Abstract:
A substrate processing system having a hot reactor with two load locks and two associated load/unload units, and a related method of operating the system, are disclosed. Substrates are concurrently moved from the reactor into one of two load locks and from the other of the two load locks into the reactor. A bidirectional transfer mechanism is used for the concurrent transfers, such that successive transfers in opposite directions are interleaved. Substrates are heated in the load locks prior to processing in the reactor. The reactor applies processing to substrates, to form processed substrates. Processed substrates are cooled in the load locks after processing in the reactor. Respective load and unload units load substrates into the load locks and unload processed substrates from the load locks. The interleaved concurrent transfers minimize or make zero the idle time of the reactor.

Description:
TECHNICAL FIELD 
       [0001]    The technical field of the present disclosure relates to substrate processing and load locks, more particularly to systems and methods that transfer substrates to and from a processing chamber or reactor and to and from a load lock. 
       BACKGROUND ART 
       [0002]    When processing one or more substrates in a reactor, such as a chemical vapor deposition reactor, a load lock is generally employed. A load lock functions similarly to an airlock, and serves to prevent cross-contamination between an ambient environment and the reactor environment. The load lock holds one or more substrates, which are transferred from the load lock into the reactor for processing. Some systems have two load locks, one on either side of the reactor, and the second load lock receives wafers or other substrates from the reactor after processing. Such systems have a unidirectional substrate flow, as the substrates are moved from one load lock into the reactor for processing, and then from the reactor to the other load lock after processing. Each load lock employs an isolation seal, such as a door or a gate or other isolation device such as a gas curtain, between the load lock and the reactor. The other side of the load lock also employs an isolation seal, separating the load lock from either the ambient environment or a load and unload unit. The isolation seals can support pressure and/or temperature differences from one chamber or unit to the next. Load and unload units can be robotic in nature and provide automated loading and unloading of load locks. 
         [0003]    Types of substrates eligible for processing in a reactor include both glass, e.g. as used in flat-panel displays, and semiconductor wafer substrates, such as those used to make solar photovoltaic cells or integrated circuits. Substrates may be mounted in a substrate carrier or on a susceptor. The substrates can be processed individually or in groups, depending on substrate size, reactor chamber size, processing sequence and other factors. Substrates can be moved using a transport mechanism, which can include a conveyor belt, one or more shuttles operated individually or in a train, rollers, air or other gas levitation, or magnetic coupling. 
         [0004]    A reactor can include one or more processing chambers, and may perform one or more types of semiconductor processing steps such as diffusion, etching, deposition, or cleaning. Often, the amount of time substrates spend in the reactor, being processed, is the major factor affecting processing throughput and operating efficiency of a system. Reactor idle time, during which the reactor is not applying processing, reduces throughput and operating efficiency. Reactor idle time may occur while the reactor is waiting for wafers to be preheated, waiting for wafers be cooled, waiting for wafers to be moved into or out of the reactor and at other waiting times. Improvements in processing throughput and operating efficiency of systems using reactors for substrate processing are sought. 
       SUMMARY 
       [0005]    A method for operating a hot reactor between two load locks, and a related system for substrate processing are disclosed herein. The method and system are suitable for processing various substrates singly or in groups. Concurrent transfers of substrates from the reactor to the first load lock and from the second load lock to the reactor are interleaved with concurrent transfers of substrates from the reactor to the second load lock and from the first load lock to the reactor. 
         [0006]    In an embodiment of the method, a hot reactor has two load locks. Substrates are concurrently moved from the reactor to a second load lock and from a first load lock into the reactor, in transfers in a first direction. Further substrates are concurrently moved from the reactor to the first load lock and from the second load lock into the reactor, in transfers in a second direction. The transfers in the first direction are interleaved with the transfers in the second direction, during a continuous operation of the reactor and the first and second load locks. The interleaved transfers minimize or make zero the reactor idle time. The substrates and the further substrates are transferred and processed individually or in groups. 
