Abstract:
Methods and apparatus for enabling a stage apparatus to scan an object within a vacuum environment while isolating actuators, cables, and hoses from the vacuum environment are disclosed. According to one aspect of the present invention, a stage apparatus includes a first stage and a first actuator. The first stage is effectively configured such that an interior space is defined substantially within the first stage. The first actuator is positioned within the interior space, and drives the first stage in a first direction.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates generally to semiconductor processing equipment. More particularly, the present invention relates to a stage assembly which is suitable for use in a vacuum environment and includes motors which are substantially out of contact with the vacuum environment.  
         [0003]     2. Description of the Related Art  
         [0004]     For precision instruments such as photolithography machines which are used in semiconductor processing, factors which affect the performance, e.g., accuracy, of the precision instrument generally must be dealt with and, insofar as possible, eliminated. When the performance of a precision instrument is adversely affected, as for example by contamination, products formed using the precision instrument may be improperly formed and, hence, function improperly. For example, if a vacuum environment in which a photolithography machine operates is contaminated, the vacuum level associated with the environment may be compromised, thereby affecting an overall photolithography process.  
         [0005]     Lithography processes, e.g., photolithography processes, are integral to the fabrication of wafers and, hence, semiconductor chips. Systems used for lithography include optical lithography systems, electron beam projection systems, and extreme ultraviolet lithography (EUVL) systems. The development of EUVL systems is becoming more widespread, as the capabilities of EUVL systems generally exceed those of conventional optical lithography systems and electron beam projection systems.  
         [0006]     In an EUVL system, beams of extreme ultraviolet (EUV) light are reflected off of a reflective reticle, which contains a circuit pattern, onto a semiconductor wafer. Reticle scanning stages are generally used to position a reticle over a wafer such that portions of the wafer may be exposed as appropriate for masking or etching. Patterns are generally resident on the reticle, which effectively serves as a mask or a negative for the wafer. When a reticle is positioned with respect to a wafer as desired, a beam of EUV light may be reflected off of the reticle on which a thin metal pattern is placed and effectively focused onto the wafer.  
         [0007]     Many scanning stage devices include a coarse stage and a fine stage which cooperate to position an object such as a reticle or a wafer. Specifically, many high precision machines used in semiconductor fabrication use a coarse stage for relatively large motion and a fine stage for smaller, or more precise, motion. A coarse stage is used to coarsely position a wafer, for example, near a desired position, while a fine stage is used to finely tune the position of the wafer once the wafer is positioned near its desired position by the coarse stage.  
         [0008]      FIG. 1  is a block diagram representation of a coarse stage and a fine stage which may be used as a part of an EUVL system. A coarse stage  112  and a fine stage  108 , which is carried on coarse stage  112 , are positioned within a vacuum chamber  104 . Coarse stage  112  is coupled to a counter mass  116 . A reticle (not shown) that is supported on fine stage  108  may be positioned such that a beam of EUV light may be reflected off of the reticle (not shown) onto a surface of a wafer (not shown).  
         [0009]     In general, an EUVL system must operate in a relatively high vacuum environment, which may be expensive to maintain, as any gas leakage into the vacuum environment must be corrected as the gas leakage typically compromises the vacuum level. Since flexible hoses or cables which are associated with typical EUVL systems often outgas or leak within the vacuum environment, the use of such hoses and cables may compromise the vacuum level associated with the vacuum environment. Further, air bearings in an EUVL system may also leak. Maintaining the vacuum level in a vacuum environment such as a chamber to compensate for gas leakage and other contamination is often difficult or impractical.  
         [0010]     As is the case with many scanning stages, the scanning stages used in an EUVL system are typically moved using motors such as linear motors. When it is necessary to service the motors, since the motors are positioned within a vacuum chamber, the vacuum chamber is generally opened to enable the motors to be accessed. Opening and closing, i.e., unsealing and resealing, the vacuum chamber is often a tedious process. The accessing of motors within a vacuum chamber exposes the vacuum chamber to contaminants and moisture, which may contaminate the surfaces of components within the vacuum chamber. The moisture within the vacuum chamber generally must be removed before the vacuum chamber may be used again, which increases the time associated with an overall pump down process used to create a vacuum within the vacuum chamber once the vacuum chamber is resealed.  
         [0011]     Within a vacuum chamber, it is difficult to maintain an acceptable operational temperature, as motors used to move a reticle scanning stage often heat up during operation. When the temperature within the vacuum chamber is too high, the operation of sensors within the vacuum chamber may be compromised. Since there is no air available in the vacuum chamber during an EUVL process, the only cooling that is available within the vacuum chamber results from conduction and radiation. As such, maintaining an acceptable temperature within the vacuum chamber is often a difficult process.  
