Abstract:
An overhead hoist transport vehicle comprising: an overhead hoist; a translating stage; and a gripper coupled to the translating stage, the gripper being configured to grip a material unit; wherein the overhead hoist is configured to transport the material unit to one of a load port and a storage location by performing operations comprising: the overhead hoist being configured to vertically move the gripper to the load port and the storage location; and the translating stage being configured to horizontally move the overhead hoist to the load port and the storage location; and wherein the load port is beneath an overhead rail; and wherein at least a portion of the storage location is disposed lateral to the overhead rail.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 10/393,526 filed Mar. 20, 2003 entitled AUTOMATED MATERIAL HANDLING SYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELS AND OVERHEAD HOISTS. This application claims benefit of U.S. Provisional Patent Application No. 60/389,993 filed Jun. 19, 2002 entitled AUTOMATED MATERIAL HANDLING SYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELS AND OVERHEAD HOISTS, and U.S. Provisional Patent Application No. 60/417,993 filed Oct. 11, 2002 entitled OFFSET ZERO FOOTPRINT STORAGE (ZFS) USING MOVING SHELVES OR A TRANSLATING HOIST PLATFORM. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates generally to automated material handling systems, and more specifically to an automated material handling system that allows an overhead hoist to access work-in-process (WIP) parts directly from a WIP storage unit to increase the efficiency of the overall material handling system. 
         [0004]    Automated material handling systems are known that employ WIP storage units and overhead hoists to store and transport WIP parts between various workstations and/or processing machines in a product manufacturing environment. For example, such an Automated Material Handling System (AMHS) is commonly employed in the manufacturing of Integrated Circuit (IC) chips. A typical process for fabricating an IC chip comprises various steps including deposition, cleaning, ion implantation, etching, and passivation steps. Further, each of these steps in the IC chip fabrication process is usually performed by a different processing machine such as a chemical vapor deposition chamber, an ion implantation chamber, or an etcher. Accordingly, the WIP parts, e.g., semiconductor wafers, are typically transported between the different workstations and/or processing machines multiple times to perform the various process steps required for fabricating the IC chips. 
         [0005]    A conventional AMHS for manufacturing IC chips comprises a plurality of WIP storage units (also known as “stockers”) for storing the semiconductor wafers, and one or more overhead hoist transport vehicles for transporting the wafers between the various workstations and processing machines on the IC chip manufacturing floor. The semiconductor wafers stored in the WIP stockers are typically loaded into cassette pods such as Front Opening Unified Pods (FOUPs), which are subsequently transferred to an overhead transport vehicle configured to travel on a suspended track. In the conventional AMHS, each stocker is typically provided with a plurality of active input/output ports that work in conjunction with an internal robotic arm (which may provide up to three or more axes of movement) for loading and unloading the FOUPs to/from the stocker. The FOUPs are picked and placed from/to the input/output ports by the overhead hoist vehicle. 
         [0006]    One drawback of the conventional AMHS is that the efficiency of the overall system is limited by the time required for the robotic arm to access the FOUPs at the WIP stocker&#39;s active input/output ports. Because of the generally delicate nature of the semiconductor wafers, strict limits are normally imposed on the acceleration rate of the robotic arm. For this reason, a minimum amount of time is typically required for moving the FOUPs to and from the stocker&#39;s input/output ports. This minimum move time generally determines the stocker throughput, which dictates the number of stockers needed to support the desired IC chip production level and thus the total cost of the AMES. Although the material handling efficiency of the AMHS might be improved by increasing the number of active input/output ports on each stocker and by allowing the overhead transport vehicle to access multiple input/output ports simultaneously, providing additional input/output ports can significantly increase the cost of the stocker. 
         [0007]    In addition, the combination of a three or more axis internal robot in the stocker with several input/output ports, each having 1-3 axes of motion, means that a typical stocker may have between 5 and 16 axes of motion. This is a very complex, low reliability, and costly solution for storing material. 
