Patent Publication Number: US-8529715-B2

Title: Apparatus for attaching substrates and gap control unit thereof

Description:
This application is a divisional of U.S. patent application Ser. No. 11/867,958, filed Oct. 5, 2007, which claims priority under 35 U.S.C. §119 to Korean Patent Applications Nos. 10-2006-0123232 &amp; 10-2006-0125010, filed in Korea on Dec. 6, 2006 and Dec. 8, 2006, respectively, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to an apparatus for attaching substrates and a gap control unit thereof. 
     2. Background 
     An apparatus for attaching substrates is used to attach two substrates of a flat panel display device to each other. The thin panel display device could be thin film transistor liquid crystal display (MT-LCD) panel, a plasma display panel (PDP), an OLED or some other type of display device. 
     A TFT-LCD device typically includes, a TFT substrate on which a plurality of TFTs (thin film transistors) are formed in a matrix, and a color filter substrate on which a color filter or a light shielding film is formed. The two substrates oppose each other and are attached to each other with a gap of a few micrometers. 
     The substrate attachment is performed by first aligning the substrates with respect to each other, attaching them to each other, and then pressing the two substrates together using pressure. An apparatus for attaching substrates typically includes a first chamber and a second chamber spaced apart from the first chamber. An inside surface of each chamber is provided with an electrostatic chuck (ESC) for holding the substrates before the attachment. The upper chamber may also include a vacuum chuck as well. 
     During the attachment process, the two substrates are carried into the apparatus and they are mounted on the upper and lower chambers. The first and the second chambers come together to form a sealed attaching space. The sealed attaching space is then vacuum exhausted by a pump so as to form a vacuum state in the inside thereof. A sealing member is provided between the first and the second chambers to maintain the vacuum in the sealed attaching space. The substrates are then aligned with each other, and the two substrates are attached to each other. 
     The attachment of the two substrates is performed only after the two substrates have been brought closely adjacent to each other. The substrates must be brought into close proximity to precisely align them, which is very important to the quality of the resulting display device. 
     When the substrates are brought close to each other, the above mentioned seal member is used to maintain the vacuum in the sealed attaching space. The sealing member also helps to control the gap between the substrates when they are in close proximity to each other, and before the attachment. The gap between the substrates can be determined by a depression amount of the seal member. 
     Another important factor in the apparatus for attaching substrates is the ability to perform horizontal movements of one or both chambers to properly align the substrates. In a conventional apparatus for attaching substrates, the gap maintenance and the horizontal movement are performed separately while maintaining the vacuum state. However, when these processes are performed sequentially, it takes a long time to accomplish the entire process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a side sectional view illustrating a first embodiment of an apparatus for attaching substrates; 
         FIG. 2  is an exploded perspective view illustrating an alignment control part of an apparatus for attaching substrates; 
         FIGS. 3 and 4  illustrate an operation of the alignment control part; 
         FIG. 5  is a side sectional view illustrating another embodiment of an apparatus for attaching substrates; 
         FIG. 6  is an enlarged view illustrating an alignment control part of the apparatus shown in  FIG. 5 ; 
         FIG. 7  illustrates an operation of the alignment control part of the apparatus shown in  FIG. 5 ; 
         FIG. 8  is an exploded perspective view illustrating another embodiment of an alignment control part of an apparatus for attaching substrates; 
         FIG. 9  is a plan view of the apparatus shown in  FIG. 8 ; 
         FIG. 10  is an exploded perspective view illustrating another embodiment of an alignment control part of an apparatus for attaching substrates; 
         FIG. 11  is a plan view of the apparatus shown in  FIG. 10 ; 
         FIG. 12  is an enlarged view illustrating another embodiment of an alignment control part of an apparatus for attaching substrates; 
         FIG. 13  is an exploded perspective view illustrating the alignment control part shown in  FIG. 12 ; 
         FIG. 14  is a plan view of the apparatus shown in  FIG. 13 ; 
         FIG. 15  is an exploded perspective view illustrating a further embodiment of the alignment control part of an apparatus for attaching substrates; and 
         FIG. 16  is a plan view of the apparatus shown in  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION 
     Multiple embodiments will be described in greater detail with reference to the accompanying drawings. Whenever possible, the same reference symbols will be used to designate elements having the same functions. 
