Abstract:
A vertical furnace processing system for processing semiconductor substrates, comprising the following modules:—a processing module including a vertical furnace; an I/O-station module including at least one load port to which a substrate cassette is dockable; a wafer handling module configured to transfer semiconductor substrates between the processing module and a substrate cassette docked to the load port of the I/O-station module; and a gas supply module including at least one gas supply or gas supply connection for providing the vertical furnace of the processing module with process gas, wherein at least two of the said modules are mutually decouplably coupled, such that said at least two modules are decouplable from one another to facilitate servicing of the system, and in particular the vertical furnace thereof.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of semiconductor processing equipment, and more in particular to a modular vertical furnace processing system that facilitates servicing. 
       BACKGROUND 
       [0002]    Semiconductor processing equipment for the processing of semiconductor substrates is typically placed in a clean room because clean, dust free processing is required. At the front side of the system, facing the clean room, substrate cassettes with wafers to be processed are received and substrate cassette handling and storage equipment and wafer handling equipment is typically provided. At the rear side of the system the processing chamber is provided and at the extreme end opposite to the clean room side a gas cabinet is provided with gas control components and optionally pressure control or vacuum components. Vertical furnaces for batch processing of substrates are preferably placed side by side, without any space in between the systems, to minimize the joint footprint of a plurality of systems. This implies that access to the system can only be provided at the front and the rear side and not via the sides. 
         [0003]    A solution described in U.S. Pat. No. 6,332,898 (Tometsuka et al.) is that substrate cassette and wafer handling and storage components at the front side of the system are movable between a processing time position and a maintenance time position. When moved in a maintenance time position, the components can be accessed for maintenance from the front side of the system. The vertical furnace can be accessed from the rear side of the system. 
         [0004]    However, the design proposed by US&#39;898 has the disadvantage that all maintenance actions on the substrate cassette and wafer handling and storage components are performed in intimate communication with the clean room. E.g. if a wafer handling robot needs to be replaced, the broken robot and the replacement robot need to be transported through the clean room. Further, the substrate cassette handling and storage components and wafer handling components remain in the system and may hinder accessibility of other components. Further, a gas component cabinet is provided at the rear side of the system and this may hinder the accessibility of the vertical furnace when maintenance needs to be performed. During replacement of e.g. a quartz process tube, which is a large component, sufficient space needs to be available and the gas cabinet can be a significant obstacle. 
         [0005]    With the transition to a wafer size of 450 mm all components grow in size and the space requirements become even stronger. For the handling of large components such as process tubes, flanges, heating elements etc. large tools are required that occupy a lot of space. A solution would be to place the gas cabinet remote from the vertical furnace with the disadvantage of long gas supply lines and control lines between furnace and gas cabinet. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to obviate or at least mitigate one or more of the aforementioned problems and disadvantages, and to provide for a vertical furnace processing system with a system design that facilitates service access to all major components of the system. 
         [0007]    It is another object of the present invention to provide for a semiconductor processing facility including one or more vertical furnace processing systems that are economically arranged and conveniently serviceable. 
         [0008]    It is yet another object of the present invention to provide for a method of conveniently servicing a vertical furnace processing system. 
         [0009]    To this end, a first aspect of the present invention is directed to a vertical furnace processing system according to claim  1 . 
         [0010]    A second aspect of the present invention is directed to a semiconductor processing facility including at least one vertical furnace processing system according to the first aspect of the invention, as defined by claim  15 . 
         [0011]    A third aspect of the present invention is directed to a method of servicing a vertical furnace processing system according to the first aspect of the invention, as defined by claim  18 . 