         [0007]    More specifically, a hot reactor is located between two load locks. A processed first substrate is moved from the reactor to the first load lock. Concurrently with this move, a heated second substrate is moved from the second load lock to the reactor. The first substrate is cooled in the first load lock. The cooled first substrate is unloaded from the first load lock. A third substrate is loaded into the first load lock. The third substrate is heated in the first load lock. Substrate processing is applied to the second substrate in the reactor. The substrate processing is applied while the first substrate is being cooled in and then unloaded from the first load lock and the third substrate is being loaded into the first load lock and heated therein. The processed second substrate is moved from the reactor to the second load lock. Concurrently with this move, the heated third substrate is moved from the first load lock to the reactor. The second substrate is cooled in the second load lock. The cooled second substrate is unloaded from the second load lock. A fourth substrate is loaded into the second load lock. The fourth substrate is heated in the second load lock. Further substrate processing is applied to the third substrate in the reactor. The substrate processing is applied while the second substrate is being cooled in and then unloaded from the second load lock and the fourth substrate is being loaded into the second load lock and heated therein. A processing duration as applied to substrates being processed in the reactor is greater than an unload duration as applied to unloading substrates from the load locks plus a load duration is applied to loading substrates into the load locks. A cycle time of processing multiple such substrates is reduced and a throughput is increased as compared to using only a single load lock with the reactor. 
         [0008]    The system for substrate processing includes a reactor, first and second load locks, first and second load and unload units and a bidirectional transfer mechanism. The first and second load locks are both connected to the reactor, can heat substrates therein before the substrates are moved into the reactor, and can also cool substrates after they are moved from the reactor. The first and second load and unload units are connected to the respective first and second load locks so as to be able to load and unload substrates into and out of those load locks. The bidirectional transfer mechanism can, in a first transfer direction, concurrently transfer (1) heated substrates from the first load lock into the reactor and (2) processed substrates from the reactor into the second load lock. Likewise, the bidirectional transfer mechanism can, in a second transfer direction, concurrently transfer (1) heated substrates from the second load lock into the reactor and (2) processed substrates from the reactor into the first load lock. 
         [0009]    In an alternate embodiment, there can be two parallel reactor systems, each with their own sets of load and unload units and load locks, but both sharing a common gas box and related plumbing to supply the process gas to the respective reactors. In such a case, it may be advantageous to stagger the load-process-unload cycles of the parallel reactor systems so that the reactors do not require simultaneous use of the shared gas box. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIGS. 1-16  are schematic diagrams showing interleaved transfers of substrates in a reactor-based system for substrate processing, in accordance with the present invention. The system includes a central reactor, two load locks and two load and unload units. 
           [0011]      FIG. 17  is a timing diagram showing in the upper half of the diagram the operation of the reactor-based system of  FIG. 1 . 
           [0012]      FIG. 18  is a schematic diagram of a further embodiment of a reactor-based system, as in  FIG. 1  but including two reactors, four load locks and four load and unload units.  FIG. 17  further shows, in both upper and lower halves of the diagram, staggered operation of this embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As shown in  FIGS. 1-18 , embodiments of a reactor-based system  100  for substrate processing and a related method of operation thereof achieve high efficiency and substrate processing throughput. Transfers of substrates are coordinated in an interleaved manner so that idle time for the reactor is minimized or made zero, thus improving efficiency and throughput. In particular, preheating and post-process cooling of substrates take place inside load locks at the same time that processing of another substrate is performed within the reactor. Transfers into and out of the reactor occur concurrently through separate load locks. 
         [0014]    With reference to  FIG. 1 , the reactor-based system  100  for substrate processing includes a reactor  106 . Examples of suitable reactors include chemical vapor deposition reactors, showerhead reactors and semiconductor processing reactors. A first load lock  104  and a second load lock  108  are connected to opposite sides of the reactor  106 , although other arrangements may be used. A first load and unload unit  102  is connected to the first load lock  104 . A second load and unload unit  110  is connected to the second load lock  108 . Respective isolation seals  112 ,  114 ,  116 ,  118 ,  120 ,  122  can be individually opened or closed to allow passage of substrates or isolate neighboring units in support of differing pressures and/or temperatures. 
         [0015]    The embodiment of  FIG. 1  has a linear arrangement of the first load and unload unit  102 , the first load lock  104 , the reactor  106 , the second load lock  108  and the second load and unload unit  110 , although other arrangements can be used in further embodiments. A first (optional) isolation seal  112  isolates one end of the first load and unload unit  102  from the ambient environment or further equipment, or selectively opens thereto: A second isolation seal  114  opens to connect or seals to isolate the first load and unload unit  102  and the first load lock  104 . A third isolation seal  116  opens to connect or seals to isolate the first load lock  104  and the reactor  106 . A fourth isolation seal  118  opens to connect or seals to isolate the reactor  106  and the second load lock  108 . A fifth isolation seal  120  opens to connect or seals to isolate the second load lock  108  and the second load and unload unit  110 . A sixth (optional) isolation seal  122  seals one end of the second load and unload unit  110  from the ambient environment or further equipment, or selectively opens thereto. 
