JP4603780B2 - Method for manufacturing light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to light emitting elements including display elements, particularly organic EL display elements, and more particularly to the structure and manufacturing method of these light emitting elements.
[0002]
[Prior art]
2. Description of the Related Art In recent years, research on self-luminous organic EL display devices has been actively conducted as a display that can obtain high brightness while being thin. The organic EL element has a structure in which an organic layer serving as a light emitting layer is sandwiched between opposing electrodes, and a display device is configured by controlling light emission by turning on / off a current to the electrode. There are two types of display devices: passive matrix and active matrix. The former is used for backlights and display devices with relatively low definition, and the latter is used for display devices with relatively high definition such as televisions and monitors. .
[0003]
In the organic EL element constituting such an organic EL display device, a major problem is that the lifetime of the organic layer as the light emitting layer is short. In recent years, the light emission time has become longer due to various studies. However, for example, when it is used as a television or a monitor, the current element lifetime is still short, and the luminance is halved in 2000 to 3000 hours during continuous lighting. As the reason for the short lifetime of the element, the penetration of moisture into the organic layer as the light emitting layer and the thermal destruction due to the heating after the organic layer is formed and the heat generation of the element are remarkable, and various improvements have been proposed.
[0004]
Patent Document 1 is characterized by having a protective film having a multilayer structure including two layers of an organic layer and a metal layer or two layers of an inorganic layer and a metal layer.
[0005]
Patent Document 2 is characterized in that a metal heat radiating plate is provided as a heat radiating member via an adhesive layer on one electrode forming the organic EL element.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-275680
[0007]
[Patent Document 2]
JP 2002-343559 A
[0008]
[Problems to be solved by the invention]
In Patent Document 1, when two layers of an organic layer and a metal layer are employed as a protective film, the heat conductivity of the organic layer is low, and there is a problem that heat generated in the element cannot be sufficiently diffused and released. In addition, in the case of two layers of an inorganic layer and a metal layer, when SiO2 is adopted as a semiconductor compound for forming the inorganic protective film exemplified in this document, the thermal conductivity of SiO2 is low and the heat generated in the element is sufficiently diffused. In addition to being unable to release, there is a problem that moisture cannot sufficiently be prevented as a protective film.
[0009]
According to Patent Document 2, the problem of heat dissipation can be avoided, but there is a space in the separation part between the light emitting elements having a passive matrix configuration, and the organic solvent or moisture generated from the adhesive remains in this part. If the adhesive is mixed in, the most important light emitting layer cannot be reliably protected, resulting in a problem that the lifetime of the device is reduced.
[0010]
Furthermore, since the method for forming the protective film is generally performed at a temperature that does not decompose the organic layer, a dense thin film cannot be formed, and several hundreds of nanometers to several hundreds of nanometers can be used to suppress moisture and organic matter permeation. A protective film having a thickness of micron has to be formed, resulting in an increase in thermal resistance and an increase in element temperature, resulting in a problem of shortening the lifetime.
[0011]
As described above, in order to extend the lifetime of the organic EL element and the organic EL display device, it is essential to efficiently remove moisture, organic substances, and heat generation in the light emitting layer and the electrode layer. Nevertheless, no effective means has been proposed yet.
[0012]
As another problem of the present invention, the transparent conductive electrode represented by ITO in the past has a low work function, so the work function with the hole transport layer or the organic EL layer is not suitable, and therefore a buffer layer is provided, but the efficiency is high. Unfortunately, this leads to deterioration in light emission efficiency and increase in light emission voltage, resulting in increase in heat during operation and shortening of life. Therefore, it is required to use an electrode suitable for the work function of the hole transport layer or the organic EL layer.
[0013]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and provides an organic EL element and an organic EL display device having a long life, and a manufacturing method and a manufacturing apparatus thereof, and specifically described below. The
[0014]
That is, the present invention relates to a transparent conductive electrode, a counter electrode facing the transparent conductive electrode, an organic EL light emitting layer provided between the transparent conductive electrode and the counter electrode, and the organic EL light emitting layer. In the organic EL light-emitting device having the electron transport layer and the hole transport layer provided on both surfaces thereof so as to be in contact with the transparent conductive electrode, the electron transport layer, the organic EL light-emitting layer, the hole transport layer, and the facing The electrode provides an organic EL light emitting device characterized by being laminated in this order. According to the present invention, the transparent conductive electrode, the electron transport layer provided on the transparent conductive electrode, the organic EL light emitting layer provided on the electron transport layer, and the organic EL light emitting layer An organic EL light emitting device comprising a hole transport layer provided and a counter electrode made of a conductive material having a work function of 4 eV to 6 eV provided on the hole transport layer is obtained. The transparent conductive electrode preferably includes ITO, and the conductive material of the counter electrode preferably includes at least one of Co, Ni, Rh, Pd, Ir, Pt, and Au as a simple substance or an alloy. ITO has a work function of about 4.8 eV and matches the work function of the electron transport layer, while Co, Ni, Rh, Pd, Ir, Pt, Au, etc. have a work function of about 6 eV that matches the work function of the organic EL layer. Have a work function of
[0015]
In the light emitting device of the present invention, the transparent conductive electrode may be provided on a transparent substrate, light emitted from the organic EL light emitting layer may be extracted via the transparent substrate, and the counter electrode may be provided on the substrate. The emitted light from the organic EL light emitting layer may be extracted via the transparent conductive electrode.
[0016]
Furthermore, in the present invention, an organic EL light emitting device is obtained, wherein an insulating protective layer is provided so as to cover at least the organic EL light emitting layer, and a heat dissipation layer is further provided so as to be in contact with the insulating protective layer. The insulating protective layer is made of at least one of compounds of nitrogen and at least one element of Ti, Zr, Hf, V, Nb, Ta, Cr, B, Al, and Si, and has a thickness of 100 nm or less. Preferably, the nitride film includes at least one of silicon nitride, titanium nitride, tantalum nitride, and aluminum nitride. Since the nitride film is denser than the oxide film, the water blocking effect and the heat dissipation effect are superior to the oxide film. The thinner the thickness, the higher the heat dissipation efficiency. Therefore, it is necessary to make it as thin as the function of the protective film permits. From this viewpoint, the thickness is 100 nm or less, preferably 30 nm to 50 nm. The insulating protective layer may be composed of an insulating layer that covers the organic EL light emitting layer via the counter electrode and a protective layer that covers the insulating layer, and this configuration is necessary particularly when the protective layer is conductive. is there.
[0017]
The present invention is also applicable to general display elements other than organic EL elements, and includes a transparent conductive electrode, a counter electrode facing the transparent conductive electrode, and the transparent conductive electrode and the counter electrode. In a display element having a light emitting layer provided and an insulating protective layer provided to cover at least the light emitting layer directly or indirectly,
The insulating protective layer includes a nitride film formed by low-temperature vapor phase growth using microwave-excited plasma. The nitride film is preferably at least one of a compound of nitrogen and an element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, B, Al, and Si. It is also a feature of the present invention that the insulating protective layer contains at least an element selected from the group consisting of Ar, Kr, and Xe.
