Abstract:
A photolithographic system and a method for driving the same is disclosed that prevents a no-load operation and imbalance in a fabrication process generated by time differences between different stages of the fabrication process. The apparatus includes a first plate storing a substrate coated with a photosensitive layer before an exposure process, a second plate storing an exposed substrate before a development process, and an auxiliary buffer plate part storing the exposed substrate before the development process when another exposed substrate has been previously stored in the second plate.

Description:
PRIORITY CLAIM  
       [0001]     This application claims the benefit of priority to Korean Application Nos. P2003-78747 filed on Nov. 7, 2003, and P2004-36334 filed on May 20, 2004, which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a photolithographic system for fabricating a liquid crystal display (LCD) device, and more particularly, to a photolithographic system and a method for driving the same, to prevent no-load operation and imbalance of the fabrication process generated by time difference of the fabrication process.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, a liquid crystal display (hereinafter, referred to as an LCD) device has low power consumption, a driving low voltage, full-color realization, a thin profile and is lightweight. The LCD device is used in various fields for watches, calculators, PC monitors, notebook computers, aircrafts monitors and personal mobile terminals.  
         [0006]     The LCD device includes an LCD panel displaying a picture image, and a driving circuit part driving the LCD panel.  FIG. 1  is a layout illustrating a general LCD panel. As shown in  FIG. 1 , the general LCD panel includes a first substrate  1  for a thin film transistor array, a second substrate  2  for a color filter array, and a liquid crystal layer  3  between the two substrates  1  and  2 .  
         [0007]     More specifically, the first substrate  1  includes a plurality of gate lines  4  arranged in one direction at fixed intervals, a plurality of data lines  5  perpendicular to the gate lines  4  to define a plurality of pixel regions P, a plurality of pixel electrodes  6  in the respective pixel regions P to display the image, and a plurality of thin film transistors T formed in the respective pixel regions at crossing portions of the plurality of gate and data lines  4  and  5 . The thin film transistors T are turned on/off by driving signals of the gate lines  4  to transmit video signals of the data lines to the respective pixel electrodes  6 . Also, the second substrate  2  for the color filter array includes a black matrix layer  7  preventing light leakage on the portions except the pixel regions P, R/G/B color filter layers  8  displaying various colors in the respective pixel regions P, and a common electrode  9  formed on an entire surface of the substrate including the color filter layers  8 . In case of an In-Plane Switching (IPS) mode LCD device, the common electrode  9  is formed on the first substrate  1  rather than the second substrate  9 .  
         [0008]     The thin film transistor T includes a gate electrode projecting from the gate line  4 , a gate insulating layer on an entire surface of the first substrate including the gate electrode, an island-shaped active layer on the gate insulating layer above the gate electrode, a source electrode projecting from the data line  5  and overlapped with one side of the active layer, and a drain electrode opposite to the source electrode and overlapped with the other side of the active layer. Also, the pixel electrode  6  is formed of transparent conductive metal having a high transmittance such as ITO (Indium-Tin-Oxide).  
         [0009]     A method for fabricating the aforementioned LCD panel includes three steps, an array process forming switching devices such as line patterns and thin film transistors TFT on a glass substrate, a cell process forming a liquid crystal layer between opposing two substrates after alignment and spacer arrangement steps, and a module process mounting a driver IC and a backlight. The array process includes deposition of a material for patterning on the substrate, a photolithographic process of defining regions for patterning, and etching process of the material. Also, the photolithographic process includes steps of loading the substrate having the material layer for patterning, pretreatment of cleaning and carrying out a thermal treatment to the loaded substrate, coating a photosensitive layer on the substrate, arranging a mask having the pattern thereon, exposing the photosensitive layer by irradiating ultraviolet rays on the mask, and developing the exposed photosensitive layer by developer, and unloading the substrate.  