         [0016]    In sequence,  FIGS. 1-16  show substrates being moved in an interleaved manner in a cycle of transfers involving the reactor  106 , the first and second load locks  104 ,  108  and the first and second load and unload units  102 ,  110 . In an ongoing or continuous process flow, the cycle of  FIGS. 1-16  is repeated continuously. Initial steps for bringing up the system from a cold, unloaded state are not shown, and are readily devised. Such initial steps include initial loading of either or both of the load and unload units  102 ,  110 , initial transfer to one of the load locks  104 ,  108 , and loading of a substrate or group of substrates into the reactor  106  for the initial processing. 
         [0017]      FIG. 1  starts the cycle from a steady state of operation. A group of processed substrates  124  (shown with diagonal shading bars) is present in the reactor  106 . A group of substrates (shown with dotted shading)  126  is present in the second load lock  108 , awaiting their turn for processing in the reactor  106 . The substrates  126  may be unprocessed or preprocessed substrates, i.e. the substrates  126  have not yet received the next processing in the reactor  106 , but may have received previous processing. Isolation seals  114 ,  120  between the load locks  104 ,  108  and the load and unload units  102 ,  110  are closed, and isolation seals  116 ,  118  at opposed sides of the reactor  106 , i.e. between the reactor  106  and the load locks  104 ,  108  are opened. The reactor  106  and the load locks  104 ,  108  are pressure equalized and heated to a uniform, elevated temperature (shown as square grid shading), for example 400° C. Heating may be accomplished by convection, conduction or radiation, by using an electric heating element, heating lamps or other heat source. In the example shown, the substrates are in a group of three subgroups of sixteen substrates each, with each subgroup of sixteen substrates as four groups of four substrates. In further examples, a single substrate could be in the reactor  106  and a further single substrate could be in the second load lock  108 , or other groups of substrates could be used. Multiple substrates may be moved on a carrier. Multiple carriers may be moved together in a group and processed in a chamber. 
         [0018]      FIG. 2  follows  FIG. 1  in the cycle. The processed substrates  124  and the substrates  126  that await processing are both moved concurrently in a two-one direction  230  (leftward in the drawing), for example by a transport mechanism that moves the substrates simultaneously. The processed substrates  124  are moved from the reactor  106  to the first load lock  104 , and the substrates  126  are moved from the second load lock  108  to the reactor  106 . In  FIG. 2 , the isolation seals  114 ,  116 ,  118 ,  120  and temperature equalizing remain as in  FIG. 1 . The concurrent moving of substrates out of and into the reactor  106  minimizes the reactor idle time. By comparison, sequentially moving the processed substrates  124  from the reactor to the first load lock  104 , followed by moving the substrates  126  awaiting processing from the second load lock  108  to the reactor  106  would add to the reactor idle time because of the delay between the two sequential moves. 
         [0019]    In  FIG. 3 , the isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  are closed, which support differing pressures and/or temperatures. Isolation seals  114 ,  120  between the load locks  104 ,  108  and the respective load and unload units  102 ,  110  remained closed. The processed substrates  124  are being cooled in the first load lock  104  (shown as horizontal shading bars). Cooling may be accomplished by air cooling, gas cooling or liquid cooling, for example by circulating a cooling liquid through passages in a plate. The load lock  104  is being filled with gas, for example nitrogen, to raise the pressure to match that of the load and unload unit  102 . Alternatively, load lock  104  can be cycle purged to reduce residual process gas species from reactor  106  prior to raising the pressure to match that of the load and unload unit  102 . The substrates  126  in the reactor are being heated to a further elevated temperature (shown as vertical shading bars), for example 800° C. 
         [0020]      FIG. 4  shows the substrates  126  receiving processing and becoming processed substrates  426  in the reactor  106 , under the same temperature conditions as shown in  FIG. 3 . 
