Abstract:
The present invention relates to a wafer transport system and a method of operating the same. The wafer transport system comprises at least one semiconductor apparatus, a track, a transfer device, a positioning device, a carrier and a cleaning device. The wafer transport system transports wafers along the at least one semiconductor apparatus via the carrier riding on the track. The transfer device transfers the wafers from the carrier to the at least one semiconductor apparatus. The positioning device identifies and controls the position of the carrier on the track. The cleaning device maintains the cleanliness of the wafers. The present invention provides advantages for improving the yield rate of a wafer, shortening the fabrication time of a wafer, and offering the flexibility and the extendibility to a wafer transport system.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a wafer transport system and a method for operating the same. More particularly, the present invention relates to a wafer transport system with a low-capacity carrier and a method for operating the same. 
     2. Description of the Related Art 
     Recently, the applications of wafers have greatly expanded from conventional electronic industry to the other fields, such as the solar industry. Therefore, the requirement of wafers and silicon thin-films has been greatly increased in the past few years. 
     The conventional manufacture of wafers is composed of several production processes and fabrication tools. For example, the production processes may comprise photolithography, measuring, etching, ion implantation, and deposition; and, the production process may be completed with the cooperation of multiple fabrication tools and measurement instruments. For harmonizing these production processes and fabrication tools to increase the productive efficiency, semiconductor foundries usually integrated the automated material handling system (AMHS) into the production process to control the movement, distribution and storage of materials. 
     The conventional AMHS equipment include overhead hoist transfer (OHT), rail guided vehicle (RGV), overhead shuttle (OHS), automated guided vehicle (AGV), and person rail guided vehicle (PRV). The AMHS equipment usually collocates with front opening unified pods (FOUP) capable of performing batch transfer of wafers among the workstations in a fabrication plant (FAB). In some situations, such batch transfer may be accomplished artificially by a worker who transports a fully loaded FOUP from one workstation to another for further processes. 
     Conventional FOUPs may, based on the design, accommodate wafers or substrates in a diameter of 300 mm (12-inch) or 450 mm (18-inch). The most common FOUPs are available with a capacity of 25 wafers. The AMHS would transfer a FOUP loaded with 25 semi-processed wafers from a first workstation to a second workstation for the following procedures, and request another FOUP full of untreated wafers to enter the first workstation to initiate another production cycle. For the wafers in a FOUP, the fabrication time of one production processes comprises the time for transporting in, the time for processing all the 25 wafers, and the time for transporting out. 
     Several problems have emerged from conventional AMHS and known transport systems in a sub-20 nm process of the semiconductor industry. The wafers become highly sensitive to several factors in such advanced production processes where the factors are required to be precisely controlled. The problems are as follows: (1) The patterns and the active regions on a wafer are damaged and inactivated easily when expose to oxygen or moisture. (2) The patterns on wafers with increasing diameter require multiple steps of photolithography which result in a long fabrication time. Additionally, the first processed wafer in a FOUP cannot continue to the following steps unless the other 24 wafers have undergone the same procedures; therefore, the fabrication time is further elongated. (3) Invisible micro cracks are easily formed on the patterns due to collisions. Especially when large-sized wafers are stacked in a wafer pod, a lot of wafers may be crushed due to the heavy weight. (4) For protecting the wafers from environmental contaminants and atmospheric gases, the entire system constructed in a clean room is supposed to be shut down for an engineer to enter to replace or repair the apparatus in the system. 
     Accordingly, there is a need for a novel wafer transport system to overcome the aforementioned defects. 
     SUMMARY 
     At least one embodiment in accordance with the present invention relates to a wafer transport system and a method for operating the same. More particularly, at least one embodiment relates to a wafer transport system with a low-capacity carrier and a method for operating the same. An objective of the present invention is to improve the yield rate of the wafers. Another objective of the present invention is to shorten the fabrication time of a wafer. Still another objective of the present invention is to offer flexibility and extendibility to a wafer transport system. 
