Patent Publication Number: US-2023133865-A1

Title: Substrate transfer system

Description:
This application claims priority to Korean Patent Application No. 10-2021-0142403, filed on Oct. 25, 2021, and all the benefits accruing therefrom under 35 U.S.C. §119, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present inventive concept relates to a substrate transfer system. More specifically, the present inventive concept relates to a substrate transfer system which performs a distribution exchange between fabricating facilities (FAB). 
     2. Description of the Related Art 
     In order to transport a substrate (i.e. a semiconductor wafer) in a production line for fabricating a semiconductor element, a transfer system which transports a carrier (for example, Front Opening Unified Pod (FOUP) or a shipping box (Front Opening Shipping Box (FOST)) in which a plurality of substrates are accommodated is adopted. Such a substrate transfer system is gradually being automated using an overhead hoist transport (OHT). 
     On the other hand, to maximize the capacity to handle different semiconductor elements and an effective area of the equipment, a cluster type/cloud type fabricating facility (Cluster/Cloud FAB) that integrally produces the semiconductor elements by connecting a plurality of fabricating facilities (FAB) to each other is required. However, at present, because the distribution control system divides the control system for each fabricating facility to minimize the production damage due to unexpected sudden failure, there is a problem in direct movement and transport between the fabricating facilities using the distribution transport device. Therefore, an efficient interface zone operation for distribution exchange between fabricating facilities is indispensable. 
     SUMMARY 
     Aspects of the present inventive concept provide a substrate transfer system capable of performing efficient distribution exchange between fabricating facilities. 
     However, aspects of the present inventive concept are not restricted to the exemplary embodiments set forth herein. The above and other aspects of the present inventive concept will become more apparent to one of skill in the art to which the present inventive concept pertains by referencing the detailed description of the present inventive concept given below. 
     According to an aspect of the present inventive concept, there is provided a substrate transfer system comprising a lower rail, an upper rail which is located above the lower rail from the ground, and extends to be parallel to the lower rail, a conveyor which extends to intersect the lower rail and the upper rail, below the lower rail, a first lower transport unit which transports a first carrier along the lower rail and unloads the first carrier onto the conveyor, and a first upper transport unit which transports a second carrier along the upper rail and unloads the second carrier onto the conveyor, wherein the conveyor includes a linear module which moves the first carrier and the second carrier in a linear direction, and a turning module which turns the first carrier and the second carrier. 
     According to an aspect of the present inventive concept, there is provided a substrate transfer system comprising a lower rail, a lower transport unit which transports a first carrier along the lower rail, an upper rail which is placed above the lower rail from a ground and overlaps the lower rail in a vertical direction, an upper transport unit which transports a second carrier along the upper rail, and a conveyor on which the first carrier and the second carrier are loaded or unloaded, below the lower rail, wherein the lower transport unit includes a first grip portion which moves in the vertical direction to perform a loading operation or an unloading operation on the first carrier, and the upper transport unit includes a second grip portion which moves in the vertical direction to perform the loading operation or the unloading operation on the second carrier, and a slider which slides the second grip portion so as not to overlap the lower rail. 
     According to an aspect of the present inventive concept, there is provided a substrate transfer system comprising a first fabricating facility, a second fabricating facility, and an interface zone which connects the first fabricating facility and the second fabricating facility, wherein the interface zone includes a conveyor, a lower rail which intersects the conveyor, a first lower transport unit which transports a first carrier from the first fabricating facility along the lower rail and unloads the first carrier onto the conveyor, a second lower transport unit which loads the first carrier from the conveyor, and transports the first carrier to the second fabricating facility along the lower rail, an upper rail which is placed above the lower rail from a ground and overlaps the lower rail in a vertical direction, a first upper transport unit which transports a second carrier from the first fabricating facility along the upper rail and unloads the second carrier onto the conveyor, and a second upper transport unit which loads the second carrier from the conveyor and transports the second carrier to the second fabricating facility along the upper rail, wherein the conveyor includes a linear module which moves the first carrier and the second carrier in a linear direction, and a turning module which turns the first carrier and the second carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and features of the present inventive concept will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which: 
         FIG.  1    is a schematic diagram for describing the substrate transfer system according to some exemplary embodiments. 
         FIG.  2    is a schematic diagram for describing a lower transport unit of  FIG.  1   . 
         FIG.  3    is a schematic diagram for describing an upper transport unit of  FIG.  1   . 
         FIG.  4    is a schematic diagram for describing a conveyor of  FIG.  1   . 
         FIGS.  5 – 11   12 A  12 B  12 C  13 – 15    are diagrams for describing the operation of the substrate transfer system according to some exemplary embodiments. 
         FIG.  16    is a schematic block diagram for describing a semiconductor fabricating facility including the substrate transfer system according to some exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present specification, although terms such as first and second are used to describe various elements or components, it goes without saying that these elements or components are not limited by these terms in any numerical sense. These terms are only used to distinguish a single element or component from other elements or components. Therefore, it goes without saying that a first element or component referred to below may be a second element or component within the present inventive concept. 
     Hereinafter, a substrate transfer system according to exemplary embodiments will be described referring to  FIGS.  1 – 11   12 A  12 B  12 C  13 – 16   . 
