(19) Japan Patent
`
`(12) Publication of
`
`(11) Publication Number of Patent
`
`Office (JP)
`
`Patent Application
`
`Application: 11-135400
`
`
`
`(A)
`
`
`
`(51) Int. Cl.6: Domestic
`Classification Symbol
`H01L 21/027
`
`G03F 7/20 521
`
`
`
`(21) Application Number: Patent
`Application
`9-299775
`
`
`(22) Application Date:
`
`
`
`October 31,
`1997
`
`(43) Date of Publication of Application:
`
`May 21, 1999
`
`FI:
`H01L21/30 516 B
`G03F7/20
`521
`H01L21/30 516 C
`
`
`518
`Request for Examination: Not made
`Number of Claims: 15 OL (13 pages
`in total)
`
`
`000004112
`(71) Applicant:
`
`Nikon Corporation
`
`2-3, Marunouchi 3-chome,
`
`Chiyoda-ku, Tokyo
`
`Tetsuo Taniguchi
`(72) Inventors:
`
`c/o Nikon Corporation
`
`2-3, Marunouchi 3-chome,
`
`Chiyoda-ku, Tokyo
`
`(74) Agent: Patent Attorney, Satoshi
`Ohmori
`
`Nikon Exhibit 1013 Page 1
`
`

`

`
`(54) [Title of the Invention]
`LITHOGRAPHIC PRINTER
`(57) [Abstract]
`[Problem] to reduce the size of the reticle or wafer aligning stage while maintaining
`the function to measure the exposure light state or the imaging characteristics.
`[Means for Resolution] A wafer W is put on a wafer stage WST that is arranged to
`move in X and Y directions over a base 13. A reticle-pattern image is printed in an
`exposure area 12 over the wafer W and the reticle and the wafer W are scanned in the Y
`direction, thereby effecting a printing. A measurement stage 14 is arranged over the
`base 13, to move in X and Y directions independently of the wafer stage WST. On the
`measurement stage 14, there is formed a spatial-image detecting system including an
`illumination-dosage monitor 18, an illuminance-nonuniformity sensor 19 and a
`measurement plate 20 with a slit formed thereon. Because the wafer stage WST is
`satisfactorily provided with the minimally required functions for printing, the wafer
`stage WST can be reduced in size and weight.
`
`
`
`
`
`
`
`Nikon Exhibit 1013 Page 2
`
`

`

`[Claims]
`[Claim 1] A printer that transfers a pattern formed on a mask onto a substrate by use of
`an exposure beam, the printer comprising: a first stage that holds either the mask or the
`substrate and moves across a predetermined area; a second stage that is independent of
`the first stage; and a measuring instrument that is attached on the second stage and
`measures a state of the exposure beam.
`[Claim 2] A printer according to claim 1, wherein the second stage is arranged to move
`independently of the first stage.
`[Claim 3] A printer according to claim 1, comprising a control unit that causes the first
`stage to move between a position to which the exposure beam is to be irradiated and a
`position to which the exposure beam is not to be irradiated.
`[Claim 4] A printer according to claim 2, comprising a control unit that causes the
`second stage to move between a position to which the exposure beam is to be irradiated
`and a position to which the exposure beam is not to be irradiated.
`[Claim 5] A printer according to claim 1, comprising a control unit that aligns the
`second stage to a position to which the exposure beam is not to be irradiated when the
`first stage is in a position to which the exposure beam is to be irradiated.
`[Claim 6] A printer that projects a pattern formed on a mask onto a substrate through a
`projection optical system, the printer comprising: a first stage that holds the substrate
`and moves across a predetermined area; a second stage that is independent of the first
`stage; and a measuring instrument that is arranged on the second stage and measures an
`imaging characteristic of the projection optical system.
`[Claim 7] A printer according to claim 6, wherein the second stage is arranged to move
`independently of the first stage.
`[Claim 8] A printer according to claim 6, comprising a control unit that causes the first
`stage to move between a position within an exposure area of the projection optical
`
`Nikon Exhibit 1013 Page 3
`
`