         [0012]     Maintaining an acceptable vacuum level and an acceptable temperature within a vacuum chamber is important in order to ensure a high level of performance for an EUVL process. Ensuring that motors are properly serviced is also important, as the accuracy with which a wafer scanning stage may be moved is dependent upon the operation of the motors. Since maintaining a desired vacuum level, maintaining a desired temperature, and ensuring the proper operation of motors are crucial to an EUVL system, the ability to efficiently and relatively easily maintain a desired vacuum level, maintain a desired temperature, and ensure the proper operation of motors is important.  
         [0013]     Therefore, what is needed is a method and an apparatus for enabling is a relatively easy to maintain EUVL system. That is, what is desired is an EUVL system which has motors that are relatively easy to service, and enables both a desired vacuum level and a desired temperature to be accurately and efficiently maintained.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention relates to a stage apparatus which scans an object in a vacuum environment while isolating actuators, cables, and hoses from the vacuum environment. According to one aspect of the present invention, a stage apparatus includes a first stage and a first actuator. The first stage is effectively configured such that an interior space is defined substantially within the first stage. The first actuator is positioned within the interior space, and drives the first stage in a first direction.  
         [0015]     In one embodiment, the apparatus also includes a stage assembly that is supported by the first stage. The stage assembly includes a second stage and a second actuator that drives the second stage in a second direction. In such an embodiment, the apparatus may also include an interface plate that is coupled to the first stage and the second stage assembly such that the second stage assembly is supported by the first stage through the interface plate.  
         [0016]     A stage assembly which includes a coarse stage with an associated actuator that may be isolated from a vacuum environment while a fine stage of the stage assembly is positioned within the vacuum environment enables the vacuum environment to be efficiently maintained without significant issues associated with heat that is generated by the actuator, or contamination that results from the servicing of the actuator. Further, since the actuator associated with the coarse stage is external to the vacuum environment, substantially any moving hoses or cables associated with the coarse stage are also external to the vacuum environment, thereby reducing the likelihood of gas leakage and outgassing within the vacuum environment. Hence, when the stage assembly is used in a system such as an extreme ultraviolet lithography (EUVL) system, the performance and the efficiency of the EUVL system may be improved.  
         [0017]     According to another aspect of the present invention, an apparatus includes a vacuum chamber arrangement, a first stage assembly, a second stage assembly, and an interface plate. The vacuum chamber arrangement provides a vacuum environment such as a low vacuum environment. The first stage assembly includes a first stage and a first actuator that drives the first stage. The first stage defines an interior section, and the first actuator is positioned within the interior section such that the first actuator is substantially unexposed to the vacuum environment. The second stage assembly includes a second stage and an actuator arrangement that drives the second stage. The second stage is arranged within the vacuum chamber arrangement such that the second stage is exposed to the vacuum environment, while the interface plate couples the first stage assembly to the second stage assembly. In one embodiment, the first actuator is drives the first stage along a first axis and the second actuator drives the second stage along at least one of the first axis and a second axis.  
         [0018]     These and other advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:  
         [0020]      FIG. 1  is a block diagram representation of a coarse stage and a fine stage which may be used as a part of an extreme ultraviolet lithography (EUVL) system.  
         [0021]      FIG. 2  is a block diagram representation of an EUVL system in accordance with an embodiment of the present invention.  
         [0022]      FIG. 3  is a diagrammatic cross-sectional representation of an EUVL system which includes an actuator that is substantially isolated from a vacuum environment in accordance with an embodiment of the present invention.  
         [0023]      FIGS. 4   a  and  4   b  are diagrammatic representations of a stage assembly in accordance with an embodiment of the present invention.  
         [0024]      FIG. 5  is a diagrammatic cut-away representation of a stage assembly, i.e., stage assembly  400  of  FIG. 4   b , in accordance with an embodiment of the present invention.  
         [0025]      FIG. 6  is a diagrammatic representation of a coarse stage and a stage interface plate, i.e., coarse stage  404  and stage interface plate  410  of  FIG. 4   b , in accordance with an embodiment of the present invention.  
         [0026]      FIG. 7  is a diagrammatic exploded representation of a stage assembly, i.e., stage assembly  400  of  FIG. 4   b , in accordance with an embodiment of the present invention.  
         [0027]      FIG. 8  is a diagrammatic representation of a counter mass, i.e., counter mass  406  of  FIG. 7 , in accordance with an embodiment of the present invention.  
         [0028]      FIG. 9  is a diagrammatic representation of a photolithography apparatus in accordance with an embodiment of the present invention.  
         [0029]      FIG. 10  is a process flow diagram which illustrates the steps associated with fabricating a semiconductor device in accordance with an embodiment of the present invention.  
         [0030]      FIG. 11  is a process flow diagram which illustrates the steps associated with processing a wafer, i.e., step  1304  of  FIG. 10 , in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0031]     The performance of extreme ultraviolet lithography (EUVL) system is often compromised when an acceptable vacuum level or an acceptable temperature within a vacuum chamber may not be maintained. Further, the performance of an EUVL system may also be compromised whenever contaminants enter the vacuum chamber, e.g., during the maintenance of motors within the vacuum chamber. Hence, the ability to efficiently and relatively easily maintain a desired vacuum level, maintain a desired temperature, and ensure the proper operation of motors associated with an EUVL system is critical.  
