(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0061469 A1
`(43) Pub. Date:
`May 23, 2002
`Tanaka
`
`US 20020061469A1
`
`(54)
`
`PROJECTION APPARATUS, METHOD OF
`MANUFACTURING THE
`APPARATUS,METHOD OF EXPOSURE
`USING THE APPARATUS, AND METHOD OF
`MANUFACTURING CIRCUIT DEVICES BY
`USING THE APPARATUS
`
`(75)
`
`Inventor: Yasuaki Tanaka, Tokyo (JP)
`
`Correspondence Address:
`ARMSTRONG,WESTERMAN & HATTORI,
`LLP
`1725 K STREET, NW.
`SUITE 1000
`WASHINGTON, DC 20006 (US)
`
`(73)
`(21)
`(22)
`
`(63)
`
`Assignee: NIKON CORPORATION, Tokyo (JP)
`
`Appl. No.:
`
`10/042,345
`
`Filed:
`
`Jan. 11, 2002
`
`Related US. Application Data
`
`Continuation of application No. 09/469,229, ?led on
`Dec. 22, 1999, Which is a continuation of application
`No. PCT/JP98/02840, ?led on Jun. 25, 1998.
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 25, 1997 (JP) ..................................... .. 168406/1997
`
`Publication Classi?cation
`
`(51) Int. Cl? ............................ .. G03B 27/00; G03F 7/20
`(52) U.S. c1. ........................... .. 430/311; 430/396; 355/18
`(57)
`ABSTRACT
`The quantity of ultraviolet light (IL) incident on a projection
`optical system (PL) is measured by means of an integrator
`sensor (9), and the quantity of ultraviolet pulse light (IL) that
`has passed through the projection optical system (PL) is
`measured by means of an irradiation monitor (32). The
`quantity of transmitted light is divided by the quantity of
`incident light to calculate the proportion at Which the
`ultraviolet pulse light (IL) is attenuated in the projection
`optical system (PL), or an attenuation factor. The attenuation
`factor is determined as a function of the integrated value of
`the quantity of incident light. During exposure, the inte
`grated value as quantity measured by means of the integrator
`sensor (9) is substituted into the function to estimate the
`transmissivity (attenuation factor) of the projection optical
`system (PL). The output of an excimer laser source (1) is
`controlled according to this attenuation factor to control the
`exposure thereby preventing loWering of exposure control
`precision due to illumination variations (or pulse energy
`variations) on the substrate caused by attenuation variations
`(transmissivity variations) in the projection optical system.
`
`171
`
`LOAD RETICLE R ON RETICLE STAGE
`
`1721
`DEPOSIT METALLIC FILM
`1'
`ON WAFER W
`\l/
`173-1
`COAT METALLIO FILM wfra RESIST,
`&. WAD WAFER w ON WAFER STAGE
`
`1741
`
`l
`
`EXPOSE PATTERN IMAGE OF RETICLE R TO
`EACH SHOT AREA OF WAFER H IN A SCANNING
`EXPOSURE SYSTEM WHILE CORRECTING LIGl-I'lI
`QUANTITY OF ULTRAVIOLET PULSE LIGHT
`SO AS ‘1'0 OFFSET TRANSMIT'I‘ANCE VARIATION
`OF PROJECTION OPTICAL SYSTEM PL
`
`{DEVELOP PHO'I'ORESIST ON WAFER W
`I
`176j
`
`E'I‘CH RESIST PATTERN ON
`WAFER W AS A MASK
`
`N‘EXI' PROCESS
`
`Nikon Exhibit 1023 Page 1
`
`

`

`Patent Application Publication May 23, 2002 Sheet 1 0f 7
`
`US 2002/0061469 A1
`
`Fig. 1
`
`16
`
`14
`
`158 W
`7L-
`
`18
`
`{
`
`i \56
`L19,
`
`'RE'I‘ICLE 12'
`
`20A
`Q3
`
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`T
`AX
`
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`SYSTEM
`
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`
`57
`
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`
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`
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`
`5
`
`Z!
`
`i Y X I
`
`52
`
`i
`25
`
`SCANNING
`DIRECTION
`
`'VPL
`
`WAFER W
`W
`
`J\\_ J
`24 z 24
`}
`24XY
`
`Nikon Exhibit 1023 Page 2
`
`