`

`system and a position outside the exposure area.
`[Claim 9] A printer according to claim 6, comprising a control unit that causes the
`second stage to move between a position of within an exposure area of the projection
`optical system and a position outside the exposure area.
`[Claim 10] A printer that transfers a pattern formed on a mask onto a substrate by use
`of an exposure beam, the printer comprising: a stage arranged with a measuring
`instrument that measures a state of the exposure beam; and a cooling device that is
`provided on the stage and cools the measuring instrument.
`[Claim 11] A printer that projects a pattern formed on a mask onto a substrate through
`a projection optical system, the printer comprising: a stage arranged with a measuring
`instrument that measures an imaging characteristic of the projection optical system; and
`a cooling device that is provided on the stage and cools the measuring instrument.
`[Claim 12] A printer that transfers a pattern formed on a mask onto a substrate by use
`of an exposure beam, the printer comprising: a first stage that holds either the mask or
`the substrate and moves across a predetermined area; a second stage mounted with a
`measuring instrument that measures a state of the exposure beam; and a heat insulation
`member that is arranged between the first stage and the second stage and cuts off heat
`conducting from the second stage.
`[Claim 13] A printer according to claim 12, wherein the heat insulation member is of a
`solid material low in thermal conductivity or a gas regulated in temperature.
`[Claim 14] A printer that projects a pattern formed on a mask onto a substrate through
`a projection optical system, the printer comprising: a first stage that holds the substrate
`and moves across a predetermined area; a second stage mounted with a measuring
`instrument that measures an imaging characteristic of the projection optical system; and
`a heat insulation member that is arranged between the first stage and the second stage
`and cuts off heat conducting from the second stage.
`
`Nikon Exhibit 1013 Page 4
`
`

`

`[Claim 15] A printer according to claim 14, wherein the heat insulation member is of a
`solid material low in thermal conductivity or a gas regulated in temperature.
`[Detailed description of the Invention]
`[0001]
`[Technical field to Which the Invention Belongs] The present invention relates to a
`lithographic printer for use in transferring a mask pattern onto a photosensitive substrate
`in a lithography process to manufacture, say, a semiconductor device, a liquid-crystal
`device or a thin-film magnetic head, which more particularly is suited in use on a printer
`having a measuring instrument that measures an exposure beam state, an imaging
`characteristic or the like.
`[0002]
`[Prior Art] In the manufacture of a semiconductor device or the like, the printer of the
`one-shot exposure type (stepper) conventionally is frequently used in the transfer
`process of an on-reticle pattern, as a mask, onto a resist-applied wafer (or a glass plate or
`the like) under the existence of predetermined exposure light. Recently, attentions are
`also drawn to such a scanning-exposure type projection printer (scanning printer) as of a
`step-and-scan scheme that performs a printing by synchronously scanning the reticle and
`the wafer relative to a projection optical system, in order to accurately transfer a reticle
`pattern having a great area without increasing the size of the projection optical system.
`[0003] Those printers are required to make a printing at a proper exposure and in a
`state maintaining the imaging characteristics high. For this reason, a measuring
`instrument is provided on a reticle stage to align the reticle or on a wafer stage to align
`the wafer, in order to measure the illuminance state of exposure light, etc. and the
`imaging characteristics including projective magnification, etc. For example, the
`measuring instruments provided on the wafer stage include an irradiation-dosage
`monitor that measures the incident energy of exposure light upon the projection optical
`
`Nikon Exhibit 1013 Page 5
`
`

