United States Patent
`Tanaka et al.
`
`[19]
`
`US005.940528A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`5,940,528
`Aug. 17, 1999
`
`[54] PROCESS FOR POSITIONING OF A MASK
`RELATIVE TO ANOTHER MASK, OR
`MASKS RELATIVE TO A WORKPIECE AND
`DEVICE FOR EXECUTING THE PROCESS
`
`Attorney, Agent, or Firm—Sixbey, Friedman, Leedom &
`Ferguson; David S. Safran
`[57]
`ABSTRACT
`
`[75] Inventors: Yoneta Tanaka, Kanagawa-ken;
`Manabu Goto, Yokohama, both of
`Japan
`
`[73] Assignee: Ushiodenki Kabushiki Kaisha, Tokyo,
`Japan
`
`A process for positioning, in which a dummy is not used, in
`which multichromatic light can be used as the light source
`for purposes of alignment, and in which aberration correc
`tion is unnecessary, and a device for executing the process
`is achieved according to the invention by executing projec
`tion onto a first mask by projection lenses in which at least
`the workpiece facing sides of the lenses are telocentric. In a
`[21] Appl. No.: 08/688,006
`state in which a workpiece is remote, light with exposure
`[22] Filed:
`Jul. 29, 1996
`wavelengths is emitted from a light irradiation part onto a
`[30]
`Foreign Application Priority Data
`second mask. The first mask (or second mask) is moved such
`that the projected images of the alignment marks of the
`Jul. 28, 1995
`|JP]
`Japan .................................... 7–1929.47
`second mask and the alignment marks of the first mask come
`[51] Int. Cl." … G06K 9/00
`to lie on top of one another. Furthermore, the irradiation light
`[52] U.S. Cl. ..................
`... 382/151; 382/145
`is branched off by beam splitters and positions of the
`[58] Field of Search ..................................... 382/151, 152,
`alignment marks of the second mask are stored. Next,
`382/153; 356/139.04, 139.05, 399, 400,
`emission of the light with exposure wavelengths is stopped,
`401; 430/22, 5; 359/754, 760
`a workpiece is inserted into a predetermined position, from
`another light irradiation part light multichrome with nonex
`posure wavelengths is emitted, positions of the alignment
`marks of the workpiece are determined and the workpiece is
`moved to bring these alignment marks into position on top
`of the stored position of the alignment marks of the second
`mask.
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,159,496 10/1992 Kataoka .................................... 430/22
`5,418,092 5/1995 Okamoto ..................................... 430/5
`5,721,079 2/1998 Goto .......................................... 430/22
`Primary Examiner—Jose L. Couso
`Assistant Examiner—Duy M. Dang
`
`
`
`
`
`Upper Lamp
`Housing
`
`Upper
`M1
`Mask
`S
`
`HM1
`
`MA1
`
`
`
`5 Claims, 7 Drawing Sheets
`
`Alignment Unit
`
`Align. º AD1
`Insertion
`Removal Dev.] c'MSD1
`
`(X,Y,0)
`Mosk/Projection
`tºwn
`(Z Axis)
`
`-
`
`(X,Y,0)
`WSD
`
`Mask Carrier
`Movement Device for
`th
`e Upper Mask
`
`M/LD
`Workpiece Corrier
`Movement Device
`
`-
`
`-
`
`AD2
`
`CCD2
`
`------
`
`-
`-
`Aign. Unit
`Insertion/
`
`Device
`
`Bedm
`
`BS- Splitter
`ign. Mark WA1.
`7; ; ;
`W
`HM2 i?...]:
`:
`5 i Alignment Mark WA2
`LE
`:
`
`Aliqn.