         [0010]     A photolithographic device for the photolithographic process will be described as follows.  FIG. 2  is a schematic view illustrating the fabrication process line for photolithography according to the related art. Referring to  FIG. 2 , the process line for photolithography includes a loading/unloading part  10  for loading and unloading a substrate, pretreatment parts  12   a  and  12   b  for cleaning and heating the loaded substrate, coating parts  14   a  and  14   b  for coating a photosensitive layer on the substrate, an exposure part  16  for exposing the coated substrate after arranging a mask on the substrate, development parts  15   a  and  15   b  for developing the photosensitive layer on the exposed substrate, a plurality of robot parts  11   a  to  11   e  transferring the substrate loaded by the loading/unloading part  10  to the respective process steps, and a plurality of buffer plate parts  13   a  to  13   d  temporarily storing the substrate before and after the process steps.  
         [0011]     An operation of the process line for photolithography according to the related art will be described as follows.  
         [0012]     When the substrate is loaded to the loading/unloading part  10 , the robot part  1   a  loads the substrate to the pretreatment parts  12   a  and  12   b  for carrying out cleaning and heating. Then, the substrate is loaded to the coating parts  14   a  and  14   b  by the robot part  11   b , so that the photosensitive layer is coated on the loaded substrate. After that, the robot part  11   c  unloads the coated substrate, and then the unloaded substrate is provided to the buffer plate part  13   c.    
         [0013]     Then, the robot part  11   d  loads the substrate provided in the buffer plate part  13   c  to the buffer plate part  13   d . Subsequently, the robot part  11   e  loads the substrate provided in the buffer plate part  13   d  to the exposure part  16 , whereby the substrate is exposed with light after arranging the mask thereon. Also, the robot part  11   e  loads the exposed substrate to the buffer plate part  13   d . At this time, the robot part  11   d  provides the exposed substrate to the development parts  15   a  and  15   b , thereby carrying out the development process on the substrate. After completing the development process, the substrate is provided to the buffer plate part  13   c , and then the substrate is unloaded by the robot parts  11   a ,  11   b  and  11   c.    
         [0014]     Hereinafter, the coating parts  14   a  and  14   b , the development parts  15   a  and  15   b , the exposure part  16 , the buffer plate part  13   d  and the robot parts  11   d  and  11   e  will be described in detail.  
         [0015]      FIG. 3  only illustrates the coating parts  14   a  and  14   b , the development parts  15   a  and  15   b , the exposure part  16 , the buffer plate part  13   d  and the robot parts  11   d  and  11   e , and  FIG. 4  schematically illustrates the buffer plate part and the robot part. The coating parts  14   a  and  14   b  are referred to as a coating part  14 , the development parts  15   a  and  15   b  are referred to as a development part  15 , the buffer plate part  13   d  is referred to as a buffer plate part  40 , and the robot parts  11   d  and  11   e  are referred to as a first robot part  11   d  and a second robot part  11   e.    
         [0016]     In  FIG. 3 , as described above, the coated substrate is temporarily stored in the buffer plate part  40  before the substrate is provided to the exposure part  16 . Also, the exposed substrate is temporarily stored in the buffer plate part  40  before the substrate is loaded to the development part  15 . Accordingly, the buffer plate part  40  is provided with a lower plate  41  temporarily storing the coated substrate before loading to the exposure process, and an upper plate  42  provided above the lower plate  41  to temporarily store the exposed substrate before loading to the development process.  
         [0017]     The first and second robot parts  11   d  and  11   e  are provided at both sides of the buffer plate part  40 . At this time, the coated substrate is stored in the lower plate  41 , and the exposed substrate stored in the upper plate  42  is loaded to the development part  15  by the first robot part  11   d . Also, the coated substrate stored in the lower plate  41  is loaded to the exposure part  16  by the second robot part  11   e . Further, the exposed substrate is unloaded from the exposure part  16 , and then stored in the upper plate  42  by the second robot part  11   e . At this time, the first robot part  11   d  unloads the developed substrate.  
         [0018]     In  FIG. 3 , letters A, B, C and D show the movement of the substrate in the process line for photolithography. That is, the substrate is transferred to the lower plate  41  of the buffer plate part  40  from the coating part  14  (A), and then temporarily stored in the lower plate  41  of the buffer plate  40 . Then, the substrate is loaded to the exposure part  16  (B), and transferred to the upper plate  42  of the buffer plate part  40  (C) after completing the exposure process. Thereafter, the substrate stored in the upper plate  42  is loaded to the development part  15  (D), and then the substrate is unloaded after completing the development process. The exposure process of the exposure part  16  is classified into an FDC (Fast Distortion Control) for simple alignment, and an ADC (All Distortion Control) for precise alignment, on the basis of the alignment level between the substrate and mask. Thus, in the exposure process, some glass substrates from the set of the loaded substrates are precisely aligned when exposed. If there are no errors in alignment between the substrate and mask, the other substrates are exposed using simple alignment.  
