Abstract:
The apparatus includes a load lock adapted to store the workpiece inside and to be switched between atmosphere and vacuum; vacuum transport chambers connected to the load lock and to the corresponding process chambers in a state where the load lock and each of the process chambers are isolated mutually; transfer means for transferring the workpiece between each of the process chambers and the load lock via the corresponding vacuum transport chamber; load lock valves adapted to switch between interrupt and opening at a position between the load lock and the corresponding vacuum transport chambers; process chamber valves adapted to switch between interrupt and opening at a position between the process chambers and the corresponding vacuum transport chambers; and control means for controlling timing of the opening and closing of the valves whose timings are controlled in synchronization with the transfer of the workpieces.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese patent application JP 2010-059645 filed on Mar. 16, 2010, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a vacuum processing apparatus used for processing a board-like workpiece such as a semiconductor wafer or a liquid crystal display to perform processing such as fine patterning or the like by use of a plurality of gases. 
         [0004]    2. Description of the Related Art 
         [0005]    A vacuum processing apparatus is provided with a processing unit including a vacuum vessel internally having a process chamber called a process unit, an exhaust device, a plasma forming device and the like. Such a vacuum, processing apparatus requires low costs and improved productivity. In particular, the vacuum processing apparatus has a major problem in that throughput (the number of boards processed per unit hour) is improved to increase efficiency of processing per apparatus. In the following, a semiconductor processing apparatus is partially described as an example; however, the present invention is not limited to the semiconductor processing apparatus. The processing performed by the semiconductor processing apparatus, one of the vacuum processing apparatuses, includes a step of subjecting a workpiece such as a semiconductor wafer which is a board to be processed, to processing under vacuum, e.g., plasma processing such as etching or the like. In order to perform such processing with high throughput, i.e., to increase efficiency of processing per apparatus, a semiconductor processing apparatus provided with a plurality of process chambers is used. Semiconductor processing apparatuses are generally known that include a process chamber and an atmospheric transport chamber under ordinary pressure. 
         [0006]    A cassette storing the predetermined number of, e.g.  25 , wafers is mounted on the front side of the semiconductor processing apparatus as described above. A transfer robot takes the wafers one by one out of the cassette and transfers those to a load lock that is adopted to be switched between atmosphere and vacuum. Thereafter, the wafer is transferred from the load lock depressurized through vacuum evacuation via a depressurized transfer path into any one of process chambers in which the wafer is processed. After the processing, the wafer is transferred from such a process chamber, passing through the path in a direction reverse to that during the loading, via the load lock to under the atmospheric pressure. Thereafter, the wafer is returned to the same position in the same cassette from which it was transferred by the transfer robot. This is the general order of the actions in processing the wafer in the semiconductor processing apparatus. 
         [0007]    In order to improve throughput in a series of actions in the semiconductor processing apparatus, it is conceivable to improve a transfer rate of a workpiece or to reduce processing time. In recent years, the processing time has been reduced; therefore, the semiconductor processing apparatus requires an improvement in transfer rate. 
         [0008]    JP-A-2009-94530 (patent document 1) discloses a mechanism in which a transfer robot can concurrently transfer workpieces to a plurality of corresponding process chambers by extension and retraction of two arms thereof, and a method of achieving high-throughput by use of the mechanism. However, processing gases may be different in type from each other. In such a case, it is necessary to transfer the workpieces in such a manner as to prevent gases from mixing with each other, in order to prevent processing accuracy from being degraded and a workpiece from being contaminated. 
         [0009]    To meet the necessity, patent document 1 discloses the method of preventing the gases from mixing with each other by increasing the pressure outside the process chamber to reduce an amount of contaminated matter containing the processing gases that is discharged outwardly from the process chamber. 
       SUMMARY OF THE INVENTION 
       [0010]    In order to improve the throughput of the vacuum processing apparatus in which a plurality of process chambers are installed, it is necessary to concurrently transfer workpieces to the process chambers without mixing of the gases in the process chambers. 
         [0011]    To meet the necessity, in patent document 1, the workpieces are concurrently transferred to the plurality of process chambers without mixing of the gases by adjusting pressure without sequentially switching between the opening and closing of the valves of the process chambers for the transfer of the workpieces. However, it is difficult to completely prevent the mixing of gases. There is a moment when the process chambers have a pressure difference but share a space not isolated by a valve. Thus, gases may mix with each other in some cases. 
         [0012]    Accordingly, it is an object of the present invention to provide a semiconductor processing apparatus as follows. In the semiconductor processing apparatus having a plurality of conventional process chambers, concurrently transfer of workpieces to the process chambers without mixing of gases is realized while wafer processing capacity of the semiconductor processing apparatus is not impaired. 
