Abstract:
A method is provided. The method includes disposing a plurality of robotic facilities to form a semiconductor handling system, controlling the semiconductor handling system with a controller to handoff a workpiece between neighboring robotic facilities, and providing a software interface for the controller, wherein the software interface permits a user to view alternate configurations of the handling system in order to optimize a characteristic of the handling system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 11/679,829 filed on Feb. 27, 2007, which claims the benefit of U.S. Prov. App. No. 60/777,443 filed on Feb. 27, 2006, and is a continuation-in-part of U.S. application Ser. No. 10/985,834 filed on Nov. 10, 2004 which claims the benefit of U.S. Prov. App. No. 60/518,823 filed on Nov. 10, 2003 and U.S. Prov. App. No. 60/607,649 filed on Sep. 7, 2004. 
     This application also claims the benefit of the following U.S. applications: U.S. Prov. App. No. 60/779,684 filed on Mar. 5, 2006; U.S. Prov. App. No. 60/779,707 filed on Mar. 5, 2006; U.S. Prov. App. No. 60/779,478 filed on Mar. 5, 2006; U.S. Prov. App. No. 60/779,463 filed on Mar. 5, 2006; U.S. Prov. App. No. 60/779,609 filed on Mar. 5, 2006; U.S. Prov. App. No. 60/784,832 filed on Mar. 21, 2006; U.S. Prov. App. No. 60/746,163 filed on May 1, 2006; U.S. Prov. App. No. 60/807,189 filed on Jul. 12, 2006; and U.S. Prov. App. No. 60/823,454 filed on Aug. 24, 2006. 
     All of the foregoing applications are commonly owned, and all of the foregoing applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The invention herein disclosed generally relates to semiconductor processing systems in a vacuum environment, and specifically relates to configurations of handling and process chambers for semiconductor processing in a vacuum environment. 
     2. Description of the Related Art 
     In a conventional semiconductor manufacturing system, a number of different process modules are interconnected within a vacuum or other environment and controlled to collectively process semiconductor wafers for various uses. The complexity of these manufacturing systems continues to grow both due to the increased complexity of processing larger wafers with smaller features, and due to the increasing possibilities for using a single system for several different end-to-end processes, as described for example in commonly-owned U.S. application Ser. No. 11/679,829 filed on Feb. 27, 2007. As the complexity of a fabrication system grows, it becomes increasingly difficult to schedule resources within the system in a manner that maintains good utilization of all the various process modules. While a part of this difficulty flows from the complexity of the processing recipe itself, another part of the difficulty comes from the differences in processing time for various processing steps. The generally high acquisition and operating costs of production semiconductor vacuum processing systems dictate high utilization of the handling, processing, and other modules within the systems. 
     Within a family of similar semiconductor products, or within a range of families within a technology, at least some of the processing steps may be commonly applied to all wafers. However, because of the unique processing requirements to achieve the final semiconductor device, sharing common processing steps may be very difficult with fixed processing systems. While it may be possible to share these common process steps by configuring them as separate machines, every machine-to-machine transfer imposes time delays and risks of contamination As a result, duplication of equipment, and the resulting underutilization of the equipment, is a common challenge with semiconductor vacuum processing operation in a semiconductor fabrication facility. 
     There remains a need for process modules adapted to current semiconductor manufacturing needs, and in particular, for process modules that can help to balance load, increase throughput, and improve utilization within complex processing systems. 
     SUMMARY 
     A variety of process modules are described for use in semiconductor manufacturing processes. 
     In one aspect, a device disclosed herein includes a single entry shaped and sized for passage of a single wafer; an interior chamber adapted to hold a plurality of wafers in a side-by-side configuration; a slot valve operable to selectively isolate the interior chamber; and a tool for processing the plurality of wafers within the interior chamber. 
     The plurality of wafers may consist of two wafers. The two wafers may be equidistant from the single entry. The two wafers may be in line with the single entry. The plurality of wafers may consist of three entries. The plurality of wafers may be arranged in a triangle. The device may include a wafer handler within the interior chamber, the wafer handler rotatable to position one of the plurality of wafers nearest to the single entry. The tool may process one of the plurality of wafers at a time. The device may include a single robotic arm adapted to place or retrieve any one of the plurality of wafers within the interior chamber. 
     In another aspect, a device disclosed herein includes an interior chamber adapted to hold a plurality of wafers; a first entry to the interior chamber shaped and size for passage of a single wafer and selectively isolated with a first slot valve; a second entry to the interior chamber shaped and size for passage of a single wafer and selectively isolated with a second slot valve; and a tool for processing the plurality of wafers within the interior chamber. 
