FIELD OF THE INVENTIONThe present invention relates generally to fabrication systems and more particularly to an improved method and apparatus for loading and unloading wafer carriers to and from a tool.[0001]
BACKGROUND OF THE INVENTIONA factory for manufacturing semiconductor substrates (e.g., patterned or unpatterned wafers) is conventionally known as a “FAB.” Within a FAB, an overhead transport mechanism may transport semiconductor wafers in what is known as a wafer carrier (e.g., a sealed pod, a cassette, a container, etc.) between various processing systems, wherein a wafer carrier is placed on a mechanism known as a loadport (i.e., a mechanism or location which receives and supports a wafer carrier at a given tool). Certain loadports referred to herein as fabrication tool loadports, support a wafer carrier while wafers are extracted from the wafer carrier and transported into a processing system coupled thereto. Others simply receive a wafer carrier within a storage buffer, where the wafer carrier is stored for subsequent transport to a fabrication tool loadport.[0002]
Typically, wafer carriers are received in a storage buffer via an elevated or overhead loadport that receives wafer carriers from an overhead transport mechanism. Thereafter a storage buffer robot may transfer the wafer carrier from the overhead loadport to another storage shelf or to a fabrication tool loadport or to a conventional SEMI Standard E15 loadport that exchanges wafer carriers with an overhead transport mechanism. To lower the wafer carrier from an overhead transport mechanism to an overhead loadport, a robot capable of multi-axis movement may be employed, etc. The complex multi-axis movement required by such a loader robot in order to transfer a wafer carrier between the overhead transfer mechanism and the overhead loadport increases equipment expense and reduces equipment reliability.[0003]
Also, conventionally wafer carriers have kinematic mounts (i.e., mechanical couplings used to align a wafer carrier on a platform, such as a loadport), which engage corresponding kinematic mount locations on a loadport. Thus, the loader robot must be tightly toleranced to accurately position the wafer carrier on the loadport such that the wafer carrier's kinematic mounts may engage the loadport's kinematic mount locations. Such tight tolerance requirements may increase equipment costs while reducing equipment throughput.[0004]
Accordingly, there is a need for an improved system that may transfer wafer carriers between an overhead transport mechanism and a loadport.[0005]
SUMMARY OF THE INVENTIONThe present invention provides a system adapted to exchange wafer carriers between an overhead transport mechanism and a platform. The system employs a wafer carrier having at least one handle extending therefrom, an overhead transfer mechanism, a transporter coupled to the overhead transfer mechanism and adapted to move therealong and having a wafer carrier coupling mechanism adapted to couple to the at least one wafer carrier handle, a platform positioned below the overhead transfer mechanism such that wafer carriers traveling along the overhead transfer mechanism travel over the platform, and an actuator coupled to the platform and adapted so as to elevate the platform to an elevation wherein the loading platform may contact the bottom of a wafer carrier coupled to the overhead transfer mechanism.[0006]
The invention further comprises a method of transferring wafer carriers between an overhead transport mechanism and a platform, by elevating the platform so as to contact a wafer carrier supported by the overhead transport mechanism, and so as to release the wafer carrier from the overhead transport mechanism. Thereafter the platform is lowered to an overhead loadport height.[0007]
An inventive wafer carrier comprising at least a first handle comprising a groove, such as an inverted “v-shaped” groove, along a lower surface thereof, is further provided.[0008]
Other features and aspects of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.[0009]
BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a side schematic view, in pertinent part, of an overhead transport system and an inventive loadport for use therewith;[0010]
FIG. 2 is a front perspective view of the wafer carrier having a conventional bar-type handle attached thereto, shown coupled to an overhead transporter;[0011]
FIG. 3 is a front perspective view of a wafer carrier having an inventive V-shaped handle attached thereto, shown coupled to an overhead transporter;[0012]
FIGS.[0013]4A-D are schematic side plan views of the overhead transport system and the inventive loadport system;
FIGS.[0014]5A-D respectively are the front plan views that correspond to the side views of FIGS.4A-D;
FIG. 6 is a side view of a storage apparatus that may comprise the loading platform; and[0015]
FIG. 7 is a schematic top plan view, in pertinent part, of an overhead transport system coupled to a processing system useful in describing exemplary locations where the inventive loadport may be employed.[0016]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSFIG. 1 is a side schematic view, in pertinent part, of an inventive[0017]overhead transport system11 that comprises aninventive loadport12, having alift actuator13 that may elevate a platform15) to an elevation wherein theplatform15 may contact a wafer carrier17 (e.g., a sealed pod, an open cassette, etc.) being transported by an overhead transport mechanism19 (e.g., an overhead conveyor). The inventiveoverhead transport system11 may further comprise thewafer carrier17, theoverhead transport mechanism19, a plurality oftransporters21 adapted to move along theoverhead transport mechanism19. The inventiveoverhead transport system11 may also comprise alignment marks orsensors51 and53 (FIGS.4A-5D) adapted to transmit a signal when thewafer carrier17 is in a predetermined position relative to theloading platform15.
