BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to a control apparatus for controlling transfer of semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for organic EL devices, substrates for FEDs (Field Emission Displays), substrates for optical displays, substrates for magnetic disks, substrates for magnetic optical disks, substrates for photomasks, or substrates for solar cells (hereinafter called simply substrates), along with pods, to and from an interior of a substrate treating apparatus, and for controlling transfer of the pods to and from a carrier transport system. The invention relates also to a substrate treating method, a substrate treating system, a method of operating a substrate treating system, a load port control apparatus, and a substrate treating system having the load port control apparatus. 
     (2) Description of the Related Art 
     Conventionally, a substrate treating system of this type includes a substrate treating apparatus, and a carrier transport system for transporting pods upon instructions of a host computer which performs overall control of the treating system. The substrate treating apparatus has a substrate treating unit, a pod storage and transport unit, a load port, and a load port control device. 
     The substrate treating unit carries out various types of treatment for substrates. The pod storage and transport unit is juxtaposed to the substrate treating unit for storing and transporting FOUPs (Front Opening Unified Pods) containing the substrates. The load port is juxtaposed to the pod storage and transport unit for receiving the FOUPs. The load port control device controls transfer of the FOUPs to and from the pod storage and transport unit and to and from the carrier transport system. The carrier transport system is an automated material handling system having automatic guided vehicles (AGV), or an overhead hoist transfer, which transfers the FOUPS to and from the load port. The host computer carries out controls relating to transportation of the pods through communication with the load port control device and the carrier transport system. 
     Generally, one substrate treating apparatus has a plurality of load ports. With an improvement in treatment efficiency of the substrate treating unit, the number of pods to be transported will increase. The efficiency of the substrate treating unit cannot be used to full advantage without reducing transport intervals of the pods by the carrier transport system. However, with this type of carrier transport system, a plurality of transport vehicles in the carrier transport system do not load the pods into one load port at the same time. In general use (standard), only one transport vehicle loads the pods into one load port. And under restrictions imposed by the layout of the carrier transport system, for example, the time taken for one transport vehicle to load the pods into one load port cannot be shortened to be less than a certain level. Consequently, transportation by the carrier transport system cannot keep up an expected pace, resulting in a problem of reduced treatment efficiency. 
     In the circumstances, a first apparatus has been proposed, which has the number of load ports increased in a height direction, with a corresponding increase in the running lane of the carrier transport system to two (see Patent Document 1, for example). Further, a second apparatus has been proposed, which provides a movable buffer adjacent a load port to serve as a temporary turnout for pods, so that the load port may be made vacant in a short time (see Japanese Unexamined Patent Publication No. 2010-192855, for example). 
     However, the conventional examples with such constructions have the following drawbacks. 
     The first conventional apparatus requires increases in the number of load ports and the number of running lanes of the carrier transport system. This poses a problem of increased apparatus cost. 
     The second conventional apparatus requires the special movable buffer provided adjacent the load port, which again poses a problem of increased apparatus cost. 
     SUMMARY OF THE INVENTION 
     This invention has been made having regard to the state of the art noted above, and its object is to provide a control apparatus, a substrate treating method, a substrate treating system, a method of operating a substrate treating system, a load port control apparatus, and a substrate treating system having the load port control apparatus, which are capable of improving the efficiency of transporting pods while holding down apparatus cost, without increasing or complicating mechanical components such as load ports. 
     The above object is fulfilled, according to this invention, by a control apparatus in a substrate treating system with a substrate treating apparatus having a physical load port for receiving pods for storing substrates, and a carrier transport system for transporting the pods to and from the physical load port, the control apparatus comprising a virtual load port control device for allotting a virtual load port to the physical load port, and instructing the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. 
     In another aspect of this invention, there is provided a substrate treating method for a substrate treating system with a substrate treating apparatus having a physical load port for receiving pods for storing substrates, and a carrier transport system for transporting the pods to and from the physical load port, the substrate treating method comprising allotting a virtual load port to the physical load port, and instructing the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. 
     In a further aspect of this invention, there is provided a substrate treating system with a substrate treating apparatus having a physical load port for receiving pods for storing substrates, and a carrier transport system for transporting the pods to and from the physical load port, the substrate treating system comprising a virtual load port control device for allotting a virtual load port to the physical load port, and instructing the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. 
     According to the invention described above, the virtual load port control device allots a virtual load port to the physical load port, and instructs the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. Therefore, the carrier transport system can be made to perform a transporting operation as if there were more physical load ports than the actual number thereof. As a result, the control apparatus, substrate treating method, and substrate treating system which are capable of improving the efficiency of transporting the pods are realized while holding down apparatus cost, without increasing the mechanical components of the substrate treating apparatus. 
     This invention further provides a method of operating a substrate treating system with a substrate treating apparatus having a physical load port for receiving pods for storing substrates and a physical load port control device for controlling operation of the physical load port, and a carrier transport system for transporting the pods to and from the physical load port, the method of operating the substrate treating system comprising interposing a virtual load port control device between the physical load port control device and the carrier transport system for allotting a virtual load port to the physical load port, and instructing the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. 
     According to the invention, with the virtual load port control device interposed between the physical load port control device and the carrier transport system of a common substrate treating apparatus, a virtual load port can be allotted to the physical load port, and the carrier transport system can be instructed to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists. Therefore, the carrier transport system can be made to perform a transporting operation for the common substrate treating apparatus or an existing substrate treating apparatus as if there were more physical load ports than the actual number thereof. As a result, the efficiency of transporting the pods can easily be improved also for the common substrate treating apparatus or the existing substrate treating apparatus. 
     This invention further provides a load port control apparatus in a substrate treating system with a substrate treating apparatus having a substrate treating unit for carrying out predetermined treatments of substrates, a physical load port for receiving pods for storing the substrates, the load port transferring the pods to and from the substrate treating unit, and an internal buffer interposed between the substrate treating unit and the load port for transferring the substrates to and from the substrate treating unit, transferring the pods to and from the load port, and storing the pods transferred, a carrier transport system for transferring the pods to and from the load port, and a host computer for communicating with the substrate treating apparatus and the carrier transport system, and instructing the carrier transport system to transport the pods according to a situation of the substrate treating apparatus, the load port control apparatus comprising a virtual load port management unit for allotting a plurality of virtual load ports to the physical load port, and causing the carrier transport system and the host computer to treat the plurality of virtual load ports as a plurality of physical load ports. 
     According to this invention, the virtual load port management unit allots a plurality of virtual load ports to the physical load port. Further, the virtual load port management unit causes the carrier transport system and the host computer to treat the plurality of virtual load ports as a plurality of physical load ports. Therefore, the pods can be transported as if there were more load ports than the number of physical load ports, and the number of load ports can in appearance be increased. As a result, the load port control apparatus which is capable of improving the efficiency of transporting the pods can be realized while holding down apparatus cost, without increasing the mechanical components of the substrate treating apparatus. 