         [0032]     A stage arrangement which is arranged to be positioned such that components of the stage, as for example hoses and actuators, are positioned substantially outside of a vacuum environment may improve the performance of an EUVL system while allowing for the EUVL system to be more readily maintained. Keeping hoses, e.g., moving hoses, substantially outside of a vacuum environment reduces the amount of contamination and outgassing within the vacuum environment, while maintaining actuators substantially outside of the vacuum environment enables the actuators to be serviced without affecting the vacuum environment, and relaxes cooling requirements associated with the operation of the motors. While hoses and actuators associated with a stage arrangement are maintained outside of a vacuum environment, as for example in a low vacuum environment, an object such as a reticle may be scanned within the vacuum environment.  
         [0033]      FIG. 2  is a block diagram representation of an EUVL system in accordance with an embodiment of the present invention. An EUVL system  200  includes a coarse stage  208  and a fine stage  204  which are arranged to scan a reticle (not shown) that is supported on fine stage  204 . Fine stage  204  is positioned such that a reticle (not shown) supported thereon is scanned within a vacuum chamber arrangement  214 . Coarse stage  208  is positioned substantially between sections  214   a ,  214   b  of vacuum chamber arrangement  214  such that a plurality of exterior surfaces of coarse stage  208  are effectively in contact with a vacuum environment within vacuum chamber arrangement  214  while interior surfaces of coarse stage  208  are substantially not in contact with the relatively high vacuum within the vacuum environment. In other words, an interior of coarse stage  208  is essentially not exposed to a vacuum environment, as for example a high vacuum environment, within vacuum chamber arrangement  214 , and is, instead, exposed to the atmosphere, or a relatively low vacuum environment, surrounding vacuum chamber arrangement  214 .  
         [0034]     An actuator or motor  210  which allows coarse stage  208  to scan in either an x-direction  218   a  or  a  y-direction  218   b  is positioned such that motor  210  is essentially not exposed to the vacuum environment within vacuum chamber arrangement  214 , i.e., motor  210  is substantially isolated from the vacuum environment within vacuum chamber arrangement  214 . In one embodiment, an interior of coarse stage  208  is exposed to the atmosphere surrounding vacuum chamber arrangement  214  such that motor  210  is exposed to the atmosphere. When motor  210  is substantially external to the vacuum environment within vacuum chamber arrangement  214 , maintenance of motor  210  may be performed without compromising the vacuum environment within vacuum chamber arrangement  214 . In other words, it is generally unnecessary to open vacuum chamber arrangement  214  and, hence, expose the vacuum environment within vacuum chamber arrangement  214  to contaminants and moisture, in order to perform maintenance on motor  210 .  
         [0035]     Configuring coarse stage  208  such that motor  210  is external to vacuum chamber arrangement  214  enables motor  210  to be cooled using convection, in addition to or in lieu of conduction and radiation. When motor  210  may be cooled outside of vacuum chamber arrangement  214 , air may be used to cool motor  210 , thereby providing a relatively easy to implement and relatively inexpensive cooling process. As a result, motor  210  may have a higher elevated temperature when motor  210  is external to vacuum chamber arrangement  214  than when a motor which moves a coarse stage is internal to a vacuum chamber, since the motor may be more readily cooled, and heat generated by motor  210  is less likely to affect the temperature within vacuum chamber arrangement  214 .  
         [0036]     Additionally, since motor  210  is located outside of vacuum chamber arrangement  214 , any cables and hoses which are coupled to motor  210  are also external to vacuum chamber arrangement. Such cables and hoses are typically flexible, as they often undergo some movement while motor  210  is in operation. As a result, any outgassing associated with such cables and hoses has substantially no effect on the vacuum environment within vacuum chamber arrangement  214 . Since the outgassing associated with cables and hoses, especially cables and hoses formed from flexible materials such as rubber, that are coupled to motor  210  have substantially no effect on the vacuum environment within vacuum chamber arrangement  214 , substantially any suitable material may be used to form such cables and hoses.  
         [0037]     Air bearings  222  are used to enable motor  210  to scan coarse stage  208  substantially without friction along either x-axis  218   a  or  y -axis  218   b . Since coarse stage  208  is substantially external to vacuum chamber arrangement  214 , leakage from air bearings  222  with a pump-out-grove design generally does not have a significant effect on the vacuum level within vacuum chamber arrangement  214 . In addition, since hoses which supply fluid such as air to air bearings  222  are typically relatively flexible and may be located outside of vacuum chamber arrangement  214 , the outgassing associated with such hoses may not have a significant effect on the vacuum level within vacuum chamber arrangement  214 .  
