Abstract:
The invention relates to a device for exposing substrate materials comprising: at least one optical exposure device, at least one substrate platform; a device for generating a relative displacement between the exposure device and the substrate platform in two transversal directions, whereby the relative displacement in a primary direction occurs with a greater dynamic response than in a secondary direction; at least one primary drive for generating the relative displacement in the primary direction; and at least one secondary drive for generating the relative displacement in the secondary direction. The aim of the invention is to position the substrate platform with the greatest possible accuarcy and the greatest possible dynamic response. To achieve this, the device comprises two substrate platforms that move substantially in opposition to one another in the primary direction.

Description:
This application is a continuation of international application number PCT/EP03/02578 filed on Mar. 13, 2003. 

   The present disclosure relates to the subject matter disclosed in international application No. PCT/EP03/02578 of Mar. 13, 2003 and German application No. 102 12 344.6 of Mar. 15, 2002, which are incorporated herein by reference in their entirety and for all purposes. 
   BACKGROUND OF THE INVENTION 
   The invention relates to an apparatus for exposing substrate materials, comprising at least one optical exposure device, at least one substrate table, an apparatus for generating a relative movement between the exposure device and the substrate table in two directions running transversely with respect to one another, the relative movement being effected with a greater dynamic in a main direction than in a secondary direction, at least one main drive for generating the relative movement in the main direction and at least one secondary drive for generating the relative movement in the secondary direction. 
   With known apparatuses of this type, the problem constantly arises of combining the highest possible precision of positioning of the substrate table with the highest possible dynamics when moving the latter. 
   The invention is therefore based on the object of improving an apparatus of the type described in the introduction in such a manner that this apparatus, while having the highest possible dynamics, also has the highest possible positional accuracy when the substrate table is being positioned. 
   SUMMARY OF THE INVENTION 
   In an apparatus of the type described in the introduction, this object is achieved, according to the invention, by virtue of the fact that the apparatus has two substrate tables which move substantially in opposite directions in the main direction. 
   This solution creates the possibility of moving the substrate tables with high dynamics, in particular great accelerations, without great acceleration forces having to be absorbed, since the movement of the substrate tables in opposite directions substantially cancels out the acceleration forces. 
   To realize this, it is preferably provided that a main drive is associated with each substrate table. 
   There is a very wide range of conceivable options in terms of the interaction between the main drive and the substrate table. By way of example, the main drive could be disposed in such a way that it drives the substrate table directly or indirectly. 
   However, it is particularly expedient if the main drive is disposed separately from the substrate table. 
   This solution leads to good thermal decoupling and good mechanical coupling of the main drive from the substrate table, and in particular its guidance. 
   To allow favorable realization of a coupling between the main drive and the substrate table, it is preferably provided that a traveller of the main drive drives the respectively associated substrate table via a drive connection which is rigid in the main direction. 
   This on the one hand produces a rigid coupling between the traveller of the main drive and the substrate table, allowing accurate guidance and positioning of the substrate table, and on the other hand produces sufficiently good thermal decoupling, and in particular also vibrational decoupling between the two, reducing the vibrations generated by the main drive and transmitted to the substrate table to a minimum. 
   In this context, it is expedient for each substrate table to be disposed on a carrier carriage and to be guided in the main direction by the latter. 
   One particularly expedient form of coupling between the traveller and the substrate table is made possible by the traveller and the carrier carriage of the substrate table being coupled to one another via the drive connection which is rigid in the main direction. 
   As an alternative or in addition, the object specified in the introduction is also achieved, in an apparatus in accordance with the invention, by virtue of the fact that the traveller of the main drive is guided in the X direction on guide surfaces which are separate from guide surfaces running in the X direction for the carrier carriage. This solution also allows as far as possible optimum decoupling of the traveller of the main drive from the guide carriage and the carrier carriage which carries the guide carriage, in order likewise to minimize the thermal influence of the main drive on the guidance of the carrier carriage and on the other hand also to optimize the vibrational decoupling of the two. 
   There are two favorable options with regard to the way in which the substrate tables and the main drives are disposed relative to one another. 
   One possibility provides for the substrate tables to be disposed between the main drives. 
   Another possibility provides for the main drives to be disposed between the substrate tables. 
   It is particularly expedient in this context if the main drives for the substrate tables are combined in a common drive unit, so that the oppositely running acceleration forces act on this common drive unit and can cancel themselves out therein. 
   In this context, it is preferable for the drive unit to be realized in such a way that the drive carriage carries the common drive unit, and therefore the drive carriage for its part does not have to absorb high acceleration forces, since these forces all at least substantially compensate for one another in the drive unit. 
   An apparatus of this type can be realized particularly effectively by virtue of the substrate tables being disposed on opposite sides, as seen in the main direction, of the drive unit. 
   In order in this case to realize a solution which is as compact as possible, it is preferably provided that the main drives work in drive planes running at a spacing from another in a direction that is transverse with respect to the main direction and transverse with respect to the secondary direction, thereby creating the possibility of minimizing the space required for the drive unit in the main direction. 
   In this context, it is particularly expedient if the traveller of the main drive for one substrate table works in one drive plane and the traveller of the main drive for the other substrate table works in the other drive plane, which is parallel to the one drive plane. 
   Furthermore, one advantageous solution to the object identified in the introduction provides, as an alternative or in addition to the exemplary embodiments which have been described hitherto, in an apparatus of the type described in the introduction, that, according to the invention, the relative position of substrate table and exposure device can be recorded by an interferometric measuring device. 