     The first entry and the second entry may be positioned for access by two robotic arms positioned for a robot-to-robot hand off. The first entry and the second entry may be positioned for access by two robotic arms having center axes spaced apart by less than twice a wafer diameter. The first entry and the second entry may be positioned for access by two adjacent robotic arms positioned for hand off using a buffer location. The device may include two robotic arms, each one of the robotic arms positioned to access one of the first and second entries, and the robotic arms operable to concurrently place at least two wafers into the interior chamber substantially simultaneously. The device may include two robotic arms and a buffer sharing a common isolation environment, each one of the robotic arms positioned to access one of the first and second entries and adapted to transfer one of the plurality of wafers to the other one of the robotic arms using the buffer. The device may include a third entry to the interior chamber shaped and size for passage of a single wafer and selectively isolated with a third slot valve. 
     In another aspect, a device disclosed herein includes an entry shaped and size for passage of at least one wafer, the entry having a width substantially larger than the diameter of the at least one wafer; an interior chamber adapted to hold a plurality of wafers; a slot valve operable to selectively isolate the interior of the chamber; and a tool for processing the plurality of wafers within the interior chamber. 
     The entry may be adapted to accommodate linear access by a robot to a plurality of wafers within the interior chamber. The entry may have a width at least twice the diameter of one of the plurality of wafers. 
     In another aspect, a device disclosed herein includes a first entry shaped and sized for passage of a wafer; a first interior accessible through the first entry; a first slot valve operable to selectively isolate the first interior; a second entry shaped and sized for passage of the wafer; a second interior accessible through the second entry; and a second slot valve operable to selectively isolate the second interior. 
     The device may include a robotic arm adapted to access the first interior and the second interior. The robotic arm may include a four-link SCARA arm. The device may include two robotic arms, including a first robotic arm adapted to access the first interior and a second robotic arm adapted to access the second interior. The first robotic arm and the second robotic arm may be separated by a buffer station. The first interior may include a vacuum sub-chamber adapted for independent processing of wafers. The second interior may include a second vacuum sub-chamber having a different processing tool than the first interior. The second interior may be separated from the first interior by a wall. The first entry and the second entry may be substantially coplanar. The first entry may form a first plane angled to a second plane formed by the first entry. The device may include a robotic arm adapted to access the first entry and the second entry, wherein the first plane and the second plane are substantially normal to a line through a center axis of the robotic arm. The device may include a third entry shaped and sized for passage of a wafer, a third interior accessible through the third entry, and a third slot valve operable to selectively isolate the third interior. 
     In another aspect, a device disclosed herein includes a first entry shaped and sized for passage of a wafer; an interior chamber adapted to hold a wafer; a second entry shaped and sized for passage of the wafer, the second entry on an opposing side of the interior chamber from the first entry; a slot valve at each of the first and second entries, the slot valves operable to selectively isolate the interior chamber; and a tool for processing the wafer within the interior chamber. 
     The devices disclosed herein may be combined in various ways within a semiconductor fabrication system, for example to form fabrication facilities adapted to balance processing load among relatively fast and relatively slow processes, or between processes amenable to batch processing and processes that are dedicated to a single wafer. 
     In one aspect, a system disclosed herein includes a plurality of process modules coupled together to form a vacuum environment, the plurality of process modules including at least one process module selected from the group consisting of an in-line process module, a dual-entry process module, and a wide-entry process module; one or more robot handlers within the vacuum environment adapted to transfer wafers among the plurality of process modules; and at least one load lock adapted to transfer wafers between the vacuum environment and an external environment. 
     The system may include at least one multi-wafer process module having an entry shaped and sized for passage of a single wafer. 
     These and other systems, methods, objects, features, and advantages of the present invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiment and the drawings. All documents mentioned herein are hereby incorporated in their entirety by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention and the following detailed description of certain embodiments thereof may be understood by reference to the following figures: 
         FIG. 1  depicts a generalized layout of a vacuum semiconductor manufacturing system. 
         FIG. 2  shows a multi-wafer process module. 
         FIG. 3  shows a multi-wafer process module. 
         FIG. 4  shows a multi-wafer process module. 
         FIG. 5  shows a multi-wafer process module. 
         FIG. 6  shows adjacent process modules sharing a controller. 
         FIG. 7  shows two robotic arms sharing a buffer. 
         FIG. 8  shows dual entry process modules. 
         FIG. 9  shows dual entry process modules. 
         FIG. 10  shows a process module with an oversized entry. 
         FIG. 11  shows side-by-side process modules. 
         FIG. 12  shows multi-process modules. 
         FIG. 13  shows multi-process modules. 
         FIG. 14  shows multi-process modules. 
         FIG. 15  shows an in-line process module in a layout. 
         FIG. 16  shows a layout using dual entry process modules. 
         FIG. 17  shows a layout using dual entry process modules. 
         FIG. 18  shows a process module containing a scanning electron microscope. 
         FIG. 19  shows a process module containing an ion implantation system. 