`

`system, a spatial-image detecting system that measures the position, contrast, etc. of a
`projection image. Meanwhile, the measuring instruments provided on the reticle stage
`include, say, a reference plate with an index mark formed thereon for use in measuring
`the imaging characteristics of the projection optical system.
`[0004]
`[Problem that the Invention is to Solve] In the conventional printer like the above,
`exposure is kept properly while maintaining the imaging characteristics high, by use of
`the measuring instruments provided on the reticle or wafer stage. On the contrary, the
`recent printer is required to enhance the throughput (productivity) in the printing process,
`in the manufacture of a semiconductor device or the like. The throughput-improving
`methods include a method to increase the exposure energy per unit time. Besides, there
`is a method in which the stage drive rate is increased to reduce the stepping time in the
`one-shot exposure type and to reduce the time of stepping and scanning exposure in the
`scanning exposure type.
`[0005] In this manner, in order to improve the stage drive rate, it is satisfactory to use
`a drive motor having a greater output when the stage systems are in the same size.
`Conversely, in order to improve the drive rate by means of a drive motor equal in output
`to the conventional one, the stage systems must be reduced in size and weight.
`However, when using a drive motor having a high output as in the former case, there is
`an increase of the heat caused at the drive motor. The increasing amount of heat causes
`delicately a thermal deformation in the stage system, possibly making it difficult to
`obtain such a high alignment accuracy as required for the printer. Therefore, there is a
`desire to make the stage system smaller in size and lighter in weight to a possible extent
`as in the latter case, in order to prevent the deterioration of alignment accuracy and
`improve the drive rate.
`[0006] Particularly, the scanning-exposure type printer has the major advantage that
`
`Nikon Exhibit 1013 Page 6
`
`

`

`the improvement of drive rate reduces the scanning exposure time and greatly improves
`the throughput while the size reduction of the stage system improves the synchronous
`accuracy between a reticle and a wafer, thereby improving also the imaging
`characteristics and overlay accuracy. Nevertheless, there encounters a difficulty in
`size-reducing the stage where various measuring instruments are provided on the reticle
`or wafer stage.
`[0007] Furthermore, when the reticle or wafer stage has a measuring instrument that
`measures an exposure light state, an imaging characteristic or the like, the measuring
`instrument usually includes a heat source such as an amplifier wherein the temperature
`of the measuring instrument is increased gradually by the irradiation of exposure light
`during measurement. As a result, the reticle or wafer stage delicately deforms to
`possibly deteriorate the alignment accuracy, overlay accuracy, etc. In the present
`situation, the deterioration of alignment accuracy, etc. are less in extent on the measuring
`instrument. In the future, the measuring instrument is expectedly required to suppress
`the effect of temperature rise to a greater extent as the circuit pattern is downscaled
`furthermore for a semiconductor device or the like.
`[0008] The present invention is in view of the foregoing points, and it is a first object
`of the present invention to provide a printer that the reticle or wafer aligning stage can
`be reduced in size in the state maintaining the function to measure the exposure light
`state or the imaging characteristics. The invention has a second object to provide a
`printer having a measuring instrument to measure the exposure light state or the imaging
`characteristics and capable of reducing the adverse effect of temperature rise during
`measurement by use of the measuring instrument.
`[0009]
`[Means for Solving the Problem] A first printer according to the invention is a printer
`that transfers a pattern formed on a mask (R) onto a substrate (W) by use of an exposure
`
`Nikon Exhibit 1013 Page 7
`
`

`

`beam, the printer comprising: a first stage (RST, WST) that holds either the mask or the
`substrate and moves across a predetermined area; a second stage (5, 14) that is
`independent of the first stage; and a measuring instrument (6, 18) that is attached on the
`second stage and measures a state of the exposure beam.
`[0010] According to the invention, the first stage for primary use in printing is
`provided with a minimally required function for printing so that the first stage can be
`made in a minimally required size, thereby making it possible to make the stage smaller
`in size and lighter in weight. Meanwhile, the measuring instrument for measuring the
`illuminance, etc. of an exposure beam ,not directly required for printing, is mounted on
`the separate second stage, thus enabling also to measure the state of an exposure beam.
`[0011] In this case, the measuring instrument is, say, a photoelectric sensor that
`measures the total power of an exposure beam, an illuminance-nonuniformity sensor that
`measures the illuminance distribution of such an exposure beam, or the like.
`Meanwhile, the second stage is, say, arranged to move independently of the first stage
`on the movement plane of the first stage. At this time, by arranging the second stage in
`place of the first stage, the state of an exposure beam can be measured in the vicinity of
`the plane where the substrate is actually put.
`[0012] Meanwhile, a control unit (10) is desirably included that causes the first stage
`to move between a position to which the exposure beam is to be irradiated and a position
`to which the exposure beam is not to be irradiated. At this time, during measurement,
`the first stage is retracted from the position where an exposure beam is irradiated.
`Meanwhile, a control unit (10) is desirably included that causes the second stage to
`move between a position to which the exposure beam is to be irradiated and a position to
`which the exposure beam is not to be irradiated. This allows the measuring instrument
`of the second stage to move to the position to which an exposure beam is to be
`irradiated.
`
`Nikon Exhibit 1013 Page 8
`
`

