Organic light emitting display device and method for fabricating the same

An organic light emitting display device includes a light shield layer formed on a substrate and a buffer layer formed on an entire surface of the substrate, an oxide semiconductor layer and first electrode formed on the buffer layer, a gate insulation film and gate electrode formed on the oxide semiconductor layer while being deposited to expose both edges of the oxide semiconductor layer, an interlayer insulation film formed to expose both the exposed edges of the oxide semiconductor layer and the first electrode, source and drain electrodes connected with one edge and the other edge of the oxide semiconductor layer, respectively, and a protective film formed to cover the source and drain electrodes while exposing a region of the first electrode so as to define a luminescent region and a non-luminescent region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Republic of Korea Patent Application No. 10-2012-0013173, filed on Feb. 9, 2012, and to Republic of Korea Patent Application No. 10-2012-0119615, filed on Oct. 26, 2012, both of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light emitting display device and a method for fabricating the same capable of simplifying a fabrication process.

2. Discussion of the Related Art

For an image display device which embodies a variety of information on a screen as a core technology in advanced information and communication, there is continuous progress in development of thin, light-weight, and portable devices with improved performance. Hereupon, an Organic Light Emitting Display (OLED) device for controlling a luminescent amount of an organic luminescent layer is recently receiving attention as a flat panel display device, along with need of a flexible display capable of being bent pursuant to convenience and utilization of space.

The OLED device includes a Thin Film Transistor (TFT) array part formed on a substrate, an organic luminescent cell located on the TFT array part, and a glass cap to isolate the organic luminescent cell from the outside. The OLED device applies an electric field to a cathode and anode formed at both ends of an organic luminescent layer so as to inject and transfer electrons and holes into the organic luminescent layer, thereby utilizing an electroluminescence phenomenon which emits light by bonding energy during combination of the electrons and holes. The electrons and holes, which are paired with each other in the organic luminescent layer, emit light while falling from an excited state to a ground state.

In detail, the OLED device includes a plurality of sub-pixels arranged at a pixel region defined by intersection of a gate line and a data line. Each of the sub-pixels receives a data signal from the data line when a gate pulse is supplied to the gate line, thereby generating light corresponding to the data signal. In this case, each sub-pixel includes a TFT formed on the substrate and an organic luminescent cell connected to the TFT.

FIG. 1is a sectional view illustrating a conventional OLED device. The following description will be given of a method for fabricating the conventional OLED device with reference toFIG. 1.

As shown inFIG. 1, the conventional OLED device includes a TFT formed on a substrate10, and an organic luminescent cell connected to the TFT while including a first electrode18, an organic luminescent layer (not shown), and a second electrode (not shown) formed on the organic luminescent layer.

On the substrate10, a light shield layer11is formed using a first mask and a buffer layer12is formed to cover the light shield layer11. An oxide semiconductor layer13is formed on the buffer layer12using a second mask, and a gate insulation film14and gate electrode14aare deposited in turn on the oxide semiconductor layer13using a third mask.

The oxide semiconductor layer13is exposed, at both edges thereof, by an interlayer insulation film15formed to cover the gate electrode14ausing a fourth mask. Source electrode16aand drain electrode16bare formed to be respectively connected to both the exposed edges of the oxide semiconductor layer13, using a fifth mask. The drain electrode16bis exposed by a protective film17formed on the interlayer insulation film15using a sixth mask.

The exposed drain electrode16bis connected to the first electrode18formed on the protective film17using a seventh mask, and a bank insulation film19is formed on the first electrode18using an eighth mask so as to define a luminescent region and non-luminescent region of each sub-pixel. Although not shown, on the exposed first electrode18, the organic luminescent layer is formed and the second electrode is further formed to cover the organic luminescent layer.

