Patent Publication Number: US-2012037475-A1

Title: Substrate inverting system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to a system used to rapidly invert and clean photovoltaic substrates during fabrication processes. 
     2. Description of the Related Art 
     Solar cells are photovoltaic (PV) devices that convert sunlight directly into electrical power. PV devices typically have one or more p-n junctions. Each junction comprises two different regions within a semiconductor material where one side is denoted as the p-type region and the other as the n-type region. When the p-n junction of the PV cell is exposed to sunlight (consisting of energy from photons), the sunlight is directly converted to electricity through the PV effect. PV solar cells generate a specific amount of electric power and cells are tiled into modules sized to deliver the desired amount of system power. PV modules are joined into panels with specific frames and connectors. The solar cells are commonly formed on a silicon substrate, which may be in the form of single or multicrystalline silicon substrates. A typical PV cell includes a p type silicon wafer, substrate or sheet typically less than about 0.3 mm thick with a thin layer of n-type silicon on top of a p-type region formed in a substrate. 
     The photovoltaic market has experienced annual growth rates exceeding 30% for the last ten years. Some articles have suggested that solar cell power production worldwide may exceed 10 GWp in the near future. It has been estimated that more than 95% of all photovoltaic modules are silicon wafer based. The high market growth rate in combination with the need to substantially reduce solar electricity costs has resulted in a number of challenges for inexpensively forming high quality photovoltaic devices. Therefore, one major component in making commercially viable solar cells lies in reducing the manufacturing costs required to form the solar cells by improving the device yield and increasing the substrate throughput. 
     To economically produce solar cells fabrication processes are typically integrated into highly automated modular systems which have been optimized to quickly handle and process large quantities of substrates. To fabricate a solar cell both sides of the substrate must be processed by these automated systems. To minimize process station complexity within the automated systems, substrates may be processed on only one side at a time, which necessitates the substrate be inverted to gain access to the opposite side for additional processing. Currently, inverting of substrates involves a mechanism that temporally removes the substrate entirely from the substrate production flow plane while it pivots the substrate. For example, a substrate conveyor, of automated substrate production system, places a substrate into a slot and then stops, whereupon the inverting mechanism pivots the slot along with the substrate vertically about an axis that is usually near the leading edge of the substrate. As the slot approaches vertical the substrate may slide down into a stop in the slot that is nearest the pivot point of the inverting mechanism. As the inverting mechanism pivots past vertical, the substrate falls over onto the support surface on the opposite side of the slot. The mechanism continues to pivot until the inverted substrate is inline with the substrate production transfer direction and resting on the conveyor of the automated substrate production system, which then transports the substrate to the next processing station. In other art, vacuum end effectors are positioned to secure substrates at three or four points similar during inverting operations. 
     Solar cell substrates are typically fragile and vulnerable to breakage even from minimal mechanical shocks and torsional loads. Consequently, current substrate inverting devices often minimize the potential for damage by operating at slower than desirable speed, which may directly reduce overall throughput of the automated substrate production system. Furthermore, substrate surfaces can become contaminated with processing byproducts or from other environmental sources, which compromise capture and retention of substrates during inverting steps and device yield. 
     A substrate inverting mechanism is needed that can provide positive, uniform, substrate retention, allowing the mechanism to operate extremely fast while at the same time reducing the potential for substrate damage. It is desirable for the substrate inverting mechanism to be minimal in size, and have an operational envelope that is centered about the substrate production flow plane of an automated substrate production system. In cases where additional processing of the current substrate surface is required and/or where substrates are being sorted and organized it is desirable for the substrate inverting mechanism to be capable of transporting substrates directly along the substrate production flow plane without inverting. Additionally, it is desirable to have an inverting mechanism that can continually clean interfaces that come into contact with the substrate and also facilitate cleaning of substrate surfaces. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention generally provide an apparatus for performing high-speed substrate inverting to facilitate photovoltaic fabrication processing of either substrate surface, comprising two stacked conveyors which are rotated in tandem and positioned to engage one or both major surfaces of a substrate to enable loading, inverting, and dispensing of substrates traveling along the substrate production flow plane of an automated production system. 
     Embodiments of the invention may further provide an apparatus for inverting substrates, comprising a first conveyor assembly having a first supporting surface and a first belt disposed over the first supporting surface, a second conveyor assembly having a second supporting surface and a second belt disposed over the second supporting surface, wherein the first supporting surface is adjacently positioned over the second supporting surface to form a gap, at least one first actuator coupled to the first belt so that the first belt can be positioned relative to the first supporting surface, and at least one second actuator coupled to the second belt so that the second belt can be positioned relative to the second supporting surface; and an inversion actuator that is coupled to the first conveyor assembly and the second conveyor assembly and is adapted to orient the first conveyor assembly and second conveyor assembly so that the first supporting surface can be disposed over the second supporting surface, or the second supporting surface can be disposed over the first supporting surface. 
     Embodiments of the invention may further provide a method for inverting substrates, comprising positioning a substrate having a surface in a face-down orientation on a system conveyor, transferring the substrate from the system conveyor to a first surface of a porous belt found in a first conveyor assembly, restraining the surface of the substrate against the first surface of the porous belt by applying a vacuum to a second surface of the porous belt, reorienting the surface of the substrate in a face-up orientation by rotating the first conveyor assembly, and disposing the substrate on a first surface of a porous belt found in a second conveyor assembly after reorienting the substrate. 