[0018]
Further, according to the method for manufacturing a display element of the present invention, the transparent conductive electrode, the counter electrode facing the transparent conductive electrode, and the light emitting layer provided between the transparent conductive electrode and the counter electrode And a protective layer provided so as to cover at least the light emitting layer, wherein the protective layer is formed of a plasma mainly composed of a gas selected from the group consisting of Ar, Kr, and Xe. It is characterized by forming into a film. The plasma is preferably a high frequency excitation plasma, particularly a microwave excitation plasma. The film formation is performed by low-temperature vapor deposition, and the low-temperature vapor deposition is performed at 100 ° C. or less, preferably at room temperature. The low temperature vapor phase growth is preferably performed without heating except for heating by plasma.
[0019]
Further, according to the present invention, a plurality of gate lines arranged in a matrix, a plurality of signal lines, a switching element provided near the intersection of the gate lines and the signal lines, a transparent conductive electrode, A counter electrode facing the transparent conductive electrode; an organic EL light emitting layer provided between the transparent conductive electrode and the counter electrode; and an electron transport layer provided in contact with the organic EL light emitting layer. In an organic EL display device having a hole transport layer, a protective layer provided so as to cover at least the organic EL light emitting layer, and a heat dissipation layer provided so as to be in contact with the protective layer, the switching element is a TFT. A gate electrode connected to the gate line; a signal line electrode connected to the signal line; and a contact hole formed in an insulating film covering the TFT to the transparent conductive electrode or the counter electrode. The transparent conductive electrode, the electron transport layer, the organic EL light emitting layer, the hole transport layer, and the counter electrode are stacked in this order. An EL display device is obtained.
[0020]
Alternatively, a plurality of gate lines arranged in a matrix on the substrate, a plurality of signal lines, a switching element provided near an intersection of the gate lines and the signal lines, a transparent conductive electrode, and the transparent A counter electrode facing the conductive electrode, an organic EL light emitting layer provided between the transparent conductive electrode and the counter electrode, a protective layer provided to cover at least the organic EL light emitting layer, In the organic EL display device having a heat dissipation layer provided in contact with the protective layer, the switching element is a TFT, a gate electrode connected to a gate line, a signal line electrode connected to a signal line, A transparent conductive electrode or a pixel electrode connected to the counter electrode, and the gate line and the gate electrode are embedded in an insulating film formed in contact with the substrate or the substrate. The organic EL display device comprising Rukoto is obtained.
[0021]
In these organic EL display devices, the protective layer preferably includes a nitride film having a thickness of 100 nm or less.
[0022]
In addition, according to the present invention, there is obtained a method for producing a conductive transparent film, characterized in that sputtering film formation is performed with plasma mainly containing Kr and Xe. Furthermore, according to the present invention, there is provided a method for producing a conductive transparent film comprising a step of forming an ITO film by sputtering a target containing indium oxide and tin oxide with high frequency excitation plasma, wherein the sputtering comprises at least Kr and Xe. A method for producing a conductive transparent film can be obtained, which is performed using plasma having one as a main component.
[0023]
Furthermore, the present invention relates to a nitride film forming method in which a nitride film is vapor-grown by microwave-excited plasma, wherein the vapor-phase growth is performed with plasma mainly containing at least one of Ar, Kr and Xe There is also provided a method for forming a nitride film, which is performed at a low temperature without heating except for heating by the above. The microwave-excited plasma vapor deposition is performed in a plasma processing apparatus having a two-stage shower plate, and a gas containing at least one of Ar, Kr, and Xe is introduced into the apparatus from the upper shower plate to generate the plasma. Preferably, the material gas of the nitride film is introduced into the plasma from the lower shower plate, and a high frequency is applied to the film forming member during vapor phase growth of the nitride film to form the film forming member. It is also preferable to apply a bias potential to the surface.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
Example 1
A display element according to Example 1 of the present invention will be described with reference to FIG. FIGS. 1A and 1B are a cross-sectional view and a plan view showing the structure of a bottom emission type passive display element, a transparent substrate, a conductive transparent electrode formed on the transparent substrate, and the conductive transparent As an organic layer laminated on the electrode, an electron transport layer, a light emitting layer, a hole transport layer, a counter electrode laminated on the organic layer, a protective layer formed so as to cover them, and a protective layer It consists of a heat dissipation layer formed so as to be in contact. The transparent substrate may be any material that transmits light emitted from the light emitting layer, and a glass substrate is used in this embodiment. For the counter electrode, a Pt film, which is a high work function material, was used in order to increase the work function of the surface in contact with the organic layer and improve the hole injection efficiency into the device. As a result, a hole injection layer and a buffer layer that are generally required become unnecessary. An organic layer consists of an electron carrying layer, a light emitting layer, and a hole carrying layer, and is not specifically limited, Even if it uses any well-known material, the effect | action and effect of this invention are acquired. The hole transport layer efficiently moves holes to the light-emitting layer and suppresses electrons from the counter electrode from moving beyond the light-emitting layer to the transparent conductive electrode side. It has a role of increasing the recombination efficiency. The material constituting the hole transport layer is not particularly limited, and for example, 1,1-bis (4-di-paminophenyl) cyclohexane, galbazole and derivatives thereof, triphenylamine and derivatives thereof, and the like can be used. . Although a light emitting layer is not specifically limited, Quinolinol aluminum complex containing a dopant, DPVi biphenyl, etc. can be used. Depending on the application, red, green, and blue light emitters may be stacked and used, and in a display device or the like, red, green, and blue light emitters may be arranged in a matrix. As the electron transport layer, silole derivatives, cyclopentadiene derivatives, and the like can be used. The material for forming the counter electrode is not particularly limited, but a low work function material having high electron injection efficiency while being transparent is preferable, and ITO having a work function of 4.5 to 4.8 eV can be used. Nitriding of an element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, B, Al, and Si as a protective layer to prevent moisture and oxidizing gas from entering the organic EL light emitting layer Things are preferred. From the viewpoint of reducing thermal resistance, a thinner one is preferable, but in order to suppress the transmission of moisture, oxidizing gas, etc., about 10 nm to 100 nm is preferable, and 30 nm to 50 nm is more preferable. When the protective layer is made of the above-mentioned nitride, the thermal conductivity is high and the thermal resistance can be reduced, so the protective layer can also serve as a heat dissipation layer, but even if a heat dissipation layer is provided for more efficient heat dissipation Good. As the heat dissipation layer, aluminum or copper having high thermal conductivity is preferable.
