Abstract:
An exposing apparatus maintains uniformly a gap between a substrate and a mask stage. The substrate is disposed on a substrate chuck and the substrate chuck is supported by gap motors and air cylinders. The gap motors control the gap between the substrate and the mask stage and the air cylinders support the deflect portion of the substrate chuck to maintain the flatness of the whole area of the substrate.

Description:
The present application claims the benefit of Korean Patent Application No. 45802/2005 filed in Korea on May 30, 2005, which is hereby incorporated by reference. 
     FIELD 
     The present invention relates to a proximity type exposing apparatus, and more particularly, to a proximity type exposing apparatus having a flatness maintaining unit capable of maintaining a flatness of a large glass substrate and a flatness of a substrate chuck for supporting the glass substrate. 
     BACKGROUND 
     In order to fabricate a semiconductor device or a liquid crystal display (LCD) device, a process for forming a plurality of thin films is required. The thin film forming process is mainly performed by exposing technique, photolithography technique. Ultraviolet rays or X-rays are irradiated onto a substrate through a mask having a certain pattern thus to expose a photo-sensitive material deposited on the substrate, thereby forming the certain pattern on the substrate. 
     The exposing technique is utilized to pattern gate lines, data lines, and unit pixels of a liquid crystal display (LCD) device, and to form a color filter layer of a color filter substrate. Therefore, the exposing apparatus is very important in forming a precise pattern on the substrate. 
     Generally, the exposing apparatus is largely divided into a projection type for extraction/enlarge-transferring a mask pattern onto a substrate, and a proximity type for transferring a pattern onto a substrate by one to one using horizontal type parallel light. 
     The projection type exposing apparatus that can perform a contraction exposure is mainly used to fabricate a device requiring an integration such as a semiconductor device, and the proximity type exposing apparatus using a large mask is mainly used to fabricate an LCD device or a PDP having a large area on which same patterns are formed. 
     In the proximity type exposing apparatus, a mask has to be close to a substrate in order to completely transfer a mask pattern onto the substrate. In this case, the mask can come in contact with the substrate, which is called a contact type exposing apparatus. However, in case of the contact type exposing apparatus, foreign materials of the substrate may damage the mask. Therefore, it is a task to fabricate a mask stage proximate to a substrate without contact in the proximity type exposing apparatus. 
     The proximity type exposing apparatus and the projection type exposing apparatus respectively comprise a lighting device for generating light for exposure, a mask stage for supporting a mask having a certain pattern, a substrate chuck on which a substrate onto which the mask pattern is to be transferred is placed, and a supporter for supporting the substrate chuck. 
     The exposing apparatus is provided with a plurality of alignment cameras for certifying each position of the substrate and the mask stage in order to correctly align the substrate and the mask stage so as to precisely transfer the mask pattern onto the substrate. The alignment cameras correctly align the substrate and the mask stage by recognizing alignment keys formed on the substrate chuck or the substrate. 
     Accordingly as size of an LCD device is increasing recently, a mask stage for supporting a mask also becomes larger. A mask is fixed to a lower portion of the mask stage by a fixing means so that the mask can be proximate to a substrate. 
     The proximity type exposing apparatus will be explained with reference to  FIG. 1 . 
     Referring to  FIG. 1 , the proximity type exposing apparatus comprises a lighting device  101 , a mask stage  105  formed at a lower portion of the lighting device  101  for supporting the mask  110 , a supporter  120  for supporting four edges of the mask stage, a substrate chuck  130  formed at a lower portion of the mask stage  105  for supporting a substrate  114 , a Y-axis driving stage  113  and an X-axis driving stage  112  for supporting and moving the substrate chuck  130 , and a base stage  150  on which the X-axis driving stage  112  and the Y-axis driving stage  113  are formed. 
     The lighting device  101  generates light such as ultraviolet rays or X-rays thereby to transfer a mask pattern onto a substrate. 
