Abstract:
A pattern transcription apparatus comprises a cliché including a concave portion, a convex portion and a printing stopper, the printing stopper formed on a bottom surface of the concave portion; and a blanket, on which a resist material layer is coated, rotatable on the cliché, wherein a surface energy density of the blanket is greater than a surface energy density of the printing stopper and is smaller than a surface energy of the cliché.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of Korean Patent Application No. 2007-0010069 filed in Korea on Jan. 31, 2007, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pattern transcription device, and more particularly, to a transcription device and a method of fabricating a cliché for the pattern transcription device being capable of forming a fine pattern without damages on the pattern. 
     2. Discussion of the Related Art 
     A flat panel display device, such as a liquid crystal display (LCD) device, includes a thin film transistor (TFT) as a switching element in each pixel. A fabricating process of the TFT requires many mask processes including a process of forming a photoresist pattern (PR). The PR pattern has a great effect on characteristics of the TFT. Characteristics of the TFT are the subject of significant research and development. Particularly, significant efforts have been devoted to improve characteristics of the TFT using a fine metal pattern. 
     Generally, a fabricating process of the PR pattern includes a step of forming a PR layer by coating a photosensitive PR material, a step of exposing the PR layer using a mask and a step of developing the exposed PR layer to form the PR pattern. However, since many process steps for fabricating the PR pattern, which are very complicated, are required to fabricate the TFT, production costs increase and production yield decreases. 
     To resolves these problems, a method of fabricating a resist pattern using a printing method is suggested.  FIGS. 1A to 1D  show a process of fabricating a resist pattern by a conventional reverse offset method. First, as shown in  FIG. 1A , a resist material layer  32  is coated on an outer surface of a blanket  30 . The blanket  30  covers along a circumference of a roller  31 . The blanket  30  has a circumference being substantially the same as a length of a substrate, on which a resist pattern is to be formed. 
     Next, as shown in  FIG. 1B , the blanket  30 , on which the resist material layer  32  is coated, is rotated on a cliché  20  on a printing table  40 . The cliché  20  includes a plurality of concave portions  22  and a plurality of convex portions  24  to resulting in an uneven surface. Each convex portion  24  is disposed between two adjacent concave portions  22 . When the roller  31  is rotated on the cliché  20 , a concave-counter pattern  34  is formed on the blanket  30  and a convex-counter pattern  36  is formed on the convex portion  24  because the resist material has a greater adhesive strength to the cliché  20  than the blanket  30 . Namely, portions of the resist material layer  32  corresponding to the convex portion  24  are transferred on the convex portion  24 , and the other portions of the resist material layer  32  corresponding to the concave portion  22  remains on the blanket  30 , thereby forming the concave-counter pattern  34  on the blanket  30 . 
     Next, as shown in  FIG. 1C , the blanket  30  including the concave-counter pattern  34  contacts and is rotated on a process-object layer  11  disposed on a substrate  10 . Then, the concave-counter pattern  34  is transferred on the process-object layer  11 . By applying UV light to the concave-counter pattern  34  and hardening it, a resist pattern  38  is formed on the process-object layer  11 , as shown in  FIG. 1D . 
     Generally, the blanket  30  is formed of an elastic material, such as silicon or rubber. Accordingly, when the blanket  30  is rolled on the cliché  20 , the blanket  30  is crushed and contacts a ground surface of the concave portion  22  of the cliché  20  because of an elastic property, as shown in  FIG. 2A , such that the resist material is partially stuck to the ground surface of the concave portion  22  and the desired remained pattern  38  (of  FIG. 1D ) can not be obtained. Consequently, there are some undesired resist patterns on the process-object layer  11 , as shown in  FIG. 2B . These problems are easily caused as the resist pattern  38  is large in size. 
     To resolve these problems, it is possible to form the concave portions more deep so as not to contact the blanket with the ground surface of the concave portions. However, when the concave portion has a greater depth, there are losses on a critical dimension. The concave portion is formed by a wet-etching, which has isotropic properties, using an etchant. The greater depth the concave portion has, the greater width the concave portion has. Namely, the width is proportional to the depth. It is difficult to form a fine pattern with a great width. 
     SUMMARY OF THE DISCLOSURE 
     A pattern transcription apparatus comprises a cliché including a concave portion, a convex portion and a printing stopper. The printing stopper is formed on a bottom surface of the concave portion. The apparatus also includes a blanket, on which a resist material layer is coated, rotatable on the cliché, wherein a surface energy density of the blanket is greater than a surface energy density of the printing stopper and is smaller than a surface energy of the cliché. 
