Patent Publication Number: US-2010111650-A1

Title: Automatic substrate loading station

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is continuation-in-part of the co-pending U.S. patent application Ser. No. 12/023,572 (Docket No. 11978), filed Jan. 31, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to the manufacture of semiconductor devices, such as light emitting diodes (LEDs). More particularly, embodiments of the present invention relate to method and apparatus for loading and unloading substrates to a substrate processing system. 
     2. Description of the Related Art 
     Semiconductor devices are generally formed on some kind of substrates, such as semiconductor substrates, glass substrates or sapphire substrates. During semiconductor manufacturing, substrates generally are loaded into a processing system, processed in the processing system, and unloaded from the processing system. The processing system may be a single chamber, or a cluster tool having one or more transfer chambers connected to two or more processing chambers. 
     During processing, substrates may be transferred substrate by substrate or batch by batch. For example, substrates used in manufacturing of light emitting diodes (LED), such as sapphire substrates, are usually transferred by batch. A plurality of substrates are disposed and transferred in a substrate carrier in a processing chamber or a cluster tool during processing. The substrate carrier may have a plurality of pockets, each pocket adapted to retain a substrate and allow a processing surface exposed to processing environment in a processing chamber. 
     Traditionally, sapphire substrates used in forming LED devices are manually loaded into a substrate carrier, then being transferred to a processing chamber or a processing system having multiple processing chambers. After processing, the substrates are manually unloaded from the substrate carrier. The processes are tedious and prone to human error. 
     Embodiments of the present invention provide method and apparatus of automatic loading and unloading substrates to a substrate carrier. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention generally relate to the manufacture of semiconductor devices, such as light emitting diodes (LEDs). More particularly, embodiments of the present invention relate to method and apparatus for loading and unloading substrates to a substrate processing system. 
     One embodiment of the present invention provides a substrate loading station comprising a cassette handling mechanism, wherein the cassette handling mechanism supports one or more substrate storage cassettes and moves each of the one or more substrate storage cassettes into and out of a loading position, a substrate aligner configured to align a substrate, a first robot configured to transfer substrates between the substrate aligner and the substrate storage cassettes in the loading position, a carrier tray aligner configured to support and rotate a carrier tray, wherein the carrier tray aligner rotates the carrier tray to position the carrier tray in condition for substrate transferring, and a second robot configured to transfer substrates between the substrate aligner and the carrier tray disposed on the carrier tray aligner. 
     Another embodiment of the present invention provides a substrate processing system comprising a transfer chamber defining a transfer region, wherein the transfer region maintains a vacuum environment, one or more processing chambers coupled to the transfer chamber, where the one ore more processing chambers are operable to form one or more compound nitride semiconductor layers on a substrate, a load lock chamber coupled to the transfer chamber, wherein the load lock chamber comprises a first slit valve and a second slit valve, and the load lock chamber is connected to the transfer region via the first slit valve, a robot disposed in the transfer region configured to transfer substrate carrier trays among the load lock chamber and the one or more processing chambers, and a loading station connected to the load lock chamber via the second slit valve. The loading station comprises a cassette handling mechanism, wherein the cassette handling mechanism supports one or more substrate storage cassettes and moves each of the one or more substrate storage cassettes into and out of a loading position, a substrate aligner configured to align a substrate, a first robot configured to transfer substrates between the substrate aligner and the substrate storage cassettes in the loading position, a carrier tray aligner configured to support and rotate a substrate carrier tray, wherein the carrier tray aligner rotates the carrier tray to position the substrate carrier tray in condition for substrate transferring, a second robot configured to transfer substrates between the substrate aligner and the substrate carrier tray disposed on the carrier tray aligner, and a third robot configured to transfer a substrate carrier tray between the carrier tray aligner and the load lock chamber. 
     Yet another embodiment of the present invention provides a method for handling substrates comprising disposing a substrate carrier tray having a plurality of substrate pockets on a carrier aligner and rotating the substrate carrier tray to a transferring position, disposing one or more substrate storage cassettes on a cassette carousel, rotating the cassette carousel to position one substrate storage cassette in a loading position, transferring a substrate from the substrate storage cassette in the loading position to a substrate aligner, aligning the substrate in the substrate aligner, and transferring the substrate in the substrate aligner to the substrate carrier tray on the carrier aligner. 