[0026]
Next, the manufacturing method of the display element in a present Example is demonstrated. An ITO film was formed on the cleaned glass substrate by a sputtering method. For the film formation, a sputtering method using an ITO target (preferably a sintered body of indium oxide and tin oxide) was used. At the time of sputtering, Xe having a large collision cross section was used as a plasma excitation gas, and plasma having a sufficiently low electron temperature was generated. The substrate temperature was 100 ° C. and the film thickness was 200 Å. Since sputtering was performed using Xe plasma, the electron temperature was sufficiently low, and plasma damage to the ITO film was suppressed even when filming was performed while irradiating the surface of the ITO film with Xe ions to improve film quality. Therefore, a high quality film could be formed even at a low temperature of 100 ° C. or lower. The ITO film thus formed was patterned into a predetermined shape. Patterning was performed by photolithography. A novolak-type resist was used as a photoresist. After exposure with a mask aligner and development with a predetermined developer, surface organic substance removal cleaning by ultraviolet light irradiation was performed for 10 minutes. Next, an electron transport layer, a light emitting layer, and a hole transport layer were continuously formed by an organic film deposition apparatus. Next, without exposing the substrate to the atmosphere, Pt was deposited by a Pt sputtering apparatus adjacent to the organic film deposition apparatus to form a counter electrode. Instead of Pt, a material having a high work function such as Co, Ni, Rh, Pd, Ir, or Au may be used. During sputtering, sputtering was performed using Xe plasma to prevent plasma damage from being mixed into the organic layer. Next, without exposing the substrate to the atmosphere, the substrate was transported to an insulating protective film forming apparatus, and the silicon nitride film was volumed to form an insulating protective film. In forming the silicon nitride film, a plasma CVD method using microwave-excited plasma was used, and a gas having a volume ratio of Ar: N2: H2: SiH4 = 80: 18: 1.5: 0.5 was used. The process pressure is preferably 0.1 to 1 Torr, and in the present example, it was 0.5 Torr. A high frequency of 13.56 MHz was applied from the back surface of the substrate, a potential of about −5 V was generated as a bias potential on the substrate surface, and ions in the plasma were irradiated. The substrate temperature at the time of silicon nitride film formation was room temperature, and heating by a heating means was not performed other than inevitably heating by plasma. A film thickness of 50 nm was formed. FIG. 15 shows a two-stage shower plate type microwave excitation high-density plasma film forming apparatus used for film formation. Since microwave-excited plasma is used and the process region can be arranged at a position away from the plasma excitation region, the electron temperature in the process region is 1.0 eV or less even when Ar is used, and the plasma density is 10 ¹¹ /cm ² That's it. Since it has a two-stage shower plate structure, a source gas such as silane can be introduced into a process area away from the plasma excitation area, so that excessive dissociation of silane can be suppressed, and even at room temperature, a light-emitting element and a formed film can be protected A dense film could be formed without causing defects in the film. By applying a high frequency from the substrate, a bias potential is generated on the substrate surface, and by irradiating the substrate surface with ions from microwave-excited plasma, a nitride film can be formed densely, which can further improve the film quality. did it. Although the substrate is heated by the plasma as described above, it is also important not to perform any other heating. Vapor phase growth may be performed while cooling the substrate in order to suppress heating by plasma.
[0027]
Thereafter, aluminum was further formed to a thickness of 1 micron with an aluminum vapor deposition apparatus to form a heat dissipation layer.
[0028]
Instead of aluminum vapor deposition, aluminum sputter film formation may be performed. In that case, sputtering film formation using Xe plasma having a low electron temperature is effective.
[0029]
Through the above steps, the light-emitting element of Example 1 was obtained. As a result of measuring the element lifetime of the light emitting element of this example, the luminance half-life, which was 2000 hours in the past, was 6000 hours, and the effect of the protective layer was confirmed.
[0030]
(Example 2)
A display element according to Example 2 of the present invention will be described with reference to FIG. 2A and 2B are a cross-sectional view and a plan view showing the structure of a top emission type passive display element, a substrate, a counter electrode formed on the substrate and facing the conductive transparent electrode, and a counter electrode. As an organic layer laminated thereon, a hole transport layer, a light emitting layer, an electron transport layer, a conductive transparent electrode laminated on the organic layer, a protective layer formed so as to cover them, and the protective layer The heat dissipation layer is formed so as to be in contact with the heat dissipation layer. Since it is a top emission type, the substrate material is not particularly limited, but metal, silicon nitride, aluminum nitride, boron nitride and the like are preferable from the viewpoint of heat dissipation. When using a metal substrate, the substrate may also be used as a counter electrode. Pt was used as a counter electrode also serving as a metal substrate. A hole transport layer, a light emitting layer, and an electron transport layer were laminated in the same manner as described in Example 1. As the material of each layer, known materials can be used, and the materials shown in Example 1 are exemplified. The light emitting layer may be a single layer or a stack of red, green and blue light emitters depending on the application. Next, an ITO film was formed by the method shown in Example 1 to obtain a conductive transparent electrode. Since the ITO film is formed by sputtering with Xe plasma having a low electron temperature, damage due to the plasma is not observed in the lower organic layer and the formed ITO film, and high-quality film formation can be performed at a low temperature. It was. Silicon nitride was formed by the method shown in Example 1 so as to cover the thus obtained top emission type organic EL device, and an insulating protective film serving also as a heat dissipation layer was obtained. The thickness of the insulating protective film was 50 nm. Silicon nitride has a high thermal conductivity of 80 W / (m · K), and a dense thin film can be formed by microwave-excited plasma, so that the thermal resistance can be sufficiently reduced and the temperature rise of the device is suppressed. Therefore, it functions sufficiently as a heat dissipation layer while being a protective layer. If a metal is used as the substrate and silicon nitride is used as the insulating protective layer, sufficient heat dissipation can be obtained. However, a separate heat dissipation layer may be used for efficient heat dissipation. The transparent heat dissipation layer used for the top emission type is not particularly limited as long as it has a high thermal conductivity and is a transparent material, and examples thereof include ITO. When the luminance half life of the organic EL element thus completed was measured, it was 9000 hours, which was 3000 hours in the past, and the effect of the protective layer was confirmed.
[0031]
(Example 3)
A display device according to Embodiment 3 of the present invention will be described with reference to FIG. FIGS. 3A and 3B are a cross-sectional view and a plan view showing some pixels of a bottom emission type passive matrix organic EL display device, on a transparent substrate, a conductive transparent electrode, and a conductive transparent electrode. As an organic layer to be formed, an electron transport layer, a light emitting layer, a hole transport layer, a counter electrode formed on the organic layer, a protective layer formed so as to directly or indirectly cover the light emitting layer, and a heat dissipation layer It consists of. Since the bottom emission type organic EL display element shown in Example 1 is arranged in a matrix, the element selected by the conductive transparent electrode and the counter electrode emits light. The conductive transparent electrode and the counter electrode are patterned in a matrix, and a plurality of elements are arranged. As the protective film, silicon nitride, aluminum nitride, boron nitride and the like are preferable from the viewpoint of insulation between different counter electrodes. In this example, silicon nitride formed by the method described in Example 1 was used. Since the elements shown in Example 1 are arranged on a matrix, the same effect as that of Example 1 can be obtained while easily configuring a display device, and the luminance half life of the element is improved by a dense and thin protective layer. As a result of the measurement, the luminance half life, which was 2000 hours in the past, was 6000 hours.
