Abstract:
A substrate handling robot includes an arm drive mechanism. A first arm is connected to the arm drive mechanism. A multiple substrate batch loader is connected to the first arm. A second arm is also connected to the arm drive mechanism. A single plane end effector is connected to the second arm. The multiple substrate batch loader produces a vacuum signal indicative of how many substrates are held by the multiple substrate batch loader. A vacuum signal interpreter alters the movement of the first arm in response to the substrate load number. An object sensor is connected to the second arm. The object sensor assesses the number of substrates in a cassette adjacent to the multiple substrate batch loader. A substrate loading sequence controller controls the first arm and the second arm in response to the number of substrates in the cassette, such that the second arm removes substrates from the cassette in such a manner as to facilitate complete loading of the multiple substrate batch loader.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to prior U.S. application Ser. No. 09/113,599, filed Jul. 10, 1998, the disclosure of which is incorporated by reference herein. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION  
         [0002]    This invention relates generally to automated systems for transporting materials More particularly, this invention relates to a dual arm substrate handling robot with a batch loader.  
         BACKGROUND OF THE INVENTION  
         [0003]    Robots are used in a variety of industrial processes. For example, robots are used to handle substrates in the electronics industry. The term substrate includes such devices as semiconductor wafers, liquid crystal displays, flat panel displays, disk drives, and the like. Substrates are commonly stored in cassettes. In the case of a semiconductor wafer, a cassette of wafers is delivered to a work area. A robotic arm is used to take a single wafer from the cassette and deliver it to a pre-aligner. Once the wafer is pre-aligned, the robotic arm delivers the wafer to a testing apparatus. When testing is completed, the wafer is returned to the original cassette or a different cassette by the robotic arm. While existing robotic arms are acceptable for individual manipulation of substrates in a cassette, they are relatively inefficient for rapidly dispatching a set of substrates from one cassette to another or performing other types of bulk transfer operations.  
           [0004]    Thus, it would be highly desirable to provide an improved technique for robotic-based bulk transfers of substrates. Ideally, the bulk transfer technique would be capable of transferring various numerical combinations of substrates to optimize transfer operations. The bulk transfer technique would preferably have a low cost mechanism for determining the number of substrates being transferred at any given time and would adjust the speed of its motion accordingly. Such a device should use known materials and techniques and otherwise be compatible with existing robotic processes.  
         SUMMARY OF THE INVENTION  
         [0005]    The apparatus of the invention includes a substrate handling robot with an arm drive mechanism. A first arm is connected to the arm drive mechanism. A multiple substrate batch loader is connected to the first arm. A second arm is also connected to the arm drive mechanism. A single plane end effector is connected to the second arm. The multiple substrate batch loader senses a vacuum signal indicative of how many substrates are held by the multiple substrate batch loader. A vacuum signal interpreter selectively alters the movement of the first arm in response to the substrate load number. An object sensor is connected to the second arm. The object sensor assesses the number of substrates in a cassette adjacent to the multiple substrate batch loader. A substrate loading sequence controller controls the first arm and the second arm in response to the number of substrates in the cassette, such that the second arm removes substrates from the cassette in such a manner as to facilitate complete loading of the multiple substrate batch loader.  
           [0006]    The method of the invention includes the step of removing a first substrate from a storage site with a single paddle. A set of substrates are removed from the storage site with a multiple substrate batch loader. A vacuum signal indicative of how many substrates are held by the multiple substrate batch loader is obtained. The motion of the multiple substrate batch loader is altered when the vacuum signal indicates that the multiple substrate batch loader is not fully loaded. The method may also include the step of assessing the number of substrates in the storage site. Individual substrates may be removed from the storage site to facilitate complete loading of the multiple substrate batch loader.  
