Abstract:
Embodiments of the invention relate to methods and apparatus for minimizing electrostatic discharge in processing and testing systems utilizing large area substrates in the production of flat panel displays, solar panels, and the like. In one embodiment, an apparatus is described. The apparatus includes a testing chamber, a substrate support disposed in the testing chamber, the substrate support having a substrate support surface, a structure disposed in the testing chamber, the structure having a length that spans a width of the substrate support surface, the structure being linearly movable relative to the substrate support, and a brush device having a plurality of conductive bristles coupled to the structure and spaced a distance away from the substrate support surface of the substrate support, the brush device electrically coupling the support surface to ground through the structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/411,902 (APPM 15794L), filed Nov. 9, 2010, which is hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to methods and apparatus for minimizing electrostatic discharge in substrate processing and testing systems. More particularly, the invention relates to methods and apparatus for minimizing electrostatic discharge in processing and testing systems utilizing large area substrates in the production of flat panel displays, solar panels, and the like. 
         [0004]    2. Description of the Related Art 
         [0005]    Electronic devices, such as thin film transistors (TFT&#39;s), photovoltaic (PV) devices or solar cells, and other electronic devices, have been fabricated on substrates for many years. The TFT&#39;s and PV devices are typically interconnected to form a product, such as a flat panel display or solar panel, that is packaged and marketed to consumers. 
         [0006]    The electronic devices are formed by numerous processes, which are often performed in different chambers. Moving the substrates between support surfaces in various chambers sometimes generates static electricity, which may produce an electrostatic discharge (ESD) event. ESD events may cause damage to finished electronic devices, as well as partially finished electronic devices. The damage may result in an unusable electronic device, which may render the product unusable. 
         [0007]    Therefore, there is a need for apparatus and methods to prevent electrostatic discharge from occurring in the manufacture and/or testing of electronic devices. 
       SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the invention relate to methods and apparatus for minimizing electrostatic discharge in processing and testing systems utilizing large area substrates in the production of flat panel displays, solar panels, and the like. 
         [0009]    In one embodiment, an apparatus is described. The apparatus includes a testing chamber, a substrate support disposed in the testing chamber, the substrate support having a substrate support surface, a structure disposed in the testing chamber, the structure having a length that spans a width of the substrate support surface, the structure being linearly movable relative to the substrate support, and a brush device having a plurality of conductive bristles coupled to the structure and spaced a distance away from the substrate support surface of the substrate support, the brush device electrically coupling the support surface to ground through the structure. 
         [0010]    In another embodiment, an apparatus is described that includes a testing chamber coupled to a load lock chamber, a substrate support disposed in the testing chamber, the substrate support being movable in a first linear direction, an end effector that is movably coupled to the substrate support, the end effector being movable in a second linear direction relative to the substrate support, and a brush device coupled to the end effector and disposed adjacent a processing surface of the substrate support, the brush device comprising a length that spans a width of the processing surface, wherein the brush device electrically couples the substrate support to ground through the end effector. 
         [0011]    In another embodiment, an apparatus is described that includes a chamber coupled to a load lock chamber, a substrate support disposed in the chamber, the substrate support being movable in a first linear direction, an end effector movably disposed on the substrate support, a prober device that is movably coupled to the substrate support, the prober device being independently movable in a second linear direction relative to the substrate support, and a plurality of conductive bristles coupled to the prober device and spanning a width of the processing surface, each of the conductive bristles being spaced a distance from the processing surface of the substrate support, wherein the plurality of conductive bristles electrically couples the processing surface to ground through the prober device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0013]      FIG. 1  is an isometric view of one embodiment of a test system. 
           [0014]      FIG. 2A  is a sectional side view of the test system shown in  FIG. 1 . 
           [0015]      FIG. 2B  is an isometric view of a portion of the substrate support shown in  FIG. 2A . 
           [0016]      FIG. 3  is an isometric view of a portion of a substrate support that may be utilized in the test system shown in  FIG. 1 . 
