Abstract:
A container is placed at a predetermined position on a purge device to prevent the container from getting caught on a nozzle. When the container is lowered and placed on the purge device, the two facing sides of the front end of the container&#39;s bottom surface and the front end of a recessed part, and the two facing sides of both left and right side ends of the container&#39;s bottom surface are guided by a front guide, side guides and a center guide. Following that, the nozzle is brought into contact with the bottom surface of the container.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a device for purging a container such as a FOUP (Front Opening Unified Pod) and a purge method. 
       BACKGROUND ART 
       [0002]    A purge gas such as a nitrogen gas or a clean dry air is injected through a nozzle into a container such as a FOUP that houses a semiconductor wafer, and thereby the inside of the container is purged. The position of the container is determined by engaging a pin with a recessed part for positioning located at the bottom surface of the container, however there are some containers in which the depth of a receiving hole of a nozzle is deeper than the recessed part for positioning. In such a container, the height of the nozzle becomes taller than the pin, so that the container gets caught on the nozzle, preventing it from being positioned. 
         [0003]    Patent literature 1 (JP2011-187539) suggests that an actuator which raises and lowers a nozzle is provided on a purge device to determine the position of a container by using a pin in a state wherein the nozzle is being lowered and then subsequently raise the nozzle. 
       CITATION LIST 
     Patent Literature 
       [0004]    [Patent Literature 1] JP2011-187539 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In such a manner suggested in Patent Literature 1, the actuator is required to raise and lower the nozzle, thereby creating a complicated structure of the purge device. Moreover, there is a need to control the actuator, and it becomes troublesome to perform, for example, adjustment and maintenance of the actuator. 
         [0006]    An object of the present invention is to be able to place a container at a predetermined position on a purge device without relying on an actuator and without the container getting caught on a nozzle. 
       Solution to Problem 
       [0007]    The present invention provides a purge device that has a nozzle for supplying a purge gas into a container, and the purge device includes: a front guide for guiding the front end of the bottom surface of the container; a pair of left and right side guides for guiding both left and right side ends of the bottom surface of the container; and a center guide for guiding the front end of a recessed part located on the center part of the bottom surface of the container. The front guide, side guides and center guide are all configured to start guiding the container from a position higher than the nozzle. 
         [0008]    The present invention also provides a purge method in which a purge gas is supplied through a nozzle on a purge device into a container, wherein the purge device are provided with: a front guide for guiding the front end of the bottom surface of the container; a pair of left and right side guides for guiding both left and right side ends of the bottom surface of the container; and a center guide for guiding a recessed part located on the center part of the bottom surface of the container. The front guide, side guides and center guide are all taller than the nozzle. The purge method comprises the steps of: having the front guide, side guides and center guide guide the two facing sides of the front end of the container&#39;s bottom surface and the front end of the recessed part, and the two facing sides of both left and right side ends of the container&#39;s bottom surface when the container is lowered and placed on the purge device; and bringing the nozzle into contact with the bottom surface of the container after having started guiding the two facing sides of the front end of the container&#39;s bottom surface and the front end of the recessed part, and the two facing sides of both left and right side ends of the container&#39;s bottom surface. 
         [0009]    In the present invention, the front guide, side guides and center guide guide the two facing sides of the front end of the container&#39;s bottom surface and the front end of the recessed part, and the two facing sides of both left and right side ends of the container&#39;s bottom surface, so that the container can be guided almost to the correct position. This can prevent the nozzle from getting caught on the bottom surface of the container and from not enabling the placement in the predetermined position. The present invention does not require an actuator which raises and lowers the nozzle, and there is also no need to control, adjust and maintain the actuator. Here, the height (tall/short) described in this specification is determined according to the height above a horizontal reference surface. 
         [0010]    Preferably, the container subject to purging is provided on the bottom surface with: a receiving hole for receiving the nozzle; and a plurality of recessed parts for positioning. The purge device further includes a plurality of fixed positioning pins which are shorter than the nozzle. The purge device is configured in such a way that by having the container guided by the front guide, side guides and center guide, the nozzle is received in the receiving hole, the positioning pin is engaged with the recessed part for positioning, and the position of the container is determined to the purge device. Thus, even when the nozzle impedes the positioning because the nozzle is taller than the positioning pin, the nozzle is housed in the receiving hole and the position can be determined by the positioning pin after the container has been guided almost to the correct position by the guides. 