     Some embodiments of the present invention relates to a wafer transport system comprising a semiconductor apparatus, a track, a carrier, a positioning device, a transfer device, and a cleaning device. The track is located along the semiconductor apparatus. The carrier is riding on the track and is for housing and transporting the wafer along the track. The positioning device is connected to the track for identifying and controlling the position of the carrier. The transfer device located between the semiconductor apparatus and the track is configured for transferring the wafer between the semiconductor apparatus and the track. The cleaning device may comprise a pipe and a pump. The pipe connects the pump to a first air valve of the carrier to clean the internal environment of the carrier. 
     In some aspects of the aforementioned embodiments, the wafer transport system is constituted by multiple small, isolated environments, and the wafers are delivered from one isolated environment to another isolated environment during transport. Therefore, even in a situation that the wafer transport system is built outside a clean room, wafers in the wafer transport system are still protected from exposing to the environmental contaminants. For example, a wafer may be transferred between a carrier and a semiconductor apparatus which each is with a clean and isolated environment. 
     In some cases, the wafer may be temporarily exposed to the environmental contaminants and atmospheric gases when it is transferring between the aforementioned carrier and the semiconductor apparatus. Accordingly, a nozzle may be configured on the transfer device for purging the wafer with clean gas which forms a protective layer on surfaces of the wafer. In some other cases, there is a risk that the carrier opened for receiving the wafer from the semiconductor apparatus may be temporarily exposed to the environmental contaminants. Accordingly, a pipe of the cleaning device may immediately connect to the carrier for cleaning the internal environment of the carrier. 
     Some embodiments of the present invention relates to a wafer transport system comprising at least one semiconductor apparatus, an entry port, an exit port, a track, a carrier, at least one positioning device, at least three transfer devices, and a cleaning device. The track is located along the at least one semiconductor apparatus, the entry port, and the exit port. The carrier is riding on the track and is for housing and transporting the wafer along the track. The positioning device is connected to the track for identifying and controlling the position of the carrier. The at least three transfer devices are located between the at least one semiconductor apparatus and the track, the entry port and the track, and the exit port and the track respectively. The at least three transfer devices are configured for transferring the wafer between the at least one semiconductor apparatus, the entry port, and the exit port. The cleaning device may comprise a pipe and a pump. The pipe connects the pump to a first air valve of the carrier to clean the internal environment of the carrier. 
     In some aspects of the aforementioned embodiments, the wafer transport system is constituted by multiple isolated environments, and the wafers are delivered therebetween. A wafer transport system comprising multiple separated environments comes with several advantages. For example, as a worker walking into the room to repair or replace a semiconductor apparatus, the operation of the wafer transport system may continue operating without contaminating the wafers because the wafers are remained in independent and enclosed environments. Similarly, since the transport system is constituted by multiple independent environments, the wafer transport system may easily skip some semiconductor apparatuses based on the requirements and system configurations. Unlike the conventional transport system, the carrier transports a single wafer immediately after it has been processed in some embodiments of the present invention; therefore, the fabrication time of a wafer may be largely shortened and the yield rate of a wafer may be improved. 
     Some embodiments of the present invention relates to a method for operating a wafer transport system. In the wafer transport system, a wafer may be transported along a track via a carrier. While the carrier moves along the track, a positioning device identifies the position of the carrier and controls the carrier to stop at a first location. The first location may be near to the opening of a semiconductor apparatus. Once the movement of the carrier has been stopped, a transfer device may be activated to transfer the wafer from the carrier to the semiconductor apparatus. After the wafer is processed, the transfer device is activated to transfer the wafer from the semiconductor apparatus back to the carrier. To clean the carrier which has once been opened, a pipe of a cleaning device may connect to a first air valve of the carrier for cleaning the internal environment of the carrier. Finally, the pipe disconnects from the first air valve if the cleaning process is over and the cleaned carrier transports the wafer along the track to a second location. 
     In some aspects of the aforementioned embodiments, the carrier is aligned with the opening of the semiconductor apparatus. Therefore, the transfer device may simply transfer the wafer without additional movements such as lifting and rotation. The reduction of unnecessary movements may shorten the fabrication time of a wafer and prevent the wafer from possible collisions. In some other aspects, the low-capacity carrier used in this method further reduces the possibility that the stacking wafers are crushed due to their own weight. 
