on the wafer are exposed. 30
`The wafer is then removed and a new wafer is exchanged in
`its place.
`Immersion lithography systems utilize a layer of immer(cid:173)
`sion fluid that completely fills a gap between the optical
`assembly and the wafer during the exposure of the wafer. 35
`The optic properties of the immersion fluid, along with the
`optical assembly, allow the projection of smaller feature
`sizes than is currently possible using standard optical lithog(cid:173)
`raphy. For example, immersion lithography is currently
`being considered for next generation semiconductor tech- 40
`nologies including 65 nanometers, 45 nanometers, and
`beyond. Immersion lithography therefore represents a sig(cid:173)
`nificant technological breakthrough that will likely enable
`the continued use of optical lithography for the foreseeable
`future.
`After a wafer is exposed, it is removed and exchanged
`with a new wafer. As currently contemplated in immersion
`systems, the immersion fluid would be removed from the
`gap and then replenished after the wafer is exchanged. More
`specifically, when a wafer is to be exchanged, the fluid 50
`supply to the gap is turned off, the fluid is removed from the
`gap (i.e., by vacuum), the old wafer is removed, a new wafer
`is aligned and placed under the optical assembly, and then
`the gap is re-filled with fresh immersion fluid. Once all of the
`above steps are complete, exposure of the new wafer can 55
`begin.
`Wafer exchange with immersion lithography as described
`above is problematic for a number of reasons. The repeated
`filling and draining of the gap may cause variations in the
`immersion fluid and may cause bubbles to form within the 60
`immersion fluid. Bubbles and the unsteady fluid may inter(cid:173)
`fere with the projection of the image on the reticle onto the
`wafer, thereby reducing yields. The overall process also
`involves many steps and is time consuming, which reduces
`the overall throughput of the machine.
`An apparatus and method for maintaining immersion fluid
`in the gap adjacent to the projection lens when the wafer
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention will be described in conjunction with the
`following drawings of exemplary embodiments in which
`like reference numerals designate like elements, and in
`which:
`FIG. 1 is an illustration of an immersion lithography
`machine having features of the invention;
`FIG. 2 is a cross section of an immersion lithography
`machine according to one embodiment of the invention;
`FIGS. 3A and 3B are a cross section and a top down view
`of an immersion lithography machine according to another
`embodiment of the invention;
`FIGS. 4A and 4B are cross section views of an immersion
`lithography machine according to another embodiment of
`the invention;
`FIGS. SA and SB are top down views of two different twin
`wafer stages according to other embodiments of the inven(cid:173)
`tion;
`FIG. 6A is a top down view of a twin stage lithography
`machine according to another embodiment of the invention;
`FIGS. 6B-6E are a series of diagrams illustrating a wafer
`exchange according to the invention;
`FIG. 7A is a flow chart that outlines a process for
`manufacturing a work piece in accordance with the inven(cid:173)
`tion; and
`FIG. 7B is a flow chart that outlines work piece process(cid:173)
`ing in more detail.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`
`45
`
`FIG. 1 is a schematic illustration of a lithography machine
`10 having features of the invention. The lithography
`machine 10 includes a frame 12, an illumination system 14
`(irradiation apparatus), an optical assembly 16, a reticle
`stage assembly 18, a work piece stage assembly 20, a
`measurement system 22, a control system 24, and a fluid
`environmental system 26. The design of the components of
`the lithography machine 10 can be varied to suit the design
`requirements of the lithography machine 10.
`In one embodiment, the lithography machine 10 is used to
`transfer a pattern (not shown) of an integrated circuit from
`a reticle 28 onto a semiconductor wafer 30 (illustrated in
`65 phantom). The lithography machine 10 mounts to a mount(cid:173)
`ing base 32, e.g., the ground, a base, or floor or some other
`supporting structure.
`
`Nikon Exhibit 1016 Page 13
`
`

`
`US 7,372,538 B2
`
`3
`In various embodiments of the invention, the lithography
`machine 10 can be used as a scarming type photolithography
`system that exposes the pattern from the reticle 28 onto the
`wafer 30 with the reticle 28 and the wafer 30 moving
`synchronously. In a scanning type lithographic machine, the
`reticle 28 is moved perpendicularly to an optical axis of the
`optical assembly 16 by the reticle stage assembly 18, and the
`wafer 30 is moved perpendicularly to the optical axis of the
`optical assembly 16 by the wafer stage assembly 20. Scan(cid:173)
`ning of the reticle 28 and the wafer 30 occurs while the
`reticle 28 and the wafer 30 are moving synchronously.