         [0013]    (1) According to the present invention, there is provided a vacuum processing apparatus provided with a plurality of process chambers for processing workpieces, the apparatus including: a load lock having means for storing the workpiece in the inside thereof and switching the inside between atmosphere and vacuum; vacuum transport chambers connected to the load lock and to the corresponding process chambers in a state where the load lock and each of the process chambers are isolated from each other; transfer means, installed in each of the vacuum transport chambers, for transferring the workpiece between the vacuum transport chamber and the load lock or between the vacuum transport chamber and the corresponding process chamber; load lock valves for controlling the loading and unloading of the workpieces through opening and closing actions at connecting portions between the load lock and the corresponding vacuum transport chambers; process chamber valves for controlling the loading and unloading of the workpieces through opening and closing actions at connecting portions between the process chambers and the corresponding vacuum transport chambers; and control means for controlling timing of the opening and closing actions of the load lock valves and of the process chamber valves; wherein, in a state where all the load lock valves are closed, the control means allows each of the process chamber valves to perform opening and closing actions regardless of a state where a plurality of the process chamber valves at the corresponding connecting portions with the associated vacuum transport chambers are each opened or closed. 
         [0014]    (2) Preferably, in the vacuum processing apparatus described in the above item (1), the load lock includes holding means capable of holding a plurality of workpieces, and the plurality of workpieces held by the holding means are each transferred from the load lock via the vacuum transport chamber to each of the process chambers in a period of time where the load lock is maintained in a vacuum state. 
         [0015]    (3) Preferably, in the vacuum processing apparatus described in the above item (2), the load lock is provided with holding means capable of aligning the plurality of workpieces in a direction perpendicular to an installation plane on which the load lock is installed. 
         [0016]    (4) Preferably, the vacuum processing apparatus described in any one of the above items (1), (2) and (3), includes a plurality of first valves connected to a plurality of corresponding vacuum transport chambers disposed on the same installation plane; a second valve connected to the load lock disposed in a position having a height different from that of the installation plane; and conveying means for conveying the workpiece carried in from the second valve to the first valve. 
         [0017]    Because of employing the configuration described in the above item (1), the process chambers will not share the vacuum transport chamber. In the state of blocking between the load lock and each of the vacuum transport chambers, the valve of one of the process chambers may be opened. Also in such a state, the gas used in this process chamber will not enter another process chamber even if the valve thereof is opened in view of configuration. Thus, regardless of the opening and closing state of the valve of one of the process chambers, it is possible to open and close the valve of another process chamber independently. 
         [0018]    It is not necessary to transfer the workpieces by adjusting pressure instead of transferring the workpieces by sequentially switching between the opening and closing of the valves of the process chambers, in order to concurrently the transfer workpieces to the process chambers without mixing of the gases of the process chambers. 
         [0019]    Thanks to these features, the opening and closing of the valve of one of the process chambers can be controlled without being influenced by the opening and closing timing of the valve of another process chamber, i.e., without a provision of waiting time for waiting the opening of the valve of one of the process chambers until the valve of another process chamber will be closed. Thus, the throughput of the entire system can be improved. 
         [0020]    The configuration of the vacuum processing apparatus according to the present invention can concurrently transfer wafers to the plurality of process chambers without mixing of the gases used in the process chambers, thereby allowing for an improvement in throughput. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  illustrates a configuration of an apparatus according to the present invention. 
           [0022]      FIG. 2  illustrates a Gantt chart for an action of transferring a workpiece in a conventional apparatus and a Gantt chart for an action of transferring a workpiece in the apparatus of the present invention. 
           [0023]      FIG. 3A  illustrates a basic action of a transfer means installed in a transport chamber. 
           [0024]      FIG. 3B  illustrates the basic action of the transfer means installed in the transport chamber. 
           [0025]      FIG. 3C  illustrates the basic action of the transfer means installed in the transport chamber. 
           [0026]      FIG. 3D  illustrates the basic action of the transfer means installed in the transport chamber. 
           [0027]      FIG. 3E  illustrates the basic action of the transfer means installed in the transport chamber. 
           [0028]      FIG. 3F  illustrates the basic action of the transfer means installed in the transport chamber. 
           [0029]      FIG. 4A  illustrates an action of the conventional apparatus in  FIG. 2 . 
           [0030]      FIG. 4B  illustrates the action of the conventional apparatus in  FIG. 2 . 
           [0031]      FIG. 4C  illustrates the action of the conventional apparatus in  FIG. 2 . 
           [0032]      FIG. 4D  illustrates the action of the conventional apparatus in  FIG. 2 . 
           [0033]      FIG. 5A  illustrates an action of the apparatus according to the present invention in  FIG. 2 . 
           [0034]      FIG. 5B  illustrates the action of the apparatus according to the present invention in  FIG. 2 . 
           [0035]      FIG. 5C  illustrates the action of the apparatus according to the present invention in  FIG. 2 . 
           [0036]      FIG. 6  illustrates the configuration of the conventional apparatus. 
           [0037]      FIG. 7A  illustrates a configuration of holding workpieces in a load lock. 
           [0038]      FIG. 78  illustrates a configuration of holding workpieces in the load lock. 
           [0039]      FIG. 8A  illustrates arm actions of vacuum transfer robots. 
