Abstract:
A stage for processing a substrate, especially useful for vacuum applications, has a recess just large enough to hold a substantially flat substrate and a chuck or holder, but not much more. The perimeter of both top and bottom of the stage has air bearing surfaces separated from the recess by differentially pumped grooves and seal lands. The air bearing lands are guided between two reference surfaces and the seal lands, being substantially coplanar, create a resistance to flow between the bearings and the recess. On the other side of one of the reference plates mounts the radiation source or process. The opposite reference plate may have a large aperture, non-contact pumping port. This improves vacuum capability and stage precision. The stage may operate in a vacuum environment itself or can provide multiple stages moving between processes or inspection steps within the same tool or process sequence.

Description:
REFERENCE TO RELATED APPLICATIONS 
   The present application claims the benefit of U.S. Provisional Patent Application No. 60/796,563, filed May 2, 2006. Related information is disclosed in U.S. patent application Ser. No. 11/206,296, filed Aug. 18, 2005 (U.S. Patent Application Publication No. 2006/0060259 A1), currently pending. The disclosures of both of the above-captioned applications are hereby incorporated by reference in their entireties into the present disclosure. 

   FIELD OF THE INVENTION 
   This invention relates generally to equipment used in the manufacture of semiconductor devices and masks and more particularly to equipment used in vacuum processes. Applications are anticipated in areas including, but not limited to, ion implant and milling, deposition, etch, ash, clean, lithography, inspection and CD SEM. 
   BACKGROUND OF THE INVENTION AND DESCRIPTION OF RELATED ART 
   Because of the shrinking feature sizes in semiconductor wafers, greater degrees of precision are required in the stages used to provide the necessary motions. Because air-bearing stages allow for higher precision, they are commonly used to pattern and inspect semiconductor wafers. A point has been reached where optical techniques are limiting because of the width of the wavelength of light. Deep UV and even EUV processing will be required because of their shorter wavelength. The same or higher degree of precision is required in these processes, but they also require a vacuum environment. There are technical difficulties in attempting to use air-bearing stages in vacuum, as the escaping air increases the pressure in the vacuum chamber. 
   Many techniques have been employed to effect motion inside a vacuum chamber. Use of rolling element or plane bearing technology has been used but it is difficult to achieve the required precision. Air bearing systems with differentially pumped scavenge grooves have been employed inside a vacuum chamber. The difficulty here is that the stages quickly become very large to provide the required travels, necessitating large vacuum chambers, and because there is so much scavenging groove perimeter, it is difficult to achieve the low pressures required in the chamber. Another complicating factor in both these methods is that drives, encoders and services all have to be contained inside the vacuum chamber, causing problems with particulation and out gassing. 
   Methods to keep the mechanization outside of the vacuum chamber have been employed. These include linear and rotary contact seals, rotary ferro fluidic seals, expanding and contracting bellows. Also air bearings structures separated from the vacuum chamber by integral differentially pumped grooves that support some sort of a moving member through an aperture in the vacuum chamber wall. (Note U.S. Pat. No. 4,726,689 February 1988 Pollock, Varian; U.S. Pat. No. 5,898,179 April 1999 Smick, Applied Materials; U.S. Pat. No. 6,515,288 February 2003 Ryding, Applied Materials) have been tried and are the current state of the art in ion implantation. However, the above-noted problems with the prior art have not been successfully overcome. 
   The above-cited US 2006/0060259 A1 will be summarized. The disclosure in that application is somewhat similar to that of the present application and is summarized here for background information. Features of the devices and methods disclosed in the parent application can be incorporated into the present invention as appropriate. 
     FIG. 1   a  is a side view sectional schematic of a vacuum chamber stage  100  used for precision positioning of the semiconductor wafer or substrate  103  while the substrate is maintained in a vacuum chamber  117 . The object of the apparatus is to expose the substrate to some sort of a manufacturing, processing or inspection for the purpose of manufacturing microelectronics circuits there on. Typically the substrate is exposed to some sort of radiation; examples of the many species of radiation would include but are not limited to Ions, x-rays, ultraviolet or extreme ultraviolet, electron beams, DUV (deep ultraviolet), extreme ultraviolet (soft x-rays) and visible light. Often this radiation needs to be conditioned by such devices as analyzers, magnets, mirrors or optics. This conditioning of radiation in this illustration is provided for in the area indicated by  119 . This conditioning assembly is connected directly to the base reference member  104  with its output aperture  118  aligned with a consummate aperture  101  in the first reference plate  104 . 