     The wafer transport system in the present invention provides an improved performance as to the conventional systems. More particularly, some embodiments of the present invention relate to a wafer transport system comprising multiple clean and isolated environments for the wafers to be transferred therebetween. The embodiments of the present invention provide advantages for improving the yield rate of a wafer, shortening the fabrication time of a wafer, and offering the flexibility and the extendibility to the wafer transport system. Moreover, the present invention also provides a cleaning device to maintain the cleanliness of the internal environment of the wafer transport system immediately. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an exemplary wafer transport system in accordance with at least one embodiment of the present invention. 
         FIG. 2A  is a top perspective view of an exemplary carrier in accordance with at least one embodiment of the present invention. 
         FIG. 2B  is a bottom perspective view of an exemplary carrier in accordance with at least one embodiment of the present invention. 
         FIG. 3A  is a schematic diagram illustrating an exemplary side-open carrier in accordance with at least one embodiment of the present invention. 
         FIG. 3B  is a schematic diagram illustrating an exemplary hinged carrier in accordance with at least one embodiment of the present invention. 
         FIG. 3C  is a schematic diagram illustrating an exemplary two-piece carrier in accordance with at least one embodiment of the present invention. 
         FIG. 4  is a schematic diagram illustrating an exemplary transfer device in accordance with at least one embodiment of the present invention. 
         FIG. 5  is a schematic diagram illustrating an exemplary cleaning device in accordance with at least one embodiment of the present invention. 
         FIG. 6  is a schematic diagram illustrating an exemplary sensor positioning controller in accordance with at least one embodiment of the present invention. 
         FIG. 7  is a schematic diagram illustrating an exemplary mechanical positioning controller in accordance with at least one embodiment of the present invention. 
         FIG. 8  is a flow diagram illustrating a method for operating a wafer transport system in accordance with at least one embodiment of the present invention. 
         FIG. 9  is a flow diagram illustrating a method for operating a transfer device in accordance with at least one embodiment of the present invention. 
         FIG. 10  is a flow diagram illustrating a method for operating a cleaning device in accordance with at least one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In a general aspect, at least one embodiment in accordance with the present invention relates to a wafer transport system and a method for operating the same. More particularly, at least one embodiment relates to a wafer transport system with a low-capacity carrier and a method for operating the same. The embodiments and drawings provided here show different aspects of the present invention. However, the present invention is neither limited to any embodiment nor drawing thereof. 
       FIG. 1  is a schematic diagram illustrating an exemplary wafer transport system in accordance with at least one embodiment of the present invention. In  FIG. 1 , a wafer transport system may comprise at least one semiconductor apparatus  10 , an entry port  11 , an exit port  12 , a track  20 , a carrier  30 , at least one positioning device  50 , at least three transfer devices  60 , and a cleaning device  70 . The track  20  is located along the at least one semiconductor apparatus  10 , the entry port  11 , and the exit port  12 . The carrier  30  is riding on the track  20  and is for housing and transporting the wafer  40  along the track  20 . The positioning device  50  is connected to the track  20  for identifying and controlling the position of the carrier  30  on the track  20 . The at least three transfer devices  60  are located between the at least one semiconductor apparatus  10  and the track  20 , the entry port  11  and the track  20 , and the exit port  12  and the track  20 , respectively. The at least three transfer devices  60  are configured for transferring the wafer  40  between the at least one semiconductor apparatus  10 , the entry port  11 , and the exit port  12 . The cleaning device  70  may comprise a pipe  71  and a pump  72 . The pipe  71  connects the pump  72  to a first air valve  31  of the carrier  20  to clean the internal environment of the carrier  30 . 
       FIGS. 2A-2B  are the top perspective view and the bottom perspective view of a carrier  30  in accordance with at least one embodiment of the present invention. In some aspects of the aforementioned embodiments, the capacity of the carrier  30  is less than ten wafers. In some other aspects, the carrier  30  carries only one wafer  40  at a time. The internal environment of the carrier  30  may be a vacuum or be filled with clean gas. 