   Hitherto, no further details have been given in terms of the way in which the at least one exposure device and the substrate tables are associated with one another. The apparatus according to the invention is particularly advantageous in terms of the efficiency of exposure of substrates if an exposure device is associated with each of the substrate tables. 
   In this context, it is preferably provided that the substrate table and the respectively associated exposure device are movable relative to one another in the main direction and in the secondary direction, so that as a result controllable exposure of the substrate can be carried out at each of the substrate tables in conjunction with the exposure device. 
   An interferometric measuring device of this type has the major advantage of allowing the position of the substrate table to be measured with an accuracy in particular in the nanometer range. 
   A particularly high measurement accuracy during determination of the position of the substrate table can be achieved if the interferometric measuring device works with an optics head of the optical exposure device as reference point, i.e. all the measurements carried out by the interferometric measuring device are referenced to the position of the optics head as reference position. 
   The interferometric measuring device can in this case be integrated spatially in a particularly effective way in an apparatus according to the invention if this device records the position of the optics head in a reference plane running parallel to the main direction and to the secondary direction and records the position of the substrate table in a measuring plane running parallel to the reference plane. 
   To record the individual positions, it is preferably provided that the interferometric measuring device works, in the reference plane and in the measuring plane, with measuring beams which impinge on mirrors extending in the main direction and the secondary direction. This makes it possible in particular to determine distances via interference in a simple way. 
   A particularly expedient implementation option provides for the optics head to be provided with a reflection mirror extending in the main direction and a reflection mirror extending in the secondary direction. 
   With regard to the recording of the substrate table, it is expedient if the substrate table is provided with a mirror extending over the maximum path of the substrate table at least in the main direction. This allows favorable recording of the position of the substrate table in the secondary direction in particular even if the substrate table moves. 
   Furthermore, it is preferably provided that the substrate table is provided with a mirror which extends at least over the maximum path in the secondary direction, by means of which mirror, in the event of the substrate table moving, the position of the latter in the main direction can also be expediently determined. 
   A particularly high measurement accuracy can be achieved using the interferometric measuring device if the interferometric measuring device carries out measurement using laser light of the same wavelength in both the main direction and the secondary direction. 
   This can be achieved particularly advantageously if the interferometric measuring device works using laser light from a common laser radiation source. 
   To optimize the focusing of the light from the optical exposure device on the substrate which is to be exposed, it is preferably provided that the optical exposure device is provided with an autofocusing system, which at the same time also balances out minor inaccuracies in the guidance of the substrate table relative to the guide plane. 
   Hitherto, no more detailed information has been provided with regard to the way in which the substrate table is fed with substrate materials. For example, it would be conceivable for the substrate materials to be positioned manually on the substrate table and to be oriented manually for exposure using the exposure device. 
   However, a particularly expedient solution provides that the apparatus has a transport system which can be used to transport substrate materials from a preparation station onto the substrate table. An apparatus of this type has the advantage of allowing the time required for positioning of the substrate materials on the substrate table to be reduced. 
   This is particularly expedient if the substrate materials can be pre-positioned in the preparation station and can be placed on the substrate table in a pre-positionable manner by the transport system. 
   This provides the option of carrying out the time-consuming preliminary positioning of the substrate materials in the preparation station, so that substrate materials which are already present on the substrate table can be exposed, for example, during the preliminary positioning of the substrate materials, and then the substrate materials which have been pre-positioned can be placed on the substrate table by the transport system, while maintaining the pre-positioning, after the exposed substrate materials have been removed from the substrate table. 
   In order also to make the removal of the exposed substrate materials as efficient as possible, it is preferably provided that the apparatus has a transport system which can be used to transport exposed substrate materials from the substrate table into a removal station. 
   The object identified in the introduction is, as an alternative or in addition, achieved, in an apparatus of the type described in the introduction, by virtue of the fact that, according to the invention, the drive for the main direction is seated on a drive pedestal body, which is disposed so as to be physically separate from a pedestal body which carries the exposure device and the substrate table. 
   The advantage of the solution according to the invention is therefore considered to reside in the fact that all negative influences of the main drive for the main direction, such as for example strong accelerations and temperature changes, do not have a direct effect on the positioning accuracy of the substrate table relative to the exposure device, since both the substrate table and the exposure device are carried by a pedestal body which is disposed so as to be physically separate from the drive pedestal body. 
   If it is also taken into consideration that pedestal bodies of this type are preferably bodies of a large mass, in particular in the range of tonnes, the physically separate pedestal bodies produce optimum decoupling between the drive pedestal body and the pedestal body for the exposure device and the substrate table. 
   No further details have been provided with regard to the form of the apparatus for generating the relative movement between the exposure device and the substrate table in connection with the basic concept of the invention. By way of example, it would be conceivable on the one hand to move the exposure device in one axis direction and on the other hand to move the substrate table in the other direction. 
   However, it is particularly advantageous if the exposure device is held in a stationary position on the pedestal body. This has the advantage that the stationary position of the exposure device relative to the pedestal body allows all the mechanical damping properties of the pedestal body to be utilized in order to minimize the transmission of shaking and vibration to the exposure device. 
   Furthermore, this solution has the advantage that it is possible to simplify recording of the relative position between the exposure device and the substrate table by virtue of the stationary positioning of the exposure device on the pedestal body producing, in a simple way, a reference point for the measuring device for determining the position of the substrate table. 