     Embodiments of the invention may further provide a method for inverting substrates, comprising positioning a substrate having a first substrate surface in a face-down orientation in a gap formed between a first conveyor assembly and a second conveyor assembly, wherein the first substrate surface is in contact with a first surface of a belt contained in the first conveyor assembly when it is positioned in the gap, reorienting the first conveyor assembly and the substrate so that the first substrate surface is in a face-up orientation, and disposing the substrate on a first surface of a belt in the second conveyor assembly after reorienting the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is an isometric view of a substrate inverter system positioned along the substrate production transfer direction according to one embodiment of the invention. 
         FIG. 2  is an isometric view of one substrate inverter system according to one embodiment of the invention. 
         FIGS. 3A-3C  are isometric schematic views of a substrate inverting process according to one embodiment of the invention. 
         FIGS. 4A and 4B  illustrate a tandem conveyor motion sequence according to one embodiment of the invention. 
         FIGS. 5A and 5B  illustrate a tandem conveyor motion sequence according to one embodiment of the invention. 
         FIG. 6  is an isometric view of one substrate inverter system according to another embodiment of the invention. 
         FIGS. 7A-7C  are isometric schematic views of a substrate inverting process according to one embodiment of the invention. 
         FIGS. 8A and 8B  illustrate a tandem conveyor motion sequence according to one embodiment of the invention. 
         FIGS. 9A and 9B  illustrate a tandem conveyor motion sequence according to one embodiment of the invention. 
         FIG. 10  illustrates a schematic view of the tandem conveyors according to one embodiment of the invention. 
         FIG. 11  illustrates an exploded isometric schematic view of a substrate inverter system according to one embodiment of the invention. 
         FIGS. 12A-12C  illustrate a belt actuator motion sequence according to one embodiment of the invention. 
         FIGS. 13A and 13B  illustrate a cleaning process according to one embodiment of the invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention generally provide a small footprint apparatus for performing high-speed substrate inversion to facilitate photovoltaic fabrication processing on either major surface of a substrate in an automated production system. In one embodiment, the substrate inversion apparatus, or substrate inverter system, comprises two stacked conveyors which are rotated in tandem to enable loading, inverting, and dispensing of the substrates from the substrate inverter system. In one embodiment, the stacked conveyors are positioned to simultaneously engage both surfaces of a substrate during the orientation operation in the automated production system. In another embodiment, the stacked conveyors have a sufficient gap, between the upper and lower conveyor belts, so that the lower conveyor belt engages, captures, transports, inverts, and dispenses a substrate through contact with only one of the major surface of the substrate. In another embodiment, the apparatus may further have provisions to clean the conveyor belts and remove processing and environmental debris from the surface of a substrate. 
       FIG. 1  is an isometric view that illustrates one embodiment of a substrate inverter system  100 . In this configuration the substrate inverter system  100  is positioned to receive and transfer substrates from automatic production system conveyors  102 , which are used to transfer substrates between various processing stages (not shown) in a larger substrate processing system, such as a Softline™ tool available from Baccini S.p.A. Conveyor assemblies  110 A and  110 B are generally positioned above and below a transfer plane that is aligned along a substrate transfer direction A to engage and support at least one surface of a substrate that is to be inverted in the substrate inverter system  100 . The conveyor assemblies  110 A and  110 B are aligned in a stacked orientation with a gap “G” formed there between to accept, transfer, invert, and dispense substrates traveling along the substrate transfer direction A. Embodiments of the present substrate inverter system  100  can invert the substrate  104 B through rotation near or about either of substrate centerlines  106 ,  108 . Inverting through rotation about either substrate centerline  106  or  108  minimizes and balances the moments of inertia being induced on the edges of substrate  104 B, thus facilitating high speed inversion. The stacked tandem conveyor assemblies  110 A and  110 B are generally configured to be inline with the substrate transfer direction A to enable a substrate  104 A to be loaded into the substrate inverter system  100  while an already inverted substrate  104 C is simultaneously exiting the substrate inverter system  100  to an automatic production system conveyor  102 . To minimize the stress delivered to a substrate and conveyor belt wear the velocities of the conveyor belts on the conveyor assemblies  110 A and  110 B are speed matched to the automated substrate production system conveyors  102  during exchanges. Additionally, the stacked conveyor assemblies  110 A and  110 B facilitate the option of transferring a substrate through the substrate inverter system  100  without performing a substrate inversion step. It should be noted that inverting a substrate about one of the substrate centerlines  106  or  108  also serves to minimize the volume needed within the automated production system. The inline operation of the small footprint substrate inverter system  100  allows substrates to be quickly oriented and conveyed along the substrate transfer direction A. 