`Alternatively, the lithography machine 10 can be a step(cid:173)
`and-repeat type photolithography system that exposes the
`reticle 28 while the reticle 28 and the wafer 30 are stationary.
`In the step and repeat process, the wafer 30 is in a constant
`position relative to the reticle 28 and the optical assembly 16
`during the exposure of an individual field. Subsequently,
`between consecutive exposure steps, the wafer 30 is con(cid:173)
`secutively moved with the wafer stage assembly 20 perpen(cid:173)
`dicularly to the optical axis of the optical assembly 16 so that
`the next field of the wafer 30 is brought into position relative
`to the optical assembly 16 and the reticle 28 for exposure.
`Following this process, the images on the reticle 28 are
`sequentially exposed onto the fields of the wafer 30, and
`then the next field of the wafer 30 is brought into position
`relative to the optical assembly 16 and the reticle 28.
`However, the use of the lithography machine 10 provided
`herein is not necessarily limited to a photolithography for
`semiconductor manufacturing. The lithography machine 10,
`for example, can be used as an LCD photolithography
`system that exposes a liquid crystal display work piece
`pattern onto a rectangular glass plate or a photolithography
`system for manufacturing a thin film magnetic head.
`Accordingly, the term "work piece" is generically used
`herein to refer to any device that may be patterned using
`lithography, such as but not limited to wafers or LCD
`substrates.
`The apparatus frame 12 supports the components of the
`lithography machine 10. The apparatus frame 12 illustrated
`in FIG. 1 supports the reticle stage assembly 18, the wafer 40
`stage assembly 20, the optical assembly 16 and the illumi(cid:173)
`nation system 14 above the mounting base 32.
`The illumination system 14 includes an illumination
`source 34 and an illumination optical assembly 36. The
`illumination source 34 emits a beam (irradiation) of light 45
`energy. The illumination optical assembly 36 guides the
`beam of light energy from the illumination source 34 to the
`optical assembly 16. The beam illuminates selectively dif(cid:173)
`ferent portions of the reticle 28 and exposes the wafer 30. In
`FIG. 1, the illumination source 34 is illustrated as being 50
`supported above the reticle stage assembly 18. Typically,
`however, the illumination source 34 is secured to one of the
`sides of the apparatus frame 12 and the energy beam from
`the illumination source 34 is directed to above the reticle
`stage assembly 18 with the illumination optical assembly 36. 55
`The illumination source 34 can be a g-line source (436
`nm), an i-line source (365 nm), a KrF excimer laser (248
`nm), anArF excimer laser (193 nm) or a F2 laser (157 nm).
`Alternatively, the illumination source 34 can generate an
`x-ray.
`The optical assembly 16 projects and/or focuses the light
`passing through the reticle 28 to the wafer 30. Depending
`upon the design of the lithography machine 10, the optical
`assembly 16 can magnify or reduce the image illuminated on
`the reticle 28. The optical assembly 16 need not be limited
`to a reduction system. It could also be a 1 x or greater
`magnification system.
`
`4
`Also, with an exposure work piece that employs vacuum
`ultra-violet radiation (VlN) of wavelength 200 nm or lower,
`use of a catadioptric type optical system can be considered.
`Examples of a catadioptric type of optical system are
`disclosed in Japanese Laid-Open Patent Application Publi(cid:173)
`cation No. 8-171054 and its counterpart U.S. Pat. No.
`5,668,672, as well as Japanese Laid-Open Patent Publication
`No. 10-20195 and its counterpart U.S. Pat. No. 5,835,275. In
`these cases, the reflecting optical system can be a catadiop-
`10 tric optical system incorporating a beam splitter and concave
`mirror. Japanese Laid-Open Patent Application Publication
`No. 8-334695 and its counterpart U.S. Pat. No. 5,689,377 as
`well as Japanese Laid-Open Patent Application Publication
`No. 10-3039 and its counterpart U.S. patent application No.