    
    
     
       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 a schematic plan view of a processing system in accordance with one embodiment of the present invention. 
         FIG. 2  is a schematic top view of an automatic substrate loader in accordance with one embodiment of the present invention. 
         FIG. 3  is a schematic sectional side view of the automatic substrate loader of  FIG. 2 . 
         FIG. 4  is a schematic top view of a substrate carrier disposed in a substrate carrier aligner in accordance with one embodiment of the present invention. 
         FIG. 5  is a flow chart showing a method for loading a substrate carrier in accordance with one embodiment of the present invention. 
         FIG. 6  is a flow chart showing a method for unloading a substrate carrier in accordance with one embodiment of the present 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 disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention generally relate to the manufacture of semiconductor devices, such as light emitting diodes (LEDs). More particularly, embodiments of the present invention relate to method and apparatus for loading and unloading substrates to a substrate processing system. 
     The present invention generally provides an apparatus and method for simultaneously processing substrates using a multi-chamber processing system (e.g. a cluster tool) that has an increased system throughput, increased system reliability, and increased substrate to substrate uniformity. 
     In one embodiment, the multi-chamber processing system is adapted to fabricate compound nitride semiconductor devices in which a substrate is disposed in a HVPE chamber where a first layer is deposited on the substrate and then the substrate is transferred to a MOCVD chamber where a second layer is deposited over the first layer. In one embodiment, the first layer is deposited over the substrate with a thermal chemical-vapor-deposition process using a first group-III element and a nitrogen precursor and the second layer is deposited over the first layer with a thermal chemical-vapor deposition process using a second group-III precursor and a second nitrogen precursor. Although described in connection to a processing system that comprises one MOCVD chamber and one HVPE chamber, alternate embodiments may integrate one or more MOCVD and HVPE chambers. 
     In one embodiment, the multi-chamber processing system comprises an automatic substrate loader for loading and unloading substrates to and from the multi-chamber processing system. The automatic substrate loader comprises a cassette handling mechanism, a substrate aligner configured to align a substrate, and a carrier tray aligner. The automatic substrate loader further comprises a first robot configured to transfer substrates between the substrate aligner and the substrate storage cassettes, and a second robot configured to transfer substrates between the substrate aligner and the carrier tray disposed on the carrier tray aligner. The automatic substrate loader further comprises a third robot configured to transfer a substrate carrier tray between the automatic substrate loader and a substrate processing system. In one embodiment, the cassette handling mechanism, the substrate aligner and the carrier tray aligner are arranged to enable the first, second, and third robots to have only linear motions therefore simplifies the system. 
       FIG. 1  a schematic plan view of a processing system  200  in accordance with one embodiment of the present invention. The processing system  200  comprises a transfer chamber  206  housing a robot assembly  217 , and two or more processing chambers coupled with the transfer chamber  206 , such as a MOCVD chamber  202  and a HVPE chamber  204 . The processing system  200  further comprises a load lock chamber  208  coupled with the transfer chamber  206 , a batch load lock chamber  209  also coupled to the transfer chamber  206 . The load lock chamber  208  provides an interface between an outside atmospheric environment and a controlled environment in the transfer chamber  206 . The batch load lock chamber  209  is configured for storing substrates. The processing system  200  further comprises a loading station  210  coupled to the load lock chamber  208  and configured for loading substrates to be processed and unloading processed substrate via with the load lock chamber  208 . The processing system  200  may further comprise a system controller  260  configured to control and monitor the operation of the entire system. 
     The transfer chamber  206  may define a transfer region  215 . The transfer region  215  may be maintained at a vacuum condition during processing. The transfer chamber  206  comprises a robot assembly  217  disposed in the transfer regions  215  and operable to pick up and transfer substrates between the load lock chamber  208 , the batch load lock chamber  209 , the MOCVD chamber  202  and the HVPE chamber  204 . The movement of the robot assembly  217  may be controlled by a motor drive system, which may include a servo or stepper motor. 
