Patent Publication Number: US-11380567-B2

Title: Wafer purging-type shelf assembly and buffer module having the same

Description:
RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2018-0115097, filed on Sep. 27, 2018, which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Field 
     The present invention relates to a shelf assembly used in a semiconductor manufacturing process and capable of purging wafers, and a buffer module having the same. 
     Description of the Related Art 
     Generally, a semiconductor manufacturing process includes a step of producing a wafer, a step of processing the produced wafer through various equipments, and a step of inspecting a semiconductor package produced through processing. 
     In such a processing step, the wafers may not be continuously put into various equipments, and are sequentially put into the next equipment as needed after being stored for a predetermined time. Therefore, facilities for such storage are needed. The facilities for storage may be installed on a ground of a semiconductor factory or may also be installed while being suspended from a ceiling. 
     During storage in the facilities for storage, a surface of the wafer may be damaged by oxidation over time. In order to prevent such damage, an inert gas may be injected into a container receiving the wafer during storage in the facilities for storage. 
     A mass flow controller (MFC) is used to detect an injection amount of the inert gas. However, since the mass flow controller is expensive, the cost of widely installing the mass flow controller for each container receiving the wafer is enormous. In addition, since the mass flow controller has a large volume, there is a space restriction to install the mass flow controller in a facility for integrating and storing containers. 
     Accordingly, in a case in which the mass flow controller is not used, the inert gas is continuously injected into the container in a predetermined amount. This increases the injection amount of the inert gas more than necessary, resulting in an enormous waste of the inert gas. 
     SUMMARY 
     An object of the present invention is to provide a wafer purging type shelf assembly which precisely controls an inert gas supplied into a wafer receiving container to eliminate a waste of the inert gas and may eliminate the use of components which are expensive and require a large space, and a buffer module having the same. 
     Another object of the present invention is to provide a wafer purging type shelf assembly which may stably supply a large amount of flow rate even when the flow rate of an inert gas supplied into a wafer receiving container needs to be sharply increased, and a buffer module having the same. 
     According to an exemplary embodiment of the present invention, there is provided a wafer purging-type shelf assembly including: a shelf formed to support a wafer receiving container; a supply nozzle configured to be connected to an injection port of the wafer receiving container; and a gas supply line configured to supply an inert gas discharged from a factory gas facility to the wafer receiving container through the supply nozzle, wherein the gas supply line includes a proportional pressure control valve unit that adjusts a supply flow rate of the inert gas to the wafer receiving container by an area control method. 
     The proportional pressure control valve unit may include a valve housing including an input port and an output port; and a piezo valve seat being installed in the valve housing and adjusting a flow area of the inert gas through the input port according to an input voltage to control a flow rate of the inert gas output through the output port. 
     The proportional pressure control valve unit may further include a restoring spring that pressurizes the piezo valve seat in a direction of closing the input port. 
     The proportional pressure control valve unit may further include a pressure sensor that measures a pressure of the inert gas output through the output port. 
     The gas supply line may further include a shelf-dedicated regulator installed at an upstream side of the proportional pressure control valve unit and configured to supply the inert gas only to the proportional pressure control valve unit at a uniform pressure. 
     The shelf-dedicated regulator may be disposed below the shelf. 
     The gas supply line may further include a flow rate sensor disposed between the proportional pressure control valve unit and the supply nozzle to output a flow rate of the inert gas passing through the proportional pressure control valve unit. 
     The gas supply line may further include a filter installed at an upstream side of the supply nozzle to filter foreign materials of the inert gas. 
     According to another exemplary embodiment of the present invention, there is provided a wafer purging-type shelf assembly including: a shelf on which a wafer receiving container is seated; a proportional pressure control valve unit configured to adjust a supply flow rate of an inert gas supplied to the wafer receiving container from a factory gas facility by an area control method; and a shelf-dedicated regulator positioned at an upstream side of the proportional pressure control valve unit and configured to input the inert gas only to the proportional pressure control valve unit corresponding to the shelf at a uniform pressure. 
