Abstract:
A storage unit includes carousels each including a plurality of levels and including a plurality of spaces for storing containers on each level, the carousels rotating around a vertical shaft; a loading port for loading and unloading the containers; transport units for transporting the containers between the loading port and the storage spaces; and pipes for feeding clean gas such that feeding is turned on and off for each storage space, the pipes being configured to be connected to an intake port provided for each container.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of international application PCT/JP2012/062613, filed on May 17, 2012, and claims the benefit of priority under 35 USC 119 of Japanese application 2011-142651, filed on Jun. 28, 2011, which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to storage units and storage methods for storing articles such as reticles and wafers. 
     2. Description of the Related Art 
     Patent Literature 1 (JP 4215079B) discloses, regarding a unit for storing articles such as reticles: 
     providing a reticle carousel and a pod carousel, and superposing the reticle carousel over the pod carousel; 
     providing two hands configured to move up and down, a pod opener, a buffer for temporary placement of a pod, and a loading port for bringing in or out the pods, and transferring the pods and reticles; and blowing clean air into the carousels in a down-flow manner. 
     Patent Literature 2 (JP 2008-219032A) discloses handling reticles by accommodating each reticle in a double case constituted by an inner case and an outer case (pod). 
     To store more delicate wafers or reticles that record a more delicate pattern, a cleaner atmosphere needs to be provided, and simply blowing clean air into carousels in a down-flow manner is insufficient. In particular, when storing reticles to be exposed with EUV (Extreme Ultra Violet) light, reticles having an extremely fine pattern, or the like, the atmosphere for storage not only needs to simply have a low dust concentration, but also needs to be chemically clean and have an extremely low moisture content. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 4215079B 
     Patent Literature 2: JP 2008-219032A 
     SUMMARY OF THE INVENTION 
     An object of this invention is to enable articles to be stored in a significantly clean gas. 
     A storage unit of this invention includes: a carousel including a plurality of levels and including a plurality of spaces for storing a container on each level, the carousel rotating around a vertical axis; 
     a loading port for loading and unloading the container; 
     a transport unit for transporting the container between the loading port and the container storage spaces; and 
     a pipe configured to be connected a first valve provided at a bottom of the container for feeding clean gas such that feeding is turned on and off for each container storage space, 
     the first valve being configured to open a flow channel for clean gas when pressure outside a container is higher than internal pressure of the container, and 
     the pipe including, at its end, a second valve configured to open a flow channel for clean gas as a result of coming into contact with the first valve. 
     A storage method of this invention uses a storage unit including: a carousel including a plurality of levels and including a plurality of spaces for storing a container on each level, the carousel rotating around a vertical axis; a loading port for loading and unloading the container; a transport unit for transporting the container between the loading port and the container storage spaces; and a pipe for feeding clean gas to each container storage space, 
     the pipe including, at its end, a second valve configured to open a flow channel for clean gas as a result of coming into contact with a first valve provided at a bottom of a container, 
     the first valve being configured to open a flow channel for clean gas when pressure outside a container is higher than internal pressure of the container, and the method includes: 
     a step for transporting a container accommodating a reticle or a semiconductor wafer and including the first valve at the bottom, between the loading port and the container storage spaces by the transport unit; and 
     a step for connecting the second valve at the end of the pipe to the first valve of the container stored in the container storage space, and feeding clean gas into the container by opening both the second valve and the first valve. 
     According to this invention, since the feeding of clean gas is turned on and off for each container storage space, the container can be kept clean, and clean gas will not be fed to unnecessary space. Note that clean gas means dry N 2  gas, CDA (Clean Dry Air: highly clean air with a low dew point), or the like, and is different from mere clean air in that the content of chemically active gas such as SO 2  or NH 3  is extremely low, and that the water vapor content is extremely low, for example, the dew point is −60° C. or lower. In this specification, the articles include not only bare articles such as reticles and semiconductor wafers, but also cases for accommodating articles to be accommodated within the containers. 
     It is preferable that said carousel is a first carousel, and that said storage unit further includes: a second carousel disposed above the first carousel so as to be superposed over the first carousel in a plan view, the second carousel rotating around a vertical axis independently of the first carousel, the second carousel including a plurality of levels and including a plurality of article storage spaces on each level, and the article storage spaces being able to be opened and closed; a filter fan unit for feeding clean air in a down-flow manner from above the second carousel; an opening and closing unit for bringing the article into and out of the container; a second transport unit for transporting the article between the opening and closing unit and the second carousel; a second pipe for feeding clean gas such that feeding is turned on and off for each article storage space; and a storage unit housing. With this configuration, the second carousel that is required to have a higher degree of cleanness can be surrounded by cleaner clean air, and the interior of the storage unit can be made substantially air-tight with the housing and filled with clean air. Moreover, articles can be transported between the opening and closing unit and the second carousel by the second transport unit. Articles can be kept clean by feeding clean gas by turning on and off the feeding of clean gas for each article storage space. 