`

`[0013] Meanwhile, a control unit (10) is desirably included that aligns the second
`stage in a position to which the exposure beam is not to be irradiated when the first stage
`is in a position to which the exposure beam is to be irradiated. This makes it possible
`to use the two stages in turn with efficiency during printing or during measurement.
`Next, a second printer according to the invention is a printer that projects a pattern
`formed on a mask (R) onto a substrate (W) through a projection optical system (PL), the
`printer comprising: a first stage (WST) that holds the substrate and moves across a
`predetermined area; a second stage (14) that is independent of the first stage; and a
`measuring instrument (20) that is arranged on the second stage and measures an imaging
`characteristic of the projection optical system.
`[0014] According to the invention, the first stage for primary use in printing is
`provided with a minimally required function for printing so that the first stage can be
`made in a minimally required size, thereby making it possible to make the first stage
`smaller in size and lighter in weight. Meanwhile, the measuring instrument, for
`measuring the imaging characteristics such as distortion , not directly required for
`printing, is mounted on the separate second stage, thus enabling also to measure the
`imaging characteristics.
`[0015] In this case, the measuring instrument is, say, a projection-image position
`sensor, a measuring index mark, a measuring reference plane or the like. Meanwhile,
`the second stage is, say, arranged to move independently of the first stage on the
`movement plane of the first stage. At this time, by arranging the second stage in place
`of the first stage, the imaging characteristics can be measured on the plane where the
`substrate is actually put.
`[0016] Meanwhile, a control unit (10) is desirably included that causes the first stage
`to move between a position within an exposure area of the projection optical system and
`a position outside the exposure area. At this time, during measurement, the first stage
`
`Nikon Exhibit 1013 Page 9
`
`

`

`is retracted from the exposure area. Likewise, a control unit (10) is desirably included
`that causes the second stage to move between a position within an exposure area of the
`projection optical system and a position outside the exposure area. At this time, during
`measurement, the measuring instrument of the second stage moves to the exposure area.
`[0017] Next, a third printer according to the invention is a printer that transfers a
`pattern formed on a mask (R) onto a substrate (W) by use of an exposure beam, the
`printer comprising: a stage (41) arranged with a measuring instrument (18, 19) that
`measures a state of the exposure beam; and a cooling device (44, 45A, 45B) that is
`provided on the stage and cools the measuring instrument. According to the invention,
`even in case the measuring instrument is used and the temperature of the measuring
`instrument rises upon measuring the illuminance, etc. of the exposure beam, it can be
`cooled by the cooling device, thus exerting no effects of temperature rise to the exposure
`area.
`[0018] Next, a fourth printer according to the invention is a printer that projects a
`pattern formed on a mask (R) onto a substrate (W) through a projection optical system
`(PL), the printer comprising: a stage (41) arranged with a measuring instrument (20, 42,
`43) that measures an imaging characteristic of the projection optical system; and a
`cooling device (44, 45A, 45B) that is provided on the stage and cools the measuring
`instrument. According to the invention, even in case the measuring instrument is used
`and the temperature of the measuring instrument rises upon measuring the imaging
`characteristics, it can be cooled by the cooling device, thus exerting no effects of
`temperature rise to the exposure area.
`[0019] Next, a fifth printer according to the invention is a printer that transfers a
`pattern formed on a mask (R) onto a substrate (W) by use of an exposure beam, the
`printer comprising: a first stage (WST, 41A) that holds either the mask or the substrate
`and moves across a predetermined area; a second stage (14, 41Aa) mounted with a
`
`Nikon Exhibit 1013 Page 10
`
`

