Abstract:
A hoisting method and device for use in an overhead traveling carriage system are disclosed. The hoisting device includes an engager for engaging an object and a linearly expandable structure coupling the engager to a base point. A single hoist member is coupled at a first end to the engager and at a second end to a motorized drum, coupled to the base point, for substantially vertically retracting and extending the single member. Since a single hoist member is used, the amount of precision machining and technician training are reduced. The linearly expandable structure includes at least one lazy-tong linkage or a telescoping structure, which provides sway stability and compactness. The invention may also include a six-degree adjustment structure that may include a feedback system for use with the linearly expandable structure to provide increased accuracy.

Description:
BACKGROUND OF INVENTION  
       [0001]     The present invention relates generally to hoisting, and more particularly to a hoisting device for use with an overhead traveling carriage system such as used in a semiconductor fabrication facility.  
         [0002]     Semiconductor fabrication facilities use automation for delivery of wafers between processing stations that include bays therebetween. There are various methods of delivering and placing wafers or a wafer holding pod, sometimes referred to as a front opening unified pod (FOUP), at a load port of a processing station. One approach is disclosed in U.S. Pat. No. 5,765,703 to Shiwaku. In this disclosure, FOUPs are delivered via an overhead vehicle that is mounted to, and movable, on a rail that is positioned over the necessary load ports. The overhead traveling carriage includes a hoisting device to lower/raise the FOUP. Conventionally, hoisting devices use three cables to lower/raise the FOUP via, for example, a three-roller drive that is driven via a motor(s) and gearing.  
         [0003]     Unfortunately, conventional hoisting devices that use cables present a number of problems. First, conventional hoisting devices do not provide sway stability. In particular, cables are very susceptible to sway and vibration during lowering of the FOUP. To address this issue, sway sensing systems have been employed to deactivate hoisting if sway is excessive. Sway sensing systems, however, create other problems such as false triggers that needlessly deactivate the hoisting device. Second, conventional cable hoisting devices require precision machining and high tolerance parts to provide the necessary synchronization of three rollers, gearing and motor(s). As a result, conventional hoisting devices are very expensive. Lastly, conventional hoisting devices require excessive amounts of time to assemble and align, and require a highly skilled technician to implement.  
         [0004]     Another approach uses three window-blind type rollers to lower a FOUP, which provides better stability. The devices are available from companies such as PRI-Brooks, Daifuku and Shinko. These devices, however, still require high precision gearing and mechanisms to hoist the FOUP.  
         [0005]     Another disadvantage of conventional hoisting devices is that accurate placement of a wafer holding pod is difficult when position adjustment of the wafer holding pod is only possible in two-degrees of motion, i.e., hoist (vertical) direction and a travel (rail) direction, but the wafer holding pod can move spatially in all six degrees of motion. That is, the wafer holding pod can move in the travel X, lateral Y, hoist Z, roll, pitch, and yaw directions. In addition, accurate placement is made more difficult by the fact that there is no physical connection, other than a number of non-rigid cables and distant floors, ceiling and walls, connecting the wafer holding pod relative to a load port.  
         [0006]     In view of the foregoing, there is a need in the art for a hoisting system that overcomes the problems of the related art.  
       SUMMARY OF INVENTION  
       [0007]     The invention includes a hoisting method and device for use in an overhead traveling carriage system. The hoisting device includes an engager for engaging an object and a linearly expandable structure coupling the engager to a base point. A single hoist member is coupled at a first end to the engager and at a second end to a motorized drum, coupled to the base point, for substantially vertically retracting and extending the single member. Since a single hoist member is used, the amount of precision machining and technician training are reduced. The linearly expandable structure includes at least one lazy-tong linkage or a telescoping structure, which provides sway stability and compactness. The invention may also include a six-degree adjustment structure that may include a feedback system for use with the linearly expandable structure to provide increased accuracy.  
         [0008]     A first aspect of the invention is directed to an overhead traveling carriage system for use in a semiconductor fabrication facility, the system including an overhead traveling carriage, the carriage comprising: a main body movably engaged with an elevated rail; a hoisting device including: an object engager for engaging an object; a linearly expandable structure coupling the object engager to the main body; and a hoist for hoisting the object engager.  
         [0009]     A second aspect of the invention is directed to a method of hoisting a wafer holding pod in a semiconductor manufacturing facility, the method comprising the steps of: engaging an engager to the wafer holding pod to be hoisted; hoisting the engager while linearly directing the engager with a linearly expandable structure.  
