Patent Publication Number: US-9412634-B2

Title: Atmosphere replacement apparatus, substrate transport apparatus, substrate transport system, and EFEM

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priorities of Japanese Patent Application No. 2013-233572 filed on Nov. 11, 2013 and Japanese Patent Application No. 2013-233573 filed on Nov. 11, 2013. The contents of the application are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an atmosphere replacement apparatus capable of replacing an atmosphere around a substrate during transportation, a substrate transport apparatus, a substrate transport system, and an Equipment Front End Module (EFEM). 
     2. Description of the Related Art 
     Conventionally, production of semiconductors has been carried out by various processing steps performed on a wafer as a substrate. In recent years, circuit miniaturization and high integration of elements have been increasingly promoted. It has been required to maintain a high level of cleanliness around a wafer to prevent adhesion of water and particles to a surface of a wafer. Further, to prevent changes in properties of a surface of a wafer, such as oxidization, it has been performed to make a periphery of a wafer vacuum or nitrogen atmosphere that is an inert gas. 
     In order to properly maintain such an atmosphere around a wafer, a wafer is managed by placing in a sealable storage pod called a Front-Opening Unified Pod (FOUP), and nitrogen is filled inside the pod. Further, to transfer a wafer between a FOUP and a processing apparatus for processing a wafer, an Equipment Front End Module (EFEM) as disclosed in Patent Application Publication No. 2012-49382 is provided. An EFEM constitutes a wafer transport chamber that is substantially closed inside a housing, comprises a load port that functions as an interface unit between the FOUP on one of opposite wall surfaces, and is connected to a load lock chamber that is a part of a processing apparatus on the other of the wall surfaces. In a wafer transport chamber, a wafer transport apparatus is provided, constituting a wafer transport system for transporting a wafer. By using a wafer transport apparatus, a wafer is loaded and unloaded between a load lock chamber and a FOUP connected to a load port. 
     In other words, a wafer is taken out from the FOUP (a load port) that is one transfer position by using the wafer transport apparatus, and transported to the load lock chamber that is the other transfer position. The processing apparatus performs processing for a wafer transported through the load lock chamber within a processing unit called a process chamber. After the processing is completed, the wafer is taken out through the load lock chamber, and returned to the FOUP. 
     The interior of the processing apparatus is made to a special atmosphere, a vacuum or the like in accordance with the processing, to enable quickly the processing for a wafer. The interior of the wafer transport chamber in the EFEM is kept in a clean air atmosphere at a high level of cleanliness by introducing the air cleaned through a chemical filter or the like, to prevent contamination due to adhesion of particles or the like to the surface of a wafer during transport. 
     However, in recent years, as the cleanliness has been advanced more and more, although the cleanliness is high in the wafer transport chamber of EFEM, the influence of the air atmosphere different from the interior of the FOUP or the processing apparatus has been concerned. 
     In other words, the air atmosphere has a possibility of adhesion of moisture and oxygen to the surface of a substrate, causing corrosion and oxidation. Further, when a corrosive gas or the like used in the processing apparatus remains on the surface of a wafer, it may cause corrosion of a wiring material on the wafer surface and deterioration in yield. To avoid such a problem, as in the FOUP, when the atmosphere replacement apparatus is provided to make a nitrogen atmosphere inside the wafer transport chamber, since the volume of the wafer transport chamber is large, a large amount of nitrogen gas is required, increasing the cost, and it takes a long time to replace nitrogen. Further, if nitrogen leaks from the EFEM, it may cause a problem of oxygen deficiency in the surrounding. Further, in recent years, an EFEM capable of connecting multiple FOUPs has been proposed in order to increase the efficiency. This increases the volume of the wafer transport chamber, and the above problem may become conspicuous. 
     In addition, the above problem arises similarly during transportation of a substrate other than a wafer, as long as the transportation is done in an atmosphere different from a processing or storage location. 
     The present invention has been made to solve efficiently the above problems. In particular, it is an object of the invention to provide an atmosphere replacement apparatus capable of replacing atmosphere on a surface of a substrate during transportation by a small amount of gas, a substrate transport apparatus, a substrate transport system, and an Equipment Front End Module (EFEM). 
     SUMMARY OF THE INVENTION 
     In order to achieve the above object, the present invention has taken the measures as described below. 
     An atmosphere replacement apparatus according to an embodiment of the present invention comprises a cover that is able to face and cover a substrate to be transported, and a gas supply means that supplies gas having properties different from a surrounding atmosphere from the cover, and replaces an atmosphere on a surface of a substrate by the gas. 
     In such a configuration, by supplying a gas having properties different from a surrounding atmosphere to the surface of a substrate with the cover faced to the substrate, it is possible to appropriately replace an atmosphere around the surface of the substrate, and prevent adverse effects on the substrate. In addition, as compared with the case of replacing all atmospheres around the substrate transport apparatus, it is possible to reduce the supply amount of gas, the cost of gas, and the time required to replace the atmosphere. Further, even when the gas leaks to the surroundings, as the supply amount of gas is small, it is possible to suppress deterioration in the working environment. 
     Further, in order to make the cover movable independently of a substrate, cause to perform a preparatory operation for a substrate to be next transported, and retract to be unused when the gas supply is unnecessary, it is preferable to configure the atmosphere replacement apparatus to be used in a substrate transport system that transports a substrate between multiple transfer positions by a substrate transport apparatus, and to comprise a cover moving means that supports the cover movable independently of the substrate transport apparatus, wherein when the substrate transport apparatus transports a substrate, the cover moving means moves the cover to a position opposite to a substrate. 
     In order to replace an atmosphere around the surface of a substrate with a small amount of gas, and avoid interference between the cover and the substrate and the substrate transfer apparatus, it is preferable to comprise a cover approach and separation means that approaches or separates the cover from the surface of a substrate. 
     In order to further reduce the supply amount of gas by decreasing the amount of gas leaking to other than the substrate surface, it is preferable that the cover comprises a main body part able to face a substrate and a wall part provided on a periphery of the main body part, and a substrate is housed in an internal space formed between the main body part and the wall part, when the cover approach and separation means moves the cover close to a substrate. 
     In order to be able to reduce the supply amount of gas, it is preferable to provide a cover receiving member in the substrate transport apparatus, which substantially closes the internal space in cooperation with the cover, when the cover is approaches a substrate, and an open end of the cover wall part approaches or contacts the cover receiving member. 
     In order to replace efficiently an atmosphere on the surface of a substrate by supplying gas to the entire surface of a substrate only by introducing gas as easily as general piping, it is preferable that the gas supply means comprises a gas inlet for introducing gas from outside, and a gas diffusion means for diffusing gas downward the cover from the gas inlet. 
     In order to eliminate moisture effectively by increasing a temperature of the surface of a substrate, it is preferable that the gas supply means comprises a heating means for heating the gas. 
     In order to configure easily and inexpensively a substrate transport system comprising the atmosphere replacement apparatus and the substrate transport apparatus, it is preferable to configure the cover moving means by using a guide rail that constitutes a part of the substrate transport apparatus. 
     It is possible to configure as an effective EFEM capable of transferring between a FOUP and a processing apparatus, while maintaining good properties on the surface of a wafer, by configuring as an EFEM that comprises the substrate transport system, and a housing for covering the substrate transport system, wherein the substrate is a wafer, and the transfer position is set adjacent to a wall surface of the housing. 
     It is possible to configure as an effective EFEM capable of transferring between a FOUP and a processing apparatus, while maintaining good properties of the surface of a wafer, by configuring as an EFEM comprising a substrate transport system that includes the atmosphere replacement apparatus and the substrate transport apparatus, and a housing for covering the substrate transport system, wherein the substrate is a wafer, and the cover moving means is supported on a ceiling provided within the housing, and the transfer position is set adjacent to a wall surface of the housing. 
     Further, the substrate transport apparatus according to an embodiment of the invention comprises the atmosphere replacement apparatus described above, and further comprises a transport arm that is supported by a base, and holds and transports a substrate, and a support bar that is provided on the same base as the transport arm, wherein the cover is located at a position able to face the transport arm via the support bar. 
     In such a configuration, when the transport arm transports a substrate, the gas supply means supplies a gas having properties different from a surrounding atmosphere to the surface of a substrate from the cover arranged above the transport arm, and the atmosphere around the surface of a substrate can be replaced with the gas. Thus, the surrounding atmosphere having an influence upon the substrate surface can be appropriately changed. In addition, as compared with the case of replacing all atmospheres around the substrate transport apparatus, it is also possible to reduce the supply amount of gas, the cost of gas, and the time required to replace the atmosphere. Further, even when the gas leaks to the surroundings, as the amount of gas is small, it is possible to suppress deterioration in the working environment. Further, since the cover having the gas supply means is provided on the same base as the transport arm, it is possible to reduce the installation area by making the entire structure compact. 
     In order to avoid interference of the cover to the transport arm and substrate, and to enable to replace the atmosphere around the surface of a substrate with smaller amount of gas by moving the cover close to a substrate depending upon a transport state, and, it is preferable to be configured to include a cover approach and separation means that approaches or separates the cover from the surface of a substrate. 
     In order to reduce the supply amount of gas by decreasing the amount of gas leaking to the parts other than the surface of a substrate, it is preferable that the cover comprises a main body part able to face a substrate and a wall part provided on the periphery of the main body part, and a substrate is housed in an internal space formed between the main body part and the wall part, when the cover approach and separation means approaches or separates the cover from a substrate. 
     In order to further reduce the supply amount of gas, it is preferable to be configured to comprise a cover receiving member that substantially closes the internal space in cooperation with the cover, when the cover approaches a substrate, and an open end of the cover wall part approaches or contacts the cover receiving member. 
     In order to expand a range capable of transporting a substrate without increasing the length of the transport arm, it is preferable to be configured to comprise a guide rail that supports the base movable. 