`

`measuring instrument (18, 19) that measures a state of the exposure beam; and a heat
`insulation member (48) that is arranged between the first stage and the second stage and
`cuts off heat conducting from the second stage. According to the invention, even in
`case the measuring instrument includes a heat source or the temperature of the
`measuring instrument rises upon measuring the illuminance, etc. of the exposure beam
`by use of the measuring instrument, the heat insulation member hinders the conduction
`of heat, thus exerting no effects of temperature rise to the exposure area.
`[0020] In this case, the heat insulation member is, say, of a solid material (48) low in
`thermal conductivity or a gas regulated in temperature. Such a gas regulated in
`temperature uses a gas air-conditioned or the like. Next, a sixth printer according to the
`invention is a printer that projects a pattern formed on a mask (R) onto a substrate (W)
`through a projection optical system (PL), the printer comprising: a first stage (WST,
`41A) that holds the substrate and moves across a predetermined area; a second stage (14,
`41Aa) mounted with a measuring instrument (20) that measures an imaging
`characteristic of the projection optical system; and a heat insulation member (48) that is
`arranged between the first stage and the second stage and cuts off heat conducting from
`the second stage. According to the invention, even in case the measuring instrument is
`used and the temperature of the measuring instrument rises upon measuring the imaging
`characteristics or the measuring instrument includes a heat source, the heat insulation
`member hinders the conduction of heat, thus exerting no effects of temperature rise to
`the exposure area.
`[0021] In this case, the heat insulation member is, say, of a solid material (48) low in
`thermal conductivity or a gas regulated in temperature.
`[0022]
`[Mode for Carrying Out the Invention] With reference to Figs. 1 to 4, explanation will
`be now made below on a first embodiment of the present invention. Fig. 1 shows a
`
`Nikon Exhibit 1013 Page 11
`
`

`

`projection printer of a step-and-scan scheme to be used in the present embodiment.
`During exposure in Fig. 1, the exposure light IL, emitted from an illumination system 1,
`including an exposure light source, a beam-forming optical system, an
`illuminance-uniformizing fly's-eye lens, a light-amount monitor, a variable aperture stop,
`a field stop and a relay lens, illuminates a reticle R at its slit-like illumination area of a
`pattern surface (lower surface) thereof through a mirror 2 and a condenser lens 3. As
`exposure light IL, excimer laser light such as KrF (wavelength: 248 nm) or ArF
`(wavelength: 193 nm), YAG-laser higher harmonics, mercury-lamp at i-line
`(wavelength: 365 nm) or the like can be used. By switching the variable aperture stop
`in the illumination system 1, illumination can be selected at choice from among the
`usual illumination, orbicular illumination, so-called modified illumination, illumination
`with a small coherent factor (σ value) and the like. In the case that the exposure light
`source is a laser light source, its emission timing, etc. are under control of the main
`control system 10 taking control of the apparatus overall operation, through a laser
`power source, (not shown).
`[0023] The pattern image of the reticle R, formed in an illumination area 9 (see Fig. 3)
`of the exposure light IL, is reduced at a projective magnification β (β: 1/4 times, 1/5
`times or the like) and projected to a slit-like exposure area 12 over a wafer W applied
`with photoresist. From now on, explanation is made with a Z-axis taken in parallel
`with an optical axis AX of the projection optical system PL, with an X-axis taken along
`the non-scanning direction (i.e. direction vertical to Fig. 1) orthogonal to the scanning
`direction of the reticle R and wafer W in scan exposure on a plane vertical to the Z-axis,
`and with a Y-axis taken along the scanning direction (i.e. direction parallel with Fig. 1).
`[0024] In the outset, an alignment sensor 16 of an image-processing scheme is
`provided adjacent to the projection optical system PL, according to an off-axis scheme
`for wafer-W alignment. The alignment sensor 16 has a detection signal that is supplied
`
`Nikon Exhibit 1013 Page 12
`
`