         [0038]     The cables and hoses associated coarse stage  208 , respectively, generally move when coarse stage  208  scans, as mentioned above. Hence, by positioning such cables or hoses substantially outside of vacuum chamber arrangement  214 , most of the cables or hoses that remain positioned within vacuum chamber arrangement  214  do not move, i.e., are generally relatively stationary. Cables or hoses which generally do not move may be formed from rigid materials which are less likely to outgas. As a result, substantially all fluid transfer inside of vacuum chamber arrangement  214  may be performed using rigid pipes.  
         [0039]     The design of an EUVL system which includes at least one motor, e.g., a motor which drives a scanning stage, that is external to a vacuum environment may vary widely.  FIG. 3  is a diagrammatic cross-sectional representation of one EUVL system which includes a motor that is substantially isolated from a vacuum environment in accordance with an embodiment of the present invention. A system  300  includes a coarse stage  308 , or a coarse stage box, which has an interior section  309  that is exposed to an environment  350  that substantially surrounds a vacuum chamber arrangement  314 . Environment  350  is generally arranged at approximately atmospheric pressure, while the interior of vacuum chamber arrangement  314  is maintained at a vacuum level.  
         [0040]     Interior section  309  is arranged to accommodate a coil assembly  312  which cooperates with a magnet track  310  to allow coarse stage  308  to translate in an x-direction  318   a . Interior section  309  also accommodates a counter mass (not shown) associated with coarse stage  308 . Cables, as for example cable  352 , associated with coarse stage  308  and coil assembly  312  are arranged such that such cables pass through interior section  309 . In other words, cables such as cable  352  that are associated with coarse stage  308 , coil assembly  312 , and air bearings  360  are arranged to come into contact with atmosphere  350 , and not a vacuum environment within vacuum chamber arrangement  314 . As a result, when such cables outgas or leak, the outgassing or leakage generally does not have a significant effect on the vacuum environment.  
         [0041]     A fine stage  340  is coupled to coarse stage  308  through a stage interface plate  346 . Fine stage  340  is arranged to carry a reticle  348 . In one embodiment, an illumination source  334  is arranged to provide a beam of EUV light which reflects off of reticle  348  onto a wafer  330  that is being processed. Coarse stage  308  allows reticle  348  to be scanned relatively coarsely, while fine stage  340  enables reticle  348  to be scanned relatively finely. Within system  300 , reticle  348  may have a relatively long travel direction with respect to x-axis  318   a , and a relatively short travel direction with respect to a y-axis  318   b . Hence, coarse stage  308  may be arranged to move substantially only along x-axis  318   a , while fine stage  340  is arranged to be carried by coarse stage  308  along x-axis  318   a  and to scan along y-axis  318   b  using a motor  342 . It should be appreciated, however, that additional motors may be coupled to fine stage  340  to allow additional movement of fine stage  340 , e.g., a motor (not shown) may be coupled to fine stage  340  to allow fine stage  340  to translate along a z-axis  318   c  and motors (not shown) may be coupled to fine stage  340  to allow rotational motion about x-axis  318   a  and  y -axis  318   b.    
         [0042]     In one embodiment, as for example when fine stage  340  is arranged to have either three or six degrees of freedom, fine stage  340  may be preloaded. The mechanism (not showed) that is used to provide a preload force on fine stage  340  may vary widely. Suitable preload mechanisms may include, but are not limited to, a spring suspension system that is coupled to coarse stage  308  and a vacuum preload.  
         [0043]     Vacuum chamber arrangement  314  includes a first vacuum chamber portion  314   a  and a second vacuum chamber portion  314   b . Air bearings  360 , which are a part of vacuum chamber arrangement  314  are arranged to cooperate with air bearing surfaces  322  of coarse stage  308  to allow for coarse stage  308  to move along x-axis  318   a  substantially without friction.  
         [0044]     The configuration of a coarse stage assembly which includes coarse stage  308  and the configuration of a fine stage assembly which includes fine stage  340  may vary widely. With reference to  FIGS. 4   a  and  4   b , one embodiment of an overall stage assembly which includes a coarse stage and a fine stage will be described in accordance with an embodiment of the present invention. A stage assembly  400  is positioned such that stage assembly  400  is at least partially surrounded by a sleeve  402  which may be coupled to a body, i.e., a body of a vacuum chamber arrangement such as vacuum chamber arrangement  314  of  FIG. 3 .  
         [0045]     Stage assembly  400  includes a coarse stage  404  which is arranged to scan along an x-axis  418   a  and a counter mass  406 . As shown in  FIG. 4   b , coarse stage  404  is effectively coupled to a fine stage  412  through a stage interface plate  410 . An actuator  416   a  is arranged substantially on stage interface plate  410  to allow fine stage  412  to undergo fine movements move along a y-axis  418   b . In the described embodiment, fine stage  412  is also coupled to stage interface plate  410  through an actuator  416   a  which allows fine stage  412  to undergo fine movements along x-axis  418   a . When actuator  416   a  is present, actuator  416   a  may effectively finely position fine stage  412  along x-axis  418   a  after scanning of coarse stage  404  essentially coarsely positions fine stage  412  relative to x-axis  418   a . Air bearing assemblies  420 , which are vacuum isolated, interface with an air bearing surface (not shown) of coarse stage  404  to facilitate the translational movement of coarse stage  404  along x-axis  418   a  while effectively reducing any leakage of gas into a vacuum environment when stage assembly  400  is used within an EUVL system.  