That is, the conventional OLED device as described above is fabricated using eighth masks up to formation of the bank insulation film19, thereby increasing fabrication costs and process time.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an organic light emitting display device and a method for fabricating the same capable of simultaneously forming an oxide semiconductor layer and a first electrode and removing a bank insulation film so as to decrease the number of masks, and adjusting a work function of the first electrode, thereby achieving simplification of a fabrication process and a reduction in fabrication costs.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an organic light emitting display device includes a light shield layer formed on a substrate, and a buffer layer formed on an entire surface of the substrate so as to cover the light shield layer, an oxide semiconductor layer and first electrode formed on the buffer layer, a gate insulation film and gate electrode formed on the oxide semiconductor layer while being deposited in turn to expose both edges of the oxide semiconductor layer, an interlayer insulation film formed to expose both the exposed edges of the oxide semiconductor layer and the first electrode, source and drain electrodes connected with one edge and the other edge of the oxide semiconductor layer, which are exposed through the interlayer insulation film, respectively, the drain electrode being connected with the exposed first electrode, and a protective film formed to cover the source and drain electrodes while exposing a partial region of the first electrode so as to define a luminescent region and a non-luminescent region.

The oxide semiconductor layer and the first electrode may be made of a material selected from among indium tin zinc oxide (ITZO), indium gallium zinc oxide (IGZO), and indium aluminum zinc oxide (IAZO).

The oxide semiconductor layer may overlap with the light shield layer while interposing the buffer layer therebetween, and the light shield layer may have a greater width than the oxide semiconductor layer.

Both the edges of the oxide semiconductor layer, which are exposed through the gate insulation film and the gate electrode, may be made of a conductor.

The first electrode exposed through the protective film may have a greater work function than the oxide semiconductor layer.

The organic light emitting display device may further include a reflective layer formed between the substrate and the buffer layer so as to overlap with the first electrode.

In another aspect of the present invention, a method for fabricating an organic light emitting display device includes forming a light shield layer on a substrate using a first mask and forming a buffer layer on an entire surface of the substrate so as to cover the light shield layer, forming an oxide semiconductor layer and a first electrode on the buffer layer using a second mask, forming a gate insulation film and a gate electrode on the oxide semiconductor layer using a third mask while being deposited in turn to expose both edges of the oxide semiconductor layer, forming an interlayer insulation film to expose both the exposed edges of the oxide semiconductor layer and the first electrode using a fourth mask, forming source and drain electrodes connected with one edge and the other edge of the oxide semiconductor layer, which are exposed through the interlayer insulation film, respectively, using a fifth mask, the drain electrode being connected with the exposed first electrode, and forming a protective film to cover the source and drain electrodes using a sixth mask while exposing a partial region of the first electrode so as to define a luminescent region and a non-luminescent region.

A first embodiment of forming the gate insulation film and the gate electrode may include forming a gate insulation material and a gate electrode material in turn on the substrate formed with the oxide semiconductor layer and the first electrode, forming a photoresist pattern having first and second heights different from each other on the gate electrode material, patterning the gate electrode material and the gate insulation material by an etching process using the photoresist pattern as a mask so as to form the gate insulation film and the gate electrode on each of the oxide semiconductor layer and the first electrode, treating both edges of the oxide semiconductor layer, which are exposed by the photoresist pattern, with at least one plasma of helium (He), hydrogen (H2), and nitrogen (N2), ashing the photoresist pattern so that the photoresist pattern having the first height is removed and the photoresist pattern having the second height is reduced in height, removing the gate electrode and the gate insulation film on the first electrode, which are exposed by the removed photoresist pattern having the first height, so as to expose the first electrode, and removing the photoresist pattern over the oxide semiconductor layer.

A second embodiment of forming the gate insulation film and the gate electrode may include forming a gate insulation material and a gate electrode material in turn on the substrate formed with the oxide semiconductor layer and the first electrode, forming a photoresist pattern on the gate electrode material, patterning the gate electrode material and the gate insulation material by an etching process using the photoresist pattern as a mask so as to form the gate insulation film and the gate electrode on the oxide semiconductor layer, treating both edges of the oxide semiconductor layer, which are exposed by the photoresist pattern, with at least one plasma of He, H2, and N2, and removing the photoresist pattern over the oxide semiconductor layer.

