Abstract:
A substrate processing apparatus includes at least two processing units provided around a substrate transfer chamber including a substrate transfer device for transferring substrates, wherein said at least two processing units include at least one batch processing unit, an M number of product substrates being processed simultaneously in one batch process with M being set to be less than or equal to the number of product substrates carried by a product substrate carrier, and all the product substrates contained in a product substrate carried by the product substrate carrier being processed in one batch process of said at least one batch processing unit. A method for fabricating a semiconductor device includes the step of sequentially processing plural product substrates in at least two processing units arranged around a substrate transfer chamber.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a substrate processing apparatus and method used in fabricating a semiconductor device; and, more particularly, to a substrate processing apparatus and method capable of sequentially forming various kinds of thin films, such as an oxide layer, a nitride layer, or a metallic layer, on a substrate, e.g., a semiconductor wafer (hereinafter referred to as a wafer), on which integrated circuits including therein semiconductor devices are fabricated, wherein the surface of the substrate is maintained in a highly clean condition during the film forming process.  
         BACKGROUND OF THE INVENTION  
         [0002]    Japanese Patent Application Laid-Open Publication No. 1995-101675 discloses a vertical diffusion and CVD apparatus for fabricating semiconductor devices by forming, e.g., a silicon oxide layer, a silicon nitride layer, or a metallic layer on a wafer while preventing a formation of a natural oxide film thereon. The vertical diffusion and CVD apparatus includes a hermetically sealed cassette chamber capable of receiving a cassette (wafer carrier) having a plurality of wafers accommodated therein; a loadlock chamber (wafer transfer chamber) having a wafer transfer device for transferring the wafers between the cassette disposed in the cassette chamber and a boat; and a reaction chamber (process tube), the boat being transferred between the loadlock chamber and the reaction chamber. The cassette chamber and the loadlock chamber are in communication with the loadlock chamber and the reaction chamber through gate valves, respectively. A nitrogen atmosphere is maintained in the loadlock chamber, which is not evacuated into vacuum.  
           [0003]    However, the vertical diffusion and CVD apparatus suffers from a drawback of a low throughput. That is, since the film formed wafers are transferred to a subsequent processing equipment after being returned to the cassette, the throughput of the aforementioned apparatus is deteriorated by the time required in returning the wafers to the cassette, unloading the cassette from the apparatus and transferring cassette to the subsequent equipment. Further, a cassette is usually made of a resin or the like. For this reason, the processed wafers need be cooled down to room temperature and thus the throughput of the aforementioned apparatus is further deteriorated by the time required in cooling down to a temperature acceptable for wafer transferring (for example, 5 to 60° C.) from a temperature (e.g., 600° C.) of the wafers immediately after being unloaded from the reaction chamber.  
           [0004]    Japanese Patent No. 2759368 describes a vertical type heat treatment apparatus capable of sequentially performing various processes on a substrate. The vertical type heat treatment apparatus includes a process tube for forming CVD films on a plurality of wafers loaded in a boat; a first loadlock chamber installed under the process tube to airtightly surround a vertical moving region of the boat; a second loadlock chamber airtightly connected to the first loadlock chamber; a third loadlock chamber installed between the second loadlock chamber and the atmosphere and having a stocker for receiving plural wafers; a transfer arm installed in the second loadlock chamber and for transferring the wafers between the boat and the stocker; and a natural oxide film removing device, airtightly combined with the second loadlock chamber, for processing the wafers one by one to remove a natural oxide film on the each wafer before forming a CVD film thereon. Further, in the vertical type heat treatment apparatus, the wafers loaded in the stocker are transferred one by one to the natural oxide film removing device by the transfer arm. After removing the natural oxide film on a wafer provided from the stocker, the wafer is returned from the natural oxide film removing device to the stocker by the transfer arm. Thereafter, the natural oxide film removed wafer returned to the stocker is batch-processed in the process tube after being transferred from the stocker to the first loadlock chamber by the transfer arm.  
           [0005]    In the above-mentioned vertical heat treatment apparatus, the processes, i.e., unloading wafers from the wafer stocker accommodating therein plural wafers, processing wafer, and returning the processed wafers to the same wafer stocker are carried out on a single wafer basis. Therefore, there occur waiting periods during the processes, lowering the throughput of the apparatus.  
         SUMMARY OF THE INVENTION  
         [0006]    It is, therefore, an object of the present invention to provide a substrate processing apparatus and method for fabricating semiconductor devices, which is capable of performing sequential processes in a highly clean surface condition while preventing a deterioration of throughput or an increase in cost.  
           [0007]    In accordance with one aspect of the invention, there is provided a substrate processing apparatus including: at least two processing units provided around a substrate transfer chamber which includes a substrate transfer device for transferring substrates; wherein said at least two processing units include at least one batch processing unit, M number of product substrates being processed simultaneously in one batch process, with M being set to be less than or equal to the maximum number of product substrates to be contained in a product substrate carrier, and all the product substrates contained in the product substrate carrier being processed in one batch process carried out in said at least one batch processing unit.  