[0032]
Example 4
A display device according to Embodiment 4 of the present invention will be described with reference to FIG. 4A and 4B are a cross-sectional view and a plan view showing some pixels of a top emission type passive matrix organic EL display device. A substrate, a counter electrode facing the conductive transparent electrode, an organic layer formed on the counter electrode, a hole transport layer, a light emitting layer, an electron transport layer, and a conductive transparent electrode formed on the organic layer Since the top emission type organic EL display element shown in Example 2 is arranged in a matrix, the protective layer is formed so as to directly or indirectly cover the light emitting layer and the heat dissipation layer. The element selected by the conductive transparent electrode and the counter electrode emits light. In order to select an element that emits light between the counter electrode and the conductive transparent electrode disposed on the substrate, the substrate is insulative, and a glass or quartz substrate, a silicon nitride substrate, an aluminum nitride substrate, a boron nitride substrate, or the like is preferable. From the viewpoint of heat dissipation, a silicon nitride substrate, an aluminum nitride substrate, a boron nitride substrate, or the like with high thermal conductivity is more preferable. In this example, silicon nitride formed by the method described in Example 1 was used.
[0033]
The conductive transparent electrode and the counter electrode are patterned in a matrix, and a plurality of elements are arranged. The same effect as in Example 2 is obtained, and the luminance half life of the device is improved by the dense and thin protective layer. As a result of the measurement, the luminance half life, which was 3000 hours in the past, was 9000 hours.
[0034]
(Example 5)
A display device according to Embodiment 5 of the present invention will be described with reference to FIG. FIGS. 5A and 5B are a cross-sectional view and a plan view showing some pixels of the bottom emission type active matrix organic EL display device. A substrate, a plurality of gate wirings, a plurality of signal lines intersecting the gate wirings, a switching element installed near the intersection of the gate wirings and the signal lines, and a conductive transparent pixel electrode connected to the switching elements, The organic layer formed on the transparent pixel electrode includes an electron transport layer, a light emitting layer, a hole transport layer, a counter electrode formed on the organic film so as to face the transparent pixel electrode, and at least an organic layer. The protective layer is formed so as to cover the protective layer directly or indirectly, and the heat dissipation layer is formed so as to be in contact with the protective layer. In the organic layer, an electron transport layer, a light emitting layer, and a hole transport layer are formed from the side close to the transparent pixel electrode.
[0035]
The switching element is preferably a TFT element or an MIM element that can control ON / OFF of the current, and the TFT element is preferable in terms of controllability of the luminance of the organic EL element.
[0036]
Although the TFT element depends on the specifications of the display device, a known amorphous TFT or polysilicon TFT can be suitably used.
[0037]
A method for manufacturing the active matrix organic EL display device according to the fifth embodiment will be described next. First, Al was sputtered to a thickness of 300 nm on a cleaned glass substrate. In sputtering, Ar, Kr, and Xe gases can be preferably used. However, when Xe is used, since the electron collision cross section is large and the electron temperature is low, damage to the deposited Al due to plasma is suppressed, which is more preferable. It is. Next, the deposited Al was patterned by photolithography to form gate wirings and gate electrodes. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, the substrate temperature was 200 ° C., Ar: N 2: H 2: SiH 4 = 80: 18: 1.5: 0.5, and silicon nitride was A film having a thickness of 300 nm was formed as a gate insulating film. By setting the substrate temperature to 200 ° C., high-quality silicon nitride that can be used as a gate insulating film and has high withstand voltage and low interface state density could be formed. Next, using the same apparatus, a 50 nm amorphous silicon film is formed at a substrate temperature of 200 ° C. and a volume ratio of Ar: SiH 4 = 95: 5, and then n + amorphous silicon is formed at Ar: SiH 4: PH 3 = 94: 5: 1. A 30 nm film was formed. An element region was formed by patterning the deposited amorphous silicon and n + silicon laminated film by a photolithography method. Next, a signal line, a signal line electrode, and a conductive transparent pixel electrode were obtained by forming an ITO film with a thickness of 350 nm by the same method as shown in Example 1 and patterning the film by a photolithography method. Next, using the patterned ITO film as a mask, the n + amorphous silicon layer was etched by a known ion etching method, thereby forming a channel portion isolation region of the TFT. By forming a silicon nitride film at room temperature using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, and patterning the organic EL element region by a photolithography method, a protective film for the TFT channel separation portion and an organic film It was set as the insulating layer which prevents the short circuit with the electroconductive transparent electrode of an EL element, and a counter electrode. Next, by the method described in Example 1, as an organic layer, an electron transport layer, a light-emitting layer, and a hole transport layer are continuously formed, and by a Pt sputtering apparatus used for gate wiring formation without being exposed to the atmosphere, Pt was deposited using Xe plasma having a low electron temperature to form a counter electrode. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, 50 nm of silicon nitride was formed at room temperature to form a protective layer. The protective layer has a high thermal conductivity of 80 W / (m · K), and is sufficiently thin. Therefore, the thermal resistance is small, and the protective layer can also serve as a heat dissipation layer alone. A heat dissipation layer may be provided separately. In this example, Al was formed by using an Xe plasma having a low electron temperature by using an Al sputtering apparatus used for forming the gate wiring to form a heat dissipation layer.
[0038]
The bottom emission type active matrix organic EL display device thus obtained can emit light with high efficiency because the buffer layer and the hole injection layer are not required due to the high work function of Pt. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 2000 hours was improved to 6000 hours.
[0039]
(Example 6)
Example 6 of the present invention shown in FIGS. 6A and 6B has a configuration in which a planarizing film is formed on a TFT, and thereafter an organic EL element is formed. By doing in this way, since an organic EL element can be formed in a flat surface, a manufacturing yield improves. Further, since the organic EL layer is formed in a layer different from the signal line layer, the pixel electrode can be extended and arranged on the signal wiring, and the area of the light emitting element can be increased. Further, since the signal line can be formed of a material different from that of the pixel electrode, it is not necessary to use a conductive transparent material, wiring resistance when the display device is enlarged can be reduced, and display gradation can be increased. . The bottom emission type active matrix organic EL display device of Example 6 is formed as follows. First, gate lines, TFT elements, and signal lines are formed by the method described in Example 5. The signal line was obtained by forming a 300 nm Al film by sputtering using the Xe gas shown in Example 6 and patterning by photolithography. Next, a photosensitive transparent resin was applied by spin coating, exposed and developed, and then dried at 150 ° C. for 30 minutes to obtain a flattened film. By the exposure and development process, a connection hole for connecting the pixel side electrode of the TFT and the organic EL element is provided in the planarizing film. Examples of the photosensitive transparent resin include an acrylic resin, a polyolefin resin, and an alicyclic olefin resin, but an alicyclic olefin resin that has low moisture content and release and excellent transparency is preferable. An alicyclic olefin resin was used. Next, an ITO film was formed by the method described in Example 1, and patterned by photolithography to obtain a conductive transparent pixel electrode. Subsequently, an electron transport layer, a light-emitting layer, and a hole transport layer were continuously formed by the method shown in Example 1, and Pt was formed by the sputtering method using the Xe plasma shown in Example 1 as a counter electrode. The light emitting layer may be formed by arbitrarily stacking materials that emit red, green, and blue light, or may be formed in a single layer and arranged on a matrix. Next, by the method shown in Example 1, a silicon nitride film was deposited to a thickness of 50 nm to form a protective film. Since the silicon nitride film has a high thermal conductivity and is sufficiently thin, it becomes a protective layer that also serves as a heat dissipation layer in this state. However, in order to perform heat dissipation more efficiently, the Xe plasma shown in Example 1 is used. Al was deposited by a conventional sputtering method to form a heat dissipation layer.