         [0046]      FIG. 5  is a diagrammatic representation of a stage assembly, e.g., stage assembly  400  of  FIGS. 4   a  and  4   b , as shown without a sleeve, e.g., sleeve  402  of  FIGS. 4   a  and  4   b , in accordance with an embodiment of the present invention. In general, when coarse stage  404  scans in x-direction  418   a , since stage interface plate  410  is coupled to both coarse stage  404  and fine stage  412 , fine stage  412  also scans in x-direction  418   a . An actuator (not shown) which enables coarse stage  404  to scan is positioned within coarse stage  404 , as will be described below with reference to  FIG. 7 .  
         [0047]     Coarse stage  404  is shown in  FIG. 6 , along with stage interface plate  410 . Stage interface plate  410  is fixed or otherwise coupled to a bottom surface of coarse stage  404 . The bottom surface of coarse stage  404  is arranged as an air bearing surface. Stage interface plate  410  supports a magnet coil  604  which is a part of actuator  416   a , as shown in  FIG. 4   b , and a magnet coil  602  which is a part of actuator  416   b , as shown in  FIG. 4   b.    
         [0048]     Within coarse stage  404 , components which include an actuator and a counter mass, or a bearing box, are housed. With reference to  FIG. 7 , the components contained within coarse stage  404  will be described.  FIG. 7  is an exploded representation of stage assembly  400  of  FIG. 4   a  in accordance with an embodiment of the present invention. Coarse stage  404 , which is effectively a hollow box, is arranged to substantially house an actuator  710  which, in the described embodiment, includes a coil  712   a  and a magnet track  712   b . Since actuator  710  is housed within coarse stage  404 , actuator  710  is exposed to an atmosphere external to a vacuum chamber arrangement, rather than to a vacuum environment within a vacuum chamber arrangement. Hence, when actuator  710  generates heat during operation, the generated heat does not have a significant effect on the vacuum environment. In addition, since substantially any cables (not shown) which are associated with actuator  710  are also external to the vacuum chamber arrangement, any outgassing of such cables also does not have a significant effect on the vacuum environment.  
         [0049]     Coil  712   a  is arranged to scan over magnet track  712   b , and is further arranged to be coupled to an interior surface of coarse stage  404 . Magnet track  712   b  is coupled to counter mass  406  which effectively includes two bearing boxes on which guide bearings  708  are mounted. Guide bearings  708  facilitate the movement of coarse stage  404  relative to counter mass  406 , which is arranged to substantially cancel out reaction forces associated with actuator  710 , when actuator  710  causes coarse stage  404  to scan along x-axis  418   a . It should be appreciated that since guide bearings  708  are exposed to the atmosphere around a vacuum chamber arrangement, substantially any cables or hoses (not shown) which are coupled to guide bearings  708 , e.g., air supply hoses, are also external to the vacuum chamber arrangement. Thus, any leakage or outgassing of such hoses generally has an insignificant effect on the vacuum environment within the vacuum chamber arrangement.  
         [0050]     As shown in more detail in  FIG. 8 , magnet track  712   b  is effectively a shaft which is coupled to halves, or bearing boxes, of counter mass  406 . Counter mass  406  is arranged such that there are guide bearings  708  on three sides of counter mass  406 . As shown, counter mass  406  may include five guide bearings  708  on each half. However, that the number of guide bearings  708  associated with counter mass  406 , as well as the location of guide bearings  708 , may vary widely. It should be appreciated that although counter mass  406  may be coupled to a trim motor, as for example a trim motor that is coupled between counter mass  406  and an exterior of a vacuum chamber, a trim motor has not been shown for ease of illustration.  
         [0051]     When counter mass  406  is arranged to be positioned substantially within coarse stage  404 , as shown in  FIG. 4   a , coarse stage  404  may be driven through an approximate center of gravity associated with stage assembly  400 . Hence, disturbances associated with driving coarse stage  404  may be substantially minimized. Counter mass  406  may be shaped to effectively match the driving forces associated with coarse stage  404 .  