     In this invention, the virtual load port management unit may have a conversion table specifying a correspondence relationship between the plurality of virtual load ports and the physical load port, and when the plurality of virtual load ports are set for loading purposes, (A1) the virtual load port management unit reports to the host computer whether each of the virtual load ports is available for loading; (A2) the host computer instructs the carrier transport system to load a pod into one of the virtual load ports; (A3) the carrier transport system holding the pod moves to the substrate treating apparatus in order to transport the pod to the designated one of the virtual load ports; (A4) the carrier transport system, in order to start loading the pod into the one virtual load port, notifies the virtual load port management unit of loading of the pod into the one virtual load port; (A5) the virtual load port management unit matches the one virtual load port with the physical load port based on the conversion table; (A6) the virtual load port management unit notifies the host computer that loading of the pod to the one virtual load port has been started; (A7) the virtual load port management unit accepts the loading into the virtual load port, and sends a load request to the carrier transport system; (A8) the carrier transport system transports the pod to the physical load port allotted to the one virtual load port; (A9) the substrate treating apparatus transports the pod loaded into the one virtual load port to the internal buffer; and (A10) when notifying the host computer of a situation of loading into the one virtual load port in the is loading step, the virtual load port management unit notifies the host computer that a different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for loading, from a point of time when the carrier transport system starts moving to the substrate treating apparatus in order to transport the one designated pod, until before the one designated pod is placed on the physical load port corresponding to the one virtual load port, and notifies the host computer that the different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for loading, at a point of time when the pod begins to be transported to the internal buffer from the physical load port corresponding to the one virtual load port. 
     At the time of loading, the virtual load port management unit notifies the host computer of a situation of loading into one virtual load port. At this time, the virtual load port management unit notifies the host computer that a different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for loading, from a point of time when the carrier transport system starts moving to the substrate treating apparatus in order to transport the one designated pod, until the one designated pod is placed on the physical load port corresponding to the one virtual load port. Further, the virtual load port management unit notifies the host computer that the different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for loading, at a point of time when the pod begins to be transported to the internal buffer from the physical load port corresponding to the one virtual load port. Therefore, also in the conventionally occupied periods at the time of loading, the host computer can give loading instructions, thereby to realize an efficient loading process. 
     In this invention, the virtual load port management unit may have a conversion table specifying a correspondence relationship between the plurality of virtual load ports and the physical load port, and when the plurality of virtual load ports are set for unloading purposes, (B1) the host computer instructs the substrate treating apparatus to deliver a designated pod to one of the virtual load ports; (B2) the substrate treating apparatus, when the designated pod can be delivered to the one virtual load port, notifies the host computer that the pod is ready for unloading; (B3) the host computer instructs the carrier transport system to transport the designated pod; (B4) the carrier transport system moves to the substrate treating apparatus having the designated pod; (B5) the carrier transport system, in order to unload the designated pod from the one virtual load port, instructs the virtual load port management unit to deliver the pod to the one virtual load port; (B6) the virtual load port management unit matches the one virtual load port with the physical load port based on the conversion table; (B8) the substrate treating apparatus delivers the designated pod to the physical load port allotted to the one virtual load port; (B9) the substrate treating apparatus sends an unload request to the carrier transport system; (B10) the carrier transport system unloads the pod from the one virtual load port; and (B11) when notifying the host computer of a situation of unloading from the one virtual load port during the unloading process, the virtual load port management unit is capable of notifying the host computer that a different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for unloading. 
     At the time of unloading, the virtual load port management unit notifies the host computer of a situation of unloading from one virtual load port. At this time, the virtual load port management unit is capable of notifying the host computer that a different virtual load port allotted to the physical load port corresponding to the one virtual load port is available for unloading. Therefore, also in the conventionally occupied period at the time of unloading, the host computer can give unloading instructions, thereby to realize an efficient unloading process. 
     In this invention, the virtual load port management unit may set the virtual load ports only for loading. The virtual load port management unit may set the virtual load ports only for unloading. The virtual load port management unit may set the virtual load ports for loading or unloading. 
     The virtual load port management unit enables flexible operation by setting the virtual load ports only for loading, only for unloading, or mixing these functions. 
     This invention further provides a substrate treating system comprising a substrate treating apparatus having a substrate treating unit for carrying out predetermined treatments of substrates, a physical load port for receiving pods for storing the substrates, the load port transferring the pods to and from the substrate treating unit, and an internal buffer interposed between the substrate treating unit and the load port for transferring the substrates to and from the substrate treating unit, transferring the pods to and from the load port, and storing the pods transferred; a carrier transport system for transferring the pods to and from the load port; a host computer for communicating with the substrate treating apparatus and the carrier transport system, and instructing the carrier transport system to transport the pods according to a situation of the substrate treating apparatus; and a load port control device having a virtual load port management unit for allotting a plurality of virtual load ports to the physical load port, and causing the carrier transport system and the host computer to treat the plurality of virtual load ports as a plurality of physical load ports. 
     According to this invention, the virtual load port management unit of the load port control device allots a plurality of virtual load ports to the physical load port. Further, the virtual load port management unit causes the carrier transport system and the host computer to treat the plurality of virtual load ports as a plurality of physical load ports. Therefore, the pods can be transported as if there were more load ports than the number of physical load ports, and the number of load ports can in appearance be increased. As a result, the substrate treating system which is capable of improving the efficiency of transporting the pods is realized while holding down apparatus cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown. 
         FIG. 1  is a plan view showing an outline of a substrate treating system according to this invention; 
         FIG. 2  is a block diagram showing an outline construction of the substrate treating system; 
         FIG. 3  is a time chart showing a sequence of a loading process; 
         FIG. 4  is a schematic view showing the loading process and a notice to a host computer; 
         FIG. 5  is a schematic view showing the loading process and transport instructions from the host computer; 
         FIG. 6  is a schematic view showing the loading process and a movement of a carrier transport system; 
         FIG. 7  is a schematic view showing the loading process and a start of loading by the carrier transport system; 
         FIG. 8  is a schematic view showing the loading process and matching of load ports; 
         FIG. 9  is a schematic view showing the loading process and a report on a state change of a virtual load port; 
         FIG. 10  is a schematic view showing the loading process and a load reception; 
         FIG. 11  is a schematic view showing the loading process and a movement of the carrier transport system; 
         FIG. 12  is a schematic view showing the loading process and movement of a FOUP to an internal buffer; 
         FIG. 13  is a schematic view showing the loading process and a report on a loading situation; 
         FIG. 14  is a time chart showing a sequence of an unloading process; 
         FIG. 15  is a schematic view showing the unloading process and unload instructions from the host computer; 
         FIG. 16  is a schematic view showing the unloading process and an unload ready notice to the host computer; 
         FIG. 17  is a schematic view showing the unloading process and unload instructions from the host computer; 
         FIG. 18  is a schematic view showing the unloading process and a movement of the carrier transport system; 
         FIG. 19  is a schematic view showing the unloading process and a start of unloading by the carrier transport system; 
         FIG. 20  is a schematic view showing the unloading process and matching of the load ports; 
         FIG. 21  is a schematic view showing the unloading process and a report on a state change of a virtual load port; 
         FIG. 22  is a schematic view showing the unloading process and showing a delivery; 
         FIG. 23  is a schematic view showing the unloading process and a transport request to the carrier transport system; 
         FIG. 24  is a schematic view showing the unloading process and unloading of a FOUP by the carrier transport system; 
         FIG. 25  is a schematic view showing the unloading process and a report on an unloading situation; 
         FIG. 26  is a schematic view showing an exchange of signals among the components during the loading process; and 
         FIG. 27  is a schematic view showing an exchange of signals among the components during the unloading process. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of this invention will be described hereinafter with reference to the drawings. 