     The mask stage  105  is composed of a lower stage  103  to which the mask  110  is directly coupled, and an upper stage  102  for supporting the lower stage and serving as a base of the mask stage. 
     In order for the mask  110  to be proximate to the substrate  114  as much as possible, the lower stage  103  to which the mask is directly coupled is coupled to a lower surface of the upper stage  102  thus to support the mask  110 . 
     Each middle portion of the upper stage  102  and the lower stage  103  is empty so that light generated from the lighting device  101  can be irradiated onto the substrate  114  through the mask  110 . 
     Four edges of the mask stage  105  are supported by the supporter  120  of a bar shape. 
     The substrate  114  supported by the substrate chuck  130 , and the Y-axis driving stage  113  and the X-axis driving stage  112  for moving the substrate chuck  130  are installed below the mask stage  105 . 
     The X-axis driving stage  112  can be installed on the base stage  150 , or can be installed on a supporting chuck (not shown) formed on the base stage  150 . A rail is installed on the base stage  150  or the supporting chuck in an X-axis direction, and the X-axis driving stage  112  is coupled onto the rail. A rail is installed on the X-axis driving stage  112  in a Y-axis direction, and a Y-axis driving stage  113  is coupled onto the rail. 
     The substrate chuck  130  is installed on the Y-axis driving stage  113 , and the substrate  114  loaded onto the substrate chuck  130  is moved to a certain coordinate by the X-axis driving stage  112  and the Y-axis driving stage  113 . Generally, a mask has a size larger than that of a substrate. Therefore, a plurality of exposures are performed by moving the substrate under a state that the mask is fixed, thereby transferring a mask pattern onto the entire substrate. 
     In the exposing apparatus for transferring minute mask patterns onto the substrate, the mask stage and the substrate have to be correctly aligned. Accordingly, an alignment camera (not shown) for a correct alignment between the substrate and the mask stage is provided on the mask stage. Also, an alignment key detected by the alignment camera is installed on the substrate or the X-axis driving stage. 
     The alignment camera certifies the alignment key thus to correctly align the substrate and the mask stage. 
     However, the conventional method for aligning the substrate and the mask stage has a problem. That is, since the substrate is moved by the X-axis driving stage  112  and the Y-axis driving stage  113  at the time of aligning the substrate and the mask stage, there is a limitation in aligning the substrate and the mask stage for a unit less than micro-meter. 
     Furthermore, since the substrate chuck is positioned on the X-axis driving stage and the Y-axis driving stage and the substrate to be exposed is placed on the substrate chuck, there is a limitation in obtaining a minute flatness of the substrate. In the proximity type exposing apparatus, a correct alignment of the substrate and the mask and a minute gap maintenance therebetween are very important. 
     SUMMARY 
     An exposing apparatus comprises a mask stage, a supporter that supports the mask stage, a substrate below the mask stage, and a substrate chuck that supports the substrate. The exposing apparatus further comprises a substrate chuck moving mechanism that moves the substrate chuck, a gap motor unit installed on the substrate chuck moving mechanism that controls a gap between the substrate and the mask stage, and a substrate chuck flatness maintaining mechanism that maintains a flatness of the substrate chuck. 
     In another aspect of the present invention, an exposing apparatus, comprises a substrate chuck, a gap motor unit that moves the substrate chuck up and down, a plurality of flatness maintaining mechanism that maintains a flatness of the substrate chuck, and a substrate chuck flatness detecting mechanism that detects a flatness of the substrate chuck. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a sectional view showing a proximity type exposing apparatus in accordance with the conventional art; 
         FIG. 2  is a perspective view showing a mask stage of a proximity type exposing apparatus according to the present invention; 
         FIG. 3  is a perspective view showing a lower device including a substrate chuck of the proximity type exposing apparatus according to the present invention; 
         FIGS. 4A and 4B  are respectively a plane view and a sectional view of the substrate chuck having a substrate chuck flatness maintaining means according to the present invention; 
         FIG. 5  is an enlarged sectional view showing the substrate chuck flatness maintaining means according to the present invention; and 
         FIG. 6  is a sectional view showing the substrate chuck according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     Hereinafter, we will describe a proximity type exposing apparatus according to the present invention accompanying drawings. 
