Abstract:
A robotic is provided which comprises a hub ( 203 ); (b) a first lower arm ( 209 ) comprising first ( 213 ) and second ( 215 ) lower arm segments and having a first set of upper arms ( 229, 231 ) attached thereto; and (c) a first adjusting means ( 241 ) for adjusting the height of the first lower arm segment with respect to the second lower arm segment.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to robots, and more particularly to adjustment mechanisms for leveling end effectors and robotic arms. 
     BACKGROUND OF THE DISCLOSURE 
     The use of robots is widespread in the semiconductor industry, due to their ability to process a large number of semiconductor wafers through many different processing technologies, and to perform repetitive tasks quickly and accurately. The use of robots is especially advantageous in portions of semiconductor fabrication lines where human handling of semiconductor wafers is inefficient or undesirable. For example, many semiconductor fabrication processes, such as etching, deposition, and passivation, occur in reaction chambers having sealed environments. The use of robots allows these environments to be carefully maintained in order to minimize the likelihood of contamination and to optimize processing conditions. 
     Many of the robots currently utilized in the semiconductor industry are equipped with an end effector (also known as a blade or carrier) which is attached to one or more robotic arms. These robots are commonly used to transport semiconductor wafers from a loading port into various processing ports within a multiple chamber reaction system. The robotic arms are then employed to retrieve the wafer from a particular port after the wafer has been processed. The wafer is then shuttled by the robotic arms to the next port for additional processing. When all processing within the reaction system is complete, the robotic arm returns the semiconductor wafer to the loading port, and the next wafer is placed into the system by the robotic arm for processing. Typically, a stack of several semiconductor wafers is handled in this manner during each process run. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, a robotic is provided which comprises (a) a hub; (b) a first lower arm comprising first and second lower arm segments and having a first set of upper arms attached thereto; and (c) a first adjusting means for adjusting the height of the first lower arm segment with respect to the second lower arm segment. The robot may further comprise a second lower arm, wherein said second lower arm comprises third and fourth lower arm segments and has a second set of upper arms attached thereto, and may also comprise a second adjusting means for adjusting the height of the fourth lower arm segment with respect to the third lower arm segment. The first and second adjusting means may comprise, for example, bolts or screws. 
     In some embodiments, a first radius is disposed between the first lower arm segment and said hub, wherein said the first lower arm segment is attached to the first radius by a first fastener, wherein said first lower arm segment is rotatable with respect to the first radius when the first fastener is in a loosened state, and wherein said the first lower arm segment is not rotatable with respect to the first radius when the first fastener is in a tightened state. The first lower arm segment is rotatable with respect to the first radius by an angle φ when the first fastener is in a loosened state. Preferably, φ is within the range of about ±15°, more preferably |φ| is within the range of about 5° to about 15°, and most preferably |φ| is within the range of about 5° to about 10°. 
     In another aspect, a robotic is provided which comprises (a) a hub; (b) a first lower arm comprising first and second lower arm segments and having first and second upper arms attached thereto; (c) a first fastener (which may be, for example, a screw or a bolt) adapted to adjust the height of the second lower arm segment with respect to the first lower arm segment; (d) a second lower arm comprising third and fourth lower arm segments and having third and fourth upper arms attached thereto; (e) a second fastener (which may be, for example, a screw or a bolt) adapted to adjust the height of the fourth lower arm segment with respect to the third lower arm segment; (f) a first wrist assembly attached to said first and third upper arms; and (g) a second wrist assembly attached to said second and fourth upper arms. 
     In some embodiments, a first radius is disposed between the first lower arm segment and the hub, wherein the first lower arm segment is attached to the radius by a third fastener, wherein the first lower arm segment is rotatable with respect to the first radius when the third fastener is in a loosened state, and wherein the first lower arm segment is not rotatable with respect to the first radius when the third fastener is in a tightened state. Preferably, the first lower arm segment is rotatable with respect to the first radius by an angle φ 1  when the third fastener is in said loosened state. Preferably, φ 1  is within the range of about ±15°, more preferably φ 1 | is within the range of about 5° to about 15°, and most preferably |φ 1 | is within the range of about 5° to about 10°. 
     In other embodiments, a second radius is disposed between the third lower arm segment and the hub, wherein the third lower arm segment is attached to the second radius by a fourth fastener, wherein the third lower arm segment is rotatable with respect to the second radius when the fourth fastener is in a loosened state, and wherein the third lower arm segment is not rotatable with respect to the second radius when the fourth fastener is in a tightened state. Preferably, the third lower arm segment is rotatable with respect to the second radius by an angle φ 2  when the fourth fastener is in the loosened state, wherein φ 2  is preferably within the range of about ±15°. More preferably, |φ 1 | is within the range of about 5° to about 15°, and most preferably, |φ 1 | is within the range of about 5° to about 15°. 