The operation of the inventive[0018]overhead transport system11 is further described below with reference to FIGS.4A-D and FIGS.5A-D, which illustrate the inventiveoverhead transport system11 in more detail than that shown in FIG. 1. Before discussing the overall operation of the inventiveoverhead transport system11, it is best to understand the configuration of the exemplary types of wafer carriers that may be employed therewith. Specifically, the opposing sides of thewafer carrier17 may have a twist-on location (e.g., a threaded or Bayonette extension) such that a handle (e.g., having corresponding threads or wings) may be removably coupled to the twist-on location as in conventional ______. The twist-on location35 (FIGS. 2 and 3) may be positioned at thewafer carrier17's center of gravity so as to minimize vibration of thewater carrier17 while thewafer carrier17 is being transported by theoverhead transfer mechanism19. Two types of handles may be used with thewafer carrier17. The first type of handle may comprise a conventional bar as described further below with reference to FIG. 2, and the second type of handle may comprise an inventive inverted V-shaped handle as described further below with reference to FIG. 3.
FIG. 2 is a front perspective view of a[0019]wafer carrier17 having a conventional bar-type handle26 attached thereto, shown coupled to thetransporter21a.Thetransporter21amay comprise a pair ofgrippers27 adapted to be positioned on opposing sides of thewafer carrier17, and acoupling mechanism29 adapted to couple thetransporter21ato theoverhead transfer mechanism19 and to allow thetransporter21ato move therealong as is conventionally known. In one aspect, thegrippers27 have no moving components (i.e., are fixed). Specifically, thegrippers27 extend downwardly from thecoupling mechanism29, and the distance between thegrippers27 is larger than the width of thewafer carrier17. Thegrippers27 may comprise anend effector31 adapted to couple to the conventional bar-type handle26. As shown in FIG. 2, theend effector31 may have agroove33 that has, for example, a V-shape (as shown), a U-shape (not shown), or any other similar shape which may “grasp”, cradle or otherwise engage the conventional bar-type handle26 from below. The twist-on location35 (FIGS. 2 and 3) may be positioned at thewafer carrier17's center of gravity so as to minimize vibration of thewafer carrier17 while thewafer carrier17 is being manually transported or is being transported by theoverhead transfer mechanism19.
The[0020]transporter21amay further comprise arocking restraint37 such as a pair of rigid extensions that extend downwardly from thecoupling mechanism29 to a position close to the top of thewafer carrier17, and are thus adapted to minimize rocking (e.g., forward and backward) of thewafer carrier17 as thewafer carrier17 is being transported by theoverhead transfer mechanism19.