       FIG. 1  is a plan view showing an outline of a substrate treating system according to this invention.  FIG. 2  is a block diagram showing an outline construction of the substrate treating system. 
     The substrate treating system  1  in this embodiment has functions to receive wafers W along with FOUPs  3 , treat the wafers W and deliver the treated wafers W along with the FOUPs  3 . FOUP is an abbreviation of Front Opening Unified Pod, and the FOUPs  3  store wafers W in a sealed condition to secure clean environment. 
     This substrate treating system  1  includes substrate treating apparatus  5 , a carrier transport system  7 , and a host computer  9 . It is general practice to provide a plurality of substrate treating apparatus  5 , and  FIG. 1  shows two substrate treating apparatus  5  by way of example. 
     Each substrate treating apparatus  5  has a substrate treating unit  11 , a load port  13 , and an internal buffer  15 . The substrate treating unit  11  carries out predetermined treatments of the wafers W taken out of the FOUPs  3 . The predetermined treatments include cleaning treatment, etching treatment, and photoresist removing treatment, for example. The load port  13  serves for transferring the FOUPs  3  between the substrate treating apparatus  5  and the carrier transport system  7 . In this example, the load port  13  includes two physical load ports R-LP 1  and R-LP 2 . The internal buffer  15  is disposed between the substrate treating unit  11  and the load port  13  for transferring FOUPs  3  to and from the load port  13 , and transferring the wafers W taken out of the FOUPs  3  to and from the substrate treating unit  11 . The internal buffer  15  has a buffering function to store temporarily the FOUPs  3  loaded from the load port  13  when the substrate treating unit  11  is in a state not capable of accepting the wafers W, and store temporarily the FOUPs  3  when the load port  13  is in a state not capable of accepting delivery of the FOUPs  3 . 
     The above FOUPs  3  correspond to the “pods” in this invention. 
     The carrier transport system  7  transports FOUPs  3  between the substrate treating apparatus  5  and a depository (not shown) which stores a plurality of FOUPs  3 , or to and from other substrate treating apparatus. The carrier transport system  7  may be AMHS (Automated Material Handling Systems) such as AGV (Automatic Guided Vehicle) or OHT (Overhead Hoist Transport), for example. This embodiment employs a construction, as an example, in which a plurality of OHTs  17  circulate in an area adjacent the two substrate treating apparatus  5 . 
     The host computer  9  communicates with the substrate treating apparatus  5  and carrier transport system  7  described above. The host computer  9  instructs for transportation of the FOUPs  3  by the carrier transport system  7  according to situations of the substrate treating apparatus  5 . The “transportation” here refers to “loading” which is transportation for carrying the FOUPs  3  into the substrate treating apparatus  5 , and “unloading” which is transportation for carrying the FOUPs  3  out of the substrate treating apparatus  5 . 
     As shown in  FIG. 2 , each substrate treating apparatus  5  includes a load port control device  20  formed of a host-related control unit  21 , a load port management unit  23 , and a transport-related control unit  25 . These host-related control unit  21 , load port management unit  23 , and transport-related control unit  25  constituting the load port control device  20  have the same functions as included in a common substrate treating apparatus. That is, in a common substrate treating system, the load port management unit  23  is connected to the physical load ports R-LP 1  and R-LP 2  of the load port  13  and the internal buffer  15  provided for each substrate treating apparatus  5 , to recognize states of these components through communication therewith and manage them such as by controlling operations thereof. In the common substrate treating system, the host-related control unit  21  is connected to the host computer  9  to communicate a request for loading FOUPs  3  to the host computer  9 , for example, by referring to the states of the physical load ports R-LP 1  and R-LP 2  recognized by the load port management unit  23 . In the common substrate treating system, the transport-related control unit  25  is connected to the carrier transport system  7  to perform communications relating to control of loading of the FOUPs  3  (such as CS signals to be described hereinafter) with the carrier transport system  7  by referring to the states of the physical load ports R-LP 1  and R-LP 2  recognized by the load port management unit  23 , for example. 
     In this embodiment, as distinct from the common substrate treating system noted above, a virtual load port control device  19  is interposed and connected between the host-related control unit  21  and the host computer  9 , and between the transport-related control unit  25  and the carrier transport system  7 . That is, the substrate treating system  1  in this embodiment is constructed by post-installing the virtual load port control device  19  between the common substrate treating apparatus and the host computer  9  and carrier transport system  7 . Here, the virtual load port control device  19  connected in post-installation is considered also to be included in the substrate treating apparatus  5 . 
     The load port control device  19  allots a plurality of virtual load ports to each of the two physical load ports R-LP 1  and R-LP 2 . The load port control device  19  causes the carrier transport system  7  and host computer  9  to treat the plurality of virtual load ports as a plurality of physical load ports. In other words, the virtual load port control device  19  carries out signal processing and communication in a way to indicate to the carrier transport system  7  and host computer  9  as if there were more physical load ports than the two real physical load ports R-LP 1  and R-LP 2 . 
     Regarding operations of the host computer  5  and carrier transport system  7  which behave as if there were more physical load ports than there actually are, the host-related control unit  21  and transport-related control unit  25  allot the required responses to the two real physical load ports R-LP 1  and R-LP 2 . Specifically, the virtual load port control device  19  includes a host-related control unit  27 , a virtual load port management unit  29 , and a transport-related control unit  31 . The virtual load port management unit  29  has a conversion table storage unit  33 . The conversion table storage unit  33  stores, inputted thereto beforehand, a “conversion table” which specifies a correspondence relationship between physical load ports and virtual load ports. This conversion table is set as appropriate by the operator through a setting unit  35 . 
