Abstract:
Disclosed herein is an apparatus including: a table configured to receive a container that stores an object therein, the container including a bottom surface provided with a positioning groove and including a charging inlet through which a gas is charged into the container; a positioning pin projecting from the table and adapted to engage with the positioning groove of the container; a nozzle configured to charge the gas into the container through the charging inlet; and a drive unit configured to move the nozzle into contact with the charging inlet of the container after the positioning pin is engaged with the positioning groove.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a gas charging apparatus for charging a gas into a container such as a carrier cassette for storing semiconductor wafer substrates or glass substrates in the fabrication of semiconductor devices or any other devices using glass substrates, a gas discharging apparatus for discharging a gas from the container, a gas charging method using the gas charging apparatus, and a gas discharging method using the gas discharging apparatus. 
         [0003]    2. Description of the Related Art 
         [0004]    In the fabrication of semiconductor devices, a carrier cassette for storing a plurality of semiconductor wafers is used to transport the wafers between fabrication units. As an example of the carrier cassette, there is a closed container called a FOUP (Front Opening Unified Pod) configured to be filled with an inert gas for the purpose of preventing the oxidation of the surface of each wafer. 
         [0005]    Japanese Patent Laid-open No. 2009-38074 discloses a technique of charging an inert gas into a container such as FOUP set on a load port. In this technique, the load port is provided with a door and a door opening/closing mechanism for opening and closing the door. When a lid of the container is held by the door and the door is opened by the door opening/closing mechanism, the lid is removed from a body of the container to thereby expose an opening of the body. In this condition, the inert gas is supplied from this opening (see paragraphs [0018], [0020], and [0024] in the specification of the above citation, for example). 
         [0006]    In recent years, the following technique has also been adopted to increase the concentration of an inert gas in a container in association with finer wiring patterns. That is, the bottom of the container is provided with a charge valve (charging hole) for charging the inert gas into the container, and a nozzle for charging the inert gas is provided to charge the inert gas through the charge valve into the container. 
       SUMMARY OF THE INVENTION 
       [0007]    In an apparatus adopting such an inert gas charging technique, the nozzle is provided on a table for mounting the container in a load port. The container is mounted on the table, and the nozzle is next brought into contact with the charge valve. In this condition, the inert gas is charged into the container. A positioning pin is provided on the table, so as to position the container on the table. On the other hand, the bottom of the container is formed with a groove for engaging the positioning pin. Accordingly, by the engagement of the positioning pin and the groove, the container is positioned on the table. Further, in order to improve the contact between the nozzle and the charge valve of the container in charging the inert gas, the nozzle is provided so as to project from the table and elastically supported to the table by using a spring. More specifically, when the container is mounted on the table, the charge valve of the container is brought into contact with the nozzle. At this time, the nozzle is depressed by the weight of the container against the elastic force of the spring. 
         [0008]    However, when the container is mounted on the table, there is a possibility that the nozzle may interfere with the charge valve or its periphery, so that the container is not properly positioned on the table. 
         [0009]    Further, the nozzle is brought into close contact with the charge valve of the container by the spring force. Accordingly, if the spring force is too large, there is a possibility that the container may not be vertically positioned with high accuracy. 
         [0010]    It is accordingly an object of the present invention to provide a gas charging apparatus, gas discharging apparatus, gas charging method, and gas discharging method which can reliably position a container on a table even in an apparatus having a structure that a nozzle for charging a gas into the container or discharging a gas from the container is provided on the table. 
         [0011]    In accordance with a first aspect of the present invention, there is provided an apparatus including: a table configured to receive a container that stores an object therein, the container including a bottom surface provided with a positioning groove and including a charging inlet through which a gas is charged into the container; a positioning pin projecting from the table and adapted to engage with the positioning groove of the container; a nozzle configured to charge the gas into the container through the charging inlet; and a drive unit configured to move the nozzle into contact with the charging inlet of the container after the positioning pin is engaged with the positioning groove. 
