Abstract:
Apparatus for multi-chambered semiconductor wafer processing comprising a polygonal structure having at least two semiconductor process chambers disposed on one side. An area between the process chambers provides a maintenance access to the semiconductor processing equipment. Additionally, the apparatus may be clustered or daisy-chained together to enable a wafer to access additional processing chambers without leaving the controlled environment of the semiconductor wafer processing equipment.

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of Invention 
     The present invention relates to a multiple chambered semiconductor wafer processing system and, more particularly, an apparatus containing two or more buffer chambers containing robots for transporting wafers to and from semiconductor wafer processing equipment. 
     2. Background of Prior Art 
     Semiconductor wafer processing is performed by subjecting a wafer to a plurality of sequential processes. These processes are performed in a plurality of process chambers. An assemblage of process chambers served by a wafer transport robot is known as a multi-chamber semiconductor wafer processing tool or cluster tool. 
     Previous cluster tools consisted of a single buffer chamber which housed a wafer transport robot that distributed wafers and managed a plurality of processing chambers. FIG. 1 depicts a schematic diagram illustrative of a multiple process chamber, single buffer chamber semiconductor wafer processing tool known as the Centura® Platform manufactured by Applied Materials, Inc. of Santa Clara, Calif. FIG. 2 depicts a schematic diagram illustrative of a multiple process chamber, single buffer chamber semiconductor wafer processing tool having a “daisy-chained” preparation chamber known as the Endura® Platform manufactured by Applied Materials, Inc. of Santa Clara, Calif. Both Centura® and Endura® are trademarks of Applied Materials, Inc. of Santa Clara, Calif. These tools can be adapted to utilize either single, dual or multiple blade robots to transfer wafers from chamber to chamber. 
     The cluster tool  100  depicted in FIG. 1 contains, for example, a plurality of process chambers,  104 ,  106 ,  108 ,  110 , a buffer chamber  124 , and a pair of load lock chambers  116  and  118 . To effectuate transport of a wafer amongst the chambers, the buffer chamber  124  contains a robotic transport mechanism  102 . The transport mechanism  102  shown has a pair of wafer transport blades  112  and  114  attached to the distal ends of a pair of extendible arms  113   a ,  113   b ,  115   a  and  115   b , respectively. The blades  112  and  114  are used for carrying individual wafers to and from the process chambers. In operation, one of the wafer transport blades (e.g. blade  112 ) of the transport mechanism  102  retrieves a wafer  122  from a cassette  120  in one of the load lock chambers (e.g.  116 ) and carries that wafer to a first stage of processing, for example, physical vapor deposition (PVD) in chamber  104 . If the chamber is occupied, the robot waits until the processing is complete and then swaps wafers, i.e., removes the processed wafer from the chamber with one blade (e.g., blade  114 ) and inserts a new wafer with a second blade (e.g., blade  112 ). Once the wafer is processed (i.e., PVD of material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. For each move, the transport mechanism  102  generally has one blade carrying a wafer and one blade empty to execute a wafer swap. The transport mechanism  102  waits at each chamber until a swap can be accomplished. 
     Once processing is complete within the process chambers, the transport mechanism  102  moves the wafer  122  from the last process chamber and transports the wafer  122  to a cassette  120  within the load lock chamber  118 . 
     The cluster tool  200  with daisy-chained wafer preparation chamber  204  depicted in FIG. 2 contains, for example, four process chambers  250 ,  252 ,  254 ,  256 , a buffer chamber  258 , a preclean chamber  210 , a cooldown chamber  212 , a prep chamber  204 , a wafer-orienter/degas chamber  202 , and a pair of load lock chambers  260  and  262 . The prep chamber  204  is centrally located with respect to the load lock chambers  260  and  262 , the wafer orienter/degas chamber  202 , the preclean chamber  210 , and the cooldown chamber  212 . To effectuate wafer transfer amongst these chambers, the prep chamber  204  contains a prep robotic transfer mechanism  206 , e.g., a single blade robot (SBR). The wafers  122  are typically carried from storage to the tool  200  in a cassette  120  that is placed within one of the load lock chambers  260  or  262 . The SBR  206  transports the wafers  122 , one at a time, from the cassette  120  to any of the three chambers  202 ,  210  or  212 . Typically, a given wafer is first placed in the wafer orienter/degas chamber  202 , then moved to the preclean chamber  210 . The cooldown chamber  212  is generally not used until after the wafer is processed within the process chambers  250 ,  252 ,  254  and  256 . Individual wafers are carried upon a prep wafer transport blade  208  that is located at a distal ends of a pair of extendible arms  264   a  and  264   b  of the SBR  206 . The transport operation is controlled by a sequencer (not shown). 
     The buffer chamber  258  is surrounded by, and has access to, the four process chambers  250 ,  252 ,  254  and  256 , as well as the preclean chamber  210  and the cooldown chamber  212 . To effectuate transport of a wafer amongst the chambers, the buffer chamber  258  contains a second transport mechanism  214 , e.g., a dual blade robot (DBR). The DBR  214  has a pair of wafer transport blades  112  and  114  attached to the distal ends of a pair of extendible arms  266   a ,  266   b  and  268   a ,  268   b , respectively. In operation, one of the wafer transport blades (e.g., blade  114 ) of the DBR  214  retrieves a wafer  122  from the preclean chamber  210  and carries that wafer to a first stage of processing, for example, physical vapor deposition (PVD) in chamber  250 . If the chamber is occupied, the robot waits until the processing is complete and then swaps wafers, i.e., removes the processed wafer from the chamber with one blade (e.g., blade  114 ) and inserts a new wafer with a second blade (e.g., blade  112 ). Once the wafer is processed (i.e., PVD of material upon the wafer), the wafer can then be moved to a second stage of processing, and so on. For each move, the DBR  214  generally has one blade carrying a wafer and one blade empty to execute a wafer swap. The DBR  214  waits at each chamber until a swap can be accomplished. 
     Once processing is complete within the process chambers, the transport mechanism  214  moves the wafer from the process chamber and transports the wafer  122  to the cooldown chamber  212 . The wafer is then removed from the cooldown chamber using the prep transport mechanism  206  within the prep chamber  204 . Lastly, the wafer is placed in the cassette  120  within one of the load lock chambers,  260  or  262 . 
     Although the prior art has shown itself to be a dependable tool for processing semiconductor wafers, a number of design shortcomings are apparent. One example is the limited number of process chambers which can be serviced by the wafer transfer mechanism. Although the size of the buffer chamber can be increased to house a mechanism with a greater range of motion thus allowing for an increase in the number of processing chambers, this solution is not favored since the foot-print (or consumed floor space) of the cluster tool would become prohibitively large. A minimal tool foot-print is an important design criteria. 
