Abstract:
A method for transporting semiconductor wafers in semiconductor factory automation system, includes the steps of: a) processing a lot of semiconductor wafers to be contained in a semiconductor wafer cassette in a process equipment; b) sending a cassette transportation request from the process equipment to a cell management server when the process equipment has processed the lot of semiconductor wafers; c) generating a transportation instruction in response to the cassette transportation request; and d) if the semiconductor wafer cassette is transported from the process equipment to a stocker by an automatic guide vehicle (AGV), simultaneously activating the AGV and the stocker by simultaneously sending the transportation instruction to the AGV and the stocker. The method in accordance with the present invention can reduce a time taken to transport the semiconductor wafers.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a semiconductor factory automation (FA) system; and, more particularly, to a semiconductor FA system and method for transporting semiconductor wafers. 
     DESCRIPTION OF THE PRIOR ART 
     Generally, a conventional semiconductor factory automation (FA) system automatically processes semiconductor wafers. The conventional semiconductor FA system includes process equipments, stockers and an automatic guide vehicle (AGV). A process equipment applies a semiconductor process to the semiconductor wafers. A stocker loads the semiconductor wafers to be processed in the process equipment. Further, the stocker loads the semiconductor wafers, which have been already processed in the process equipment. The AGV transports the semiconductor wafers from the process equipment to another process equipment. Further, the AGV transports the semiconductor wafers from the stocker to the process equipment. Furthermore, the AGV transports the semiconductor wafers from the process equipment to the stocker. 
     Where the semiconductor wafers processed in the process equipment are transported to another process equipment by the AGV, the AGV and another process equipment are sequentially activated. That is, after the AGV has been activated, the another process equipment is activated. Accordingly, where the AGV and another process equipment are sequentially activated, it takes much time to transport the semiconductor wafers from the process equipment to another process equipment by the AGV. 
     Similarly, where the semiconductor wafers loaded to the stocker are transported to the process equipment by the AGV, the AGV and the process equipment are sequentially activated. That is, after the AGV has been activated, the process equipment is activated. Accordingly, where the AGV and the process equipment are sequentially activated, it takes much time to transport the semiconductor wafers from the stocker to the process equipment by the AGV. 
     Similarly, where the semiconductor wafers processed in the process equipment are transported to the stocker by the AGV, the AGV and the stocker are sequentially activated. That is, after the AGV has been activated, the stocker is activated. Accordingly, where the AGV and the stocker are sequentially activated, it takes much time to transport the semiconductor wafers from the process equipment to the stocker by the AGV. 
     As a result, there is a problem that the conventional semiconductor FA system increases a time taken to transport the semiconductor wafers by the AGV. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a semiconductor FA system and method for transporting semiconductor wafers that can reduce a time taken to transport the semiconductor wafers. 
     It is, therefore, another object of the present invention to provide a computer-readable media storing program instructions, the program instructions disposed on a computer to perform a method for transporting semiconductor wafers that can reduce a time taken to transport the semiconductor wafers. 
     In accordance with an aspect of the present invention, there is provided a semiconductor factory automation (FA) system, comprising: a common communication line; a plurality of process means for processing a lot of semiconductor wafers to be contained in a semiconductor wafer cassette, wherein one of said process means sends a cassette transportation request when the one of said process means has processed the lot of semiconductor wafers; an instruction generation means coupled to said common communication line for generating a transportation instruction in response to the cassette transportation request; a transportation control means coupled to said common communication line for controlling a semiconductor wafer cassette transportation in response to the transportation instruction; a plurality of transportation means for transporting the semiconductor wafer cassette, wherein said transportation means are controlled by said transportation control means; and a plurality of stocker means coupled to said transportation control means for loading the semiconductor wafer cassette, wherein said transportation control means simultaneously activates one of said transportation means and one of said stocker means by simultaneously sending the transportation instruction to the one of said transportation means and the one of said stocker means if the semiconductor wafer cassette is transported from the one of said process means to the one of said stocker means by the one of said transportation means. 
     In accordance with another aspect of the present invention, there is provided a method for transporting semiconductor wafers in semiconductor factory automation system, comprising the steps of: a) processing a lot of semiconductor wafers to be contained in a semiconductor wafer cassette in a process equipment; b) sending a cassette transportation request from the process equipment to a cell management server when the process equipment has processed the lot of semiconductor wafers; c) generating a transportation instruction in response to the cassette transportation request; and d) if the semiconductor wafer cassette is transported from the process equipment to a stocker by an automatic guide vehicle (AGV), simultaneously activating the AGV and the stocker by simultaneously sending the transportation instruction to the AGV and the stocker. 