     In order to further reduce the supply amount of gas by reducing the size of the cover, it is preferable be configured to comprise a cover moving means that supports the cover movable in a direction orthogonal to the guide rail. 
     In order to effectively supply gas to the surface of a substrate during transportation with a simple structure, it is preferable to be configured to set a transfer position for transferring a substrate to the transfer arm on both sides of the guide rail, across the guide rail, and to extend the cover in a direction orthogonal to the guide rail. 
     In order to effectively replace the atmosphere on the substrate surface by diffusing and supplying gas to the entire surface of a substrate, while a gas inlet is configured as simple as general piping, it is preferable that the gas supply means comprises a gas inlet for introducing gas from outside, and a gas diffusion means for diffusing gas below the cover from the gas inlet. 
     In order to eliminate moisture effectively by increasing a temperature of the surface of a substrate by the supplied gas, it is preferable that the gas supply means comprises a heating means for heating the gas. 
     It is possible to configure as an effective EFEM capable of transferring between a FOUP and a processing apparatus, while maintaining good properties on the surface of a wafer, by configuring as an EFEM that comprises the substrate transport apparatus, and a housing for covering the substrate transport apparatus, wherein the substrate is a wafer, and a transfer position for transferring a substrate is set adjacent to a wall surface of the housing. 
     According to the invention described above, it is possible to provide an atmosphere replacement apparatus capable of replacing an atmosphere around a substrate during transportation by a small amount of gas without increasing the cost and time required for the replacement, a substrate transport apparatus, a substrate transport system, and an Equipment Front End Module (EFEM). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view schematically showing a positional relationship between an EFEM that comprises a substrate transport system including an atmosphere replacement apparatus according to a first embodiment, and a processing apparatus. 
         FIGS. 2( a ) and ( b )  are explanatory drawings schematically showing the essential parts of a substrate transport system including the atmosphere replacement apparatus. 
         FIGS. 3( a ) and ( b )  are explanatory views showing a positional relation with a cover when a transport arm in the substrate transport system is operated from the state shown in  FIG. 2 . 
         FIG. 4  is a plan view schematically showing the state that the transport arm of the substrate transport system is inserted into a FOUP. 
         FIG. 5  is a plan view schematically showing the state that the transport arm of the substrate transport system is inserted into a load lock chamber. 
         FIG. 6  is a plan view showing the state before the transport arm of the substrate transport system is inserted into a FOUP. 
         FIG. 7  is a plan view showing the state that the transport arm of the substrate transport system is inserted into a FOUP from the state of  FIG. 6 . 
         FIG. 8  is an explanatory drawing showing the state that the transfer arm takes out a wafer from a FOUP from the state of  FIG. 7 . 
         FIG. 9  is an explanatory drawing showing the state that a wafer is moved onto a guide rail from the state of  FIG. 8 . 
         FIG. 10  is an explanatory drawing showing the state that the transport arm moves along the guide rail from the state of  FIG. 9 , and located at a position before the load lock chamber. 
         FIG. 11  is an explanatory drawing showing the state that the transport arm moves close to the load lock chamber from the state of  FIG. 10 . 
         FIG. 12  is an explanatory drawing showing the state that the transport arm enters the load lock chamber from the state of  FIG. 11 . 
         FIGS. 13( a ) and ( b )  are explanatory drawings showing the structure of a cover constituting the atmosphere replacement apparatus. 
         FIGS. 14( a ) and ( b )  are explanatory drawings showing the structure of a cover different from  FIG. 13 . 
         FIG. 15( a )-( c )  are explanatory drawings showing the structure of a cover different from those shown in  FIG. 13  and  FIG. 14 . 
         FIGS. 16( a ) and ( b )  are explanatory drawings showing an atmosphere replacement apparatus according to a second embodiment of the invention, and the structure of a substrate transport system that comprises the apparatus. 
         FIG. 17  is an explanatory drawing showing the structure of a substrate transport system according to a third embodiment of the invention. 
         FIG. 18  is a plan view schematically showing a positional relationship between a processing apparatus and an EFEM comprising a wafer transport apparatus according to a fourth embodiment of the invention. 
         FIGS. 19( a ) and ( b )  are explanatory drawings schematically showing enlarged essential parts of the wafer transport apparatus. 
         FIGS. 20( a ) and ( b )  are explanatory drawings showing the state that the transport arm is operated from the state of  FIG. 19 . 
         FIGS. 21( a ) and ( b )  are explanatory drawings for explaining a cover support means in the wafer transport apparatus of  FIG. 19 . 
         FIG. 22  is a plan view schematically showing the state that the transport arm of the wafer transport apparatus enters a FOUP. 
         FIG. 23  is a plan view schematically showing the state that the transport arm of the wafer transport apparatus enters a load lock chamber. 
         FIGS. 24( a ) and ( b )  are explanatory drawings showing the structure of a cover constituting the wafer transport apparatus. 
         FIGS. 25( a ) and ( b )  are explanatory drawings showing the structure of a cover different from that shown in  FIG. 24 . 
         FIG. 26( a )-( c )  are explanatory drawings showing the structure of a cover different from those shown in  FIG. 24  and  FIG. 25 . 
         FIGS. 27( a ) and ( b )  are explanatory drawings schematically showing enlarged essential parts of a wafer transport apparatus according to a fifth embodiment of the invention. 
         FIGS. 28( a ) and ( b )  are explanatory drawings showing the state that the transport arm is operated from the state of  FIG. 27 . 
         FIG. 29  is a plan view schematically showing an EFEM comprising a wafer transport apparatus according to a sixth embodiment of the invention. 
         FIGS. 30( a ) and ( b )  are explanatory drawings schematically showing enlarged essential parts of the wafer transport apparatus. 
         FIGS. 31( a ) and ( b )  are explanatory drawings showing the state that the transport arm is operated from the state of  FIG. 30 . 
         FIG. 32  is a plan view schematically showing the state that the transport arm of the wafer transport apparatus enters a FOUP. 
         FIG. 33  is a plan view schematically showing the state that the transport arm of the wafer transport apparatus enters the load lock chamber. 
         FIG. 34  is an explanatory drawing for explaining the structure of a wafer transport apparatus according to a seventh embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings. 
     First Embodiment 
     As shown in  FIG. 1 , an atmosphere replacement apparatus  1  of a first embodiment configures a wafer transport apparatus  2  or a substrate transport apparatus, and a wafer transport system TS or a substrate transport system. A wafer transport chamber  5  is substantially closed by a housing  51  surrounding the apparatus or system. A plurality of load ports  61  (four in the drawing) is provided adjacent to one wall surface  51   a  of the housing. The load ports and the wafer transport system TS configure an EFEM. The drawing schematically shows the state that a FOUP  62  is placed on the load port  61 . Each load port  61  has a door  61   a . As the door  61   a  moves in conjunction with a lid  62   a  of the FOUP  62 , the FOUP  62  is opened to the wafer transport chamber  5 . In the FOUP  62 , a plurality of placing portions  62   b  for supporting one wafer W in pairs is provided in the vertical direction. By using them, a plurality of wafers W can be stored. A nitrogen gas can be filled in the FOUP  62 , and an atmosphere in the FOUP  62  can be replaced with nitrogen via the load port  61 . 
     The wafer transport chamber  5  constituting an EFEM can be connected to the load lock chamber  81  that constitutes a part of a processing unit PE adjacent to a wall surface  51   b  opposite to the load port  61 . By opening a door  81   a  of the load lock chamber  81 , the load lock chamber  81  can communicate with the wafer transport chamber  5 . A variety of configurations can be used as a processing unit PE. Generally, a transport chamber  82  is provided adjacent to the load lock chamber  81 , and a plurality of processing units  83  (three in the drawing) is provided adjacent to the transport chamber  82 . A door  82   a  is provided between the load lock chamber  81  and the transport chamber  82 , and a door  83   a  is provided between a processing unit  83  and the transport chamber  82 . By opening the doors, the chambers and the unit can communicate each other, and a transport robot  82   b  provided within the transport chamber  82  can transfer a wafer W between the load lock chamber  81  and the processing unit  83 . 
       FIG. 2  and  FIG. 3  are schematic diagrams showing an enlarged view of a wafer transport system TS in the embodiment.  FIG. 2( a )  is a plan view when each part is set to a reference position.  FIG. 2( b )  is a front view in that state.  FIG. 3( a )  is a plan view showing the state that a transport arm  22  described later extends so as to enter the FOUP  62 .  FIG. 3( b )  is a front view in that state. Hereinafter, a configuration of the wafer transport system TS will be explained with reference to  FIG. 2  and  FIG. 3 . 
     A wafer transport apparatus  2 , constituting the wafer transport system TS with the atmosphere replacement apparatus  1 , comprises a guide rail  24  arranged in a straight line on the bottom of the wafer transport chamber  5  to be parallel to the wall surface  51   a ,  51   b  (see  FIG. 1 ), a base  21  that is supported on the guide rail  24  and movable along the guide rail  24 , and a transport arm  22  supported on the base  21 . 
     The transport arm  22  can be a variety of structures that is generally known. For example, it is possible to appropriately use a SCARA type horizontal articulated robot or a link type arm robot. In the embodiment, the transport arm comprises a plurality of arm elements  22   a  to  22   c , and the entire transport arm  22  can be extended by moving them relatively. At the tip of the end arm element  22   c , a U-shaped plate-like end effector  23  is provided to place a wafer W thereon. The transport arm  22  is able to pivot horizontally with respect to the base  21  so as to turn the end effector  23  in either direction of the wall surfaces  51   a  and  51   b.    
     By configuring as above, the wafer transport apparatus  2  can move a wafer W placed on the end effector  23  constituting the transport arm  22  in two axes, in the directions parallel to and orthogonal to the wall surfaces  51   a  and  51   b . Further, the base  21  can move up and down. By combining these movements, it is possible to lift the wafer W by the end effector  23 , and to move the wafer W placed on the end effector  23  to a predetermined transfer position. In the EFEM in the embodiment, the FOUP  62  provided in a plurality of load ports  61  and the load lock chamber  81  (see  FIG. 1 ) opposite to them are set as a transfer position for transferring the wafer W, and the wafer transport apparatus  2  can move the wafer W between them. 