       FIG. 2  illustrates one embodiment of a substrate inverter system  100  having tandem conveyor assemblies  110 A and  110 B positioned coplanar with the substrate transfer direction A. The substrate inverter system controller  120 , using rotational actuators  152  ( FIG. 11 ) mounted inside each conveyor assembly  110 A and  110 B activates the conveyor belts  170  to facilitate loading and dispensing substrates along the substrate transfer direction A. If substrate inverting is required, the conveyor belts  170  are halted when the substrate is positioned between the conveyor belts, so that a vacuum may be applied to further secure the substrate to at least one of the conveyor belts  170 . The substrate inverter system  100  inverts the substrate by rotating the tandem conveyors in unison using a rotational actuator  122  ( FIG. 11 ) which is mounted inside the substrate inverter system controller  120  and is coupled to the supporting structural elements within each of the conveyor assemblies  110 A and  110 B. The inverting operation can be performed about any rotation axis on, or proximate to, the substrate centerline. In this embodiment, inverting rotation takes place about substrate centerline  106  which lies 90 degrees from the substrate transfer direction A. Inverting substrates about any axis which is consistent with substrate centerline  106  results in the pre-inverted leading edge of the substrate becoming the post inverted trailing edge, with respect to the substrate transfer direction A. In automated substrate production systems, control of substrate edge orientation with respect to the substrate transfer direction A may be desirable for processing. Additionally, this method allows substrates traveling on the substrate transfer direction A to be loaded, inverted, and unloaded from either side of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 3A  illustrates an inverting method provided by the substrate inverter system illustrated in  FIG. 2  where substrate  104 B is loaded along path B 1  that is aligned along the substrate transfer direction A into a position between the conveyor assemblies  110 A and  110 B within the substrate inverter system  100  ( FIG. 2 ). The substrate inverter system controller  120  then sequentially rotates the conveyor assemblies  110 A and  110 B along a 180 degree clockwise path B 2  about the substrate centerline  106 . The inverted substrate  104 B is then dispensed along path B 4  while another substrate is simultaneously being loaded into the substrate inverter system. The substrate inverter system controller  120  then sequentially rotates the conveyor assemblies  110 A and  110 B along a 180 degree counterclockwise path B 3  to invert a second substrate. The second inverted substrate is then dispensed along path B 4  onto the substrate transfer direction A while another substrate is simultaneously being loaded into the substrate inverter system. 
       FIG. 3B  illustrates an inversion method provided by the substrate inverter system illustrated in  FIG. 2  where substrate  104 B is loaded along path C 1  that is aligned along the substrate transfer direction A into the inverting position within the substrate inverter system  100 . The substrate inverter system controller  120  then rotates the conveyor assemblies  110 A and  110 B in 180 degree clockwise increments along paths C 2  and C 3  about the substrate centerline  106  to sequentially invert each substrate placed between the conveyor assemblies  110 A and  110 B. Alternately, the substrate inverter system controller  120  could also rotate the conveyor assemblies  110 A and  110 B in 180 degree counterclockwise increments about the substrate centerline  106 . In one embodiment, each of the sequentially inverted substrates  104 B are then dispensed along path C 4  while another substrate is simultaneously being loaded into the substrate inverter system. 
       FIG. 3C  illustrates a direct substrate transfer method provided by the substrate inverter system illustrated in  FIG. 2  where substrate  104 B is loaded along path F 1  that is aligned along the substrate transfer direction A, transferred through the substrate inverter along path F 2  where it is then dispensed along path F 3 , while another substrate is simultaneously being loaded into the substrate inverter system. 
       FIG. 4A  illustrates the rotation of conveyor assemblies  110 A and  110 B to provide the rotation along path B 2  illustrated in  FIG. 3A  by use of a rotational actuator  122  ( FIG. 11 ) that is coupled to conveyor assemblies  110 A and  110 B. For clarity the left side of conveyor assembly  110 A has been marked with a dark “dot.” In one example, initially conveyor assembly  110 A is positioned above conveyor assembly  110 B and the conveyor assemblies  110 A and  110 B are positioned and aligned to accept a substrate traveling along the substrate transfer direction A. In this case rotation is performed in a 180 degree clockwise direction about the substrate centerline  106  and reoriented to the substrate transfer direction A whereupon the inverted substrate is transferred along the substrate transfer direction A. This rotation results in conveyor assembly  110 B being positioned above conveyor assembly  110 A. This method allows the next substrate to be loaded into the substrate inverter system while simultaneously dispensing the inverted substrate onto the substrate transfer direction A. Additionally, this method allows substrates traveling on the substrate transfer direction A to be loaded, inverted, and dispensed from either side of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would be otherwise be required to reset the inverter to collect another substrate. 