   Vacuum ports  225  for high vacuum conductance can be arrayed around the aperture  202  and connected on the opposite side of the base reference plate  206  to a manifold  203  connected to a cryopump or other low-pressure device. This arrangement allows for excellent conductance of pressure away from the area of interest. The ports may breakthrough into the wall of the aperture as in  102 , or they may be completely through base reference plate  206  and arrayed around the aperture  202 , as in  FIG. 2   a . Alternatively, or in addition, ports  102  could be used for directing radiation on an angle rather than normal to the surface of the substrate  103  with appropriate detectors arranged as needed, as for example is often the case in thin film measuring (ex. scatterometry and ellipsometry). The first reference plate  104  may be made from hard coated or nickel coated aluminum, nickel coated steel or stainless steel. Other materials such as ceramics or carbon fiber could also be considered. Important considerations are that the material be vacuum compatible, and the undersurface  106  may be made suitably flat to be used as an air bearing surface, and that the material have the structural strength to withstand the significant atmospheric pressures that may be applied to it without experiencing unaccepted distortions. The first reference plate  104  is shown as a simple plate for simplicity. It could easily be designed with structural ribs on the back; these ribs could also couple to additional mounting points for the radiation conditioning device providing a stiffer, firmer mount than the flange mount shown for simplicity. Avoiding distortions from atmospheric pressures is not a trivial issue; thousands of pounds of force will be equally distributed across a face of the vacuum chamber which will move around on the base reference plate. It is important that the reference base plate  104  remain flat because the smaller the air gap that can be used in the air bearing without contact the more efficient the lands between the differentially pumped grooves become. Engineering techniques for calculating and modeling these forces, including finite element analysis, are well-known in the art and need not be repeated here. 
   The vacuum chamber stage  114  with air bearing  115  and differentially vacuum pumped grooves  116  is urged against the lower surface  106  of the first reference plate  104  by thousands of pounds of atmospheric pressure. As air bearing surfaces  115  on the vacuum chamber stage  114  come within a thousandth of an inch of the reference base plate surface  106 , pressure builds up in the gap  156  between them until equilibrium is reached. The stage then rides on this pressurized film of air, using atmospheric pressure as a preload force to create a very stiff, well damped air bearing free to translate in X, Y and theta. As with the first reference base plate  104 , it is important that the vacuum chamber stage  114  have the requisite stiffness not to deform from the thousands of pounds of atmospheric pressure urging it toward the reference plate  104 . The air bearing surface  115  in this preferred embodiment employs porous media compensation. Other air bearing compensation may be employed including but not limited to orifice and step compensation. Air bearings are a widely accepted art, much has been written about orifice and porous type air bearings, for porous media air bearings (see  FIG. 1   b ). Porous media air bearings are most commonly made from porous carbon or graphite but may be made from porous alumina or silicon carbide. Carbon and graphite have excellent crash resistance and are very tolerant of inadvertent bearing face contact. Differentially pumped grooves are also well known in the art and are illustrated in  FIG. 1   b . Notice that in this preferred embodiment the grooves get wider and deeper progressively with lower air pressures. This is consistent with minimizing restriction and maximizing conductance of pressure away from the air bearing land areas. 
   This embodiment can be arranged so as to make it relatively simple to get a wafer  103  in and out of the vacuum chamber stage  114 . A 25 mm×325 mm aperture  105  can be arranged in the side of a vacuum chamber stage  114 , the vacuum chamber stage  114  can be physically docked against the load-unload station  107  see  FIGS. 1   c  and  2   c  for the passing of wafers  103  in and out of the chamber without the introduction of atmospheric pressure to the chamber. Commercially available, but not shown, vacuum gates will be required. 
   By allowing for X and Y motions in a single plane it becomes convenient to use reference mirrors in the plane of the wafer and to drive the vacuum chamber stage through its center of mass. It is also possible to use reaction masses and service stages to improve the stage performance. 