   For this reason, the substrate table is preferably movable in the main direction and the secondary direction. 
   To allow favorable realization of this movability of the substrate table, it is preferably provided that the substrate table is disposed on a carrier carriage which is movable relative to the pedestal body in the main direction and the secondary direction. 
   On the other hand, however, this movability must be associated with accurate guidance of the carrier carriage. 
   Therefore, for accurate guidance of the carrier carriage, it is preferably provided that the carrier carriage is guided on a guide carriage in such a manner that it is movable in the direction of the main direction, with the guide carriage for its part being movable relative to the pedestal body at least in the secondary direction. 
   To ensure that the carrier carriage is guided as accurately as possible on the guide carriage, it is preferably provided that the carrier carriage is guided on the guide carriage so as to prevent relative movement only in the secondary direction, but not in any further direction, so that the guidance of the carrier carriage on the guide carriage can be defined with a high degree of accuracy and the guides for the other directions have no adverse effect on the accuracy of the guidance of the carrier carriage on the guide carriage. 
   Particularly accurate and easy guidance can be achieved if the carrier carriage is guided on the guide carriage using air guides, with the guidance being effected in particular by air cushions. Air cushions of this type not only have the advantage of providing easy guidance, but also have the advantage of a high level of attenuation of mechanical vibrations. 
   To provide accurate guidance for the carrier carriage during movement transversely with respect to the main direction and secondary direction, it is preferably provided that the carrier carriage is guided in a direction which is transverse with respect to the main direction and secondary direction on a guide plane of the pedestal body. 
   The guide plane therefore allows a movement of the carrier carriage both in the main direction and in the secondary direction and effects particularly accurate guidance in the direction perpendicular to these directions. 
   In this context, it is particularly expedient if the carrier carriage is guided on the pedestal body using air guides, so that very easy yet nevertheless accurate guidance, in particular with vibration attenuation, is provided for the carrier carriage. 
   Since the accuracy of guidance of the carrier carriage in the direction transverse with respect to the main direction and with respect to the secondary direction is dependent on the quality of the guide plane, it is preferably provided that the guide plane be formed by a ground surface, or even more preferably by a polished surface. 
   In this context, it is preferable for the pedestal body to be formed from a heavy material which, as guide plane, has a ground and polished surface. In this context, it is particularly expedient if the pedestal body is produced from a rock, in particular granite. 
   To achieve the highest possible accuracy, it is particularly advantageous if the substrate table can be oriented in the direction of the secondary direction relative to the guide carriage, so that it is possible to carry out positional corrections, in particular translational and/or rotational corrections, to the substrate table by means of movements in the direction of the secondary direction and thereby to retrospectively compensate for inaccuracies resulting from the mechanical structure or the thermal behavior of the mechanical structure. 
   In this context, it is particularly expedient if the substrate table can be oriented relative to the guide carriage by positioning elements acting in the secondary direction, which elements allow accurate repositioning of the substrate carriage. 
   The positioning elements may in this case be manually actuable. A particularly expedient solution provides for the positioning elements to be actuable by a control unit, thereby providing the option of controlled correction of the orientation of the substrate table in the secondary direction at any desired operating time. 
   The positioning elements may be formed in a wide variety of ways. They may be Lorenz motors or moving coil servomotors. A particularly expedient embodiment provides for the positioning elements to be piezo elements. 
   Hitherto, no more detailed information has been given with regard to the positioning of the guide carriage in the secondary direction itself. Therefore, a particularly expedient solution provides that the guide carriage can be moved in the secondary direction by two secondary drives which are disposed at a spacing from one another in the main direction. This solution has the advantage that it is possible to achieve highly accurate guidance of the guide carriage in the secondary direction, since synchronous operation of the two secondary drives allows the guide carriage to be moved with an accurate orientation in the secondary direction by means of controlled orientation. 
   As an alternative or in addition to the exemplary embodiments described above, the object described in the introduction is also achieved, in an apparatus of the type described in the introduction, by virtue of the fact that, according to the invention, the main drive is seated on a drive carriage which is separate from the guide carriage and for its part is guided movably in the secondary direction on the drive pedestal body by a secondary drive. 
   This separation of the main drive from the guide carriage, which for its part guides the carrier carriage, likewise serves to optimize the thermal and also mechanical decoupling of the main drive from the guide for the carrier carriage, which can be realized with an extremely high level of accuracy. 
   There is also a very wide range of options with regard to the guidance of the drive carriage transversely with respect to the main direction and secondary direction. 
   In this context, it is particularly expedient if the drive carriage is guided, transversely with respect to the main direction and transversely with respect to the secondary direction, on a guide plane of the drive pedestal body. 
   The guide plane should likewise have an optimum guide quality for the drive carriage. 
   For this reason, it is preferably provided that the guide plane be formed as a ground surface, and it is even more expedient for the guide plane to be formed as a polished surface. 
   In this context, the drive pedestal body is in particular likewise a body which is as heavy as possible, preferably made from granite. 
   To guide the drive carriage as easily as possible, it is preferably provided that the drive carriage be guided on the drive pedestal body using air guides. 
   In order, in the event of a movement of the guide carriage in the secondary direction, to ensure that there is no guide inaccuracy whatsoever caused by an offset relative to the movement of the drive carriage, it is preferably provided that the drive carriage is movable synchronously with respect to the guide carriage. 