         FIG. 20  shows a layout using a scanning electron microscope module. 
         FIG. 21  shows a layout using an ion implantation module. 
         FIG. 22  illustrates a fabrication facility including the placement of optical sensors for detection of robotic arm position and materials in accordance with embodiments of the invention. 
         FIGS. 23A ,  23 B and  23 C illustrate a fabrication facility in a cross-sectional side view showing optical beam paths and alternatives beam paths. 
         FIGS. 24A and 24B  illustrate how optical sensors can be used to determine the center of the material handled by a robotic arm. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a generalized layout of a semiconductor manufacturing system. The system  100  may include one or more wafers  102 , a load lock  112 , one or more transfer robots  104 , one or more process modules  108 , one or more buffer modules  110 , and a plurality of slot valves  114  or other isolation valves for selectively isolated chambers of the system  100 , such as during various processing steps. In general operation, the system  100  operates to process wafers for use in, for example, semiconductor devices. 
     Wafers  102  may be moved from atmosphere to the vacuum environment through the load lock  112  for processing by the process modules  108 . It will be understood that, while the following description is generally directed to wafers, a variety of other objects may be handled within the system  100  including a production wafer, a test wafer, a cleaning wafer, a calibration wafer, or the like, as well as other substrates (such as for reticles, magnetic heads, flat panels, and the like), including square or rectangular substrates, that might usefully be processed in a vacuum or other controlled environment. All such workpieces are intended to fall within the scope of the term “wafer” as used herein unless a different meaning is explicitly provided or otherwise clear from the context. 
     The transfer robots  104 , which may include robotic arms and the like, move wafers within the vacuum environment such as between process modules, or to and from the load lock  112 . 
     The process modules  108  may include any process modules suitable for use in a semiconductor manufacturing process. In general, a process module  108  includes at least one tool for processing a wafer  102 , such as tools for epitaxy, chemical vapor deposition, physical vapor deposition, etching, plasma processing, lithography, plating, cleaning, spin coating, and so forth. In general, the particular tool or tools provided by a module  108  are not important to the systems and methods disclosed herein, except to the extent that particular processes or tools have physical configuration requirements that constrain the module design  108  or wafer handling. Thus, in the following description, references to a tool or process module will be understood to refer to any tool or process module suitable for use in a semiconductor manufacturing process unless a different meaning is explicitly provided or otherwise clear from the context. 
     Various process modules  108  will be described below. By way of example and not limitation, the process modules  108  may have various widths, such as a standard width, a doublewide width, a stretched width, or the like. The width may be selected to accommodate other system components, such as two side-by-side transfer robot modules, two transfer robot modules separated by a buffer module, two transfer robot modules separated by a transfer station, or the like. It will be understood that the width may instead be selected to accommodate more robots, such as three robots, four robots, or more, either with or without buffers and/or transfer stations. In addition, a process module  108  may accommodate a plurality of vacuum sub-chamber modules within the process module  108 , where access to the vacuum sub-chamber modules may be from a plurality of transfer robot modules through a plurality of isolation valves. Vacuum sub-chamber modules may also accommodate single wafers or groups of wafers. Each sub-chamber module may be individually controlled, to accommodate different processes running in different vacuum sub-chamber modules. 
     A number of buffer modules  110  may be employed in the system  100  to temporarily store wafers  102 , or facilitate transfer of wafers  102  between robots  104 . Buffer modules  110  may be placed adjacent to a transfer robot module  104 , between two transfer robot modules  104 , between a transfer robot module  104  and an equipment front-end module (“EFEM”), between a plurality of robots  104  associated with modules, or the like. The buffer module  110  may hold a plurality of wafers  102 , and the wafers  102  in the buffer module  110  may be accessed individually or in batches. The buffer module  110  may also offer storage for a plurality of wafers  102  by incorporating a work piece elevator, or multi-level shelving (with suitable corresponding robotics). Wafers  102  may undergo a process step while in the buffer module  110 , such as heating, cooling, cleaning, testing, metrology, marking, handling, alignment, or the like. 
     The load lock  112  permits movement of wafers  102  into and out of the vacuum environment. In general, a vacuum system evacuates the load lock  112  before opening to a vacuum environment in the interior of the system, and vents the load lock  112  before opening to an exterior environment such as the atmosphere. The system  100  may include a number of load locks at different locations, such as at the front of the system, back of the system, middle of the system, and the like. There may be a number of load locks  112  associated with one location within the system, such as multiple load locks  112  located at the front of the linear processing system. In addition, front-end load locks  112  may have a dedicated robot and isolation valve associated with them for machine assisted loading and unloading of the system. These systems, which may include EFEMs, front opening unified pods (“FOUPs”), and the like, are used to control wafer movement of wafers into and out of the vacuum processing environment. 