     The proportional pressure control valve unit may be configured to adjust the supply flow rate of the inert gas over the time after the wafer receiving container is seated on the shelf. 
     The proportional pressure control valve unit may include a valve housing including an input port and an output port; and a piezo valve seat being installed in the valve housing and adjusting a flow area of the inert gas through the input port according to an input voltage to control a flow rate of the inert gas output through the output port. 
     The proportional pressure control valve unit may further include a pressure sensor that measures a pressure of the inert gas output through the output port. 
     The wafer purging-type shelf assembly may further include a flow rate sensor installed at a downstream side of the proportional pressure control valve unit to output the flow rate of the inert gas passing through the proportional pressure control valve unit. 
     According to still another exemplary embodiment of the present invention, there is provided a wafer purging-type buffer module including: a storage housing including a receiving space; a shelf disposed to support a wafer receiving container in the receiving space; and a proportional pressure control valve unit configured to adjust a supply flow rate of an inert gas supplied to the wafer receiving container from a factory gas facility by an area control method. 
     The wafer purging-type buffer module may further include a shelf-dedicated regulator positioned at an upstream side of the proportional pressure control valve unit and configured to input the inert gas only to the proportional pressure control valve unit corresponding to the shelf at a uniform pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an EFEM  100  including a buffer module  170  according to an exemplary embodiment of the present invention; 
         FIG. 2  is an assembled perspective view showing a configuration related to a buffer port  220  of a buffer module  200  of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of a principal part of a configuration related to the buffer port  220  of  FIG. 2 ; 
         FIG. 4  is a block diagram describing a gas supply line  260  installed in the buffer module  200  of  FIG. 3 ; 
         FIG. 5  is a conceptual view showing a configuration of a proportional pressure control valve unit  300  of  FIG. 4 ; 
         FIG. 6  is a graph showing an experiment result on the proportional pressure control valve unit  300  of  FIG. 5 ; 
         FIG. 7  is a graph showing an ideal change of an inert gas flow rate supplied to a FOUP C by the proportional pressure control valve unit  300  of  FIG. 5 ; and 
         FIG. 8  is a control block diagram for the EFEM  100  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a wafer purging-type shelf assembly and a buffer module according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Throughout the present specification, components that are the same as or similar to each other will be denoted by reference numerals that are the same as or similar to each other, and a description therefor will be replaced with a first description, even in different exemplary embodiments. 
       FIG. 1  is a perspective view showing an EFEM  100  including a buffer module  170  according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , the EFEM  100  may selectively include a transfer chamber  110 , a load port module  130 , a wafer transfer robot  150  (see  FIG. 8 ), and a buffer module  170 . 
     The transfer chamber  110  occupies a rear portion of the EFEM  100  and forms an internal space in which the wafer transfer robot  150  operates. The transfer chamber  110  is disposed to face process equipment, for example, deposition equipment, etching equipment, and the like. 
     The load port module  130  occupies a front portion of the EFEM  100 . The load port module  130  may be disposed to face the transfer chamber  110 . The load port module  130  has a support  131  on which a wafer receiving container, for example, a front-opening unified pod (FOUP) C is seated. In the present exemplary embodiment, the load port module  130  includes three supports  131  so that three FOUPs C may be seated on the load port module  130  at a time. In order to allow the wafer transfer robot  150  to access the FOUP C, a door  135  is formed in the load port module  130  to correspond to each support  131 . 
     The wafer transfer robot  150  operates in the transfer chamber  110 , and is configured to transfer a wafer before processing in the FOUP C to a process equipment side. Further, the wafer transfer robot  150  transfers a wafer after processing to a load port module  130  side and puts it into the FOUP C. 