   In this case, it is preferable for the secondary drives for moving the drive carriage and the guide carriage to be synchronized with one another. 
   Hitherto, it is also the case that no further details have been given with regard to the realization of the main drive. Therefore, a particularly advantageous exemplary embodiment provides for a traveller of the main drive to be guided movably in the main direction on the drive carriage. 
   To transmit the movements of the traveller to the carrier carriage, it is preferably provided that a drive connection which is rigid in the main direction be provided between the traveller and the carrier carriage, this drive connection preferably also being formed in such a way as to have a certain movability transversely with respect to the main direction. 
   Further features and advantages of the invention form the subject matter of the following description and of the illustration of a number of exemplary embodiments in the drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective view of an apparatus according to the invention for exposing substrate materials, with the exposure device represented just by an optics head; 
       FIG. 2  shows an enlarged view of one half of the apparatus illustrated in  FIG. 1 , seen in the direction of arrow A in  FIG. 1 ; 
       FIG. 3  shows a section on line  3 — 3  in  FIG. 2 ; 
       FIG. 4  shows an overall view of the first exemplary embodiment, illustrated in  FIG. 1 , of the apparatus according to the invention, seen in the direction of arrow A in  FIG. 1 ; 
       FIG. 5  shows a section on line  5 — 5  in  FIG. 2 ; 
       FIG. 6  shows a plan view of the first exemplary embodiment shown in  FIG. 1 , seen in the direction of arrow B in  FIG. 1 ; 
       FIG. 7  shows an enlarged illustration of a substrate table having the transport carriage of the first exemplary embodiment of the apparatus according to the invention, together with a measuring device according to the invention for determining a position of the substrate table; 
       FIG. 8  shows a section on line  8 — 8  in  FIG. 3 ; 
       FIG. 9  shows an enlarged perspective illustration, similar to  FIG. 1 , of part of the first exemplary embodiment of the apparatus according to the invention, with the exposure device illustrated in full; 
       FIG. 10  shows an excerpt plan view similar to  FIG. 6  of a second exemplary embodiment of an apparatus according to the invention; 
       FIG. 11  shows an illustration similar to  FIG. 4  of a third exemplary embodiment of the apparatus according to the invention; 
       FIG. 12  shows an illustration similar to  FIG. 6  of the third exemplary embodiment of the apparatus according to the invention; 
       FIG. 13  shows an illustration similar to  FIG. 9  of the third exemplary embodiment of the apparatus according to the invention; and 
       FIG. 14  shows an illustration similar to  FIG. 6  of a fourth exemplary embodiment of an apparatus according to the invention for exposing substrate materials. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An exemplary embodiment of an apparatus according to the invention for exposing substrate materials, illustrated in part in  FIGS. 1 and 2 , comprises two exposure devices  10   a, b , each of the exposure devices  10   a, b  in  FIGS. 1 and 2  being represented only by an optics head  12   a, b;  the way in which they are disposed will be explained in detail below. 
   Furthermore, the apparatus according to the invention comprises two substrate tables  14   a, b , on which substrates  16 ,  18  which are to be exposed are disposed in order for them to be exposed by means of the optical exposure devices  10   a, b.    
   This requires a relative movement between the respective substrate table  14   a, b  with the substrates  16 ,  18  and the respective optics head  12   a, b.    
   For reasons of simplicity, there will first of all follow a description of the conditions which result for one of the optics heads  12   a, b  and the corresponding one of the substrate tables  14   a, b , but since the description applies equally to both optics heads  12   a, b  and the corresponding substrate tables  14   a, b , the letters a, b are omitted. 
   In the exemplary embodiment of the apparatus for exposing substrate materials, such as for example wafers, according to the invention which is illustrated, this relative movement is realized by virtue of the fact that the substrate table  14  is movable in an X direction and a Y direction relative to the exposure device  10 . 
   For this purpose, the substrate table  14  is disposed on a carrier carriage  20 , which is guided slidably on a guide plane  22  running parallel to the X direction and parallel to the Y direction, with the guide plane  22  extending transversely, preferably approximately in the horizontal, with respect to a vertical. 
   Furthermore, the carrier carriage  20  is for its part guided on a guide carriage  24  which extends with a longitudinal guide  26  parallel to the X direction, along which guide the carrier carriage  20  can be moved in the X direction but is guided such that it cannot move in the Y direction. 
   As illustrated in  FIG. 2 , the longitudinal guide  26  is preferably formed by an elongate guide bar  28  which has side guide surfaces  30   a  and  30   b  on opposite sides, which extend transversely with respect to the Y direction and preferably in planes running parallel to the X direction and parallel to the Z direction, which for its part is perpendicular to the X and Y directions. 
   For its part, the carrier carriage  20  engages, by means of side limbs  32   a, b , around the guide bar  28  in an inverted U shape, so that the side limbs  32   a, b  of the carrier carriage  20  extend on both sides of the guide bar  28 , with their ends  33   a, b  facing the guide plane  22  ( FIG. 3 ). 
   These side limbs  32   a, b  carry, on their sides facing the guide surfaces  30   a, b , devices  34   a, b  for generating air cushions, so that air cushions which guide the carrier carriage  20  in the Y direction on the guide bar  28  are formed between these devices  34   a, b  and the guide surfaces  30   a, b.    
   Furthermore, the side limbs  30   a, b  are likewise provided, at their ends  33   a, b  facing the guide plane  22 , with devices  36   a, b  for generating air cushions, which each generate air cushions between them and the guide plane  22 , so that the carrier carriage  20  can slide over the guide plane  22  on these air cushions. 