`
`L2
`Projection Lens
`
`
`
`LH2
`
`Lower Lamp
`Housing
`
`Alignment Mark
`MA2
`
`--------------------
`
`MSD2
`
`Mosk Corrier
`Movement Device for
`the Lower Mask
`
`Legend3D, Inc. Ex. 2026-0001
`IPR2016-01243
`
`

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`U.S. Patent
`
`Aug. 17, 1999
`
`Sheet 1 of 7
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`5,940,528
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`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Sheet 2 of 7
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`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Sheet 3 of 7
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`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Legend3D, Inc. Ex. 2026-0005
`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Sheet 5 of 7
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`Legend3D, Inc. Ex. 2026-0006
`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Sheet 6 of 7
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`5,940,528
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`Legend3D, Inc. Ex. 2026-0007
`IPR2016-01243
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`U.S. Patent
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`Aug. 17, 1999
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`Sheet 7 of 7
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`5,940,528
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`Legend3D, Inc. Ex. 2026-0008
`IPR2016-01243
`
`

`

`1
`PROCESS FOR POSITIONING OF A MASK
`RELATIVE TO ANOTHER MASK, OR
`MASKS RELATIVE TO A WORKPIECE AND
`DEVICE FOR EXECUTING THE PROCESS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The invention relates to a process for positioning of one
`mask relative to another mask or positioning of a plurality of
`masks relative to a workpiece, and to a device for executing
`the process in an exposure device which is used for produc
`tion of a semiconductor device, a printed board, a liquid
`crystal display and the like.
`2. Description of Related Art
`Production of electrical and electronic components and
`parts of different types in which processing of structures in
`the micron range is necessary comprises an exposure pro
`cess. These electronic parts are semiconductor components,
`liquid crystal displays, printer heads of the ink jet type,
`multichip modules in which a plurality of various electronic
`components are produced on a substrate and thus a module
`is formed, and the like.
`A double-sided exposure system is used as one of these
`exposure systems, in which mask patterns, which are located
`above and below the workpiece, are transferred to both of its
`sides. In such double-sided exposure systems, the masks
`located above and below are positioned relative to one
`another, and thus, the patterns which are transferred to the
`surface and back of the workpiece are positioned relative to
`one another. Then, the masks are positioned relative to the
`workpiece. Patterns to be subsequently transferred are posi
`tioned exactly relative to the patterns on the workpiece
`which were formed beforehand.
`The above described positioning is conventionally done
`such that alignment marks of the two masks come to lie on
`top of one another, and that the alignment marks of the
`masks and the workpiece come to lie on top of one another.
`FIG. 6 schematically shows the conventional positioning
`of the masks relative to one another and of the masks relative
`to the workpiece in the above described double-sided expo
`sure system.
`In the drawing, the arrangement of a top mask M1, a
`bottom mask M2, top and bottom projection lenses L1 and
`L2, and alignment units A1, A2, each of which comprise, for
`example, a mirror, two lenses and an imager (CCD), is
`shown. Furthermore, a dummy D for positioning of upper
`mask M1 relative to lower mask M2 is provided having
`dummy alignment marks DAM on both side thereof.
`In the following, using FIG. 6, the positioning of the
`masks relative to one another and the positioning of the
`masks relative to the workpiece are described:
`A. Positioning of the masks relative to one another
`(1) The dummy D is inserted between the projection lens
`L1 and the projection lens L2. On both sides of the
`dummy D alignment marks DAM are recorded.
`(2) By irradiation with light of exposure wavelengths, the
`alignment marks MA1 of upper mask M1 and align
`ment marks MA2 of lower mask M2 are projected onto
`the respective sides of the dummy.
`(3) Alignment unit A1 is inserted between projection lens
`L1 and dummy D and Alignment unit A2 is inserted
`between projection lens L2 and dummy D.
`(4) Upper mask M1 and lower mask M2 are moved by a
`mask carrier movement device (not shown in this
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`figure), such that the projected images of the alignment
`marks MA1 of upper mask M1, the projected images of
`the alignment marks MA2 of the lower mask M2 and
`the dummy alignment marks DAM are brought to lie on
`top of one another by monitoring of the projected
`images on dummy D by means of the imagers of
`alignment units A1 and A2. In this way positioning is
`performed.