     The host-related control unit  27  receives a notice concerning the physical load ports R-LP 1  and R-LP 2  from the load port management unit  23 , refers to the information in the virtual load port management unit  29 , converts the notice into a notice concerning the virtual load ports allotted to such physical load ports, and transmits the converted notice to the host computer  9 . 
     The transport-related control unit  31  receives a notice concerning virtual load ports V-LP 1 -V-LP 4  from the carrier transport system  7 , refers to the information in the virtual load port management unit  29 , converts the notice into a notice concerning the physical load ports allotted to such virtual load ports, and transmits the converted notice to the transport-related control unit  25 . Conversely, the transport-related control unit  31  receives a notice concerning the physical load ports R-LP 1  and R-LP 2  from the transport-related control unit  25 , refers to the information in the virtual load port management unit  29 , converts the notice into a notice concerning the virtual load ports allotted to such physical load ports, and transmits the converted notice to the carrier transport system  7 . 
     &lt;A: Loading Process&gt; 
     Next, a flow of “loading” of the FOUPs  3  by the above substrate treating system  1  will be described with reference to  FIGS. 3-13  and  FIG. 26 . 
       FIG. 3  is a time chart showing a sequence of a loading process.  FIGS. 4-13  are schematic views showing the loading process.  FIG. 4  shows a notice to the host computer.  FIG. 5  shows transport instructions from the host computer.  FIG. 6  shows a movement of the carrier transport system.  FIG. 7  shows a start of loading by the carrier transport system.  FIG. 8  shows matching of the load ports.  FIG. 9  shows a report on a state change of a virtual load port.  FIG. 10  shows a load reception.  FIG. 11  shows a movement of the carrier transport system.  FIG. 12  shows movement of a FOUP to the internal buffer.  FIG. 13  shows a report on a loading situation.  FIG. 26  is a schematic view showing an exchange of signals among the components during the loading process. 
     In the following description, it is assumed that, as shown in  FIG. 4 , the physical load port R-LP 1  is matched with two virtual load ports V-LP 1  and V-LP 2 , and the physical load port R-LP 2  with two virtual load ports V-LP 3  and V-LP 4 . This correspondence relationship is specified on the conversion table in the conversion table storage unit  33  noted hereinbefore. It is also assumed here that the two virtual load ports V-LP 1  and V-LP 2  are set for loading purposes. To facilitate understanding, description will be made hereinafter only of the virtual load ports V-LP 1  and V-LP 2 . 
     1. The substrate treating apparatus  5  notifies the host computer  9  as to whether the two virtual load ports V-LP 1  and V-LP 2  are available for loading ( FIG. 4 ). Specifically, the host-related control unit  27  of the virtual load port control device  19  refers to the virtual load port management unit  29 , and notifies the host computer  9  that the load ports named virtual load ports V-LP 1  and V-LP 2  are available for loading. 
     To describe this in greater detail, the load port management unit  23  which manages the physical load port R-LP 1  first recognizes the state of the physical load port R-LP 1  as “available for loading”. In response to this, the host-related control unit  21  refers to the recognition by the load port management unit  23  and outputs an “available” notice. With the conventional common construction, this output would be transmitted directly to the host computer  9 . However, in this invention, the “available” notice outputted from the host-related control unit  21  is transmitted to the host-related control unit  27  of the virtual load port control unit  19 . Upon receipt of this notice, the load port management unit  29  refers to the conversion table stored in the internal conversion table storage unit  33 , and recognizes that the physical load port R-LP 1  notified as “available” is matched with the virtual load ports V-LP 1  and V-LP 2 . Then, the virtual load port management unit  29  notifies the host-related control unit  27  that, instead of the physical load port R-LP 1  notified as “available”, both virtual load ports V-LP 1  and V-LP 2  are to be treated as “available”. Based on such notice, the host-related control unit  27  notifies the host computer  9  that both virtual load ports V-LP 1  and V-LP 2  are “available”. 
     2. Having received the above notice, the host computer  9  instructs the carrier transport system  7  to load two FOUPs  3  to be processed by the substrate treating apparatus  5 , into both virtual load ports V-LP 1  and V-LP 2 , respectively ( FIG. 5 ). 
     3. The carrier transport system  7  fetches a first and a second FOUPs  3  from a substrate treating apparatus at an upstream stage or from the depository. With a first OHT  17  holding the first FOUP  3  and a second OHT  17  holding the second FOUP  3 , each starts moving toward the substrate treating apparatus  5  from which the loading instructions have originated. It is assumed here that both the first OHT  17  and second OHT  17  carry out the loading into the same substrate treating apparatus  5 , and that the first OHT  17  is in a position to reach the substrate treating apparatus  5  earlier, with the second OHT  17  in a position to reach the substrate treating apparatus  5  thereafter. 
     4. When the first OHT  17  arrives at the substrate treating apparatus  5 , the carrier transport system  7  notifies the substrate treating apparatus  5  that the first FOUP  3  will be loaded into the virtual load port V-LP 1  ( FIG. 7 ). Specifically, the carrier transport system  7  turns on CS_ 0  signal, further turns on a VALID signal indicating a transport start, and transmits the signals to the transport-related control unit  31 . The CS signal is a carrier stage signal used for designation of the load ports, and is prescribed by SEMI standard E 84 . 
     5. The substrate treating apparatus  5  refers to the CS_ 0  signal (indicating the virtual load port V-LP 1 ) received from the carrier transport system  7  and the conversion table, and matches the virtual load port V-LP 1  with one corresponding physical load port R-LP 1  ( FIG. 8 ). Specifically, based on the signal received by the transport-related control unit  31 , the virtual load port management unit  29  performs the matching. 
     6-1. The substrate treating apparatus  5  reports to the host computer  9  the start of loading into the virtual load port V-LP 1  as a change of state ( FIG. 9 ). Specifically, the virtual load port management unit  29  reports it to the host computer  9  through the host-related control unit  27 . 
     6-2. The host computer  9  having received the report recognizes that loading has started at the virtual load port V-LP 1  ( FIG. 9 ). 
     7. In order to accept in the physical load port R-LP 1  the first FOUP  3  transported by the carrier transport system  7  toward the virtual load port V-LP 1 , the substrate treating apparatus  5  instructs the physical load port R-LP 1  to accept the first FOUP  3 , and requests the carrier transport system  7  to carry out a loading operation ( FIG. 10 ). Specifically, the virtual load port management unit  29  communicates instructions to the transport-related control unit  25  through the transport-related control unit  31  for loading into the physical load port R-LP  1 . Upon receipt of this communication, the transport-related control unit  25  instructs the load port management unit  23  to carry out an operation for loading into the physical load port R-LP 1 , and requests the transport-related control unit  31  to make a “loading start” for the physical load port R-LP 1 . Such a request signal would be transmitted to the carrier transport system  7  if this were a conventional substrate treating system. In this invention, this request signal is transmitted to the transport-related control unit  31  of the virtual load port control device  19 . 