[0040]
As a result of measuring the luminance half-life of the display device thus obtained, the lifetime of 2000 hours was 6000 hours, and the light emitting area was 80% of the conventional device area ratio of 60%. As a result, the surface brightness increased by 20%. Since the organic layer is formed on the planarization film, there is no occurrence of film formation failure and the manufacturing yield is improved.
[0041]
(Example 7)
A display device according to Example 7 of the present invention will be described with reference to FIG. FIGS. 7A and 7B are a cross-sectional view and a plan view showing some pixels of the top emission type active matrix organic EL display device of this embodiment. A substrate, a plurality of gate wirings, a plurality of signal lines intersecting the gate wirings, a switching element installed near an intersection of the gate wirings and the signal lines, a counter electrode connected to the switching elements, and the counter As an organic layer formed on the electrode, a hole transport layer, a light emitting layer, an electron transport layer, a conductive transparent electrode formed on the organic film so as to face the counter electrode, and at least the organic layer directly or It consists of a protective layer formed so as to cover indirectly and a heat dissipation layer formed so as to be in contact with the protective layer. In the organic layer, a hole transport layer, a light emitting layer, and an electron transport layer are formed from the side close to the transparent pixel electrode.
[0042]
The switching element is preferably a TFT element or an MIM element that can control ON / OFF of the current, and the TFT element is preferable in terms of controllability of the luminance of the organic EL element.
[0043]
Although the TFT element depends on the specifications of the display device, a known amorphous TFT or polysilicon TFT can be suitably used.
[0044]
Next, a method for manufacturing the active matrix organic EL display device according to the seventh embodiment will be described. First, Al was sputtered to a thickness of 300 nm on a cleaned glass substrate. In sputtering, Ar, Kr, and Xe gases can be preferably used. However, when Xe is used, since the electron collision cross section is large and the electron temperature is low, damage to the deposited Al due to plasma is suppressed, which is more preferable. It is. Next, the deposited Al was patterned by photolithography to form gate wirings and gate electrodes. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, the substrate temperature was 200 ° C., Ar: N 2: H 2: SiH 4 = 80: 18: 1.5: 0.5, and silicon nitride was A film having a thickness of 300 nm was formed as a gate insulating film. By setting the substrate temperature to 200 ° C., high-quality silicon nitride that can be used as a gate insulating film and has high withstand voltage and low interface state density could be formed. Next, using the same apparatus, a 50 nm amorphous silicon film is formed at a substrate temperature of 200 ° C. and a volume ratio of Ar: SiH 4 = 95: 5, and then n + amorphous silicon is formed at Ar: SiH 4: PH 3 = 94: 5: 1. A 30 nm film was formed. An element region was formed by patterning the deposited amorphous silicon and n + silicon laminated film by a photolithography method. Next, a photoresist was applied, exposed and developed to form a resist mask in a region other than the signal line, the signal line electrode, and the counter electrode portion. Subsequently, a Pt film is formed using Xe plasma without damaging the element and patterned by the lift-off method in the same manner as shown in the first embodiment, so that the signal line and the signal line electrode are opposed to each other. An electrode was obtained. Next, using the patterned Pt film as a mask, the n + amorphous silicon layer was etched by a known ion etching method, thereby forming a channel portion isolation region of the TFT. By forming a silicon nitride film at room temperature using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, and patterning the organic EL element region by a photolithography method, a protective film for the TFT channel separation portion and an organic film It was set as the insulating layer which prevents the short circuit with the electroconductive transparent electrode of an EL element, and a counter electrode. Next, a hole transport layer, a light emitting layer, and an electron transport layer are continuously formed as an organic layer by the method described in Example 1, and the ITO film is formed by the method described in Example 1 without exposing to the atmosphere. Was formed into a conductive transparent electrode. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, 50 nm of silicon nitride was formed at room temperature to form a protective layer. The protective layer has a high thermal conductivity of 80 W / (m · K), and is sufficiently thin. Therefore, the thermal resistance is small, and the protective layer can also serve as a heat dissipation layer alone. A heat dissipation layer may be provided separately. The transparent heat dissipation layer used for the top emission type is not particularly limited as long as it has a high thermal conductivity and is transparent, and examples thereof include ITO.
[0045]
The top emission type active matrix organic EL display device thus obtained can emit light with high efficiency since the buffer layer and the hole injection layer are not required due to the high work function of the Pt film. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 3000 hours was improved to 9000 hours.
[0046]
(Example 8)
Example 8 shown in FIGS. 8A and 8B has a configuration in which a planarizing film is formed on a TFT, and an organic EL element is formed thereafter. By doing in this way, since an organic EL element can be formed in a flat surface, a manufacturing yield improves. Further, since the organic EL layer is formed in a layer different from the signal line layer, the pixel electrode can be extended and arranged on the signal wiring, and the area of the light emitting element can be increased. Further, since the signal line can be formed of a material different from that of the pixel electrode, it is not necessary to use a conductive transparent material, wiring resistance when the display device is enlarged can be reduced, and display gradation can be increased. . The top emission type active matrix organic EL display device of Example 8 is formed as follows. First, gate lines, TFT elements, and signal lines are formed by the method described in Example 7. The signal line was obtained by forming a 300 nm Al film by sputtering using the Xe gas shown in Example 6 and patterning by photolithography. Next, a photosensitive transparent resin was applied by spin coating, exposed and developed, and then dried at 150 ° C. for 30 minutes to obtain a flattened film. By the exposure and development process, a connection hole for connecting the pixel side electrode of the TFT and the organic EL element is provided in the planarizing film. Examples of the photosensitive transparent resin include an acrylic resin, a polyolefin resin, and an alicyclic olefin resin, but an alicyclic olefin resin that has low moisture content and release and excellent transparency is preferable. An alicyclic olefin resin was used. Next, by the method described in Example 1, a Pt film was formed by sputtering using Xe plasma and patterned by a lift-off method to obtain a counter electrode. Subsequently, a hole transport layer, a light-emitting layer, and an electron transport layer are continuously formed by the method shown in Example 1, and an ITO film is formed by the method shown in Example 1 to obtain a conductive transparent pixel electrode. It was. The light emitting layer may be formed by arbitrarily stacking materials that emit red, green, and blue light, or may be formed in a single layer and arranged on a matrix. Next, by the method shown in Example 1, a silicon nitride film was deposited to a thickness of 50 nm to form a protective film. Since the silicon nitride film has a high thermal conductivity and is sufficiently thin, even in this state, it becomes a protective layer that also serves as a heat dissipation layer. However, a heat dissipation layer may be provided separately for more efficient heat dissipation. The transparent heat dissipation layer used for the top emission type is not particularly limited as long as it has a high thermal conductivity and is transparent, and examples thereof include ITO.