`

`to an alignment processing system of the main control system 10. The alignment
`sensor 16 is used to detect the position of an alignment mark (wafer mark) and the like
`formed on the wafer W. The spacing (baseline amount), between a detection center of
`the alignment sensor 16 and a center of a reticle-R projection image given by the
`projection optical system PL, is previously determined with accuracy and stored in an
`alignment processing system of the main control system 10. From the detection result
`of the alignment sensor 16 and the baseline amount thereof, alignment is accurately
`effected between a wafer-W shot area and a reticle-R projection image. Though not
`shown, a reticle-alignment microscope is arranged above the reticle R in order to detect
`the alignment mark on the reticle R.
`[0025] The reticle R is held on a reticle stage RST by vacuum clamp. The reticle
`stage RST is rested, moveable in the Y direction, over two guides 4A, 4B arranged
`parallel in the Y direction through bearings. Furthermore, in this embodiment, a
`measurement stage 5 is arranged, movable in the Y direction and independently of the
`reticle stage, over the guides 4A, 4B through air bearings.
`[0026] Fig. 3 is a plan view showing the reticle stage RST and measurement stage 5.
`In Fig. 3, the reticle stage RST and the measurement stage 5 are rested along the guide
`4A, 4B extending in the Y direction so that those can be each driven in the Y direction
`by means of a linear motor or the like (not-shown). The guides 4A, 4B have a length
`set up longer by at least a width of the measurement stage 5 than the movement stroke of
`the reticle stage RST during scan exposure. Meanwhile, the reticle stage RST is
`structured by a combination of a rough stage to move in the Y direction and a fine stage
`that is adjustable finely in position two-dimensionally over the rough stage.
`[0027] On the measurement stage 5, a reference plate 6 formed of a glass plate
`elongate in the X direction is fixed. On the reference plate 6, a plurality of index marks
`are formed in a predetermined arrangement in order to measure a imaging characteristics
`
`Nikon Exhibit 1013 Page 13
`
`

`

`of the projection optical system PL. The reference plate 6 has a size to cover the
`slit-like illumination area 9 of exposure light to the reticle R, more specifically a
`field-of-vision of the projection optical system PL on the side closer to the reticle R.
`The use of the reference plate 6 eliminates the need to prepare a exclusive reticle for
`imaging-characteristic measurement. Moreover, the exchange time is made
`unnecessary between the reticle R for actual printing and the exclusive reticle. This
`enables the frequent measurement of imaging characteristics, thus making it possible to
`correctly follow the change over time of the projection optical system PL.
`[0028] In this manner, the embodiment independently provide with the measurement
`stage 5 for the reference plate 6 wherein no measuring members but the reticle R are
`mounted on the reticle stage RST itself. Namely, because the reticle stage RST is
`satisfactorily provided with minimally required scanning and alignment functions for
`scan exposure, the reticle stage RST smaller in size and lighter in weight is realized.
`Accordingly, because the reticle stage RST can be scanned at faster rate, throughput
`improves in the printing process. Particularly in the case of reduced projection, the
`scan rate of the reticle stage RST is given 1/β times (e.g. four times or five times) the
`scan rate of the wafer stage. Thus, the upper limit of scan rate possibly is determined
`mostly by the reticle stage, in which case throughput particularly is improved
`significantly in the present embodiment.
`[0029] Meanwhile, from a laser interferometer 7Y set up in a +Y direction to the
`guides 4A, 4B, a laser beam is irradiated to a movement mirror on a +Y-directional side
`surface of the reticle stage RST. From biaxial laser interferometers 7X1, 7X2 set up in
`a +X direction, laser beams are irradiated to a movement mirror on a +X-directional side
`surface of the reticle stage RST. The laser interferometers 7Y, 7X1, 7X2 measure the
`X and Y coordinates and rotation angle of the reticle stage RST, of which measurement
`values are supplied to the main control system 10 in Fig. 1. The main control system
`
`Nikon Exhibit 1013 Page 14
`
`