         [0010]     A third aspect of the invention is directed to a hoisting device comprising: an engager for engaging an object; a linearly expandable structure coupling the engager to a base point; a single hoist member coupled at a first end to the engager and at a second end to a motorized drum, coupled to the base point, for substantially vertically retracting and extending the single hoist member; and an adjustment system for adjusting the position of the linearly expandable structure relative to a load port in greater than two-degrees of motion.  
         [0011]     The foregoing and other features of the invention will be apparent from the following more particular description of embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]     The embodiments of this invention will be described in detail, with reference to the following figures, wherein like designations denote like elements, and wherein:  
         [0013]      FIG. 1  shows an overhead traveling carriage system according to the invention.  
         [0014]      FIGS. 2A and 2B  show a hoisting device used with the carriage system of  FIG. 1  including a first embodiment of a linearly extendable structure in the form of a lazy-tong linkage.  
         [0015]      FIGS. 3A, 3B  and  3 C show a variety of lazy-tong linkage arrangements.  
         [0016]      FIG. 4  shows a detail of a couple of lazy-tong linkages.  
         [0017]      FIG. 5  shows a canopy for use with the lazy-tong link-age(s).  
         [0018]      FIG. 6  shows a second embodiment of a linearly extendable structure in the form of a telescoping structure.  
         [0019]      FIG. 7  shows an alternative embodiment of a linearly extendable structure according to the invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]     With reference to the accompanying drawings,  FIG. 1  shows an illustrative overhead traveling carriage system  10  for use in a semiconductor fabrication facility.  
         [0021]     System  10  includes at least one and, in most cases, a plurality of overhead traveling carriages  14 . Each carriage  14  includes a main body  16  movably engaged with an elevated rail  18 , and including a traveling motor(s)  20  for moving main body  16  along elevated rail  18 . Main body  16  provides a base point  22  from which hoisting of an object, as will be described below, may occur. Elevated rail  18  may be supported in a variety of ways such as being hung from a ceiling of the facility or supported on poles. System  10  may also include a controller  24  for controlling a plurality of overhead traveling carriages  14  in the semi-conductor fabrication facility.  
         [0022]      FIG. 1  also shows a plurality of objects  30  to be hoisted and moved by system  10  between various load ports  32  of any now known or later developed processing stations. In one embodiment, each object  30  includes a wafer holding pod  34  that may each hold a plurality of wafers (not shown). Wafer holding pod(s)  34  may take the form of a well-known front opening unified pod (hereinafter “FOUP”). As used herein, “hoist” or “hoisting” refers to the act of raising or lowering of an object  30 . Each main body  16  may also include an object protector(s)  36  for enclosing and protecting a respective object  30  when raised to main body  16 .  
         [0023]     Referring to  FIGS. 2A and 2B , each carriage  14  also includes a hoisting device  40  according to the invention. Each hoisting device  40  includes an object engager  42  for engaging an object  30 , a linearly expandable structure  44  coupling object engager  42  to main body  16  and a hoist  46  for hoisting a respective object engager  42 . Object engager  42  may be any now known or later developed mechanism for engaging and holding object  30  such as wafer holding pod  34 . For example, object engager  42  may be a vacuum grasper that engages an object  30  by applying a vacuum to an upper surface thereof or a mechanical grasper.  
         [0024]     Hoist  46  includes a single hoist member  48  coupled at a first end  50  to object engager  42  and at a second end  52  to a motorized drum  54 . Motorized drum  54  is coupled to main body  16  for retracting and extending single hoist member  48 . In one embodiment, single hoist member  48  is provided as a cable  60 , as shown in  FIGS. 2A and 2B . In a second alternative embodiment, shown in  FIG. 6 , single hoist member  48  is provided as a belt  60 . It should be recognized, however, that single hoist member  48  may be provided as any of now known or later developed mechanism for linearly moving an object  30  so long as it is structurally compatible with linearly extendable structure  44 . Hoist  46  may also include other components such as positioning rollers (not shown), as necessary, for proper positioning and operation of single hoist member  48 .  
         [0025]     Linearly extendable structure  44  is coupled at an upper end  66  to main body  16  and at a lower end  68  to object engager  42 , and is linearly extendable from main body  16 . Linearly extendable structure  14  is used to, among other things, provide some rigidity to the hoisting movement against sway of object  30 . In a first embodiment, shown in  FIGS. 2A and 2B , linearly extendable structure  44  is provided as at least one lazy-tong linkage  70 . Each lazy-tong linkage  70  (sometimes referred to as an “accordian linkage”) includes any number of pivotally coupled links  72  that are configured to linearly expand and contract in a scissor-like fashion. Since each lazy-tong linkage  70  is fairly rigid in the plane in which it rests, each linkage resists movement within the plane. In this embodiment, each link  72  adjacent upper end  66  and lower end  68  are pivotally coupled to main body  16  and object engager  42 , respectively, in any known fashion. One link  72  at each end of each lazy-tong linkage  70  includes a sliding bearing  73  connection to main body  16  or object engager  42  to allow expansion/contraction of the linkage within the plane of movement.  