       FIG. 1  illustrates an apparatus  100  for attaching substrates. As shown in  FIG. 1 , the apparatus  100  for attaching substrates is provided with a supporting frame  190  which forms an external appearance of the apparatus. A first chamber  110  is located at an inside upper part of the supporting frame  190 . A second chamber  120  is located below the first chamber  110 . The first chamber  110  and the second chamber  120  can be brought together to form a sealed attachment space therebetween. The substrates S 1  and S 2  may be the upper and lower substrates of any display device, such as a TFT substrate or a color filter substrate of an LCD display. 
     The first chamber  110  supports the first substrate S 1  and the second chamber  120  supports the second substrate S 2 . To this end, inside surfaces of the first chamber  110  and the second chamber  120  are respectively provided with a first chuck  102  and a second chuck  158 . The first chuck  102  and the second chuck  158  may be electrostatic chucks (ESCs), vacuum chucks, combinations of the ESC and vacuum chucks, and any other type of chuck capable of securely holding the substrates on the upper and lower chambers. 
     An ESC chuck holds the substrates S 1  and S 2  by an electrostatic force produced by application of DC power. This ESC may be one in which a film is attached onto an aluminum body. Various types of films may be used, such as a type in which a polyimide electrode is inserted. 
     Also, though not shown, the first chamber  110  and the second chamber  120  may be provided with a plurality of stages for aligning the substrates S 1  and S 2 . The stages would be used to move one or both of the substrates in X, Y and possibly in a rotational fashion to properly align the substrates. One or more cameras or imaging devices may also be used to detect alignment marks for purposes of alignment of the substrates. 
     A driving part can be used to move one or both of the chambers to bring them together. Also, one or more vacuum pumps may be used to generate a vacuum in the sealed attachment space. 
     An alignment control part  140  extends around a periphery of the first and second chambers. The alignment control part permits a sliding movement of the second chamber  120  with respect to the first chamber  110 . The alignment control part  140  is provided between the first chamber  110  and the second chamber  120  so as to maintain a seal of the attachment space. The alignment control part is also used to control a gap between the chambers, and thus the gap between the substrates. The alignment control part allows the substrates to move with respect to each other, to accomplish alignment, while still maintaining the seal and the gap. 
     As shown in  FIGS. 3 and 4 , a main seal member  132  maintains a seal and a gap between the substrates  51  and S 2 . The main seal member  132  is fixed to the first chamber  110 , and serves to control the gap between the substrates S 1  and S 2 . The main seal member  132  is fixed by a fixing plate  182 . 
     As shown in  FIG. 2 , the alignment control part  140  includes an auxiliary seal member  112  which is in close contact with the second chamber  120 , and which maintains the sealed state regardless of the movement of the second chamber  120 . A main body  142  receives the auxiliary seal member  112 , and a bolt  144  fixes the main body  142  to the second chamber  120  while maintaining a predetermined gap. The main body  142  is also provided with a ball flange  150  which is in contact with the second chamber  120 . 
     An installing hole  142   a  has a larger diameter than the bolt  144  so as to allow the bolt  144  to be inserted therein and to move therein. One or more washers  152  formed with an elongated hole  152   a  are provided between the installing hole  142   a  and the bolt  144  so that the bolt  144  is supported on the main body  142 . The washers  152  formed with the elongated hole  152   a  and the installing hole  142   a  having a diameter larger than the bolt  144  allow the second chamber  120  to move horizontally relative to the first chamber  110 , while maintaining the vacuum in the sealed attachment space, and the gap. 
     The movements of the alignment control part  140  and the second chamber  120  are illustrated in  FIGS. 3 and 4 .  FIGS. 3 and 4  illustrate the interface between the first and second chambers after the substrates S 1  and S 2  have been mounted on the first and second chambers, and after the first and second chambers have been brought together to form the sealed attachment space. A check is then performed to determine whether a depression of the main seal member  132  is uniform. Maintenance of a uniform depression of the main seal member  132  means that the gap between the substrates S 1  and S 2  is maintained uniformly. The vacuum-exhaustion of the sealed attachment space can then be performed. 