       FIG.  1    is a schematic diagram for describing the substrate transfer system according to some exemplary embodiments.  FIG.  2    is a schematic diagram for describing a lower transport unit of  FIG.  1   .  FIG.  3    is a schematic diagram for describing an upper transport unit of  FIG.  1   .  FIG.  4    is a schematic diagram for explaining a conveyor of  FIG.  1   . 
     Referring to  FIGS.  1  to  4   , the substrate transfer system according to some exemplary embodiments includes an interface zone IZ. 
     The interface zone IZ may be a zone in which the distribution exchange between fabricating facilities FAB is performed. For example, the interface zone IZ which connects a first fabricating facility F1 and a second fabricating facility F2 may be provided. Such an interface zone IZ may exchange the carriers  10  of the first fabricating facility F1 and the carriers  10  of the second fabricating facility F2 with each other. The carriers  10  may be, but are not limited to, a front opening unified pod (FOUP) or a shipping box (front opening shipping box (FOSB)) in which a plurality of substrates (i.e,, semiconductor wafers) are accommodated. 
     Although not specifically shown, the first fabricating facility F1 and the second fabricating facility F2 may each include a series of processing equipment for fabricating semiconductor elements. The processing equipment may include, for example, etching processing equipment, deposition processing equipment, ashing processing equipment, a cleaning process equipment, and the like. Each processing equipment is provided with a substrate ( i.e., a semiconductor wafer) from the carrier  10  and may perform a semiconductor process on the substrate. 
     Further, the substrate transfer system according to some exemplary embodiments may include a lower rail LR, an upper rail UR, first transport units  110 L and  110 U, second transport units  120 L and  120 U, and a conveyor  130 . 
     Each of the lower rail LR and the upper rail UR may be spaced apart from the ground plane of the semiconductor fabricating facility. For example, each of the lower rail LR and the upper rail UR may be suspended from and fixed to the ceiling of the semiconductor fabricating facility. The upper rail UR may be placed to be above the lower rail LR from the ground of the semiconductor fabricating facility. In some exemplary embodiments, the upper rail UR may extend parallel to the lower rail LR in the interface zone IZ. In some exemplary embodiments, the upper rail UR may overlap the lower rail LR in the interface zone IZ in a vertical direction. Here, the vertical direction refers to a direction in which gravity acts ( i.e., a direction perpendicular to the ground of the semiconductor fabricating facility). 
     The first transport units  110 L and  110 U may load and unload the carrier  10  in the first fabricating facility F1 and the interface zone IZ. The first transport units  110 L and  110 U may include a first lower transport unit  110 L and a first upper transport unit  110 U. The first lower transport unit  110 L may travel along the lower rail LR extending over the first fabricating facility F1 and the interface zone IZ, and the first upper transport unit  110 U may travel along the upper rail UR extending over the first fabricating facility F1 and the interface zone IZ. As a result, the first transport units  110 L and  110 U may transport the carriers  10  between the first fabricating facility F1 and the interface zone IZ. 
     In some exemplary embodiments, the first lower transport unit  110 L may include a first sub-lower transport unit  110 L 1  and a second sub-lower transport unit  110 L 2 , which are spaced apart from each other and each travel on the lower rail LR. Although only an example in which the traveling directions of the first sub-lower transport unit  110 L 1  and the second sub-lower transport unit  110 L 2  are different from each other is shown, this is only an example, and the transport units may travel in the same direction as each other. 
     In some exemplary embodiments, the first upper transport unit  110 U may include a first sub-upper transport unit  110 U 1  and a second sub-upper transport unit  110 U 2 , which are spaced apart from each other and each travel on the upper rail UR. Although only an example in which the traveling directions of the first sub-upper transport unit  110 U 1  and the second sub-upper transport unit  110 U 2  are different from each other is shown, this is only one example, and the transport units may travel in the same direction as each other. 
     The second transport units  120 L and  120 U may load and unload the carriers  10  in the second fabricating facility F2 and the interface zone IZ. The second transport units  120 L and  120 U may include a second lower transport unit  120 L and a second upper transport unit  120 U. The second lower transport unit  120 L may travel along the lower rail LR extending over the second fabricating facility F2 and the interface zone IZ, and the second upper transport unit  120 U may travel along the upper rail UR extending over the second fabricating facility F2 and the interface zone IZ. As a result, the second transport units  120 L and  120 U may transport the carriers  10  between the second fabricating facility F2 and the interface zone IZ. 
     In some exemplary embodiments, the second lower transport unit  120 L may include a third sub-lower transport unit  120 L 1  and a fourth sub-lower transport unit  120 L 2 , which are spaced apart from each other and each travel on the lower rail LR. Although only an example in which the traveling directions of the third sub-lower transport unit  120 L 1  and the fourth sub-lower transport unit  120 L 2  are different from each other is shown, this is only one example, and the transport units may travel in the same direction as each other. Further, only an example in which the traveling directions of the first sub-lower transport unit  110 L 1  and the third sub-lower transport unit  120 L 1  are the same as each other, and the traveling directions of the second sub-lower transport unit  110 L 2  and the fourth sub-lower transport unit  120 L 2  are the same as each other, this is only one example, and the transport units may travel in different directions from each other. 