         [0012]    When the container is mounted on the table, the positioning pin comes into engagement with the positioning groove formed on the bottom portion of the container, thereby positioning the container on the table. In this condition, the drive unit is operated to bring the nozzle into contact with the charge valve of the container. Accordingly, there is no possibility that the nozzle may interfere with the charge valve before the container is positioned on the table. That is, the container can be reliably positioned on the table according to the present invention. 
         [0013]    Even in the case that the nozzle is elastically supported to the table by using a spring and that the spring force of this spring is too large, the container can be vertically positioned on the table by suitably controlling the drive force of the drive unit. In the case that the spring force of this spring is too small, the contact force between the charge valve of the container and the nozzle may lack. Accordingly, in the case that a spring is provided for the nozzle, a high design accuracy in designing the spring force is required. However, such a problem can be eliminated by using the drive unit according to the present invention because such a spring is not required. Even when such a spring is used, a high design accuracy in designing the spring force is not required. 
         [0014]    Preferably, the drive unit drives the nozzle between a standby position and a contact position where the nozzle comes into contact with the charge valve of the container; and the standby position is defined as a position where the upper end of the nozzle is lower in height than the charge valve of the container in the condition where the container is mounted on the table so that the positioning pin is engaged with the positioning groove of the container. 
         [0015]    In the standby position of the nozzle, the upper end of the nozzle is lower in height than the bottom portion of the container in the condition where the container is positioned on the table. Accordingly, in positioning the container on the table, there is no possibility of interference between the nozzle and the container, so that the container can be reliably positioned on the table. 
         [0016]    In accordance with a second aspect of the present invention, there is provided an apparatus including: a table configured to receive a container that stores an object therein, the container including a bottom surface provided with a positioning groove and including a discharging outlet through which a gas is discharged from the container; a positioning pin projecting from the table and adapted to engage with the positioning groove of the container; a nozzle configured to discharge the gas from the container through the discharging outlet thereof; and a drive unit configured to move the nozzle into contact with the discharging outlet of the container after the positioning pin is engaged with the positioning groove. 
         [0017]    When the container is mounted on the table, the positioning pin comes into engagement with the positioning groove formed on the bottom portion of the container, thereby positioning the container on the table. In this condition, the drive unit is operated to bring the nozzle into contact with the discharge valve of the container. Accordingly, there is no possibility that the nozzle may interfere with the discharge valve before the container is positioned on the table. That is, the container can be reliably positioned on the table according to the present invention. 
         [0018]    In the case that the nozzle is elastically supported to the table by using a spring and that the spring force of this spring is too small, there is a possibility that the contact force between the discharge valve of the container and the nozzle may lack. Accordingly, a high design accuracy in designing the spring force is required. However, such a problem can be eliminated by using the drive unit according to the present invention because such a spring is not required. Even when such a spring is used, a high design accuracy in designing the spring force is not required. 
         [0019]    In accordance with a third aspect of the present invention, there is provided a method including: positioning a container, that stores an object therein, on a table, the container including a bottom surface provided with a positioning groove and including a charging inlet thereon, and a positioning pin projecting from the table and adapted to engage with the positioning groove of the container; moving a nozzle, that is configured to charge a gas into the container, into contact with the charging inlet of the container after the positioning pin is engaged with the positioning groove; and charging the gas from the nozzle into the container through the charging inlet. 
         [0020]    When the container is mounted on the table, the positioning pin comes into engagement with the positioning groove formed on the bottom portion of the container, thereby positioning the container on the table. In this condition, the nozzle is brought into contact with the charge valve of the container. Accordingly, there is no possibility that the nozzle may interfere with the charge valve before the container is positioned on the table. That is, the container can be reliably positioned on the table according to the present invention. Further, a high design accuracy for a spring is not required as mentioned above. 
         [0021]    In accordance with a fourth aspect of the present invention, there is provided a method including: positioning a container, that stores an object therein, on a table, the container including a bottom surface provided with a positioning groove and including a discharging outlet, and a positioning pin projecting from the table and adapted to engage with the positioning groove of the container; moving a nozzle, that is configured to discharge a gas from the container, into contact with the discharging outlet of the container after the positioning pin is engaged with the positioning groove; and discharging the gas from the container into the nozzle through the discharging outlet. 