         [0008]    It would therefore be desirable to have an automated material handling system that provides enhanced material handling efficiency while overcoming the drawbacks of conventional automated material handling systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    In accordance with the present invention, a highly efficient Automated Material Handling System (AMHS) is provided that allows an overhead hoist to load and unload Work-In-Process (WIP) parts directly to/from one or more WIP storage units included in the system. 
         [0010]    In one embodiment, the improved AMHS comprises an overhead hoist transport subsystem and at least one vertical carousel WIP storage unit (“stocker”) including a plurality of storage bins. The overhead hoist transport subsystem includes at least one overhead hoist transport vehicle configured to travel along a suspended track defining at least one predetermined route. The predetermined route passes over the vertical carousel stocker, which is configured to allow the overhead hoist to access one or more WIP parts directly from a selected one of the carousel storage bins. In this first embodiment, the selected carousel storage bin containing the desired WIP lot(s) is positioned at the top of the vertical carousel stocker substantially directly underneath the suspended track. Next, the overhead hoist transport vehicle is moved along the suspended track to a position substantially directly above the selected carousel storage bin. The overhead hoist is then lowered toward the selected storage bin. Finally, the overhead hoist is operated to pick the desired WIP lot directly from the carousel storage bin, or to place one or more WIP lots in the carousel storage bin. 
         [0011]    In a second embodiment, the predetermined route defined by the suspended track passes parallel to the vertical carousel WIP stocker, which is configured to allow the overhead hoist to access one or more WIP parts directly from one of the carousel storage bins. The AMHS further includes an extraction mechanism, which works in conjunction with the vertical carousel stocker to suitably position the selected carousel storage bin containing the desired WIP lot(s) relative to the track. For example, the extraction mechanism may be configured to move the selected carousel storage bin (e.g., a movable shelf) along a single servo-controlled axis from a first position adjacent the track to a second position substantially directly underneath the track. In the second embodiment, the overhead transport vehicle is moved along the track to a position substantially directly above the second position. Next, the overhead hoist is lowered toward the second position. In an alternative embodiment, the selected carousel storage bin comprises a shelf positioned alongside the track, and the overhead hoist is mounted to a translating stage for picking and placing one or more WIP lots to the shelf at the side of the overhead transport vehicle. Finally, the overhead hoist is operated to pick the desired WIP lot directly from the selected storage bin, or to place one or more WIP lots in the selected storage bin. 
         [0012]    By configuring the AMHS to allow the overhead hoist to directly load and unload WIP parts to/from the carousel storage bins from a position above the respective storage bin, more efficient AMHS operation can be achieved. 
         [0013]    Other features, functions, and aspects of the invention will be evident from the Detailed Description of the Invention that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]    The invention will be more fully understood with reference to the following Detailed Description of the Invention in conjunction with the drawings of which: 
           [0015]      FIG. 1  is a perspective view of a conventional automated material handling system; 
           [0016]      FIG. 2  is block diagram of a first embodiment of an automated material handling system according to the present invention; 
           [0017]      FIG. 3  is a block diagram of a second embodiment of the automated material handling system of  FIG. 2 ; 
           [0018]      FIG. 4  is a block diagram of a third embodiment of the automated material handling system of  FIG. 2 ; 
           [0019]      FIGS. 5   a - 5   b  are block diagrams of a translating hoist vehicle accessing fixed storage positions according to the present invention; 
           [0020]      FIG. 6  is a block diagram of the translating hoist vehicle of  FIGS. 5   a - 5   b  accessing material on a conveyer; and 
           [0021]      FIG. 7  is a flow diagram of a method of operating the automated material handling system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The entire disclosures of U.S. patent application Ser. No. 10/393,526 filed Mar. 20, 2003 entitled AUTOMATED MATERIAL HANDLING SYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELS AND OVERHEAD HOISTS, U.S. Provisional Patent Application No. 60/389,993 filed Jun. 19, 2002 entitled AUTOMATED MATERIAL HANDLING SYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELS AND OVERHEAD HOISTS, and U.S. Provisional Patent Application No. 60/417,993 filed Oct. 11, 2002 entitled OFFSET ZERO FOOTPRINT STORAGE (ZFS) USING MOVING SHELVES OR A TRANSLATING HOIST PLATFORM, are incorporated herein by reference. 