   It is not necessary but it would be wise to provide another mechanism to urge the vacuum chamber stage  114  against the first reference plate  104 . In the event that the vacuum chamber stage  114  loses the vacuum in the chamber  117 , gravity would separate the vacuum chamber stage  114  from the first reference plate  106 . This would result in a temporary unrecoverable situation. To avoid this situation, air bearings  111  acting upon a second reference plate or base  110  can be employed to urge the vacuum chamber stage  114  against the first reference plate  104  through a constant force springs mechanism  112 . 
   The chuck  109  may be an electrostatic chuck or another chuck technology appropriate for vacuum. The chuck  109  may be mounted on a Z actuator or lifter mechanism  108  for the purpose of raising or lowering the substrate  103  in the VCS, for instance to facilitate substrate changes or to achieve a depth of field adjustment or fine planerization of the substrate. Many techniques known in the art are possible including piezos, super Z&#39;s, flexures or other mechanical lifters. 
     FIG. 2   a  shows a side view sectional view of a second preferred embodiment. This embodiment allows for the VCS  210  to contain an isolated vacuum chamber  223  as before but also operate in a vacuum  207 . This can be a important feature minimizing problems which could occur regarding water vapor adhering to the first  222  or second  216  reference surfaces while the VCS is not over that area. This is accomplished by repeating the air bearing  214  and differentially pumped grooves  211  on the underside of the vacuum chamber stage  210 . This is essentially two opposed mirror images. 
   A radiation source  201  can have a high conductance manifold  203  arrayed around the interface with the base reference plate  206 . This manifold is attached to a vacuum pump via large aperture tube  204 . Ports  225  through the first reference plate  206  surround the area of interest for good conduction, but are not necessary in all applications. The annular air bearing  214  is separated from the vacuum chamber  223  by differentially pumped grooves and seal lands  211  which are serviced by tubes from the motion system. This pattern is repeated exactly on the opposite side of the vacuum chamber stage  210 . This second set of air bearing lands and differentially pumped grooves bear on surface  216  which is the top of the second reference plate  209 . The opportunity exists to make the air bearing land area  214  smaller because in this embodiment the opposite pressures in the air bearing lands, grooves and chamber are exactly equal due to the fact that they are ported through common connections  217 ,  218 ,  220  and  221  to their source through  250 ,  251 ,  252  and  253 . The pressurized air gaps  215  are preloaded against each other only. The air bearing  214  running on the second reference base  209  will be carrying the gravity load of the vacuum chamber stage  210  which would likely be 20 lbs. plus or minus an order of magnitude. The preload force between the bearings can easily be 10 times (one order of magnitude more than this gravity force), making the gravity force inconsequential. This allows the VCS to operate in a vacuum with the lowest pressure inside the VCS and isolated from contamination or pressure. 
     FIGS. 3   a  and  3   b  are sectional views of an X and Y vacuum chamber stage with rotation, and a differentially pumped port for transfer of the wafers or substrates and or high conductance pumping port, as in a third preferred embodiment. 
   Some applications, like thin film characterization, often employ rotation of the wafer. The embodiment of  FIGS. 3   a  and  3   b  provides for rotation inside of an XY stage. By employing annular 360 degree radial air bearing surfaces isolated from the pass though by 360 degree radial differential pumped grooves and lands. As the XY stage is moved about, the radial bearings keep the rotating part centered. The XY stage carries a rotary actuator to spin the rotation part of the stage; it is possible to add an encoder. It is possible with differentially pumped grooves on outside of these bearings to operate the whole assembly in a vacuum environment. It will be necessary to vent the volume that the upper and lower  3  bearing set commonly leak into, it will also be necessary to vent the area under the rotating member to avoid pressure build up. An area  314  is provided for the motor and the encoder. 
     FIG. 4   a, b, c  show a device and method for ion implantation of substrates such a semiconductor wafers as in a fourth preferred embodiment. Ion implantation has moved from batch processing to serial processing. Serial processing provides more flexibility in the recipe that is administered to each wafer and more flexibility in the attitude of the wafer to the ion radiation, being able to pitch and rotate the wafer so as to dope or expose the sides of the via and the trenches equally. In order to keep throughput high, makers of ion implantation equipment have been migrating from spot or point beams that were scanned across the wafer in batch process to “ribbon” type beams. Ribbon type beams are slightly wider than the substrate or wafer being processed. The substrate may then be passed through the ribbon beam, exposing the whole substrate surface to the radiation. The beam may be a thin ribbon; 0.25 in, or a thick ribbon; 4 in. The thickness of the ribbon beam has an effect on the required travel of the wafer, which must pass though the entire ribbon before reversal. 