         [0022]    When the container is mounted on the table, the positioning pin comes into engagement with the positioning groove formed on the bottom portion of the container, thereby positioning the container on the table. In this condition, the nozzle is brought into contact with the discharge valve of the container. Accordingly, there is no possibility that the nozzle may interfere with the discharge valve before the container is positioned on the table. That is, the container can be reliably positioned on the table according to the present invention. Further, a high design accuracy for a spring is not required as mentioned above. 
         [0023]    In accordance with a fifth aspect of the present invention, there is provided an apparatus including: a table configured to receive a container that stores an object therein, the container including a gas inlet through which a gas is charged into the container; a positioning mechanism configured to position the container onto the table; a charging unit configured to charge the gas into the container through the gas inlet; a moving mechanism configured to move the charging unit between a first position and a second position, the charging unit in the first position not interfering the positioning of the container onto the table, and the charging unit in the second position contacting with the gas inlet of the container after the positioning mechanism positions the container onto the table. 
         [0024]    In accordance with a sixth aspect of the present invention, there is provided an apparatus including: a table configured to receive a container that stores an object therein, the container including a gas inlet through which a gas is charged into the container; positioning means for positioning the container onto the table; charging means for charging the gas into the container through the gas inlet; moving means for moving the charging means between a first position and a second position, the charging means in the first position not interfering the positioning of the container onto the table, and the charging means in the second position contacting with the gas inlet of the container after the positioning meaning means positions the container onto the table. 
         [0025]    In accordance with a seventh aspect of the present invention, there is provided a load port including: a table configured to receive a FOUP (front opening unified pod), a first positioning portion being provided on the table, the FOUP including a bottom surface including a gas inlet and a second positioning portion to engage with the first positioning portion; a sensor configured to detect when the first and second positioning portions being engaged with each other and determine that the FOUP is properly positioned on the table; a nozzle configured to charge a gas into the FOUP through the gas inlet; a moving unit configured to translate the nozzle between a first position and a second position in response to a detection signal from the sensor, the nozzle in the first position not interfering the positioning of the FOUP onto the tale, and the nozzle in the second position contacting the gas inlet of the FOUP and charging the gas into the FOUP through the gas inlet. 
         [0026]    According to the present invention, even in an apparatus having a structure that a nozzle for charging a gas into a container or discharging a gas from the container is provided on a table for mounting the container, the container can be reliably positioned on the table. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective view showing a load port as a gas charging apparatus according to a first preferred embodiment of the present invention; 
           [0028]      FIG. 2  is a top plan view of the load port shown in  FIG. 1 ; 
           [0029]      FIG. 3  is a schematic sectional side view showing an essential part of a table; 
           [0030]      FIG. 4  is an enlarged sectional view of a charge nozzle located on the front side of the load port and a peripheral portion near the charge nozzle; 
           [0031]      FIG. 5  is a bottom plan view showing a bottom portion of a carrier; 
           [0032]      FIG. 6  is a view similar to  FIG. 4 , showing a condition where a drive unit is operated to raise the charge nozzle until the upper end of the nozzle comes into contact with a grommet of a charge valve provided in the bottom portion of the carrier; and 
           [0033]      FIG. 7  is a view similar to  FIG. 4 , showing a drive unit according to a second preferred embodiment of the present invention applied to a load port. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Some preferred embodiments of the present invention will now be described with reference to the drawings. 
       First Preferred Embodiment 
       [0035]      FIG. 1  is a perspective view of a load port  100  as a gas charging apparatus according to a first preferred embodiment of the present invention.  FIG. 2  is a top plan view of the load port  100  shown in  FIG. 1 . 
         [0036]    The load port  100  functions as an interface between fabrication units used in various fabrication steps for semiconductor devices. 
         [0037]    The load port  100  has a table  2  for mounting a carrier  10  (carrier cassette) as a container for storing a plurality of semiconductor wafer substrates (which will be hereinafter referred to simply as wafers) W. For example, a FOUP (Front Opening Unified Pod) as a closed container is used for the carrier  10 . 