     A second example of the shortcomings in the prior art is the lack of serviceability of the buffer chamber. As depicted in both FIGS. 1 and 2, the buffer chamber is surrounded by processing chambers and other chambers. When either the wafer transfer mechanism or other components located within the buffer chamber requires service, access is extremely limited. As such, the removal of one of the surrounding chambers is required to gain access to the buffer chamber. This causes an extended period of time to be expended for service, while increasing the probability of component wear and damage due to the removal and handling of the above mentioned components. 
     Another example of the shortcomings in the prior art is the inability to cluster buffer chambers for use in serial wafer processing. Serial processing often requires more processing chambers than are available on a cluster tools found in the prior art. When additional processing is required, the wafer must be removed, transported and inserted from one cluster tool to a second cluster tool. This interruption and removal of the wafer from a tool&#39;s controlled environment results in additional time required to complete wafer processing and an increase in the probability of damage or contamination of the wafer. 
     As illustrated above, a need exists in the art for a multiple process chamber semiconductor wafer processing tool which allows for an increased number of processing chambers while minimizing tool foot-print, increasing wafer processing throughput, and consolidating peripheral components while allowing access for service and maintenance. 
     SUMMARY OF INVENTION 
     The disadvantages heretofore associated with the prior art are overcome by an invention of a method and apparatus for transporting wafers to and from wafer processing chambers utilizing a dual buffer chamber within a multiple process chamber semiconductor wafer processing system or cluster tool. The invention provides for additional number of processing chambers in the cluster tool without compromising system foot-print. The invention also provides increased throughput, accessibility to the buffer chamber and the ability to cluster buffer chambers to facilitate serial wafer processing. 
     One embodiment of the invention contains at least one polygonal structure having a plurality of sides and at least one of said sides having at least two process chambers disposed thereupon. The process chambers define an access area to said polygonal structure. Further, the polygonal structure has a first buffer chamber, a second buffer chamber and at least one wafer transfer location disposed within said polygonal structure. The first and second buffer chambers further have a first and a second lid disposed thereabove, respectively, thereby defining single environment within said first and second buffer chambers. Additionally, the first and second buffer chambers may contain a plurality of slit valves disposed about and selectively isolating said first and second buffer chamber, thereby defining a first and second environment within said first and second buffer chambers, respectively. 
     A second embodiment of the invention comprises a first polygonal module having a plurality of sides, at least a second polygonal module having a plurality of sides, and at least one mating chamber for connecting said first and said at least second polygonal modules. The first and at least second polygonal modules each further comprise a first and a second process chamber disposed on at least one of their sides that define an access area. Additionally, the apparatus contains at least one wafer transfer location and at least one buffer chamber disposed within said first polygonal module and preferably a first buffer chamber and a second buffer chamber. Said first and second buffer chambers further comprise a plurality of slit valves creating a first and a second environment within said first and said second buffer chamber, respectfully. The advantage of this configuration utilizing multiple buffer chambers is that the wafer may be transported from one modular buffer chamber to a second modular dual buffer chamber without the wafer leaving the controlled environment created within the cluster tool. This allows for expedited serial processing of wafers while minimizing wafer damage and contamination. Specifically, two or more modular buffer chambers may be daisy chained together through the use of a mating chamber to form the modular dual buffer chamber. 
     In a third embodiment of the invention, a semiconductor workpiece processing apparatus comprises at least one polygonal structure having a plurality of sides; a buffer chamber disposed within said at least one polygonal structure; a lid disposed above said at least one polygonal structure thereby defining a single environment within said buffer chamber; and at least two wafer transfer mechanisms disposed within said buffer chamber. The lack of a center wall allows for a reduction in tool&#39;s foot-print. If the demands on foot-print size outweigh the need for ease of access to the buffer chamber, the access area may be reduced or eliminated to further minimize the foot-print area. This embodiment allows for faster wafer processing and greater throughput since the time required to open and close slit valves, and match environments is eliminated. The apparatus further comprises at least six slit valves disposed within said buffer chamber and a first and second process chamber disposed on one of said sides defining an access area between said first and second process chamber and said one side. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
     FIG. 1 depicts a detailed schematic diagram of a prior art single buffer chamber, multiple process chamber semiconductor wafer processing tool; 
     FIG. 2 depicts a detailed schematic diagram of a prior art single buffer chamber, multiple process chamber semiconductor wafer processing tool chamber with daisy-chained preparation chamber; 
     FIG. 3 depicts a simplified schematic diagram of a dual buffer chamber, multiple process chamber semiconductor wafer processing tool in accordance with the present invention; 
     FIG. 4 depicts an elevation view of FIG. 3; 
     FIG. 5 depicts a simplified schematic diagram of a second embodiment of the invention of two dual buffer chamber, multiple process chamber semiconductor wafer processing tools clustered together; 
     FIG. 6 depicts an elevation view of FIG. 5; 
     FIG. 7 depicts a simplified schematic diagram of a third embodiment of the invention of a modular dual buffer chamber, multiple process chamber semiconductor wafer processing tool fabricated by joining two modular buffer chambers; 
     FIG. 8 depicts an elevation view of FIG. 7; 
     FIG. 9 depicts a simplified schematic diagram of a fourth embodiment of the invention of a non-isolated environment dual buffer chamber; 
     FIG. 10 depicts an elevation view of FIG. 9; 
     FIG. 11 depicts a simplified schematic diagram of a fifth embodiment of the invention of a “squeezed” dual buffer chamber; and 
     FIG. 12 depicts an elevation view of FIG.  11 . 
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
    
    
     DETAILED DESCRIPTION 
     Although the subject invention contains various embodiments have differentiating features which make a particular embodiment more desirable to a particular user, all the embodiments share the important attributes of increased mounting facets for additional processing chambers, smaller foot-prints of systems with a comparable number of processing chambers, shared peripheral components (pumps, controllers, power supplies and the like), access to buffer chambers, and increased wafer processing throughput. One important feature of the subject invention is accessibility of the central, or buffer chamber, from a number of access areas located between designated process chamber. More importantly, the improved serviceability of the tool was achieved while reducing the tool&#39;s overall foot-print. Additionally, the tool features more than one wafer transport mechanism servicing the process chambers, and more specifically, the division of wafer transfer responsibility in that a particular robot serves a designated group of process chambers. This feature allows for the additional number of process chambers to be utilized, increasing wafer throughput without quality degradation. Other features and benefits will be apparent upon review of the details of the specific embodiments disclosed below. 