     The isolation valves  114  are generally employed to isolate process modules during processing, or to otherwise isolate a portion of the vacuum environment from other interior regions. Isolation valves  114  may be placed between other components to temporarily isolate the environments of the system  100 , such as the interior chambers of process modules  108  during wafer processing. An isolation valve  114  may open and close, and provide a vacuum seal when closed. Isolation valves  114  may have a variety of sizes, and may control entrances that are serviced by one or more robots. A number of isolation valves  114  are described in greater detail below. 
     Other components may be included in the system  100 . For example, the system  100  may include a scanning electron microscope module, an ion implantation module, a flow through module, a multifunction module, a thermal bypass module, a vacuum extension module, a storage module, a transfer module, a metrology module, a heating or cooling station, or any other process module or the like. In addition these modules may be vertically stacked, such as two load locks stacked one on top of the other, two process modules stacked one on top of the other, or the like. 
     It will be understood that, while  FIG. 1  shows a particular arrangement of modules and so forth, that numerous combinations of process modules, robots, load locks, buffers, and the like may suitably be employed in a semiconductor manufacturing process. The components of the system  100  may be changed, varied, and configured in numerous ways to accommodate different semiconductor processing schemes and customized to adapt to a unique function or group of functions. All such arrangements are intended to fall within this description. In particular, a number of process modules are described below that may be used with a semiconductor processing system such as the system  100  described with reference to  FIG. 1 . 
       FIG. 2  shows a multi-wafer process module. The module  202  may include a processing tool (not shown) for processing wafers  204  disposed in an interior thereof. Access to the interior may be through an entry  206  that includes an isolation valve or the like operable to selectively isolate the interior of the module  202 . A robot  208  may be positioned outside the entry  206 , and adapted to place wafers  204  in the interior, or to retrieve the wafers  204  from the interior. In the embodiment of  FIG. 2 , the module  202  is adapted to receive two wafers  204  side by side and substantially equidistant from the entry  206  and the robot  208 . In this arrangement, a clear access path is provided for the robot  208  to each wafer  204 , and the symmetry may advantageously simplify design of the module  202 . 
     In general the size of the entry  206  would be only wide enough and tall enough to accommodate a single wafer  204 , along with an end effector and any other portions of the robot that must pass into the interior during handling. This size may be optimized by having the robot  208  move wafers straight through a center of the entry  206 , which advantageously conserves valuable volume within the vacuum environment. However, it will be understood that the size of the wafer  204  may vary. For example, while 300 mm is a conventional size for current wafers, new standards for semiconductor manufacturing provide for wafers over 400 mm in size. Thus it will be understood that the shape and size of components (and voids) designed for wafer handling may vary, and one skilled in the art would understand how to adapt components such as the entry  206  to particular wafer dimensions. In other embodiments, the entry  206  may be positioned and sized to provide a straight-line path from the wafer&#39;s position within the module  202  and the wafer&#39;s position when at a center  210  of a chamber  212  housing the robot  208 . In other embodiments, the entry  206  may be positioned and sized to provide a straight-line path from the wafer&#39;s position within the module  202  and a center axis of the robot  208  (which will vary according to the type of robotic arm employed). 
       FIG. 3  shows a multi-wafer process module. The module  302  typically includes one or more tools to process wafers  304  therein. As depicted, the three wafers  304  may be oriented in a triangle. The entry  306  may be shaped and sized for passage of a single wafer, or may be somewhat wider to accommodate different paths for wafer passage in and out of an interior of the module  302 . It will be understood that other arrangements of three wafers  304  may be employed, including wafers spaced radially equidistant from a center  310  of a robot handling module  312 , or linearly in various configurations. It will also be understood that, unless the robot  308  has z-axis or vertical movement capability, the wafer  304  closest to the entrance  306  must generally be placed in last and removed first. 
       FIG. 4  shows a multi-wafer process module. This module  402  positions two wafers  404  in-line with the entry  406 , which may advantageously permit the robot  408  to employ a single linear motion for accessing both wafers  404 . 
       FIG. 5  shows a multi-wafer process module. This module  502  includes a wafer handler  520  adapted to move wafers  504  within the module  502 . In one embodiment, the wafer handler  520  may operate in a lazy-Suzan configuration to rotate one of the wafers  504  nearest to the entry  512 . In this configuration, the wafer handler  520  may also rotate wafers  504  on the rotating handler  520  (using, for example, individual motors or a planetary gear train) to maintain rotational alignment of each wafer relative to the module  502 . It will be understood that, while a rotating handler is one possible configuration for the handler  520  that advantageously provides a relatively simple mechanical configuration, other arrangements are also possible including a conveyer belt, a Ferris wheel, a vertical conveyer belt with shelves for wafers, an elevator, and so forth. In general, any mechanical system suitable for accommodating loading of multiple wafers into the module  502 , and preferable systems that accommodate use of an entry  512  sized for a single wafer and/or systems that reduce the required reach of robots into the module, may be useful employed in a multi-wafer process module as described herein. 
