Abstract:
In the vacuum substrate processing equipment of the present invention, a posttreatment chamber for carrying out a posttreatment in an atmospheric atmosphere adjoins a load-lock chamber. Products produced on a substrate during a vacuum process are removed by processing the substrate in the posttreatment chamber before the substrate is carried to an atmospheric carrying chamber in order to avoid or reduce adverse influence on the atmospheric carrying chamber. A carrying means installed in the said atmospheric carrying chamber carries the substrate to and from the said posttreatment chamber. The said posttreatment chamber and the atmospheric carrying chamber are separated from each other by a partition wall, and the partition wall is provided with an opening having the shape of a slit through which the said carrying means and the substrate can pass. The said carrying means carries the substrate into and out of the posttreatment chamber through the slit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-229626 filed on Aug. 25, 2006 and the Preliminary U.S. Pat. App. No. 60/844,650 filed on Sep. 15, 2006, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of techniques for avoiding or reducing the adverse influence of a product formed on a substrate by a vacuum process and exposed to the atmosphere on the components of an atmospheric carrying chamber when the substrate processed by the vacuum process is carried to the atmospheric carrying chamber. 
     2. Description of the Related Art 
     A substrate, such as a semiconductor wafer (hereinafter, referred to simply as “wafer”), is subjected to a vacuum process, such as a plasma processing process, for example, an etching process, to fabricate a semiconductor devices. A vacuum processing system called a multichamber system is used to carry out such a process at a high throughput. 
       FIG. 11  shows a known vacuum processing system provided with a vacuum processing chamber and an atmospheric carrying chamber by way of example. Referring to  FIG. 11 , this known vacuum processing system includes front opening unified pod (abbreviated to “FOUP”)) tables  10  for supporting thereon a FOUP, namely, a carrying container containing a plurality of wafers, for example twenty-five wafers, a transfer module (TM)  11  provided with a carrying arm for carrying a wafer and maintaining a vacuum atmosphere, four process modules (PM)  12   a ,  12   b ,  12   c  and  12   d  for processing a wafer by predetermined processes in a vacuum atmosphere, a loader module (LM)  14  provided with a carrying mechanism including a carrying arm for carrying a wafer and maintained in an atmospheric atmosphere, two load-lock modules (LLM)  15   a  and  15   b  disposed between the loader module  14  and the transfer module  11 , and capable of being selectively set in either of a vacuum atmosphere and a normal-pressure atmosphere, and an orienter (ORT), not shown, disposed so as to adjoin the loader module  14  for the prealignment of a wafer. In  FIG. 11 , indicated at G 11  to G 14  are gate valves. 
     A wafer carrying route in the vacuum processing system will be briefly described. A wafer to be processed taken out from a FOUP supported on the FOUP table  10  is carried along a carrying route passing the LM, the ORT, the LLM, the TM and the PM in that order. The wafer is processed by, for example, an etching process in the process module  12   a  ( 12   b ,  12   c ,  12   d ) in an atmosphere of a process gas. The wafer thus processed is carried along a carrying route passing the TM, the LLM and LM in that order and is returned to the FOUP supported on the FOUP table  10 . 
     In some cases, gases generated by the reaction of byproducts produced on the wafer during processing the wafer with moisture contained in the atmosphere condense in liquids on wafers not yet processed during the operation for returning the processed wafer to the FOUP placed on the FOUP table  10 . The liquids thus produced can cause defects in devices. A purge storage  13  is connected to the loader module  14  as indicated by broken lines in  FIG. 11 . The processed wafer is held temporarily in the purge storage  13  to prevent such cross-contamination. 
     However, the following problem arises when the processed wafer is carried from the load-lock module  15   a  (or  15   b ) through the loader module  14  to the purge storage  13 . For example, a process gas, such as HBr gas or Cl 2  gas, is ionized in the process module  12   a  ( 12   b ,  12   c ,  12   d ) to generate a plasma for etching a polysilicon film formed on a wafer by an etching process. During the etching process, a byproduct, such as silicon bromide or silicon chloride, is produced on the wafer. When the wafer carrying the byproduct is carried into the loader module  14  in the atmospheric atmosphere, the silicon bromide or the silicon chloride react with moisture contained in the atmosphere and, consequently, a corrosive gas, such as hydrogen bromide gas or hydrogen chloride gas, is produced. The corrosive gas diffuses, and the corrosive gas reacts with a small amount of ammonia contained in the atmosphere to produce ammonium bromide particles or ammonium chloride particles. The particles diffuse in the loader module  14 . Consequently, metal parts of the loader module  14 , such as walls defining a carrying chamber, and components of the carrying mechanism, are corroded. It is possible that the corroded parts are abraded during mechanical motions and cause metal contamination. It is also possible that the particles adhere to the internal parts of the loader module  14  and cause particle contamination. 
