JPH07192872A - Manufacture of electroluminescence element - Google Patents

Abstract

PURPOSE:To manufacture an EL element with the excellent reproducibility by dropping or jetting the light emitting central raw material, which is dissolved in the organic solvent, into a reaction furnace during the reaction of the base material of a light emitting layer, and quickly vaporizing it, and supplying a constant quantity. CONSTITUTION:At the time of manufacturing a thin film EL element, a first transparent electrode 12 and a first insulating layer 13 are formed on a glass substrate 11. A light emitting layer 14, in which Sm and Cl as the light emitting center are added to ZnS a the base material, is formed on the first insulating layer 13 by a MOCVD device. At the time of forming the light emitting layer 14, the substrate 11 is maintained at a constant temperature, and H2 carrier gas is used, and Zn (C2H5)2 and H2S are flown to form a ZnS thin film. As the light emitting center, Sm (C11H19O2)3 as a raw material is dissolved in the organic solvent C4H8C, and it is transferred and dropped onto a hot plate maintained at a constant temperature by the H2 gas, of which flow quantity can be finely adjusted, and quickly vaporized so that a predetermined quantity can be added. A second insulating layer 15 and a second transparent layer 16 are formed on the light emitting layer 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence element (hereinafter referred to as EL element) used for, for example, self-luminous segment display or matrix display of instruments, or display of various information terminal devices.
Element)).

[0002]

2. Description of the Related Art EL elements utilize the phenomenon of light emission when an electric field is applied to a phosphor such as zinc sulfide (ZnS), and have hitherto attracted attention as constituting a self-luminous flat display. . FIG. 3 is a schematic diagram showing a typical cross-sectional structure of the conventional EL element 10. The EL element 10 is an optically transparent ITO (In) on the glass substrate 1 which is an insulating substrate.
a first electrode 2 made of a dium tin oxide film, a first insulating layer 3 made of tantalum pentoxide (Ta ₂ O ₅ ) and the like, a light emitting layer 4, a second insulating layer 5 and a second electrode 6 made of an ITO film. It is formed by stacking. The ITO film is a transparent conductive film obtained by doping indium oxide (In ₂ O ₃ ) with tin (Sn), and has been widely used for transparent electrodes since it has a low resistivity.
As the light emitting layer 4, for example, when zinc sulfide (ZnS) is used as the base material, the emission color is determined by the type of additive in the base material. For example, when terbium (Tb) is added as the emission center, a yellowish green color is obtained. Luminescence, red-orange when samarium (Sm) is added, blue when thulium (Tm) is added, and blue when cerium (Ce) is added as the emission center when the base material is strontium sulfide (SrS). A green emission is obtained.

[0003]

An EL having the above structure.
In the device 10, the light emission brightness and the life are not practically sufficient in the past, and as a constituent material of the light emitting layer 4 in order to improve the light emission brightness, for example, zinc sulfide added with terbium (Tb), zinc selenide, or the like. Sulfur compounds and selenium compounds have been studied by EB (electron beam) vapor deposition method, sputtering method, etc., and in recent years, CVD (Chemical Vapor Depositi
on) method has also come to be examined.

As the CVD method, for example, Journal of Crystal Growth, Vol. 117, published in 1992, P991-99
As shown in Fig. 6, there are a method of transporting a halogen element gas and a method of vaporizing a halogen compound at a high temperature and transporting it into a reaction furnace. But according to the above method,
The vaporization temperature is high, it is difficult to control the amount of vapor, and the ratio of group II gas to group VI gas and the emission center substance supplied to the reactor is likely to change, and stable and high-quality emission is achieved. You can't get layers.

In order to solve this problem, for example, metal organic chemical vapor deposition using a dipivaloyl methane compound as shown in Technical Paper Proceeding 22 Vol. Metal Organic C
The chemical vapor deposition (MOCVD) method is drawing attention.

In the MOCVD method, hydrogen (H ₂ ) is generally bubbled through a liquid organic metal so that the organic metal is contained in hydrogen (H ₂ ), and the hydrogen is supplied into the reaction furnace. . However, organic metals such as rare earth elements and alkaline earth metal elements are generally powder (solid) at room temperature and have a melting point of 1
It is above 50 ℃. Therefore, as a source gas supply method,
A raw material container filled with an organic metal such as a rare earth element or an alkaline earth metal element is heated in a heating oven or the like, and a carrier gas such as hydrogen (H ₂ ) is introduced to vaporize the organic metal in hydrogen (H ₂ ). Is contained and is supplied to the reaction furnace. However, when the organic metal is a solid, the amount of vaporization largely changes depending on the surface area of the filled raw material, and it is very difficult to keep the amount of vaporization constant.