     In another aspect of the present disclosure, a pattern transcription apparatus comprises a cliché including a concave portion and a convex portion; and a blanket, on which a resist material layer is coated, rotatable on the cliché and including first, second and third layers. The first layer contacts the resist material layer, and the second layer is disposed between the first and third layers, wherein a hardness of the first layer is lower than a hardness of the second layer and greater than a hardness of the third layer. 
     In another aspect of the present invention, a pattern transcription apparatus comprises a cliché including a concave portion and a convex portion; and a blanket, on which a resist material layer is coated, rotatable on the cliché and including first, second and third layers. The first layer contacts the resist material layer, and the second layer is disposed between the first and third layers, wherein the third layer has a greater thickness than both the first and second layers. 
     In another aspect of the present invention, a method of fabricating a cliché for a pattern transcription apparatus comprises forming a metal pattern on a substrate; etching the substrate using the metal pattern as an etching mask to form a concave portion and a convex portion; and forming a printing stopper on a bottom surface of the concave portion, wherein the printing stopper has a surface energy density smaller than the substrate. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       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. 
         FIGS. 1A to 1D  show a process of fabricating a resist pattern by a conventional reverse offset method. 
         FIG. 2A  is an enlarging view showing a concave portion contacting a resist material. 
         FIG. 2B  is a plane perspective view showing a process-objected layer having an undesired resist pattern. 
         FIGS. 3A to 3D  show a process of fabricating a resist pattern by a reverse offset method according to an embodiment of the present invention. 
         FIGS. 4A to 4F  are cross-sectional views showing a process of fabricating a cliché according to an embodiment of the present disclosure. 
         FIGS. 5A to 5E  are cross-sectional views showing a process of fabricating a cliché according to another embodiment of the present disclosure. 
         FIG. 6  is a schematic cross-sectional view of a blanket with a roller according to an embodiment of the present invention. 
         FIG. 7  is a cross-sectional view taken along the line VII-VII of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings. 
       FIGS. 3A to 3D  show a process of fabricating a resist pattern by a reverse offset method according to an embodiment of the present disclosure. First, as shown in  FIG. 3A , a blanket  130  covers along a circumference of a roller  131 , and a resist material layer  132  is coated on an outer surface of the blanket  130 . When the blanket  130  with roller  131  is rotated, a resist supplier  136  supplies a resist material to the outer surface of the blanket  130  such that the resist material layer  132  is uniformly formed on the outer surface of the blanket  130 . 
     Next, as shown in  FIG. 3B , the blanket  130 , on which the resist material layer  132  is coated, contacts and is rotated on a cliché  120  formed on a printing table  140 . The cliché  120  includes a plurality of concave portions  122  and a plurality of convex portions  124 . Namely, the cliché  120  has an uneven surface. Each convex portion  124  is disposed between two concave portions  122 . Each of the concave portions  122  corresponds to a pattern that is desired to be formed on a substrate. In addition, a printing stopper  126  is formed in each concave portion  122  to prevent the resist material being printed on the concave portions  122 . The printing stopper  126  is formed of a material having a surface energy density smaller than that of a blanket  130 . For example, the printing stopper  126  is formed of teflon. A material of the blanket  130  has a surface energy density with a range between 20 mJ/cm 2  and 23 mJ/cm 2 , while a material of printing stopper  126 , such as teflon, has a surface energy density with a range between 13 mJ/cm 2  and 18 mJ/cm 2 . In brief, a material of the printing stopper  126  has a surface energy density smaller than a material of the blanket  130 . This means that the resist material is much stickier with respect to the blanket  130  than the printing stopper  126 . Namely, the resist material has a first adhesive strength to the blanket  130  and a second adhesive strength, smaller than the first adhesive strength, to the printing stopper  126 . Moreover, the resist material has a third adhesive strength to the cliché  120 . The third adhesive strength is greater than the first and second adhesive strengths. Namely, a surface energy density of the blanket  130  is greater than that of the printing stopper  126  and smaller than that of the cliché  120 . Accordingly, when the blanket  130  contacts and is rotated on the cliché  120 , a convex-counter pattern  136  is formed on the convex pattern  124  and a concave-counter pattern  134  is formed on the blanket  130 . Namely, since the resist material layer  132  is much stickier to the cliché  120  than the blanket  130 , the resist material layer  132  on the blanket  130  is transferred to the convex portions  124  to form the convex-counter pattern  136  on the convex portion  124  when the resist material layer  132  contacts the cliché  120 . However, since the resist material layer  132  is much stickier to the blanket  130  than the printing stopper  126 , the resist material layer  132  on the blanket  130  is never transferred to the printing stopper  126  even if the resist material layer  132  contacts the cliché  120 . Accordingly, the concave-counter pattern  134  is formed on the blanket  130 . 