After the forming the protective film, the first electrode may have a greater work function than the oxide semiconductor layer by annealing of the first electrode for 30 minutes to 2 hours at a temperature of 200° C. to 300° C.

The oxide semiconductor layer may overlap with the light shield layer with the buffer layer interposed therebetween, and the light shield layer may have a greater width than the oxide semiconductor layer.

The method for fabricating the organic light emitting display device may further include forming a reflective layer between the substrate and the buffer layer so as to overlap with the first electrode.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to an organic light emitting display device and a method for fabricating the same according to an exemplary embodiment of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

FIG. 2is a sectional view illustrating an Organic Light Emitting Display (OLED) device according to an embodiment of the present invention.FIG. 3is a sectional view illustrating a case in which the OLED device ofFIG. 2is a top emission type OLED device according to an embodiment.

As shown inFIG. 2, a light shield layer110is formed on a substrate100. The light shield layer110serves to absorb light and to prevent external light from being incident upon an oxide semiconductor layer to be described later. The light shield layer110is made of a metal material such as molybdenum (Mo) or made of a black organic material. The substrate100is formed, at an entire surface thereof, with a buffer layer120to cover the light shield layer110.

An oxide semiconductor layer130and a first electrode180are formed on the buffer layer120, and the oxide semiconductor layer130and the first electrode180are made of an oxide such as indium gallium zinc oxide (IGZO), indium tin zinc oxide (ITZO), or indium aluminum zinc oxide (IAZO). In this case, the oxide semiconductor layer130is formed to overlap with the light shield layer110, and thus external light may be prevented from being incident upon the oxide semiconductor layer130. Furthermore, the light shield layer110may have a greater width than the oxide semiconductor layer130so as to completely block incidence of external light upon the oxide semiconductor layer130. The oxide semiconductor layer130includes a source region130aconnected to a source electrode160a, a drain region130bconnected to a drain electrode160b, and a channel region130coverlapping with a gate electrode140awith a gate insulation film140interposed therebetween.

In order to expose the source region130aand the drain region130bwhich are located at both edges of the oxide semiconductor layer130, the gate insulation film140and the gate electrode140aare formed to be deposited in turn on the oxide semiconductor layer130. Particularly, both the exposed edges of the oxide semiconductor layer130are made of a conductor by plasma treatment. Accordingly, when the edges of the oxide semiconductor layer130are connected to the respective source and drain electrodes to be described later, resistance of the oxide semiconductor layer130is decreased to improve contact characteristics.

An interlayer insulation film150is formed to expose a partial region of the first electrode180on the gate electrode140a. The interlayer insulation film150exposes both the plasma-treated edges of the oxide semiconductor layer130, and both the exposed edges of the oxide semiconductor layer130are connected to the source and drain electrodes160aand160b, respectively. The drain electrode160balso extends onto the exposed first electrode180, thereby being directly connected to the first electrode180.

As described above, the oxide semiconductor layer130, the gate insulation film140, the gate electrode140a, and the source and drain electrodes160aand160bare included in an oxide Thin Film Transistor (TFT) having advantages such as higher mobility and lower leakage current characteristics, compared with a silicon TFT. Furthermore, the TFT, using a crystallization process, such as the silicon TFT has poor uniformity during the crystallization process such as becoming a large area, thereby being unfavorable to the large area. On the other hand, the oxide TFT has an advantage to be formed in the large area.

A protective film170is formed to cover the source and drain electrodes160aand160b. In this case, the protective film170exposes a partial region of the first electrode180so as to define a luminescent region and non-luminescent region of a sub-pixel. Accordingly, since the protective film170functions as a bank insulation film, the OLED device according to the illustrated embodiment of the present invention may remove a process of forming the bank insulation film. In addition, a work function is adjusted through annealing of the exposed first electrode180.