       FIG. 6  shows a controller shared by a number of process modules. In a conventional system, each process module has a controller adapted specifically for control of hardware within the process module. The system  600  of  FIG. 6  includes a plurality of process modules  602  which may be any of the process modules described above, and may perform identical, similar, or different processes from one another. As depicted, two of the modules  602  are placed side-by-side and share a controller  604 . The controller  604  may control hardware for both of the side-by-side modules  602 , and provide an interface for external access/control. The interface may be part of a software system and permits the user to run a simulation of the system. The interface may allow the user to view the linking and configuration of various links, robotic arms and other components, to optimize a configuration of the hardware (such as by moving the flow of materials through various components, moving process modules, moving robots, or the like). In embodiments the interface may be a web interface. In addition, sensors may be associated with the modules  602  to provide data to the controller  604 , as well as to recognize when a module is attached to an integrated processing system. Using a shared controller  604 , which may be a generic controller suitable for use with many different types of modules  602  or a module-specific controller, advantageously conserves space around process modules  602  permitting denser configurations of various tools, and may reduce costs associated with providing a separate controller for each process module  602 . The modules  602  may also, or instead, share facilities such as a gas supply, exhaust(s), water, air, electricity, and the like. In an embodiment, the shared controller  604  may control shared facilities coupled to the modules  602 . 
       FIG. 7  shows two robotic arms sharing a buffer. In this system  700 , two robots  702  transfer wafers via a buffer  704 . It will be noted that no isolation valves are employed between the robots  702  and/or the buffer  704 . This arrangement may advantageously reduce or eliminate the need for direct robot-to-robot hand offs (due to the buffer  704 ), and permit closer spacing of robots  702  because no spacing is required for isolation valves. The buffer  704  may include multiple shelves or other hardware for temporary storage of wafers. In one embodiment, the buffer  704  has a number of vertically stacked shelves, and remains stationary while robotic arms  702  move vertically to pick and place on different shelves. In another embodiment, the buffer  704  has a number of vertically stacked shelves, and the buffer  704  moves vertically to bring a specific shelf to the height of one of the robots  702 . In this embodiment, each robot may have an end effector or the like with a different elevation so that both robots  702  can access the buffer  704  simultaneously without collision. In other embodiments, the end effectors of different robots  702  may have complementary shapes to accommodate simultaneous linear access, or may have offset linear positions so that fingers of each end effector do not collide when both robots  702  are accessing the buffer  704 . More generally, it will be appreciated that numerous physical arrangements may be devised for a robotic system  700  that includes two or more robots  702  sharing a buffer  704  within a single isolation chamber. In other embodiments, two or more buffers  704  may also be employed. Each robot may also have multiple end effectors stacked vertically, which allows the robot to transfer multiple wafers simultaneously. 
       FIG. 8  shows a layout for dual-entry process modules. In the system  800  of  FIG. 8 , double-wide process modules  802  include two different entries  804 , each having an isolation valve for selectively coupling an interior of the process module  802  to an external environment. As depicted, the external environment of  FIG. 8  includes a single volume  806  (i.e., a shared or common environment without isolation valves) that contains two robots  808  and a buffer  810 . In this embodiment, the robots  808  may hand off to one another using shelves or the like within the buffer  810 , as generally described above. It will be understood that the robots  808  may also, or instead, directly hand off to one another. Each process module  802  may concurrently hold and process a number of wafers, such as two wafers, three wafers, four wafers, and so forth. It will be readily understood that two wafers may be directly accessed by the two robots  808  and entries  804 , permitting parallel handling of wafers through the side-by-side entries  804 . Thus, for example, two wafers (or more wafers using, e.g., batch end effectors or the like), may be simultaneously transferred from the process module  802  depicted on the left of  FIG. 8  and the process module  802  depicted on the right of  FIG. 8 . In addition, the dual processing chamber may advantageously employ shared facilities, such as gasses, vacuum, water, electrical, and the like, which may reduce cost and overall footprint. This arrangement may be particularly useful for a module  802  having long process times (for example, in the range of several minutes) by permitting concurrent processing and/or handling of multiple wafers. 
       FIG. 9  shows a layout for a dual-entry process module. In the embodiment of  FIG. 9 , the robotic handlers are in chambers  902  isolated from one another by a buffer  904  with isolation valves  906 . This configuration of robotics provides significant advantages. For example, the buffer  904  may be isolated to accommodate interim processing steps such as metrology or alignment, and may physically accommodate more wafers. In addition, this arrangement permits one of the robotic handlers to access a load lock/EFEM in isolation from the other robotic handler and process modules. However, this configuration requires greater separation between the robotic handlers, and requires a correspondingly wider process module  908 . As noted above, various internal transport mechanisms may be provided within the process module  908  to permit movement of wafers within the module to a position close to the entry or entries. However, in some embodiments, the process module  908  may only process two wafers simultaneously. 