         [0052]     With reference to  FIG. 9 , a photolithography apparatus which may include a stage with isolated actuators will be described in accordance with an embodiment of the present invention. It should be appreciated that although a stage with isolated actuators has been described as being suitable for use as a part of an EUVL system, such a stage may generally be used as a part of substantially any suitable photolithography apparatus. A photolithography apparatus (exposure apparatus)  40  includes a wafer positioning stage  52  that may be driven by a planar motor (not shown), as well as a wafer table  51  that is magnetically coupled to wafer positioning stage  52  by utilizing an EI-core actuator, e.g., an EI-core actuator with a top coil and a bottom coil which are substantially independently controlled. The planar motor which drives wafer positioning stage  52  generally uses an electromagnetic force generated by magnets and corresponding armature coils arranged in two dimensions. A wafer  64  is held in place on a wafer holder or chuck  74  which is coupled to wafer table  51 . Wafer positioning stage  52  is arranged to move in multiple degrees of freedom, e.g., between three to six degrees of freedom, under the control of a control unit  60  and a system controller  62 . In one embodiment, wafer positioning stage  52  may include a plurality of actuators and have a configuration as described above. The movement of wafer positioning stage  52  allows wafer  64  to be positioned at a desired position and orientation relative to a projection optical system  46 .  
         [0053]     Wafer table  51  may be levitated in a z-direction  10   b  by any number of voice coil motors (not shown), e.g., three voice coil motors. In the described embodiment, at least three magnetic bearings (not shown) couple and move wafer table  51  along a y-axis  10   a . The motor array of wafer positioning stage  52  is typically supported by a base  70 . Base  70  is supported to a ground via isolators  54 . Reaction forces generated by motion of wafer stage  52  may be mechanically released to a ground surface through a frame  66 . One suitable frame  66  is described in JP Hei 8-166475 and U.S. Pat. No. 5,528,118, which are each herein incorporated by reference in their entireties.  
         [0054]     An illumination system  42  is supported by a frame  72 . Frame  72  is supported to the ground via isolators  54 . Illumination system  42  includes an illumination source, which may provide a beam of EUV light that may be reflected off of a reticle. In one embodiment, illumination system  42  may be arranged to project a radiant energy, e.g., light, through a mask pattern on a reticle  68  that is supported by and scanned using a reticle stage  44  which includes a coarse stage and a fine stage. It should be appreciated that for such an embodiment, photolithography apparatus  40  may be a part of a system other than an EUVL system. In general, a stage with isolated actuators may be used as a part of substantially any suitable photolithography apparatus, and is not limited to being used as a part of an EUVL system. The radiant energy is focused through projection optical system  46 , which is supported on a projection optics frame  50  and may be supported the ground through isolators  54 . Suitable isolators  54  include those described in JP Hei 8-330224 and U.S. Pat. No. 5,874,820, which are each incorporated herein by reference in their entireties.  
         [0055]     A first interferometer  56  is supported on projection optics frame  50 , and functions to detect the position of wafer table  51 . Interferometer  56  outputs information on the position of wafer table  51  to system controller  62 . In one embodiment, wafer table  51  has a force damper which reduces vibrations associated with wafer table  51  such that interferometer  56  may accurately detect the position of wafer table  51 . A second interferometer  58  is supported on projection optical system  46 , and detects the position of reticle stage  44  which supports a reticle  68 . Interferometer  58  also outputs position information to system controller  62 .  
         [0056]     It should be appreciated that there are a number of different types of photolithographic apparatuses or devices. For example, photolithography apparatus  40 , or an exposure apparatus, may be used as a scanning type photolithography system which exposes the pattern from reticle  68  onto wafer  64  with reticle  68  and wafer  64  moving substantially synchronously. In a scanning type lithographic device, reticle  68  is moved perpendicularly with respect to an optical axis of a lens assembly (projection optical system  46 ) or illumination system  42  by reticle stage  44 . Wafer  64  is moved perpendicularly to the optical axis of projection optical system  46  by a wafer stage  52 . Scanning of reticle  68  and wafer  64  generally occurs while reticle  68  and wafer  64  are moving substantially synchronously.  
         [0057]     Alternatively, photolithography apparatus or exposure apparatus  40  may be a step-and-repeat type photolithography system that exposes reticle  68  while reticle  68  and wafer  64  are stationary, i.e., at a substantially constant velocity of approximately zero meters per second. In one step and repeat process, wafer  64  is in a substantially constant position relative to reticle  68  and projection optical system  46  during the exposure of an individual field. Subsequently, between consecutive exposure steps, wafer  64  is consecutively moved by wafer positioning stage  52  perpendicularly to the optical axis of projection optical system  46  and reticle  68  for exposure. Following this process, the images on reticle  68  may be sequentially exposed onto the fields of wafer  64  so that the next field of semiconductor wafer  64  is brought into position relative to illumination system  42 , reticle  68 , and projection optical system  46 .  
         [0058]     It should be understood that the use of photolithography apparatus or exposure apparatus  40 , as described above, is not limited to being used in a photolithography system for semiconductor manufacturing. For example, photolithography apparatus  40  may be used as a part of a liquid crystal display (LCD) photolithography system that exposes an LCD device pattern onto a rectangular glass plate or a photolithography system for manufacturing a thin film magnetic head.  