           [0007]    The invention provides an improved technique for robotic-based bulk transfers of substrates. The bulk transfer technique of the invention allows for the transfer of various numerical combinations of substrates to optimize transfer operations. The vacuum sensor associated with the multiple substrate batch loader facilitates a low cost assessment of the number of substrates being transferred at any given time. Based upon this information, the motion of the robot may be altered. Advantageously, the invention utilizes known materials and techniques and is otherwise compatible with existing processes.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    For a better understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0009]    [0009]FIG. 1 is a perspective view of a dual arm batch loading robot in accordance with an embodiment of the invention.  
         [0010]    [0010]FIG. 2 is a side view of the apparatus of FIG. 1.  
         [0011]    [0011]FIG. 3 is an exploded view of the dual arm structure of the apparatus of FIG. 1.  
         [0012]    [0012]FIGS. 4A and 4B provide cross sectional views of a portion of the apparatus of FIG. 1.  
         [0013]    [0013]FIG. 5 is an exploded view of a single plane end effector utilized in accordance with the apparatus of FIG. 1.  
         [0014]    [0014]FIG. 6 is an exploded view of a multiple substrate batch loader utilized in accordance with the apparatus of FIG. 1.  
         [0015]    [0015]FIG. 7 illustrates the apparatus of FIG. 1 being operated in connection with a control device in the form of a general purpose computer.  
         [0016]    Like reference numerals refer to corresponding parts throughout the drawings. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    [0017]FIG. 1 is a perspective view of a dual arm batch loading robot  20  in accordance with an embodiment of the invention. The robot  20  includes a first arm  22 , which supports a multiple substrate batch loader  24 . The robot also includes a second arm  26 , which supports a single plane end effector  28 .  
         [0018]    The first arm  22  includes a base arm  30  with a proximal end  32  connected to an arm drive mechanism  34 . The base arm  30  also includes a distal end  36 . The first arm also includes a forearm  38 . The proximal end  40  of the forearm  38  is connected to the distal end  36  of the base arm  30 . The distal end  42  of the forearm  38  supports a batch loader support mechanism  44 .  
         [0019]    The second arm  26  includes a base arm  46  with a proximal end  48  and a distal end  50 . A forearm  52  has a proximal end  54  connected to the distal end  50  of the base arm  46 . An object sensor  58  is connected to the distal end  56  of the forearm  52 . FIG. 1 also illustrates a housing  60 , which encloses a motor and other components.  
         [0020]    Those skilled in the art will recognize a number of benefits associated with the apparatus of FIG. 1. The multiple substrate batch loader  24  allows a set of substrates to be transported, thereby increasing processing efficiency. The single plane end effector  28  allows the robot  20  to perform traditional substrate handling operations. Other advantages and benefits of the invention are highlighted with the following discussion.  
         [0021]    [0021]FIG. 2 is a side view of the robot  20 . The figure illustrates the housing  60 , the arm drive mechanism  34 , the single plane end effector  28 , and the multiple substrate batch loader  24 .  
         [0022]    [0022]FIG. 3 is an exploded rear view of the first arm  22  and second arm  26 . The figure illustrates the first arm  22  and its base arm  30 , the distal end  36  of which receives a pivot mechanism  70 . The proximal end  40  of the forearm  38  is also attached to the pivot mechanism  70 . Similarly, the distal end  50  of the second arm  26  has an aperture  51  to receive a pivot mechanism  72  associated with forearm  52 .  
         [0023]    [0023]FIG. 3 also illustrates a portion of the arm drive mechanism  34 . The arm drive mechanism  34  includes a dual shaft drive mechanism  74 , which is used to provide motive force for the arms  22  and  26 . A drive shaft housing  76  encloses the dual shaft drive mechanism  74 . The drive shaft housing  76  rests on top of a motor housing frame  78 . A motor (not shown) is positioned within the motor housing frame  78 . A motor housing exterior  80  encloses the motor housing frame  78 .  