     It is preferable that the container storage space includes a door configured to be opened and closed by a hand of the transport unit for transporting the container, the article storage space includes a door configured to be opened and closed by a hand of the second transport unit for transporting the article, and the second pipe includes a third valve for opening a flow channel for clean gas as a result of coming into contact with the article. With this configuration, clean gas can be fed upon the valve being mechanically opened, as a result of a container or an article being placed in the storage space. Moreover, the storage space can be made substantially air-tight due to provision of the door, and the door can be opened and closed by the hand. 
     It is particularly preferable that the second pipe and the first pipe are configured to be connected to the first valve provided in the container include rotary joints connected to a clean gas feeding source and downstream pipes branching from the rotary joints and supplying clean gas to the container storage spaces and the article storage spaces. With this configuration, even if the carousels rotate, clean gas can be easily fed to the container storage space and the article storage space. 
     It is most preferable that the first carousel and the second carousel include vertical shafts, and the downstream pipes extend upward from below along the shafts. With this configuration, the downstream pipe can be provided so as to extend upward from below the storage unit, so as to rotate together with the carousels. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a horizontal cross-sectional view of a storage unit in an embodiment. 
         FIG. 2  is a vertical cross-sectional view of the storage unit in the embodiment. 
         FIG. 3  is a view schematically showing an atmosphere flow in the storage unit in the embodiment. 
         FIG. 4  is a view showing a rotary joint used in the embodiment. 
         FIG. 5  is a vertical cross-sectional view showing a mechanism for supplying and discharging air to and from a pod storage room. 
         FIG. 6  is a vertical cross-sectional view showing a mechanism for supplying and discharging air to and from a reticle storage room. 
         FIG. 7  is a vertical cross-sectional view showing a door of the pod storage room. 
         FIG. 8  is a vertical cross-sectional view showing a mechanical valve. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a best embodiment for carrying out the present invention will be described. The scope of the invention is to be defined based on the description of the claims, in view of the description of the specification and well known techniques in the field of the invention, and in accordance with the understanding of a person skilled in the art. 
     Embodiment 
       FIGS. 1 to 8  show a storage unit  2  in an embodiment. In the drawings, reference numeral  4  denotes a reticle carousel, and reference numeral  6  denotes a pod carousel. Reticles (not shown) are accommodated and stored in inner cases  10 , and each inner case  10  is lighter than each pod  54  and is required to have a higher degree of cleanness than the pod  54  does. For this reason, the reticle carousel  4  is disposed above the pod carousel  6  so as to be superposed over it in a plan view, and the carousels  4  and  6  are allowed to rotate independently of each other around a vertical shaft. 
     As shown in  FIG. 2 , the reticle carousel  4  has a plurality of shelves  9 , and a plurality of reticle storage rooms  8 , each serving as an example of a reticle storage space, are radially provided on each shelf  9 . The reticle carousel  4  is rotated by a vertical shaft  12  and a motor  20 , and provided with air supply pipes  14  and  16  along the shaft  12  to feed N 2  or CDA (Clean Dry Air) to the reticle storage rooms  8 . Reference numeral  18  denotes a base member of the reticle carousel  4 . The air supply pipes  16  extend upward from below along the shaft  12 , and feed clean gas to the air supply pipes  14 . 