`B. Positioning of the masks relative to the workpiece
`(1) Dummy D and alignment unit A2 are removed and the
`workpiece is inserted in place of the dummy D. Work
`piece alignment marks for positioning relative to the
`alignment marks of the above described masks are
`recorded on the workpiece.
`(2) Light with nonexposure wavelengths is radiated
`through the upper mask M1 and projection lens L1.
`(3) As a result of the optical construction of projection
`lens L1 (likewise projection lens L2) with regard to the
`exposure light wavelengths, an imaging error or aber
`ration occurs, by which deviations of the imaging
`positions of the alignment marks MA1 of mask M1
`from the positions on the top of the workpiece occur.
`Upper mask M1 and projection lens L1 are, therefore,
`moved in the direction of the Z-axis (up and down in
`FIG. 6) at the same time by means of a Z-axis move
`ment device which is not shown in the drawings, and
`thus the above described deviations are corrected (for
`this principle, reference is made to Japanese patent
`application HEI 6-242532 and its counterpart, U.S. Ser.
`No. 08/540,390, which was filed in the name of one of
`the present inventors, and which is commonly owned
`with this application).
`(4) The workpiece is moved such that the workpiece
`alignment marks on the top of the workpiece agree with
`the projection images of alignment marks MA1 of
`upper mask M1 by monitoring by means of the imagers
`of alignment unit A1. In this way, alignment is per
`formed.
`(5) Alignment unit A1 are removed. Upper mask M1
`which was moved according to above described item
`(3) and projection lens L1 are moved back into their
`previous positions.
`In the above described art, however, the following is
`considered disadvantageous:
`A. Positioning of the upper mask relative to the lower
`mask
`(1) It is difficult to produce dummy D in which alignment
`marks DAM of the two sides are in a set positional
`relationship with respect to one another.
`(2) The workpiece does not always have a constant
`thickness, and can have different thicknesses. It is,
`therefore, necessary to make available a dummy D for
`each thickness of the workpiece. Furthermore, there are
`workpieces in which the positions of the alignment
`marks are different, the dummy must be prepared
`according to the workpiece alignment marks.
`Especially in the case of alignment using dummy D with
`a thickness which differs from the thickness of the
`workpiece, the two sides of the workpiece cannot be
`exposed at the same time, and step-by-step exposure must be
`performed. This means that, here, it is necessary to move the
`positions of the projection lens and the workpiece in the
`direction of the Z-axis, and to expose the other side of the
`workpiece after alignment and exposure have been per
`formed for the first side of the workpiece.
`(3) It is necessary to position the upper mask relative to
`the lower mask every two to five minutes, and to insert
`
`Legend3D, Inc. Ex. 2026-0009
`IPR2016-01243
`
`

`

`3
`the dummy each time in order to correct deviations of
`the positional relationship of the upper mask to the
`lower mask which occur due to temperature changes.
`Especially when the device is started, there are large
`temperature changes within it. In this case, it is neces
`sary to frequently correct the above described posi
`tional deviations.
`B. Positioning of the upper and lower masks relative to
`the workpiece and in double-sided exposure
`(1) Due to use of light with nonexposure wavelengths
`during workpiece alignment, the aberration correction
`described in item (3) in the above described prior art must
`be done for the respective alignment.
`However, it is unnecessary to accomplish the above
`described aberration correction if, with respect to the
`light with the exposure wavelengths (for example of
`the g-line), high image resolution is accomplished
`and a projection lens with a small aberration both
`with respect to light with exposure wavelengths and
`also with respect to light with nonexposure wave
`lengths (for example of the e-line) is used, as is
`shown in FIG. 7. However it is difficult to produce a
`lens of this type.