           [0017]      FIG. 4A  is a side view of one embodiment of a support member having one embodiment of a brush device disposed thereon. 
           [0018]      FIG. 4B  is an isometric view of the support member and the brush device shown in  FIG. 4A . 
       
    
    
       [0019]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
       DETAILED DESCRIPTION 
       [0020]    The term substrate as used herein refers generally to large area substrates made of glass, a polymeric material, or other substrate materials suitable for having an electronic device formed thereon. Various embodiments are described herein relate to electrostatic discharge (ESD) prevention during testing of electronic devices, such as thin-film transistors (TFT&#39;s) and pixels located on flat panel displays. The testing procedures are exemplarily described using an electron beam or charged particle emitter, but certain embodiments described herein may be equally effective using optical devices, such as charge coupled device (CCD) cameras, charge sensing devices, or other testing applications configured to test electronic devices on large substrates in vacuum conditions, or at or near atmospheric pressure. Other electronic devices that may be located on a large area substrate and tested include photovoltaic cells for solar cell arrays, organic light emitting diodes (OLED&#39;s), among other devices. The methods and apparatus for ESD prevention as described herein may also be applicable for these other electronic devices. 
         [0021]      FIG. 1  is an isometric view of one embodiment of a test system  100  adapted to test the operability of electronic devices located on substrates, for example, substrates having dimensions up to and exceeding about 2200 mm by about 2600 mm. The test system  100  includes a testing chamber  110 , a load lock chamber  120 , and a plurality of testing columns  115  (seven are shown in  FIG. 1 ), which are exemplarily described as electron beam columns adapted to test electronic devices located on substrates, such as TFT&#39;s. The test system  100  is typically located in a clean room environment and may be part of a manufacturing system that includes substrate handling equipment such as robotic equipment or a conveyor system that transports one or more substrates  105  to and from the testing chamber  110 . 
         [0022]    The interior of the testing chamber  110  is accessible at least through a valve  135  located between the load lock chamber  120  and the testing chamber  110 . The load lock chamber  120  is selectively sealable from ambient environment and is typically coupled to one or more vacuum pumps  122 . The testing chamber  110  may be coupled to one or more vacuum pumps  122  that are separate from the vacuum pumps of the load lock chamber  120 . The load lock chamber  120  is adapted to receive the substrate  105  from the clean room environment through a sealable entry port  130 , facilitate transfer of the substrate  105  from the load lock chamber  120  to the testing chamber  110  through the valve  135 , and return the substrate  105  to the clean room environment through the load lock chamber  120  in a converse manner. 
         [0023]      FIG. 2A  is a side view of the test system  100  shown in  FIG. 1 . The testing chamber  110  is shown coupled to the load lock chamber  120 , which includes a substrate  105  disposed therein. The testing chamber  110  includes an interior volume  200 , which includes a substrate support  210  disposed and movable along frames  214 A,  214 B (only  214 A is shown in  FIG. 2A ), two prober assemblies, such as prober  205 A and prober  205 B. The probers  205 A and  205 B are utilized to selectively contact conductive areas on the substrate  105  in order to test the operability of the electronic devices on the substrate  105 . In one aspect, each of the probers  205 A and  205 B are configured as gantry structures that span a width of the substrate  105  and the substrate support  210 . 
         [0024]    The substrate support  210  is movable throughout the length of the interior volume  200  along the frame  214 A by a drive (not shown) coupled between the frame  214 A and the substrate support  210 . The probers  205 A,  205 B are at least partially supported and movable along a prober support  240 A,  240 B on opposing sides (only  240 A is shown in  FIG. 2A ) of the substrate support  210 . 
         [0025]    An upper stage  212  is configured to support the substrate  105  during testing and includes multiple panels having slots therebetween to receive a plurality of fingers  218  of an end effector  219  (shown in  FIG. 2B ). The upper stage  212  may be fabricated from a conductive material, such as aluminum. The upper stage  212  moves at least in the Z direction and the fingers  218  of the end effector  219  extend laterally (Y direction) therefrom to transfer the substrate  105  to and from the load lock chamber  120 . 