         [0038]    The table  2  has a base frame  22  and a platelike carrier base  21  provided on the base frame  22 . The carrier base  21  is so configured as to mount the carrier  10  thereon. A port window  16  for passing the wafers W is formed on the front side of the carrier  10  mounted on the carrier base  21 , i.e., on the back side in the Y direction shown in  FIG. 1 . A port door  15  for opening and closing a lid  105  of the carrier  10  is provided so as to be opposed to the port window  16 . 
         [0039]    The port door  15  has a key to be inserted into a keyhole (not shown) formed in the lid  105  of the carrier  10 . By using this key of the port door  15 , the lid  105  of the carrier  10  is locked or unlocked and then removed from or mounted to the body of the carrier  10 . For example, the port door  15  can move the lid  105  removed from the body of the carrier  10  in a downward direction or a lateral direction. As a result, a front opening of the body of the carrier  10  is opposed to the port window  16 , so that the inside of a fabrication unit (not shown) is brought into communication with the inside of the carrier  10 . 
         [0040]    The carrier base  21  is movable in the Y direction by a slider mechanism (not shown) provided in the base frame  22 . Accordingly, the carrier  10  mounted on the carrier base  21  can be moved to a position where the port door  15  performs an operation of opening and closing the lid  105  of the carrier  10 . 
         [0041]    Three charge nozzles  5  ( 5   a,    5   b,  and  5   c ) for charging an inert gas into the carrier  10  mounted on the carrier base  21  are located in the periphery of the carrier base  21 . Further, one discharge nozzle  5 ′ for discharging a gas from the carrier  10  is located in the periphery of the carrier base  21 . Each of these charge nozzles  5  and the discharge nozzle  5 ′ is held by a nozzle holder  6 . A mounting bracket  9  is connected to the nozzle holder  6 , so that the nozzle holder  6  is mounted at a predetermined position in the periphery of the carrier base  21  through the mounting bracket  9 . Accordingly, all of the charge nozzles  5  and the discharge nozzle  5 ′ are movable together with the carrier base  21  by the slider mechanism. 
         [0042]      FIG. 3  is a schematic sectional side view showing an essential part of the table  2 . The base frame  22  of the table  2  is formed with an upper hole  221 . The charge nozzles  5  and the discharge nozzle  5 ′ provided in the base frame  22  are upwardly exposed from this upper hole  221 . The charge nozzles  5  are connected to any elements (not shown) required for the supply of an inert gas, i.e., an inert gas source such as a gas cylinder, piping connected to this inert gas source, and on-off valves connected to this piping. A part of the piping and the on-off valves are contained in the base frame  22 . Further, the discharge nozzle  5 ′ is connected through piping and an on-off valve to a blower or a vacuum pump. Nitrogen, helium, argon, etc. may be used as the inert gas. 
         [0043]    Of the three charge nozzles  5   a,    5   b,  and  5   c,  for example,  FIG. 4  is an enlarged sectional view of the charge nozzle  5   a  located on the front side of the load port  100  (on the back side of the carrier  10 ) and a peripheral portion near the charge nozzle  5   a.  The load port  100  includes a drive unit  4  for vertically moving the charge nozzle  5   a.    
         [0044]    The configuration of the other charge nozzles  5   b  and  5   c  is the same as that of the charge nozzle  5   a,  and these charge nozzles  5   b  and  5   c  are also provided with the same nozzle holders  6  and drive units  4  as those of the charge nozzle  5   a.  The discharge nozzle  5 ′ is also provided with the same nozzle holder  6  and drive unit  4  as those of the charge nozzle  5   a.  Each charge nozzle  5  and the discharge nozzle  5 ′ are slightly functionally different in configuration, but they are substantially the same. 
         [0045]    As shown in  FIG. 4 , the drive unit  4  has two air cylinders  41  mounted on the opposite side surfaces of the nozzle holder  6 , wherein each air cylinder  41  functions as a cylinder drive mechanism adapted to drive by using a fluid pressure. A mounting plate  42  is connected to the working ends of the air cylinders  41 , and the charge nozzle  5   a  is mounted on the mounting plate  42 . Accordingly, the air cylinders  41  are operated to vertically move the mounting plate  42 , thereby vertically moving the charge nozzle  5   a.    