     Dual Buffer Chamber Cluster Tool 
     The first embodiment of the invention, a dual buffer chamber, multiple process chamber semiconductor processing tool or dual buffer chamber cluster tool, is depicted in FIG.  3  and FIG.  4 . As such, the reader should refer to FIGS. 3 and 4 simultaneously for the best understanding of the invention. The tool  300  has a first buffer chamber and a second buffer chamber,  346  and  350 , respectively, and a first wafer transfer location and a second wafer transfer location,  314  and  316 , respectively, disposed within a hexagonal structure  344 . The wafer transfer locations may be a chamber. The hexagonal structure  344  has four sides of equal length  330 ,  332 ,  334  and  336 , and two longer sides of equal length  338  and  340 . Side  334  is bordered by sides  338  and  336 . Side  338  is bordered by  330  and is parallel to side  340 . Side  340  is bordered by sides  332  and  336 . Sides  332  and  330  border each other. A first and second load lock chamber  326  and  328 , respectively, are disposed on the sides  330  and  332 . A pair of process chambers  302  and  306  are disposed on side  338 . A second pair of process chambers  304  and  312  are disposed on side  340 . Process chambers  308  and  310  are disposed on sides  334  and  336 , respectively. The process chambers are orientated perpendicularly in with respect to their respective walls. 
     All process and load lock chambers  212  are selectively isolated from the buffer chambers  346  and  350  by plurality of slit valves  324  (i.e., eight) creating a first and second environment,  374  and  376 , respectively. The use of slit valves to isolate a process chamber from other chambers is known in the art and is described in U.S. Pat. No. 5,730,801 by Avi Tepman et al, and is hereby incorporated by reference. 
     The hexagonal structure  344  has a central wall  342  which runs perpendicular to the sides  338  and  340 . The central wall  342  separates the buffer chambers  346  and  350 . The wafer transfer locations  314  and  316  provide individual passage though the central wall  342  to the buffer chambers  346  and  350 . The wafer transfer locations  314  and  316  are selectively isolated from adjoining buffer chambers  346  and  350  by a plurality (i.e., four) of slit valves  322 . Specifically, one slit valve is provided between first buffer chamber  346  and the first transfer chamber  314 , one additional slit valve is provided between first transfer chamber  314  and second buffer chamber  350 , one slit valve is provided between first buffer chamber  346  and second transfer chamber  316  and one slit valve is provided between second buffer chamber  350  and second transfer chamber  316 . The use of the slit valves allows for the pressure in each chamber to be individually controlled. Each wafer transfer location  314  and  316  additionally has a wafer pedestal  370  and  372 , respectively, for supporting the wafer in the chamber. 
     The first buffer chamber  346  is circumscribed by the load lock chambers  326  and  328 , process chambers  302  and  304 , and wafer transfer locations  314  and  316 . Each of the process chambers  302  and  304 , and the load lock chambers  326  and  328  are selectively isolated from the buffer chamber  346  by slit valve  324 . Located within buffer chamber  346  is a first vacuum port  366  and a first robotic wafer transport mechanism  348 , e.g., a single blade robot (SBR). Other types of transport mechanisms may be substituted. The first robotic wafer transport mechanism  348  shown has a wafer transport blade  358  attached to the distal ends of a pair of extendible arms,  362   a  and  362   b . The blade  358  is used by first robotic wafer transport mechanism  348  for carrying the individual wafers to and from the chambers circumscribing the first buffer chamber  346 . 
     The second buffer chamber  350  is circumscribed by the process chambers  306 ,  308 ,  310  and  312 , and wafer transfer locations  314  and  316 . Located within buffer chamber  350  is a second vacuum port  368  and a second robotic wafer transport mechanism  352 , e.g., a single blade robot (SBR). Other types of transport mechanisms may be substituted. The second robotic wafer transport mechanism  352  shown has a wafer transport blade  360  attached to the distal ends of a pair of extendible arms  364   a  and  364   b . The blade  360  is used by second robotic wafer transport mechanism  352  for carrying the individual wafers to and from the chambers circumscribing the second buffer chamber  350 . 
     Both buffer chambers  346  and  350  have an independently operable lid  354  and  356  (see FIG. 4) attached to the hexagonal structure  344  that allows access to the chambers  346  and  350 . First and second access areas  318  and  320 , respectively, are defined by the process chambers  302 ,  306 ,  304  and  312 , and the intersection of the central wall  342  and the sides  338  and  340  respectively. 
     The vacuum ports  366  and  368  are connected to a pumping mechanism (not shown) such as a turbo molecular pump, which is capable of evacuating the environments of chambers  346  Fand  350 , respectively. The configuration and location of the vacuum ports may vary dependent on design criteria for individual systems, for example the use of a single port in conjunction with a high volume pump. 
     In operation, the slit valves  322  and  324  isolating the buffer chamber  346  from the surrounding chambers, remain closed unless wafer transfer requires access to a particular chamber. The slit valves  322  and  324  isolating buffer chamber  350  operate similarly. Wafer processing, for example, begins with the buffer chambers  346  and  350  being pumped down to a vacuum condition by the pumping mechanism. The first robotic wafer transport mechanism  348  retrieves a wafer from one of the load lock chambers (e.g.  326 ) and carries that wafer to the first stage of processing, for example, physical vapor deposition (PVD) in chamber  302 . Once the first robotic wafer transport mechanism  348  is no longer is carrying a wafer, first robotic wafer transport mechanism  348  can tend wafers in the other chambers surrounding buffer chamber  346 . Once the wafer is processed and PVD stage deposits material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. 
     If the required processing chamber is located adjacent to second buffer chamber  350 , then the wafer must be transported into one of the wafer transfer locations (e.g.  314 ). The slit valve  322  separating buffer chamber  346  and wafer transfer location  314  is opened. The first robotic wafer transport mechanism  348  transports the wafer into the wafer transfer location  314 . The wafer transport blade  358  connected to first robotic wafer transport mechanism  348  is removed from wafer transfer location  314  leaving the wafer on the pedestal  370 . After the slit valve separating the buffer chamber  346  and the transfer chamber  314  is closed, a second slit valve separating the buffer chamber  350  and the transfer chamber  314  is opened, allowing the wafer transport blade  360  connected to the second robotic wafer transport mechanism  352  to be inserted into wafer transfer location  314  to retrieve the wafer. Once the wafer is inside buffer chamber  350 , the second slit valve is closed and the second robotic wafer transport mechanism  352  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  350  and second robotic wafer transport mechanism  352 . 
     After wafer processing is complete, the wafer is loaded into a cassette (not shown)in a load lock (e.g.  328 ), moving the wafer back through the wafer transfer location when necessary. 
     After a number of complete processing cycles, the buffer chambers  346  and  350  may require service. Maintenance personnel can service the buffer chambers  346  and  350  at either access area  318  or  320 . Access to the buffer chambers  346  and  350  may also be achieved by opening or removing the lids  354  and  356 . 
     Clustered Dual Buffer Chamber Tool 
     An alternate embodiment of the invention is the clustering of two or more dual buffer chamber cluster tools, creating a multiple buffer chamber, multiple process chamber semiconductor processing tool or clustered dual buffer chamber. This embodiment is depicted in FIGS. 5 and 6. As such, the reader is encouraged to refer to FIGS. 5 and 6 simultaneously for the best understanding of the invention. 