           [0040]      FIG. 8B  illustrates the arm actions of the vacuum transfer robots. 
           [0041]      FIG. 8C  illustrates the arm actions of the vacuum transfer robots. 
           [0042]      FIG. 9A  illustrates a mechanism of a load lock holding a plurality of workpieces. 
           [0043]      FIG. 9B  illustrates the mechanism of the load lock holding the plurality of workpieces. 
           [0044]      FIG. 10  illustrates an apparatus in which omnidirectional valves lying on the same horizontal plane as the load lock are connected to corresponding vacuum transport chambers. 
           [0045]      FIG. 11A  is a cross-sectional view taken along line A-A in  FIG. 10 . 
           [0046]      FIG. 11B  is a cross-sectional view taken along line A-A in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0047]    A vacuum processing apparatus according to the present invention will hereinafter be described in detail with reference to  FIGS. 1 to 5C  taking a semiconductor processing apparatus as a first embodiment. 
         [0048]    A semiconductor processing apparatus forms a fine pattern on the surface of a workpiece such as a semiconductor wafer in semiconductor manufacturing processes. The workpieces such as semiconductor wafers are stored in a cassette and is transferred to the semiconductor processing apparatus. Thereafter, the workpiece is transferred by a transfer robot from the cassette in the atmospheric state via a load lock adopted to be switched between atmosphere and vacuum, to a process chamber maintained in a vacuum state. After the workpiece has been subjected to pattern forming processing, it is returned to the cassette again. As described above, the semiconductor processing apparatus is composed of an atmospheric area, a vacuum area, and chambers adapted to be switched between atmosphere and vacuum. 
         [0049]      FIG. 1  illustrates a configuration of a semiconductor processing apparatus according to an embodiment of the present invention. A control section  100  controls the action of the entire apparatus based on signals transmitted and received via a signal line  112 . An atmospheric side block  101  transfers, stores and positions a workpiece to be processed such as a wafer under atmospheric pressure. 
         [0050]    A vacuum side block  102  is a block that transfers board-like workpieces such as wafers under pressure reduced from the atmospheric pressure and processes them in predetermined process chambers. A load lock  105  connects the atmospheric block  101  with the vacuum block  102 . 
         [0051]    A description is first given of the constituent elements of the atmospheric block  101 . A plurality of cassette tables  107  are installed in the atmospheric block  101 . Cassettes in which workpieces to be processed or cleaned are stored are put on the corresponding cassette tables  107 . A housing  106  is connected to the cassette tables  107  and provided with a mechanism for transferring the workpieces stored in the cassettes to the inside of the apparatus and a mechanism for positioning the workpieces. An atmospheric transfer robot  109  is installed inside the housing  106  for performing taking out and putting in of a workpiece between the cassette put on the cassette table  107  and the housing  106  by extending and retracting an arm on which the workpiece is put to be hold. 
         [0052]    The atmospheric side valve  120  is connected to the load lock  105  and has a role of blocking the flow of air between the housing  106  and the load lock  105  by being closed. 
         [0053]    A description is next given of constituent elements of the vacuum block  102 . One or a plurality of the load locks  105  are installed between the atmospheric side block  101  and the vacuum side block  102 , and adopted to be switched between the atmosphere and vacuum in the state where the workpieces are stored therein. A vacuum side valve  121   a  is connected to the load lock  105  and has a role of keeping the load lock air-tight by being closed along with the atmospheric side valve  120 . Also a vacuum side valve  121   b  has the same role. 
         [0054]    A vacuum transport chamber  103   a  is internally provided with a mechanism for transferring a workpiece. The vacuum transport chamber  103   a  shares a space along with the load lock  105  via the vacuum side valve  121   a . When the inside of the load lock is at the atmospheric pressure, the vacuum side valve  121   a  is closed. When the inside of the load lock is depressurized, the inside of the vacuum transport chamber is constantly kept in the vacuum state by controlling the vacuum valve  121   a  so as to be opened. Also the vacuum transport chamber  103   b  is constantly kept in the vacuum state by opening and closing the vacuum side valve  121   b . A vacuum transfer robot  108   a  is installed at a center of the vacuum transport chamber  103   a  and transfers a workpiece between the load lock  105  and the vacuum transport chamber  103   a , under vacuum, by extending and retracting an arm on which the workpiece is put to be hold. 
         [0055]    A process chamber valve  131   a  is connected to the vacuum transport chamber  103   a  and has a role of maintaining the air tight of the vacuum transport chamber  103   a  by being closed along with the vacuum side valve  121   a . Also a process chamber valve  131   b  has the same mechanism and has a role of maintaining the air tight of the vacuum transport chamber  103   b  by being closed along with the vacuum side valve  121   b.    