         [0023]    An Automated Material Handling System (AMHS) is disclosed that can load and unload Work-In-Process (WIP) parts to/from a WIP storage unit with increased efficiency. The presently disclosed AMHS achieves such increased material handling efficiency by allowing top-loading/unloading of storage bins in a vertical carousel WIP storage unit by an overhead hoist positioned above the respective storage bin. 
         [0024]      FIG. 1  depicts a conventional AMHS  100 , which may be employed to automatically store and transport WIP parts between various workstations and/or processing machines in a product manufacturing environment, e.g., a clean environment for manufacturing Integrated Circuit (IC) chips. As shown in  FIG. 1 , the conventional AMHS  100  comprises a WIP storage unit (“stocker”)  102  and an overhead hoist transport subsystem  104 . The WIP stocker  102  includes input and output ports  111 - 112 , and the overhead hoist transport subsystem  104  includes a suspended track  108  and a plurality of overhead hoist transport vehicles  105 - 106  configured to travel on the track  108 . In a typical mode of operation, the WIP parts are transported in a cassette pod  110  such as a Front Opening Unified Pod (FOUP). The first overhead transport vehicle  105  travels along the track  108  and stops at a position suitable for unloading the FOUP  110  into the input port  111  or for loading another FOUP from the output port  112  of the stocker  102 . Further, the second overhead transport vehicle  106  waits on the track  108  until the first overhead transport vehicle  105  finishes unloading/loading the FOUP and moves out of the way. 
         [0025]    In the conventional AMHS  100 , FOUPs are unloaded from the overhead hoist into the input port  111 , loaded from the output port  112  into the overhead hoist, or otherwise accessed from within the stocker  102  by a robotic arm  107 , which may provide up to three or more axes of movement. Further, the minimum amount of time required to access the FOUPs from the stocker  102  generally determines the stocker throughput, which dictates the number of stockers needed to support the desired production level. Accordingly, complex movements of the multi-axis robotic arm  107  for accessing the FOUPs may cause the minimum move time to increase, thereby increasing both the number of stockers needed in the AMHS  100  and the overall cost of the material handling system. 
         [0026]      FIG. 2  depicts an illustrative embodiment of an Automated Material Handling System (AMHS)  200 , in accordance with the present invention. In the illustrated embodiment, the AMHS  200  comprises an overhead hoist transport subsystem  204 , and at least one vertical carousel WIP storage unit (“stocker”)  202  including a plurality of storage bins such as a carousel storage bin  203 . The vertical carousel WIP stocker  202  is configured to allow an overhead hoist in the overhead hoist transport subsystem  204  to access WIP parts directly from a selected one of the carousel storage bins. 
         [0027]    It is noted that like the conventional AMHS  100  (see  FIG. 1 ), the AMHS  200  of  FIG. 2  may be employed in a clean environment for manufacturing IC chips such as a 200 mm or 300 mm FAB plant, or any other suitable product manufacturing environment. As shown in  FIG. 2 , the IC chip manufacturing environment includes first and second floors  220  and  226 , and a ceiling  214 . The first floor  220  typically comprises a waffle slab made of reinforced concrete, and the second floor  226  comprises a raised floor located above the waffle slab  220 . The vertical carousel stocker  202  is positioned on the waffle slab  220 . Further, workstations and/or processing machines (not shown) configured to perform various process steps for fabricating the IC chips are positioned on the raised floor  226 , which is typically covered with an electrically nonconductive material and designed to meet specific loading and seismic requirements. For example, the raised floor  226  may be located a distance  228  (about 0.6 m) above the waffle slab  220  and a distance  224  (greater than or equal to about 4.15 m) below the ceiling  214 . 