           [0008]    In accordance with another aspect of the invention, there is provided a substrate processing apparatus including: at least one batch processing unit, provided around a substrate transfer chamber including a substrate transfer device for transferring substrates, for processing N number of product substrates simultaneously in one batch process; a single substrate processing unit provided around the substrate transfer chamber for processing one or P number of product substrates at a time, P being smaller than N; and a stocker provided around the substrate transfer chamber for temporarily storing said one or P number of product substrates processed by the single substrate processing unit.  
           [0009]    In accordance with still another aspect of the invention, there is provided a method for fabricating a semiconductor device, including the steps of: processing one or more product substrates in a first processing unit arranged around a substrate transfer chamber, transferring the product substrates from the first processing unit to a second processing unit arranged around the substrate transfer chamber; processing the product substrates in the second processing unit, wherein said two processing units include at least one batch processing unit, M number of product substrates being processed simultaneously in one batch process by said at least one batch processing unit with M being set to be less than or equal to the maximum number of product substrates which to be contained in a product substrate carrier, and all the product substrates contained in the product substrate carrier being processed in one batch process carried out in said at least one batch processing unit.  
           [0010]    In accordance with still another aspect of the invention, there is provided a method for fabricating a semiconductor device, comprising the steps of: processing at least one substrate in one processing unit; introducing an inert or a neutral gas into the processing unit after the processing step, to increase a pressure level therein to be higher than that during a process of transferring substrates; lowering the pressure level of said processing unit down to the pressure level during the process of transferring substrates; and transferring the substrates processed in said processing unit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 shows a horizontal cross sectional view of a multi-chamber type CVD apparatus in accordance with a first preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 2 describes a side cross sectional view of the multi-chamber type CVD apparatus of FIG. 1;  
         [0014]    [0014]FIG. 3 illustrates a rear cross sectional view of a first CVD unit of the multi-chamber type CVD apparatus of FIG. 1;  
         [0015]    [0015]FIG. 4 offers a rear cross sectional view of the first CVD unit during the film forming process; and  
         [0016]    [0016]FIG. 5 provides a horizontal cross sectional view of a multi-chamber type CVD apparatus in accordance with a second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Hereinafter, a first preferred embodiment of the present invention will now be described with reference to the accompanying drawings of FIGS.  1  to  4 .  
         [0018]    As shown in FIGS. 1 and 2, a substrate processing apparatus in accordance with the first preferred embodiment of the present invention, is a multi-chamber type CVD apparatus (hereinafter referred to as a CVD apparatus), which is used to form an insulating layer, e.g., composed of a silicon oxide or a silicon nitride and/or a metallic layer, e.g., composed of Ta 2 O 5  or Ru on a wafer in the course of manufacturing semiconductor integrated circuit (hereinafter referred to as IC).  
         [0019]    Further, in the CVD apparatus in accordance with the first preferred embodiment, a FOUP (front opening unified pod, hereinafter referred to as a pod) is used as a wafer carrier. Throughout the specification, a front, a rear, a left and a right side of the apparatus are defined with reference to FIG. 1. That is, the front side refers where a pod opener  50  is located; the rear side refers to a side opposite to the front side, i.e., where a second CVD unit  62  is located; the left side refers where a loading chamber  20  is located; and the right side refers where a unloading chamber  30  is located.  
         [0020]    As shown in FIGS. 1 and 2, the CVD apparatus is provided with a negative pressure wafer transfer chamber  11  having a wafer transfer device  10  at a center portion thereof for transferring wafers W under a pressure lower than the atmospheric pressure (hereinafter referred to as a negative pressure). A housing  12  of the negative pressure wafer transfer chamber  11  has a heptagonal prism shape with two top and bottom ends closed and is of a loadlock chamber structure capable of maintaining therein negative pressure under an airtight condition. The wafer transfer device  10  is formed of a scara (selective compliance assembly robot arm) type robot and is configured to be hermetically raised or lowered by an elevator  13  installed at a lower wall of the housing  12  of the negative pressure wafer transfer chamber  11 . As shown in FIG. 2, an elevating stroke L 1  of the wafer transfer device  10  is smaller than a wafer charging range L 2  of a boat  79  which will be described later, and a shortage length L 3  can be accommodated by an elevator  80  of the boat  79 . Thus, the size of the elevator  13  of the wafer transfer device  10  can be reduced by that much.  
         [0021]    Adjacently connected to the two front side walls of the housing  12  of the negative pressure wafer transfer chamber  11  are the loading chamber  20  and the unloading chamber  30 , respectively. Each of a housing  21  of the loading chamber  20  and a housing  31  of the unloading chamber  30  has a hexagonal prism shape with two closed top and bottom ends and is of a loadlock chamber structure capable of enduring negative pressure therein. Loading openings  22  and  23  are installed at adjoining side walls of the housing  21  of the loading chamber  20  and the housing  12  of the negative pressure wafer transfer chamber  11 , respectively, and installed at the loading opening  23  of the negative pressure wafer transfer chamber  11  is a gate valve  24  for opening or closing the loading openings  22  and  23 . Similarly, unloading openings  32  and  33  are installed at adjoining side walls of the housing  31  of the unloading chamber  30  and the housing  12  of the negative pressure wafer transfer chamber  11 , respectively, and installed at the unloading opening  33  of the negative pressure wafer transfer chamber  11  is a gate valve  34  for opening or closing the unloading openings  32  and  33 .  