     It will be understood that the embodiments of  FIGS. 8-9  may be readily adapted to accommodate three, four, or more entries with suitable modifications to entries, modules, and robotics. All such variations are intended to fall within the scope of this disclosure. As with other process modules described herein, these modules may also be readily adapted to batch processing by providing, for example, vertically stacked shelves and robots with dual or other multiple end effectors. 
       FIG. 10  shows a process module with an over-sized entry. In the embodiment of  FIG. 10 , an entry  1002  to a process module  1004  may be substantially wider than the diameter of wafers handled by the system  1000 . In general, the increased width of the entry  1002  and a corresponding isolation valve permits linear access by a robot  1006  to more of the space within an interior chamber of the process module  1004 . In embodiments, the entry  1002  may have a width that is 50% greater than the diameter of a wafer, twice the diameter of a wafer, or more than twice the diameter of a wafer. In embodiments, the entry  1002  has a width determined by clearance for linear robotic access (with a wafer) to predetermined positions within the process module  1004 , such as the corners of the module  1004  opposing the entry  1002 , or other positions within the module  1004 . While it is possible for robots to reach around corners and the like, linear access or substantially linear access simplifies robotic handling and requires less total length of links within a robotic arm. In one aspect, two such process modules  1004  may share a robotic handler, thereby permitting a high degree of flexibility in placement and retrieval motions for wafers among the modules  1004 . 
       FIG. 11  shows a dual entry process module. Each process module  1102  may be a dual-entry process module having two entries as described, for example with reference to  FIG. 9  above. In the embodiment of  FIG. 11 , a single robot  1104  may service each entry  1106  of one or more of the process modules  1102 . Due to the long reach requirements, the robot  1104  may include a four-link SCARA arm, a combination of telescoping and SCARA components, or any other combination of robotic links suitable for reaching into each entry  1106  to place and retrieve wafers in the process module(s)  1102 . 
       FIG. 12  shows multi-process modules. In the embodiment of  FIG. 12 , a process module  1202  may include two (or more) vacuum sub-chambers  1204  for independently processing wafers  1206 . Each vacuum sub-chamber  1204  may be separated from the other by a wall or similar divider that forms two isolated interiors within the module  1202 . Each vacuum sub-chamber  1204  may, for example include one or more independent processing tools and an independent vacuum environment in the corresponding interior chamber selectively isolated with an isolation valve. In other embodiments, each sub-chamber  1204  may include a shared tool that independently processes each wafer  1206 , so that a single environment is employed within the process module  1202  even through wafers are processed separately and/or independently.  FIG. 13  shows a multi-process module system  1300  employing a buffer  1302  between robots  1304 . The isolation entries and/or isolation valves may be substantially coplanar, such as to abut linearly arranged robotic handlers or other planar surfaces of handling systems. 
       FIG. 14  shows multi-process modules. In the embodiment of  FIG. 14 , each process module  1402  may include a number of entries  1404  for selective isolation of the processing environment within the process modules  1402 . In this embodiment, the entries  1404  for each module  1402  form planes that are angled with respect to one another. In one embodiment, these planes are oriented substantially normal to a ray from a wafer center within the module  1402  to a center of the robotic handler  1408  or a center axis of the robotic handler  1408 . This configuration provides a number of advantages. For example, in this arrangement, a single robot  1408  may have linear access to each process module  1402  sub-chamber. Further, three process modules  1402  may be arranged around a single robot  1408 . As a significant advantage, this general configuration affords the versatility of a cluster tool in combination with the modularity of individual process modules. It will be understood that while  FIG. 14  depicts each entry  1404  as servicing a single sub-chamber within a process module  1402 , the process module  1402  may have a single, common interior where multiple wafers are exposed to a single process. 
       FIG. 15  shows an in-line process module in a layout. In the system  1500 , each linear process module  1502  includes two entries  1504  on substantially opposite sides of the module  1502 . This configuration facilitates linear arrangements of modules by permitting a wafer to be passed into the module  1502  on one side, processed with a tool (which may be, for example, any of the tools described above, and retrieved from the module  1502  on an opposing side so that multiple linear modules  1502  and/or other modules may be linked together in a manner that effectively permits processing during transport from one EFEM  1506  (or the like) to another EFEM  1508 . In one embodiment, the in-line process modules may provide processes used for all wafers in the system  1500 , while the other process modules may provide optional processes used only on some of the wafers. As a significant advantage, this layout permits use of a common system for different processes having partially similar processing requirements. 