`

`10 takes control of the rate and position of the reticle stage RST through the linear motor,
`etc., depending upon the measurement values. Meanwhile, from a laser interferometer
`8Y set up in a -Y direction relative to the guides 4A, 4B, a laser beam is irradiated to a
`movement mirror on a -Y-directional side surface of the measurement stage 5. The
`laser interferometer 8Y measures the Y coordinate of the measurement stage 5 that is
`supplied to the main control system 10. The Y-axis laser interferometers 7Y, 8Y have
`optical axes that respectively extend in the Y direction and pass the center of the
`illumination area 9, i.e. the optical axis AX of the projection optical system PL. The
`laser interferometers 7Y, 8Y both measure, at all times, the position of the reticle stage
`RST and measurement stage 5 in a scanning direction.
`[0030] During the measurement of imaging characteristics, in case the reticle stage
`RST is retracted in the +Y direction and the measurement stage 5 is moved in the Y
`direction in a manner the reference plate 6 covers the illumination area 9, the laser
`beams from the laser interferometers 7X1, 7X2 are moved off the side surface of the
`reticle stage RST and illuminated to the movement mirror on the +X-directional side
`surface of the measurement stage 5. Depending upon the measurement value obtained
`from the laser interferometers 8Y ,7X1 and 7X2 at this time, the main control system 10
`accurately controls the position of the measurement stage 5 through the linear motor, etc.
`Incidentally, on this occasion, in the case the reference plate 6 is desirably aligned more
`accurately with the illumination area 9, an alignment mark is satisfactorily formed on the
`reference plate 6 so that the mark can be detected in position by use of the
`reticle-alignment microscope.
`[0031] Meanwhile, during measurement, the reticle stage RS is not measured for the
`position in the non-scanning direction. However, when the reticle stage RST reaches
`below the illumination area 9 for printing, the laser beams from the laser interferometers
`7X1, 7X2 become irradiated again to the movement mirror of the reticle stage RST.
`
`Nikon Exhibit 1013 Page 15
`
`

`

`Because the final alignment is done by use of the reticle-alignment microscope, there are
`no inconvenient disconnections in the laser beam from the laser interferometers 7X1,
`7X2.
`[0032] Referring back to Fig. 1, the wafer W is held on the wafer stage WST through a
`wafer holder (not-shown). The wafer stage WST is arranged, for movement in the X
`and Y directions, upon the base 13 through an air bearing. The wafer stage WST is
`built therein with a focus-leveling mechanism taking control of the Z-directional
`position (in-focus position) and inclination angle of the wafer W. Meanwhile,
`separately from the wafer stage WST, a measurement stage 14 having a variety of
`measuring instruments is arranged upon the base 13 through an air bearing in a manner
`to move in the X and Y directions. The measurement stage 14 also is built therein with
`a mechanism taking control of an in-focus position on the upper surface thereof.
`[0033] Fig. 2 is a plan view showing a wafer stage WST and a measurement stage 14.
`In Fig. 2, a coil string is buried, say, in a predetermined arrangement in the interior of
`the base 13 near the surface thereof. Magnet strings are buried, together with yokes,
`respectively in the bottoms of the wafer state WST and measurement stage 14. The
`coil string and the corresponding magnet string constitute a plane motor respectively.
`By means of the plane motors, the wafer stage WST and the measurement stage 14 are
`independently controlled in X and Y directional positions and rotation angle.
`Incidentally, such a plane motor is disclosed in greater detail in JP-A-H8-51756, for
`example.
`[0034] The wafer stage WST in the embodiment has the minimal functions required
`for printing. Namely, the wafer stage WST has a focus-leveling function. Moreover,
`on the wafer stage WST, two members, i.e. a wafer holder (on wafer-W bottom side) to
`vacuum-clamp the wafer W and a reference mark plate 17 for use in measuring the
`position of the wafer state WST are fixed. A reference mark (not shown) is formed on
`
`Nikon Exhibit 1013 Page 16
`
`

`

`the reference mark plate 17, to provide a positional reference in the X and Y directions.
`By detecting the position of the reference mark by means of the alignment sensor 16, the
`wafer stage WST (wafer W) is detected in its positional relationship, say, to a reticle-R
`projection image.
`[0035] Meanwhile, the measurement stage 14 has a surface set up nearly equal in
`height to the surface of the wafer W on the wafer stage WST. Fixed on the
`measurement stage 14 are a irradiation-dosage monitor 18 formed by a photoelectric
`sensor to measure the energy (incident energy) per unit time of the whole part of
`exposure light having passed the projection optical system PL, an
`illumination-nonuniformity sensor 19 formed by a photoelectric sensor to measure the
`il