(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0103832 A1
`(43) Pub. Date:
`May 18, 2006
`Hazelton et al.
`
`US 20060103832A1
`
`(54)
`
`(75)
`
`(73)
`
`(21)
`
`(22)
`
`(63)
`
`(60)
`
`WAFER TABLE FOR IMMERSION
`LITHOGRAPHY
`
`Inventors: Andrew J. Hazelton, Tokyo (JP);
`Hiroaki TakaiWa, Kumagaya-shi (JP)
`
`Publication Classi?cation
`
`(51) Int. Cl.
`(2006.01)
`G03B 27/58
`(52) Us. or. ............................................... ..355/72;355/53
`
`Correspondence Address:
`OLIFF & BERRIDGE, PLC
`PO. BOX 19928
`ALEXANDRIA, VA 22320 (US)
`
`Assignee: Nikon Corporation, Tokyo (JP)
`
`Appl. No.:
`
`11/319,399
`
`Filed:
`
`Dec. 29, 2005
`
`Related US. Application Data
`
`Continuation of application No. PCT/US04/l7452,
`?led on Jun. 2, 2004.
`
`Provisional application No. 60/485,868, ?led on Jul.
`8, 2003.
`
`(57)
`
`ABSTRACT
`
`Methods and apparatus alloW a liquid to be substantially
`contained between a lens and a Wafer table assembly of an
`immersion lithography system. According to one example,
`an exposure apparatus includes a lens and a Wafer table
`assembly. The Wafer table assembly has a top surface, and
`is arranged to support a Wafer to be moved With respect to
`the lens as Well as at least one component. The top surface
`of the Wafer and the top surface of the component are each
`at substantially a same height as the top surface of the Wafer
`table assembly. An overall top surface of the Wafer table
`assembly Which includes the top surface of the Wafer, the top
`surface of the Wafer table assembly, and the top surface of
`the at least one component is substantially planar.
`
`352/“
`
`SENSOR *"350
`
`r310
`WAFER HOLDER‘
`
`WAFER TABLE
`
`Nikon Exhibit 1015 Page 1
`
`

`

`Patent Application Publication May 18, 2006 Sheet 1 0f 9
`
`US 2006/0103832 A1
`
`100 \V\/
`
`>
`
`116\—.—\
`l @ ”‘
`
`—/—1 04
`
`® /-120
`__|_/—108
`——112
`
`Z
`
`y
`
`X
`
`Fig .‘ 1
`
`100\
`
`' V
`
`-
`
`‘
`
`120\®
`
`104
`
`116
`
`'
`
`1
`k
`112
`
`2
`
`Fig. 2
`
`y
`
`X
`
`Nikon Exhibit 1015 Page 2
`
`

`

`Patent Application Publication May 18, 2006 Sheet 2 0f 9
`
`US 2006/0103832 A1
`
`352_/_
`
`-
`SENSOR '"350 WAFER HOLDER
`
`310
`
`WAFER TABLE
`
`I" 312
`
`.
`F lg. 3
`
`Z
`
`yl—x
`
`402
`
`452—
`
`450-/©
`
`— 452
`
`GA 450
`
`409
`
`“£414
`
`452 —
`
`450-%
`
`—- 452
`
`@w
`
`Fig. 4
`
`Nikon Exhibit 1015 Page 3
`
`

`

`Patent Application Publication May 18, 2006 Sheet 3 0f 9
`
`US 2006/0103832 A1
`
`502
`
`552
`
`556
`
`DOSE
`SENSOR
`
`552-~ FID,
`
`562" __ MARK
`
`508
`509
`
`-’—514
`
`REF. ~I~552
`
`FLAT ___.,-——560
`
`.V
`
`Fig. 5
`
`Z
`
`X
`
`Nikon Exhibit 1015 Page 4
`
`

`

`Patent Application Publication May 18, 2006 Sheet 4 0f 9
`
`US 2006/0103832 A1
`
`600
`
`I r
`
`670
`
`650
`1
`l
`
`608
`i
`
`2
`
`602
`
`650
`r
`I
`
`W614
`Z
`
`L. x
`
`y
`
`Fig. 6A
`
`670
`
`.I
`
`650
`
`".1
`
`682
`
`608
`
`g
`
`I‘
`602
`
`684
`
`680
`
`650
`
`2
`
`We”
`
`z
`
`6903
`
`y \X
`
`684
`
`682
`
`680
`
`6,08
`
`|
`
`650
`I
`
`l
`
`W614
`
`]
`I
`670
`
`I
`I
`I
`650
`
`1
`I
`602
`
`Fig. BC
`
`z
`
`690a
`
`y
`
`x
`
`6900
`
`690b
`
`Nikon Exhibit 1015 Page 5
`
`