     In accordance with further another aspect of the present invention, there is provided a computer-readable media storing program instructions, the program instructions disposed on a computer to perform a method for transporting semiconductor wafers in semiconductor factory automation system, comprising the steps of: a) processing a lot of semiconductor wafers to be contained in a semiconductor wafer cassette in a process equipment; b) sending a cassette transportation request from the process equipment to a cell management server when the process equipment has processed the lot of semiconductor wafers; c) generating a transportation instruction in response to the cassette transportation request; and d) if the semiconductor wafer cassette is transported from the process equipment to a stocker by an automatic guide vehicle (AGV), simultaneously activating the AGV and the stocker by simultaneously sending the transportation instruction to the AGV and the stocker. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the instant invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which: 
     FIG. 1A is a block diagram showing a semiconductor factory automation (FA) system in accordance with the present invention; 
     FIG. 1B is a block diagram illustrating a transportation control portion shown in FIG. 1A; 
     FIG. 2 depicts an operator interface screen provided by an operator interface server (OIS) shown in FIG. 1A; 
     FIG. 3 depicts another operator interface screen provided by an operator interface server (OIS) shown in FIG. 1A; 
     FIG. 4 is a flowchart showing a method for transporting a semiconductor wafer cassette in accordance with the present invention; 
     FIGS. 5 to  16  are flowcharts showing a procedure of transporting a semiconductor wafer cassette from an EQ to another EQ shown in FIG. 4; 
     FIGS. 17 to  20  are flowcharts showing a procedure of transporting a semiconductor wafer cassette from an EQ to a stocker shown in FIG. 4; and 
     FIGS. 21 and 26 are flowcharts showing a procedure of transporting a semiconductor wafer cassette from a stocker to an EQ shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1A, there is shown a block diagram showing a semiconductor factory automation (FA) system in accordance with the present invention. As shown, the semiconductor factory FA system includes at least one cell which has a predetermined number, e.g., 4, of semiconductor production bays. A semiconductor production bay  160  or  162 . The semiconductor production bay  160  is provided with process equipments (EQs)  136  and  138 , stockers  124  and  126  and an automatic guide vehicle (AGV)  132 . The semiconductor production bay  162  is provided with EQs  150  and  152 , stockers  140  and  142  and an AGV  148 . The EQ  136 ,  138 ,  150  or  152  processes semiconductor wafers in order to obtain semiconductor devices. The process equipment includes, e.g., an etching equipment, a photo-lithography equipment and the like. The stocker  124 ,  126 ,  140  or  142  temporarily stores a number of semiconductor wafer cassettes. Each of semiconductor wafer cassettes has a predetermined number of semiconductor wafers which is referred to as a lot. The semiconductor wafer cassettes are selectively transported to a process equipment (EQ) by using the AGV  132  or  148 . The semiconductor wafer cassette stored in the stocker  124  is conveyed to another semiconductor production bay  162 . 
     An equipment server (EQS)  134 ,  138  or  156  is coupled to a common communication line  170 , e.g., Ethernet™ supplied by Xerox Corporation. AGV controllers (AGVCs)  128  and  130  control the AGV  132 , respectively. AGVCs  144  and  146  control the AGV  148 , respectively. 
     The semiconductor FA system also includes a cell management portion  100 , a real-time database  108  connected to the cell management portion  100 , a temporary storage unit  110 , a history management portion  112  connected to the temporary storage unit  110  and a history database  114  connected to the history management portion  112 . The cell management portion  100 , the history management portion  112  and the history database  114  are respectively connected to the common communication line  170  for communication therebetween. 
     The cell management portion  100  includes a cell management server (CMS)  104 , an operator interface server (OIS)  106  and a data gathering server (DGS)  102 . The DGS  102  stores process data associated with the lot in the real-time database  108 . 
     The EQ  136  sends a cassette transportation request when the EQ  136  has processed the lot of semiconductor wafers. The CMS  104  generates a transportation instruction in response to the cassette transportation request. If the semiconductor wafer cassette is transported from the EQ  136  to the stocker  124  or  126  by the AGV  132 , a transportation control portion  116  simultaneously activates the AGV  132  and the stocker  124  or  126  by simultaneously sending the transportation instruction to the AGV  132  and the stocker  124  or  126 . 