The conventional OLED device has a great difference between a work function of a first electrode and a Highest Occupied Molecular Orbital (HOMO) level of an organic luminescent layer when holes are injected from the first electrode to the organic luminescent layer. Consequently, no holes may be smoothly injected into the organic luminescent layer. Accordingly, the conventional OLED device should further form functional layers such as a hole injection layer and a hole transport layer between the first electrode and the organic luminescent layer, thereby causing increase of fabrication costs and complicating processes.

On the other hand, the OLED device according to the illustrated embodiment of the present invention performs annealing of the first electrode180. By annealing the first electrode180, the first electrode180has a greater work function than the oxide semiconductor layer130. That is, the work function of the first electrode180is increased through annealing, thereby decreasing the difference between the work function of the first electrode180and a HOMO level of an organic luminescent layer. Hence, even when the hole injection layer and hole transport layer are removed, the holes may be smoothly injected into the organic luminescent layer.

Although not shown inFIGS. 2 and 3, on the exposed first electrode180, an organic luminescent layer is formed and a second electrode made of a material such as aluminum (Al) or silver (Ag) is formed to cover the organic luminescent layer. In particular, when the OLED device according to the illustrated embodiment of the present invention is a bottom emission type OLED device, light generated from the organic luminescent layer is reflected at the second electrode by adjusting a thickness of the second electrode so as to progress toward the first electrode180.

Meanwhile, when the OLED device according to the illustrated embodiment of the present invention is a top emission type OLED device, a reflective layer110ais further formed between the substrate100and the buffer layer120so as to overlap with the first electrode180, as shown in FIG.3. The reflective layer110ais made of a material such as aluminum neodymium (AlNd). Consequently, light, which is generated from the organic luminescent layer (not shown) and progresses toward the first electrode180, is reflected at the reflective layer110aso as to progress toward the second electrode (not shown). Particularly, the top emission type OLED device may include a second electrode having a thinner thickness than the second electrode of a bottom emission type OLED device, in order to emit light through the second electrode to the outside.

Although shown as being also formed on the light shield layer110overlapping with the TFT in the drawing, the reflective layer110amay alternatively be formed to overlap with only the first electrode180or may be formed to overlap with the first electrode180and the oxide semiconductor layer130of the TFT without the light shield layer.

Hereinafter, the following description will be given of a method for fabricating the OLED device according to the illustrated embodiment of the present invention with reference to the accompanying drawings in detail.

FIG. 4is a flowchart illustrating process steps of fabricating the OLED device according to the illustrated embodiment of the present invention.FIGS. 5A to 5Fare sectional views illustrating a process of fabricating the OLED device according to the illustrated embodiment of the present invention.

As shown inFIGS. 4 and 5A, the light shield layer110is formed on the substrate100using a first mask (S5). The light shield layer110serves to prevent external light from being incident upon the oxide semiconductor layer130. Then, the buffer layer120is formed on the surface of the substrate100so as to cover the light shield layer110.

Particularly, when the OLED device according to the illustrated embodiment of the present invention is a top emission type OLED device as shown inFIG. 3, a light shield material and a reflective material are deposited in turn on the substrate100and are then simultaneously etched using the first mask. Accordingly, the light shield layer110and the reflective layer110aare deposited in turn at regions overlapping with the TFT and the first electrode180, so that the light progressing toward the first electrode180, among light emitted from the organic luminescent layer, is reflected through the reflective layer110aand progresses upwards.

Meanwhile, the light shield layer110may be formed at a region overlapping with the TFT using a half tone mask as the first mask, and the light shield layer110and the reflective layer110ahaving a lamination structure in this order may also be formed at a region overlapping with the first electrode180. In addition, the light shield layer110may be formed on the substrate100overlapping with the TFT, and the reflective layer110amay also be formed on the substrate100overlapping with the first electrode180. Since this, however, should form the light shield layer110and the reflective layer110ausing different mask processes, respectively, a mask process is added.

Thereafter, the oxide semiconductor layer130and the first electrode180are formed on the buffer layer120using a second mask (S10), as shown inFIG. 5B. That is, the oxide semiconductor layer130and the first electrode180are simultaneously formed, thereby enabling removal of a separate process for formation of the first electrode180. In this case, the oxide semiconductor layer130and the first electrode180are made of a material such as IGZO, ITZO, or IAZO.