         [0059]     The illumination source of illumination system  42  may be g-line (436 nanometers (nm)), i-line (365 mm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), and an F 2 -type laser (157 nm). Alternatively, illumination system  42  may also use charged particle beams such as x-ray and electron beams. For instance, in the case where an electron beam is used, thermionic emission type lanthanum hexaboride (LaB 6 ) or tantalum (Ta) may be used as an electron gun. Furthermore, in the case where an electron beam is used, the structure may be such that either a mask is used or a pattern may be directly formed on a substrate without the use of a mask.  
         [0060]     With respect to projection optical system  46 , when far ultra-violet rays such as an excimer laser is used, glass materials such as quartz and fluorite that transmit far ultra-violet rays is preferably used. When either an F 2 -type laser or an x-ray is used, projection optical system  46  may be either catadioptric or refractive (a reticle may be of a corresponding reflective type), and when an electron beam is used, electron optics may comprise electron lenses and deflectors. As will be appreciated by those skilled in the art, the optical path for the electron beams is generally in a vacuum.  
         [0061]     In addition, with an exposure device that employs vacuum ultra-violet (VUV) radiation of a wavelength that is approximately 200 nm or lower, use of a catadioptric type optical system may be considered. Examples of a catadioptric type of optical system include, but are not limited to, those described in Japan Patent Application Disclosure No. 8-171054 published in the Official gazette for Laid-Open Patent Applications and its counterpart U.S. Pat. No. 5,668,672, as well as in Japan Patent Application Disclosure No. 10-20195 and its counterpart U.S. Pat. No. 5,835,275, which are all incorporated herein by reference in their entireties. In these examples, the reflecting optical device may be a catadioptric optical system incorporating a beam splitter and a concave mirror. Japan Patent Application Disclosure (Hei) No. 8-334695 published in the Official gazette for Laid-Open Patent Applications and its counterpart U.S. Pat. No. 5,689,377, as well as Japan Patent Application Disclosure No. 10-3039 and its counterpart U.S. Pat. No. 5,892,117, which are all incorporated herein by reference in their entireties. These examples describe a reflecting-refracting type of optical system that incorporates a concave mirror, but without a beam splitter, and may also be suitable for use with the present invention.  
         [0062]     Further, in photolithography systems, when linear motors (see U.S. Pat. No. 5,623,853 or 5,528,118, which are each incorporated herein by reference in their entireties) are used in a wafer stage or a reticle stage, the linear motors may be either an air levitation type that employs air bearings or a magnetic levitation type that uses Lorentz forces or reactance forces. Additionally, the stage may also move along a guide, or may be a guideless type stage which uses no guide.  
         [0063]     Alternatively, a wafer stage or a reticle stage may be driven by a planar motor which drives a stage through the use of electromagnetic forces generated by a magnet unit that has magnets arranged in two dimensions and an armature coil unit that has coil in facing positions in two dimensions. With this type of drive system, one of the magnet unit or the armature coil unit is connected to the stage, while the other is mounted on the moving plane side of the stage.  
         [0064]     Movement of the stages as described above generates reaction forces which may affect performance of an overall photolithography system. Reaction forces generated by the wafer (substrate) stage motion may be mechanically released to the floor or ground by use of a frame member as described above, as well as in U.S. Pat. No. 5,528,118 and published Japanese Patent Application Disclosure No. 8-166475. Additionally, reaction forces generated by the reticle (mask) stage motion may be mechanically released to the floor (ground) by use of a frame member as described in U.S. Pat. No. 5,874,820 and published Japanese Patent Application Disclosure No. 8-330224, which are each incorporated herein by reference in their entireties.  
         [0065]     Isolaters such as isolators  54  may generally be associated with an active vibration isolation system (AVIS). An AVIS generally controls vibrations associated with forces  112 , i.e., vibrational forces, which are experienced by a stage assembly or, more generally, by a photolithography machine such as photolithography apparatus  40  which includes a stage assembly.  
         [0066]     A photolithography system according to the above-described embodiments, e.g., a photolithography apparatus which may include one or more dual force actuators, may be built by assembling various subsystems in such a manner that prescribed mechanical accuracy, electrical accuracy, and optical accuracy are maintained. In order to maintain the various accuracies, prior to and following assembly, substantially every optical system may be adjusted to achieve its optical accuracy. Similarly, substantially every mechanical system and substantially every electrical system may be adjusted to achieve their respective desired mechanical and electrical accuracies. The process of assembling each subsystem into a photolithography system includes, but is not limited to, developing mechanical interfaces, electrical circuit wiring connections, and air pressure plumbing connections between each subsystem. There is also a process where each subsystem is assembled prior to assembling a photolithography system from the various subsystems. Once a photolithography system is assembled using the various subsystems, an overall adjustment is generally performed to ensure that substantially every desired accuracy is maintained within the overall photolithography system. Additionally, it may be desirable to manufacture an exposure system in a clean room where the temperature and humidity are controlled.  