         [0028]    In the presently disclosed embodiment, the vertical carousel stocker  202  includes a housing  252 , and first and second pulleys  250 - 251  and a belt  254  disposed within the housing  252 . As shown in  FIG. 2 , the carousel storage bins (e.g., the storage bin  203 ) are coupled to the belt  254  at various spaced locations along the belt, and the belt  254  is looped between the first and second pulleys  250 - 251  to allow the storage bins to be rotatably positioned along the belt path by driving one of the pulleys  250 - 251 . For example, the vertical carousel stocker  202  may have a height  218  (about 3.85 m). The top of the vertical carousel stocker  202  may therefore be a distance  216  (about 3.25 m) above the raised floor  226 . 
         [0029]    As described above, the vertical carousel stocker  202  is configured to allow an overhead hoist to access WIP parts, e.g., semiconductor wafers, directly from one of the carousel storage bins. In the illustrated embodiment, the portion of the stocker housing  252  near the ceiling  214  is at least partially open to allow top-loading/unloading of the selected carousel storage bin. Further, each carousel storage bin comprises a fixed shelf, and the semiconductor wafers are loaded into cassette pods such as a Front Opening Unified Pod (FOUP)  210  disposed on the shelf  203 . For example, each FOUP  210  may hold one or more semiconductor wafer lots, thereby allowing the overhead hoist to access multiple wafer lots in a single carousel storage bin simultaneously. 
         [0030]    The overhead hoist transport subsystem  204  includes a suspended track  208  and at least one overhead hoist transport vehicle  205  configured for traveling on the track  208 . The suspended track  208  defines at least one predetermined route passing over the vertical carousel stocker  202 , thereby allowing the overhead transport vehicle  205  to access a FOUP directly from one of the carousel storage bins positioned approximately at the top of the stocker  202 . For example, the overhead transport vehicle  205  may extend a distance  222  (about 0.9 m) from the ceiling  214 . 
         [0031]    In an illustrative mode of operation, the selected carousel storage bin, e.g., the storage bin  203  containing the FOUP  210 , is positioned approximately at the top of the vertical carousel stocker  202  underneath the track  208 . The overhead transport vehicle  205  is then moved along the track  208  to a position substantially directly above the storage bin  203 . Next, the overhead hoist is lowered from the overhead transport vehicle  205  through the opening in the stocker housing  252  toward the storage bin  203 . For example, the overhead hoist may be lowered in a direction parallel to the longitudinal axis L 1  of the stocker. The overhead hoist is then operated to pick the FOUP  210  directly from the storage bin  203  for subsequent transport to a workstation or processing machine on the IC chip manufacturing floor. It is understood that the overhead hoist may alternatively be operated to place a FOUP in the carousel storage bin  203 . 
         [0032]      FIG. 3  depicts an alternative embodiment  300  of the AMHS  200  (see  FIG. 2 ). As shown in  FIG. 3 , the AMHS  300  comprises an overhead hoist transport system  304 , and at least one vertical carousel WIP stocker  302  including a plurality of storage bins such as a slide-mounted storage bin  332 . Like the vertical carousel stocker  202 , the vertical carousel stocker  302  is configured to allow an overhead hoist in the overhead hoist transport system  304  to access WIP parts, e.g., semiconductor wafers, directly from a selected one of the carousel storage bins. 
         [0033]    Specifically, the AMHS  300  may be employed in an IC chip manufacturing environment including a ceiling  314 , a waffle slab  320 , and a raised floor  326  located above the waffle slab  320 . As shown in  FIG. 3 , the vertical carousel stocker  302  is positioned on the waffle slab  320 . For example, the raised floor  326  may be located a distance  328  (about 0.6 m) above the waffle slab  320  and a distance  324  (greater than about 5.4 m) below the ceiling  314 . Further, the vertical carousel stocker  302  includes a housing  352 , and first and second pulleys  350 - 351  and a belt  354  disposed within the housing  352 . The carousel storage bins (e.g., the slide-mounted storage bin  332 ) are coupleable to the belt  354  at various spaced locations along the belt, and the belt  354  is looped between the first and second pulleys  350 - 351  to allow the storage bins to be rotatably positioned along the belt path by driving one of the pulleys  350 - 351 . For example, the vertical carousel stocker  302  may have a height  318  (about 6 m). 