         [0046]    The nozzle holder  6  has a body  62  as a lower member having a circular cylindrical recess  62   a  and a cover  61  as an upper member provided on the upper end of the body  62  so as to close the recess  62   a.  The nozzle holder  6  functions to vertically movably hold the charge nozzle  5   a.  The cylindrical surface of the charge nozzle  5   a  is formed with a flange portion  51 , and the charge nozzle  5   a  is held by the nozzle holder  6  so that the flange portion  51  is accommodated in the recess  62   a  of the nozzle holder  6 . The cover  61  functions as a stopper for defining an upper limit of the upward movement of the charge nozzle  5   a  driven by the air cylinders  41  in relation to the flange portion  51  of the charge nozzle  5   a.  A pass line  52  is formed in the charge nozzle  5   a,  and piping (not shown) is connected to a lower portion of the pass line  52 . 
         [0047]    The piping provided in the base frame  22  is flexible. As a modification, a spring as a support member for supporting the charge nozzle  5   a  may be provided on the lower side of the flange portion  51  of the charge nozzle  5   a.  In this case, the spring does not function to press the charge nozzle  5   a  to a charge valve  102  (see  FIG. 5 ) of the carrier  10  as in the related art, but functions to merely support the charge nozzle  5   a.  Accordingly, it is not necessary to ensure a high design accuracy in designing a spring constant having a proper balance. 
         [0048]    As shown in  FIGS. 2 to 4 , the carrier base  21  is provided with a plurality of (three in this preferred embodiment) kinematic pins  7  as positioning pins for positioning the carrier  10 . The kinematic pins  7  project from the upper surface of the carrier base  21 . While the three kinematic pins  7  are provided in this preferred embodiment, the number of the kinematic pins  7  is not limited. Further, a single placement sensor  8  for detecting whether or not the carrier  10  is positioned on the carrier base  21  is provided on the upper surface of the carrier base  21 . A plurality of placement sensors may be provided. 
         [0049]      FIG. 5  is a bottom plan view showing a bottom portion  103  of the carrier  10 . The bottom portion  103  of the carrier  10  is provided with a plurality of (three in this preferred embodiment) positioning grooves  101  for respectively engaging the kinematic pins  7 . The bottom portion  103  is further provided with a plurality of (three in this preferred embodiment) charge valves  102  respectively adapted to come into contact with the charge nozzles  5  and one discharge valve  102 ′ adapted to come into contact with the discharge nozzle  5 ′. 
         [0050]    As shown in  FIG. 4 , the charge valve  102  corresponding to the charge nozzle  5   a  has an opening  1021  formed through the bottom portion  103  of the carrier  10  and a grommet seal  1022  fitted in the opening  1021 . The outer diameter and inner diameter of the grommet seal  1022  are preliminarily decided in relation to the diameter of the pass line  52  in the charge nozzle  5   a  and the outer diameter of the charge nozzle  5   a.  The charge valves  102  corresponding to the other charge nozzles  5   b  and  5   c  and the discharge valve  102 ′ corresponding to the discharge nozzle  5 ′ are substantially the same in configuration as the charge valve  102  corresponding to the charge nozzle  5   a  mentioned above. 
         [0051]    Each positioning groove  101  is V-shaped in cross section as shown in  FIG. 4 , and the upper curved surface of each kinematic pin  7  is adapted to come into contact with the V-shaped wall surface of the corresponding positioning groove  101  with a good balance, thereby positioning the carrier  10 . 
         [0052]    The number and location of the charge nozzles  5 , the discharge nozzle  5 ′, and the kinematic pins  7  provided in the load port  100  are not especially limited provided that they match with those of the charge valves  102 , the discharge valve  102 ′, and the positioning grooves  101  provided in the carrier  10 , respectively. The number and location of these parts are set in accordance with a given standard. 
         [0053]    The operation of the load port  100  will now be described. 