     It is mentioned in JP-A 2005-50852 that entrained contaminants adhered to a sample in a plasma processing system react with moisture contained in the atmosphere to produce new contaminants or to create a corrosive environment that corrodes structural members. A carrying procedure intended to prevent such troubles mentioned in JP-A 2005-50852 carries a sample into or carries out a sample from an evacuated load-lock chamber in a state where a gas is supplied through a gas inlet port into the load-lock chamber, a gate valve on the side of the atmosphere is opened, the gas is supplied continuously into the load-lock chamber, a gas is supplied through a gas inlet port formed in a cover, and an atmosphere in the load-lock chamber is discharged through an exhaust port formed in the cover. However, even if currents is generated in the load-lock chamber to remove contaminants adhering to a wafer, the contaminants cannot be removed by the currents in a short time because the wafer can be held in the load-lock chamber only a short time in consideration of throughput. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of such problems and it is therefore an object of the present invention to provide techniques capable of avoiding or reducing the adverse influence of a product formed on a substrate by a process executed in a vacuum chamber on an atmospheric carrying chamber when the substrate processed in the vacuum chamber is carried to the atmospheric carrying chamber. 
     A substrate processing system according to the present invention includes: a carrier table for supporting thereon a substrate carrier containing a plurality of substrates; a vacuum processing chamber in which a substrate is processed in a vacuum atmosphere; a load-lock chamber, through which a substrate is sent out to and received from the vacuum processing chamber, capable of being selectively set in either of a vacuum atmosphere and a normal-pressure atmosphere; a posttreatment chamber adjoining the load-lock chamber to process in an atmospheric atmosphere a processed substrate processed by a vacuum process to remove products produced on the substrate by the vacuum process; and an atmospheric carrying chamber interposed between the load-lock chamber and the carrier table and provided with a carrying means for carrying a substrate in an atmospheric atmosphere. 
     Preferably, a substrate is carried into and carried out of the posttreatment chamber by the carrying means installed in the atmospheric carrying chamber. Preferably, the following constitution is employed when a substrate is carried into and carried out of the posttreatment chamber. 
     (1) The posttreatment chamber and the atmospheric carrying chamber are separated from each other by a partition wall, and the partition wall is provided with an opening having the shape of a slit through which the carrying means and a substrate can pass. 
     (2) A gate valve disposed between the atmospheric carrying chamber and the load-lock chamber serves also as a gate valve between the load-lock chamber and the posttreatment chamber. 
     (3) The load-lock chamber is provided with a gateway bent with respect to a longitudinal direction, and the gate valve has a valve element bent so as to conform to the gateway. 
     A condition expressed by “bent” is either of a condition where a structure is bent in the shape of a chevron and a condition where a structure is bent in the shape of a circular arc (curved). 
     Preferably, the load-lock chamber of the substrate processing system according to the present invention includes a first load-lock chamber and a second load-lock chamber disposed symmetrically with respectively to a longitudinal direction behind the atmospheric carrying chamber, and the posttreatment chamber is disposed between the first and the second load-lock chamber. The posttreatment chamber may be provided with, for example, a substrate holding unit capable of holding substrates in a plurality of layers. Preferably, the substrate holding unit of the posttreatment chamber can be vertically moved by a lifting means. The posttreatment chamber is used for promoting the reaction of products formed on a substrate while the substrate is being processed with moisture contained in the atmosphere. 
