Abstract:
A method of forming an oxide semiconductor device may be provided. In the method, a substrate comprising a first major surface and a second major surface that faces away from the first major surface may be provided. An oxide semiconductor device may be formed over the first major surface to provide an intermediate device, and the semiconductor device may comprise an oxide active layer. The intermediate device may be subjected to ultraviolet (UV) light (e.g., ultraviolet ray irradiation process) for a first period, and subjected to heat (e.g., thermal treatment process) for a second period. The first and second periods may at least partly overlap.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. §119 to Korean patent Application No. 10-2013-0138985, filed on Nov. 15, 2013, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     Technical Field 
     Example embodiments of the invention relate to methods of forming oxide semiconductor devices and methods of manufacturing display devices having oxide semiconductor devices. More particularly, example embodiments of the invention relate to methods of forming oxide semiconductor devices having enhanced electrical characteristics by simultaneously performing an ultraviolet ray irradiation process and a thermal treatment process, and methods of manufacturing display devices including the oxide semiconductor devices. 
     Description of the Related Art 
     An oxide semiconductor device including an active pattern containing an oxide semiconductor device may be employed in various display devices such as an active matrix liquid crystal display, an active matrix organic light emitting device, etc. 
     In conventional methods of forming the oxide semiconductor device, damage to an active pattern may be caused during a process in which a metal thin film for forming a source electrode and a drain electrode is deposited on the active pattern and/or a process in which the metal thin film for forming the source electrode and the drain electrode is patterned. As a result, electrical characteristics of the oxide semiconductor device such as operating current, threshold voltage distribution, mobility, etc. may be degraded because of the damage to the active pattern. 
     SUMMARY 
     Example embodiments provide methods of forming oxide semiconductor devices having enhanced electrical characteristics by simultaneously performing an ultraviolet ray irradiation process and a thermal treatment process after forming a source electrode and a drain electrode. 
     Example embodiments provide methods of manufacturing display devices including the oxide semiconductor devices with enhanced electrical characteristics. 
     According to one aspect of the invention, there is provided a method of making an oxide semiconductor device. In the method, a substrate comprising a first major surface and a second major surface that faces away from the first major surface may be provided. An oxide semiconductor device may be formed over the first major surface to provide an intermediate device, and the semiconductor device may comprise an oxide active layer. The intermediate device may be subjected to ultraviolet (UV) light (e.g., ultraviolet ray irradiation process) for a first period, and subjected to heat (e.g., thermal treatment process) for a second period. The first and second periods may at least partly overlap. 
     In example embodiments, the ultraviolet ray irradiation process may be carried out for about 10 second to about 1 hour. 
     In example embodiments, the ultraviolet ray irradiation process may be executed using an ultraviolet ray having a wavelength between about 185 nm and about 370 nm. 
     In example embodiments, the ultraviolet ray irradiation process may be performed using the ultraviolet ray generated from an ultraviolet ray lamp or a short wavelength light emitting diode (LED). For example, the ultraviolet ray may have an energy density less than about 254 mW/cm 2 . 
     In example embodiments, the thermal treatment process may be carried out under an atmosphere including air, oxygen, ozone, nitrogen, or argon. 
     In example embodiments, the thermal treatment process may be performed for about 10 second to about 1 hour. 
     In example embodiments, the thermal treatment process may be executed at a temperature less than about 400° C. 
     In example embodiments, the thermal treatment process may be performed using a hot plate or a furnace. 
     In example embodiments, the ultraviolet ray irradiation process may comprise applying the UV light from a side of the first major surface of the substrate or from a side of the second major surface of the substrate. Additionally, the thermal treatment process may comprise applying the heat from the side of the first major surface or the second major surface. 
     In some example embodiments, the ultraviolet ray irradiation process may comprise applying the UV light from both the side of the first major surface and the side of the second major surface. Further, the thermal treatment process may comprise applying the heat from both the side of the first major surface and the side of the second major surface. 
     In example embodiments, the oxide active layer may include a semiconductor oxide containing a binary compound (ABx), a ternary compound (ABxCy) and/or a quaternary compound (ABxCyDz). 
     In example embodiments, the oxide active layer may include the semiconductor oxide containing indium (In), zinc (Zn), gallium (Ga), stannum (Sn), titanium (Ti), aluminum (Al), hafnium (Hf), zirconium (Zr) and/or magnesium (Mg). 
