Abstract:
A two piece shell is employed for intermediate and long term storage of substrates. The shell is formed of two halves that can be juxtaposed in vacuum and externally vented, with the internal vacuum retaining the halves in vacuum-sealed engagement. One of the halves also provides a vacuum-sealing perimeter for selectively sealing to a process chamber during loading and/or unloading of the shell with a substrate. A vacuum monitor or the like may be employed to monitor pressure during storage and provide alerts if the vacuum within the sealed shell is compromised.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Prov. App. No. 60/940,811 filed on May 30, 2007 and U.S. Prov. App. No. 61/049,440 filed on May 1, 2008. The entire content of these applications is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Reticles, wafers, and other semiconductor substrates and the like have very high cost. Exposure to air brings with it the risk of contamination and damage to the substrate, so vacuum environments are commonly used in processing, handling, and using these substrates. While it is possible to store substrates within a vacuum processing environment for short durations, this consumes valuable in-vacuum space and is not generally suitable for longer term storage, particularly where numerous substrates (e.g., the hundreds of reticles that might be needed in a wafer stepper). This approach is also unsuitable where transfer is required between separate vacuum processing environments. 
         [0003]    Batch transfer techniques such as multi-wafer carriers have long been employed to transfer wafers among processing systems. In addition, the storage of individual substrates in tightly sealed boxes either under atmospheric or vacuum pressure conditions or under inert environments such as Nitrogen or Argon has been used in the past. However to the present day, these storage boxes require the box to be opened and the substrate to be exposed to a regular air environment, while the substrate is being transferred from the box to a working environment. 
         [0004]    There remains a need for single-wafer storage and transportation alternatives that permit transfer of substrates while reducing exposure to the harmful effects of contamination from airborne particles and particles that might be disturbed during pumping and venting cycles. 
       SUMMARY 
       [0005]    A two piece shell is employed for intermediate and long term storage of substrates. The shell is formed of two halves that can be juxtaposed in vacuum and externally vented, with the internal vacuum retaining the halves in vacuum-sealed engagement. One of the halves also provides a vacuum-sealing perimeter for selectively sealing to a process chamber during loading and/or unloading of the shell with a substrate. A vacuum monitor or the like may be employed to monitor pressure during storage and provide alerts if the vacuum within the sealed shell is compromised. 
         [0006]    In one aspect, a device disclosed herein includes a first half with a recessed interior shaped and sized to receive a single substrate, a perimeter around the recessed interior including a vacuum gasket; and a second half adjacent to the first half, the second half including an interior face including a surface contacting the vacuum gasket to form a vacuum seal capable of retaining a vacuum within the recessed interior. 
         [0007]    The second half may have an interior formed by a perimeter wall, the interior enclosing the first half and the perimeter wall including a second vacuum gasket shaped and sized to form a vacuum seal with a substrate handling device. At least one of the first half and the second half may have a pressure sensor disposed thereon for monitoring a vacuum level within the recessed interior. The pressure sensor may include an active vacuum gauge for measuring pressure based upon a measurement from an interior of the device. The pressure sensor may include an external sensor for measuring pressure based upon a measurement of an exterior of the device. The substrate may include one or more of a wafer and a reticle. The vacuum gasket may be an o-ring, the perimeter including a groove for retaining the o-ring in a predetermined position. 
         [0008]    In another aspect, a device disclosed herein includes a container with a recessed interior shaped and sized to receive a single substrate, the recessed interior formed by a bottom and a side wall along a perimeter of the bottom, the side wall having a top edge with an asymmetric vertical feature and a vacuum gasket along an entire length of the top edge including along the asymmetrical vertical feature around the recessed interior including a vacuum gasket; and a lid, the lid having a second asymmetric vertical feature that permits placement of the lid on the container only in a single, predetermined orientation, the lid mating to the top edge to form a vacuum-sealed interior within the container. 
         [0009]    The device may include a pressure sensor disposed on one or more of the container or the lid to monitor a vacuum within the vacuum-sealed interior. 
         [0010]    In another aspect, a method disclosed herein includes sealing a vacuum chamber with a removable plate; providing a tray within the vacuum chamber; placing a substrate within the tray; moving the tray into a vacuum-sealed engagement with the removable plate to form an enclosed substrate carrier; and venting the vacuum from the vacuum chamber, thereby providing an enclosed substrate carrier containing a substrate in vacuum. 