     The buffer module  170  is located above the load port module  130  and the transfer chamber  110  and provides a space for storing the FOUP C therein. To this end, the buffer module  170  may have a storage housing  171 , a buffer port  173 , and a lift unit  175 . The storage housing  171 , which is a box having substantially a form of a rectangular parallelepiped, may have a receiving space of the form in which a front thereof is opened. It is also possible that not only the front of the receiving space but also the upper, rear, and the like are further opened. In addition, the storage housing  171  may be the storage housing  171  as a part of the configuration of the EFEM  100  as well as a storage housing put next to a rail R while being suspended from a ceiling. Further, the storage housing  171  may be a housing of a wafer stocker that is installed on a ground. The buffer port  173  may be configured to be moved between an inside and an outside of the storage housing  171  through the front opened space of the storage housing  171 . The lift unit  175  is configured to transfer the FOUP C seated on the buffer port  173  to the load port module  130 , or transfer the FOUP C in an opposite direction. The FOUP C is stored in the buffer module  170  before or after it is seated on the load port module  130 , and is injected with an inert gas while being seated in the buffer port  173 . The inert gas may be, for example, nitrogen, and the wafer in the FOUP C is purged by the inert gas to prevent oxidation. In the present exemplary embodiment, four buffer ports  173  are provided and the number of buffer ports  173  is one more than three supports  131  of the load port module  130 . Here, the buffer ports corresponding to the three supports  131  of the buffer port  173  may be referred to as a corresponding buffer port, and the other one may be referred to as a non-corresponding buffer port. The lift unit  175  is configured to be moved between positions corresponding to both the corresponding buffer port and the non-corresponding buffer port. 
     According to such a configuration, a vehicle V constituting an overhead hoist transport (OHT) system reaches a position corresponding to the EFEM  100  while moving along a rail R. The vehicle V may unload the FOUP C that is being transferred to the buffer port  173  of the buffer module  170 . To this end, the buffer port  173  may be moved to the outside of the storage housing  171  and wait to take over the FOUP C. The buffer port  173  taking over the FOUP C may move to the inside of the storage housing  171 . Further, the FOUP C is injected with the inert gas while being stored in the buffer module  170  and the wafer in the FOUP C may be purged. 
     The lift unit  175  may put down the FOUP C subjected to the purge on the load port module  130 . With respect to the FOUP C put down on the load port module  130 , the wafer transfer robot  150  in the transfer chamber  110  may transfer the purged wafer to the process equipment side. When a work on the wafer is completed on the process equipment side, the wafer transfer robot  150  puts the wafer into the FOUP C seated on the load port module  130 . The FOUP C receiving the processed wafer is transferred to the buffer port  173  by the lift unit  175 . When the FOUP C receiving the processed wafer needs to wait for a long time, the buffer module  170  additionally injects the inert gas into the FOUP C. Thereafter, the vehicle V grasps the FOUP C and moves along the rail R toward the other process equipment. 
     In such a process, the injection of the inert gas to the FOUP C and hence the purge of the wafer is performed at a step before or after the FOUP C is seated on the load port module  130 , not a step in which the FOUP C is seated on the load port module  130 . In other words, the injection of the inert gas to the FOUP C is performed in the buffer module  170  which is separate from the load port module  130 . Even if the injection of the inert gas to the FOUP is performed in the load port module  130 , this is at a level that complements a function of the buffer module  170 , so that the waiting time of the FOUP C in the load port module  130  does not become long. 
     The buffer module  170  described above will be described in more detail with reference to  FIG. 2 . For convenience of explanation, the buffer module  170  is also referred to as  200  by reference numeral. 
       FIG. 2  is an assembled perspective view showing a configuration related to a buffer port  220  of a buffer module  200  of  FIG. 1 ,  FIG. 3  is an exploded perspective view of a configuration related to the buffer port  220  of  FIG. 2 , and  FIG. 4  is a block diagram describing a gas supply line  260  installed in the buffer module  200  of  FIG. 3 . 
     Referring to the present drawings, the buffer module  200  includes a mount  210 , a buffer port  220 , a shelf installation  230 , an information management unit  240 , a chucking unit  250 , and a gas supply line  260 . 