         [0011]    In addition, the center guide is preferably configured to be freely lowered by the weight of the container. This can prevent a head of the center guide from touching the bottom of the recessed part and from not enabling the container to be lowered. The depth of the recessed part may vary. 
         [0012]    The nozzle is preferably configured to be freely lowered by the weight of the container. This can surely prevent the pin from not being able to carry out the positioning due to the height of the nozzle. 
         [0013]    The nozzle preferably includes a guide surface at the upper part and is configured in such a way that the guide surface guides the receiving hole. Thus, the guide surface can resolve the nozzle and the receiving hole being caught on each other. 
         [0014]    A base is preferably further included, the front guide, side guides, center guide, nozzle and nozzle are attached to the base, and the nozzle is attached to the base as such to be freely tilted via an elastic spacer. Thus, if the nozzle is not evenly in contact with the receiving hole, the nozzle is tilted, thereby bringing it evenly in contact with the receiving hole. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is a bottom view of a FOUP. 
           [0016]      FIG. 2  is a plan view of a purge device according to one embodiment. 
           [0017]      FIG. 3  is a plan view of a center guide. 
           [0018]      FIG. 4  is a side view of the center guide. 
           [0019]      FIG. 5  is a side view of a nozzle. 
           [0020]      FIG. 6  is a cross-sectional view showing the purge device and the FOUP that is being lowered. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]    A preferred embodiment of the present invention will be explained hereinafter. The scope of the invention shall be determined in accordance with the understanding of a person having ordinary skill in the art, while taking into consideration the description in the specification and a well-known art in this field based on the description in the scope of claims. 
         [0022]      FIGS. 1-6  show a purge device  20  of the embodiment.  FIG. 1  shows a bottom surface of a FOUP  2  that is subject to purging, and a purge gas refers to nitrogen, a clean dry air, or the like. A container which is purged is not limited to a FOUP, and an article which is housed in the container is not limited to a semiconductor wafer, but for example, a reticle may be used. The FOUP  2  includes, for example, four receiving holes  4  which receive nozzles of the purge gas, and valves  6 ,  7  are provided at the bottom part of the receiving holes  4 . The valve  6  is used for injecting the purge gas, and the valve  7  is used for discharging the gas, however the valves  6 ,  7  may not be required. 
         [0023]    According to international standards on the FOUP  2 , three coupling grooves  8  are provided, and a front reference surface  13  and a side reference surface  14  have the standardized position.  15  is a forklift flange,  16  is a rear surface of the FOUP  2 , and the position of the rear surface  16  is not specified in the international standards. The front reference surface  13  is a surface to which a lid of the FOUP  2  is attached, and this specification regards the front reference surface  13  as being located at the front of the FOUP  2  and the rear surface  16  as being located at the back of the FOUP  2 . In addition, a direction of connecting both lateral sides of the FOUP  2  is called left and right. The international standards define that a center groove  10  is provided at a predetermined position on the center part of the bottom surface in order to set the FOUP  2  in place and also specify the positions of the front and rear surfaces of the center groove  10 . And with that, the front surface of the center groove  10  is regarded as a reference surface  11 , and the lower end of the reference surface  11  is used for guiding the FOUP  2 . However, the depth of the receiving hole  4  and the center groove  10  vary. Here, when the purge nozzle becomes taller than the coupling pin because the receiving hole  4  is deeper than the coupling groove  8 , the preferred embodiment is suitably used. 
         [0024]    As shown in  FIG. 6 , the FOUP  2  includes a top flange  17  on an upper part, the top flange  17  is chucked by a lifting platform  18  of an overhead traveling vehicle not illustrated, and the FOUP  2  is elevated and lowered by a belt  19 . 