         [0012]    These and other features and advantages of the invention will be more fully understood from the following detailed description of certain embodiments of the invention, taken together with the accompanying drawings, which are meant to illustrate and not to limit the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1A  shows a top plan view and a side view of an embodiment of the invention; 
           [0014]      FIGS. 1B and 1C  show two other embodiments of the invention; 
           [0015]      FIG. 2A-2D  show in a side view sequential steps in a service operation of the system of  FIG. 1A ; 
           [0016]      FIG. 3A-3C  are top plan views and correspond to  FIG. 2A-2C  respectively; 
           [0017]      FIG. 4A-4D  show in a side view sequential steps in a service operation of the system of  FIG. 1B ; 
           [0018]      FIG. 5A-5D  are top plan views corresponding to  FIG. 4A-4D ; 
           [0019]      FIG. 6  shows sequential steps in a service operation in further detail; and 
           [0020]      FIG. 7  shows sequential steps in a service operation using a service cart; 
           [0021]      FIG. 8  shows a perspective view of an example of a kinematic coupling; and 
           [0022]      FIGS. 9A-9C  show partial cross sectional views along a horizontal plane through the gates of the processing module and the wafer handling module in various stages of a decoupled condition to a coupled condition. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Below the invention is explained in general terms, and where appropriate with reference to the Figures, in which similar parts are indicated by similar reference numerals. 
         [0024]    In  FIG. 1A  a vertical furnace processing system  1  comprises a substrate cassette receiving platform  10  for receiving substrate cassettes  12 , a gas supply module  60 , a processing module  20  having a housing  20   a , a wafer handling module  30  having a housing  30   a  and a substrate cassette I/O-station module  40 . 
         [0025]    The processing module  20  comprises a vertical furnace  21  in an upper region thereof, the furnace comprising a heating element  23  and a process tube  24  delimiting a reaction space and being supported on a flange  25 . A housing around the vertical furnace  21  is typically provided but not shown for simplicity. A boat elevator  22  can move a wafer boat  26  holding a plurality of wafers into the process tube  24  from the space below and vice versa. The boat is supported on a pedestal  27  and a door plate  28 . A mini-environment  70 , comprising a housing  70   a , is provided in the space below the furnace. Typically, mini-environment  70  may comprise a particle filter and a blower for circulating filter air or nitrogen (N 2 ), and cooling means for removing heat released after unloading a hot wafer boat. 
         [0026]    The wafer handling module  30  may comprise a wafer handling robot  33  with an axis  34  for vertical movement and a multi axis arm  35  for gripping wafers. Further, wafer handling module  30  may comprise a particle filter and a blower both not shown, for circulating clean filtered air or nitrogen (N 2 ) in the wafer handling space. 
         [0027]    The gas cabinet  60  may accommodate all primary electrical components and process gas facilities, including for example pressure gauges, flow controllers, valves, a process gas controller, and peripheral equipment of the vertical furnace processing system  1 , and distribute gas and electrical facilities to the processing module  20  including a vertical furnace  21 , the wafer handling module  30  including a substrate handling robot  33 , and the I/O-station module  40 . The gas system in gas supply module  60  may be in communication with furnace  21  through gas conduits  62 . Permanent connection with the facilities is schematically indicated with  64  for the power connection of the heating element to a power supply, typically located in a basement underneath the clean room  80  and not shown, and  66  for the connection of the gas supply module to the process gas facilities. The system  1  may be placed such that the gas supply module  60  faces the clean room  80  and the I/O-station module  40  is facing the service area or grey room  81 . Operator  14  can access the gas supply module from the clean room  80  for performing service to the gas supply module. 
         [0028]    Process module  20  and gas supply module  60  may be modules that are large in size and weight, and that are connected to each other and to the facilities through many complicated connections such as high power connection  64  and the gas connections  62  and  66  for a plurality of reactive process gases. The wafer handling module  30  and substrate cassette I/O-station module  40 , on the other hand, may be relatively simple modules with a relatively simple connection to the facilities; e.g. connections for electrical power of modest wattage, electrical control signals, compressed air, vacuum (to enable vacuum suction gripping a wafer by the wafer handling robot) and nitrogen gas (N 2 ). 
         [0029]    In an embodiment of the invention, one or more connections of wafer handling module  30  and I/O-station module  40  to the facilities and to the remainder of the system may be provided with connectors that allow easy disconnection and reconnection. 
         [0030]    In another embodiment the wafer handling module  30  and/or I/O-station module  40  may be provided with supportive transport means  36 , such as, for instance, wheels, a rail-guided carriage, or preferably gas/air cushion devices or generators for generating gas/air cushions, so that they may easily be removed from the system  1  and reinserted again. Wafer handling module  30  may be removed in its entirety, i.e. together with housing  30   a , wafer handling robot  33 , and particle filter, so that all its components are protected and remain clean. 