`

`Patent Application Publication May 23, 2002 Sheet 2 0f 7
`
`US 2002/0061469 A1
`
`Fig. 2
`
`RETICLE R
`
`AIF EXCIMER
`
`:12 .
`5/
`f»
`T (now)
`
`CONTROL T(e)
`PART
`1K 1
`6
`
`F\
`2
`
`#5193 x?
`
`Nikon Exhibit 1023 Page 3
`
`

`

`Patent Application Publication May 23, 2002 Sheet 3 0f 7
`
`US 2002/0061469 A1
`
`Fig. _3
`
`BEFORE EXPOSURE
`
`DURING EXPOSURE
`
`START MEASUREMENT OF
`
`START SCANNING
`
`
`
`TRANSMITTANCB VARIATION 10h .
`
`105w
`
`A
`
`START IRRADIATION
`WITH LASER
`
`START IRRADIATION
`WITH LASER
`
`4
`102w
`MEAbURE E‘ITERED
`ENERGY
`& TRANSMITTED
`ENERGY
`103w
`COMPUTE TOTAL
`gNTEgggTgiANggGY &
`RAN
`E OF
`OPTICAL SYSTEM
`
`104
`
`MEASUREMENT
`
`Yes
`105\
`STORE TRANSMITTANCE
`VARIATION OF
`ENTERED ENERGY
`
`107a
`
`r
`MEASURE
`ENTERED ENERGY
`108w
`COMPUTE TOTAL
`ENTERED ENERGY FROM
`START OF EXPOSURE
`m9_\
`
`READ
`'—"‘> TRANSMITTANCE DATA
`110?
`COMPUTE TARGET
`LASER OUTPUT &
`CHANGE LASER OUTPUT
`
`1 I
`
`1
`
`CANNING EXPOSURE
`FINISHED ?
`
`1 12“
`
`Yes
`STOP EMISSION
`OF LASER
`
`1 l3-\
`FINISH XPOSURE
`BY ONE SHOT
`
`H4
`
`START EXPOSURE
`BY NEXT SHOT
`
`Nikon Exhibit 1023 Page 4
`
`

`

`Patent Application Publication May 23, 2002 Sheet 4 0f 7
`
`US 2002/0061469 A1
`
`Fig. 4
`
`BEFORE EXPOSURE
`
`DURING EXPOSURE
`
`_ START MEASUREMENT OF
`ION
`
`TRANSMIT'I'ANCE VARIAT
`121w
`
`LOAD RETICLE
`
`122x
`CALL RETICLE DATA
`& CALCULATE PATTERN
`TRANSHIT'I’ANCE
`CORRESPONDING To
`RETIcLE POSITION
`
`‘
`
`12% SCAN RETICLE /
`
`
`& START IRRADIA'I'ION
`WITH LASER
`
`124“
`
`MEASURE RETICLE POSI‘I'IQN,
`ENTERED ENERGY a
`TRANSMITTED ENERGY
`
`125A
`COMPUTE TOTAL ENTERED
`ENERGY & TRANSMIT'I'ANCE OF
`OPTICAL SYSTEM
`
`1 5
`2
`
`No A
`
`"as
`127"\
`STORE TRANSMITTANCE
`VARIATION OF ENTERED
`ENERGY
`
`CSTART SCANNING EXPOSURE)
`128\
`sm?éi‘f?ég?“
`
`129\
`MEASURE RETIcLE POSITION
`& EnTznagog?ngg?gEp
`COMI’UTE
`33%?“ START OF
`
`130w
`READ TRANSMIT'I'ANCE DATA
`
`i 31\
`COMPUTE TARGET
`LASER OUTPUT &
`CHANGE} LASER. OUTPUT
`
`132
`
`SCANNING EXPOSUR
`
`Yes
`
`i33\
`STOP EMISSION OF LASER
`
`134*‘
`FINISH EXPOSURE
`BiONE SHOT
`
`‘353
`START EXPOSURE
`BY NEXj/I‘ SHOT
`
`Nikon Exhibit 1023 Page 5
`
`