`

`Patent Application Publication May 18, 2006 Sheet 5 of 9
`
`US 2006/0103832 A1
`
`
`
`10b
`
`1 00
`
`10a
`
`Fig. 7
`
`Nikon
`
`Exhibit1015
`
`PageG
`
`Nikon Exhibit 1015 Page 6
`
`

`

`Patent Application Publication May 18, 2006 Sheet 6 0f 9
`
`US 2006/0103832 A1
`
`1301
`DESIGN (FUNCTION,
`PERFORMANCE, /
`PATTERN)
`
`1302
`MASK MAKING r
`
`1303
`WAFER FABRICATION /
`
`1
`
`i
`
`1304
`WAFER PROCESSING /'
`
`I
`1305
`DEVICE ASSEMBLY /'
`
`Y
`
`INSPECTION
`
`1306
`/'
`
`(DELIVERY)
`
`Fig. 8
`
`Nikon Exhibit 1015 Page 7
`
`

`

`Patent Application Publication May 18, 2006 Sheet 7 of 9
`
`US 2006/0103832 A1
`
`0N
`IMPLANENHON
`
`
`
`
`
`
`
`
`
`
`
` 1317
`
` 1318
`
`
`
`
`1313
`
`ELECTRODE
`FORMAHON
`
`‘*- PREPROCESSING
`STEPS
`
`i
`.
`i
`
`II
`
`POST-
`
`‘x- PROCESSING
`,’
`STEPS
`
`PHOTORESIST
`FORMATION
`
`EXPOSURE
`
`1316
`
`DEVELOPING
`
`ETCHNG
`
`PHOTORE$ST
`REMOVAL
`
`Nikon
`
`Exhibit1015
`
`PageB
`
`Nikon Exhibit 1015 Page 8
`
`

`

`Patent Application Publication May 18, 2006 Sheet 8 0f 9
`
`US 2006/0103832 A1
`
`816 808
`808
`808 812
`814 808 816
`/
`/
`/
`/
`/
`SENSOR % WAFER % SENSQR
`WAFER TABLE
`
`~ 804
`
`Fig. 108
`
`Nikon Exhibit 1015 Page 9
`
`

`

`Patent Application Publication May 18, 2006 Sheet 9 0f 9
`
`US 2006/0103832 A1
`
`900
`
`914
`I
`T
`
`924
`
`960
`
`908
`
`960
`
`924
`
`SENSOR
`
`'“916
`
`912
`./
`WAFER
`
`SENSOR #916
`
`WAFER TABLE
`
`#904
`
`Fig. 1 1A
`
`900
`
`914
`(I
`
`908
`960 /
`l
`
`916
`I
`I)
`‘ SENSOR
`
`912
`
`WAFER '
`
`960 916
`J
`SENSOR ‘
`
`WAFER TABLE
`
`~904
`
`Fig. 118
`
`Nikon Exhibit 1015 Page 10
`
`

