JP2005100992A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device of an active matrix type, since characteristic values such as a threshold value fluctuate due to contaminated alkali metal in the case of a TFT formed with the use of a semiconductor film. <P>SOLUTION: An insulating layer each with a blocking property against the alkali metal is provided at an upper layer side and a lower layer side of a semiconductor layer constituting the TFT, an insulating layer each with a blocking property against oxygen and hydrogen is provided at an upper layer side and a lower layer side of a light-emitting element constituted with a layer of an organic compound contained, and a thin-film transistor and the light-emitting element are integrated with an interposition of an inter-layer insulating film. Thus, elements with different characteristics against impurities are combined to complete the light-emitting device without interference with each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light-emitting body capable of obtaining luminescence (Electro Luminescence) generated by applying an electric field, and a light-emitting device using the light-emitting body. In particular, the present invention relates to a light emitting device using an organic compound as a light emitter.

  A display device using liquid crystal has a structure in which a backlight or a front light is used as a representative form and an image is displayed by the light. The liquid crystal display device has been adopted as an image display means in various electronic devices, but has a drawback in the structure that the viewing angle is narrow. On the other hand, a display device using a light emitter that can obtain electroluminescence has been attracting attention as a next-generation display device because of its wide viewing angle and excellent visibility.

  A light-emitting element using an organic compound as a light emitter (hereinafter referred to as an organic light-emitting element) has a structure of a hole injection layer, a hole transport layer, a light-emitting layer formed of an organic compound between a cathode and an anode, It has a structure in which an electron transport layer and an electron injection layer are properly combined. Here, the hole injection layer and the hole transport layer are distinguished from each other, but these are the same in the sense that the hole transport property (hole mobility) is a particularly important characteristic. For the sake of convenience, the hole injection layer is a layer in contact with the anode, and the layer in contact with the light emitting layer is called a hole transport layer. The layer in contact with the cathode is called an electron injection layer, and the layer in contact with the light emitting layer is called an electron transport layer. The light emitting layer may also serve as an electron transport layer, and is also referred to as a light emitting electron transport layer. A light-emitting element formed by combining these layers exhibits rectification characteristics and has a structure similar to that of a diode.

The light emission mechanism by electroluminescence is such that electrons injected from the cathode and holes injected from the anode recombine in a layer made of a phosphor (light emitting layer) to form an exciton, and the exciton returns to the ground state. It is considered as a phenomenon that emits light when returning. Electroluminescence includes fluorescence and phosphorescence, which are understood as emission from a singlet state (fluorescence) in an excited state and emission from a triplet state (phosphorescence). Since the luminance due to light emission ranges from several thousand to several tens of thousands cd / m ² , it is considered that in principle it can be applied to a display device or the like. However, on the other hand, various deterioration phenomena exist and remain as problems that impede practical use.

  As a cause of deterioration of a light-emitting body or an organic light-emitting element composed of an organic compound, (1) chemical deterioration of the organic compound (via an excited state), (2) melting of the organic compound due to heat generated during driving, (3) There are considered five types: dielectric breakdown due to macro defects (4) degradation of the electrode or electrode / organic layer interface, and (5) degradation due to instability in the amorphous structure of the organic compound.

  Said (1)-(3) deteriorates by driving an organic light emitting element. Heat generation inevitably occurs when the current in the element is converted to Joule heat. It is considered that the organic compound melts when its melting point or glass transition temperature is low. In addition, due to the presence of pinholes and cracks, the electric field concentrates on the portions, causing dielectric breakdown. (4) and (5) deteriorate even when stored at room temperature. (4) is known as a dark spot and is caused by oxidation of the cathode and reaction with moisture. In (5), the organic compounds used in the organic light-emitting device are all amorphous materials, and it is considered that there are few that can stably store the amorphous structure by crystallization due to long-term storage, aging, and heat generation. .

  Dark spots have been considerably suppressed by the improvement of sealing technology, but actual deterioration is caused by a combination of the above factors, and it is difficult to understand them uniformly. A typical sealing technique is known as a method of sealing an organic light-emitting element formed on a substrate with a sealing material and providing a desiccant in the space. However, it is considered that the phenomenon in which the emission luminance decreases with a decrease in the current flowing through the organic light emitting element when a constant voltage is continuously applied is derived from the physical properties of the organic compound.

As organic compounds for forming an organic light emitting device, both low molecular organic compounds and high molecular organic compounds are known. An example of a low molecular weight organic compound is α-NPD (4,4′-bis- [N- (naphthyl) -N-phenyl-amino]), which is a copper phthalocyanine (CuPc) aromatic amine material as a hole injection layer. Biphenyl), MTDATA (4,4 ', 4 "-tris (N-3-methylphenyl-N-phenyl-amino) triphenylamine), tris-8-quinolinolato aluminum complex (Alq ₃ ) as the light emitting layer, etc. As the polymer organic light emitting material, polyaniline, polythiophene derivative (PEDOT) and the like are known.

  From the viewpoint of the diversity of materials, it is said that low molecular weight organic compounds produced by vapor deposition have a great variety compared to high molecular weight organic materials. However, in any case, organic compounds that are purely composed only of basic structural units are rare, and different types of bonds and impurities are mixed in during the production process, and various additives such as pigments may be added. . These materials include materials that deteriorate due to moisture and materials that are easily oxidized. Moisture, oxygen, etc. can be easily mixed from the atmosphere, and handling is necessary.

It is known that when an organic compound undergoes photodegradation, the chemical bond changes to a structure containing double bonds and oxygen (—OH, —OOH,> C═O, —COOH, etc.). Therefore, when an organic compound is placed in an atmosphere containing oxygen, or when oxygen or H ₂ O is contained as an impurity in an organic compound, it is considered that the bonding state changes to promote deterioration.

  As seen in diodes that are one of the semiconductor elements, in semiconductor elements with semiconductor junctions, impurities caused by oxygen form localized levels in the forbidden band, reducing junction leakage and carrier lifetime. It is known that the characteristics of the semiconductor element are significantly reduced.