     In a further aspect, a robot is provided which comprises (a) a hub having a first rotatable ring disposed thereon; (b) a first radius attached to said first ring; and (c) a first arm repositionably attached to said first radius. The first arm is preferably repositionably attached or repositionably attachable to the first radius by way of a first fastener which is adapted to be loosened to permit an angular adjustment of the first arm from a first position to a second position with respect to the first radius, and which is preferably further adapted to be tightened to secure the first arm in the second position. 
     In some embodiments, the first fastener comprises a threaded fastener with an axial portion which extends through a slot provided in a wall of the first arm and into an aperture provided in the first radius. The slot is preferably sufficiently larger than the axial portion to permit the first arm to be rotatable with respect to the first radius by an angle φ 1  when the first fastener is loosened but still inserted into the aperture provided in the first radius. Preferably, φ 1  is within the range of about ±15°, more preferably, |φ 1 | is within the range of about 10° to about 15°, and most preferably, |φ 1 | is within the range of about 5° to about 10°. 
     In some embodiments, the robot further comprises a second rotatable ring disposed on the hub; and a second radius attached to the second ring; wherein the second arm is repositionably attached to the second radius by way of a second fastening means which is adapted to be loosened to permit an adjustment of the first arm from a third position to a fourth position with respect to the second radius (preferably the adjustment involves an angular rotation of the first arm across the surface of the first radius). The second fastening means is preferably further adapted to be tightened to secure the second arm in the fourth position. In some such embodiments, the second fastening means comprises a threaded fastener with an axial portion which extends through a slot provided in a wall of the second arm and into an aperture provided in the second radius, wherein the slot is sufficiently larger than the axial portion to permit the second arm to be rotatable with respect to the second radius by an angle φ 2  when the second fastener is loosened but still inserted into the aperture provided in the second radius. Preferably, φ 2  is within the range of about ±15°, more preferably, |φ 2 | is within the range of about 10° to about 15°, and most preferably, |φ 2 | is within the range of about 5° to about 10°. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein: 
         FIG. 1  is an illustration of a prior art robot. 
         FIG. 2  is a cross-sectional view of one particular, non-limiting embodiment of a robot made in accordance with the teachings herein. 
         FIG. 3  is a top view of the arm assembly of the robot of  FIG. 2 . 
         FIG. 4  is a magnified view of the first lower arm segment of the robotic arm of  FIG. 2 . 
         FIGS. 5-6  illustrate the means by which the lower arm segment of the robotic arm of  FIG. 2  may be utilized to permit a slight angle of rotation of the lower arm segment with respect to the radius. 
         FIGS. 7-9  illustrate the use of a lower arm segment of the type described herein to achieve a Z-axis height adjustment. 
     
    
    
     DETAILED DESCRIPTION 
     Many different types of robots are utilized in the semiconductor industry.  FIG. 1  depicts one such robot. Robots of this type are utilized, for example, in the ENDURA® and CENTURA® 200 nm/300 nm platforms sold by Applied Materials (Santa Clara, Calif.). The robot  101  includes a central hub  103  and two lower arms  105 ,  107 . The lower arms  105 ,  107  are rotatingly attached to the hub  103  and are driven by servo drives housed within the hub  103 . 
     First  109  and second  111  pairs of forearms are attached to the lower arms  105 ,  107  by way of elbow joints  113 , and first  115  and second  117  wafer blades are attached to the first  109  and second  111  pairs of forearms, respectively, by way of wrist assemblies (not shown). The wafer blades  115 ,  117  are spaced 180° apart from each other and are adapted for handling semiconductor wafers and other objects utilized in semiconductor fabrication processes. The forearms  109 ,  111  of the robot can be extended or retracted by rotating the servo drives in opposite directions to each other, and can be rotated about the hub  103  (in the so-called theta direction) by rotating the servo drives in the same direction. The configuration of the arm assemblies (including lower arms  105  and  107 , forearms  109  and  111 , and wafer blades  115  and  117 ) in the robot  101  depicted in  FIG. 1  is referred to in the art as a “frog-leg” design. Since the robot  101  shown therein has two such configurations, it is referred to as a “dual frog-leg” design. 
     While robots of the type depicted in  FIG. 1  have many desirable attributes, they also suffer from some infirmities. One such infirmity relates to the configuration of the elbow joints  113  currently utilized in these robots. In particular, the robot  101  depicted in  FIG. 1  includes four elbow joints  113 . These elbow joints  113  are independently adjustable to attain the correct height and level of the wafer blades  115 ,  117  with respect to an axis (the so-called z-axis) which is perpendicular to the plane along which the robotic arm assemblies operate (this axis is also perpendicular to the major top surface of hub  103 ). The process of making adjustments to the attitude of the robot  101  via these elbow joints  113  is an inaccurate and time consuming process. 