     A substrate processing method according to the present invention includes the steps of: processing a substrate in a vacuum processing chamber; carrying the processed substrate from the vacuum processing chamber to a load-lock chamber; changing a vacuum atmosphere in the load-lock chamber for a normal-pressure atmosphere; carrying the substrate from the load-lock chamber to a posttreatment chamber adjoining the load-lock chamber; processing the substrate by a posttreatment in an atmospheric atmosphere to remove products produced by a vacuum process from the substrate; and carrying the substrate from the posttreatment chamber to an atmospheric carrying chamber disposed between a carrier table on which a carrying container containing a plurality of substrates is placed and the load-lock chamber, and provided with a carrying means for carrying the substrate in an atmospheric atmosphere. 
     A storage medium according to the present invention storing a computer program to be executed by a substrate processing system for processing a substrate in a vacuum atmosphere; wherein the computer program specifies the steps of a substrate processing method according to the present invention. 
     According to the present invention, the products produced on the substrate by the vacuum process are removed in the posttreatment chamber adjoining the load-lock chamber before the substrate is carried to the atmospheric carrying chamber. Therefore, adverse effects of the products on the components of the atmospheric carrying chamber, such as the walls of the atmospheric carrying chamber and components of a carrying mechanism installed in the atmospheric carrying chamber, can be prevented or reduced. The posttreatment chamber does not need to be provided with a special carrying means when the carrying means installed in the atmospheric carrying camber is used for carrying a substrate into and carrying a substrate out of the posttreatment chamber. Thus the substrate processing system can be built in simple construction and at a low cost. A substrate can be efficiently carried when one and the same gate valve is used to separate the atmospheric carrying chamber and the load-lock chamber from each other, and to separate the load-lock chamber and the posttreatment chamber from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a substrate processing system in a first embodiment according to the present invention; 
         FIG. 2  is a perspective view of an important part of the substrate processing system shown in  FIG. 1 ; 
         FIG. 3  is a schematic sectional view of a purge storage; 
         FIG. 4  is a schematic perspective view of a gate valve interposed between a load-lock module and the purge storage; 
         FIGS. 5A and 5B  are schematic views of assistance in explaining operations of the gate valve shown in  FIG. 4 ; 
         FIG. 6  is a schematic perspective view of another gate valve disposed between the load-lock module and the purge storage; 
         FIGS. 7A and 7B  are schematic views of assistance in explaining operations of the gate valve shown in  FIG. 6 ; 
         FIG. 8  is a view of assistance in explaining operations of a carrying arm included in a loader module; 
         FIG. 9  is a view of assistance in explaining operations of the carrying arm included in the loader module; 
         FIG. 10  is a plan view of a substrate processing system in a second embodiment according to the present invention; and 
         FIG. 11  is schematic plan view of a known substrate processing system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a plan view of a substrate processing system in a first embodiment according to the present invention, and  FIG. 2  is a schematic perspective view of an important part of the substrate processing system shown in  FIG. 1 . Referring to  FIG. 1 , the substrate processing system  2  carries semiconductor wafers (hereinafter, referred to simply as “wafers”) W, namely, substrates, one by one and processes the wafers W by a predetermined process. The substrate processing system  2  includes a transfer module (TM)  20  having a longitudinally elongate hexagonal shape in a plane, two process modules (PM)  30   a  and  30   b  disposed near one longitudinal side surface of the transfer module  20  extending in a longitudinal direction parallel to the Y-axis, two process modules  30   c  and  30   d  disposed near the other longitudinal side surface of the transfer module  20 , two load-lock modules (LLM)  40   a  and  40   b  connected to two oblique end surfaces of the transfer module  20  inclined to a transverse direction parallel to the X-axis, and a loader module  50  extending beside the load-lock modules  40   a  and  40   b . The load-lock modules  40   a  and  40   b  correspond to a first load-lock chamber and a second load-lock chamber, respectively. 
     The process modules  30   a  to  30   d  are provided with wafer stages  31   a  to  31   d  for supporting a wafer in a vacuum processing chamber, electrodes for generating a plasma, and process gas supply systems for supplying a process gas, such as hydrogen bromide gas (HBr gas) into the vacuum processing chambers, respectively. High-frequency power is supplied to the electrodes to generate a plasma by ionizing the process gas. An etching process etches, for example, a polysilicon film formed on a wafer W by using the plasma. 