FIG. 11 shows the depth distribution of oxygen (O), nitrogen (N), hydrogen (H), silicon (Si), and copper (Cu) in an organic light-emitting device measured by secondary ion mass separation (SIMS). It is a graph to show. The structure of the sample used for the measurement was tris-8-quinolinolato aluminum complex (Alq ₃ ) / carbazole-based material (Ir (ppy) ₃ + CBP) / copper phthalocyanine (CuPc) / oxide conductive material (ITO) / It is a glass substrate. Alq ₃ contains oxygen in the molecule as represented by the following chemical formula (Formula 1).

On the other hand, Ir (ppy) ₃ + CBP and CuPc represented by the following chemical formulas (Chemical Formula 2 and Chemical Formula 3) have a structure in which oxygen is not included in the molecule.

In the concentration distribution of each element shown in FIG. 11, the oxygen concentration is high in the Alq ₃ region and the ITO region. On the other hand, the oxygen concentration is decreased in the Ir (ppy) ₃ + CBP and CuPc layer. However, ions are detected at about 7 × 10 ² count / sec, and the presence of oxygen can be confirmed in a region where there should be no oxygen.

Since the highest occupied level (HOMO) of the molecular orbital is degenerate, the oxygen molecule is a unique molecule in the ground state and in the triplet state. Usually, the triplet to singlet excitation process is forbidden because it is a forbidden transition (spin forbidden), so that no singlet oxygen molecules are generated. However, if there is a triplet excited state molecule ( ³ M *) in an energy state higher than the singlet state around the oxygen molecule, the following energy transfer occurs, so that the singlet state oxygen molecule becomes The reaction that occurs can be guided.

  It is said that 75% of the excited state of molecules in the light emitting layer of the organic light emitting device is a triplet state. Therefore, when oxygen molecules are mixed in the organic light emitting device, singlet oxygen molecules can be generated by energy transfer of Formula 1. Since oxygen molecules in a singlet excited state have an ionic property (charge is biased), there is a possibility of reacting with the charge bias generated in the organic compound.

  For example, in bathocuproine (hereinafter referred to as BCP), the methyl group is electron donating, and therefore the carbon directly bonded to the conjugated ring is positively charged. As shown in the following chemical formula 4, there is a possibility that a singlet oxygen having ionic properties reacts with a positively charged carbon to form a carboxylic acid and hydrogen as shown in the chemical formula 5 below. As a result, it is expected that the electron transport property is lowered.

Based on such considerations, in organic light-emitting elements and organic light-emitting devices using the same, impurities such as oxygen and H ₂ O contained in organic compounds are impurities that cause various deteriorations such as a decrease in luminance. I found out.

  The present invention relates to an organic light emitting device having a layer made of an organic compound between a cathode and an anode, and a light emitting device configured using the organic light emitting device. The first object is to reduce the concentration of oxygen produced.

  A preferred application example using an organic light emitting element is an active matrix driving type light emitting device in which a pixel portion is formed by the organic light emitting element. Each pixel is provided with a thin film transistor (hereinafter referred to as TFT) as an active element. It is known that a characteristic value such as a threshold voltage fluctuates in a TFT formed using a semiconductor film due to alkali metal contamination. A second object of the present invention is to provide a structure suitable for forming a pixel portion by combining an organic light emitting element using an alkali metal having a small work function as a cathode and a TFT.

The present invention is characterized by reducing oxygen-containing impurities such as oxygen and H ₂ O contained in an organic compound forming an organic light-emitting element in order to prevent deterioration of the light-emitting device. Needless to say, oxygen, hydrogen, and the like are included as constituent elements of the organic compound. In the present invention, the impurity for the organic compound refers to an exogenous impurity that is not included in the original molecular structure. These impurities are presumed to exist in organic compounds as atomic, molecular, free radicals and oligomers.

  Furthermore, the present invention is characterized in that, in a light-emitting device that performs active matrix driving, an alkali metal such as sodium or potassium has a structure for preventing TFT voltage from fluctuating and causing fluctuations in threshold voltage. .

The present invention removes such impurities, and the impurities contained in a layer made of an organic compound used to form an organic light emitting device such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. The concentration is reduced to an average concentration of 5 × 10 ¹⁹ / cm ² or less, preferably 1 × 10 ¹⁹ / cm ² or less. In particular, it is required to reduce the oxygen concentration in the light emitting layer and its vicinity.

When the organic light emitting device emits light with a luminance of 1000 Cd / cm ² , this corresponds to an emission amount of 10 ¹⁶ / sec · cm ² when converted into photons. Assuming that the quantum efficiency of the organic light emitting device is 1%, the required current density is required to be 100 mA / cm ² . According to an empirical rule based on a semiconductor element such as a solar cell or a photodiode using an amorphous semiconductor, in order to obtain good characteristics in an element through which a current of this level flows, the density of defect states is 10 ^16. / cm ³ or less is required. In order to realize this value, it is necessary to reduce the concentration of the malignant impurity element forming the defect level to 5 × 10 ¹⁹ / cm ² or less, preferably 1 × 10 ¹⁹ / cm ² or less as described above. is there.

  In order to reduce impurities of the organic compound forming the organic light emitting element, an apparatus for forming the organic light emitting element has the following configuration.

In a vapor deposition apparatus for forming a layer made of a low molecular organic compound, the wall surface in the film forming chamber is mirror-polished by electrolytic polishing to reduce the amount of gas released. The film forming chamber is made of stainless steel or aluminum. For the purpose of preventing gas release from the inner wall, a baking process is performed by providing a heater outside the film formation chamber. Although the gas emission can be considerably reduced by the baking treatment, it is preferable to cool with a refrigerant. The exhaust system uses a turbo molecular pump and a dry pump to prevent back diffusion of oil vapor from the exhaust system. Further, a cryopump may be provided in order to remove residual H ₂ O.

  The evaporation source is basically a resistance heating type, but a Knudsen cell may be used. The material for vapor deposition is carried in from a load lock type exchange chamber attached to the reaction chamber. In this way, the reaction chamber is prevented from being opened to the atmosphere as much as possible when the vapor deposition material is attached. The evaporation source is mainly an organic material, but sublimation purification is performed in the reaction chamber before vapor deposition. Further, a zone purification method may be applied.