     The atmosphere replacement apparatus  1  comprises broadly a cover  3  for supplying a gas G for replacing an atmosphere while covering the surface of the wafer W, and a cover support means  4  for supporting the cover  3 . 
     The cover  3  is formed in a hood shape, including a disk-shaped main body part  31 , and a wall part  32  extending downward from a peripheral edge of the main body part. The cover  3  is formed slightly larger than the wafer W in a plan view so as to cover the wafer W. Thus, it is possible to house the wafer W in the downwardly opened internal space S (see  FIG. 13 ) formed by the main body part part  31  and the wall part  32 , and opened downward. 
     The cover  3  can be a variety of structures as described later in detail. Here, a structure of a cover  3 B shown in  FIG. 13( b )  is adopted. In other words, a gas supply port  34  is provided at the center of an upper surface  31   b  to enable to release the gas G supplied through the gas supply port  34  from a not-shown gas supply source downward, while diffusing by a diffusion plate  33 . The gas supply source can selectively change supply and stop of the gas G to enable to supply the gas G only when necessary. It is possible to be configured to change a supply pressure and a flow rate. A gas supply means MG for supplying the gas G from the cover  3  is comprised of the gas supply source, and a gas G supply structure from the gas supply port  34  to diffusion plate  33  provided in the cover  3 . Here, a nitrogen gas is used as the gas G. 
     Returning to  FIG. 2  and  FIG. 3 , in addition to a base for the cover  41  that is supported by the guide rail  24  and movable along the guide rail  24 , the cover support means  4  comprises a rail  42  for the cover, a movable block  43 , a support bar  44 , a lifting block  45 , and a support arm  46 , which are sequentially supported on the base for the cover. 
     In particular, on the base for the cover  41 , the rail for the cover  42  is provided so as to extend in a horizontal direction orthogonal to the guide rail  24 . The movable block  43  is supported movable on the rail for the cover  42 . By configuring like this, the movable block  43  can move in a direction orthogonal to the wall surfaces  51   a  and  51   b  (see  FIG. 1 ). On the movable block  43 , the support bar  44  is provided standing upward and movable with the movable block  43 . The support bar  44  is provided with the lifting block  45  movable in the vertical direction along the support bar  44 , so that the support arm  46  extends from the lifting block  45  in parallel to the guide rail  24 , and supports the center of the upper surface  31   b  of the main body part  31  constituting the cover  3  at the tip (see  FIG. 13 ). 
     Further, as shown in  FIG. 2( a ) , when the base for the cover  41  approaches the base  21  of the wafer transport apparatus  2 , and the movable block  43  is set at a reference position located above the guide rail  24 , the cover  3  supported by the support arm  46  is located right above the wafer transport apparatus  2 . At this time, when the wafer transport apparatus  2  contracts the transport arm  22 , and moves the wafer W supported on the end effector  23  onto the base  2 , the wafer W is placed to be covered by the cover  3  in a plan view. 
     By configuring as above, it is possible to move the cover  3  in a direction parallel to the wall surfaces  51   a  and  51   b  by the base for the cover  41  and the guide rail  24 , and in a direction vertical to the wall surfaces  51   a  and  51   b  by the rail for the cover  42  and the movable block  43 . In other words, the base for the cover  41 , the guide rail  24 , the rail for the cover  42 , and the movable block  43  constitute a cover moving means MH capable of operating the cover  3  to follow the wafer W moved by the transport arm  22 . Further, it is possible to move the cover  3  in the vertical direction by the support bar  44  and the lifting block  45 , so that the cover  3  approaches to or separates from a wafer surface F as a substrate surface formed by the surface of the wafer W. In other words, the support bar  44  and the lifting block  45  constitute a cover approach and separation means MV that approaches and separates the cover with respect to the wafer surface F. 
     By operating the wafer transport system TS comprising the atmosphere replacement apparatus  1  configured as described above under the control of a controller Cp (see  FIG. 1 ), the wafer W can be transported in the following manner. The controller Cp is appropriately configured to control the entire EFEM, and moves the cover  3  in synchronization with the wafer transport apparatus  2  by the cover moving means MH and the cover approach and separation means MV, and can supply the gas G from the cover  3  by the gas supply means MG. 
     As shown in  FIG. 4 , the wafer transport apparatus  2  constituting the substrate transport system TS moves the base  21  to the front of the FOUP  62 , a target to take out the wafer W, along the guide rail  24 , extends the transport arm  22  to insert the end effector  23  into the FOUP  62 , and takes out the wafer W from the FOUP  62 . And, as shown in  FIG. 5 , the wafer transport apparatus  2  moves the base  21  to the front of the load lock chamber  81 , extends the transport arm  22  in the reverse direction to insert the end effector  23  into the load lock chamber  81 , and transfers the wafer W. In a part of the transport route, while moving to follow and face the wafer W, the cover  3  can supply the gas G to the surface of the wafer W by the gas supply means MG (see  FIG. 13 ), and can replace the atmosphere on the surface of the wafer W. 
     The above operation will be explained in detail by using  FIG. 6  to  FIG. 12 . 
       FIG. 6  shows the state that the base  21  of the wafer transport apparatus  2  moves along the guide rail  24  for transporting the wafer W, and the transport arm  22  is positioned before the load port  61  that is one transfer position. In the drawing, the other load port  61  that is not related to the transportation is omitted. Since the cover moving means MH can move the cover  3  independently of the base  21 , the cover  3  can be set at an appropriate position. Since the base  21  is operable independently of the cover  3 , the base can move accurately in lightweight. 
       FIG. 7  shows the state that the door  61   a  of the load port  61  and the lid  62   a  of the FOUP  62  are open, and the transport arm  22  extends to insert the end effector  23  into the FOUP  62 , from the state of  FIG. 6 . The end effector  23  enters with a small gap just below the wafer W to be taken out, and can lift and hold the wafer W by raising the base  21  a predetermined amount. In this state, the cover moving means MH moves the cover  3  to the front of the FOUP  62 . At this time, the cover approach and separation means MV sets the open end  32   a  of the wall part  32  of the cover  3  (see  FIG. 13 ) to a position higher than the upper surface of the wafer (the wafer surface F) placed on the end effector  23 . 
       FIG. 8  shows the state that the transport arm  22  contracts from the state of  FIG. 7  to take out the wafer W (see  FIG. 7 ) from the FOUP  62 . Since the cover  3  has been waiting in front of the FOUP  62 , the cover  3  can face and cover the wafer W immediately after the wafer W is taken out to the front of the FOUP  62 . In this state, the cover approach and separation means MV moves the cover  3  downward to house the upper part of the wafer W in the internal space S. Further, the gas supply means MG (see  FIG. 13 ) starts supplying the gas G, and the atmosphere on the wafer W surface is replaced to the atmosphere of the gas G from the same air atmosphere as the atmosphere in the wafer transport chamber  5 . The load port  61  closes the door  61   a  and the lid  62   a  of the FOUP  62  at a position where the wafer W does not interfere, and fills the FOUP  62  with a nitrogen gas, thereby preventing oxidation or adhesion of moisture on the surface of the housed wafer W other than the taken-out wafer W. 
       FIG. 9  shows the state that the transport arm  22  contracts further from the state of  FIG. 8  to position the end effector  23  (see  FIG. 7 ) at the center of the base  21  in a plan view. In conjunction with the movement of the transfer arm  22  as described above, the cover moving means MH moves the cover  3 . Thus, it is possible to replace the atmosphere on the wafer W surface (see  FIG. 7 ) efficiently for a long time. Therefore, there is no wasting the time required to transport the wafer W. 
       FIG. 10  shows the state that the base  21  moves from the state of  FIG. 9  to the front of the load lock chamber  81  as the other transfer position. In conjunction with the movement of the base  21 , the base  41  for the cover constituting the cover moving means MH can move on the guide rail  24 , and can keep the cover  3  opposite to the wafer W (see  FIG. 7 ). Thus, the gas G can be continuously supplied to the wafer W surface during the movement. 
       FIG. 11  shows the state that the transport arm  22  extends into the load lock chamber  81  from the state of  FIG. 10  to position the end effector  23  (see  FIG. 7 ) to the front of the door  81   a  of the load lock chamber  81 . At this time as well, the cover moving means MH causes the cover  3  to follow the wafer W (see  FIG. 7 ) to keep the position opposite to the wafer W. Thus, the gas G can be continuously supplied to the wafer W surface. 
       FIG. 12  shows the state that the door  81   a  of the load lock chamber  81  is open, and the transport arm  22  extends further from the state of  FIG. 11  to insert the end effector  23  into the load lock chamber. At this time, the cover  3  stops in front of the load lock chamber  81 , and is lifted by the cover approach and separation means MV, so as not interfere with the load lock chamber  82 , the wafer W, and the transport arm  22 . In this state, the transport arm  22  is lowered by lowering the base  21 , and the wafer W on the end effector  23  is transferred into the load lock chamber  81 . At this time, the cover  3  may perform a preparatory operation to move in advance near the position where a wafer W to be next transported is present, for the next transport operation, independently of the movement of the transport arm  22 . When transporting a wafer W that is unnecessary to replace the atmosphere on the surface, it is also possible to retract the cover  3  near the end of the guide rail  24 . 
     As described above, by using the wafer transport system TS comprising the atmosphere replacement apparatus  1 , when transporting a wafer W to the load lock chamber  81  from the FOUP  62 , it is possible to maintain a proper surface state of the wafer W by replacing a local atmosphere around the wafer W surface via the cover  3 , without replacing the entire atmosphere in the wafer transport chamber  5 . 