       FIG. 4B  illustrates the rotation of tandem conveyor assemblies  110 A and  110 B to provide rotation along path B 3  illustrated in  FIG. 3A  using a rotational actuator  122  ( FIG. 11 ) contained within the substrate inverter system  100 . In one example, initially conveyor assembly  110 B is positioned above conveyor assembly  110 A and the conveyors  110 B and  110 A are positioned and aligned to accept a substrate that is transferred along the substrate transfer direction A. In this case rotation is performed in a 180 degree counterclockwise direction about the substrate centerline  106 , whereupon the inverted substrate is dispensed in the substrate transfer direction A. This rotation results in conveyor assembly  110 A being repositioned above conveyor assembly  110 B, consistent with  FIG. 4A , so that the process sequence can be repeated. This method allows the next substrate to be loaded into the substrate inverter system  100  while simultaneously dispensing the inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates traveling on the substrate transfer direction A to be loaded, inverted, and dispensed from either of the conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 5A  illustrates the rotation of conveyor assemblies  110 A and  110 B to provide rotation along path C 2  in  FIG. 3B  using a rotational actuator  122  ( FIG. 11 ) contained in the substrate inverter system  100 . For clarity the left side of conveyor assembly  110 A has been marked with a “dot.” In one example, initially the conveyor assembly  110 A is positioned over conveyor assembly  110 B and the tandem conveyor assemblies  110 A and  110 B are positioned and aligned to accept a substrate traveling along the substrate transfer direction A. In this case rotation is performed in a 180 degree clockwise direction about the substrate centerline  106  to reorient the substrate. This rotation results in conveyor assembly  110 B being positioned over conveyor assembly  110 A. This method allows the next substrate to be loaded into the substrate inverter system  100  while simultaneously dispensing the inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates to be loaded, inverted, and dispensed from either of the tandem conveyor assemblies  110 A and  110 B, thus avoiding the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 5B  illustrates the rotation of conveyor assemblies  110 A and  110 B to provide rotation along path C 3  as shown in  FIG. 3B  using a rotational actuator  122  ( FIG. 11 ) contained within the substrate inverter system  100 . In one example, initially conveyor assembly  110 B is positioned over conveyor assembly  110 A and the conveyors  110 B and  110 A are positioned and aligned to accept a substrate travelling along the substrate transfer direction A. In this case rotation is performed in a 180 degree clockwise direction about the substrate centerline  106 , whereupon the inverted substrate is dispensed in a substrate transfer direction A. This rotation results in conveyor assembly  110 A being repositioned over conveyor assembly  110 B, consistent with  FIG. 5A  where the process sequence is repeated. This method allows the next substrate to be loaded into the substrate inverter system  100  while simultaneously dispensing an inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates traveling along the substrate transfer direction A to be loaded, inverted, and dispensed from either of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 6  illustrates another embodiment of a substrate inverter system  600  with conveyor assemblies  110 A and  110 B being positioned coplanar with a horizontal plane that is aligned along the substrate transfer direction A. The substrate inverter system controller  120  is generally coupled to one or more rotational actuators  152  ( FIG. 11 ) mounted inside each of the conveyor assemblies  110 A and  110 B, which are each used to control the movement of the conveyor belts  170  to facilitate loading and dispensing of the substrates along the substrate transfer direction A. If substrate inversion is required, the conveyor belts  170  are halted when the substrate is positioned between the conveyor assemblies  110 A and  110 B where vacuum may be applied to a major surface of the substrate through at least one of the conveyor belts  170  to secure the substrate during the inversion process. The substrate inverter system  600  then inverts the substrate by rotating the conveyor assemblies  110 A and  110 B in unison using a rotational actuator  122  ( FIG. 11 ) which is mounted inside the substrate inverter system controller  120  and coupled to the structural components (e.g., reference numerals  151  and  159  in  FIG. 11 ) contained in each of the conveyor assembly  110 A and  110 B. In one embodiment, a ring gear (not shown) that is disposed within the housing  180  and coupled to the structural components contained in each of the conveyor assemblies  110 A and  110 B, is driven by the rotational actuator found in the substrate inverter system controller  120  to cause the conveyor assembly  110 A and  110 B and substrate to be inverted. The inversion operation can be performed about any rotation axis on, or proximate to, a substrate centerline. In one embodiment, the rotation takes place about a rotation axis that is parallel to the substrate centerline  108  which is also aligned along the substrate transfer direction A. Inverting substrates about any axis which is consistent with substrate centerline  108  results in the pre-inverted leading edge of the substrate remaining the leading edge after inversion. In automated substrate production systems, control of substrate edge orientation with respect to the substrate transfer direction A may be desirable for alignment and processing. Additionally, this method allows substrates traveling along the substrate transfer direction A to be loaded, inverted, and dispensed from either end of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. It should be noted that the conveyor assemblies  110 A and  110 B and other supporting components discussed in conjunction with  FIGS. 1 ,  2 ,  10  and  11  are similar to the components illustrated in  FIG. 6 , and thus like reference numerals have been used where appropriate. 
       FIG. 7A  illustrates an inverting method provided by the substrate inverter system  600  illustrated in  FIG. 6  where substrate  104 B is loaded along path D 1  into the inverting position within the substrate inverter system  600 . The substrate inverter system controller  120  can generally rotate the conveyor assemblies  110 A and  110 B alternately in a clockwise path D 2  and counterclockwise path D 3  about the substrate centerline  108 . In one embodiment, during processing the substrate inverter system controller  120  then sequentially rotates the conveyor assemblies  110 A and  110 B along a 180 degree clockwise path D 2  about the substrate centerline  108 . The inverted substrate  104 B is then dispensed along path D 4  onto the substrate transfer direction A while another substrate is simultaneously being loaded into the substrate inverter system. The substrate inverter system controller  120  then sequentially rotates the conveyor assemblies  110 A and  110 B along a 180 degree counterclockwise path D 3  to invert a second substrate. The second inverted substrate is then dispensed along path D 4  onto the substrate transfer direction A while another substrate is simultaneously being loaded into the substrate inverter system. 