`(2) The light with nonexposure wavelengths must be
`monochrome light. This means that width AZ in the
`imaging positions (aberration becomes greater), and as
`a result thereof, a deviation occurs if the light with
`nonexposure wavelengths has a wavelength width of
`A), to a certain extent, as is shown in FIG. 8. It is
`therefore necessary to use monochrome light for the
`light with nonexposure wavelengths. The wavelength
`width as monochrome light is a half width of roughly
`+2 nm.
`In the case of using monochrome light however inter
`ference of light which is reflected from the photore
`sist surface occurs with the light which is reflected
`from the workpiece surface (or the surface of the
`base). This means that the resist layer thickness is
`roughly 1 to 5 microns; however, it has a variation of
`roughly 0.1 micron to 0.2 microns, as is shown in
`FIG. 9. Therefore as a result of the variation of the
`resist layer thickness, interference bands occur, as is
`shown for example in FIG. 10; this makes alignment
`difficult.
`(3) If, hypothetically, the light with exposure wavelengths
`is emitted as alignment light, it is necessary to sepa
`rately place an irradiation unit for the light with expo
`sure wavelengths (inserting it above the upper mask
`M1) for purposes of partial illumination and to irradiate
`the alignment marks of upper mask M1. However, even
`if the irradiation unit for light with exposure wave
`lengths is used for purposes of partial illumination, in
`the areas used for positioning on the workpiece, a
`circuit pattern or the like cannot be formed since,
`during positioning, the resist in the vicinity of the
`workpiece alignment marks is exposed to the action of
`exposure light. As a result, the areas which can be used
`become smaller.
`(4) In the case of using light with exposure wavelengths,
`it is difficult for the light to reach the surface of the
`workpiece (or the surface of the base), since the light
`with exposure wavelengths is easily absorbed by the
`photoresist. Therefore, it becomes difficult to determine
`the alignment marks.
`SUMMARY OF THE INVENTION
`The invention was made to eliminate the above described
`disadvantages in the prior art.
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`Therefore, a first object of the invention is to devise a
`process for positioning of one mask relative to another, in
`which a dummy is not used, and in which, furthermore,
`deviations of the positional relationship of an upper mask to
`a lower mask as a result of temperature changes can be
`easily corrected, and to devise a device for executing the
`process.
`A second object of the invention is to devise a process for
`positioning an upper mask and a lower mask relative to a
`workpiece, in which no aberration correction is necessary, in
`which, furthermore, it is unnecessary to produce a projection
`lens which has small aberration both with respect to the light
`with exposure wavelengths and also with respect to the light
`with nonexposure wavelengths, and to devise a device for
`executing the process.
`A third object of the invention is to devise a process for
`positioning an upper mask and a lower mask relative to a
`workpiece, in which multichromatic light can be used as the
`light source for alignment, in which no interference bands
`are formed which are caused by variation of the resist layer
`thickness, and in which alignment marks are easily
`determined, and to devise a device for executing the process.
`A fourth object of the invention is to devise a process for
`positioning an upper mask and a lower mask relative to a
`workpiece in which, during positioning, the resist on the
`workpiece is not exposed to the action of exposure light, and
`in which circuit patterns can be formed in the areas used for
`positioning, and to devise a device for executing the process.
`The above described objects are achieved according to a
`first embodiment in that positioning of one mask relative to
`another mask is done by emitting light with exposure
`wavelengths from a first light irradiation part onto alignment
`marks of a first mask, by recording alignment marks of the
`second mask and the projection images of the alignment
`marks of the first mask and subjecting them to image
`processing, projecting them through a first projection lens
`and a second projection lens onto the second mask, in which
`at least the sides opposite the mask sides are telecentric, by
`computing the data of the relative positions of the two
`alignment marks, and by moving the second mask and/or the
`first mask such that the above described two alignment
`marks come to lie on top of one another.