     In some example embodiments, the oxide active layer pattern may have a composition in which lithium (Li), natrium (Na), manganese (Mn), nickel (Ni), palladium (Pd), copper (Cu), carbon (C), nitrogen (N), phosphorus (P), titanium (Ti), zirconium (Zr), vanadium (V), rubidium (Ru), germanium (Ge), stannum (Sn) and/or fluorine (F) is or are added to the semiconductor oxide. 
     In example embodiments, an etching stop layer may be additionally formed on the oxide active layer. A protection layer may be formed to cover the etching stop layer, a source electrode and a drain electrode. 
     In example embodiments, the etching stop layer and the protection layer may be formed after the ultraviolet ray irradiation process and the thermal treatment process. 
     According to another aspect of the invention, there is provided a method of manufacturing a display device. In the method, a substrate comprising a first major surface and a second major surface that faces away from the first major surface may be provided. An oxide semiconductor device may be formed over the first major surface to provide an intermediate device, and the semiconductor device may comprise an oxide active layer. The intermediate device may include a gate electrode formed on the first major surface and a gate insulation layer formed on the first major surface over the gate electrode. The intermediate device may be subjected to ultraviolet (UV) light (e.g., ultraviolet ray irradiation process) for a first period, and subjected to heat (e.g., thermal treatment process) for a second period. The first and second periods may at least partly overlap. Subsequent to subjecting the UV light and the heat, a light emitting diode may be formed over the intermediate device. The light emitting diode may be connected to the oxide semiconductor device and comprise an organic light emitting layer. 
     In example embodiments, the ultraviolet ray irradiation process may comprise applying the UV light from a side of the first major surface of the substrate or from a side of the second major surface of the substrate. Alternatively, the ultraviolet ray irradiation process may comprise applying the UV light from both the side of the first major surface and the side of the second major surface. The thermal treatment process may comprise applying the heat from the side of the first major surface or the second major surface. Alternatively, the thermal treatment process may comprise applying the heat from both the side of the first major surface and the side of the second major surface. 
     In example embodiments, an etching stop layer may be additionally formed on the oxide active layer, and a protection layer may be formed to cover the etching stop layer, a source electrode, and a drain electrode. 
     In example embodiments, the etching stop layer and the protection layer may be formed after the ultraviolet ray irradiation process and the thermal treatment process. 
     According to example embodiments, the ultraviolet ray irradiation process and the thermal treatment process may be simultaneously carried out after forming a source electrode and a drain electrode on the gate insulation layer and the oxide active layer. Therefore, damage caused to the oxide active layer while forming the source and the drain electrodes may be prevented. In addition, moisture and/or hydroxyl group generated during the process of forming the oxide semiconductor device may be efficiently reduced or removed. Accordingly, the oxide semiconductor device according to example embodiments may ensure enhanced electrical characteristics such as reduction of operating current, increase of threshold voltage distribution, reduction of mobility, etc. As a result, when the oxide semiconductor device is employed in the display device such as the organic light emitting display device, the liquid crystal display device, the flexible display device, etc., the display device may have increased quality of images and also may ensure enhanced operating speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative, non-limiting example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
         FIGS. 1 through 6  are cross-sectional views illustrating a method of forming an oxide semiconductor device in accordance with example embodiments. 
         FIG. 7  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with a wavelength of an irradiated ultraviolet ray when an ultraviolet ray irradiation process is performed on the oxide semiconductor device. 
         FIG. 8  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with an energy density of an irradiated ultraviolet ray when an ultraviolet ray irradiation process is performed on the oxide semiconductor device. 
         FIG. 9  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with process time when an ultraviolet ray irradiation process and a thermal treatment process are performed on the oxide semiconductor device at the same time. 
         FIGS. 10 through 18  are cross-sectional views illustrating a method of manufacturing a display device in accordance with example embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, methods of forming oxide semiconductor devices and methods of manufacturing display devices having oxide semiconductor devices in accordance with example embodiments will be explained in detail with reference to the accompanying drawings. 