     Further, when transporting a wafer W to the FOUP  62  from the load lock chamber  81 , it is possible to replace a local atmosphere around the surface of the wafer W as well by reversely performing the operations of  FIG. 6  to  FIG. 12  described above. 
     Here, a specific structure of the cover  3  will be explained. It is possible to employ any type of cover  3 A- 3 G shown in  FIGS. 13 to 15 , and use them selectively depending on a purpose. 
     The cover  3 A shown in  FIG. 13( a )  has a simple structure, and is formed by suspending the wall part  32  from the peripheral edge  31   a  of the aforementioned disk-shaped main body part  31 . At the center of the upper surface  31 , the gas supply port  34  configured similar to a common gas supply pipe opening is provided to enable to supply the gas G through the support arm  46  (see  FIGS. 2 and 3 ). The gas supply port  34  communicates with the internal space S, and the supplied gas G can be released downward while filling the inner space. At this time, when a nitrogen gas is used as the gas G, because of its nature lighter than air, it is possible to increase the concentration of the nitrogen gas in the internal space S by excluding air easily from the internal space S. Thus, since the concentration of the nitrogen gas has been increased to a certain level or higher, the supply amount of the nitrogen gas may be reduced. Also in this way, it is possible to maintain the state that the atmosphere on the wafer W surface is replaced with the nitrogen gas. 
     The cover  3 B shown in  FIG. 13( b )  is configured based on the structure of the cover  3 A, and is provided with a diffusion plate  33  as a diffusion means below the main body part  31 . The diffusion plate  33  has a large number of small holes  33   a . By passing through the diffusion plate, the gas G is diffused substantially uniformly and released downward. Thus, when using the diffusion plate, it is possible to supply the gas G appropriately at any position on the wafer W surface. 
     The cover  3 C shown in  FIG. 14( a )  is configured based on the structure of the cover  3 A (see  FIG. 13 ), and is provided with a heater  35  as a heating means inside the main body part  31 . Being configured like this, it is possible to supply the gas G to the wafer W surface by heating the gas G, thereby increasing an atmospheric temperature of the wafer W surface. Thus, it is possible to eliminate moisture by increasing the temperature of the wafer W surface. Further, when a process of increasing the temperature inside the processing apparatus PE (see  FIG. 1 ) is required, it is also possible to reduce the processing time by preheating. 
     The cover  3 D shown in  FIG. 14( b )  is configured based on the structure of the cover  3 A (see  FIG. 13 ), and is provided with a branch pipe  37  as a diffusion means for diffusing the gas G inside the main body part  31 . Being configured like this, it is possible to uniformly diffuse and release the gas G, and supply the gas G properly at any position on the wafer W surface. 
     The cover  3 E shown in  FIG. 15( a )  combines the structure of the cover  3 B (see  FIG. 13 ) and the structure of the cover  3 C (see  FIG. 14 ). Being configured like this, it is possible to heat, diffuse, and supply the gas G properly to the wafer W surface. As shown in this example, the diffusion plate  33  may be provided more than one ( 2  in the drawing), and it is possible to further diffuse and uniformly supply the gas G. 
     The cover  3 F shown in  FIG. 15( b )  is configured based on the structure of the cover  3 E, and the open end  32   a  of the wall part  32  extends downward. Being configured like this, the internal space S can cover not only the entire transport arm  22 , but also the wafer W. Thus, it is possible to increase the concentration of the gas G filled in a space around the wafer W. 
     The cover  3 G shown in  FIG. 15( c )  is configured based on the structure of the cover  3 E, and the heating means is changed from the heater  35  to a heating lamp  36 . Even in this structure, it is possible to heat, diffuse, and supply the gas G properly to the wafer W surface. Being configured such that light radiated from the heating lamp  36  reaches the wafer W, the temperature on the wafer W surface is directly increased without the gas G. 
     As described above, the atmosphere replacement apparatus  1  in the embodiment is configured to include the cover  3  able to face and cover a wafer W as a substrate to be transported, and the gas supply means MG that supplies the gas G having the properties different from those of the surrounding atmosphere from the cover  3 , and replaces the atmosphere on the wafer W surface by the gas G. 
     Being configured as above, it is possible to face the cover  3  to the wafer W, supply the gas G, having the properties different from the surrounding atmosphere, to the wafer W surface from the cover  3 , and replace the atmosphere around the wafer W surface. Thus, it is possible to avoid adverse effects on the wafer W surface by changing properly the surrounding atmosphere having an influence to the wafer W surface. In addition, as compared with the case of replacing all the surrounding atmospheres, it is possible to reduce the supply amount of gas G, and reduce the cost and time required for replacing the atmosphere. Further, even when the gas G leaks to the surroundings, as the amount of gas is small, it is possible to suppress deterioration in the working environment. 
     Further, the atmosphere replacement apparatus  1  in the embodiment is configured to be used in a wafer transport system TS as a substrate transport system that transports a wafer W between multiple transfer positions by the wafer transport apparatus  2  as a substrate transport apparatus. The apparatus  1  is further provided with a cover moving means MH that supports the cover  3  movable independently of the wafer transport apparatus  2 , and is configured such that when the wafer transport apparatus  2  transports a wafer W, the cover moving means MH moves the cover  3  to a position opposite to the wafer. 
     Being configured as described above, it is possible to move the cover  3  so as to face the wafer W transported by the wafer transport apparatus  2  by using the cover moving means MH, supply the gas G having the properties different from the surrounding atmosphere to the wafer W surface from the cover  3 , and replace the atmosphere around the wafer W surface with the gas G. Thus, it is possible to avoid adverse effects on the wafer W surface by changing properly the surrounding atmosphere having an influence upon the wafer W surface. In addition, as compared with the case of replacing all the surrounding atmospheres, it is possible to reduce the supply amount of gas G, and reduce the cost and time required for replacing the atmosphere. Further, even when the gas G leaks to the surroundings, as the amount of gas is small, it is possible to suppress deterioration in the working environment. Further, since the cover moving means MH can move the cover  3  independently of the wafer W, it is possible to perform a preparatory operation for a wafer W to be next transported, and retract to be unused when the supply of gas G is unnecessary. This enables more efficient use. 
     Being configured to include a cover approach and separation means MV that approaches or separates the cover  3  from the wafer surface F as a substrate surface, it is possible to prevent interference with the wafer W and the transport arm  22  constituting the wafer transport apparatus  2 . In addition, it is also possible to replace the atmosphere around the wafer W surface with a small amount of gas G by approaching the cover according to the transportation state. 
     Further, as the cover  3  is configured to comprise the main body part  31  capable of facing a wafer W, and the wall part  32  provided on the periphery of the main body part  31 , and the wafer W can be housed in the internal space S formed between the main body part  31  and the wall part  32 , when the cover approach and separation means MV moves the cover  3  close to the wafer W. Thus, it is possible to reduce the supply amount of gas G by decreasing the amount of the gas G leaking to the parts other than the wafer W surface by supplying the gas G in the state that the wafer W is housed in the internal space S. 
     Further, as the gas supply means MG is configured to include the gas inlet port  34  for introducing the gas G from outside, and the diffusion plate  33  or the branch pipe  37  as a diffusion means for diffusing the gas G downward the cover  3  from the gas inlet port  34 , it is possible to replace efficiently the atmosphere on the surface of a wafer W by effectively diffusing and efficiently supplying the gas G to the entire surface of the wafer W, while making the structure of the gas inlet port  34  as simple as a general piping. 
     Further, as the gas supply means MG is configured to include the heater  35  or the heating lamp  36  as a heating means for heating the gas G, it is possible to increase the temperature of the wafer W surface by heating the supplied gas G, and it is also possible to eliminate moisture. When temperature increases is necessary in the processing apparatus PE, it is possible to reduce the processing time by preheating. 
     Further, the wafer transport system TS, as a substrate transport system in the embodiment, comprises the atmosphere replacement apparatus  1  configured as described above, and the wafer transport apparatus  2 , and the cover moving means MV is configured is configured to use the guide rail  24  constituting a part of the wafer transport apparatus  2 . It is possible to reduce the installation space of the entire equipment, while reducing the overall production costs. It is also possible to configure by easily adding to an existing EFEM that is provided only the wafer transport apparatus  2 . 
     Further, being configured to use a wafer W as a substrate, and to include the wafer transport system TS, and the housing  51  for housing the wafer transport system TS, and to set the load port  61  and the load lock chamber  81  as a transfer position adjacent to the wall surfaces  51   a  and  51   b  of the housing  51 , it is possible to configure as an effective EFEM that performs transfer between the transfer positions while maintaining the suitable atmosphere on the wafer W surface, by using the wafer transport system TS provided in the housing  51 . 
     Second Embodiment 
       FIG. 16  is a schematic view showing an atmosphere replacement apparatus  101  of the second embodiment. Also in this case, the atmosphere replacement apparatus  101  constitutes the wafer transport system TS as a substrate transport system, and the wafer transport apparatus  2  as a substrate transport apparatus. In the drawing, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted. 
     In the embodiment, the wafer transport apparatus  2  is the same as that explained in the first embodiment, except the structure of the atmosphere replacement apparatus  101 . 
       FIG. 16( a )  schematically shows the positional relationship of the wafer transport system TS when viewed from a direction that the guide rail  24  (see  FIG. 1 ) constituting the wafer transport apparatus  2  extends. 
     The atmosphere replacement apparatus  101  is supported in a state being suspended from a ceiling surface  51  provided in a housing  51  constituting a wafer transport chamber  5  via a cover support means  104 . The cover support means  104  comprises a cover moving means MH that moves the cover  3  horizontally along the guide rail  24  (see  FIG. 1 ), and a cover approach and separation means MV that approaches or separates the cover  3  from a wafer surface F by moving the cover  3  in a vertical direction. 
