Abstract:
The fluid delivery mechanism of the present disclosure provides a solution for use in a single axis of motion that allows the connection of one or more fluid flow paths over a wide range of temperatures into a vacuum environment. The mechanism does not employ flexible tubing that is prone to fatigue, especially at very low temperatures. In one embodiment, a tube is axially moved within a sealed piston to allow for fluid delivery. In a second embodiment, bellows are used to provide the required functionality. In another embodiment, it is possible to achieve movement in two or more axis of motion by utilizing two or more appropriately configured mechanisms.

Description:
BACKGROUND OF THE INVENTION 
     Ion implanters are commonly used in the production of semiconductor wafers. An ion source is used to create an ion beam, which is then directed toward the wafer. As the ions strike the wafer, they dope a particular region of the wafer. The configuration of doped regions defines their functionality, and through the use of conductive interconnects, these wafers can be transformed into complex circuits. 
     A block diagram of a representative ion implanter  100  is shown in  FIG. 1 . An ion source  110  generates ions of a desired species. In some embodiments, these species are atomic ions, which may be best suited for high implant energies. In other embodiments, these species are molecular ions, which may be better suited for low implant energies. These ions are formed into a beam, which then passes through a source filter  120 . The source filter is preferably located near the ion source. The ions within the beam are accelerated/decelerated in column  130  to the desired energy level. A mass analyzer magnet  140 , having an aperture  145 , is used to remove unwanted components from the ion beam, resulting in an ion beam  150  having the desired energy and mass characteristics passing through resolving aperture  145 . 
     In certain embodiments, the ion beam  150  is a spot beam. In this scenario, the ion beam passes through a scanner  160 , which can be either an electrostatic or magnetic scanner, which deflects the ion beam  150  to produce a scanned beam  155 - 157 . In certain embodiments, the scanner  160  comprises separated scan plates in communication with a scan generator. The scan generator creates a scan voltage waveform, such as a sine, sawtooth or triangle waveform having amplitude and frequency components, which is applied to the scan plates. In a preferred embodiment, the scanning waveform is typically very close to being a triangle wave (constant slope), so as to leave the scanned beam at every position for nearly the same amount of time. Deviations from the triangle are used to make the beam uniform. The resultant electric field causes the ion beam to diverge as shown in  FIG. 1 . 
     In an alternate embodiment, the ion beam  150  is a ribbon beam. In such an embodiment, there is no need for a scanner, so the ribbon beam is already properly shaped. 
     An angle corrector  170  is adapted to deflect the divergent ion beamlets  155 - 157  into a set of beamlets having substantially parallel trajectories. Preferably, the angle corrector  170  comprises a magnet coil and magnetic pole pieces that are spaced apart to form a gap, through which the ion beamlets pass. The coil is energized so as to create a magnetic field within the gap, which deflects the ion beamlets in accordance with the strength and direction of the applied magnetic field. The magnetic field is adjusted by varying the current through the magnet coil. Alternatively, other structures, such as parallelizing lenses, can also be utilized to perform this function. 
     Following the angle corrector  170 , the scanned beam is targeted toward the workpiece  175 . The workpiece is attached to a workpiece support. The workpiece support provides a variety of degrees of movement. 
     The workpiece support is used to both hold the wafer in position, and to orient the wafer so as to be properly implanted by the ion beam. To effectively hold the wafer in place, most workpiece supports typically use a circular surface on which the workpiece rests, known as a platen. Often, the platen uses electrostatic force to hold the workpiece in position. By creating a strong electrostatic force on the platen, also known as the electrostatic chuck, the workpiece or wafer can be held in place without any mechanical fastening devices. This minimizes contamination and also improves cycle time, since the wafer does not need to be unfastened after it has been implanted. These chucks typically use one of two types of force to hold the wafer in place: coulombic or Johnson-Rahbeck force. 
     The workpiece support typically is capable of moving the workpiece in one or more directions. For example, in ion implantation, the ion beam is typically a scanned or ribbon beam, having a width much greater than its height. Assume that the width of the beam is defined as the x axis, the height of the beam is defined as the y axis, and the path of travel of the beam is defined as the z axis. The width of the beam is typically wider than the workpiece, such that the workpiece does not have to be moved in the x direction. However, it is common to move the workpiece along the y axis to expose the entire workpiece to the beam. 