         [0026]     Referring to  FIGS. 3A, 3B  and  3 C, in order to provide substantial rigidity against sway, a number of lazy tong linkages  70  may be implemented simultaneously.  FIG. 3A  conceptually illustrates implementation of two linkages  70 A,  70 B arranged in a non-parallel fashion to one another, which provides three connection points  74 A- 74 C to object engager  42  and main body  16  and, hence, provides substantial resistance to sway.  FIGS. 3B and 3C  illustrate embodiments in which linearly expandable structure  44  includes at least three lazy-tong linkages  70 . In particular,  FIG. 3B  conceptually illustrates implementation of three linkages  70 A,  70 B,  70 C, arranged in a non-parallel fashion to one another, which provides three connection points  74 A- 74 C to object engager  42  and main body  16 . The  FIG. 3B  arrangement may provide further resistance to sway compared to the  FIG. 3A  arrangement.  FIG. 3C  conceptually illustrates implementation of four linkages  70 A,  70 B,  70 C and  70 D arranged substantially perpendicular to one another, which provides four connection points  74 A- 74 D, and may provide further resistance to sway compared to the  FIGS. 3A and 3B  arrangements.  
         [0027]     Referring to  FIGS. 4 and 5 , additional optional embodiments for lazy-tong linkage(s)  70  are shown. In  FIG. 4 , links  72  of adjacent lazy tong linkages  44  may be coupled together by a coupling  80  to assure mimicking movement of adjacent links  72  and provide further rigidity against sway. Coupling  80 , as shown, includes an angled member  82  that is pivotally pinned through openings in, or adjacent to, joints  84  of links  72 . Other mechanisms of coupling adjacent links  72  together may also be possible. In  FIG. 5 , a canopy  86  may be provided about lazy-tong linkage(s)  70  for protection and other purposes.  
         [0028]     In an alternative second embodiment, shown in  FIG. 6 , a linearly expandable structure  144  is provided as a telescoping structure  180 . Telescoping structure  180  may include a number of telescoping members  182  that linearly expand and retract, and provide some rigidity to the hoisting movement against sway, of object  30 .  
         [0029]     Returning to  FIGS. 2A and 2B , in operation, object engager  42  engages an object  30  such as a wafer holding pod  34  to be hoisted as shown in  FIG. 2A . As shown in  FIG. 2B , object engager  42  can be hoisted using hoist  46  while object engager  42  and, hence, object  30 , is linearly directed with linearly expandable structure  44 ,  144 . Single hoisting member  48  runs down the middle of linearly extendable structure  44 ,  144 . As object  30  is hoisted, linearly extendible structure  44 ,  144  folds inside of itself and folds to a shallow stacked height, as shown in  FIG. 2B . The size of linearly extendable structure  44 ,  144 , and the number of link  72  pairs or telescoping members  182 , will depend on the drop height. For example, for an approximately ninety inch drop height, a lazy-tong linkage may use 12-15 linkage members that are 10-12 inches long and up to half an inch in width. Linearly extendable structure  44 ,  144  may be made of various synthetic materials that are lightweight and have a high modulus of strength and rigidity. Since the invention requires a single motorized drum central to linearly extendable structure  44 ,  144 , few high tolerance machined parts are required and the system is easy to assemble and align.  
         [0030]     Turning to  FIG. 7 , an alternative embodiment of a linearly extending structure according to the invention is shown. As noted above and as shown in  FIG. 7 , a carriage  14 , i.e., main body  16 , moves spatially in all 6 degrees of freedom, i.e., travel X, lateral Y, hoist Z, roll, pitch, and yaw. In this embodiment, linearly extending structure  44  is provided as part of a six-degree adjustment system  200 , which may include a feedback system  202 . Adjustment in the hoist Z direction is provided, as described above, via hoisting device  40  including, inter alia, hoist  46 , cable  50  and motorized drum  54 , and in the travel X direction by traveling motor  20 . Adjustment is provided by adjustment system  200  greater than two-degrees of motion: in a lateral Y direction by a lateral adjuster  204 , in a roll direction by a roll adjuster  206 , in a pitch direction by a pitch adjuster  208 , and in a yaw direction by a yaw adjuster  210 .  