     It will be understood that although the terms “first” and “second” are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element, and similarly, a second element may be termed a first element without departing from the teachings of this disclosure. 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. 
     In the drawings, the sizes and the thicknesses of layers and regions are exaggerated for convenience of explanation, and thus the sizes and the thicknesses are not limited thereto. 
       FIGS. 1 through 6  are cross-sectional views illustrating a method of forming an oxide semiconductor device in accordance with example embodiments. 
     Referring to  FIG. 1 , a buffer layer  120  may be formed on a first face (e.g. the surface that faces upward in  FIG. 1 ) of a substrate  110 . The substrate  110  may include a transparent insulation substrate. For example, the substrate  110  may include a glass substrate, a transparent resin substrate, a transparent metal oxide substrate, etc. 
     The buffer layer  120  may prevent diffusion of impurities from the substrate  110 . In addition, the buffer layer  120  may enhance flatness of the surface of the substrate  110 . When the substrate  110  has a relatively irregular surface, the buffer layer  120  may enhance a flatness of the surface of the first substrate  10 . Furthermore, in a case that the buffer layer  120  is formed on the substrate  110 , a gate electrode  130  may be more easily formed because stress generated while forming the gate electrode  130  may be decreased by the buffer layer  120 . The buffer layer  120  may be formed using a silicon compound. For example, the buffer layer  120  may include silicon oxide (SiOx), silicon oxycarbide (SiOxCy), etc. These may be used alone or in any mixture thereof. The buffer layer  120  may have a single layer structure or a multi layer structure including the silicon compound. 
     The gate electrode  130  may be formed on the buffer layer  120 . The gate electrode  130  may be connected to a gate line of a display device including the oxide semiconductor device. The gate electrode  130  may include metal, alloy, conductive metal oxide, a transparent conductive material, etc. For example, the gate electrode  130  may be formed using any of aluminum (Al), alloy containing aluminum, aluminum nitride (AlNx), silver (Ag), alloy containing silver, tungsten (W), tungsten nitride (WNx), copper (Cu), alloy containing copper, nickel (Ni), alloy containing nickel, chrome (Cr), molybdenum (Mo), alloy containing molybdenum, titanium (Ti), titanium nitride (TiNx), platinum (Pt), tantalum (Ta), tantalum nitride (TaNx), neodymium (Nd), scandium (Sc), strontium ruthenium oxide (SrRuxOy), zinc oxide (ZnOx), indium tin oxide (ITO), tin oxide (SnOx), indium oxide (InOx), gallium oxide (GaOx), indium zinc oxide (IZO), etc. These may be used alone or in any combination thereof. 
     Referring to  FIG. 2 , a gate insulation layer  140  may be formed on the buffer layer  120  to cover the gate electrode  130 . The gate insulation layer  140  may include a silicon compound, metal oxide, etc. For example, the gate insulation layer  140  may be formed using any of silicon oxide, silicon nitride, silicon oxynitride (SiOxNy), aluminum oxide (AlOx), tantalum oxide (TaOx), hafnium oxide (HfOx), zirconium oxide (ZrOx), titanium oxide (TiOx), etc. These may be used alone or in any combination thereof. In addition, the gate insulation layer  140  may have a single layer structure or a multi layer structure including the silicon compound and/or the metal oxide. 
     Referring to  FIG. 3 , a semiconductor layer (not illustrated) may be formed on the gate insulation layer  140 , and then the semiconductor layer may be patterned to form an active pattern (e.g., active layer)  150 . In example embodiments, the active pattern  150  include a binary compound (ABx) containing indium (In), zinc (Zn), gallium (Ga), tin (Sn), titanium (Ti), aluminum (Al), halfnium (Hf), zirconium (Zr), magnesium (Mg), etc., a ternary compound (ABxCy), for example, including such elements, or a quaternary compound (ABxCyDz), for example, including such elements, etc. For example, the active pattern  150  may include any of indium-gallium-zinc oxide (IGZO), gallium zinc oxide (GaZnxOy), indium tin oxide (ITO), indium zinc oxide (IZO), zinc magnesium oxide (ZnMgxOy), zinc tin oxide (ZnSnxOy), zinc zirconium oxide (ZnZrxOy), zinc oxide (ZnOx), gallium oxide (GaOx), titanium oxide (TiOx), tin oxide (SnOx), indium oxide (SnOx), indium-gallium-hafnium oxide (IGHO), tin-aluminum-zinc oxide (TAZO), indium-gallium-tin oxide (IGSO), etc. These may be used alone or in any combination thereof. In some example embodiments, the active pattern  150  may include a semiconductor oxide doped with any of lithium (Li), sodium (Na), manganese (Mn), nickel (Ni), palladium (Pd), copper (Cu), carbon (C), nitrogen (N), phosphorus (P), titanium, zirconium, vanadium (V), rubidium (Ru), germanium (Ge), tin, fluorine (F), etc. These may be used alone or in any mixture thereof. The active pattern  150  may have a single layer structure or a multi layer structure including the semiconductor oxide. 