     In some exemplary embodiments, the second upper transport unit  120 U may include a third sub-upper transport unit  120 U 1  and a fourth sub-upper transport unit  120 U 2 , which are spaced apart from each other and each travel on the upper rail UR. Although only an example in which the traveling directions of the third sub-upper transport unit  120 U 1  and the fourth sub-upper transport unit  120 U 2  are different from each other, this is only one example, and the transport units may travel in the same direction. Further, although only an example in which the traveling directions of the first sub-upper transport unit  110 U 1  and the third sub-upper transport unit  120 U 1  are the same as each other, and the traveling directions of the second sub-upper transport unit  110 U 2  and the fourth sub-upper transport unit  120 U 2  are the same as each other, this is only one example, and the transport units may travel in different directions from each other. 
     The first transport units  110 L and  110 U and the second transport units  120 L and  120 U may each perform a loading operation or an unloading operation on the carrier  10 . Therefore, the first transport units  110 L and  110 U may be provided with the carriers  10  from the first fabricating facility F1 or the conveyor  130 ,or may provide the carriers  10  to the first fabricating facility F1 or the conveyor  130 . Further, the second transport units  120 L and  120 U may be provided with the carriers  10  from the second fabricating facility F2 or the conveyor  130 ,or may provide the carriers  10  to the second fabricating facility F2 or the conveyor  130 . 
     As an example, as shown in  FIG.  2   , the first lower transport unit  110 L may include a first cover portion  111   a , a first transport portion  113   a , a first elevating portion  115   a , and a first grip portion  117   a . In  FIG.  2   , although the first lower transport unit  110 L is mainly described, it goes without saying that the second lower transport unit  120 L may be similar. 
     The first cover portion  111   a  may provide a space for accommodating the first elevating portion  115   a , the first grip portion  117   a , and the carriers  10 . The first transport portion  113   a  is placed on the lower rail LR and may move along the lower rail LR. As the first transport portion  113   a  moves, the carriers  10  accommodated in the first lower transport unit  110 L may be transported along the lower rail LR. The first transport portion  113   a  may be, for example, but not limited to, a transfer vehicle that moves along the lower rail LR. The first elevating portion  115   a  may be placed inside the first cover portion  111   a . The first elevating portion  115   a  may raise or lower the first grip portion  117   a  in the vertical direction VD. For example, the first elevating portion  115   a  may lower or raise the first grip portion  117   a  by loosening or winding a belt connected to the first grip portion  117   a . The first grip portion  117   a  is attachable to and detachable from the carrier  10  to perform a loading operation or an unloading operation on the carrier  10 . 
     A length of the first grip portion  117   a  raised and lowered in the vertical direction VD by the first elevating portion  115   a  may be, for example, about 1,000 mm or less (for example, about 100 mm to about 1,000 mm). 
     Further, as an example, as shown in  FIG.  3   , the first upper transport unit  110 U may include a second cover portion  111   b , a second transport portion  113   b , a second elevating portion  115   b , and a second grip portion  117   b . In  FIG.  3   , although the first upper transport unit  110 U is mainly described, it goes without saying that the second upper transport unit  120 U may be similar. 
     The second cover portion  111   b  may provide a space for accommodating the second elevating portion  115   b , the second grip portion  117   b , and the carriers  10 . The second transport portion  113   b  is placed on the upper rail UR and may move along the upper rail UR. As the second transport portion  113   b  moves, the carriers  10  accommodated in the second lower transport unit  120 L may be transported along the upper rail UR. The second transport portion  113   b  may be, for example, but not limited to, a transfer vehicle that moves along the upper rail UR. The second elevating portion  115   b  may be placed inside the second cover portion  111   b . The second elevating portion  115   b  may raise and lower the second grip portion  117   b  in the vertical direction VD. For example, the second elevating portion  115   b  may lower or raise the second grip portion  117   b  by loosening or winding the belt connected to the second grip portion  117   b . The second grip portion  117   b  is attachable to and detachable from the carrier  10  to perform a loading operation or an unloading operation on the carrier  10 . 
     A length of the second grip portion  117   b  raised or lowered in the vertical direction VD by the second elevating portion  115   b  may be greater than the raised or lowered length of the first grip portion  117   a . For example, the length of the second grip portion  117   b  raised and lowered in the vertical direction VD by the second elevating portion  115   b  may be about 1,000 mm or more (for example, about 1,000 mm to about 2,000 mm). 
     In some exemplary embodiments, the first upper transport unit  110 U and the second upper transport unit  120 U may each perform a sliding operation on the carrier  10 . As a result, even when the upper rail UR overlaps the lower rail LR in the vertical direction, the first upper transport unit  110 U and the second upper transport unit  120 U may be prevented from overlapping the first lower transport unit  110 L and the second lower transport unit  120 L. 
     As an example, as shown in  FIG.  3   , the first upper transport unit  110 U may further include a slider  112   b . In  FIG.  3   , although the first upper transport unit  110 U is mainly shown, it goes without saying that the second upper transport unit  120 U may be similar. 
