GB2329518A

GB2329518A - Electromagnetic alignment and scanning apparatus

Info

Publication number: GB2329518A
Application number: GB9900929A
Authority: GB
Inventors: Akimitsu Ebihara; Thomas Novak
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 1994-06-27
Filing date: 1995-06-21
Publication date: 1999-03-24
Anticipated expiration: 2015-06-21
Also published as: HK1025842A1; GB2329517B; JP3804786B2; GB2329516B; HK1035435A1; JP2006258817A; GB2329519A; GB2325565A; GB2290658B; KR100281858B1; HK1035431A1; KR100281859B1; JP2007242034A; GB2325564A; GB2325566B; JP2003197519A; GB2329521A; GB2329518B; KR960002519A; JP2003158073A

Abstract

A scanning type exposure apparatus which exposes a pattern onto an object while a stage 14 is moved in a scanning direction comprises apparatus capable of high accuracy position and motion control using one or more linear commutated motors to move a stage 14 in one long linear direction and a small yaw rotation in plane. The stage is freely suspended above the base by air bearings 48. One element of the linear commutated motor is mounted upon a drive frame 22, called a balancing portion, which moves in the opposite direction to the stage by a reaction force to maintain the centre of gravity of the apparatus, the balancing portion may be freely suspended above the base by air bearings 32.

Description

1 2329518 ELECTROMAGNETIC ALIGNMENT AND SCARRING APPARATUS The present

invention relates to a movable stale apparatus capable of precise movement, and particularly relates to a stale apparatus movable in one linear direction capable of high accuracy positioning and high speed movement, which can be especially favorably utilized in a microlitpayraphic system.

io In wafer steppers, the alignment of an exposure field to the reticle beinj imaged affects the success of the circuit of that field. in a scanning exposure system, the reticle and wafer are moved simultaneously and scanned across one another during the exposure sequence. This is invention discloses an apparatus to achieve precise scanning motion for such a system.

To attain high accuracy, the stale should be isolated from mechanical disturbances. This is achieved by employing electromagnetic forces to position and move the stage. it should also have high ccntrol bandwidth, which requires that the stage be a light, structure with no moving parts. Furthermore, the stage should be free from excessive heat generation which might cause interferometer interference or mechanical changes that c=romises alignment accuracy.

Commutatorless electromagnetic a i5nment apparatuses such as the ones disclosed in U.S. Pai.

Nos. 4,506,204, i,506,205 and C507,597 are not feasibl e because they reauire the manufacture of large magnet and coil assembl that are not commercially available. The weight of the stage and the heat generated also render these designs inappropriate for high adcuracy applications.

ies A.n imDrovement over these commutatorless apparatuses was disclosed in U. S. Pat. No. 4,952,858, which employs a conventional XY mechanically guided sub-stage to provide the large displacement motion in the plane, thereby eliminating the need for large magnet and coil- assemblies.

The electromagnet ic means mounted on the sub-stage isolates the stage from mechanical disturbances. Nevertheless, the combined weight of the sub-stage and stage still results in low control bandwidth and the heat aenerated by the electromagnetic elements supporting the stage is still is substantial.

Even though current apparatus us- - Lng commutated electromagnt--ic means is a significant improvement over Drior commutatorless ones, the r)roblems of low control bandwidth and interferometer interference nersist. in such an anDaratus, a substace is moved magnetically in one linear direction and L-he commutated electromaanet-Jc means mounted on the sub-stage in turn moves the stage in the normal direction. The sub-stage is heavy because it ca rries the magnet tracks to move the stage. MO--eOver, heat dissimation on the stage compromises inter..ELerometer accuracy.

Tt L is also well known to move a movable me,-,Der (stage) in one long linear direction (e.a. more than 10 cm) by usJnc7 two of the linear motors in parallel where coil and magnet are co-mbined- In this case, the stag=is gu'.ded by some sort of a linear guiding me7,-dDer and driven in one linear direction by a linear motor installed parallel to the guiding member. When driving the stage only to the extent of extremely small stroke. the guidless structure based on the combination of several electromagnetic actuators, as disclosed in the prior art mentioned before, can be adopted. However, in order to move the guideless io is 2.5 stage to a long distance in one linear direction, a s-,Dec-ially structured electromagnet ic actuator as in the urior arts becomes necessary, causing the size of the arr)aratus to become large--, and as a result, generating a nroblem of consuming more electricity.

it is an object of the present invention to make i possible for a guidless stage to move in the direction of a long linear motion usingelectromagnetic force, and to provide a light- weight apparatus in which low inertia and hich resnonse are achieved.

Furthermore, it is an object ofi- L-he uresent invention to wrovide a cn-,-idless stage usin.g cc,-,i-,-,ierc-ialiv available reaular linear motors as elec-roma-jnetic a--zua--o---s for one linear direction motion.

Furthermol-e, it is an object of the present invention to Drovide a cuideless stage apparatus canable of active and precise position control for s-mall displacements without any contact ir. the direction ortho-onal to the long linear motion direction.

Furthermore, it is an object of the r)resen-k- invention to Drov--'Lde a completely non-cont-act st-age annp---atx-,s by providing a movable rie,-, iDer (stage body) to move in one linear direction and the second movable ne,,Lber to move se,-uentially in the sa-,-ie direction, constantly k-eet)-i.-a certain snace in between, and providing the electromacnetic fo--ce- (action and reaction force) in the direction 4 orthogonal to the linear direction between this second movable member and the stage body.

Furthermore, it is an object of the present invention to provide a noncontact stage apparatus capable of preventing the positioning and running accuracy from deteriorating by changing tension of various cables and tubes to be connected to the non-contact stage body which moves as it supports an object.

Furthermore, it is an object of the present invention to provide a non-contact apparatus which is short in its height, by arranging the first movable member and the second movable member in parallel which move in the opposite linear direction to one another.

Furthermore, it is an object of the present invention to provide an apparatus which is structured so as not to change the location of the centre of the gravity of the entire apparatus even when the non-contact stage body mores in one linear direction.

According to one aspect of the present invention there 20 is provided a stage apparatus having a movable stage which is movably supported on a base, comprising, a drive device for driving said movable stage, a balancing portion disposed outside said movable stage, and a non-contactbearing which opposes said balancing portion to said base without contact therebetween, whereby said balancing portion moves in response to a movement of said movable stage, with a movement component in the direction opposite to the direction of movement of said movable stage without any mechanical contact with said base.

As a specific feature o the invention linear commutated motors can be located on opposite sides of the sr-age and each commutated motor includes a coil member and a magnetic member one of which is mounted on one of the opposed sides of the stage and the other or which is mounted on the driving frame. Both motors drive in the same direction. By driving the motors slightly different amounts small yaw rotation of the stage is produced.