     In some applications, it is necessary to pass fluids, in the form of gas and/or liquid into the vacuum environment. For example, in some embodiments, the platen is maintained at a constant, or nearly constant temperature, by running fluid through conduits located within the platen. Depending on the type of ion implantation being performed, this fluid may be for the purpose of heating the workpiece or cooling the workpiece. 
     This entire system is typically maintained at very low pressure, such as less than 100 mTorr. Although the pressure is greater than 0, this environment is commonly referred to as a vacuum. The task to delivering fluids to a vacuum environment is further complicated by several factors. First, in many instances, the fluid must be delivered to a terminus or endpoint that is not stationary. As described above, it is typical for the workpiece support to move along the y axis to irradiate the entire surface of the workpiece. The movement of the terminus typically necessitates the use of flexible tubing or some other moveable conduit. Making this endeavor even more difficult, at times the fluids that are being delivered are at very low temperatures, such as cryogenic temperatures. In extremely low temperatures, the flexible tubing is susceptible to fatigue due to the bending stresses from the cyclic movement, and therefore cannot be used. Alternative coupling mechanisms, such as rotary or linear sliding seals, are difficult to produce without leakage. They are also typically physically quite large and hence difficult to package near the moving workpiece. 
     As an example, for cryogenic ion implantation, it is necessary to maintain the temperature of wafer at very low temperatures, despite the fact that constant ion bombardment tends to increase its temperature. One method of achieving this is to pass low temperature fluids through conduits in the platen. By keeping the platen extremely cold, the wafer, by virtue of its contact with the platen, preserves its low operating temperature. However, as explained above, the wafer (and therefore the platen) is typically moved axially through the ion beam so as to insure that the entire wafer is exposed to the ion beam. Reliably delivering cryogenic fluid to a moving platen in a vacuum environment is extremely difficult. 
     These constraints make it very different to provide a fluid delivery system to a workpiece support, such as a platen, in a vacuum wafer processing system. Therefore, a system that allows the delivery of fluid, such as extremely cold fluid, into a vacuum environment would be extremely beneficial, especially if delivered to a non-stationary terminus. 
     SUMMARY OF THE INVENTION 
     The problems of the prior art are overcome by the fluid delivery mechanism described in the present disclosure. In some embodiments, this mechanism provides a solution for use in a single axis of motion that allows the connection of one or more fluid flow paths over a wide range of temperatures into a vacuum environment. The mechanism does not employ flexible tubing that is prone to fatigue, especially at very low temperatures. In one particular embodiment, a tube is axially moved within a sealed piston to allow for fluid delivery. In a second particular embodiment, bellows are used to provide the required functionality. In another embodiment, it is possible to achieve movement in two or three axis of motion by utilizing two or more mechanisms configured appropriately. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  represents a traditional ion implanter; 
         FIG. 2  represents a linear fluid sliding seal having a single fluid path; 
         FIG. 3  represents the sliding seal of  FIG. 2  as used when connected to a moving apparatus; 
         FIG. 4  represents the side view of a process chamber layout utilizing two of the sliding seals of  FIG. 2 ; 
         FIGS. 5   a - 5   b  represent cross-sectional views of tubes having multiple conduits; 
         FIGS. 6   a - 6   c  represents embodiments of a linear fluid sliding seal having a plurality of fluid conduits, using the tubes shown in  FIGS. 5   a  and  5   b;    
         FIG. 7  represents the side view of a process chamber layout utilizing embodiments of the sliding seals shown in  FIGS. 6   a - 6   c;    
         FIG. 8   a - c  show the various elements used in a second embodiment; 
         FIG. 9  shows the operation of an embodiment utilizing bellows; 
         FIG. 10  shows the front view of a process chamber using the embodiment of  FIG. 8 ; 
         FIG. 11  shows a second embodiment utilizing bellows; 
         FIG. 12  shows a third embodiment utilizing bellows; and 
         FIG. 13  shows an embodiment that provides movement along two axis. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As described above, delivering fluids, particularly extremely cold fluids, into a vacuum environment is very difficult. This is further complicated when the destination for that delivered fluid is not stationary. In one embodiment, the present mechanism provides a delivery system that allows movement along one axis of motion. This allows fluids to be delivered to devices or termini that are being moved along one axis of motion. 