         [0024]    [0024]FIG. 4A is a cross sectional view of a portion of the robot  20 . In particular, the figure illustrates the first arm  22  and a portion of housing  60  in cross-section. The figure illustrates the dual shaft drive mechanism  74  with a first shaft  82 . The shaft  82  is connected to a belt  84 , which is linked to a pulley  86 . A similar arrangement is used in connection with the second arm  26 . The particular internal arm drive mechanism used in connection with the invention is immaterial, since any number of configurations may be used in accordance with the invention. The invention is not directed toward robotic arm movements, but to the use of a multiple substrate batch loader  24 , a single plane end effector  28 , and the associated utilization of these devices, as further discussed below.  
         [0025]    Although the particular internal arm drive mechanism that is used is not critical to the operation of the invention, one particular configuration has been found to be advantageous. FIG. 4B illustrates the use of a harmonic drive mechanism (gear reduction unit) which is instrumental in providing smooth motion and enough torque to move multiple wafers The gear reduction unit reduces moving parts, provides a strong drive system, avoids the problem of belt wear, and is relatively compact In addition, it is housed in the arm base for easy accessibility for servicing.  
         [0026]    [0026]FIG. 4B illustrates that the pulley  86  rotates the shaft  87 , which drives the input portion of the harmonic drive  88 . The output portion of the harmonic drive  88  is attached to a radial link  89 , which in turn is attached to the arm base  30  through spacer  91 .  
         [0027]    [0027]FIG. 5 is an exploded view of a single plane end effector  28  in accordance with an embodiment of the invention. The device  28  has a connector  90  for attachment to the second arm  26 . An intermediate support member  92  is attached to the connector  90 . A single plane paddle  96  is attached to the intermediate support member  92 . An object sensor  58  is connected to the base of the single plane paddle  96 . The object sensor  58  may be an optical sensor, a laser sensor, or the like. The object sensor  58  is used to identify whether substrates are stored at a storage site, such as a cassette. The second arm  26  is manipulated through a variety of positions to allow the object sensor  58  to identify where objects are stored. FIG. 5 also illustrates that the paddle  96  includes a vacuum aperture  98 . The vacuum aperture is linked to a vacuum pump (not shown). The vacuum pump establishes suction that secures a substrate to the paddle  96 .  
         [0028]    [0028]FIG. 6 illustrates a multiple substrate batch loader  24  in accordance with an embodiment of the invention. The device  24  includes a first arm connector  100  for connection with the first arm  22 . A stand-off  102  is positioned on the first arm connector  100 . An elevated base member  104  is positioned on the stand-off  102 . A first paddle  106  is positioned and secured between the first arm connector  100  and the elevated base member  104 . The first paddle  106  includes a vacuum aperture  108 , which operates in the manner described with respect to the vacuum aperture  98  of paddle  96 . FIG. 6 illustrates that the multiple substrate batch loader  24  may also include any number of additional paddles  116 . Each additional paddle  116  includes a paddle plateau  117 , which operates as a stand-off for an adjacent paddle. Each additional paddle  116  also includes a vacuum aperture  108 . A paddle cap  118  may be used to secure the vertical arrangement of paddles  116 . Each paddle in the multiple substrate batch loader  24  contains an internal vacuum channel. An  0 -ring is used to seal the vacuum channel between components.  
         [0029]    [0029]FIG. 7 is a simplified illustration of the dual arm batch loading robot  20 . The figure illustrates in simplified form the multiple substrate batch loader  24  and the single plane end effector  28 . As previously discussed, these components are attached to an arm drive mechanism  34 . The arm drive mechanism  34  preferably includes a vacuum sensor  119 . The vacuum sensor is used to measure the vacuum signals associated with the various vacuum apertures of the multiple substrate batch loader  24 , as further discussed below. FIG. 7 illustrates that the dual arm batch loading robot  20  may operate in connection with a cassette  140 , which holds a set of substrates  141 .  