  In the pretreatment of the substrate introduced into the reaction chamber, gas emission treatment by heating or plasma treatment using argon is performed to reduce impurities released from the substrate as much as possible. In a light emitting device driven by an active matrix, a TFT is formed in advance on a substrate on which an organic light emitting element is formed. When an insulating layer using an organic resin material is appropriately used as a component of the substrate, it is necessary to reduce gas emission from the member. Further, nitrogen gas and argon gas introduced into the reaction chamber are purified at the supply port.

  On the other hand, in the case of forming a layer composed of a high molecular organic compound, the degree of polymerization cannot be completely controlled, so that there is a case where the molecular weight is widened and the melting point cannot be uniquely determined. In that case, dialysis and high performance liquid chromatography are suitable. Particularly in dialysis, electrodialysis is suitable for efficiently removing ionic impurities.

  By using the means as described above, the oxygen concentration that causes a decrease in luminance and deterioration of electrode materials such as dark spots is reduced.

  In an active matrix driving method in which a pixel portion is formed by an organic light emitting element formed in this manner and each pixel of the pixel is controlled by an active element, a semiconductor film, a gate insulating film, a gate electrode are formed on a substrate as one form of the structure. TFT is formed, and an organic light emitting element is formed thereon. A typical example of a substrate to be used is a glass substrate. Barium borosilicate glass or alumino borosilicate glass contains a trace amount of alkali metal. The semiconductor film is covered with silicon nitride or silicon oxynitride in order to prevent alkali metal contamination from the lower glass substrate and the upper organic light emitting element.

On the other hand, an organic light emitting element that is desirably formed on a flattened surface is formed on a flattened film made of an organic resin material such as polyimide or acrylic. However, such an organic resin material is hygroscopic. An organic light-emitting element that is deteriorated by oxygen or H ₂ O is covered with silicon nitride, silicon oxynitride, or diamond-like carbon (DLC) having gas barrier properties.

  FIG. 12 is a diagram for explaining the concept of the active matrix driving type light emitting device of the present invention. As constituent elements of the light emitting device 1200, a TFT 1201 and an organic light emitting element 1202 are formed on the same substrate. The constituent elements of the TFT 1201 are a semiconductor film, a gate insulating film, a gate electrode, and the like, and the elements included include silicon, hydrogen, oxygen, nitrogen, and other metals that form the gate electrode. On the other hand, the organic light emitting element 1202 contains an alkali metal such as lithium as an element in addition to carbon which is a main component of the organic compound material.

Silicon nitride or silicon oxynitride 1205 is formed as a blocking layer on the lower layer side (the glass substrate 1203 side) of the TFT 1201. On the opposite upper layer side, silicon oxynitride 1206 is formed as a protective film. On the other hand, silicon nitride or silicon oxynitride 1207 is formed as a protective film on the lower layer side of the organic light emitting element 1202. A DLC film 1208 is formed as a protective film on the upper layer side. Between them, an organic resin interlayer insulating film 1204 is formed and integrated. An alkali metal such as sodium which is most hated by the TFT 1201 is blocked by silicon nitride or silicon oxynitride 1205 and silicon oxynitride 1206. On the other hand, since the organic light emitting element 1202 most hates oxygen and H ₂ O, silicon nitride or silicon oxynitride 1207 and a DLC film 1208 are formed to block it. These also have a function of preventing the alkali metal element included in the organic light emitting element 1202 from coming out.

Thus, a light-emitting device configured by combining a TFT and an organic light-emitting element is formed by skillfully combining insulating films having blocking properties against oxygen and H ₂ O in order to satisfy the conflicting properties against impurity contamination. To prevent deterioration due to cross-contamination of impurities.

  In this specification, the light emitting device refers to all devices using the light emitter. In addition, a module in which a TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package) is attached to an element having a layer containing the light emitter between the anode and the cathode (hereinafter referred to as a light emitting element), a TAB tape or TCP Further, a module in which a printed wiring board is provided first, or a module in which an IC is mounted on a substrate on which a light emitting element is formed by a COG (Chip On Glass) method is included in the category of the light emitting device.

  The oxygen concentration as an impurity element in this specification refers to the lowest concentration measured by secondary ion mass spectrometry (SIMS).

As described above, by using the present invention, the concentration of oxygen as an impurity element in a layer made of an organic compound having functions such as a hole injection layer, a hole transport layer, and a light emitting layer of an organic light emitting element is set to 5 × 10 5. It can be reduced to ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁹ / cm ³ or less. The organic compound film forming apparatus and film forming method disclosed in the present invention make it possible to reduce the impurity element contained in the organic compound to the aforementioned level. Accordingly, deterioration of the light emitting device can be reduced.

Further, according to the present invention, a semiconductor film, a gate insulating film, and a gate electrode, which are main components of a TFT, are surrounded by a blocking layer and a protective film made of silicon nitride or silicon oxynitride on the lower layer side and the upper layer side. It has a structure that prevents contamination of metals and organic matter. On the other hand, the organic light-emitting element contains alkali metal in part and is surrounded by a protective film made of silicon nitride or silicon oxynitride and a gas barrier layer made of an insulating film containing silicon nitride or carbon as a main component. _A structure that prevents ₂ O from entering is realized. Then, elements having different characteristics with respect to impurities can be combined to complete the light emitting device without interfering with each other.

  Of course, the present invention can suppress the deterioration of the organic light emitting element not only in the active matrix driving type light emitting device but also in the passive matrix driving type light emitting device.

[Embodiment 1]
An example of an organic light emitting device manufacturing apparatus capable of reducing the concentration of impurities such as oxygen and H ₂ O contained in an organic compound will be described with reference to FIG. FIG. 1 shows an apparatus for forming and sealing a layer made of an organic compound and a cathode. The transfer chamber 101 is connected to the load chamber 104, the pretreatment chamber 105, the intermediate chamber 106, the film formation chamber (A) to the film formation chamber (C) 107 to 109, and gates 100a to 100f. The pretreatment chamber 105 is provided for the purpose of gas release treatment and surface modification of the substrate to be treated, and heat treatment in vacuum or plasma treatment using an inert gas is possible.