     The carrier  30  may comprise a first air valve  31 , a carrier connector  33 , a carrier door  34 , and a carrier sensor  37 . The first air valve  31  is configured to connect with a pipe  71  of a cleaning device  40  for cleaning the internal environment of the carrier  30 . The carrier connector  33  is configured for mounting the carrier  30  to the track  20 . Moreover, the carrier connector  33  may be deposited on different sides of the carrier  30  in accordance with the type of track  20  used in the wafer transport system. For example, the carrier connector  33  may be an overhead hoist and is deposited on the top surface of the carrier  30 . The carrier door  34  is configured for the wafer  40  to enter or exit the carrier  30 . The carrier sensor  37  may be a wafer sensor for detecting the amount of wafers  40  inside the carrier  30 , or a RFID sensor capable of cooperating with a positioning device  50  in the wafer transport system. In some embodiments of  FIGS. 2A-2B , the carrier  30  further comprises a second air valve  32  configured for expelling the excessive gas. 
       FIGS. 3A-3C  are schematic diagrams of the exemplary carriers in accordance with some embodiments of the present invention.  FIG. 3A  illustrates a side-opening carrier which is similar to a conventional FOUP defined in SEMI E47.1 but further characterized by a first air valve  31 , a smaller volume, and a reduced capacity.  FIG. 3B  illustrates a hinged carrier which may comprise a carrier cover  35 , a carrier base  36 , and a first air valve  31 . The carrier cover  35  is attached to the carrier base  36  at one side to form a movable joint which provides the hinged carrier the ability to be opened and closed in a way similar to a book. In some embodiments of  FIG. 3B , the hinged carrier further comprises an actuator for driving the hinged carrier to open or close.  FIG. 3C  illustrates a two-piece carrier which may comprise a carrier cover  35 , a carrier base  36 , a carrier connector  33 , and a first air valve  31 . The carrier cover  35  and the carrier base  36  are separated components and each connects to another indirectly. In some embodiments of  FIG. 3C , the two-piece carrier is placed onto a track  20  in a wafer transport system. In the aforementioned embodiments, the wafer transport system transports the two-piece carrier by moving the track and opens the two-piece carrier by lifting the carrier cover  35  through the carrier connector  33 . 
       FIG. 4  is a schematic diagram illustrating an exemplary transfer device in accordance with at least one embodiment of the present invention. The transfer device  60  in  FIG. 4  may be a robot arm and is configured between a track  20  and a semiconductor apparatus  10 . In some aspects, the wafer  40  may be temporarily exposed to the environmental contaminants and atmospheric gases when moving between the carrier and the semiconductor apparatus. Accordingly, a nozzle  61  may be configured onto the transfer device  60  for purging the wafer  40  with clean gas which forms a protective layer on the wafer  40  to protect the wafer  40  from the environmental contaminants. 
       FIG. 5  is a schematic diagram illustrating an exemplary cleaning device in accordance with at least one embodiment of the present invention.  FIG. 5  shows a cleaning device  70  comprising a pipe  71  and a pump  72  for cleaning the internal environment of carrier  30 . The pipe  71  connects the pump  72  to a first air valve  31  of a carrier  30 . In some embodiments of  FIG. 5 , the pipe  71  is fixedly connected to the first air valve  31  and moves with the carrier  30  in a wafer transport system. In the aforementioned embodiments, the pump  72  is activated to clean the internal environment of the carrier  30  based on the requests for cleaning, and is inactivated when the cleaning process is completed. In some other embodiments of  FIG. 5 , the pipe  71  is fixedly connected to the first air valve  31  and moves with the carrier  30  in a wafer transport system. In the aforementioned embodiments, the pump  72  cleans the internal environment of the carrier  30  continuously during the movement of the carrier  30 . In yet some other embodiments of  FIG. 5 , the pipe  71  is removably connected to the first air valve  31  of the carrier  70 . In the aforementioned embodiments, the pipe  71  temporarily connects to the first air valve  31  when the cleaning device  70  is activated to clean the internal environment of the carrier  30 , and disconnects from the first air valve  71  when the cleaning process is completed. 