         [0056]    A process chamber  104   a  is internally provided with a workpiece table used to process a workpiece put thereon. The workpiece is put on the workpiece table and processed by filling up the inside of the process chamber with processing gas. The process chamber  104   a  shares a space along with the vacuum transport chamber  103   a  via the process chamber valve  131   a . The inside of the process chamber  104   a  is kept air-tight by closing the process chamber valve  131   a . A taking out and putting in of the workpiece is performed between the process chamber  104   a  and the vacuum transport chamber  103   a  by extending and retracting the arm of the vacuum transfer robot  108   a  installed in the vacuum transport chamber  103   a . Also a process chamber  104   b  has the same mechanism, processes a workpiece put on the workpiece table therein, and is kept more air-tight by closing the process chamber valve  131   b . In addition, a vacuum transfer robot  108   b  performs taking out and putting in of the workpiece between the vacuum transport chamber  103   b  and the process chamber  104   b . In  FIG. 1 , the number of the vacuum transport chambers connected to the load lock  105  is two. However, the apparatus can be configured such that the load lock  105  is connected to one or three vacuum transport chambers. If the vacuum transport chamber is connected to a valve connected to the load lock, also its position can be changed freely. If the shape of the load lock is changed, four or more vacuum transport chambers can be connected to such a load lock. As for the process chamber, in  FIG. 1 , although the number of the process chamber connected to the vacuum transport chamber is one, a plurality of the process chambers may be connected to the vacuum transport chamber. 
         [0057]    A description is next given of a transfer process during the processing of workpieces similarly referring to  FIG. 1 . A cassette in which workpieces are stored is put on any one of the cassette tables  107  of the semiconductor processing apparatus. The atmospheric transfer robot  109  takes out a specified workpiece stored in the cassette put on the cassette table  107  and puts it in the housing  106  side by extending and retracting the arm to put the workpiece on the arm. 
         [0058]    The action of the atmospheric transfer robot  109  is here described with reference to  FIGS. 3A to 3F .  FIGS. 3A to 3F  illustrate the action of removing a workpiece from a carrying-out place  110  in which a workpiece is previously stored and placing it in a predetermined carrying-in place  111  by extension and retraction of an arm. 
         [0059]    The transfer robot  122  is provided with an arm used to transfer a workpiece. The number of the arms is one in the present embodiment; however, it may be two or more. Alternatively, the housing and the vacuum transport chamber may be provided with a plurality of the transfer robots. Each of arms has such an individually operable configuration as to be extended and retracted in a direction of turning around an axis of an arm root side end portion, in a vertical direction and in a horizontal direction. 
         [0060]    The arm of the transfer robot  122  is extended from the state of  FIG. 3A  toward under the workpiece, as a target to be taken out, stored in the carrying-out place  110  as in  FIG. 3B . The transfer robot is shifted upward to put the workpiece on the arm. Thereafter, the arm on which the workpiece is put is retracted as in  FIG. 3C  to take out the workpiece. Next, the transfer robot is changed in facing direction as in  FIG. 3D  so that the arm of the transfer robot can be extended inside the carrying-in place  111 . The workpiece put on the arm is transferred into the inside of the predetermined carrying-in place  111  by extending the arm as in  FIG. 3E . Thereafter, the arm is retracted as in  FIG. 3F . In the previous description with  FIG. 1 , the transfer robot  122  corresponds to the atmospheric transfer robot  109 , the carrying-out place  110  corresponds to the cassette and the carrying-in place  111  corresponds to the load lock  105 . 
         [0061]    Returning to the description with  FIG. 1 , after the workpiece is taken out by the atmospheric transfer robot  109 , the atmospheric side valve  120  is opened. In addition, the workpiece held on the arm is stored inside the load lock  105  by extending and retracting the arm of the atmospheric transfer robot  109 . After the atmospheric side valve  120  has been closed to make the load lock air-tight, the inside of the load lock  105  is depressurized from the atmospheric pressure to a predetermined pressure. The vacuum side valve  121   a  is opened and the arm of the vacuum transfer robot  108   a  installed in the vacuum transport chamber  103   a  is extended and retracted to put the workpiece on the arm to be held. In this way, the workpiece stored in the load lock  105  is taken out and placed on the vacuum transport chamber  103   a  side. 
         [0062]    Although there is a difference between under vacuum and under atmospheric pressure, the vacuum transfer robot performs the same actions as the atmospheric transfer robot as in  FIGS. 3A to 3   f . Incidentally, the transfer robot  122  corresponds to the vacuum transfer robot  108   a , the carrying-out place  110  corresponds to the load lock  105  and the carrying-in place  111  corresponds to the Process chamber  104   a . After the workpiece has been taken out by the vacuum transfer robot  108   a , the air tight of the vacuum transport chamber is maintained by closing the vacuum side valve. 