`15 873,605 (Application Date: Jun. 12, 1997) also use a reflect(cid:173)
`ing-refracting type of optical system incorporating a con(cid:173)
`cave mirror, etc., but without a beam splitter, and also can be
`employed with this invention. The disclosures of the above(cid:173)
`mentioned U.S. patents and applications, as well as the
`20 Japanese Laid-Open patent application publications are
`incorporated herein by reference in their entireties.
`The reticle stage assembly 18 holds and positions the
`reticle 28 relative to the optical assembly 16 and the wafer
`30. In one embodiment, the reticle stage assembly 18
`25 includes a reticle stage 38 that retains the reticle 28 and a
`reticle stage mover assembly 40 that moves and positions
`the reticle stage 38 and reticle 28.
`Each stage mover assembly 40, 44 can move the respec(cid:173)
`tive stage 38, 42 with three degrees of freedom, less than
`30 three degrees of freedom, or more than three degrees of
`freedom. For example, in alternative embodiments, each
`stage mover assembly 40, 44 can move the respective stage
`38, 42 with one, two, three, four, five or six degrees of
`freedom. The reticle stage mover assembly 40 and the work
`35 piece stage mover assembly 44 can each include one or more
`movers, such as rotary motors, voice coil motors, linear
`motors utilizing a Lorentz force to generate drive force,
`electromagnetic movers, planar motors, or some other force
`movers.
`In photolithography systems, when linear motors (see
`U.S. Pat. No. 5,623,853 or 5,528,118 which are incorporated
`by reference herein in their entireties) are used in the wafer
`stage assembly or the reticle stage assembly, the linear
`motors can be either an air levitation type employing air
`bearings or a magnetic levitation type using Lorentz force or
`reactance force. Additionally, the stage could move along a
`guide, or it could be a guideless type stage that uses no
`guide.
`Alternatively, one of the stages could be driven by a
`planar motor, which drives the stage by an electromagnetic
`force generated by a magnet unit having two-dimensionally
`arranged magnets and an armature coil nnit having two(cid:173)
`dimensionally arranged coils in facing positions. With this
`type of driving system, either the magnet unit or the arma-
`ture coil unit is connected to the stage base and the other unit
`is mounted on the moving plane side of the stage.
`Movement of the stages as described above generates
`reaction forces that can affect performance of the photoli(cid:173)
`thography system. Reaction forces generated by the wafer
`60 (substrate) stage motion can be mechanically transferred to
`the floor (ground) by use of a frame member as described in
`U.S. Pat. No. 5,528,100 and Japanese Laid-Open Patent
`Application Publication No. 8-136475. Additionally, reac(cid:173)
`tion forces generated by the reticle (mask) stage motion can
`65 be mechanically transferred to the floor (gronnd) by use of
`a frame member as described in U.S. Pat. No. 5,874,820 and
`Japanese Laid-Open Patent Application Publication No.
`
`Nikon Exhibit 1016 Page 14
`
`

`
`US 7,372,538 B2
`
`5
`8-330224. The disclosures of U.S. Pat. Nos. 5,528,100 and
`5,874,820 and Japanese Paid-Open Patent Application Pub(cid:173)
`lication Nos. 8-136475 and 8-330224 are incorporated
`herein by reference in their entireties.
`The measurement system 22 monitors movement of the 5
`reticle 28 and the wafer 30 relative to the optical assembly
`16 or some other reference. With this information, the
`control system 24 can control the reticle stage assembly 18
`to precisely position the reticle 28 and the work piece stage
`assembly 20 to precisely position the wafer 30. The design 10
`of the measurement system 22 can vary. For example, the
`measurement system 22 can utilize multiple laser interfer(cid:173)
`ometers, encoders, mirrors, and/or other measuring devices.
`The control system 24 receives information from the
`measurement system 22 and controls the stage assemblies 15
`18, 20 to precisely position the reticle 28 and the wafer 30.
`Additionally, the control system 24 can control the operation
`of the components of the environmental system 26. The
`control system 24 can include one or more processors and
`circuits.