     The clustered tool  400  as shown in FIG. 5, has two dual buffer chambers  402  and  406 , connect by a cluster mating chamber  404 . Dual buffer chamber  402  has a septigonal structure  408  which features sides  450  and  452  having an equal length, sides  444  and  446  having an equal length longer than the length of side  450 , sides  448  and  454  having an equal length longer than side  444 , and a seventh shortest side  456 . Sides  448  and  454  are parallel to each other. Side  448  is bounded by side  450  and  444 . Side  450  is also bounded by side  456 . Side  456  is also bounded by side  452 . Side  452  is also bounded by side  454 . Side  454  is also bounded by side  446 . Side  446  is also bounded by side  444 . Two load lock chambers  432  and  434  are disposed on sides  444  and  446  respectively. A cluster mating chamber  404  is disposed on side  456 . A pair of process chambers  436  and  438  are disposed on side  448 . An access area  458  is defined by and separates chambers  436  and  438 . A second pair of process chambers  440  and  442  are disposed on side  454 . An access area  460  is defined by and separates process chambers  440  and  442 . The access areas  458  and  460  are large enough to provide maintenance access to dual buffer chamber  402 . 
     Disposed within the septigonal structure  408  are buffer chambers  410  and  416 , and wafer transfer locations  412  and  414 . The wafer transfer locations may be chambers. A central wall  418  runs perpendicular to sides  448  and  454  and separates buffer chambers  410  and  416 . Wafer transfer locations  412  and  414  provide a passage through the central wall  418 , with each transfer chamber  412  and  414  individually connecting buffer chambers  410  and  416 . The wafer transfer locations  412  and  414  are selectively isolated from adjoining buffer chamber  410  and  416  by a plurality (i.e., four) slit valves  428 . Each wafer transfer location  412  and  414 , and the cluster mating chamber  404  has a pedestal  534 ,  536 , and  538 , respectively. Both buffer chambers  410  and  416  have an independently operable lid  516  and  518  respectively (see FIG. 6) attached to septigonal structure  408  that allows access to said buffer chambers  410  and  416 . 
     The buffer chamber  410  is circumscribed by the load lock chambers  432  and  434 , process chambers  436  and  440 , and wafer transfer locations  412  and  414 . The load lock chambers  432  and  434 , and process chambers  436  and  440  are selectively isolated from adjoining buffer chamber  410  by a plurality (i.e., four) of slit valves  424 . Located within buffer chamber  410  is first vacuum port  526  and a first robotic wafer transport mechanism  420 , e.g., a single blade robot (SBR). Other types of transfer mechanisms may be substituted. The first robotic wafer transport mechanism  420  shown has a wafer transport blade  422  attached to the distal ends of a pair of extendible arms  423   a  and  423   b . The blade  422  is used by first robotic wafer transport mechanism  420  for carrying the individual wafers to and from the chambers surrounding buffer chamber  410 . 
     The second buffer chamber  416  is circumscribed by the process chambers  438  and  442 , the cluster mating chamber  404 , and wafer transfer locations  412  and  414 . Each of the process chambers  438  and  442  are selectively isolated from adjoining buffer chamber  416  by a plurality (i.e., two) slit valves  424 . The cluster mating chamber  404  is selectively isolated from the adjoining buffer chamber  416  by slit valve  430 . Located within buffer chamber  416  is a second vacuum port  528  and a second robotic wafer transport mechanism  426 , e.g., a single blade robot (SBR). The second robotic wafer transport mechanism  426  shown has a wafer transport blade  427  attached to the distal ends of a pair of extendible arms  429   a  and  429   b . The blade  427  is used by second robotic wafer transport mechanism  426  for carrying the individual wafers to and from the chambers surrounding buffer chamber  416 . 
     Dual buffer chamber  406  has a septigonal structure  500  which features sides  474  and  480  having an equal length, sides  476  and  478  having an equal length shorter than  474 , sides  472  and  482  having an equal length shorter than  476 , and a seventh shortest side  470 . Sides  474  and  480  are parallel. Side  476  is bounded by  478  on one side and side  474  on the other. Side  478  is also bounded by side  480 . Side  480  also bounded by side  482 . Side  482  is also bounded by side  470 . Side  470  is also bounded by side  472 . Mating chamber  404  is disposed on side  470 . Two process chambers  488  and  490  are disposed on sides  476  and  478  respectively. A pair of process chambers  484  and  486  are disposed on side  474 . An access area  466  is defined by and separates chamber process chambers  484  and  486 . A second pair of process chambers  492  and  494  are disposed on side  480 . An access area  468  is defined by and separates chamber process chambers  492  and  494 . The access areas  466  and  468  are large enough to provide maintenance access to dual buffer chamber  406 . 
     Disposed within the septigonal structure  500  are buffer chambers  504  and  510 , and wafer transfer locations  496  and  498 . A central wall  502  runs perpendicular to sides  474  and  480  and separate buffer chambers  504  and  510 . Wafer transfer locations  496  and  498  provide a passage through the central wall  502 , with each transfer chamber  496  and  498  individually connecting buffer chambers  504  and  510 . The wafer transfer locations  496  and  498  are selectively isolated from adjoining buffer chamber  504  and  510  by a plurality (i.e., four) slit valves  428 . Each wafer transfer location  496  and  498  additionally has a pedestal  540  and  542 , respectively. Both buffer chambers  504  and  510  having an independently operable lid  520  and  522  respectively (FIG. 6) attached to septigonal structure  500  that allows for access to chamber  504  and  510 . 
     The buffer chamber  504  is circumscribed by the cluster mating chamber  404 , process chambers  484  and  494 , and wafer transfer locations  496  and  498 . Each of the process chambers  484  and  494  are selectively isolated from adjoining buffer chamber  504  by a plurality (i.e., two) slit valve  424 . The cluster mating chamber  404  is selectively isolated from the buffer chamber  504  by a slit valve  430 . Located within buffer chamber  504  is a third vacuum port  530  and a third robotic wafer transport mechanism  506 , e.g., a single blade robot (SBR). Other types of transfer mechanisms may be substituted. The third robotic wafer transport mechanism  506  shown has a wafer transport blade  508  attached to the distal ends of a pair of extendible arms  507   a  and  507   b . The blade  508  is used by third robotic wafer transport mechanism  506  for carrying the individual wafers to and from the chambers surrounding buffer chamber  504 . 
     The second buffer chamber  510  is circumscribed by the process chambers  486 ,  488 ,  490  and  492 , and wafer transfer locations  496  and  498 . Each process chamber  486 ,  488 ,  490  and  492  is selectively isolated from buffer chamber  510  by a plurality (i.e., four) slit valves  424 . Located within buffer chamber  510  is a fourth vacuum port  532  and a fourth robotic wafer transport mechanism  512 , e.g., a single blade robot (SBR). The fourth robotic wafer transport mechanism  512  shown has a wafer transport blade  514  attached to the distal ends of a pair of extendible arms  524   a  and  524   b . The blade  514  is used by fourth robotic wafer transport mechanism  512  for carrying the individual wafers to and from the chambers surrounding buffer chamber  510 . 