         [0019]     However, the exposure process using precise alignment requires a longer exposure time (hereinafter, referred to as a cycle time) than that of the exposure process using simple alignment. For example, the cycle time of the exposure process using simple alignment is about 67 seconds, and the cycle time of the exposure process using precise alignment is about 101 seconds. Also, the development process is about 70 seconds, and the cycle time of the coating process is shorter than that of the exposure process or the development process. Accordingly, each photolithographic process has a different cycle time, thereby generating time differences. If the substrate is exposed using precise alignment, the time required for photolithography depends on the exposure process. On the other hand, if the substrate is exposed using simple alignment, the time required for photolithography depends on the development process.  
         [0020]     However, the related art photolithographic system, especially, the buffer plate part, has the following disadvantages.  
         [0021]     At the beginning of photolithography, three substrates are exposed using precise alignment. If the aforementioned cycle time exists in each process, the development part  15  has a no-load operation or has to pause the system twice during the exposure process of the three substrates. As the number of the substrates exposed in precise alignment increases, the length of time increases due to increasing numbers of no-load operations or system pauses. If the substrate is exposed using simple alignment, the exposure process is processed rapidly as compared with the development process. This means that the second robot part  11   e  adjacent to the exposure part  16  waits, thereby lowering productivity.  
       SUMMARY OF THE INVENTION  
       [0022]     A photolithographic system and a method for driving the same, is provided to prevent no-load operation and imbalance of the fabrication process generated by time differences between various individual processes in the overall fabrication process.  
         [0023]     In one aspect of the invention, as embodied and broadly described herein, a photolithographic system includes a first plate storing a substrate coated with a photosensitive layer before an exposure process; a second plate to store an exposed substrate before a development process; and an auxiliary buffer plate part to store the exposed substrate before the development process when a different exposed substrate is stored in the second plate.  
         [0024]     In another aspect of the invention, the photolithographic system includes a coating part coating a photosensitive layer on a substrate; an exposure part exposing the coated substrate using precise alignment or simple alignment, exposure using precise alignment having a longer cycle time than exposure using simple alignment; a development part developing the exposed substrate; a main buffer plate part storing the coated substrate before the coated substrate is provided to the exposure part, and storing the exposed substrate before the exposed substrate is provided to the development part; an auxiliary buffer plate part storing the exposed substrate before the exposed substrates is provided to the development part when another exposed substrate is stored in the main buffer plate part; a first robot part loading the coated substrate to the main buffer plate part, or providing the exposed substrate loaded on the main buffer plate part or the auxiliary buffer plate part to the development part; and a second robot part providing the coated substrate loaded on the main buffer plate part to the exposure part, or loading the exposed substrate in the exposure part to the main buffer plate part or the auxiliary buffer plate part.  
         [0025]     In another aspect of the invention, the photolithographic system includes a coating part coating a photosensitive layer on a substrate; an exposure part exposing the coated substrate using precise alignment or simple alignment, exposure using precise alignment having a longer cycle time than exposure using simple alignment; a development part developing the exposed substrate; a main buffer plate part having first and second plates storing the coated substrate before the coated substrate is provided to the exposure part and the exposed substrate before the exposed substrate is provided to the development part; a first robot part loading the coated substrate to the main buffer plate part or providing the exposed substrate loaded on the main buffer plate part to the development part; and a second robot part providing the coated substrate loaded on the main buffer plate part to the exposure part or loading the exposed substrate in the exposure part to the main buffer plate part.  
         [0026]     A method for driving a photolithographic system includes providing a Look-up Table recording a specific ID, a processing state and position of each substrate in the system; loading a coated substrate to a first unoccupied plate of the main buffer plate part using the first robot part or loading an exposed substrate to a second unoccupied plate of the main buffer plate part using the second robot part; and providing the coated substrate loaded on the main buffer plate part to the exposure part using the second robot part or providing the exposed substrate loaded on the main buffer plate part to the development part using the first robot part.  
