Abstract:
A wafer handling robot system ( 10 ) operates in a wafer chamber ( 40 ) and comprises two independent robot blades, an upper blade ( 18 ) surmounting a lower blade ( 26 ). A pair of wafers ( 28, 32 ) are supported and positioned at the outer ends ( 78 ) of the upper and lower blades ( 18, 26 ). The upper robot blade ( 18 ) keeps an upper wafer ( 28 ) at a level just above the level at which the lower robot blade ( 26 ) keeps a lower wafer ( 32 ). Because the wafers are virtually at the same level, the same wafer lift mechanism can be used in the wafer chamber to lift and remove or replace the wafers on the two blades. By offsetting the height of the wafers by minimal amounts, the throughput of the system can be increased by up to a factor of two over a single robot blade system, particularly if the robot is the limiting factor on throughput. This throughput enhancement represents a substantial gain with a relatively simple and inexpensive addition to the equipment.

Description:
BACKGROUND OF THE INVENTION 
     In semiconductor manufacturing, robots are commonly used to move wafers from one location to another. The use of efficient robots is particularly important for manufacturing processes in which the wafers are subjected to many chemical processes. Because the different processes are carried out in separate reaction chambers, the wafers have to be transported from one reaction chamber to another in a multiple chamber system. U.S. Pat. No. 5,292,393 to Maydan et al. discloses an example of an integrated modular multiple chamber vacuum processing system. A robot employs a dual four-bar link mechanism for imparting selected R-theta movement to the blade to load and unload wafers in the system of Maydan et al. Other robots of a four-bar link configuration are found in U.S. Pat. No. 5,280,983 to Maydan et al. and U.S. Pat. No. 5,452,521 to Niewmierzycki. 
     Another type of robot arm mechanism is known as the frog-leg type mechanism. U.S. Pat. No. 5,655,060 to Lucas discloses a cluster tool robot that employs a frog-leg type dual arm mechanism driven by a drive system to rotate and to stretch or translate in and out of process modules. U.S. Pat. Nos. 5,435,682 and 5,020,475 to Crabb et al., disclose substrate handling subsystems employing frog-leg mechanisms for moving wafers or substrates to and from processing subsystems. A frog-leg robot having walking-beams is disclosed in U.S. Pat. No. 5,569,014 to Hofmeister. 
     The robot speed is one key factor that limits the production capability or throughput of the equipment, especially in processes that require quick and frequent transport between chambers. To achieve higher throughput, a pair of four-bar link arms have been used to operate a pair of robot blades that are stacked together and spaced from one another. The two robot arms rotate together, but may move in and out independently. After the robot rotates the arms to a chamber and aligns the upper arm with the chamber inlet, the upper arm moves into the chamber to load or unload a wafer. The upper arm is then withdrawn from the chamber, and the robot moves the arms vertically upwardly to align the lower arm with the chamber inlet. The lower robot arm then moves in and out of the chamber to load or unload a wafer. The use of the dual robot arm mechanism essentially increases the overall speed of the robot. While the use of the dual arms increases throughput, the requirement for vertical movement of the robot arms decreases the overall speed and may be undesirable in certain systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a simple and effective wafer handling robot mechanism that operates in a wafer chamber and comprises two independent robot blades for handling wafers, an upper blade surmounting a lower blade, at virtually the same level. Because the two blades are at virtually the same level, they can independently access different wafer chambers or simultaneously access the same chamber without requiring any vertical indexing. As a result, the same wafer lift mechanism can be used in the wafer chamber to lift and remove or replace the wafers on the two blades. Because no vertical indexing is required for the two blades, the present robot system is more efficient and versatile, and can improve throughput by up to about 100% over existing single blade systems. 