         [0054]    The carrier  10  containing the wafers W is transported from another location to the load port  100  by an OHT (OverHead Transportation) or a transport robot (both not shown), and then mounted on the table  2  of the load port  100 . At this time, as shown in  FIG. 3 , the carrier base  21  is set at the front position (right position as viewed in  FIG. 3 ). Further, as shown in  FIG. 4 , the charge nozzle  5   a  is set at the standby position. Although not shown, the other charge nozzles  5   b  and  5   c  and the discharge nozzle  5 ′ are also set at the same standby position. 
         [0055]    When the carrier  10  is transferred from the transport robot to the carrier base  21 , the carrier  10  is positioned by the operation of the kinematic pins  7  of the carrier base  21  and the positioning grooves  101  of the carrier  10 . At this time, the placement sensor  8  detects that the carrier  10  is positioned on the carrier base  21 . Even in the condition where the carrier  10  is positioned on the carrier base  21 , the upper ends of the charge nozzles  5  (and the discharge nozzle  5 ′) still remain in noncontact with the respective charge valves  102  (and the discharge valve  102 ′) provided in the bottom portion  103  of the carrier  10  as shown in  FIG. 4 . That is, the standby position of the charge nozzles  5  (and the discharge nozzle  5 ′) is set as a position where the upper ends of the charge nozzles  5  (and the discharge nozzle  5 ′) are lower in height than the bottom portion  103  (especially, the charge valves  102  and the discharge valve  102 ′) of the carrier  10  in the condition where the carrier  10  is mounted on the carrier base  21  by the engagement of the kinematic pins  7  and the positioning grooves  101 . 
         [0056]    After the carrier  10  is positioned, i.e., after the seated condition of the carrier  10  is confirmed by the placement sensor  8 , the drive units  4  are operated to raise the charge nozzles  5  (and the discharge nozzle  5 ′) until the upper ends of the charge nozzles  5  (and the discharge nozzle  5 ′) come into contact with the grommet seals  1022  of the respective charge valves  102  (and the discharge valve  102 ′) as shown in  FIG. 6 . Thereafter, the on-off valves are opened to supply an inert gas from the gas source (not shown) to the charge nozzles  5  and charge the inert gas through the charge nozzles  5  and the charge valves  102  into the carrier  10 . Further, with the same timing as the timing of this charging operation, the air present in the carrier  10  is discharged through the discharge valve  102 ′ and the discharge nozzle  5 ′. Alternatively, after the air present in the carrier  10  is discharged through the discharge nozzle  5 ′ to some extent to thereby reduce the pressure in the carrier  10 , the inert gas may be charged into the carrier  10 . 
         [0057]    After the inert gas is charged into the carrier  10  or while the inert gas is being charged into the carrier  10 , the carrier base  21  is moved toward the back side (left side as viewed in  FIG. 3 ) in the Y direction until the lid  105  of the carrier  10  comes into contact with the inner wall of the port window  16 . In this condition, the lid  105  of the carrier  10  is unlocked and next removed from the body of the carrier  10  by the port door  15 , so that the inside of the carrier  10  comes into communication with the inside of a fabrication unit through the port window  16 . Thereafter, a transport robot (not shown) in this fabrication unit operates to take the wafers W out of the carrier  10 , and this fabrication unit then performs predetermined processing on the wafers W. 
         [0058]    After performing the predetermined processing on the wafers W, the transport robot in this fabrication unit operates to store the processed wafers W through the port window  16  into the carrier  10 . When a predetermined number of processed wafers W are stored into the carrier  10 , the lid  105  is mounted to the body of the carrier  10  and next locked by the port door  15 . Thereafter, the carrier base  21  is moved toward the front side (right side as viewed in  FIG. 3 ) in the Y direction until the carrier  10  is returned to the initial mounted position. 
         [0059]    As described above, when the carrier  10  is mounted on the carrier base  21 , the kinematic pins  7  come into engagement with the respective positioning grooves  101  formed on the bottom portion  103  of the carrier  10 , so that the carrier  10  is positioned on the table  2 . In this condition, the drive units  4  are operated to bring the charge nozzles  5  (or the discharge nozzle  5 ′) into contact with the charge valves  102  (or the discharge valve  102 ′) of the carrier  10 . Accordingly, there is no possibility that the charge nozzles  5  (or the discharge nozzle  5 ′) may interfere with the charge valves  102  (or the discharge valve  102 ′) of the carrier  10  before the carrier  10  is positioned on the table  2 . In other words, the carrier  10  can be reliably positioned on the table  2  according to this preferred embodiment. 