         [0022]    Installed inside the loading chamber  20  is a temporary storage  25 , and installed inside the unloading chamber  30  is a temporary storage  35 . The temporary storages  25  and  35  have identical structures to that of the boat  79  and are configured such that a plurality of wafers W are horizontally maintained by maintenance grooves. As shown in FIG. 2, the temporary storage  25  is configured to rotate in a horizontal plane by a rotary actuator  26 . Though not shown, the temporary storage  35  has a configuration identical to that of the temporary storage  25 .  
         [0023]    Disposed in front of the loading chamber  20  and the unloading chamber  30  is a positive pressure wafer transfer chamber  40  having a wafer transfer device  42  for transferring the wafers W under a pressure higher than the atmospheric pressure (hereinafter referred to as a positive pressure). A housing  41  of the positive pressure wafer transfer chamber  40  has an airtight structure capable of maintaining positive pressure therein. The wafer transfer device  42  has an elevator  43  for vertically raising or lowering a rotary actuator  44 , which is configured to rotate a linear actuator  45  installed at top surface thereof in a horizontal plane. Installed at the top surface of the linear actuator  45  is a moving stage  46 , which is configured to be horizontally moved by the linear actuator  45 . Horizontally mounted on the moving stage  46  are tweezers  47  for supporting the wafers W thereunder.  
         [0024]    As shown in FIG. 1, a clean air supplying unit  48  is installed in the positive pressure wafer transfer chamber  40  to supply clean air thereinto. Installed at a side wall of the housing  21  of the loading chamber  20  adjoining the positive pressure wafer transfer chamber  40  is a loading opening  27  for connecting the positive pressure wafer transfer chamber  40  to the loading chamber  20 , and installed at a side of the loading opening  27  toward the positive pressure wafer transfer chamber  40  is a gate valve  28  for opening and closing the loading opening  27 . Further, installed at a side wall of the housing  31  of the unloading chamber adjoining the positive pressure wafer transfer chamber  40  is an unloading opening  37  provided in order to connect the positive pressure wafer transfer chamber  40  to the unloading chamber  30 , and installed at a side of the unloading opening  37  toward the positive pressure wafer transfer chamber  40  is a gate valve  38  for opening and closing the unloading opening  37 .  
         [0025]    As shown in FIGS. 1 and 2, provided at a front side wall of the housing  41  of the positive pressure wafer transfer chamber  40  is a wafer loading/unloading opening  49  for loading and unloading the wafers W into and from the positive pressure wafer transfer chamber  40 , and a pod opener  50  is provided at the wafer loading/unloading opening  49 . The pod opener  50  has a loading stage  51  for loading a pod P and a cap removing/restoring device  52  for removing or restoring a cap of the pod P loaded on the loading stage  51 , wherein a wafer transfer opening of the pod P is opened or closed by removing or restoring the cap of the pod P loaded on the loading stage  51  by the cap removing/restoring device  52 . The pod P is provided to or evacuated from the loading stage  51  of the pod opener  50  by a pod transport system (not shown) such as a rail-guided vehicle (RGV).  
         [0026]    As shown in FIG. 1, adjacently connected to three rear side walls of the housing  12  of the negative pressure wafer transfer chamber  11  are a first CVD unit  61  serving as a first processing section, a second CVD unit  62  serving as a second processing section and a third CVD unit  63  serving as a third processing section, respectively. The number of product wafers which can be processed at a time in each of the batch processing CVD units  61 - 63  is  25 , which is identical to that of the product wafers which can be contained in one pod P at a time. Since the first CVD unit  61 , the second CVD unit  62  and the third CVD unit  63  basically have identical structures, a configuration of the above-mentioned CVD units will be described with reference to the first CVD unit  61 .  
         [0027]    As shown in FIGS.  1  to  3 , the first CVD unit  61  has an antechamber  64  where the boat  79  waits. A housing  65  of the antechamber  64  has a pentagonal prism shape with two closed top and bottom ends and is of a loadlock chamber structure capable of enduring negative pressure. The antechamber  64  is large enough to accommodate the boat  79  therein. Installed at a front wall of the housing  65  of the antechamber  64  and its adjoining rear wall of the housing  12  of the negative pressure wafer transfer chamber  11  are wafer loading/unloading openings  66  and  67 , respectively, which are opened or closed by a gate valve  68 . Installed at a rear wall of the housing  65  of the antechamber  64  is a maintenance opening  69  to be used in loading and unloading the boat  79  to and from the antechamber  64  therethrough for maintenance. The maintenance opening  69  is normally closed by a gate valve  70 .  