     Gate valves G 1 , G 2 , G 3  and G 4  are disposed at the joints of the transfer module  20  and the process modules  30   a  to  30   d , respectively. The transfer module  20  is provided with a carrying arm unit  21  installed in a vacuum carrying chamber and including two scalar arm type carrying arms. The carrying arm unit  21  moves along guide rails  22  extended longitudinally i.e., in parallel to the Y-axis, in the transfer module  20  to carry a wafer W to and from the process modules  30   a  to  30   d  and the load-lock modules  40   a  and  40   b.    
     The loader module  50  has the shape of a transversely elongate box. As shown in  FIG. 3 , a filter fan unit (FFU)  55  formed by combining a filter and a fan is attached to the top wall of the loader module  50 . An exhaust fan unit  56  is combined with the floor of the loader module  50 . The exhaust fan unit  56  is connected to a plant exhaust system provided with a detoxification unit. A downward stream of clean air is produced between the FFU  55  and the exhaust fan unit  56 . The rear wall  57  of the loader module  50  is provided with an opening  53  having the shape of a slit. 
     A carrying arm mechanism  51  is installed in the loader module  50 . As shown in  FIG. 2 , three openings  51   a ,  51   b  and  51   c  are formed in the front wall of the loader module  50  facing FOUP tables  70 . Wafers W are carried into and out of the loader module  50  through the openings  51   a ,  51   b  and  51   c . The carrying arm mechanism  51  includes an X-axis moving member electromagnetically driven for reciprocation along a guide rail  52  transversely extended in the loader module  50 , a horizontal swivel table supported for turning in a horizontal plane by an X-axis lifting mechanism on the X-axis moving member, and an articulated carrying arm  54  mounted on the swivel table and capable of extending in radial directions and horizontal directions. The carrying arm  54  has a fork-shaped holding part as shown in  FIG. 2 . A peripheral part of the lower surface of a wafer W is seated on the holding part. 
     The load-lock modules  40   a  and  40   b  are disposed symmetrically with respect to the longitudinal axis of the transfer module  20  between the rear wall of the loader module  50  and the transfer module  20 . Gate valve G 5  and G 6  are disposed at the joints of the load-lock modules  40   a  and  40   b  and the transfer module  20 , respectively. The load-lock modules  40   a  and  40   b  are provided with wafer stages  41   a  and  41   b  for supporting a wafer W thereon, respectively. The respective internal spaces of the load-lock modules  40   a  and  40   b  can be selectively set in a vacuum atmosphere or a normal-pressure atmosphere of, for example, nitrogen gas. 
     The load-lock modules  40   a  and  40   b  have a pentagonal cross-sectional shape. An opening  42   a  ( 42   b ) through which a wafer is carried into and carried out from the load-lock module  42   a  ( 42   b ) is formed in a side wall of the load-lock module  40   a  ( 40   b ) facing the load-lock module  42   b  ( 42   a ). The openings  42   a  and  42   b  are closed by gate valves G 7  and G 8 , respectively. As shown in  FIGS. 1 and 2 , each of the gate valves G 7  and G 8  is bent, for example, in the shape of a chevron so as to extend along the two adjacent sides of the pentagonal cross-sectional shape. The gate valves G 7  and G 8  separate the respective interiors of the load-lock modules  40   a  and  40   b  from the loader module  50  and a purge storage (PST)  60 , respectively. The gate valves G 7  and G 8  isolate the load-lock modules  40   a  and  40   b , respectively, from the purge storage  60 . The construction and operation of the gate valves G 7  and G 8  will be described later. 
     In the substrate processing system  2 , the rear wall  57  of the loader module  50 , the two sides of each of the load-lock modules  40   a  and  40   b , and one side of the transfer module  20  define a processing chamber of the purge storage  60 , namely, a posttreatment chamber. A posttreatment is carried out by the purge storage  60  to convert products produced by a plasma processing process, namely, a vacuum process, and capable of changing into a substance detrimental to the components of the loader module  50  when exposed to an atmospheric atmosphere into a corrosive gas by making the products react with moisture contained in the atmosphere and to dissipate the corrosive gas. 