FIG. 3 is a front perspective view of the[0021]wafer carrier17 having an inventive V-shaped handle41 attached thereto, shown coupled to thetransporter21b.Thetransporter21bmay comprise the same components as thetransporter21aof FIG. 2. In this aspect, however, theend effector31 may comprise arod43 that is adapted to couple to the V-shaped handle41 of thewafer carrier17. As previously described, the inventive V-shaped handle41 may comprise a threaded region that may be screwed onto a threaded region of the twist-onlocation35. In operation, thegroove33 of the inventive V-shaped handle41 may “grasp”, cradle or otherwise engage therod43 of thetransporter21b,such that thetransporter21bmay be lifted and lowered thereby.
The components of the inventive[0022]overhead transport system11 are described further with joint reference to FIGS.4A-5D, which are useful in describing the operation of the inventiveoverhead transport system11, as awafer carrier17 is transferred between theoverhead transport mechanism19 and theloading platform15. FIGS.4A-D are schematic side plan views of the inventiveoverhead transport system11, and FIGS.5A-D are the respective front plan views of the inventiveoverhead transport system11 that correspond to FIGS.4A-4D.
Generally, in operation, a[0023]transporter21 carries awafer carrier17 into position above theinventive loadport17. Theinventive loadport17 then elevates such that thehandles41 of thewafer carrier17 disengage the transporter's end effectors. The transporter then moves forward and the inventive loadport is able to lower the wafer carrier to a position from which thewafer carrier17 can be extracted and loaded to a fabrication tool. To accomplish such wafer carrier transfer between an overhead transporter and a fabrication tool, thelift actuator13 is coupled to theplatform15 so as to elevate theplatform15 to an elevation wherein theplatform15 may contact the bottom of awafer carrier17 being transported by theoverhead transfer mechanism19. Thelift actuator13 may lift and lower theplatform15 between various positions including: (1) an upper position in which theplatform15 has elevated thewafer carrier17 such that the handle thereof is above the level of thetransporter21a,21b'send effector33 thus lifting thewafer carrier17 off of thetransporter21; and (2) a lower position in which theplatform15 has lowered thewafer carrier17 so that arobot45,65 (FIGS. 6 and 7) may access thewafer carrier17.
In order to avoid collision, the distance between the top of a[0024]wafer carrier17 supported by theplatform15 and theoverhead transport mechanism19 is larger than the distance between theoverhead transport mechanism19 and the bottom of awafer carrier17 being transported thereby (the distance being measured when theplatform15 is in the lower position). Thus, thewafer carrier17 may not contact theoverhead transport mechanism19 or any overhead portion of thetransporter21a,21bwhen theloading platform15 is in the upper position (assuming thewafer carrier17 is disengaged form the rods). Also, the distance between the top of thewafer carrier17 and the rockingrestraint37 measured before theplatform15 contacts thewafer carrier17, is larger than the distance between the top of thewafer carrier17 and the rockingrestraint37 measured when theloading platform15 is in the upper position. Thus, thewafer carrier17 may not contact the rockingrestraint37 when theloading platform15 is in the upper position, unless thewafer carrier17 rocks forward or backward.
The[0025]platform15 may be positioned below theoverhead transport mechanism19 such that awafer carrier17 that is being transported by theoverhead transport mechanism19 may travel over theloading platform15. In one aspect, theplatform15 may be a top shelf of a storage apparatus (e.g., a local buffer) that may comprise a plurality of shelves and one or more loadports as described further below with reference to FIG. 6.
The alignment sensors may comprise a[0026]light transmitter51, such as a light emitting diode (LED) and areceiver53, such as a photodetector. Amicrocontroller55 may be coupled to thelift actuator13 and adapted to control the operation thereof. Themicrocontroller55 may be further adapted to receive a signal from thereceiver53 indicating thewafer carrier17 is in position above theplatform15. Specifically, in one aspect, the alignment sensors25 may employ the use of a “through-beam” technique whereby thelight transmitter51 is positioned so as to transmit a light beam to thereceiver53 “through” a path traveled by awafer carrier17 as it travels along theoverhead transfer mechanism19. Thelight transmitter51 may be positioned on theplatform15 and thereceiver53 may be positioned on theoverhead transfer mechanism19.