[0047]
As a result of measuring the luminance half-life of the display device thus obtained, the lifetime of 3000 hours is 9000 hours, and the light emitting area is 80% of the conventional device area ratio of 60%. As a result, the surface brightness increased by 20%. Since the organic layer is formed on the planarization film, there is no occurrence of film formation failure and the manufacturing yield is improved.
[0048]
Example 9
A display device according to Embodiment 9 of the present invention will be described with reference to FIG. FIGS. 9A and 9B are a cross-sectional view and a plan view showing some pixels of the bottom emission type active matrix organic EL display device of this embodiment. A substrate, a plurality of gate wirings, a plurality of signal lines intersecting the gate wirings, a switching element installed near the intersection of the gate wirings and the signal lines, and a conductive transparent pixel electrode connected to the switching elements, The organic layer formed on the transparent pixel electrode includes an electron transport layer, a light emitting layer, a hole transport layer, a counter electrode formed on the organic film so as to face the transparent pixel electrode, and at least an organic layer. The protective layer is formed so as to cover the protective layer directly or indirectly, and the heat dissipation layer is formed so as to be in contact with the protective layer. In the organic layer, an electron transport layer, a light emitting layer, and a hole transport layer are formed from the side close to the transparent pixel electrode.
[0049]
The switching element is preferably a TFT element or an MIM element that can control ON / OFF of the current, and the TFT element is preferable in terms of controllability of the luminance of the organic EL element.
[0050]
Although the TFT element depends on the specifications of the display device, a known amorphous TFT or polysilicon TFT can be suitably used.
[0051]
Next, a method for manufacturing the active matrix organic EL display device according to the ninth embodiment will be described. First, a high temperature of 13.56 MHz was applied from the substrate to the cleaned glass substrate by the two-stage shower plate microwave excitation plasma film forming apparatus used in Example 1, and the substrate temperature was 200 ° C. while performing ion irradiation. A polysilicon film having a volume ratio of Ar: SiH 4 = 95: 5 was formed to a thickness of 50 nm and patterned by a photolithography method to obtain a TFT element region. Next, using the same apparatus, a silicon nitride film was formed to a thickness of 300 nm at a substrate temperature of 200 ° C., Ar: N 2: H 2: SiH 4 = 80: 18: 1.5: 0.5, and used as a gate insulating film. By setting the substrate temperature to 200 ° C., high-quality silicon nitride that can be used as a gate insulating film and has high withstand voltage and low interface state density could be formed. Subsequently, 300 nm of sputtered Al was deposited. In sputtering, Ar, Kr, and Xe gases can be preferably used. However, when Xe is used, since the electron collision cross section is large and the electron temperature is low, damage to the deposited Al due to plasma is suppressed, which is more preferable. It is. Next, the deposited Al was patterned by photolithography to form gate wirings and gate electrodes. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, the substrate temperature was 200 ° C., Ar: N 2: H 2: SiH 4 = 80: 18: 1.5 using the same apparatus. : 0.5, and a silicon nitride film having a thickness of 300 nm was formed. A contact hole is formed in the formed silicon nitride by photolithography, an ITO film is formed to a thickness of 350 nm by the same method as shown in Example 1, and patterning is performed by photolithography. A line electrode and a conductive transparent pixel electrode were obtained. Next, by the method described in Example 1, as an organic layer, an electron transport layer, a light-emitting layer, and a hole transport layer are continuously formed, and by a Pt sputtering apparatus used for gate wiring formation without being exposed to the atmosphere, Pt was deposited using Xe plasma having a low electron temperature to form a counter electrode. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, 50 nm of silicon nitride was formed at room temperature to form a protective layer. The protective layer has a high thermal conductivity of 80 W / (m · K), and is sufficiently thin. Therefore, the thermal resistance is small, and the protective layer can also serve as a heat dissipation layer alone. A heat dissipation layer may be provided separately. In this example, Al was formed by using an Xe plasma having a low electron temperature by using an Al sputtering apparatus used for forming the gate wiring to form a heat dissipation layer.
[0052]
The bottom emission type active matrix organic EL display device thus obtained can emit light with high efficiency because the buffer layer and the hole injection layer are not required due to the high work function of Pt. Furthermore, since polysilicon is used as the TFT element, the current drive capability is improved, the controllability of the organic EL element is good, and high-quality display is possible. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 2000 hours was improved to 6000 hours.
[0053]
(Example 10)
Example 10 shown in FIGS. 10A and 10B has a configuration in which a planarizing film is formed on a TFT, and thereafter an organic EL element is formed. By doing in this way, since an organic EL element can be formed in a flat surface, a manufacturing yield improves. Further, since the organic EL layer is formed in a layer different from the signal line layer, the pixel electrode can be extended and arranged on the signal wiring, and the area of the light emitting element can be increased. Further, since the signal line can be formed of a material different from that of the pixel electrode, it is not necessary to use a conductive transparent material, wiring resistance when the display device is enlarged can be reduced, and display gradation can be increased. . The bottom emission type active matrix organic EL display device of Example 10 is formed as follows. First, TFT elements, gate lines, and signal lines are formed by the method described in Example 9. The signal line was obtained by forming a 300 nm Al film by sputtering using the Xe gas shown in Example 6 and patterning by photolithography. Next, a photosensitive transparent resin was applied by spin coating, exposed and developed, and then dried at 150 ° C. for 30 minutes to obtain a flattened film. By the exposure and development process, a connection hole for connecting the pixel side electrode of the TFT and the organic EL element is provided in the planarizing film. Examples of the photosensitive transparent resin include an acrylic resin, a polyolefin resin, and an alicyclic olefin resin, but an alicyclic olefin resin that has low moisture content and release and excellent transparency is preferable. An alicyclic olefin resin was used. Next, an ITO film was formed by the method described in Example 1, and patterned by photolithography to obtain a conductive transparent pixel electrode. Subsequently, an electron transport layer, a light-emitting layer, and a hole transport layer were continuously formed by the method shown in Example 1, and Pt was formed by the sputtering method using the Xe plasma shown in Example 1 as a counter electrode. The light emitting layer may be formed by arbitrarily stacking materials that emit red, green, and blue light, or may be formed in a single layer and arranged on a matrix. Next, by the method shown in Example 1, a silicon nitride film was deposited to a thickness of 50 nm to form a protective film. Since the silicon nitride film has a high thermal conductivity and is sufficiently thin, it becomes a protective layer that also serves as a heat dissipation layer in this state. However, in order to perform heat dissipation more efficiently, the Xe plasma shown in Example 1 is used. Al was deposited by a conventional sputtering method to form a heat dissipation layer.
[0054]
As a result of measuring the luminance half-life of the display device thus obtained, the lifetime of 2000 hours was 6000 hours, and the light emitting area was 80% of the conventional device area ratio of 60%. As a result, the surface brightness increased by 20%. Since the organic layer is formed on the planarization film, there is no occurrence of film formation failure and the manufacturing yield is improved. Furthermore, since polysilicon is used as the TFT element, the current drive capability is improved, the controllability of the organic EL element is good, and high-quality display is possible.