         [0027]     In another aspect, the method includes coating a substrate with a photosensitive layer; transferring the coated substrate to a first holder of a storage unit; storing the coated substrate using the first holder until no other substrate is present in an exposure part; transferring the coated substrate to the exposure part; exposing the coated substrate in the exposure part to radiation; transferring the exposed substrate to a second holder of the storage unit if no substrate is present in the second holder and transferring the exposed substrate to a third holder of the storage unit if another exposed substrate is present in the second holder; storing all exposed substrates in different holders of the storage unit until no other substrate is present in a development part; transferring one of the exposed substrates stored in the storage unit to the development part; and developing the exposed substrate in the development part.  
         [0028]     In another aspect, the method includes coating a substrate with a photosensitive layer; transferring the coated substrate to a storage unit having multiple holders using a first transfer apparatus; storing the coated substrate in the storage unit until no other substrate is present in an exposure part; transferring the coated substrate to the exposure part using a second transfer apparatus; exposing the coated substrate in the exposure part to radiation; transferring the exposed substrate to the storage unit using the second transfer apparatus; storing the exposed substrate in the storage unit until no other substrate is present in a development part; transferring one of the exposed substrates stored in the storage unit to the development part using the first transfer apparatus; and developing the exposed substrate in the development part. In this aspect, the first and second transfer apparatuses are capable of synchronous transfer of different substrates to different locations.  
         [0029]     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0031]      FIG. 1  is a perspective view illustrating some portions of a general LCD device;  
         [0032]      FIG. 2  is a schematic view illustrating the process line for photolithography according to the related art;  
         [0033]      FIG. 3  is a schematic view illustrating a coating part, a development part, an exposure part and a buffer plate part of  FIG. 2 ;  
         [0034]      FIG. 4  is a cross-sectional view illustrating a buffer plate part and a robot part according to the related art;  
         [0035]      FIG. 5  is a block diagram illustrating a driving circuit of a buffer plate assembly in a photolithographic system according to the present invention;  
         [0036]      FIG. 6  is a cross-sectional view illustrating a buffer plate part and a robot part in a buffer plate assembly of a photolithographic system according to the first embodiment of the present invention;  
         [0037]      FIG. 7  is a cross-sectional view illustrating a buffer plate part and a robot part in a buffer plate assembly of a photolithographic system according to the second embodiment of the present invention; and  
         [0038]      FIG. 8A  to  FIG. 8C  are explanation views illustrating a Look-Up Table according to the second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0040]     Hereinafter, a buffer plate assembly according to the present invention and a method for driving the same will be described with reference to the accompanying drawings.  
         [0041]      FIG. 5  is a block diagram illustrating a driving circuit of a buffer plate assembly according to the present invention.  FIG. 6  is a cross-sectional view illustrating a main buffer plate part, an auxiliary buffer plate and a robot part in a buffer plate assembly according to the first embodiment of the present invention.  
         [0042]     Like the photolithographic system according to the related art, the photolithographic system according to the first embodiment of the present invention includes a coating process, an exposure process and a development process. Accordingly, a coating part, an exposure part and a development part of the photolithographic system according to the present invention have the same structure as those of the related art shown in  FIG. 2  and  FIG. 3 . However, a buffer plate assembly according to the present invention includes a main buffer plate part and an auxiliary buffer plate part. Also, the exposure process includes different steps, depending on whether simple alignment or precise alignment is carried out. For example, some substrates from a set of the coated substrates are exposed using precise alignment, which has a long cycle time. If there are no errors in alignment of the substrate and mask, the remaining substrates are exposed using simple alignment, which has a short cycle time.  