     In general, the embodiments depicted above may be further expanded to incorporate additional processing modules and transfer robot modules. The following figures illustrate a number of layouts using the process modules described above. 
       FIG. 16  shows a layout using dual entry process modules. In this system  1600 , two dual-entry process modules share a robotic handling system with a conventional, single process module. In an example deployment, the dual-entry process modules may implement relatively long processes, while the conventional module provides a single, short process. The robotics may quickly transfer a series of wafers between the buffer and the short process module while a number of wafers are being processed in the dual entry process modules. 
       FIG. 17  shows a layout using dual entry process modules. In this system  1700 , two additional process modules are added. This may be useful, for example, to balance the duty cycles of various process modules thereby providing higher utilization of each module, or provide for more efficient integration of relatively fast and slow processes or process modules within a single environment. 
       FIG. 18  shows a process module containing a scanning electron microscope. The system  1800  may include an EFEM or FOUP  1802 , an entry  1804  including an isolation valve, a robotic handler  1806 , and a scanning electron microscope  1808 . The entry  1804  may provide selective isolation to the robotic handler  1806  and/or microscope  1808 , and the robotic handler  1806  may transfer wafers between the microscope  1808  and the rest of the system  1800 . This general configuration may be employed to add a scanning electron microscope to a semiconductor manufacturing system in a manner similar to any other process module, which advantageously permits microscopic inspection of wafers without removing wafers from the vacuum environment, or to add a stand-alone microscope to a vacuum environment fabrication facility 
       FIG. 19  shows a process module containing an ion implantation system. The system  1900  may include an EFEM or FOUP  1902 , an entry  1904  including an isolation valve, a robotic handler  1906 , and an ion implantation system  1908 . The entry  1904  may provide selective isolation to the robotic handler  1906  and/or ion implantation system  1908 , and the robotic handler  1906  may transfer wafers between the ion implantation system  1908  and the rest of the system  1900 . This general configuration may be employed to add an ion implantation tool to a semiconductor manufacturing system in a manner similar to any other process module, which advantageously permits ion implantation on wafers without removing wafers from the vacuum environment, or to add a stand-alone implantation system to a vacuum environment fabrication facility. 
       FIG. 20  shows a layout using a scanning electron microscope module. As illustrated, the system  2000  includes a scanning electron microscope module  2002  with an integrated transfer robot  2004 . This hardware is incorporated into the semiconductor processing system  2000 , including additional transfer robotics, process modules, and EFEM. Such an embodiment may be useful for handling and setup of a microscopic scanning function within a vacuum processing environment, allowing the semiconductor work piece to be kept in vacuum throughout the process, including intermittent or final inspection using electron microscopy. While the illustrated system  2000  includes two dual-entry process modules as additional processing hardware, it will be understood that any suitable combination of process modules may be employed with the systems described herein. 
       FIG. 21  shows a layout using an ion implantation module. As illustrated, the system  2100  includes an ion implantation system  2102  and two robotic handlers  2104 . This hardware is incorporated into the semiconductor processing system  2100 , which includes additional transfer robotics, process modules, and two EFEMs. Such an embodiment may be useful for handling and setup of ion implantation within a vacuum-processing environment, allowing the wafer to be kept in vacuum throughout a multi-step process that includes one or more ion implantation steps. The process system is configured such that wafers that do not require ion implantation may bypass the ion implantation system through two robots and a buffer. Such a wafer may nonetheless be processed in other process modules connected to the system  2100 . 
     A linear process module  2106  may also be provided. This configuration may be particularly useful in high-throughput processes so that a bottleneck is avoided at either entry to or exit from the vacuum environment. In addition, the linear process module  2106  may be simultaneously or nearly simultaneously loaded from one entry while being unloaded from the other entry. 
       FIG. 22  illustrates a fabrication facility including a series of sensors  35002 . In many fabrication facilities such sensors  35002  are commonly used to detect whether a material  35014  is still present on a robotic arm  35018 . Such sensors  35002  may be commonly placed at each vacuum chamber  4012  entry and exit point. Such sensors  35002  may consist of a vertical optical beam, either employing an emitter and detector, or employing a combination emitter/detector and a reflector. In a vacuum handling facility, the training of robotic stations is commonly accomplished by a skilled operator who views the position of the robot arm and materials and adjusts the robot position to ensure that the material  35014  is deposited in the correct location. However, frequently these positions are very difficult to observe, and parallax and other optical problems present significant obstacles in properly training a robotic system. Hence a training procedure can consume many hours of equipment downtime. 