[0055]
(Example 11)
In the bottom emission type active matrix display device shown in Example 9, by changing the formation order of the counter electrode and the conductive transparent electrode, the hole transport layer and the electron transport layer in the same manner as in the method of Example 7, A top emission type active matrix display device can be obtained.
[0056]
FIGS. 11A and 11B are a cross-sectional view and a plan view of the top emission type active matrix display element formed thereby, and the substrate may be any surface as long as it has insulating properties. A metal substrate on which a film was formed was used. The polysilicon TFT shown in Example 10 was used as the TFT element.
[0057]
The bottom emission type active matrix organic EL display device thus obtained can emit light with high efficiency because the buffer layer and the hole injection layer are not necessary due to the high work function of the Pt film. Furthermore, since polysilicon is used as the TFT element, the current drive capability is improved, the controllability of the organic EL element is good, and high-quality display is possible. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 3000 hours was improved to 9000 hours.
[0058]
(Example 12)
In the bottom emission type active matrix display device shown in Example 10, by changing the formation order of the counter electrode and the conductive transparent electrode, the hole transport layer and the electron transport layer in the same manner as in Example 8, A top emission type active matrix display device can be obtained.
[0059]
12A and 12B are a cross-sectional view and a plan view of the top emission type active matrix display element formed thereby, and the substrate is not limited as long as the surface has an insulating property. A metal substrate on which a film was formed was used. A polysilicon TFT shown in Example 11 was used as the TFT element.
[0060]
The bottom emission type active matrix organic EL display device thus obtained can emit light with high efficiency because the buffer layer and the hole injection layer are not necessary due to the high work function of the Pt film. Furthermore, since polysilicon is used as the TFT element, the current drive capability is improved, the controllability of the organic EL element is good, and high-quality display is possible. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 3000 hours was improved to 9000 hours. The light emitting area was 80% of the conventional element area ratio of 60%, and the surface luminance was increased by 20%. Furthermore, since the organic layer is formed on the planarization film, there is no occurrence of film formation failure and the manufacturing yield is improved.
[0061]
(Example 13)
The structure of the TFT in Example 13 and the display element using the TFT will be described with reference to FIG. FIGS. 13A and 13B are a cross-sectional view and a plan view of the bottom emission type organic EL display device according to the present embodiment, in which a substrate, a plurality of gate lines, a plurality of signal lines intersecting the gate lines, A switching element installed near the intersection of the gate wiring and the signal line, a conductive transparent pixel electrode connected to the switching element, and an electron transport layer and a light emitting layer as an organic layer formed on the transparent pixel electrode A layer, a hole transport layer, a counter electrode formed on the organic film so as to face the transparent pixel electrode, a protective layer formed to cover at least the organic layer directly or indirectly, and in contact with the protective layer The heat dissipation layer is formed as described above. In the organic layer, an electron transport layer, a light emitting layer, and a hole transport layer are formed from the side close to the transparent pixel electrode.
[0062]
The TFT element and the display device of this example are formed as follows. First, a photosensitive transparent resin is applied to a cleaned substrate at 350 nm, exposed and developed to provide openings in the gate line and the gate electrode region. Next, a metal film is formed in the opening with a thickness equivalent to that of the photosensitive transparent resin by a screen printing method, an ink jet printing method, a plating method, or the like, and a gate wiring and a gate electrode are obtained. The material of the metal film can be appropriately selected depending on the production method, but Au, Cu, Ag, Al, etc. having low resistivity are preferable. In this embodiment, Ag is selected as the wiring material. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, the substrate temperature was 200 ° C., Ar: N 2: H 2: SiH 4 = 80: 18: 1.5: 0.5, and silicon nitride was A film having a thickness of 300 nm was formed as a gate insulating film. By setting the substrate temperature to 200 ° C., high-quality silicon nitride that can be used as a gate insulating film and has high withstand voltage and low interface state density could be formed. Next, using the same apparatus, a 50 nm amorphous silicon film is formed at a substrate temperature of 200 ° C. and a volume ratio of Ar: SiH 4 = 95: 5, and then n + amorphous silicon is formed at Ar: SiH 4: PH 3 = 94: 5: 1. A 30 nm film was formed. An element region was formed by patterning the deposited amorphous silicon and n + silicon laminated film by a photolithography method. Next, a signal line, a signal line electrode, and a conductive transparent pixel electrode were obtained by forming an ITO film with a thickness of 350 nm by the same method as shown in Example 1 and patterning the film by a photolithography method. Next, using the patterned ITO film as a mask, the n + amorphous silicon layer was etched by a known ion etching method, thereby forming a channel portion isolation region of the TFT. By forming a silicon nitride film at room temperature using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, and patterning the organic EL element region by a photolithography method, a protective film for the TFT channel separation portion and an organic film It was set as the insulating layer which prevents the short circuit with the electroconductive transparent electrode of an EL element, and a counter electrode. Next, by the method described in Example 1, as an organic layer, an electron transport layer, a light-emitting layer, and a hole transport layer are continuously formed, and by a Pt sputtering apparatus used for gate wiring formation without being exposed to the atmosphere, Pt was deposited using Xe plasma having a low electron temperature to form a counter electrode. Next, using the two-stage shower plate microwave plasma film forming apparatus used in Example 1, 50 nm of silicon nitride was formed at room temperature to form a protective layer. The protective layer has a high thermal conductivity of 80 W / (m · K), and is sufficiently thin. Therefore, the thermal resistance is small, and the protective layer can also serve as a heat dissipation layer alone. A heat dissipation layer may be provided separately. In this example, Al was formed by using an Xe plasma having a low electron temperature by using an Al sputtering apparatus used for forming the gate wiring to form a heat dissipation layer.
[0063]
The bottom emission type active matrix organic EL display device thus obtained can emit light with high efficiency because the buffer layer and the hole injection layer are not necessary due to the high work function of the Pt film. Furthermore, since the thermal conductivity is high and a thin protective layer is used, an increase in the temperature of the element can be suppressed while sufficiently fulfilling the function of the protective layer, so that the element life can be significantly improved. As a result of measuring the luminance half life of the display device shown in this example, what was conventionally 2000 hours was improved to 6000 hours. Furthermore, since the gate electrode is embedded, the semiconductor layer constituting the TFT can be formed on a smooth surface and the current variation of the TFT can be suppressed, so that not only the display quality is improved, but also the organic due to the current variation. Variations in the lifetime of the EL element can be suppressed.
[0064]
According to the method shown in Example 9, a polysilicon layer may be used instead of the amorphous silicon layer. In this case, the current drive capability of the TFT is improved, so that the light emission controllability of the organic EL element is improved and the display is improved. The quality can be improved.
[0065]
Furthermore, as shown in Example 7 and Example 11, a top emission type configuration may be obtained by replacing the counter electrode and the conductive transparent electrode, and the hole transport layer and the electron transport layer, respectively. The light extraction efficiency from the EL element can be improved.
[0066]
Furthermore, as shown in Example 6, Example 8, Example 10, and Example 12, a planarization film may be formed on the TFT and an organic EL element may be formed thereon, and in this case, organic Since the EL layer is formed flat, defects in film formation and the like are suppressed, so that the element lifetime is improved, and further, variation in luminance and variation in lifetime can be suppressed.