       FIGS. 2 and 3  are the views showing a mask stage and a base stage. 
     Referring to  FIG. 2 , a mask stage  200  of the present invention comprises a mask base stage  201  having a square shape; a mask fixing stage  204  formed in the middle of the base stage  201  for fixing a mask  210 ; a supporter  202  formed at an edge of the mask base stage  201  for supporting the mask base stage  201 ; a weight supporter  206  for overcoming a weight of the mask fixing stage  204  and connecting the mask fixing stage  204  and the mask base stage  201  to each other; and a plurality of guide units  205   a ,  205   b , and  205   c  for minutely moving the mask fixing stage  204 . 
     The mask base stage  201  of the mask stage  200  has a square shape. The supporter  202  for supporting the mask stage  200  is installed at four edges of the mask base stages  201 . 
     The supporters  202  can be four pillars formed at four edges of the mask base stage, and are constructed to control a height of the mask stage  200 . The supporter  202  is connected to the mask base stage  201  of the proximity type exposing apparatus. 
     The mask fixing stage  204  is installed at an empty space in the middle of the mask base stages  201 . The mask fixing stage  204  also has an empty space therein, and the mask  210  is installed at the empty space. Light from a lighting device (not shown) is irradiated onto a substrate through the mask  210 . 
     The proximity type exposing apparatus of the present invention is suitable to expose an LCD panel having a large area, in which a large mask is used. Therefore, the mask fixing stage  204  for fixing the mask is also large and is formed of a metal material, which has a considerable weight of a ton unit. Accordingly, a weight supporter  206  for supporting the weight of the mask fixing stage  204  and connecting the mask fixing stage  204  to the mask base stage  201  is provided. 
     At least one weight supporter  206  is formed at each edge of the mask fixing stage  204 . One portion of the weight supporter  206  is coupled to the mask fixing stage  204  by a coupling means, and another portion thereof is connected to the mask base stage  201  under a state that a ball bearing is interposed therebetween. More concretely, the weight supporter  206  is constructed so as to be minutely movable on the mask base stage  201  by directly coming in contact with the ball bearing formed on the mask base stage  201 . 
     A guide unit for guiding the mask fixing stage in X, Y, and {circle around (-)} directions is installed on the base stage, thereby minutely moving the mask fixing stage in X, Y, and {circle around (-)} directions thus aligning the mask fixing stage and the substrate. 
     A plurality of alignment keys for correctly aligning the mask fixed on the mask stage and the substrate installed on the base stage are provided on the substrate or a substrate driving stage. Also, an alignment camera for detecting the alignment keys is provided at the mask stage. The alignment of the substrate and the mask is detected by the alignment camera, and the mask is minutely aligned with the substrate using the guide unit. 
     Since the mask stage is fixed by the supporter  202 , a substrate driving means for moving the substrate for a correct alignment between the mask and the substrate is required. 
     The substrate is installed on the base stage provided below the mask stage. Hereinafter, the substrate driving means installed on the base stage and the substrate chuck for supporting the substrate will be explained with reference to  FIG. 3 . 
     Referring to  FIG. 3 , a substrate chuck  304  and substrate driving means  302  and  303  provided below the mask stage are formed on a base stage  301  of the proximity type exposing apparatus. A supporter installing unit  315  having a square shape for installing the supporter  202  to support the mask stage is formed at four edges of the base stage  301 . The supporter  202  is installed at the supporter installing unit  315  thus to be driven up and down, thereby firstly determining a gap between the mask and the substrate. 