`

`US 2006/0103832 A1
`
`May 18, 2006
`
`WAFER TABLE FOR IMMERSION
`LITHOGRAPHY
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This is a continuation of International Application
`No. PCT/US2004/0l7452 ?led Jun. 2, 2004, Which claims
`priority to US. Provisional Patent Application No. 60/485,
`868 ?led Jul. 8, 2003. The disclosures of these applications
`are incorporated herein by reference in their entireties.
`
`BACKGROUND
`
`[0002] The invention relates generally to semiconductor
`processing equipment. More particularly, the invention
`relates to methods and apparatus for enabling liquid in an
`immersion lithography system to effectively be contained
`betWeen a surface of a lens and a plane that is moved relative
`to the lens.
`
`[0003] For precision instruments such as photolithography
`machines that are used in semiconductor processing, factors
`that affect the performance, e.g., accuracy, of the precision
`instrument generally must be dealt With and, insofar as
`possible, eliminated. When the performance of a precision
`instrument such as an immersion lithography exposure sys
`tem is adversely affected, products formed using the preci
`sion instrument may be improperly formed and, hence,
`function improperly.
`
`[0004] In an immersion lithography system, a liquid is
`provided betWeen a lens and the surface of a Wafer in order
`to improve the imaging performance of the lens. The use of
`liquid alloWs a numerical aperture associated With the lens,
`i.e., an effective numerical aperture of the lens, to essentially
`be increased substantially Without altering characteristics of
`the lens, since a liquid such as Water generally has a
`refractive index that is greater than one. In general, a higher
`numerical aperture enables a sharper image to be formed on
`the Wafer. As Will be appreciated by those skilled in the art,
`a high refractive index liquid alloWs for a high numerical
`aperture of the lens because an effective numerical aperture
`of a lens system of an immersion lithography system is
`generally de?ned to be approximately equal to the sine of an
`angle of diffraction of light that passes through a lens and
`re?ects off a surface multiplied by the refractive index of the
`liquid. Because the refractive index of the liquid is greater
`than one, the use of liquid alloWs the effective numerical
`aperture of the lens to be increased, thereby enabling the
`resolution associated With the lens to essentially be
`improved.
`[0005] Within most conventional lithography systems, air
`is present betWeen a lens and a surface that passes under the
`lens, e.g., the surface of a Wafer. In such systems, the
`numerical aperture associated With the lens is often in the
`range of approximately 0.8 to 0.9. Increasing the numerical
`aperture of a lens to achieve an improved resolution is
`generally impractical, because the diameter of a lens gen
`erally must be increased, Which adds signi?cant di?iculty to
`a lens manufacturing process. In addition, the numerical
`aperture of a lens in air is theoretically limited to one, and,
`in practice, is limited to being someWhat less than one.
`Hence, immersion lithography systems enable the effective
`numerical aperture of a lens to be increased substantially
`beyond What is possible With a lens in air.
`
`[0006] FIG. 1 is a diagrammatic cross-sectional represen
`tation of a portion of an immersion lithography apparatus.
`An immersion lithography apparatus 100 includes a lens
`assembly 104 that is positioned over a Wafer table 112 that
`supports a Wafer 108. Wafer table 112 is arranged to be
`scanned or otherWise moved under lens assembly 104. A
`liquid 116, Which may be Water in a typical application that
`uses approximately 193 nanometers (nm) of radiation, is
`present in a gap betWeen lens assembly 104 and Wafer 108.
`In order to effectively prevent liquid 116 from leaking out
`from under lens assembly 104, i.e., to effectively laterally
`contain liquid 116 betWeen lens assembly 104 and Wafer
`108, a retaining ring 120 may be positioned such that
`retaining ring 120 enables liquid 116 to remain betWeen lens
`assembly 104 and Wafer 108, and Within an area de?ned by
`retaining ring 120.
`[0007] While retaining ring 120 is generally effective in
`containing liquid 116 When lens assembly 104 is positioned
`such that a small gap betWeen retaining ring 120 and a
`surface of Wafer 108 is maintained, for a situation in Which
`at least a part of retaining ring 120 is above Wafer 108, liquid
`116 may leak out from betWeen lens assembly 104 and Wafer
`108. By Way of example, When an edge of Wafer 108 is to
`be patterned, lens assembly 104 may be substantially cen
`tered over the edge such that a portion of retaining ring 120
`fails to maintain the small gap under the bottom surface of
`retaining ring 120, and liquid 116 is alloWed to leak out from
`betWeen lens assembly 104 and Wafer 108. As shoWn in
`FIG. 2, When lens assembly 104 is positioned such that at
`least part of a bottom surface of retaining ring 120 is not in
`contact With Wafer 108, liquid 116 may not be contained in
`an area de?ned by retaining ring 120 betWeen lens assembly
`104 and Wafer 108.
`
`[0008] In an immersion lithography apparatus, a Wafer
`table may support sensors and other components, e.g., a
`reference ?at that is used to calibrate automatic focusing
`operations. Such sensors and other components generally
`may be positioned beneath a lens at some point. That is,
`sensors and other components associated With a Wafer table
`may be occasionally positioned beneath a lens during the
`course of operating the lens and the Wafer table. While the
`use of a retaining ring may prevent liquid from leaking out
`of a gap betWeen a lens assembly and the top surface of the
`Wafer, liquid may leak out from betWeen the lens assembly
`and top surfaces of sensors and other components When the
`lens assembly is positioned over the sensors or other com
`ponents.
`
`[0009] FIG. 3 is a block diagram representation of a Wafer
`table that supports a sensor and a Wafer holder that holds a
`Wafer. A Wafer table 312 supports a Wafer holder 310 that is
`arranged to hold a Wafer (not shoWn), a sensor 350, and an
`interferometer mirror 352. Sensor 350 may be used through
`a lens (not shoWn) With liquid (not shoWn) betWeen the lens
`and sensor 350. HoWever, liquid Will often ?oW out of the
`gap betWeen a lens (not shoWn) and sensor 350 particularly
`When an edge of sensor 350 is positioned substantially
`beneath a center of the lens. The effectiveness of sensor 350
`may be compromised When sensor 350 is designed and
`calibrated to operate in a liquid, and there is insufficient
`liquid present betWeen a lens (not shoWn) and sensor 350.
`Further, When liquid (not shoWn) ?oWs out of the gap
`betWeen a lens (not shoWn) and sensor 350, the liquid that
`?oWed out of the gap is effectively lost such that When the
`
`Nikon Exhibit 1015 Page 11
`
`