Subsequently, the gate insulation film140and the gate electrode140aare formed in turn on the oxide semiconductor layer130using a third mask (S15), as shown inFIG. 5C.

Specifically, a gate insulation material and a gate electrode material are deposited in turn on an entire surface of the buffer layer120, which includes the oxide semiconductor layer130. Then, the gate insulation material and the gate electrode material are patterned so as to form the gate insulation film140and the gate electrode140afor exposing both edges of the oxide semiconductor layer130.

In this case, the exposed both edges of the oxide semiconductor layer130are made of the conductor by plasma such as helium (He), hydrogen (H2), or nitrogen (N2) to form the source and drain regions130aand130b. Resistance of the oxide semiconductor layer130is decreased when the source and drain regions130aand130bof the oxide semiconductor layer130are respectively connected to the source and drain electrodes160aand160b, thereby improving contact characteristics. Specifically, the plasma treatment process and the third mask process to pattern the gate insulation film140and the gate electrode140awill be described later with reference toFIGS. 6A to 6Eand7A to7D.

Subsequently, the interlayer insulation film150is formed on the gate electrode140ausing a fourth mask so as to expose a partial region of the first electrode180(S20), as shown inFIG. 5D. In this case, the interlayer insulation film150exposes the plasma-treated edges of the oxide semiconductor layer130.

As shown inFIG. 5E, the source electrode160ais formed to be connected with one exposed edge of the oxide semiconductor layer130and the drain electrode160bis formed to be connected with another exposed edge thereof, using a fifth mask (S25). In this case, the drain electrode160bextends up to the exposed first electrode180, thereby being directly connected to the first electrode180.

Subsequently, the protective film170is formed to cover the source and drain electrodes160aand160busing a sixth mask (S30), as shown inFIG. 5F. In this case, the protective film170exposes a partial region of the first electrode180so as to define the luminescent region and the non-luminescent region, thereby functioning as the bank insulation film. Accordingly, it may be possible to remove the process of forming the bank insulation film.

In addition, the first electrode180has a greater work function than the oxide semiconductor layer130by annealing of the exposed first electrode180, thereby enabling a decrease of the difference between the work function of the first electrode180and the HOMO level of the organic luminescent layer. In one embodiment, the annealing is executed for 30 minutes to 2 hours at a temperature of 200 to 300° C.

Meanwhile, the gate insulation film140, interlayer insulation film150, and protective film170formed on the oxide semiconductor layer130may prevent heat from being transferred to the oxide semiconductor layer130, during an annealing process. As a result, it may be possible to prevent variations of the work function and sheet resistance in the oxide semiconductor layer130.

A conventional OLED device further forms the functional layers such as the hole injection layer and the hole transport layer between the first electrode180and the organic luminescent layer so as to smoothly inject holes from the first electrode180which is an anode. The OLED device according to the illustrated embodiment of the present invention may increase the work function of the first electrode180through annealing thereof, thereby enabling removal of the functional layers between the first electrode180and the organic luminescent layer. Accordingly, holes may be smoothly injected into the organic luminescent layer by formation of the organic luminescent layer directly on the first electrode180, thereby achieving an improvement in luminous efficiency. Thus, it is possible to accomplish simplification of a fabrication process and a reduction in fabrication costs by removal of the above-mentioned functional layers.

FIGS. 6A to 6Eare sectional views for specifically explaining a first embodiment of the plasma treatment process and the third mask process illustrated inFIG. 5C.

As shown inFIG. 6A, a gate insulation material220aand a gate electrode material220bare deposited in turn on the surface of the substrate100formed with the oxide semiconductor layer130. Then, a photoresist pattern230is formed on the gate electrode material220bthrough a photolithographic process using a photo mask (not shown) such as a half tone mask and a slit mask. The photoresist pattern230having a first height is formed at a semi-transmission region P3of the photo mask, whereas the photoresist pattern230having a greater second height than the first height is formed at a cut-off region P1of the photo mask. Also, a transmission region P2of the photo mask is formed to expose the gate electrode material220b.