   Furthermore, the guide carriage  24  is for its part also guided slidably by devices  38   a, b  for generating air cushions on the guide plane  22 , these devices  38   a, b  likewise forming air cushions between them and the guide plane  22 , so as to guide the entire guide carriage  24  slidably on the guide plane  22 . 
   In the apparatus according to the invention for exposing substrate materials, the guide plane  22  is preferably formed by a surface of a pedestal body  40 , the pedestal body  40  preferably being a granite block with a polished surface which represents the guide plane  22  and is therefore a highly accurate surface for guiding the carrier carriage  20 . 
   The pedestal body  40  is preferably seated, by means of an underside  42 , on a standing surface  44  for the apparatus according to the invention. 
   Furthermore, the pedestal body  40  is provided with two guide grooves  46 ,  48  which, starting from the guide plane  22 , extend into the pedestal body and run in the Y direction, each of the guide grooves  46 ,  48  forming, by means of their mutually opposite groove walls, guide surfaces  50   a ,  50   b  which extend parallel to the Y direction and parallel to the Z direction, thereby in each case forming a guide preventing movement in the X direction. 
   Guide bodies  52  and  54  of the guide carriage  24 , which are fixedly connected to the guide bar  28  and on opposite sides each carry devices  56   a ,  56   b  for generating air cushions, which between them and the guide surfaces  50   a, b  form an air cushion which guides the respective body  52  and  54  in the guide grooves  46  and  48 , respectively, so that the guide carriage  24  is thereby guided such that it cannot move in the X direction relative to the pedestal body  40 , are provided in these guide grooves  46  and  48 . 
   Linear motors  60  and  62 , which are disposed in the guide grooves  46  and  48  and the winding body  64  of which is preferably disposed in a stationary position on a groove base  66  of the guide grooves  46  and  48 , are provided for displacement of the guide carriage  24  in the Y direction, while a traveller  68 , which can be displaced by suitable energization of the winding body  64 , is movable in the guide grooves  46  and  48 , in each case guided in the Y direction. 
   It is preferable for the traveller  68  of the respective linear motor  60 ,  62  likewise to be guided by air cushions in the guide grooves  46  and  48 . 
   The connection between the traveller  68  and the guide carriage  24  is preferably effected by means of a coupling rod  70  which is rigid in the Y direction and is provided between the respective traveller  68  and the corresponding guide body  52  or  54 . 
   The movement of the substrate table  14  in the Y direction constitutes a movement in a secondary direction, while the main direction of the movement is the X direction, since during the exposure of the substrate materials  16  and  18  by means of the exposure device  10 , the movement in the X direction has a far higher dynamic, on account of the considerable movement displacement compared to the movement in the Y direction. 
   For this reason, a separate drive unit  78  is provided, comprising a linear drive  80  for moving the substrate table  14  in the X direction, which linear drive is disposed on a drive carriage  82 , the drive carriage  82  for its part being guided, in such a manner that it is movable in the Y direction, on a guide plane  84  which extends parallel to the X and Y directions ( FIGS. 1 ,  4 ,  5 ). 
   For this purpose, the drive carriage  82  preferably has devices  88  disposed on its underside  86 , for generating an air cushion between them and the guide plane  84  so that the drive carriage  82  is movable with respect to the guide plane  84  with guidance provided by the air cushions. 
   The guide plane  84  is in this case formed by a drive pedestal body  90 , the underside  92  of which likewise stands on the standing surface  44 . 
   In this context, the drive pedestal body  90  is completely physically separate from the pedestal body  40  for the carrier carriage  20  and the guide carriage  24 . 
   It is preferable for the drive pedestal body  90  likewise to be formed as a granite block with a polished surface as guide plane  84 . 
   The linear drive  80  for moving the carrier carriage  20  in the X direction comprises a winding body  92 , which is disposed in a fixed position on a base  94  of a U-shaped recess  95  of the drive carriage  82 , and a traveller  98 , which is guided between lateral guide surfaces  96   a  and  96   b  of the U-shaped recess and, between the guide surfaces  96   a, b , is guided movably in the X direction, the guidance for the traveller  98  preferably being effected by means of devices  100   a ,  100   b  for generating air cushions, which, between these devices  100   a, b  and the guide surfaces  96 , guide the traveller  98  so that it cannot move in the Y direction. 
   The coupling between the traveller  98  and the carrier carriage  20  is in this case preferably effected by a coupling rod  102  which is rigid in the X direction and engages both on the traveller  98  and on the carrier carriage  20 . 
   The drive carriage  82  is preferably guided on the drive pedestal body  90  by a guide groove  106  which is provided in the drive pedestal body  90 , extends into the latter starting from the guide plane  84  and has guide surfaces  108   a ,  108   b , which are formed by the side walls of the guide groove  106  and between which a guide body  110  is guided such that it can move in the Y direction but cannot move in the X direction; the guide body  110  is fixedly connected to the drive carriage  82 . 
   For its part, the guide body  110  is provided with devices  112   a ,  112   b  for generating an air cushion facing the guide surfaces  108   a, b , the air cushion being located between these devices  112   a ,  112   b  and the guide surfaces  108   a, b.    