         [0021]    In  FIG. 5 , the processed substrates  124  that were moved out of the reactor  106  in  FIG. 2  and cooled in the first load lock  104  are now moved from the first load lock  104  to the first load and unload unit  102 . The isolation seal  114  between the first load and unload unit  102  and the first load lock  104  is open to permit passage of the processed substrates  124 , and the first load and unload unit  102  and the first load lock  104  are at equal pressure, for example, atmospheric pressure (shown without shading). The substrates becoming processed substrates  426  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The second load lock  108  remains at the elevated temperature. The isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0022]    In  FIG. 6 , the processed substrates  124  in the first load and unload unit  102  are exchanged for substrates  624 , which may be unprocessed or preprocessed substrates. This is accomplished using a substrate handler, a robotic handler, or other automated or manual unloading of the processed substrates  124  and loading of the substrates  624 . The substrates becoming processed substrates  426  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The second load lock  108  remains at the elevated temperature. The isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0023]    In  FIG. 7 , the substrates  624  are moved from the first load and unload unit  102  into the first load lock  104 . The isolation seal  114  between the first load and unload unit  102  and the first load lock  104  is open to permit passage of the substrates  624 , and the first load and unload unit  102  and the first load lock  104  are at equal pressure (shown without shading). The substrates becoming processed substrates  426  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The second load lock  108  remains at the elevated temperature. The isolation seals,  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0024]    In  FIG. 8 , the isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  are closed, which support differing pressures and/or temperatures. Isolation seals  114 ,  120  between the load locks  104 ,  108  and the respective load and unload units  102 ,  110  are closed. The processed substrates  426  are being cooled in the reactor  106  (shown as horizontal shading bars). Cooling may be accomplished by reducing the power input to the reactor heater. The substrates  624  in the first load lock  104  are being heated to an elevated temperature (shown as vertical shading bars), for example 400° C. The load lock  104  is being evacuated to lower the pressure to match that of the reactor  106 . Alternatively, load lock  104  can be cycle purged to reduce residual contaminant gas species from the load and unload unit  102  prior to lowering the pressure to match that of reactor  106 . 
         [0025]      FIG. 9  shows the isolation seals  114 ,  120  between the load locks  104 ,  108  and the load and unload units  102 ,  110  are closed, and the isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  are opened to support passage of substrates. The reactor  106  and the load locks  104 ,  108  are pressure equalized and at a uniform, elevated temperature (shown as square grid shading), for example 400° C. The processed substrates  426  are no longer receiving processing in the reactor  106 . 
         [0026]    In  FIG. 10 , the processed substrates  426  and the substrates  624  awaiting processing are both moved concurrently in a one-two direction  930  (rightward in the drawing), for example by a transport mechanism that moves the substrates simultaneously. The processed substrates  426  are moved from the reactor  106  to the second load lock  108 , and the substrates  624  are moved from the first load lock  104  to the reactor  106 . In  FIG. 10 , the isolation seals  114 ,  116 ,  118 ,  120  and temperature equalizing remain as in  FIG. 9 . The concurrent moving of substrates out of and into the reactor  106  minimizes the reactor idle time. 
         [0027]    In  FIG. 11 , the isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  are closed, which supports differing pressures and/or temperatures. Isolation seals  114 ,  120  between the load locks  104 ,  108  and the respective load and unload units  102 ,  110  remained closed. The processed substrates  426  are being cooled in the second load lock  108  (shown as horizontal shading bars). Cooling may be accomplished by air cooling, gas cooling or liquid cooling, for example by circulating a cooling liquid through passages in a plate. The load lock  108  is being filled with gas, for example nitrogen, to raise the pressure to match that of the load and unload unit  110 . Alternatively, load lock  108  can be cycle purged to reduce residual process gas species from reactor  106  prior to raising the pressure to match that of the load and unload unit  110 . The substrates  624  in the reactor are being heated to a further elevated temperature (shown as vertical shading bars), for example 800° C. 
         [0028]      FIG. 12  shows the substrates  624  receiving processing and becoming processed substrates  1124  in the reactor  106 , under the same temperature conditions as shown in  FIG. 11 . 