     Referring to  FIG. 4 , a source electrode  160  and a drain electrode  170  may be formed on the gate insulation layer  140  and the active pattern  150 . In example embodiments, an electrode layer (not illustrated) may be formed on the gate insulation layer  140  and the active pattern  150 , and then a mask (not illustrated) may be formed over the electrode layer. Here, the electrode layer may be patterned to form the source electrode  160  and the drain electrode  170  separated from each other by a predetermined distance substantially centering the active pattern  150 . The source electrode  160  and the drain electrode  170  may extend on the gate insulation layer  140  and may expose a central portion of the active pattern  150  (e.g., neither the source electrode  160  nor the drain electrode  170  is formed on the central portion of the active pattern  150 ). 
     Each of the source electrode  160  and the drain electrode  170  may be formed using any of metal, alloy, metal nitride, conductive metal oxide, a transparent conductive material, etc. For example, the source electrode  160  and the drain electrode  170  may be formed using any of aluminum, copper, molybdenum, titanium, chrome, tantalum, tungsten, neodymium, scandium, an alloy thereof, a nitride thereof, strontium ruthenium oxide, indium tin oxide, indium zinc oxide, zinc oxide, tin oxide, carbon nano tube (CNT), etc. These may be used alone or in any combination thereof. In addition, each of the source electrode  160  and the drain electrode  170  may have a single layer structure or a multi layer structure including any of the metal, the alloy, the metal nitride, the conductive metal oxide, the transparent conductive material, etc. 
     In a conventional method of forming a source electrode and a drain electrode of an oxide semiconductor device, damage to an active pattern may be caused during a process in which the electrode layer for forming the source electrode and the drain electrode are patterned because a metal thin film may be patterned as the electrode layer using plasma and/or an etchant. When the damage to the active pattern is generated, electrical characteristics of the oxide semiconductor device, such as operating current, threshold voltage distribution, mobility, etc. may be degraded because of the damage to the active pattern. Although the conventional method of forming the oxide semiconductor device may perform an ultraviolet ray irradiation process under an air atmosphere using an ultraviolet ray to improve electrical characteristics of the active pattern, the conventional ultraviolet ray irradiation process may not sufficiently enhance the electrical characteristic of the active pattern because the threshold voltage distribution may be easily shifted even if the ultraviolet ray is irradiated for a short irradiation time. 
     In example embodiments, as illustrated in  FIG. 5 , an ultraviolet ray irradiation process in which an ultraviolet ray is irradiated onto a first face of the substrate  110  (e.g., the top surface in  FIG. 5 ), and also a thermal treatment process in which a heat is applied to a second face of the substrate  110  (e.g., the bottom surface in  FIG. 5 ) opposed to the first face of the substrate  110  may be performed at the same time. For example, the ultraviolet ray irradiation process may be carried out for about 10 second to about 1 hour using an ultraviolet ray having a wavelength between about 185 nm and about 370 nm and an energy density less than about 254 mW/cm 2 . In this case, the ultraviolet ray may be generated from an ultraviolet ray lamp or a short wavelength light emitting diode (LED). The thermal treatment process may be executed under an atmosphere including air, oxygen, ozone, nitrogen, or argon. In addition, the thermal treatment process may be performed at a temperature less than about 400° C. for about 10 second to about 1 hour. For example, the thermal treatment process may be carried out after that the substrate  110  may be disposed on a hot plate or the substrate  110  may be loaded in a furnace. Thus, the active pattern  150  may be cured, so that damage to the active pattern  150  generated in forming of the source electrode  160  and the drain electrode  170  may be efficiently reduced or removed. Furthermore, moisture and/or hydroxyl group at a surface of the active pattern  150  generated while forming the source and the drain electrodes  160  and  170  may be efficiently reduced or removed. Accordingly, the oxide semiconductor device may have enhanced electrical characteristics. 
     In example embodiments, the ultraviolet ray irradiation process may be performed on the second face of the substrate  110  (e.g., the bottom surface in  FIG. 5 ), and the thermal treatment process may be executed on the first face of the substrate  110  (e.g., the top surface in  FIG. 5 ). In some example embodiments, the ultraviolet ray irradiation process and the thermal treatment process may be simultaneously performed on the first and the second faces of the substrate  110 . Therefore, electrical characteristics of the oxide semiconductor device may be efficiently improved. 
     In one embodiment, the ultraviolet ray irradiation process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 . In another embodiment, the ultraviolet ray irradiation process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 . In one embodiment, the thermal treatment process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 . In another embodiment, the thermal treatment process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 . 