When a[0027]wafer carrier17 being transported by theoverhead transport mechanism19 is above theloading platform15, thewafer carrier17 may block a beam of light that is transmitted by thetransmitter51. When awafer carrier17 is not above theloading platform15, thereceiver53 may detect a beam of light that is transmitted by the light transmitter51 (i.e., the beam of light may pass through). An output of thereceiver53 may have a “first signal” value when the beam of light contacts thereceiver53, and may have a “second signal” when the beam of light does not contact thereceiver53. As a further precaution, thelift actuator13 may lift and lower theplatform15 only when themicrocontroller55 receives a “second signal” from thereceiver53.
The operation of the inventive[0028]overhead transport system11, employing thetransporter21bof FIG. 3 (with thewafer carrier17 having the inventive V-shapedhandle41 attached thereto) is described with reference to the sequential views of FIGS.4A-D and FIGS.5A-D, which show the movement of thewafer carrier17 as thewafer carrier17 travels between theoverhead transfer mechanism19 and theplatform15.
FIGS. 4A and 5A show the[0029]wafer carrier17 coupled to thetransporter21b,and thewafer carrier17 positioned above theplatform15. Theplatform15 is shown in the retracted position prior to contacting thewafer carrier17. Thereceiver53 outputs a “second signal” because the beam of light transmitted by thelight transmitter51 is blocked by thewafer carrier17. Themicrocontroller55 receives the second signal from thereceiver53, and actuates thelift actuator13.
Upon actuation, the[0030]lift actuator13 elevates theplatform15 to the upper position, wherein theplatform15 contacts and elevates thewafer carrier17 such that the bottom of the inventive V-shapedhandle41 is above the level of therod43, thus lifting thewafer carrier17 off of thetransporter21b.As shown in FIGS. 4B and 5B, theplatform15 is in the upper position and thewafer carrier17 is positioned thereon. Once theplatform15 is in the upper position and because the inventive V-shapedhandle41 is above the level of therod43, thetransporter21bmay then move along theoverhead transport mechanism19, as shown in FIGS. 4C and 5C. Thereafter, thelift actuator13 retracts carrying theplatform15, to the lower position, wherein therobot45 may access thewafer carrier17, as shown in FIGS. 4D and 5D. Therobot45 may then transfer thewafer carrier17 to a storage shelf (FIG. 6) below theplatform15 or to the processing apparatus63 (FIG. 7).
After all the wafers have been processed in the[0031]wafer carrier17, the inventiveoverhead transport system11 may reverse the steps described above, to thereby return thewafer carrier17 to theoverhead transport mechanism19 for transport to another processing tool. Because the inventive transport system may employ only linear motion, wafer carrier loading and unloading may be more efficient. In one aspect, the overall transfer time may be about 5 to 10 seconds for thewafer carrier17 to travel between the platform15 (e.g., when configured as an overhead loadport) and theoverhead transport mechanism19.
When the inventive[0032]overhead transport system11 employs thetransporter21aof FIG. 2 so as to transport awafer carrier17 having aconventional bar26 attached thereto, the operation is similar to that described above. Upon actuation, thelift actuator13 elevates theplatform15 to the upper position, wherein theconventional bar26 is above the top of the V-shapedgroove33 of the transporter's end effector31 a (rather than the V-shaped handle being above the bar shapedend effector31 as shown in FIG. 3). Thus, thewafer carrier17 is lifted off of thetransporter21a.