  The film formation chamber (A) 107 and the film formation chamber (B) 108 are treatment chambers for forming a film mainly composed of a low molecular organic compound by vapor deposition, and the film formation chamber 109 has a cathode containing an alkali metal. It is a processing chamber for film formation by vapor deposition. The film forming chamber (A) 107 to the film forming chamber (C) 109 are connected to material exchange chambers 112 to 114 for loading evaporation materials into the evaporation source through gates 100h to 100j. The material exchange chambers 112 to 114 are used for filling the deposition material without opening the deposition chamber (A) 107 to the deposition chamber (C) 109 to the atmosphere.

Initially, the substrate 103 on which the film is deposited is mounted in the load chamber 104 and is moved to the pretreatment chamber and each film formation chamber by the transfer mechanism (A) 102 in the transfer chamber 101. The load chamber 104, the transfer chamber 101, the pretreatment chamber 105, the intermediate chamber 106, the film formation chamber (A) 107 to the film formation chamber (C) 109, and the material exchange chambers 112 to 114 are kept in a reduced pressure state by the exhaust means. . The exhaust means is evacuated from an atmospheric pressure to about 1 Pa by an oil-free dry pump, and a pressure higher than that is evacuated by a magnetic levitation turbo molecular pump or a composite molecular pump. A cryopump may be provided in the film formation chamber in order to remove H ₂ O. Thus, back diffusion of oil vapor from the exhaust means is prevented.

The inner wall surfaces of these evacuated rooms are mirror-finished by electropolishing to reduce the surface area and prevent gas emission. The material is stainless steel or aluminum. For the purpose of reducing gas emission from the inner wall, it is desirable to perform a baking process by providing a heater outside the film formation chamber. Baking can significantly reduce outgassing. Further, in order to prevent impurity contamination due to outgassing, it is preferable to cool using a refrigerant during vapor deposition. Thus, a vacuum degree of up to 1 × 10 ⁻⁶ Pa is realized.

  The intermediate chamber 106 is connected to a coating chamber 110 provided with a spinner 111 via a gate 100g. The coating chamber 110 is a processing chamber for forming a film of an organic compound mainly made of a polymer material by a spin coating method, and this processing is performed at atmospheric pressure. For this reason, the substrate is carried out and carried in via the intermediate chamber 106, and is adjusted by adjusting the pressure to be the same as the chamber on the side where the substrate moves. The polymer organic material supplied to the coating chamber is purified and supplied by a dialysis method, an electrodialysis method, or a high performance liquid chromatograph. Purification is performed at the supply port.

In the pretreatment of the substrate to be introduced into the film formation chamber, gas release treatment by heating and surface treatment by argon plasma are performed in the pretreatment chamber 105 to reduce impurities released from the substrate as much as possible. In particular, when an interlayer insulating film made of an organic resin material or a pattern is formed on the substrate, H ₂ O or the like occluded by the organic resin material is released under reduced pressure. It will be contaminated. Therefore, the amount of gas emission is reduced by heating the substrate in the pretreatment chamber 105 to perform gas emission treatment or plasma treatment to densify the surface. Here, the nitrogen gas or argon gas introduced into the reaction chamber is purified by a purification means using a getter material.

The vapor deposition method is a resistance heating type, but a Knudsen cell may be used to control the temperature with high accuracy and to control the evaporation amount. The material for vapor deposition is introduced from a dedicated material exchange chamber attached to the reaction chamber. In this way, the opening of the reaction chamber to the atmosphere is avoided as much as possible. By opening the film formation chamber to the atmosphere, various gases such as H ₂ O are adsorbed on the inner wall, and these gases are released again by evacuation. It takes several tens to several hundreds of hours until the release of the adsorbed gas is settled and the degree of vacuum is stabilized at the equilibrium value. For this reason, the wall of the film forming chamber is baked to shorten the time. However, since repeated release to the atmosphere is not an efficient method, it is desirable to provide a dedicated material exchange chamber as shown in FIG. The evaporation source is mainly an organic material, but sublimation purification is performed in the reaction chamber before vapor deposition. A zone purification method may also be applied.

  On the other hand, the sealing chamber 115 partitioned by the load chamber 104 performs a process for sealing the substrate that has been completed up to the formation of the cathode with a sealing material without being exposed to the atmosphere. When the sealing material is fixed with an ultraviolet curable resin, an ultraviolet irradiation mechanism 116 is used. A delivery mechanism (B) 118 is provided in the delivery chamber 117, and the substrate that has been finished sealing in the sealing chamber 115 is stored.

  FIG. 2 is a diagram illustrating the detailed configuration of the transfer chamber 101, the pretreatment chamber 105, and the film formation chamber (A) 107. A transfer mechanism 102 is provided in the transfer chamber 101. The evacuation means of the transfer chamber 101 is performed by a magnetic levitation type composite molecular pump or turbo molecular pump 207a and a dry pump 208a. The pretreatment chamber 105 and the film formation chamber 107 are connected to the transfer chamber 101 by gates 100b and 100d, respectively. The pretreatment chamber 105 is provided with a high-frequency electrode 201 to which a high-frequency power source 202 is connected, and the substrate 103 is held by a counter electrode provided with substrate heating means 214a and 214b. Impurities such as moisture adsorbed on the substrate 103 can be desorbed by heating in a vacuum at about 50 to 120 ° C. by the substrate heating means 214a and 214b. The gas introduction means connected to the pretreatment chamber 105 includes a cylinder 216a, a flow rate controller 216b, and a purifier 203 such as a getter material.

Surface treatment with plasma is performed by purifying an inert gas such as helium, argon, krypton, or neon, or a mixture of an inert gas and hydrogen with a purifier 203, and applying the high frequency power to the plasma in an atmosphere. Do by exposure. The purity of the gas used is desirably 2 ppm or less, preferably 1 ppm or less for each of the concentrations of CH ₄ , CO, CO ₂ , H ₂ O, and O ₂ .

  The evacuation means is performed by a magnetic levitation type composite molecular pump 207b and a dry pump 208b. The pressure in the pretreatment chamber 105 during the surface treatment is controlled by controlling the exhaust speed with a control valve provided in the exhaust means.