     The cover  3  comprises a main body part  131 , and a wall part  132  that is provided on a periphery of the main body part part and suspended therefrom. These parts of the cover form an internal space S opened downward. A gas supply port  134  is provided at the center of the upper surface  131   b  to enable to supply the gas G via a cover support means  104 . The main body part  131  includes a diffusion plate  33  to enable to diffuse and supply the gas G downward. 
     Further, as shown in  FIG. 16( b ) , when the transport arm  22  contracts and positions a wafer W with an end effector  23  on a base  21 , the cover  3  covers the entire transport arm  22  to contain in the internal space S. Thus, it is possible to increase the concentration of gas G around the wafer W, and enhance the effect by the replacement of atmosphere. 
     Even when configuring as above, being provided with the atmosphere replacement apparatus  101  comprising the cover  3  that is able to face and cover a wafer W to be transported, and the gas supply means MG that supplies a gas G different from a surrounding atmosphere from the cover  3 , and replaces the atmosphere on the surface of the wafer W with the gas G, it is possible to obtain the same effect as the first embodiment, and further increase the independence of the atmosphere replacement apparatus  101  and the wafer transport apparatus  2 . 
     In other words, as the embodiment is configured to comprise the wafer transport system TS that includes the atmosphere replacement apparatus  101  and the wafer transport apparatus  2 , and the housing  51  for covering the substrate transfer system TS, wherein a wafer W is used as a substrate, the cover moving means MH is supported on the ceiling surface  51   c  provided in the housing, and the load port  61  and the load lock chamber  81  are set as a transfer position adjacent to the wall surfaces  51   a  and  51   b  of the housing  51 , it is possible to be configured as an effective EFEM that can transport a wafer W by easily moving the atmosphere replacement apparatus  101  with a high degree of freedom without interfering with the wafer transport apparatus  2  provided in the housing  51 . 
     Third Embodiment 
       FIG. 17  schematically shows a configuration of a wafer transport system TS in the third embodiment. In the drawing, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and the explanation thereof is omitted. The wafer transport system TS is a modified from the structure of the wafer transport apparatus  202  by using the atmosphere replacement apparatus  101  explained in the second embodiment. 
     In particular, a disk-shaped cover receiving member  225  is provided on the base  221  that constitutes a wafer transport apparatus  202  and supports a transport arm  22 . The cover receiving member  225  has a diameter slightly larger than the cover  103  in a plan view to enable to substantially close the internal space S in cooperation with the cover, when the cover  103  moves downward, and an open end  132   a  of a wall part  132  in the cover  103  approaches the upper surface  225   a  of the cover receiving member  225 . Thus, it is possible to further increase the concentration of gas G, when the gas G is supplied to the internal space S, and increase the effect by the replacement of atmosphere. 
     Of course, it is permitted to make contact between the open end  132   a  and the upper surface  225   a . By contacting and sealing the both after the atmosphere is replaced with the gas G, the atmosphere replaced state can be maintained even after the supply of the gas G is stopped, and the wafer W surface is not contaminated. 
     Even when configuring as above, being provided with the atmosphere replacement apparatus  101  comprising the cover  3  that is able to face and cover a wafer W to be transported, and the gas supply means MG that supplies a gas G different from a surrounding atmosphere from the cover  3 , and replaces the atmosphere on the surface of the wafer W with the gas G, it is possible to obtain the same effect as the first embodiment and the second embodiment. In addition, since the wafer transport apparatus  202  is configured to include the cover receiving member  225  that can substantially close the internal space S in cooperation with the cover, when the cover  103  approaches the wafer W, and the open end  132   a  of the wall part  132  of the cover  103  approaches or contacts the cover receiving member, a substantially closed space is formed between the cover  103  and the cover receiving member  225 , and the supply amount of gas G can be further reduced by housing the wafer W into the space. 
     Fourth Embodiment 
     A substrate transport apparatus of the fourth embodiment is, as shown in FIG.  18 , configured as a wafer transport apparatus  302 , and transports a wafer W as a substrate. In the drawing, the same parts as those in the first to third embodiments are denoted by the same reference numerals. A wafer transport chamber  5  is configured to be substantially closed by a housing  51 . A plurality of load ports  61  (four in the drawing) is provided adjacent to one wall surface  51   a  of the housing. The load ports and the wafer transport apparatus  302  configure an EFEM. The drawing schematically shows the state that a FOUP  62  is placed on the load port  61 . Each load port  61  has a door  61   a . As the door  61   a  moves in conjunction with a lid  62   a  of the FOUP  62 , the FOUP  62  is opened to the wafer transport chamber  5 . In the FOUP  62 , a plurality of placing portions  62   b  for supporting one wafer W in pairs is provided in the vertical direction. By using them, a plurality of wafers W can be stored. A nitrogen gas can be filled in the FOUP  62 , and the atmosphere in the FOUP can be replaced with nitrogen via the load port  61 . 
     The wafer transport chamber  5  constituting an EFEM can be connected to the load lock chamber  81  which constitutes a part of a processing unit PE adjacent to the wall surface  51   b  that faces the load port  61 . By opening a door  81   a  of the load lock chamber  81 , the load lock chamber  81  can communicate with the wafer transport chamber  5 . A variety of configurations can be used as a processing unit PE. Generally, a transport chamber  82  is provided adjacent to the load lock chamber  81 , and a plurality of processing units  83  (three in the drawing) is provided adjacent to the transport chamber  82 . A door  82   a  is provided between the load lock chamber  81  and the transport chamber  82 , and a door  83   a  is provided between a processing unit  83  and the transport chamber  82 . By opening the doors, the chambers and the unit can communicate each other, and a transport robot  82   b  provided within the transport chamber  82  can transfer a wafer W between the load lock chamber  81  and the processing unit  83 . 
       FIG. 19  and  FIG. 20  are schematic diagrams showing an enlarged view of a wafer transport apparatus  302  in the embodiment.  FIG. 19( a )  is a plan view when each part is set to a reference position.  FIG. 19( b )  is a front view in that state.  FIG. 20( a )  is a plan view showing the state that a transport arm  322  described later is extended to enter the FOUP  62 .  FIG. 20( b )  is a front view in that state. Hereinafter, the configuration of the wafer transport apparatus  302  will be explained with reference to  FIG. 19  and  FIG. 20 . 
     The wafer transport apparatus  302  comprises a guide rail  324  arranged in a straight line on the bottom of the wafer transport chamber  5  to be parallel to the wall surface  51   a ,  51   b  (see  FIG. 18 ), a base  321  that is supported on the guide rail  324  and movable along the guide rail  324 , and a transport arm  322  supported on the base  321 , and a cover  303  that is supported by a cover support means  304  above the transport arm  322 . 
     The transport arm  322  can be a variety of structures that are generally known. For example, it is possible to appropriately use a SCARA type horizontal articulated robot or a link type arm robot. In the embodiment, the transport arm comprises a plurality of arm elements  322   a  to  322   c , and the entire transport arm  322  can be extended by moving them relatively. At the tip of the end arm element  322   c , a U-shaped plate-like end effector  323  is provided to enable to mount a wafer W thereon. The transport arm  322  is able to pivot horizontally with respect to the base  321  so as to turn the end effector  323  in either direction of the wall surfaces  51   a  and  51   b.    
     By configuring as above, the wafer transport apparatus  302  can move the wafer W placed on the end effector  323  constituting the transport arm  322  in two axes in the directions parallel to and orthogonal to the wall surfaces  51   a  and  51   b . Further, the base  321  can move up and down. By combining these movements, it is possible to lift the wafer W with the end effector  323 , and to move the wafer W placed on the end effector  323  to a predetermined transfer position. In other words, the base  321  in the embodiment is configured to support the transport arm  322  on the guide rail  324 , and at the same time, it is configured to cause the transport arm  322  to move along the guide rails  324 , and to contract/extend and move up/down toward the wall surfaces  51   a  and  51   b , by using an actuator (not shown) incorporated inside. In the EFEM in the embodiment, the FOUP  62  provided in a plurality of load ports  61  and the load lock chamber  81  (see  FIG. 18 ) opposite to them are set as a transfer position for transferring the wafer W, and it is possible to move the wafer W between them by using the wafer transport apparatus  302 . 
     The wafer transport apparatus  302  in the embodiment is particularly characterized by comprising the cover  303  provided on the transport arm  322 , as described above, and the cover support means  304  that supports the cover  303  on the base  321 . 
     The cover  303  is formed in a hood shape, including a disk-shaped main body part  331 , and a wall part  332  extending downward from a peripheral edge of the main body part. The cover  3  is formed slightly larger than the wafer W in a plan view to be able to cover the wafer W. Thus, it is possible to house the wafer W in the internal space S (see  FIG. 24 ) that is formed by the main body part  331  and the wall part  332 , and opened downward. 
     The cover  303  can be a variety of structures as described later in detail. Here, the structure of a cover  303 B shown in  FIG. 24( b )  is adopted. In other words, a gas supply port  334  is provided in the middle of the upper surface  331   b , so that a gas G supplied through the gas supply port  334  from a not-shown gas supply source can be released downward while diffusing by a diffusion plate  333 . A gas supply source can selectively change supply and stop of the gas G, and can supply the gas G only when necessary. It is possible to configure to change a supply pressure and a flow rate. A gas supply means MG for supplying the gas G from the cover  303  comprises a gas supply source, and a gas G supply structure in the cover  303 , from the gas supply port  334  to the diffusion plate  333 . Here, a nitrogen gas is used as the gas G. 
     Returning to  FIG. 19  and  FIG. 20 , the cover support means  304  comprises a pair of support bars  341  that is separated in the extending direction of the guide rail  324  and erected from the base  321  at an appropriate position not to interfere with the transport arm  322 , and lifting blocks  342  supported by the support bars  341  movable in a vertical direction. The lifting blocks  342  supports the upper surface  331   b  of the main body part  331  of the cover  303  (see  FIG. 24 ). 