         [0063]    Next, after the vacuum side valve  121   a  has fully been closed, the process chamber valve  131   a  connected to the vacuum transport chamber  103   a  is opened. In this case, if the process chamber valve  131   a  is opened before the vacuum side valve  121   a  is fully closed, there is a possibility that residual gas in the process chamber enters inside the load lock to contaminate the workpiece. Therefore, after the vacuum side valve  121   a  is closed without fail, the process chamber valve  131   a  is opened. The vacuum transfer robot  108   a  extends and retracts the arm with the workpiece put on the arm to load the workpiece into the predetermined process chamber  104   a . After the workpiece is transferred in the process chamber  104   a , the process chamber valve  131   a  is closed to seal the process chamber  104   a . Thereafter, processing gas is led into the process chamber  104   a , a vacuum is produced in the process chamber and the workpiece is processed. 
         [0064]    After the processing of the workpiece is finished, the process chamber valve  131   a  opening and closing between the process chamber  104   a  and the vacuum transport chamber  103   a  described above is opened. The vacuum transfer robot  108   a  takes the processed workpiece out of the process chamber  104   a  and places it on the vacuum transport chamber  103   a  side reversely to the case where the workpiece is transferred into the process chamber, by extending and retracting the arm to put the workpiece thereon. Thereafter, the process chamber valve  131   a  connected to the vacuum transport chamber  103   a  is closed to seal the vacuum transport chamber  103   a . After the process chamber valve  131   a  is closed, the vacuum side valve  121   a  is opened. Also in this case, to prevent gas from entering the load lock, after the process chamber valve is closed without fail, the vacuum side valve is opened. The vacuum transfer robot  108   a  transfers the held processed workpiece from the vacuum transport chamber  103   a  into the load lock  105  while extending and retracting the arm. In  FIGS. 3A-3F , the transfer robot  122  corresponds to the vacuum transfer robot  108   a , the carrying-out place  110  corresponds to the process chamber  104   a  and the carrying-in place  111  corresponds to the load lock  105 . After the processed workpiece is stored in the load lock  105 , the vacuum side valve  121   a  connecting the load lock  105  with the vacuum transport chamber  103   a  is closed to seal the load lock  105 . Thereafter, the pressure in the load lock is raised to the atmospheric pressure. 
         [0065]    After the pressure inside the load lock has reached the atmospheric pressure, the atmospheric side valve  120  connected to the load lock  105  and to the housing  106  is opened. The atmospheric side transfer robot  109  takes the workpiece out of the load lock  105  and transfers it to the original cassette to return it to the original position, by extending and retracting the arm for putting the workpiece thereon. 
         [0066]    The above is a series of the actions of transferring the workpiece from the cassette via the load lock  105  and the vacuum transport chamber  103   a  to the process chamber  104   a  and returning it to the original cassette after the processing. The same actions are performed on the case where the workpiece is transferred from the cassette via the load lock  105  and the vacuum transport chamber  103   b  to the process chamber  104   b  for processing. 
         [0067]    The usefulness of the present invention is described by use of  FIG. 2 , comparing the transfer actions between the conventional apparatus and the apparatus of the present invention.  FIG. 2  includes Gantt charts illustrating comparison in the vacuum block between the actions of the conventional apparatus and those of the apparatus of the present invention. A Gantt chart is a diagram in which the constituent elements of the apparatus are allocated in the vertical direction, time is allocated on the horizontal axis, and times required for the respective actions of the constituent elements are denoted with horizontal bars having respective lengths proportional to the corresponding times. In  FIG. 2 , the load lock and the process chambers are allocated in the vertical direction and times required for the respective transfer actions in the corresponding chambers are shown. In this way, a comparison in the time required for transfer action is made between the conventional apparatus and the apparatus of the present invention. 
         [0068]    The configuration of the conventional apparatus is first described with reference to  FIG. 6 . Similarly to the apparatus of the present invention, the conventional apparatus includes an atmospheric block  101 , a load lock  105  adapted to be switched between the atmosphere and vacuum, and a vacuum block  102 . A workpiece is also transferred by the same transfer actions to a process chamber  104   a  and the processed workpiece is returned to a cassette. 
         [0069]    To compare the convention apparatus with the apparatus of the present invention under the same conditions, the configuration of the conventional apparatus is such that for example the number of process chambers is two and the number of the vacuum transfer robots is two. A difference between the configuration of the conventional apparatus and the apparatus of the present invention is as below. In the conventional apparatus, a transfer path from the load lock  105  to the process chambers  104   a  and  104   b  is a single vacuum transport chamber  103   a . On the other hand, in the apparatus of the present invention, the transfer path from the load lock  105  to the process chambers  104   a  and  104   b  is divided into the two vacuum transfer paths  103   a  and  103   b.    
         [0070]    A difference in the actions of the vacuum block between the conventional apparatus and the apparatus of the present invention is described by use of the Gantt charts in  FIG. 2  and with reference to  FIGS. 4A to 4D  and  5 A to  5 C.  FIG. 4A to 4D  illustrate the order of the actions for transferring the workpiece in the conventional apparatus. 
         [0071]      FIGS. 5A to 5C  illustrate the order of the actions for transferring the workpiece in the apparatus of the present invention. 
         [0072]    The conventional apparatus on the upper part of the Gantt chart in  FIG. 2  is described with reference to  FIG. 4A to 4D . 
