Abstract:
An apparatus for transporting a wafer-shaped article, comprises a holder configured to hold a wafer-shaped article of a predetermined diameter, attached to a robot arm that is horizontally movable, via a linkage. The holder is vertically movable relative to the distal end of the robot arm via the linkage from a retracted position to an extended position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to an apparatus and method for transporting wafer-shaped articles, such as semiconductor wafers, in which a wafer-shaped article is introduced into a process chamber. 
         [0003]    2. Description of Related Art 
         [0004]    Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668. Alternatively, a chuck in the form of a ring rotor adapted to support a wafer may be driven without physical contact through an active magnetic bearing, as is described for example in International Publication No. WO 2007/101764 and U.S. Pat. No. 6,485,531. 
         [0005]    Such chucks are sometimes mounted in closed process chambers to contain the hazardous substances used for wafer processing, as well as to maintain a superatmospheric pressure for those processes requiring such a condition. Closed process chambers are provided with a door or cover to permit loading and unloading of wafers on the chuck inside the process chamber. 
         [0006]    Wafers are conventionally loaded and unloaded from open process modules by wafer-handling robots, wherein the end effector of such robots grips the wafer by any of various techniques, such as edge contact only (ECO), as described for example in U.S. Pat. Nos. 5,022,695, 5,700,046, 5,955,858, 6,100,677, 6,491,330, or by application of the Bernoulli principle, as described for example in DE 19948572A1 and U.S. Pat. No. 7,100,954. 
         [0007]    Typically wafers are loaded on top of a chuck in a closed chamber. In order to facilitate the transfer of the wafer from an end effector to the chuck, lifting pins are provided that help to lower a wafer from a higher position on an end effector to a lower position on a chuck. 
         [0008]    However, conventional end effectors for loading and unloading wafers are ill-suited for use with chucks that are housed within a closed process chamber, unless the process chamber is provided with a relatively large door or cover that unnecessarily exposes the chamber ambient when it is opened during loading and unloading of wafers. Loading is especially a problem if the level of the opening in the closed chamber is lower than the level of the position of the wafer when held by the chuck. 
       SUMMARY OF THE INVENTION 
       [0009]    The present inventors have developed an improved apparatus and method for transporting wafer-shaped articles, in which a holder carrying a wafer-shaped article can pass horizontally through a relatively narrow process chamber door, and can thereafter transport the wafer-shaped article within the process chamber in a vertical direction, to bring the wafer-shaped article to a loading and unloading position. 
         [0010]    The holder may have the form of a blade or a fork, on which the wafer rests. The wafer may rest on the blade via the wafer&#39;s lower side, or may contact the blade via its edge only, or its peripheral bevel region. The wafer may also be gripped by gripping pins of the holder, in which case the holder may be referred to as a gripper. 
         [0011]    Thus, the invention in one aspect relates to an apparatus for transporting a wafer-shaped article, comprising a holder configured to hold a wafer-shaped article of a predetermined diameter, a robot arm that is horizontally movable, and a linkage interconnecting a distal end of the robot arm and the holder. The holder is vertically movable relative to the distal end of the robot arm via the linkage from a retracted position to an extended position. 
         [0012]    In preferred embodiments of the apparatus according to the present invention, the distal end of the robot arm, the holder and the linkage collectively have a first vertical extent in the retracted position and a second vertical extent in the extended position, the second vertical extent being at least twice that of the first extent. 
         [0013]    In preferred embodiments of the apparatus according to the present invention, the holder and the linkage constitute an end effector of a wafer transport robot. 
         [0014]    In preferred embodiments of the apparatus according to the present invention, the end effector fits through an opening whose vertical clearance is less than 6 cm. Even more preferably, the end effector fits through an opening whose the vertical clearance is less than 3 cm. 
