Patent Publication Number: US-8969128-B2

Title: Method of fabricating thin film transistor substrate and organic light emitting display device using the same

Description:
This application claims the benefit of Korean Patent Application No. 10-2012-0025458, filed on Mar. 13, 2012, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a method of fabricating a thin film transistor substrate and an organic light emitting display device using the thin film transistor substrate, and more particularly, to a method of fabricating a thin film transistor substrate and an organic light emitting display device using the thin film transistor substrate where a flexible display is obtained. 
     2. Discussion of the Related Art 
     Recently, multimedia devices, such as an organic light emitting display (OLED) device, a liquid crystal display (LCD) device, an electrophoretic display (EPD) device, a plasma display panel (PDP) device, a thin film transistor (TFT), a microprocessor and a random access memory (RAM), have been developed, and thus the importance of a flexible electric element has increased. Regarding the various display devices, it has been an interest of the industry whether a typical process of a thin film transistor (TFT) can be applied for an active matrix organic light emitting display (AMOLED) device having a highest possibility for a flexible display. 
     Specifically, properties, such as a thin profile, a light weight and an unbreakable property, are required for a mobile device, such as a digital camera, a video camera, a personal digital assistant (PDA) and a portable phone. Accordingly, a flat panel display (FPD) is fabricated by using a thin glass substrate. Alternatively, after a FPD is fabricated using a typical glass substrate, a thickness of the typical glass substrate is reduced through a mechanical method or a chemical method. 
     A typical glass substrate for a FPD has an advantage of stability in a process for forming an electrode or a TFT. However, since the typical glass substrate is hard and heavy, the typical glass substrate is not adequate for a flexible display as a display for mobile communication. Accordingly, a transparent and pliable plastic substrate has been suggested for a flexible display. 
     However, a plastic substrate is heat-resistant up to a relatively low range of about 150° C. to about 200° C. Since it is hard to perform a heat treatment for a transparent electrode formed on a plastic substrate through a sputtering method using indium-tin oxide (ITO), there exist several limitations on reduction of resistivity of the transparent electrode. In addition, since a thermal expansion coefficient of an ITO electrode is smaller as compared with that of a polymer plastic substrate, the ITO electrode and the plastic substrate expand with different rates from each other due to long heat history during a fabrication process or during an operation of a FPD. As a result, the plastic substrate is deformed. In a fabrication process of a low temperature polycrystalline silicon (LTPS), specifically, since a temperature of a substrate increases up to a range of about 400° C. to about 500° C., it is hard to adopt a plastic substrate. 
     In addition, since a plastic substrate has a relatively low strength, the plastic substrate is easy to be broken or cracked. Further, the plastic substrate may be warped and a resistance of an electrode on the plastic substrate may increase. 
     For the purpose of solving the above problems, a method using a carrier substrate has been suggested. After a separation layer is formed on a carrier substrate, such as a glass substrate, a plastic substrate is formed on the separation layer by coating a plastic material, and a thin film transistor array is formed on the plastics substrate. Next, the plastics substrate is separated from the carrier substrate. 
     However, the above method using a carrier substrate has a disadvantage of forming an additional separation layer. In addition, since a carrier substrate is hard to support a weight due to a property of a plastic substrate, it is hard to handle the plastic substrate. 
     SUMMARY 
     The present disclosure is directed to a method of fabricating a thin film transistor substrate and an organic light emitting display device using the thin film transistor substrate that obviate one or more of the problems due to limitations and disadvantages of the related art. 
     One of advantages of the present disclosure is to provide a method of fabricating a thin film transistor substrate and an organic light emitting display device using the thin film transistor substrate where a flexible display is obtained without an additional process of forming a separation layer and an adhesive layer and deterioration due to a foreign substance is improved. 
     Additional features and advantages of the invention will be set forth in the description herein, and in part will be apparent from the description, or may be learned by practice of the invention. These and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     In one aspect, to achieve these and other advantages and in accordance with some purposes of the present invention a method of fabricating a thin film transistor substrate may include: forming a polymer layer on a glass substrate; forming a passivation layer on the polymer layer; forming a thin film transistor array on the passivation layer; and separating the glass substrate from the polymer layer by irradiating a laser from a rear surface of the glass substrate. 
     In another aspect, a method of fabricating an organic light emitting display device may include: forming a polymer layer on a glass substrate; forming a passivation layer on the polymer layer; forming a thin film transistor array including a gate electrode, a source electrode, a drain electrode and a semiconductor layer contacting the source and drain electrodes on the passivation layer; forming a first electrode electrically connected to one of the source and drain electrodes; forming an organic emitting layer and a second electrode on the first electrode; and separating the glass substrate from the polymer layer by irradiating a laser from a rear surface of the glass substrate. 
     In another aspect, an organic light emitting display device may include: a polymer layer including a polyimide (PI) material having a repeating unit expressed by a first chemical formula; a passivation layer on the polymer layer; a thin film transistor array including a gate electrode, a source electrode, a drain electrode and a semiconductor layer on the passivation layer; and a first electrode electrically connected to one of the source and drain electrodes, an organic emitting layer and a second electrode. 
     