`

`Patent Application Publication May 23, 2002 Sheet 5 0f 7
`
`US 2002/0061469 A1
`
`Fig. 5
`
`BEFORE EXPOSURE
`
`DURING EXPOSURE
`
`MENT
`START MEAS
`OF TRANSMITTANCE
`VARIATIO
`
`34m
`
`START IRRADIATION
`WITH LASER
`Mal
`MEASURE ENTEREE
`ENERGY & TRANS»
`MITTED ENERGY
`
`143a '
`COMPUTE TOTAL
`ENTERED ENERGY s.
`TRANSMITTANCE 0F
`OPTICAL SYSTEM
`
`144
`
`MEASUREMENT
`FINISHED ?
`
`Yes
`145x
`STORE TRANSNITTANCE
`VARIATION OF ENTERED
`ENERGY
`
`»\
`
`STOP EMISSION
`OF LASER
`
`MEASURE
`ELAPOSED TIME
`
`COMPUTB TRANSMITTANCE
`OF OPTICAL SYSTEM BY
`INSTANTANEOUS IRRAD~
`IATION WITH LASER
`
`COMPUTEVTOTAL
`ENTERED ENERGY mom
`START OF EXPOSURE
`
`1 56“
`COMPUTE TOTAL
`ENTERED ENERGY FROM
`START OF EXPOSURE
`
`READ TRANSMITTANCE
`> VARIATION OF ENTERED
`ENERGY
`
`READ TRANSMITTANCE
`> VARIATION DATA FOR ‘
`SUSPENDED TIME
`
`154—\
`COMPUTE TARGET LASER
`OUTPUT & Q‘IANGE
`LASER OUTPUT
`
`I
`158\
`g-gigg?ggmc? OF
`OPTICAL SYSTEM
`
`155
`
`cANNING EXPOSURE
`rnusuzv
`
`Yes
`1S9\
`FINISH EXPOSURE
`BY SHOT
`
`160
`
`OSURE
`ALL SHOTS BY
`FINISHED?
`
`No
`
`END EXPOSURE
`OPERATION
`
`
`
`VARIATION DURING EXPOSURE
`
`
`
`VARIATION AFTER MEASUREMENT OF TRANSMITTANCE
`
`
`
`
`
`MEASUREMENT OF TRANSMIT'I‘ANCE I
`
`
`
`STOP OF IRRADIATION
`
`FINISHED '1'
`
`Yes
`150x
`STORE TRANSMI'I‘TANCE
`VARIATION FOR
`SUSPENDED TIME
`L___.___.
`
`Nikon Exhibit 1023 Page 6
`
`

`

`Patent Application Publication May 23, 2002 Sheet 6 0f 7
`
`US 2002/0061469 A1
`
`Fig.6
`
`A
`
`L?!
`
`v
`m
`,9.
`
`A
`.
`
`LU
`
`\
`o
`LU
`V
`O
`I2
`
`A
`m
`
`v
`
`O
`
`m
`1 N
`
`N
`
`‘m
`1
`
`E
`
`o
`
`v
`
`E
`H
`
`O
`r
`
`LO
`
`00
`
`to
`
`‘
`O
`<1‘ N o
`
`TRANSMITTANCE (RELATIVE VALUE)
`
`Nikon Exhibit 1023 Page 7
`
`

`

`Patent Application Publication May 23, 2002 Sheet 7 0f 7
`
`US 2002/0061469 A1
`
`Fig. 7
`
`i'ilj
`
`LOAD RETICLE R ON RETICLE STAGE
`
`I721
`
`DEPOSIT METALLIC FILM
`ON WAFER W
`
`AL
`173*‘
`com METALLIC FILM WITH RESIST,
`8% LOAD WAFER w ON WAFER STAGE
`
`174-1
`
`EXPOSE PATTERN IMAGE OF RE'I'ICLE R TO
`EACH SHOT AREA OF WAFER W IN A SCANNING
`EXPOSURE SYSTEM WHILE CORRECTING LIGHT
`QUANTITY OF ULTRAVIOLET PULSE LIGHT
`SO AS TO OFFSET TRANSMITTANCE VARIATION
`OF PROJECTION OPTICAL SYSTEM PL
`
`175"\
`DEVELOP PHOTORESIST 0N WAFER W
`
`1761
`
`A,
`ETCH RESIST PATTERN ON
`WAFER W AS A MASK
`
`NEXT PROCESS
`
`Nikon Exhibit 1023 Page 8
`
`