     The transport-related control unit  31  can recognize that the “loading start” request signal from the transport-related control unit  25  is a response to the notice of loading of the first FOUP  3  into the virtual load port V-LP 1  received from the carrier transport system  7  in step  4  above. Based on such recognition, the transport-related control unit  31  transmits such “loading start” request signal to the carrier transport system  7  as “loading start” request relating to the virtual load port V-LP  1 . As such request signal, the transport-related control unit  31  turns on L_REQ signal for the carrier transport system  7 . L_REQ stands for load request. 
     8. In response to the “loading start” request from the transport-related control unit  31 , the carrier transport system carries out an operation for transporting the first FOUP  3  held by the first OHT  17  toward the virtual load port V-LP 1 . The carrier transport system  7  has an actual position of the physical load port R-LP 1  set thereto as position information on the virtual load port V-LP 1  which is the destination of the transportation at this time. Thus, the transportation to the virtual load port V-LP 1  by the carrier transport system  7  will be performed in reality as transportation to the physical load port R-LP 1  ( FIG. 11 ). 
     9. The substrate treating apparatus  5  transports the first FOUP  3  loaded into the physical load port R-LP 1  to an appropriate position in the internal buffer  15  ( FIG. 12 ). 
     10. In the above loading process, the substrate treating apparatus  5  reports to the host computer  9  completion of the loading of the first FOUP  3  into the physical load port R-LP  1  as completion of the loading into the virtual load port V-LP 1  ( FIG. 13 ). Specifically, the load port management unit  23  recognizes the situation of the physical load port R-LP 1 , and reports it to the host computer  9  through the host-related control unit  21  and host-related control unit  27 . 
     At this time, the host-related control unit  21  transmits to the host-related control unit  27  the “loading completion” report on the physical load port R-LP 1  received from the load port management unit  23 . The host-related control unit  27  can recognize that the “loading completion” report from the host-related control unit  21  is a response to the notice of the start of loading the first FOUP  3  into the virtual load port V-LP 1 , which notice has been received from the virtual load port management unit  29  in step  6  above. Based on such recognition, the host-related control unit  27  transmits the “loading completion” report to the host computer  9  as a “loading completion” report on the virtual load port V-LP  1 . 
     When, in step  9  above, the first FOUP  3  loaded into the physical load port R-LP 1  has been transported to the internal buffer  15 , the physical load port R-LP 1  becomes capable of accepting a FOUP  3  again. Thus, as in step  1  above, the load port management unit  23  recognizes the state of the physical load port R-LP 1  as “available”. Consequently, the host-related control unit  21  refers to the recognition by the load port management unit  23 , and transmits an “available” notice to the host-related control unit  27  of the virtual load port control device  19 . In response thereto, the host-related control unit  27  recognizes that the virtual load port V-LP  1  has become “available”, as in the case of the above “loading completion” report, and notifies this to the host computer  9 . Such “available” notice will be made immediately or with a slight delay after the above “loading completion” report, depending on the timing of transportation of the FOUP  3  to the internal buffer  15 . In the described case, the “available” state of the virtual load port V-LP 2  has already been reported in step  1  above, and accordingly, the second OHT  17  has already started transporting the second FOUP  3 . Here, therefore, no new notice is made with regard to the virtual load port V-LP 2 . 
     11. When the second OHT  17  arrives at the substrate treating apparatus  5  slightly later than the first OHT  17 , the carrier transport system  7 , as in step  4  above, notifies the substrate treating apparatus  5  that the second FOUP  3  will be loaded into the virtual load port V-LP 2 . Specifically, the carrier transport system  7  turns on CS_ 1  (indicating the virtual load port V-LP 2 ), further turns on the VALID signal indicating a transport start, and transmits the signals to the transport-related control unit  31 . Subsequently, as described hereinbefore, a loading into the physical load port R-LP 1  is carried out as loading into the virtual load port V-LP 2 . 
     When there is only one FOUP  3 , i.e. the first FOUP  3 , to be treated by the substrate treating apparatus  5  at the time of step  2  above, the host computer  9  instructs for transportation to the virtual load port V-LP 1 , but does not instruct for transportation to the virtual load port V-LP 2  immediately. The host computer  9  will wait until a second FOUP  3  to be treated becomes ready. 
     According to this embodiment, two virtual load ports V-LP 1  and V-LP 2  are allotted to one physical load port V-LP 1 , with both of the virtual load ports V-LP 1  and V-LP 2  being “available”, two OHTs  17  can be moved at the same time to transport FOUPs  3  to the respective load ports V-LP 1  and V-LP 2 . Compared with the case of only one OHT  17  engaging in the transporting operation for one physical load port R-LP 1 , this embodiment can increase the number of FOUPs  3  transportable per unit time. In other words, the time taken for transporting each FOUP  3  can be shortened. 
     As seen also from  FIG. 26 , the virtual load port control device  19  handles only signals relating to the physical load port R-LP 1  in the communication with the host-related control unit  21  and transport-related control unit  25  which are inherent in the substrate treating apparatus  5 , and handles only signals relating to the virtual load ports V-LP 1  and V-LP 2  in the communication with the host computer  9  and carrier transport system  7 . That is, the virtual load port control device  19  is interposed between the substrate treating apparatus  5  and the host computer  9 /carrier transport system  7  to carry out matching of the physical load port R-LP 1  and the virtual load ports V-LP 1  and V-LP 2 , and conversion of the signals. The controls according to this invention can be implemented easily, without changing in any way the constructions of hardware and software of the conventional substrate treating apparatus  5 , host computer  9  and carrier transport system  7 , and only by interposing the virtual load port control device  19  in between. The construction of the conventional substrate treating system can easily be reinstated only by removing the virtual load port control device  19 . 
     The virtual load port V-LP 2  is another virtual load port matched with the same physical load port R-LP 1 . In the above loading process, from the point of time when an OHT  17  of the carrier transport system  7  starts moving to the substrate treating apparatus  5  in order to transport one FOUP  3  until the FOUP  3  is actually placed in the physical load port R-LP  1  corresponding to one virtual load port V-LP 1 , the virtual load port control device  19  reports to the host computer  9  that loading can be made into the virtual load port V-LP 2  which is the another virtual load port. Further, at the point of time when the FOUP  3  begins to be transported to the internal buffer  15  from the physical load port R-LP  1  corresponding to the one virtual load port V-LP 1 , the virtual load port control device  19  reports to the host computer  9  that loading can be made into the virtual load port V-LP 2  which is the another virtual load port different from the virtual load port V-LP 1 , and is matched with the physical load port R-LP 1  corresponding to the virtual load port V-LP 1 . 