     One such application of this device is the process chamber of an ion implantation system. In certain embodiments, the wafer must be maintained within a certain temperature range. To accomplish this, the platen, which holds the wafer, is cooled (or heated) by a fluid being passed through conduits located within it. For example, in ion implantations that occur at extremely low temperatures, it is essential to continuously cool the platen, since the ions being directed at the wafer tend to heat the wafer and, indirectly, the platen. To maintain the temperature of the wafer within the desired range, it is necessary to pass cryogenic fluids to and from the platen. These fluids may be gasses, such as helium, nitrogen or CDA (clean dry air), or may be liquids, such as liquid nitrogen, Flourinert or other low temperature coolants. 
     As stated above, in many applications, the wafer is scanned by an ion beam. This beam is very narrow and therefore, it is necessary to move the wafer to insure that all portions of the wafer are exposed to the beam. This is typically done by moving the platen, to which the wafer is attached, in a linear manner to subject different parts of the wafer to the beam. Therefore, to cool or heat the platen as described above, it is essential that the device used to carry the fluid to the platen be capable of adapting to the varying position of the platen. 
       FIG. 2  shows one embodiment of the present device. The device comprises a column or cylinder  200 , which is separated into one or more chambers  210  through the use of sealing elements  220 . The column is preferably constructed of stainless steel, although other suitable materials may be used. The sealing elements, which are made from Teflon® or another suitable material, create seals that are nearly fluid and airtight. These sealing elements define adjacent chambers  210  within the column  200 . Within the column or cylinder  200  is a tube  230 , having a hollow center, which allows the passage of fluid. Each of the sealing elements  220  also has a hole, preferably in its center, through which the tube  230  passes. The interface between the sealing elements  220  and the tube  230  is also nearly fluid and air tight. 
     One end of the tube  230  exits cylinder  200 , while the opposite end remains within the tube, and preferably is confined within one chamber  210   a . To insure that the tube  230  remains within a single compartment, the proximate end of the tube is preferably made wider, such as through the use of a flange  235 , so that it cannot pass through the opening in the sealing element  220 . Thus, the length of travel of the tube  230  is confined to the length of the chamber  210   a , where the wider end of tube  230  is located. While a flange is illustrated in this figure, those skilled in the art will appreciate that other mechanisms can be used to insure that the proximate end of central tube  230  remains within chamber  210   a . Those mechanisms are within the scope of this disclosure. 
     As noted above, the column  200  can be separated into any number of chambers  210 , each separated and defined by sealing elements  220 . The open end of the column  200  is preferably closed with a sealing element  220   d , similar to those used to separate the chambers. 
     In one embodiment, the fluid (either gas or liquid) enters the column  200  via fluid inlet  240 . Since the tube  230  is hollow, the fluid passes from the compartment  210   a , into the tube  230  and flows to the terminus. Since the sealing elements  220  provide nearly fluid and air tight barriers, a small amount of fluid may be introduced into the adjacent compartment. To address this, each compartment is in communication with a differential pump, which serves to lower the pressure of each compartment, relative to the one adjacent to it. Thus, the pressure within chamber  210   b  is lower than that within chamber  210   a , but higher than that in chamber  210   c . The pressure within each chamber is reduced as the chambers near the open end of the cylinder  200 . 
     Often, the fluid introduced into compartment  210   a  is at or near normal atmospheric pressure. The environment outside of the column  200 , and specifically on the exterior of sealing element  220   d , is near vacuum pressure. Therefore, it may be beneficial to include a number of chambers  210   b - d , which serve to reduce the differential pressure across sealing elements  220   a - d . In other words, in the case where only one chamber is used, the differential pressure across with lone seal is equal to the difference in the pressure of the fluid in the chamber and the external vacuum. By utilizing four chambers, as shown in  FIG. 2 , the differential pressure across any sealing element is reduced by 75%. To achieve this, differential pumps are used to regulate the pressure within each chamber via inlets  250 . In the column shown in  FIG. 2 , the pressure within each chamber decreases moving from top to bottom, as the pressure at the uppermost chamber is near atmospheric pressure, and the pressure below the bottommost chamber is near vacuum. While four chambers  210  are shown in  FIG. 2 , any number (either more or less) can be used, as required. For example, if sealing element  220   d  can provide a fluid and airtight seal, it is not necessary to provide any additional chambers  210  within cylinder  200 . 