`

`US 2002/0061469 A1
`
`May 23, 2002
`
`PROJECTION APPARATUS, METHOD OF
`MANUFACTURING THE APPARATUS,METHOD
`OF EXPOSURE USING THE APPARATUS, AND
`METHOD OF MANUFACTURING CIRCUIT
`DEVICES BY USING THE APPARATUS
`
`BACKGROUND OF THE INVENTION
`
`[0001] The present invention relates to a projection appa
`ratus for use in transcribing a pattern on a mask onto a
`substrate through a projection optical system in a lithogra
`phy process for manufacturing, for example, semiconductor
`elements, liquid crystal display elements, thin ?lm magnetic
`heads, and so on, to a method for manufacturing the pro
`jection apparatus, to an exposure method for exposure using
`the projection apparatus, and to a method for manufacturing
`circuit devices by using the projection apparatus.
`
`[0002] In order to meet With improvements in an extent of
`integration and a degree of ?neness of semiconductor
`devices, demands have been made to increase characteris
`tics, such as a resolving poWer and ?delity of transcription,
`for an exposure apparatus involved in a lithography process
`(representatively, consisting of a resist coating step, expos
`ing step, and a resist developing step) for manufacturing
`semiconductor devices. In order to enhance the resolving
`poWer and the ?delity of transcription, it is required as the
`?rst point that an exposure quality for exposing a resist
`coated on a Water as a substrate to light at an optimal
`exposure quantity.
`
`[0003] Recent years, at plants Where semiconductor
`devices are being manufactured, there have been extensively
`used a reduced projection exposure apparatus (stepper) of a
`step-and-repeat type using a reduced projection optical
`system having a l/s-fold magni?cation of projection from a
`reticle to a Wafer, Which mainly uses i-rays of a 365 nm
`Wavelength, among brilliant light rays of a mercury dis
`charge lamp, as an exposing illumination light. Further, as
`the recent trend during these several years, attention has
`been draWn to a reduced projection exposure apparatus of a
`step-and-scan type for scanning and exposing an entire
`image of a circuit pattern of a reticle in each region on the
`Wafer by scanning the reticle at an equal speed in a prede
`termined direction in a vision ?eld of the reduced projection
`optical system on its object plane side and by scanning the
`Wafer in the corresponding direction in the vision ?eld of the
`reduced projection optical system on the image plane side at
`a speed rate equal to a reduced magni?cation, in order to
`avoid that the projection vision ?eld of the reduced projec
`tion optical system becomes extremely large as the siZe (chip
`siZe) of the circuit device to be formed on the Wafer becomes
`larger.
`[0004] For a conventional Way of controlling the exposure
`quality, the exposure quantity on the surface of the Wafer is
`calculated from the light quantity of the illumination light
`divided in the illumination optical system and the transmit
`tance or transmissivity thereof on the basis of the transmit
`tance or transmissivity of the projection optical system, for
`example, measured at a certain point of time immediately
`before exposure, supposed that the transmittance or trans
`missivity of the projection optical system for the exposing
`illumination light does not ?uctuate in a short time. For a
`conventional stepper of a step-and-scan type, the output and
`the scanning velocity of a light source is controlled so as to
`
`make the exposure quantity to be calculated a constant
`value, by controlling the exposing time so as to make an