     Thus, during the above periods, the host computer  9  can instruct the carrier transport system  7  to load a FOUP into the physical load port R-LP 1  by turning on the CS_ 1  signal indicating the virtual load port V-LP 2 . Therefore, also in the conventionally occupied periods, the host computer  9  can give loading instructions, thereby to realize an efficient loading process. 
     In the above example, the transportation of the preceding (first) FOUP  3  to the virtual load port V-LP 1  is completed, this FOUP  3  is taken into the internal buffer  15 , and then the following (second) FOUP  3  is loaded into the virtual load port V-LP 2  allotted to the same physical load port R-LP 1 . Therefore, no problem arises in the loading into the same physical load port R-LP  1 . If time is consumed in taking in the preceding (first) FOUP  3  and the following (second) FOUP  3  arrives at the same physical load port R-LP 1 , the following (second) FOUP  3  will be put on standby on the spot. This control is realized, for example, by carrying out the following process. In step  4  above, the notice of starting loading of the first FOUP  3  into the virtual load port V-LP 1  is inputted from the carrier transport system  7  to the transport-related control unit  31 . Even if a notice of starting loading of the second FOUP  3  to the other virtual load port V-LP 2  is inputted immediately thereafter, operation will be suspended instead of proceeding to the next step  5 , in response to the notice of starting loading of the second FOUP  3 . When the “loading completion” notice to the physical load port R-LP 1  of the first FOUP  3  is transmitted to the host-related control unit  27  in step  10  above, the host-related control unit  27  may notify this to the transport-related control unit  31 , thereby to cancel this suspended state. In another conceivable process, after the notice of starting loading of the first FOUP  3  to the virtual load port V-LP 1  is inputted from the carrier transport system  7  to the transport-related control unit  31  in step  4  above, even if the notice of starting loading to the other virtual load port V-LP 2 , operation in response to this loading start notice is suspended, instead of proceeding to the next step  5 , for at least a predetermined time from the point of time when the notice of starting loading of the first FOUP  3  is inputted (e.g. for a time sufficient to enable the transportation from the load port  13  to the internal buffer  15 ). 
     Even if the start of loading of the FOUP  3  is suspended as described above, compared with the conventional substrate treating system in which instructions for loading the next (second) FOUP  3  are given only after the preceding FOUP  3  is taken into the internal buffer  15 , making the physical load port R-LP 1  available for the next loading, this invention, with the transportation of the next (second) FOUP  3  started early, can carry out a more efficient transportation despite such an idle situation than the prior art. 
     &lt;B: Unloading Process&gt; 
     Next, a flow of unloading of FOUPs  3  by the above substrate treating system  1  will be described with reference to  FIGS. 14-25  and  FIG. 27 . 
       FIG. 14  is a time chart showing a sequence of an unloading process.  FIGS. 15-25  are schematic views showing the unloading process.  FIG. 15  shows unload instructions from the host computer.  FIG. 16  shows an unload ready notice to the host computer.  FIG. 17  shows unload instructions from the host computer.  FIG. 18  shows a movement of the carrier transport system.  FIG. 19  shows a start of unloading by the carrier transport system.  FIG. 20  shows matching of the load ports.  FIG. 21  shows a report on a state change of a virtual load port.  FIG. 22  shows a delivery.  FIG. 23  shows a transport request to the carrier transport system.  FIG. 24  shows unloading of a FOUP by the carrier transport system.  FIG. 25  shows a report on an unloading situation.  FIG. 27  is a schematic view showing an exchange of signals among the components during the unloading process. 
     In the following description, it is assumed that, as shown in  FIG. 15 , the physical load port R-LP 1  is matched with the two virtual load ports V-LP 1  and V-LP 2 , and the physical load port R-LP 2  with the two virtual load ports V-LP 3  and V-LP 4 . It is also assumed here that the two virtual load ports V-LP 3  and V-LP 4  are set for unloading purposes. To facilitate understanding, description will be made hereinafter only of the virtual load ports V-LP 3  and V-LP 4 . 
     1. The host computer  9  instructs the substrate treating apparatus  5  to deliver FOUPs  3  storing treated wafers W ( FIG. 15 ). It is assumed here, for example, that instructions require processed FOUPs  3  stored in the internal buffer  15  of the substrate treating apparatus  5  to be delivered successively to a substrate treating apparatus at a downstream stage or to the depository of FOUPs  3  not shown. These instructions are given to the load port management unit  23  via the host-related control unit  27  and host-related control unit  21  (not shown in  FIG. 27 ). 
     2. When the designated FOUPs  3  become ready for delivery to the physical load port R-LP 2 , the substrate treating apparatus  5  notifies the host computer  9  that the FOUPs  3  are ready for unloading, without actually delivering the FOUPs  3  ( FIG. 16 ). 
     To describe this in greater detail, the load port management unit  23 , which manages the physical load port R-LP 2  for unloading, first confirms states of the physical load port R-LP 2  and internal buffer  15 . And in response to the instructions from the host computer  9 , the load port management unit  23  recognizes that the processed FOUPs  3   a  and  3   b  stored in the internal buffer  15  are “ready for unloading” from the physical load port R-LP 2 . Based on this, the host-related control unit  21  refers to the recognition by the load port management unit  23 , and outputs a notice of the FOUPs  3   a  and  3   b  being “ready for unloading” from the physical load port R-LP 2 . With the conventional common construction, this output of “ready for unloading” notice would be transmitted directly to the host computer  9 . However, in this invention, the “ready for unloading” notice outputted from the host-related control unit  21  is transmitted to the host-related control unit  27  of the virtual load port control unit  19 . The host-related control unit  27  notifies the virtual load port management unit  29  of the receipt of this notice. Upon receipt of this notice, the virtual load port management unit  29  refers to the conversion table stored in the internal conversion table storage unit  33 , and recognizes that the physical load port R-LP 2  notified as “ready for unloading” is matched with the virtual load ports V-LP 3  and V-LP 4 . Then, the virtual load port management unit  29  notifies the host-related control unit  27  that, instead of the physical load port R-LP 2  notified as “ready for unloading”, both virtual load ports V-LP 3  and V-LP 4  are to be treated as “ready for unloading”. Based on such notice, the host-related control unit  27  notifies the host computer  9  that both virtual load ports V-LP 3  and V-LP 4  are “ready for unloading” of the FOUPs  3   a  and  3   b.    
     3. The host computer  9  instructs the carrier transport system  7  to carry out transportation for fetching the designated FOUPs  3   a  and  3   b  ( FIG. 17 ). 