         [0025]      FIGS. 2-5  show the structure of the purge device  20 . The purge device  20  is configured in such a way that the overhead traveling vehicle freely transfers the FOUP  2  and a transfer apparatus equipped with an arm that is capable of elevating/lowering and moving back and forth the FOUP  2  without any impediments also freely transfers the FOUP  2 . The purge device  20  is used, for example, in a stocker for storing the FOUP  20 , a buffer for being located in the vicinity of a track of the overhead traveling vehicle and a buffer for being located on the front surface of a processing device, and a purge gas source not illustrated is provided separately. 
         [0026]      22  is a base, and the FOUP  2  is placed on the upper surface of the base.  24  is a lower plate,  26  and  27  are purge nozzles, the nozzle  26  is used for injecting the purge gas, the nozzle  27  is used for discharging the gas, and the nozzle  27  may not be required. In addition, one to three nozzles  26  are provided. Preferably, a guide surface  28 , which is formed of a fine tapered surface, is provided on the upper part of the nozzles  26 ,  27  and guides the receiving hole  4  of the FOUP  2 .  29  is a pipe used for injecting the purge gas, and  30  is an exhaust pipe and may not be required. 
         [0027]    In order to guide the lower end of the front reference surface  13  of the FOUP  2  (front end of the bottom surface), for example, a pair of front guides  35  is set protruded from the base  22 . In addition, in order to guide the lower end of the side reference surfaces  14  (left and right ends of the bottom surface), at least a pair of left and right side guides  36  is set protruded from the base  22 . Hereinafter, the front guide  35  is simply referred to as a guide  35  and the side guide  36  is simply referred to as a guide  36 . The guides  35 ,  36  include guide surfaces  37  that are formed of tapered surfaces and guide the lower ends of the reference surfaces  13 ,  14  of the FOUP  2 . 
         [0028]    For example, three pins  32  are provided on the base  22  to kinematically couple with the coupling grooves  8  on the FOUP  2  and then determine the position of the FOUP  2 . In addition, a center guide  34  protrudes, for example, from the lower plate  22  above a notch  33  on the base  22  in order to guide the lower end of the reference surface  11  of the center groove  10  on the FOUP  2 . With respect to the height using the upper surface of the base  22  as reference, the guide surface  37  and a guide surface  41  of the center guide  34  ( FIGS. 3 and 4 ) are the tallest followed by the nozzles  26 ,  27 , and the pin  32  is the shortest. As shown in  FIG. 6 , the base  22  and the lower plate  24  are connected by a support part  38 . 
         [0029]      FIGS. 3 and 4  show the structure of the center guide  34 . A protruding part  40  protrudes so as to engage with the center groove  10  on the FOUP  2 , and the guide surface  41  that is formed of a tapered surface is provided in such a way as to guide the lower end of the reference surface  11 , for example. The protruding part  40  is fixed to a pedestal  42 , and is mounted on the lower plate  24  so as to be freely lowered by, for example, a pair of pins  45  attached to the pedestal  42 , and is urged upward by, for example, a pair of elastic bodies  44  such as springs. The reason for allowing the protruding part  40  to be freely lowered is because the depth of the center groove  10  on the FOUP  2  varies. If the upper part of the protruding part  40  does not interfere with the bottom part of the center groove  10 , the height of the protruding part  40  may be fixed. To cope with the center groove  10  having various depths, it is preferred that the protruding part  40  is urged upward by the elastic body and can be freely lowered by the weight of the FOUP  2 . 
         [0030]      FIG. 5  shows the preferred embodiment of the nozzles  26 ,  27 .  50  is a head of the nozzle which is brought into close contact with the bottom part of the receiving hole  4 , thereby maintaining the airtightness. A hollow shaft  51  extends downward and connects to a pedestal  56 . The head  50  is urged upward by an elastic body  52  such as a spring and can be freely lowered by the weight of the FOUP  2 . In addition, an elastic spacer  54  such as a synthetic resin is positioned between the base  22  and the pedestal  56 , and it allows the head  50  to be tilted from the vertically upward position.  57  is a connection part with the pipe. It is preferred that the nozzles  26 ,  27  are urged upward by the elastic body and can be freely lowered by the weight of the FOUP  2 . Additionally, the direction of the nozzle (the direction of the nozzle axis) can preferably be tilted from the vertically upward position. 