     In accordance with an aspect of the present invention, a robot blade system for moving substrates into and out of a chamber through an opening comprises a first robot blade for supporting a first substrate. A second robot blade is disposed generally above and spaced from the first robot blade by a small distance for supporting a second substrate. A first robot arm is coupled to the first robot blade for moving the first substrate and at least a portion of the first robot blade through the opening into the chamber and moving the first substrate and the first robot blade out of the chamber. A second robot arm is coupled to the second robot blade for moving the second substrate and at least a portion of the second robot blade through the opening into the chamber and moving the second substrate and the second robot blade out of the chamber. The second robot arm is independently movable from the first robot arm. This structure allows the first and second robot arms to move independently the first and second substrates, respectively, on the first and second robot blades into and out of the chamber. Because the second robot blade is spaced from the first robot blade by a small distance, the two robot blades are at virtually the same level and can access the same chamber without requiring any vertical indexing. 
     In addition, the robot blades can be tapered and include hollow portions to reduce the weight of the blades, thereby minimizing deflection and vibration of the blades, especially if they are long. The blades are advantageously made of a material having a strength-to-weight ratio that provides a bending deflection of the blades of under about 0.5 mm. In one example, the robot blades are up to about 300 mm in length and comprise sapphire. 
     Another aspect of the invention is a system for moving substrates into a housing through an opening which defines a plane spaced between an upper boundary and a lower boundary, where the plane is spaced from the lower boundary by a lower gap and spaced from the upper boundary by an upper gap. The system comprises a lower blade for supporting a lower substrate and an upper blade closely spaced from the lower blade for supporting an upper substrate. The system comprises first member, coupled to the lower blade, for moving the lower substrate through the lower gap into and out of the housing. The system further comprises second member, coupled to the upper blade and independent from the first member, for moving the upper substrate through the upper gap into and out of the housing. Because of the positions and spacings of the upper and lower blades, they can move simultaneously or separately into and out of the opening smoothly without interference. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of this invention, illustrating all their features, will now be discussed in detail. These embodiments depict the novel and nonobvious robot system of this invention shown in the accompanying drawings, which are included for illustrative purposes only, and are not drawn to scale. These drawings include the following figures, with like numerals indicating like parts: 
     FIG. 1 is an elevational view of a wafer handling robot system with dual independent robot blades schematically illustrating an embodiment of the invention; 
     FIG. 2 is an enlarged elevational view of the ends of the dual robot blades in the robot handling system of FIG. 1 schematically illustrating the wafers disposed near the blade tips; 
     FIG. 3 is a top plan view of the wafer handling robot system of FIG. 1 in a multiple chamber integrated process system schematically illustrated to show the operating environment of the robot system; 
     FIG. 4 is a top plan view of a frog-leg robot arm mechanism for operating the dual independent robot blades of FIG. 1; and 
     FIG. 5 is a top plan view of a four-bar link robot arm mechanism for operating the dual independent robot blades of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Wafer Handling Dual Independent Robot Blades 
     FIGS. 1-3 show, in schematic form, a wafer or substrate handling robot mechanism or system  10  that includes a first robot  12  controlling a first robot arm  16  coupled to a first robot blade  18 , and a second robot  20  controlling a second robot arm  22  coupled to a second robot blade  26 . The first robot blade  18  supports a first wafer or substrate  28 , and is disposed above and vertically spaced from the second robot blade  26  by a small gap  30 . The second robot blade  26  supports a second wafer or substrate  32 . The first and second blades  18 ,  26  desirably include indented seats or pockets  34  at the ends to support respectively the first and second wafers  28 ,  32  as best seen in FIG.  2 . The robot system  10  employs a dual independent robot mechanism in that the two robot blades  18 ,  26  are independent, as discussed in more detail below. 
     FIGS. 1 and 2 show a chamber opening  36  through which wafers are transported by the robot system  10 . The opening  36  typically has a height of about ¾ inch or 19 mm. The wafers  28 ,  32  each have a thickness of about 0.675 mm. To allow both robot blades  18 ,  26  to move the wafers  28 ,  32  smoothly through the chamber opening  36 , the maximum thickness of the robot blades  18 ,  26  are desirably equal to or less than about 6 mm each and the gap  30  between them is desirably less than 5.0 mm, more desirably about 2.5 mm. In the embodiment shown, the robot blades  18 ,  26  tapers in height respectively from the robot arms  16 ,  22  to thinner ends. As best seen in FIG. 3, the robot blades  18 ,  26  desirably also taper in width respectively from the robot arms  16 ,  22  to the narrower ends. 