         [0028]    As shown in FIGS. 2 and 3, installed at the top wall of the housing  65  of the antechamber  64  is a boat loading/unloading opening  71 , which is configured to be opened or closed by a shutter  72 . Vertically installed above the housing  65  of the antechamber  64  is a heater unit  73 , and provided inside the heater unit  73  is a process tube  75  for forming a process room  74 . The process tube  75  is of a cylindrical shape having a closed upper end and an open lower end, and is concentrically disposed in the heater unit  73 , wherein a cylindrical hollow portion of the process tube  75  serves as the process room  74 . The process tube  75  is supported via a manifold  76  disposed on the top wall of the housing  65  of the antechamber  64 , and connected to the manifold  76  are a gas supply line  77  for introducing a source gas or a purge gas into the process room  74  formed by the cylindrical hollow portion of the process tube  75  and an exhaust line  78  for evacuating the inside of the process tube  75 . The manifold  76  is concentrically arranged on the boat loading/unloading opening  71  disposed at the housing  65  of the antechamber  64 .  
         [0029]    As shown in FIG. 1, installed at a rear-left corner portion of the antechamber  64  is a boat elevator  80  for raising or lowering the boat  79 . As shown in FIGS. 1 and 3, the boat elevator  80  has a guide rail  83  and a feed screw shaft  84 , which are vertically installed by an upper installing plate  81  and a lower installing plate  82 . An elevating stage  85  is fittedly engaged with the guide rail  83 , so that the elevating stage  85  can vertically move up and down along the guide rail  83 . The elevating stage  85  is screw-coupled to the feed screw shaft  84  so as to vertically advance and retreat with respect thereto. Further, it is preferable to use a ball screw mechanism for the connection between the feed screw shaft  84  and the elevating stage  85  in order to confer smooth operation on the boat elevator  80  without incurring backlash. An upper portion of the feed screw shaft  84  is protruded outside the antechamber  84  by passing through the top wall of the upper installing plate  81  and the housing  65  of the antechamber  64 , and is connected to a motor  86  installed outside the antechamber  64  which enables the feed screw shaft  84  to rotate in forward and reverse directions.  
         [0030]    A horizontally protruded arm  87  is installed on a side surface of the elevating stage  85 , and a sealing cap  88  is horizontally installed at an end portion of the arm  87 . The sealing cap  88  functions to airtightly seal the boat loading/unloading opening  71  disposed at the housing  65  of the antechamber  64  serving as a furnace mouth of the process tube  75  and also vertically supports the boat  79 . The boat  79  is configured to be loaded into or unloaded from the process room  74  of the process tube  75  in unison with the ascent and descent movement of the sealing cap  88  rendered by the ascending and the descending motion of the boat elevator  80  while horizontally holding a plural number, e.g., from 25 to 50, of the wafers W.  
         [0031]    As shown in FIG. 3, in accordance with the first embodiment, a first bellows  91  serving as a first hollow extension/retraction body and a second bellows  92  serving as a second hollow extension/retraction body, respectively, are installed at top and bottom portions of the elevating stage  85 , i.e., an outside portion of the guide rail  83  and the feed screw shaft  84 , wherein hollow portions of the first bellows  91  and the second bellows  92  are airtightly separated from the antechamber  64 . A first through hole  93  is provided at a position, corresponding to the hollow portion of the first bellows  91 , in the top wall of the housing  65  of the antechamber  64  and the upper installing plate  81 ; and a second through hole  94  is provided at a position, corresponding to the hollow portion of the second bellows  92 , in the bottom wall of the housing  65  of the antechamber  65  and the lower installing plate  82 . Therefore, the hollow portions of the first bellows  91  and the second bellows  92  can be in communication with the atmosphere.  
         [0032]    Hereinafter, film forming processes in the course of an IC manufacturing method will now be described with reference to the foregoing CVD apparatus in the first preferred embodiment of the invention.  
         [0033]    25 sheets of wafers W loaded in the pod P are transferred by the pod transport system, to the CVD apparatus for performing the film forming process thereon. As shown in FIGS. 1 and 2, the transferred pod P is mounted on the loading stage  51  of the pod opener  50  after being transferred by the pod transport system. Then, the cap of the pod P is separated by the cap removing/restoring device  52  to open the wafer transfer opening of the pod P.  
         [0034]    If the pod p is opened by the pod opener  50 , the wafers W are sequentially picked up one at a time from the pod P are transferred to the temporary storage  25  of the loading chamber  20  though the loading opening  27  by the wafer transfer device  42  installed in the positive pressure wafer transfer chamber  40  of the loading chamber  20 . During the transfer operation, the loading openings  22  and  23  are closed by the gate valve  24  and the negative pressure wafer transfer chamber  11  is maintained at negative pressure. If the 25 sheets of wafers are completely loaded and transferred to the temporary storage  25 , the loading opening  27  provided toward the negative pressure wafer transfer chamber  40  is closed by the gate valve  28  and then the loading chamber  20  is evacuated to negative pressure by an evacuating device (not shown).  
         [0035]    If the loading chamber  20  is depressurizeded to a predetermined pressure level, the loading openings  22  and  23  disposed at the negative pressure wafer transfer chamber  11  are opened by the gate valve  24  and, further, the wafer loading/unloading openings  66  and  67  provided at the antechamber  64  of the first CVD unit  61  are opened by the gate valve  68 . Subsequently, the wafers W are sequentially picked up one at a time from the temporary storage  25  through the loading openings  22  and  23  and are charged into the boat  79  disposed in the antechamber  64  through the wafer loading/unloading openings  66  and  67  of the antechamber  64  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11 . In the meantime, a facing direction of the temporary storage  25  is regulated by the rotation of the rotary actuator  26 . If the 25 sheets of wafers are completely charged into the boat  79 , the wafer loading/unloading openings  66  and  67  located at the antechamber  64  are closed by the gate valve  68 .  