     In an alternate embodiment of  FIG. 5 , a wafer transport system comprises a track  20 , a carrier  30 , an entry port  11 , a first semiconductor apparatus, a second semiconductor apparatus, an exit port  12 , and a cleaning device  70 . The cleaning device  70  further comprises a first pipe, a second pipe, a third pipe, and a fourth pipe. The first pipe extends to the entry port  11 ; the second pipe extends to the first semiconductor apparatus; the third pipe extends to the second semiconductor apparatus; and the fourth pipe extends to the exit port  12 . In this embodiment, a wafer  40  may be fed to the wafer transport system via the entry port  11 . The wafer  40  is then transferred from the entry port  11  to the carrier  30  riding on the track  20 , and the first pipe simultaneously connects to a first valve  31  of the carrier  30  to clean the internal environment of the carrier  30 . In the next stage, the wafer  40  is transferred from the first semiconductor apparatus back to the carrier  30  once the first process is completed, and the second pipe simultaneously connects to the first valve  31  to clean the internal environment of the carrier  30 . In the third stage, the wafer  40  is transferred from the second semiconductor apparatus back to the carrier  30  once the second process is completed, and the third pipe simultaneously connects to the first valve  31  to clean the internal environment of the carrier  30 . In the final stage, the wafer  40  exits the wafer transport system via the exit port  12 , and the fourth pipe connects to the first valve  31  to clean the internal environment of the carrier  30 . 
     A risk arouse that the carrier  30  opened for receiving the wafer  40  from the semiconductor apparatus  10  may temporarily be exposed to the environmental contaminants. In some embodiments of  FIG. 5 , the cleaning device  70  cleans the internal environment of a carrier  30  by vacuuming the contaminated air inside the carrier  30 . In some other embodiments of  FIG. 5 , the cleaning device  70  cleans the internal environment of a carrier  30  by filling the carrier  30  with clean gas and simultaneously expelling the contaminated air from the carrier  30  through a second air valve  32  of the carrier  30 . 
       FIG. 6  is a schematic diagram illustrating an exemplary positioning device in accordance with at least one embodiment of the present invention. The positioning device  50  may be a sensor positioning controller, and multiple sensor positioning controllers may coexist in a wafer transport system to form a sensor array to increase the identification accuracy. In some embodiments of  FIG. 6 , the sensor positioning controller is an optical sensor connected with a track  20  for identifying the location of a carrier  30  on the track  20 . The optical sensor may temporarily stop the movement of the track  20  based on an event that the carrier  30  is identified at a first location by the optical sensor. In some other embodiments of  FIG. 6 , the sensor positioning controller is a RFID sensor connected with a track  20  for identifying the location of a carrier. In the aforementioned embodiments, the carrier  30  may further comprise a RFID chip for assisting the identification processes of the sensor positioning controller. 
       FIG. 7  is a schematic diagram illustrating an exemplary positioning device in accordance with at least one embodiment of the present invention. The positioning device  50  may be a mechanical positioning controller, and multiple mechanical positioning controllers may coexist in a wafer transport system to increase the flexibility. In some embodiments of  FIG. 7 , the mechanical positioning controller is a retractable barrier configured on a track  20  for stopping the movement of a carrier  30  at a first location. To control the position of the carrier  30 , the retractable barrier is activated and temperately extends across the moving path of the carrier  30  to stop the carrier  30  from moving. In some other embodiments of  FIG. 7 , the mechanical positioning controller is a movable recess on a track  20  for stopping the movement of a carrier  30  at the first location. As part of the track  20 , the movable recess is activated to control the position of the carrier  30  by forming a recess on the track  20  which stops the carrier  30  from moving with the track  20 , and is inactivated to release the carrier  30  by removing the recess. 