`

`US 2006/0103832 A1
`
`May 18, 2006
`
`lens is subsequently positioned over a Wafer (not shown)
`supported by Wafer holder 310, the amount of liquid
`betWeen the lens and the Wafer may not be suf?cient to
`enable the e?fective numerical aperture of the lens to be as
`high as desired. Hence, When liquid is not successfully
`contained betWeen a lens (not shoWn) and sensor 350 While
`sensor 350 is at least partially positioned under the lens, an
`overall lithography process that involves the lens and sensor
`350 may be compromised.
`
`[0010] Therefore, What is needed is a method and an
`apparatus for allowing liquid to be maintained in a relatively
`small gap de?ned betWeen a surface of a lens and a surface
`of substantially any sensors or components that are sup
`ported by a Wafer table. That is, What is desired is a system
`that is suitable for preventing liquid positioned betWeen a
`lens and substantially any surface on a Wafer table that is
`moved under the lens from leaking out from betWeen the
`lens and the surface.
`
`SUMMARY
`
`[0011] The invention relates to a Wafer table arrangement
`that is suitable for use in an immersion lithography system.
`According to one aspect of the invention, an exposure
`apparatus includes a lens and a Wafer table assembly. The
`Wafer table assembly has a top surface, and is arranged to
`support a Wafer to be moved With respect to the lens as Well
`as at least one component. The top surface of the Wafer and
`the top surface of the component are each at substantially a
`same height as the top surface of the Wafer table assembly.
`An overall top surface of the Wafer table assembly that
`includes the top surface of the Wafer, the top surface of the
`Wafer table assembly, and the top surface of the at least one
`component is substantially planar.
`[0012] In one embodiment, the component may be at least
`one of a reference ?at, an aerial image sensor, a dose sensor,
`and a dose uniformity sensor. In another embodiment, the
`Wafer table assembly is arranged to support a Wafer holder
`that holds the Wafer such that the top surface of the Wafer is
`at substantially the same height as the top surface of the
`Wafer table assembly.
`[0013] A Wafer table arrangement that is con?gured to
`enable surfaces that are to be vieWed through a lens to form
`a relatively planar overall surface of substantially the same
`height facilitates an immersion lithography process. When
`substantially all elements carried on a Wafer table have top
`surfaces that are substantially level With the top surface of
`the Wafer table, and any gaps betWeen the sides of the
`components and the sides of openings in the Wafer table are
`relatively small, the overall top surface of a Wafer table
`arrangement may traverse under a lens While a layer or a ?lm
`of liquid is e?cectively maintained betWeen a surface of the
`lens and the overall top surface. Hence, an immersion
`lithography process may be performed substantially Without
`the integrity of the layer of liquid betWeen the surface of the
`lens and the overall top surface of the Wafer table arrange
`ment being compromised by the loss of liquid from the layer
`of liquid betWeen the surface of the lens and the overall top
`surface of the Wafer table arrangement.
`
`[0014] According to another aspect of the invention, an
`immersion lithography apparatus includes a lens that has a
`?rst surface and an associated e?fective numerical aperture.
`The apparatus also includes a liquid that is suitable for
`
`enhancing the e?fective numerical aperture of the lens, and
`a table arrangement. The table arrangement has a substan
`tially ?at top surface that opposes the ?rst surface, and the
`liquid is arranged substantially betWeen the substantially ?at
`top surface and the ?rst surface. The substantially ?at top
`surface includes a top surface of an object to be scanned and
`a top surface of at least one sensor.
`
`[0015] These and other advantages of the invention Will
`become apparent upon reading the folloWing detailed
`descriptions and studying the various ?gures of the draW
`ings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0016] The invention Will be described in conjunction With
`the accompanying draWings of exemplary embodiments in
`Which like reference numerals designate like elements and in
`Which:
`
`[0017] FIG. 1 is a diagrammatic cross-sectional represen
`tation of a portion of an immersion lithography apparatus in
`a ?rst orientation;
`
`[0018] FIG. 2 is a diagrammatic cross-sectional represen
`tation of a portion of an immersion lithography apparatus,
`i.e., apparatus 100 of FIG. 1, in a second orientation;
`
`[0019] FIG. 3 is a block diagram representation of a Wafer
`table that supports a sensor and a Wafer holder that holds a
`Wafer;
`[0020] FIG. 4 is a block diagram representation of a top
`vieW of a Wafer table assembly in accordance With an
`embodiment of the invention;
`
`[0021] FIG. 5 is a block diagram representation of a top
`vieW of components that are supported by a Wafer table
`assembly With a substantially uniform, planar overall top
`surface in accordance With an embodiment of the invention;
`
`[0022] FIG. 6a is a diagrammatic cross-sectional repre
`sentation of a Wafer table assembly that has a substantially
`uniform, planar overall top surface in accordance With an
`embodiment of the invention;
`
`[0023] FIG. 6b is a diagrammatic representation of a
`Wafer table assembly, e.g., Wafer table assembly 600 of FIG.
`6a, With a lens assembly positioned over a Wafer holder in
`accordance With an embodiment of the invention;
`
`[0024] FIG. 60 is a diagrammatic representation of a
`Wafer table assembly, e.g., Wafer table assembly 600 of FIG.
`6a, With a lens assembly positioned over a component in
`accordance With an embodiment of the invention;
`
`[0025] FIG. 7 is a diagrammatic representation of a pho
`tolithography apparatus in accordance With an embodiment
`of the invention;
`
`[0026] FIG. 8 is a process How diagram that illustrates the
`steps associated With fabricating a semiconductor device in
`accordance With an embodiment of the invention;
`
`[0027] FIG. 9 is a process How diagram that illustrates the
`steps associated With processing a Wafer, i.e., step 1304 of
`FIG. 8, in accordance With an embodiment of the invention;
`
`[0028] FIG. 10a is a diagrammatic representation of a
`Wafer table surface plate and a Wafer table in accordance
`With an embodiment of the invention;
`
`Nikon Exhibit 1015 Page 12
`
`