     Referring to  FIGS. 2 and 3 , a substrate holding device  63  is disposed in the purge storage  60 . The substrate holding device  63  in this embodiment can hold a plurality of wafers @, four wafers W in this embodiment, in layers. The substrate holding device  63  includes a base  64  set on the bottom wall the purge storage  60 , a post  65  set upright at one end of the base  64 , a plurality of support arms  66 , four support arms  66  in this embodiment, and a lifting mechanism  67  for vertically moving the post  65 . As shown in  FIG. 2  by way of example, the support arms  66  are formed in a U-shape to form a central space  66   a . The carrying arm  54  can enter the central space  66   a . The lifting mechanism  67  can position the selected one of the four support arms  66  at a position corresponding to a transfer level where the carrying arm  54  can transfer a wafer W to the selected one of the four support arms  66 . 
     An exhaust pipe  68  has one end connected to the bottom wall of the purge storage  60  and the other end connected to a plant exhaust system provided with a detoxification unit. Clean air flowed from the loader module  50  through the slit-shaped opening  53  into the purge storage  60  is discharged through the exhaust pipe  68  into the plant exhaust system. 
     FOUP tables  70   a  to  70   c  are disposed on the side of the front wall of the loader module  50 . FOUPs (front opening unified pods), namely, wafer carriers, each containing a plurality of wafers W, for example twenty-five wafers W and carried through the openings  51   a  to  51   c  are placed on the FOUP tables  70   a  to  70   c , respectively. An orienter (ORT)  71  adjoins the left wall, as viewed in  FIG. 1 , of the loader module  50 . The orienter  71  aligns beforehand the wafer W carried from each of the FOUP tables  70   a  to  70   c  into the loader module  50 . 
     The gate valves G 7  and G 8  linked with the walls of the load-lock modules  40   a  and  40   b , respectively, will be described. Referring to  FIG. 4 , the gate valve G 7  (G 8 ) includes a chevron-shaped valve element  80 , a valve stem  81  supporting the valve element  80 , and a valve element moving mechanism  82  connected to the lower end of the valve stem  81 . An O ring  83 , namely, a resin ring, is attached to the inner surface of the valve element  80  t seal the joint of the wall of the load-lock module  40   a  ( 40   b ) and the valve element  80 . To close the gate valve G 7  (G 8 ), first the valve element driving mechanism  82  raises the valve element  80  to a position at a predetermined height as shown in  FIG. 5A . Subsequently, the valve element driving mechanism  82  tilts the valve stem  81  to press the valve element  80  against the side wall of the load-lock module  40   a  ( 40   b ) so as to close the opening  42   a  ( 42   b ) in an airtight fashion as shown in  FIG. 5B . To open the gate valve G 7  (G 8 ), the foregoing closing procedure is reversed. 
     A gate valve G 7  (G 8 ) shown in  FIG. 6  may be used. When the gate valve G 7  (G 8 ) shown in  FIG. 6  is used, sealing surfaces facing down are formed along edges of the opening  42   a  ( 42   b ), and sealing surfaces facing up are formed in the gate valve G 7  (G 8 ). The gate valve G 7  (G 8 ) is raised to bring the sealing surfaces of the gate valve G 7 (G 8 ) into close contact with the sealing surfaces of the opening  42   a  ( 42   b ) of the load-lock module  40   a  ( 40   b ) to seal the load-lock module  40   a  ( 40   b ). As shown in  FIG. 7 , the load-lock module  40   a  ( 40   b ) is provided with a lower sealing surface  95  facing down and extending along the lower edge of the opening  42   a  ( 42   b ) on the inner side of the outer end of the opening  42   a  ( 42   b ), an upper sealing surface  94  facing down and extending along the upper edge of the opening  42   a  ( 42   b ) on the outer side of the outer end of the opening  42   a  ( 42   b ), and side sealing surfaces, not shown, facing down and extending along the side edges of the opening  42   a  ( 42   b ) between the upper sealing surface  94  and the lower sealing surface  95 . The valve element  90  is provided with sealing surfaces  91  and  92  facing up, extending along the upper and the lower edge of valve element  90 , respectively, and corresponding to the upper sealing surface  94  and the lower sealing surface  95  of the load-lock module  40   a  ( 40   b ), respectively, and sealing surfaces  97  facing up and extending between the sealing surfaces  91  and  92 . An O ring  93 , namely, a resin ring, is attached to the sealing surfaces  91 ,  92  and  97 . The valve element  90  is raised to bring the sealing surfaces  91 ,  92  and  97  facing up of the valve element  90  into close contact with the sealing surfaces  94  and  95  facing down of the opening  42   a  ( 42   b ) as shown in  FIG. 78 . Thus the horizontally elongate opening  42   a  ( 42   b ) formed in the wall of load-lock module  40   a  ( 40   b ) is closed in an airtight fashion as shown in  FIG. 7B . 