`integrated value of the exposure quantity to be calculated a
`predetermined value.
`
`[0005] Recently, in order to improve the resolving poWer
`by making the exposing Wavelength shorter, projection
`exposure apparatuses of a step-and-repeat type and projec
`tion exposure apparatuses of a step-and-scan type have been
`developed, Which use an ultraviolet pulse light having a
`Wavelength of 250 nm or less from an excimer laser light
`source as an exposing illumination light. Aprojection expo
`sure apparatus using a KrF excimer laser light source having
`a Wavelength of 248 nm has started being launched on a
`large scale in actually manufacturing lines. Moreover, an
`ArF excimer laser light source emitting an ultraviolet pulse
`light having a Wavelength as short as 193 nm has been
`developed, and this light source is promising as a future light
`source for exposure.
`
`[0006] If such an ArF excimer laser light source is used as
`an exposing light source, the Wavelength features of the
`ultraviolet pulse light are required to be narroWed to a
`Wavelength that lacks some absorption bands of oxygen
`because there are such absorption bands of oxygen in a
`Wavelength band region of the ultraviolet pulse light in its
`natural oscillation state. Further, it is required that the
`illumination light path extending from the exposing light
`source to the reticle and the projection light path extending
`from the reticle to the Wafer are brought each in an envi
`ronment in Which oxygen is contained in the possible least
`amount, that is to say, that a majority of those illumination
`light path and projection light path is replaced With an inert
`gas such as nitrogen gas or helium gas. Examples of the
`projection exposure apparatuses using such an ArF excimer
`laser light source are disclosed in, for example, US. Pat. No.
`5,559,584 (corresponding to Japanese Patent Application
`Laid-Open Nos. 6-260,385 and 6-260,386).
`[0007] There are currently knoWn only tWo of optical glass
`materials having a desired transmittance for an ultraviolet
`pulse light (having a Wavelength of about 250 nm or shorter)
`from the above-described excimer laser light source, Which
`can be practically applicable. They are quartZ (SiO2) and
`?uorite (CaFZ). In addition, there are knoWn, for example,
`magnesium ?uoride and lithium ?uoride, but they suffer
`from the problems With, for example, processing ability and
`durability in order to alloW them to be used as an optical
`glass material for use With a projection exposure apparatus.
`
`[0008] As a projection optical system to be loaded on a
`projection exposure apparatus, there may also be used a
`catadioptric type (a re?ective-refractive system) consisting
`of a combination of a refractive optical element (a lens
`element) With a re?ective optical element (particularly a
`concave mirror), in addition to a dioptric type (a refractive
`system). Even if a projection optical system of Which type,
`Whether a dioptric type or a catadioptric type, is used,
`hoWever, a refractive optical element (a transmitting optical
`element) has to be used, and only tWo kinds of optical glass
`materials, i.e. quartZ or ?uorite, have to be used for a
`refractive optical element at the current time. Moreover,
`Whether a refractive optical element or a re?ective optical
`element is used, a multiple layer ?lm such as a re?ection
`preventive ?lm or a protective layer for example, may be
`deposited on the surface of such an optical element in order
`
`Nikon Exhibit 1023 Page 9
`
`