     As shown in  FIG. 2 , the pod carousel  6  is provided below the reticle carousel  4  and includes a plurality of shelves  41 , and a plurality of pod storage rooms  40 , each serving as an example of a pod storage space, are radially provided on each shelf. In addition, a pair of elevating members  22  and  24  are provided inward of an outer wall  30  of the storage unit  2  and move up and down along vertical guides  25  and  26 , for example. The elevating members  22  and  24  have hands  28  and  29 , respectively. The hand  28  transfers the pods  54 , and the hand  29  transfers the inner cases  10 . The outer wall  30  maintains the interior of the storage unit  2  in a substantially air-tight state with respect to the outside. Reference numeral  32  denotes a pod opening and closing unit, which opens and closes the pods  54  to enable the inner cases  10  to be brought in or out. Reference numeral  34  denotes a loading port, which is provided with a conveyer and the like (not shown) and transfers the pods  54  to and from overhead travelling vehicles, operators, or the like. Pod buffers  42  buffer the pods  54 . The hand  28  transfers the pods  54  to and from the pod carousel  6 , the pod buffers  42 , the pod opening and closing unit  32 , and the loading port  34 . Meanwhile, the hand  29  transfers the inner cases  10  to and from the reticle carousel  4  and the pod opening and closing unit  32 . Note that the pod carousel  6  is also provided with a vertical shaft (not shown), and an air supply pipe for supplying clean gas extends upward from below along this shaft. Pipes for supplying clean gas branch out from the aforementioned air supply pipe so as to extend to each pod storage room  40 . 
     Since reticles that are stored in this embodiment are to be exposed with EUV light, the reticles are accommodated in the inner cases  10 , and one inner case  10  is accommodated in each pod  54 , for example. However, a plurality of inner cases  10  may be stored in each pod  54 . If semiconductor wafers are stored in place of the reticles, the wafers may be stored in a bare state in the reticle storage rooms  8  without using the inner cases  10 . 
     Reference numeral  44  denotes an air supply pipe, which feeds clean gas such as N 2  or CDA to the carousels  4  and  6 . A pair of filter fan units  45  and  46  are provided at a ceiling of the storage unit  2 , for example. The filter fan unit  45  feeds a down-flow of clean air from above the reticle carousel  4 , thereby maintaining the surroundings of the carousels  4  and  6  in a clean state. The filter fan unit  46  feeds a down-flow of clean air toward the pod buffers  42 , the hands  28  and  29 , the pod opening and closing unit  32 , and the like, thus preventing contamination when the inner cases  10  and the pods  54  are handled with the hands  28  and  29  and the pods  54  are stored at the pod buffers  42 . 
       FIG. 3  shows the feeding of clean gas and clean air to the storage unit  2 . The clean gas from the air supply pipe  44  passes through a rotary joint  48  shown in  FIG. 4 , or the like, is supplied by the air supply pipes  16  and the like extending upward from below along the vertical shaft or the like of the carousels  4  and  6 , and is fed to each reticle storage room  8  and pod storage room  40 . A down-flow of clean air is provided to the surroundings of the carousels  4  and  6  by the filter fan unit  45 , and a down-flow of clean air is provided to the surroundings of the pod buffers  42  and the like by the filter fan unit  46 . In this way, articles are stored in clean gas in the storage rooms  8  and  40  on the shelves  4  and  6 , and the reticle carousel  4  and the pod carousel  6  are enveloped with down-flows of clean air, thus making the surroundings of the reticle carousel  4  is particularly clean. When the inner cases  10  and the pods  54  are handled with the hands  28  and  29 , and when they are temporarily placed on the pod buffers  42  or the like, contamination is prevented by clean air. 
       FIG. 4  shows the rotary joint  48  provided at downstream of the air supply pipe  44 , and the reticle carousel  4  and the pod carousel  6  are each provided with one rotary joint  48 , for example. An inner member  50  is rotatably supported to an outer member  49  by a bearing or the like, an air supply pipe  51  is connected to the member  49  so as to be in communication with a vent path within the member  50 , and this vent path branches into a plurality of air supply pipes  52  to supply air. The air supply pipes  52  extend along the shaft of the carousels  4  and  6  and then become the aforementioned air supply pipes  14  and  16  or the like, and extend to the individual storage rooms  8  and  40 . Note that the configuration of the rotary joint  48  is arbitrary. 
       FIG. 5  shows the pod  54  stored in one of the pod storage rooms  40 . The pod  54  has an intake valve  55  and an exhaust valve  56  at its bottom, for example, and accommodates only one inner case  10 , for example, in a substantially air-tight manner. The pod storage room  40  is configured so as to be substantially air-tight as a result of being surrounded by walls  60 , a door  70  shown in  FIG. 7 , and the like, feeds clean gas from an air supply pipe  58  and further from the valve  57  to the interior of the pod  54  via the intake valve  55 . Further, the clean gas is discharged to the interior of the storage room  40  from the exhaust valve  56  via an exhaust groove  50 . Note that the exhaust valve  56  and the groove  59  do not need to be provided. The valve  57  normally closes an end of the air supply pipe  58 , and is mechanically opened as a result of coming into contact with the intake valve  55  to feed clean gas. The intake valve  55  opens when the pressure outside the pod  54  is higher than the internal pressure thereof to introduce clean gas, and the exhaust valve  56  opens when the internal pressure is higher than the pressure outside to discharge clean gas from the groove  59 . Note that if the exhaust valve  56  is not provided, clean gas is discharged by allowing it to leak out from gaps in the pod  54 . 