     The substrate processing system  2  is provided with a controller  100 . For example, the controller  100  is a computer. The controller executes control operations according to a computer program to control the sequential operations of the carrying arm unit  21 , the carrying arm mechanism  51 , the lifting mechanism  67  and the gate valves G 1  to G 8 , and sequential steps of vacuum processes to be executed by the process modules  30   a  to  30   d . The computer program is stored in a storage medium, such as a hard disk, a flexible disk, a compact disk, a magnetooptical disk (MO) or a memory card. The computer program stored in the storage medium is loaded into the controller  100 . 
     Operation of the substrate processing system  2  will be described. A FOUP containing wafers W is delivered to the substrate processing system  2  and is placed on, for example, the FOUP table  70   a , and the lid of the FOUP is removed. Then, the carrying arm  54  takes out a wafer W from the FOUP and brings the wafer W through the opening  51   a  into the loader module (LM)  50 . The wafer W to be processed is transferred from the loader module  50  to the orienter (ORT)  71 . The orienter  71  aligns the wafer W with respect to a predetermined direction. Then, the wafer W carried out of the orienter  71  by the carrying arm  54  is carried from the loader module (LM)  50  to the load-lock module  40   a.    
     A carrying procedure for carrying the wafer W from the loader module (LM)  50  to the load-lock module (LLM)  40   a  by the carrying arm  54  will be described with reference to  FIG. 8 . The carrying arm mechanism  51  is positioned in front of, for example, the load-lock module (LLM)  40   a  as shown in  FIG. 8A . Then, the carrying arm  54  is stretched out to advance the carrying arm  54  through the opening  42   a  formed in the wall of the load-lock module  40   a  into the load-lock module (LLM)  40   a  as shown in  FIG. 8B . In  FIG. 8 , the wafer W supported on the carrying arm  54  is indicated by a chain line for the convenience of explanation. 
     Subsequently, the carrying arm unit  21  picks up the wafer W placed on the wafer stage  41   a  of the load-lock module (LLM)  40   a  and carries the wafer W into the transfer module (TM)  20 . The wafer W is carried in the transfer module  TM  to, for example, the process module (PM)  30   a . The process module (PM)  30   a  processes the wafer W by a plasma processing process, such as an etching process. 
     Then, the carrying arm unit  21  carries the processed wafer W from the process module (PM)  30   a  through the transfer module (TM)  20  to the load-lock module (LLM)  40   a . Subsequently, a vent valve, not shown, is opened and, for example, nitrogen gas is supplied from an inert gas source, not shown, into the load-lock module (LLM)  40   a  to change a vacuum atmosphere in the load-lock module (LLM)  40   a  for a normal-pressure atmosphere. Then, the gate valve G 7  is opened, and the carrying arm  54  carries the processed wafer W from the load-lock module (LLM)  40   a  to the purge storage (PST)  60 . 
     A procedure for carrying the processed wafer W by the carrying arm  54  from the load-lock module (LLM)  40   a  to the purge storage (PST)  60  will be described with reference to  FIG. 9 . The carrying arm mechanism  51  is positioned in front of the load-lock module (LLM)  40   a , the carrying arm  54  is stretched out to advance the carrying arm  54  through the slit-shaped opening  53  formed in the rear partition wall  57  of the loader module (LM)  50  into the load-lock module (LLM)  40   a . The processed wafer W is lifted up from the wafer stage  41   a  by lifting pins, not shown, the carrying arm  54  is raided from under the wafer W to transfer the wafer W to the carrying arm  54 . Then, the carrying arm  54  is retracted to take out the wafer W from the load-lock module  40   a , the carrying arm  54  is turned clockwise through a small angle, the carrying arm  54  is moved along the X-axis such that the holding part of the carrying arm  54  is positioned in a region extending over a space surrounded by the U-shaped support arm  66 . Then, the support arms  66  are raised to pickup the wafer W from the carrying arm  54  so that a peripheral part of the wafer W is seated on the support arm  66 . Then, the carrying arm  54  is retracted to a position in front of the support arms  66 . Then, the support arms  66  are moved vertically and the carrying arm  54  is stretched out to receive a processed wafer W supported on another support arm  66  of the substrate holding device  63 . The carrying arm  54  is formed in a transverse width smaller than the transverse width of a space  66   a  surrounded by the U-shaped support arm  66  to prevent the support arm  54  from interfering with the support arm  66  in a plane. The support arms  66  are moved down to transfer a wafer W supported on the support arm  66  to the carrying arm  54 . Then, the carrying arm  54  returns the wafer W supported thereon to the FOUP placed on, for example, the FOUP table  70   a.    