         [0011]    Moving the tray into a vacuum-sealed engagement with the removable plate may include vertically lifting the tray into the removable plate. Moving the tray into a vacuum-sealed engagement may include concurrently physically isolating the tray from the vacuum chamber in a subchamber. Venting the vacuum may include venting only the subchamber. The method may include transporting the substrate in the enclosed substrate carrier. The method may include storing the substrate in the enclosed substrate carrier. The method may include monitoring a vacuum within the enclosed substrate carrier. The substrate may include one or more of a wafer and a reticle. The method may include returning the enclosed substrate carrier to a vacuum processing chamber. The method may include opening the enclosed substrate carrier within the vacuum processing chamber and removing the substrate from the enclosed substrate carrier. Returning the enclosed substrate carrier to a vacuum processing chamber may include returning the enclosed substrate carrier to the vacuum chamber from which the substrate was removed. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES  
         [0012]    The foregoing and other objects and advantages of the invention will be appreciated more fully from the following further description thereof, with reference to the accompanying drawings, wherein: 
           [0013]      FIG. 1  shows a cross section of a single-substrate carrier. 
           [0014]      FIG. 2  illustrates the introduction of a carrier to a vacuum chamber. 
           [0015]      FIG. 3  illustrates the introduction of a carrier to a vacuum chamber. 
           [0016]      FIG. 4  illustrates the introduction of a carrier to a vacuum chamber. 
           [0017]      FIG. 5  illustrates the removal of a carrier from a vacuum chamber. 
           [0018]      FIG. 6  illustrates the removal of a carrier from a vacuum chamber. 
           [0019]      FIG. 7  illustrates the removal of a carrier from a vacuum chamber. 
           [0020]      FIG. 8  shows another embodiment of a carrier system. 
           [0021]      FIG. 9  shows another embodiment of a carrier system. 
           [0022]      FIG. 10  shows an embodiment of a carrier. 
       
    
    
     DETAILED DESCRIPTION  
       [0023]    The following description emphasizes single substrate carriers for use with vacuum processing. While the following description emphasizes reticles and semiconductor wafers—items that are commonly processed or used in vacuum—it will be appreciated that the principles of this disclosure may be suitably adapted to a wide array of vacuum-based processing and handling systems, and that all such adaptations that would be apparent to one of ordinary skill in the art are intended to fall within the scope of this disclosure. 
         [0024]      FIG. 1  shows a cross section of a single-substrate carrier. In general, the carrier  100  includes a first half  102  and a second half  104  that collectively enclose a substrate  106  in a recessed interior  108  of the first half  102 . A perimeter  110  around the first half  102  includes a vacuum gasket  112  where the perimeter  110  meets an interior face  114  of the second half  104 . Thus, more generally, the carrier  100  is formed of two shells that cooperate to retain a vacuum seal and hold a wafer or the like in a vacuum environment. With a suitable gasket or other sealing material, this self-sealing, single-wafer carrier can retain a wafer in vacuum for extended periods. 
         [0025]    The first half  102  may be formed of aluminum or any other material suitable for use in vacuum environments. In general, the first half  102  serves as a receptacle for a substrate  106  that is to be stored within the carrier  100 . The recessed interior  108  is in general shaped and sized to receive the substrate  106 . This may include a circular (e.g., wafer) 300 or 450 mm shape, a rectangular (e.g., reticle) shape, or any other shape corresponding to a substrate that is to be sealed and stored within the carrier  100 . In general a depth of the recessed interior  108  is minimized in order to reduce the volume of a vacuum environment that is maintained within the carrier  100 . It will be understood that, while not depicted, the first half  102  may include stand-offs or the like to support the substrate  106  off an interior surface of the first half  102 , and to facilitate handling of the substrate  106  such as placing or removing the substrate  106  with a robotic handler. The perimeter  110  extends generally around an edge of the first half  102  and provides a continuous side wall to form the recessed interior  108 . The perimeter may include a groove  118  or the like to support the vacuum gasket  112  in a predetermined position, such as a position to seal against the interior face  114  of the second half  104  when the two halves  102 ,  104  are placed together. The vacuum gasket  112  may, for example, be an o-ring or the like formed of a material such as Viton suitable for creating a vacuum seal. 