       FIG. 6  shows the inner case  10  stored in one of the reticle storage rooms  8 . The storage room  8  is made substantially air-tight by walls  65  and a door, which will be described later, and the like. An air supply valve  61  is provided at an end of the air supply pipe  63  to feed clean gas into the inner case  10 , and the clean gas is discharged into the storage room  8  via an exhaust groove  64 . Upon the inner case  10  being placed on the valve  61 , the valve  61  opens due to the weight of the inner case  10  or the like and feeds clean gas into the inner case  10 . 
       FIG. 7  schematically shows a door of the pod storage room  40 . The door  70  is slidable in an up-down direction and provided with projection  72 . The projection  72  is elevated by an inclined face or the like provided in the hand  28 , and thus the door  70  opens and closes. A similar door is also provided in each reticle storage room  8 , for example. 
       FIG. 8  shows a structure of the valve  57 , and the valve  61  also has a similar structure, for example. A projection  80  protrudes from a floor surface of the pod storage room  40 , and has an air supply opening  81  and a hole  82  that is in communication therewith. A valve body  83  is provided below the projection  80 , and blocks the entry to a flow channel  86  due to an elastic member  84 . Reference numeral  85  denotes a gas chamber, which is connected to a pipe for supplying clean gas. Upon a pod being placed on the valve  61 , the valve body  83  lowers together with the projection  80 , and thus, the gas chamber  85  comes into communication with the flow channel  86 , and clean gas is fed from the air supply opening  81 . 
     The embodiment achieves the following advantageous effects. 
     (1) Articles in the inner cases  10 , the pods  54 , and the like can be stored in an extremely clean state by protecting the surroundings of the reticle carousel  4  and the pod carousel  6  with down-flows of clean air and feeding clean gas to each storage room  8  and  40 .
 
(2) Since down-flows of clean air are fed to the hands  28  and  29 , the pod buffers  42 , and the like, contamination can be prevented when the inner cases  10  and the pods  54  are handled with the hands  28  and  29  or the like, and when the pods  54  are stored in the pod buffers  42 .
 
(3) A door is provided for each of the storage rooms  8  and  40 , the storage rooms are substantially air-tight, and a channel for feeding clean gas is provided for each storage room. For this reason, the inside of the storage rooms can be kept clean with a small amount of clean gas.
 
(4) Clean gas is fed into the reticle storage rooms  8  and the pod storage rooms  40  due to the valve  57  and the like being opened by a mechanical mechanism. Accordingly, wiring on the shelves  9  and  41  is not necessary, and clean gas can be fed reliably. Note that clean gas may be supplied under the control of a controller (not shown), using an electromagnetic valve in place of the mechanical valve. However, this configuration will require wiring on the storage rooms  8  and  40 .
 
(5) Since one pod  54  or one inner case  10  is stored in one storage room, the number of times that the door  70  or the like is opened is minimized, and the contamination of articles can be prevented.
 
(6) Due to the rotary joint  48 , clean gas can be fed even if the storage rooms  40  and  8  are rotated.
 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               2  storage unit 
               4  reticle carousel 
               6  pod carousel 
               8  reticle storage room 
               9 ,  41  shelf 
               10  inner case 
               12  shaft 
               14 ,  16  air supply pipe 
               18  base member 
               20  motor 
               22 ,  24  elevating member 
               25 ,  26  guide 
               28 ,  29  hand 
               30  outer wall 
               32  pod opening and closing unit 
               34  loading port 
               40  pod storage room 
               42  pod buffer 
               44  air supply pipe 
               45 ,  46  filter fan unit 
               48  rotary joint 
               49 ,  50  member 
               51 ,  52  air supply pipe 
               54  pod 
               55  intake valve 
               56  exhaust valve 
               57  valve 
               58 ,  63  air supply pipe 
               59 ,  64  exhaust groove 
               60 ,  65  wall 
               61  air supply valve 
               70  door 
               72 ,  80  projection 
               81  air supply opening 
               82  hole 
               83  valve body 
               84  elastic member 
               85  gas chamber 
               86  flow channel