`The above described objects are achieved according to a
`second embodiment in that positioning of masks relative to
`a workpiece is performed in a state in which the workpiece
`is remote, light with exposure wavelengths is emitted from
`a first light irradiation part onto alignment marks of a first
`mask, the alignment marks of a second mask and projection
`images of the alignment marks of the first mask are recorded
`and are projected onto the second mask through a first
`projection lens and a second projection lens, in which at
`least the workpiece sides are telecentric, then the relative
`positions of the two alignment marks are determined, and
`based on data of the relative positions of the above described
`two alignment marks, the second mask and/or the first mask
`is/are moved such that the two alignment marks come to lie
`on top of one another. Furthermore, the light which irradi
`ates the alignment marks of the first mask is deflected or
`branched between the first projection lens and the second
`projection lens, the alignment marks of the first mask are
`recorded, the relative positions thereof are determined/
`stored, after which emission of the light with the exposure
`wavelengths from the first light irradiation part is stopped, a
`workpiece is inserted in a predetermined position between
`the first projection lens and the second projection lens, and
`light with nonexposure wavelengths is emitted from a sec
`
`Legend3D, Inc. Ex. 2026-0010
`IPR2016-01243
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`

`5
`ond light irradiation part onto alignment marks of the
`workpiece, the alignment marks of the workpiece are
`recorded and their relative positions are determined/stored.
`Based on the previously stored data of the relative positions
`of the alignment marks of the first mask and based on data
`of the relative positions of the alignment marks of the
`workpiece, the workpiece is moved such that the two come
`to lie on top of one another.
`The above described objects are achieved according to a
`third embodiment in that positioning of masks to a work
`piece is done by the fact that in a state in which the
`workpiece is remote, from a first light irradiation part light
`with exposure wavelengths is emitted onto alignment marks
`of a first mask, that the light which irradiates the alignment
`marks of the above described first mask is transmitted by a
`first projection lens, in which at least the workpiece side is
`telecentric, that the above described transmission light is
`branched into first branched light and second branched light,
`that the above described first branched light is transmitted by
`a second projection lens in which at least the workpiece side
`is telecentric, that projection images of the alignment marks
`of the first mask which are projected onto the second mask,
`and alignment marks of the second mask are recorded, that
`relative positions of the two alignment marks are
`determined, that using the above described second branched
`light the alignment marks of the above described first mask
`are recorded, that the relative positions thereof are
`determined/stored, that based on data of the relative posi
`tions of the above described two alignment marks the second
`mask and/or the first mask is/are moved such that the above
`described two alignment marks come to lie on top of one
`another, that emission of the light with exposure wave
`lengths from the first light irradiation part is stopped, that a
`workpiece is inserted in a stipulated position between the
`first projection lens and the second projection lens, that from
`a second light irradiation part light with nonexposure wave
`lengths is emitted onto alignment marks of the workpiece,
`that the alignment marks of the above described workpiece
`are recorded and their relative positions are determined/
`stored, that based on the previously stored data of the
`relative positions of the alignment marks of the first mask
`and based on data of the relative positions of the alignment
`marks of the above described workpiece, the workpiece is
`moved such that the two come to lie on top of one another.
`The above described objects are achieved according to a
`fourth embodiment in that, in a device for positioning one
`mask relative to another mask, there are a first mask, a first
`mask carrier movement device for moving the first mask, a
`first projection lens, of which at least the side opposite the
`mask side is telecentric, a second mask, a second mask
`carrier movement device for moving the second mask, a
`second projection lens, of which at least the side opposite the
`mask side is telecentric, a light irradiation part for irradiating
`alignment marks of the first mask with light with the
`exposure wavelengths, a camera means which records pro
`jection images of the alignment marks of the first mask by
`the light with exposure wavelengths emitted from the light
`irradiation part and records the alignment marks of the
`second mask, and a control means which, based on the
`image data recorded by the camera means controls the first
`mask carrier movement part and/or the second mask carrier
`movement part. Furthermore, the control means records the
`alignment marks of the second mask and the projection
`images of the alignment marks of the first mask which are
`projected through the first projection lens and the second
`projection lens onto the second mask, performs image
`processing and determines the relative positions thereof, if
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`the light irradiation part emits light with exposure
`wavelengths, and the control means computes the data of the
`relative positions of the two alignment marks and moves the
`second mask and/or the first mask such that the two align
`ment marks come to lie on top of one another.