         [0031]    Substrate cassettes  12  may typically be supplied to the substrate cassette receiving platform  10  from the clean room side by a an Over Head Transport (OHT) system indicated by  50 , and then be transported to the opposing side of the system  1 , namely to the I/O-station module  40 , by a substrate cassette transport mechanism  52 . In another embodiment, the OHT system  50  may supply the substrate cassettes  12  directly to the I/O-station module  40  in the service area or grey room  81 . Optionally, a clean corridor may then be provided for the part of the OHT system  50  that is located in the service area  81 . 
         [0032]    In  FIGS. 1B and 1C  two alternative embodiments are shown. Only the differences with  FIG. 1A  will be explained. 
         [0033]    As illustrated in  FIG. 1B , the housing  70   a  of the mini-environment  70  may be provided with supportive transport means  36 , while the connections of the mini-environment  70  to the facilities and remainder of the system  1  may be provided with connectors allowing easy disconnection and reconnection. Access for servicing the furnace  21  may be provided for by disconnecting and removing mini-environment  70 , including housing  70   a.    
         [0034]      FIG. 1C  shows an embodiment similar to the one of  FIG. 1B  with additional storage locations  42  for substrate cassettes  12  in the space above wafer handling module  30 , so that the additional substrate cassette storage capacity does not increase the foot print of the system  1 . Alternatively, storage locations may be provided in the space of the service area or grey room  81  behind the system  1 , preferably above the ergonomic minimum height (SEMI S8; 1980 mm) and/or above the I/O-station module  40 . 
         [0035]    A service operation of the system  1  of  FIG. 1A  will now be described with reference to  FIGS. 2 and 3 . 
         [0036]    In  FIG. 2A ,  3 A, in a first step  91   a , removable I/O-station module  40  may be disconnected and moved apart from wafer handling module  30  into service area or grey room  81 ; in a second step  91   b  the I/O-station module  40  may further transported away through corridor  82 . In  FIG. 2B ,  3 B, in a first step  92   a , wafer handling module  30 , including housing  30   a  and particle filter, may be disconnected and moved apart from processing module  20  into service area  81 ; in a second step  92   b  the wafer handling module  30  may further be transported away through corridor  82 . In  FIG. 2C ,  3 C, in step  93 , the furnace  21  may be moved away from a position above mini-environment  70  into service area or grey room  81  so that it can be serviced. This may be done by, for instance, a slide mechanism or a swing mechanism (not shown). As shown in  FIG. 2D , a service engineer  15  may perform service actions such as  94  removing process tube  24  from heating element  23 , or  95  removing a boat  26  from mini-environment  70 . It will be clear that for the removal of a boat it may not be necessary that furnace  21  is in a moved away position but may still be in its processing position above mini-environment  70 . For the removal of process tube  24  a tool may be used. It may be clear that not only the process tube  24  may be removed but also flange  25  and optionally also heating element  23 . 
         [0037]    A service operation of the system of  FIG. 1B  will now be described with reference to  FIGS. 4 and 5 . 
         [0038]    In  FIG. 4A ,  5 A, in a first step  91   a , removable I/O-station module  40  is disconnected and moved away from wafer handling module  30  into service area  81  and in a second step  91   b  transported away through corridor  82 . In  FIG. 4B ,  5 B, in a first step  92   a , wafer handling module  30 , including housing  30   a  and particle filter, is disconnected and moved away from processing module  20  into service area  81  and in a second step  92   b  transported away through corridor  82 . In  FIG. 4C ,  5 C, in a first step  96   a , mini-environment  70 , including housing  70   a  and boat elevator  22  is disconnected and moved away into service area  81  and in a second step  96   b  transported away through corridor  82 . As illustrated in  FIG. 4D ,  5 D, a service engineer  15  may perform service actions, such as removing process tube  24  from heating element  23  or removing a boat  26 . For the removal of parts, a tool may be used. I may be clear that not only the process tube  24  or boat  26  may be removed but also flange  25  and optionally also heating element  23 . 
         [0039]      FIG. 6  shows in further detail a service operation that can be performed in connection with the system as described in  FIGS. 2 and 3 . 