[0067]
(Example 14)
The display element in Example 14 will be described with reference to FIG. FIG. 14 is a cross-sectional view showing an example of the heat dissipation layer of the present example, and shows an example of the heat dissipation layer of the display element in Example 1. The heat dissipation layer of this embodiment has a comb-shaped pattern disposed on the surface, thereby improving the area in contact with an external layer, for example, the air layer, and improving the heat dissipation efficiency. Thus, by using the comb-shaped electrode, the heat radiation efficiency was improved, and the luminance half life of the device was improved by 20%. In this embodiment, a comb-shaped structure is used. However, any structure that can increase the contact area with an external layer may be used. Further, when the heat dissipation layer does not serve as the protective layer, it is not necessary to cover the entire surface of the element, and at least the light emitting region may be covered. Another heat radiating means such as a heat sink or a Peltier element may be provided outside the element by connecting adjacent heat radiating layers.
[0068]
Furthermore, in the case of the top emission type, unevenness of about several nanometers to several tens of nanometers, which is sufficiently shorter than the wavelength of light, may be provided, and a matrix shape having a height of several microns in accordance with the shape of the black matrix. In this case, the heat dissipation effect can be improved by several percent.
[0069]
In the above embodiment, Pt is used as the counter electrode. However, the present invention is not limited to this, and a high work function material such as Co, Ni, Rh, Pd, Ir, or Au may be used, and at least one of these may be used alone. Or it can be used in alloys.
[0070]
【The invention's effect】
According to the present invention, since a high work function material such as Co, Ni, Rh, Pd, Ir, Pt, or Au is used as the anode-side counter electrode facing the transparent electrode, the hole injection efficiency in the organic EL element is improved. In addition, since a hole injection layer and a buffer layer that are generally required are not required, the light emission efficiency is improved, and thus the luminance can be improved. Furthermore, since the energy barrier to the light emitting layer is reduced, the amount of heat generation is reduced, and the lifetime of the organic EL element can be improved. Furthermore, according to the present invention, since a nitride is used as a protective layer of the organic EL light emitting layer, a stable protective layer having high thermal conductivity and no permeation of moisture or oxidizing gas can be obtained even in a thin film. Since the heat generated in the light emitting layer can be efficiently emitted to the outside, the lifetime of the organic EL element can be improved. According to the display element of the present invention, since the nitride protective film is formed by low-temperature vapor phase growth, damage to the organic EL layer can be prevented. Furthermore, according to the display element of the present invention, since an organic EL element can be formed on a flat structure, film formation defects and the like can be reduced, and the life of the element can be improved. Further, according to the display element of the present invention, since the organic EL electrode and the signal line can be arranged in separate wiring layers, the display area can be increased and the screen luminance can be improved. Furthermore, according to the display element of the present invention, since the electrode of the organic EL and the signal line can be arranged in different wiring layers, the signal line and the electrode of the organic EL element can be made of different materials, thereby reducing the electric resistance of the signal line. And a large display device can be formed. Furthermore, according to the display device of the present invention, since a TFT having a buried gate structure can be used, the semiconductor region of the TFT element can be made substantially flat, and the current variation of the TFT element can be reduced. It is possible to suppress the variation in the lifetime of the organic EL element while realizing easy display.
[Brief description of the drawings]
FIGS. 1A and 1B are a cross-sectional view and a plan view showing the structure of a bottom emission type passive display device according to Example 1 of the invention. FIGS.
FIGS. 2A and 2B are a cross-sectional view and a plan view showing the structure of a top emission type passive display element according to Example 2 of the invention. FIGS.
FIGS. 3A and 3B are a cross-sectional view and a plan view showing some pixels of a bottom emission type passive matrix organic EL display device according to Example 3 of the present invention. FIGS.
FIGS. 4A and 4B are a cross-sectional view and a plan view showing some pixels of a top emission type passive matrix organic EL display device according to Example 4 of the present invention. FIGS.
FIGS. 5A and 5B are a cross-sectional view and a plan view showing some pixels of a bottom emission type active matrix organic EL display device according to Embodiment 5 of the present invention. FIGS.
6A and 6B are a cross-sectional view and a plan view showing a part of an organic EL element according to Example 6 of the present invention.
FIGS. 7A and 7B are a cross-sectional view and a plan view showing some pixels of a top emission type active matrix organic EL display device according to Example 7 of the present invention. FIGS.
FIGS. 8A and 8B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Example 8 of the present invention.
FIGS. 9A and 9B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Embodiment 9 of the present invention. FIGS.
FIGS. 10A and 10B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Example 10 of the invention. FIGS.
FIGS. 11A and 11B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Example 11 of the invention. FIGS.
FIGS. 12A and 12B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Embodiment 12 of the present invention. FIGS.
FIGS. 13A and 13B are a cross-sectional view and a plan view showing a part of an organic EL display device according to Example 13 of the invention. FIGS.
FIG. 14 is a cross-sectional view showing an example of a heat dissipation layer according to Example 14 of the present invention.
FIG. 15 is a diagram showing a schematic configuration of a two-stage shower plate type microwave-excited high-density plasma film forming apparatus used in the embodiment described above.

Claims (2)

  Forming a transparent conductive electrode on a transparent substrate; providing an electron transport layer on the transparent conductive electrode; forming a light emitting layer on the electron transport layer; providing a hole transport layer on the light emitting layer; A counter electrode is provided on the transport layer, and the counter electrode contains Xe, prevents plasma damage to the hole transport layer, and covers silicon nitride, titanium nitride, tantalum nitride, and aluminum nitride so as to cover the light emitting layer. A nitride film made of at least one is formed with a thickness of 100 nm or less, the nitride film is formed by low-temperature vapor deposition using microwave-excited plasma, and low-temperature vapor-phase growth using the microwave-excited plasma is A gas containing at least one of Ar, Kr and Xe is introduced from the upper shower plate, and a material gas for the nitride film is introduced from the lower shower plate. Method of fabricating a light emitting device which is a low-temperature vapor deposition performed in a plasma processing apparatus having a two-stage shower plate being.   A counter electrode is formed on the substrate, a hole transport layer is provided on the counter electrode, a light-emitting layer is formed on the hole transport layer, an electron transport layer is provided on the light-emitting layer, and transparent on the electron transport layer A conductive electrode is provided, and the transparent conductive electrode contains Xe, prevents plasma damage to the electron transport layer, and covers at least silicon nitride, titanium nitride, tantalum nitride, and aluminum nitride so as to cover the light emitting layer. A single nitride film is formed with a thickness of 100 nm or less, the nitride film is formed by low-temperature vapor deposition using microwave-excited plasma, and low-temperature vapor-phase growth using the microwave-excited plasma is: A gas containing at least one of Ar, Kr and Xe is introduced from the upper shower plate, and a material gas for the nitride film is introduced from the lower shower plate. Method of fabricating a light emitting device which is a low-temperature vapor deposition performed in a plasma processing apparatus having a two-stage shower plate.

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