       FIGS. 3   a - c  show the device of  FIG. 2  as used with a terminus, such as a workpiece support  350  The workpiece support  350  includes a stationary portion  345  and a movable portion  343 . At the distal end of the moveable portion  343  is the platen  300 . As described earlier, the platen  300  is moved in the vertical direction in order that the ion beam can scan the entire attached wafer. To do this, the movable portion  343  of the workpiece support  350  moves up and down. The three figures illustrate 3 representative positions of the movable portion  343  and the platen  300 . It should be obvious to one skilled in the art that the platen  300  moves in a continuous motion, and therefore there are an arbitrary number of positions for the platen  300 . This figure simply attempts to describe the operation of the device by showing 3 distinct positions. In the  FIG. 3   a , the platen  300  is in the middle of its range of motion, or midrange position. Therefore, the tube  230  is partially extended from the cylinder  200 . Thus, the proximate end of the tube  230  is located approximately in the middle of the chamber  210   a . In  FIG. 3   b , the platen  300  has moved downward to its lowest point, and further away from the cylinder  200 . This motion by the moveable portion  343  forces the tube  230  to extend further from the cylinder  200 . In this position, the tube  230  is in its most extended position, as the wider end of the tube  230  is in contact, or nearly in contact with sealing element  220   a .  FIG. 3   c  shows the movable portion  343  and the platen at its highest point, where the tube  230  is in its least extended position. Thus, the wider proximate end of tube  230  is in contact, or nearly in contact with, the closed end of the cylinder  200 .  FIGS. 3   b  and  3   c  define the range of motion for the tube  230  and the platen  300 . This length of this range of motion must be less than, or equal to, the height of the first chamber  210   a . The length of chamber  210   a  may be much longer than the range of motion of the platen, if desired. The sole requirement is that its length must be at least the same as the required range of motion of the tube. 
     Although not shown in  FIG. 3 , tube  230  is preferably affixed to movable portion  343 , such as through a weld, a screw type fitting or other attachment means. Conduits within the movable portion  343  lead from that point of attachment to the platen  300 . 
     As described above, in certain embodiments, the platen  300  is cooled by passing a fluid through it. In such embodiments, there is a need for at least two fluid delivery paths; a first path to bring fluid to the platen  300 , and a second path to serve as a return path for that delivered fluid. 
       FIG. 4  shows a side view of a process chamber layout. In this embodiment, two cylinders  260   a ,  260   b  are used, where one serves to deliver the fluid to the platen  300  and the other serves as the return path. The chamber  270 , defined by wall  275 , is kept at near vacuum pressure, while the exterior environment  278  is maintained at atmospheric pressure. Two devices, as described in conjunction with  FIG. 2 , are used to circulate fluid through the platen  300 . In  FIG. 4 , these devices are shown with the tubes  280   a ,  280   b  in their most extended positions. The movable portion  343  and the platen  300  can move upwardly until the tubes  280  reaches the closed end of the cylinders  260 . In this embodiment, the distal ends of the two tubes  280  are affixed to the movable portion  343  of the workpiece support  350 . Within the movable portion, 2 conduits  341   a ,  341   b  are used to direct the paths of the fluid flow so as to contact the proper locations on the platen  300 . Other methods of attaching the tubes to the workpiece support are well known and within the scope of this disclosure. 
     In operation, fluid enters the upper chamber of cylinder  260   a  via inlet  265   a . This fluid passes through tube  280   a  and into the fluid conduits  341   a  in movable portion  343 . The fluid then passes through the platen  300  and returns via fluid conduits  341   b  to tube  280   b . The fluid travels up the tube  280   b  and into the upper chamber of cylinder  260   b . The fluid then exits via outlet  265   b . The source and terminus of the fluid path is kept outside the vacuum environment. In some embodiments, the fluid is recirculated and is pumped from the outlet  265   b  back to the inlet  265   a . In some embodiments, the fluid is conditioned, such as cooled, before being reused. 