         [0026]    The second half  102  may be formed of aluminum or any other material suitable for use in vacuum environments. In general, the second half  102  serves to seal the carrier  100  and retain the substrate  106  in a vacuum environment for transportation or storage. The second half  104  provides an interior face  114  that generally serves to enclose the recessed interior  108  and seal the carrier. While a generally planar interior face  114  is contemplated, other shapes such as concave, convex, compound, mechanically keyed (to the perimeter  118 ), and the like, as well as combinations of the foregoing, may suitably be employed. The second half  104  may include a perimeter wall  120  forming an interior  122  that encloses the first half  102 . The perimeter wall  120  may also include a second vacuum gasket  124  shaped and sized to form a vacuum seal for the interior  122  when placed against a substrate handling device. In general, the substrate handling device may be any device used to handle or process a substrate in a vacuum environment including without limitation, vacuum robotic handlers, load locks, process modules, cluster tools, or any other device or group of devices that maintain a vacuum environment for substrates. Conforming the perimeter wall  120  and second vacuum gasket  124  to such a device depends upon the shape and size of the device, which is generally flexible except that the second vacuum gasket  124  must form a continuous seal capable of preserving a vacuum. 
         [0027]    An auxiliary device  116  may be provided to support or enhance operation and use of the carrier  100 . For example, the auxiliary device  116  may include a pressure monitor that monitors vacuum within the carrier  100  to ensure that the seal for the carrier  100  is maintained. A number of suitable pressure sensors are known in the art including generally active vacuum gauges and external sensors. Active vacuum gauges such as ionization gauges, thermocouple gauges, baratron gauges, can be employed to measure pressure directly within a vacuum environment. While numerous suitable gauges are commercially available, these devices require the presence of sensors on the interior of the carrier  100 . External sensors may also or instead be employed to measure a vacuum within the carrier  100  by observations taken from outside the carrier  100 . For example, strain gauges or lasers can be employed to measure deflection of an exterior surface of the carrier, and infer interior pressure from this measurement. A pressure sensor may be adapted to create an audible alert or transmit an alert over a wireless network if the vacuum seal is broken or pressure within the interior of the carrier  100  is otherwise rising irregularly or rapidly. The auxiliary device  116  may also or instead include a vent for releasing a vacuum in the interior of the carrier  100  to facilitate physically opening the carrier  100  to remove the substrate  106 . The vent may be mechanically, magnetically, or electrically operated, or some combination of these. The auxiliary device  116  may also or instead include a vacuum pump connector for increasing, restoring, preserving or otherwise controlling vacuum within the carrier  100 . More generally, any number and combination of auxiliary devices  116  may be employed consistent with the scope of this disclosure. 
         [0028]    As noted generally above, once the recessed interior  108  has been evacuated and the two carrier halves have been pressed together, the atmospheric pressure around the carrier  100  may provide pressure the keep the two halves  102 ,  104  tightly pressed together. The carrier  100  may also be sealed by mechanical means such as screws, clasps, latches or the like. It will be understood that while single-substrate embodiments are emphasized in this description, other embodiments may store two or more substrates without departing from the scope of this disclosure. 
         [0029]    Having described an embodiment of a carrier  100 , a process for using the carrier  100  in a vacuum system is now described in greater detail with reference to a number of images that graphically depict various steps of operation.  FIGS. 2 through 7  generally depict a complete loading and unloading cycle in which a substrate is transferred from a self-sealing carrier into a vacuum system and subsequently transferred from the vacuum system into a self-sealing carrier. However, it will be understood that individual steps of the method depicted below may be usefully performed in other contexts. For example, an empty carrier may be added to a vacuum system in order to retrieve a substrate, or a substrate may be transferred into the vacuum and the carrier retrieved without any substrate contained therein. All such variations are intended to fall within the scope of this disclosure, notwithstanding the specific loading/unloading cycle depicted below which is provided by way of example and not of limitation. 