         [0030]    [0030]FIG. 7 also illustrates that the dual arm batch loading robot  20  may be controlled by a control circuit in the form of a general purpose computer  120 . The computer  120  includes a set of input/output devices  122  to interface with the robot  20 . The input/output devices  122  also include such items as a keyboard, mouse, monitor, printer, and the like. Control signals to and from the robot  20  are exchanged through the input/output devices  122 . The control signals include vacuum sensor signals from the vacuum sensor  119  and sensed object signals from the object sensor  58 . These signals are passed to the central processing unit (CPU) over bus  126 . The bus  126  is also connected to a memory (e.g., RAM, disc memory, or the like)  128 , allowing the CPU  124  to execute programs stored within the memory  128 . The operation of a computer in connection with input/output devices  122 , a CPU  124 , and a memory  128  is well known in the art. An aspect of the invention is directed toward the particular types of programs executed by the computer  120 .  
         [0031]    In accordance with the invention, the memory  128  preferably stores a substrate loading sequence controller program  130 , a vacuum signal interpreter program  132 , and a motion control unit program  134 . The motion control unit program is a standard program for generating control signal for the arm drive mechanism  34 . As known in the art, the motion control unit  134  relies upon information from the map sensor  121 .  
         [0032]    The substrate loading sequence controller  130  is executed by the CPU  124  to select an optimal transport sequence to be performed by the robot  20 . The substrate loading sequence controller  130  determines which arm to use when dealing with a partially filled cassette. For example, if the object sensor  58  detects three substrates in the bottom slots of a cassette, a missing substrate above those three, and a group of five substrates above that, the controller  130  can select the single plane end effector  28  to move the first three substrates individually, skip the empty slot, then move the group of five with the multiple substrate batch loader  24 . Thus, based upon the information accumulated by the object sensor  58 , the controller  130  executes a set of rules to optimize the utilization of the multiple substrate batch loader  24 . The execution of these rules typically results in the use of the single plane end effector  28  to move substrates such that groups of substrates are subsequently dispatched with the multiple substrate batch loader  24 .  
         [0033]    The vacuum signal interpreter  132  as executed by the CPU  124  processes the control signal from the vacuum sensor  119 . The vacuum sensor  119  is tied to each of the vacuum apertures of the individual paddles of the batch loader  24 . Since the batch loader  24  has all of its blades tied into a single vacuum source, there is only one vacuum sensor which is used to detect the presence of the substrates. If only four out of five wafers are present, a “vacuum leak” on the blade without a wafer is reflected in an altered vacuum signal. The vacuum leak results in reduced suction at the remaining substrates. In response to this condition, the vacuum signal interpreter reduces the speed of the arm  22  to insure safe transport of the substrates. Observe that the object sensor  58  will typically provide information as to how many substrates will be carried at any given time. However, the vacuum signal interpreter  132  operates as a redundant failsafe mechanism, or alternatively, as a substitute mechanism if an object sensor  58  is not available. The vacuum signal interpreter  132  may be implemented as simple circuit that determines whether any paddle is not carrying a substrate. In response to such a condition, the altered movement of the robotic arm can be adjusted. In other words, in this embodiment the vacuum signal is not mapped to a specific number of substrates that are missing in the batch loader. Instead, if only a single substrate is missing the motion of the arm is adjusted.  
         [0034]    Those skilled in the art will appreciate that the invention provides an improved technique for robotic-based bulk transfers of substrates. The bulk transfer technique of the invention allows for the transfer of various numerical combinations of substrates to optimize transfer operations. The vacuum sensor associated with the multiple substrate batch loader facilitates a low cost assessment of the number of substrates being transferred at any given time. Based upon this information, the motion of the robot may be altered. Advantageously, the invention utilizes known materials and techniques and is otherwise compatible with existing robotic processes.  
         [0035]    The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. In other instances, well known circuits and devices are shown in block diagram form in order to avoid unnecessary distraction from the underlying invention. Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.