     Cylinders  260   a ,  260   b  are partially in the vacuum environment  270 , and partially outside of the vacuum. To maintain the integrity of the vacuum environment  270 , sealing elements  267  are used to provide a fluid and airtight seal between the wall  275  and the cylinders  260   a ,  260   b . In  FIG. 4 , conduits  261  are used to attach the differential pumps to the various chambers within the cylinders  260   a ,  260   b . Preferably the differential pumps are kept in normal atmospheric environment  278 , and thus, seals are also used to maintain the integrity of the vacuum between the conduits  261  and the wall  275 . 
     As explained above, in many embodiments, it is typical and necessary to have two separate fluid paths (as shown in  FIG. 4 ).  FIG. 5   a  shows the cross section of a single tube that accomplishes this. In this embodiment, the central tube  600 , rather than having a single conduit, has a plurality of conduits  602 ,  604 . This can be accomplished using numerous techniques. In one embodiment, shown in  FIG. 5   a , a coaxial tube  600  is used, which has an inner conduit  602 , and an outer conduit  604  that surrounds the inner conduit  602 . These conduits can be dimensioned such that they are of equal cross-sectional area, or can be dimensioned in any other suitable ratio. In one embodiment, shown in  FIG. 6   a , these conduits terminate in different chambers. The inner conduit  602  terminates in the rightmost chamber  210   a , while the outer conduit  604  terminates in the adjacent chamber  210   b . These two chambers  210   a ,  210   b  are preferably of equal length, and the inner conduit  602  extends beyond the outer conduit  604  by this length, such that each conduit terminates in the same relative position within its respective chamber. Inlet  290   a  is used to supply fluid to the mechanism, while outlet  290   b  is used to remove the return fluid from chamber  210   b . Note that sealing element  620   a  is different from the remaining sealing elements in that it has an opening to accommodate only the inner conduit  602 . Alternatively, the outer conduit  604  may extend the length of the tube and be sealed at the far end, as shown in  FIG. 6   b . In this embodiment, the outer conduit  604  may contain an opening  605  along its circumference in the second chamber  210   b . The inner conduit  602  is in communication with the chamber  210   a  through an opening  607  on the proximate end of the tube  600 . In this embodiment, all sealing elements  620  are identical in size. 
     In this embodiment, the inner conduit  602  is used to provide fluid to the destination, such as a platen, while the outer conduit  604  is used as the return path. Those skilled in the art will appreciate that the conduits can be employed in other ways. While  FIG. 5   a  shows coaxial conduits, the disclosure is not limited to this embodiment. For example, the conduits can be disposed adjacent to one another in the tube as shown in  FIG. 5   b .  FIG. 6   c  shows an embodiment using the tube shown in  FIG. 5   b . In this figure, an opening  608  exists in one side of the tube  600  in the first chamber  210   a  for allowing fluid to enter the tube  600  and a second opening  609  exists on the opposite side of the tube  600  in the second chamber  210   b  to serve as the fluid outlet. As described above, fluid enters and exits the cylinder through inlet  290   a  and outlet  290   b , respectively. 
     While the tubes shown in  FIGS. 5   a  and  5   b  illustrate embodiments with 2 fluid conduits, other embodiments are envisioned. For example, an arbitrary number of coaxial conduits can be employed in the tube of  FIG. 5   a . Similarly, the tube shown in  FIG. 5   b  can be divided into as many conduits as are desired. 
     In all embodiments, multiple sealing elements  620  and compartments are used to alleviate the pressure differential experienced at the sealing elements, and to accommodate the fact that each sealing element is not perfectly airtight. 