     Moreover, such adjustments can place undue stress or strain upon the components of the robot, including the lower arms  105 ,  107  and forearms  109 ,  111 , the wrist assemblies (not shown), the elbow joints  113 , and the rotating rings (not shown) which are disposed upon or within the hub  103 . Such stresses can reduce the average lifetime of the arm assembly. In some instances, the presence of friction may even cause these stresses to be stored as potential energy while the forearms  109 ,  111  of the robot  101  are being extended or retracted. This stored energy may be released suddenly and rapidly, thereby imparting a jerky motion to the arm assembly that can cause harmful contact between the robotic arm assembly and surrounding equipment. This motion can also change the position of a wafer disposed on the blades  115 ,  117 , which can give rise to manufacturing defects. In some instances, this undesirable motion of the arm assemblies may even cause wafers to “hop” off of the wafer blades  115 ,  117 . This can result in serious damage to the wafer and to the processing equipment, and may require significant downtime while clean-up and repairs are implemented. 
     It has also been found that, in robots of the type depicted in  FIG. 1 , the rings upon which the lower arms  105 ,  107  are mounted may deviate from optimal concentricity and perpendicularity. During use, these deviations can transfer to the robotic arm assemblies, thus causing second order stresses within the elbow joints  113 , wrist assembly and hub  103 . It will be appreciated that such deviations from concentricity and perpendicularity, and the foregoing problems arising from attitude adjustments and the associated stresses they can impart, will tend to be exacerbated at higher throughputs. Since the current trend in the semiconductor industry is toward higher throughputs, these problems pose significant challenges to the implementation of current process technologies. 
     It has now been found that the foregoing problems may be alleviated or eliminated through the provision of a leveling mechanism which allows accurate leveling of wafer blades in robots of the type depicted in  FIG. 1 , so that the two wafer blades may be maintained in the same horizontal plane at all times. It has further been found that the foregoing problems may be alleviated or eliminated through the provision of a robotic arm assembly which includes a lower arm segment and a radius, and wherein the lower arm segment is adapted to permit a slight angle of rotation of the lower arm segment about the radius. 
     In contrast to the design depicted in  FIG. 1  in which the elbow joints are independently adjustable, robots may be made in accordance with the teachings herein in which the elbow joints are preferably machined to tight tolerances to each other, thus providing an accurate, stress free assembly. Height adjustment and leveling along the z-axis are preformed using the lower arm assembly, as described in greater detail below. In some embodiments, a secondary component may also be designed into one or more of the lower arms to provide stress free attachment to the magnetic rings of the hub. 
       FIGS. 2-4  depict a first particular, non-limiting embodiment of a robot made in accordance with the teachings herein. The robot  201  depicted therein comprises a hub  203 , a first radius  212  which is attached to a first rotating ring  205  or column in the hub  203 , a second radius  232  which is attached to a second rotating ring  207  or column in the hub  203 , and first  209  and second  211  lower arms. A first radius  212  is attached to the first rotating ring  205  by way of a fastener  217 , and a second radius  232  is attached to the second rotating ring  207  by way of a fastener  237 . Preferably, the fasteners  217  and  237  are threaded bolts or screws. 
     The first  209  lower arm comprises first  213  and second  215  lower arm segments. The first lower arm segment  213  is attached to the first radius  212  by way of fasteners  219  and  221  (which are preferably threaded bolts), and is attached to the second lower arm segment  215  by way of fastener  223  (which is also preferably a threaded bolt). Similarly, the second lower arm  211  comprises first  233  and second  235  lower arm segments. The first lower arm segment  233  is attached to the second radius  232  by way of fasteners  239  and  241  (which are preferably threaded bolts, and which are shown removed from the second radius  232  for greater clarity), and is attached to the second lower arm segment  235  by way of fastener  243  (which is also preferably a threaded bolt). The first lower arm segment  233  is of a slightly different geometry than first lower arm segment  213 , due to the need to attain co-planarity of the second arm segments  215  and  235  and the relative vertical disposition of the rings  205  and  207  to which the first lower arm segments  213  and  233  are attached. 