     The mount  210  is a member installed in a frame  171   a  of the storage housing  171  (see  FIG. 1 ). The mount  210  may have a generally rectangular plate shape. A guide  211  extending along an outward direction F and an inward direction R may be installed on an upper surface of the mount  210 . The guide  211  supports the buffer port  220  moving in the outward direction F and the inward direction R and guides a movement of the buffer port  220 . In addition, a buffer port driving unit  215  may be installed parallel to the guide  211 . The buffer port driving unit  215  which, is an actuator for driving the buffer port  220  in the outward direction F and the inward direction R, may be, for example, a rodless cylinder. 
     The buffer port  220  supports the FOUP C (see  FIG. 1 ) and is a configuration that assists filling of the inert gas with FOUP C. The buffer port  220  may structurally include a shelf  221 , a cover  223 , and a base  225 . The shelf  221  is exposed to an upper portion to support the FOUP C in contact with the FOUP C. The cover  223  is disposed to surround a periphery of the shelf  221 . The base  225  may be disposed substantially parallel to the shelf  221  below the shelf  221 . The chucking unit  250  and the like may be disposed in a space defined by the shelf  221 , the cover  223 , and the base  225 . The base  225  is slidably coupled to the guide  211  and is connected to the buffer port driving unit  215  to be slidably moved in the outward direction F and the inward direction R. 
     The shelf installation  230  may include various structures installed on the shelf  221  and interacting with the FOUP C. The shelf installation  230  may have a reference pin  231 , a supply nozzle  233 , an exhaust nozzle  234 , and a seating detection sensor  235  in detail. The reference pin  231  is a configuration inserted into a reference groove (not shown) of the FOUP C to guide the FOUP C to be correctly positioned on the shelf  221 . The supply nozzle  233  is a configuration connected to an injection port of the FOUP C pressed on the shelf  221  to inject the inert gas into the FOUP C. The number of the supply nozzles  233  is plural, and for example, three supply nozzles may be located in each corner region of the shelf. Further, similarly to the supply nozzle  233 , the exhaust nozzle  234  may also be constituted by one nozzle. The exhaust nozzle  234  is a passage through which the inert gas supplied into the FOUP C is discharged to the outside of the FOUP C through an exhaust gas line (not shown). The seating detection sensor  235  is installed on the shelf  221  to detect the seating of the FOUP C, Further, since a plurality of seating detection sensors  235  are configured, another detection result according to a shape of the FOUP C is obtained. Accordingly, the shape of the FOUP C may be determined through the detection result of the seating detection sensor  235 . 
     The information management unit  240  is installed in the shelf  221  and is configured to communicate with an information storage unit (not shown) of the FOUP C. Specifically, the information storage unit of the FOUP C stores wafer information about the wafer received in the FOUP C. The information management unit  240  may communicate with the information storage unit to acquire the wafer information and further transmit new information to the information storage unit to add to the wafer information. Here, the new information may be purge information which is information on the purge of the wafer. The purge information may include information on a purge time, a flow rate of gas injected for purge, and the like. To this end, the information management unit  240  may be a radio frequency identification (RFID) reader/writer, and the information storage unit may be an RFID tag. 
     The chucking unit  250  is a configuration put at the center of the shelf  221  to chuck the FOUP C placed on the shelf  221 . 
     The gas supply line  260  is a configuration that communicates with a gas supply facility of a semiconductor production factory so as to fill the inert gas in the FOUP C. The gas supply line  260  may specifically include a shelf-dedicated regulator  261 , a proportional pressure control valve unit  263 , a flow rate sensor  265 , and a filter  267 . 
     The shelf-dedicated regulator  261  is a configuration that communicates with the gas supply facility of the factory through a pipe, and depressurizes the inert gas supplied from the gas supply facility to maintain it at a constant pressure. Since the shelf-dedicated regulator  261  is provided for each shelf  221 , it is exclusively used for only the gas supply line  260  installed in the shelf  221 . The inert gas supplied to the proportional pressure control valve unit  263  located on a downstream side of the gas supply line  260  by the shelf-dedicated regulator  261  always maintains a set pressure and is free from a hunting phenomenon. 