         [0029]    In  FIG. 13 , the processed substrates  426  that were moved out of the reactor  106  in  FIG. 10  and cooled in the second load lock  108  are moved from the second load lock  108  to the second load and unload unit  110 . The isolation seal  120  between the second load and unload unit  110  and the second load lock  108  is open to permit passage of the processed substrates  426 , and the second load and unload unit  110  and the second load lock  108  are at equal pressure (shown without shading). The substrates becoming processed substrates  1124  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The first load lock  104  remains at the elevated temperature. The isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0030]    In  FIG. 14 , the processed substrates  426  in the second load and unload unit  110  are exchanged for substrates  1326 , which may be unprocessed or preprocessed substrates. This is accomplished using a substrate handler, a robotic handler, or other automated or manual unloading of the processed substrates  426  and loading of the substrates  1326 . The substrates becoming processed substrates  1124  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The first load lock  104  remains at the elevated temperature. The isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0031]    In  FIG. 15 , the substrates  1326  are moved from the second load and unload unit  110  into the second load lock  108 . The isolation seal  120  between the second load and unload unit  110  and the second load lock  108  is open to permit passage of the substrates  1326 , and the second load and unload unit  110  and the second load lock  108  are at equal pressure (shown without shading). The substrates becoming processed substrates  1124  continue to receive processing in the reactor  106 , which remains at the further elevated temperature. The first load lock  104  remains at the elevated temperature. The isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  remain closed, supporting the pressure and/or temperature difference. 
         [0032]    In  FIG. 16 , the isolation seals  116 ,  118  between the reactor  106  and the load locks  104 ,  108  are closed, which support differing pressures and/or temperatures. Isolation seals  114 ,  120  between the load locks  104 ,  108  and the respective load and unload units  102 ,  110  are closed. The processed substrates  1124  are being cooled in the reactor  106  (shown as horizontal shading bars). Cooling may be accomplished by reducing the power input to the reactor heater. The substrates  1326  in the second load lock  108  are being heated to an elevated temperature (shown as vertical shading bars), for example 400° C. The load lock  108  is being evacuated to lower the pressure to match that of the reactor  106 . Alternatively, load lock  108  can be cycle purged to reduce residual contaminant gas species from the load and unload unit  110  prior to lowering the pressure to match that of reactor  106 . In an ongoing, continuous operation,  FIG. 1  would follow  FIG. 16 , and the reactor would continue to receive substrates alternately from the first and second load locks, with interleaved concurrent transfers. The reactor would continue to move processed substrates alternately to the first and second load locks, with the interleaved concurrent transfers. 
         [0033]    With reference to  FIG. 17 , a timing diagram  1700  is shown. The timing diagram  1700  shows an embodiment of an operation of the reactor-based system  100 , as discussed below, and further shows an embodiment of an operation of the reactor-based system  1800  as will be discussed following presentation of  FIG. 18 . 
         [0034]    From top to bottom, the timing diagram  1700  shows operation of components of the reactor-based system  100 . A first region  1702  of the timing diagram  1700  shows operation of the first load and unload unit  102 . A second region  1704  shows operation of the first load lock  104 . A third region  1706  shows operation of the reactor  106 , which may also be called the first reactor in a further embodiment. A fourth region  1708  shows operation of the second load lock  108 . A fifth region  1710  shows operation of the second load and unload unit  110 . The regions  1712 - 1720  show operations of a parallel system as considered below with reference to  FIG. 18 . Each of the regions  1702 - 1710  will now be described individually as they relate to the others, which complements the event-driven description of the reactor-based system  100  as described above with reference to  FIGS. 1-16 . 
         [0035]    Starting with the first load and unload unit  102 , from time zero on the timing diagram  1700 , the unit  102  is initially idle or at least not involved in any transfers to or from the first load lock  104 . Next, there is a transfer  1721  of processed substrates from the first load lock  104  to the first load and unload unit  102 . Next, there is an index operation  1722 . Next, there is a transfer  1723  of unprocessed or preprocessed substrates from the first load and unload unit  102  to the first load lock  104 . Next there is a load and unload operation  1724  in the first load and unload unit  102 , in which the processed substrates are unloaded and unprocessed or preprocessed substrates are loaded in preparation for the next transfer towards the reactor  106 , i.e. a subsequent transfer from the first load and unload unit  102  to the first load lock  104 . For the remainder of the time on the timing diagram  1700 , the first load and unload unit  102  is idle or at least not involved in any transfers to or from the first load lock  104 . The cycle then repeats (not shown). 
         [0036]    Turning to the first load lock  104 , from time zero on the timing diagram  1700 , the first load lock  104  is performing a vent and/or cooling operation  1725  on processed substrates recently received from the reactor  106 . Next, there is the transfer  1721  of the now cooled processed substrates from the first load lock  104  to the first load and unload unit  102 . Next, there is the transfer  1723  of unprocessed or preprocessed substrates from the first load and unload unit  102  to the first load lock  104 . Next, the substrates in the first load lock  104  awaiting processing are heated  1726 , e.g. to 400° C. This may be performed by using a heating device or a heat pump. Next, after a brief idle time  1727  following the heating, there is a transfer  1728  of the now heated substrates from the first load lock  104  to the reactor  106 . This transfer  1728  is included in a concurrent transfer  1733 , discussed below. After these substrates are processed in the reactor  106 , during which time the first load lock  104  is idle or at least not involved in any transfers, there is a transfer  1729  of the substrates from the reactor  106  to the first load lock  104 . This transfer  1729  is included in a concurrent transfer  1737 , discussed below. The cycle then repeats (not shown). 