     The substrate driving means  302  and  303  for moving the substrate are installed on the base stage  301 . The substrate driving means  302  is an X-axis driving stage  302  for driving the substrate chuck  304  in an X-direction, and the substrate driving means  303  is a Y-axis driving stage  303  for driving the substrate chuck  304  in a Y-direction. The X-axis driving stage  302  is coupled to an X-axis driving rail  310  formed on the base stage  301  thus to be moved in an X-axis direction, and the Y-axis driving stage  303  is coupled to a Y-axis driving rail  311  formed on the X-axis driving stage  302  thus to be moved in a Y-axis direction. 
     The substrate chuck  304  installed on the Y-axis driving stage  303  is moved in X and Y directions by the X-axis driving stage  302  and the Y-axis driving stage  303  thus to be moved to a certain coordinate. Since the mask is fixedly installed at the mask stage, the substrate below the mask is moved to be aligned with the mask and then an exposure process is performed. 
     The substrate chuck  304  for supporting the substrate is formed on the Y-axis driving stage  303 . The substrate chuck  304  is provided with a gap motor unit  313  for minutely controlling a gap between the mask and the substrate. Three gap motor units installed with a triangular shape support the substrate chuck  304 . The first purpose of the gap motor unit  313  is to constantly maintain a gap between the substrate and the mask in several hundred micrometers range of a high minuteness, and thus three gap motor units are provided. The gap between the substrate and the mask is firstly controlled by the thee gap motor units, and then a flatness of the substrate is controlled by two gap motor units and then by one gap motor unit. 
     The gap between the mask and the substrate is firstly controlled by the supporter  202  for supporting the mask stage, and then is minutely controlled by the gap motor unit  304  in several hundred micrometers range. 
     As an image display device such as an LCD device and a PDP device becomes larger, a substrate and a substrate chuck also become larger. 
     Since a large glass substrate has a size of several meters, a substrate chuck for supporting the substrate has a size of several meters. The substrate chuck is formed of a metal material thus with a heavy weight of several tons. When the substrate chuck  304  is supported by the gap motor unit  313 , parts of the substrate chuck  304  that are not supported by the gap motor unit  313  are deflected and thus a uniform flatness is not maintained. In order to prevent the deflection of the substrate chuck, the substrate chuck can be formed to be thicker. However, in this case, the substrate chuck becomes heavier thus not to be smoothly operatable. 
     Accordingly, the present invention is further provided with a substrate chuck flatness maintaining means  314  for constantly maintaining a gap between the substrate chuck and the mask. 
     As one example of the substrate chuck flatness maintaining means, a plurality of floating air cylinders  314  are installed below the substrate chuck thus to prevent a deflection of the substrate chuck at each position. 
     In the proximity type exposing apparatus of the present invention, a substrate chuck flatness detecting means (not shown) for detecting a flatness of the substrate chuck is further installed on the mask stage. The substrate chuck flatness detecting means detects a flatness of the substrate chuck. Then, if the flatness of the substrate chuck is changed according to a position change, the substrate chuck flatness detecting means feeds back the information to a controller. Accordingly, the substrate can have a certain flatness by the floating air cylinder  314 . 
     Hereinafter, the substrate chuck and the substrate chuck flatness maintaining means will be explained with reference to  FIGS. 4A and 4B . 
     Referring to  FIG. 4A , three gap motor units  313  arranged as a triangular shape support the substrate chuck  304  at edges of the substrate chuck  304 . The gap motor units  313  lift or lower the substrate chuck  304  thereby to set a gap between the substrate chuck and the mask. 