     FIG. 4   a  represents the preferred embodiment of the vacuum chamber stage device and method for modern ion implantation. The beam  409  in this case comes from below with the first reference plate  405  and vacuum chamber stage  403  nominally horizontal, although this could easily be reversed or at 45 degrees. The vacuum chamber stage  403 , as in previous embodiments is urged against the opposite side  413  of the first reference plate  405  from the radiation source by atmospheric pressure 
   The vacuum chamber stage  403  is actuated by a motion system  417  outside of the vacuum area  402 . The guidance for the motion system  418  could be from air bearings or rolling element bearings. In ion implantation motion characteristics are not as critical as in other precision applications and roller bearings would be an appropriate choice. The connection between the vacuum chamber stage  403  and the motion system  417  and actuators  418  could be with a blade flexure  450  which would decouple the vacuum chamber stage  403  from the drive and guide system in the Z direction which is constrained by the air bearing and atmospheric pressure against the vacuum chamber stage as in  FIG. 4   c . In this embodiment is not necessary to run vacuum services to the vacuum chamber stage  403 . Because the motion on the vacuum chamber stage is linear only with respect to the base reference plate  405 , holes or ports  415  through the first reference plate which aligned to the grooves  411  can be used to conduct pressure out of the grooves  411 . Holes or ports  414  through the first reference plate  405  may also be used to conduct pressure from the chamber directly around the area of interest. These holes may be on an angle to clear the beam  409  during tilting. The chuck  406  holding the substrate or wafer  407  is mounted to a rotary actuator  401  through a Ferro fluidic, mechanical contact seal or air bearing with differentially pumped grooves. Continuous rotation is not required in this embodiment, only the ability to index 90 or 180 degrees, 90° in order to be able to get all the orthogonal groves and trenches, and 180 degrees in order to avoid tilting the plate in both directions as shown in  FIG. 4   b . Notice the whole reference plate may be tilted with respect to the Ion or radiation source. This tilting action, combined with a rotary motion allows complete coverage of all surfaces on the substrate including the sides of the via and trenches. This embodiment also allows for constant focus or distance from the Ion or radiation source providing the most uniform doping of the substrate. 
   Still further embodiments are possible, as will be described with reference to  FIGS. 5   a - 5   c .  FIG. 5   a  shows two VCS&#39;s on reference members on opposite sides of a cylindrical member. One stage is a long travel and the other, a short travel high speed stage.  FIG. 5   b  shows a VCS on a reference member incorporating components for writing and measuring a workpiece.  FIG. 5   c  shows two VCS&#39;s on opposite sides of an opening in a single reference member. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to improve deep vacuum performance and stage precision. 
   To achieve the above and other objects, an important design feature in this invention is that instead of trying to build a stage inside a vacuum chamber or reach through a chamber wall, the stage itself becomes the vacuum chamber. Such a stage is called a vacuum chamber stage (VCS). By having the primary or only vacuum chamber completely contained inside the moving stage, all motion systems can exist outside of the vacuum. Because the vacuum chamber size is reduced to little more than the volume of the substrate, the vacuum pumping requirements and pump down times are dramatically reduced, and the requirement for a large conventional vacuum chamber is eliminated. At the same time, the structural loop between the source and the substrate, say a wafer, is dramatically shortened and stiffened. 
   The stage is guided between two reference surfaces, one of which is the underside of the base reference member to which the optics, ion source or electron source would mount. Guidance of the stage in the plane established between the surfaces in X and Y is achieved with annular air bearings separated from the vacuum section of the stage by differentially pumped grooves on both sides of the stage. This type of stage would be very appropriate for electron beam writing or inspection, Deep UV lithography or ion implantation. This stage architecture may also be useful for many non-vacuum processes because of improvements in the structural loop. 