`The environmental system 26 controls the environment in
`a gap (not shown) between the optical assembly 16 and the
`wafer 30. The gap includes an imaging field. The imaging
`field includes the area adjacent to the region of the wafer 30
`that is being exposed and the area in which the beam oflight
`energy travels between the optical assembly 16 and the
`wafer 30. With this design, the environmental system 26 can
`control the environment in the imaging field. The desired
`environment created and/or controlled in the gap by the
`environmental system 26 can vary accordingly to the wafer
`30 and the design of the rest of the components of the
`lithography machine 10, including the illumination system
`14. For example, the desired controlled environment can be
`a fluid such as water. Alternatively, the desired controlled
`environment can be another type of fluid such as a gas. In
`various embodiments, the gap may range from 0.1 mm to 10
`mm in height between top surface of the wafer 30 and the
`last optical element of the optical assembly 16.
`In one embodiment, the environmental system 26 fills the
`imaging field and the rest of the gap with an immersion fluid.
`The design of the environmental system 26 and the com(cid:173)
`ponents of the environmental system 26 can be varied. In
`different embodiments, the environmental system 26 deliv-
`ers and/or injects immersion fluid into the gap using spray
`nozzles, electro-kinetic sponges, porous materials, etc. and
`removes the fluid from the gap using vacuum pumps,
`sponges, and the like. The design of the environmental
`system 26 can vary. For example, it can inject the immersion
`fluid at one or more locations at or near the gap. Further, the
`immersion fluid system can assist in removing and/or scav(cid:173)
`enging the immersion fluid at one or more locations at or
`near the work piece 30, the gap and/or the edge of the optical
`assembly 16. For additional details on various environmen-
`tal systems, see U.S. provisional patent application 60/462,
`142 entitled "Immersion Lithography Fluid Control System"
`filed on Apr. 9, 2003, 60/462,112 entitled "Vacuum Ring
`System and Wick Ring System for Immersion Lithography"
`filed on Apr. 10,2003, 60/500,312 entitled "Noiseless Fluid
`Recovery With Porous Material" filed on Sep. 3, 2003, and
`60/541,329 entitled "Nozzle Design for Immersion Lithog(cid:173)
`raphy" filed on Feb. 2, 2004, all incorporated by reference
`herein in their entireties.
`Referring to FIG. 2, a cross section of a lithography
`machine illustrating one embodiment of the invention is
`shown. The lithography machine 200 includes a optical
`assembly 16 and a stage assembly 202 that includes a wafer
`table 204 and a wafer stage 206. The wafer table 204 is
`
`6
`configured to support a wafer 208 (or any other type of work
`piece) under the optical assembly 16. An environmental
`system 26, surrounding the optical assembly 16, is used to
`supply and remove immersion fluid 212 from the gap
`between the wafer 208 and the last optical element of the
`optical assembly 16. A work piece exchange system 216,
`including a wafer loader 218 (i.e., a robot) and an alignment
`tool 220 (i.e., a microscope and CCD camera), is configured
`to remove the wafer 208 on the wafer table 204 and replace
`it with a second wafer. This is typically accomplished using
`the wafer loader 218 to lift and remove the wafer 208 from
`the wafer table 204. Subsequently, the second wafer (not
`shown) is placed onto the wafer chuck 218, aligned using the
`alignment tool 220, and then positioned under the optical
`assembly 16 on the wafer table 204.
`With this embodiment, the wafer stage 206 includes an
`immersion fluid containment system 214 that is configured
`to maintain the immersion fluid 212 in the gap adjacent to
`the last optical element of the optical assembly 16 during
`20 wafer exchange. The immersion fluid containment system
`214 includes a pad 222 that is adjacent to the wafer table
`204. A support member 224, provided between the pad 222
`and the wafer stage 206, is used to support the pad 222. The
`wafer table 204 has a flat upper surface that is coplanar with
`25 a surface of the wafer 208. The pad 222 also has a flat upper
`surface that is coplanar with the upper surface of the wafer
`table 204 and the wafer surface. The pad 222 is arranged
`adjacent to the wafer table 204 with a very small gap (e.g.,
`0.1-1.0 mm) so that the immersion fluid 212 is movable
`30 between the wafer table 204 and the pad 222 without
`leaking. During a wafer exchange, the wafer stage 206 is
`moved in the direction of arrow 226 so that the pad 222 is
`positioned under the optical assembly 16 in place of the
`wafer table 204, maintaining the fluid in the gap or main-
`35 taining the size of the fluid gap. After the ne