         [0043]     In the driving circuit of the buffer plate assembly in the process line for photolithography according to the present invention, as shown in  FIG. 5 , a photosensitive layer is coated on the substrate by the coating part (‘ 14 ’ of  FIG. 3 ). Then, before the coated substrate is provided to the exposure part (‘ 16 ’ of  FIG. 3 ) or the exposed substrate is provided to the development part (‘ 15 ’ of  FIG. 3 ), the substrate is temporarily stored in the main buffer plate part  400 . If no substrate is present to load into the development part (‘ 15 ’ of  FIG. 3 ) in the main buffer plate part  400 , the auxiliary buffer plate  450  temporarily stores the exposed substrate. Also, a first robot part  411  is provided at one side of the main buffer plate part  400  and the auxiliary buffer plate  450 , whereby the substrate unloaded from the coating part (‘ 14 ’ of  FIG. 3 ) is loaded into the main buffer plate part  400 , or the substrate temporarily stored in the main buffer plate part  400  or the auxiliary buffer plate part  450  is loaded into the development part (‘ 15 ’ of  FIG. 3 ) by the first robot part  411 . Then, a second robot part  412  loads the substrate stored in the main buffer plate part  400  into the exposure part (‘ 16 ’ of  FIG. 3 ), or loads the substrate unloaded from the exposure part (‘ 16 ’ of  FIG. 3 ) into the main buffer plate part  400  or the auxiliary buffer plate part  450 . A sensing part  416  is provided to sense whether the substrate is loaded to the main buffer plate part  400  and the auxiliary buffer plate part  450  or not. Also, first and second robot control parts  413  and  414  respectively control the first and second robot parts  411  and  412 , and a programmable logic circuit (PLC)  415  calculates a value sensed by the sensing part  416 , and transmits the calculated value to the first and second robot control parts  413  and  414 .  
         [0044]     As shown in  FIG. 6 , the buffer plate assembly of the photolithographic system according to the first embodiment of the present invention is provided with the main buffer plate part  400 , and the auxiliary buffer plate part  450 . The main buffer plate part  400  includes a first plate  410  and a second plate  420 . The first plate  410  temporarily stores the coated substrate before loading the coated substrate to the exposure part. The second plate  420  is provided below the first plate  410  to temporarily store the substrate that has been unloaded from the exposure part (‘ 16 ’ of  FIG. 3 ) before loading this exposed substrate to the development part  15 . The auxiliary buffer plate part  450  includes third and fourth plates  430  and  440 . The third and fourth plates  430  and  440  temporarily store exposed substrates in case the substrate not loaded to the development part (‘ 15 ’ of  FIG. 3 ) is maintained in the second plate  420  of the main buffer plate  400 .  
         [0045]     Like the related art, the exposure cycle time using simple alignment requires about 67 seconds and the exposure cycle time using precise alignment requires about 101 seconds. The development process requires a cycle time of about 70 seconds. If the cycle time of the coating process is shorter than that of the exposure process or the development process, the auxiliary buffer plate part  450  stores the extra substrates that have completed the exposure process as the exposure process of the substrate progresses using simple alignment.  
         [0046]     If the substrate is not provided to the development part (‘ 15 ’ of  FIG. 3 ) by the second plate  420 , the auxiliary buffer plate part  450  provides the substrate for the development process. Preferably, if the exposure process uses precise alignment, the auxiliary buffer plate part  450  stores the substrates, corresponding to the number of times of no-load operations or pauses of the system exist in the development part of the related art photolithographic system. That is, like the related art, the cycle time of the exposure process using simple alignment is about 67 seconds, and the cycle time of the exposure process using precise alignment is about 101 seconds. Also, the cycle time in the development process is about 70 seconds. Accordingly, the substrate is exposed using precise alignment by the exposure part (‘ 16 ’ of  FIG. 3 ), the development part (‘ 15 ’ of  FIG. 3 ) has two no-load operations, so that it is preferable for the auxiliary buffer plate part  450  to have at least two plates.  
         [0047]     The first robot part  411  is provided at one side of the buffer plate assembly  400 . The first robot part  411  loads the coated substrate to the first plate  410 . If a substrate is stored in the second plate  420 , the first robot part  411  loads the substrate stored in the second plate  420  to the development part (‘ 15 ’ of  FIG. 3 ). If a substrate is not stored in the second plate  420 , the first robot part  411  loads a substrate stored in the auxiliary buffer plate part  450  to the development part (‘ 15 ’ of  FIG. 3 ).  