         [0026]      FIG. 2B  is an isometric view of a portion of the substrate support  210  shown in  FIG. 2A . A substrate  105  is located on the upper stage  212  of the substrate support  210 . Probers  205 A,  205 B are shown on an upper surface of the prober supports  240 A,  240 B above the substrate  105 . The probers  205 A,  205 B are adapted to move along the length of the prober supports  240 A,  240 B by a plurality of drives  224  coupled between the prober supports  240 A,  240 B and opposing sides of each prober  205 A,  205 B. The probers  205 A and  205 B are utilized to selectively contact conductive areas on the substrate  105  and provide, or sense, electrical signals from the electronic devices on the substrate  105 . 
         [0027]    The end effector  219  is shown proximate the upper stage  212  of the substrate support  210 . In one aspect, the end effector  219  comprises gantry structure that spans the width of the substrate support  210 . The gantry structure may be configured as a wrist  221  that supports the fingers  218 . During testing, the fingers  218  are disposed in slots  223  formed in the upper stage  212 . When the fingers  218  are disposed in the slots  223 , the substrate  105  may contact the upper surface of the upper stage  212 . During substrate transfer, the wrist  221  travels along the length of the upper stage  212 . The wrist  221  is adapted to move adjacent the upper surface  315  of the upper stage  212 . Both of the wrist  221  and the probers  205 A,  205 B are shown coupled to ground in  FIG. 2B . One or both of the wrist  221  and probers  205 A,  205 B may be utilized to minimize ESD and removal of charge(s) from the substrate  105 , the upper stage  212 , and combinations thereof, as will be explained further below. 
         [0028]    ESD is a sudden electric current that runs through one or more objects having a different electrical potential caused by direct contact or electrostatic field(s). ESD is usually created by tribocharging. Tribocharging may occur when two materials that have been in contact are separated. Tribocharging may also occur by friction from relative motion between two materials. ESD causes damages on circuits within the electronic devices on the substrate  105 . The potential for ESD may be present during transfer of the substrate  105  to and from the fingers  218  and the upper stage  212 . Thus, an electrical potential between the substrate  105  and the end effector  219  may be present before and after transfer of the substrate  105 . Different electrical potentials may also remain during testing of the substrate  105 . 
         [0029]      FIG. 3  is an isometric view of a portion of a substrate support  210  that may be utilized in the test system  100  shown in  FIG. 1 . The wrist  221  includes a brush device  310  coupled thereon. The brush device  310  is coupled to the wrist  221  and is adapted to be adjacent or contact an upper surface  315  of the upper stage  212 . The brush device  310  is adapted to move across the upper surface  315  along with the wrist  221  during substrate transfer. The brush device  310  is configured to remove electrical charge(s) from the upper stage  212 . For example, electrical charges from the upper surface  315  may be transferred to ground through the brush device  310  to the wrist  221 , which is coupled to ground as shown in  FIG. 2B . 
         [0030]    Thus, the brush device  310  is adapted to remove or dissipate any electrical potential that may have been generated by the substrate  105 , the upper surface  315  of the upper stage  212 , and combinations thereof. The electrical charge may go to ground from the upper surface  315  of the upper stage  212  through the wrist  221  and the brush device  310 . 
         [0031]      FIG. 4A  is a side view of one embodiment of a support member  400  having one embodiment of a brush device  310  disposed thereon. The support member  400  is depicted adjacent the upper stage  212  shown in  FIG. 3 . The support member  400  may be any structure having a dimension greater than the width of a substrate and/or a dimension greater than the width of the upper stage  212 . The support member  400  may also be movable relative to the upper stage  212 . For example, the support member  400  may be a surface of a prober  205 A,  205 B (shown in  FIGS. 2A-3 ) or the wrist  221  (shown in  FIGS. 2B and 3 ). One embodiment of the brush device  310  is shown coupled to the support member  400 .  FIG. 4B  is an isometric view of the support member  400  and the brush device  310  shown in  FIG. 4A . 