     4. In order to unload the designated FOUPs  3   a  and  3   b , the carrier transport system  7  moves two OHTs  17   a  and  17   b  to the substrate treating apparatus  5  having the FOUPs  3   a  and  3   b  ( FIG. 18 ). The OHT  17   a  takes charge of transportation of the FOUP  3   a  from the virtual load port V-LP 3 , and the OHT  17   b  transportation of the FOUP  3   b  from the virtual load port V-LP 4 . The carrier transport system  7  has an actual position of the physical load port R-LP 2  set thereto as position information on the virtual load ports V-LP 1  and V-LP 2  which are the destinations at this time. Thus, the movement of the OHTs  17   a  and  17   b  of the carrier transport system  7  will be performed in reality as movement to the physical load port R-LP 2 . 
     5. When the OHT  17   a  which is due to unload the FOUP  3   a  arrives at the virtual load port V-LP 3  (physical load port R-LP 2 ) of the substrate treating apparatus  5 , the carrier transport system  7 , in order to start unloading from the virtual load port V-LP 3 , turns on the CS_ 0  signal indicating the virtual load port V-LP 3 , and turns on the VALID signal (transport start) ( FIG. 19 ). These signals are received by the virtual load port management unit  29  through the transport-related control unit  31 . 
     6. The substrate treating apparatus  5  identifies the virtual load port V-LP 3  in response to the CS_ 0  signal ( FIG. 20 ). Specifically, the virtual load port management unit  29  identifies the virtual load port V-LP 3 . 
     7-1. With the start of unloading from the virtual load port V-LP 3 , the substrate treating apparatus  5  reports a change of state of the virtual load port V-LP 3  to the host computer  9  ( FIG. 21 ). Specifically, the virtual load port management unit  29  reports this to the host computer  9  through the host-related control unit  27 . 
     7-2. The host computer  9  having received the report recognizes that unloading has started at the virtual load port V-LP 3  ( FIG. 21 ). 
     8. The substrate treating apparatus  5  delivers the designated FOUP  3   a  to the virtual load port V-LP 3  ( FIG. 22 ). In practice, since the virtual load port V-LP 3  is matched with the physical load port R-LP 2 , the FOUP  3   a  is delivered to the physical load port R-LP 2 . To describe this specifically, the virtual load port management unit  29 , which identified the virtual load port V-LP 3  in step  6  above, recognizes from the conversion table stored in the conversion table storage unit  33  that the virtual load port V-LP 3  identified corresponds to the physical load port R-LP 2 , and instructs the transport-related control unit  31  to perform unloading from the physical load port R-LP 2 . Upon such instructions, the transport-related control unit  31  communicates the instructions to the transport-related control unit  25  that unloading should be made from the physical load port R-LP 2 . The transport-related control unit  25  having received this communication instructs the load port management unit  23  to carry out an operation to unload the FOUP  3   a  from the physical load port R-LP 2 , and transmits an “unload start” request to the transport-related control unit  31 . Such a request signal would be transmitted to the carrier transport system  7  if this were a conventional substrate treating system. In this invention, this request signal is transmitted to the transport-related control unit  31  of the virtual load port control device  19 . Based on such instructions, the load port management unit  23  carries out an operation for delivering the FOUP  3   a  stored in the internal buffer  15  to the physical load port R-LP 2 . 
     9. The substrate treating apparatus  5  turns on a signal indicating a transport request for the carrier transport system  7  ( FIG. 23 ). Specifically, the transport-related control unit  31  can recognize that the request signal received from the transport-related control unit  25  and indicating “unload start” for the above physical load port R-LP 2  is a response to the notice of unloading of the FOUP  3   a  from the virtual load port V-LP 3  received from the carrier transport system  7  in step  5  above. Based on such recognition, the transport-related control unit  31  transmits such request signal of “unload start” to the carrier transport system  7  as “unload start” request relating to the virtual load port V-LP 3 . As such request signal, the transport-related control unit  31  turns on U_REQ signal for the carrier transport system  7 . U_REQ stands for unload request. 
     10. The carrier transport system  7  unloads the FOUP  3   a  from the virtual load port V-LP 3  ( FIG. 24 ). In practice, since the virtual load port V-LP 3  corresponds to the physical load port R-LP 2 , the FOUP  3   a  is unloaded from the physical load port R-LP 2 . 
     11. The substrate treating apparatus  5  reports to the host computer  9  that the unloading has been carried out at the virtual load port V-LP 3  in the above unloading process ( FIG. 25 ). Specifically, the load port management unit  23  recognizes the situation of the physical load port R-LP 2 , and transmits a report to the host computer  9  through the host-related control unit  21  and host-related control unit  27 . 
     At this time, the host-related control unit  21  transmits to the host-related control unit  27  the “unloading completion” report on the physical load port R-LP 2  received from the load port management unit  23 . The host-related control unit  27  can recognize that the “unloading completion” report from the host-related control unit  21  is a response to the notice of the start of unloading the FOUP  3   a  from the virtual load port V-LP 3 , which notice was received from the virtual load port management unit  29  in step  7  above. Based on such recognition, the host-related control unit  27  transmits the “unloading completion” report to the host computer  9  as an “unloading completion” report on the virtual load port V-LP 3 . 
     When a new next FOUP  3   c  (Not shown) storing treated wafers W is subsequently transported to the internal buffer  15 , the physical load port R-LP 2  will become ready for unloading again. That is, the virtual load port V-LP 3  corresponding to the physical load port R-LP 2  becomes ready for unloading again. Thus, as in step  2  above, the load port management unit  23  recognizes the state of the physical load port R-LP 2  as “ready for unloading”. Consequently, the host-related control unit  21  refers to the recognition by the load port management unit  23 , and transmits a “ready” notice to the host-related control unit  27  of the virtual load port control device  19 . In response thereto, the host-related control unit  27  recognizes that the virtual load port V-LP 3  has become “ready”, as in the case of the above “unloading completion” report, and notifies this to the host computer  9 . Such “ready” notice will be made immediately or with a slight delay after the above “unloading completion” report, depending on the timing of transportation of the FOUP  3   c  to the internal buffer  15 . In the described case, the “ready” state of the virtual load port V-LP 4  has already been reported in step  2  above, and accordingly, the OHT  17   b  has already started moving to the substrate treating apparatus  5 . Here, therefore, no new notice is made with regard to the virtual load port V-LP 4 . 
     12. When the OHT  17   b  arrives at the substrate treating apparatus  5  slightly later than the OHT  17   a , the carrier transport system  7 , as in step  4  above, notifies the substrate treating apparatus  5  that the FOUP  3   b  will be unloaded from the virtual load port V-LP 4 . Specifically, the carrier transport system  7  turns on CS_ 1  (indicating the virtual load port V-LP 4 ), further turns on the VALID signal indicating a transport start, and transmits the signals to the transport-related control unit  31 . Subsequently, as described hereinbefore, an unloading from the physical load port R-LP 2  is carried out as unloading from the virtual load port V-LP 4 . 