Further, it is known that even a slight change in the amount of the added luminescent center in the luminescent layer has a significant effect on the luminescent brightness of the EL device. Therefore, even in the light emitting layer raw material, especially for the rare earth element which becomes the emission center, it is necessary to stably supply a constant amount during film formation. However, in the case of using the organic compound of the rare earth element as the emission center raw material, The variation in the amount of vaporization was large, and the reproducibility of the EL element was poor. Further, according to the above method, which has been generally used for powdery organic metal, the organic metal is directly placed on the metal mesh. There was a problem that it would end up.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a manufacturing method capable of manufacturing an EL element with good reproducibility.

[0009]

A feature of the present invention for solving the above-mentioned problems is that the first electrode, the first insulating layer, the light emitting layer, the second insulating layer and the second electrode are at least a material on the light extraction side. In the manufacturing process of an electroluminescent element sequentially laminated with an optically transparent material, when forming a light emitting layer made of a II-VI group compound to which an emission center element is added by using a vapor phase growth method, An organic metal dissolved in an organic solvent is used as a raw material of the emission center gas, and the raw material is rapidly vaporized by dropping or spraying the raw material to a heating body heated to a high temperature, and the vaporized gas is converted into hydrogen (H ₂ ) Or supplying with an inert carrier gas into the reaction furnace. Another feature is that the temperature of the heating element is set to a temperature equal to or higher than the boiling point of the organic solvent used and lower than the decomposition temperature of the organic metal luminescence center raw material used. Yet another configuration is
It is characterized in that these raw material gases are independently supplied into the reaction furnace. By such a method, the supply amount of the emission center can be kept constant, and the above object can be achieved.

[0010]

According to the method of the present invention, when the light emitting layer made of the II-VI group compound to which the light emitting center element is added is formed by the vapor phase growth method, the light source of the light emitting center gas is used. By using an organic metal dissolved in an organic solvent as a certain substance and dropping or spraying an appropriate amount of this raw material onto a heating body heated to a high temperature, the emission center raw material contained in the solvent is rapidly vaporized together with the solvent. Therefore, it is possible to always ensure a fixed amount and a fixed amount of vapor of the emission center source gas in the vaporization chamber. Further, the emission center raw material can be supplied by transporting it into the reaction furnace with a carrier gas, and the amount of the emission center element supplied into the reaction furnace can be easily controlled by adjusting the carrier gas flow rate.
The emission center material can be stably obtained, and the controllability is remarkably improved. As a result, it is possible to stably provide an EL element that emits light with high brightness. Further, by using the metal organic chemical vapor deposition (MOCVD) apparatus according to the present invention,
There is also an effect that it can be used for manufacturing capacitor materials such as strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₃ ) for LSI, superconducting materials and the like.

[0011]

EXAMPLES The present invention will be described below based on specific examples. (Embodiment 1) FIG. 2 shows an EL device 1 having a thin film structure according to the present invention.
It is the schematic diagram which showed the cross section of 00. In addition, the EL element 1 of FIG.
At 00, light is extracted in the arrow direction. The thin film EL device 100 is formed on the glass substrate 11 which is an insulating substrate in order.
The following thin films are laminated and configured. A first transparent electrode (first electrode) 12 made of optically transparent zinc oxide (ZnO) is formed on a glass substrate 11, and an optically transparent tantalum pentoxide (Ta ₂ O ₅ ) is formed on the upper surface thereof. ), A first insulating layer 13 made of), a luminescent layer 14 made of zinc sulfide (ZnS) doped with samarium (Sm) as an emission center, and a second insulating layer made of optically transparent tantalum pentoxide (Ta ₂ O ₅ ). 15, a second transparent electrode (second electrode) 16 made of optically transparent zinc oxide (ZnO) is formed.