     Each processing chamber comprises a chamber body (such as element  212  for the MOCVD chamber  202  and element  214  for the HVPE chamber  204 ) forming a processing region where a substrate is placed to undergo processing, a chemical delivery module (such as element  216  for the MOCVD chamber  202  and element  218  for the HVPE chamber  204 ) from which gas precursors are delivered to the chamber body, and an electrical module (such as element  220  for the MOCVD chamber  202  and element  222  for the HVPE chamber  204 ) that includes the electrical system for each processing chamber of the processing system  200 . The MOCVD chamber  202  is adapted to perform CVD processes in which metalorganic compounds react with metal hydride compounds to form thin layers of compound nitride semiconductor materials. The HVPE chamber  204  is adapted to perform HVPE processes in which gaseous metal halides are used to epitaxially grow thick layers of compound nitride semiconductor materials on heated substrates. In alternate embodiments, one or more additional chambers  270  may be coupled with the transfer chamber  206 . These additional chambers may include, for example, anneal chambers, clean chambers for cleaning carrier plates, or substrate removal chambers. The structure of the processing system permits substrate transfers to occur in a defined ambient environment, including under vacuum, in the presence of a selected gas, under defined temperature conditions, and the like. 
     The load lock chamber  208  provides an interface between the atmospheric environment of the load station  210  and the controlled environment of the transfer chamber  206 . Substrates are transferred between the load lock chamber  208  and the load station  210  via a first slit valve and between the load lock chamber  208  and the transfer chamber  206  via a second slit valve. The load lock chamber  208  comprises a carrier support adapted to support incoming and outgoing carrier trays thereon. In one embodiment, the load lock chamber  208  may comprise multiple carrier supports that are vertically stacked. To facilitate loading and unloading of a carrier tray, the carrier support may be coupled to a stem vertically movable to adjust the height of the carrier support. The load lock chamber  208  is coupled to a pressure control system which pumps down and vents the load lock chamber  208  to facilitate passing the substrate between the vacuum environment of the transfer chamber  206  and the substantially ambient (e.g., atmospheric) environment of the load station  210 . In addition, the load lock chamber  208  may also comprise features for temperature control, such as a degas module to heat substrates and remove moisture, or a cooling station for cooling substrates during transfer. Once a carrier tray loaded with substrates has been conditioned in the load lock chamber  208 , the carrier plate may be transferred into the MOCVD chamber  202  or the HVPE chamber  204  for processing, or to the batch load lock chamber  209  where multiple carrier plates are stored in standby for processing. 
     The batch load lock chamber  209  may have a chamber body defining a cavity and a storage cassette moveably disposed within the cavity. The storage cassette comprises a plurality of storage shelves supported by a frame. In one embodiment, the storage shelves are spaced vertically apart and parallel within the storage cassette to define a plurality of storage spaces. Each substrate storage space is adapted to store at least one carrier tray therein supported on a plurality of support pins. The storage shelves above and below each carrier tray establish the upper and lower boundary of the storage space. 
     During processing, substrates to be processed generally are brought to the loading station  210  in cassettes, which are used to store substrates and transfer substrates among processing systems. Cassettes with substrates to be processed are loaded in the loading station  210 , where substrates are extracted from the cassettes and loaded on substrate carrier trays. The carrier trays loaded with substrates are then transferred to the load lock chamber  208 . The carrier trays loaded with the substrates are then picked up by the robot assembly  217  within the transfer chamber  206 . The substrates in the carrier trays are transferred among the processing chambers  202 ,  204 , and the batch load lock chamber  209  according to the process recipe. When the process is complete, the robot assembly  217  disposed the substrates within the carrier tray back to the load lock chamber  208 . The carrier tray loaded with processed substrates is then transferred back to the loading station  210 , where the substrates are unloaded from the carrier tray and returned to empty cassettes. The cassettes with processed substrates can then be moved from the loading station  210  for subsequent processing. 
     Embodiments of the present invention provide a loading station having automatic means to complete substrate transferring between cassettes and carrier trays. 
       FIG. 2  is a schematic top view of an automatic substrate loader  300  in accordance with one embodiment of the present invention.  FIG. 3  is a schematic sectional side view of the automatic substrate loader  300  of  FIG. 2 . The automatic substrate loader  300  may be used to load and unload substrates to processing systems. The automatic substrate loader  300  may be used to load substrates of various sizes, such as 3, 4, or 6 inch substrates. In one embodiment, the automatic substrate loader  300  is adapted to load and unload substrates having diameter of about 4 inches. In another embodiment, the automatic substrate loader  300  is adapted to load and unload substrates having diameter of about 6 inches. In one embodiment, the automatic substrate loader  300  may be used in place of the loading station  210  of the processing system  200 . 