       FIG. 7B  illustrates an inverting method provided by the substrate inverter system  600  illustrated in  FIG. 6  where substrate  104 B is loaded along path E 1  into the inverting position within the substrate inverter system  600 . The substrate inverter system controller  120  rotates the conveyor assemblies  110 A and  110 B alternately in 180 degree clockwise increments along paths E 2  and E 3  about the substrate centerline  108  to sequentially invert each substrate placed between the conveyor assemblies  110 A and  110 B. Alternately, the substrate inverter system controller  120  could also rotate the conveyor assemblies  110 A and  110 B in 180 degree counterclockwise increments about the substrate centerline  108 . The inverted substrate is then dispensed along path E 4  onto the substrate transfer direction A, while another substrate is simultaneously being loaded into the substrate inverter system  600 . 
       FIG. 7C  illustrates a direct substrate transfer method provided by the substrate inverter system  600  illustrated in  FIG. 6  where substrate  104 B is loaded along path F 1 , transferred through the substrate inverter system  600  along path F 2 , where it is then dispensed along path F 3 , while another substrate is simultaneously being loaded into the substrate inverter system. 
       FIG. 8A  illustrates the rotation of the conveyor assemblies  110 A and  110 B, viewed from a position along the substrate transfer direction A using the substrate inverter system  600  illustrated in  FIG. 6 . For clarity the left corner of conveyor assembly  110 A has been marked with a “dot.” In one example, initially conveyor assembly  110 A is positioned over conveyor assembly  110 B, and the conveyor assemblies  110 A and  110 B are positioned and aligned to accept a substrate traveling along the substrate transfer direction A. In this case rotation is performed in a clockwise direction about the substrate centerline  108  to reorient the substrate. In this case the substrate centerline  108  coincides with the substrate transfer direction A. This rotation results in conveyor assembly  110 B being positioned over conveyor assembly  110 A. This method allows the next substrate to be loaded into the substrate inverter system  600  while simultaneously dispensing the inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates traveling along the substrate transfer direction A to be loaded, inverted, and dispensed from either orientation of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would be otherwise be required to reset the inverter to collect another substrate. 
       FIG. 8B  illustrates the rotation of the conveyor assemblies  110 A and  110 B, viewed from a position along the substrate transfer direction A using the substrate inverter system  600  illustrated in  FIG. 6 . In one example, initially conveyor assembly  110 B is positioned over conveyor assembly  110 A, and the conveyor assemblies  110 B and  110 A are positioned and aligned to accept a substrate along the substrate transfer direction A. In this case rotation is performed in a counterclockwise direction about the substrate centerline  108 , whereupon the inverted substrate is delivered along the substrate transfer direction A. In this case the substrate centerline  108  coincides with the substrate transfer direction A. This rotation results in conveyor assembly  110 A being repositioned over conveyor assembly  110 B, consistent with  FIG. 8A  where the process sequence is repeated. This method allows the next substrate to be loaded into the substrate inverter system  600  while simultaneously dispensing an inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates traveling on the substrate transfer direction A to be loaded, inverted, and dispensed from either orientation of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 9A  illustrates the rotation of tandem conveyor assemblies  110 A and  110 B, viewed from a position along the substrate transfer direction A using the substrate inverter system  600  illustrated in  FIG. 6 . For clarity the left side of conveyor assembly  110 A has been marked with a “dot.” Initially conveyor assembly  110 A is positioned over conveyor assembly  110 B, and conveyor assemblies  110 A and  110 B are positioned and aligned to accept a substrate traveling along the substrate transfer direction A. In this case rotation is performed in a clockwise direction about the substrate centerline  108  whereupon the inverted substrate is then delivered along the substrate transfer direction A. This rotation results in conveyor assembly  110 B being positioned above conveyor assembly  110 A. This method allows the next substrate to be loaded into the substrate inverter system  600  while simultaneously delivering the inverted substrate along the substrate transfer direction A. Additionally, this method allows substrates traveling along the substrate transfer direction A to be loaded, inverted, and dispensed from either orientation of the tandem conveyor assemblies  110 A and  110 B, thus avoiding the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 9B  illustrates the rotation of tandem conveyor assemblies  110 A and  110 B, viewed from a position along the substrate transfer direction A using the substrate inverter system  600  illustrated in  FIG. 6 . In one example, initially conveyor assembly  110 B is positioned over conveyor assembly  110 A, and conveyor assemblies  110 A and  110 B are positioned and aligned to accept a substrate along the substrate transfer direction A. In this case rotation is performed in a clockwise direction about the substrate centerline  108  whereupon the inverted substrate is delivered along the substrate transfer direction A. This rotation results in conveyor assembly  110 A being repositioned over conveyor assembly  110 B, consistent with  FIG. 9A  where the process sequence is repeated. This method allows the next substrate to be loaded into the substrate inverter system  600  while simultaneously dispensing the inverted substrate onto the substrate transfer direction A. Additionally, this method allows substrates traveling along the substrate transfer direction A to be loaded, inverted, and unloaded from either end of the tandem conveyor assemblies  110 A and  110 B, thus eliminating the time that would otherwise be required to reset the inverter to collect another substrate. 