     In one embodiment, the ultraviolet ray irradiation process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 , and the thermal treatment process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 . In another embodiment, the ultraviolet ray irradiation process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 , and the thermal treatment process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 . In one embodiment, the ultraviolet ray irradiation process is performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 , and the thermal treatment process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 . In another embodiment, the ultraviolet ray irradiation process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 , and the thermal treatment process is performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 . In one embodiment, the ultraviolet ray irradiation process and the thermal treatment process are both performed on the first surface (e.g., top surface in  FIG. 5 ) of the substrate  110 . In another embodiment, the ultraviolet ray irradiation process and the thermal treatment process are both performed on the second surface (e.g., bottom surface in  FIG. 5 ) of the substrate  110 . 
     Referring to  FIG. 6 , an etching stop layer  180  may be formed on the active pattern  150  exposed by the source electrode  160  and the drain electrode  170 . For example, the etching stop layer  180  may be formed using any of silicon oxide, silicon nitride, silicon oxynitride, semiconductor oxide, etc. These may be used alone or in any combination thereof. 
     A protection layer  190  may be formed on the gate insulation layer  140  to cover the source electrode  160 , the drain electrode  170 , and the etching stop layer  180 . For example, the protection layer  190  may include any of silicon oxide, silicon nitride, silicon oxynitride, etc. 
     In the oxide semiconductor device described with reference to  FIG. 6 , the oxide semiconductor device may have a bottom gate construction in which the gate electrode  130  is disposed under the active pattern  150 . However, the construction of the oxide semiconductor device may not be limited thereto. For example, the oxide semiconductor device may have a top gate construction in which the gate electrode  130  is disposed on the active pattern  150 . 
       FIG. 7  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with a wavelength of an irradiated ultraviolet ray when an ultraviolet ray irradiation process is performed on the oxide semiconductor device. 
     Referring to  FIG. 7 , ultraviolet rays having different wavelengths (e.g., about 185 nm and about 365 nm) were irradiated onto an oxide semiconductor device for about 30 minutes. In this case, the mobility of the oxide semiconductor device onto which an ultraviolet ray having a wavelength of about 185 nm was irradiated was higher than the mobility of the oxide semiconductor device onto which an ultraviolet ray having a wavelength of about 365 nm. In addition, the threshold voltage distribution of the oxide semiconductor device onto which an ultraviolet ray having the wavelength of about 185 nm was irradiated was lower than the threshold voltage distribution of the oxide semiconductor device onto which an ultraviolet ray having the wavelength of about 365 nm. Therefore, it may be appropriate that an ultraviolet ray irradiation process may be performed using an ultraviolet ray having a wavelength between about 185 nm and about 370 nm. 
       FIG. 8  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with an energy density of an irradiated ultraviolet ray when an ultraviolet ray irradiation process is performed on the oxide semiconductor device. 
     Referring to  FIG. 8 , ultraviolet rays having different energy densities (e.g., about 64 mW/cm 2  and about 254 mW/cm 2 ) were irradiated onto an oxide semiconductor device for about 30 minutes. In this case, the mobility of the oxide semiconductor device onto which an ultraviolet ray having an energy density of about 64 mW/cm 2  was irradiated was lower than the mobility of the oxide semiconductor device onto which an ultraviolet ray having an energy density of about 254 mW/cm 2 . Further, the threshold voltage distribution of the oxide semiconductor device onto which an ultraviolet ray having the energy density of about 64 mW/cm 2  was irradiated was higher than the threshold voltage distribution of the oxide semiconductor device onto which an ultraviolet ray having the energy density of about 254 mW/cm 2 . Therefore, it may be appropriate that an ultraviolet ray irradiation process may be performed using an ultraviolet ray the having an energy density less than about 254 mW/cm 2 . 
       FIG. 9  is a graph illustrating the transfer characteristic of an oxide semiconductor device in accordance with process time when an ultraviolet ray irradiation process and a thermal treatment process are performed on the oxide semiconductor device at the same time. 
     Referring to  FIG. 9 , an ultraviolet ray irradiation process and a thermal treatment process were simultaneously executed on the oxide semiconductor device for different process times. Here, the thermal treatment process was performed under an atmosphere including air at a temperature less than about 200° C., and the ultraviolet ray irradiation process was carried out using an the ultraviolet ray having a wavelength of about 365 nm and an energy density having about 254 mW/cm 2 . 
     Table 1 shows mobilities of oxide semiconductor devices and threshold voltage distributions of oxide semiconductor devices in accordance with Comparative Example, Example 1, Example 2, Example 3, and Example 4. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Mobility of an oxide 
                 Threshold voltage 
               