`

`US 2006/0103832 A1
`
`May 18, 2006
`
`[0029] FIG. 10b is a diagrammatic cross-sectional repre
`sentation of a Wafer table assembly that includes a Wafer
`table and a Wafer table surface plate in accordance With an
`embodiment of the invention;
`
`[0030] FIG. 11 a is a diagrammatic cross-sectional rep
`resentation of a Wafer table and a Wafer table surface plate
`With WindoWs in accordance With an embodiment of the
`invention; and
`[0031] FIG. 11b is a diagrammatic cross-sectional repre
`sentation of a Wafer table assembly that includes a Wafer
`table and a Wafer table surface plate With WindoWs, i.e.,
`Wafer table 904 and Wafer table surface plate 908 of FIG.
`11a, in accordance With an embodiment of the invention.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`
`[0032] In immersion lithography systems, a Wafer surface
`must generally be vieWed through a lens With a layer of
`liquid such as a relatively thin ?lm of liquid betWeen the lens
`and the Wafer surface. Some components such as sensors
`and/ or reference members may often be vieWed through the
`lens With a layer of liquid betWeen the lens and the surfaces
`of the components. Maintaining the layer of liquid in a gap
`betWeen the lens and the surface of the Wafer, even When the
`lens is arranged to vieW edge portions of the Wafer, alloWs
`the immersion lithography system to operate substantially as
`desired. Similarly, maintaining the layer of liquid in a gap
`betWeen the lens and the surface of components such as
`sensors and/or reference members also facilitates the e?i
`cient operation of the immersion lithography system.
`[0033] By utiliZing the Wafer table arrangement, surfaces
`that are to be vieWed through a lens and a top surface of the
`Wafer table arrangement form a relatively planar, substan
`tially uniform overall surface. When substantially all com
`ponents associated With the Wafer table arrangement have a
`surface that is substantially level With the top surface of a
`Wafer and the top surface of a Wafer table, and any gaps
`betWeen the sides of the components and the sides of
`openings in the Wafer table are relatively small, the overall
`top surface of the Wafer table arrangement may traverse
`under a lens While a layer or a ?lm of liquid is effectively
`maintained betWeen a surface of the lens and the overall top
`surface. As a result, an immersion lithography process may
`be performed substantially Without having the integrity of
`the layer of liquid, i.e., the layer of liquid betWeen the
`surface of the lens and the overall top surface of the Wafer
`table arrangement, compromised.
`[0034] AWafer table that has a substantially raised, ?at top
`surface of a uniform height alloWs a Wafer and other
`components, e.g., sensors, to be installed such that a ?at
`surface of the Wafer and ?at surfaces of the components are
`at substantially the same level or height as the raised, ?at top
`surface of the Wafer table. In one embodiment, an overall
`Wafer table assembly includes openings Within Which a
`Wafer, or a Wafer holder on Which the Wafer is supported,
`and sensors may be positioned. FIG. 4 is a block diagram
`representation of a top vieW of a Wafer table assembly in
`accordance With an embodiment of the invention. A Wafer
`table assembly 402 includes openings 409, 452 that are siZed
`to effectively house a Wafer 408 and components 450,
`respectively, such that top surfaces of Wafer 408 and com
`ponents 450 are at substantially the same level as a top
`surface 414 of Wafer table assembly 402. Typically, open
`