     The slider  112   b  may slide the second elevating portion  115   b  placed in the second cover portion  111   b  in a horizontal direction HD intersecting the upper rail UR. The second grip portion  117   b  connected to the second elevating portion  115   b  may also slide in the horizontal direction HD. The sliding second elevating portion  115   b  may raise and lower the second grip portion  117   b  in the vertical direction VD. As a result, the second grip portion  117   b  may avoid an overlap with the lower rail LR and perform a loading operation or an unloading operation on the carrier  10 . 
     A length at which the second grip portion  117   b  slides in the horizontal direction HD by the slider  112   b  may be, for example, about 440 mm or more (for example, about 440 mm to about 1,000 mm). 
     Although only an example in which the sliding operation is performed by the first upper transport unit  110 U and the second upper transport unit  120 U, the first lower transport unit  110 L and the second lower transport unit  120 L may also perform a predetermined sliding operation. As an example, the first lower transport unit  110 L and the second lower transport unit  120 L may each further include the slider  112   b  described above in connection with  FIG.  3   . 
     The length at which the first grip portion  117   a  slides in the horizontal direction HD by the slider  112   b  may be shorter than the length at which the second grip portion  117   b  slides. For example, the length at which the first grip portion  117   a  slides in the horizontal direction HD by the slider  112   b  may be about 440 mm or less (for example, about 100 mm to about 440 mm). 
     The conveyor  130  may be placed inside the interface zone IZ. The conveyor  130  may be placed below the lower rail LR. The lower rail LR and the upper rail UR may each intersect the conveyor  130  inside the interface zone IZ. For example, the conveyor  130  may extend to intersect the lower rail LR and the upper rail UR. In some exemplary embodiments, the conveyor  130  may be spaced apart from the ground plane of the semiconductor fabricating facility. For example, the conveyor  130  may be suspended from and fixed to the ceiling of a semiconductor fabricating facility. The lower rail LR may be placed above the conveyor  130  from the ground of the semiconductor fabricating facility. 
     The conveyor  130  may move the carriers  10  unloaded from the first transport units  110 L and  110 U and the second transport units  120 L and  120 U close to each other. As an example, the conveyor  130  may convey the carriers  10 , which are unloaded from the first lower transport unit  110 L and the first upper transport unit  110 U, to the second lower transport unit  120 L and the second upper transport unit  120 U. Alternatively, for example, the conveyor  130  may convey the carriers  10 , which are unloaded from the second lower transport unit  120 L and the second upper transport unit  120 U, to the first lower transport unit  110 L and the first upper transport unit  110 U. As a result, the conveyor  130  may exchange the carriers  10  of the first fabricating facility F1 with the carriers  10  of the second fabricating facility F2. 
     In some exemplary embodiments, the conveyor  130  may include a first conveyor  132  and a second conveyor  134  that move the unloaded carriers  10  in different linear directions from each other. As an example, as shown in  FIG.  4   , the first conveyor  132  may move the unloaded carriers  10  in the first linear direction MD 1 , and the second conveyor  134  may move the unloaded carriers  10  in a second linear direction MD 2  opposite to the first linear direction MD 1 . 
     In some exemplary embodiments, the conveyor  130  may turn at least a part of the unloaded carriers  10 . As an example, as shown in  FIG.  4   , the first conveyor  132  may include a first turning module  132 T, and the second conveyor  134  may include a second turning module  134 T. The first turning module  132 T and the second turning module  134 T may each reverse the facing direction of the carriers  10  by turning the unloaded carriers  10 . 
     In some exemplary embodiments, the first conveyor  132  may include a first linear module  132 L 1 , a first turning module  132 T, and a second linear module  132 L 2 . The first linear module  132 L 1  and the second linear module  132 L 2  may each move the unloaded carriers  10  in the first linear direction MD 1 . The first turning module  132 T may be interposed between the first linear module  132 L 1  and the second linear module  132 L 2 . The first turning module  132 T may produce the carriers  10 , which are provided from the first linear module  132 L 1 , to the second linear module  132 L 2 , by turning or without turning the carriers. 
     In some exemplary embodiments, the second conveyor  134  may include a third linear module  134 L 1 , a second turning module  134 T, and a fourth linear module  134 L 2 . The third linear module  134 L 1  and the fourth linear module  134 L 2  may each move the unloaded carriers  10  in the second linear direction MD 2 . The second turning module  134 T may be interposed between the third linear module  134 L 1  and the fourth linear module  134 L 2 . The second turning module  134 T may produce the carriers  10 , which are provided from the third linear module  134 L 1 , to the fourth linear module  134 L 2 , by turning or without turning the carriers. 
     In some exemplary embodiments, the lower rail LR may include a first working rail LR 1  and a first non-working rail LR 2 . The first working rail LR 1  and the first non-working rail LR 2  may extend parallel to each other in the interface zone IZ. The first transport units  110 L and  110 U and the second transport units  120 L and  120 U traveling on the first working rail LR 1  may perform a loading operation or an unloading operation of the carriers  10  at a point where the transport units intersect the conveyor  130 , respectively. The first transport units  110 L and  110 U and the second transport units  120 L and  120 U traveling on the first non-working rail LR 2  may pass through the conveyor (130) without performing a loading operation or an unloading operation of the carrier  10 . As a result, the first non-working rail LR 2  may function as a lower high-speed rail that does not perform the distribution exchange in the interface zone IZ, from the plurality of lower rails LR. 