     The proportional pressure control valve unit  263  is a configuration that controls the flow rate of the inert gas to supply the inert gas having the constant pressure input through the shelf-dedicated regulator  261  to the FOUP C to a required level. The proportional pressure control valve unit  263  is a configuration that adjusts an area of the portion through which the inert gas passes in the valve to adjust the pressure of the inert gas and further the flow rate thereof. Thereby, the flow rate of the inert gas may be adjusted analogously, and the degree of precision of the flow rate adjustment may be significantly increased. According to the inventor&#39;s experiment, an error of the flow rate adjustment is only 0.4%. Three proportional pressure control valve units  263  may be provided corresponding to the three supply nozzles  233 . The inert gas passing through the shelf-dedicated regulator  261  branches into three lines and is input to each proportional pressure control valve unit  263 . 
     The flow rate sensor  265  is a configuration disposed downstream of the proportional pressure control valve unit  263  to indicate the flow rate regulated through the proportional pressure control valve unit  263 . Since the flow rate sensor  265  is exposed to the outside through an opening of the cover  223 , an operator may visually detect the flow rate. 
     The filter  267  is a configuration disposed between the flow rate sensor  265  and the supply nozzle  233  to remove foreign materials from the inert gas. 
     In the above description, the shelf-dedicated regulator  261 , the proportional pressure control valve unit  263 , and the like constituting the gas supply line  260  are illustrated as being mounted on the base  225 , but in the absence of the base  225 , the shelf-dedicated regulator  261 , the proportional pressure control valve unit  263 , and the like may also be mounted on a bottom surface of the shelf  221 . Further, a configuration in which the shelf  221 , the shelf installation  230 , and the gas supply line  260  are combined may be referred to as a wafer purging-type shelf assembly. 
     The proportional pressure control valve unit  263  will be described with reference to  FIGS. 5 and 6 . For convenience of explanation, the proportional pressure control valve unit  263  is also referred to as  300  by reference numeral. 
       FIG. 5  is a conceptual view showing a configuration of a proportional pressure control valve unit  300  of  FIG. 4 . 
     Referring to  FIG. 5 , the proportional pressure control valve unit  300  may include a valve housing  310 , a piezo valve seat  330 , a return spring  350 , and a pressure sensor  370 . 
     The valve housing  310  may be a hollow body having an internal space. A plurality of ports may be opened in the valve housing  310 . As the plurality of ports, an input port  311 , an output port  313 , and a relief port  315  are illustrated in the present exemplary embodiment. The inert gas having a constant pressure flows into the input port  311  through the shelf-dedicated regulator  261  (see  FIG. 4 ). The inert gas whose flow rate is adjusted by the piezo valve seat  330  is output through the output port  313  to flow toward the flow rate sensor  265  (see  FIG. 4 ). The relief port  315  is used to exhaust a part of the inert gas in the internal space. 
     The piezo valve seat  330  is disposed in the internal space and opens and closes the input port  311  and the relief port  315 . The piezo valve seat  330  includes a piezo material and is deformed by an applied voltage to vary the degree of opening and closing of the input port  311  and the like. Specifically, depending on how far the piezo valve seat  330  closing the input port  311  is bent away from the input port  311 , the pressure and the flow rate of the inert gas, which pass through the input port  311  and are output to the output port  313 , are varied. This is because an area that the inert gas passes through a space between the input port  311  and the piezo valve seat  330  is varied depending on the degree of bending of the piezo valve seat  330 . 
     The return spring  350  is installed to connect the piezo valve seat  330  and the valve housing  310  to each other. Thereby, the return spring  350  serves to return the piezo valve seat  330  which is bent away from the input port  311  or the like while being bent according to the voltage application toward the input port  311  or the like when the voltage application is reduced/released. 