In accordance with another aspect of the present invention there is provided a stage driving method for dr-iv--"na a movable stage which is movably supported on a base, comprising, opposing a balancing portion disposed outside said movable stage to said base without contact therebetween by means of a non- contact bearing, and moving, in response to a movement of said movable stage, said balancing portion with a movement component in a direction opposite to I-he direction of movement of said movable stage without any mechanical contact with said base.

BY restricting the stage motion to the three specified degrees of freedom, the apparatus is simple. using electromagnetic components that are commercially available, the apparatus design is easily adaptable to changes in the size of the stacre. This high accuracy is ideally suited for use as a is By nositionina an;Dara-Lus reticle scanner in a scanning exposure system by providing smooth and precise scanning motion in one linear direction and ensuring accurate alignment by controlling small disolacement motion perpendicular to the scanning direction and small yaw rotation in the plane.

other asDects and features and advantages of the present i nvention will become more apparent upon a perusal of the following snecification taken in conjunction with the accompanying drawinas - wherein similar characters of reference indicate similar elements in each of the several views, and in which.

is Fig. 1 is a schematic perspective view of apparatus in accordance with the present invention.

Fig. 2 is a top plan view of the apparatus shovn in Fig. 1.

Fig. 3 is an end elevational vie,.,; of the structure show- in Fig. 2 taken aloncr line 3-31 in the direction of the arrows.

Fic. 4A is an enlarged -Derspective, partially exploded, view showing the carrier/f ol lower structure of Fig. 1 and exploded from the positioning guide.

Fig. 4B_is an enlarged horizontal sectional view or a portion of the structure shown in Fig. 5 taken along line 4B in the direction of the arrow.

Fig. 4C is an enlarged elevational sectional view of a portion of the structure show-n in Pia. 2 taken along line 4C in the direction of the arrow but with the voice coil motor removed.

Fig. 5 is an elevational -sectional view o--17 a Dortion of the structure shown in Fig.. 2 taken along line 5-5' in the direction of the arrows.

Fia. 6 is a block diagram schema t, ically:L--1-1us-Lra-1,1C the sensinc: and control systems Afor controlling the -josition of the stage.

Fa. 7 is a plane view, simillar to Pig. 2, illustrating the preferred embodiment of the present invenon.

I- J.

Fic. 8 is an elevational sectional view of the structure shown in Fg. 7 taken along line 881 in the d---ecion off the arrows.

-ics. 9 and 10 are much simnlified scherna-.-c views similar to Fics. 7 and 8 and illi--,Stral.--ing still another embodirnent of the present invent-icn.

is While the present invention has applicability generally to electromagnetic alignment systems, the prelerred embodiment involves a scanning apparatus for a ret.icle stage as illustrated in Figs. 1-6.

Re-ferring now to the drawings, the au,Daratus 10 ofF the ureser. invention incIludes a base structure 12 above wh-cl-- a reticle stage 14 is suspended and moved as desired, a reticle stage position tracking laser interferometer system 15, a position sensor 13 and a position control system 16 operating from a CPU 161 (see Fig. 6) An elongate positioning guide 17 is mounted on the base 12, and support brackets 18 (two brackets in the illustrated embodiment) are movably supported on the guide 17 such as by air bearings 20. The support brackets 18 are connected to a driving assembly 22 in.the of a mawnetic track assembly or drivina frame for driving the reticle stace 14 in the X direction and srnall yaw rotation.

The driving Erame includes a -oair of parallel spaced apart magnetic track ar-ms 24 and 206 which are connected together to form an oDen rectangle by cross arms 28 and 30. Tn the p--eferred embordiment L-he driving frame 22 is movably supported on the base structure 12 such as by air bearings 32 so that the frarne is free to move on-the base structure Ln a direct-Lon aligned with the longitudinal axis of the guide 17, the -Drine-iDal direction in which t'l-,e scanning -motion of' the reticle stage is desired. P-s used herein "one directionll or a Ilfirst directionll azDr)!-,:es to move-,.nert of.': the frame 22 or the retilc-le stage ILeither,:"o--ward or back in the X direction along a line aligned with the loncitudinal axis of the guide 17.

i 0 is Referring now to Figs. 1 and 5 to explain further in detail, the elongate guiding member 17 in the X direction has front and rear guiding surfaces 17A and 173 which are almost ner-jendicular to the surface 12A of the base structure 12. The front guiding surface 17A is against the rectangular driving frame 22 and cn-,5des the air bearing 20 which is fixed to the inner side o--1 the sunnort bracket 18. A support bracket 18 is mounted on each end of the upper surface of the arm 2,- which is parallel to the guiding member!7 of -the driving frame 22- Further-more, each sur)1Dort bracket 18 is formed in a hook shape so as to st-raddle Lhe gding member 17 in the Y direction and with the free end against the rear guiding surface 173 of the rear side of the guiding member 17. The air bearing 20' is fixed inside the 're L. e end o' the support brackets!8 and against the rear guidina surface 173. Therefore, each of the suiDnort brackets 18 -jLs constrained in its displacement in the Y direction by the guiding member 17 and air bearincs 20 and 201 and is able to move only in the X direction.

Now, accord-nc-: to thils first embodiment o--,"" the present -i--ve7.-ion, the air bearings 32, which are fixed to the bottom surfaces of the four rectangular parts of the driving frame 22, make an air layer leaving a constant can (i several pm) between the r)a--.' surface and the surface i2A or the base structure!2. The driving frarane is buoyed up from, the surface 12A and sunnorted;-)e--pe,-id-cularly (in z direction) by the air layer. it will- be exnlained in detail- later, but in Fig. 1, the carrier/fol lower 60 5 ' now---1 nosit.Loned above the upper part of the elongate arm 24 is 1Dositione,d laterally in the Y d- lrection by air bearings and 669 supported by a bracket 62 acainst opposite surlfaces 17A and 173 of guiding member 1-7 and ve--tically in the Z direction by air bearings 66 above the surface 12A of the base structure 12. Thus, the carrier/follower GO is positioned so as not to contact any part of the driving frame 22. Accordingly, the drivina trame 22 moves only in one linear X direction, a-u-ided above the base surfac,. 12A and laterally by the guiding member 17.

Referring now to both Fig. 1 and _Fig. 2,. tne structure of the re-ele stage!4 and the driving forame 22 0 111 be exulained. The reticle stacre!4 includes a main body 42 on which the reticle 14 is nositioned above an opening 46. The reticle body 42 includes a pair of: onzosed sides 42-A and-422 and is positioned or suspended above the base structure 12 such as by air bearings 48. A plurality o-.: interferometer mirrors 50 are provided on the main body 42 of the reticle stacre!d.! for operation with the laser in-er'erometer position sensing system 15 (see Fig. 6) for L J- - determining the exact position of the reticle stage which - - L- - is fed to the -nostiOn control system..IC in order to direct:

the anmronr-ia!---e dr-Lve signals.9 tor moving L-he reticle stawe 14 as desired- Primary movement of the reticle sta-le!4 is accorn,Dlis'.ned with first drive asse-,,Lbly means in -the for-,n of separate drive assemblies 52A and 52B on each of the oiDposed sides 42A and 4-213, respectively The drive assemblies 52r"'s. and 525 include drive coils and 5,2 fixedly mounted on the reticle stage!4 at the sides 42-1. and 425, respectiveiv, for cocQeratina with macnet C) ' uracks 56A and 563 on the magnet track ar-ms 24 and 25 resDectively, of the d-rive -frame 22.

r ' 5.njle jin t:,nn pre.ferred embodiment of _ the il on t-'- e rr,-a-ne!--- co.-:i. 1 s are mounted on the reticle stage and the magnets are mounted on -he drive _frame 22, the nositions o. these e2-ments of tIne e -I e c t- -- om a gn e t i c asser-,.bly 52 could be reversed.