     After confirming that the main seal member  132  is pressed uniformly, alignment of the substrates is performed by moving the substrates relative to each other, and detecting the state of alignment with the above-described imaging cameras. The cameras detect images of alignment marks on the substrates. The substrates are moved relative to each other until the alignment marks are brought into registration. 
     If the alignment marks of the substrates S 1  and S 2  are not in registration, a process of horizontally moving the second chamber  120  relative to the first chamber  110  is performed. As the second chamber  120  is moved, the bolt  144  fixed to the second chamber  120  is allowed to move within gaps l between the bolt and the sidewalls of the installing hole  142   a . Because the bolt  144  can move within the gaps l and within the elongated holes  152   a  formed in the washers  152 , the alignment control part  140  including the main body  142  can maintain the vacuum state, and the substrates can be moved relative to each other. 
     In the prior art, movement of the second chamber  120  to accomplish alignment had to be performed separately from the process of maintaining the seal and the gap. However, with the above-described alignment control part, both processes can be performed simultaneously, thereby shortening a process time. 
     The ball flange  150  provided in the main body  140  serves to set a maintenance height of the auxiliary seal member  112  so that the auxiliary seal member  112  is maintained in close contact with the second chamber  120 . The ball  154  also functions to reduce friction with the second chamber  120 , making movement of the second chamber easier to accomplish. In order to further reduce the friction due to the horizontal movement of the second chamber  120 , grease may be applied to contact surfaces between the auxiliary seal member  112  and the second chamber  120 . 
       FIG. 5  illustrates another embodiment of an apparatus for attaching substrates  200  having a gap control unit  230 . As shown in the drawing, and similar to the embodiment described above, the apparatus  200  for attaching substrates is provided with a supporting frame  290  which forms an external appearance of the apparatus. A first chamber  210  is located at an inside upper part of the supporting frame  290 . A second chamber  220  is located at a lower part of the first chamber  210 , spaced apart from the first chamber  210 . The first chamber  210  and the second chamber  220  come together to form a sealed attaching space in which a first substrate S 1  and a second substrate S 2  are attached. 
     The gap control unit  230  is located at a periphery where the first chamber  210  and the second chamber  220  come into close contact with each other. The gap control unit  230  includes, as shown in  FIG. 6 , a main seal member  232  which comes into close contact with the first chamber  210  to maintain a seal. A second seal member  234  maintains a seal between an upper plate  242  and the second chamber  220 . A depression control part  240  is placed between the main seal member  232  and the second seal member  234  so as to control a compression of the second seal member  234 . 
     The main seal member  232  comes into close contact with the first chamber  210  and serves to maintain a gap between the substrates. However, if the main seal member is not uniformly compressed at all points around the periphery of the first and second chambers, the gap between the substrates may be uneven. The second seal member  234  compensates for differences in the compression amount of the main seal member  232  so that a uniform gap is maintained between the two substrates. 
     The depression control part  240  includes, as shown, an upper plate  242  placed between the main seal member  232  and the second seal member  234 . Fastening bolts  244  located on either side of the second seal member  234  ensure that the second seal member  234  is in close contact with the second chamber  220 . The fastening bolts also attach the upper plate  242  to the second chamber  220 . Springs  246  are provided around the fastening bolts  244  between the second chamber  220  and the upper plate  242 . 
     The fastening bolts  244  control a gap g 2  of the second seal member  234 . When one portion of the main seal member  232  is depressed more than other portions by the first chamber  210 , the upper plate  242  is allowed to move downward, against the force of the springs  246 , and the second seal member  234  is compressed. 
       FIG. 7  shows a situation where the main seal member  232  is compressed more on one side of the apparatus than on the other side. Referring to the drawing, the main seal member  232  is depressed as the first chamber  210  and the second chamber  220  come into close contact with each other. It can be appreciated that, when comparing the portion of the main seal member  232  located on the left side of the apparatus to the portion of the main seal member  232 ′ located on the right, the left main seal member  232  is depressed more than the right main seal member  232 ′ (g 1 ′&gt;g 1 ). In this case, it can be judged that the gap between the substrates S 1  and S 2  is also not uniform over the entire area of the substrates. 