         [0048]     The second robot part  412  is provided at the other side of the buffer plate assembly  400 . The second robot part  412  loads the substrate stored in the first plate  410  to the exposure part (‘ 16 ’ of  FIG. 3 ), and loads the exposed substrate unloaded from the exposure part (‘ 16 ’ of  FIG. 3 ) to the second plate  420 . If the second plate  420  stores a substrate which has not yet been loaded to the development part (‘ 15 ’ of  FIG. 3 ), the second robot part  412  loads the substrate which was to be stored in the second plate  420  to the third or fourth plate  430  or  440 . In the aforementioned description, it is possible to change the position of the upper and lower plates in the buffer plate assembly. Also, the buffer plate assembly  400  is provided with a sensing part  416  to sense whether substrates are provided in the respective plates  410 ,  420 ,  430  and  440 .  
         [0049]     Operation of the photolithographic system having the aforementioned buffer plate assembly according to the first embodiment of the present invention will be described as follows.  
         [0050]     First, if the coated substrate is stored in the first plate  410  of the main buffer plate part  400  by the first robot part  411 , the second robot part  412  loads the substrate stored in the first plate  410  to the exposure part (‘ 16 ’ of  FIG. 3 ). At the beginning of photolithography, some substrates are exposed using precise alignment, and then unloaded from the exposure part (‘ 16 ’ of  FIG. 3 ) by the second robot part  412 . Subsequently, one of the exposed substrates is stored in the second plate  420 , and this substrate stored in the second plate  420  is loaded to the development part (‘ 15 ’ of  FIG. 3 ) by the first robot part  411 , whereby the development process is carried out.  
         [0051]     After some substrates complete the exposure process in the exposure part (‘ 16 ’ of  FIG. 3 ) using precise alignment, the substrate stored in the first plate  410  is loaded to the exposure part (‘ 16 ’ of  FIG. 3 ) and the exposure process using simple alignment is carried out. As the number of substrates exposed increases because simple alignment has been used, the second plate  420  has an exposed substrate already stored therein. Ann exposed substrate is unloaded from the exposure part by the second robot part  412  and the sensing part  416  senses that the second plate  420  already has an exposed substrate contained therein. Accordingly, the second robot part  412  loads the exposed substrate to the auxiliary buffer plate part  450  rather than the second plate  420 .  
         [0052]     Then, the new set of substrates is loaded and the exposure process using precise alignment is carried out, whereby the exposure time increases. To prevent a no-load operation of the development part (‘ 15 ’ of  FIG. 3 ), the first robot part  411  loads the substrate temporarily stored in the second plate  420  of the main buffer plate part  400  to the development part (‘ 15 ’ of  FIG. 3 ). If the second plate  420  does not contain an exposed substrate, a substrate stored in the auxiliary buffer plate part  450  is loaded to the development part (‘ 15 ’ of  FIG. 3 ). Supporters provided in the first robot part  411  and the second robot part  412  move up and down or the buffer plate assembly  400  may be moved up and down to store the substrate in the auxiliary buffer plate part  450  or to unload the substrate stored in the auxiliary buffer plate part  450 .  
         [0053]     In the buffer plate assembly according to the present invention, it is possible to prevent a no-load operation or pause of the system by controlling the first and second robot parts without additional auxiliary buffer plate parts being used. This will be described as follows.  
         [0054]      FIG. 7  is a cross-sectional view illustrating a buffer plate part and a robot part in a buffer plate assembly of a photolithographic system according to the second embodiment of the present invention.  
         [0055]     Referring to  FIG. 7 , the buffer plate assembly according to the second embodiment of the present invention uses a main buffer plate part  500  having a first plate  510  and a second plate  520 . Each of the first and second plates  510  and  520  is operated using a bi-directional transfer method. As a result, the photolithographic system according to the second embodiment of the present invention enables synchronous transfer, making it possible to drive the buffer plate assembly according to the second embodiment of the present invention without an auxiliary buffer plate part.  
         [0056]     First and second robot parts  511  and  512  are provided at both sides of the main buffer plate part  500 . The first and second robot parts  511  and  512  load substrates to the respective plates  510  and  520  of the main buffer plate part  500  and unload the substrates from the plates  510  and  520  of the main buffer plate part  500 . It is possible to load the substrates to the first plate  510  and to unload the substrates therefrom using the first and second robot parts  511  and  512 . Also, it is possible to load the substrates to the second plate  520  and to unload the substrates therefrom by the first and second robot parts  511  and  512 .  