FIG. 6 is a side view of a[0033]storage apparatus57 that may comprise theloading platform15. As stated above, thestorage apparatus57 may comprise a plurality ofshelves59 and a plurality of loadports61 positioned below theshelves59 and adjacent a processing system63 (FIG. 7). In one aspect, theshelves59 are within the footprint of (e.g., above or below) the loadports61. Thestorage apparatus57 may also comprise arobot45, which may transfer thewafer carrier17 between theshelves59 and the loadports61a-e.As shown, the loadports61a-bare overhead loadports, for receiving a wafer carrier from an overhead transport mechanism, and theloadport61cis a SEMI standard E15 loadport which conventionally receives wafer carriers either manually or from a robot. Because a clear path exists between the loadports61a-cthese loadports may advantageously be configured in accordance with the invention so as to include an actuator as previously described. Similarly theloadports61d-e,if positioned in front of theshelves59 rather than below them (e.g., positioned outside the footprint of the shelves59), may also be configured in accordance with the invention. Accordingly, with use of the present invention a loadport positioned for manual loading at a height set by SEMI Standard E15 may also receive wafer carriers from an overhead transport mechanism. A specific aspect of thestorage apparatus57 is described in detail in U.S. Pat. No. 09/201,737, the entire disclosure of which is incorporated herein by this reference.
FIG. 7 is a schematic top plan view, in pertinent part, of a[0034]processing system63 having a factoryinterface wafer handler65 adapted to transport wafers between the plurality ofloadports61c-eand aprocessing tool67, which may comprise a plurality ofprocessing chambers69. FIG. 7 shows exemplary positions in which the inventive loadports61a-emay be employed.
As is evident from the description above, the inventive[0035]overhead transport system11 may reduce equipment expense and increase equipment reliability. The inventiveoverhead transport system11 may allow for loose wafer carrier positioning tolerance when robots are not employed, as wafer carriers need not be positioned as accurately.
It will be understood that, depending on the configuration of the inventive loadport, situations may arise where a wafer carrier being transported by an overhead transport mechanism will need to travel past an overhead loadport that has a wafer carrier positioned thereon. To avoid enough, and the actuator can have a long enough stroke so that there is sufficient vertical space for both wafer carriers. Alternatively the inventive loadport may have a cantilever extension (not shown) on the platform so that a wafer carrier can be temporarily extended out of the path of the overhead transport mechanism. A further alternative configuration may employ a rotatable platform as shown and described with reference to FIG. 8.[0036]
FIG. 8 is a schematic top plan view of an inventive transport system that employs a[0037]rotatable platform81 having the inventive loadport12 (of FIG. 1) mounted thereon. Accordingly, the rotatable platform may be installed below anoverhead transport mechanism19 such that theinventive loadport12 may be rotated to a position below theoverhead transport mechanism19 such that wafer carriers may be exchanged between theinventive loadport12 and theoverhead transport mechanism19. After receiving awafer carrier17 from theoverhead transport mechanism19, the rotatable platform may rotate to position thewafer carrier17 at a location where a fabrication tool robot may extract the wafer carrier (e.g., the location shown in phantom).
In the specific aspect shown in FIG. 8, the[0038]rotatable platform81 may be employed within thestorage apparatus57 of FIG. 6 (e.g., therotatable platform81 may be employed within theinventive loadport61bof FIG. 6). In such an aspect, the storage apparatus'srobot47 would move along track83 (FIG. 6) in order to transport wafer carriers between the inventive loadport (when therotatable platform81 is in the location shown in phantom) and the plurality of storage shelves59 (FIG. 6). Accordingly, the aspect shown in FIG. 8 may be employed within a fabrication system such as that described in a U.S. patent application Ser. No. 09/517,227, filed Mar. 2, 2000 titled “FABRICATION SYSTEM WITH EXTENSIBLE EQUIPMENT SETS”, the entire disclosure of which is incorporated herein by reference.
The foregoing description discloses only the exemplary embodiments of the invention, modifications of the above-disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the[0039]transporter21 may support thewafer carrier17 via a hook-shaped end effector that couples to the flange positioned on top of aconventional wafer carrier17. The V-shapedgroove33 may be replaced by any other similar shape.
Accordingly, while the present invention has been disclosed in connection with the preferred embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.[0040]