The film formation chamber 107 is provided with an evaporation source 211, a suction plate 212, a shutter 218, and a shadow mask 217. The substrate 103 is provided on the shadow mask 217. The shutter 218 is openable and opens during vapor deposition. The evaporation source 211 and the adsorption plate 212 are controlled in temperature, and are connected to the heating means 213d and 213e, respectively. The exhaust system is a turbo molecular pump 207c and a dry pump 208c, and a cryopump 209 is further added to remove residual moisture in the film formation chamber. The film forming chamber can be baked to reduce the amount of gas released from the inner wall of the film forming chamber. In the baking process, the film formation chamber is heated to about 50 to 120 ° C. and evacuated by an exhaust system to which a turbo molecular pump or a cryopump is connected. Thereafter, the reaction chamber can be evacuated to about 1 × 10 ⁻⁶ Pa by cooling it to room temperature or liquid nitrogen temperature with a refrigerant.

  The material exchange chamber 112 separated by the gate 100h is provided with evaporation sources 210 and 211, and the temperature is controlled by the heating means 213a and 213b. For the exhaust system, a turbo molecular pump 207d and a dry pump 208d are used. The evaporation source 211 is movable between the material exchange chamber 112 and the film formation chamber 107, and is used as a means for purifying the supplied evaporation material.

  Although there is no limitation on the purification method of the material for vapor deposition, it is preferable to employ a sublimation purification method for performing in situ in the film forming apparatus. Of course, other zone purification methods may be used. 3 and 4 are diagrams for explaining a method of performing sublimation purification in the film forming apparatus described in FIG.

Many organic compounds for forming an organic light emitting element are easily deteriorated by oxygen or H ₂ O. This tendency is particularly strong for low molecular weight organic compounds. Therefore, even if it is sufficiently purified and highly purified at the beginning, oxygen and H ₂ O may be easily taken in by subsequent handling. As described above, oxygen incorporated into an organic compound is considered to be a malignant impurity that changes the binding state of molecules. This causes a change with time of the organic light emitting element and causes deterioration of characteristics.

FIG. 3 is a diagram illustrating the concept of sublimation purification of organic compound materials. It is assumed that the originally intended organic compound is M2, and the vapor pressure under a certain pressure is between temperatures T1 and T2. M1 having a high vapor pressure below T1 corresponds to impurities such as H ₂ O. Further, M3 having a vapor pressure higher than T2 corresponds to impurities such as transition metals and organic metals.

  In this way, materials containing M1, M2, and M3 having different vapor pressures are placed in the first evaporation source 210 and heated at a temperature lower than T2, as shown in FIG. 4A. The materials that sublimate from the first evaporation source are M1 and M2. At this time, if the second evaporation source 211 is provided above and maintained at a temperature lower than T1, it can be adsorbed thereto. Next, as shown in FIG. 4B, when the second evaporation source 211 is heated to a temperature of T1, M1 sublimates and is adsorbed on the adsorption plate 212. In the second evaporation source 211, M1 and M3 are removed, and M2 remains. Thereafter, as shown in FIG. 4C, the second evaporation source 211 is heated to a temperature of about T2 to form an organic compound layer on the substrate.

4 can be performed in the material exchange chamber 112 and the film formation chamber 107 of the film formation apparatus described in FIG. The cleanliness in the deposition chamber is increased by mirror finishing of the inner wall and exhausting with a turbo molecular pump or cryopump, so that the oxygen concentration in the organic compound deposited on the substrate is 1 × 10 ¹⁹ / cm ^3. Hereinafter, it can be preferably reduced to 1 × 10 ¹⁹ / cm ³ or less.

[Embodiment 2]
There is no particular limitation on the structure of the organic light-emitting element manufactured using the film formation apparatus described in Embodiment 1. An organic light-emitting element is formed with an anode made of a light-transmitting conductive film, a cathode containing an alkali metal, and a layer made of an organic compound therebetween. The layer made of an organic compound is composed of one layer or a plurality of layers. Each layer is referred to as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, or the like depending on its purpose and function. These can be formed by either a low molecular organic compound material, a high molecular organic compound material, or a combination of both.

  For the hole injection layer and the hole transport layer, an organic compound material having excellent hole transport properties is selected, and typically, a phthalocyanine-based or aromatic amine-based material is employed. In addition, a metal chain having an excellent electron transport property is used for the electron injection layer.

FIG. 5 shows an example of the structure of the organic light emitting device. FIG. 5A illustrates an example of an organic light-emitting element using a low molecular organic compound, which includes an anode 300 formed of indium tin oxide (ITO), a hole injection layer 301 formed of copper phthalocyanine (CuPc), and an aromatic group. Hole transport layers 302 and 303 formed of amine-based material MTDATA and α-NPD, electron injection layer / light-emitting layer 304 formed of tris-8-quinolinolato aluminum complex (Alq ₃ ), ytterbium (Yb The cathode 305 made of Alq ₃ enables light emission (fluorescence) from a singlet excited state.

In order to increase luminance, it is preferable to use light emission (phosphorescence) from a triplet excited state. FIG. 5B shows an example of such an element structure. On the anode 310 formed of ITO, the hole injection layer 311 formed of CuPc which is a phthalocyanine-based material, and the hole transport layer 312 formed of α-NPD which is an aromatic amine-based material, a carbazole-based CBP + Ir ( The light emitting layer 313 is formed using (ppy) ₃ . Further, a hole blocking layer 314 is formed using bathocuproine (BCP), and an electron injection layer 315 made of Alq ₃ and a cathode 316 containing an alkali metal such as ytterbium (Yb) or lithium are formed.

The above two structures are examples using a low molecular weight organic compound, but an organic light emitting device combining a high molecular weight organic compound and a low molecular weight organic compound can be realized. FIG. 5C shows an example of this. A hole injection layer 321 is formed of a polythiophene derivative (PEDOT) of a high molecular organic compound on an anode 320 formed of ITO, and a hole transport layer formed of α-NPD. A light emitting layer 323 made of CBP + Ir (ppy) ₃ , a hole blocking layer 324 made of BCP, an electron injection layer 325 made of Alq ₃ , and a cathode 316 containing an alkali metal such as ytterbium (Yb) or lithium are formed. By changing the hole injection layer to PEDOT, the hole injection characteristics can be improved and the light emission efficiency can be improved.