       
         
         
             
             
         
       
     
     where X includes one of alkyl, aryl, alkoxy, acyl, aralkyl, amino, arylamino, alkylamino, aralkylamino, alkoxy, aryloxy or aralkyloxy (e.g. —O—, —CO—, —S—, —SO 2 —, —C(CH 3 ) 2 —, —CONH—, —(CH 2 ) n1 —, —O(CH 2 ) n2 O—, —COO(CH 2 ) n3 OCO— and halogen, where each of n1, n2 and n3 is independently an integer equal to or greater than 1 and equal to or smaller than 100), 
     where m is an integer equal to or greater than 1 and equal to or smaller than 10000, and 
     where Y is a 2-valent aromatic moiety expressed by a second chemical formula. 
     
       
         
         
             
             
         
       
     
     where Z is selected from a group including a carbonyl group, a phosphate group, an anhydride group and a thiol group. 
     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 exemplary embodiments of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a flow chart showing a method of fabricating a thin film transistor substrate according to some embodiments of the present invention; 
         FIGS. 2 to 4  are cross-sectional views showing a method of fabricating a thin film transistor substrate according to additional embodiments of the present invention; 
         FIG. 5  is a cross-sectional view showing a method of fabricating an organic light emitting display device according to yet additional embodiment of the present invention; 
         FIG. 6  is a cross-sectional view showing a method of separating a glass substrate from a polymer layer of an organic light emitting display device according to further embodiments of the present invention; 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Reference will be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, similar reference numbers will be used to refer to the same or similar parts. 
       FIG. 1  is a flow chart showing a method of fabricating a thin film transistor substrate according to some embodiments of the present invention, and  FIGS. 2 to 4  are cross-sectional views showing a method of fabricating a thin film transistor substrate according to additional embodiments of the present invention. 
     Referring to  FIGS. 1 and 2 , a polymer layer  110  may be formed on a glass substrate  101  (step S 10 ). The polymer layer  110  may be formed of a polyimide material including one or more of a carbonyl group, a phosphate group, an anhydride group and a thiol group. For example, the polymer layer  110  may be formed of a polyimide (PI) material having a repeating unit expressed by a first chemical formula below or a photopolymer having at least one of a carbonyl group, a phosphate group, an anhydride group and a thiol group. 
     