         [0057]     The photolithographic system according to the second embodiment of the present invention is provided with a coating part (‘ 14 ’ of  FIG. 3 ), an exposure part (‘ 16 ’ of  FIG. 3 ), a development part (‘ 15 ’ of  FIG. 3 ), the main buffer plate part  500  having the first and second plates  510  and  520 , the first robot part  511 , and the second robot part  512 . In detail, a photosensitive layer is coated on the substrate in the coating part. Some substrates coated with the photosensitive layer are exposed using precise alignment having a long cycle time, and the remaining substrates are exposed using simple alignment having a short cycle time. In the development part, the exposed substrates are developed. The first and second plates  510  and  520  temporarily store the coated substrates before the exposure process and temporarily store the exposed substrates before the development process. The first robot part  511  loads the coated substrates to the main buffer plate part  500  and provides the exposed substrate in the main buffer plate part  500  to the development part. The second robot part  512  provides the coated substrates of the main buffer plate part  500  to the exposure part and loads the exposed substrates to the main buffer plate part  500 .  
         [0058]     This will be described in detail. In  FIG. 5 , a Look-up Table is provided to a PLC  415  or first and second robot control parts  413  and  414 . The Look-up Table records specific IDs, the processing state and position of the respective substrates. By controlling the first and second robot parts  411  and  412  according to the Look-up Table, it is possible to prevent a no-load operation of the development part (‘ 15 ’ of  FIG. 3 ) without formation of an auxiliary buffer plate part.  
         [0059]      FIG. 8A  to  FIG. 8C  illustrate the Look-Up Table according to the second embodiment of the present invention. As described above, if the recording state of  FIG. 8A  is provided in the Look-up Table of the PLC  415  or the first and second robot control parts  413  and  414 , the first robot control part  413  controls the first robot part  511  to transfer the substrate  0001  stored in the second plate  520  to the development part (‘ 15 ’ of  FIG. 3 ). Simultaneously, the second robot control part  414  controls the second robot part  512  to transfer the substrate  0002  stored in the first plate  510  to the exposure part (‘ 16 ’ of  FIG. 3 ), or to load the coated substrate  0003  of the coating part (‘ 14 ’ of  FIG. 3 ) to the second plate  520 . Then, the position and the processing state corresponding to the ID of the respective substrates are newly recorded as shown in  FIG. 8B .  
         [0060]     In the state of  FIG. 8B , after completion of the process in the exposure part and the development part, the second robot part  512  unloads the exposed substrate  0002  from the exposure part (‘ 16 ’ of  FIG. 3 ), and then loads the unloaded substrate  0002  to the first plate  510 . Also, the second robot part  512  unloads the developed substrate  0001 . After that, the first robot part  511  transfers the substrate  0003  of the second plate  520  to the exposure part (‘ 16 ’ of  FIG. 3 ), and the second robot part  512  transfers the substrate  0002  of the first plate  510  to the development part (‘ 15 ’ of  FIG. 3 ). Also, the first robot part  511  loads the coated substrate  0004  to the second plate  520 .  
         [0061]     The Look-up Table of the aforementioned process is then recorded as shown in  FIG. 8C . In this method, the coated or exposed substrates may be loaded to the first or second plates  510  and  520  if the plates have no substrate thereon, so that it is possible to prevent a no-load operation of the development part without an additional auxiliary buffer plate part. In addition, the aforementioned buffer plate assemblies  400  and  500  may be applied to any system having the problem of processing imbalance, as well as the photolithographic system according to the preferred embodiment of the present invention.  
         [0062]     As mentioned above, the photolithographic system according to the present invention and the method for driving the same have the following advantages.  
         [0063]     First, the auxiliary buffer plate assembly stores the extra substrates, so that it is possible to provide an exposed substrate to the development part when an exposure process using precise alignment is processed, thereby preventing a no-load operation or pause of the robot and development parts. As a result, it is possible to improve productivity owing to the prevention of a no-load operation or pause of the system.  
         [0064]     Furthermore, the robot parts are controlled by the Look-up Table recording the processing state and position of the respective substrates. This makes it is possible to prevent a no-load operation or pause of the robot parts without formation of an auxiliary buffer plate part, thereby improving productivity.  
         [0065]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.