     The carrying arm  54  takes out another wafer W from the FOUP and carries the wafer W to the load-lock module (LLM)  40   a . In  FIG. 9 , the wafer W supported on the carrying arm  54  is indicated by a chain line for the convenience of explanation. 
     A process to be carried out by the purge storage (PST)  60  to process a wafer W will be described. The purge storage (PST)  60  is evacuated continuously through the exhaust pipe  68  to maintain the interior of the purge storage (PST)  60  at a negative pressure. Therefore, the atmosphere flows from the loader module (LM)  50  through the slit-shaped opening  53  of the rear partition wall  57  of the loader module (LM)  50  into the purge storage (PST)  60 . When a wafer W is subjected to a plasma etching process, a product produced during the plasma etching process, such as a silicon halide (for example, silicon bromide) adheres o the wafer W. The silicon halide reacts with moisture contained in the atmosphere to produce hydrogen bromide gas. The hydrogen bromide gas reacts with a small amount of ammonia contained in the atmosphere to produce ammonium bromide particles. The hydrogen bromide, namely, a corrosive gas, and the ammonium bromide particles are carried away by exhaust currents through the exhaust pipe  68 . The hydrogen bromide gas is removed by a chemical filter, not shown, placed in the exhaust passage. 
     Sequential carrying operations for carrying the wafer W are determined by taking into consideration the number of the process modules (PM) to be used, processing times respectively needed by the process modules (PM)  30   a  to  30   d , and time needed by the posttreatment to be carried out by the purge storage (PST)  60 . Suppose that the four process modules (PM)  30   a  to  30   d  are used in a parallel operating mode for etching and the wafer W is held in each process module (PM) for a stay time t1 in this example. Then, a time needed by the posttreatment is expected to be (¾)t1. Thus a time that can be allotted for carrying a processed wafer W to either of the load-lock modules (LLM)  40   a  and  40   b  is (¼)t1. Therefore, the four support arms  66  are used; the three support arms  66  are used to enable each wafer W to stay in the purge storage (PST) for (¾)t1, and the one support arm  66  is used as a buffer. The processing time mentioned herein is only an example for typical explanation. 
     The sequential carrying operations may give priority to carrying a wafer W to and from the load-lock modules (LLM)  40   a  and  40   b  over carrying out a wafer W processed by the posttreatment from the purge storage (PST)  60 . For example, even if a wafer W processed by the posttreatment is held in the purge storage (PST)  60  after a wafer W has been transferred from the load-lock module (LLM)  40  to the purge storage (PST)  60 , first a wafer W may be carried from a FOUP placed on the FOUP table  70   a  to the empty load-lock module (LLM)  40   a , and then the processed wafer W may be returned from the purge storage (PST)  60  to the FOUP placed on the FOUP table  70   a.    
     Although either of the load-lock modules  40   a  and  40   b  may be used both for receiving a wafer W to be processed and for sending out a processed wafer W, either of the load-lock modules  40   a  and  40   b  may be used exclusively for receiving a wafer W to be processed and the other may be used exclusively for sending out a processed wafer W. 
     The foregoing embodiment exposes a wafer W processed by the plasma etching process to the atmospheric atmosphere in the purge storage (PST) adjoining the load-lock module (LLM)  40   a  or  40   b  to produce the corrosive gas by making the products produced during the etching process react with moisture contained in the atmosphere, dissipates the corrosive gas, and then carries the wafer to the loader module (LM)  50 . Consequently, the production of particles through the reaction of the products with moisture can be suppressed, corrosion of the component parts of the loader module (LM)  50 , namely, the walls of the atmospheric carrying chamber and the carrying mechanism installed in the atmospheric carrying chamber, can be suppressed, adhesion of particles to the component members can be suppressed, and contamination of the wafer W with the particles can be reduce. 