       
         
         
             
             
         
       
     
     Here, X may be alkyl, aryl, alkoxy, acyl, aralkyl, amino, arylamino, alkylamino, aralkylamino, alkoxy, aryloxy or aralkyloxy. In some embodiments, X may be substituted. In further embodiments, X may include at least one of —O—, —CO—, —S—, —SO 2 —, —C(CH 3 ) 2 —, —CONH—, —(CH 2 ) n1 —, —O(CH 2 ) n2 O—, —COO(CH 2 ) n3 OCO— and halogen, where each of n1, n2 and n3 is independently an integer equal to or greater than 1 and equal to or smaller than 100, and m is an integer equal to or greater than 1 and equal to or smaller than 10000. In additional embodiments, each of n1, n2 and n3 is independently an integer equal to or greater than 1 and equal to or smaller than 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 300, 1000, or 10000, and m is an integer equal to or greater than 1 and equal to or smaller than 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 5000, or 10000 
     In addition, Y is a 2-valent aromatic moiety expressed by a second chemical formula below. 
     
       
         
         
             
             
         
       
     
     Here, Z may be selected from the group including a carbonyl group, a phosphate group, an anhydride group, a thiol group, and a mixture thereof. 
     The polyimide material having the repeating unit expressed by the first chemical formula may be synthesized from acid dianhydride and diamine. For example, acid dianhydride and diamine may be copolymerized and imidized to form a polyimide material. In addition, one or a mixture of alicyclic acid dianhydride and aromatic acid dianhydride may be used as acid dianhydride. 
     Here, alicyclic acid dianhydride may include one or a mixture of 1,2,3,4-cyclobutane tetracarboxylic dianhydride (CBDA), 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA), bicyclooctene-2,3,5,6-tetracarboxylic dianhydride (BODA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA), 1,2,4-tricarboxy-3-methylcarboxy cyclopentane dianhydride, 1,2,3,4-tetracarboxy cyclopentane dianhydride and 4,10-dioxa-tricyclo[6.3.1.0 2,7 ]dodecane-3,5,9,11-tetraone. 
     In addition, aromatic acid dianhydride may include one or a mixture of 4,4′-oxydiphthalic dianhydride (ODPA), pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA), 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA), Ethylene glycol bis(anhydro trimellitate) (TMEG) and 2,2′-bis[4-(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). 
     For example, 4,4′-oxydiphthalic dianhydride (ODPA) may be expressed by a third chemical formula below. 
     
       
         
         
             
             
         
       
     
     Since Y of the third formula is a 2-valent aromatic moiety including at least one of a carbonyl group, a phosphate group, an anhydride group and a thiol group, adhesion force exists between the glass substrate  101  and the polymer layer  110  when the polymer layer  110  includes 4,4′-oxydiphthalic dianhydride (ODPA) expressed by the third chemical formula. As a result, an additional separation layer or an additional adhesive layer is not required. 
     In addition, when a laser is irradiated onto the polymer layer  110  including a 2-valent aromatic moiety (e.g. Y expressed by the second chemical formula) including at least one of a carbonyl group, a phosphate group, an anhydride group and a thiol group (step S 40 ), some of the chemical bonds (e.g. C═O, P═O or S═O) of polymer layer  110  are broken, and a gas, (e.g. CO 2 , SO 2  or PO 3 ) is generated. Accordingly, here, performance of separation of the glass substrate  101  and the polymer layer  110  is improved. As a result, irradiation time may be reduced even when the intensity of laser is decreased 
     On the other hand, when the polymer layer includes oxydiphthalic anhydride-oxydianiline (ODPA-ODA) expressed by a fourth chemical formula below, where Y is a 2-valent aromatic moiety including an ether group, an additional adhesive layer may be required because the glass substrate and the polymer layer have a poor adhesion force. In addition, since a gas is not generated at the step of laser irradiation, performance of separation of the glass substrate and the polymer layer may be poor as compared with using the polymer layer with the third chemical formula above. 
     