`ings 409, 452 are siZed to accommodate Wafer 408 and
`components 450, respectively, such that a spacing betWeen
`the outer edges of Wafer 408 or components 450 and their
`respective openings 409, 452 is relatively small, e.g.,
`betWeen approximately ten and approximately 500
`micrometers.
`
`[0035] In general, the spacing betWeen Wafer 408, or in
`some cases, a Wafer holder (not shoWn) and opening 409, as
`Well as the spacing betWeen components 450 and their
`corresponding openings 452 does not signi?cantly affect the
`overall planar quality of an overall top surface of Wafer table
`assembly 402. That is, an overall top surface of Wafer table
`assembly 402 Which includes top surface 414, the top
`surface of Wafer 408, and the top surfaces of components
`450 is substantially planar, With the planarity of the overall
`top surface being substantially unaffected by the presence of
`the small gaps betWeen the sides of Wafer 408 and opening
`409, and the sides of components 450 and openings 452.
`
`[0036] Components 450 may include, but are not limited
`to, various sensors and reference marks. With reference to
`FIG. 5, components that are supported by a Wafer table
`assembly With a substantially uniform, planar overall top
`surface Will be described in accordance With an embodiment
`of the invention. A Wafer table assembly 502 includes a
`raised, substantially uniform top surface 514 in Which open
`ings 509, 552 are de?ned. Opening 509 is arranged to hold
`a Wafer 508 Which may be supported by a Wafer holder (not
`shoWn). Openings 552 are arranged to support any number
`of components. In the described embodiment, openings 552
`are arranged to support a dose sensor or a dose uniformity
`sensor 556, an aerial image sensor 558, a reference ?at 560,
`and a ?ducial mark 562, Which each have top surfaces that
`are arranged to be of substantially the same height as top
`surface 514 such that an overall, substantially uniform,
`planar top surface is formed. Examples of a suitable dose
`sensor or dose uniformity sensor 556 are described in US.
`Pat. No. 4,465,368, US. Pat. No. 6,078,380, and US. Patent
`Publication No. 2002/0061469Al, Which are each incorpo
`rated herein by reference in their entireties. An example of
`an aerial image sensor 558 is described in US. Patent
`Publication No. 2002/0041377Al, Which is incorporated
`herein by reference in its entirety. An example of a reference
`?at 560 is described in US. Pat. No. 5,985,495, Which is
`incorporated herein by reference in its entirety, While an
`example of a ?ducial mark 562 is described in US. Pat. No.
`5,243,195, Which is incorporated herein by reference in its
`entirety.
`
`[0037] It should be appreciated that openings 552 are siZed
`to accommodate components such that gaps betWeen the
`sides of components, as for example dose sensor or dose
`uniformity sensor 556, aerial image sensor 558, reference
`?at 560, and ?ducial mark 562, and edges of openings 552
`are not large enough to signi?cantly affect the uniformity
`and planarity of the overall top surface. In other Words,
`components are relatively tightly ?t Within openings 552.
`
`[0038] Dose sensor or a dose uniformity sensor 556, one
`or both of Which may be included in openings 552, is/are
`arranged to be used to determine a strength of a light source
`associated With a lens assembly (not shoWn) by studying
`light energy at the level of the top surface of Wafer 508. In
`one embodiment, only a dose uniformity sensor is typically
`included. A dose sensor generally measures absolute illumi
`
`Nikon Exhibit 1015 Page 13
`
`