         [0036]    In the charging operation of the 25 sheets of wafers to the boat  79 , even though the elevating stroke L 1  of the wafer transfer device  10  is smaller than the wafer charging range L 2  of the boat  79  as shown in FIG. 2, the shortage length L 3  can be accommodated by the elevator  80  of the boat  79 . Therefore, the 25 sheets of wafers can be completely charged to the boat  79  by the wafer transfer device  10 . Thus, since the elevator  13  of the wafer transfer device  10  can be reduced in size as much as the storage length L 3 , a manufacturing or operating cost for the wafer transfer device  10  and the negative pressure wafer transfer chamber  11 , and further the whole CVD apparatus, can be reduced.  
         [0037]    During the charging operation of the wafers from the temporary storage  25  to the boat  79  by the wafer transfer device  10 , the boat loading/unloading opening  71  is closed by the shutter  72 . Therefore, the high temperature atmosphere of the process tube  75  is prevented from being flowed into the antechamber  64 . Accordingly, the wafers W which have been already charged or in the process of being charged are not exposed to the high temperature atmosphere, so that such adverse effects as natural oxidation of the wafers which can be caused by the exposure to the high temperature ambience can be prevented.  
         [0038]    As shown in FIGS. 2 and 3, if the predetermined numbers of wafers W are charged to the boat  79 , the boat loading/unloading opening  71  is opened by the shutter  72  as shown in FIG. 4. Thereafter, the boat  79  supported by the sealing cap  88  is raised by the elevating stage  85  of the boat elevator  80 , thereby being loaded into the process room  74  of the process tube  75 . When the boat  79  reaches its uppermost position, the boat loading/unloading opening  71  is closed by being sealed by the periphery of the top surface of the sealing cap  88  supporting the boat  79 , so that the process room  74  disposed in the process tube  75  becomes in a hermetically closed state. Since the antechamber  64  is evacuated to be in a vacuum condition and therefore oxygen and moisture are removed therefrom before starting the loading process of the boat  79  into the process room  74 , oxygen and moisture are prevented from being introduced into the process room  74  by loading the boat  79  into the process room  74 .  
         [0039]    Here, in the case where the elevating stage  85  is raised to load the boat  79  into the process room  74 , the first bellows  91  should be retracted in an upper direction and, further, the second bellows  92  should be extended in an upper direction thereof. Since the inner space of the hollow portion of the first bellows  91  is in communication with the atmosphere through the first through hole  93 , and that of the second bellows  92  is in communication with the atmosphere via the second through hole  94 , the first bellows  91  and the second bellows  92  can be retracted and extended in the upper direction. Further, since the inner space of the hollow portion of the first bellows  91  and that of the second bellows  92  are separated from the antechamber  64 , oxygen and moisture of the atmosphere in the hollow portions of the first and second bellows  91  and  92  and evaporated gas generated from grease coated on the feed screw shaft  84 , etc are prevented from being introduced into the antechamber  64  in the course of retraction of the first bellows  91  and extension of the second bellows  92  (especially, retraction of the first bellows  91 ).  
         [0040]    Thereafter, the process room  74  in the process tube  75  is evacuated via the exhaust line  78 , while being airtightly isolated, in order to have a predetermined pressure by and heated to a predetermined temperature by the heater unit  73  and, thereafter, a predetermined source gas is provided therein via the gas supply line  77 . As a result, a desired first film corresponding to the predetermined processing condition is formed on the wafers W.  
         [0041]    During the film forming process performed in the first CVD unit  61 , 25 sheets of wafers of a subsequent batch (hereinafter referred to as a second batch) are transferred from the pod P loaded on the loading stage  51  of the pod opener  50  to the temporary storage  25  of the loading chamber  20  by the aforementioned wafer transfer operation preformed by the wafer transfer device  42 , so that 25 sheets of second batch wafers W are prepared in the loading chamber  20  in advance. During the preparing operation, since the loading openings  22  and  23  formed at the negative pressure wafer transfer chamber  11  are closed by the gate valve  24 , the negative pressure wafer transfer chamber  11  is maintained at the negative pressure.  
         [0042]    In the first CVD unit  61 , if a predetermined processing time for forming the film is passed, the boat  79  is lowered by the elevating stage  85  of the boat elevator  80  as shown in FIGS. 2 and 3, so that the boat  79  having the film formed wafers W is unloaded to the antechamber  64  of the first CVD unit  61 . After the boat  79  is unloaded to the antechamber  64 , the boat loading/unloading opening  71  is closed by the shutter  72 . Then, a loadlock of the antechamber  64  is released and, simultaneously, a nitrogen gas is supplied into the antechamber  64  via an inert gas or a neutral gas, e.g., N 2  gas supply path (not shown). The processed wafers W in the boat  79  conveyed to the antechamber  64  of the first CVD unit  61  are then cooled down by the supply of nitrogen gas to a temperature (about 200° C.) at which the wafer transfer operation can be performed by the wafer transfer device  10 . If the wafers W are cooled down to the predetermined temperature, the antechamber  64  is depressurized to the predetermined negative pressure again.  