       
         
         
             
             
         
       
     
     Referring to  FIGS. 1 and 3 , a passivation layer  111  may be formed on the polymer layer  110  (step S 20 ). For example, the passivation layer  111  may include an inorganic insulating material, such as silicon nitride (SiNx) and silicon oxide (SiOx). The passivation layer  111  may prevent external moisture or external gas from permeating and/or diffusing into the polymer layer  110  and may planarize the polymer layer  110 . 
     Referring to  FIGS. 1 and 4 , a thin film transistor (TFT) array  120  may be formed on the passivation layer  111  (step S 30 ). For example, the TFT array  120  may include a semiconductor layer  121 , a first insulating layer  122 , a gate electrode  123 , a second insulating layer  124 , first contact holes  125 , a source electrode  126   a , a drain electrode  126   b  and a planarizing layer  127  sequentially formed on the passivation layer  111 . 
     The semiconductor layer  121  may include amorphous silicon and/or polycrystalline silicon. In some embodiments, after the semiconductor layer  121  is formed of amorphous silicon, amorphous silicon may be crystallized through a low temperature polycrystalline silicon (LTPS) process to become polycrystalline silicon. In the LTPS process, a temperature of a substrate may increase up to a range of about 400° C. to about 500° C. Since the polymer layer  110  has an excellent heat-resistance, the LTPS process may be performed to the semiconductor layer  121  over the polymer layer  110  without deterioration. The heat-resistance property of the polymer layer  110  is also illustrated herein. 
     The first insulating layer  122  insulates the gate electrode  123  from the semiconductor layer  121 . For example, the first insulating layer  122  may include at least one of an inorganic insulating material (e.g. silicon nitride (SiNx) and silicon oxide (SiOx)) and an organic insulating material (e.g. benzocyclobutene (BCB) and acrylic resin). In addition, the second insulating layer  124  may include at least one of an inorganic insulating material (e.g. silicon nitride (SiNx) and silicon oxide (SiOx)) and an organic insulating material (e.g. benzocyclobutene (BCB) and acrylic resin). 
     The gate electrode  123  may include a conductive material. For example, the gate electrode  123  may include at least one of magnesium (Mg), aluminum (Al), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), molybdenum tungsten (MoW) and gold (Au). In addition, the gate electrode  123  may have a single-layered structure or a multiple-layered structure. 
     The first contact holes  125  may be formed in the first and second insulating layers  122  and  124  by selectively removing a portion of the first and second insulating layers  122  and  124  to expose source and drain regions of the semiconductor layer  121 . 
     The source and drain electrodes  126   a  and  126   b  are formed on the second insulating layer  124 . Each of the source and drain electrodes  126   a  and  126   b  may include a conductive material, such as magnesium (Mg), aluminum (Al), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), molybdenum tungsten (MoW) and gold (Au), for example, and may have a single-layered structure or a multiple-layered structure. The source and drain electrodes  126   a  and  126   b  may be connected to the source and drain regions, respectively, through the first contact holes  125 . The semiconductor layer  121 , the first insulating layer  122 , the gate electrode  123 , the source electrode  126   a  and the drain electrode  126   b  may constitute a thin film transistor (TFT). 
     The planarizing layer  127  is formed on the source and drain electrodes  126   a  and  126   b . The planarizing layer  127  may planarize and protect the TFT. For example, the planarizing layer  127  may include at least one of an inorganic insulating material (e.g. silicon nitride (SiNx) and silicon oxide (SiOx)) and an organic insulating material (e.g. benzocyclobutene (BCB) and acrylic resin). In addition, the planarizing layer  127  may have a single-layered structure or a multiple-layered structure. 
     An organic light emitting diode may be formed on the TFT array. Although an organic light emitting diode is formed on the TFT array in an embodiment of  FIG. 5 , any of other various display elements, such as a liquid crystal display element and an electrophoretic display element, may be formed on the TFT array in additional embodiments. 
     In some embodiments, the organic light emitting diode may include an organic light emitting array having a bank layer and a sealing means (not shown). 
       FIG. 5  is a cross-sectional view showing a method of fabricating an organic light emitting display device according to some embodiments of the present disclosure. 