     Advantageously, the two sets of robot arms  16 ,  22  and blades  18 ,  26  can independently access several different chambers or the same chamber simultaneously without requiring any vertical movement. To do so, we designed robot arms  16 ,  22  so that both sets of arms  16 ,  22  and blades  18 ,  26  can simultaneously go into the same slit valve opening  36  (although it is possible for each set to access different chambers). Because no vertical indexing is required, the present robot system  10  is more efficient and versatile. 
     FIG. 2 shows the details at the ends or tips of one example of the robot blades  18 ,  26  with the wafers  28 ,  32 . The blade height or thickness  33  is under about 1.05 mm at position A adjacent the tips where the wafers  28 ,  32  are disposed. The blade thickness  33 a increases gradually to about 6 mm at position B away from the blade tips, where the blades  18 ,  26  desirably are hollow as shown. This tapering thickness is not shown in the figures. The gap  30  is about 2.5 mm. The blade width is about 50 mm at position A near the blade tips, and increases to about 60 mm at position B away from the blade tips (see FIG.  4 ). The length of the blades  18 ,  26  may range up to about 200 to 300 mm. The tapering of the blades  18 ,  26  and the use of hollow portions reduce the weight, thereby minimizing deflection and vibration of the blades  18 ,  26 . 
     Other dimensions and shapes are possible depending on the operating environments. In addition, the robot blades  18 ,  26  are disposed near the center of the chamber opening  36 . In this manner, the two robot blades  18 ,  26  may move smoothly in and out of the chamber simultaneously or one after the other. The spacing  30  between the blades  18 ,  26  is such that no adjustment in the chamber height is required to allow the wafers  28 ,  32  to be properly placed in the wafer chamber by the robots  12 ,  20 . Because of the small gap  30  separating the two vertically offset blades  18 ,  26 , the wafers  28 ,  32 , the same wafer lift mechanism (see, e.g.,  31  schematically shown in one of the chambers in FIG. 3 for illustrative purposes) can be used in the wafer chamber to lift and remove or replace the wafers  28 ,  32  on the two blades  18 ,  26 , thereby increasing the throughput of the system. 
     In addition to being independent in translational movement in and out of the chamber, the two robot blades  18 ,  26  are independently moved by the two robots  12 ,  20  respectively in rotation, as best seen in FIG.  3 . FIG. 3 shows a multiple chamber integrated process system  40  comprising an enclosed, generally pentagonal main frame or housing  42  having five sidewalls  44  that define an enclosure, which may be a vacuum load lock enclosure, for the dual independent robot system  10 . There are four vacuum processing chambers  46 ,  47 ,  48 ,  49  connected to four of the sidewalls  44 . The process chambers  46 ,  47 ,  48 ,  49  and the associated sidewalls  44  have communication slots or slits  50  similar to the chamber opening  36  of FIGS. 1 and 2. Doors or slit valves  54  are provided for sealing the access slits  50 . An external cassette chamber  56  is coupled to the remaining sidewall  44  for supplying wafers to the main housing  42 . The main housing  42  typically also includes an internal cassette storage assembly which is not shown for simplicity. 
     The robot system  10  transfers wafers or substrates between the external cassette chamber  56  and the individual process chambers  46 ,  47 ,  48 ,  49 . Because the two robot blades  18 ,  26  are independent in rotation and translation, they may transfer the wafers  28 ,  32  at different chambers or at the same chamber. Details of individual structural components and sensors and of the operations of the multiple chamber integrated process system  40  are known in the art, such as U.S. Pat. Nos. 5,292,393 and 5,452,521 identified above, and will not be repeated here. 
     As discussed above, the use of the dual independent robot blade system  10  will increase the throughput by a factor of up to two over a single robot blade system. This factor is higher for systems that require quick and frequent movements of the robot blades  18 ,  26  with short stays at any one chamber (robot over-tasking) over those with infrequent movements and longer stays (robot under-tasking). Another advantage of the dual independent robot blade system  10  is that the system  10  is still operational if one of the two blades  18 ,  26  breaks down. 