`

`US 2006/0103832 A1
`
`May 18, 2006
`
`nation intensity, While a dose uniformity sensor typically
`measures variations over an area. As such, dose sensor or
`does uniformity sensor 556 is positioned in the same plane
`as the top surface of Wafer 508. Aerial image sensor 558 is
`arranged to effectively measure an aerial image that is to be
`projected onto the surface of Wafer 508 and, hence, exposed
`on photoresist. In order for aerial image sensor to accurately
`measure an aerial image, aerial image sensor 558 is essen
`tially positioned at the same level or plane as the top surface
`of Wafer 508.
`
`[0039] Reference ?at 560 is generally used to calibrate the
`automatic focus functionality of a lens assembly (not
`shoWn), While ?ducial mark 562 is a pattern that is used to
`enable Wafer 508 to be aligned With respect to the lens
`assembly and reticle, as Will be understood by those skilled
`in the art. Both reference ?at 560 and ?ducial mark 562 are
`positioned in the same plane as Wafer 508.
`
`[0040] FIG. 6a is a diagrammatic cross-sectional repre
`sentation of a Wafer table assembly that has a substantially
`uniform, planar overall top surface in accordance With an
`embodiment of the invention. An overall Wafer table assem
`bly 600 includes a Wafer table 602 that is arranged to support
`a Wafer holder 608 that holds a Wafer (not shoWn) such that
`a top surface of the Wafer is substantially ?ush With an
`overall top surface 614 of Wafer table assembly 600. Wafer
`table 602 also supports components 650, Which may include
`sensors and reference marks, such that top surfaces of
`components 650 are also substantially ?ush With overall top
`surface 614, as discussed above. In other Words, top surfaces
`of components 650, Wafer holder 608 When supporting a
`Wafer (not shoWn), and Wafer table 602 effectively form a
`substantially ?at overall top surface 614 of relatively uni
`form height. Wafer holder 608 and components 650 are
`arranged to be relatively tightly ?t into openings de?ned
`Within Wafer table 602 such that a gap betWeen the side of
`Wafer holder 608 and the sides of an associated opening
`Within Wafer table 602, as Well as gaps betWeen components
`650 and the sides of associated openings Within Wafer table
`602, are each relatively small, and do not have a signi?cant
`effect on the uniformity of overall top surface 614.
`
`[0041] Wafer table 602 may support additional compo
`nents or elements in addition to Wafer holder 608, a Wafer
`(not shoWn), and components 650. By Way of example,
`Wafer table 602 may support an interferometer mirror 670.
`It should be appreciated that a top surface of interferometer
`mirror 670 may also be substantially level With overall top
`surface 614. Hence, in one embodiment, overall top surface
`614 may include interferometer mirror 670.
`
`[0042] Overall top surface 614 enables liquid to be main
`tained in a gap betWeen a lens assembly and overall top
`surface 614 When a component 650 or Wafer holder 608
`traverses beneath the lens. FIG. 6b is a diagrammatic
`representation of a Wafer table assembly, e.g., Wafer table
`assembly 600 of FIG. 611, that is arranged to scan beneath a
`lens assembly in accordance With an embodiment of the
`invention. A lens assembly 684, Which is arranged to be
`positioned over overall top surface 614 is effectively sepa
`rated from overall top surface 614 along a Z-axis 69011 by a
`layer of liquid 682. The siZe of the immersion area covered
`by liquid 682 is relatively small, e.g., the siZe of the
`immersion area may be smaller than that of the Wafer (not
`shoWn). Local ?ll methods that are used to provide the liquid
`
`of the immersion area are described in PCT International
`Patent Application No. PCT/US04/ 10055 (?led Mar. 29,
`2004), PCT International Patent Application No. PCT/
`US04/09994 (?led Apr. 1, 2004), and PCT International