       FIG. 7  shows a front view of a process chamber layout that utilizes the tube having multiple conduits as shown in  FIGS. 5 and 6 . In this embodiment, fluid enters chamber  210   a  through inlet  290   a . The fluid travels through tube  600 , specifically the inner conduit  602  of tube  600 , and is affixed to the movable portion  343  of workpiece support  350 . As explained above, internal conduit  341   a  passes the fluid from the tube attachment point to the platen  300 . After the fluid circulates through the platen  300 , it returns through a second internal conduit  341   b  to the attachment point. The fluid then passes through the outer conduit  604  in tube  600 , and exits the cylinder via outlet  290   b . As described earlier, the sealing elements  620   b - e  serve to separate the cylinder into chambers, where each chamber is maintained at a lower pressure than the adjacent chamber. 
     Other embodiments other than those disclosed in  FIGS. 2-7  can also be employed to create the fluid delivery mechanism. 
       FIG. 8   a  shows the various components of a bellows mechanism. The bellows  800  is compressible unit, preferably made of metal such as stainless steel, Inconel® or Monel®, which can expand and contract within a specified range. The bellows  800  attach to the coupler  810  and form a fluid and airtight seal. Couplers  810  are used to link together a number of bellows to create a longer structure. One end of a bellows  800   a  attaches to the coupler  810 , and the end of a second bellows  800   b  attaches to the opposite side of the coupler  810 . An arbitrary number of bellows  800  can be joined together using couplers  810 . 
     A side view of the coupler  810  is shown in  FIG. 8   b . Typically, the coupler  810  has a central opening or passage  820 , adapted to allow a tube  830  to pass through it. This tube  830  is fitted into the passage  820  so as to create a fluid and airtight seal. In certain embodiments, the coupler  810  also has a number of additional openings or passages  822 . These passages  822  are preferably in communication with the interior volume  825  of the bellows  810 . Thus, when two or more bellows  800  are joined together using couplers, the interior volume  825  of all of the bellows is in communication, due to the presence of the additional openings  822  on all of the couplers. 
       FIG. 8   c  shows a cross section of a bellows  800  with two couplers  810  and a tube  830 . In one embodiment, the fluid is supplied via tube  830  from its source to a terminus. The return path for the fluid is via the additional passages  822  in the coupler  810 , so that the interior volume of the bellows is filled with fluid returning from the terminus. 
     The bellows configuration can be used to supply fluid to a movable terminus within the vacuum environment, as shown in  FIGS. 9   a  and  9   b . In one embodiment, the fluid is supplied in the non-pressurized environment  278 . The tube  830  and a portion of coupler  810   a  pass through the wall  275  that defines the vacuum environment  270 . Sealing elements are used to insure a fluid and airtight seal between the coupler  810  and the wall  275 . The fluid passes through the tube  830  and into the vacuum environment  270 , where it eventually reaches the workpiece support (not shown). As the workpiece moves further from the wall  275 , the tube  830  is pulled into the vacuum environment  270 , as best shown in  FIG. 9   b . As the workpiece support moves toward the wall  275 , the tube  830  extends further into the non-pressurized environment  278 , as shown in  FIG. 9   a . The coupler located near the distal end of the tube  830  is also affixed to the workpiece support, and therefore tracks the movements of the tube  830 . However, since bellows  800  terminate within the vacuum environment  270 , the bellows are forced to extend and compress as the workpiece support (not shown) moves relative to the wall  275 .  FIG. 9   a  shows the bellows maximally compressed, while  FIG. 9   b  shows the bellows maximally extended. As described above, the return path for the fluid is via the interior volume  825  of the bellows  800 . The fluid is then passed through the wall  275  either via the coupler  810 , or a separate conduit in the wall itself. 
       FIG. 10  shows a front view of a process chamber layout using the bellows system of  FIGS. 8 and 9 . In the embodiment shown, one or more bellows  800  are joined together using couplers  810 . The bellows is located within the vacuum environment  270 , with one end preferably pressed against the wall  275  of the chamber. In this embodiment, the opposite end of the bellows  800  attached to the workpiece support  350 . The central tube  830  is in communication with the movable portion  343  of the workpiece support  350 , with its distal end extending outside the vacuum environment  270 . The lowest coupler  810   a  is in communication with the workpiece support  350 , and is sealed to form a fluid and airtight seal. As explained in conjunction with  FIG. 3 , the workpiece support and platen  300  moves in an up and down (vertical) direction. The bellows, being constrained by the chamber wall  275  and the movable portion  343  compresses and expands in response to this movement. As the movable portion  343  moves upward, the central tube  830  simply extends further out into the non-vacuum environment. In this configuration, there is a fluid and airtight seal between the coupler  810  and the tube  830 . Thus, the differential pumps described in conjunction with the previous embodiment are not required. 