         [0040]    In  FIG. 6A , the furnace  21  is in process position and is shown for simplicity without heating element  23 . In this embodiment, the furnace is provided with an outer process tube  24   a  and an inner process tube  24   b . The process tubes  24  are supported on flanges  25 . This configuration is typically used for low pressure applications wherein the process gases flow in upward direction within inner tube  24   a  and in downward direction, towards an exhaust opening, in the space between inner process tube  24   b  and outer process tube  24   a . A plenum  68  is in communication with a vacuum pump for exhausting the process gases. A boat  26 , supported on pedestal  27 , door plate  28  and lower plate  72  is positioned in mini environment  70 , enclosed by a housing  70   a . An elevator, not shown, may lift the lower plate  72 , including door plate  28 , pedestal  27  and boat  26  to an uppermost position wherein lower plate  72  seals against a top surface  74  of mini-environment  70  and simultaneously door plate  28  seals against flanges  25 , as shown in  FIG. 6B . Further, door plate  28  may be secured against flanges  25  with locking means, not shown. Then, as shown in  FIG. 6C , the furnace  21  in its entirety might be elevated by action  97   a , optionally after disconnection of gas, vacuum and other tubing and connections, as needed. Finally, in an action  97   b , the furnace  21  may be moved horizontally away from a position above mini-environment  70 , together with wafer boat  26 , pedestal  27  and door plate  28  to allow the performance of service actions. During the removal of the furnace, the mini-environment  70  may be sealed by lower plate  72 , while the process tube  24  may be sealed by door plate  28 , so that contamination during the service operation is avoided. 
         [0041]    In  FIG. 7  the use of a service cart  100  that can be used during service procedures of a vertical furnace  21  is illustrated. 
         [0042]    The cart  100  may be provided with a housing  100   a  and a removable closure  102  in an upper wall of the housing. The cart  100  may also be provided with supportive transport means  136 , such as, for instance, wheels or preferably air cushion devices for generating air cushions. Air cushions may allow for the practically frictionless displacement of the cart  100  in all directions. 
         [0043]    In  FIG. 7A , furnace  21  is shown as comprising a boat  26 , a pedestal  27  and a doorplate  28 ; for clarity, a heating element is omitted from the drawing. An available height underneath the furnace  21  may be greater than a height of the cart  100 . The cart  100  may be moved underneath the furnace  21 . The furnace  21  may be moved relative to the cart  100 , in a vertical direction toward the cart  100 , so that a lower surface of the furnace  21  sealingly engages an upper surface of the cart  100 , and the door plate  28  rests on removable closure  102 . In  FIG. 7B  removable closure  102  is lowered by an elevator (not shown), until the boat  26  is fully accommodated in the housing  100   a  of the cart  100 . Then the furnace  21  is moved relative to the cart  100 , in a vertical direction away from the cart  100 , so that the furnace  21  and the cart  100  are disengaged. Then, in  FIG. 7C , the cart  100 , together with its content of boat  26 , pedestal  27  and doorplate  28  may be transported away from the furnace  21  in a horizontal direction. During transport, a closure (not shown), may be placed on the top surface of the cart  100  to prevent any contamination from entering the housing  100   a  of the cart  100  and falling on the boat  26 . Similarly, a closure may be placed on the lower surface of the furnace  21  to prevent any contamination from entering the process tube  24 . 
         [0044]    The cart  100  as shown in  FIG. 7  may be used in different ways. 
         [0045]    It may be used in connection with the system  1  of  FIGS. 2 and 3 . When the furnace  21  is in a moved away position, as shown in  FIGS. 2C ,  2 D and  3 C, cart  100  may be placed underneath the furnace  21  to receive a boat. Although in  FIGS. 2 ,  3  the boat  26  is left in the mini-environment  70 , it is also possible to lift the boat  26  into the furnace  21 , and move furnace and boat together sideways. Alternatively, the cart  100  may be designed to receive the flange  25  with the process tube  24 . 
         [0046]    The cart  100  may also be used in connection with the system  1  of  FIGS. 4 ,  5 . When the mini-environment  70  has been removed, the cart  100  may be moved in the space underneath the furnace  21  to receive a boat  26 . In a second step, using a second cart  100 , the flange  25  with process tube  24  may be received. 