     When such a problem arises, it is necessary to take steps to ensure that a uniform gap is maintained between the substrates S 1  and S 2 . Ideally, we want to ensure that the total combined height of the main seal member  232  and the second seal member  234  located on the left and right sides are equal to one another (g 1 +g 2 =g 1 ′+g 2 ′). In this case, the gap problem can be solved by controlling the fastening bolts  244 ′ to compress the right buffering seal member  234 ′ with the upper plate  242 ′. In other words, the right buffering seal member  234 ′ is compressed by pressing the right upper plate  242 ′ so that a compression amount of the second seal member  234 ′ equals a compression amount of the main seal member  232 . As a result, the gap between the substrates becomes uniform across the entire area of the substrates. 
     The gap control unit described above could actually be constructed in a variety of different ways. As shown in  FIG. 8 , the upper plate  242  may be formed into a rectangular plate having a vertical through-hole at its center. The gap control unit  230  could then be installed in the second chamber  220  as shown in  FIG. 9 . 
     The gap control unit also could be formed from a plurality of the upper plates segments which, when combined together, form a ring around the periphery of the second chamber  220 . As shown in  FIG. 10 , the upper plate  242  may be formed by a plurality of panel segments  242   a ,  242   b ,  242   c  and  242   d  which are separately installed on the second chamber  220 , as shown in  FIG. 11 . In this case, a separate seal member may be provided among the plurality of panel segments  242   a ,  242   b ,  242   c  and  242   d  which form the upper plate  242 . 
       FIG. 12  shows another embodiment of a gap control unit  330 . This embodiment includes a main seal member  232  which is placed between the first chamber  210  and the second chamber  220  and which comes into close contact with the first chamber  210  to maintain a seal. A second seal member  234  is used to compensate for uneven compression of the main seal member  232 . A depression control part  240  is placed between the main seal member  232  and the second seal member  234  and controls a compression amount of the second seal member  234  so as to control the gap between the substrates. 
     The depression control part  240  includes, as shown, an upper plate  242  placed between the main seal member  232  and the second seal member  234 . A lower plate  342  is placed between the second seal member  234  and the second chamber  220 . An auxiliary seal member  380  is placed between the lower plate  342  and the second chamber  220 , and fastening bolts are located on either side of the second seal member  234  for coupling the upper plate  242  and the lower plate  342 . Springs  246  are provided on an outer periphery of the fastening bolts  244 . 
     If there is a difference in the amount of compression of the main seal member  232 , this gap control unit  330  compresses the second seal member  234  to compensate for this difference, thereby ensuring that the gap between the substrates S 1  and S 2  is uniform. If a height g 3  of the main seal member  232  located at one portion is different from a height g 3 ′ of the main seal member  232 ′ located at another portion, the gap control unit  330  selectively compresses a portion of the second seal member  234  so that the combined heights of the main seal member  232  and the second seal member  234  is the same at all points. For instance, the fastening bolts  244 ′ are used to press the second seal member  234 ′ at a portion with the upper plate  242 ′. 
     The gap control unit  330  shown in  FIG. 12  may be formed in various different ways. As shown in  FIG. 13 , the upper plate  242  and the lower plate  342  may be may be rectangular, with a vertical through-hole in the center. In this instance, the gap control unit  330  can be installed in the second chamber  220  as shown in  FIG. 14 . 
     Alternatively, the upper plate  242  and the lower plates  342  can be formed from a plurality of segments. As shown in  FIG. 15 , the upper segments  242   a ,  242   b ,  242   c  and  242   d  and the lower plate segments  342   a ,  342   b ,  342   c    342   d  can be connected to each other to form the gap control apparatus. In this instance, the gap control unit  330  can be installed in the second chamber  220  as shown in  FIG. 16 . Separate seal members for sealing are placed among the plurality of segments  242   a ,  242   b ,  242   c  and  242   d  and  342   a ,  342   b ,  342   c  and  342   d.    
     As described above, the gap control members make it possible to accomplish a horizontal movements of a chamber while a vacuum state is maintained, thereby shortening a process time. In addition, because it is possible to compensate for uneven compression of a main seal member by selectively compressing a second seal member, a more uniform gap can be obtained between the substrates. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although a number of illustrative embodiments have been described, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combinations which would fall within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.