     The pressure sensor  370  is a configuration that measures a pressure of the inert gas whose flow rate is adjusted through the output port  313  of the valve housing  310  and is output. Since the pressure sensor  370  is embedded in the proportional pressure control valve unit  300  as described above, it is not necessary to provide a separate pressure sensor on the outside. In addition, since the pressure sensor  370  measures the pressure of the inert gas input to the FOUP C through the supply nozzle  233  in the gas supply line  260  (see  FIG. 4 ), the pressure sensor  370  may provide pressure information that allows the detection as to whether the inert gas is properly input to the FOUP C or leaks without being input to the FOUP C. Specifically, when the inert gas is normally injected into the FOUP C, the pressure is higher than when the inert gas leaks. This is because the pressure of the inert gas is increased by a reaction force of the filter installed at the injection port of the FOUP C. By using the above-mentioned point, it is necessary to provide a separate pressure sensor or a flow rate sensor to check the gas leakage between the supply nozzle  233  and the FOUP C on the gas exhaust line through which the gas exhausted from the FOUP C flows. 
     A change in the pressure of the shelf-dedicated regulator  261  in such a proportional pressure control valve unit  300  and a change in an output flow rate of the inert gas according to the change in the voltage applied to the piezo valve seat  330  will be described with reference to  FIG. 6 . 
       FIG. 6  is a graph showing an experiment result on the proportional pressure control valve unit  300  of  FIG. 5  and  FIG. 7  is a graph showing an ideal change of an inert gas flow rate supplied to a FOUP C by the proportional pressure control valve unit  300  of  FIG. 5 . 
     Referring to  FIG. 6 , the input pressure of the inert gas adjusted by the shelf-dedicated regulator  261  (see  FIG. 4 ) is adjusted to 2 Bar, 3 Bar, and 4 Bar, respectively. Despite such a change in pressure, when the voltage applied to the piezo valve seat  330  is 0.80 V or less, the flow rate through the proportional pressure control valve unit  300  shows the same value. For example, at 0.80 V, the flow rate is 13.0 l/min regardless of the input pressure of the inert gas, and the flow rate at 0.30 V is 7.9 l/min. 
     When the pressure of the inert gas adjusted by the shelf-dedicated regulator  261  is 2 Bar, if the applied voltage is 0.94 V or more, the flow rate shows the same value of 13.6 l/min. In other words, even when the applied voltage exceeds 0.94 V and reaches 3.00 V, the flow rate does not exceed 13.6 l/min. 
     In contrast, when the pressure of the inert gas adjusted by the shelf-dedicated regulator  261  is 3 Bar, if the applied voltage is 1.76 V or more, the flow rate shows the same value of 19.7 l/min. 
     When the input pressure of the inert gas adjusted by the shelf-dedicated regulator  261  is 4 Bar, the flow rate continuously increases to 26.3 l/min while the applied voltage is increased to 3.00 V. As the flow rate increases, rapid filling of the inert gas to the FOUP C becomes possible. Accordingly, when the FOUP C is just put on the shelf  221 , the rapid filling to the FOUP C may be performed. 
     Specifically, referring to  FIG. 7 , the FOUP C put on the shelf  221  need not always be supplied with the same flow rate of the inert gas. In an initial stage, the supply flow rate should be large, but after the inert gas is sufficiently filled in the FOUP C after a certain time passes and an inert gas atmosphere is formed, the supply flow rate does not need to be large. Thereby, a proper supply amount of the inert gas sharply decreases after a certain time passes, and thereafter, it is maintained at a minimum amount. On the other hand, if the inert gas is supplied to the FOUP C at the same flow rate, this causes a great waste of the inert gas. 
     It may be seen from these results that there is a limit to increase the flow rate of the inert gas output from the proportional pressure control valve unit  300  only by increasing the applied voltage applied to the piezo valve seat  330  in the proportional pressure control valve unit  300 . In order to solve such a limit, the input pressure of the inert gas supplied to the proportional pressure control valve unit  300  needs to be increased. In such a process, when the pressure of the inert gas supplied to the proportional pressure control valve unit  300  is not uniform and the hunting phenomenon occurs, the proportional pressure control valve unit  300  does not output a set flow rate. Therefore, it is important that the shelf-dedicated regulator  261  for supplying the inert gas of a predetermined pressure to the proportional pressure control valve unit  300  is disposed at an upstream side of the proportional pressure control valve unit  300 . 