         [0031]      FIG. 6  shows the positioning of the FOUP  2 . When the FOUP  2  is being lowered, the nozzle  26  gets caught on the receiving hole  4  without the guide  35  or the like as the nozzle  26  is taller than the pin  32 , whereby the pin  32  may not be able to do the guide. Therefore, the guides  35 ,  36  are provided to guide three sides of the lower ends of the front reference surface  13  and the side reference surfaces  14  of the FOUP  2 . In addition, the center guide  34  guides the lower end of the reference surface  11  of the FOUP  2 . This enables the FOUP  2  to be guided almost to the correct position, and thereby the chance of being caught on the nozzles  26 ,  27  is reduced. If the center groove  10  is shallow, the protruding part  40  of the center guide  34  contacts the bottom part of the center groove  10 , thereby lowering the protruding part  40 . 
         [0032]    As shown in  FIG. 5 , the nozzles  26 ,  27  include the guide surface  28  on its upper part, preferably at its tip. Therefore, if the nozzles  26 ,  27  get caught on the receiving hole  4 , the receiving hole  4  is guided along the guide surface  28 , thereby resolving the nozzles being caught. In addition, since the nozzles  26 ,  27  can be freely lowered, the nozzles are lowered by the weight of the FOUP  2  and are lowered to a position where the positioning by the pin  32  is not hindered. Furthermore, if the nozzles  26 ,  27  are not evenly in contact with the receiving hole  4 , unbalanced load is applied to the elastic spacer  54  and then the nozzles  26 ,  27  are tilted, thereby bringing them evenly in contact with the receiving hole  4 . 
         [0033]    The embodiment has the following characteristics:
   1) The guide  35  and the center guide  34  guide the two facing sides of the lower end of the front reference surface  13  of the FOUP  2  (front end of the bottom surface) and the lower end of the reference surface  11  of the center groove  10 . Additionally, a pair of left and right guides  36  guide the lower ends of the left and right side reference surfaces  14  (left and right ends of the bottom surface), so that the chance of the FOUP  2  and nozzles  26 ,  27  being caught on each other is reduced.   2) The center guide  34  is lowered by the weight of the FOUP  2 , and thereby the protruding part  40  of the center guide  34  does not impede lowering the FOUP 2 .   3) The guide surface  28  is capable of resolving the nozzles  26 ,  27  and the receiving hole  4  being caught on each other.   4) The nozzles  26 ,  27  are lowered by the weight of the FOUP  2  and do not impede the positioning by the pin  32 .   5) If the nozzles  26 ,  27  are not evenly in contact with the receiving hole  4 , the nozzles  26 ,  27  are tilted so as to come evenly in contact with the receiving hole.   
 
         [0039]    When the transfer using an arm such as a stacker crane is not necessary, the lower plate  24  and the notch  33  on the base  22  are not required, so that the center guide  34  is supported by the base  22 . In addition, when the purge device  20  is provided at a load port where the front lid of the FOUP  2  is opened/closed and a semiconductor wafer is deposited and retrieved into/from the FOUP, it is preferred that the guide  35  is freely elevated and lowered without impeding the opening and closing of the lid. 
       REFERENCE SIGNS LIST 
       [0040]      2  . . . FOUP,  4  . . . Receiving hole,  6 ,  7  . . . Valve,  8  . . . Coupling groove,  10  . . . Center groove,  11  . . . Reference surface,  13  . . . Front reference surface,  14  . . . Side reference surface,  15  . . . Forklift flange,  16  . . . Rear surface,  17  . . . Top flange,  18  . . . Lifting platform,  19  . . . Belt,  20  . . . Purge device,  22  . . . Base,  24  . . . Lower plate,  26 ,  27  . . . Nozzle,  28  . . . Guide surface,  29 ,  30  . . . Pipe,  32  . . . Pin,  33  . . . Notch,  34  . . . Center guide,  35  . . . Front guide,  36  . . . Side guide,  37  . . . Guide surface,  38  . . . Support part,  40  . . . Protruding part,  41  . . . Guide surface,  42  . . . Pedestal,  44  . . . Elastic body,  45  . . . Pin,  50  . . . Head,  51  . . . Hollow shaft,  52  . . . Elastic body,  54  . . . Elastic spacer,  56  . . . Pedestal,  57  . . . Connection part