Here, the structure of the reticle stage 14 will be exnlained.Lu--ther in detail. As shown in Fig. 1, the stage body 42 is installed so that it is free to move in the Y direction-in the rectangular space inside the driving frame 22. The air bearing 48 fixed under each of the four corners of the stage body 42 makes an extremely- small air gap between the pad surface and the base surface 12A, and buoys up and supports the entilre stage 14 from the surface 12A. These air bearings 48 should -preferably be pre-loaded types with. a recess for vacuum attraction to the surface 12A.

As shown in Fig. 2, a rectangle opening 46 in I-Che center 0,40 the stage body 42 is provided so that the projected image of the pattern. fo--7-,ed on the reticle 4 can go through. in order for the projected imace via the rectangle o-men-na 46 to pass through the projection oDt.,'-cal system PL (See F-1.g. 5) which is installed below the rectangle cDen-.nc, there is another cnenina 129 iDrov-ide,-'; at the center oart of the base structure 1-2.

The reticle C41 is loaded on the too surface of the L_ - - stawe body by clamping mer-.be--s 42C which are protrusively placed at rour poilints around the rectangle opening 46, and clamped by the vacuum pressure.

the -interferometer SOY, which is f -i-xe,--' near the side 423 of the stage body 2 near the arm 26-, has a ve--tical elongate reflecting surface in the x direct-ion which leng:h is someh-wat Ionger than the movable stroke oES the st--aae 14 --'In the X direction, and the laser beam., T.EY trom the Y-axis interferometer is perpendicularly on the reflecting surface.

in F-ig. 2, the laser beam LEY Js bent at a rich angle by the mirror 12D which Js fixed on the silde of the base structure 12.

Re.ferrina now to Fig. 3 as a partial cross-sectional drawing of the 3-3' view in Fig. 2, the laser beam LBY which is incident on the reflecting surface of the interferometer mirror SOY is placed so as to be on the same plane as the bottom surface (the surface where the pattern is formed) of the reticle 44 whicln is mounted on the clamping member 42C. Furthermore, in Fig. 3, the air bearing 20 on the end side of the sun- cort brackets 18 against the guidlina surface 17B of the guiding member 17 is also shown. ' Referring once again to Figs. 1 and 2, the laser bean, LBX! from the Xlaxis in,---.e----,erometer is incident and reflected on the interferometer mirror 50Xl, and the laser beam LBX2 from the X2axis interferometer is incident and reflected on the interferometer mirror 5OX2. These two mirrors SOXI and 50X2 are structured as corner tube type,. 1j-f-rors, and even when th.e stage 14 is in yaw rotation, they always maintain the -'-Incident axis and re-f-lecting axis o.E the laser beams 1Dara-;,-lel within the XY plane. Furthermore, the block 12C in Fig. 2 is an o)t-cal block such as a r_)rism to orient the laser beams L5Xl and L5X2 to each of the mirrors 5OX1 and 50X2, and is fixed to a part of the base structure 12. The corresponding block 'Lor the LBy laser beam is not shown.

in Fig. 2, the distance BL in the Y direction between each of the center lines of the two laser beams LBX! and LBX2 is the lenath. of the base line used to calculate the amount of yaw rotation. A-c-cordingly, the value of the difZ"erence between the measured value,XI in-the X direction of the Xi-axis interiferometer and the measured,alue jX2 in the X direction of the X2-axis 4-nter.=erometedivided by the base line length BL is the approximate amount of yaw rotation in an extremely small range. Also, half the value of the sum of t_he cXl and csX2 represents the X coordinate position of the entire stage 14. These calculations are done on the high speed digital processor in the -position control system!6 shown in Fig. 6.

Furthermore, the center lines of each of thc laser beams L3Xl and LEX2 are set on the same surface where the par-tern is formed on the reticle 44. The extension o; - the line GX, which is show-- i in Fig. 2 and divides in half the soace between eac." of' the center lines of laser beams LBX1 and LEX2, and the extension of the laser beam LBY intersect within the same surface where the pattern is formed. And furthermore, the oDtical axis AX (See Figs. i and 5) als crosses at this intersection as shown in Fa. 1. in 1, a slit shape illumination field ILS which includes the is ootical axis AX is shown over the reticle 4.!-, and the pattern image of the reticle -4 is scanned and exposed onto the nhoto-sensitive substrate via the -projection optical system PL.

Further-more, there are two recta ngula-- blocks 9C.A and 90B Zixed on the silde 42A of the stacre body 42 in Fic-s. 1 and 2. These blocks 90A and 902 are to reCeive the driving force in the Y direction from the second electro-magnetic actuator 70 which is mounted on the carrier/f_ol lower GO. Details will be e=lained later.

The driving coils 54-2k and 545 which are fixed on the both sides o-E the stage body 2 ai-e formed f:lat,:)ara-llel to t ' ne XY nlane, and -Dass through the magnetic -Elux s,:ace in the slot which extends in the X d-'lrect-ioi- of the magnetic track 56A and 56B without any contact. The assembly of tn-- drilving coil 54 and the magnetilc track 56 used in the p_resent e-.,,bod-ment is a commercially easilly accessible linear motor for general purposes, and it could be either or without a commutator.

Here, considering the actual design, the moving stroke of the reticle stage 14 is mostly determined by the size of the re-Licle 44 (the amount of movement required at the time of scanning-for exposure and the amount of movement needed at the time of removal of the reticle 'Erom the illumination optical system to change the reticle). In the case of the Dresent, embodiment, when a (15.24 cm) r-er-icle is used, the rpc),,-iIng:st:roke is about. 30 cm.

As mentioned be-fore, the driving frame 22 and the C) stage 14 are independently buoyed up and supported on the base -surface 12A, and at the same time, magnetic action eand reaction force-is applied to one another in the X direction only by the linear motor 52. Because of that, the law of the conservation momentum is.seen between the driving J: _k el is frame 22 and the stace--- Now, suppose the weigh.t of the entire stage 14 is about one -fifth of the entire we-aht of' the frame 22 which includes the sun-Dort brackets 18., t'-,ien the movement c'-':: 30 cm of,' the stage IL- in the X rnakes the dr--'lv-nT frame 22 move by 6 cm backwards in the X This- means that the location the center of the cravty o' the apparatus on the base structure 12 Js essentially fixed in the X direction. In the y direction, L-here is no movement of_ any heavy object.