Next, a method of manufacturing the above-mentioned thin film EL element 100 will be described below. Further, the film thickness of each layer below is described with reference to the central portion thereof. (a) First, the first transparent electrode 12 was formed on the glass substrate 11. As the vapor deposition material, zinc oxide (ZnO) powder to which gallium oxide (Ga ₂ O ₃ ) was added and mixed and molded into a pellet was used, and an ion plating device was used as a film forming device. Specifically, the inside of the ion plating apparatus was evacuated while keeping the temperature of the glass substrate 11 constant. After that, argon (Ar) gas was introduced to keep the pressure constant, and the beam power and the high frequency power were adjusted so that the film formation rate was in the range of 6 to 18 nm / min. (b) Next, tantalum pentoxide was deposited on the first transparent electrode 12.
The first insulating layer 13 made of (Ta ₂ O ₅ ) was formed by the sputtering method. Specifically, the temperature of the glass substrate 11 was kept constant, a mixed gas of argon (Ar) and oxygen (O ₂ ) was introduced into the sputtering apparatus, and film formation was performed with a high frequency power of 1 KW. (c) On the first insulating layer 13, zinc sulfide (ZnS) is used as a host material, and samarium (Sm) and chlorine (C
The zinc sulfide: samarium (ZnS: Sm, Cl) light emitting layer 14 added with l) was formed by using the MOCVD apparatus (schematic diagram) 400 shown in FIG. The actual arrangement of the nozzle 48 shown in FIG. 4 is such that the gas containing the emission center is diethylzinc (Z
It is located in the center of the n (C ₂ H ₅ ) ₂ ) supply nozzle and the hydrogen sulfide (H ₂ S) supply nozzle. The film-forming substrate in FIG. 4 was fixed to a susceptor with a temperature controller, and the temperature was controlled by feedback control using a thermocouple. (d) As a method for forming the light emitting layer, the glass substrate 11 is kept at a constant temperature, the inside of the film forming chamber is under a reduced pressure atmosphere, and then diethyl zinc (Zn (C ₂ H ₅ ) ₂ ) is used by using a hydrogen carrier gas. To
At the same time, hydrogen sulfide (H ₂ S) diluted with hydrogen was flowed to form a zinc sulfide (ZnS) thin film. (e) As a method of adding the luminescence center, first, powder (solid) samarium dipivaloyl methanide (Sm (C ₁₁ H ₁₉ O ₂ ) ₃ ), which is the luminescence center feed material, is added to tetrahydrofuran (organic solvent) It was dissolved in THF: C ₄ H ₈ O) to a concentration of 1.0 mol%, and this was filled in the raw material container 43. At this time, when samarium dipivaloyl methanide (Sm (C ₁₁ H ₁₉ O ₂ ) ₃ ) was added at a concentration of 5 mol% or more with respect to the organic solvent, tetrahydrofuran (THF: C ₄ H ₈ O), luminescence in the solvent Since the central raw material precipitates, the amount of addition in the film changes with respect to the number of times the light emitting layer is formed (the number of times the light emitting layer forming process is repeated for each lot).
On the contrary, if the concentration is less than 0.1 mol%, a large amount of organic solvent must be supplied in order to obtain a certain amount of the luminescent center material to be supplied onto the heating plate. This is because the heating plate is cooled by the supplied emission center raw material, so that the heating temperature cannot be kept constant, and the emission center raw material that has not been rapidly vaporized remains on the heating plate. This is because the supply amount of the raw material gas cannot be kept constant. (f) Next, hydrogen (H ₂ ) is supplied to the container 43 filled with the emission center raw material through a flow meter (MFC) 44 for hydrogen (H ₂ ) gas to push out the emission center raw material from the container 43, and vaporize the source material. The emission center raw material was transported to the chamber 42. At this time, the amount of the raw material pushed out from the emission center raw material container is measured by the liquid flow meter (MF
C) Measured by 45, in order to improve the accuracy of this flow rate, feedback control is performed from the liquid flow meter (MFC) 45 to the hydrogen (H ₂ ) gas flow meter (MFC) 44 for pushing out the raw material. Then, the flow rate of the gas for extrusion was finely adjusted. A quartz plate heating plate 47 is installed on the heating heater 46 provided in the heating chamber.
The emission center raw material supplied into the vaporization chamber is maintained at a constant temperature in the range of 250 ° C. and dropped onto the heating plate 47 to be rapidly vaporized and gasified. Hydrogen (H ₂ ) gas having a flow rate of 25 to 100 cc / min was used as a carrier gas for supplying the gasified raw material into the reaction furnace 40. The lower limit of the carrier gas flow rate used to supply the emission center raw material gas was set to 25 cc / min because of the capability of the MOCVD apparatus used in this example. It is because there is a possibility that the supply amount of will vary, and does not specify the conditions of the invention,
This is a preferable value for suppressing variations. Also the upper limit
The value of 100 cc / min is a recommended value to prevent the flow of other gas supplied into the reaction furnace when it is supplied into the reaction furnace at a flow rate exceeding this flow rate.