               
                   
                   
                 semiconductor 
                 distribution of an oxide 
               
               
                   
                 No 
                 device (cm 2 /vs) 
                 semiconductor device (V) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Comparative 
                 4.84 
                 5.98 
               
               
                   
                 Example 
               
               
                   
                 Example 1 
                 8.47 
                 2.16 
               
               
                   
                 Example 2 
                 9.02 
                 1.64 
               
               
                   
                 Example 3 
                 11.92 
                 0.76 
               
               
                   
                 Example 4 
                 10.71 
                 1.69 
               
               
                   
                   
               
             
          
         
       
     
     Example 1 
     An ultraviolet ray having a wavelength of about 365 nm and an energy density of about 254 mW/cm 2  was irradiated onto an oxide semiconductor device for about 10 minutes while heating the oxide semiconductor device for about 10 minutes under an air atmosphere at a temperature of about 200° C. 
     Example 2 
     An ultraviolet ray having a wavelength of about 365 nm and an energy density of about 254 mW/cm 2  was irradiated onto an oxide semiconductor device for about 20 minutes while heating the oxide semiconductor device for about 20 minutes under an air atmosphere at a temperature of about 200° C. 
     Example 3 
     An ultraviolet ray having a wavelength of about 365 nm and an energy density of about 254 mW/cm 2  was irradiated onto an oxide semiconductor device for about 30 minutes while heating the oxide semiconductor device for about 30 minutes under an air atmosphere at a temperature of about 200° C. 
     Example 4 
     An ultraviolet ray having a wavelength of about 365 nm and an energy density of about 254 mW/cm 2  was irradiated onto an oxide semiconductor device for about 1 hour while heating the oxide semiconductor device for about 1 hour under an air atmosphere at a temperature of about 200° C. 
     Comparative Example 
     An ultraviolet ray irradiation process and a thermal treatment process were not performed on an oxide semiconductor device. 
     As illustrated in  FIG. 9 , the mobilities of the oxide semiconductor devices in accordance with Example 1 to Example 3 were gradually increased from Example 1 to Example 3, and the threshold voltage distributions of the oxide semiconductor devices in accordance with Example 1 to Example 3 were gradually decreased from Example 1 to Example 3. As the process times of the ultraviolet ray irradiation process and the thermal treatment process was further increased, electrical characteristics of the oxide semiconductor device were more enhanced. In the case that the ultraviolet ray irradiation process and the thermal treatment process were performed for about 30 minutes, the electrical characteristics of the oxide semiconductor device were efficiently improved. However, in Example 4, the mobility of the oxide semiconductor device was decreased, and the threshold voltage distribution of the oxide semiconductor device was increased. Accordingly, it may be appropriate that the ultraviolet irradiation process and the thermal treatment process may be performed for about 1 hour. That is, when an ultraviolet ray was irradiated onto the oxide semiconductor device for about 1 hour while heating the oxide semiconductor device for about 1 hour under an air atmosphere at a temperature of about 200° C., the electrical characteristics of the oxide semiconductor devices were efficiently enhanced. 
       FIGS. 10 through 18  are cross-sectional views illustrating a method of manufacturing a display device in accordance with example embodiments. 
     Referring to  FIG. 10 , a gate electrode  230  may be formed on a substrate  210 . For example, a conductive layer (not illustrated) may be formed on the substrate  210 , and then the conductive layer may be patterned to form the gate electrode  230 . 
     Referring to  FIG. 11 , a gate insulation layer  240  may be formed on the substrate  210  to cover the gate electrode  230 . In example embodiments, the gate insulation layer  240  may have a relatively thick thickness to sufficiently cover the gate electrode  230 . In some example embodiments, the gate insulation layer  240  having a substantially uniform thickness may be formed on the gate insulating layer  200  along a profile of the gate electrode  230 . In some example embodiments, the gate insulation layer  240  having a relatively thin thickness may be formed on the gate insulating layer  200  along the profile of the gate electrode  230 . 
     Referring to  FIG. 12 , an active pattern  250  may be formed on the gate insulation layer  240 . In example embodiments, the active pattern  250  may be formed using a semiconductor oxide. 