         [0030]      FIG. 2  illustrates the introduction of a carrier to a vacuum chamber. As depicted, a carrier  202  such as any of the carriers  100  described above is introduced to a vacuum chamber  204 . The carrier  202  may include a tray  206  such as the first half  102  of a carrier  100  described above, in which a substrate  208  has been placed, along with a removable plate  210 , such as the second half  104  of the carrier  100  described above, that seals the substrate  208  within a vacuum  211 . The removable plate  210  of the carrier  202  may be placed in position against the vacuum chamber  204 , thus sealing the vacuum chamber  204  with the removable plate  210 . It will be understood that the removable plate  210  is removable both with respect to the vacuum chamber  204  and with respect to the tray  206 . A vertical lift  212 , which may be any suitable robotic handler or the like, may be positioned under the tray  206 . Although the tray  206  is retained in position in this illustration by the vacuum  211 , it will be understood that once the vacuum chamber  204  is evacuated the tray  206  will drop under the force of gravity unless retained in position by other means. It will be understood that, while described as a method for introducing a substrate to a vacuum chamber, the method described herein may similarly be employed to return a substrate to a vacuum chamber from which it has been removed, or into a different vacuum chamber. 
         [0031]      FIG. 3  illustrates the introduction of a carrier to a vacuum chamber. More specifically,  FIG. 3  illustrates evacuation of a vacuum chamber during an introduction process. The vacuum chamber  304 , which may be any of the vacuum chambers described above, may be evacuated by operation of a vacuum pump as illustrated generally by an arrow  306 . In a typical operation, this evacuation proceeds until the pressure within a first interior  308  of the vacuum chamber  304  is substantially equal to the pressure within a second interior  310  of the carrier  312 . At this point, the vacuum chamber  304  is sealed by the removable plate of the carrier  312  and secured in position by the vacuum relative to an external environment. It will be appreciated that while  FIGS. 2 and 3  depict the introduction of a substrate into a vacuum environment, that the process may also, or instead, be employed to retrieve a substrate. In such embodiments, the carrier may be placed into position (optionally held together by an interior vacuum), and the vacuum chamber may be pumped down to equalize pressure thus releasing the tray from the removable plate, at which point the tray may be lowered to receive a substrate. In other embodiments, the removable plate may be separately employed to seal the vacuum chamber, with a tray and substrate provided from elsewhere within a vacuum processing system such as a process module, cluster tool, or robotic handler. 
         [0032]      FIG. 4  illustrates the introduction of a carrier to a vacuum chamber. More particularly,  FIG. 4  illustrates a substrate lowering into a vacuum chamber during an introduction process. Once pressure has been equalized between the interior of the carrier and the interior of the vacuum chamber, the tray  402  may be lowered into the vacuum chamber  404  by operation of the vertical lift  406 , as generally indicated by an arrow  408 . At this point, the vacuum chamber  404  remains sealed by the removable plate  410 , thus preserving a vacuum  412  within the vacuum chamber  404 . The substrate  414  may be moved within the vacuum chamber  404  and an associated vacuum processing system by any suitable robotic handlers or the like. In one embodiment, the substrate  414  may be removed from the tray  402  for subsequent handling. In other embodiments, subject to the type of process(es) to be performed, the substrate  414  may remain in the tray  402 , which may itself be transported within the vacuum processing system. 
         [0033]      FIG. 5  illustrates the removal of a carrier from a vacuum chamber. With a substrate  502  in a tray  504 , the process may begin by moving the tray  504  into a vacuum-sealed engagement with a removable plate  506  to form an enclosed substrate carrier. This move may be performed, for example, by a vertical lift  508  or the like, which may raise the tray  504  into position as generally indicated by an arrow  510 . 
         [0034]      FIG. 6  illustrates the removal of a carrier from a vacuum chamber. More particularly,  FIG. 6  illustrates venting of a vacuum chamber during a removal process. During this process, atmospheric air and/or other gasses may be introduced into the vacuum chamber  602  as generally indicated by an arrow  604 . With the tray  606  engaged to the removable plate  608 , a vacuum may be retained between the tray  606  and the removable plate  608  to form an enclosed substrate carrier  610  with a substrate sealed therein for transportation and/or storage. 