     A plurality of floating air cylinders  314  for maintaining a uniform flatness of the substrate chuck are formed at a lower surface of the substrate chuck  304 . The floating air cylinders are installed at positions where the substrate chuck can be easily deflected. For instance, when the gap motor units  313  are installed at each edge of the substrate chuck  304 , the deflection of the substrate chuck is easily generated at a middle portion and at positions far from the gap motor units  313 . Therefore, the air cylinders  314  are installed at the middle portion and at the positions far from the gap motor units  313 . Referring to  FIG. 4A , three air cylinders  314  are installed in the middle of the substrate chuck  304  with a certain gap therebetween and two air cylinders  314  are installed at each corner of the edge of the substrate chuck  304  where one gap motor unit  313  is installed, so that five air cylinders  314  are totally installed. 
     Hereinafter, the operation of the floating air cylinder will be explained with reference to  FIG. 4B . 
     A plurality of detecting sensors  410  are installed at the mask stage for supporting the mask. The detecting sensors  410  detect a flatness of the substrate chuck  304 , and transmit a signal to a controller (not shown) if the substrate chuck is deflected. Then, the controller transmits the signal to the air cylinders  314  thus to control an air pressure of the air cylinders. As the result, the air cylinders  314  support the substrate chuck  304  with being lifted or lowered, thereby constantly maintaining a flatness of the substrate chuck. An operator sets an initial pressure value of the air cylinder by which the flatness of the substrate chuck is maintained. Then, if the flatness of the substrate chuck detected by the substrate chuck detecting means is changed, the information is sent to the air cylinder and thus the air cylinder is controlled to have the initial pressure value. The present invention is further provided with an electronic regulator for constantly maintaining a pressure of the air cylinder by receiving deflection information of the substrate chuck from the controller. 
     Referring to  FIG. 5 , the electronic regulator  314  is provided with a piston  510  and a cylinder  511 , and can be further provided with supporters respectively contacting the substrate chuck  304  and the Y-axis driving stage  303  at upper and lower portions thereof. Air is filled between the piston  510  and the cylinder  511 , and a pressure of the air can be constantly maintained by the electronic regulator  314  installed at each air cylinder  304 . 
     A substrate supporting pin chuck having a substrate supporting pin for unloading a substrate that has been loaded onto the substrate chuck  304  from the substrate chuck by a certain height is further provided below the substrate chuck  304 . The supporting pin unloads the substrate from the substrate chuck by a certain height when the substrate is loaded and unloaded onto/from the substrate chuck by a robot arm. 
     Hereinafter, the substrate supporting pin and the substrate supporting pin chuck for supporting the substrate supporting pin will be explained with reference to  FIG. 6 . 
     Referring to  FIG. 6 , the substrate chuck  304  is supported by the gap motor unit  313  and the air cylinder  314 . Also, a substrate  400  is positioned on an upper surface of the substrate chuck  304 . 
     A substrate supporting pin chuck  501  is further provided below the substrate supporting chuck  304 . A plurality of substrate supporting pins  502  are installed at the substrate supporting pin chuck  501  with a certain gap therebetween. The substrate supporting pins  502  support the substrate via the substrate supporting chuck. The substrate supporting pin chuck  501  is fixed by additional supporting shafts  503 . 
     The air cylinder  314  and the gap motor unit  313  support the substrate chuck  304  via the substrate supporting pin chuck  501 . 
     Since the substrate supporting pin chuck  304  and the substrate supporting pin installed thereon are fixed, the substrate  400  is loaded/unloaded onto/from the substrate chuck  304  by moving the gap motor unit  313  up and down. 
     As aforementioned, in the present invention, the gap motor unit for approaching the substrate chuck to the mask is provided, thereby setting a gap between the substrate and the mask of a high minuteness and thus enhancing an exposure function. 
     In case of exposing a large substrate, a flatness maintaining means for preventing the substrate chuck from being deflected is further provided, thereby constantly maintaining a gap between the substrate and the mask at the time of performing a proximate exposure. Furthermore, since the flatness maintaining means is provided, an excellent flatness can be obtained even if the substrate chuck is thin. Accordingly, a mask pattern can be precisely transferred onto the substrate at the time of performing a proximate exposure. 
     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.