7-.here--":ore, the chance in the location ofF the center of the cravity lin the Y direction is also relatively f-Fixed.

The stace 1,11 can be moved in the X d-rect-cn as described above, but the moving coils (54.P, and the stators 56B) of the linear motors 52 interllere with each other (colilde) lin the Y di-rection w.-'rho,",z an X d-.-ect--lon actuator. Therefore, the carr lower 6C and the second electro-magnetic actuator 70, are the - Is- i 0 is characteristic components of the present invention, are provided to control the stage 14 in the Y direction.

Referring now to Figs. 1, 2, 3, and 5, the structures 0them will be explained here.

f- L.

As shown in Fig. 1, the carrier/f ol lower 60 is movably installed in the Y direction via the hook like sunnort bracket 62 which straddles over the guiding me-.,ber 17. Furthermore as evident from Figr. 2, the carrier/followe_- 60 -is olaced above the a= 24, so as to maintain a certain space between the stage 14 (the body 42) and to the arm 24, respectively. One end 60E.E of the carrier/ f oll ower 60, is substantially protruding inward (toward the stage body 42) over the a---,,i 24. inside this end part 60E is fixed a driving coil,68 (same shape as the coil 54) which enters a slot space c-LE the magnetic track -urthermore, the bracket 62 supported air bearing 661 (See Figs. 2, 3, 4A and 5) against the, guiding s,-,r.-.E'ace 17A of the suidina member 17 is fixed in the space between the guiding member 17 of L-he carrier/follower 60 and the a--,n. 24. The air bearing 66 to buoy un and support the carrier/-jE:ol lower 60 on the base surface 12A is also sho,,,;p n Fig. 3.

The air bearing 662 against the quiding surface 17B of the c-uiding member 17 is also fixed to the f--ee end of sunnort bracket 62 on the other side of: L-he hook _fromm air bearing 661-1. with Su:Lding member 17 therebetween.

Now, as evident from Fria. 5, the carrJe.-/-Ec-1 lower 60 is arranced so as to keep certain spaces wJth resz--ct to both the -...ac:netic track 56A and the stace body 42 in the Y and Z directions, respectively. Shown in Fic. 5 are the Projection optical system PL and coil-lm-n, rod CS to suppor the base structure 12 above the projection opzical i 0 is PL. Such an arrangement is typical for a projection aligner, and unnecessary shift of the center of the gravity of the structures above the base structure 12 would cause a lateral shift (mechanical distortion) between the coluMn rod CS and the projection optical system PL, and thus result in a deflection of the image on the photosensitive substrate at the time of ex-,)osure. -;ence, the merit of the device as in the -D-- esent embodilment where the motion of the stage 14 does not shi..L:t the center of the cravity above the base structure 12 is substantial.

Furthermore referring now -to Fig. 4A, the structure O.f the carrier/ JEol lower 60 will be e=lained. In Fig. 4A, the carrier/follower 60 is disassembled into two parts, 60A and 60B, for the sake of facilitatina one's understanding. As evident from Fig. 4A, the driving coil 68 to move the carrier/-follower 60 itself in the X direction is fixed at end GOE of the carrier/follower 60. bearing 66C is paced acalinst the base bottom surface of the end GOE and the lower Dart of the Furthermore, the air structure 12.-' on the helps to buoy up zhe ca--r-Jp-r/--Eollowe-- 60.

Hence the carr-er/--ollower 60 is supported in the Z drection with the -follow-:ng three points, the two air bearings 66 and one air bearing 66C, and is constrained in the Y direction for movement in the X direction by air bearinSs 661A_ and 66B. What is imDortant in this structure s that the second electro-naar.etic actuator 70 is arranged back to back with the sun:)o--t bracket 62 so that when the actuator cenerates the driving force in the Y d-j--ection, reaction forces in the Y direction between the stace 1, and the car-r lower 70 actively act upon the air bearings 66A and 663 wn-ch are -fixed -'.nside -the sur)Dcrt bracket 62.

11 n other words, a.--rar-g--"ng the actuator 70 and the air in the _Lnas 66A, 663 on the line parallel to y-axis - - 1 i 0 7 XY plane helps prevent generating unwanted stress, which M,ght deform the carrier/follower 60 mechanically when the actuator 701 is in oneration. Conversely. it means that it is r)ossible to reduce the weight of the carrier/flollower 60.

As evident from Figs. 2, 4A and 4C described above, the magnetic track 56A -Ln the arm 24 of the driving framie 22 nrovides magnetic flux for the driving coil 5,-A on the stage body 42 side, and concurrently provides magnetic flux for the drivina coil 68 for the carrier/follower 60. AS for L-he air bearings 66A, 66B and 66C, a vacuum pre-loaded type is preferable, since the carrier/-A;'ollower 60 is light. Besides the vacuum pre-loaded type, a magnetic pre-loaded type is also acceptable.

Next w-Lth ref-erenc e to Figs. 3, -B and 5, the second actuator mounted on the carrier/follower 60 will be e=lained. A second electromagnetic drive assembly in the form, of a voice coil motor 70 is made ur) of a voice coJ2 74 attached to the main body 42 of the reticle stage 14 and a h magnet 72 attached to the carrier/follower 60 to move tle stage!, for small displacements in the Y direction in the plane of the travel of the stage 14 orthogonal to the X direction long linear motion produced by the driving assembly 22. The positions of the coil- 74 and magnet 72 could be reversed. A schematic structure of' the voice coil motor (VCM) 70 is as shown in Figs. 3 and 5, and the detailed structure is shown in Fig. 45. Snown in Fig. 41 is a cross - sect _Jonal view of the VCM 70 sectioned at thhorizontal -jlane shown- with an arrow,='S in _Fig. 5, In 4E, the magnets 72 of the VCM 70 are fixed onto the carr; ier/follower 60 side. And the coil of the VCY, 70 comnrises r_he coil body 74A and its supportng part 74E, L and the supporting mart 743 is úp-yed to a conneczing pial-e 1 18 - 92 (a plate vertical to the XY plane) which is rigidly laid across the two rectangular blocks 90A and 905. A center line KX of the VCM 70 shows the direction of the driving force of the coil 74, and when an electric current flows through the coil- bod,. 74A, the coil 74 displaces Jnto either positive c-?-- negative movement in the Y dilrection in accordance with the direction ofE the current, and generates a force cc--resiDonden-- to the amount of the curren!--. Normally, in a commonlyused VCM, a rina- like damper or bellows are provided between the coil and magnet so as to keep the gap between the coil and magnet, but according to the present embodiment, that gan is kept by a follow-un motion of the carrier/follower 60, and therefore, such supporting elements as a damper or bellows are not necessary.