`

`US 2002/0061469 A1
`
`May 23, 2002
`
`to allow the resulting optical element to demonstrate
`improved performance to a predetermined extent as a single
`optical element. The performance that draWs particular
`attention herein is hoW larger the absolute value of the
`transmittance of a single body of the lens element or the
`absolute value of the re?ectance or re?ectivity of a single
`body of the re?ective optical element can be made.
`
`[0009] For instance, for a single body of a lens element, it
`has been attempted that the transmittance is made as large as
`possible generally by coating each of the light entering plane
`and the light leaving plane of the lens element With a
`re?ection preventive ?lm or the like. Moreover, for an
`precise imaging optical system such as a projection optical
`system, as many as 20 to 30 lens elements are used for
`correcting a variety of aberration features to an appropriate
`extent. Accordingly, even in the event Where the transmit
`tance of each lens element is loWered slightly beloW 100%,
`the transmittance of the projection optical system as a Whole
`becomes considerably loW, so that an attenuation factor of
`the projection optical system as a Whole becomes consider
`ably larger. Further, for a projection optical system contain
`ing some re?ection optical elements, too, the transmittance
`of the entire projection optical system becomes loW, on the
`one hand, and the attenuation factor of the entire projection
`optical system becomes considerably large, on the other,
`When the re?ectance of each of the re?ective optical ele
`ments is For instance, When it is supposed that the imaging
`light path of an projection optical system is composed of
`tWenty-?ve lens elements and the transmittance of each lens
`element is set to be 96%, the transmittance e of the projec
`tion optical system as a Whole becomes as loW as 36%
`(z0.9625><100). In cases Where the transmittance of the
`projection optical system is loW, the exposing time may
`become so longer that a throughput may be decreased unless
`measures Would be taken that the intensity (energy) of an
`illumination light for exposing the image of a circuit pattern
`of a reticle to a Wafer is increased or that a resist for
`ultraviolet rays having a higher sensitivity is used. There
`fore, it is considered that an excimer laser light source
`having a higher output is prepared as measures that can be
`realiZed on the side of the projection optical system.
`[0010] Some experiments made by a projection optical
`system using an excimer laser light source and having a
`relatively large ?eld siZe reveal a neW phenomenon, hoW
`ever, has been found that the transmittance of an optical
`element Within a projection optical system or a coating
`material of an optical element, including, for example, a thin
`?lm, such as a re?ection preventive ?lm or the like, ?uctu
`ates dynamically in a short time by irradiation With an
`illumination light having an ultraviolet Wavelength region,
`such as KrF excimer laser light or ArF excimer laser light.
`It has further been found from the results of the experiments
`that this phenomenon occurs in the entirely equal manner for
`an optical element in the illumination optical system for
`illuminating a reticle or for a reticle (made of a quartZ plate)
`itself, as Well as for an optical element in a projection optical
`system.
`
`[0011] It is considered that a such phenomenon may occur
`due to the attachment of impurities to the surface of an
`optical element or contamination of the illumination light
`path With such impurities or ?oating of such impurities in the
`illumination light path, the such impurities being contained
`in a gas (air, oxygen gas, etc.) present in a space Within a
`
`projection light path or a projection light path or the such
`impurities (e.g., Water molecules, hydrocarbon molecules,
`other substances diffusing the illumination light, etc.) being
`derived from molecules of organic substances, adhesive or
`the like for ?xing an optical element to a lens barrel, or from
`the inner Wall (i.e., a coated surface for preventing the
`re?ection of light, etc.) of a lens barrel. As a consequence,
`some draWbacks may occur in that the transmittance (the
`attenuation factor) of the projection optical system or the
`transmittance (the attenuation factor) of the illumination
`optical system ?uctuates to a relatively large extent.
`
`[0012] For instance, if the transmittance of each lens
`element Would be loWered by 1% for the above-mentioned
`projection optical system being composed of tWenty-?ve
`lens elements and having the transmittance E of the entire
`projection optical system as loW as approximately 36%, as
`in the manner as described above, the transmittance e of the
`projection optical system as a Whole becomes loWered to a
`level as loW as approximately 27.7% (z0.9525><100).
`[0013] There is the risk, hoWever, that the ?uctuation of
`the transmittance of an optical element may vary the expo
`sure quantity to be provided on the Wafer from its optimal
`value and deteriorate in the ?delity of transcribing a ?ne
`pattern having a design line Width as ?ne as approximately
`0.25 to 0.18 micron to be transcribed on the Wafer. As
`disclosed in Japanese Patent Application Laid-Open No.
`2-135,723 (corresponding to US. Pat. No. 5,191,374), a
`conventional projection exposure apparatus is con?gured
`such that the light intensity of the pulse light (an energy per
`pulse) from an excimer laser light source is adjusted so as to
`provide an optimal exposure quantity on the basis of the
`light intensity of the illumination light detected at a prede
`termined position in a light path of the illumination optical
`system. From this con?guration, such a conventional pro
`jection exposure apparatus has the risk that the exposure
`quantity cannot be controlled accurately because the ?uc
`tuation in the transmittance of the illumination optical
`system and the projection optical system behind the portion
`in the illumination light path at Which the light intensity of
`the illumination light is being detected for controlling the
`exposure quantity.
`[0014] When the irradiation of the projection optical sys
`tem With an ultraviolet pulse light is suspended, a phenom
`enon is being found such that the transmittance of the
`projection optical system becomes recovered or ?uctuating
`gradually. In such a case, if the exposure is resumed by
`starting the re-irradiation of an ultraviolet pulse light, there
`is the risk that the accurate control of the exposure quantity
`becomes dif?cult because the transmittance of the projection
`optical system ?uctuates.
`SUMMARY OF THE INVENTION
`[0015] From the foregoing background, the present inven
`tion has the primary object to provide a projection exposure
`apparatus and a method for manufacturing the same, the
`projection exposure apparatus being con?gured such that the
`deterioration in the precision of controlling the exposure
`quantity is prevented, the deterioration being caused to
`occur by the ?uctuation in illuminance or the ?uctuation in
`energy on a substrate resulting from a ?uctuation in the
`transmittance of the projection optical system.
`[0016] Further, the present invention has a second object
`to provide an exposure method that can achieve a favorable
`
`Nikon Exhibit 1023 Page 10
`
`