     Referring to  FIG. 13 , an electrode layer (not illustrated) may be formed on the gate insulation layer  240  and the active pattern  250 . The electrode layer may be substantially uniformly formed on the gate insulation layer  240  and the active pattern  250 . The electrode layer may be patterned to form a source electrode  260  and a drain electrode  270 . The source electrode  260  and the drain electrode  270  may be separated from each other by a predetermined distance substantially centering the active pattern  250 . The source electrode  260  and the drain electrode  270  may extend on the gate insulation layer  240 . 
     In the conventional method of forming a source electrode and a drain electrode of an oxide semiconductor device, damage to an active pattern may be caused while forming the source electrode and the drain electrode. When the damage to the active pattern may cause deterioration of electrical characteristics of the oxide semiconductor device, such as reduction of operating current, increase of threshold voltage distribution, reduction of mobility, etc. Although the conventional method of forming the oxide semiconductor device may include an ultraviolet ray irradiation process performed under an air atmosphere using an ultraviolet ray to enhance electrical characteristics of the active pattern, the conventional ultraviolet ray irradiation process may not sufficiently enhance the electrical characteristics of the active pattern because the threshold voltage distribution may be easily shifted even if the ultraviolet ray is irradiated for a short irradiation time. As a result, when the oxide semiconductor device is employed in the display device such as the organic light emitting display device, the liquid crystal display device, the flexible display device, etc., the display device including the oxide semiconductor device may have poor quality of images and relatively slow operating speed. 
     Considering these problems, as illustrated in  FIG. 14  according to example embodiments, an ultraviolet ray irradiation process in which an ultraviolet ray may be irradiated onto the first face of the substrate  210 , and simultaneously a thermal treatment process in which a heat may be applied to a second face of the substrate  210  opposed to the first face of the substrate  210 . For example, the ultraviolet ray irradiation process may be performed for about 10 second to about 1 hour using an ultraviolet ray having a wavelength between about 185 nm and about 370 nm and an energy density less than about 254 mW/cm 2 . In this case, the ultraviolet ray may be generated from an ultraviolet ray lamp or a short wavelength light emitting diode (LED). The thermal treatment process may be executed under an atmosphere including air, oxygen, ozone, nitrogen, or argon. In addition, the thermal treatment process may be carried out at a temperature less than about 400° C. for about 10 second to about 1 hour. The thermal treatment process may be performed using a hot plate or a furnace. 
     In some example embodiments, the ultraviolet ray irradiation process may be performed on the second face of the substrate  210 , and the thermal treatment process may be executed about the first face of the substrate  210 . In other example embodiments, the ultraviolet ray irradiation process and the thermal treatment process may be performed on the first and the second faces of the substrate  210  at the same time. Thus, the active pattern  250  may be cured, so that damage to the active pattern  250  generated in forming of the source electrode  260  and the drain electrode  270  may be efficiently reduced or removed. Additionally, moisture and/or hydroxyl group at a surface of the active pattern  250  generated while forming the source electrode  260  and the drain electrode  270  may be efficiently reduced or removed. Accordingly, the oxide semiconductor device may ensure enhanced electrical characteristics. 
     Referring to  FIG. 15 , an etching stop layer  280  may be formed on the active pattern  250  exposed by the source electrode  260  and the drain electrode  270 . For example, the etching stop layer  280  may be formed using any of silicon oxide, silicon nitride, silicon oxynitride, semiconductor oxide, etc. 
     A protection layer  290  may be formed on the gate insulation layer  240  to cover the source electrode  260 , the drain electrode  270 , and the etching stop layer  280 . For example, the protection layer  290  may include any of silicon oxide, silicon nitride, silicon oxynitride, etc. 
     Accordingly, the oxide semiconductor device including the gate electrode  230 , the gate insulation layer  240 , the active pattern  250 , the source electrode  260 , the drain electrode  270 , the etching stop layer  280 , and the protection layer  290  may be formed on the substrate  210 . 
     Referring to  FIG. 16 , an insulation layer  300  may be formed on the substrate  210  to cover the oxide semiconductor device. For example, the insulation layer  300  may be formed using a transparent insulation material. In example embodiments, a planarization process may be executed on the insulation layer  300  to enhance the flatness of an upper surface of the insulation layer  300 . 
     Referring to  FIG. 17 , the insulation layer  300  may be partially etched to form a hole partially exposing the drain electrode  270 . The hole of the insulation layer  300  may be formed by a photolithography process. 