     In some exemplary embodiments, the upper rail UR may include a second working rail UR 1  and a second non-working rail UR 2 . The second working rail UR 1  and the second non-working rail UR 2  may extend parallel to each other in the interface zone IZ. The first transport units  110 L and  110 U and the second transport units  120 L and  120 U traveling on the second working rail UR 1  may each perform a loading operation or an unloading operation of the carrier  10  at a point where the transport units intersect the conveyor  130 . The first transport units  110 L and  110 U and the second transport units  120 L and  120 U traveling on the second non-working rail UR 2  may pass through the conveyor  130 , without performing a loading operation or an unloading operation of the carriers  10 . As a result, the second non-working rail UR 2  may function as an upper high-speed rail that does not perform the distribution exchange in the interface zone IZ from the plurality of upper rails UR. 
     In the following description, the operation of the substrate transfer system according to exemplary embodiments will be described more specifically referring to FIGS.  5 – 11   12 A  12 B  12 C  13 – 15   . 
       FIGS.  5 – 11   12 A  12 B  12 C  13 – 15    are diagrams for describing the operation of the substrate transfer system according to some exemplary embodiments. For reference,  FIG.  5    is a flowchart for describing the operation of the substrate transfer system according to some exemplary embodiments. Although  FIGS.  5 – 11   12 A  12 B  12 C  13 – 15    mostly describe the distribution transported from the first fabricating facility F1 to the second fabricating facility F2, this is merely an example, and the person who has common knowledge in the technical field to which the present inventive concept pertains may easily understand the distribution transported from the second fabricating facility F2 to the first fabricating facility F1. 
     Referring to  FIGS.  5  and  6   , the first transport units  110 L and  110 U are located in the interface zone IZ (S 10 ). 
     For example, the first lower transport unit  110 L into which the first carrier  10   a  is loaded may travel along the first working rail LR 1  of the lower rail LR and then stop at a point where it intersects the conveyor  130 . Further, the first upper transport unit  110 U into which the second carrier  10   b  is loaded may travel along the second working rail UR 1  of the upper rail UR and then stop at a point where it intersects the conveyor  130 . 
       FIG.  6    shows an example in which the first sub-lower transport unit  110 L 1  and the first sub-upper transport unit  110 U 1  each travel in the first traveling direction TD 1  and then stop at the first linear module  132 L 1  of the first conveyor  132 , and the second sub-lower transport unit  110 L 2  and the second sub-upper transport unit  110 U 2  each travel in the second travel direction TD 2  opposite to the first travel direction TD 1  and then stop at the first linear module  132 L 1  of the first conveyor  132 . 
     Although not specifically shown, the first lower transport unit  110 L traveling along the first non-working rail LR 2  of the lower rail LR may travel continuously, without stopping in the interface zone IZ. As a result, the first lower transport unit  110 L traveling along the first non-working rail LR 2  may function as the lower high-speed transport unit. Further, the first upper transport unit  110 U traveling along the second non-working rail UR 2  of the upper rail UR may travel continuously, without stopping in the interface zone IZ. As a result, the first upper transport unit  110 U traveling along the second non-working rail UR 2  may function as the upper high-speed transport unit. 
     Referring to  FIGS.  5  and  7  to  9   , the carriers (the first carrier  10   a  and the second carrier  10   b ) are unloaded from the first transport units  110 L and  110 U onto the conveyor  130  (S 20 ). 
     For example, the first lower transport unit  110 L may unload the first carrier  10   a  onto the first linear module  132 L 1  of the first conveyor  132 , and the first upper transport unit  110 U may unload the second carrier  10   b  onto the first linear module  132 L 1  of the first conveyor  132 . 
     In some exemplary embodiments, unloading (S 20 ) of the first carrier  10   a  and the second carrier  10   b  onto the conveyor  130  may include a determination (S 22 ) as to whether the first transport units  110 L and  110 U are placed on the upper rail UR. 
     If the first transport units  110 L and  110 U are not the transport units placed on the upper rail UR (for example, if the first transport units  110 L and  110 U are not the first lower transport unit  110 L), the first transport units  110 L and  110 U do not slide the first carrier  10   a  and unload the first carrier  10   a  onto the conveyor  130  (S 26 A) (see  FIG.  9   ). As an example, as described above in  FIG.  2   , the first elevating portion  115   a  may lower the first grip portion  117   a  fastened to the first carrier  10   a  toward the conveyor  130 . The first grip portion  117   a  may unload the first carrier  10   a  onto the conveyor  130  by releasing the fastening with the first carrier  10   a . As a result, the first carrier  10   a  may be unloaded onto the first linear module  132 L 1  of the first conveyor  132 . 