As the light-emitting layer, carbazole-based CBP + Ir (ppy) ₃ is an organic compound capable of obtaining light emission (phosphorescence) from a triplet excited state. Examples of the triplet compound include organic compounds described in the following papers as typical materials. (1) T. Tsutsui, C. Adachi, S. Saito, Photochemical Processes in Organized Molecular Systems, ed. K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p.437. (2) MABaldo, DFO ' Brien, Y.You, A.Shoustikov, S.Sibley, METhompson, SRForrest, Nature 395 (1998) p.151. This paper discloses an organic compound represented by the following formula. (3) MABaldo, S. Lamansky, PEBurrrows, METhompson, SRForrest, Appl. Phys. Lett., 75 (1999) p. 4. (4) T. Tsutsui, M.-J. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T. tsuji, Y. Fukuda, T. Wakimoto, S. Mayaguchi, Jpn. Appl. Phys., 38 (12B) (1999) L1502.

  In addition to the luminescent material described in the above paper, it is considered possible to use a luminescent material represented by the following molecular formula (specifically, a metal complex or an organic compound).

  In the above molecular formula, M is an element belonging to groups 8 to 10 of the periodic table. In the above paper, platinum and iridium are used. Further, the present inventor believes that nickel, cobalt, or palladium is preferable in terms of reducing the manufacturing cost of the EL display device because it is cheaper than platinum or iridium. In particular, nickel is considered preferable because it is easy to form a complex and has high productivity. In any case, light emission from the triplet excited state (phosphorescence) has higher emission efficiency than light emission from the singlet excited state (fluorescence), and the operating voltage (light emission from the organic light emitting element) can be obtained with the same light emission luminance. The voltage required for making it low) can be lowered.

Phthalocyanine-based CuPc, aromatic amine-based α-NPD, MTDATA, carbazole-based CBP, and the like are all organic compounds that do not contain oxygen. When oxygen or H ₂ O is mixed into such an organic compound, a change in the bonding state described with reference to Chemical Formula 4 and Chemical Formula 5 occurs, and hole transport characteristics and light emission characteristics are deteriorated. In forming such an organic compound layer, the film formation apparatus and the film formation method described in Embodiment 1 with reference to FIGS. Accordingly, in an organic light emitting device having an oxygen concentration of 1 × 10 ¹⁹ / cm ³ or less in a light emitting device, or a phthalocyanine-based or aromatic amine-based hole injection layer or hole transport layer, or a carbazole-based light emitting layer. In addition, the oxygen concentration in the hole injection layer or the hole transport layer and in the vicinity thereof can be set to 1 × 10 ¹⁹ / cm ³ or less.

[Embodiment 3]
FIG. 6 shows an example of the structure of an active matrix light-emitting device. The TFT is provided in the pixel portion and various functional circuits around it. Amorphous silicon or polycrystalline silicon can be selected as the material of the semiconductor film forming the channel formation region of the TFT, but either may be adopted in the present invention.

  The substrate 601 is a glass substrate or an organic resin substrate. The organic resin material is lighter than the glass material, and effectively works to reduce the weight of the light emitting device itself. As a material applicable for manufacturing a light-emitting device, an organic resin material such as polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), or aramid can be used. It is desirable to use barium borosilicate glass or alumino borosilicate glass called non-alkali glass for the glass substrate. A glass substrate having a thickness of 0.5 to 1.1 mm is employed, but it is necessary to reduce the thickness in order to reduce the weight. Further, in order to further reduce the weight, it is desirable to employ a specific gravity as small as 2.37 g / cc.

In FIG. 6, an n-channel TFT 652 and a p-channel TFT 653 are formed in the driver circuit portion 650, and a switching TFT 654 and a current control TFT 655 are formed in the pixel portion 651. These TFTs use a semiconductor film 603 to 606, a gate insulating film 607, a gate electrode 608 to 611, and the like on a first insulating layer 602 made of silicon nitride or silicon oxynitride (expressed by SiO _x N _y ). Is formed.

Over the gate electrode, a second insulating layer 618 made of silicon nitride or silicon oxynitride is formed and used as a protective film. Further, an organic insulating film 619 made of polyimide or acrylic is formed as a planarizing film. Since this organic insulating film is hygroscopic, it has a property of absorbing H ₂ O. When the H ₂ O is re-released, oxygen is supplied to the organic compound and causes deterioration of the organic light emitting device. Therefore, in order to prevent occlusion and re-release of H ₂ O, nitriding is performed on the organic insulating film 619. A third insulating film 620 made of silicon or silicon oxynitride is formed.

  The circuit configuration of the drive circuit unit 650 differs between the gate signal side drive circuit and the data signal side drive circuit, but is omitted here. Wirings 612 and 613 are connected to the n-channel TFT 652 and the p-channel TFT 653, and a shift register, a latch circuit, a buffer circuit, or the like can be formed using these TFTs.

  In the pixel portion 651, the data wiring 614 is connected to the source side of the switching TFT 654, and the drain side wiring 615 is connected to the gate electrode 611 of the current control TFT 655. The source side of the current control TFT 655 is connected to the power supply wiring 617, and the drain side electrode 616 is connected to the anode of the EL element.

  The organic light emitting element 656 is formed on the protective insulating film 620 and is formed of an anode 621 made of ITO (indium tin oxide), an organic compound layer 623 including a hole injection layer, a hole transport layer, a light emitting layer, and the like, MgAg And a cathode 624 formed using a material such as alkali metal or alkaline earth metal such as LiF. Although the structure of the organic light emitting element is arbitrary, the structure shown in FIG. 5 can be adopted. The bank 622 is formed of an organic resin such as polyimide or acrylic. The bank 622 is formed with a thickness of about 1 μm, and its end is formed in a tapered shape. It is formed so as to cover the TFT wiring and the end portion of the anode 621, and is provided to prevent a short circuit between the cathode and the anode at this portion.

However, since the polyimide forming the bank has a hygroscopic property, the surface is densified by plasma treatment using argon, and the surface is modified so as not to occlude H ₂ O or the like. In this way, the amount of gas re-released from the bank is reduced so that the organic compound does not deteriorate.