         [0047]    The vertical movement of the furnace  21  relative to the cart  100  may be achieved by vertically moving the furnace  21  while the cart  100  is kept stationary. Alternatively, the cart  100  may be moved vertically while the furnace  21  remains stationary. In the embodiment of  FIGS. 1B ,  4  and  5 , where there is no need to displace the furnace  21  horizontally during a service operation like a tube exchange, it may simplify the entire operation if the furnace  21  also remains vertically stationary. 
         [0048]    Although with reference to the Figures it has been described that the modules are removed one by one, as an alternative it is possible to remove the modules jointly. E.g. it would be possible to remove the I/O-station module  40  and wafer handling module  30  from the system  1  jointly, in a connected together state. It would even be possible to remove I/O-station module  40 , wafer handling module  30  and mini-environment  70  in a connected together state. Removal a combination of modules may requires more space to manoeuvre, and may be difficult to perform, but may save time since fewer internal connections need to be disconnected upon removal and reconnected upon repositioning. 
         [0049]    In one embodiment, at least one of the I/O-ports of the I/O-station module  40  may be provided at a height specified by SEMI for Personal Guided Vehicles (PGV). This may allow loading by PGV when the OHT system  50  malfunctions or during startup of the system  1 . 
         [0050]    In another embodiment, the system  1  may be provided with a facility for purging the FOUPs with an inert gas after receipt in the system  1 . 
         [0051]    In another embodiment, the substrate cassette transport system  52  may be configured such that a substrate cassette  12  is exchangeble between neighbouring systems  1 , without interaction of the OHT system. 
         [0052]    In yet another embodiment a wafer handling module  30  of a processing system  1  is provided with a coupling provision provided in at least one of the side walls of the housing  30   a , and configured for cooperation with a coupling provision of the wafer handling module  30  of another processing system so as to interconnect the respective processing units and to define an optionally closable substrate transfer passage between the wafer handling modules, as disclosed in U.S. patent application Ser. No. 13/248,468, co-assigned herewith. 
         [0053]    In still another embodiment the system  1  may be provided with a store for storing a batch of wafers, e.g. a rack disposed in the mini-environment  70  at a side thereof holding a plurality of wafers in a vertically spaced arrangement. The store may be accessible by the wafer handling robot  33 , and be used as, for instance, a cool-down location for wafers. Alternatively the store might be located in the wafer handling module  30  or even at a location intermediate between the wafer handling module  30  and the mini-environment  70 . 
         [0054]    The invention has been described in relation to a bay lay-out of the clean room wherein a substrate cassette receiving side of the system is facing the clean room and an opposing side of the system is placed in a service area. However, a ball room lay-out may be used wherein an entire system is placed within a clean room and wherein there is no distinction anymore between clean room  80  and service area  81 . It will be obvious that a system  1  of the invention, having disconnectable and reconnectable modules provides similarly in a ball room lay-out the advantage of a close, side by side packing of system while access for service is provided by disconnecting and removing one or more modules. 
         [0055]    It may be obvious that the modular design of the vertical furnace processing system does not only have advantages for servicing but has also many advantages during manufacturing, testing and installation of systems. E.g. a module can be easily connected to another system for testing. And during installing a system at an end users&#39; facility, the modules can be transported in their entirety and quickly coupled together, reducing installation time. 
         [0056]    Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments. 
         [0057]    When removing wafer handling module  30  and repositioning it again, it is important that the module is repositioned at the same position that it had before removing to ensure proper alignment of the wafer handling robot relative to the processing module  20 . This can be achieved by supporting the wafer handling module  30  on a kinematic coupling, similar to the kinematic coupling of a FOUP cassette, see  FIG. 8 . Such a coupling comprises three stationary blocks  140  having a V-groove in which a mating element  142  fits. The mating element  142  can be a sphere or an element having partly a spherical surface. The block  140  and element  142  accurately position relative to each other and have a high span of correction for any misalignment at the beginning of the positioning procedure. The stationary blocks may be fixedly connected to a first base plate  144  and the mating elements  142  may be mounted on a second base plate  146 . The first base plate  144  may, for example, be placed on the floor and the second base plate  146  may be mounted on the bottom of, for example, the processing module  20  and/or the wafer handling module  30 . Nowadays, kinematic couplings are available for high payloads. The kinematic coupling can also be used in vertical orientation, to define the position and orientation of two side surfaces of the two modules relative to each other. In that case the first base plate  144  of at least one kinematic coupling may be mounted on a side wall of, for example, the processing module  20  and the second base plate  146  said kinematic coupling may be mounted on a side wall of, for example, the wafer handling module  30 . In addition, auto levelling can be used, using jack lifts in combination with a level sensor for positioning the two modules  20 ,  30  relative to each other. 