     Next, as shown in  FIG. 3C , the blanket  130  having a plurality of concave-counter patterns  134  contacts and rotated on a process-object layer  111  to from the plurality of concave-counter patterns  134  on the process-object layer  111  on a substrate  110 . Since the resist material is much stickier to the process-object layer  111  than the blanket  130 , the concave-counter patterns  134  on the blanket  130  are transferred onto the process-object layer  111  when the concave-counter patterns  134  contacts the process-object layer  111 . Since a circumference of the blanket  130  is substantially the same as a length of the substrate  110 , the plurality of concave-counter patterns  134  on the blanket  130  are wholly transferred onto the process-object layer  111  by a single rotation. 
     Next, the concave-counter patterns  134  on the process-object layer  111  is irradiated by UV light and hardened to form resist patterns  138  on the process-object layer  111 . 
     The process-object layer  111  may be a metal layer, from which metal patterns, e.g., a gate electrode, a source electrode and a data electrode of a thin film transistor (TFT), are formed, and an insulating layer including one of silicon oxide and silicon nitride. The process-object layer  111  may be etched using the resist patterns  138  as an etching mask to form the metal patterns or a contact hole in the insulating layer. 
     As explained above, since the printing stopper  126 , which is less sticky to the resist material than the blanket  130 , is formed on the concave portions  122  of the clicke  120 , the resist material is never transferred to the concave portions  122  even if the resist material on the blanket  130  contacting printing stopper  126 . Accordingly, a desired concave-counter pattern  134  is formed on the blanket  130  without a sticky portion on the printing stopper  126 . The problem in the related art is improved. 
       FIGS. 4A to 4F  are cross-sectional views showing a process of fabricating a cliché according to an embodiment of the present disclosure. As shown in  FIG. 4A , a metal layer  212  is formed on a substrate  211  by depositing at least one metallic material selected from a metal group including molybdenum (Mo), chromium (Cr) and nickel (Ni). Next, as shown in  FIG. 4B , a photosensitive material layer  214  is formed on the metal layer  212  by depositing photoresist. Next, a mask (not shown) having a transmitting portion and a blocking portion is disposed over the photosensitive material layer  214 . The transmitting portion has a relatively high transmittance so that light through the transmitting portion can completely change the photosensitive material layer  214  chemically. The blocking portion shields light completely. Namely, a transmittance of the transmitting portion is greater than that of the blocking portion. The blocking portion of the mask corresponds to a position that is desired to form a convex portion, and transmitting portion of the mask corresponds to a position that is desired to form a concave portion. Then, the photosensitive material layer  214  is exposed through the mask (not shown) and developed to form a photosensitive material pattern  216 , as shown in  FIG. 4C . 
     Next, as shown in  FIG. 4D , the metal layer  212  (of  FIG. 4C ) exposed through the photosensitive material patterns  216  is etched using the photosensitive material pattern  216  as an etching mask to form a metal pattern  218 . The metal pattern  218  corresponds to the photosensitive material pattern  216 . And then, the substrate  211  exposed through the metal patterns  218  is etched using the metal pattern  218  as an etching mask to form a plurality of concave portions  222 . Moreover, since the substrate  211  is etched to form the plurality of concave portions  222 , other portions of the substrate  211  protrude. The protruding portions are defined as a plurality of convex portions  224 . Next, as shown in  FIG. 4E , a low surface energy density material layer  225  is formed on the substrate  211  including photosensitive material pattern  216 . The low surface energy density material layer  225  is formed on both the photosensitive material pattern  216  and a ground surface of the concave portions  222 . The low surface energy density material layer  225  may include teflon. Next, the photosensitive material pattern  216  and the metal pattern  218  are removed from the substrate  211 . The low surface energy density material layer  225  on the ground surface of the concave portions  222  is defined as a printing stopper  226 , as shown in  FIG. 4F . The substrate  211  including the plurality of concave portions  222 , the plurality of convex portions  224  and the printing stopper  126  is called a cliché  220 . 
     On other hand, a cliché may be formed without a metal layer  212  (of  FIG. 4A ) to decrease a process time and increase production yield. However, since a photosensitive material layer  214  (of  FIG. 4B ) has a poor adhesive strength to the substrate  211  (of  FIG. 4A ) of glass, it is difficult to obtain a fine pattern without the metal layer  212  (of  FIG. 4A ). 