     A first electrode layer (not illustrated) may be formed on the insulation layer  300 . The first electrode layer may be formed on the drain electrode  270  and the insulation layer  300  along a profile of the insulation layer  300 . The first electrode layer may have a substantially uniform thickness. The first electrode layer may include any of a transparent conductive material, a semi-transparent conductive material, a reflective conductive material, etc. 
     The first electrode layer may be patterned to form a first electrode  310  connected to the drain electrode  270 . In this case, the first electrode  310  may correspond to a pixel electrode of the display device. The first electrode  310  may be formed on an exposed drain electrode  270 , a sidewall of the hole, and the insulation layer  300 . 
     A pixel defining layer  320  may be formed on the first electrode  310 . In example embodiments, the pixel defining layer  320  may be formed using a transparent insulating material. For example, the pixel defining layer  320  may be formed using any of an organic material (e.g., polyacryl-based resin, polyimide-based resin, etc.), a silica-based inorganic material, etc. 
     The pixel defining layer  320  may be partially etched to form an opening that exposes the first electrode  310 . For example, the opening may have a sidewall inclined by a predetermined angle relative to the substrate  210 . Thus, an organic light emitting layer  330  and/or a second electrode  340  (e.g., as shown in  FIG. 18 ) may be subsequently easily formed in accordance with the predetermined angle of the sidewall of the opening. 
     As illustrated in  FIG. 18 , an organic light emitting layer  330  may be formed on the first electrode  310 , the sidewall of the opening, and the pixel defining layer  320 . The organic light emitting layer  330  may be formed on a first electrode  310  exposed along a profile of the opening, the sidewall of the opening, and the pixel defining layer  320 . The organic light emitting layer  330  may include low molecular organic materials, high molecular inorganic materials generating a red color of light, a material generating a green color of light or a material generating a blue color of light. Additionally, the organic light emitting layer  330  may have a multi-layer structure, which may include any of a hole injection layer, a hole transfer layer, an emitting layer, an electron transfer layer, an electron injection layer, etc. 
     A second electrode  340  may be formed on the organic light emitting layer  330 . The second electrode  340  may include any of a transparent conductive material, a semi-transparent conductive material, a reflective conductive material, etc. The second electrode  340  may be formed on the organic light emitting layer  330 . In some example embodiments, when the organic light emitting layer  330  is formed on only the first electrode  310 , the second electrode  340  may be formed in only the opening of the pixel defining layer  320 . For example, the organic light emitting layer  330  may be formed on only the first electrode  310  and the sidewall of the opening, and the second electrode  340  may be formed on the organic light emitting layer  330 . For example, a second electrode layer may be formed on the organic light emitting layer  330  and the pixel defining layer  320 , and then the second electrode layer may be patterned to form the second electrode  340 . 
     A second substrate  350  opposed to the substrate  210  (e.g., on the opposite side of the substrate  210  as shown in  FIG. 18 ) may be provided over the second electrode  340 . For example, the second substrate  350  may include a transparent insulation material. 
     As illustrated above, the display device may include the oxide semiconductor device having enhanced electrical characteristics, so that the display device may have increased quality of images and enhances operating speed. 
     According to example embodiments, an ultraviolet ray irradiation process and a thermal treatment process may be simultaneously performed after forming of a source electrode and a drain electrode. Thus, damage caused to an active pattern while forming the source and the drain electrodes may be prevented. In addition, moisture and/or hydroxyl group generated in process of forming the oxide semiconductor device may be efficiently reduced or removed. Accordingly, the oxide semiconductor device according to example embodiments may ensure enhanced electrical characteristics such as reduction of operating current, increase of threshold voltage distribution, reduction of mobility, etc. As a result, when the oxide semiconductor device is employed in the display device such as the organic light emitting display device, the liquid crystal display device, the flexible display device, etc., the display device may have increased quality of images and enhanced operating speed. 
     The foregoing is illustrative of example embodiments and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the present inventive concept. Accordingly, all such modifications are intended to be included within the scope of the present inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be construed as limited to the specific example embodiments disclosed, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the appended claims.