`

`US 2002/0061469 A1
`
`May 23, 2002
`
`precision in controlling the exposure quantity by using such
`a projection exposure apparatus.
`
`[0017] Moreover, the present invention has a third object
`to provide a method for manufacturing a circuit device that
`can form a circuit pattern on a substrate With a high ?delity
`of transcription by using such a projection exposure appa
`ratus.
`
`[0018] The projection exposure apparatuses according to
`the present invention is con?gured such that a pattern
`formed on a mask is irradiated With an exposing energy
`beam and an image of the pattern formed on the mask is
`projected onto a substrate through a projection optical
`system, the projection exposure apparatus being provided
`With an attenuation factor characteristic storage system for
`storing a ?uctuation or variation in an attenuation factor of
`the projection optical system in accordance With a total
`entered energy entering into the projection optical system
`and With an attenuation factor acquisition system for acquir
`ing an attenuation factor of the projection optical system at
`the time of exposure on the basis of the value of the total
`entering energy and the ?uctuation or variation in the
`attenuation factor stored in the attenuation factor character
`istic storage system by calculating the total entered energy
`entering into the projection optical system through the mask.
`
`[0019] The ?uctuation or variation in the attenuation fac
`tor is a function of the value of the total entered energy
`entering into the projection optical system through the mask.
`The total entered energy entering into the projection optical
`system can be calculated through the mask on the basis of
`the transmittance of the mask.
`
`[0020] The projection exposure apparatus may be of a type
`that can project an image of the pattern formed on the mask
`onto a substrate by scanning the mask relative to the
`exposing energy beam.
`[0021] The total entered energy entering into the projec
`tion optical system through the mask may also be calculated
`by taking advantage of information of the relative positions
`betWeen the exposing energy beam and the mask. The
`information on the relative positions is an optical charac
`teristic of the mask in accordance With the relative positions
`of the exposing energy beams and the mask, and the optical
`characteristic of the mask contains a transmittance charac
`teristic of the mask.
`
`[0022] The projection exposure apparatus according to the
`present invention may further be provided With an entering
`energy measurement system for measuring the total entered
`energy entering into the projection optical system through
`the mask. In addition, the projection exposure apparatus may
`further be provided With a leaving energy measurement
`system for measuring a leaving energy leaving from the
`projection optical system. Moreover, the ?uctuation or
`variation in the attenuation factor may be measured on the
`basis of a result of measurement by means of the entering
`energy measurement system and the leaving energy mea
`surement system. The projection exposure apparatus may
`further be provided With an exposure control system for
`controlling the exposure quantity to be provided on the
`substrate on the basis of the ?uctuation in the attenuation
`factor.
`
`[0023] The attenuation factor characteristic storage system
`may be con?gured so as to store the ?uctuation or variation
`
`in the attenuation factor of the projection optical system in
`the elapse of time after the suspension of the irradiation of
`the projection optical system With the exposing energy
`beam, in addition to the attenuation factor of the projection
`optical system for the total entering energy.
`[0024] As the exposing energy beams, there may be used
`energy beams having a Wavelength of an ultraviolet region.
`[0025] When a dioptric type (a refractive system) is used
`as a projection optical system PL, the variation in the
`transmittance of the lens element mainly exerts in?uence
`greatly upon the optical characteristics of the projection
`optical system PL and causes ?uctuating in the attenuation
`factor of the projection optical system PL. On the other
`hand, When a catadioptric type (a re?ective-refractive sys
`tem) is used as a projection optical system PL, the variation
`in the re?ectance of a re?ective optical element greatly
`exerts in?uence upon the optical characteristics of the pro
`jection optical system PL, in addition to the variation in the
`transmittance of the lens element, and the variation in the
`transmittance of the lens element and the variation in the
`re?ectance of the re?ective optical element may cause
`?uctuating in the attenuation factor of the projection optical
`system PL.
`[0026] The ?uctuation or variation in the attenuation fac
`tor of the projection optical system PL referred to in the
`speci?cation is intended to mean a ?uctuation or variation in
`the transmittance, on the one hand, in the case of the
`projection optical system PL using the dioptric type (refrac
`tive system) and to mean a ?uctuation or variation in the
`transmittance and the re?ectance, on the other hand, in the
`case of the projection optical system PL using the catadiop
`tric type (re?ective-refractive system).
`[0027] For the projection exposure apparatus according to
`the present invention, the attenuation factor of the projection
`optical system can be assumed With a high precision at a
`nearly real time by storing the ?uctuation or variation in the
`attenuation factor of the projection optical system as a
`function of the energy value of the total entered energy
`entering into the projection optical system, measuring the
`energy entering into the projection optical system from the
`start of exposure upon actual exposure, that is, from the start
`of irradiation With the exposing energy beams, and substi
`tuting the energy value for the ?uctuation or variation in the
`attenuation factor of the projection optical system previously
`stored. Therefore, the precision of controlling the exposure
`quantity can be prevented from deteriorating, Which may be
`caused by the ?uctuation in illuminance or the ?uctuation in
`the pulse energy on the substrate resulting from the ?uctua
`tion in the attenuation factor of the projection optical system
`by controlling the exposure quantity by offsetting the varia
`tion in the attenuation factor.
`[0028] It is further preferred that the attenuation factor
`characteristic storage system be con?gured so as to store the
`?uctuation in the attenuation factor of the projection optical
`system for an elapse of time after the suspension of the
`irradiation With the exposing energy beams. This con?gu
`ration of the system permits the presumption of the variation
`in the attenuation factor of the projection optical system With
`high precision, even if the optical characteristics of the
`projection optical system, such as the transmittance, re?ec
`tance and so on, Would not be recovered immediately after
`interruption of the irradiation With the exposing energy
`beam.
`
`Nikon Exhibit 1023 Page 11
`
`