FIG. 6 shows the samarium (Sm) concentration in the light emitting layer thin film with respect to the flow rate of hydrogen (H ₂ ) carrier gas when samarium (Sm) is added to the light emitting layer thin film by using the above-mentioned luminescent center material transport method. It was In FIG. 6, ○ represents the average value of the samarium (Sm) concentration in the light emitting layer thin film in the conventional manufacturing method, and ●
Is the average value of the samarium (Sm) concentration in the light emitting layer thin film in the method of the present invention. The line above the mark is
The maximum value of the variation is shown, and the lower line shows the minimum value of the variation. The conventional product referred to here means that the luminescent layer is formed by using a raw material gas obtained by directly vaporizing powder (solid) samarium dipivaloyl methanide (Sm (C ₁₁ H ₁₉ O ₂ ) ₃ ) as the luminescent center raw material. It is a film. As is clear from FIG. 6, the control of the addition amount of the luminescent center was significantly improved by the method of the present invention.

(G) In addition to the above-mentioned pipes, hydrogen chloride (HCl) gas as a source gas for the halogen element was introduced by providing an independent pipe. Hydrogen chloride (HCl) to be introduced was diluted with hydrogen (H ₂ ) and was introduced into the reaction furnace at the same time as the emission center element. (h) Next, on the light emitting layer 14, tantalum pentoxide (Ta
₂ O ₅ ) and the second insulating layer 15 is replaced with the above-mentioned first insulating layer 13
It was formed in the same manner as. Then, the second transparent electrode 16 made of a zinc oxide (ZnO) film was formed on the second insulating layer 15 by the same method as the above-mentioned first transparent electrode 12.

The thickness of each layer formed is 300 nm for the first and second transparent electrodes 12 and 16 and 300 nm for the first and second insulating layers 13 and 15.
400 nm and the emission layer 14 is 800 nm.

FIG. 1 is a graph showing variations in emission luminance when an alternating voltage of 1 kHz is used and a voltage exceeding the threshold voltage by 60 V is applied to the actually manufactured sample. In FIG. 1, the circle indicates the average value of the light emission luminance, the upper line indicates the highest luminance among the measured EL elements, and the lower line indicates the lowest emission luminance on the contrary. In FIG. 1, the conventional product is a powdered samarium dipivaloyl methanide (Sm (C ₁₁ H
₁₉ shows variations in emission luminance among EL elements having a light emitting layer formed using ₁₉ O ₂ ) ₃ ).
As shown in FIG. 1, by using the method according to the present invention, variations in emission luminance of the manufactured EL element are reduced, reproducibility is remarkably improved, and an EL element having higher reliability than the conventional method is obtained. Can be manufactured with good reproducibility.

Example 2 Another method of manufacturing an EL element different from the above method will be described. This is also a method using MOCVD equipment, but the method of supplying the raw material gas is different. (i) The first transparent electrode, the first insulating layer, the second insulating layer, and the second transparent electrode were manufactured by the method described in Example 1. (j) Next, a zinc sulfide: samarium (ZnS: Sm: Cl) light emitting layer containing zinc sulfide (ZnS) as a base material, samarium (Sm) as an emission center, and chlorine (Cl) as a halogen was added to the MOC layer.
It was formed by the VD method. Specifically, the glass substrate 11
Is maintained at a constant temperature and the inside of the film forming chamber is under a reduced pressure atmosphere, and then hydrogen zinc gas is used to remove diethyl zinc (Zn (C
₂ H ₅ ) ₂ ) and hydrogen sulfide (H ₂ S) diluted with hydrogen at the same time were made to flow, and a zinc sulfide (ZnS) thin film was formed using the MOCVD apparatus (schematic diagram) 500 shown in FIG. (k) As a method for adding the luminescence center, as in Example 1 of the present invention, powder (solid) samarium dipivaloyl methanide (Sm (C ₁₁ H ₁₉ O ₂ )) as a luminescence center supply material is used. ₃ ) was dissolved in tetrahydrofuran (THF: C ₄ H ₈ O), which is an organic solvent, and the raw material container 53 was filled. Hydrogen (H ₂ ) was sent to the raw material container 53, the raw material was pushed out of the container, and this was sent to the raw material vaporization chamber 52. At this time, the emission center raw material is supplied to the raw material vaporization chamber 52 via the liquid flow meter 55,
Further, the flow rate measured by the liquid flow meter 55 is output to the hydrogen (H ₂ ) flow meter 54 fed into the raw material container 53 by feedback control, and the flow rate is controlled with higher accuracy. The emission center raw material measured with high precision is the raw material vaporization chamber 52.
Before being introduced into the injector (58) into the hydrogen (H ₂ ) carrier gas.
It was jetted at. Hydrogen (H
₂ ) The gas is sent into the raw material vaporization chamber 52, sprayed on a quartz heating plate 57 kept at a constant temperature to be rapidly vaporized, and a hydrogen (H ₂ ) carrier gas for transporting the vaporized gas. A line is provided separately from the above hydrogen (H ₂ ) carrier gas line,
This hydrogen (H ₂ ) carrier gas was introduced into the reaction furnace 50. Further, diethyl zinc (Zn (C ₂ H ₅ ) ₂ ) gas and hydrogen-diluted hydrogen sulfide (H ₂ S) gas were simultaneously supplied into the reaction furnace 50. Further, hydrogen chloride (HCl) gas diluted with hydrogen (H ₂ ) was supplied into the reaction furnace 50 simultaneously with the emission center described above and in a system independent of other gases.