     If the first transport units  110 L and  110 U are transport units placed on the upper rail UR (for example, if the first transport units  110 L and  110 U are the first upper transport unit  110 U), the first transport units  110 L and  110 U slide the second carrier  10   b  (S 24 ) (see  FIG.  8   ), and unload the second carrier  10   b  onto the conveyor  130  (S26B) (see  FIG.  9   ). As an example, as described above in  FIG.  3   , the slider  112   b  may slide the second elevating portion  115   b  in the outward direction of the second cover portion  111   b . The sliding second elevating portion  115   b  may lower the second grip portion  117   b  fastened to the carriers  10  toward the conveyor  130 . The second grip portion  117   b  may unload the second carrier  10   b  onto the conveyor  130  by releasing the fastening with the carrier  10 . Accordingly, the second carrier  10   b  may be unloaded onto the first linear module  132 L 1  of the first conveyor  132 . 
     In some exemplary embodiments, the first carrier  10   a  and the second carrier  10   b  may be unloaded at the same time. For example, as shown in  FIG.  9   , the operation in which the first lower transport unit  110 L unloads the first carrier  10   a  onto the first linear module  132 L 1  may be performed at the same time as the operation in which the first upper transport unit  110 U unloads the second carrier  10   b  onto the first linear module  132 L 1 . 
     Referring to  FIGS.  5 ,  10  and  11   , the conveyor  130  is in operation (S 30 ). 
     As the conveyor  130  is in operation, the first carrier  10   a  and the second carrier  10   b  unloaded onto the conveyor  130  may be moved. For example, the first conveyor  132  may move the unloaded first carrier  10   a  and second carrier  10   b  in the first linear direction MD 1 . 
     In some exemplary embodiments, operating (S 30 ) the conveyor  130  may include a determination (S 32 ) as to whether the traveling directions of the first transport units  110 L and  110 U are different from the traveling directions of the second transport units  120 L and  120 U. 
     If the traveling directions of the first transport units  110 L and  110 U are not different from the traveling directions of the second transport units  120 L and  120 U (for example, if the traveling direction of the first lower transport unit  110 L is the same as the traveling direction of the second lower transport unit  120 L), the carriers (the first carrier  10   a  or the second carrier  10   b ) are moved without turning (S 36 A). As an example, as described in  FIG.  4   , the first linear module  132 L 1  may move the unloaded first carrier  10   a  and second carrier  10   b  in the first linear direction MD 1 . The first turning module  132 T may produce the first carrier  10   a  or the second carrier  10   b , which is provided from the first linear module  132 L 1 , to the second linear module  132 L 2  without turning. Therefore, the first carrier  10   a  or the second carrier  10   b  which is not reversed may be provided onto the second linear module  132 L 2 . The second linear module  132 L 2  may move the first carrier  10   a  and the second carrier  10   b , which are provided from the first turning module  132 T, in the first linear direction MD 1 . 
     If the traveling directions of the first transport units  110 L and  110 U are different from the traveling directions of the second transport units  120 L and  120 U (for example, if the traveling direction of the first lower transport unit  110 L is different from the traveling direction of the second lower transport unit  120 L), the carriers (the first carrier  10   a  or the second carrier  10   b ) are turned (S 34 ), and the carriers (the first carrier  10   a  or the second carrier  10   b ) are moved (S 36 B). As an example, as described above in  FIG.  4   , the first linear module  132 L 1  may move the unloaded first carrier  10   a  and second carrier  10   b  in the first linear direction MD 1 . The first turning module  132 T may turn the first carrier  10   a  or the second carrier  10   b  provided from the first linear module  132 L 1 , and may provide them to the second linear module  132 L 2 . Accordingly, the reversed first carrier  10   a  or second carrier  10   b  may be provided onto the second linear module  132 L 2 . The second linear module  132 L 2  may move the first carrier  10   a  and the second carrier  10   b  provided from the first turning module  132 T in the first linear direction MD 1 . 
     Referring to  FIGS.  5  and  12 A to  12 C , the second transport units  120 L and  120 U are located in the interface zone IZ (S 40 ). 
     For example, the second lower transport unit  120 L, into which the carrier is not loaded, may travel along the first working rail LR 1  of the lower rail LR and then stop at a point where it intersects the conveyor  130 . Further, the second upper transport unit  120 U, into which the carrier is not loaded, may travel along the second working rail UR 1  of the upper rail UR and then stop at a point where it intersects the conveyor  130 . 
     Although not specifically shown, the second lower transport unit  120 L traveling along the first non-working rail LR 2  of the lower rail LR may travel continuously without stopping in the interface zone IZ. Accordingly, the second lower transport unit  120 L traveling along the first non-working rail LR 2  may function as the lower high-speed transport unit. Further, the second upper transport unit  120 U traveling along the second non-working rail UR 2  of the upper rail UR may travel continuously without stopping in the interface zone IZ. Accordingly, the second upper transport unit  120 U traveling along the second non-working rail UR 2  may function as the upper high-speed transport unit. 
       FIG.  12 A  shows an example in which the third sub-lower transport unit  120 L 1  and the third sub-upper transport unit  120 U 1  each travel in the first traveling direction TD 1  and then stop on the second linear module  132 L 2  of the first conveyor  132 , and the fourth sub-lower transport unit  120 L 2  and the fourth sub-upper transport unit  120 U 2  each travel in the second traveling direction TD 2  and then stop on the second linear module  132 L 2  of the first conveyor  132 . 