         [0035]      FIG. 7  illustrates the removal of a carrier from a vacuum chamber. More particularly,  FIG. 7  shows the physical separation of an enclosed substrate carrier  702 . A vacuum within an interior  706  of the enclosed substrate carrier  702  may maintain the two halves of the carrier  702  in a vacuum-sealed engagement for transportation and/or storage of a substrate contained therein. 
         [0036]      FIG. 8  shows another embodiment of a carrier system. The system  800  of  FIG. 8  is generally similar in design and operation to the systems described above, with differences as noted below. The vertical lift  802  or other handling hardware may include a platform  804  which may be attached to or separate from the vertical lift  802 . The bottom edge of the platform  804  may include a flange  806  and a vacuum gasket  808  that cooperate to seal the vacuum chamber  808  from the inside when a tray  810  is moved into contact with a removable plate  812 . This arrangement concurrently physically isolates the tray (and more generally the carrier) from the vacuum chamber  816  in a subchamber above the platform  804 . Thus only a small volume of space bounded by the exterior of the tray  810 , the interior of the removable plate  812 , and the platform  804  needs to be vented in order to remove the carrier  814  from the vacuum chamber  816 . By venting only this relatively small subchamber, the vacuum chamber  816  may remain in vacuum, thus permitting continued processing of other substrates and mitigating additional pump down of the relatively large interior of the vacuum chamber  816 . Conversely, when a new substrate is introduced to the vacuum chamber  816 , it is only necessary to pump down the subchamber volume before lowering the vertical lift  802  and retracting the substrate into the vacuum chamber  816 . 
         [0037]      FIG. 9  shows another embodiment of a carrier system. The system  900  of  FIG. 9  is generally similar in design and operation to the systems described above, with differences as noted below. In this embodiment, a platform  902  such as that described above may be employed to isolate the carrier  904  in a subchamber that reduces the volume of space that must be vented or pumped down during substrate transfers. As a further advantage, this approach places a vacuum gasket  906  on a lip  908  within the removable plate  910  of the carrier  904 . With this arrangement, the tray  912  no longer requires any perimeter wall or edge, and a substrate on the tray  912  can be readily placed on or retrieved from stand-offs or the like using a conventional end effector that accesses the substrate vertically from the side. 
         [0038]      FIG. 10  shows an embodiment of a carrier  1000  that may be employed as a self-sealing, self-aligning, single-substrate storage container with the systems and methods described herein. Although described below as a container and a lid, it will be understood that the following is another embodiment of a self-sealing carrier formed of two halves with mating geometries and an enclosed interior. In general, the carrier  1000  includes a container  1002  and a lid  1004 . 
         [0039]    The container includes a recessed interior  1006  shaped and sized to receive a single substrate. The container may include a bottom  1008  and a side wall  1010  along a perimeter of the bottom  1008 . On a top edge  1012  of the sidewall  1010 , a vacuum gasket  1020  may be provided to improve the vacuum seal between the container  1002  and the lid  1004 . The top edge  1012  may also include an asymmetric vertical feature  1022  such as a notch, groove, series of steps or protuberances, or the like. The asymmetric vertical feature  1022  generally serves to align the lid  1002  with the container  1004  in a unique alignment thus prevent misalignment or mis-orientation of the lid  1002 . 
         [0040]    The lid  1002  may include a second asymmetric vertical feature  10024  that is complementary to the asymmetric vertical feature  1022  of the container  1004 . Thus the features of the lid  1002  and container  1004  cooperate to self-align in a desired orientation. By sloping one or more surfaces of the features  1024 ,  1022 , they may also actively align the lid  1002  and container  1004  while the lid  1002  and container  1004  are physically moved together. Thus slight misalignments may be automatically adjusted as the carrier is sealed. 
         [0041]    A pressure sensor or any of the other auxiliary devices described above may be disposed on the lid  1002  or the container  1004  as generally described above. 
         [0042]    In certain embodiments, the systems and methods described herein may be used in place of a load lock for a vacuum processing system, particularly where it is desired to retain a substrate in a vacuum environment between processes or the like. In other embodiments, the systems and methods described herein may be used in addition to a conventional load lock so that some substrates can be individually stored in vacuum (while other substrates are removed from a vacuum processing system using a conventional load lock). 
         [0043]    While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.