         [0043]    After the antechamber  64  of the first CVD unit  61  is depressurized to the predetermined negative pressure, the wafer loading/unloading openings  66  and  67  of the antechamber  64  of the first CVD unit  61  are opened by the gate valve  68  and, at the same time, the wafer loading/unloading openings  66  and  67  at the antechamber  64  of the second CVD unit  62  are opened by the gate valve  68 . Subsequently, the film formed wafers W are sequentially picked up one at a time from the boat  79  located in the antechamber  64  of the first CVD unit  61  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11  and are then loaded into the boat  79  of the antechamber  64  of the second CVD unit  62  through the wafer loading/unloading openings  66  and  67 . After the 25 sheets of wafers are completely transferred from the first CVD unit  61  to the boat  79  of the second CVD unit  62 , the wafer loading/unloading openings  66  and  67  at the antechamber  64  of the second CVD unit  62  are closed by the gate valve  68 .  
         [0044]    As described, since the transferring operation of the 25 sheets of wafers W, on each of which the first film is formed, from the first CVD unit  61  to the second CVD unit  62  is performed in the first CVD unit  61 , the second CVD unit  62  and the negative pressure wafer transfer chamber  11  all of which are maintained at the negative pressure, the formation of the natural oxide film and/or the adhesion of impurities on the first film surface of each wafer W can be prevented during the wafer transferring operation.  
         [0045]    After the wafer loading/unloading openings  66  and  67  disposed at the second CVD unit  62  are closed by the gate valve  68  after charging the 25 sheets of wafers W to the boat  79  in the second CVD unit  62 , a second film is formed on the first film of the wafers W in the process room  74  of the process tube  75  disposed in the second CVD unit  62  in the same manner as in the aforementioned first CVD unit  61 .  
         [0046]    During the second film forming process in the second CVD unit  62 , the 25 sheets of wafers of the second batch previously prepared at the temporary storage  25  in the loading chamber  20  are charged to the empty boat  79  of the antechamber  64  of the first CVD unit  61  by the transfer operation of the wafer transfer device  10  disposed in the aforementioned negative pressure wafer transfer chamber  11 . During the transfer operation, the loading opening  27  of the loading chamber  20  disposed toward the negative pressure wafer transfer chamber  11  is closed by the gate valve  28 , so that the loading chamber  20  and the negative pressure wafer transfer chamber  11  are maintained at the negative pressure.  
         [0047]    After the 25 sheets of wafers of the second batch are completely charged to the boat  79  in the first CVD unit  61 , the wafer loading/unloading openings  66  and  67  of the first CVD unit  61  are closed by the gate valve  68  and, then, the first film is formed on the wafers W of the second batch in the process room  74  of the process tube  75  disposed in the first CVD unit  61  by the aforementioned film forming process. Further, during the first film forming operation on the second batch wafers, 25 sheets of wafers W of a third batch are prepared on the temporary storage  25  of the loading chamber  20  by the preparing operation mentioned above.  
         [0048]    Similarly as in the aforementioned first CVD unit  61 , if the predetermined processing time for the second film formation is passed in the second CVD unit  62 , the boat  79  is lowered by the elevating stage  85  of the boat elevator  80 , so that the boat  79  having the wafers W on which the second films are formed is unloaded to the antechamber  64  of the second CVD unit  62 . Thereafter, the wafers W are cooled down by the supply of nitrogen gas to a temperature (about 200° C.), at which the wafer transfer operation can be performed by the wafer transfer device  10 . If the temperature of the second film formed wafers W is reduced down to a predetermined level, the antechamber  64  of the second CVD unit  62  is depressurized to the predetermined negative pressure again.  
         [0049]    If the pressure inside the antechamber  64  of the second CVD unit  62  is lowered to the predetermined negative pressure level, the wafer loading/unloading openings  66  and  67  disposed at the antechamber  64  of the second CVD unit  62  are opened by the gate valve  68  and, at the same time, the wafer loading/unloading openings  66  and  67  disposed at the antechamber  64  of the third CVD unit  63  are opened by the gate valve  68 . Then, the second film formed wafers W are sequentially picked up one by one from the boat  79  of the second CVD unit  62  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11  and are loaded to the boat  79  in the antechamber  64  of the third CVD unit  63  through the wafer loading/unloading openings  66  and  67  disposed at the antechamber  64  of the third CVD unit  63 . If the 25 sheets of wafers each having the second film formed thereon are completely transferred from the second CVD unit  62  to the third CVD unit  63 , the wafer loading/unloading openings  66  and  67  disposed at the antechamber  64  of the third CVD unit  63  are closed by the gate valve  68 .  