         [0058]    Another critical item is the sealing between the wafer handling module  30  and the processing module  20  to obtain integrity of the mini-environment after repeated removal and replacement of the wafer handling module  30  and/or the mini-environment of the processing module  20 . For this purpose the seal between the wafer handling module  30  and the mini-environment of the process module  20  can be made flexible, such that a hermetic seal is achieved without exerting significant forces on the modules  20 ,  30  that would result in deformation. An inflatable seal is proposed.  FIGS. 9A to 9C  show an example of an embodiment of a flexible seal  156 ,  160 , more particularly an inflatable seal, in a cross section along a horizontal plane through the gate  150  of the processing module  20  and through the gate  152  of the wafer handling module  30 . Preferably, a double inflatable seal  156  is used on the side surface of one module, in example shown in  FIG. 9  on the side surface  154  of the processing module  20 , in combination with a collar  160  on the side surface  158  of the other module, in the example shown in  FIG. 9  on the side surface  158  of the wafer handling module  30 . The collar  160  may be a rigid metal collar  160  or a flexible collar  160 . By moving the two modules  20 ,  30  towards each other, the collar  160  is moved (as indicated with arrow A in  FIG. 9A ) in between the double inflatable seal  156  when the seal is in non-inflated condition (as shown in  FIG. 9B ). Then the double seal  156  is inflated and seals against both sides of the collar  160  (as shown in  FIG. 9C ). In this way a minimum of forces are exerted by the inflatable seal  156  and the collar  160  on the respective modules  20 ,  30  while obtaining adequate sealing. Furthermore, the seal is not affected by small displacements of the modules  20 ,  30  in a direction away from or toward each other. 
         [0059]    In an embodiment of the invention, the substrate cassette I/O-station module  40  with the load port may be mounted on the wafer handling module  30  and both modules  40 ,  30  may be removed simultaneously, as one piece. 
       LIST OF ELEMENTS 
       [0000]    
       
           1  vertical furnace processing platform 
           10  substrate cassette receiving platform 
           12  substrate cassette 
           14  operator 
           15  service engineer 
           20  processing module 
           20   a  housing 
           21  vertical furnace 
           22  boat elevator 
           23  heating element 
           24  process tube 
           24   a  outer process tube 
           24   b  inner process tube 
           25  flange 
           26  wafer boat 
           27  pedestal 
           28  door plate 
           30  wafer handling module 
           30   a  housing 
           33  wafer handling robot 
           34  axis 
           35  multi axis arm 
           36  supportive transport means 
           40  substrate cassette I/O-station module 
           42  storage (locations) for substrate cassettes 
           50  Over Head Transport (OHT) system 
           52  substrate cassette transport system 
           60  gas supply module 
           62  gas conduit between gas supply module and vertical furnace 
           64  permanent high-power connection between facilities and heating element of vertical furnace 
           66  permanent gas connection between facilities and gas supply module 
           68  plenum 
           70  mini-environment 
           70   a  housing 
           72  lower plate 
           74  top surface of mini-environment 
           80  clean room 
           81  service area/grey room 
           82  corridor 
           91   a,b  first (a) and second (b) step in removing I/O-station module  40   
           92   a,b  first (a) and second (b) step in removing wafer handing module  30   
           93  step of removal of furnace from above mini-environment 
           94  step of removal of process tube 
           95  step of removing boat from mini-environment 
           97   a  action of elevating furnace 
           97   b  action of horizontally moving furnace away from above mini-environment 
           100  service cart 
           100   a  housing 
           102  removable closure 
           136  supportive transport means 
           140  stationary blocks 
           142  mating element 
           144  first base plate 
           146  second base plate 
           150  gate of processing module 
           152  gate of wafer handling module 
           154  side surface of the processing module 
           156  double inflatable seal 
           158  side surface of the wafer handling module 
           160  collar