     As described above in  FIGS.  10  and  11   , if the traveling directions of the first transport units  110 L and  110 U are the same as the traveling directions of the second transport units  120 L and  120 U, the carriers (the first carrier  10   a  or the second carrier  10   b ) may not be reversed, and if the traveling directions of the first transport units  110 L and  110 U are different from the traveling directions of the second transport units  120 L and  120 U, the carriers (the first carrier  10   a  or the second carrier  10   b ) may be reversed. As an example, as shown in  FIGS.  6  and  12 A , since both traveling directions of the first sub-lower transport unit  110 L 1  and the third sub-lower transport unit  120 L 1  are the same as the first traveling direction TD 1 , the first turning module  132 T may provide the first carrier  10   a  to the second linear module  132 L 2  without turning the first carrier  10   a . As another example, since both traveling directions of the first sub-upper transport unit  110 U 1  and the third sub-upper transport unit  120 U 1  are the same as the first traveling direction TD 1 , the first turning module  132 T may provide the second carrier  10   b  to the second linear module  132 L 2  without turning the second carrier  10   b . 
       FIG.  12 B  shows an example in which all the second lower transport units  120 L travel in the first traveling direction TD 1  and then stop on the second linear module  132 L 2   of the first conveyor  132 , and all the second upper transport units  120 U travel in the second traveling direction TD 2  and then stop on the second linear module  132 L 2  of the first conveyor  132 . 
     As described above in  FIGS.  10  and  11   , if the traveling directions of the first transport units  110 L and  110 U and the second transport units  120 L and  120 U are the same, the carriers (the first carrier  10   a  or the second carrier  10   b ) may not be reversed, and if the traveling directions of the first transport units  110 L and  110 U and the second transport units  120 L and  120 U are different, the carriers (the first carrier  10   a  or the second carrier  10   b ) may be reversed. As an example, as shown in  FIGS.  6  and  12 B , since both the traveling directions of the first sub-lower transport unit  110 L 1  and the third sub-lower transport unit  120 L 1  are the same as the first traveling direction TD 1 , the first turning module  132 T may provide the first carrier  10   a  to the second linear module  132 L 2  without turning the first carrier  10   a . As another example, since the first traveling direction TD 1  of the first sub-upper transport unit  110 U 1  and the second traveling direction TD 2  of the third sub-upper transport unit  120 U 1  are different from each other, the first turning module  132 T may turn the second carrier  10   b  and provide it to the second linear module  132 L 2 . 
       FIG.  12 C  shows an example in which both the second lower transport unit  120 L and the second upper transport unit  120 U travel in the second traveling direction TD 2  and then stop at the second linear module  132 L 2  of the first conveyor  132 . 
     As described above in  FIGS.  10  and  11   , if the traveling directions of the first transport units  110 L and  110 U and the second transport units  120 L and  120 U are the same, the carriers (the first carrier  10   a  or the second carrier  10   b ) may not be reversed, and if the traveling directions of the first transport units  110 L and  110 U and the second transport units  120 L and  120 U are different, the carriers (the first carrier  10   a  or the second carrier  10   b ) may be reversed. As an example, as shown in  FIGS.  6  and  12 C , since the first traveling direction TD 1  of the first sub-lower transport unit  110 L 1  and the second traveling direction TD 2  of the third sub-lower transport unit  120 L 1  are different from each other, the first turning module  132 T may turn the first carrier  10   a  and provide it to the second linear module  132 L 2 . As another example, since the first traveling direction TD 1  of the first sub-upper transport unit  110 U 1  and the second traveling direction TD 2  of the third sub-upper transport unit  120 U 1  are different from each other, the first turning module  132 T may turn the second carrier  10   b  and provide it to the second linear module  132 L 2 . 
     Referring to  FIGS.  5  and  13  to  15   , the carriers (the first carrier  10   a  and the second carrier  10   b ) are loaded from the conveyor  130  to the second transport units  120 L and  120 U (S 50 ). 
     For example, the second lower transport unit  120 L may load the first carrier  10   a  from the second linear module  132 L 2  of the first conveyor  132 , and the second upper transport unit  120 U may load the second carrier  10   b  from the second linear module  132 L 2  of the second conveyor  132 . 
     In some exemplary embodiments, loading of the first carrier  10   a  and the second carrier  10   b  into the second transport units  120 L and  120 U may include determining whether the second transport units  120 L and  120 U are placed on the upper rail UR. 
     If the second transport units  120 L and  120 U are not transport units placed on the upper rail UR (for example, if the second transport units  120 L and  120 U are the second lower transport unit  120 L), the first carrier  10   a  may be loaded without sliding (see  FIGS.  13  and  14   ). As an example, as described above in  FIG.  2   , the first elevating portion  115   a  may lower the first grip portion  117   a  toward the conveyor  130  on which the first carrier  10   a  is placed, and the first grip portion  117   a  may be fastened to the first carrier  10   a . The first elevating portion  115   a  may load the first carrier  10   a  from the conveyor  130 , by raising the first elevating portion  115   a  fastened to the first carrier  10   a . Accordingly, the first carrier  10   a  may be loaded from the second linear module  132 L 2  of the first conveyor  132 . 