     Although the configuration of dual buffer chambers  402  and  406  illustrate the cluster mating chamber  404  positioned as to create a linear relation between the respective buffer chambers, this is illustrative only. The number of dual buffer chambers, process chambers per buffer chamber, geometry of the buffers and the location of the cluster mating chamber is dependent on a number of parameters unique to each user&#39;s needs, including but not limited to desired wafer throughput, available factory floor space, production line layouts and capital constraints. Many other configurations which embody the teachings of the invention will be readily apparent to those skilled in the arts. 
     The vacuum ports  526 ,  528 ,  530 , and  532  are connected to a pumping mechanism (not shown) such as a turbo molecular pump, which is capable of evacuating the environments of chambers  410 ,  416 ,  504  and  510 , respectively. The configuration and location of the vacuum ports may vary dependent on design criteria for individual systems, for example the use of a single port in conjunction with a high volume pump. 
     In operation, the slit valves  424  and  428  isolating the buffer chamber  410  from the surrounding chambers remain closed unless wafer transfer requires access to a particular chamber. The slit valves  424 ,  428  and  430  isolating buffer chambers  416 ,  504  and  510  operate similarly. Wafer processing, for example, begins when the chambers  410 ,  416 ,  504 , and  510  are pumped down to a vacuum condition by the pumping mechanism. The first wafer transfer robot  420  retrieves a wafer from one of the load lock chambers (e.g.  432 ) and carries that wafer to the first stage of processing, for example, a physical vapor deposition (PVD) in chamber  436 . If the chamber is occupied, the first robotic wafer transport mechanism  420  can either wait for the chamber  436  to become available or move the wafer to a pedestal  534  located within wafer transfer location (e.g.  412 ). Once the first robotic wafer transport mechanism  420  no longer is carrying a wafer, first robotic wafer transport mechanism  420  can tend wafers in the other chambers surrounding buffer chamber  410 . If chamber  436  is available, the first robotic wafer transport mechanism  420  deposits the wafer in chamber  436 . Once the wafer is processed and PVD stage deposits material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. 
     If the required processing chamber is located adjacent to buffer chamber  416 ,  504  or  510 , then the wafer must be transported into one of the wafer transfer locations (e.g.,  412 ). The slit valve  428  isolating the wafer transfer location  412  from the buffer chamber  410  opens, allowing the wafer to be inserted into the wafer transfer location  412 . The wafer transport blade  422  connected to first robotic wafer transport mechanism  420  is removed from wafer transport chamber  412  leaving the wafer on the pedestal  534 . After the slit valve  428  separating the buffer chamber  410  and the transport chamber  412  is closed, a second slit valve  428  separating the buffer chamber  416  and the transport chamber  412  is opened, allowing a wafer transport blade  427  connected to the second robotic wafer transport mechanism  426  to be inserted into wafer transport chamber  412  to retrieve the wafer. Once the wafer is inside buffer chamber  416 , the second slit valve  428  is closed and the second robotic wafer transport mechanism  426  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  416  and second robotic wafer transport mechanism  426 . 
     If the processing chamber is not serviced by buffer chamber  416 , the wafer is then transported by second robotic wafer transport mechanism  426  to the cluster mating chamber  404  and deposited on a pedestal  538 . After the slit valve  430  separating the buffer chamber  416  and the cluster mating chamber  404  is closed, a second slit valve  430  separating the buffer chamber  504  and the cluster mating chamber  404  is opened, allowing a wafer transport blade  508  connected to the third robotic wafer transport mechanism  506  to be inserted into the cluster mating chamber  404  to retrieve the wafer. Once the wafer is inside buffer chamber  504 , the second slit valve  430  is closed and the third robotic wafer transport mechanism  506  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  504  and third robotic wafer transport mechanism  506 . 
     If the processing chamber is not located within buffer chamber  504 , the wafer is then transported by third robotic wafer transport mechanism  506  into one of the wafer transfer location (e.g.,  496 ). The wafer transport blade  508  connected to third robotic wafer transport mechanism  506  is removed from wafer transport chamber  496  leaving the wafer on the pedestal  540 . After the third slit valve  428  separating the buffer chamber  504  and the transport chamber  496  is closed, a fourth slit valve  428  separating the buffer chamber  510  and the transport chamber  496  is opened, allowing a wafer transport blade  514  connected to the fourth robotic wafer transport mechanism  512  to be inserted into wafer transport chamber  496  to retrieve the wafer. Once the wafer is inside buffer chamber  510 , the second slit valve  428  is closed and the fourth robotic wafer transport mechanism  512  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  510  and fourth robotic wafer transport mechanism  512 . 
     After wafer processing is complete, the wafer is loaded into a cassette (not shown) in a load lock (e.g.,  434 ), moving back through the wafer transfer and cluster mating chambers when necessary. Although the example is illustrative of wafer movement towards the right in FIG. 5, wafer processing requirements in buffer chambers to the left of wafer location may require movement to the left during over the course of wafer processing. This may be accomplished by reversing the order of the steps required to transfer the wafer through any of the transfer or cluster mating chambers as needed. Additionally, the sequencing of the slit valves between the buffer chambers  410 ,  416 ,  504 , and  510 , transfer chambers  412 ,  414 ,  496  and  498  and the cluster mating chamber  404  is for example only. Some slit valves remain open dependant upon desired vacuum condition in the adjoining chamber or to reduce wafer transfer time as necessary. 
     After a number of complete processing cycles, the chambers  410 ,  416 ,  504  and  510  may require service. Maintenance personnel can reach the chambers  410 ,  416 ,  504  and  510  at access areas  458 ,  460 ,  466  and  468 , and gain access to the interior of said chambers by opening or removing the lids  516 ,  518 ,  520  and  522 . 
     As set forth by this embodiment, serial processing of wafers is facilitated by allowing a large number of process chambers to be clustered within one tool. This yields the important benefits of maintaining the wafer within a controlled environment, saving time and preventing costly damage and contamination to the wafer, minimizing tool footprint, increasing wafer throughput by having more process chambers available within a tool and having more robots available for the increased demands of wafer transfer, and allowing the tool to share peripheral components which assist in keeping capital costs at a minimum. 
     Modular Dual Buffer Chamber 
     A third embodiment of the invention, a modular dual buffer chamber cluster tool  700  is shown in FIG.  7  and FIG.  8 . As such, the reader should refer to FIGS. 7 and 8 simultaneously for the best understanding of the invention. 