       FIGS. 11   a - c  shows a second embodiment utilizing bellows. In this embodiment, the lowest coupler  810   a  is not in direct contact with the movable portion  343 . Rather, a tube  835  connects the lowest coupler  810   a  to the movable portion  343 . This tube  835  is much shorter than central tube  830 . In this embodiment, the bellows  800  is confined between the chamber wall  275  and the end of tube  835 . Thus, as the movable portion  343  moves, the tube  835  moves accordingly. This action then causes the bellows to expand or contract as required. 
     As the wafer is being scanned, the workpiece support  350  moves in the vertical direction. When the platen reaches its lowest point, as shown in  FIG. 11   a , the bellows  800  is maximally extended. The proximate end of the bellows assembly is in communication, preferably via a fluid and airtight seal, with the wall  275  of the chamber. Thus, as the platen moves downward, the bellows assembly is extended. The central tube  830  moves in accordance with the movable portion  830  and therefore, in this position, the tube is mostly within the vacuum environment  270 . 
     When the platen moves in the upward direction, as shown in  FIG. 11   b , the bellows  800  begins to compress, and the central tube  830  extends further outside of the vacuum chamber  270 . 
     When the platen reaches its highest point, as shown in  FIG. 11   c , the central tube  830  is maximally extended out of the vacuum environment  270  and the bellows is maximally compressed. 
     While the sequence shown in  FIG. 11  utilizes a tube  835  to connect the movable portion  343  to the bellows  810 , the explanation is equally applicable to the embodiment illustrated in  FIG. 10 , where the bellows is in direct contact with the movable portion  343 . 
     It should be noted that while two fluid paths to the platen, one for supply and one for return are typical, other embodiments are possible. For example, in some applications, it may be necessary to supply backside gas into the vacuum environment. Backside gas refers to a gas injected between the wafer and the platen. This gas is in the cooling path for heat that must be removed from the wafer. The mechanisms described in the present disclosure can be used to provide this gas. For example,  FIG. 12  shows an embodiment utilizing 2 bellows assemblies  900   a ,  900   b . The first bellows assembly  900   a  can be used to provide fluid to the platen as described above. The second bellows assembly can be used to supply a second fluid to the workpiece support. In certain embodiments, this fluid is the backside gas described above. In other embodiments, this fluid may be a second fluid that is passed through the platen. For example, assume the implant process requires that a portion of the ion implantation be performed at a first temperature and a second portion of the implantation be performed at a second temperature, where one of these temperatures is cryogenic. The first bellows assembly  900   a  may provide the supply and return path for liquid nitrogen (or other cryogenic fluids). This path is enabled while the ion implantation is being performed at low temperature. The second bellows assembly  900   b  is used to supply a second fluid (such as water or CDA), which is used during the implantation performed at the higher temperature. Valves, such as within the workpiece support  350 , can be used to enable the appropriate fluid path. While the delivery of a cryogenic fluid is contemplated, it is not a requirement of the present disclosure. For example, the two fluids may be used for two different temperature ranges, where neither is cryogenic. 
     The previous figures show a fluid delivery mechanism that provides axial movement in one dimension. By combining several of these mechanisms, as shown in  FIG. 13 , it is possible to achieve movement along two axis.  FIG. 13  shows a vacuum chamber  270  that has two fluid delivery mechanisms  950   a ,  950   b . Each can be of either of the embodiments described above, or of another embodiment with the same functionality. The first fluid delivery mechanism  950   a  is located partly within the vacuum environment  270 , as described above. However, instead of connecting to the workpiece support, it is connected to a second fluid delivery mechanism  950   b , oriented in a different direction. In the embodiment shown in  FIG. 13 , the two fluid delivery mechanisms are oriented perpendicular to one another, however, this is not a requirement. In this embodiment, the platen can be moved vertically, as in the previous embodiments. However, the platen can also move horizontally, thereby allowing any desired motion in the x-y plane.