         [0000]    (i) Step  1 ( a ) Illustrated in  FIG. 2   
         [0073]    As illustrated in  FIG. 4A , transfer is started from a state, as an initial state, where an unprocessed workpiece is stored in a load lock  105  and a processed workpiece is stored in the process chamber  104   b . A vacuum side valve  121   a  between the load lock  105  and the vacuum transport chamber  103   a  is opened and a vacuum robot  108   a  unloads the workpiece from the load lock and places it on the vacuum transport chamber side by extending its arm. Thereafter, the vacuum side valve  121   a  is closed to seal the vacuum transport chamber  103   a . In this way, the state of  FIG. 4B  is achieved. 
         [0000]    (ii) Step  2 ( a ) Illustrated in  FIG. 2   
         [0074]    In  FIG. 4B , the vacuum side valve  121   a  is fully closed to prevent the gas in the process chamber from entering the load lock. Thereafter, a valve  131   a  between the vacuum transport chamber  103   a  and the process chamber  104   a  is opened. In this case, it is conceivable that the vacuum transfer robot  108   b  unloads the processed workpiece from the process chamber  104   b . However, the workpiece cannot be transferred from the process chamber  104   b  because of the following reason. A plurality of the process chambers  104   a  and  104   b  are connected to the vacuum transport chamber  103   a . In the case where any of the process chamber valves  131   a  and  131   b  is opened, if the other process chamber valve is opened, gases in the process chambers will mix each other. This poses a problem of safety. 
         [0075]    After the process chamber valve  131   a  has been opened, the transfer robot  108   a  loads the workpiece into the process chamber  104   a  by extending the arm. Thereafter, the process chamber valve  131   a  is closed to seal the process chamber  104   a . These actions achieve the state of  FIG. 4C . 
         [0000]    (iii) Step  3 ( a ) Illustrated in  FIG. 2   
         [0076]    To prevent the gases in the process chamber from mixing with each other, after the process chamber valve  131   a  has fully been closed, the process chamber valve  131   b  is opened. The vacuum transfer robot  108   b  unloads the workpiece from the process chamber  104   b  by extending the arm. Thereafter, the process chamber valve  131   b  is closed to seal the process chamber  104   b . In this way, the state of  FIG. 4D  is achieved in which the workpiece is transferred in the process chamber  104   a  and the workpiece is transferred from the process chamber  104   b.    
         [0077]    The present invention in the lower part of the Gantt chart in  FIG. 2  is next described with reference to  FIGS. 5A to 5C . 
         [0000]    (i) Step  1 ( b ) Illustrated in  FIG. 2   
         [0078]    As illustrated in  FIG. 5A , transfer is started from a state, as an initial state, where an unprocessed workpiece is stored in the load lock  105  and a processed workpiece is stored in the process chamber  104   b . Similarly to the conventional apparatus, the vacuum side valve  121   a  between the vacuum transport chamber  103   a  and the load lock  105  is opened and the transfer robot  108   a  unloads the workpiece by elongating the arm. Thereafter, the vacuum side valve  121   a  is closed to seal the vacuum transport chamber  103   a . In this way, the state of  FIG. 5B  is achieved. 
         [0000]    (ii) Step  2 ( b ) Illustrated in  FIG. 2 . 
         [0079]    Referring to  FIG. 5B , after the vacuum side valve  121   a  has been closed, the process chamber valve  131   a  between the vacuum transport chamber  103   a  and the process chamber  104   a  is opened. In addition, the process chamber valve  131   b  between the vacuum transport chamber  103   b  and the process chamber  104   b  is opened. In this case, the reason that the process chamber valve  131   b  can be opened even though the process chamber valve  131   a  is opened is as below. Since the vacuum side valve  121   a  and the vacuum side valve  121   b  are closed, the respective gases in the process chamber  104   a  and the process chamber  104   b  will not mix with each other. 
         [0080]    After the process chamber valve  131   a  has been opened, the vacuum robot  108   a  loads the workpiece into the process chamber  104   a  from the vacuum transport chamber  103   a  by elongating the arm. In addition, the vacuum robot  108   b  loads the workpiece having been processed in the process chamber  104   b , into the vacuum transport chamber  103   b  by elongating the arm. Thereafter, the process chamber valve  131   a  and the process chamber valve  131   b  are closed to seal the vacuum transport chamber  103   a  and the vacuum transport chamber  103   b , respectively. In this way, the state of  FIG. 5C  is achieved where the workpiece is transferred into the process chamber  104   a  and the workpiece is transferred from the process chamber  104   b.    