         [0050]    As described above, since the wafer transferring operation of the 25 sheets of wafers W each having the second film formed thereon from the second CVD unit  62  to the third CVD unit  63  is performed in the second CVD unit  62 , the negative pressure wafer transfer chamber  11 , and the third CVD unit  63  all of which are maintained at the negative pressure, the formation of the natural oxide film and/or the adhesion of impurities can also be prevented during the wafer transferring operation from the second CVD unit  62  to the third CVD unit  63 .  
         [0051]    After the wafer loading/unloading openings  66  and  67  disposed at the third CVD unit  63  are closed by the gate valve  68  after charging the 25 sheets of wafers W to the boat  79  in the third CVD unit  63 , a third film is formed on the second film of each wafer W in the process room  74  of the process tube  75  disposed in the third CVD unit  63  in the same manner as in the aforementioned first CVD unit  61  and second CVD unit  62 .  
         [0052]    Further, the transferring operation of the aforementioned first film formed wafers W of the second batch can be preformed while the third film forming operation in the third CVD unit  63 .  
         [0053]    If the predetermined processing time for the third film formation is passed in the third CVD unit  63 , the boat  79  is lowered by the elevating stage  85  of the boat elevator  80  in the same manner as in the aforementioned first CVD unit  61  and second CVD unit  62 , so that the boat  79  having the wafers W on which the third films are formed is unloaded to the antechamber  64  of the third CVD unit  63 . Thereafter, the wafers W are cooled down by the supply of nitrogen gas to a temperature (about 200° C.), at which the wafer transfer operation of the wafers W can be performed by the wafer transfer device  10 . If the temperature of the third film formed wafers W is lowered down to a predetermined level, the antechamber  64  of the third CVD unit  63  is decompressed to the predetermined negative pressure again.  
         [0054]    If the pressure inside the antechamber  64  of the third CVD unit  63  is lowered to the predetermined negative pressure, the wafer loading/unloading openings  66  and  67  disposed at the antechamber  64  of the third CVD unit  63  are opened by the gate valve  68  and, at the same time, the unloading openings  32  and  33  disposed at the unloading chamber  30  are opened by the gate valve  34 . Thereafter, the third film formed wafers W are sequentially picked up one at a time from the boat  79  of the third CVD unit  63  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11  and, then, loaded to the temporary storage  35  in the unloading chamber  30  through the unloading openings  32  and  33  disposed at the unloading chamber  30 . If the 25 sheets of wafers having the third films formed thereon are completely transferred from the third CVD unit  63  to the temporary storage  35 , the unloading openings  32  and  33  disposed at the unloading chamber  30  are closed by the gate valve  34 , and a loadlock of the unloading chamber  30  is released.  
         [0055]    After the loadlock of the unloading chamber  30  is released, the unloading opening  37  of the unloading chamber  30  is opened by gate valve  38  and, further, the cap of the empty pod P loaded on the loading stage  51  is opened by the pod opener  50 . Thereafter, the wafers W are sequentially picked up one by one from the temporary storage  35  by the wafer transfer device  42  of the positive pressure wafer transfer chamber  40  and are then charged to the pod P through the wafer loading/unloading opening  49  formed in positive pressure wafer transfer chamber  40 . For the wafer unloading process, the facing direction of the temporary storage  35  is adjusted by a turn table (not shown). If all the 25 sheets of wafers W, on which the film formation is completed, are accommodated in the pod P, the cap of the pod P is restored to the wafer transfer opening of the pod P by the cap removing/restoring device  52  to thereby close the pod P.  
         [0056]    The closed pod P is then transferred from the loading stage  51  for a subsequent process by the pod transport system.  
         [0057]    By repeating the aforementioned film forming operations, the 25 sheets of wafers contained in one pod P are batch-processed for the formation of the first, the second and the third film sequentially.  
         [0058]    Following effects can be achieved by the preferred embodiment of the present invention.  
         [0059]    1) By arranging the CVD units each having the antechamber of the loadlock chamber structure, around the negative pressure wafer transfer chamber having the wafer transferr device, the transferring operation of the film formed wafers between the CVD units can be performed under the negative pressure, so that the formation of the natural oxide film and/or the adhesion of the impurities on the surface of a wafer and the surface of a film can be prevented.  
         [0060]    2) By setting up the number of product wafers which can be processed simultaneously in each CVD unit being not greater than 25, which is the maximum number of wafers which can be carried by one pod for use in carrying product wafers and configuring the substrate processing apparatus such that each CVD unit can simultaneously process the whole product wafers carried by one pod, the formation of the first, the second and the third film can be sequentially batch-processed on a pod basis, so that the throughput of the CVD apparatus can be increased significantly compared with a single wafer process.  
         [0061]    3) By arranging the loading chamber and the unloading chamber having the loadlock chamber structure, around the negative pressure wafer transfer chamber having the wafer transfer device, the loading operation of the wafers to be processed and the unloading operation of the processed wafers can be carried out while the film forming process are performed in the CVD units, so that the throughput of the CVD apparatus can be further increased.  
         [0062]    4) By enabling the nitrogen to be supplied to the antechamber of the each of CVD unit, the processed wafers can be forcedly cooled down, so that the throughput of the CVD apparatus can be still further increased.  
         [0063]    Referring to FIG. 5, there is illustrated a horizontal cross-sectional view of a multichamber CVD apparatus in accordance with a second preferred embodiment in the present invention.  