         [0067]     Further, semiconductor devices may be fabricated using systems described above, as will be discussed with reference to  FIG. 10 . The process begins at step  1301  in which the function and performance characteristics of a semiconductor device are designed or otherwise determined. Next, in step  1302 , a reticle (mask) in which has a pattern is designed based upon the design of the semiconductor device. It should be appreciated that in a parallel step  1303 , a wafer is made from a silicon material. The mask pattern designed in step  1302  is exposed onto the wafer fabricated in step  1303  in step  1304  by a photolithography system. One process of exposing a mask pattern onto a wafer will be described below with respect to  FIG. 11 . In step  1305 , the semiconductor device is assembled. The assembly of the semiconductor device generally includes, but is not limited to, wafer dicing processes, bonding processes, and packaging processes. Finally, the completed device is inspected in step  1306 .  
         [0068]      FIG. 11  is a process flow diagram which illustrates the steps associated with wafer processing in the case of fabricating semiconductor devices in accordance with an embodiment of the present invention. In step  1311 , the surface of a wafer is oxidized. Then, in step  1312  which is a chemical vapor deposition (CVD) step, an insulation film may be formed on the wafer surface. Once the insulation film is formed, in step  1313 , electrodes are formed on the wafer by vapor deposition. Then, ions may be implanted in the wafer using substantially any suitable method in step  1314 . As will be appreciated by those skilled in the art, steps  1311 - 1314  are generally considered to be preprocessing steps for wafers during wafer processing. Further, it should be understood that selections made in each step, e.g., the concentration of various chemicals to use in forming an insulation film in step  1312 , may be made based upon processing requirements.  
         [0069]     At each stage of wafer processing, when preprocessing steps have been completed, post-processing steps may be implemented. During post-processing, initially, in step  1315 , photoresist is applied to a wafer. Then, in step  1316 , an exposure device may be used to transfer the circuit pattern of a reticle to a wafer. Transferring the circuit pattern of the reticle of the wafer generally includes scanning a reticle scanning stage which may, in one embodiment, include a force damper to dampen vibrations.  
         [0070]     After the circuit pattern on a reticle is transferred to a wafer, the exposed wafer is developed in step  1317 . Once the exposed wafer is developed, parts other than residual photoresist, e.g., the exposed material surface, may be removed by etching. Finally, in step  1319 , any unnecessary photoresist that remains after etching may be removed. As will be appreciated by those skilled in the art, multiple circuit patterns may be formed through the repetition of the preprocessing and post-processing steps.  
         [0071]     Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, while a stage arrangement which substantially isolates actuators and moving cables associated with a coarse stage from a vacuum environment has been described as being suitable for use as a part of an EUVL system, such a stage arrangement may be used for substantially any suitable application, e.g., any suitable application that requires the use of a vacuum. In other words, a stage arrangement as described above is not limited to being used as a part of an EUVL system, and may generally be used as a part of a variety of different systems including, but not limited to, systems which operate using a vacuum environment.  
         [0072]     A stage assembly with isolated actuators has been shown as being substantially “box-like” in shape. Such a shape of a stage assembly, which allows a counter mass and an actuator to be nestled within a coarse stage, is relatively easy to manufacture, and facilitates the matching of driving forces associated with the stage assembly. That is, the box-like shape of a stage assembly enables a coarse stage in the stage assembly to be efficiently driven through a center of gravity associated with the coarse stage. It should be appreciated, however, that the stage assembly may have substantially any suitable shape. Other suitable shapes may include, but are not limited to, pipe-like shapes.  
         [0073]     The use of a counter mass within a coarse stage has been described as being suitable for substantially canceling out reaction forces associated with an actuator which drives the coarse stage. In some embodiments, a counter mass may not be used. When a counter mass is not used, then a magnet track associated with the actuator may be mounted to an external wall of a vacuum chamber arrangement without departing from the spirit or the scope of the present invention.  
         [0074]     A coarse stage has generally been described as having a single translational degree of freedom, while a fine stage has been described as having one or two translational degrees of freedom. While a stage assembly, as described above, is particularly suitable for use in a system where translation along one axis, i.e., the axis along which the coarse stage is driven, is relatively large while translation along another axis, i.e., an axis that is perpendicular to the axis along which the coarse stage is driven, is relatively small, such a stage assembly may be used in systems in which translation along more than one axis is relatively large. For example, an additional coarse stage actuator may be added to a stage assembly when the stage assembly is to have relatively large translational motion relative to two axes.  
         [0075]     In general, a stage assembly has been described as including both a coarse stage and a fine stage. It should be appreciated, however, that a stage assembly which includes a coarse stage with isolated actuators, e.g., a coarse stage actuator and a trim motor for a counter mass associated with the coarse stage, may not necessarily include a fine stage. That is, a single stage with isolated actuators may be included in a stage assembly without departing from the spirit or the scope of the present invention. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.