       FIG. 10  illustrates a schematic cross-sectional view of one embodiment of the conveyor assemblies  110 A and  110 B. In one embodiment, a conveyor belt  170  is coupled to drive shafts  200  and  202  contained in conveyor assembly  110 A, and a second conveyor belt  170  is coupled to drive shafts  204  and  206  contained in conveyor assembly  110 B. In one embodiment, a rotational actuator  152  ( FIG. 11 ), which is controlled by the substrate inverter system controller  120 , is coupled to one of the drive shafts  200  and  202  in the conveyor assembly  110 A, and a second rotational actuator  152  ( FIG. 11 ), which is also controlled by the substrate inverter system controller  120 , is coupled to the drive shafts  204  and  206  in the conveyor assembly  110 B. In one embodiment, the conveyor belts  170  in each of the conveyor assemblies  110 A and  110 B are operated independently, through use of commands sent by the substrate inverter system controller  120  to each of the rotational actuators  152 . In one embodiment, the elastic properties of the conveyor belts  170 , in combination with the spacing between the two conveyor assemblies  110 A and  110 B is used to adjust for variations in substrate thickness, substrate warpage and planarity of the conveyors. 
     Additionally, each of the conveyor belts  170  may be porous to allow a fluid to be transferred from one side of a conveyor belt  170  to the other. In one embodiment, the conveyor belts  170  are formed from a soft, compliant and porous material, such as a polyurethane foam, or other similar material. In one embodiment, isolation valves  153 ,  154 , which are controlled by the substrate inverter system controller  120 , can be used to selectively control the flow of gas between the gas source  194  and the plenum  190 . In one example, a sub-atmospheric pressure (e.g., vacuum) can be created at one surface of a conveyor belt  170  due to the application of a vacuum applied to an opposing surface that is in fluid communication with a fluid source  194 . In one aspect, a substrate is captured and retained on a porous conveyor belt  170  disposed over the supporting surface  192  by providing a vacuum pressure within the ports  193 . In one configuration, the fluid source  194  is a vacuum pump, or vacuum ejector, that is adapted to provide a vacuum to a surface of the conveyor belt  170  from one or more ports  193  formed in the plenum  190 . 
     Alternatively, a gas can be delivered to a surface of a conveyor belt  170  and/or substrate due to the application of a positive gas pressure applied to an opposing surface of the conveyor belt  170  that is in fluid communication with a fluid source  194 . In one embodiment, each of the conveyor assemblies  110 A and  110 B has a plenum  190  that is used to spread and direct a flow of fluid through one or more ports  193  formed in a supporting surface  192  onto the inside surface of the conveyor belts, through the conveyor belt and to the opposing surface of the conveyor belt. In one embodiment, the gas source  194  is adapted to deliver an inert gas, such as nitrogen to a conveyor belt  170  from one or more ports  193  formed in the plenum  190 . 
     In one embodiment, the conveyor assemblies  110 A and  110 B each has at least one conveyor belt cleaning station components  160 ,  162 , and  164  that are positioned within each conveyor assembly  110 A and  110 B to optionally clean the conveyor belts  170  during transferring or maintenance activities. In one embodiment, the conveyor belt cleaning station components  160 ,  162 , and  164  can each be configured to remove any accumulated debris transferred from substrate surfaces to the conveyor belt  170 . In one configuration, the cleaning station components  160 ,  162 , and  164  use a wiping process, electrostatic particle attraction process, air knife, or chemical cleaning process to clean a surface of the conveyor belt  170 . In some cases, the collected material debris is transported away from the cleaning station components  160 ,  162 , and  164  manually or through the use of a negative pressure exhaust line (not shown). 
       FIG. 11  illustrates an exploded isometric view of one embodiment of the functional elements typically found in the substrate inverter system  100  illustrated in  FIGS. 1 and 2 . In one embodiment, the substrate inverter system controller  120  incorporates a gas source  194 , a motion sequencing module  123 , a hollow shaft rotational actuator  122 , and an electrical interface coupling slot  121 . In one embodiment, the gas source  194  comprises a vacuum control module  125  that facilitates the control and delivery of vacuum, exhaust and/or clean dry air to one the plenums  190  found in the conveyor assemblies  110 A and  110 B. In one configuration, the delivery of vacuum, exhaust, and clean dry air is delivered to one the plenums  190  using a conventional rotating fluid coupling  179  and tubing (not shown) that are positioned between the plenums  190  and fluid source  194 . In one configuration, the vacuum, exhaust and clean dry air is selectively controlled by use of one or more isolation valves  153  and  154  that are positioned between the gas source  194  and the plenums  190 . In one configuration, an isolation valve  153 ,  154  (e.g., electromechnical valve) is mounted on the structural support plate  151  found in each of the conveyor assemblies  110 A and  110 B, and is used to selectivity provide vacuum to the plenum  190  and/or the conveyor cleaning stations  160 . In one embodiment, the plenum  190 , drive shafts (e.g., reference numerals  200  and  202 ), rotational actuator  152 , and conveyor cleaning station  160  components are all supported and mounted to the structural support plates  151  and  159  so that the components in each of the conveyor assemblies  110 A and  110 B can be maintained in a desired fixed configuration. 