Through an etching process using the photoresist pattern230as a mask, the gate insulation and gate electrode materials220aand220bare etched to form the gate insulation film140and gate electrode140ahaving the same pattern, as shown inFIG. 6B. In this case, the gate insulation film140and gate electrode140aon the oxide semiconductor layer130are formed to expose both edges of the oxide semiconductor layer130. On the other hand, the gate insulation film140and gate electrode140aon the first electrode180are formed to enclose the first electrode180in the form of a pattern equal to or wider than the first electrode180, thereby protecting the first electrode180.

Thereafter, both the exposed edges of the oxide semiconductor layer130are treated with plasma such as He, H2, or N2, using the photoresist pattern230as a mask, as shown inFIG. 6C. Accordingly, only both edges of the oxide semiconductor layer130are selectively made of the conductor so as to form the source and drain regions130aand130bof the oxide semiconductor layer130and the channel region130cmaintaining a semiconductor state between the source region130aand the drain region130b.

Then, by an ashing process using oxygen (O2) plasma, a thickness of the photoresist pattern230having the second height becomes thin, and the photoresist pattern230having the first height is removed, as shown inFIG. 6D. Consequently, the gate insulation film140and gate electrode140aon the first electrode180are exposed. The exposed gate insulation film140and gate electrode140aon the first electrode180are removed through an etching process using the ashed photoresist pattern230as a mask.

Subsequently, the photoresist pattern230remaining over the channel region130cof the oxide semiconductor layer is removed through a strip process, as shown inFIG. 6E.

FIGS. 7A to 7Dare sectional views for specifically explaining a second embodiment of the plasma treatment process and the third mask process illustrated inFIG. 5C.

As shown inFIG. 7A, a gate insulation material220aand a gate electrode material220bare deposited in turn on the entire surface of the substrate100formed with the oxide semiconductor layer130. Then, a photoresist pattern230is formed on the gate electrode material220bthrough a photolithographic process using a photo mask (not shown). The photoresist pattern230is formed at a cut-off region P1of the photo mask, and a transmission region P2of the photo mask is formed to expose the gate electrode material220b.

The gate insulation and gate electrode materials220aand220bare etched through an etching process using the photoresist pattern230as a mask, as shown inFIG. 7B. Consequently, the gate insulation film140and gate electrode140ahaving the same pattern are formed on the oxide semiconductor layer130, and the gate insulation and gate electrode materials220aand220bon the first electrode180are removed to expose the first electrode180. In this case, the gate insulation film140and gate electrode140aon the oxide semiconductor layer130are formed to expose both edges of the oxide semiconductor layer130.

Thereafter, both the exposed edges of the oxide semiconductor layer130are treated with at least one plasma of He, H2, and N2, using the photoresist pattern230as a mask, as shown inFIG. 7C. Accordingly, both edges of the oxide semiconductor layer130are made of the conductor so as to form the source and drain regions130aand130bof the oxide semiconductor layer and the channel region130cmaintaining a semiconductor state between the source region130aand the drain region130b. Meanwhile, the exposed first electrode180is also treated with plasma during plasma treatment of both edges of the oxide semiconductor layer130. In this case, the plasma-treated first electrode180has the desired sheet resistance and work function through the annealing process, as shown inFIG. 5F.

Subsequently, the photoresist pattern230remaining over the channel region130cof the oxide semiconductor layer is removed through a strip process, as shown inFIG. 7D.

Meanwhile, the source and drain regions130aand130bof the oxide semiconductor layer have been illustrated, for example, as formed by the plasma treatment using the photoresist pattern, which is formed through the photolithographic process using the photo mask, as the mask. However, the source and drain regions130aand130bmay be formed by ultraviolet (UV) irradiation on only the oxide semiconductor layer using the gate electrode140aas a mask without the photo mask.