     The tool  700 , for example, has first and second modules  702  and  704 , respectively, joined by a module mating chamber  706 . The first module  702  has a septigonal chamber body  708  featuring sides  710 ,  712 ,  714  and  722  having an equal length, sides  716  and  720  having an equal length, and a seventh side  718 . Sides  716  and  720  are shorter than the other sides. Side  714  is parallel to side  722  and is bordered by sides  712  and  716 . Side  712  is also bordered by side  710 . Side  710  is also bordered by side  722 . Side  722  is also bordered by side  720 . Side  720  is also bordered by side  718 . Load lock chambers  726  and  728  are disposed on sides  710  and  712 , respectively. Process chambers  724  and  730  are disposed on sides  722  and  714 , respectively. The module mating chamber  706  is disposed on side  718 . 
     A buffer chamber  732  is centrally located within chamber body  708 . A plurality (i.e., four) of slit valves  738  selectively isolate the buffer chamber  732  from the process chambers  730  and  724 , and the load lock chambers  726  and  728 . A slit valve  740  selectively isolates the module mating chamber  706  from buffer chamber  732 . The module mating chamber  706  additionally has a pedestal  784 . Located within chamber  732  is a first vacuum port  780  and a first robotic wafer transport mechanism  734 , e.g., a single blade robot (SBR). Other types of transport mechanisms may be substituted. The first robotic wafer transport mechanism  734  shown has a wafer transport blade  736  attached to the distal ends of a pair of extendible arms  786   a  and  796 o. The blade  736  is used by first robotic wafer transport mechanism  734  for carrying the individual wafers to and from the chambers surrounding chamber  732 . 
     The second module  704  has a chamber body  746  featuring sides  754 ,  756 ,  758  and  760  having an equal length, sides  748  and  752  having an equal length, and a seventh side  750 . Side  754  is parallel to side  760 . Sides  748  and  752  are shorter than the other sides. Side  754  is bordered by sides  752  and  756 . Side  752  is also bordered by side  750 . Side  750  is also bordered by side  748 . Sides  748  is also bordered by  760 . Side  760  is also bordered by side  758 . Side  758  is also bordered by side  756 . Process chambers  762 ,  764 ,  766  and  768  are disposed to sides  760 ,  754 ,  756  and  758  respectively. The module mating chamber  706  is disposed to side  750 . 
     A buffer chamber  770  is centrally located within chamber body  746 . The buffer chamber  770  is circumscribed by the process chambers  762 ,  764 ,  766  and  768 , and a module mating chamber  706 . A plurality (i.e., four) of slit valves  738  isolate the buffer chamber  770  from the process chambers  762 ,  764 ,  766  and  768 . A slit valve  740  isolates the module mating chamber  706  from buffer chamber  770 . Located within buffer chamber  770  is a second vacuum port  782  and a second robotic wafer transport mechanism  772 , e.g., a single blade robot (SBR). Other types of transport mechanisms may be substituted. The second robotic wafer transport mechanism  772  shown has a wafer transport blade  774  attached to the distal ends of a pair of extendible arms  738   a  and  738   b . The blade  774  is used by second robotic wafer transport mechanism  772  for carrying the individual wafers to and from the chambers surrounding chamber  770 . Both buffer chambers  732  and  770  have an independently operable lid  776  and  778  (see FIG. 8) respectively attached to chamber bodies  708  and  746  that allow access to buffer chambers  732  and  770 . 
     Although the configuration of modules  702  and  704  illustrate the cluster mating chamber  706  secured to a particular side of the modules, this is for example only. The particular side attached to the mating chamber  706 , the number of buffer chambers, process chambers per buffer chamber, geometry of the modules and the location of the cluster mating chamber is dependent on a number of parameters unique to each user&#39;s needs, including but not limited to the wafer throughput desired, available factory floor space, production line layout and capital constraints. A person skilled in the art may readily use these teaching to obtain varied embodiments while remaining within the spirit of invention. 
     The vacuum ports  780  and  782  are connected to a pumping mechanism (not shown) such as a turbo molecular pump, which is capable of evacuating the environments of chambers  732  and  770 , respectively. The configuration and location of the vacuum ports may vary dependent on design criteria for individual systems, for example the use of a single port in conjunction with a high volume pump. 
     In operation, the slit valves isolating the buffer chamber  732  from the surrounding chambers remain closed unless wafer transfer requires access to a particular chamber. The slit valves isolating buffer chamber  770  operate similarly. Wafer processing, for example, begins when the buffer chambers  732  and  770  are pumped to a vacuum condition by the pumping mechanism. The first robotic wafer transport mechanism  734  retrieves a wafer from one of the load lock chambers (e.g.  728 ) and carries that wafer to the first stage of processing, for example, physical vapor deposition (PVD) in process chamber  730 . If the chamber is occupied, the first robotic wafer transport mechanism  734  can either wait for the process chamber  730  to become available or move the wafer to a pedestal  784  located within the module mating chamber  706 . Once the first robotic wafer transport mechanism  734  no longer is carrying a wafer, first robotic wafer transport mechanism  734  can tend wafers in the other chambers surrounding buffer chamber  732 . If process chamber  730  is available, the first robotic wafer transport mechanism  734  deposits the wafer in process chamber  730 . Once the wafer is processed and PVD stage deposits material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. 
     If the required processing chamber is located adjacent to buffer chamber  770 , then the wafer must be transported into the module mating chamber  706 . The slit valve  740  isolating the buffer chamber  732  and the mating chamber  706  is opened to allow the water to enter the mating chamber  706 . The wafer transport blade  736  connected to first robotic wafer transport mechanism  734  is removed from the module mating chamber  706  leaving the wafer on the pedestal  784 . After the slit valve  740  separating the buffer chamber  732  and the cluster mating chamber  706  is closed, a second slit valve  740  separating the buffer chamber  770  and the module mating chamber  706  is opened, allowing a wafer transport blade  774  connected to the second robotic wafer transport mechanism  772  to be inserted into the module mating chamber  706  to retrieve the wafer. Once the wafer is inside buffer chamber  770 , the second slit valve  740  is closed and the second robotic wafer transport mechanism  772  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  770  and second robotic wafer transport mechanism  772 . 
     After wafer processing is complete, the wafer is loaded into a cassette (not shown) in a load lock (e.g.,  726 ), moving back through the module mating chamber  706  when necessary. 
     After a number of complete processing cycles, the buffer chambers  732  and  770  may require service. Maintenance personnel can reach the buffer chambers  732  and  770  at service locations  742  and  744 , and gain access to the interior of buffer chambers  732  and  770  by opening or removing the lids  776  and  778 . 
     Non-Isolation of Buffer Environments 
     Although an important feature of many of the embodiments of the invention is the isolation of the buffer chambers which allow the buffer chambers to run at different environmental conditions, some users may find this feature unnecessary for their particular processing application. Since wafer throughput is also an important feature, some users find it advantageous to run the buffer chambers at identical environmental conditions eliminating the need for slit valves. When configured for non-isolated conditions in the buffer chambers, the robots can directly access the pedestals within the transfer and mating chambers. The direct access increases the speed of wafer transfer and throughput while allowing for a more cost effective and smaller tool. 