     The substrate inverter system controller  120  is also generally used to facilitate the control and automation of the substrate inverter system  100 ,  600 , and also other components that are coupled to the substrate inverter system  100 ,  600 . The substrate inverter system controller  120  may also include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various chamber processes and hardware (e.g., conveyors, detectors, motors, fluid delivery hardware, etc.) and monitor the system and chamber processes (e.g., substrate position, process time, detector signal, etc.). The memory is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by the substrate inverter system controller  120  determines which tasks are performable on a substrate. Preferably, the program is software readable by the substrate inverter system controller  120 , which includes code to generate and store at least substrate positional information, the sequence of movement of the various controlled hardware components, and any combination thereof. 
     The motion sequencing module  123  electrically communicates with the substrate inverter system controller  120 , and is used to control the operational modes and behaviors of the substrate inverter system  100 ,  600 , based on the software instructions and data coded and stored within the memory and task status and diagnostic information received. The motion sequencing module  123  interfaces with the hollow shaft rotational actuator  122  which is used to rotationally position the conveyor assemblies  110 A and  110 B about centerline axis  109 . In one embodiment, the centerline axis  109  is aligned with the substrate centerline  106  ( FIG. 1 ). The hollow shaft rotational actuator  122  may be a servomotor, a stepper motor, or a pneumatic rotation actuator device that has rotational position encoders and/or limit switch  124  positional feedback to define the actual rotational position of the conveyor assemblies  110 A and  110 B. In one embodiment, the motion sequencing module  123  also interfaces with the rotational actuators  152  which are coupled to one of the drive shafts  200 ,  202 ,  204  and/or  206  and positioned on the support plates  151  found in the conveyor assemblies  110 A and  110 B. The rotational actuators  152  may be a servomotor or a stepper motor that are each adapted to drive and control the rotational position of a conveyor belt  170  by commands sent from the substrate inverter system controller  120 . In one configuration, the rotational actuators  152  are coupled directly to a primary conveyor drive shaft in each of the conveyor assemblies  110 A and  110 B, such the conveyor drive shaft  200  in conveyor assembly  110 A and conveyor drive shaft  206  in conveyor assembly  110 B. Drive belts  205  may be used to positively couple the rotation of the primary conveyor belt drive shafts  200 ,  206  to the secondary conveyor belt drive shafts  202 ,  204  in each conveyor assembly  110 A and  110 B. In one configuration, the rotational actuators  152  are each rotationally coupled to its respective conveyor belt  170  through the friction created between the conveyor belt  170  and the primary conveyor drive shafts  200 ,  204 , due to a pre-applied tension created between the conveyor belt  170  and the drive shafts  200  and  202 , or drive shafts  204  and  206 . 
     In one embodiment, electrical connections made between the motion sequencing module  123  and the various electrical components in the conveyor assemblies  110 A and  110 B can be provided through a flexible cable harness (not shown). The electrical interconnection can be maintained through the use of the flexible cable harness disposed through a electrical interface coupling slot  121  located on the substrate inverter system controller  120 , or through the use a rotating electrical interface  132 , such as a slip ring type connection or mercury type rotation feed-through. 
       FIGS. 12A through 12C  illustrate one embodiment of an operation sequence in which the conveyor assemblies  110 A and  110 B are used to load, invert, and deliver a substrate along the substrate transfer direction A.  FIG. 12A  illustrates one example of a loading operation which starts with the conveyor assembly  110 A positioned over conveyor assembly  110 B. During the loading operation the conveyor belt drive shafts  200 ,  202 ,  204 , and  206  are operated at substantially the same speed, and in a direction “H” that is consistent with the automatic production system conveyors  102  ( FIG. 1 ). This speed matching serves to minimize the stress delivered to the substrates, and minimize the particles generated from the abrasion of the conveyor belt surfaces and the substrate “S” surface during the loading operation. 
     As illustrated in  FIG. 12B , during the inversion process the conveyor drive shafts  200 ,  202 ,  204 , and  206  are halted with the substrate “S” positioned between the conveyor assemblies  110 A and  110 B. Vacuum may be applied to further secure the substrate “S” to a conveyor belt  170  and its respective supporting surface  192  in at least one of the conveyor assemblies  110 A and  110 B. Securing the substrate to at least one of the supporting surfaces  192  can further facilitate high speed inversion of the substrate. The substrate “S” is then inverted by use of the hollow shaft rotational actuator  122  ( FIG. 11 ) that is used to rotate the conveyor assemblies  110 A and  110 B and the secured substrate. In one configuration, after the substrate has been re-oriented the vacuum applied to the substrate “S” is then released to allow the substrate “S” and conveyor belt  170  to be freely moved during the subsequent dispensing operation step. In one example, the substrate “S” is released from the supporting surface  192  contained within the conveyor assembly  110 B so that the other major surface of the substrate “S” can now primarily contact, or drop-on, the surface of the conveyor belt  170  found in the conveyor assembly  110 A. 