`The above described objects are achieved according to a
`fifth embodiment by the fact that, in a device for positioning
`of masks relative to a workpiece, there are a first mask, a first
`mask carrier movement device for moving the above
`described first mask, a first projection lens, of which at least
`the side opposite the mask side is telecentric, a workpiece,
`a workpiece carrier movement device for moving the
`workpiece, a second mask, a second mask carrier movement
`device for moving the second mask, a second projection
`lens, in which at least the side opposite the mask side is
`telecentric, a first light irradiation part for irradiating align
`ment marks of the first mask with light with exposure
`wavelengths, a second light irradiation part for irradiating
`alignment marks of the workpiece with light with nonex
`posure wavelengths, a first camera means which records
`projection images of the alignment marks of the first mask
`by the light with exposure wavelengths emitted from the first
`light irradiation part and records the alignment marks of the
`second mask, a light branching means for branching the light
`which irradiates the alignment marks of the first mask
`between the first projection lens and the second projections
`lens, or a light deflection means for deflecting the irradiation
`light, and a second camera means which records projection
`images of the alignment marks of the first mask by the light
`branched by means of the light branching means, or the light
`deflected by the light deflection means, and records the
`alignment marks of the workpiece by the light with nonex
`posure wavelengths emitted from the second light irradiation
`part. Furthermore, a control means which, based on the
`image data recorded by the first camera means, controls the
`first mask carrier movement device and/or the second mask
`carrier movement device, which controls the first mask
`carrier movement device and/or the second mask carrier
`movement device based on the image data recorded by the
`first camera means, and which controls the workpiece carrier
`movement device based on the image data recorded by the
`second camera means. In the state in which the workpiece is
`remote, the control means has the light irradiation part emit
`light with exposure wavelengths, the control means records
`the alignment marks of the second mask and the projection
`images of the alignment marks of the first mask which are
`projected through the first projection lens and the second
`projection lens onto the second mask, performs image
`processing and determines the relative positions thereof,
`then the control means computes data of the relative posi
`tions of the alignment marks of the second mask and the
`projection images of the alignment marks of the first mask,
`moves the second mask and/or the first mask such that the
`two come to lie on top of one another. Additionally, the
`control means records the projection images of the align
`ment marks of the above described first mask by the
`branched light in which the light irradiating the alignment
`marks of the above described first mask was branched
`between the first projection lens and the second projection
`lens, or by the deflected light in which the irradiation light
`was deflected, performs image processing and determines/
`stores the relative positions thereof, after which the control
`means stops emission of light with exposure wavelengths
`from the first light irradiation part and inserts the workpiece
`in a predetermined position between the first projection lens
`and the second projection lens. Then, the control means has
`the second light irradiation part emit light with nonexposure
`
`Legend3D, Inc. Ex. 2026-0011
`IPR2016-01243
`
`

`

`7
`wavelengths, records the alignment marks of the workpiece,
`performs image processing and determines the relative posi
`tions thereof, and based on the previously stored data of the
`relative positions of the alignment marks of the first mask
`and based on the data of the relative positions of the
`alignment marks of the workpiece, the control means moves
`the workpiece such that the two come to rest on top of one
`another.