       FIG. 21( a )  shows the wafer transport apparatus  302  of  FIGS. 19( a ) and ( b )  viewed from a different angle of 90°. The base  321  is supported movable on the guide rail  24  as described above, supports the transport arm  322 , and enables the transport arm  322  to extend/contract and move up/down. The pair of support bars  341  extends from the side of the base  321  toward the direction along the guide rail  324 , and stands upward. The upper parts of the support bars  341  support the lifting blocks  342 . 
     Instead of the above configuration, it is allowed to have the structure of a wafer transport apparatus  702  as shown in  FIG. 21( b ) . In other words, a base  721  comprises a liner motion plate part  721   a  including a moving mechanism along the guide rail  324 , and a main body part  721   b  including a mechanism for performing extension/contraction and lifting operation of the transport arm  322 . A cover support means  704  for supporting the cover  303  may be comprised of a support bar  741  erected upward from the linear motion plate part  721   a , and a lifting block  742  that is supported movable vertically on the support bar. 
     Returning to  FIG. 19  and  FIG. 20 , the cover  303  constituting the wafer transport apparatus  302  in the embodiment is supported on the same base  321  as the transport arm  322 , and can be moved along the guide rail  324  together with the transport arm  322 . Further, it is possible to move the cover  303  by the relative movement of the support bar  341  and the lifting block  342 , and approach to or separate from the wafer surface F as a substrate surface formed by the wafer W surface. In other words, when viewing functionally the support bar  341  and the lifting block  342 , it can be said that they constitute the cover approach and separation means MV that approaches or separates the cover  303  from the wafer surface F. 
     To the gas supply port  334  provided in the cover  303 , the pipe  343  through which a gas G is supplied from the gas supply source described above is connected. 
     As described above, the wafer transport apparatus  302  of the embodiment comprises the cover  303  that is able to face and cover a wafer W to be transported, the gas supply means MG that supplies a gas G different from a surrounding atmosphere from the cover  303  and replaces the atmosphere on the wafer W surface with the gas G, and as in the first to third embodiments, an atmosphere replacement apparatus including the cover  303  and the gas supply means MG. 
     The wafer transport apparatus  302  configured as described above is operated under the control of the controller Cp (see  FIG. 18 ), and the wafer W can be transported as follows. The controller Cp is appropriately configured to control the entire EFEM to be able to move the cover  303  by the cover approach and separation means MV in synchronization with the operation of the transport arm  322 , and to supply the gas G from the gas supply means MG. 
     Here, as an example, an explanation will be made on the case of transporting a wafer W to the load lock chamber  81  from the FOUP connected to the load port  61  as one transfer position. 
     In other words, as shown in  FIG. 22 , the wafer transport apparatus  302  moves the base  321  along the guide rail  324 , and positions the transport arm  322  in front of the load port  61  as one transfer position. Then, the wafer transport apparatus opens the door  61   a  of the load port  61  and the lid  62   a  of the FOUP  62  connected to the load port, and extends the transport arm  322  to insert the end effector  323  into the FOUP  62 . At this time, as shown in  FIG. 20 , the end effector  323  enters with a slight gap just below the wafer W to be taken out, and lifts and holds the wafer W when the base  321  is raised a predetermined amount. At this time, the cover approach and separation means MV sets the open end  332   a  of the wall part  332  in the cover  303  (see  FIG. 24 ) at a position higher than the upper surface of the wafer W (the wafer surface F) placed on the end effector  323 . 
     And, as shown in  FIG. 19 , the transport arm  322  contracts to position the wafer W held by the end effector  323  above the base  321 . Thus, the wafer W is opposed to the cover  303 . In this state, the cover approach and separation means MV moves the cover  303  downward so as to contain slightly the top of the wafer W in the internal space S of the cover  303 . Further, the gas supply means MG (see  FIG. 24 ) starts supplying the gas G so as to replace the atmosphere on the wafer W surface from the air atmosphere that is the same as that inside the wafer transport chamber  5  to the atmosphere of the gas G. 
     In this case, as the cover  303  is slightly larger than the wafer W in a plan view as described above, even when the wafer W is housed in the internal space S, a gap is formed around the wafer W. Thus, by supplying the gas G from the gas supply port  334 , the air, forming the atmosphere on the wafer W surface is efficiently discharged to the outside through the gap around the wafer W, and the atmosphere in the internal space S can be replaced with the nitrogen gas. 
     Reaching the position where the wafer W does not interfere, the load port  61  closes the door  61   a  and the lid  62   a  of the FOUP  62  so as to fill the FOUP  62  with a nitrogen gas, and prevents oxidation or adhesion of moisture on the surface of the housed wafer W other than the taken-out one. 
     As described above, in parallel with the replacement of the atmosphere on the surface of the wafer W, the base  321  moves along the guide rail  324 , and reaches the front of the load lock chamber  81 . By replacing the atmosphere on the surface of the wafer W in parallel with a part of the transportation, an increase in time is prevented. 
     Then, as shown in  FIG. 23 , the door  81   a  of the load lock chamber  81  (see FIG.  22 ) is opened, and the end effector  323  of the transport arm  322  enters inside the chamber. At this time, the cover approach and separation means MV raises the cover  303  not to interfere with the wafer W and the transport arm  322 . Then, the base  321  is lowered to move down the transport arm  322  so as to transfer the wafer W on the end effector  323  into the load lock chamber  81 . 
     As described above, by using the wafer transport apparatus  302 , when transporting the wafer W from the FOUP to the load lock chamber  81 , it is possible to maintain a proper surface state of the wafer W by replacing a local atmosphere around the wafer W surface via the cover  303 , without replacing the entire atmosphere inside the wafer transport chamber  5 . 
     Further, when transporting the wafer W from the load lock chamber  81  to the FOUP  62 , it is possible to replace a local atmosphere around the wafer W surface as well by performing the above operation in reverse. 
     Here, a specific structure of the cover  303  will be explained. Any type of the covers  303 A to  303 G shown in  FIGS. 24 to 26  can be employed, and used depending on the purpose. 
     The cover  303 A shown in  FIG. 24( a )  has a simple structure, and is formed by suspending the wall part  332  from a peripheral edge  331   a  of the aforementioned disk-shaped main body part  331 . At the center of the upper surface  331   b , the gas supply port  334  configured similar to a common gas supply pipe opening is provided to enable to supply the gas G through the pipe  343  (see  FIGS. 19 and 20 ). The gas supply port  334  communicates with the internal space S, and the supplied gas G can be released downward while filling the inner space. At this time, when a nitrogen gas is used as the gas G, because of its nature lighter than air, it is possible to increase the concentration of the nitrogen gas in the internal space S by excluding air easily from the internal space S. Thus, since the concentration of the nitrogen gas has been increased to a certain level or higher, the supply amount of the nitrogen gas may be reduced. Also in this way, it is possible to maintain the state that the atmosphere on the wafer W surface is replaced with the nitrogen gas. 
     The cover  303 B shown in  FIG. 24( b )  is based on the structure of the cover  303 A, and is provided with a diffusion plate  333  as a diffusion means below the main body part  331 . The diffusion plate  333  has a large number of small holes  333   a . Passing through the diffusion plate, the gas G is diffused substantially uniformly and discharged downward. Thus, when using the diffusion plate, the gas G can be appropriately supplied at any position on the wafer W surface. 
     The cover  303 C shown in  FIG. 25( a )  is based on the structure of the cover  303 A (see  FIG. 24 ), and is provided with a heater  335  as a heating means inside the main body part  331 . By configuring like this, it is possible to supply a gas G to the wafer W surface by heating the gas G, and increase the atmospheric temperature of the wafer W surface. Thus, it is possible to eliminate moisture by increasing the temperature on the wafer W surface. Further, when a process of increasing the temperature inside the processing apparatus PE (see  FIG. 18 ) is required, it leads to a reduction of the processing time by preheating. 
     The cover  303 D shown in  FIG. 25( b )  is based on the structure of the cover  303 A (see  FIG. 24 ), and is provided with a branch pipe  337  as a diffusion means of diffusing the gas G inside the main body part  331 . By configuring like this, it is possible to uniformly diffuse and release the gas G, and supply the gas G properly at any position on the wafer W surface. 
     The cover  303 E shown in  FIG. 26( a )  combines the structure of the cover  303 B (see  FIG. 24 ) and the structure of the cover  303 C (see  FIG. 25 ). By configuring like this, it is possible to heat, diffuse, and properly supply the gas G to the wafer W surface. As shown in this example, the diffusion plate  333  may be provided more than one ( 2  in the drawing), and it is possible to further diffuse the gas G and supply uniformly. 
     The cover  303 F shown in  FIG. 26( b )  is based on the structure of the cover  303 E, and the open end  332   a  of the wall part  332  is extended downward. By configuring like this, it is possible to cover not only the wafer W, but also the entire transport arm  322  by the internal space S. Thus, it is possible to further increase the concentration of the gas G filled in the space around the wafer W. 
     The cover  303 G shown in  FIG. 26( c )  is based on the structure of the cover  303 E, and the heating means is changed from the heater  335  to a heating lamp  336 . Even in this structure, it is possible to heat, diffuse, and supply the gas G properly to the wafer W surface. By configuring so that the light radiated from the heating lamp  336  reaches the wafer W, the temperature on the wafer W surface may be increased directly without the gas G. 
     As described above, the wafer transport apparatus  302  as a substrate transport apparatus in the embodiment includes an atmosphere replacement apparatus similar to the atmosphere replacement apparatus  1  and  101  described in the first to third embodiments. In particular, the atmosphere replacement apparatus comprises the cover  303  capable of facing and covering a wafer W to be transported as a substrate, and the gas supply means MG that supplies a gas G having the properties different from a surrounding atmosphere from the cover  303 , and replaces the atmosphere on the wafer W surface with the gas G. Further, the wafer transport apparatus  302  of the embodiment comprises the transport arm  322  that is supported on the base  321 , and holds and transports the wafer W, and the support bar  341  that is provided on the same base  321  as the transport arm  322 . The cover  303  is disposed at a position capable of facing the transport arm  322  via the support bar  341 . 