         [0060]    Even in the case that the charge nozzles  5  are elastically supported to the carrier base  21  by using the supporting springs mentioned above and that the spring force of these springs is too large, the carrier  10  can be vertically positioned on the carrier base  21  by suitably controlling the drive force of the air cylinders  41 . In the case that the spring force of these springs is too small, the contact force between the charge nozzles  5  and the respective charge valves  102  of the carrier  10  may lack. Accordingly, in the case that a spring is provided for each charge nozzle, a high design accuracy in designing the spring force is required. However, such a problem can be eliminated in this preferred embodiment by suitably controlling the drive force of the air cylinders  41 . 
         [0061]    Particularly in the case that the carrier  10  is transported from an upper position to the load port  100  by using an OHT and then mounted on the table  2 , the carrier  10  swings mainly in a lateral direction, so that it is difficult to position the carrier  10  on the table in the related art load port having such a structure that the nozzle projects largely from the table due to the spring force. In this preferred embodiment, even when the carrier  10  is transported by an OHT and swings laterally, there is no possibility that the charge nozzles  5  may come into contact with the carrier  10  before the carrier  10  is positioned on the table  2 . 
         [0062]    Further, the grommet seal  1022  formed of rubber is used in each charge valve  102  (or the discharge valve  102 ′), so that the coefficient of friction between the charge nozzles  5  and the respective grommet seals  1022  is larger than that between the kinematic pins  7  and the respective positioning grooves  101  of the carrier  10 . Accordingly, in the related art structure, the charge nozzles are apt to interfere with the respective charge valves of the carrier. The charge nozzles  5  are formed of metal, the kinematic pins  7  are formed of metal or resin, and the body of the carrier  10  is formed of resin. 
         [0063]    In this preferred embodiment, as shown in  FIG. 4 , the upper ends of the charge nozzles  5  (or the discharge nozzle  5 ′) in their standby position are lower in height than the respective charge valves  102  of the carrier  10  in its positioned condition. Accordingly, in positioning the carrier  10  on the table  2 , there is no possibility that the charge nozzles  5  (or the discharge nozzle  5 ′) may interfere with the carrier  10 . As a result, the carrier  10  can be reliably positioned on the table  2 . 
         [0064]    In this preferred embodiment, the air cylinders  41  are used as each drive unit  4 . By using the air cylinders  41 , a constant drive force can be obtained irrespective of a stroke unlike a spring force. Accordingly, the charge nozzles  5  (or the discharge nozzle  5 ′) can be easily brought into contact with the charge valves  102  (or the discharge valve  102 ′) of the carrier  10  by a desired force. Further, as compared with another drive source using an electromagnetic motor, the configuration of each air cylinder  41  is simpler and the control is also simpler because of driving by air pressure. Therefore, the use of the air cylinders  41  can provide a merit from the viewpoints of weight reduction, maintainability, and durability. 
       Second Preferred Embodiment 
       [0065]      FIG. 7  is a sectional view showing a drive unit  54  according to a second preferred embodiment of the present invention applied to a load port as similar to the first preferred embodiment. In the following description of the second preferred embodiment, substantially the same parts as those of the load port  100  in the first preferred embodiment are denoted by the same reference numerals, and the description thereof will be simplified or omitted. The difference between the first preferred embodiment and the second preferred embodiment will be mainly described. 
         [0066]    The drive unit  54  has a housing  541  containing a charge nozzle  55  adapted to be vertically moved. The upper surface of the housing  541  is formed with a hole  541   a,  and a part of the charge nozzle  55  is exposed from this hole  541   a.  The outer circumferential surface of the charge nozzle  55  is formed with a flange portion  551 . The inner wall surface (cylindrical surface) of the housing  541  is formed with a connecting portion  547 . A cylindrical bellows  542  for vertically movably supporting the charge nozzle  55  is connected between the flange portion  551  of the charge nozzle  55  and the connecting portion  547  of the housing  541 . The bellows  542  partitions the inside space of the housing  541  to define two pressure chambers (first and second pressure chambers)  545  and  546 . The pressure chamber  545  is provided with an inlet port  543  for introducing an inert gas into the pressure chamber  545 . The pressure chamber  546  is provided with an outlet port  544  for discharging a gas from the pressure chamber  546 . The charge nozzle  55  is formed with a pass line  552  for passing the inert gas. The pass line  552  communicates with the pressure chamber  545 . 