         [0037]    Considering now the reactor  106 , from time zero on the timing diagram  1700 , the reactor  106  is heating  1730 , e.g. from 400° C. to 800° C., with substrates therein. These substrates were previously preheated, e.g. to 400° C., inside the second load lock  108  prior to being transferred into the reactor  106 . Next, the reactor performs a processing operation  1731  on, for or with the substrates, such as a chemical vapor deposition. Next, the reactor is cooled  1732 , e.g. from 800° C. to 400° C., with the processed substrates therein. Next, there is a concurrent transfer  1733  of the now processed substrates from the reactor  106  to the second load lock  108  and of the heated substrates from the first load lock  104  to the reactor  106 . Next, the heated substrates recently transferred from the first load lock  104  are further heated  1734  in the reactor  106 , e.g. from 400° C. to 800° C. Next, the reactor  106  performs a processing operation  1735  on, for or with the substrates, such as a chemical vapor deposition. Next, the reactor  106  is cooled  1736 , e.g. from 800° C. to 400° C., with the processed substrates therein. Next, there is a concurrent transfer  1737  of the now processed substrates from the reactor  106  to the first load lock  104  and of the heated substrates from the second load lock  108  to the reactor  106 . The cycle then repeats (not shown). As a result of the concurrent transfers  1733 ,  1737 , the reactor experiences minimal or zero idle time. 
         [0038]    Turning to the second load lock  108 , from time zero on the timing diagram  1700 , the second load lock  108  is idle or at least not involved in any transfers. After the substrates previously transferred from the second load lock  108  have finished being processed in the reactor  106 , there is a transfer  1738  of processed substrates from the reactor  106  to the second load lock  108 . This transfer  1738  is included in the concurrent transfer  1733 . Next, the second load lock  108  performs a vent and/or cooling operation  1739  on the processed substrates recently received from the reactor  106 . Next, there is a transfer  1740  of the now cooled processed substrates from the second load lock  108  to the second load and unload unit  110 . Next, there is a transfer  1741  of unprocessed or preprocessed substrates from the second load and unload unit  110  to the second load lock  108 . Next, the substrates in the second load lock  108  awaiting processing are heated  1742 , e.g. to 400° C. This may be performed by using a heating device or a heat pump. Next, after a brief idle time  1744  following the heating, there is a transfer  1745  of the now heated substrates from the second load lock  108  to the reactor  106 . This transfer  1745  is included in the concurrent transfer  1737 , discussed above. The cycle then repeats (not shown). 
         [0039]    And finally, considering the second load and unload unit, from time zero on the timing diagram  1700 , the unit  110  is initially idle or at least not involved in any transfers to or from the second load lock  108 . Next, there is the transfer  1740  of processed substrates from the second load lock  108  to the second load and unload unit  110 . Next, there is an index operation  1746 . Next, there is the transfer  1741  of unprocessed or preprocessed substrates from the second load and unload unit  110  to the second load lock  108 . Next, there is a load and unload operation  1747  in the second load and unload unit  110 , in which the processed substrates are unloaded and unprocessed or preprocessed substrates are loaded in preparation for the next transfer towards the reactor  106 , i.e. a subsequent transfer from the second load and unload unit  110  to the second load lock  108 . The cycle then repeats (not shown). 
         [0040]    Operation of the second load lock  108  and second load and unload unit  110  with respect to the reactor  106  resembles a mirror image of the operation of the first load and unload unit  102  and the first load lock  104 , except that the two sections of the reactor-based system  100  are 180 degrees or 50% out of phase with each other. The concurrent transfers  1733 ,  1737  are interleaved so that the reactor  106  is receiving substrates alternately from the first load lock  104  and the second load lock  108 , and is sending processed substrates alternately to the first load lock  104  and the second load lock  108 . 