         [0081]    A major difference between the conventional apparatus and the apparatus of the present invention is whether or not the process chamber valve  131   a  and the process chamber valve  131   b  can be opened/closed individually. In the conventional apparatus, if the process chamber valve  131   a  is opened, the process chamber valve  131   b  cannot be opened. Therefore, the loading of the workpiece into the process chamber  104   a  cannot be done concurrently with the unloading of the workpiece from the process chamber  103   b  in  FIG. 6 . However, in the present invention, even if the process chamber valve  131   a  is opened, the process chamber valve  131   b  can be opened without mixing of the gasses in the process chambers. Therefore, the loading of the workpiece into the process chamber  104   a  can be done concurrently with the unloading of the workpiece from the process chamber  104   b  in  FIG. 2 . Thus, the configuration of the apparatus of the present invention takes a smaller amount of time required to transfer the workpiece than the conventional apparatus, thereby allowing for an improvement in throughput. 
         [0082]    A description is next given of a method of concurrently transferring a plurality of workpieces in a configuration adapted to allow the load lock to store the workpieces in the first embodiment described above. 
         [0083]    The configuration of the load lock storing the plurality of workpieces and the method of concurrently transferring the workpieces in the semiconductor processing apparatus of the present invention are described in detail with reference to  FIGS. 7A ,  7 B, and  8 A- 8 C. 
         [0084]    Modes of holding the workpieces in the load locks are first described with reference to  FIGS. 7A and 7B .  FIGS. 7A and 7B  illustrates the modes of holding the workpieces in the load locks. The modes of holding the workpieces in the load locks can conceivably include a mode of holding the workpieces aligned in the same plane as the load lock as shown in  FIG. 7A  and a mode of holding the workpieces aligned in the direction vertical to the plane where the load lock lies as shown in  FIG. 7B . In any of these cases, it is possible to concurrently transfer the plurality of workpieces between the load lock and a plurality of vacuum transport chambers connected to the load lock by use of a plurality of transfer robots corresponding to associated valves. However, the mode of aligning the workpieces on the plane as in  FIG. 7A  has a larger footprint than the mode of aligning the workpieces in the direction vertical to the plane in which the load lock lies as in  FIG. 7B . Thus, the mode of holding the workpieces as in  FIG. 7B  is more advantageous than that as in  FIG. 7A  in view of space saving. For this reason, the method of concurrently transferring the plurality of workpieces in the mode of aligning the workpieces in the load lock as in  FIG. 7B  is described with reference to  FIG. 8A to 8C . 
         [0085]      FIGS. 8A to 8C  illustrate actions in which the vacuum transfer robot  108   a  elongates the arm to take the workpiece out of the load lock and also another vacuum transfer robot  108   b  elongates the arm to take the workpiece out of the load lock. 
         [0086]    As seen from  FIGS. 8A to 8C , the plurality of vacuum transport chambers  103   a  and  103   b  are connected to the load lock  105  and the vacuum transfer robots  108   a  and  108   b  are respectively installed in the vacuum transport chambers  103   a  and  103   b . In this case, the two vacuum transfer robots, i.e., the vacuum transfer robot  108   a  and the vacuum transfer robot  108   b , can concurrently transfer the corresponding workpieces stored in the load lock. Specifically, while one vacuum transfer robot  108   a  continues the action of transferring the workpiece from the load lock, the other vacuum transfer robot  108   b  can start the action of transferring the workpiece from the load lock. More preferably, the control section  100  controls the action of the apparatus so that two vacuum transfer robots  108   a  and  108   b  simultaneously may start the transfer of the workpieces. Also in the case where the number of the vacuum transport chambers connected to the load lock is three or more, i.e., the case where the number of the vacuum transfer robots is three or more, similarly the vacuum robots can concurrently transfer the workpieces. 
         [0087]    A detailed description is here given of the actions of the two vacuum transfer robots  108   a  and  108   b  concurrently transferring the workpieces with reference to  FIG. 8C . When transferring the workpiece, the vacuum transfer robot inserts the arm under the workpiece, raises the arm to put the workpiece thereon, and transfers it. In this case, even if the plurality of vacuum transfer robots insert the respective arms into the load lock, they will not come into contact with each other because the arms are vertically offset from each other. In this way, the two vacuum transfer robots  108   a  and  108   b  concurrently transfer the workpieces. 
         [0088]    In the configuration of the apparatus according to the present invention, a comparison is made between the case where the plurality of vacuum transfer robots sequentially transfer the plurality of workpieces and the case where they concurrently transfer the plurality of workpieces. The concurrent transfer of the workpieces takes a smaller amount of time required for the transfer. Thus, throughput can be improved. As the number of the vacuum transport chambers connected to the load lock is progressively increased, a difference in the amount of time required to transfer the workpieces between the case where the vacuum transfer robots sequentially transfer the workpieces and the case where they concurrently transfer the workpieces. Thus, also a difference in throughput is increased. 
         [0089]    A description is next given of a mechanism of holding in the load lock the plurality of workpieces aligned in a direction vertical to the plane in which the load lock lies in the case where the load lock has the plurality of valves and the plurality of workpieces can be held as described above, in the first embodiment. 