     Being configured as above, when the transport arm  322  transports a wafer W, the gas supply means MG supply a gas G having properties different from a surrounding atmosphere to the surface of the wafer W from the cover  303  arranged above the transport arm  322 , and the atmosphere around the wafer W surface can be replaced with the gas G. Thus, it is possible to avoid adverse effects on the wafer W surface by changing properly the atmosphere around the wafer W surface. In addition, as compared with the case of replacing all atmospheres around the wafer transport apparatus  302 , it is possible to reduce the supply amount of gas G, and the cost and time required for replacing the atmosphere. Further, even when the gas G leaks to the surroundings, as the amount of gas is small, it is possible to suppress deterioration in the working environment. Further, as the cover  303  having the gas supply means MG is provided on the same base  321  as the transport arm  322 , it is possible to reduce the size of the whole structure, and suppress the installation area. 
     Further, being configured to include the cover approach and separation means MV that approaches or separates the cover  303  from the wafer surface F as a substrate surface, it is possible to avoid interference between the cover  303  and the wafer W or the transport arm  322  by operating the cover  303  by the cover approach and separation means MV, and it is also possible to replace the atmosphere around the wafer W surface with a less mount of gas G by approaching the cover  303  to the wafer W depending on the transport state. 
     In addition, the cover  303  comprises the main body part  331  capable of facing the wafer W, and the wall part  332  provided on the peripheral edge  331   a  of the main body part  331 , and the wafer W can be housed in the internal space S formed between the main body part  331  and the wall part  332 , when the cover  303  is moved close to the wafer W by the cover approach and separation means MV. Thus, it is possible to reduce the supply amount of gas G by decreasing the amount of gas G leaking to the parts other than the wafer W surface by the wall part  332  provided in the cover  303 . 
     Since the guide rail  24  is provided to support the base  321  movable, it is possible to expand the range of transporting the wafer W without increasing the length of the transport arm  322 . Further, the transport arm  322  and the cover  303  can be simultaneously moved along with the base  321 , and the atmosphere on the wafer W surface can be continuously replaced, when the wafer W is transported in the direction along the guide rail  324 . 
     Further, the gas supply means MG is configured to include the gas inlet port  334  for introducing a gas G from the outside, and the diffusion plate  333  or the branch pipe  337  as a diffusing means of diffusing the gas G downward the cover  303  from the gas inlet port  34 . It is possible to replace the atmosphere on the wafer W surface efficiently by diffusing the gas G efficiently, while the gas inlet port  334  is configured as simple as general piping. 
     The gas supply means MG is configured to further include the heater  335  or the heating lamp  336  as a heating means for heating the gas G. It is possible to increase the temperature on the wafer W surface and eliminate moisture by heating the supplied gas G When temperature increases is necessary in the processing apparatus PE, it is possible to reduce the processing time by preheating. 
     Further, being configured to use a wafer W as a substrate, include the wafer transport apparatus  302 , and the housing  51  for housing this, and set the load port  61  and the load lock chamber  81  as a transfer position adjacent to the wall surfaces  51   a  and  51   b  of the housing  51 , it is possible to configure as an effective EFEM that performs transfer between the transfer positions while maintaining the suitable atmosphere on the wafer W surface, by using the wafer transport apparatus  302  provided in the housing  51 . 
     Fifth Embodiment 
       FIG. 27  is a schematic view showing a wafer transport apparatus  402  as a substrate transport apparatus of the fifth embodiment. In the drawing, the same parts as those in the fourth embodiment are denoted by the same reference numerals, and the explanation thereof is omitted. 
     In the wafer transport apparatus  402  of the embodiment, the shape of a base  421  for supporting the transport arm  322  is rectangular in a plan view, and the structure of a cover support means  404  that supports the cover  303 , is different from that in the fourth embodiment. 
     In particular, a support bar  441  is erected on a side of the transport arm  322 , a rail  444  for the cover extending in the horizontal direction orthogonal to the guide rail  324  is provided on the support bar  441 , and a movable block  445  is supported movable on the rail  444  for the cover. Thus, the movable block  445  can move in the direction orthogonal to the wall surfaces  51   a  and  51   b  (see  FIG. 18 ). Further, a lifting block  466  is supported on the movable block  445  to be movable in the vertical direction, and the cover  303  is supported by the lifting block  446 . 
     In the above configuration, the movable block  445  and the rail  444  for the cover can move the cover  303  following a wafer that is moved by the transport arm  322 . A cover moving means MH is configured as above. As the lifting block  446  moves relative to the movable block  445 , the cover  303  can move in the vertical direction. A cover approach and separation means MV, configured in this manner, approaches and separates the cover  303  relative to the wafer surface F. 
     The gas supply port  334  provided in the cover  303  is connected to a pipe  443  from the gas supply source. 
     The wafer transport apparatus  402  can transport a wafer W as follows by under the control of the controller cp (see  FIG. 18 ). At this time, the controller Cp moves the cover  303  by the cover moving means MH and the cover approach and separation means MV in synchronization with the movement of the transport arm  322 , and the gas supply means MG supplies a gas G from the cover  303 . 
     First, as shown in  FIG. 28 , the cover moving means MH can move the cover  303  to the front of the load port  61 . Thus, before taking out the wafer W by extending the transport arm  322  to enter the FOUP  62 , the cover  303  can stand in front of the FOUP  62 , and go into the state to face and cover the wafer W. In this state, the cover approach and separation means MV moves the cover  303  close to the wafer W so as to supply the gas G. Thus, it is possible to reduce the time to expose the wafer W to the air atmosphere. 
     Then, the cover moving means MH moves the cover  303  in conjunction with the contraction of the transport arm  322 , and through the state of  FIG. 27 , the gas G is continuously supplied in the state that the cover  303  faces the wafer W, until the cover is moved to the front of the load lock chamber  81  (see  FIG. 2 ) that is the other transfer position. The cover  303  stops the movement linked to the transport arm  322  just before the load lock chamber  81 , and is raised by the cover approach and separation means MV. And, the transport arm  322  transfers the wafer W into the load lock chamber  81 . 
     As described above, as well as providing the same effect as that in the fourth embodiment, the wafer transport apparatus  402  can supply the gas G to the wafer W during transport by the transport arm  322  for a long time, and enhance the effect by the replacement of the atmosphere on the wafer W surface. In addition, the gas G can be effectively supplied while the size of the cover  303  is maintained substantially the same as the wafer W, and it is possible to avoid the waste of gas G. 
     As described above, since the wafer transport apparatus  402  in the embodiment comprises the cover  303  that can face and cover a wafer to be transferred, and the gas supply means MG that supplies a gas G different from a surrounding atmosphere from the cover  303 , and replaces the atmosphere on the wafer W surface by the gas G, as in the aforementioned embodiment, it can be said that the wafer transport apparatus includes an atmosphere replacement apparatus comprising the cover  303  and the gas supply means MG, and it is possible to provide substantially the same effect as the aforementioned embodiment. 
     Further, since the wafer transport apparatus  402  is configured to include a cover moving means MH that supports the cover  303  movable in the direction rectangular to the guide rail  324 , it is possible to cover the wafer for a long time by moving the cover  303  by the cover moving means MH in conjunction with the movement of the transport arm  322 . Thus, it is possible to enhance the effect by the replacement of the atmosphere on the wafer W. It is also possible to further reduce the supply amount of gas G by reducing the size of the cover  303 . 
     Sixth Embodiment 
       FIG. 29  a schematic view showing a wafer transport apparatus  502  of the sixth embodiment. In the drawing, the same parts as those in the fourth and fifth embodiments are denoted by the same reference numerals, and the explanation thereof is omitted. 
     The wafer transport apparatus  502  in the embodiment is characterized in that the shape of a cover  503  supported by a cover support means  504  on the base  321  is substantially rectangular in a plan view. In particular, the cover  503  is arranged with the longitudinal side orthogonal to the guide rail  324 , and across the guide rail  324 , the short sides are close respectively to the wall surface  51   a  adjacent to the load port  61  that is one transfer position, and the wall surface  51   b  adjacent to the load lock chamber  81  that is the other transfer position. The length of the short side is slightly longer than the base  321 . 
       FIG. 30  and  FIG. 31  is an enlarged schematic view of a wafer transfer apparatus  502  in the embodiment.  FIG. 30( a )  is a plan view that each part is set to a reference position.  FIG. 30( b )  is a front view of that state.  FIG. 31( a )  is a plan view showing the state that a transport arm  322  described later extends to enter the FOUP  62 .  FIG. 31( b )  is a front view of that state. In the drawings, the same parts as those in the fourth and fifth embodiments are denoted by the same reference numerals, and the explanation thereof is omitted. 
     Hereinafter, the structure of the wafer transport apparatus  502  will be explained with reference to  FIG. 30  and  FIG. 31 . 
     The wafer transport apparatus  502  includes a cover  503  formed substantially rectangular in a plan view, and the transport arm  322  is arranged below the cover. The cover  503  is supported on the base  321  by a cover support means  504 , and is able to move together with the movement of the base  321  along the guide rail  324 . 
     Except the rectangular shape, the structure of the cover  503  is substantially the same as that of the cover  303 B (see  FIG. 24 ). The cover comprises a main body part  531  formed rectangular, and a wall part  532  provided suspending from a peripheral edge of the main body part. They form an internal space S opened downward. To prevent extremely uneven supply of gas G in the longitudinal direction, as well as a gas supply port  534  provided at the center of the upper surface  531   b  of the main body part  531 , gas supply ports  534  are provided at a position apart on both sides in the longitudinal direction, and a gas supply pipe  543  is branched and connected to these three gas supply ports  534 . In this configuration, it is possible to supply the gas G from three locations in the longitudinal direction, and to make uniform the distribution of the gas G supplied downward the cover  503 . Of course, the gas supply port  534  may be provided at four or more positions, not only in three places. Similar to  FIG. 24 , a gas supply means MG is also configured. 