In the present embodiment, canacitance ga.D sensors i3A and 13B are nrovided as a Dositionna sensor 13 (see In Fig. S, electrodes for Fig. 6) as shown in Fig. 4BI. caz-,ac-tance sensors are niaced so as to detect the change n the waD in the X direction between the side s u rZE a c e of the re--tanglala-- blocks 90A a-rid 902 -..':ac-J---g with each other the X direction and the side surface of a case 70' of' j -1 the VCM 70. Such a positioning sensor 13 can be placed anywhere as far as it can detect the gap change i_n the Y direction between the carrier/fol lower 60 and the stage (or the body 42). Furthermore, the ty-ce c--" the senscr can ,e any of a non-coni:act tv.-je such as -jhotoeiectr--'c, inductive, ultrasonic, c-- system.

The case 701 in Priz. 5 is LPom,ed wit', zi ca--rier/-:ol-lower 60 iln one, and placed so as Pot to contact any meT-,,ber on the reticle, szace 14- side. As or the gar) bet,..jeen the case 701 and the recianc:u2ar blocks 90A and 903 in the X direction (scannJna when ig- is the gap on the sensor 13A side becomes wider, the gap on the sensor 13 B side becomes smaller. There-fore, if the difference between the measured gap value by the sensor 13A and the measured caiD'value by the sensor 13B is obtained by either digital operation or analog operation, and a direct servo (.-L'eeclback) control system which controls the dr-iv; ing current of' the driving coil 68 for the ca=ier/-Eol lower 60 is desianed using a ser-jo driving circuit which makes the 5aiD difference zero, then the carrier/f ol lower 60 will automatically perform a follow- up movement in the X direction always keeping a certain siDace to the stage body 42. or, it is also possible to design an indirect servo controll-system which controls an electric current flow to the driving coil- 68, with the operation of nosition control system 1-6 in Fic. 6 using the measured cap value obtained only from one o_f the sensors and the X coordinate position of the stace 14 measured from the X axis interferometer, wit-nout using the two c-:ar) sensors 13A and 132 diff erentially.

In the VCM 70 as described in F-,a. 43, the gap between the coil body 7,-A and the T-Iac---iet 72 in the X direction (non-energizing direction) is in actuality about 2 - 3 mm. Therefore, a follow-up accuracy of the ca--r'Ler/follo,,qe-.- 60 with respect to the stage body 42 would be acceptable a-t around --.5 - 1 mm. This accuracy depends on how much o_f the yaw rota?_-ion of the stage body is allowed, and also depends on the lenSth of the line the KX direction (energizing direction) of t.rie coilbody 7,-A. ollS the VCm, 70. Furthermore, the degree of the accuracy for this can be_subst-antially lower than the precise DOSitioning accuracy for the stage body 2 using an interferomneter (e.a., -1-0.03 gm supposing the resolution c) the -;n-L-er.-'L;erc-.eter Is 0.01- pm.) This means that the se-rvo system for a follower can be designed fairly simply, and the amount of cost to install the ifollower control syst-em. would be small. Furthermore, the line KX in Fig. 45 is set so as to go through the center of the grav 1 ity of the entire stage 14 on the XY plane, and each of centers of the pair Of' the air bearing 66-k and 663 provided inside the s=ort brackets 62 shown in Fia. is also positioned on the line M -Ln the XY niane.

Sho,,..,n in C-C is a crosssectional drawing of the part which includes the guiding member 17, the carrier/ fol lower 60, and the magnetic track 56A sectioned from the direction of- the arrow 4C in Fig. 2. The arm 4 storin- the magnetic track 56A is buoyed up and supported on the base surface 12A by the air bearing 32, and the carrier/follower 60 is buoyed up and supported on the base surface 12A by -the air bea--i-ng 66. At this time, the height of the air bea.----'lng 48 at the bottom sur-Eace o_ the stace body C2 (see 3 or 5) and the he-Jgh-- o' -he a- bearing 32 are so as to place tIne driving coil 54A on st-aae body 12 side keeping a 2 - 3 mm, gap in Z direct-Lon in the slot s-Dace of the macnetic track 557-'_.

Each cf: the spaces between the carrier/ fl ol lower 60 and the arm 24 2Ln the Z and Y directions hardly changes because they are both guided by the common me-mber 17 and the base surface 12A. Furthe=ore, even i-f therc il s a in the he--a-ht-- in the Z direction between the T:)art on the base sur-Eace _12x'-_ wz.,ere the air bearing 32 at the bottom, surface of the driving frame 22 (ar-m. 24) iS g-.-,-ided and the part on the base surface 12A_ where the air b-.-arng 8 at the bottom surface of the sta-e body is guided, as long as the dif-ference is precisely constant within the moving st--c'ze, the gap in the Z direct- ion between the magnetic track 56A and the driving coil 54A is also preserved constant.

Furthermore, since the driving coil 68 for the carrier/follower 60 is originally fixed to the carrier/follower 60, it is arranged, maintaining a certain gap of 2 - 3 mm above and below in the slot space of the magnetic track 56A. And the driving coil 68 hardly shifts in the Y direction with respect to the magnetic track 56A.

Cables 82 (see Fig. 2) are provided for directing the signals to the drive coils 54A and 542 on stage 14, the voice coil motor coil 74 and the carri er/f ol lower drive coil 68, and these cables 82 are mounted on the carrier/follow-er 60 and guide 17 thereby eliminating drag on the reticle stage 14. The voice coil motor 70 acts as a buffer by denying transmission of external mechanical disturbances to the stage 14.

Therefore, referring now to Pigs. 2 and 4A, the cable issues will be described further in detail. As shown in Fig. 2, a connector 80 which connects wires of the electric system and tubes of the air pressure and the vacuum system (hereinafter called "cables") is mounted on the base structure 12 on one end of the guiding member 17. The connector 80 connects a cable 81 from the external control system (including the control system of air pressure and vacuum system besides the electric system contrcl system shown in Fig. 6) to a flexible cable 82. The cable 82 is further connected to the end wart 60E of the carrier/follower 60, and electric system wires and the air pressure and the vacuum system tubes necessary for the stale body 42 are distributed as the cable 83.