         [0015]    In preferred embodiments of the apparatus according to the present invention, the linkage is a parallelogram linkage comprising at least two links. Advantageously, the apparatus is configured so that the vertical extent of the linkage beneath the wafer-shaped article as the wafer-shaped article is placed on the holder is less than 2 cm. 
         [0016]    In preferred embodiments of the apparatus according to the present invention, a powered actuating element engages at least one of the at least two links, and is operable to pivot the link about one of its pivot pins so as to cause the holder to move from a collapsed entry position to an extended loading and unloading position. 
         [0017]    In preferred embodiments of the apparatus according to the present invention, the powered actuating element comprises a pneumatic cylinder. Alternatively, the powered actuating element may be piezo-electrically driven. 
         [0018]    In preferred embodiments of the apparatus according to the present invention, the powered actuating element is operable to move the holder vertically while the distal end of the robot arm remains stationary. It is particularly preferred that the robot arm remains stationary with respect to the vertical axis. However, if desired the robot arm may move horizontally in order to compensate the horizontal movement of the holder when it is vertically moved. 
         [0019]    In preferred embodiments of the apparatus according to the present invention, the holder is designed to hold a wafer-shaped article by edge contact only. 
         [0020]    In preferred embodiments of the apparatus according to the present invention, the holder is configured to hold a wafer-shaped article of a predetermined thickness, and wherein the linkage permits the holder to be moved vertically relative to the distal end of the robot arm by a distance that is at least 15 times greater than the predetermined thickness of the wafer-shaped article. 
         [0021]    The present invention in another aspect relates to a method of transporting a wafer-shaped article, comprising positioning a wafer-shaped article on a holder of a robot arm, moving the robot arm so as to cause the holder to pass horizontally through a lateral opening in a process chamber, and displacing the holder vertically relative to the robot arm so as to bring the wafer-shaped article to a loading and unloading position. 
         [0022]    In preferred embodiments of the method according to the present invention, the displacing is effected by a linkage interconnecting the holder and a distal end of the robot arm. 
         [0023]    In preferred embodiments of the method according to the present invention, a powered actuating element mounted on the robot arm acts on the linkage to effect the displacing. 
         [0024]    In preferred embodiments of the method according to the present invention, the lateral opening is greater than 30 cm in width and has a vertical clearance of less than 6 cm. The vertical clearance is still more preferably less than 3 cm. 
         [0025]    The present invention in yet another aspect relates to a method of unloading a wafer-shaped article from a process chamber, comprising moving a robot arm comprising a holder mounted at a distal end of the robot arm so as to cause the holder to pass horizontally into a process chamber through a lateral opening in a process chamber, displacing the holder vertically relative to the distal end of the robot arm so as to bring the holder to an unloading position, positioning a wafer-shaped article on the holder at the unloading position, and withdrawing the wafer-shaped article from the process chamber by displacing the holder vertically relative to the distal end of the robot arm and by moving the robot arm so as to cause the holder to pass horizontally out of the process chamber through the lateral opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1  is perspective view from above of an end effector utilized in one embodiment of an apparatus according to the present invention, with a wafer positioned thereon; 
           [0028]      FIG. 2  a perspective view from below of the configuration depicted in  FIG. 1 ; 
           [0029]      FIG. 3  is a view corresponding to that of  FIG. 1 , with the holder displaced vertically relative to the distal end of the robot arm; 
           [0030]      FIG. 4  a perspective view from below of the configuration depicted in  FIG. 3 ; 
           [0031]      FIG. 5  is a fragmentary side view showing in greater detail the linkage in the configuration of  FIGS. 3 and 4 ; 