     Referring to  FIG. 5 , an organic light emitting array  130  may include a first electrode  132 , an organic emitting layer  133  and a second electrode  134 . The first electrode  132  may be formed on the planarizing layer  127 , and the organic emitting layer  133  and the second electrode  134  may be sequentially formed on the first electrode  132 . A second contact hole  131  is formed in the planarizing layer  127  to expose one of the source and drain electrodes  126   a  and  126   b . The first electrode  132  is electrically connected to one of the source and drain electrodes  126   a  and  126   b  through the second contact hole  131 . 
     The first electrode  132  may include a conductive material and may function as one electrode of an organic light emitting diode. In addition, the first electrode  132  may have a transparent electrode and/or a reflective electrode. For example, the first electrode  132  of a transparent electrode may include at least one of indium-tin oxide (ITO), indium-zinc-oxide (IZO), zinc-oxide (ZnO) and indium-oxide (In 2 O 3 ). In addition, the first electrode  132  of a reflective electrode array may include at least one of silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr) and compound thereof. Further, a transparent conductive material layer including one of indium-tin oxide (ITO), indium-zinc-oxide (IZO), zinc-oxide (ZnO) and indium-oxide (In 2 O 3 ) may be formed on a reflective conductive material layer including one of silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr) and compound thereof to form the first electrode  132  of a reflective electrode. 
     A bank layer  135  may be formed between the first and second electrodes  132  and  134 . The bank layer  135  may have an open portion exposing the first electrode  132  corresponding to a pixel region, and the organic emitting layer  133  may be formed in the open portion of the bank layer  135  on the first electrode  132 . The bank layer  135  may include at least one of an inorganic insulating material (e.g. silicon nitride (SiNx) and silicon oxide (SiOx)) and an organic insulating material (e.g. benzocyclobutene (BCB) and acrylic resin). 
     The organic emitting layer  133  may have a single-layered structure of an emitting material. Alternatively, the organic emitting layer  133  may have a multiple-layered structure for improving an emission efficiency. For example, the organic emitting layer  133  of a multiple-layered structure may include a hole injecting layer (HIL), a hole transporting layer (HTL), an emitting material layer (EML), an electron transporting layer (ETL) and an electron injecting layer (EIL). 
     The second electrode  134  may have a transparent electrode and/or a reflective electrode. For example, the second electrode  134  of a transparent electrode may include at least one of lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), aluminum (Al), magnesium (Mg) and compound thereof. In addition, a transparent conductive material layer may include at least one of indium-tin oxide (ITO), indium-zinc-oxide (IZO), zinc-oxide (ZnO) and indium-oxide (In 2 O 3 ) and may be formed on a reflective conductive material layer to form the second electrode  134  of a transparent electrode. Here, the reflective conductive material layer may include at least one of lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), aluminum (Al), magnesium (Mg) and compound thereof. The transparent conductive material layer may be used for an auxiliary electrode or a bus line. Further, the second electrode  138  of a reflective electrode may include at least one of lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), aluminum (Al), magnesium (Mg) and compound thereof. 
     Accordingly, in an organic light emitting display (OLED) device according to some embodiments of the present invention, when voltages corresponding to a selected color signal are applied to the first and second electrodes  132  and  134 , a hole and an electron may be transported to the organic emitting layer  133  to constitute an exciton. When the exciton in an excited state changes to a ground state, a light may be generated and emitted as a visible ray. The light emitted from the organic emitting layer  133  may pass through the second electrode  134  to display an image. 
     Although not shown, an encapsulation process may be performed for protecting the organic light emitting diode from an exterior. For example, an encapsulation process may be performed using a thin film encapsulation method. 
     Referring again to  FIG. 1 , a laser may be irradiated to the polymer layer  110  to soften the polymer layer  110 , and the glass substrate  101  may be separated from the polymer layer  110  (step S 40 ). 
       FIG. 6  is a cross-sectional view showing a method of separating a glass substrate from a polymer layer of an organic light emitting display device according to additional embodiments of the present disclosure. 