   This embodiment includes an additional novelty which provides for conductance of air pressure or molecules away from the substrate or the possibility to process both sides of the wafer at one time by providing thru a hole in the base reference member opposite the area of interest. We believe that first embodiment described in the above-cited US 2006/0060259 A1 can realize 10 −7  torr with vacuum services coupled to the vacuum chamber stage via tubes carried by or integrated into the motion system that is driving the stage. The present embodiment is a way to more easily create lower pressure in the vacuum chamber stage. Because very low pressure requires large aperture conductance it can be inconvenient to attach such large tubes to the vacuum chamber stage directly. The following non-contact methods allow improvements in vacuum and precision. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will be disclosed in detail with reference to the drawings, in which: 
       FIGS. 1   a - 1   c  show a first embodiment disclosed in the above-cited parent application; 
       FIG. 2   a  shows a second embodiment disclosed in the above-cited parent application; 
       FIGS. 3   a  and  3   b  show a third embodiment disclosed in the above-cited parent application; 
       FIGS. 4   a - 4   c  show a fourth embodiment disclosed in the above-cited parent application; 
       FIGS. 5   a - 5   c  show other embodiments disclosed in the above-cited parent application; 
       FIG. 6  shows a first preferred embodiment of the present invention; 
       FIGS. 7A-7D  show a second preferred embodiment of the present invention; 
       FIGS. 8A-8C  show a third preferred embodiment of the present invention; 
       FIGS. 9A-9C  show a fourth preferred embodiment of the present invention; and 
       FIG. 10  shows a fifth preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will now be set forth in detail with reference to the drawings, in which like reference numerals refer to like elements or steps throughout. 
   Pump from Below without Outside Vacuum 
   This embodiment is shown in  FIG. 6 . This novelty allows large aperture conductance  617  to be ported into the vacuum chamber stage  612  though the sub base plate  615  without any physical contact. This is accomplished by repeating the air bearing  607  and differentially pumped grooves  608 ,  609 ,  614  on the underside of the vacuum chamber stage  612 . This is essentially two opposed mirror images. This large aperture  617  though the sub base plate  615  can then be ported in to the last differentially pumped groove  614  or into the chamber  627  directly. This dramatically improves vacuum conductance in the chamber and improves stage motion performance by minimizing the vacuum tube size. The stage no longer sees the atmospheric pressure so the air bearing lands may be smaller and the stage is subject to less physical distortion. 
   A radiation or other process source  601  can have a high conductance manifold  602  arrayed around the interface with the base reference plate  606 . This manifold is attached to a vacuum pump via large aperture tube  605 . Ports  603  through the base reference plate  606  surround the area of interest for good conduction but are not necessary in all applications. The annular air bearing  607  is separated from the vacuum chamber  627  by differentially pumped grooves  608 ,  609 ,  614  which are serviced by tubes from the motion system. This pattern is repeated exactly on the opposite side of the vacuum chamber stage. This second set of air bearing lands and differentially pumped grooves bear on surface  618  which is the top of the sub base  615 . The opportunity exists to make the air Bearing land area smaller because in this embodiment the various pressures in the air bearing lands, grooves and chamber are exactly equal due to the fact that they are ported through common connections  620 ,  621 ,  622 ,  623  to their source through  651 ,  652 ,  653  though the stage  612  and  617  though the sub base plate  615 . The pressurized air gaps  624  are preloaded against each other only. The air bearing running on this sub base  615  will be carrying the gravity load of the vacuum chamber stage  612  which could be 20 lbs. plus or minus an order of magnitude give or take. The preload force between the bearings can easily be 10 times (one order of magnitude) more than this gravity force, making the gravity force inconsequential. In this embodiment it is necessary to have a functioning vacuum gate on the stage  612  that closes the load unload aperture  610  and so maintains vacuum in the stage  612  by separating the internal chamber  626  from the larger chamber outside the stage  625  that in this case is at ambient pressure. Piezo actuators  616  may be used for substrate  604  planarization and fine ‘Z’ axis motion. 
   The preferred embodiment employs porous air bearing technology. Other air bearing compensation may be employed including, but not limited to, orifice and step compensation. Air bearings are a widely accepted art. Much has been written about orifice and porous type air bearings. Porous media air bearings are most commonly made from porous carbon or graphite but may be made from porous alumina or silicon carbide. Carbon and graphite have excellent crash resistance and are very tolerant to inadvertent bearing face contact. 
   In the preferred embodiment, it is recommended to drive on the center of mass and measure on the plane of the wafer. The use of reaction masses is anticipated for optimum stage control. 