   To move the drive carriage  82  in the Y direction there is a linear motor  114 , the winding carrier  116  of which is disposed on a groove base  118  of the guide groove  106  and the traveller  120  of which is movable in the Y direction in the guide groove  106 , the traveller  120  preferably likewise being guided by air cushions between the guide surfaces  108   a, b.    
   A connection between the traveller  120  and the guide body  110 , which is connected to the drive carriage  82 , is effected by means of a coupling rod  122  which is rigid in the Y direction. 
   The accelerations in the X direction which are generated by the linear drive  80  in order for the carrier carriage  20  together with the substrate table  14  to be displaced in the X direction would, on account of the high dynamics and the constant reversal of movement after they have passed over the two substrate materials  16 ,  18  or wafers, lead to high loads on the guidance provided by the guide body  110  between the guide surfaces  108   a, b.    
   For this reason, the apparatus according to the invention advantageously provides a pedestal body  40   a ,  40   b  with a carrier carriage  20   a, b  which can be displaced thereon in the X direction on each of opposite sides of the drive carriage  82 . Furthermore, two linear drives  80   a  and  80   b  are provided in the drive unit in the drive carriage  82 , the linear drive  80   a  being intended to move the carrier carriage  20   a  and the drive  80   b  being intended to move the carrier carriage  20   b , which are located on opposite sides of the drive carriage  82 . Furthermore, the linear drives  80   a  and  80   b  are actuated by a control unit  130  in such a way that the travellers  98   a  and  98   b  always move substantially in opposite directions, i.e. either both carrier carriages  20   a ,  20   b  are moved away from the drive unit  78  or both carrier carriages  20   a ,  20   b  are moved toward the drive unit  78 . This allows the high accelerations generated by the linear drives  80   a  and  80   b  to at least substantially compensate for each other, so that only slight forces have to be absorbed by the guide body  110  guided between the guide surfaces  108   a, b , guiding the drive carriage  82  in the X direction accurately into its X position. 
   Disposing the linear drives  80   a  and  80   b  one above the other leads, as illustrated in  FIGS. 4 and 5 , to the coupling rod  102   a  acting in a first drive plane  132 , while the coupling rod  102   b  acts in a drive plane  134  which runs parallel to the drive plane  132  but is offset with respect to it, for example running closer to the standing surface  44 . 
   The guide planes  22   a  and  22   b  of the pedestal bodies  40   a  and  40   b  also have the same offset as the drive planes  132  and  134 , so that the carrier carriages  20   a  and  20   b  are also guided at different heights, with the carrier carriages  20   a  and  20   b  and the guide carriage  24  preferably being of identical construction and being guided on the pedestal body  40   a, b.    
   For this reason, all the statements which have been made hitherto with regard to the form, guidance and structure of the carrier carriages also apply to both carrier carriages  20   a ,  20   b.    
   Furthermore, the pedestal bodies  40   a  and  40   b  are also disposed so as to be physically separate, preferably without any connection, with respect to the drive pedestal body  90 . This is primarily associated with the fact that on account of the high dynamics associated with the driving of the carrier carriages  20   a ,  20   b  in the Z direction, high levels of heat are evolved at the linear drives  80   a ,  80   b , which in turn is detrimental to the accurate positioning of the carrier carriages  20   a, b.    
   Furthermore, the high dynamics mean that accelerations also have to be absorbed by the drive pedestal body  90 , and these accelerations, if there is a physical separation between the drive pedestal body  90  and the pedestal bodies  40   a  and  40   b , are not transmitted, or at least are only transmitted to a much lesser extent, to these pedestal bodies  40   a ,  40   b.    
   Therefore, as a result of the drive pedestal body  90  being separate from the pedestal bodies  40   a  and  40   b , it is possible to improve the accuracy of the highly accurate guidance of the carrier carriages  20   a ,  20   b  in the guide planes  22   a ,  22   b.    
   As illustrated in  FIG. 6 , the control unit  130  then controls the movement of the carrier carriages  20   a ,  20   b  by corresponding movement of the guide carriages  24   a ,  24   b  by means of the linear motors  60  and  62  and the movement of the drive carriage  82  by means of the linear motor  114  in the Y direction, in such a manner that the movement of the carrier carriages  20   a  and  20   b  and of the drive carriage  82  takes place synchronously, in such a manner that a center axis  136   a  which is in the drive plane  132  and a center axis  136   b  which is in the drive plane  134  are always located in a common orientation plane  138  which runs perpendicular to the drive planes  132  and  134  and therefore parallel to the Z direction. 
   For exact positioning of the respective substrate table  14  relative to the optics head  12 , an interferometric measuring device  140  is provided, as illustrated in  FIG. 7 , comprising a mirror bar  142  extending in the Y direction and having a mirror surface  144  which extends parallel to the Y direction and parallel to the Z direction over the width of the substrate table  14 . Furthermore, a mirror bar  146 , which extends in the X direction and carries a mirror surface  148  extending in the X direction and in the Z direction, is provided on a longitudinal side on the substrate table  14 . 
   The mirror surfaces  144  and  148  are therefore disposed in a fixed position relative to the substrate table  14 . 
   Furthermore, the optics head  12  is provided with a mirror surface  150  which extends parallel to the Y direction and the Z direction and therefore parallel to the mirror surface  144  and with a mirror surface  152  which extends parallel to the X direction and to the Z direction and therefore parallel to the mirror surface  148 . 
   Both mirror surfaces  150  and  152  are fixedly connected to the optics head  12 . 