     The automatic substrate loader  300  comprises a body  301  providing a frame for components. In one embodiment, the automatic substrate loader  300  comprises a cassette carousel  310  configured to secure, support and transfer a plurality of cassettes  312 . 
     The automatic substrate loader  300  further comprises a substrate aligner  330  disposed above the cassette carousel  310 , and a cassette interfacing robot  320 . The substrate aligner  330  is configured to position a substrate in a certain orientation. The cassette interfacing robot  320  is configured to transfer substrates between the substrate aligner  330  and the cassettes  312  on the cassette carousel  310 . 
     The automatic substrate loader  300  further comprises a carrier tray aligner  350  and a carrier tray loading robot  340 . The carrier tray aligner  350  is configured to support and rotate a substrate carrier tray  303  so that a substrate pocket on the substrate carrier tray  303  is in position to be loaded or unloaded by the carrier tray loading robot  340 . The carrier tray loading robot  340  is configured to transfer substrate among the substrate aligner  330  and the substrate carrier  303  disposed on the carrier tray aligner  350 . 
     The automatic substrate loader  300  further comprises a carrier tray transferring robot  360  configured to transfer a carrier tray  303  between the carrier tray aligner  330  and a substrate processing system, such as the load lock  208  of the processing system  200 . 
     The cassette carousel  310  may be rotatable about a central axis  316 . In one embodiment, the cassette carousel  310  has a plurality of snaps  311  on a supporting surface  317 . The snaps  311  are configured to secure a plurality of cassettes  312  on the supporting surface  317 . In one embodiment, the plurality of snaps  311  are arranged to along the same radius from the central axis  316  so that the plurality of cassettes  312  are disposed in the same distance from the central axis  316 . In one embodiment, the cassette carousel  310  is configured to support and rotate twelve cassettes  312 . 
     The cassette carousel  310  is configured to rotate and position each of cassettes  312  in a loading position near the substrate aligner  330  so that substrates can be transferred between the substrate aligner  330  and the cassette  312  in the loading position. In one embodiment, each cassette  312  may have a plurality of slots, each slot configured to support a substrate  302  thereon. In one embodiment, the substrates  302  may be vertically stacked within the cassettes  312  when the cassettes  312  are disposed on the cassette carousel  310 . In one embodiment, a cassette  312  is directly below the substrate aligner  330  when in the loading position. During processing, the cassette  312  may be disposed on or removed from the cassette carousel  310  when the cassettes  312  are in a non-loading position. 
     In one embodiment, the cassette carousel  310  may have a central opening  313  formed therein. The central opening  313  allows the cassette interfacing robot  320  to be driven by drive mechanism  324  disposed under the cassette carousel  310 . 
     The cassette interfacing robot  320  comprises a robot blade  321  configured to support a substrate in a substantially horizontal orientation. In one embodiment, the robot blade  321  comprises a vacuum chuck configured to secure the substrate during transferring. 
     In one embodiment, the cassette interfacing robot  320  is configured to move the robot blade  321  horizontally and vertically. The robot blade  321  moves vertically to align with different slots in the cassette  312  in the loading position, to access the substrate aligner  330  disposed vertically above the cassette  312  in the loading position, and to drop off and to pick up a substrate to and from the cassette  312  and the substrate aligner  330 . The robot blade  321  moves horizontally to get in and out the cassette  312  and the substrate aligner  330 . 
     In one embodiment, the cassette interfacing robot  320  comprises a sensor assembly moving vertically with the robot blade  321 . The sensor assembly is configured to detect the presence of a substrate in the slots of the cassette  312  and to count the number of substrates within the cassette  312 . In one embodiment, the sensor assembly is an optical sensor comprising a light emitter  322  and a light receiver  323  disposed on opposite sides of a cassette  312  in the loading position. In one embodiment, the cassette carousel  310  has a plurality of sensor openings  314  located for each set of snaps  311 . The sensor openings  314  are configured to allow motions of the sensor assembly. 
     The substrate aligner  330  is configured to align a substrate and prepare the substrate to be loaded in a substrate carrier. In one embodiment, the substrate aligner  330  may comprise a substrate support  331  configured to rotate a substrate disposed thereon and a centering mechanism  332 . The centering mechanism  332  is configured to center the substrate on the substrate support  331 . In one embodiment, the centering mechanism  332  may comprise two alignment blocks configured to move symmetrically to a center axis  333  of the substrate support  331 . 