     Implementation of the Wafer Handling System 
     As discussed above, different robot arms have been used in wafer or substrate handling systems. The following discusses examples of robot arms that may be used to implement the dual independent robot system  10 , which are provided merely for illustrative purposes. 
     Frog-Leg Robot Arm Mechanism 
     In FIG. 4, a frog-leg robot arm mechanism  60  is used to support and operate the upper robot blade  18  to move the first wafer  28 . A similar frog-leg mechanism can be used for moving the second wafer  32 . The frog-leg robot arm mechanism  60  comprises a first distal link or main arm  62  rotatably coupled at its end to a first proximal link or forearm  64 , which is rotatably coupled at its end to a first rotational joint  66  at the distal end  68  of the robot blade  18 . The frog-leg robot arm mechanism  60  further comprises a second distal link or main arm  72  rotatably coupled at its end to a second proximal link or forearm  74 , which is rotatably coupled at its end to a second rotational joint  76  at the distal end  68  of the robot blade  18 . The first and second rotational joints  66 ,  76  are typically provided with bearings. A proximal end  78  (at position A) of the robot blade  18  supports the wafer  28  near the blade tip. At the rotational coupling between the first distal link  62  and first proximal link  64  is typically a first bearing  82  or similar structure. Similarly, a second bearing  84  is disposed at the rotational coupling between the second distal link  72  and the second proximal link  74 . The frog-leg robot arm mechanism  60  is also illustrated in FIGS. 1 and 3. 
     The first distal link  62  has a first distal end  88  that is coupled to a first drive shaft  90 . The second distal link  72  has a second distal end  92  that is coupled to a second drive shaft  94 . The upper robot  12  operates the first and second drive shafts  90 ,  94 . FIG. 4 shows the concentric drive shafts  90 ,  94  that are vertically offset from one another. Other configurations such as non-concentric drive shafts  90 ,  94  are possible. When the robot  12  drives the drive shafts  90 ,  94  in opposite rotational directions, the distal links  62 ,  72  and proximal links  64 ,  74  move in a frog-leg manner with extending and retracted folding movements. The resultant motion of the robot blade  18  is extension into and retraction out of the process chamber. When the robot  12  drives the drive shafts  90 ,  94  in the same rotational direction, the distal links  62 ,  72  and proximal links  64 ,  74  do not move in a frog-leg manner. Rather, the distal links  62 ,  72  and proximal links  64 ,  74  rotate together around the drive shafts  90 ,  94  of the robot  12  from one chamber to the next. The robot  12  includes motors, gears, and other components that are known in the art and will not be discussed here. 
     The robot arm mechanism  60  and the robot blade  18  must be sufficiently long to move the wafer  28  through the chamber opening  36  into the process chamber or other chambers to load or unload the wafer  28 . In one embodiment, the robot blade  18  is desirably made sufficiently long to facilitate the required movement. Such a long robot blade  18  typically ranges from about 200 to 300 mm. As discussed above, the maximum thickness of the robot blade  18  is desirably equal to or less than about 6 mm. 
     Alternatively, the blade  18  is made shorter (under 200 mm), and the first and second proximal links  64 ,  74  and the first and second rotational joints  66 ,  76  may extend into the chamber opening  36  with the short blade  18 . The first and second bearings  82 ,  84 , along with portions of the first and second distal links  62 ,  72 , may also extend into the chamber opening  36 . In that case, the maximum height of the proximal links  64 ,  74 , the bearings at the first and second rotational joints  66 ,  76 , the distal links  62 ,  72 , and the first and second bearings  82 ,  84  is desirably equal to or less than 6 mm. The use of a long blade  18  allows one to use thicker links and bearings, but is more susceptible to bending and vibration. The use of a short blade  18  alleviates these problems, but requires thinner links and bearings. As discussed above, a similar frog-leg robot arm mechanism as the mechanism  60  can be used to operate the lower robot blade  26 , such as shown in FIG.  1 . 