         [0032]    The brush device  310  includes a mounting plate  405  that is coupled to the support member  400 . The brush device  310  also includes a spine  415  that is pressed against a mounting bracket  410 . The mounting bracket  410  may be secured to the mounting plate  405  by one or more fasteners  420 , such as bolts or screws. A washer or spacer  425  may be utilized between the mounting plate  405  and the mounting bracket  410 . 
         [0033]    The brush device  310  comprises a plurality of conductive bristles  430 . At least the support member  400 , the mounting bracket  410  and the mounting plate  405  are made of a conductive material, such as aluminum. The plurality of conductive bristles  430  are coupled to the conductive spine  415 . Each of the conductive bristles  430  may comprise a conductive polymer, carbon fiber, fabrics or plastics coated with a conductive material, fine strands of a soft conductive metal, or combinations thereof. Likewise, the spine  415  comprises a conductive material. The spine  415  may be formed as a structure adapted to be sandwiched between the mounting bracket  410  and the mounting plate  405 . The spine  415  may be conductive fibers or fabrics binding the conductive bristles  430  to each other, or fine conductive strands or wires that bind the bristles to each other. The spine  415  may also include ends of the conductive bristles  430  that are encapsulated in a conductive binder shell. 
         [0034]    In one embodiment, the conductive bristles  430  comprise a conductive fabric, such as nylon. In another embodiment, the conductive bristles  430  comprise a acrylic fiber having a conductive coating disposed thereon, such as THUNDERON® anti-static materials. The conductive bristles  430  may have a diameter of about 15 micrometers (μm) to about 19 μm. In embodiments having a conductive coating, the conductive coating disposed on the conductive bristles  430  may have a thickness of about 300 angstroms (Å) to about 1000 Å. The conductive bristles  430  are coupled to ground through the support member  400 , which may be a surface of one or more of the probers  205 A,  205 B, or the wrist  221 , which are coupled to ground as shown in  FIG. 2B . 
         [0035]    The brush device  310  may be in close proximity with the substrate  105  (shown in  FIG. 2A ) or the upper surface  315  of the upper stage  212 , such as within a few millimeters, to remove the electrical charge(s). Alternatively, the brush device  310  may be in direct contact with the substrate  105  or the upper surface  315  of the upper stage  212  to remove the electrical charge(s). 
         [0036]    During movement of the support member  400  relative to the upper surface  315  of the upper stage  212 , the lower surface of the support member  400  may be maintained at a distance D′ from the upper surface  315 . The distance D′ may be between about 2 mm to about 10 mm, such as about 5 mm to about 10 mm. Likewise, a distal end  435  of the conductive bristles  430  may be maintained a distance D″ away from the surface to prevent the conductive bristles  430  from contacting the upper surface  315  in order to prevent particle generation. The distance D″ may be about 1 mm to about 8 mm above the upper surface  315 , such as about 3 mm to about 6 mm from the upper surface  315  of the upper stage  212 , which is close enough to the substrate  105  and/or the upper surface  315  to prevent an ESD event. 
         [0037]    Embodiments described herein provide and apparatus and method for dissipating electrical potential from a surface of a substrate or a substrate support  210  in order to prevent an ESD event. The apparatus includes a support member  400  having a dimension that is greater than the substrate width and/or greater than a width of the substrate support  210 . The support member  400  may also be configured as a gantry structure that is movable relative to the substrate and the substrate support  210 . A brush device  310  is coupled to the support member  400  and movable with the support member  400 . The support member  400  is coupled to ground to allow charge(s) that may build up on the substrate and/or the upper surface  315  of the substrate support  210  to be transferred to ground. The brush device  310  may be spaced away from the substrate and the substrate support  210  to prevent particle generation while removing charge(s). 
         [0038]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.