As mentioned before, the VCM 70 works to cancel a cable's drag or an influence by tension, but sometimes ils influence appears as moment in unexpected direction between the carrier/follower 60 and the stage body 42. In other words, the tension of the cable 82 gives the carrier/.ic-"ollower 60 a force to rotate the guiding surface of the guiding member 17 or the base surf ace 12A, and the tension of the cable 83 gives a force to the carrier/follower 60 and the stage body to rotate relatively.

one of' these moments, the constituent which shifts the carrier/follower60, is not problematic, but the one which shifts the stage body in X, Y, or e direction (yaw rotation direction) could affect the alignment or overlay accuracy. As for in X and e directions, shifts can be ' correctie-d by'c-consecu-Live drive by the two linear motors (54A,SGA,54B,56B), and as for in the Y direction, the shift is can be corrected by the 'VCM 70. In the present embodiment, since -the weight of the entire stage 14 can be reduced substantially, the resconse of the motion of the stace 14 by VC:M 70 in the Y direction- and the - esponse by the linear motor in X and 0 directions will be ext-remely hich in coonerat-ion with the completely non-contact ciaidless structure. Furthermore, even when a micro vibration (micron order) is generated in the carrier/ follower 60 and it is transferred to the stage 14 via the cable 83, the vibration (from several Hz to tens of Hz) can be sufficiently canceled by the above mentioned high response.

Now, Fig. 4A shows how each of the cables is distributed at the carrier/follower 60. Each of the driving signals to the dr-iv...nc: coil54A, 545 for the staTe body 42 and the driving cc-i-l 74 of the VCM 70 and the detection signal from the iDos----ion sens.or 1-3 (the gap sensors!3A, 133) go through the electric. system wire 82.7- Lrom the connector 80. The pressure gas and the vacuum to each the air bearnc:s 48 and 66 go through the Dneumatic 1 system tube 82B from the connector 80. On the other hand, the driving signal to the driving coil 54A and 5,B goes through the electric system wire 83A which is connected to the stage body 42, and the pressurized gas for the air bearing 48 and the vacuum for the clamoing member 42C go through the pneumatic systerr, hoses 83E.

-.0 Furthermore, it is preferable to have a separate line for the pneumatic system for the air bearings 20, 20' and 32 of the driving frame 22, - "Lnde:Dendent of the one shown in Fig. 2. Also, as shown in Fig. 4A, in case the tension or vibration of the cable 83 cannot be prevented, it is advisable to arrange the cable 83 so as to limit the momnt by the tension or vibration the stage body 42 receives only to Y direction as much as possible. in that case, the moment can be canceled only by the VCM, 70 with the h..ghest response.

Referring now to Figs. 1, 2 and 6, the positioning of the reticle stace 14 is accomnlished.1,-st knowing its existing position utilizing the laser inter-ferometer system 15. DrIve signals are sent to the reticle stage drive coils 5,A and 5,-B _for drivJ-c the staSe 14- in the X direction. A difference in the resulting drive to the opposite sides 42A and 425 of the reticle stage IA- will produce small yaw rotation of the reticle stage 14. An ar)nroDrate drive signal to the voice coil 72 of voice coil motor 70 Droduces small disnlacements of the reticle stawe 14 in the Y direction. As the position of tIne reticle stage 14 chances, a drive sianal is sent to the carr i er/f ol lower coil- 68 causing the ca- r j er/.jol lower 60 to.F 'low the reticle stage 14. Resulting reaction -o-.- forces to the aniDlied dri've Izorces will move the magnetic track assembly or drive ZErame 22 in a direction onposite to the mo-,.rem,ent of' the reticle stage 14 to substantially r,-,.a-:._nza-n i 0 is the center -of gravity of- the apparatus. T-t will be anDreciated that the counter-weight or reaction movement-- of the magnetic track assembly 22 need not be included in the apparatus in which case the magnetic track assembly 22 could be fixedly mounted on the base 12.

As described above, in order to control the stage system according to the present embodiment, a control syst-em as shown in FJa. 6 is installed. This control system in Pig. 6 will be further explained in detail here.

Xi drivina coil and X2 driving coil composed as the driv-Jna coils 54A and 5,-B of two linear motors respectively, and Y driving coil composed as the driving coil 72 of the VCM 70 are placedin the reticle stage 14, and the drivJna coil 68 is nlaced in the carrier/follower 60. Each of these drivina coils is driven in response to the driving signals SM-, SX2, SY1, and StX, respectively, from the position control system 16. The laser interferometer system w',--'ch measures the coordinates pos-ition of the stage 14 comprises the Y axis interferometer which sends/receives the beam LBY, the X! axis interfe-rometer which sends/receives the beam LBXl, and the X2 axis interferometer which s ends /receives the beam LBX2, and they send position infor-matibn for each of the directions of -the axes, IFY, control system 16 sends two driving sJcrnals SM and SX2 to the driving coils 54A and 54B so that the di-"':1.':erence between the mosition informatlion TFX1 and IFX2 in the X direction will become a nreset value, or in other words, the yaw rotation o_ the reticle stage 14 is maintained at t'n-- snecified amount. Thus, the yaw rotation (in 6 direction) by the beams L5X! and LEX2, XI axis and,X2 axis interferometers, the position control system !6, and the driving signals 5Xl and SX2 is constantly being -25 conducted, once the reticle 44 is aligned on the stace body 42, needless to mention the time of. the exposure.

Furthermore, the control system!6, which obtained the current coordinates position of the stage 14 in the X direction from the average of the sum of position information IFX1 and IFX2 in the X direction, sends the driving sanals SXI, SX2 to the driving coils 54A and 54E, respectively, based on the various commands from the -Host CPU 161 and the infor-mation CD for tne iDarameters.

Especially when scazining exposure is in motion, it is necessary to move the stage 14 straight in the X direction while correcting the yaw rotation, and the control syste-tt 16 controls the two driving coils 54A and 54B to give the same or slightly d-i-f.'zE-erent forces as needed.

Furthermore, the position IFY from the Y axis interferomneter is also sent to the control system 16, and the control system 16 sends an optimum driving siSnai SAX to the driving coil 68 otE the carr -i e lower 60. At that time, the control system 16 receives the detection signal S,d from, the iDositior. sensor 7-3 which measures the snace between the reticle stage 1,- and the carrier/.:ol-o.e- in the X direction, and sends a necessar-y signal SAX to make the sianal S p,, into the preset value As mentioned before, the -..,"ollow-uD accuracy for thle carrier/f ol lower 60 is not so strict that the detection signal S pd of the control systerm,!6 does not have to be evaluated strictly For exam:)1e, when controllincr the motion by reading the position information!---Xl, IFX2 every irnsecond from, each o_f the interferometers, the high speed 3 0 nrocessor in. the control s-ystem --. 6 samples the current of the detection signal S P,, each time, determines..,,hez:he-- the value is larwe or small compared to the reference value (acknowledge the dLrection) and if the deviation surnasses 3 0 a certain point, the signal S,X in proportion to the deviation can be sent to the driving coil 68. Furthermore as mentioned before, it is also acceptable to install a control system 95 which directly servo controls the driving coil 68, and directly controls the foilow-uz) motion of the carrier/-.L:ollower 60 without coing through the position control system 16.