         [0034]    As described above, the vertical carousel stocker  302  is configured to allow an overhead hoist to access the semiconductor wafers directly from one of the carousel storage bins. In the illustrated embodiment, at least one side of the housing  352  is at least partially open to allow the selected carousel storage bin to be extracted from within the housing  352 , and to allow subsequent top-loading/unloading of the selected storage bin by the overhead hoist. Specifically, the AMHS  300  further includes at least one extraction mechanism  330 , which works to extract the semiconductor wafers from within the stocker  302 , and to suitably position the material relative to a suspended track  308  included in the overhead hoist transport subsystem  304 . It is noted that each storage bin may comprise either a movable or fixed shelf. Further, the semiconductor wafers are loaded into cassette pods such as a FOUP  310  disposed on the shelf  332 . 
         [0035]    The overhead hoist transport subsystem  304  includes the suspended track  308  and at least one overhead hoist transport vehicle  305  configured to travel on the track  308 . The track  308  defines at least one predetermined route passing parallel to the vertical carousel stocker  302 , thereby allowing the overhead transport vehicle  305  to access a FOUP directly from a selected one of the slide-mounted storage bins. 
         [0036]    In an illustrative mode of operation, the selected slide-mounted storage bin, e.g., the storage bin  332  containing the FOUP  310 , is positioned to allow the extraction mechanism  330  to extract the storage bin  332  from within the stocker  302  and to position the storage bin  332  directly underneath the track  308 . It is noted that the extraction mechanism  330  may be incorporated into the stocker  302  and configured to move the storage bin  332  along a single servo-controlled axis  398 . The overhead transport vehicle  305  is then moved along the track  308  to a position directly above the extracted storage bin  332 . Next, the overhead hoist is lowered from the overhead transport vehicle  305  toward the storage bin  332 , e.g., in a direction parallel to the longitudinal axis L 2  of the stocker. The overhead hoist is then operated to pick the FOUP  310  directly from the storage bin  332  for subsequent transport to a workstation or processing machine on the IC chip manufacturing floor. It is appreciated that the overhead hoist may alternatively be operated to place a FOUP in the carousel storage bin  332 . 
         [0037]      FIG. 4  depicts a detailed embodiment  400  of the AMHS  300  (see  FIG. 3 ). In the illustrated embodiment, the AMHS  400  comprises an overhead hoist transport system  404  and a vertical carousel stocker  402 . The overhead hoist transport system  404  includes a suspended track  408  and an overhead hoist transport vehicle  405  configured for traveling on the track  408 . For example, the overhead transport vehicle  405  may extend a distance  436  (about 0.9 m) from the track  408 . The vertical carousel stocker  402  includes a plurality of carousel storage bins such as a storage bin  432  disposed within the stocker housing. For example, the storage bin  432  may be a distance  438  (about 2.6 m) above the raised IC chip manufacturing floor. 
         [0038]    As described above, a FOUP  410  is extracted from within the stocker housing to allow subsequent top-loading/unloading of the selected storage bin. The overhead transport vehicle  405  further includes an overhead hoist  431  having a gripper configured to top-load/unload the FOUP  410  to/from the storage bin  432 . In the preferred embodiment, the hoist gripper  430  is mounted on a translating stage to allow the overhead hoist to pick/place a cassette pod to either side of the overhead transport vehicle  405 . 
         [0039]      FIGS. 5   a - 5   b  depict a translating hoist vehicle subsystem  704  accessing fixed storage positions. In the illustrated embodiment, the translating hoist vehicle subsystem  704  includes a suspended track  708 , and an overhead hoist transport vehicle  705  configured to travel on the track. The overhead transport vehicle  705  is configured to pick/place a FOUP  710  to a fixed storage position  732 . For example, the overhead transport vehicle  705  may extend a distance  736  (about 0.9 m) below the ceiling  714 , and the storage position  732  may be disposed a distance  738  (about 2.6 m) above the raised IC chip manufacturing floor. Further, the ceiling  714  may be a distance  790  (about 3.66 m) above the raised floor. 