     A wafer W is carried to and carried out of the purge storage (PST)  60  by the carrying arm  54  in the loader module (LM)  50 , defining the atmospheric carrying chamber. Therefore, any additional carrying system which might be necessary when the purge storages (PST)  60  are disposed respectively contiguously with the load-lock modules (LLM)  40   a  and  40   b  is not necessary. Since the purge storage (PST)  60  is disposed between the load-lock modules (LLM)  40   a  and  40   b , a wafer W can be carried to and carrying out from either of the load-lock modules (LLM)  40   a  and  40   b  immediately after a wafer W has been carried to the purges storage (PST)  60  and immediately a wafer W has been carried out from the purge storage (PST)  60 , the substrate processing system can process wafers at a high throughput and can be built in compact construction. 
     The substrate holding device  63  installed in the purge storage (PST)  60  is vertically movable and hence height necessary for transferring a wafer W by the carrying arm  54  between the support arm  66  of the substrate holding device  63  and the loader module  50  is limited, i.e., the carrying arm  54  does not need to be moved vertically. Therefore, the opening  53  formed in the rear partition wall  57  of the loader module  50  may have the shape of a slit having a small area as shown in  FIG. 2 . Consequently, the leakage of the corrosive gas from the purge storage (PST)  60  into the loader module (LM)  50  can be suppressed. 
     Each of the gate valves G 7  and G 8  combined respectively with the respective walls of the load-lock modules  40   a  and  40   b  has the chevron-shaped valve element  80  shown in  FIG. 4  or the curved valve element  90  shown in  FIG. 6 . Therefore, the carrying arm  54  can carry a processed wafer W from the load-lock module  40   a  ( 40   b ) directly to the purge storage (PST)  60  by transversely moving the carrying arm  54  as shown in  FIG. 9  instead of carrying the processed wafer W indirectly through the loader module (LM)  50  to the purge storage (PST)  60 . Therefore, the stroke of the carrying arm  54  may be short, the carrying arm  54  can move along a circle of a short radius, the loader module (LM)  50  may be small and the substrate processing system can be built in compact construction. 
     The load-lock modules  40   a  and  40   b  may be provided with carrying arms, respectively, and processed wafers W may be carried from the load-lock modules  40   a  and  40   b  to the substrate holding device  63  of the purge storage  60  by the carrying arms of the load-lock modules  40   a  and  40   b , respectively, and wafers W to be processed supported on the support arms  66  of the substrate holding device  63  may be carried to the load-lock modules  40   a  and  40   b  by the carrying arms of the load-lock modules  40   a  and  40   b , respectively. 
     In the first embodiment, the purge storage  60  is disposed between the load-lock modules  40   a  and  40   b . In a substrate processing system  2  in a second embodiment, purge storages  60  are joined to the left side wall of the load-lock module  40   a  and the right side wall of the load-lock module  40   b , respectively, as shown in  FIG. 10 . In the second embodiment, a gate valve G 7  (G 8 ) disposed between the load-lock module  40   a  ( 40   b ) and the purge storage  60  has a curved valve element, a processed wafer W placed on the wafer stage  41   a  ( 41   b ) of the load-lock module  40   a  ( 40   b ) is transferred to a substrate holding device  63  disposed in the purge storage  60  by picking up the processed wafer W from the wafer stage  41   a  ( 41   b ) and transversely moving the carrying arm  54  of a loader module  50 . The second embodiment has the same effects as the first embodiment. A purge storage  60  may be connected only to either of the left side wall of the load-lock module  40   a  and the right side wall of the load-lock module  40   b . In this case, the load-lock module  40   a  or  40   b  connected to the purge storage  60  is used exclusively for sending out a processed wafer W. In the substrate processing system  2  shown in  FIG. 10 , both the load-lock modules  40   a  and  40   b  may be provided with carrying arms, respectively, to carry wafers W from the load-lock modules  40   a  and  40   b  to the purge storage  60  by those carrying arms, respectively.