     One such embodiment of a non-isolated dual buffer chamber, multiple process chamber cluster tool or nonisolated dual buffer cluster tool is depicted in FIG.  9  and FIG.  10 . As such, the reader is encouraged to refer to FIGS. 9 and 10 simultaneously for the best understanding of the invention. Tool  900  has a septigonal chamber body  902  which features a pair of equal length sides  910  and  916 , a second pair of equal length sides  912  and  914 , a third pair of equal length sides  904  and  908 , and a seventh side  906 . Side  914  is bounded by  916  on one side and side  912  on the other. Side  916  is also bounded by side  904 . Sides  910  and  916  are parallel to each other and are the longer than sides  904 ,  906  and  912 . Side  910  is bounded by sides  908  and  912 . Sides  904  and  908  are shorter than side  912 , and are separated by side  906 . Two load lock chambers  940  and  942  are disposed on sides  912  and  914  respectively. A set of process chambers  930  and  932  are disposed on side  916 . A second set of process chambers  936  and  938  are disposed on side  910 . 
     Disposed within the septigonal chamber body  902  are a first and second buffer chamber  922  and  928 , respectively, and wafer transfer locations  924  and  926 , respectively. The wafer transfer locations may be a chamber. A central wall  920  runs perpendicularly from side  910  to side  916  and separates buffer chambers  922  and  928 . Wafer transfer locations  924  and  926  provide a passage through the central wall  920 , each chamber  924  and  926  individually connects buffer chambers  922  and  928 , creating a single environment  972 . Each wafer transfer location  924  and  926  has a pedestal  968  and  970 , respectively. Both buffer chambers  922  and  928  have an independent lid  960  and  962  respectively (see FIG.  10 ). Access areas  946  and  948  are defined by process chambers  930  and  932  along side  916  and by process chamber  936  and  938  along side  910  and provide access to the buffer chambers  922  and  928 . 
     The first buffer chamber  922  is circumscribed by the load lock chambers  940  and  942 , process chambers  930  and  938 , and wafer transfer locations  924  and  926 . The load lock chambers  940  and  942 , and process chambers  930  and  938  are selectively isolated from adjoining buffer chamber  922  by a plurality (i.e., four) slit valves  958 . Located within buffer chamber  922  is a first vacuum port  962  and a first robotic wafer transport mechanism  950 , e.g., a single blade robot (SBR). Other types of transfer mechanisms may be substituted. The first robotic wafer transport mechanism  950  shown has a wafer transport blade  952  attached to the distal ends of a pair of extendible arms  960   a  and  960   b . The blade  952  is used by first robotic wafer transport mechanism  950  for carrying the individual wafers to and from the chambers surrounding buffer chamber  922 . 
     A second buffer chamber  928  is circumscribed by the process chambers  932 ,  934  and  936 , and wafer transfer locations  924  and  926 . The process chambers  932 ,  934  and  936  are selectively isolated from adjoining buffer chamber  928  by a plurality (i.e., four) slit valves  958 . Located within second buffer chamber  928  is a second vacuum port  964  and a second robotic wafer transport mechanism  954 , e.g., a single blade robot (SBR). The second robotic wafer transport mechanism  954  shown has a wafer transport blade  956  attached to the distal ends of a pair of extendible arms  966   a  and  966   b . The blade  956  is used by second robotic wafer transport mechanism  954  for carrying the individual wafers to and from the chambers surrounding buffer chamber  928 . 
     Although the configuration of the tool  900  is shown having seven sides, it is noted that a six-sided structure may be desired in certain applications where the sides  904 ,  906  and  908  are replaced with two sides equal in length to side  912 . This will allow an additional process chamber to be added to the tool. Many other configurations in addition to the one described above which embody the teachings of the invention will be readily apparent to those skilled in the arts. 
     The vacuum ports  962  and  964  are connected to a pumping mechanism (not shown) such as a turbo molecular pump, which is capable of evacuating the environments of chambers  922  and  928 , respectively. The configuration and location of the vacuum ports may vary dependent on design criteria for individual systems, for example the use of a single port in conjunction with a high volume pump. 
     In operation, the slit valves  958  isolating the buffer chamber  922  from the surrounding process chambers  930  and  938 , and load lock chambers  940  and  942  remain closed unless wafer transfer requires access to those particular chambers. The slit valves  958  isolating buffer chamber  928  operate similarly to isolate process chambers  932 ,  934  and  936 . Wafer processing, for example, begins when the chamber  922  and  928  are pumped to a vacuum condition by the pumping mechanism. The first robotic wafer transport mechanism  950  retrieves a wafer from one of the load lock chambers (e.g.,  942 ) and carries that wafer to the first stage of processing, for example, physical vapor deposition (PVD) in chamber  930 . If the chamber is occupied, the first robotic wafer transport mechanism  950  can either wait for the chamber  930  to become available or move the wafer to a pedestal  968  located within wafer transfer location (e.g.,  924 ). Once the first robotic wafer transport mechanism  950  no longer is carrying a wafer, first robotic wafer transport mechanism  950  can tend wafers in the other chambers surrounding buffer chamber  922 . If chamber  930  is available, the first robotic wafer transport mechanism  950  deposits the wafer in chamber  930 . Once the wafer is processed and PVD stage deposits material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. 
     If the required processing chamber is located adjacent to buffer chamber  922 , then the wafer must be transported into one of the wafer transfer location (e.g.,  924 ). The wafer transport blade  952  connected to first robotic wafer transport mechanism  950  is removed from wafer transport chamber  924  leaving the wafer on the pedestal  968 . Wafer transport blade  956  connected to the second robotic wafer transport mechanism  954  to be inserted into wafer transport chamber  924  to retrieve the wafer. Once the wafer is inside buffer chamber  928 , the second robotic wafer transport mechanism  954  is free to move the wafer to the desired processing chamber or sequence of chambers serviced by buffer chamber  928  and second robotic wafer transport mechanism  954 . 
     After wafer processing is complete, the wafer is loaded into a cassette (not shown) in a load lock (e.g.,  940 ), moving back through the wafer transfer locations when necessary. Although the example is illustrative of wafer movement towards the right on FIG. 9, wafer processing requirements may require additional wafer transfer between buffer chambers during the course of wafer processing. 
     After a number of complete processing cycles, the chambers  922  and  928  may require service. Maintenance personnel can reach the chambers  922  and  928  at access areas  946  and  948 , and gain access to the interior of chambers  922  and  928  by opening or removing the lids  960  and  962   
     As demonstrated by these steps, the present invention saves significant time by facilitating wafer transport between robotic wafer transport mechanisms without having to wait for the opening and closing of slit valves and environmental changes to occur within a transfer chamber. Additionally, the elimination of the slit valves allows the non-isolated tool  900  disclosed in FIG. 9 to enjoy the cost savings associated with fewer components and simpler operation as compared to prior art processing tools. 