       FIG. 8  is a flow diagram illustrating a method for operating a wafer transport system in accordance with at least one embodiment of the present invention. In the wafer transport system, a wafer  40  may be transported along a track  20  via a carrier  30 . While the carrier  30  moves, a positioning device  50  identifies the position of the carrier  30  and controls the carrier  30  to stop at a first location. The first location may be near to the opening of a semiconductor apparatus  10 . Once the movement of the carrier  30  has been stopped, a transfer device  60  may be activated to transfer the wafer  40  from the carrier  30  to the semiconductor apparatus  10 . After the wafer  40  is processed, the transfer device  60  is activated to transfer the wafer  40  from the semiconductor apparatus  10  back to the carrier  30 . To clean the carrier  30  which has once been opened, a pipe  71  of a cleaning device  70  may subsequently connect to a first air valve  31  of the carrier  30  for cleaning the internal environment of the carrier  30 . Finally, the pipe  71  disconnects from the first air valve  31  once the cleaning process is completed; and, the carrier  30  further transports the wafer  40  along the track  20  to a second location. 
     In some embodiments of  FIG. 8 , a nozzle  61  may be configured on the transfer device  60  for purging the wafer  40  with clean gas to protect the wafer  40  from the contaminants. In some embodiments of  FIG. 8 , there is a risk that the carrier  30  opened for receiving the wafer  40  from the semiconductor apparatus  10  may be temporarily exposed to the environmental contaminants. Therefore, the cleaning device  70  may clean the internal environment of a carrier  30  by vacuuming the contaminated air inside the carrier  30 , or by filling the carrier  30  with clean gas and simultaneously expelling the contaminated air from the carrier  30  through the second air valve  32  of the carrier  30 . In some other embodiments of  FIG. 8 , the positioning device  50  may be a sensor positioning controller or a mechanical positioning controller. The sensor positioning controller stops the movement of the track  20  based on that the carrier  30  is identified at the first location. The mechanical positioning controller is located at the first position on the moving path of the carrier  30  and blocks the movement of the carrier  30  at the first location when the mechanical positioning controller is activated. 
     In an alternate embodiment of  FIG. 8 , the wafer transport system comprises several carriers  30  and the method for operating is therefore modified. In the wafer transport system, a wafer  40  may be transported along a track  20  via a first carrier. While the first carrier is moving, a positioning device  50  identifies the position of the first carrier and controls the first carrier to stop at a first location. The first location may be near to the opening of a semiconductor apparatus  10 . Once the movement of the first carrier has been stopped, a transfer device  60  may be activated to transfer the wafer  40  from the first carrier to the semiconductor apparatus  10 . After the wafer  40  is processed, the transfer device  60  is activated to transfer the wafer  40  from the semiconductor apparatus  10  to a second carrier. A pipe  71  of a cleaning device  70  may connect to a first air valve  31  of the second carrier and a pump  72  of the cleaning device  70  is activated to clean the internal environment of the second carrier which has once been opened. Finally, the pipe  71  disconnects from the first air valve  31  when the cleaning process is completed and the second carrier further transports the wafer  40  to a second location. 
       FIG. 9  is a schematic diagram illustrating a method for operating a transfer device in accordance with at least one embodiment of the present invention. A positioning device  50  controls a carrier  30  to stop when the positioning device  50  identifies that the carrier  30  is located at a first location and aligned with the opening of the semiconductor apparatus  10 . At the same time, a transfer device  60  may be activated to transfer a wafer  40  from the carrier  30  to a semiconductor apparatus  10  to process the wafer  40 . Then, the transfer device  60  is activated again to transfer the wafer  40  from the semiconductor apparatus  10  to carrier  30  once the process is completed. In some embodiments, the transfer device  60  moves horizontally. Therefore, the transfer device may simply transfer the wafer without unnecessary movements such as lifting and rotation. The reduction of unnecessary movements may shorten the production cycle of a wafer and prevent the wafer from possible collisions. 
       FIG. 10  is a schematic diagram illustrating a method for operating a cleaning device in accordance with at least one embodiment of the present invention. A pipe  71  of a cleaning device  70  may extend and connect to a first air valve  31  of a carrier  30  when the transfer device  60  transferred a wafer  40  from a semiconductor apparatus  10  to the carrier  30 . Subsequently, a pump  72  of the cleaning device  70  is activated to clean the internal environment of the carrier  30 . Once the cleaning process is completed, the pipe  71  disconnects from the first air valve  31  and the carrier  30  then transports the wafer  40  away to a second location along the track  20   
     The figures and descriptions supra set forth only illustrated the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alternations, combinations or modifications easily considered by the people skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.