The cathode 624 of the organic light-emitting element uses a material containing magnesium (Mg), lithium (Li), or calcium (Ca) having a low work function. An electrode made of MgAg (a material in which Mg and Ag are mixed at Mg: Ag = 10: 1) is preferably used. Other examples include MgAgAl electrodes, LiAl electrodes, and LiFAl electrodes. Further, a third insulating film 625 is formed as an upper layer using silicon nitride or a DLC film. The DLC film is known to have high gas barrier properties such as oxygen, CO, CO ₂ , H ₂ O and the like. The protective film 625 is preferably formed continuously after the cathode 624 is formed without being released to the atmosphere. There may be a silicon nitride buffer layer under the protective film 625. This is because the interface state between the cathode 624 and the organic compound layer 623 greatly affects the light emission efficiency of the organic light emitting element.

  In FIG. 6, the switching TFT 654 has a multi-gate structure, and the current control TFT 655 is provided with a low-concentration drain (LDD) overlapping the gate electrode. Since TFTs using polycrystalline silicon exhibit a high operating speed, deterioration such as hot carrier injection is likely to occur. Therefore, as shown in FIG. 6, it is highly reliable to form TFTs having different structures (switching TFTs with sufficiently low off-state current and TFTs for current control strong against hot carrier injection) having different structures depending on functions in the pixel. And is very effective in manufacturing a display device capable of good image display (high operation performance).

As shown in FIG. 6, a first insulating film 602 is formed on the lower layer side (substrate 601 side) of the semiconductor film forming the TFTs 654 and 655. On the opposite upper layer side, a second insulating film 618 is formed. On the other hand, a third insulating film 620 is formed on the lower layer side of the organic light emitting element 656. A fourth insulating film 625 is formed on the upper layer side. An organic light emitting element 656 is formed between the two, and is integrated between the third insulating film 620 and the protective film 625. The alkali metal such as sodium which TFTs 654 and 655 dislike most is blocked by being surrounded by the first insulating film 602 and the second insulating film 618, although the substrate 601 and the organic light emitting element 656 can be considered as contamination sources. On the other hand, since the organic light emitting element 656 hates oxygen and H ₂ O most, a third insulating film 620 and a fourth insulating film 625 are formed to block it. These also have a function of preventing the alkali metal element included in the organic light emitting element 656 from coming out.

  Another form for preventing moisture absorption of organic resin such as polyimide and re-release of gas is shown in FIG. After forming the anode 621, the bank 622 is formed. Thereafter, a gas barrier layer 630 made of a silicon nitride film is formed by sputtering or plasma CVD. Since the silicon nitride film is initially formed on the entire surface, the surface of the anode 621 is exposed by an etching process. Thereafter, the organic light emitting element 656 is completed by forming the organic compound layer 623 and the cathode 624. Although not shown, a protective film is further formed on the cathode 624 with a silicon nitride oxide or a DLC film. Preferably, after forming the cathode, a protective film may be continuously formed without opening to the atmosphere. A silicon nitride film may be formed as a base for forming the protective film.

  Further, in the organic light emitting device having the structure as shown in FIG. 6, an example of an efficient manufacturing method is to continuously form the third insulating film 620 and the anode 621 made of a transparent conductive film typified by ITO by sputtering. A film forming process can be employed. The sputtering method is suitable for forming a dense silicon nitride film or silicon oxynitride film without causing significant damage to the surface of the organic insulating film 619.

As described above, a pixel portion can be formed by combining a TFT and an organic light emitting device, whereby the light emitting device can be completed. In such a light-emitting device, a driver circuit can be formed over the same substrate using TFTs. As shown in FIG. 6 or 7, the semiconductor film, the gate insulating film, and the gate electrode, which are the main components of the TFT, are surrounded by a blocking layer and a protective film made of silicon nitride or silicon oxynitride on the lower layer side and the upper layer side. Therefore, it has a structure that prevents contamination of alkali metal and organic matter. On the other hand, the organic light-emitting element contains alkali metal in part and is surrounded by a protective film made of silicon nitride, silicon oxynitride or DLC film, and a gas barrier layer made of an insulating film containing silicon nitride or carbon as a main component, and from the outside. It has a structure that prevents oxygen and H ₂ O from entering.

  Thus, the present invention provides a technique for combining elements having different characteristics with respect to impurities and completing a light emitting device without interfering with each other.

[Embodiment 4]
Although the top gate TFT structure is described in Embodiment Mode 3, it is needless to say that a bottom gate TFT or an inverted staggered TFT can be applied. In FIG. 8, a switching TFT 754 and a current control TFT 755 are formed in the pixel portion 751 by using an inverted stagger type TFT. Over the substrate 701, gate electrodes 702 and 703 made of molybdenum or tantalum or the like and a wiring 704 are formed, and a first insulating film 705 functioning as a gate insulating film is formed thereon. The first insulating film is formed with a thickness of 100 to 200 nm using silicon oxide or silicon nitride.

  In the semiconductor films 706 and 707, a channel formation region, a source or drain region, and an LDD region are formed. Insulating films 708 and 709 are provided for the purpose of forming these regions and protecting the channel formation region. The second insulating film 710 is formed of silicon nitride or silicon oxynitride, and is provided so that the semiconductor film is not contaminated by alkali metal, organic matter, or the like. Further, a planarization film 711 made of an organic resin material such as polyimide is formed. A third insulating film 712 made of silicon nitride or silicon oxide is formed thereon. The wirings 713 to 716 are formed on the third insulating film 712.

  An anode 717 of the organic light emitting element 756 is formed on the third insulating film 712, and then a bank 718 is formed of polyimide. The surface of the bank 718 may be densified by plasma pretreatment with argon as shown in FIG. 6, but a gas barrier layer 719 made of a silicon nitride film is formed as shown in FIG. May be. The structures of the organic compound layer 720, the cathode 721, and the fourth insulating film are the same as those in Embodiment Mode 2. Thus, a light-emitting device can be completed using an inverted staggered TFT.

In addition, a driver circuit can be formed over the same substrate by using an inverted staggered TFT. As shown in FIG. 8, the semiconductor film, which is a main component of the TFT, is formed by surrounding the lower layer side and the upper layer side with a first insulating film and a second insulating film made of silicon nitride or silicon oxynitride. It has a structure that prevents organic contamination. On the other hand, the organic light-emitting element includes an alkali metal in part, and has a structure that prevents oxygen and H ₂ O from entering from the outside by the third insulating film and the fourth insulating film. As described above, even when an inverted staggered TFT is used, a technique is provided in which elements having different characteristics with respect to impurities are combined to form a light emitting device without interfering with each other.