Since the moving stawe system as show---.i has no attachment to constrain it in the X direction, small influences may cause the system to drift-toward the positive or negative X direction. This would cause certain parts to colLide after this imbalance becar-ne excessive. The influences include cable forces, imprecise leveling of: the base reference surface 12A or friction between C 07, 1:)on e n t- 5 One simmie method is to use weak bumpers (not s.,-ow-..) to iDreven-L- excessive L-ravel of the drive assembly 22. A-nother simple method is.to turn off the ailr to one or more of the air bearings (32,20) used to cruide the d---ve y 22 when the d-rive assembly reaches close to the a s s L end of the stroke. The air bear-.-.9\'s) can be turned on when the drive begins to move back in the opnosite direction.

More precise methods recraire monitoring the position C- the drive asse-,,ibly by a -,-ieasur-ing means (not shown.) and applying a driving force to restore and maintain. the correct nosition. The accuracy of the measurling means need not be -orecise, but on.--he order of' 0.1 to 1.0 T'. e driving force can be obta.-;'ne-- by using another linear motor (not s'hown) attached to the drive assembly 22, or another r,-,ozor that is coupled to the drive assembly.

Finally, the one or more air bearings (GC'),66A,66B) 0= the carr-:ier/--Eol-lower 60 can be turned of...': to act as a brake during idle neriods of the stace 42. I-f:' the co--'2 68 of the is carrier/A-oollOwe-- 60 is energized with the carrier/f ol lower 60 in the braked condition the drive assembly will be driven and accelerated. Thus, the position control system 16 monitors the location of the drive assembly 22. When the drive assembly drifts out 0" poston, the drive assembly is repositioned with SU.4:f L--cient accuracy by intermittently using the coil 68 ofE the carr _Jer/f ol lower 22.

In the first embodiment of the present invention, driving frame 22 which functions as a counter weight is installed in order to prevent -the center of the gravty o the entire system from shifting, and was made to move in. the oppdsite li-re'ction from the stage body 42. However, when the structures in Figs. 1 - 5 are applied to a system where the shi-ft c= fthe center of the gravity is not a major iDroblem, it is also acceptable to fix the driving frame 22 on the base structure 12 together. In that case, except for the problem regarding the center c -f the gravity, some of the effects and function can be applied without making any chai.cres.

lhis invention provides a stage which can be used for high accuracy Position and motion control in th-ree degrees of freedom in one plane: (1) long linear mo'k:on; (2) short linear motion Der-pendicular to the long linear motion; and (3) small Yaw rotation. The stage is isolated from mechanical disturbances of surrounding, Structures bv utilizing electro-magnetic forces as the stage d.---Jver. 3v further using a structure for this suideless stage, a hich control ba-,-idw.;dt---h is attained. These two factors contribute IL_0 achieve the smooth and accurate operation tne stage.

t he Descriotjon of the ':>.y-eferred Bearing in mind the description of the embodiment illustrated in Figs. 1- 6, the preferred embodiment o_f the present invention is illustrated in Figs. 7 and 8 wherein the last two digits of the numbered elements are similar to the corresponding two digit numbered elements in Figs. 1-5.

Tn Figs. 7 and 8, differing from the previous first embodiment, the driving frame which functions as a counte-r weight is removed, and each of the magnet tracks i56A and 1565 of- the two linear motors is rigidly mounted onto the base structure 112. The stage body 143 which moves s--ra-isht in the X direction is iDlaced between the two magnetic tracks 156A and 156B. As shown in Fig. 8, all opening -112B ig- formed in the base structure 112, ' and thestage body 142 is arranged so as to straddle the opening. part i123 in the Y direction. There are four pre-loaded air bearings!,-8 fixed on the bottom surface a both ends of the stage body 142 in the Y direction, and they buoy up and suTD-jor-L the stage body -!,'-2 ac-ainst the base surface 112A.

Furt-riermore, accordin-a to the r)resen!--- embodiment, the re-L.-cle 14, C- is clamDed and sunoorted on the reticle chuck plate 143 which is separately placed on the stage body 142. ':,he straight T-,irro,-t- 150Y JEor the Y axis laser inller-,Fe--ometer and two corner mirrors 15OXI, 150X2 for the X axis laser interi-:-erome-.er are mounted on the reticle chuck mlate 143. The driving coils 154A and i54B are ly fixed at the both ends of the stage body 14-2 in th-e Y direction with resDect to the magnetic racks 156A and 1565, and due to the col-trol subsyster,-i previously described, r,-,ake the stage body 1,112 run stra- ig'--.t --:In he X d--:lrecz-on and yaw only As evident -from the r-9'.,nt side of' the is - o an extremely small amiount. track 156-" O' --a. 8, the magnetc >.

linear motor and the -,.,aznet-c track 156A of L-he left side of the linear motor are arranged so as to have a difference in level in z direction between them. In other words, the bottom surface of the both ends in the direction of the long axis of the magnetic track 156 on the left side is, as shown in Fig. 7, elevated by a certain amount with a block member 155 against the base surface 112,'--. And the carri er/f ol lower 160 where the VCM is fixed is arranged in the space below the elevated magnetic track 156A.

The carrier/follower 160 is buoyed ulp and supported by the pre-loaded air bearings 166 (at 2 points) on the base surface 112A1 of the base structure 112 which is one level ldwer. --iurthermore, two nre-loaded air bearings 164 against the vertical guiding surface 117A of the straight- is guiding me-mber i17, whic h is mounted onto the base structure 112, are fixed on the side surface of the carrier/follower 1-60. This carrier/follower 160 is different from the one in Pia. 4A accRrding to the previous embodiment, and the driving coil 168 (Fic. 7) for the carrie--/.L:ollower 160 is fixed horizontally to the 'Dart which extends vertically from the bottom c.-"' the carr.Le--/A-;:o-ll-ower 160, and positioned in the magnetic flux slot oil the magnetic track 156A without any contact. The carrier/follower 160 is arranged so as not to contact any part ofE the magnetic track i5GA within the range of the moving stroke, and has the VCM 170 which positions the stage body 1,2 precisely in the Y direction.

Furthermore, in Fig. 7, the air bearing 166 which buoys up and suDoorts the carrie--t-/-LEollower 160 is provided under the VC1.11 170. The follow-up motion to the stage body i42 of the carrier/follower 160 is also done based on the detection signal from the position sensor 13 as in the prevIous ernribodiment, -, 0 is 3 G In the second embodiment structured as above, there is an inconvenience where the center of the gravity O.E the entire system shifts in accordance with the shift oil the stage body 142 in the X direction, since there is substantially no member which functions as a counter weight. it is, however, possible to position the stage body 142 nrecisely in the Y direction with non-contact electro-magnetic force by the VCM 170 by way of following the stage body 142 without any contact using the carrier/follower 160. Furthermore, since the two linear motors are arranged with a difference in the level i-n the Z direction between them, there is a merit where the sum 01the vectors of the force moment generated by each of the linear motors can be min-Lmized at the center of the gravity of the entire reticle stage because the -force moment of each of the linear motors substantially cancels with the other.