     Four-Bar Link Robot Arm Mechanism 
     In the four-bar link robot arm mechanism  100  of FIG. 5, first and second parallel links  102 ,  104  have ends that are pivotally mounted, respectively, at first and second spaced rotational joints  106 ,  108  of the upper robot blade  18 . The other ends of the parallel links  102 ,  104  are mounted, respectively, at spaced pivot points  112 ,  114  along a connecting link  116 . The first and second parallel links  102 ,  104 , robot blade  18 , and connecting link  116  form a parallelogram. The four-bar link mechanism  100  further comprises third and fourth parallel links  122 ,  124  having ends that are pivotally coupled, respectively, to first and second spaced drive shafts  126 ,  128 , which are coupled to a bracket  130  of the upper robot  12 . The other ends of the third and fourth parallel links  122 ,  124  are also mounted, respectively, at the spaced pivot points  112 ,  114  of the connecting link  116  coupled with the ends of the first and second parallel links  102 ,  104 . The pivot points  112 ,  114  typically include bearings. The third and fourth parallel links  122 ,  124 , the bracket  130  between the first and second drive shafts  126 ,  128 , and the connecting link  116  form another parallelogram. 
     The drive shafts  126 ,  128  are driven by the robot  12  in rotation. Rotation of the drive shafts  126 ,  128  in the same direction effects a translational extension and retraction of the robot blade  118 . Because of the connection points at the first and second spaced rotational joints  106 ,  108  of the robot blade  18 , at the first and second drive shafts  126 ,  128  of the upper robot  12 , and commonly at the spaced pivot points  112 ,  114  of the connecting link  116 , the two parallelogram configurations are maintained during rotation of the four-bar link mechanism  100 . The translation movement of the blade  18  is parallel to a line through the drive shafts  126 ,  128  of the robot  12  and a line through the first and second spaced rotational joints  106 ,  108  of the robot blade  18 . 
     The bracket  130  may be rotated to rotate the fourbar link mechanism with respect to the robot  12 . To effect such a rotation, a rotation drive shaft  132  is coupled to the bracket  130  to drive the bracket  130  in rotation. In the embodiment of FIG. 5, this rotation drive shaft  132  is commonly aligned with the first drive shaft  126 , but need not be aligned in other embodiments. The rotation drive shaft  132  is desirably a hollow shaft in which the first drive shaft  126  is disposed and rotates. Other configurations are possible. In addition, other four-bar link configurations may be used. The size and shape of the robot blades  18 ,  26  have been discussed above. 
     As discussed above, a second four-bar link robot arm mechanism similar to the four-bar link mechanism  100  of FIG. 5 may be used to control the movement of the lower robot blade  26  and wafer  32 . The second mechanism may be identical to the four-bar link mechanism  100  of FIG. 5, or may be a mirror image thereof. 
     A range of metallic and nonmetallic materials can be used for the robot blades  18 ,  26  as well as the links in the frog-leg and four-bar link robot arm mechanisms  60 ,  100 . The material is desirably light weight and strong to minimize deflection and vibration. The choice of the material, as well as the dimensions, becomes more important if long blades  18 ,  26  are used, since deflection and vibration are more problematic than for short blades. In addition to the tapering of the blades  18 ,  26  as shown in FIG. 2, the material is selected for strength and light weight, such as sapphire. In one example, the use of sapphire and the hollow and tapered structure with the dimensions of FIG. 2 produces a blade having a weight of about 0.236 kg. The use of sapphire in long blades  18 ,  26  of 200-300 mm in length has reduced the bending to under about 0.5 mm maximum deflection. Other metals, composites, and ceramics may be used as well depending on the various dimensions of the blades  18 ,  26 . The key criterion is to provide a clean, non-contaminated structure optimized for strength-to-weight ratio for the robot blades  18 ,  26 . The optimization is a function, among others, of the length of the blades  18 ,  26  and the size of the gap  30  between the blades  18 ,  26 . 
     The above-described arrangements of apparatus and methods are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. For instance, other robot arm structures may be used, such as scissors and telescopic mechanism. In addition, both the upper and lower robot blades  18 ,  26  may have identical but opposing blades (not shown) that feed the chambers 180° opposed to each other. The advantage of this alternate embodiment is that the throughput can be further increased when using 4 identical chambers on a system, or when using 2 integrated chambers on such a system. 
     All patents, applications, and publications referred to above are incorporated herein by reference in their entirety.