     The virtual load port V-LP 4  is the other virtual load port matched with the same physical load port R-LP 2 . Even when only the processed FOUP  3   a  is stored in the internal buffer  15  in step  1  of the above unloading process, the virtual load port control device  19  notifies the host computer  9  that the other virtual load port V-LP 4  allotted to the physical load port R-LP 2  corresponding to the one virtual load port V-LP 3  is available for unloading at any time. 
     Therefore, the host computer  9  can instruct the carrier transport system  7  to unload from the same physical load port R-LP 2  in the above period by turning on the CS_ 1  signal indicating the virtual load port V-LP 4 . Thus, an efficient unloading can be carried out. 
     According to this embodiment, two virtual load ports V-LP 3  and V-LP 4  are allotted to one physical load port V-LP 2 , with both of the virtual load ports V-LP 3  and V-LP 4  being “ready for unloading”, and two OHTs  17  can be moved at the same time to transport FOUPs  3  from the respective load ports V-LP 3  and V-LP 4 . Compared with the case of only one OHT  17  engaging in the transporting operation for one physical load port R-LP 2 , this embodiment can increase the number of FOUPs transportable per unit time. In other words, the time taken for transporting each FOUP can be shortened. 
     As seen from  FIG. 27 , the virtual load port control device  19  handles only signals relating to the physical load port R-LP 2  in the communication with the host-related control unit  21  and transport-related control unit  25  which are inherent in the substrate treating apparatus  5 , and handles only signals relating to the virtual load ports V-LP 3  and V-LP 4  in the communication with the host computer  9  and carrier transport system  7 . That is, the virtual load port control device  19  is interposed between the substrate treating apparatus  5 , and the host computer  9 /carrier transport system  7  to carry out matching of the physical load port R-LP 2  and the virtual load ports V-LP 3  and V-LP 4 , and conversion of the signals. The controls according to this invention can be implemented easily, without changing in any way the constructions of hardware and software of the conventional substrate treating apparatus  5 , host computer  9  and carrier transport system  7 , and only by interposing the virtual load port control device  19  in between. The construction of the conventional substrate treating system can easily be reinstated only by removing the virtual load port control device  19 . 
     According to this embodiment, as described above, the virtual load port control device  19  allots two virtual load ports V-LP 1  and V-LP 2  or V-LP 3  and V-LP 4  to each of the physical load ports R-LP 1  and R-LP 2 . Further, the virtual load port control device  19  causes the carrier transport system  7  and host computer  9  to treat the four virtual load ports V-LP 1 , V-LP 2 , V-LP 3  and V-LP 4  as four physical load ports. Therefore, the FOUPs  3  can be transported as if there were more load ports than the actual number of physical load ports, and can in appearance increase the number of load ports. As a result, the efficiency of transporting FOUPs  3  can be improved while holding down apparatus cost. 
     This invention is not limited to the foregoing embodiment, but may be modified as follows: 
     (1) The foregoing embodiment allots two virtual load ports V-LP 1  and V-LP 2  to one physical load port R-LP 1 . This invention is not limited to this. For example, three or more virtual load ports may be allotted to one physics load port R-LP 1 . 
     (2) The foregoing embodiment allots two virtual load ports V-LP 1  and V-LP 2  to one physical load port R-LP 1 , allots virtual load ports V-LP 3  and V-LP 4  to the other physical load port R-LP 2 , and allots them to either loading or unloading. Apart from such allotment, this invention may allot one of the two virtual load ports allotted to one physical load port to loading, and the other to unloading. A virtual load port may be allotted to only one of the loading and unloading. 
     (3) In the foregoing embodiment, the conversion table stored in the conversion table storage unit  33  is set as fixed through the setting unit  35 . The conversion table may be rewritten as appropriate according to situations, to change use/non-use of the virtual load ports and allotment of the virtual load ports dynamically. This enables flexible operation according to situations of the substrate treating system  1 . When it is desired to perform loading quickly, an increased number of virtual load ports may be allotted to the loading. 
     (4) In the foregoing embodiment, the carrier transport system  7  is illustrated as having OHTs  17 . These may be replaced with AGVs (Automatic Guided Vehicles). 
     (5) In the foregoing embodiment, the virtual load port control device  19  is post-installed between a common substrate treating apparatus and the host computer  9 /carrier transport system  7 . The efficiency of transporting the FOUPs is improved by adding the virtual load port control device  19  of this invention to a common substrate treating apparatus or an existing substrate treating apparatus already installed in a factory or the like. Instead, for example, the substrate treating apparatus  5  may include, installed therein from the beginning, a control device having the functions of both the load port control device  20  and virtual load port control device  19 . The virtual load port control device  19  may be installed between the host computer  9  and carrier transport system  7 , independently of the substrate treating apparatus  5 . Further, the functions of the virtual load port control device  19  may be incorporated into the host computer  9  as an integral part of the latter. 
     (6) In the foregoing embodiment, two OHTs  17  perform transportation at the same time to and from two virtual load ports, for both loading and unloading of FOUPs  3  to/from the substrate treating apparatus  5 . This is effective, for example, when there is sufficient available space in the internal buffer  15  at the time of loading, and when enough FOUPs to be unloaded are stored in the internal buffer  15  at the time of unloading. When there were available space only for one FOUP in the internal buffer  15  at the time of loading, and two OHTs  17  performed transportation to two virtual load ports at the same time, there would be no space in the internal buffer  15  for storing the FOUPs transported and loaded to the substrate treating apparatus  5 , and the OHTs  17  could be kept waiting in front of the substrate treating apparatus  5  for a long time. When only one FOUP were stored in the internal buffer  15  at the time of unloading, and two OHTs  17  performed transportation from two virtual load ports at the same time, the second OHT  17  having arrived at the substrate treating apparatus  5  would have no FOUP to unload, and this OHT  17  could be kept waiting in front of the substrate treating apparatus  5  for a long time. It is therefore preferable that the virtual load port control device  19  gives an “available for loading” or “ready for unloading” notice to the host computer  9 , by taking the state of the internal buffer  15  into consideration, and only after determining or confirming that there is sufficient available space in the internal buffer  15 , or that enough FOUPs to be unloaded are stored in the internal buffer  15 . Such determination or confirmation can be made by arranging that the virtual load port control device  19  receives the state of the internal buffer  15  recognized by the load port management unit  23 , directly or via the host-related control unit  21  from the load port management unit  23 . 
     This invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
A control apparatus in a substrate treating system with a substrate treating apparatus having a physical load port for receiving pods for storing substrates, and a carrier transport system for transporting the pods to and from the physical load port. The control apparatus includes a virtual load port control device for allotting a virtual load port to the physical load port, and instructing the carrier transport system to perform a transporting operation to and from the virtual load port on an assumption that the virtual load port really exists.