     The cover support means  504  is configured to have the same structure as the cover support means  4  of the fourth embodiment (see  FIG. 19 ). The cover support means  504  comprises a pair of support bars  541  that is apart in the extending direction of the guide rail  324  and erected on the base  321 , and lifting blocks  542  that are supported movable in the vertical direction by the support bars. The lifting blocks  542  support the upper surface  531   b  of the main body part  531  of the cover  503 . When viewing functionally the support bar  541  and the lifting block  542 , it can be said that they constitute the cover approach and separation means MV, which makes the cover  503  approaches to and separate from the wafer surface. 
     When taking out the wafer W from the FOUP  62 , as shown in  FIG. 30 , first the base  321  is positioned in front of the FOUP  62 . At this time, one of the short sides of the cover  503  is positioned just before the door  61   a  of the load port  61 . 
     In this state, the door  61   a  of the load port  61  and the lid  62   a  of the FOUP  62  are opened, the transport arm  322  is extended to insert the end effector  323  into the FOUP  62 , as shown in  FIG. 31 . In this state, the base  321  is raised, and the wafer W can be held on the end effector  323 . 
       FIG. 32  is a plan view showing the whole of EFEM in this state. In this state, the transport arm  322  contracts to take out the wafer W to the outside of the FOUP  62 . Since the cover  503  has extended to just before the FOUP  62 , immediately after the wafer W is taken out to the outside of the FOUP  62 , the wafer W comes opposite to the cover  503 . In this state, the cover  503  is moved downward by the cover approach and separation means MV (see  FIGS. 30 and 31 ) to contain a part of the upper surface of the wafer W in the internal space S. Further, the gas supply means MG (see  FIG. 24 ) starts to supply the gas G. 
     The transport arm  322  contracts further, and the wafer W is positioned above the base  321 . In this process, the gas G is continuously supplied to the surface of the wafer W, and the atmosphere on the wafer W surface is continuously replaced with the gas G. At this time, if any one of the gas supply ports  534  is appropriately selected in accordance with the movement of the wafer W by the transport arm  322 , and the destination of gas G is changed, it is possible to further reduce the supply amount of gas G. 
     The base  321  moves to the front of the load lock chamber  81  along the guide rail  324 . The transport arm  322  moves to the front of the load lock chamber  81 , while supplying the gas G. Then, the cover  503  move up slightly not to interfere with the transport arm or wafer W, the door  81   a  of the load lock chamber  81  are opened, and the transport arm  322  extends further to insert the end effector  323  into the load lock chamber  81 , as shown in  FIG. 33 . At this time, since one of the short sides of the cover  503  has extended close to the load lock chamber  81 , the replacement of the atmosphere on the wafer W surface with the gas G, can be continued until just before the wafer W enters the load lock chamber  81 , and it is possible to reduce the time to expose the wafer W surface to the air by replacing the atmosphere for a longer time. In this state, the base  321  is moved down, the position of the transport arm  322  is lowered, and the wafer W can be placed in the load lock chamber  81 . 
     Even when using the wafer transfer device  502 , as in the above described embodiment, it is possible to maintain proper surface state of the wafer W by replacing a local atmosphere around the wafer W surface via the cover  503 , without replacing the entire atmosphere inside the wafer transport chamber  5 . Further, when transporting the wafer W from the load lock chamber  81  to the FOUP  62 , it is possible to replace the local atmosphere around the wafer W surface as well by performing the above operation in reverse. 
     As described above, since the wafer transport apparatus  502  in the embodiment comprises the cover  503  that can face and cover a wafer to be transferred, and the gas supply means MG that supplies a gas G different from the surrounding atmosphere from the cover  503 , and replaces the atmosphere on the wafer W surface by the gas G, as the above described embodiment, it can be said that the wafer transport apparatus includes an atmosphere replacement apparatus comprising the cover  503  and the gas supply means MG, and can provide substantially the same effect as the above described embodiment. 
     Further, the load port  61  and the load lock chamber  81  as a transfer position for transferring the wafer W to the transport arm  322  are set on both sides across the guide rail  324 , and the cover  503  is configured to extend in the direction orthogonal to the guide rail  324 . Thus, when transporting the wafer W to two axes in the extending direction of the guide rail  324  and the direction orthogonal to that direction, the cover  503  can cover the surface of the wafer W during transportation for a long time, and the gas G can be effectively supplied to the surface of a substrate during transportation, while the structure is simple. 
     Seventh Embodiment 
       FIG. 34  a schematic view showing a wafer transport apparatus  602  of the seventh embodiment. In the drawing, the same parts as those in the fourth to sixth embodiments are denoted by the same reference numerals, and the explanation thereof is omitted. 
     The wafer transport apparatus  602  is based on the structure of the wafer transport apparatus  302  in the fourth embodiment (see  FIG. 19 ). The shape of a cover  603  is changed, and a cover receiving member  625  is provided on the base  321 . 
     In particular, the cover  603  comprises a disk-shaped main body part  631 , and a wall part  632  formed suspending from a peripheral edge of the main body part. They form an internal space S opened downward. The main body part  631  is formed larger than the cover  303  of the fourth embodiment (see  FIG. 19 ), so that the entire transport arm  322  contracted on the base  321  can be housed in the internal space S. 
     On the top of the base  321 , a disk-shaped cover receiving member  625  is provided. The cover receiving member  625  has a diameter slightly larger than the cover  603  in a plan view. Thus, when the cover  603  moves downward, the open end  632   a  of the wall part  632  of the cover  603  comes close to the upper surface  625   a  of the cover receiving member  625 , and the cover receiving member can substantially close the internal space S in cooperation with the cover. Therefore, it is possible to further increase the concentration of gas G, when the gas G is supplied to the internal space S, and increase the effect by the replacement of atmosphere. 
     Of course, it is permitted to make contact between the open end  632   a  and the upper surface  625   a . By contacting and sealing the both after the atmosphere is replaced with the gas G, the atmosphere replaced state can be maintained even after the supply of gas G is stopped, and the wafer W surface is not contaminated. 
     Even when configuring as above, being provided with the cover  603  capable of facing and contacting a wafer W to be transported, and the gas supply means MG that supplies a gas G different from a surrounding atmosphere from the cover  603  and replaces the atmosphere on the wafer W surface with the gas G, as in the aforementioned embodiments, it can be said that there is provided with an atmosphere replacement apparatus that is configured to include the cover  603  and the gas supply means MG. Thus, it is possible to obtain the same effect as the aforementioned embodiments. 
     In addition, being configured to have the cover receiving member  625  on the base  321 , which can substantially close the internal space S in cooperation with the cover, when the cover  603  approaches the wafer W, and the open end  632   a  of the wall part  632  of the cover  603  approaches or contacts the cover receiving member, a substantially closed space is formed between the cover  603  and the cover receiving member  625 , and the supply amount of gas G can be further reduce by housing the wafer W in the space. 
     The specific structure of each part is not intended to be limited to only the aforementioned embodiment. 
     For example, in the aforementioned embodiment, a nitrogen gas is used as a gas G for replacing the atmosphere around a wafer W. But, various gases G such as air and ozone can be used depending on a process. A clean air atmosphere is assumed within the wafer transport chamber  5 , but it may be any atmosphere having properties different from the air constituting that atmosphere. Further, it is possible to use clean air with a higher cleanliness, or air increased in a temperature by a heating means. 
     Further, in the aforementioned embodiments, a gas G is supplied in the state that the whole or a part of a wafer W is housed in the internal space S provided in the cover  3  ( 103 ,  303 ,  503 ,  603 ). However, the same effect can be obtained by supplying the gas G in the state that the cover  3  ( 103 ,  303 ,  503 ,  603 ) approaches the surface of a wafer W without housing the wafer W in the cover  3  ( 103 ,  303 ,  503 ,  603 ). Further, the same effect can be obtained by configuring the cover  3  ( 103 ,  303 ,  503 ,  603 ) only by the main body part  31  ( 131 ,  331 ,  531 ,  631 ) without having the suspending wall part  32  ( 132 ,  332 ,  532 ,  632 ). 
     Further, the timing of starting or stopping the supply of gas G by the cover supply means MG can be changed appropriately according to a processing process. In particular, the supply of gas G may be started several seconds after a wafer is taken out of the FOUP  62 , or the supply amount may be changed according to the concentration of the gas G in the cover  3  ( 103 ,  303 ,  503 ,  603 ). The same effect can be obtained by limiting the supply of gas G to a process from taking out a processed wafer W from the load lock chamber  81  to returning to the FOUP  62 . 
     In the aforementioned embodiments, a wafer W is transferred between the load lock chamber  81  and the FOUP  62  on the load port  61 . Embodiments of the present invention are not intended to be limited to this aspect, and appropriately applied to the case where a wafer is transported between FOUPs  62 . Further, the wafer W transfer position is not limited to be apart in a horizontal direction, but may be apart in a vertical direction. In such a case, the cover  3  ( 103 ,  303 ,  503 ,  603 ) may be moved so as to face a wafer W, following to movement of the wafer W in a vertical direction, and a gas G may be supplied to replace the atmosphere around the wafer W. 
     Further, in the aforementioned embodiments, a wafer W is assumed as a substrate, and the wafer transport apparatus  2  ( 202 ,  302 ,  402 ,  502 ,  602 ) or the wafer transport system TS is configured. Embodiments of the invention are applicable to a transport system that transports various precision processed products such as a glass substrate. In other words, the embodiments can be configured as a substrate transport apparatus or a substrate transport system that handles common substrates such as a glass substrate. 
     In addition, the transport arm  22  or  322  is not limited to the link type arm robot or SCARA type horizontal articulated robot described hereinbefore. Various types of robot can be used. 
     The other configurations may be modified without departing from the spirits or essential characteristics of the present invention.