`

`US 2002/0061469 A1
`
`May 23, 2002
`
`[0029] The projection exposure apparatus according to the
`present invention may further be provided With a stage
`system for transferring each of a mask or a substrate, thereby
`scanning the mask and the substrate relative to the projection
`optical system in synchronization With each other. This
`means that the present invention is applied to the projection
`exposure apparatus of a scanning exposure type. In this case,
`the scanning velocity may also be controlled, in addition to
`controlling the output of an exposing light source, in order
`to control the exposure quantity.
`
`[0030] The method for manufacturing the projection expo
`sure apparatus according to the present invention is con?g
`ured such that an image of a pattern formed on a mask is
`irradiated With a predetermined exposing energy beam and
`the pattern image thereof is projected onto a substrate
`through a projection optical system. The method comprises
`the step of installing an attenuation factor characteristic
`storage system for storing a ?uctuation or variation in the
`attenuation factor of the projection optical system in accor
`dance With a total entered energy entering into the projection
`optical system and the step of installing an attenuation factor
`acquisition system for acquiring the attenuation factor of the
`projection optical system at the time of exposure on the basis
`of the value of the total entering energy and the ?uctuation
`or variation in the attenuation factor stored in the attenuation
`factor characteristic storage system by calculating the total
`entered energy entering into the projection optical system
`through the mask.
`
`[0031] Moreover, the exposure method according to the
`present invention is con?gured such that a pattern formed on
`a mask is irradiated With a predetermined exposing energy
`beam and an image of the pattern of the mask is projected
`onto a substrate through a projection optical system. The
`exposure method comprises obtaining a ?uctuation or varia
`tion in an attenuation factor of the projection optical system
`in accordance With a total entered energy entering into the
`projection optical system and obtaining the attenuation
`factor of the projection optical system on the basis of the
`value of the total entering energy entering into the projection
`optical system through the mask and the ?uctuation or
`variation in the attenuation factor.
`
`[0032] Upon measuring the attenuation factor of the pro
`jection optical system, it is preferred that the exposure
`quantity of the exposing energy beam for a substrate is
`controlled on the basis of the attenuation factor obtained by
`compensating With a rate of the presence of a pattern on a
`mask or a rate of pattern transmittance of the mask at the
`time of exposure to a substrate. By controlling the exposure
`quantity of the exposing energy beam in the manner as
`described above, an error can be prevented in measuring the
`attenuation factor of the projection optical system due to an
`in?uence of the rate of the presence of the pattern on the
`mask or the rate of the transmittance through the pattern on
`the mask.
`
`[0033] Further, the method for manufacturing a circuit
`device according to the present invention is con?gured such
`that a predetermined circuit device is manufactured by
`projecting an image of a pattern formed on a mask onto a
`substrate through a projection optical system. The method
`comprises the ?rst step of coating the substrate