`Patent Application No. PCT/U 804/ 10071 (?led Apr. 1,
`2004), Which are each incorporated herein by reference in
`their entireties. Layer of liquid 682 is effectively held
`betWeen overall top surface 614 and lens assembly 684 With
`respect to an x-axis 69019 and a y-axis 6900 by a retaining
`ring 680, although substantially any suitable arrangement
`may be used to effectively hold layer of liquid 682 in place
`relative to x-axis 69019 and y-axis 690c. Retaining ring 680
`is arranged as a ring-like structure With respect to x-axis
`69019 and y-axis 6900 Which contains liquid 682 in an area
`de?ned by the edges of retaining ring 680. That is, retaining
`ring 680 forms a ring-like shape about Z-axis 690a.
`
`[0043] In another embodiment, retaining ring 680 may not
`be necessary. If the gap betWeen lens assembly 684 and
`overall top surface 614 (or Wafer surface) is relatively small,
`e.g., betWeen approximately 0.5 mm and approximately 5
`mm, layer of liquid 682 may be effectively held in the gap
`With surface tension of liquid 682.
`[0044] In general, liquid 682 may be substantially any
`suitable liquid that ?lls a gap or a space betWeen a surface
`of lens assembly 684 and overall top surface 614 Within an
`area de?ned by retaining ring 680 that alloWs an effective
`numerical aperture of a lens included in lens assembly 684
`to be increased for the same Wavelength of light and the
`same physical siZe of the lens. Liquids including various
`oils, e.g., FomblinTM oil, may be suitable for use as liquid
`682. In one embodiment, as for example Within an overall
`system that uses approximately 193 nanometers (nm) of
`radiation, liquid 682 is Water. HoWever, for shorter Wave
`lengths, liquid 682 may be an oil.
`[0045] Because overall top surface 614 is substantially ?at
`and uniform, When lens assembly 684 is positioned over
`Wafer holder 608, liquid 682 does not leak out from betWeen
`overall top surface 614 and lens assembly 684, because
`retaining ring 680 remains in contact or in close proximity
`With overall top surface 614, even When lens assembly 684
`is positioned over an edge of Wafer holder 608. The unifor
`mity and planarity of overall top surface 614 also alloWs
`liquid 682 to remain betWeen lens assembly 684 and overall
`top surface 614 When lens assembly 684 is oriented over a
`component 650, as shoWn in FIG. 60.
`
`[0046] While a Wafer table arrangement may include a
`Wafer table in Which openings have been de?ned to house a
`Wafer or a Wafer holder and any number of components, a
`Wafer table arrangement may instead include a Wafer table
`that has no openings to house a Wafer or a Wafer holder and
`any number of components and structures that may coop
`erate With the Wafer table to effectively form openings in
`Which a Wafer or a Wafer holder and any number of
`components may be placed. In other Words, a substantially
`planar Wafer table arrangement may either include openings
`formed Within a Wafer table as discussed above, or openings
`de?ned by a structure or structures positioned atop a Wafer
`table.
`
`[0047] When a Wafer table arrangement includes a struc
`ture that de?nes openings that may effectively house a Wafer
`and components and provides a substantially planar top
`surface for the Wafer table arrangement, the structure may
`
`Nikon Exhibit 1015 Page 14
`
`

`

`US 2006/0103832 A1
`
`May 18, 2006
`
`generally be a plate-like structure Within Which openings are
`formed. With reference to FIG. 1011, a Wafer table arrange
`ment that includes a Wafer table and a Wafer table surface
`plate Will be described in accordance With an embodiment of
`the invention. A Wafer table arrangement 700 includes a
`Wafer table 704 and a Wafer table surface plate 708. Wafer
`table 704 supports a Wafer 712 and one or more components
`716 Which may include various sensors, a ?ducial mark, or
`a referen