         [0031]     Lateral, roll and pitch adjusters  204 ,  206 ,  208  are provided by a three-directional adjustment structure  212  that is coupled to traveling motor  20  to support main body  16  and control the position of object engager  42  relative to load port  32 . Adjustment structure  212  includes a number of members  214 ,  215 ,  220 ,  230  for allowing lateral, roll and pitch adjustments. First, adjustment structure  212  includes a lateral adjustment member  214  that is coupled to a motor coupling member  215  that is coupled to traveling motor  20 . Lateral adjustment member  214  is adjustably positionable relative to motor coupling member  215 , and hence load port  32 , via an actuator  216  and gear  217  combination, e.g., an electric servomotor and worm gear, to provide lateral adjuster  204 . Second, adjustment structure  212  includes a roll adjustment member  218  that is pivotally coupled to lateral adjustment member  214  about an axis  220  that is substantially aligned with a travel X direction. The pivotal position of roll adjustment member  218  relative to lateral adjustment member  214 , and hence load port  32 , is adjustable via an actuator  222  and gear  223  combination, e.g., an electric servomotor and worm gear, to provide roll adjuster  206 . Third, adjustment structure  212  includes a pitch adjustment member  224  that is fixed to main body  16  and is pivotally coupled to roll adjustment member  218  about an axis  226  that is substantially aligned with a lateral Y direction. The pivotal position of pitch adjustment member  224  relative to roll adjustment member  218 , and hence load port  32 , is adjustable via an actuator  228  and gear  230  combination, e.g., electric servomotor and worm gear, to provide pitch adjuster  208 . Roll and pitch adjuster  206 ,  208  allow for compensation for imperfections in the mounting of rail  18 , among other causes of roll and pitch.  
         [0032]     In one embodiment, yaw adjuster  210  is incorporated as part of object engager  42 . Yaw adjuster  210  includes a yaw adjustment member  240  is pivotally coupled to lazy-tong linkage  70 , and rotatably coupled to object engager  42  about a substantially vertical axis  242 . Adjustment of yaw adjustment member  240 , and hence object engager  42 , about substantially vertical axis  242  is possible via actuator  244  and gear(s)  246  combination, e.g., electric servomotor and gearing. Also shown in object engager  42  is a grasping actuator  290  for grasping object  30 , as is known in the art.  
         [0033]     Feedback system  202  may include a number of sensors, as will now be described, that each feed to controller  24 . First, a hoist position sensor  250  may be provided to determine the position of object engager  42  relative to main body  16 . Hoist position sensor  250  may include a camera, laser, optical device, etc.,  252  and a corresponding fiducial  254  to which it is to be aligned. Second, an engager position sensor  260  may be provided to determine the position of object engager  42  relative to load port  32 . Engager position sensor  260  may include a camera, laser, optical device, etc.,  262  and a corresponding fiducial  264  on load port  32  (or a fixed position relative thereto) to which it is to be aligned. Third, one or more linear optical encoders  268 ,  270  may be implemented to measure the movement of linkages  72 . The information gathered by optical encoders  268 ,  270  can be used to determine hoisting distance and the differential movement of object engager  42  relative to main body  16 . In this case, in addition to the above-described adjustment system  200 , in another alternative embodiment, one or more ends of a linkage  72  that is/are coupled to main body  16  and object engager  42  may be coupled thereto via a linear bearing  272  to allow for limited movement in a folding direction of the linkage. In addition to the above-described sensors, each actuator  20 ,  46 ,  216 ,  222 ,  228 ,  244  and  290  includes a rotary encoder for closed loop position identification (PID) feedback. Each actuator also includes a “normally-on” brake to prevent motion when power is removed from the motors. Another sensor(s)  300  in the form of a strain gauge(s) can also be provided on various linkages  72  to sense and detect deflections in the linkages. The above-described sensors are used to adjust the position of object engager  42  relative to load port  32 , and allow for accurate positioning of object  30  via feedback and control by controller  24 . In particular, the above-described adjustment system  200  and feedback system  202  allow for accuracy up to +/−2 mm in X and Y directions, and 0.5 degrees in yaw, pitch and roll directions relative to the exact center of load port  32 .  
         [0034]     It should be recognized that while a particular structure of adjustment system  200  and feedback system  202  have been described herein that a variety of alternatives exist to provide the same functionality, which are considered within the scope of the invention.  
         [0035]     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.