       FIG. 3  shows the upper portion  301  of the robot depicted in  FIG. 2 . As seen therein, the upper portion  301  of the robot comprises a first pair of forearms  303 ,  305  which are attached on one end to wrist assembly  307 , and which are respectively attached on the other end to second lower arm segments  215  and  235  (see  FIG. 2 ) by way of respective plates  309  and  311 . Similarly, a second pair of forearms  313 ,  315  are attached on one end to wrist assembly  317 , and are respectively attached on the other end to second lower arm segments  215  and  235  (see  FIG. 2 ) by way of respective plates  309  and  311 . First and second wafer blades (not shown) are mounted on wrist assemblies  307  and  317 , respectively. The details of the preferred construction of wrist assemblies  307  and  317  are shown in commonly assigned U.S. Ser. No. 10/919,070 (Kent), filed on Aug. 16, 2004, which is incorporated herein by reference in its entirety. 
     Referring now to  FIGS. 4-6 , one end  214  of the first lower arm segment  213  is preferably constructed with slots  220  and  222  whose diameters are slightly larger than the axial portion of respective fasteners  219  and  221 . Such a construction permits a slight angle of rotation φ of the lower arm segment  213  with respect to radius  212  (and about the longitudinal axes of the fasteners  219  and  221 ) when the fasteners  219  and  221  are sufficiently loosened, after which the first lower arm segment may be fixed in the desired orientation by tightening the fasteners  219  and  221 . The fasteners  219  and  221  may be adapted to engage either a threaded nut or a threaded aperture provided in the radius  212 . Preferably, the second  233  lower arm segment is constructed in a similar manner so as to permit a slight angle of rotation therein with respect to radius  232  (and about the longitudinal axis of the threaded fasteners  239  and  241 ). 
     In some embodiments, the aforementioned angle of rotation φ about radius  212  or  232  is preferably within the range of about ±15°, more preferably within the range of about ±10°, and most preferably within the range of about ±5°, while in other embodiments, the aforementioned angle of rotation φ about radius  212  or  232  is preferably within the range of about ±15°, more preferably within the range of about 5° to about 15°, and most preferably within the range of about 5° to about 10°. It has been found that the provision of such an angle of rotation is sufficient to relieve the stress that might otherwise be placed on the wrist, elbow and hub assemblies from the elbow joints as noted above, while also compensating for slight deviations in the rings  205  and  207  which might prevent lower arms  213  and  233  from achieving perpendicularity with respect to the hub  203 . 
     While the foregoing embodiment utilizes a construction which affords an angle of rotation φ and which is equipped with two fasteners (e.g., fasteners  219  and  221 ), it will be appreciated that embodiments are also possible in accordance with the teachings herein which provide an angle of rotation and which are equipped with a single fastener, or with more than two fasteners. Moreover, in some embodiments, such a construction may be utilized in either one of, or in both of, lower arm segments  213  and  233 . It will further be appreciated that, in some embodiments, the slots  220  and  222  into which fasteners to  219  and  221 , respectfully, extend may be extended along an axis of rotation perpendicular to fasteners  219  and  221  so as to permit an angle of rotation β of lower arm segment  213  about its longitudinal axis. In some embodiments, lower arm segment  233  may have a similar construction. 
     With reference to FIGS.  2  and  7 - 9 , an adjustment mechanism in the form of a series of cap screws  225  and  245  is provided in each of the second lower arm segments  215  and  235 . The cap screws  225  and  245  extend through apertures  351  and  353  of plates  309  and  311 , respectively (see  FIG. 3 ). As the cap screws  225  and  245  are tightened, they press against a lip  251  provided on one end of the abutting respective lower arm segments  213  or  233 , thereby adjusting the respective forearms  229  and  231  upward (as indicated by the arrows) along the longitudinal axes of the cap screws  225  and  245 . Preferably, the fasteners  223  and  243  (see  FIG. 2 ) are loosened somewhat while the orientation of the robotic arm assembly is being modified, and are tightened once the proper orientation is attained. 
     In the preferred embodiment shown in  FIGS. 2-9 , one cap screw  225  is provided in the second lower arm segment  215 , and two cap screws  245  are provided in the second lower arm segment  235 . This arrangement provides a three point leveling mechanism which allows the heights of the wafer blades attached to the wrist assemblies  307  and  317  (see  FIG. 3 ) to be adjusted while the relative horizontal plane of operation of the robotic arm assembly is maintained. Since the robotic arm assembly moves only in axial and radial directions with respect to the hub  203 , this adjustment mechanism performs the critical function of allowing both wafer blades to be maintained in the same horizontal plane. Of course, one skilled in the art will appreciate, however, that a similar end may be achieved by, for example, utilizing more than three cap screws, or through the use of other fasteners or adjustment means as are known to the art. 
     The above description of the present invention is illustrative, and is not intended to be limiting. It will thus be appreciated that various additions, substitutions and modifications may be made to the above described embodiments without departing from the scope of the present invention. Accordingly, the scope of the present invention should be construed in reference to the appended claims.