   Pump from Below with Outside Vacuum 
   This embodiment is shown in  FIG. 7A . In another preferred embodiment, it is advantageous to have the stage  710  operate in a vacuum environment  707 . To do so, differentially pumped grooves  711  can also be arrayed on the outside perimeter of the air bearing  717 . Operating the stage  710  in a controlled chamber  707  avoids adhesion of water vapor or air molecules to the base reference plate  706  or sub base  709  bearing surfaces  725 ,  719 . It would still be necessary to employ a gate between the load and unload aperture  705  and volume  707  although if volume  707  is pumped to molecular flow regime a gate will not need to be as expensive. The invention, including the various preferred embodiments, can be used in the fluid regime or the molecular regime; therefore, concepts such as conductance should be understood as encompassing either regime as appropriate. 
     FIG. 7B  is a more detailed image of the bearing and land areas.  711   a  represents the first set of ambient or pumped grooves. The four grooves  711   a  may be ported together and pumped through a single fitting on the outside of the stage  710 . The second set of pumped grooves  711   b  may also be ported through a single fitting on the outside of the stage  710  although the fitting may need to be larger for better conductance. The third grooves  711   c  may be necessary as extra insulation of the process area may be required. Because most embodiments do not have a requirement for as low a pressure in volume  707  as there is in volume  726 , it may not be necessary to have a third groove on the outside of the stage and is not shown there. 
   In  FIG. 7C , notice the relative motion between the vacuum chamber stage  710  and the base reference member  706  and sub-base  709  in  FIGS. 7A and 7C . 
     FIG. 7D  is an illustration of how an embodiment may combine functions in a single stage system with the high conductance pumping from below. Also this is an illustration of the use of three differentially pumped grooves on the inside and the outside of the air bearing lands. By having the stage operate within a vacuum, interferometric position feedback is improved. 
     FIG. 8A  shows a device for providing precision rotation in a vacuum environment, drawn in the preferred embodiment for very low pressure. A sub plate with high conductance pumping aperture  815  through to the bottom of the vacuum chamber stage  813  as disclosed in  FIG. 6  could also be employed here for rotary motion. Notice that in this embodiment, the bearing and lands are stationary. The device has a cap or lid  801  that may be on hinges as used commonly on deposition chambers. The cap  801  mounts on and seals on a stationary vessel  803  which contains the upper stationary part of the vacuum chamber. In this embodiment a target  804  or source for a deposition process is shown. This arrangement of the vacuum chamber stage allows for other embodiments including an X or an XY vacuum chamber stage with air bearing and differentially pumped grooves replacing the cap  801  and target  804 . The vessel  803  has been designed and manufactured to provide for an air bearing  807  and differentially pumped grooves  805 ,  806 . These features are shown on the vacuum chamber stage itself in most examples but, in this embodiment, the vacuum chamber stage  809  does not move in X and Y, only in rotation and so it more convenient to plumb vacuum connections through the stationary members. Notice that this embodiment employs the high conductance technique disclosed in  FIG. 6 . This may not be necessary because of the convenience of mounting vacuum conductance to stationary structures. The vacuum chamber stage  809  is supported and guided in Z on the air bearing films  808 . In this case the load on the stage  809  from the atmosphere is in perfect balance because the vacuum chamber  802 , differentially pumped grooves  805 ,  806  and air bearings  807  are in symmetry. This reduces the load and so the size of the required air bearing surface. 
   As seen in  FIG. 8B , a slot  840  providing access to the substrate  841  radially, which because of rotation allows for access to the entire surface either by a point source or detector on a linear stage transiting the radius or by a wide beam that covers the entire radius. The translation stage is not shown. In another embodiment, the thrust bearings could be integrated into the stationary members as shown in  FIG. 8A . 
     FIG. 8C  shows a side sectional view of an XY vacuum chamber stage  853  with rotation about the centerline  859  and a port  871  surrounded by differentially pumped grooves  864 ,  865  and lands for transfer of the wafers  858  or substrates and or as a high conductance pumping port. This port  871  is arranged so that it aligns with a consument port  880  though the XY stage  853 . 