         [0064]    The batch-type CVD apparatus in accordance with the second preferred embodiment of the present invention is different from that of the first preferred embodiment, in that a single wafer CVD reactor  100  is installed in a first CVD unit  61 A and a buffer chamber  101  is further arranged at one side wall of a housing  12  of a negative pressure wafer transfer chamber  11 . A housing  102  of the buffer chamber  101  has a hexahedral shape with two closed top and bottom ends and is of a loadlock chamber structure capable of maintaining the negative pressure.  
         [0065]    Installed at two adjoining side walls of the housing  102  of the buffer chamber  101  and the housing  12  of the negative pressure wafer transfer chamber  11  are wafer loading/unloading openings  103  and  104 . A gate valve  105  is installed at the wafer loading/unlading opening  104  toward the negative pressure wafer transfer chamber  11 . A temporary storage  106  having an identical structure to that of the boat  79  is installed in the buffer chamber  101 . Further, the gate valve  105  can be omitted if required.  
         [0066]    In the CVD apparatus in accordance with the second embodiment, since the single wafer CVD reactor  100  is installed in the first CVD unit  61 A, a first film forming process is carried out on one sheet of wafer at a time and upon completing the first film forming process on a wafer, the processed wafer is transferred to the temporary storage  106  of the buffer chamber  101  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11 . Further, if one batch of processed wafers W 25 sheets of wafers corresponding to one pod is accumulated in the temporary storage  106 , those wafers are moved from the buffer chamber  101  to the second CVD unit  62  by the wafer transfer device  10  of the negative pressure wafer transfer chamber  11 .  
         [0067]    As for the wafers of the first batch, it may be possible to transfer each wafer directly from the first CVD unit  61 A to the second CVD unit  62  without passing through the temporary storage  106  of the buffer chamber  101 . However, in subsequent batch, since the film forming process in the first CVD unit  61 A is performed during the second film forming process in the second CVD unit  62 . Therefore, it is impossible to directly transfer the wafers W from the first CVD unit  61 A to the second CVD unit  62 . As a result, there may occur a waiting time period. In accordance with the present invention, however, the waiting time can be considerably reduced or removed by loading and transferring the first film formed wafers W from the first CVD unit  61 A to the temporary storage  106  of the buffer chamber  101  to thereby temporarily store the wafers W.  
         [0068]    In accordance with the second embodiment, the batch process can be performed on a pod basis even with the single wafer CVD reactor employed. Therefore, the waiting time due to the single wafer process can be minimized, and, therefore, the single wafer process can be employed together with the batch process without lowering the throughput of the CVD apparatus.  
         [0069]    The present invention is not intended to be limited by the specific embodiments described above, but should be construed that the preferred embodiments described above can be modified without departing from the scope of the invention.  
         [0070]    For example, the number of the CVD units arranged around the negative pressure wafer transfer chamber is not limited to three. It can be any number greater 1.  
         [0071]    The processing units arranged around the negative pressure wafer transfer chamber can be any other units than the batch-type CVD apparatus and the single wafer CVD reactor. The processing units may include a CVD apparatus processing two wafers at a time, a plasma CVD apparatus, or a wafer processing unit having a substrate processing apparatus such as an oxidation apparatus, a diffusion apparatus, a sputtering apparatus, or a dry etching apparatus.  
         [0072]    Dummy wafers may be accommodated in a boat permanently, or they can be exchanged periodically or non-periodically. Further, the dummy wafers can be stored in a stocker provided in the negative pressure or the positive pressure wafer transfer chamber and can be charged to the boat when necessary.  
         [0073]    Even though the aforementioned preferred embodiments describe the CVD film forming processes, the present invention can be equally applied to a substrate processing apparatus which can be used in an oxidation treatment, a diffusion process, an annealing process, a plasma treatment, a sputtering process, a dry etching process and the combination thereof.  
         [0074]    Examplary sequential processes are listed in Table. It is preferable that a preprocessing in Table is carried out on a single wafer basis.  
                           TABLE                                   Fourth       First processing   Second processing   Third process-   processing       section   section   ing section   section                   Preprocessing   Forming               (removing natural   poly-silicon film       oxide film)       Preprocessing   Forming       (removing natural   epitaxial       oxide film)   silicon film       Preprocessing   Forming       (removing natural   epitaxial       oxide film)   silicon-germanium           film       Preprocessing   Forming Hi-k   Forming       (removing natural   (high dielectric)   poly-silicon       oxide film)   gate oxide film   film       Preprocessing   Forming Hi-k   Forming poly-       (removing natural   (high dielectric)   silicon-       oxide film)   gate oxide film   germanium               film       Preprocessing   Forming a HSG-Si   Forming   Forming       (removing natural   film   silicon nitride   poly-silicon       oxide film)       film   film       Previous process   Oxidation process   Forming a   Forming       (removing a natural       silicon nitride   poly-       oxide film)       film   silicon-                   germanium                   film                  
 
         [0075]    Further, the present invention can also be applied to various substrate processes for manufacturing a liquid crystal panel, a magnetic disk or an optical disk as well.  
         [0076]    While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.