           [0032]      FIG. 6  is a fragmentary side view showing in greater detail the linkage in the configuration of  FIGS. 1 and 2 ; 
           [0033]      FIG. 7  is a schematic side view of the effector arm in the configuration depicted in  FIGS. 1 and 2 ; 
           [0034]      FIG. 8  is a schematic side view of the effector arm in the configuration depicted in  FIGS. 3 and 4 ; 
           [0035]      FIG. 9  is perspective view from below of an end effector utilized in another embodiment of an apparatus according to the present invention, with a wafer positioned thereon; 
           [0036]      FIG. 10  is a view corresponding to that of  FIG. 9 , with the holder displaced vertically relative to the distal end of the robot arm; 
           [0037]      FIG. 11  is a side view of the configuration depicted in  FIG. 9 ; 
           [0038]      FIG. 12  is a side view of the configuration depicted in  FIG. 10 ; 
           [0039]      FIG. 13  shows an apparatus according to the embodiment of  FIGS. 9-12  after having introduced a wafer into a closed process chamber; and 
           [0040]      FIG. 14  shows a subsequent step to that illustrated in  FIG. 13 , after the wafer has been displaced vertically relative to the robot arm. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]    Referring now to  FIG. 1 , an embodiment of an apparatus for transporting wafer-shaped articles according to the invention comprises an end effector  10  that includes the distal end  12  of a robot arm  14 , a holder  20  that is holding a semiconductor wafer W, a parallelogram linkage comprising side links  16  and middle link  18  that interconnects the distal end  12  with the holder  20 , and a pneumatic cylinder  22  mounted on the distal end  12  and having an extensible and retractable shaft connected to the middle link  18 . 
         [0042]    As is shown in  FIG. 2 , the holder  20  of this embodiment is generally shaped like a tuning fork, and is if the “edge contact only” type as described for example in U.S. Pat. Nos. 6,100,677 and 6,491,330, although other types of holders may also be used. Links  16  and  18  form a parallelogram linkage, with each link being pivotably mounted at its proximal end to the distal end  12  of robot arm  14 , and pivotably mounted at its distal end to the holder  22 . The extensible and retractable shaft of pneumatic cylinder  22  is pivotably mounted to middle link  18  at a point closer to the distal pivot of link  18  than to the proximal pivot thereof. Pneumatic cylinder is itself pivotably mounted at its proximal end to the distal end  12  of robot arm  14 . 
         [0043]    Consequently, when the shaft of pneumatic cylinder  22  is retracted, as shown in  FIGS. 3 and 4 , it lifts up from the distal end  12  somewhat, and also lifts up the middle link  18 . This in turn causes the holder  20  to be displaced vertically upwardly, and the side links  16  follow that movement and ensure that the holder  20  and hence the wafer W retain their same angular orientation (in this case horizontal) as the holder is moved upwardly. 
         [0044]    The semiconductor wafer W held by holder  20  is for example a silicon wafer whose diameter is 300 mm. 300 mm wafers are a standard size in the semiconductor industry, and the corresponding thickness of such wafers is about 775 micron. The holder  20  in this embodiment is therefore designed to hold wafers of that diameter and thickness. However, the holder  20  may instead be configured to hold wafers of other diameters and thicknesses, for example wafers of 200 mm diameter and 726 micron thickness, or wafers of 450 mm diameter and 925 micron thickness. 
         [0045]    The linkage in this embodiment is formed by three links, with the middle link  18  being a drive link and the side links  16  follower links. Alternatively, a linkage with only two links may be used, with one link being the drive link and the other link being the follower, in which case the proximal and distal pivot points of the two links are preferably parallel to and offset from one another, rather than being aligned as with the side links  16 . 
         [0046]    Other types of linkages may be used to interconnect the distal end of the robot arm with the holder, provided that such linkage is capable of displacing the holder vertically relative to the robot arm and does not cause the end effector to become too tall in the retracted position of the holder, as will be described herein-below. For example, a set of telescoping members connected at one side to the holder and at the opposite side to the distal end of the robot arm could be used. 