Also, when the gate electrode140aand the gate insulation film140are patterned by a dry etching process using plasma, both edges of the oxide semiconductor layer130may be made of the conductor by the plasma used during the dry etching process. Consequently, the source and drain regions130aand130bmay also be formed.

FIG. 8is a table illustrating variation in a work function according to a surface treatment method of ITZO.FIG. 9Ais a sectional view illustrating an energy level of the OLED device before annealing, wherein only the first electrode, functional layer, and organic luminescent layer are illustrated.FIG. 9Bis a sectional view illustrating the energy level of the OLED device after annealing, wherein only the first electrode and organic luminescent layer are illustrated.

As shown inFIG. 8, a work function of ITZO may be adjusted by H2plasma treatment or annealing. First, when no treatment is performed for ITZO, the ITZO has the work function of 5.05 eV. In this case, it is difficult for holes to be smoothly injected into an organic luminescent layer290having a HOMO level of about 5.9 to 6.0 eV, as shown inFIG. 9A. Therefore, functional layers210such as a hole injection layer210aand a hole transport layer210bshould be formed between a first electrode280and the organic luminescent layer290. That is, since a difference between the work function of the first electrode280and the HOMO level of the organic luminescent layer290is great, the holes are gradationally injected from the first electrode280to the organic luminescent layer290through the functional layers210.

In the case of executing annealing of ITZO for one hour at a temperature of 230° C., the ITZO has the increased work function of 5.63 eV. That is, even when the functional layers such as the hole injection layer and the hole transport layer210bare not formed between a first electrode380and the organic luminescent layer390, the holes are smoothly injected from the first electrode380to the organic luminescent layer390, as shown inFIG. 9B.

Also, when ITZO is H2plasma-treated for 60 seconds under a pressure of 100 mTorr and an electric power of 500 W by injection of H2at 100 sccm, the ITZO has the decreased work function of 4.71 eV, thereby being made of the conductor, as opposed to the case of annealing.

That is, oxides including indium zinc oxide (IZO) such as indium tin zinc oxide (ITZO), indium gallium zinc oxide (IGZO), or indium aluminum zinc oxide (IAZO) may adjust the work function through H2plasma treatment or annealing. Accordingly, the OLED device, having the oxide TFT, according to the illustrated embodiment of the present invention executes annealing of the first electrode180made of the same material as the oxide semiconductor layer130, thereby enabling increase of the work function of the first electrode180. Hence, it may be possible to achieve simplification of a fabrication process and a reduction in fabrication costs by removal of the functional layers between the first electrode180and the organic luminescent layer.

Accordingly, in accordance with the organic light emitting display device and the method for fabricating the same according to the illustrated embodiment of the present invention, the oxide semiconductor layer and the first electrode are simultaneously formed, thereby enabling a decrease of one mask in the number of masks to form the first electrode. In addition, the protective film170formed on the source and drain electrodes functions as the bank insulation film defining the luminescent region and the non-luminescent region, thereby enabling a decrease of one mask in the number of masks to form the bank insulation film. Thus, the organic light emitting display device according to the illustrated embodiment of the present invention may decrease a total of two masks, compared with the conventional device. As a result, it may be possible to achieve simplification of a fabrication process and a reduction in fabrication costs.

As is apparent from the above description, an organic light emitting display device and a method for fabricating the same according to the present invention has the following effects.

First, an oxide semiconductor layer and a first electrode are simultaneously formed, thereby enabling a decrease of one mask in the number of masks to form the first electrode. Particularly, a work function of the first electrode may be adjusted by annealing the first electrode. Accordingly, even when functional layers between the first electrode and an organic luminescent layer are removed, holes are smoothly injected from the first electrode to the organic luminescent layer. Consequently, it may be possible to improve luminous efficiency of the organic light emitting display device and at the same time to achieve simplification of a fabrication process and a reduction in fabrication costs.

Second, a protective film formed on source and drain electrodes functions as a bank insulation film defining a luminescent region and non-luminescent region of a sub-pixel, thereby enabling a decrease of one mask in the number of masks to form the bank insulation film.