   Some applications, like thin film characterization, often employ rotation of the wafer  858 .  FIG. 8C  provides for rotation inside of an XY stage  853 . By employing annular 360 degree radial air bearing surfaces  863 ,  866  isolated from the pass through by 360 degree radial differential pumped grooves  864 ,  865  and lands. As the XY stage  853  is moved about the radial bearings  863 ,  866  keep the rotating part  867  centered within the XY stage  853 . The XY stage  853  carries a rotary actuator to spin the rotation part of the stage. It is possible to add an encoder. It is possible with differentially pumped grooves  854 ,  875  on outside of these bearings  855 ,  874  to operate the whole assembly in a vacuum environment. It will be necessary to vent  878  the volume that the upper and lower bearing sets  855 , 856 , 863 , 873 , 874  commonly leak into. The venting for the upper set of bearings is not shown in this figure. 
   As seen in  FIG. 9A , it is envisioned that the advantages of the foregoing embodiments could be individually or in combination applied in a larger motion system  901  with stages  902  that could be shuttled between process areas. For example, machine throughput could be increased and or the substrate could be referenced to the stage body (ex. Inferometric reference mirrors) and specific inspection or correction areas of interest located quickly. 
   In one preferred embodiment, there is a larger vacuum volume  904  in which the stages  902  operate and a much smaller vacuum volume  911  containing the substrate that can be quickly pumped to deeper vacuum by the high conductance aperture  910  from below. The volume  904  could be pumped to the molecular flow regime and or be nitrogen rich to avoid moisture on the reference surfaces  907 ,  908 . Once in the molecular flow regime, the small gap  915  that exists between the reference surface  907  and the bearing face  927 , lands  926 , differentially pumped grooves  928  and the clearance surface  925  becomes an effective seal between the larger volume  904  and the smaller volumes  911 . The small gap  915  is substantially the same as the air bearing gap as it will be convenient to face, machine or otherwise planerize surfaces  925 ,  926 ,  927  in the same operation. 
   In order to facilitate the shuttling of the vacuum stages  902  between different process areas, it is desirous to avoid the air bearing lands  927  translating over the process aperture  909  or the high conductance pumping aperture  910  below. In order to avoid this, the air bearing lands  927  may be segmented and sealed with the differentially pumped grooves  928  and lands  926  completely surrounding them. 
   One potential embodiment of a quad scan motion system could employ dual Y-axis drives  905  and a single X-axis drive  906 . This type of stage actuator is common in the art of single plane XY air bearing systems for ambient pressures and would allow for driving on the center of mass and measuring on the plane of the wafer. A wall down the center  905  gives structural column support to the base reference member  913  and sub base plate  914  against the atmospheric pressure they would be exposed to. This wall  905  would also provide structure for mounting motors, feedback positioning, cooling and other services. 
   A shuttle system  903  can be ‘handed’ a stage  902  by the XY motion system  905 ,  906 . The shuttle  903  may then translate the stage  902  with functionality switching the stage  902  from one XY system and process to another. The machine may have only two or three stages as in  FIG. 9C  or it may have five or more XY systems and processes. There must be conductance between the top side of the stage  902  vacuum volume  929  and the volume  931  on the underside of the stage  902 . as shown in figure  9 B, the holes  930  provides some conductance although more conductance may be employed as shown in  FIG. 9C . 
     FIG. 10  illustrates a new embodiment allowing for large aperture pumping from behind the wafer as it scans through a beam. The very consistent pumping from the same place behind the wafer through the whole scan allows for very clean and consistent control of the burst field from the implantation of the substrate surface. The pivotable base reference member  1009  provides the reference surface for the motion of a moving vacuum stage  1001 . The back of the moving vacuum stage  1005  is also a reference surfaces for stationary plenum  1004  which would be connected to deep pumping power. This pumping power is conducted to the moving vacuum stage  1005  through large apertures  1007  in the back of the moving vacuum stage  1005  which are sealed by the air bearing and differentially pumped grooves  1002  in the stationary plenum  1004  as described in previous embodiments. The base reference member  1009  may be tilted about axis line  1003  and the wafer/chuck  1008  may be rotated for effective implantation of the sides of vias and trenches in the substrate. 
   While preferred embodiments have been set forth in detail above, those skilled in the art who have received the present disclosure will readily appreciate that other embodiments can be realized within the scope of the invention. For example, the invention can be used in a variety of applications other than those set forth in detail, such as display screens and MEMS. Therefore, the present invention should be construed as limited only by the appended claims.