[Embodiment 5]
FIG. 9 shows a structure for sealing the organic light emitting element formed in the third or fourth embodiment. FIG. 9 shows a state where an element substrate 401 on which a driving circuit 408 and a pixel portion 409 are formed using TFTs, and a sealing substrate 402 are fixed with a sealant 405. The protective film 406 is formed of a silicon nitride film, a silicon nitride oxide film, or a DLC film. Further, a silicon nitride film may be provided as a buffer layer under the protective film 406. An organic light emitting element 403 is formed in a sealing region between the element substrate 401 and the sealing substrate 402, and the desiccant may be provided on the driving circuit 408 or in the vicinity where the sealing material 405 is formed. .

  An organic resin material such as polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), or aramid is used for the sealing substrate. A substrate having a thickness of about 30 to 120 μm is employed to provide flexibility. A DLC film 407 is formed at the end as a gas barrier layer. However, the DLC film is not formed on the external input terminal 404. An epoxy adhesive is used for the sealing material. By forming the DLC film 407 along the sealing material 405 and along the end portions of the element substrate 401 and the sealing substrate 402, water vapor penetrating from this portion can be prevented.

  FIG. 10 is a diagram showing the appearance of such a display device. The direction in which an image is displayed varies depending on the configuration of the organic light emitting element, but here, light is emitted upward and display is performed. In the structure illustrated in FIG. 10, an element substrate 401 over which a driver circuit portion 408 and a pixel portion 409 are formed using TFTs and a sealing substrate 402 are bonded to each other with a sealant 405. In addition to the drive circuit portion 408, a signal processing circuit 606 for correcting the video signal or storing the video signal may be provided. An input terminal 404 is provided at the end of the element substrate 401, and an FPC (Flexible Print Circuit) is connected to this portion. Input terminals 404 are provided with terminals for inputting image data signals, various timing signals, and power from an external circuit at a pitch of 500 μm. The wiring 410 is connected to the drive circuit unit. In addition, an IC chip 411 in which a CPU, a memory, and the like are formed as needed may be mounted on the element substrate 401 by a COG (Chip on Glass) method or the like.

  A DLC film is formed at an end adjacent to the seal material, and water vapor, oxygen, and the like enter from the seal portion to prevent the organic light emitting element from deteriorating. When an organic resin material is used for the element substrate 401 and the sealing substrate 402, a DLC film may be formed on the entire surface excluding the input terminal portion. When the DLC film is formed, the input terminal portion may be covered in advance using a masking tape or a shadow mask.

  As described above, the organic light-emitting element formed in Embodiment 3 or 4 can be sealed to form a light-emitting device. Both the TFT and the organic light emitting element are surrounded by an insulating film, and have a structure in which impurities do not enter from the outside. Further, by sticking to the element substrate using a sealing material and covering the end with DLC, the airtightness can be improved and the light emitting device can be prevented from deteriorating.

2A and 2B illustrate a structure of a film formation apparatus of the present invention. 2A and 2B illustrate a structure of a film formation apparatus of the present invention. The figure explaining the relationship between the impurity contained in organic compound material, and its vapor pressure. 10A and 10B illustrate a method for performing sublimation purification in a film formation apparatus. 3A and 3B illustrate a structure of an organic light emitting element. FIG. 6 is a partial cross-sectional view illustrating a structure of an organic light emitting device including a pixel portion and a drive circuit portion. FIG. 4 is a partial cross-sectional view illustrating a structure of a pixel portion of an organic light emitting device. FIG. 4 is a partial cross-sectional view illustrating a structure of a pixel portion of an organic light emitting device. Sectional drawing explaining the structure of an organic light-emitting device. The perspective view explaining the external appearance of an organic light-emitting device. Graph showing the depth profile of the elements of the sample having the _{Alq 3 / Ir (ppy) 3} + CBP / CuPc / ITO structure obtained by SIMS measurement. 4A and 4B illustrate a concept of a light-emitting device of the present invention.

Explanation of symbols

101 Transfer chamber 105 Pretreatment chamber 107 Film formation chamber 112 Material exchange chambers 207a to 207d Turbo molecular pumps or composite molecular pumps 208a to 208d Dry pump

Claims (5)

An insulating layer having a blocking property against an alkali metal is formed on the upper layer side and the lower layer side of the semiconductor layer constituting the thin film transistor,
An insulating layer having a blocking property with respect to oxygen and H ₂ O is formed on the upper layer side and the lower layer side of the light-emitting element including the organic compound layer,
The light-emitting device, wherein the thin film transistor and the light-emitting element are provided with an organic resin interlayer insulating film interposed therebetween. A layer of silicon nitride or silicon nitride oxide having a blocking property against alkali metal is formed on the upper layer side and lower layer side of the semiconductor layer constituting the thin film transistor,
A layer of silicon nitride, silicon oxynitride, or diamond-like carbon having a blocking property against oxygen and H ₂ O is formed on the upper layer side and the lower layer side of the light emitting element including the organic compound layer,
The light-emitting device, wherein the thin film transistor and the light-emitting element are provided with an organic resin interlayer insulating film interposed therebetween.   3. The light emitting device according to claim 1, wherein an organic resin interlayer insulating film is formed and integrated between the thin film transistor and the light emitting element. A semiconductor layer constituting a thin film transistor is provided between a first insulating layer formed of silicon nitride or silicon oxynitride and a second insulating layer formed of silicon oxynitride;
A light-emitting element including an organic compound layer between a third insulating layer formed of silicon nitride or silicon oxynitride and a fourth insulating layer formed of a film containing silicon nitride or carbon as a component Have
An organic resin interlayer insulating film is interposed between the second insulating layer and the third insulating layer. A semiconductor layer constituting a thin film transistor is provided between a first insulating layer formed of silicon nitride or silicon oxynitride and a second insulating layer formed of silicon oxynitride;
An anode, an organic compound layer, and a cathode are provided between a third insulating layer formed of silicon nitride or silicon oxynitride and a fourth insulating layer formed of a film containing silicon nitride or carbon as a component. A light-emitting element comprising:
An organic resin interlayer insulating film is interposed between the second insulating layer and the third insulating layer.

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