     The stocker  124  or  126  further sends the cassette transportation request to the AGV  132 . If the semiconductor wafer cassette is transported from the stocker  124  or  126  to the EQ  136  by the AGV  132 , the transportation control portion  116  further simultaneously activates the AGV  132  and the EQ  136  by simultaneously sending the transportation instruction to the AGV  132  and the EQ  136 . 
     Furthermore, if the semiconductor wafer cassette is transported from the EQ  136  to the EQ  138  by the AGV  132 , the transportation control portion  116  simultaneously activates the AGV  132  and the EQ  138  by simultaneously sending the transportation instruction to the AGV  132  and the EQ  138 . The EQs  136  and  138  are positioned on the same semiconductor production bay  160  as each other. 
     A vehicle  118  transports the semiconductor wafer cassette between the semiconductor production bays  160  and  162 . Still further, if the semiconductor wafer cassette is transported from the EQ- 136  to the EQ  150 , the transportation control portion  116  simultaneously activates the AGVs  132  and  148 , the EQ  150  and the vehicle  118  by simultaneously sending the transportation instruction to AGVs  132  and  148 , the EQ  150  and the vehicle  118 . The EQs  136  and  150  are positioned on different semiconductor production bays to each other. The EQ  136  and the AGV  132  are positioned on a same semiconductor production bay  160  as each other. The EQ  150  and the AGV  148  are positioned on a same semiconductor production bay  162  as each other. 
     Referring to FIG. 1B, there is shown a block diagram illustrating a transportation control portion shown in FIG.  1 A. As shown, the transportation control portion  116  includes intrabay control servers  180  and  186  coupled to the common communication line  170 , an intrabay control server  192  coupled to the common communication line  170 , SCSs  182  and  188 , AGV control servers  184  and  190 , a vehicle control server  194 . The intrabay control servers  180  and  186  and the interbay control server  192  convert the transportation message to the transportation instruction, respectively. The SCSs  182  and  188  generate a stocker control signal to control the stockers  124 ,  126 ,  140  and  142  in response to the transportation instruction. The vehicle control server  194  generates a vehicle control signal in response to the transportation instruction. The AGV control server  184  sends the transportation instruction to the AGVC  128  or  130 . The AGVC  128  or  130  generates an AGV control signal to control an AGV in response to the transportation instruction. 
     Referring to FIG. 2, there is depicted an operator interface screen provided by an operator interface server (OIS) shown in FIG.  1 A. As shown, the operator interface screen includes a plurality of display portions. A display portion  200  displays position information of EQs and AGVs. The display portions  202  and  204  display error information of the AGVs as a color. A display portion  206  displays identification information of a selected AGV. A display portion  208  displays state information of the selected AGV. A display portion  210  displays identification of semiconductor wafer cassettes conveyed by the selected AGV. A display portion  212  displays identification information of a semiconductor production bay corresponding to the selected AGV. A display portion  214  displays the number of inactivated AGVs contained the semiconductor production bay. A display portion  216  displays the number of activated AGVs contained the semiconductor production bay. A display portion  218  displays the number of erroneous AGVs. A display portion  211  displays origination information of the semiconductor wafer cassette, destination information of the semiconductor wafer cassette, identification information of the semiconductor wafer cassette and current position information of the semiconductor wafer cassette contained in the selected AGV. 
     Referring to FIG. 3, there is depicted another operator interface screen provided by an operator interface server (OIS) shown in FIG.  1 A. As shown, a display portion  300  displays stockers  304 , semiconductor production bays  302 , semiconductor wafer cassette information  308  and a vehicle  306 . The display portion  300  provides current position information of the vehicle  306 . The display portion  310  displays schedule information of the semiconductor wafer cassette contained in the vehicle  306 . A display portions  312 ,  314 ,  316  and  318  display the number of stockers, the number of inactivated stockers, the number of activated stockers and the number of erroneous stockers. 
     Referring to FIG. 4, there is shown a flowchart showing a method for transporting a semiconductor wafer cassette in accordance with the present invention. 
     At step S 402 , a CMS receives a cassette transportation request through Ethernet™ from a first EQ or a first stocker. 