     For substrates with a flat, the substrate aligner  330  may be used to position the flat in a certain direction. The substrate aligner  330  may also position the substrate according to patterns formed on the substrate 
     The carrier tray aligner  350  is configured to support a substrate carrier tray  303  during loading and unloading, and to position each of a plurality of substrate pockets  372  formed in the carrier tray  303 . The carrier tray aligner  350  may comprise a carrier support  351  configured to support the carrier tray  303  and to rotate the carrier tray  303  about a central axis  353  to position a specific substrate pocket in the carrier tray  303 . The carrier tray aligner  350  further comprises a centering mechanism  352  configured to center the carrier tray  303  relative to the central axis  353  of the carrier support  351 . In one embodiment, the centering mechanism  352  comprises three or more wheels symmetrically movable relative to the central axis  353 . 
       FIG. 4  is a schematic top view of a substrate carrier tray  303  in accordance with one embodiment of the present invention.  FIG. 4  schematically illustrates one approach to align substrates during loading. 
     The substrate carrier tray  303  is disposed in on the carrier tray aligner  350 . The carrier tray  303  is substantially circular and having a plurality of substrate pockets  372  formed therein. Each substrate pocket  372  is configured to retain a substrate therein. As shown in  FIG. 4 , each pocket  372  has a flat  373  for accommodating a substrate with a flat. In one embodiment, the pocket  373  of each pocket  372  is outward from a center of the carrier tray  303  and substantially perpendicular to a radius  374  connecting the center of the carrier tray  303  and the center of the pocket  372 . In one embodiment, the carrier tray  303  has a notch  371  as a reference for alignment. 
     Referring back to  FIG. 3 , during aligning, a carrier tray  303  is first disposed on the carrier support  351 . The carrier tray  303  on the carrier support  351  may be centered by the centering mechanism  352  when the centering wheels simultaneously moving towards the rotating carrier tray  303 . The center of the carrier tray  303  substantially coincides with the center axis  353  of the carrier support  351  when the carrier tray  303  is aligned. 
     Referring to  FIG. 4 , the carrier support  351  may rotate the carrier tray  303  so that the radius  374  of a pocket  372  aligns with a line  375  connecting the central axis  353  of the carrier support  351  and the central axis  333  of the substrate support  331  to position the pocket  372  in a transferring position. As shown in  FIG. 4 , pocket  371   a  is in a transferring position. Each pocket  372  may be positioned in its transferring position similarly. 
     The substrate  302  disposed on the substrate support  331  has been aligned and the flat on the substrate  302  is substantially parallel to the flat in the pocket  371   a  in the transferring position. A linear motion from the carrier tray loading robot  340  may transfer the substrate  302  in the substrate support  331  to the pocket  371   a,  or vise versa. 
     Referring back to  FIG. 2 , the carrier tray loading robot  340  is configured to move substrates between the substrate aligner  330  and the carrier aligner  350 . In one embodiment, the carrier tray loading robot  340  has two liner motions, a horizontal motion substantially parallel to a line from the center axis  353  of the carrier aligner  350  and the central axis  333  of the substrate aligner  330 , and a vertical motion. The vertical motion allows the carrier tray loading robot  340  to pick up and to drop off a substrate, and to accommodation different elevation between the substrate aligner  330  and the carrier aligner  350 . 
     In one embodiment, the carrier tray loading robot  340  may comprise a minimum contact chucking mechanism configured to secure to a substrate on a top surface. In one embodiment, the minimum contact chucking mechanism using the Bernoulli principle to create a low pressure region between the substrate and the robot blade by blowing a vertex flow of air. In one embodiment, a blade  341  of the carrier tray loading robot  340  may contact a substrate within 1 to 2 mm of an edge region. 
     The carrier tray transferring robot  360  is configured to pick up and transfer a substrate carrier tray  303 . In one embodiment, the carrier tray transferring robot  360  may be used to transfer a substrate carrier tray  303  from the carrier aligner  350  to a substrate support position  303   a  in a load lock chamber, and vise versa. In one embodiment, the carrier tray transferring robot  360  may have a linear horizontal motion and a vertical motion. 