When manufactured by the method of Example 2 above, the controllability of the samarium (Sm) concentration in the light emitting layer thin film with respect to the hydrogen (H ₂ ) carrier gas flow rate was as follows: When the concentration was controlled to be not more than%, it was possible to realize an EL element having high brightness with good reproducibility as compared with the one manufactured in Example 1.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a variation in emission luminance between elements of an electroluminescence element according to Example 1 of the present invention, as compared with a conventional method.

FIG. 2 is a schematic diagram showing a vertical cross section of an electroluminescence element according to Example 1 of the present invention.

FIG. 3 is a schematic diagram showing a vertical cross section of a conventional electroluminescence element.

FIG. 4 is a schematic view of a metal organic chemical vapor deposition (MOCVD) apparatus used for forming a light emitting layer of an electroluminescence device according to Example 1 of the present invention.

FIG. 5 is a schematic view of a metal organic chemical vapor deposition (MOCVD) apparatus used for forming a light emitting layer of an electroluminescence device according to Example 2 of the present invention.

FIG. 6 is a graph showing the relationship between the hydrogen (H ₂ ) carrier gas flow rate and the samarium (Sm) concentration in the light emitting layer thin film of the electroluminescence device according to Example 1 of the present invention.

[Explanation of symbols]

10, 100 EL element (electroluminescence element) 1, 11 Glass substrate (insulating substrate) 2, 12 First transparent electrode (first electrode) 3, 13 First insulating layer 4, 14 Light emitting layer 5, 15 Second insulating Layers 6 and 16 Second transparent electrode (second electrode) 44 and 54 Flowmeter (MFC, mass flow controller) 45 and 55 Liquid flowmeter 400 and 500 Metal organic chemical vapor deposition (MOCVD) device

Claims (3)

[Claims] 1. A manufacturing method of an electroluminescence device, in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are sequentially laminated with at least a material on the light extraction side being optically transparent. A method, which is a base material of the light-emitting layer, is reacted with either a zinc compound gas or an alkaline earth metal compound gas and either a sulfur compound gas or a selenium compound gas in a reaction furnace, Furthermore, when forming a light-emitting layer obtained by adding a luminescent center raw material and a halogen element to be the luminescent center in the host material by vapor phase growth, an organometallic luminescent center raw material obtained by dissolving the luminescent center raw material in an organic solvent, Manufacture of an electroluminescence device characterized in that it is dripped or injected into a heating body set to a high temperature to be rapidly vaporized and supplied as a gas of a luminescence center raw material into the reaction furnace. Law. 2. The heating element set to a high temperature according to claim 1, wherein the temperature is equal to or higher than the boiling point of the organic solvent and lower than the decomposition temperature of the organic metal luminescence center raw material. A method for manufacturing the electroluminescent element according to 1. 3. A zinc compound gas or an alkaline earth metal compound gas, a sulfur compound gas or a selenium compound gas, which is a raw material gas for forming the light emitting layer according to claim 1.
The source gas of the substance that becomes the emission center and the halogen element is
The method for manufacturing an electroluminescent element according to claim 1, wherein all of them are separately supplied into the reaction furnace.