     Referring to  FIG. 6 , a laser may be irradiated to the polymer layer  110  from a rear surface of the glass substrate  101 . Since the polymer layer  110  may be heat up to a glass transition temperature (Tg), i.e., a temperature where the polymer layer  110  of a glassy state transitions to a rubbery state, by laser irradiation, the glass substrate  101  may be easily separated from the polymer layer  110 . For example, the glass transition temperature of the polymer layer  110  may be about 300° C., and the laser having a wavelength of about 308 nm to about 355 nm may be irradiated to the polymer layer  110  to soften the layer. 
     Although the glass substrate  101  may be used for transmitting the laser in some embodiments (e.g. as shown in  FIG. 6 ), the other transparent substrate may be used in additional embodiments. In addition, although the glass substrate  101  may be separated by laser irradiation after forming the organic light emitting array in some embodiments (e.g. as shown in  FIG. 6 ), the glass substrate  101  may be separated after forming the sealing means in additional embodiments. In addition, the glass substrate  101  may be separated after forming the TFT array and various display elements may be formed on the polymer layer  110  in yet additional embodiments. 
     A heat-resistance experiment was performed depending on the kind and concentration of a polymer material to verify whether a thin film transistor substrate having a polymer layer may be adopted to a low temperature polycrystalline silicon (LTPS) process where a temperature of a substrate increases up to a range of about 400° C. to about 500° C. 
     Comparative Example 
     After a precursor layer was formed on a non-alkaline glass substrate of 150 mm×150 mm by spin-coating a solution of poly(methylene-bis-anthranilamide) 1,6-hexamethylenedicarboxylic acid (PAA-5), the precursor layer was thermally cured at about 450° C. for about 60 min to form a polymer layer. As a result, the polymer layer according to the comparative example was detached from the glass substrate in a large portion of the layer during the high temperature curing process. 
     Example 1 
     After a precursor layer was formed on a non-alkaline glass substrate of 150 mm×150 mm by spin coating a solution of 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA) of about 30 mol %, the precursor layer was thermally cured at about 450° C. for about 60 min to form a polymer layer. As a result, detachment of the polymer layer from the glass substrate during the high temperature curing process was significantly reduced as compared with the comparative example above. 
     Example 2 
     After a precursor layer was formed on a non-alkaline glass substrate of 150 mm×150 mm by spin coating a solution of 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA) of about 50 mol %, the precursor layer was thermally cured at about 450° C. for about 60 min to form a polymer layer. As a result, the polymer layer was detached from the glass substrate only in a small portion of the layer during the high temperature curing process, and the adhesion of the polymer layer was superior to that of the polymer layer from Comparative Example or Example 1. 
     Example 3 
     After a precursor layer was formed on a non-alkaline glass substrate of 150 mm×150 mm by spin coating a solution of 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA) of about 100 mol %, the precursor layer was thermally cured at about 450° C. for about 60 min to form a polymer layer. As a result, the polymer layer was not detached from the glass substrate and stayed adhered to the glass substrate in all portion during the high temperature curing process, showing superior adhesion compared to the polymer layers from the other examples. 
     Consequently, in the method of fabricating a thin film transistor substrate and an organic light emitting display device using the thin film transistor substrate, an additional process for a separation layer or an adhesive layer described herein may not be required and deterioration of the thin film transistor substrate due to a foreign substance may be improved. As a result, fabrication process may be simplified, and the separated glass substrate may be reusable. In addition, since a polymer layer has an excellent heat-resistance, the thin film transistor substrate may be adopted to a low temperature polycrystalline silicon (LTPS) process having a thermally curing step at a relatively high temperature. Accordingly, the thin film transistor substrate applicable to a flexible display may be provided, and an organic light emitting display device using the thin film transistor substrate may be provided. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure 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.