     At step S 404 , the CMS checks a process schedule of a semiconductor wafer cassette in a real-time database. 
     At step S 406 , the CMS creates a cassette transportation preparation instruction. 
     At step S 408 , it is determined whether a type of the cassette transportation preparation instruction is related to transportation of the semiconductor wafer cassette from the first EQ to a second EQ, transportation of the semiconductor wafer cassette from the first EQ to the first stocker or transportation of the semiconductor wafer cassette from the first stocker to the first EQ. 
     At step S 410 , if the type of the cassette transportation preparation instruction is related to the transportation of the semiconductor wafer cassette from the first EQ to the second EQ, the semiconductor wafer cassette is transported from the first EQ to the second EQ. 
     At step S 412 , if the type of the cassette transportation preparation instruction is related to the transportation of the semiconductor wafer cassette from the first EQ to the first stocker, the semiconductor wafer cassette is transported from the first EQ to the first stocker. 
     At step S 414 , if the type of the cassette transportation preparation instruction is related to the transportation of the semiconductor wafer cassette from the first stocker to the first EQ, the semiconductor wafer cassette is transported from the first stocker to the first EQ. 
     Referring to FIGS. 5 to  16 , there are shown flowcharts showing a procedure of transporting a semiconductor wafer cassette from the first EQ to the second EQ shown in FIG.  4 . 
     Referring to FIG. 5, at step S 502 , the CMS converts the cassette transportation preparation instruction to a cassette transportation preparation message. 
     At step S 504 , the CMS sends the cassette transportation preparation message through the Ethernet™ to a first EQS coupled to the first EQ. 
     At step S 506 , the first EQS converts the cassette transportation preparation message to the cassette transportation preparation instruction. 
     At step S 508 , the first EQS generates a first EQ control signal corresponding to the cassette transportation preparation instruction. 
     At step S 510 , the first EQS sends the first EQ control signal to the first EQ, which has sent the cassette transportation request to the CMS. 
     At step S 512 , the first EQ puts a lot of semiconductor wafers in the semiconductor wafer cassette in response to the first EQ control signal. A glossary of the lot is defined as a predetermined number of semiconductor wafers processed in the first EQ. 
     At step S 514 , the first EQ informs the first EQS that the semiconductor wafer cassette can be unloaded from the first EQ. 
     Referring to FIG. 6, at step S 516 , the first EQS informs the CMS that the semiconductor wafer cassette can be unloaded from the first EQ. 
     At step S 518 , the CMS creates a cassette transportation execution instruction. 
     At step S 520 , the CMS converts the cassette transportation execution instruction to a cassette transportation execution message. 
     At step  1522 , it is determined whether the first EQ is located in the same semiconductor production bay as the second EQ. 
     At step S 524 , if the first EQ is located in the same semiconductor production bay as the second EQ, the OMS simultaneously sends the cassette transportation execution message to a second EQS coupled to the second EQ and a first intrabay control server contained in an automatic cassette handling portion. 
     At step S 526 , the second EQS and the first intrabay control server simultaneously receives the cassette transportation execution message from the CMS. 
     At step S 528 , if the first EQ is not located in the same semiconductor production bay as the second EQ, the CMS simultaneously sends the cassette transportation execution message to the first intrabay control server, the second intrabay control server and an interbay control server contained in the automatic cassette handling portion and the second EQS coupled to the second EQ. 
     At step S 530 , the first intrabay control server, the second intrabay control server, the interbay control server and the second EQS simultaneously receives the cassette transportation execution message from the CMS. 
     Referring to FIG. 7, there is shown a flowchart illustrating a procedure after the second EQS receives the cassette transportation execution message from the CMS at step S 526  shown in FIG.  6 . 
     At step S 702 , the second EQS converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 704 , the second EQS generates a second EQ control signal corresponding to the cassette transportation execution instruction. 
     At step S 706 , the second EQS sends the second EQ control signal to the second EQ. 
     At step S 708 , the second EQ is activated in response to the second EQ control signal. 
     Referring to FIG. 8, there is shown a flowchart illustrating a procedure after the first intrabay control server receives the cassette transportation execution message from the CMS at step S 526  shown in FIG.  6 . 
     At step S 802 , the first intrabay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 804 , the first intrabay control server sends the cassette transportation execution instruction through a first AGV control server to a first AGVC. 