         [0047]      FIGS. 5 and 6  highlight the structure of the parallelogram linkage utilized in the embodiment of  FIGS. 1-4 . As is shown in those figures, the linkage permits the holder  20  to be raised substantially when in the unloading and loading position illustrated in  FIG. 5 . On the other hand, when the holder  20  is retracted as shown in  FIG. 6 , the aspect ratio of the effector arm is quite low, and the effector arm may thereby pass through even very narrow openings formed in a process chamber wall. 
         [0048]    For example, as shown in  FIGS. 7 and 8 , the end effector assembly will have a total vertical extent “a” when the holder is retracted relative to the distal end  12  of robot arm  14  ( FIG. 7 ). However, when holder is displaced vertically relative to the distal end  12  of robot arm  14 , the magnitude of the vertical extent is increased to “b.” In this example, the extent “b” is approximately 2.6 times the extent “a”. More generally, “b” is preferably at least 1.5 times “a”, more preferably at least twice “a” and most preferably at least 2.5 times “a”. The difference between “b” and “a” is a measure of how far the wafer W has been displaced vertically, which in this case is about 26 mm for a 300 mm diameter wafer. In practice, the end effector can preferably effect a vertical displacement of the holder arm relative to the robot arm by at least 10 mm, preferably at least 20 mm, and more preferably at least 25 mm. 
         [0049]      FIGS. 7 and 8  also illustrate that the thickness of distal end  12  is “c”, which in this embodiment is about 11 mm, whereas the distance “b” in this embodiment is about 42 mm and the distance “a” in this embodiment is about 16 mm. Assuming a 300 mm wafer, the aspect ratio of the end effector of this embodiment is approximately 0.05 in the  FIG. 7  configuration and approximately 0.14 in the  FIG. 8  configuration. 
         [0050]    Turning now to  FIGS. 9-12 , the end effector according to the embodiment of those Figures provides an even smaller holder  21 , and a linkage composed of links  17 ,  19  that together with distal end  13  provides an even smaller aspect ratio than in the previous embodiment. Nevertheless, as is evident from a comparison of  FIG. 9  to  FIG. 10  and  FIG. 11  to  FIG. 12 , the linkage of this embodiment still permits displacing the holder  21  and wafer W vertically a substantial distance relative to distal end  13 . 
         [0051]    In  FIGS. 13 and 14 , the apparatus of the embodiment of  FIGS. 9-12  is shown in use, loading a wafer W onto a spin chuck inside of a closed process chamber. In particular, the spin chuck  30  and process chamber  50  illustrated in  FIGS. 13 and 14  are as described more fully in commonly-owned copending U.S. patent application Ser. No. 13/276,940 filed Oct. 19, 2011. Spin chuck  30  is this embodiment is of the magnetic rotor type, and a wafer W is positioned on chuck  30  via downwardly depending pins  32  such that the wafer hangs down from the chuck. 
         [0052]    In  FIG. 13 , the door  54  covering opening  52  of chamber  50  has been opened, and a wafer transport robot depicted schematically at  40  has moved its arm including distal portion  13  into the chamber  50 , such that wafer W is positioned beneath chuck  30 . Next, as shown in  FIG. 14 , the powered actuator, such as a pneumatic cylinder as described previously, is actuated so as the raise the holder  21  relative to the distal end  13  of the robot arm, via links  17 ,  19 , to a loading position in which the eccentric pins  32  can be rotated into engagement with the edge of wafer W. 
         [0053]    Unloading of the wafer W from chuck  30  is effected by performing the above-described sequence of operations in reverse. 
         [0054]    The apparatus and method of the invention may of course also be used in a spin chuck in which the wafer is held by pins that project upwardly from the chuck. In that case, the linkage is configured so as to displace the holder vertically downwwardly in relation to the robot arm, rather than upwardly. 
         [0055]    Although in  FIGS. 13 and 14  the distal end  13  of the robot arm is positioned inside chamber  50 , it may instead, during loading and unloading of a wafer, depending upon the particular configuration of the chamber and the end effector, be positioned entirely outside the chamber or be positioned partly inside and partly outside the chamber.