       FIGS. 5A to 5E  are cross-sectional views showing a process of fabricating a cliché according to another embodiment of the present disclosure. As shown in  FIG. 5A , a metal pattern  218  and a photosensitive material pattern  216  are formed on a substrate  211 . The substrate  211  is etched using the metal pattern  218  as an etching mask to form a plurality of concave portions  222  and a plurality of convex portions  224 . The metal pattern  218  and the photosensitive material pattern  216  are formed through processes shown in  FIGS. 4A to 4D . Next, as shown in  FIG. 5B , the metal pattern  218  and the photosensitive material pattern  216  are removed. 
     Next, as shown in  FIG. 5C , a low surface energy density material layer  225  is formed on the substrate  211  including the plurality concave portions  222  and the plurality of convex portions  224 . The low surface energy density material layer  225  may include teflon. The low surface energy density material layer  225  is formed on both the concave portions  222  and the convex portions  224 . Since the substrate  211  includes the plurality concave portions  222  and the plurality of convex portions  224 , the low surface energy density material layer  225  has different thickness. The low surface energy density material layer  225  corresponding to the concave portions  222  has a first thickness “a” greater than a second thickness “b” of the low surface energy density material layer  225  corresponding to the convex portions  224 . (“a”&gt;“b”) Next, as shown in  FIG. 5D , the low surface energy density material layer  225  is partially etched to expose an upper surface of the convex patterns  224 . Namely, the low surface energy density material layer  225  is etched by the second thickness “b” such that a printing stopper  226  is formed on a ground surface of the concave portion  224 . The printing stopper  226  may have a thickness of “a-b”. As a result, a cliché  220  including the substrate  211  having the plurality of concave portions  222  and the plurality of convex portions  224  and the printing stopper  226  on the ground surface of the concave portions  222  is fabricated, as shown in  FIG. 5E . 
       FIG. 6  is a schematic cross-sectional view of a blanket with a roller according to an embodiment of the present disclosure, and  FIG. 7  is a cross-sectional view taken along the line VII-VII of  FIG. 6 . As shown in  FIG. 6 , a blanket  330  covers along a circumference of a roller  331 , and a resist material layer  332  is coated on an outer surface of the blanket  330 . The blanket  330  includes a rubber layer  311 , a support layer  313  and a cushion layer  315 , as shown in  FIG. 7 . The rubber layer  311  contacts the resist material layer  332  (of  FIG. 6 ), and the support layer  313  is disposed between the rubber layer  311  and the cushion layer  315 . The rubber layer  311  is formed of an elastic material, such as silicon and rubber. The rubber layer  311  may be polydimethylsiloxane. The resist material layer  332  is coated on the rubber layer  311 . The rubber layer  311  has a desired hardness not to be crushed when the blanket  330  contacts and is rotated on the cliché  120  (of  FIG. 3B ). The support layer  313  is formed of one of a plastic material, such as polyethylene and polyethyleneterephthalate (PET), and a metallic material. Since the support layer  313  functions as to sustain the rubber layer  311 , the support layer  313  has a relative high hardness. Moreover, the support layer  313  has a poor ductile property. The cushion layer  315  is formed of an elastic material including a foamy material  317  and one of silicon and rubber. The cushion layer  315  functions as to absorb an impact against the blanket  330  during contacting the process-object layer  111  (of  FIG. 3C ) or the cliché  120  (of  FIG. 3B ). The cushion layer  315  has a relative low hardness to absorb the impact. As a result, a hardness of the rubber layer  311  is greater than that of the cushion layer  315  and less than that of the support layer  313 . 
     On the other hand, when the blanket  330  is fast rotated on the process-object layer  111  (of  FIG. 3C ) or the cliché  120  (of  FIG. 3B ), the impact is not transferred onto the cushion layer  315 , but rubber layer  311  absorbs the impact. As a result, the rubber layer  311  becomes crushed. To avoid this problem, the cushion layer  315  has a greater thickness than both the rubber layer  311  and the support layer  313 . 
     In the present disclosure, since the rubber layer  311  has a hardness greater than the cushion layer  315 , which has a greater thickness than the rubber layer  311  and the support layer  313 , and less than the support layer  313 , the blanket  330  is not crushed and does not contact the ground surface of the concave portion  122  (of  FIG. 3B ) in the cliché  120  (of  FIG. 3B ) when the blanket contacts and is rotated on the cliché. 
     Accordingly, desired resist patterns are obtained. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the organic electroluminescent device and fabricating method thereof of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.