     At step S 806 , the first AGVC generates a first AGV control signal corresponding to the cassette transportation execution instruction. 
     At step S 808 , the first AGVC sends the first AGV control signal to a first AGV. 
     At step S 810 , the first AGV unloads the semiconductor wafer cassette from the first EQ in response to the first AGV control signal. 
     At step S 812 , the first AGV loads the semiconductor wafer cassette to the second EQ. 
     At step S 814 , the first AGV informs the first AGVC that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     At step S 816 , the first AGVC informs the first intrabay control server that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     At step S 818 , the first intrabay control server informs the CMS that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     Referring to FIGS. 9 and 11, there are shown flowcharts illustrating a procedure after the first intrabay control server receives the cassette transportation execution message from the CMS at step S 530  shown in FIG.  6 . 
     Referring to FIG. 9, at step S 902 , the first intrabay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 904 , the first intrabay control server simultaneously sends the cassette transportation execution instruction to a first SCS and the first AGVC control server. 
     At step S 906 , the first SCS and the first AGVC control server simultaneously receive the cassette transportation execution instruction from the first intrabay control server. 
     Referring to FIG. 10, there is shown a flowchart illustrating a procedure after the first SCS receives the cassette transportation execution instruction from the first intrabay control server at step S 906  shown in FIG.  9 . 
     At step S 1002 , the first SCS generates a first stocker control signal corresponding to the cassette transportation execution instruction. 
     At step S 1004 , the first SCS sends the first stocker control signal to the first stocker. 
     At step S 1006 , the first stocker is activated in response to the first stocker control signal. 
     Referring to FIG. 11, there is shown a flowchart illustrating a procedure after the first AGV control server receives the cassette transportation execution instruction from the first intrabay control server at step S 906  shown in FIG.  9 . 
     At step S 1102 , the first AGV control server sends the cassette transportation execution instruction to the first AGVC. 
     At step S 1104 , the first AGVC generates a first AGV control signal corresponding to the cassette transportation execution instruction. 
     At step S 1106 , the first AGVC sends the first AGV control signal to the first AGV. 
     At step S 1108 , the first AGV unloads the semiconductor wafer cassette from the first EQ. 
     At step S 1110 , the first AGV loads the semiconductor wafer cassette to the first stocker. 
     Referring to FIG. 12, there is shown a flowchart illustrating a procedure after the interbay control server receives the cassette transportation execution message from the CMS at step S 530  shown in FIG.  6 . 
     At step S 1202 , the interbay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 1204 , the interbay control server sends the cassette transportation execution instruction to a vehicle control server. 
     At step S 1206 , the vehicle control server generates a vehicle control signal. 
     At step S 1208 , a vehicle unloads the semiconductor wafer cassette from the first stocker. 
     At step S 1210 , the vehicle loads the semiconductor wafer cassette to a second stocker. 
     Referring to FIGS. 13 and 1S, there are shown flowcharts illustrating a procedure after the second intrabay control server receives the cassette transportation execution message from the CMS at step S 530  shown in FIG.  6 . 
     Referring to FIG. 13, at step S 1302 , the second intrabay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 1304 , the second intrabay control server simultaneously sends the cassette transportation execution instruction to a second SCS and a second AGVC control server. 
     At step S 1306 , the second SCS and the second AGVC control server simultaneously receive the cassette transportation execution instruction from the second intrabay control server. 
     Referring to FIG. 14, there is shown a flowchart illustrating a procedure after the second SCS receives the cassette transportation execution instruction from the second intrabay control server at step S 1306  shown in FIG.  13 . 
     At step S 1402 , the second SCS generates a second stocker control signal corresponding to the cassette transportation execution instruction. 
     At step S 1404 , the second SCS sends the second stocker control signal to a second stocker. 
     At step S 1406 , the second stocker is activated in response to the second stocker control signal. 
     Referring to FIG. 15, there is shown a flowchart illustrating a procedure after the second AGVC control server receives the cassette transportation execution instruction from the second intrabay control server at step S 1306  shown in FIG.  13 . 
     At step S 1502 , the second AGVC control server sends the cassette transportation execution instruction to a second AGVC. 
     At step S 1504 , the second AGVC generates a second AGV control signal corresponding to the cassette transportation execution instruction. 
     At step S 1506 , the second AGVC sends the second AGV control signal to a second AGV. 