         [0041]    With reference to  FIG. 18 , a further embodiment of the reactor-based system  100  for substrate processing is shown. The reactor-based system  1800  includes two parallel reactor-based subsystems  1804 ,  1806  sharing a common gas box  1802 , with manifolds connected thereto. Each of the subsystems  1804 ,  1806  resembles the reactor-based system  100  albeit with shared plumbing for the shared gas box  1802 . Subsystem  1804  includes a first load and unload unit  1810  connected to a first load lock  1812  and a second load and unload unit  1818  connected to a second load lock  1816 . The first and second load locks  1812 ,  1816  are connected to a first reactor  1814 . Subsystem  1806  includes a third load and unload unit  1820  connected to a third load lock  1822 , and a fourth load and unload unit  1828  connected to a fourth load lock  1826 . The third and fourth load locks  1822 ,  1826  are connected to a second reactor  1824 . The first and second reactors  1814 ,  1824  are connected to the shared gas box  1802 . 
         [0042]    When multiple reactors  1814 ,  1824  share a common gas box  1802  and associated plumbing, it may preferable that depositions or other processing operations applied by the reactors  1814 ,  1824  be staggered wherever gas flows may be insufficient for simultaneous deposition. However, if the common gas box  1802  has the capacity to handle simultaneous deposition in both reactors  1814 ,  1824 , then staggered flows are not needed and the depositions might even be synchronized.  FIG. 17 , including now the bottom half of the figure, shows operation of the parallel dual-reactor-based system  1800  employing staggered processing operations. Moving of substrates into and out of the first and second reactors  1814 ,  1824  is coordinated with staggered phasing so that the substrate processing is applied in each of the first and second reactors  1814 ,  1824  in an alternating manner. 
         [0043]    Referring back to  FIG. 17 , the timing diagram  1700  shows operation of the reactor-based system  1800 . The first reactor-based subsystem  1804  includes the first load and unload unit  1810 , the first load lock  1812 , the first reactor  1814 , the second load lock  1816  and the second load and unload unit  1818 . The first reactor-based subsystem  1804  operates in accordance with the upper half of the timing diagram  1700 , as previously described regarding the single-reactor-based system  100 . 
         [0044]    The second reactor-based subsystem  1806  operates in accordance with the lower half of the timing diagram  1700  in one embodiment, as now described. From time zero on the timing diagram  1700 , the third load and unload unit  1820  is initially idle or at least not involved in any transfers to or from the third load lock  1822 . Next, there is a transfer  1751  of processed substrates from the third load lock  1822  to the third load and unload unit  1820 . Next, there is an index operation  1752 . Next, there is a transfer  1753  of unprocessed or preprocessed substrates from the third load and unload unit  1820  to the third load lock  1822 . Next there is a load and unload operation  1754  in the third load and unload unit  1820 , in which the processed substrates are unloaded and unprocessed or preprocessed substrates are loaded in preparation for the next transfer towards the second reactor  1824 , i.e. a subsequent transfer from the third load and unload unit  1820  to the third load lock  1822 . For the remainder of the time on the timing diagram  1700 , the third load and unload unit  1820  is idle or at least not involved in any transfers to or from the third load lock  1822 . The cycle then repeats (not shown). 
         [0045]    After substrates are processed in the second reactor  1824 , during which time the third load lock  1822  is idle or at least not involved in any transfers, there is a transfer  1755  of the substrates from the second reactor  1824  to the third load lock  1822 . This transfer  1755  is included in a concurrently transfer  1763 , discussed below. Next, the third load lock  1822  is performing a vent and/or cooling operation  1756  on the processed substrates recently received from the second reactor  1824 . Next, there is the transfer  1757  of the now cooled processed substrates from the third load lock  1822  to the third load and unload unit  1820 . Next, there is the transfer  1758  of unprocessed or preprocessed substrates from the third load and unload unit  1820  to the third load lock  1822 . Next, the substrates in the third load lock  1822  awaiting processing are heated  1759 , e.g. to 400° C. This may be performed by using a heating device or a heat pump. Next, after a brief idle time  1760  following the heating, there is a transfer  1761  of the now heated substrates from the third load lock  1822  to the second reactor  1824 . This transfer  1761  is included in a concurrent transfer  1767 , discussed below. The cycle then repeats (not shown). 