   Furthermore, the measuring device  140  comprises two interferometer units  154  and  156 , each of which emits a measuring beam  158  and  160 , respectively, in the direction toward the mirror surface  144  of the substrate table  14  and, moreover, a measuring beam  162  and  164 , respectively, toward the mirror surface  150 . Each of the interferometer units  154  and  156  is therefore able, by establishing the path differences which can be determined by means of the measuring beams  158  and  162 , and  160  and  164 , respectively, to determine the spacings between the mirror surface  144  and the mirror surface  150 , which thereby indicates the precise relative position of the substrate table  14 , in this case the substrate table  14   b , relative to the optics head, in this case the optics head  12   b.    
   For this purpose, the measuring beams  158  to  164  run exactly parallel to the X direction, and it is also preferable for the measuring beams  162  and  164  to run in a reference plane  188  and the measuring beams  158  and  160  to run in a measuring plane  189 , both of which planes, for their part, run parallel to the guide plane  22 , in this case the guide plane  22   b.    
   It is preferable for the two interferometer units  154  and  160  to be disposed in such a way that their measuring beams  158  and  162 , and  160  and  164 , respectively, are disposed at a spacing from one another in the Y direction, so that it is possible not only to determine the relative position of the mirror surfaces  144  and  150  in the X direction, but also to establish whether the mirror surfaces  150  and  144  are oriented exactly parallel to one another. If there are deviations from a precisely parallel path, the substrate table  14   b  has turned about an axis parallel to the Z direction. 
   Furthermore, the measuring device  140  also comprises an interferometer unit  170  which generates a measuring beam  172 , which is directed toward the mirror surface  148  and is in the measuring plane  189 , and a measuring beam  174 , which is directed toward the mirror surface  152  and is in the reference plane  188 , and can use the path difference of these measuring beams  152  and  154 , which run in the Y direction, to determine the difference in position between the optics head  12   b  and the substrate table  14   b  in the Y direction. 
   To ensure that all the interferometer units  154 ,  156  and  170  work with the same wavelength, they have associated with them a common laser light source  176 , which generates wavelength-stabilized laser radiation  178  that is divided via beam splitters  180  to  186  between the interferometer units  154 ,  156  and  170 , so that all the interferometer units  154 ,  156  and  170  operate with laser radiation of the same wavelength. 
   All the interferometer units  154 ,  156  and  170  are disposed in a stationary position relative to the pedestal body  40 , so that the substrate table  14  moves relative to the measuring beams  158  and  160  and  172 , but in any position of the substrate table  14  these measuring beams still impinge on the corresponding mirror surface  144  or  148 , with the extent of the mirror surface  144  in the Y direction and the extent of the mirror surface  148  in the X direction preferably being greater than the paths along which the substrate table  14  is movable in the Y direction and the X direction. 
   With the relative spacings between the mirror surface  150  and the mirror surface  144  recorded by the interferometer units  154  and  156 , the control unit  130  is able to actuate the respective linear drive, in this case the linear drive  80   b , in such a way that the optics head  12  is in the desired relative position with respect to the substrate table  14  and therefore with respect to the substrate materials or wafers  16   b  and  18   b.    
   Furthermore, any rotation of the mirror surface  144  relative to the mirror surface  170  about an axis of rotation running in the Z direction which has been picked up by the interferometer units  154  and  156  can be corrected by the control unit  130  by virtue of the devices for generating an air cushion  34   a  to  34   b , which are disposed at the side limbs  32   a ,  32   b  of the carrier carriage  20 , each being seated on piezo elements  190   a  to  d , the thickness of which can be varied controllable by the control unit  130 , thereby creating the option of varying the spacing between the devices  34   a  to  34   d  for generating an air cushion from the side limbs  32   a  and  32   b , so that by suitable actuation of the piezo elements  190   a  to  190   d  it is possible to rotate the carrier carriage  20  a small amount about an axis parallel to the Z direction, enabling the mirror surface  144  to be held such that it is oriented exactly parallel to the mirror surface  150 . ( FIG. 8 ) 
   Furthermore, the control unit  130  is able to record the displacement of the substrate table  14  in the Y direction as a function of the measured spacing between the mirror surface  152  and the mirror surface  148  and to actuate the linear motors  60  and  62 , in this case the linear motors  60   b  and  62   b , accordingly, and at the same time also to synchronously actuate the linear motor  114  so as to move the drive carriage  82 . 
   The structural realization of the stationary positioning of the interferometer units  154  and  156 , and  170 , relative to the pedestal body  140  is illustrated in detail in  FIG. 9 . 
   To ensure that the positioning of the interferometer units  154  and  156  does not impede the movability of the coupling rod and of the substrate table, in this case of the coupling rod  102   a  and the substrate table  14   a , a bridge body, which is denoted overall by  200 , is seated on the pedestal body  40 , which bridge body is supported, by means of outer foot elements  202  and  204 , on the guide plane  22 , in this case the guide plane  22   a , and by means of bridge regions  206  and  208  engages over the movement range of the carrier carriage  20 , in this case of the carrier carriage  20   a , and of the substrate table  14 , in this case the substrate table  14   a.    
   In this case, by way of example, the two interferometer units  154  and  156  are seated on the bridge region  206  disposed so as to face the drive unit  78 , with the coupling rod  102   a  passing through beneath the bridge region  206 , while the exposure device  10 , which on its side facing the substrate table  14  carries the optics head  12 , is seated on the bridge region  208  which extends across the substrate table  14  and the carrier carriage  20 . 