     Several automated training applications have been developed, but they may involve running the robotic arm into a physical obstacle such as a wall or edge. This approach has significant downsides to it: physically touching the robot to an obstacle risks damage to either the robot or the obstacle, for example many robot end effectors are constructed using ceramic materials that are brittle, but that are able to withstand very high wafer temperatures. Similarly, inside many process modules there may be objects that are very fragile and easily damaged. Furthermore, it may not be possible to employ these auto-training procedures with certain materials, such as a wafer  3   1008  present on the robot end effector. Moreover, the determination of vertical position is more difficult because upward or downward force on the arm caused by running into an obstacle is much more difficult to detect. 
     In the systems described herein, a series of sensors  35002 - 35010  may include horizontal sensors  35004 - 35010  and vertical sensors  35002 . This combination of sensors  35002 - 35010  may allow detection, for example through optical beam breaking, of either a robotic end effector, arm, or a handled object. The vertical sensor  35002  may be placed slightly outside the area of the wafer  31008  when the robotic arm  3501   8  is in a retracted position. The vertical sensor  35002  may also, or instead, be placed in a location such as a point  35012  within the wafer that is centered in front of the entrance opening and covered by the wafer when the robot is fully retracted. In this position the sensor may be able to tell the robotic controller that it has successfully picked up a wafer  31008  from a peripheral module. 
     Horizontal sensors  35004 - 35010  may also be advantageously employed. In vacuum cluster tools, horizontal sensors  35004 - 35010  are sometimes impractical due to the large diameter of the vacuum chamber, which may make alignment of the horizontal sensors  35004 - 35010  more complicated. In the systems described above, the chamber size may be reduced significantly, thus may make it practical to include one or more horizontal sensors  35004 - 35010 . 
       FIG. 23A-C  illustrates other possible locations of the horizontal sensors  35004 - 35010  and vertical sensors  35002 , such as straight across the chamber ( 36002  and  36008 ) and/or through mirrors- 36006  placed inside the vacuum system. 
       FIG. 24A-B  illustrates a possible advantage of placing the sensor  35002  slightly outside the wafer  37001  radius when the robot arm is fully retracted. During a retract motion the sensor  35002  detects the leading edge of the wafer  37001  at point “a”  37002  and the trailing edge at point “b”  37004 . These results may indicate that the wafer  37001  was successfully retrieved, but by tying the sensor  35002  signal to the encoders, resolvers or other position elements present in the robotic drive, one can also calculate if the wafer  37001  is centered with respect to the end effector. The midpoint of the line segment “a-b”  37002 ,  37004  should correspond to the center of the end effector because of the circular geometry of a wafer  37001 . If the wafer  37001  slips on the end effector, inconsistent length measurements may reveal the slippage. 
     Additionally, during a subsequent rotation and movement, a second line segment “c-d”  37008 ,  37010  may be detected when the wafer  37001  edges pass through the sensor. Again, the midpoint between “c”  37008  and “d”  37010  should coincide with the center of the end effector, and may permit a measurement or confirmation of wafer centering. 
     The above method may allow the robot to detect the wafer  37001  as well as determine if the wafer  37001  is off-set from the expected location on the end effector. 
     The combination of horizontal and vertical sensors  35002 - 35010  may allow the system to be taught very rapidly using non-contact methods: the robotic arm and end effectors may be detected optically without the need for mechanical contact. Furthermore, the optical beams can be used during real-time wafer  37001  handling to verify that wafers  37001  are in the correct position during every wafer  37001  handling move. 
     It will be understood that, while specific modules and layouts are have been described in detail, these examples are not intended to be limiting, and all such variations and modifications as would be apparent to one of ordinary skill in the art are intended to fall within the scope of this disclosure. For example, while  FIG. 12  depicts two robots in a shared common environment handling wafers for the modules  1202 , a variety of other arrangements are possible. For example, all of the entries  1204  may be serviced by a single robot as described above with reference to  FIG. 11 , or the entries  1204  may be serviced by a pair of robots separated by an isolated buffer as described above with reference to  FIG. 9 . As another example, while numerous examples are provided above of dual entry or dual process modules, these concepts may be readily adapted to three entry or three process modules, or more generally, to any number of modules consistent with a particular fabrication facility or process. 
     Further, it should be understood that the devices disclosed herein may be combined in various ways within a semiconductor fabrication system, for example to form fabrication facilities adapted to balance processing load among relatively fast and relatively slow processes, or between processes amenable to batch processing and processes that are dedicated to a single wafer. Thus, while a number of specific combinations of modules are shown and described above, it will be appreciated that these combinations are provided by way of illustration and not by way of limitation, and that all combinations of the process modules disclosed herein that might usefully be employed in a semiconductor fabrication system are intended to fall within the scope of this disclosure. 
     More generally, it will be understood that, while various features of process modules are described herein by way of specific examples, that numerous combinations and variations of these features are possible and that, even where specific combinations are not illustrated or described in detail, all such combinations that might be usefully employed in a semiconductor manufacturing environment are intended to fall within the scope of this disclosure.