         [0090]      FIGS. 9A and 9B  illustrate the mechanism of the load lock where the plurality of workpieces can be held in the load lock in the form of being aligned in a direction vertical to the plane in which the load lock lies and the vacuum transfer robots can insert their arms into the load lock from a plurality of directions and transfer the workpieces. 
         [0091]    Since the conventional load lock is connected to the single vacuum transport chamber, there has been provided a workpiece holding mechanism shaped like a claw or a shelf on its inner wall not provided with the atmospheric side valve or the vacuum side valve. However, when a plurality of vacuum transport chambers are connected to the load lock, such a mechanism cannot be provided. Thus, it is necessary to provide a workpiece holding mechanism in such a manner as not to obstruct the transfer of the workpiece. For example, it can be conceivable that workpiece holding mechanisms  124  each shaped like a claw or a ledge are provided at four corners of the load lock. The provision of such workpiece holding mechanisms can hold a plurality of workpieces in the load lock and insert the arm of the atmospheric transfer robot or of the vacuum transfer robot from any directions of the load lock for transfer of the workpieces. 
       Second Embodiment 
       [0092]    A semiconductor processing apparatus according to a second embodiment is next described in which omnidirectional valves lying in the same plane as a load lock are connected to corresponding vacuum transport chambers. In general, one of the valves connected to the load lock is used as a transfer opening adapted to transfer a workpiece by an atmospheric transfer robot. In order to increase throughput, it is preferable that all the valves connected to the load lock are connected to the corresponding transport chambers. 
         [0093]    The configuration of the semiconductor processing apparatus according to the second embodiment is described with reference to  FIGS. 10 ,  11 A and  11 B. In this configuration, omnidirectional valves lying in the same plane as the load lock are connected to the corresponding vacuum transport chambers.  FIG. 10  illustrates the semiconductor processing apparatus in which the omnidirectional valves lying in the same plane as the load lock are connected to the corresponding vacuum transport chambers.  FIG. 11  is a cross-sectional view taken along line A-A in  FIG. 10 . 
         [0094]    Referring to  FIG. 10 , four vacuum transport chambers  103   a ,  103   b ,  103   c  and  103   d  are connected to a load lock  105 . process chambers  104   a ,  104   b ,  104   c  and  104   d  are connected to the vacuum transport chambers  103   a ,  103   b ,  103   c  and  103   d , respectively. An omnidirectional valve lying in the same plane as the load lock is connected to the vacuum transport chambers. Therefore, it is necessary to transfer the workpiece from above or below the load lock. In  FIG. 10 , a housing  106  and an atmospheric transfer robot  109  lying in the housing which are constituent elements of the atmospheric transfer block  101  are located above the vacuum transport chamber  103   d . A cassette table  107  is connected to the housing  106 . In this case, the load lock  105  is connected to the vacuum side valve  121   d  and to the atmospheric side valve  120  in such a manner that the vacuum side valve  121   d  and the atmospheric side valve  120  are vertically offset from each other as illustrated in  FIGS. 11A and 11B . However, the arrangement of this atmospheric block is one example. Alternatively, a configuration in which also cassettes are stored in the load lock is conceivable. A description is hereinafter given of a transfer process in the second embodiment. 
         [0095]    The transfer order of workpieces is as below. Similarly to the semiconductor processing apparatus in  FIG. 1 , cassettes in which workpieces are stored are put on the cassette table  107 . The atmospheric transfer robot  109  takes a workpiece out of the inside of a cassette toward the housing  106  by elongating and contracting the arm thereof. An atmospheric side valve  120  of the load lock  105  is opened. The atmospheric transfer robot stores the workpiece in the load lock by elongating and contracting the arm and the atmospheric side valve is closed. Thereafter, in the load lock, the workpiece is lowered to such a height that the vacuum transfer robot  108   a  can transfer the workpiece by lowering the workpiece holding mechanism  124  as in  FIG. 11A . 
         [0096]    The inside of the load lock is depressurized through vacuum evacuation. In the state where the inside of the load lock is depressurized, the vacuum side valve  121   a  is opened and the vacuum transfer robot  108   a  takes the workpiece out of the load lock and places it in the vacuum transport chamber by elongating and contracting the arm. In this case, the vacuum transfer robot  108   a  transfers a plurality of the workpieces by elongating and contracting the arm. After the vacuum side valve  121   a  has been closed, the process chamber valve  131   a  is opened and the vacuum transfer robot  108   a  transfers the workpieces into the process chamber  104   a  by elongating and contracting the arm. The process chamber valve is closed and the workpieces are processed. After the processing has been finished, the workpieces are transferred to the load lock by the actions reverse to those during the loading. After the transfer, the workpiece holding mechanism  124  is shifted upward as in  FIG. 11B , the inside of the load lock is returned to the atmospheric pressure. Then, the atmospheric side valve is opened and the workpieces are returned by the atmospheric side robot to the original position of the original cassette. 
         [0097]    The above is the transfer actions of the semiconductor processing apparatus in which the omnidirectional valves lying in the same plane as the load lock are connected to the corresponding vacuum transport chambers.