   The exposure device  10  is formed and works in the same way as described, for example, in German Patent Application 101 60 917.5, to which reference is made in full in this respect. 
   Furthermore, the interferometer unit  170  is seated on a plinth region  210  which is provided to the side of the bridge body  200  and is disposed outside a range of movement of the carrier carriage  20  and of the substrate table  14 . 
   As illustrated in  FIG. 10 , a second exemplary embodiment of the apparatus according to the invention comprises a transport system, which is denoted overall by  220  and has a gripper device  222 , which is movable, for example, in the Y direction and can be used to grip unexposed substrate materials which have been prepared in a preparation station  224 , and in particular pre-positioned, for example the wafers  16 R and  18 R, and to feed them to the substrate table  14  in the pre-positioned arrangement. 
   Furthermore, the gripper device  222  can also be moved to a removal station  226 , which is disposed on an opposite side of the pedestal body  40  from the preparation station  224  and in which the exposed wafers  16 B,  18 B can be put down. 
   This makes it possible to optimize the time required for positioning of the wafers  16 ,  18  on the substrate table  14  and therefore to optimize the times required for the exposure of the individual substrate materials  16 ,  18 . 
   In a third exemplary embodiment of the apparatus according to the invention, illustrated in  FIGS. 11 to 13 , those elements which are identical to those of the exemplary embodiments described above are provided with the same reference symbols, and consequently in this respect reference can be made in full to the statements given above. 
   In the third exemplary embodiment, the substrate tables  14   a  and  14   b  are disposed, in the same way as in the exemplary embodiments given above, on carrier carriages  20 ′ which are provided for them but are guided in the X direction on guide bars  28  which are stationary in the Y direction, the guide bars  28  being held non-displaceably on the pedestal bodies  40   a  and  40   b , so that the carrier carriages  20 ′ is movable only in the X direction relative to the pedestal bodies  40   a ,  40   b.    
   Furthermore, a drive unit  78 ′ is provided, but it is no longer disposed on a separate pedestal body, but rather, by way of example, is also seated on the pedestal body  40   b;  the linear drives  80 , which drive the carrier carriages  20 ′ in the X direction in the known way, are disposed in the drive unit  78 ′ in a known way. 
   To produce the relative movement between the optics head  12  and the respective substrate table, in  FIG. 13  the optics head  12   a  and the substrate table  14 , the entire exposure device  10 , in  FIG. 13  the exposure device  10   a , is guided in the Y direction on the bridge body denoted overall by  200 , in  FIG. 13  the bridge body  200   a , with a guide  230  extending in the Y direction provided on the bridge body  200   a , along which guide an optics carriage  232 , which carries the respective exposure device  10  and is by way of example likewise air-supported, can be moved in the Y direction by a linear drive  234 , the traveller  236  of which is connected to the optics carriage  232  and the stator  238  of which is integrated in the Y guide  230 . 
   It is therefore possible, by moving the exposure device  10  in the Y direction and moving the substrate table  14  in the X direction, to generate the relative movement between the substrate table  14  and the exposure device  10  in the desired simple way. 
   In this exemplary embodiment, the interferometric measuring device  140  in principle operates in the same way as described in connection with the first exemplary embodiment, the only difference being that it is necessary for the mirror surface  150  which is fixedly connected to the optics head  12  and which extends parallel to the Y direction to have an extent in the Y direction which corresponds to the path that can be described by the exposure device  10  in the Y direction. 
   In a fourth exemplary embodiment, illustrated in  FIG. 14 , two drive units  78 ″ a  and  78 ″ b  are provided, the drive unit  78 ″ a  being used to drive the substrate table  14   a , and the drive unit  78 ″ b  being used to drive the substrate table  14   b.    
   Each of these drive units  78 ″ is provided with a linear drive  80 ″ a  or  80 ″ b , respectively. Furthermore, each of the linear drives  80 ″ a  and  80 ″ b  is coupled to the respective substrate table  14   a  and  14   b , respectively, by means of a coupling rod  102   a  and  102   b , respectively, which has already been described in accordance with the invention. 
   Unlike in the exemplary embodiments described above, in the fourth exemplary embodiment the drive units  78 ″ a  and  78 ″ b  are furthermore disposed in such a way that the substrate tables  14   a ,  14   b  are located between them, i.e. for each substrate table  14   a ,  14   b  the associated drive unit  78 ″ a  or  78 ″ b  is disposed on the opposite side from the respective other substrate table  14   b  or  14   a.    
   This solution has the advantage that the linear drives  80 ″ a  and  80 ″ b  can easily be supplied with energy and actuated, and moreover maintenance of the linear drives  80 ″ a  and  80 ″ b  can also be simplified. 
   Furthermore, it is easier to feed the two substrate tables  14   a ,  14   b.    
   Otherwise, the substrate tables  14   a ,  14   b  are disposed in the same way as described in connection with the preceding exemplary embodiments, on carrier carriages  20 ′ which are guided in the X direction on guide bars  28 ′; in the fourth exemplary embodiment too, it is preferable for the guide bars  28 ′ to be disposed in a stationary position on the pedestal bodies  40   a  and  40   b , such that they therefore cannot move in the Y direction. The relative movement between the substrate tables  14   a  and  14   b  and the respective optics head  12   a, b  is realized in the same way as in the third exemplary embodiment, by virtue of the exposure devices  10   a ,  10   b , being disposed such that they are movable in the Y direction.