       FIG. 12C  illustrates the post inverted substrate “S” dispensing operation in which the conveyor belt drive shafts  200 ,  202 ,  204 , and  206  are operated at substantially the same speed so that the substrate “S” can be moved in a direction “H” at a consistent speed with the automatic production system conveyors  102  ( FIG. 1 ). Matching the speed of the conveyor belts  170  and the automatic production system conveyors  102  serves to minimize the stress provided to the substrate(s) and the deterioration (caused by rubbing abrasion) of conveyor belt  170  surfaces during the substrate exchange processes. During the dispensing operation another substrate may be simultaneously loaded from the substrate transfer direction A. 
       FIGS. 13A and 13B  illustrate one embodiment of substrate inverter system where at least one surface of the substrate “S” is cleaned. In one case, the conveyor belt  170  in the conveyor assembly  110 B is held stationary and a vacuum is applied to the plenum  190  to secure the substrate “S” to the supporting surface  192  in conveyor assembly  110 B, while the conveyor belt  170  in the conveyor assembly  110 A is moved in one direction, or alternating directions, across a surface of the substrate “S”. In another case, conveyor belt  170  in the conveyor assembly  110 B is held stationary and a vacuum is applied to the plenum  190  to secure the substrate “S” to the supporting surface  192  in conveyor assembly  110 A, while the conveyor belt  170  of conveyor assembly  110 B is moved in one direction, or alternating directions, across a surface of the substrate “S”. 
     In one embodiment, conveyor belt  170  cleaning can be performed through a combination of brush like wiping, electrostatic, or chemical means provided from the cleaning source assembly  162  and/or through a positive pressure differential applied across the conveyor belt  170  from a pressure supplied by the fluid source  164  which can direct clean dry air through the backside of the conveyor belt  170  to dislodge particles. Any collected materials can be transported away from the cleaning station manually or through a negative pressure exhaust line (not shown). In one embodiment, the cleaning source assembly  162  is coupled to a fluid source that is adapted to direct a fluid, such as a gas to a surface of the conveyor belt  170  found in one of the conveyor assemblies  110 A and  110 B. 
     Referring to  FIG. 1 , in one embodiment the conveyor assemblies  110 A and  110 B are aligned in a stacked orientation with a gap “G” formed there between to accept, transfer, invert, and dispense substrates traveling along the substrate transfer direction A. In one embodiment, the gap “G” formed between the conveyor assemblies  110 A and  110 B is preset so that the a substrate will only come into contact with the conveyor assembly  110 A,  110 B, and its conveyor belt  170 , that is positioned in a face-up orientation. For example, the substrate  104 B will contact the conveyor belt  170  in the conveyor assembly  110 B (e.g., face-up orientation) when the substrate inverter system  100  is oriented as shown in  FIG. 1 . As shown in  FIG. 1 , the conveyor assembly  110 A is in a face-down configuration. In one example, the gap “G” is set just large enough so that a substrate that has a standard thickness and warpage will not contact the conveyor belt  170  in the opposing conveyor assembly (e.g., conveyor assembly  110 A in  FIG. 1 ) when it is positioned on a supporting conveyor assemblies (e.g., conveyor assembly  110 B in  FIG. 1 ). This configuration may be useful to prevent particle generation due to abrasion of the unsupported surface of the substrate as it is loaded between the conveyor assemblies  110 A and  110 B, and also minimize the particle generation due to the distance the substrate will have to shift as it is transferred from one conveyor assembly to the other due to gravity during the inversion process. 
     In another embodiment, the gap “G” formed between the conveyor assemblies  110 A and  110 B is preset so that the substrate  104 B will contact both of the conveyor belts  170  in the conveyor assemblies  110 A and  110 B during the inversion process. For example, the gap “G” is set to a nominal distance equal to or just smaller than the thinnest possible substrate to assure that contact is always maintained between the conveyor belts  170  and the substrate  104 B. In this configuration, it is generally desirable to use a conveyor belt  170  that is formed from a compliant material, such as polyurethane foam. This conveyor assembly configuration may be useful to minimize particle generation and/or the possibility of damaging fragile substrates by preventing the substrate from shifting its position between the conveyor assemblies  110 A and  110 B during the inversion process. 
     In yet another embodiment, the gap “G” formed between the conveyor assemblies  110 A and  110 B is adjustable during one or more parts of the inversion process (e.g., loading, inversion, unloading) by allowing at least one of the conveyor assemblies  110 A,  110 B to be moved relative to the other conveyor assembly  110 B,  110 A. In one embodiment, a gap adjusting actuator  178  (e.g., linear motor, air cylinder) is coupled to the support components (e.g., support plates  151  and  159 ) in at least one of the conveyor assemblies  110 A and  110 B, and is thus configured to provide relative motion between the conveyor assemblies  110 A and  110 B to adjust the gap “G” formed there between. This configuration may be useful to minimize particle generation and/or the possibility of damaging the fragile substrate by bringing the conveyor assemblies into positive contact with the substrate during one or more parts of the inversion process. In another embodiment, the adjustable gap configuration is useful to facilitate one or more portions of the cleaning process discussed above in conjunction with  FIGS. 13A and 13B . 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.