     Squeezed Non-Isolated Dual Buffer Chamber 
     An embodiment which maximizes the ability to reduce further the foot-print and costs savings of the non-isolated dual buffer chamber cluster tool is a “squeezed” nonisolated dual buffer chamber, multiple process chamber semiconductor processing tool or “squeezed” dual buffer chamber cluster tool. The “squeezed” tool is depicted in FIGS. 11 and 12. As such, the reader should refer to FIGS. 11 and 12 simultaneously for the best understanding of the invention. The “squeezed” tool  1100  referring primarily to FIG. 11 has octagonal chamber body  1130  which features sides  1140  and  1146  having an equal length, sides  1142  and  1144  having an equal length shorter than side  1140 , sides  1134  and  1136  having an equal length shorter than side  1142 , and sides  1132  and  1138  having an equal length shorter than side  1134 . Sides  1140  and  1146  are parallel to each. 
     Side  1140  is bounded by  1136  and side  1142 . Side  1142  is also bounded by side  1144 . Side  1144  is also bounded by  1146 . Side  1146  is also bounded by side  1132 . Side  1132  is also bounded by  1134 . Side  1134  is also bounded by side  1136 . 
     Disposed within the octagonal chamber body  1130  is a buffer chamber  1116 . The environment  1172  of buffer chamber  1116  is selectively isolated from adjoining load locks and process chambers by a plurality (i.e., eight) of slit valves  1162 . Buffer chamber  1116  additionally has a singular lid  1150  (see FIG.  12 ). Disposed within the buffer chamber  1116  are a first robotic wafer transport mechanism  1118 , a second robotic wafer transport mechanism  1120 , a vacuum port  1164 , and a first and second pedestal  1122  and  1124 , respectively. The vacuum port connects the buffer chamber  1116  to a pumping mechanism (not shown) such as a turbo molecular pump. 
     The first robotic wafer transport mechanism  1118  is for example, a single blade robot (SBR). Other types of transport mechanism may be substituted. The first robotic wafer transport mechanism  1118  shown has a wafer transport blade  1166  attached to the distal ends of a pair of extendible arms,  1168   a  and  1168   b . The pedestals  1122  and  1124  are located along an imaginary axis  1160  which bisects sides  1140  and  1146 . Two load lock chambers  1112  and  1114  are attached to sides  1136  and  1134 , respectively. A set of process chambers  1101  and  1102  are disposed on side  1140  and define an access area  1176 . A second set of process chambers  1108  and  1110  are disposed on side  1146  and define an access area  1178 . Access area  1176  and  1178  may be eliminated if a minimized foot-print is desired. Process chambers  1104  and  1106  are disposed on sides  1142  and  1144 , respectively. The first robotic wafer transport mechanism  1118  is substantially centrally located to the load lock chambers  1112  and  1114 , process chambers  1101  and  1110  and the pedestals  1122  and  1124 . First robotic wafer transport mechanism  1118  is additionally equidistant from pedestals  1122  and  1124 . The blade  1166  is used by first robotic wafer transport mechanism  1118  to facilitate transfer of wafers among the load lock chambers  1112  and  1114 , process chambers  1101  and  1110 , and the pedestals  1122  and  1124 . 
     The second robotic wafer transport mechanism  1120  is for example, a single blade robot (SBR). Other types of transport mechanism may be substituted. The second robotic wafer transport mechanism  1120  shown has a wafer transport blade  1170  attached to the distal ends of a pair of extendible arms,  1172   a  and  1172   b . The second robotic wafer transport mechanism  1120  is substantially centrally located to the process chambers  1102 ,  1104 ,  1106  and  1108  and the pedestals  1122  and  1124 . Second robotic wafer transport mechanism  1120  is additionally equidistant from pedestals  1122  and  1124 . The blade  1166  is used by second robotic wafer transport mechanism  1120  to facilitate transfer of wafers among process chambers  1102 ,  1104 ,  1106  and  1108 , and the pedestals  1122  and  1124 . 
     Although the configuration of the tool  1100  is shown having eight sides, it is noted that other polygonal structures may be employed while remaining within the spirit and teachings of the invention. 
     The vacuum port  1164  is connected to a pumping mechanism (not shown) such as a turbo molecular pump, which is capable of evacuating the environment of buffer chamber  1116 . The configuration and location of the vacuum ports may vary dependent on design criteria for individual systems, for example the use of a single port in conjunction with a high volume pump. 
     In operation, the slit valves isolating the buffer chamber  1116  from the surrounding process chambers ( 1101 ,  1102 ,  1104 ,  1106 ,  1108 ,  1110 ) and load lock chambers ( 1112 ,  1114 ) chambers remain closed unless wafer transfer requires access to those particular chambers. Wafer processing, for example, begins when the buffer chamber  1116  is pumped down to a vacuum condition by the pumping mechanism. The first robotic wafer transfer mechanism  1118  retrieves a wafer from one of the load lock chambers (e.g.  1112 ) and carries that wafer to the first stage of processing, for example, physical vapor deposition (PVD) in chamber  1101 . If the chamber is occupied, the first robotic transfer mechanism  1118  can either wait for the chamber  1101  to become available or move the wafer to a pedestal  1122 . Once the first robotic transfer mechanism  1118  is no longer carrying a wafer, first robotic transfer mechanism  1118  can tend wafers in the other chambers and platforms serviced by first robotic transfer mechanism  1118 . If chamber  1101  is available, the first robotic transfer mechanism  1118  deposits the wafer in chamber  1101 . Once the wafer is processed and PVD stage deposits material upon the wafer, the wafer can then be moved to a second stage of processing, and so on. 
     If the required processing chamber is serviced by the second robotic transfer mechanism  1120 , then the wafer must be transported into one of the pedestals (e.g.  1122 ). The first robotic transfer mechanism  1118  leaves the wafer on the pedestal  1122 . Second robotic transfer mechanism  1120  retrieves the wafer from pedestal  1122  and delivers the wafer to the desired processing chamber or sequence of chambers serviced by second robotic transfer mechanism  1120 . 
     After wafer processing is complete, the wafer is loaded into a cassette (not shown) in a load lock (e.g.,  1114 ), moving back across the pedestals when necessary. Although the example is illustrative of wafer movement towards the right on FIG. 11, wafer processing requirements may require additional wafer transfer across the pedestals during the course of wafer processing. 
     As demonstrated by these steps, the present invention saves significant time by facilitating wafer transport between robotic mechanisms without having to wait for the opening and closing of slit valves and environmental changes to occur when using a transfer chamber. Additionally, the elimination of the transfer chambers and the use of a singular lid  1150  allow the “squeezed” tool  1100  disclosed in FIG. 11 to enjoy a reduced foot-print and the cost savings associated with fewer components and simpler operation as compared to the other embodiments. 
     Although various embodiments which incorporate the teachings of the present invention have been shown and described herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.