         [0040]    The overhead transport vehicle  705  is configured to pick (and place) the FOUP  710  to a position located directly below the suspended track  708 . To that end, the overhead hoist vehicle  705  includes a hoist gripper  731  mounted to a translating stage and configured to extend from the vehicle  705 , pick up the FOUP  710 , and retract back to the vehicle  705 , thereby moving the FOUP  710  within the overhead transport vehicle  705  (see  FIG. 5   b ). In the preferred embodiment, the translating stage is configured to allow the overhead hoist to pick/place a cassette pod to either side of the overhead transport vehicle  705 . Once the FOUP  710  is held by the hoist gripper  730 , the overhead transport vehicle  705  transports it to a workstation or processing machine on the IC chip manufacturing floor. 
         [0041]      FIG. 6  depicts a translating hoist vehicle system  800  accessing material either stored or moving on a conveyer  895 . Specifically, an overhead hoist transport subsystem  804  is employed to directly pick or place a FOUP  810  to the overhead rail-based conveyer  895 . In the illustrated embodiment, the overhead hoist transport subsystem  804  includes a suspended track  808  and an overhead hoist transport vehicle  805  configured to travel on the track  808 . For example, the overhead transport vehicle  805  may extend a distance  836  (about 0.9 m) below the track  808  and be disposed a distance  892  (about 0.35 m) above the rail-based conveyer  895 . Further, the overhead rail  898  may be a distance  838  (about 2.6 m) above the raised IC manufacturing floor. It should be understood that the rail  898  extends in a direction perpendicular to the plane of the drawing. The translating hoist vehicle system  800  further includes a process tool load port  899 . 
         [0042]    The overhead transport vehicle  805  may be employed to perform top-loading/unloading of the rail-based conveyer  895 . To that end, the overhead transport vehicle  805  includes an overhead hoist  831  having a hoist gripper  835 , which is mounted to a translating stage  833  configured to allow both horizontal and vertical motion, as indicated by the directional arrows  870  and  871 , respectively. In an illustrative mode of operation, the rail-based conveyer  895  is moved so that the FOUP  810  is positioned directly underneath the overhead hoist  831 . The hoist gripper  835  is then lowered via the translating stage  833  toward the FOUP  810 , and operated to pick the FOUP  810  directly from the conveyer  895 . Next, the hoist gripper  835  carrying the FOUP  810  is raised and retracted via the translating stage  833 , thereby moving the FOUP  810  within the overhead transport vehicle  805 . The transport vehicle  805  then transports the FOUP  810  to a workstation or processing machine on the IC chip manufacturing floor. 
         [0043]    A method of operating the presently disclosed automated material handling system is illustrated by reference to  FIG. 7 . As depicted in step  902 , a selected storage bin containing a FOUP is positioned within a vertical carousel stocker to allow access by an overhead hoist. For example, the selected carousel storage bin may be positioned at the top or at the side of the vertical carousel stocker (see  FIGS. 2-3 ). Next, the overhead hoist transport vehicle is moved along a track, as depicted in step  904 , to a position adjacent the selected storage bin. In the event the selected storage bin is positioned at the top of the stocker, the overhead transport vehicle is positioned above the storage bin. In the event the selected storage bin is positioned at the side of the stocker, the overhead transport vehicle is positioned to the side of the storage bin. The overhead hoist is then extended from the transport vehicle and lowered, as depicted in step  906 , to allow the hoist gripper to contact the FOUP in the selected storage bin. Next, the hoist gripper is operated, as depicted in step  908 , to pick the FOUP directly from the storage bin. The overhead hoist is then raised and retracted, as depicted in step  910 , to move the FOUP within the overhead transport vehicle. In this way, the FOUP is top-loaded from the selected storage bin to the overhead transport vehicle. Finally, the overhead transport vehicle transports, as depicted in step  912 , the FOUP to a workstation or processing machine on the product manufacturing floor. 
         [0044]    It will further be appreciated by those of ordinary skill in the art that modifications to and variations of the above-described automated material handling system may be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as limited except as by the scope and spirit of the appended claims.