     Further, the point of time at which the FOUP C is placed on each shelf  221  is different. Therefore, whether a rapid filling time interval T 1 , a deceleration filling time interval T 2 , or a low-speed filling time interval T 3  differs depending on each of the shelves  221 . It is important that the shelf-dedicated regulator  261  is disposed for each shelf  221  so that different filling types for each shelf  221  may be stably and reliably achieved. 
     Next, a control method for the above-mentioned EFEM  100  will be described with reference to  FIG. 8 . 
       FIG. 8  is a control block diagram for the EFEM  100  of  FIG. 1 . 
     Referring to  FIG. 8  (and the preceding drawings), the EFEM  100  may further have an EFEM control unit  190 . The EFEM control unit  190  is a configuration that controls most of the configuration of the EFEM  100  except for the buffer module  170 . For example, the EFEM control unit  190  may control the wafer transfer robot  150 . 
     Unlike the above, the buffer module  170  may be controlled by a buffer control unit  270 . The buffer control unit  270  may receive a detection result or a control command from the seating detection sensor  235  and a user input unit  271 . Here, the user input unit  271  may be an input means such as a keyboard, a touch pad, or the like. 
     The buffer control unit  270  may control the lift unit  175 , the buffer port driving unit  215 , the information management unit  240 , the chucking unit  250 , and the proportional pressure control valve unit  263  based on such a detection result. 
     For example, the buffer control unit  270  may determine the shape of the FOUP C based on the detection result of the seating detection sensor  235 . Depending on the determined shape type of the FOUP C, the buffer control unit  270  may selectively intermit the supply of the inert gas to each of the plurality of supply nozzles  233 . This may be achieved by the buffer control unit  270  closing or opening the proportional pressure control valve unit  263 . Accordingly, the inert gas may be supplied in the shape corresponding to the structure of the FOUP C even in a field in which different shapes of FOUPs C are used. 
     In addition, the buffer control unit  270  may control the gas supply line  260  for the FOUP C to purge the wafer by filling the inert gas and may then allow the purge information about the purge operation to be written to the information storage unit of the FOUP C Specifically, the buffer control unit  270  controls the information management unit  240  to cause the purge information to be transmitted to the information storage unit. Thereby, the wafer information may be updated to reflect the purge information. Then, a central control system of the semiconductor factory may read the information storage unit and may detect a current state of the FOUP C. 
     In addition, the buffer control unit  270  may adjust the voltage to be applied to the piezo valve seat  330  in the proportional pressure control valve unit  263  based on the flow rate of the inert gas to be filled into the FOUP C. By such a voltage adjustment, the flow rate of the inert gas filled in the FOUP C via the proportional pressure control valve unit  263  may be adjusted. 
     The wafer purging-type shelf assembly and the buffer module having the same as described above are not limited to the configuration and the operation method of the above-mentioned exemplary embodiments. The above-mentioned exemplary embodiments may be configured so that various modifications may be made by selective combinations of all or some of the respective exemplary embodiments. 
     According to the wafer purging type shelf assembly and the buffer module according to the exemplary embodiments of the present invention having the configurations as described above, the gas supply line may communicate with the wafer receiving container through the supply nozzle in a state in which the wafer receiving container is put on the shelf, and may precisely control the supply flow rate of the inert gas by the proportional pressure control valve unit through the area control. Since the proportional pressure control valve unit is less expensive than the conventional mass flow controller and requires only a small installation space, the proportional pressure control valve unit is suitable for wide field applications. Further, the waste of the inert gas may be eliminated by controlling the supply flow rate of the inert gas. 
     In addition, since the shelf-dedicated regulator exclusively used for the corresponding proportional pressure control valve unit to input the inert gas into the corresponding proportional pressure control valve unit at a uniform pressure is provided to the upstream side of the proportional pressure control valve unit, the flow rate of the inert gas through the proportional pressure control valve unit may be greatly increased by increasing the pressure of the inert gas input to the proportional pressure control valve unit. Thereby, the filled amount of the inert gas to the wafer receiving container may be rapidly improved at a point of time at which the wafer receiving container is put on the shelf.