         [0067]    In operation, the inert gas is introduced from the inlet port  543  into the pressure chamber  545 , and the air is discharged from the pressure chamber  546  through the outlet port  544 . Accordingly, a pressure difference in produced between the two pressure chambers  545  and  546 . In this case, the inlet port  543  and the outlet port  544  function as a pressure difference producing mechanism. Further, by setting the channel resistance of the pass line  552  in the charge nozzle  55  to a relatively large value, a pressure difference can be produced between the two pressure chambers  545  and  546 . 
         [0068]    When a pressure difference is produced between the two pressure chambers  545  and  546 , the charge nozzle  55  is raised to expand the bellows  542  until the upper end of the charge nozzle  55  comes into contact with the charge valve  102  provided in the bottom portion  103  of the carrier  10 . At this time, the gas pressure in the pressure chamber  545  is high, so that the inert gas in the pressure chamber  545  is charged through the pass line  552  in the charge nozzle  55  and the charge valve  102  into the carrier  10 . 
         [0069]    As described above, in the second preferred embodiment, a pressure difference is produced between the pressure chambers  545  and  546 , thereby driving the charge nozzle  55  connected to the bellows  542 . With this configuration, the charge nozzle  55  itself functions as a piston in a cylinder, so that the drive unit  54  can be reduced in overall size. 
         [0070]    Further, in the drive unit  54 , the charge nozzle  55  is driven by utilizing the operation of charging the inert gas into the carrier  10 , so that any specific pressure transmitting medium is not required. 
       Modifications 
       [0071]    The present invention is not limited to the above preferred embodiments, but various modifications may be made without departing from the scope of the present invention. 
         [0072]    While an inert gas is charged into the carrier  10  in the above preferred embodiments, a dry air may be charged into the carrier  10  instead of the inert gas. 
         [0073]    While the air cylinders  41  are used as the drive source of the drive unit  4  in the first preferred embodiment, any other drive sources such as a ball screw, belt, rack and pinion, and electromagnetic linear actuator. Further, the number of the air cylinders  41  in each drive unit  4  is not limited to two, but one or three or more air cylinders may be provided in each drive unit. 
         [0074]    While the gas charging or discharging apparatus is applied to the load port  100  in the above preferred embodiment, the gas charging or discharging apparatus according to the present invention is also applicable to a stocker for storing the carrier  10  and a purge station. 
         [0075]    While the semiconductor wafer substrates W are used as the object to be stored in the carrier  10  in the above preferred embodiment, the object to be stored in the carrier  10  is not limited to such wafer substrates W, but glass substrates for display devices and photoelectric conversion devices may be used. 
         [0076]    In the case of producing a pressure difference between the pressure chambers  545  and  546  in the second preferred embodiment, the air in the pressure chamber  546  may not be positively discharged from the outlet port  544 , but the inert gas may be only introduced from the inlet port  543  into the pressure chamber  545 . That is, the air in the pressure chamber  546  may be naturally discharged from the outlet port  544 . Further, the inert gas may not be introduced from the inlet port  543  into the pressure chamber  545 , but the air in the pressure chamber  546  may be positively discharged from the outlet port  544 . In this case, the inert gas may be supplied through another route to the charge nozzle  55 . Further, the drive unit in the second preferred embodiment is also applicable to a discharge nozzle for discharging the gas from the carrier  10 . 
         [0077]    The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2010-049077 filed in the Japan Patent Office on Mar. 5, 2010, the entire content of which is hereby incorporated by reference. 
         [0078]    While the invention has been described with reference to specific embodiments, the description is illustrative and is not to be construed as limiting the scope of the invention. Various modifications and changes may occur to those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.