     At step S 1508 , the second AGV unloads the semiconductor wafer cassette from the second stocker in response to the second AGV control signal. 
     At step S 1510 , the second AGV loads the semiconductor wafer cassette to the second EQ as the destination of the semiconductor wafer cassette. 
     At step S 1512 , the second AGV informs the second AGVC that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     At step S 1514 , the second AGVC informs the second intrabay control server that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     At step S 1516 , the second intrabay control server informs the CMS that the semiconductor wafer cassette has been transported from the first EQ to the second EQ. 
     Referring to FIG. 16, there are shown a flowchart illustrating a procedure after the second EQS receives the cassette transportation execution message from the CMS at step S 530  shown in FIG.  6 . 
     At step S 1602 , the second EQS converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 1604 , the second EQS generates a second EQ control signal corresponding to the cassette transportation execution instruction. 
     At step S 1606 , the second EQS sends the second EQ control signal to the second EQ. 
     At step S 1608 , the second EQ is activated in response to the second EQ control signal. 
     Referring to FIGS. 17 to  20 , there are shown flowcharts showing a procedure of transporting a semiconductor wafer cassette from the first EQ to the first stocker shown in FIG.  4 . 
     Referring to FIG. 17, at step S 1702 , the CMS converts the cassette transportation preparation instruction to the cassette transportation preparation message. 
     At step S 1704 , the CMS sends the cassette transportation preparation message through the Ethernet™ to a first EQS coupled to the first EQ. 
     At step S 1706 , the first EQS converts the cassette transportation preparation message to the cassette transportation preparation instruction. 
     At step S 1708 , the first EQS generates a first EQ control signal corresponding to the cassette transportation preparation message. 
     At step S 1710 , the first EQS sends the first EQ control signal to the first EQ, which has sent the cassette transportation request to the CMS. 
     At step S 1712 , the first EQ puts a lot of semiconductor wafers in the semiconductor wafer cassette in response to the first EQ control signal. 
     Referring to FIG. 18, at step S 1714  the first EQ informs the first EQS that the semiconductor wafer cassette can be unloaded from the first EQ. 
     At step S 1716 , the first EQS informs the CMS that the semiconductor wafer cassette can be unloaded from the first EQ. 
     At step S 1718 , the CMS creates a cassette transportation execution instruction. 
     At step S 1720 , the CMS converts the cassette transportation execution instruction to a cassette transportation execution message. 
     At step S 1722 , the CMS sends the cassette transportation execution message to the first intrabay control server. 
     At step S 1724 , the first intrabay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 1726 , the first intrabay control server simultaneously sends the cassette transportation execution instruction to the first SCS and the first AGV control server. 
     At step S 1728 , the first SCS and the first AGV control server simultaneously receives the cassette transportation execution instruction from the first intrabay control server. 
     Referring to FIG. 19, there are shown a flowchart illustrating a procedure after the first SCS receives the cassette transportation execution instruction from the first intrabay control server at step S 1728  shown in FIG.  18 . 
     At step S 1902 , the first SCS generates the first stocker control signal corresponding to the cassette transportation execution instruction. 
     At step S 1904 , the first SCS sends the first stocker control signal to the first stocker. 
     At step S 1906 , the first stocker is activated in response to the first stocker control signal. 
     Referring to FIG. 20, there is shown a flowchart illustrating a procedure after the first AGV control server receives the cassette transportation execution instruction from the first intrabay control server at step S 1728  shown in FIG.  18 . 
     At step S 2002 , the first AGV control server sends the cassette transportation execution instruction to the first AGVC. 
     At step S 2004 , the first AGVC generates the first AGV control signal corresponding to the cassette transportation execution instruction. 
     At step S 2006 , the first AGVC sends the first AGV control signal to the first AGV. 
     At step S 2008 , the first AGV unloads the semiconductor wafer cassette from the first EQ. 
     At step S 2010 , the first AGV loads the semiconductor wafer cassette to the first stocker. 
     At step S 2012 , the first AGV informs the first AGVC that the semiconductor wafer cassette has been transported from the first EQ to the first stocker. 
     At step S 2014 , the first AGVC informs the first intrabay control server that the semiconductor wafer cassette has been transported from the first EQ to the first stocker. 
     At step S 2016 , the first intrabay control server informs the CMS that the semiconductor wafer cassette has been transported from the first EQ to the first stocker. 