`The above described objects are achieved according to a
`sixth embodiment by the fact that, in a device for positioning
`of masks relative to a workpiece, there are a first mask, a first
`mask carrier movement device for moving the above
`described first mask, a first projection lens, of which at least
`the side opposite the mask is telecentric, a workpiece, a
`workpiece carrier movement device for moving the
`workpiece, a second mask, a second mask carrier movement
`device for moving the second mask, a second projection
`lens, of which at least the side opposite the mask is
`telecentric, a first light irradiation part for irradiating align
`ment marks of the first mask with light with the exposure
`wavelengths, a second light irradiation part for irradiating
`alignment marks of the workpiece with light with nonex
`posure wavelengths, a first camera means which records
`projection images of the alignment marks of the first mask
`by the light with exposure wavelengths emitted from the first
`light irradiation part and records the alignment marks of the
`second mask, a light branching means for branching of the
`light which irradiates the alignment marks of the first mask
`between the first projection lens and the second projections
`lens, a second camera means which records projection
`images of the alignment marks of the first mask by the light
`branched by means of the above described light branching
`means, and records the alignment marks of the workpiece by
`the light with nonexposure wavelengths emitted from the
`second light irradiation part, and a control means which,
`based on the image data recorded by the first camera means
`controls the first mask carrier movement device and/or the
`second mask carrier movement device and which controls
`the workpiece carrier movement device based on image data
`recorded by the second camera means. Furthermore, in the
`state in which the workpiece is remote, the control means
`has the light irradiation part emit light with exposure
`wavelengths, and the control means records the alignment
`marks of the second mask and the projection images of the
`alignment marks of the first mask which are projected
`through the first projection lens and the second projection
`lens onto the second mask, performs image processing, and
`determines the relative positions thereof. At the same time,
`the control means records the projected images of the
`alignment marks of the first mask by the branched light in
`which the light which irradiates the alignment marks of the
`first mask was branched between the first objective lens and
`the second objective lens, performs image processing and
`determines/stores the relative positions thereof. The control
`means computes data of the relative positions of the align
`ment marks of the second mask and the projected images of
`the alignment marks of the first mask, causes the second
`mask and/or the first mask to be moved such that the two
`come to lie on top of one another, and then the control means
`stops emission of the light with exposure wavelengths from
`the first light irradiation part and inserts the workpiece in a
`predetermined position between the first projection lens and
`the second projection lens, and has the second light irradia
`tion part emit light with nonexposure wavelengths, records
`the alignment marks of the workpiece, performs image
`processing and determines the relative positions thereof.
`Additionally, the control means, based on the previously
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`stored data of the relative positions of the alignment marks
`of the first mask and based on the data of the relative
`positions of the alignment marks of the workpiece causes the
`movement of the workpiece such that the two come to rest
`on top of one another.
`In the invention described above with respect to the first
`and fourth embodiments, light with exposure wavelengths is
`emitted from the light irradiation part onto the alignment
`marks of the first mask. In this case, furthermore, the
`alignment marks of the second mask and the projection
`images of the alignment marks of the first mask are recorded
`and undergo image processing and are projected through the
`first projection lens and the second projection lens onto the
`second mask, of which at least the sides opposite the mask
`sides are telecentric, and their relative positions are deter
`mined. Furthermore, the data of the relative positions of the
`two alignment marks are computed and the second mask
`and/or the first mask is moved such that the two alignment
`marks come to lie on top of one another. By this measure,
`positioning of one mask relative to another can be done
`without using a dummy which is difficult to manufacture and
`in which the alignment marks on the two sides have a set
`relationship to one another. Additionally, it is no longer
`necessary by the measure according to the invention to make
`available a dummy according to each thickness of the
`workpiece.
`In addition, according to the invention, deviations as a
`result of temperature changes can be easily corrected since,
`in the correction of the deviations of the positional relation
`ship of the upper mask relative to the lower mask as a result
`of temperature changes, no dummy need be inserted.
`In the invention described in the above relative to the
`second, third, fifth and sixth embodiments, positioning of
`one mask relative to another mask is performed in the same
`way as with respect to the first and fourth embodiments, and
`furthermore, the light which irradiates the alignment marks
`of the first mask is branched or deflected, the alignment
`marks of the first mask are recorded, their relative positions
`are determined/