         [0046]    From time zero on the timing diagram  1700 , the second reactor  1824  is cooled  1762 , e.g. from 800° C. to 400° C., with the processed substrates therein. Next, there is a concurrent transfer  1763  of the now processed substrates from the second reactor  1824  to the third load lock  1822  and of the heated substrates from the fourth load lock  1826  to the second reactor  1824 . Next, the second reactor  1824  is heating  1764 , e.g. from 400° C. to 800° C., with the recently transferred heated substrates therein. These substrates were previously heated, e.g. to 400° C., in the fourth load lock  1826  prior to being transferred to the second reactor  1824 . Next, the reactor performs a processing operation  1765  on, for or with the substrates, such as a chemical vapor deposition. Note in particular that in this staggered embodiment, the processing operation  1765  in the second reactor  1824  occurs at a different time from the corresponding processing operation  1735  in the first reactor  1814 , so that the two operations do not coincide, so that the common gas box  1802  need not have to supply process gas to both reactors at once. Next, the reactor is cooled  1766 , e.g. from 800° C. to 400° C., with the processed substrates therein. Next, there is a concurrent transfer  1767  of the now processed substrates from the second reactor  1824  to the fourth load lock  1826  and of the heated substrates from the third load lock  1822  to the second reactor  1824 . Next, the heated substrates recently transferred from the third load lock  1822  are further heated  1768  in the second reactor  1824 , e.g. from 400° C. to 800° C. Next, the second reactor  1824  performs a processing operation  1769  on, for or with the substrates, such as a chemical vapor deposition. The cycle then repeats (not shown). As a result of the concurrent transfers  1763 ,  1767 , the reactor experiences minimal or zero idle time. 
         [0047]    From time zero on the timing diagram  1700 , the substrates in the fourth load lock  1826  awaiting processing are heated  1770 , e.g. to 400° C. This may be performed by using a heating device or a heat pump. Next, there is a transfer  1771  of the now heated substrates from the fourth load lock  1826  to the second reactor  1824 . This transfer  1771  is included in the concurrent transfer  1763 , discussed above. While the substrates transferred from the fourth load lock  1826  to the second reactor  1824  are being processed in the second reactor  1824 , the fourth load lock  1826  is idle or at least not involved in any transfers. After the substrates previously transferred from the fourth load lock  1826  have finished being processed in the second reactor  1824 , there is a transfer  1772  of processed substrates from the second reactor  1824  to the fourth load lock  1826 . This transfer  1772  is included in the concurrent transfer  1767  discussed above. Next, the fourth load lock  1826  performs a vent and/or cooling operation  1773  on the processed substrates recently received from the second reactor  1824 . Next, there is a transfer  1774  of the now cooled processed substrates from the fourth load lock  1826  to the fourth load and unload unit  1828 . Next, there is a transfer  1775  of unprocessed or preprocessed substrates from the fourth load and unload unit  1828  to the fourth load lock  1826 . The cycle then repeats (not shown). 
         [0048]    From time zero on the timing diagram  1700 , there is a load and unload operation  1776  in the fourth load and unload unit  1828 , in which processed substrates are unloaded and unprocessed or preprocessed substrates are loaded in preparation for the next transfer towards the second reactor  1824 , i.e. a subsequent transfer from the fourth load and unload unit  1828  to the fourth load lock  1826 . The fourth load and unload unit  1828  is then idle or at least not involved in any transfers to or from the fourth load lock  1826 . Next, there is a transfer  1777  of processed substrates from the fourth load lock  1826  to the fourth load and unload unit  1828 . Next, there is an index operation  1778 . Next, there is a transfer  1779  of unprocessed or preprocessed substrates from the fourth load and unload unit  1828  to the fourth load lock  1826 . The cycle then repeats (not shown). 
         [0049]    Operating efficiency and substrate processing throughput of the reactor-based system  100  and the reactor-based system  1800  can be compared with another reactor-based system (not shown) that includes a single reactor, only a single load lock and only a single load and unload unit. Such a single reactor, single load lock system would have the reactor idle while substrates are exchanged out of the single load lock. The reactor would further be idle as a result of the separate unloading of processed substrates from the reactor and loading of unprocessed or preprocessed substrates into the reactor. Comparison shows that embodiments of the reactor-based system  100  have a reduced cycle time of processing substrates and an increased throughput as compared to using only a single load lock with a reactor. 
         [0050]    In the case where a processing duration as applied to substrates being processed in the reactor is greater than unload duration as applied to unloading substrates from load locks plus a load duration as applied to loading substrates into the load locks, each of the load locks has an idle time. Meanwhile, the idle time of the reactor is minimized or made zero. A capital expenditure of purchasing two load locks is thus offset by improved productivity as measured by substrate processing throughput, in that maximal use is made of reactor time.