     Referring to FIGS. 21 to  26 , there are shown flowcharts showing a procedure of transporting a semiconductor wafer cassette from the first stocker to the first EQ shown in FIG.  4 . 
     Referring to FIG. 21, at step S 2102 , the CMS converts the cassette transportation preparation instruction to the cassette transportation preparation message. 
     At step S 2104 , the CMS sends the cassette transportation preparation message through the Ethernet™ to the first intrabay control server. 
     At step S 2106 , the first intrabay control server converts the cassette transportation preparation message to the cassette transportation preparation instruction. 
     At step S 2108 , the first intrabay control server sends the cassette transportation preparation instruction to the first SCS. 
     At step S 2110 , the first SCS generates the first stocker control signal corresponding to the cassette transportation preparation instruction. 
     At step S 2112 , the first stocker is activated in response to the first stocker control signal. 
     Referring to FIG. 22, at step S 2114 , the first stocker informs the first SCS that the first stocker has been activated. 
     At step S 2116 , the first SCS informs the CMS that the first stocker has been activated. 
     At step S 2118 , the CMS creates a cassette transportation execution instruction. 
     At step S 2120 , the CMS converts the cassette transportation execution instruction to a cassette transportation execution message. 
     At step S 2122 , the CMS simultaneously sends the cassette transportation execution message to the first intrabay control server and the first EQS. 
     At step S 2124 , the first intrabay control server and the first EQS simultaneously receives the cassette transportation execution message from the CMS. 
     Referring to FIG. 23, there are shown a flowchart illustrating a procedure after the first EQS receives the cassette transportation execution instruction from the CMS at step S 2134  shown in FIG.  22 . 
     At step S 2302 , the first EQS converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 2304 , the first EQS generates a first EQ control signal corresponding to the cassette transportation execution instruction. 
     At step S 2306 , the first EQS sends the first EQ control signal to the first EQ. 
     At step S 2308 , the first EQ is activated in response to the first EQ control signal. 
     Referring to FIG. 24, there are shown a flowchart illustrating a procedure after the first intrabay control server receives the cassette transportation execution instruction from the CMS at step S 2134  shown in FIG.  22 . 
     At step S 2402 , the first intrabay control server converts the cassette transportation execution message to the cassette transportation execution instruction. 
     At step S 2404 , the first intrabay control server simultaneously sends the cassette transportation execution instruction to the first SCS and the first AGV control server. 
     At step S 2406 , the first SCS and the first AGV control server simultaneously receives the cassette transportation execution instruction from the first intrabay control server. 
     Referring to FIG. 25, there are shown a flowchart illustrating a procedure after the first SCS receives the cassette transportation execution instruction from the first intrabay control server at step S 2406  shown in FIG.  24 . 
     At step S 2502 , the first SCS generates the first stocker control signal corresponding to the cassette transportation execution instruction. 
     At step S 2504 , the first SCS sends the first stocker control signal to the first stocker. 
     At step S 2506 , the first stocker is activated in response to the first stocker control signal. 
     Referring to FIG. 26, there are shown a flowchart illustrating a procedure after the first AGV control server receives the cassette transportation execution instruction from the first intrabay control server at step S 2406  shown in FIG.  24 . 
     At step S 2602 , the first AGV control server sends the cassette transportation execution instruction to the first AGVC. 
     At step S 2604 , the first AGVC generates the first AGV control signal corresponding to the cassette transportation execution instruction. 
     At step S 2606 , the first AGVC sends the first AGV control signal to the first AGV. 
     At step S 2608 , the first AGV unloads the semiconductor wafer cassette from the first stocker. 
     At step S 2610 , the first AGV loads the semiconductor wafer cassette to the first EQ. 
     At step S 2612 , the first AGV informs the first AGVC that the semiconductor wafer cassette has been transported from the first stocker to the first EQ. 
     At step S 2614 , the first AGVC informs the first intrabay control server that the semiconductor wafer cassette has been transported from the first stocker to the first EQ. 
     At step S 2616 , the first intrabay control server informs the CMS that the semiconductor wafer cassette has been transported from the first stocker to the first EQ. 
     A computer-readable media such as an optical disk or a hard disk can store program instructions disposed on a computer to perform the method for transporting a semiconductor wafer cassette in accordance with the present invention. 
     Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.