     If the second transport units  120 L and  120 U are transport units placed on the upper rail UR (for example, if the second transport units  120 L and  120 U are the second upper transport unit  120 U), the second carrier  10   b  may be slid and loaded (see  FIGS.  13  to  15   ). As an example, as described above in  FIG.  3   , the slider  112   b  may slide the second elevating portion  115   b  in an outward direction of the second cover portion  111   b . The sliding second elevating portion  115   b  may lower the second grip portion  117   b  toward the conveyor  130  on which the carriers  10  are placed, and the second grip portion  117   b  may be fastened to the carrier  10 . The second elevating portion  115   b  raises the second elevating portion  115   b  fastened to the carriers  10 , and the slider  112   b  may slide the second elevating portion  115   b  in an inward direction of the second cover portion  111   b  again. Accordingly, the second carrier  10   b  may be loaded from the second linear module  132 L 2  of the first conveyor  132 . 
     In some exemplary embodiments, the first carrier  10   a  and the second carrier  10   b  may be loaded simultaneously. For example, as shown in  FIG.  13   , the operation in which the second lower transport unit  120 L loads the first carrier  10   a  from the second linear module  132 L 2  may be performed at the same time as the operation in which the second upper transport unit  120 U loads the second carrier  10   b  from the second linear module  132 L 2 . 
     In order to maximize the capacity to handle different semiconductor elements and the effective area of equipment, a cluster type/cloud type fabricating facility (Cluster/Cluster FAB) that integrally produces semiconductor elements by connecting the plurality of fabricating facilities (FAB) to each other is required. However, at present, since the distribution control system divides the control system for each fabricating facility to minimize the production damage due to unexpected sudden failure, there is a problem in direct movement and transport between the fabricating facilities using the distribution transport device. Therefore, an efficient interface zone operation for distribution exchange between fabricating facilities is indispensable. 
     Since the substrate transfer system according to some exemplary embodiments includes the lower rail LR, the upper rail UR, the first transport units  110 L and  110 U, the second transport units  120 L and  120 U, and the conveyor  130  placed inside the interface zone IZ, efficient distribution exchange between the fabricating facilities is possible. 
     Specifically, as described above, the substrate transfer system according to some exemplary embodiments includes multi-layer rails (the lower rail LR and the upper rail UR) that overlap in the vertical direction, and thus, has an enhanced transport capacity, compared to a substrate transfer system including only a single rail. Further, in the substrate transfer system according to some exemplary embodiments, the conveyor  130  may be spaced apart from the ground of the semiconductor fabricating facility, it is possible to utilize the space more efficiently than other interface equipment (for example, a stocker) installed on the ground. Further, in the substrate transfer system according to some exemplary embodiments, since the conveyor  130  is simply made up of the linear modules (e.g., the first linear module  132 L 1  and the second linear module  132 L 2 ) and the turning module (e.g., the first turning module  132 T), it has a reduced investment cost compared to other interface equipment (e.g., a stocker) that requires a lot of labor and is costly to install. 
       FIG.  16    is a schematic block diagram for describing a semiconductor fabricating facility including the substrate transfer system according to some exemplary embodiments. For convenience of description, repeated parts of contents described above using  FIGS.  1 – 11   12 A  12 B  12 C  13 – 15    will be either briefly described or omitted as redundant. 
     Referring to  FIG.  16   , the semiconductor fabricating facility according to some exemplary embodiments includes a plurality of fabricating facilities Fa, Fb, Fc and Fd and an interface zone IZ. 
     Each of the plurality of fabricating facilities Fa, Fb, Fc and Fd may be connected to the interface zone IZ. Each of the fabricating facilities Fa, Fb, Fc and Fd may correspond to the first fabricating facility F1 or the second fabricating facility F2 described above using  FIGS.  1 – 11   12 A  12 B  12 C  13 – 15   . The interface zone IZ may perform the distribution exchange between the fabricating facilities Fa, Fb, Fc and Fd. For example, the interface zone IZ may include the lower rail LR, the upper rail UR, the first transport units  110 L and  110 U, the second transport units  120 L and  120 U, and the conveyor  130  described above using  FIGS.  1 – 11   12 A  12 B  12 C  13 – 15   . 
     The semiconductor fabricating facility according to some exemplary embodiments may further include bridge zones Ba and Bb. The bridge zones Ba and Bb may interconnect adjacent fabricating facilities from fabricating facilities Fa, Fb, Fc and Fd. For example, a first bridge zone Ba which connects the fabricating facility Fb and the fabricating facility Fc, and a second bridge zone Bb which connects the fabricating facility Fc and the fabricating facility Fd may be provided. The bridge zones Ba and Bb may perform the distribution exchange between the adjacent fabricating facilities among the fabricating facilities Fa, Fb, Fc and Fd. For example, the bridge zones Ba and Bb may also include the lower rail LR, the upper rail UR, the first transport units  110 L and  110 U, the second transport units  120 L and  120 U, and the conveyor  130  described above using  FIGS.  1 – 11   12 A  12 B  12 C  13 – 15   . 
     While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of skill in the art that various changes in form and modifications in details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims. It is therefore desired that the present exemplary embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than the foregoing description to ascertain the scope of the invention.