Furthermore, since an eloncated a:,c-s ofE action (the line KX in F-1a. 45) of: -he VCM.170 is arranced so as to pasS through the center o1E the aravity o:':: the entire structure of the stage not only on the XY plane but also Jn the Z direction, it is more difficult for the drJvJna 'Force of the VCM 170 to give up_necessary moment to the s--ae body 1A2. Furthermore, since the method of connecting the cables 82, 83 via the carri er/l'ol lower i60 can be applied t'-e same manner as in the first erruDodiment, the rezarding the cables in the completely non-contact u-deless stage is also imDroved.

The sa-,-ic cn-,ideless iDr-nc-;Dle can be e-,.--loved -Ln anoher e-,.bodi-nent. For example, in schemnatic FiSS. 9 and 10, the stace 2=12, supportied on a bases 212, _Js driven in the lonw X direction by a single moving coJ! 254 moving w'L.th,--in a sinsle magnetic track 256. The iragnet-"c track is rigidly attached to the base 212. The center of the coil is located close to the center of gravity of the stage 242. To move the stage in the Y direction, a -oair of VCM's (274A,2742,272A,272B) are energized to r)rovide an acceleration force in the Y direction. To control yaw, the coils 274A and 274B are energized differentially under control of the electronics subsystem. The VCM magnets (272A,2723) are attached to a carrier/-J'-:'ollowe-- stage 260. The carrier/f ol lower stage is guided and driven like the first -embodiment previously described. This alternative embodiment can be utilized for a wa"Ler st.age. Where it is utilized for a reticle stage the reticld-can be-_positioned to one side of the coil 254 and track 256, and if desired to maintain the center of gravity of -he stage 2,12 passing through the coil 254 and track 256, a compensating opening in -the stage 2,112 can be provided on the cpposite side of the coil 254 and track 255 from the ret-icle.

Merits ga.'.ned from each of the e-,,-ibod-Lmei-i-Ls can be roughly listed as To preserve accuracy, the carrier/follower design eliminates the problem of cable drag for the stage since the cables connected to the stage follow the stage via the carri er/f ol lower. Cables connecting the ca--rier/-L'ol lower to external devices will have a certain amount of draq, but the staze is free from such disturbances since there is no direct connection to the carri er/fol lower which acts as a bu:E:'Eer by den,,"Jng the transmission o_f mechanical disturbances to the staseFurther-more, the counter-weight design i--rese,--ves thelocation O:E the center of gravity ofF the stace system, dur..ng anv s!---awe motion in the long stroke direction Dv us _1 ng the conservat ion oi.'-: momentum -)r-ine inle. Th. i s ar)naratus essentJ-ally eliminates any reaction forces 1 between the stage system and the base structure on which the stage system is mounted, thereby facilita ting high acceleration while minimizing vibrational effects on the system.

In addition, because the stage is designed for limited motion in the three degrees of freedom as described, the stage is substantially simpler than those which are designed for full range motions in all three degrees of freedom. Moreover, unlike a commutatorless apparatus, the instant invention uses electromagnetic comnonents that are commercially available. Because this invention does not recruire custom-made electromagnetic comDonents which become increasingly difficult to manufacture as the size -and stroke o_f' the stage increases, this invention is easily adaptable to chances in the size or stroke of the stage.

The embodiment with the single linear motor eliminates the second linear motor and. achieves yaw correction using two VCM1s.

While the Dresent invention has been described in terms of- the nreferred embodiment, the invention can take many different forms and is only limited by the scone of the following claims.

is 1 33

Claims

1. A scanning type exposure apparatus arranged to expose a pattern onto an object while a stage is moved in a scanning direction, comprising: an exposure device which exposes said pattern onto said object; a base structure which supports said stage in a manner in which said stage is movable; a non-contact bearing which opposes said stage to said base structure without any contact therebetween; a f irst drive device which moves said stage in' the scanning direction; and a balancing portion which moves in the scanning direction responsive to the movement of said stage such that the centre of gravity of said scanning type exposure apparatus does not shift substantially.

2. An exposure apparatus according to Claim 1, wherein said non-contact bearing is an air bearing.

3. An exposure apparatus according to Claim 1 or 2, wherein said first drive device has a first portion to be connected to said stage and a second portion to be connected to said balancing portion.

4. An exposure apparatus according to Claim 3, wherein said first portion and said second portion are not in contact with each other.

5. An exposure apparatus according to Claim 3 or L i k )4 wherein said first portion comprises a coil member and said second portion comprises a magnet member.

6. An exposure apparatus according to Claim 3, 4 or 5, wherein the movements of said stage and said balancing portion follow the law of conservation of momentum.

7. An exposure apparatus according to Claim 1, 2, 3, 4, 5 or 6, wherein said first drive device comprises a linear motor.

8. An exposure apparatus according to Claim 1, whdrein said balancing portion is movably supported by the base structure.

9. An exposure apparatus according to Claim 8, wherein said balancing portion is movable over a surface of said base structure via a bearing.

10. An exposure apparatus according to Claim 9, wherein said bearing is a non-contact bearing which opposes said balancing portion to said base structure without any contact therebetween.

11. An exposure apparatus according to any one of the preceding claims, further comprising a position detection device which detects a position of said stage.

12. An exposure apparatus according to Claim 11, wherein said position detection device comprises a reflective surface fixed to said stage.

13. An exposure apparatus according to Claim 12, wherein said reflective surface is a corner-cube type mirror.

14. An exposure apparatus according to Claim 11, 12 or 13, wherein said position detection device detects a position of said stage with regard to said scanning direction during the movement of said stage.

15. An exposure apparatus according to Claim 11, 12 or 13, wherein said position detection device detects a position of said stage with regard to a direction which is different from said scanning direction during the movement of said stage.

16. An exposure apparatus according to Claim 11, 12, 13, 14 or 15, further comprising a control system which corrects yaw rotation of said stage based on a detection result by said position detection device.

17. An exposure apparatus according to Claim 16, wherein said control system is connected to said first drive device.

18. An exposure apparatus according to any one of the preceding claims, further comprising a second drive dev-1-ce which moves said stage in a direction which is different from said scanning direction.

19. An exposure apparatus according to any one of the preceding claims, wherein said exposure device includes a projection system which projects said pattern onto said object.

1 36

20. An exposure apparatus according to Claim 19, wherein said stage is located above said projection system.

21. An exposure apparatus according to Claim 19 or 20, wherein said projection system projects the pattern optically.

22. An exposure apparatus according to any one of the preceding claims, wherein said exposure device includes a mask which defines said pattern.

23. An exposure apparatus according to Claim 22, wherein said stage holds said mask.

24. An exposure apparatus according to any one of the preceding claims, wherein said balancing portion operates without a drive source.

25. An exposure apparatus according to any one of the preceding claims, wherein said mask stage comprises an opening through which said exposure device exposes said pattern onto said object.

26. An exposure apparatus according to any one of the preceding claims, wherein said balancing portion is of a rectangular shape.