     The carrier tray transferring robot  360  comprises a robot blade  361  configured to support a substrate carrier tray. In one embodiment, the robot blade  361  may remain under then the substrate carrier tray during loading and unloading. 
     The automatic substrate loader  300  may be used in atmosphere environment or controlled environment. 
     It should be noted, other arrangement of the robots  320 ,  340 ,  360  and the aligners  330 ,  350  may be used to accommodate certain space requirement or to maximize usage of the space. 
     Even though, linear motions of the robots  320 ,  340 ,  360  are shown in the automatic substrate loader  300 , persons skilled in the art may apply other ranges of motions to complete the loading and unloading process. 
       FIG. 5  is a flow chart showing a method  400  for loading a substrate carrier in accordance with one embodiment of the present invention. The method  400  may be performed using an automatic substrate loader, such as the automatic substrate loader  300  described above. 
     In box  410 , a substrate carrier tray, such as the substrate carrier tray  303 , having one or more empty pockets is disposed on a carrier aligner, such as the carrier aligner  350 . In one embodiment, the substrate carrier tray may be disposed by a carrier transferring robot, such as the carrier transferring robot  360 . In another embodiment, the substrate carrier tray may be transferred out of a processing system and after processed substrates are unloaded. The carrier aligner may rotate the substrate carrier tray to position one empty pocket in a transferring position. 
     In box  420 , one or more cassettes, such as cassettes  312 , having a plurality of substrates to be processed may be disposed on a cassette carousel, such as the cassette carousel  310 . 
     In box  430 , the cassette carousel is rotated to position one cassette in a loading position. 
     In box  440 , detecting the presence of substrates in the cassette in the loading position. Detecting the presence of substrates may be performed by moving an optical sensor, such as sensors  322 ,  323  relatively to the cassette in the loading position. If no substrate is found in the cassette in the loading position, the cassette carousel may rotate again and position another cassette in the loading position. 
     In box  450 , a substrate is transferred from a slot in the cassette to a substrate aligner, such as the substrate aligner  330 . This transferring may be performed by a first robot, such as the cassette interfacing robot  320 . 
     In box  460 , the substrate in the substrate aligner may be aligned with the pocket of the carrier tray. In one embodiment, the alignment comprises aligning a flat of the substrate with a flat of the pocket in the transferring position. 
     In box  470 , the aligned substrate in the substrate aligner is transferred to the substrate carrier and dropped in the pocket in the transferring position. In one embodiment, this transferring may be performed by a second robot, such as the carrier tray loading robot  340 . 
     In box  480 , the substrate carrier may be rotated to position another empty pocket in its transferring position and operations from boxes  430  to  480  may be repeated until all the pockets are full. 
     In box  490 , when the all the pockets in the substrate carrier are loaded with substrates to be processed, the substrate carrier may be picked up from the carrier aligner and transferred to a processing system, such as the load lock chamber  208  of the processing system  200 . In one embodiment, the substrate carrier may be transferred by a third robot, such as the carrier tray transfer robot  360 . 
       FIG. 6  is a flow chart showing a method  500  for unloading a substrate carrier in accordance with one embodiment of the present invention. The method  500  may be performed using an automatic substrate loader, such as the automatic substrate loader  300  described above. 
     In box  510 , a substrate carrier tray having a plurality of substrates may be transferred to a carrier aligner, such as the carrier aligner  350 . The substrate carrier tray may be transferred by a carrier tray transferring robot, such as the robot  360 , from a processing system, such as the processing system  200 . 
     In box  520 , the substrate carrier tray is rotated and a substrate pocket having a substrate therein is positioned in a transferring position. 
     In box  530 , the substrate in the transferring position may be picked up from the substrate carrier tray and transferred to a substrate support, such as the substrate support  331  of the substrate aligner  330 . This transferring may be performed by a substrate transferring robot, such as the robot  340 . 
     In box  540 , a cassette carousel is rotated to position a cassette having one or more empty slots in a loading position. 
     In box  550 , the substrate in the substrate support is picked up and transferred to an empty slot in the cassette in the loading station. This transferring may be performed by a cassette interfacing robot, such as the robot  320 . 
     Operations in boxes  520 ,  530 ,  540 , and  550  may be repeated until the substrate carrier tray is empty. Filled cassettes may be removed from the cassette carrousel when the cassette is not in the loading position. 
     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.